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  • 1.
    af Klintberg, Tord
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Björk, Folke
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Air Gap Method: Dependence of water removal on RH in room and height of floor air gap2012In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 56, p. 1-7Article in journal (Refereed)
    Abstract [en]

    This study is performed in combined floor and wall constructions with air gaps within and with a heating cable in the vertical air gap. All surfaces of the air gap are covered with polystyrene plastic to avoid leakage into the construction. Wet gypsum boards that are weighed at start and end of experiment are used to measure the dry out process.Three different heights of the floor air gap, 25 mm, 15 mm and 5 mm are investigated. The influences of the RH in the surrounding room and of the wetness of the gypsum boards are also investigated.It is shown that the height of the floor air gap has a great impact on the rate of drying. The optimal height is less than 25 mm and somewhere between 15 and 5 mm.

  • 2.
    Assefa, Getachew
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Glaumann, Mauritz
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment.
    Malmqvist, Tove
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment.
    Eriksson, O.
    Quality versus impact: Comparing the environmental efficiency of building properties using the EcoEffect tool2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 5, p. 1095-1103Article in journal (Refereed)
    Abstract [en]

    There are tools that are developed for the assessment of the environmental impact of buildings (e.g. ATHENA). Other tools dealing with the indoor and outdoor environmental quality of building properties (referred to as real estates in other literature) are also available (e.g. GBTool). A platform where both the aspects of quality and impact are presented in an integrated fashion are few. The aim of this contribution is to present how the performance of different building properties can be assessed and compared using the concept of environmental efficiency in a Swedish assessment tool called EcoEffect. It presents the quality dimension in the form of users' satisfaction covering indoor and outdoor performance features against the weighted environmental impact covering global and local impacts. The indoor and outdoor values are collected using questionnaires combined with inspection and some measurements. Life cycle methodology is behind the calculation of the weighted external environmental impact. A case study is presented to show the application of EcoEffect using a comparative assessment of Lindas and a Reference property. The results show that Lindas block is better in internal environment quality than the Reference property. It performs slightly worse than the Reference property in the external environmental impact due to emissions and waste from energy and material use. The approach of integrated presentation of quality and impact as in EcoEffect provides with the opportunity of uncovering issues problem shifting and sub-optimisation. This avoids undesirable situations where the indoor quality is improved through measures that result in higher external environmental impact.

  • 3.
    Assefa, Getachew
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Glaumann, Mauritz
    Department of Technology and Built Environment, University of Gävle.
    Malmqvist, Tove
    KTH, School of Architecture and the Built Environment (ABE), Architecture. KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Environmental Strategies.
    Kindembe, Beatrice Isampete
    Department of Technology and Built Environment, University of Gävle.
    Hult, M.
    Swedish University of Agricultural Sciences, Landscape Architecture, Uppsala.
    Myhr, U.
    Swedish University of Agricultural Sciences, Landscape Architecture, Uppsala.
    Eriksson, O.
    Department of Technology and Built Environment, University of Gävle.
    Environmental assessment of building properties — Where natural and social sciences meet: the case of EcoEffect2007In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 42, no 3, p. 1458-1464Article in journal (Refereed)
    Abstract [en]

    The EcoEffect method of assessing external and internal impacts of building properties is briefly described. The external impacts of manufacturing and transport of the building materials, the generation of power and heat consumed during the operation phase are assessed using life-cycle methodology. Emissions and waste; natural resource depletion and toxic substances in building materials are accounted for. Here methodologies from natural sciences are employed. The internal impacts involve the assessment of the risk for discomfort and ill-being due to features and properties of both the indoor environment and outdoor environment within the boundary of the building properties. This risk is calculated based on data and information from questionnaires; measurements and inspection where methodologies mainly from social sciences are used. Life-cycle costs covering investment and utilities costs as well as maintenance costs summed up over the lifetime of the building are also calculated.

    The result presentation offers extensive layers of diagrams and data tables ranging from an aggregated diagram of environmental efficiency to quantitative indicators of different aspects and factors. Environmental efficiency provides a relative measure of the internal quality of a building property in relation to its external impact vis-à-vis its performance relative to other building properties.

  • 4.
    Bohdanowicz, Paulina
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Martinac, Ivo
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    A study of resource consumption and modelling in mid-market chain hotels in StockholmIn: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684XArticle in journal (Refereed)
  • 5.
    Brown, Nils W. O.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Environmental Strategies.
    Malmqvist, Tove
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Environmental Strategies.
    Bai, Wei
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Environmental Strategies.
    Molinari, Marco
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Sustainability assessment of renovation packages for increased energy efficiency for multi-family buildings in Sweden2012In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 61, p. 140-148Article in journal (Refereed)
    Abstract [en]

    In this paper, we propose a method for assessing renovation packages drawn up with the goal of increasing energy efficiency. The method includes calculation of bought energy demand, life-cycle cost (LCC) analysis and assessment of the building according to the Swedish environmental rating tool Miljöbyggnad (MB). In this way the methodology assesses economic, indoor environmental quality (IEQ) and specifically environmental aspects associated with energy demand of such packages from a sustainability point-of-view. Through MB, energy efficiency packages are placed in context with other necessary measures required to improve environmental performance in buildings, providing a consistent and systematic basis other than simply financial performance by which to compare capital improvements. The method is further explained and analyzed by applying it in three case studies. In each case study a multi-family building representing a typologically significant class in the Swedish building stock is considered, and for each building a base case and two renovation packages with higher initial investment requirement and higher energy efficiency are defined. It is shown that higher efficiency packages can impact IEQ indicators both positively and negatively and that packages reducing energy demand by approx. 50% have somewhat higher LCC. Identified positive IEQ impacts point to added value for packages that may not otherwise be communicated, while negative impacts identify areas where packages need to be improved, or where MB indicators may be referred to as specifications in procurement procedures.

  • 6.
    Brown, Nils W. O.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Olsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Malmqvist, Tove
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Embodied greenhouse gas emissions from refurbishment of residential building stock to achieve a 50% operational energy reduction2014In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 79, p. 46-56Article in journal (Refereed)
    Abstract [en]

    Mitigating climate change through operational energy reduction in existing buildings is of highest priority for policy-makers in Europe and elsewhere. At the same time there is increasing understanding of the significance of impacts arising from material production for buildings. The aim of this work has therefore been to evaluate the importance of embodied GWP for refurbishment for operational energy reduction on a stockwide basis. It is further intended to judge the relative significance of embodied GWP for specific refurbishment measures implemented for operational energy reduction. We study the case of operational energy reduction in the Swedish residential building stock by 50% compared to 1995. The total embodied GWP to achieve the noted operational energy reduction is 0.35 Mt CO2-e/year. 83% of this total is due to ventilation and window measures alone. Compared with previous studies assessing GWP mitigation from operational energy reduction, the "GWP payback time" is just over 3 years. Many types of measure that contribute significantly to achieving the above operational energy goal had average embodied GWP between 10 and 20 g CO2-e/kW h operational energy reduction, notably window and ventilation measures. Indoor temperature reduction (to 20 degrees C), was also significant for stockwide operational energy reduction but had a very low GWP of 0.4 g CO2-e/kW h operational energy reduction. If this measure proves unfeasible to implement on a stockwide basis then more expensive measures with higher embodied GWP will be needed to achieve the stated energy reduction goal.

  • 7.
    Calzolari, Giovanni
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Liu, Wei
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Deep learning to replace, improve, or aid CFD analysis in built environment applications: A review2021In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 206, article id 108315Article, review/survey (Refereed)
    Abstract [en]

    Fast and accurate airflow simulations in the built environment are critical to provide acceptable thermal comfort and air quality to the occupants. Computational Fluid Dynamics (CFD) offers detailed analysis on airflow motion, heat transfer, and contaminant transport in indoor environment, as well as wind flow and pollution dispersion around buildings in urban environments. However, CFD still faces many challenges mainly in terms of computational expensiveness and accuracy. With the increasing availability of large amount of data, data driven models are starting to be investigated to either replace, improve, or aid CFD simulations. More specifically, the abilities of deep learning and Artificial Neural Networks (ANN) as universal non-linear approximator, handling of high dimensionality fields, and computational inexpensiveness are very appealing. In built environment research, deep learning applications to airflow simulations shows the ANN as surrogate, replacement for expensive CFD analysis. Surrogate modeling enables fast or even real-time predictions, but usually at a cost of a degraded accuracy. The objective of this work is to critically review deep learning interactions with fluid mechanics simulations in general, to propose and inform about different techniques other than surrogate modeling for built environment applications. The literature review shows that ANNs can enhance the turbulence model in various way for coupled CFD simulations of higher accuracy, improve the efficiency of Proper Orthogonal Decomposition (POD) methods, leverage crucial physical properties and information with physics informed deep learning modeling, and even unlock new advanced methods for flow analysis such as super-resolution techniques. These promising methods are largely yet to be explored in the built environment scene. Unavoidably, deep learning models also presents challenges such as the availability of consistent large flow databases, the extrapolation task problem, and over-fitting, etc.

  • 8.
    Cehlin, Mathias
    et al.
    Division of Energy and Mechanical Engineering, Department of Technology and Built Environment, University of Gävle, Kungsbacksvagen 47, 801 76 Gavle, Sweden.
    Moshfegh, B
    Division of Energy and Mechanical Engineering, Department of Technology and Built Environment, University of Gävle, Kungsbacksvagen 47, 801 76 Gavle, Sweden b Division of Energy Systems, Department of Management and Engineering, Linköping University, Sweden.
    Numerical modeling of a complex diffuser in a room with displacement ventilation2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 10, p. 2240-2252Article in journal (Refereed)
    Abstract [en]

    A micro/macro-level approach (MMLA) has been proposed which makes it possible for HVAC engineers to easily study the effect of diffuser characteristics and diffuser placement on thermal comfort and indoor air quality. In this article the MMLA has been used to predict the flow and thermal behavior of the air in the near-zone of a complex low-velocity diffuser. A series of experiment has been carried out to validate the numerical predictions in order to ensure that simulations can be used with confidence to predict indoor airflow. The predictions have been performed by means of steady Reynolds Stress Model (RSM) and the results have good agreement both qualitatively and quantitatively with measurements. However, measurements indicated that the diffusion of the velocity and temperature was to some extent under-predicted by the RSM, which might be related to high instability of the airflow close to the diffuser. This effect might be captured by employing unsteady RSM. The present study also shows the importance of detailed inlet supply modeling in the accuracy of indoor air prediction.

  • 9. Cheng, X.
    et al.
    Yang, B.
    Olofsson, T.
    Liu, G.
    Li, Haibo
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID.
    A pilot study of online non-invasive measuring technology based on video magnification to determine skin temperature2017In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 121, p. 1-10Article in journal (Refereed)
    Abstract [en]

    Much attention was paid on human centered design strategies for environmental control systems of indoor built environments. The goal is to achieve thermally comfortable, healthy and safe working or living environments in energy efficient manners. Normally building Heating, Ventilation and Air Conditioning (HVAC) systems have fixed operating settings, which can't satisfy human thermal comfort requirements under transient and non-uniform indoor thermal environments. Therefore, human thermal physiology signal such as skin temperature, which can reflect human body thermal sensation, has to be measured over time. Several trials have been performed by minimizing measuring sensors such as i-Button and mounting measuring sensors into wearable devices such as glasses. Infrared thermography technology has also been tried to achieve non-invasive measurements. However, it would be much more convenient and feasible if normal computer camera could record images, which could be used to obtain human thermal physiology signals. In this study, skin temperature of hand back, which has a high density of blood vessels and is normally not covered by clothing, was measured by i-button sensors. Images recorded by normal camera were amplified to analyzing skin temperature variation, which are impossible to see with naked eyes. The agreement between i-button sensor measuring results and image magnification results demonstrated the possibility of non-invasive measuring technology by image magnification. Partly personalized saturation-temperature model (T = 96.5 × S + bi) can be used to predict skin temperatures for young East Asia females.

  • 10.
    Du, Chenqiu
    et al.
    Chongqing Univ, Sch Civil Engn, Joint Int Res Lab Green Bldg & Built Environm, Minist Educ, Chongqing, Peoples R China.;174 Shazheng Rd, Chongqing 400045, Peoples R China..
    Wang, Yujue
    Chongqing Univ, Sch Civil Engn, Joint Int Res Lab Green Bldg & Built Environm, Minist Educ, Chongqing, Peoples R China..
    Li, Baizhan
    Chongqing Univ, Sch Civil Engn, Joint Int Res Lab Green Bldg & Built Environm, Minist Educ, Chongqing, Peoples R China..
    Xu, Mengyu
    Chongqing Univ, Sch Civil Engn, Joint Int Res Lab Green Bldg & Built Environm, Minist Educ, Chongqing, Peoples R China..
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Grey image recognition-based mold growth assessment on the surface of typical building materials responding to dynamic thermal conditions2023In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 243, article id 110682Article in journal (Refereed)
    Abstract [en]

    Mold growth on building materials poses a threat to both the building structural integrity and occupants' well-being. However, it is generally studied under suitable conditions in laboratory; the assessment is based on visual inspection but lacks an objective criterion. This research explored the effects of simulated dynamic thermal conditions on mold growth on three typical building materials artificially contaminated with Aspergillus niger spores. Test specimens were assessed based on a developed digital image-based method, where image seg-mentation, processing, and greyscale recognition via the OpenCV visual library were introduced. The results showed that the high temperature-high humidity condition in a 24-h cyclic change facilitated mold growth on the surfaces of three materials, especially for gypsum board, with an identified area proportion of 1.13% on the 80th day. This was consistent with the changes of the counted number of mold colonies, and no significant differences were found among the gypsum board, latex paint, and wallpaper. The growth extents of mold spores were objectively evaluated by the mean greyscale values; the values decreased gradually with time, and the decrements were different compared high-temperature to low-temperature conditions. The mold growth models were developed, where the area proportion of mold growth was linearly related to the counted colonies and greyscale values under different material surfaces. This novel grey image recognition-based method provides an accurate means of evaluating mold growth abilities and extents, overcoming the inaccuracy of visual observa-tion. The findings have significant implications for visual inspection, mold prediction, and building management.

  • 11.
    Einberg, Gery
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Hagström, Kim H.
    Halton OY.
    Mustakallio, P.
    Halton OY.
    Koskela, Hannu
    Finnish Inst. of Occupational Health.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    CFD modelling of an industrial air diffuser: predicting velocity and temperature in the near zone2005In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 40, no 5, p. 601-615Article in journal (Refereed)
    Abstract [en]

    This article describes experimental and modelling results from CFD simulation of an air diffuser for industrial spaces. The main objective of this paper is to validate a manufacturer model of the diffuser. In the air diffuser, the low velocity part is placed on top of a multi-cone diffuser in order to increase airflow rates and maximize the cooling capacity of a single diffuser unit. This kind of configuration should ensure appropriate performance of industrial air diffusers, which is discussed briefly at the end of the article. The paper illustrates the importance of a simulation model jointly with the manufacturer's product model and the grid layout near the ventilation device to achieve accurate results. Parameters for diffuser modelling were adapted from literature and manufacturer's product data. Correct specification of diffuser geometry and numerical boundary conditions for CFD simulations are critical for prediction. The standard k-epsilon model was chosen to model turbulence because it represents the best-known model utilized and validated for air diffuser performance. CFD simulations were compared systematically with data from laboratory measurements; air velocity was measured by ultrasonic sensors. Results show that CFD simulation with a standard k-epsilon model accurately predicts non-isothermal airflow around the diffuser. Additionally, smoke tests revealed that the flow around the diffuser is not completely symmetrical as predicted by CFD. The cause of the observed asymmetry was not identified. This was the main reason why some simulation results deviate from the measured values.

  • 12. Elvsen, Per-Ake
    et al.
    Sandberg, Mats
    Högskolan i Gävle.
    Buoyant jet in a ventilated room: Velocity field, temperature field and airflow patterns analysed with three different whole-field methods2009In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 44, no 1, p. 137-145Article in journal (Refereed)
    Abstract [en]

    The instantaneous velocity field and temperature field were measured and file airflow patterns visualised close to a diffuser for displacement ventilation. Since the low-velocity diffuser was located above the floor and the inlet air temperature was below the room temperature, the flow was governed by both momentum and buoyancy forces. The data were recorded with whole-field measuring techniques, particle streak velocimetry (PSV), particle image velocimetry (PIV) and infrared thermography (IR), in conjunction with a low thermal mass screen. The environment is very complex, supply of buoyant air with a commercial supply terminal with 20 nozzles pointing in different directions. which makes it difficult to use point-measuring techniques or computational fluid dynamics (CFD). The aim was twofold: (a) to explore what kind of information can be derived Front whole-field measurement techniques in this context and (b) to investigate the trajectory of the flow discharged into the room and the entrainment of the flow.

  • 13. Erlandsson, M
    et al.
    Levin, Per
    KTH, Superseded Departments (pre-2005), Building Sciences and Engineering.
    Environmental assessment of rebuilding and possible performance improvements effect on a national scale2004In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 39, no 12, p. 1453-1465Article in journal (Refereed)
    Abstract [en]

    The paper deals with improvements on environmental significant activities related to the life supporting function "building and housing", using life cycle assessment (LCA). In the calculation, back-casting technique is utilised and implies to a future scenario, based on known technology. Besides heating, waste water treatment is a significant issue, according to the definition of building and housing function practised. The main conclusions from the assessment are that rebuilding is an environmentally better choice than the construction of a new building, if the same essential environmentally related functional performance is reached. Furthermore, the case study and the national estimates performed prove that the potential environmental impact can be reduced by about 70% for the heating service and 75% for the waste water system, if the suggested measures are performed.

  • 14. Erlandsson, Martin
    et al.
    Levin, Per
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Environmental assessment of rebuilding and possible performance improvements effect on a national scale2005In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 40, no 11, p. 1459-1471Article in journal (Refereed)
    Abstract [en]

    This paper deals with improvement on environmental significant activities related to the life supporting function "building and housing", using life cycle assessment. In the calculation, back-casting technique is utilised and implies to a future scenario, based on known technology. Besides heating, wastewater treatment is a significant issue, according to the definition of building and housing function practised. The main conclusions from the assessment are that rebuilding is an environmentally better choice than the construction of a new building, if the same essential environmentally related functional performance is achieved. Furthermore, the case study and the national estimates performed prove that the potential environmental impact can be reduced by about 70% for the heating service and 75% for the wastewater system, if the suggested measures are performed.

  • 15.
    Forsberg, Anna
    et al.
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    von Malmborg, F.
    Tools for environmental assessment of the built environment2004In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 39, no 2, p. 223-228Article in journal (Refereed)
    Abstract [en]

    During the last decades there has been an increasing interest in environmental assessments of the built environment. As a result, we can find several qualitative and quantitative assessment tools. With an increasing understanding of cities and the built environment as systems metabolising matter and energy, the use of quantitative tools are expected to increase, making it relevant to ask for their status of development. Aiming to give an overview of the present status of quantitative tools, as a basis for further research and development, this paper describes and compares five different tools for quantitative environmental assessment of the built environment.

  • 16.
    Fredriksson, Jan
    et al.
    KTH Research School University of Gävle, Department of Indoor Environment.
    Sandberg, Mats
    KTH Research School University of Gävle, Department of Indoor Environment.
    The effect of false ceiling on the cooling capacity of passive chilled beams2009In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 44, no 7, p. 1426-1430Article in journal (Refereed)
    Abstract [en]

    Passive chilled beams are often used to provide cooling or additional cooling when the ventilation system cannot cope with the whole cooling load. The advantage of passive cooling is that it is a silent cooling. Often the chilled beams are installed above a false ceiling and thereby the room is subdivided into two compartments. From the chilled beam a plume is generated. Make-up air (return air) needs to flow into the upper compartment to substitute the airflow generated by the chilled beam. Therefore openings for this purpose are installed in the false ceiling. Small openings constitute a resistance to the flow and the locations of the openings affect the flow pattern. The overall performance was studied in a mock-up of a real office by changing both the size and position of the openings for the make-up air. A uniform heating source was arranged by covering the floor with a heating foil. The best location and size of the openings were explored by both recording the heat absorbed by the beam and the temperature in the room. Minimum temperature attained in the room is the signature of the most efficient cooling. To achieve efficient cooling with a uniform floor-based heating source, two conditions must be fulfilled: a) the return opening area must be at least equal to the horizontal area of the chilled beam: b) the return air openings must be located at the perimeter of the room. In general we can expect conditions a) and b) to be applicable irrespective of type of heat, but for point sources we could achieve the best cooling by placing the return air opening above the heat source.

  • 17.
    Gudmundsson, Kjartan
    KTH, Superseded Departments (pre-2005), Building Sciences and Engineering.
    Tracer gas measurements of water vapour permeability of porous building materialsIn: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684XArticle in journal (Other academic)
  • 18.
    Gudmundsson, Kjartan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    af Klintberg, Tord
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Söderström, Ove
    The drying out capacity of a ventilated internal cavity with a heating cable, analytical model and empirical verification2012In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 52, p. 171-176Article in journal (Refereed)
    Abstract [en]

    This study is concerned with the use of interior air channels in walls for the drying out of surplus water in floor constructions. The floor is to be dried out by the means of an air gap, while a heating cable at the bottom of an adjacent wall channel provides a driving force for the flow. The model of this study can be used to quantify the drying out capacity of such a construction, given the geometrical configuration and the effect of the cable. By posing heat and mass balance equations for a star network equivalent to the delta network of the actual physical problem the temperature and moisture profiles for the floor channel are obtained. The wetted surface of the floor is assumed to be saturated, while the saturated moisture content varies with temperature along the surface. The temperature and moisture distributions along the air gap and the drying out capacity are obtained as a function of the flow rate. The physical problem of the wall channel is posed in terms of the governing equations of conservation. The Boussinesq approximation is used to restrict the variation in density to that of the gravitational force. The buoyancy generated by the cable is related to the frictional forces of the channel walls, providing a relationship between the flow rate and the effect of the cable. The analytical results are compared with laboratory measurements and show good agreement for a number of different heights of the air gap in the floor.

  • 19.
    Hameury, Stéphane
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Moisture buffering capacity of heavy timber structures directly exposed to an indoor climate: a numerical study2005In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 40, no 10, p. 1400-1412Article in journal (Refereed)
    Abstract [en]

    This paper introduces a hygrothermal model accounting for the moisture and heat transport in a massive wood envelope directly exposed to an indoor climate. A better knowledge of the passive interaction between an indoor climate and a heavy timber structure could lead to presenting an alternative to high air exchange rate, and to increasing the thermal comfort of the inhabitants. So far, the model is developed as a stand-alone application with a finite difference method, and is written in a Neutral Model Format, enabling a later implementation in a modular environment for indoor climate energy calculations, called IDA ICE. A numerical simulation is provided to depict the buffering capacity of a massive timber structure as a function of the air exchange rate and the effective wood wall area.

  • 20. Hang, Jian
    et al.
    Li, Yuguo
    Sandberg, Mats
    KTH.
    Claesson, Leif
    KTH.
    Wind conditions and ventilation in high-rise long street models2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 6, p. 1353-1365Article in journal (Refereed)
    Abstract [en]

    We regarded high-rise cities as obstacles and channels to wind. We first studied wind conditions and ventilations in idealized high-rise long street models experimentally and numerically with a constant street width (W = 30 mm), variable street heights (H = 2 W, 2.5W, 3W, 4W), variable street lengths (L = 47.4W, 79W. 333W, 667W) and a parallel approaching wind. The flow rates penetrating into windward entries are a little larger than the reference flow rate in the far upstream free flow through the same area with windward entries in all models. The stream-wise velocity decreases along the street as some air leaves upwardly across street roofs. Near the leeward entry, there is a downward flow which brings some air into the street and results in an accelerating process. In the neighborhood scale long streets (L = 47.4W and 79W), wind in taller streets is stronger and the ventilation is better than a lower one. For the city scale long streets (L = 333W and 667W), a constant flow region exists where the vertical velocity is zero and the stream-wise velocity remains constant. In such regions, turbulent fluctuations across the street roof are more important to air exchange than vertical mean flows. In a taller street, the process to establish the constant flow conditions is longer and the normalized balanced horizontal flow rate is smaller than those in a lower street. In the city scale long streets, the turbulence exchange rate can be 5-10 times greater than the mean flow rate.

  • 21. Hang, Jian
    et al.
    Sandberg, Mats
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Li, Yuguo
    Age of air and air exchange efficiency in idealized city models2009In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 44, no 8, p. 1714-1723Article in journal (Refereed)
    Abstract [en]

    Wind can provide relevantly clean external (rural) air into urban street network, i.e. city ventilation. The local mean age of air denotes the time it takes for the external air to reach a location after entering the urban canopy layer. The air exchange efficiency denotes the efficiency of flushing the street network with external air. However, difficulties exist in calculating the local mean age of air in a city due to open boundaries. The traditional experimental homogeneous emission method is adapted here in a CFD method to predict the urban local age of air and analyze the air exchange efficiency for city ventilation. Three simple city models are considered, including a round city model, a square city model and a long rectangular city with one main street parallel to the approaching wind or with two crossing streets. The difference in the city shape results in significant difference in the local mean age of air. In the round city of one narrow street, two inflows through street openings converge close to the city centre and exits through the street roof, so the air close to the city centre is relatively old and the air exchange efficiency is low (30%). For a round city with two crossing streets, a slightly non-parallel wind to the main street generates younger air and the higher air exchange efficiency in the city.

  • 22. Hang, Jian
    et al.
    Sandberg, Mats
    KTH Research School University of Gävle, Department of Indoor Environment.
    Li, Yuguo
    Claesson, Leif
    (KTH Research School University of Gävle, Department of Indoor Environment.
    Flow mechanisms and flow capacity in idealized long-street city models2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 4, p. 1042-1053Article in journal (Refereed)
    Abstract [en]

    It is an open question whether a street network of a city has a certain flow capacity characterizing the flow that can pass through the street network. It s our hypothesis that at least the simple street network has a certain flow capacity. With the purpose of exploring this we studied numerically and experimentally the flow capacity in some idealized long-street models continuously lined with buildings and exposed to a parallel approaching wind. The height of all the models is the same (H = 69 mm). Three groups of models were studied: models with the same uniform street width (W=H) but different lengths (L = 21.7H, 43.5H, 72.5H); models with the same length (L = 43.5H) but different uniform width (W = H, 2H. 4H); and models with a change of width at half distance, L/2. In the last of the three cases, the width of the upstream half was always the same (W1 = H), but there was a wider (W2 = 1.25H, 1.5H, 2H) or narrower (W2 = 0.75H, 0.5H) downstream half. We normalized flow rates by a reference flow rate equal to the flow rate through an opening far upstream with the same area as the windward entry. The normalized flow rate through the windward entry was about 1.0 in all cases. For a sufficiently long-street models, a flow balance is established, creating a fully developed region with a constant horizontal flow (flow capacity) and zero vertical mean velocity. The street length does not affect the flow capacity but as expected the width of the street affects the flow capacity.

  • 23.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Energy performance of low temperature heating systems in five new-built swedish dwellings: A case study using simulations and on-site measurements2013In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 64, p. 85-93Article in journal (Refereed)
    Abstract [en]

    In Europe, high energy consumption in built environments has raised the need for developing low energy heating systems both in new building and in retrofitting of existing buildings. This paper aims to contribute by presenting annual results of calculated and measured energy consumption in five new-built semi-detached dwellings in Stockholm, Sweden. All buildings were equipped with similar low temperature heating systems combining under-floor heating and ventilation radiators. Exhaust ventilation heat pumps supported the low temperature heating system. Buildings were modeled using the energy simulation tool IDA Indoor Climate and Energy (ICE) 4, and energy consumption of the heat pumps was measured. Results showed that calculated and measured results were generally in agreement for all five dwellings, and that the buildings not only met energy requirements of the Swedish building regulations but also provided good thermal comfort.

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  • 24.
    Hu, Mengqiang
    et al.
    Chongqing Univ, Sch Civil Engn, Chongqing 400044, Peoples R China.;Chongqing Univ, Minist Educ, Joint Int Res Lab Green Bldg & Built Environm, Chongqing 400044, Peoples R China.;Chongqing Univ, Natl Ctr Int Res Low Carbon & Green Bldg, Chongqing 400044, Peoples R China..
    Liu, Wei
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Xue, Kai
    Chongqing Univ, Sch Civil Engn, Chongqing 400044, Peoples R China.;Chongqing Univ, Minist Educ, Joint Int Res Lab Green Bldg & Built Environm, Chongqing 400044, Peoples R China.;Chongqing Univ, Natl Ctr Int Res Low Carbon & Green Bldg, Chongqing 400044, Peoples R China..
    Liu, Lumeng
    Chongqing Univ, Sch Civil Engn, Chongqing 400044, Peoples R China.;Chongqing Univ, Minist Educ, Joint Int Res Lab Green Bldg & Built Environm, Chongqing 400044, Peoples R China.;Chongqing Univ, Natl Ctr Int Res Low Carbon & Green Bldg, Chongqing 400044, Peoples R China..
    Liu, Huan
    Chongqing Univ, Sch Civil Engn, Chongqing 400044, Peoples R China.;Chongqing Univ, Minist Educ, Joint Int Res Lab Green Bldg & Built Environm, Chongqing 400044, Peoples R China.;Chongqing Univ, Natl Ctr Int Res Low Carbon & Green Bldg, Chongqing 400044, Peoples R China..
    Liu, Meng
    Chongqing Univ, Sch Civil Engn, Chongqing 400044, Peoples R China.;Chongqing Univ, Minist Educ, Joint Int Res Lab Green Bldg & Built Environm, Chongqing 400044, Peoples R China.;Chongqing Univ, Natl Ctr Int Res Low Carbon & Green Bldg, Chongqing 400044, Peoples R China..
    Comparing calculation methods of state transfer matrix in Markov chain models for indoor contaminant transport2022In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 207, p. 108515-, article id 108515Article in journal (Refereed)
    Abstract [en]

    Fast and accurate prediction of indoor airborne contaminant distribution is of great significance to the safety and health of occupants. Several Markov chain models have been developed and proved to be the potential solutions. However, there is a lack of comparison in terms of accuracy, computing cost, and robustness among these models, which limits their practical application. To this end, this study compared the performance of three Markov chain models, in which the state transfer matrix was calculated based on different principles, i.e., Markov chain model with flux-based method, with Lagrangian tracking, and with set theory approach. The investigation was conducted in a 2D ventilated cavity and a two-zone ventilated chamber. The simulation by Eulerian model for contaminant and experimental data were used as the benchmarks for the 2D and 3D cases, respectively. It is revealed that all three Markov chain models can provide a correct prediction. In the 2D case, the Markov chain model with set theory approach is the most accurate, followed by Lagrangian tracking. In the 3D case, the accuracy of Markov chain models with flux-based method and Lagrangian tracking is comparable. The Markov chain model with Lagrangian tracking is the fastest, and the time step size in this model can be relatively large. Finally, the selection guideline is given for the application of Markov chain models in different scenarios.

  • 25.
    Hu, Nan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Yuan, Feng
    Joint International Research Laboratory of Green Buildings and Built Environments (Ministry of Education), Chongqing University, Chongqing, China..
    Gram, Annika
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Yao, Runming
    Joint International Research Laboratory of Green Buildings and Built Environments (Ministry of Education), Chongqing University, Chongqing, China.; National Centre for International Research of Low-Carbon and Green Buildings (Ministry of Science and Technology), Chongqing University, Chongqing, China.; School of the Built Environment, University of Reading, Reading, UK..
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design. School of Business, Society and Engineering, Mälardalen University, Västerås, Sweden..
    Review of experimental measurements on particle size distribution and airflow behaviors during human respiration2024In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 247, article id 110994Article, review/survey (Refereed)
    Abstract [en]

    In recent years, pandemic outbreaks have raised concerns about the spread of respiratory infections and their impact on public health. Since the pathogen emission during human respiration is recognized as the primary source, characterizing the physical properties of exhaled particles and airflow has become a crucial focus of attention. This article critically reviews experimental studies in exhaled particles and airflow, examines the uncertainty introduced by different measurement methods, analyzes how it is reflected in measurement outcomes, and provides an in-depth understanding of particle size distribution and airflow behaviors of human respiration. The measurement techniques assessment highlights the variability among particle sizing techniques in detection size range, collection efficiency, hydration status of captured particles, and experimental protocols. A combination of sampling-based instruments and laser imaging systems is recommended for particle sizing to cover a wider detection range, with refined setups in thermal conditions, sampling distance, volume, and duration. Meanwhile, it identifies the complementary nature of qualitative and quantitative measurements of airflow characterization techniques. Image recording systems plus data reconstruction programs are suggested to capture dynamic airflow features while accuracy validation by other techniques is required at the same time. Subsequent analysis of the measurement data showed that the various experimental measurements provided substantial information, but they also revealed disagreements and challenges in quantification. The dominance of submicron aerosols in exhaled particles and jet-like transport in exhaled airflow is obvious. More efforts should be made to measure particles larger than 20 μm, capture airflow dynamics in a high temporal and spatial resolution, and quantify the impact of face coverings to improve the understanding of human respiratory emissions.

  • 26. Kobayashi, Tomohiro
    et al.
    Sagara, Kazunobu
    Yamanaka, Toshio
    Kotani, Hisashi
    Sandberg, Mats
    KTH Research School, University of Gävle.
    Power transportation inside stream tube of cross-ventilated simple shaped model and pitched roof house2009In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 44, no 7, p. 1440-1451Article in journal (Refereed)
    Abstract [en]

    The ultimate goal of this work is to establish a prediction method based on Power Balance Model for prediction of flow rate through cross-ventilated building. For the establishment of Power Balance Model, the lost power across stream tube sections must be determined in advance. However, the loss of power in the stream tube was not well studied by other researchers but this concerned critical step forms the focus of the present CFD study in which transported power in stream tubes formed at two selected models: (i) a suspended rectangular model, and (ii) a pitched roof single-storey house model standing on a flat ground surface, was documented. For the development of a new method applying to predict the lost power, decrease of the transported power across the stream tubes through both types of models will finally be shown in this paper.

  • 27.
    Lei, Lei
    et al.
    Gui Lin Univ Elect Technol, Sch Architecture & Transportat Engn, 1 Jinji Rd, Guilin 541004, Peoples R China..
    Chen, Wei
    Gui Lin Univ Elect Technol, Sch Architecture & Transportat Engn, 1 Jinji Rd, Guilin 541004, Peoples R China..
    Xue, Yu
    Dalian Univ Technol, Sch Civil Engn, 2 Linggong Rd, Dalian 116024, Peoples R China..
    Liu, Wei
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    A comprehensive evaluation method for indoor air quality of buildings based on rough sets and a wavelet neural network2019In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 162, article id UNSP 106296Article in journal (Refereed)
    Abstract [en]

    Understanding the level of indoor air quality is very important to improve the quality of air that people breathe indoors. In this paper, a comprehensive evaluation method combining rough sets and a wavelet neural network is proposed to evaluate the indoor air quality of buildings. Through on-site inspections of the indoor air in six large shopping malls in Beijing, Wuhan and Guangzhou, raw data of the environmental parameters affecting the indoor air quality of large shopping malls are obtained. First, rough sets are used to reduce the dimension of features that affect indoor air quality by removing unimportant features, and important environmental parameters that affect indoor air quality are obtained. These important environmental parameters are used as input parameters of the wavelet neural network. Then, the structure of the wavelet neural network is determined, and an evaluation model of the indoor air quality of buildings based on rough sets and the wavelet neural network is established. Finally, the model is applied to the evaluation of indoor air quality in large shopping malls, and the back propagation neural network, fuzzy neural network and Elman neural network are introduced for comparison of the testing accuracy of the wavelet neural network in the sample testing stage. The results show that the structure of the wavelet neural network is optimized by using a rough set to reduce the redundant attributes of the data, and that the comprehensive evaluation method based on rough sets and a wavelet neural network can accurately evaluate the indoor air quality level of buildings. The results of this study have significance for and can guide the evaluation of the indoor air quality of buildings.

  • 28.
    Lei, Lei
    et al.
    Zhejiang Sci Tech Univ, Sch Civil Engn & Architecture, Hangzhou 310018, Peoples R China..
    Zheng, Hao
    Coll Commun, Coll Civil Engn & Architecture, Guangxi Vocat & Tech, 1258 Kunlun Ave, Nanning 530216, Peoples R China..
    Xue, Yu
    Dalian Univ Technol, Sch Civil Engn, 2 Linggong Rd, Dalian 116024, Peoples R China..
    Liu, Wei
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Inverse modeling of thermal boundary conditions in commercial aircrafts based on Green's function and regularization method2022In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 217, article id 109062Article in journal (Refereed)
    Abstract [en]

    To quantify the thermal environment in a commercial aircraft, the accurate estimation of the thermal boundary conditions is very critical. However, there is no fast and accurate method. In this study, an inverse modeling using Computational Fluid Dynamics (CFD) combined with Green's function and regularization method is proposed to identify the convective heat transfer of inner wall by using the air temperature at monitored points in the cabin. Green's transfer matrix is used to describe the causal relationship between the monitored air temperatures and the thermal boundary conditions, which greatly improves the calculation efficiency. Due to the illposed nature of the inverse problem, regularization methods are used to ensure the stability of the inversion solution. This investigation compares the performance of Tikhonov, truncated singular value decomposition (TSVD) and damped generalized singular value decomposition (DGSVD). To verify the feasibility of the inverse modeling, the inner wall convective heat transfer of the cabin is solved by using the measured and simulated data in a small-scale cabin testbed and a full-scale aircraft cabin, respectively. The results show that the proposed inverse modeling can accurately and effectively determine the convective heat transfer on the inner wall.

  • 29. Li, Biao
    et al.
    Luo, Zhiwen
    Sandberg, Mats
    KTH. Högskolan i Gävle, Sweden.
    Liu, Jing
    Revisiting the 'Venturi effect' in passage ventilation between two non-parallel buildings2015In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 94, p. 714-722Article in journal (Refereed)
    Abstract [en]

    A recent study conducted by Blocken et al. (Numerical study on the existence of the Venturi effect in passages between perpendicular buildings. Journal of Engineering Mechanics, 2008, 134: 1021-1028) challenged the popular view of the existence of the 'Venturi effect' in building passages as the wind is exposed to an open boundary. The present research extends the work of Blocken et al. (2008a) into a more general setup with the building orientation varying from 0 degrees to 180 degrees using CFD simulations. Our results reveal that the passage flow is mainly determined by the combination of corner streams. It is also shown that converging passages have a higher wind-blocking effect compared to diverging passages, explained by a lower wind speed and higher drag coefficient. Fluxes on the top plane of the passage volume reverse from outflow to inflow in the cases of alpha = 135 degrees, 150 degrees and 165 degrees. A simple mathematical expression to explain the relationship between the flux ratio and the geometric parameters has been developed to aid wind design in an urban neighborhood. In addition, a converging passage with a = 15 is recommended for urban wind design in cold and temperate climates since the passage flow changes smoothly and a relatively lower wind speed is expected compared with that where there are no buildings. While for the high-density urban area in (sub)tropical climates such as Hong Kong where there is a desire for more wind, a diverging passage with alpha = 150 degrees is a better choice to promote ventilation at the pedestrian level.

  • 30. Lim, E.
    et al.
    Ito, K.
    Sandberg, Mats
    KTH.
    New ventilation index for evaluating imperfect mixing conditions - Analysis of Net Escape Velocity based on RANS approach2013In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 61, p. 45-56Article in journal (Refereed)
    Abstract [en]

    The concentration of contaminant in a room is not always uniformly distributed and hence it is important to evaluate the ventilation efficiency at various points or domains in the room to optimize and reduce the ventilation rate and the air-conditioning load of the room. Various ventilation indices have been developed to evaluate the ventilation efficiency of a point or a domain based on the contaminant concentration, for example, the age of air, the Scale for Ventilation Efficiency series, Visitation Frequency and Purging Flow Rate.This paper presents a new concept of ventilation index, Net Escape Velocity (hereafter NEV), as an index for ventilation efficiency in an indoor environment. NEV represents the effective velocity at which the contaminant is transported/diluted from a target point. The objectives of the present work are to clarify the definition and concept of NEV on the basis of CFD simulation and to investigate the calculation methods of NEV. NEV is defined by contaminant concentration, convective flux and diffusion flux at a point. Using NEV normalized by the convection velocity at a target point, we can obtain information of the turbulent diffusion effect for removal/dilution contaminant and of the direction of diffusion flux which is the same or not with convective flux. It can be said that NEV is an index of ventilation efficiency that can evaluate the ventilation performance at a point and enable understanding of the forming structure of a contaminant concentration at a point.

  • 31. Lim, E.
    et al.
    Ito, K.
    Sandberg, Mats
    KTH Research School University of Gävle, Sweden.
    Performance evaluation of contaminant removal and air quality control for local ventilation systems using the ventilation index Net Escape Velocity2014In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 79, p. 78-89Article in journal (Refereed)
    Abstract [en]

    A concept of ventilation efficiency, Net Escape Velocity (NEV), developed by authors presents the net and integrated velocity of contaminant transport by convection and diffusion effect at a point within the room. The NEV is the effective ventilation rate with a velocity scale determining the contaminant concentration at a target point and can be expressed by vector and scalar quantities. It is the most important characteristic of NEV concept. An expanded concept of NEV (NEV*), under an assumption that the inflow flux of a contaminant on the control volume is a contaminant generation, was proposed. We believe that the NEV and NEV* distributions can provide helpful information for ventilation design to control contaminants.The purpose of this study was to demonstrate the advantage and contribution of NEV* to current ventilation design procedure by using numerical analysis. Here, it was evaluated by the NEV* that the contaminant removal performances of local ventilation systems which are a kitchen exhaust hood in a kitchen environment, a push-pull hood in an industrial environment and an adsorptive building material in a test chamber. The distributions of the NEV* as vector quantities under the different flow and diffusion fields were analyzed to investigate contaminant leakage across the hypothetical boundaries of the control target domain of the local ventilation hood and to investigate the contaminant concentration reduction performance of the adsorptive building materials.

  • 32.
    Liu, Fei
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. Tianjin Univ, Sch Environm Sci & Engn, Tianjin Key Lab Indoor Air Environm Qual Control, 92 Weijin Rd, Tianjin 300072, Peoples R China.
    Chen, Haofu
    Tianjin Univ, Sch Environm Sci & Engn, Tianjin Key Lab Indoor Air Environm Qual Control, 92 Weijin Rd, Tianjin 300072, Peoples R China..
    Yuan, Hui
    Tianjin Univ, Sch Environm Sci & Engn, Tianjin Key Lab Indoor Air Environm Qual Control, 92 Weijin Rd, Tianjin 300072, Peoples R China..
    Zhang, Tengfei (Tim)
    Tianjin Univ, Sch Environm Sci & Engn, Tianjin Key Lab Indoor Air Environm Qual Control, 92 Weijin Rd, Tianjin 300072, Peoples R China.;Dalian Univ Technol DUT, Sch Civil Engn, 2 Linggong Rd, Dalian 116024, Peoples R China..
    Liu, Wei
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Shape optimization of the exhaust hood in machining workshops by a discrete adjoint method2023In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 244, article id 110764Article in journal (Refereed)
    Abstract [en]

    Local exhaust system is an effective but energy-consuming method for capturing oil mist particles in machining workshops. To reduce the flow resistance of an exhaust system for minimal fan energy consumption, the method of applying individually shape-optimized exhaust hoods, namely mass-production design, is feasible. However, the combined effect of multiple exhaust hoods in an exhaust system may not be optimal in reducing the flow resistance. This investigation thus firstly validated the shape optimization of an individual exhaust hood by a discrete adjoint method. The discrete adjoint method could adjust the shape of an exhaust hood automatically in the direction of reducing the flow resistance. The design variables were the coordinates of wall boundaries of the exhaust hood. The validation used measured data from a small-scale experiment. This study then applied the validated discrete adjoint method to conduct customized design through the shape optimization of multiple exhaust hoods simultaneously in the exhaust system. The flow resistance under customized design was compared with the method of mass-production design. The results revealed that the customized design led to different shapes of individual exhaust hoods and they were different from the shape of the individually optimized exhaust hood. The flow resistance of the exhaust system under customized design was reduced by 57%. However, only 36.5% reduction in flow resistance was achieved when the mass-production design method was employed. The customized design method was more effective in reducing flow resistance of the exhaust system.

  • 33.
    Liu, Wei
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Lian, Song
    School of Civil Engineering, ZJU-UIUC Institute, Zhejiang University, Haining, 314400, China.
    Fang, Xin
    Alibaba Cloud, Alibaba Group, 969 West Wen Yi Road, Hangzhou 311121, China, 969 West Wen Yi Road.
    Shang, Zhenyu
    Alibaba Cloud, Alibaba Group, 969 West Wen Yi Road, Hangzhou 311121, China, 969 West Wen Yi Road.
    Wu, Hao
    Alibaba Cloud, Alibaba Group, 969 West Wen Yi Road, Hangzhou 311121, China, 969 West Wen Yi Road.
    Zhu, Hao
    Alibaba Cloud, Alibaba Group, 969 West Wen Yi Road, Hangzhou 311121, China, 969 West Wen Yi Road.
    Hu, Simon
    School of Civil Engineering, ZJU-UIUC Institute, Zhejiang University, Haining, 314400, China.
    An open-source and experimentally guided CFD strategy for predicting air distribution in data centers with air-cooling2023In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 242, article id 110542Article in journal (Refereed)
    Abstract [en]

    Data centers are generally over cooled to ensure the trouble free running. In a data center with air-cooling, it is crucial to investigate the air distribution and temperature field to aid the design, which ensures the stable operation with less energy consumption. Computational fluid dynamics (CFD) is perfect for such a mission, but the cost is high and the user is offered with little customization as commercial software are mostly adopted. Therefore, this study presented a systematic investigation on making use of open-source software, including OpenFOAM and paraView to realize geometry preparation, mesh generation, experimentally guided numerical setup and solution, and results visualization. A JAVA program was developed to ensure the case preparation and simulation in just one command. Self-adapted momentum sources were developed to realize the desired flow rate through the servers. The strategy was validated and demonstrated by a pilot data center from Alibaba cloud, Alibaba group. The developed solver predicted the air temperature in both cold and hot isles of a data center with mean error of 0.7 K. This work initiated a starting point for achieving automated CFD simulation of data centers with open-source tools.

  • 34.
    Liu, Wei
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Sun, Haowen
    Dalian Univ Technol, Sch Civil Engn, Dalian 116024, Peoples R China..
    Lai, Dayi
    Shanghai Jiao Tong Univ, Sch Design, Dept Architecture, Shanghai 200240, Peoples R China..
    Xue, Yu
    Dalian Univ Technol, Sch Civil Engn, Dalian 116024, Peoples R China..
    Kabanshi, Alan
    Univ Gävle, Dept Bldg Engn Energy Syst & Sustainabil Sci, S-80176 Gävle, Sweden..
    Hu, Simon
    Zhejiang Univ, Sch Civil Engn, ZJU UIUC Inst, Haining 314400, Peoples R China..
    Performance of fast fluid dynamics with a semi-Lagrangian scheme and an implicit upwind scheme in simulating indoor/outdoor airflow2022In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 207, article id 108477Article in journal (Refereed)
    Abstract [en]

    Computational fluid dynamics can be time consuming for predicting indoor airflows and pollutant transport in large-scale problems or emergency management. Fast fluid dynamics (FFD) is able to accomplish efficient and accurate simulation of indoor/outdoor airflow. FFD solves the advection term of the Navier-Stokes equations either by a semi-Lagrangian (SL) scheme or an implicit upwind (IU) scheme. The SL scheme can be highly efficient, but its first-order version is not conservative and introduces significant numerical diffusion. To improve its accuracy, a high-order temporal and interpolation scheme that not only reduces dissipation and dispersion errors but also guarantees the convergence speed should be applied. Otherwise, an IU scheme instead could be used to solve the advection term. The IU scheme is conservative and introduces minor numerical diffusion, but it may increase the computation time. Therefore, this study investigated the performance of FFD with SL scheme using high-order temporal and interpolation schemes and that with IU scheme. The comparisons used experimental data of two indoor airflows and one outdoor airflow. The results showed that FFD with IU scheme was overall more accurate than FFD with SL scheme. In simulating indoor airflow, both methods were robust and the predictions were independent of time step sizes if the Courant number was less than or equal to one. In simulating the outdoor airflow, the FFD with SL scheme performed better than the FFD with IU scheme for large time step sizes. The FFD with IU scheme consumed 44%-61% computing time of the FFD with SL scheme.

  • 35.
    Liu, Wei
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    van Hooff, Twan
    Department of the Built Environment, Eindhoven University of Technology, P.O. Box 513, 5600, MB Eindhoven, The Netherlands c Department of Civil Engineering, KU Leuven, Kasteelpark Arenberg 40 - Bus 2447, 3001 Leuven, Belgium.
    An, Yuting
    Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, N.T., 999077, Hong Kong SAR, China.
    Hu, Simon
    School of Civil Engineering, ZJU-UIUC Institute, Zhejiang University, Haining, 314400, China.
    Chen, Chun
    Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, N.T., 999077, Hong Kong SAR, China.
    Modeling transient particle transport in transient indoor airflow by fast fluid dynamics with the Markov chain method2020In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 186, article id 107323Article in journal (Refereed)
    Abstract [en]

    It is crucial to accurately and efficiently predict transient particle transport in indoor environments to improve air distribution design and reduce health risks. For steady-state indoor airflow, fast fluid dynamics (FFD) + Markov chain model increased the calculation speed by around seven times compared to computational fluid dynamics (CFD) + Eulerian model and CFD + Lagrangian model, while achieving the same level of accuracy. However, the indoor airflow could be transient, if there were human behaviors involved like coughing or sneezing and air was supplied periodically. Therefore, this study developed an FFD + Markov chain model solver for predicting transient particle transport in transient indoor airflow. This investigation used two cases, transient particle transport in a ventilated two-zone chamber and a chamber with periodic air supplies, for validation. Case 1 had experimental data for validation and the results showed that the predicted particle concentration by FFD + Markov chain model matched well with the experimental data. Besides, it had similar accuracy as the CFD + Eulerian model. In the second case, the prediction by large eddy simulation (LES) was used for validating the FFD. The simulated particle concentrations by the Markov chain model and the Eulerian model were similar. The simulated particle concentrations by the Markov chain model and the Eulerian model were similar. The computational time of the FFD + Markov chain model was 7.8 times less than that of the CFD + Eulerian model.

  • 36.
    Liu, Wei
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Zhang, Tengfei (Tim)
    Tianjin Univ, Sch Environm Sci & Engn, Tianjin Key Lab Indoor Air Environm Qual Control, Tianjin 300072, Peoples R China..
    Lai, Dayi
    Shanghai Jiao Tong Univ, Sch Design, Dept Architecture, Shanghai 200240, Peoples R China..
    Inverse design of a thermally comfortable indoor environment with a coupled CFD and multi-segment human thermoregulation model2023In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 227, article id 109769Article in journal (Refereed)
    Abstract [en]

    A thermally comfortable indoor environment is critical for ensuring the health and productivity of the occupants. To design a thermally comfortable environment, CFD-based methods assume the occupants' surface temperature to be fixed values for simplicity and use PMV to estimate thermal comfort level. The constant surface temperature assumption would lead to inaccurate prediction of the indoor environment and the use of PMV would lead to a waste of the rich spatial information calculated by CFD. Therefore, this study developed and validated a coupled CFD and multi-node human thermoregulation model (HTM). The CFD and HTM synchronize data during the simulation and the occupant skin temperature could be updated. The final skin temperature could be used to quantify the thermal comfort level. The accuracy of the coupled model in predicting the skin temperature was validated by experimental data from literature. The coupled model was further integrated with genetic algorithm for inverse design. The inverse design of thermal environment in an office with two occupants and displacement ventilation was used for demonstration. With the CFD-HTM model, genetic algorithm was able to identify an optimal condition that leads to the least deviation of skin temperature of local body parts from the neutral values. The developed CFD-HTM coupling scheme can be used to effectively design indoor environment with improved thermal comfort.

  • 37.
    Ma, Shengyuan
    et al.
    Harbin Inst Technol, Sch Architecture, Key Lab Cold Reg Urban & Rural Human Settlement En, Minist Ind & Informat Technol, Harbin 150090, Peoples R China..
    Liu, Wei
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Meng, Chong
    China Acad Bldg Res, Inst Sci & Technol Res & Dev, 30 Beisanhuandonglu, Beijing 100013, Peoples R China..
    Dong, Jiankai
    Harbin Inst Technol, Sch Architecture, Key Lab Cold Reg Urban & Rural Human Settlement En, Minist Ind & Informat Technol, Harbin 150090, Peoples R China..
    Liu, Jing
    Harbin Inst Technol, Sch Architecture, Key Lab Cold Reg Urban & Rural Human Settlement En, Minist Ind & Informat Technol, Harbin 150090, Peoples R China..
    Comparison of the time-dependent characteristics between particle mass and particle number emissions during oil heating and emission mitigation strategies2023In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 242, article id 110511Article in journal (Refereed)
    Abstract [en]

    It is important to understand the cooking particles emitted over time to mitigate cooking pollution, but current control strategies fail to consider both particle mass and number emissions. Therefore, this study was designed to compare the differences in time-dependent characteristics of particle mass and number emissions and to propose comprehensive mitigation strategies that consider both characteristics. For this purpose, the effects of various factors on both emissions were analyzed, and time-dependent emission rate models were developed. The time-dependent models obtained were statistically significant (P < 0.001), with most R2 values greater than 0.90. The masses and numbers of particles emitted often varied in the opposite direction. During the smoking stage, corn oil exhibited low particle mass emissions while its particle number emission rate (TERn) reached 109#/s. However, at higher temperatures (T > TDM), the percentage difference in TERn with increasing oil volume decreased from 7.1% to 3.5%, while that in PM2.5 emission rate with decreasing oil volume was almost more than 25%. This indicated that the increased oil volumes were more effective in reducing the particle masses emitted from corn oil than in increasing the numbers of particles emitted, and similar conclusions were also drawn for decreasing oil surface area. Overall, oils exhibiting lower particle mass emissions and lower cooking temperatures were recommended for cooking. Lower oil volumes and larger pans should be used at relatively lower temperatures (T < TDM) primarily to mitigate particle number emissions, while higher oil volumes and smaller pans should be used at higher temperatures to control particle mass emissions.

  • 38.
    Malmqvist, Tove
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment.
    Glaumann, Mauritz
    University of Gävle, Dep of Technology and the Built Environment.
    Environmental efficiency in residential buildings: A simplified communication approach2009In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 44, no 5, p. 937-947Article in journal (Refereed)
    Abstract [en]

    For all actors involved with planning, developing and managing buildings, the environmental impact relating to energy use and the quality of the indoor environment are both aspects of major concern. It is crucial that a reduction in the environmental impact of a building is not achieved through compromising the indoor environment. This paper presents a method to assess user satisfaction related to the indoor environment and the environmental impact related to the energy use of the building, i.e. the environmental efficiency of the building. This environmental efficiency comprises two indices that are calculated separately but displayed in the same diagram to facilitate communication of complex information. This approach forms part of the Swedish life cycle based environmental assessment tool for buildings, EcoEffect. The present paper presents and exemplifies the environmental efficiency of buildings using data from 26 Swedish multi-family residential buildings and proposes a number of reference values. The concept can be used as an overarching objective for environmental management of a property firm’s building stock or for evaluating targets set in the planning process for a new building. It can also be used for environmental rating of buildings, which would probably increase the communication value further. The aggregated indices are rough but proportionately straightforward to calculate and easily communicated. In addition, they address the environmental impacts of buildings in a much more comprehensive way than the current practice.

     

     

     

  • 39.
    Marteinsson, Björn
    Högskolan i Gävle.
    Service life estimation and life cycle assessment in the building sector-practical view and a case.2004In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684XArticle in journal (Other academic)
  • 40.
    Mundt, Elisabeth
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    Non-buoyant pollutant sources and particles in displacement ventilation2001In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 36, no 7, p. 829-836Article in journal (Refereed)
    Abstract [en]

    Particle transportation and ventilation efficiency, with non-buoyant pollutant sources, in a displacement-ventilated room were evaluated. A resuspension of floor deposited particles caused by the influence of the supply air or people moving around may increase the number of particles in the convection flows. Particle concentrations at different positions under steady state and transient conditions were measured. The results indicate that there seem to be little risk of resuspension of particles, in the measured size interval, by the influence of the supply air. With a forced resuspension the particle concentrations in the convection flows differ from the concentration outside the convection flow. The contaminant removal effectiveness was much dependent on the position of the pollutant sources.

  • 41.
    Naseri, Arash
    et al.
    Univ Alberta, Dept Mech Engn, Edmonton, AB, Canada.;Shiraz Univ, Sch Mech Engn, Shiraz, Iran.;Univ Alberta, Dept Mech Engn, Edmonton, AB, Canada.;Shiraz Univ, Sch Mech Engn, Shiraz, Iran..
    Emdad, Homayoun
    Shiraz Univ, Sch Mech Engn, Shiraz, Iran.;Shiraz Univ, Sch Mech Engn, Shiraz, Iran..
    Mehrabi, Samrad
    Shiraz Univ Med Sci, Dept Internal Med, Shiraz, Iran.;Shiraz Univ Med Sci, Dept Internal Med, Shiraz, Iran..
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Abouali, Omid
    Shiraz Univ, Sch Mech Engn, Shiraz, Iran.;Shiraz Univ, Sch Mech Engn, Shiraz, Iran..
    Inhalability of micro -particles through the human nose breathing at high free -stream airflow velocities2020In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 179, article id 106948Article in journal (Refereed)
  • 42.
    Nourozi, Behrouz
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Wierzbicka, Aneta
    Ergonomics and Aerosol Technology, Lund University, Lund, Sweden.
    Yao, Runming
    Joint International Research Laboratory of Green Buildings and Built Environments (Ministry of Education), Chongqing University, Chongqing, 400045, China; School of the Built Environment, University of Reading, UK.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design. School of Business, Society and Engineering, Mälardalen University, Västerås, Sweden.
    A systematic review of ventilation solutions for hospital wards: Addressing cross-infection and patient safety2024In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 247, article id 110954Article, review/survey (Refereed)
    Abstract [en]

    Despite various preventive interventions, nosocomial cross-infection remains a significant challenge in healthcare facilities worldwide. Consequently, prolonged hospitalization, elevated healthcare costs, and mortality rates are major concerns. Proper ventilation has been identified as one of the possible interventions for reducing the risk of cross-infection between patients and healthcare workers in hospital wards by diluting infectious agents and their carrying particles. The use of air cleaners in conjunction with the ventilation system further reduces the concentration of indoor pathogens. This article presents a systematic review of the ventilation solutions employed in hospital wards where pathogen removal performance can be enhanced using air-cleaning techniques while maintaining the thermal comfort of patients and healthcare staff. We provide a comparative analysis of the performance of different ventilation strategies adopted in one-, two-, or multi-bed hospital wards. Additionally, we discuss the parameters that influence the aerosol removal efficiency of ventilation systems and review various air-cleaning technologies that can further complement the ventilation system to reduce contaminant concentrations. Finally, we review and discuss the impact of different ventilation strategies on the perceived thermal comfort of patients and healthcare workers. This study provides insights into the cross-contamination risks associated with various hospital ward setups and the vital role of the ventilation system in reducing the adverse effects of infection risk. The findings of this review will contribute to the development of effective ventilation solutions that ensure improved patient outcomes and the well-being of healthcare workers.

  • 43.
    Olsson, Stefan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Malmqvist, Tove
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Glaumann, Mauritz
    University of Gävle.
    An approach towards sustainable renovationd: A tool for decision support in early project stages2016In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 106, p. 20-32Article in journal (Refereed)
    Abstract [en]

    Reducing greenhouse gas (GHG) emissions through energy reduction in buildings is a high priority for policy-makers in the European Union and elsewhere. However, although long-term sustainability targets exist on the societal level, it is not obvious how these targets may trickle down to individual sectors and further down to specific organizations or buildings. The aim of this paper is to illustrate an approach for evaluating renovation measures in order to identify appropriate target levels in early project stages and what is needed to achieve a number of proposed sustainability targets. The evaluation approach is supported by a tool that can be seen as an aid to making rough estimations of the environmental impacts. Sustainability target levels in a Swedish context are presented for three issues: operational energy use, GHG emissions due to total energy use for building operation, and embodied GHG emissions due to production of materials. The approach to support well-grounded retrofit decisions is shown with a case study. The tool developed, in combination with a suggested step-by-step evaluation approach, provides an effective way to evaluate various potential improvements, and their consequences, in early project stages. However, other tools with similar functionality may be used. Results from the case illustration imply that it is possible to achieve the proposed sustainability targets for operational energy use by implementing nine measures. However, the targets for GHG emissions for operational energy use and embodied GHG emissions were not achieved because of an energy supply with too high a share of nonrenewable fuels.

    Download full text (pdf)
    fulltext
  • 44. Peng, Lei
    et al.
    Nielsen, Peter V.
    Wang, Xiaoxue
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Liu, Li
    Li, Yuguo
    Possible user-dependent CFD predictions of transitional flow in building ventilation2016In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 99, p. 130-141Article in journal (Refereed)
    Abstract [en]

    A modified backward-facing step flow with a large expansion ratio of five (5) was modeled by 19 teams without benchmark solutions or experimental data for validation in an ISHVAC-COBEE July 2015 Tianjin Workshop, entitled as "to predict low turbulent flow". Different computational fluid dynamics (CFD) codes/software, turbulence models, boundary conditions, numerical schemes and convergent criteria were adopted based on the own CFD experience of each participating team. The largest coefficient of variation is larger than 50% and the largest relative maximum difference of penetration length is larger than 150%. The predicted non-dimensional penetration lengths as a function of the Reynolds number (1-10,000) are found to be significantly diverse among different teams. Even when the same turbulence model or even the laminar model is used, the difference in the predicted results is still notable among different teams. It indicates that the combined effects of a lack of general turbulence model, and possible errors in multiple decisions based on users' experience may have caused the observed significant difference. Prediction of transitional flows, as often observed in building ventilation, is shown to be still a very challenging task. This calls for a solid approach of validation and uncertainty assessment in CFD "experiments". The users are recommended to follow an existing guideline of uncertainty assessment of CFD predictions to minimize the errors and uncertainties in the future.

  • 45.
    Pieskä, Henrikki
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. Bravida Holding AB, Mikrofonvägen 28, SE, 12637, Hägersten, Sweden.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. Uponor AB, Hackstavägen 1, SE, 72132, Västerås, Sweden.
    Design requirements for condensation-free operation of high-temperature cooling systems in mediterranean climate2020In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 185, p. 1-12, article id 107273Article in journal (Refereed)
    Abstract [en]

    Radiant cooling systems are a subject of increasing scientific interest due to their efficiency and ability to use high-temperature cooling sources. In hot and humid conditions, they have generally been studied in combination with dehumidification systems. For retrofit projects, a control system that would eliminate the need for dehu-midification would be beneficial. In the present study, a passive geothermal-based radiant high-temperature cooling system is studied in a Mediterranean climate. The system is operated with supply water temperature control using dew point temperature as a controlling variable. The system’s performance is compared with that of an all-air cooling system. The systems are evaluated using IDA-ICE building energy simulations, validated with on-site measurement data. The results show that the radiant cooling system produces the same level of thermal comfort with 40% lower energy use and 85% lower exergy consumption than the all-air system. The risk of condensation limits the cooling capacity of the radiant cooling system. Consequently, insufficient cooling ca-pacity causes thermal discomfort for the occupants due to the operative temperature exceeding 26 ◦C.

    Download full text (pdf)
    Design requirements for condensation-free operation of high-temperature cooling systems in mediterranean climate
  • 46.
    Pieskä, Henrikki
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. Bravida Holding AB, Mikrofonvagen 28, SE-12637, Hägersten, Sweden, Mikrofonvägen 28, Hägersten.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. Uponor AB, Hackstavagen 1, SE-72132, Västerås, Sweden, Hackstavägen 1.
    Life-cycle assessment of a radiant high-temperature cooling system in the Mediterranean climate2023In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 245, article id 110847Article in journal (Refereed)
    Abstract [en]

    As sustainable development increases its significance in policy-making, methods for quantifying the sustainability of a project become more important. One such method is life-cycle assessment (LCA). In this study, an LCA assessment of a radiant cooling system was conducted for a retrofit project of a small office building. The studied building is located in Sant Cugat in north-eastern Spain. The radiant cooling system was also compared with a conventional alternative, an all-air variable air volume system. The goal of the study is to provide a generalisable methodology for conducting an LCA-assessment in a retrofit project involving cooling. The methodology of the assessment consists of two parts. Building energy models in IDA-ICE 4.8 were used to determine the energy use of the systems and the resulting thermal comfort conditions in the building, while SimaPro 9.4 was used to carry out the LCA assessment. A major novelty in the study is the use of thermal comfort as the functional unit for the LCA assessment. The results show that the radiant system has a lower environmental impact in all ReCiPe2016 midpoint impact categories during the systems' estimated lifetime of 50 years. However, a sensitivity analysis revealed that while the radiant system's environmental impact is mainly dependent on the manufacturing process, the conventional system's impact is largely determined by its operational energy use. Therefore, the conventional system is significantly more sensitive to decarbonisation of electricity production.

  • 47.
    Pitsch, Stephan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Angster, Judit
    Ventilation system design for a church pipe organ using numerical simulation and on-site measurement2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 12, p. 2629-2643Article in journal (Refereed)
    Abstract [en]

    Since old churches have had heating installed, more complaints have arisen of organs sounding out of tune. Sound frequency of organ pipes is dependent on air temperature. Old churches tend to have very large volumes, so are typically heated just before and during services in wintertime, in order to reduce energy usage. Warm air plumes rise at radiators and spread out into the room, finally reaching the cold organ casing where they cause a non-uniform temperature distribution within. If pipes standing in different temperature zones are played at the same time the organ sounds out of tune due to clearly audible beats (interference between two slightly different frequencies). The purpose of this study was to design a ventilation system inside the organ casing, able to create a uniform temperature distribution around the pipes. A computational fluid dynamic (CFD) model was developed for the St. Martin church in Oberesslingen, Germany. It was validated by on-site measurements that had been carried out in the organ casing of the church. Four organ divisions containing 300-500 pipes were represented by equivalent porous material zones. Their properties were determined using an auxiliary two-dimensional model of a staggered array consisting of 392 pipes. The effect of different ventilation system settings on the temperature field in the organ casing was examined. Best results were achieved by a system consisting of two ventilation lines together with a thin, synthetic net placed at the open interface between church and organ casing in order to reduce warm air inflow.

  • 48.
    Ploskic, Adnan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Heat emission from thermal skirting boards2010In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 5, p. 1123-1133Article in journal (Refereed)
    Abstract [en]

    The performance of three hydronic skirting heating systems was investigated. The main focus of this study was to ascertain whether thermal skirting boards served by low-temperature supply flow were able to suppress strong downdraught. The evaluation was made for a two-person office room with mechanical ventilation. Computational Fluid Dynamics (CFD) simulations and three different draught rating models were employed to predict the level of thermal discomfort inside the room. CFD results were validated against several analytical calculations and four sets of experimental data presented in previous studies. Numerical simulations showed that all three skirting heating arrangements were able to cover transmission and ventilation thermal losses of the office room. Horizontal and vertical heat distribution inside the room was uniform for all heating systems. CFD simulations also showed that thermal skirting boards served by 40 and 45 degrees C supply flow had difficulty in reducing the velocity of the downdraught at ankle level. Consequently the draught rating in this region was around or slightly above 15% for these cases. In contrast, heat-emitting skirting boards supplied by 55 degrees C hot water showed a better ability to suppress downdraught, and the proportion of people sensing draught at 0.1 m above the floor was low. The conclusion of this study was that thermal performance of hydronic skirting heaters with low-temperature water supply must be improved in order to counter strong downdraughts, in particular where such systems may be combined with heat pumps of other low-valued sustainable energy sources.

  • 49.
    Ploskic, Adnan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Centres, Centre for Technology in Medicine and Health, CTMH.
    Low-temperature baseboard heaters with integrated air supply - An analytical and numerical investigation2011In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 46, no 1, p. 176-186Article in journal (Refereed)
    Abstract [en]

    The functioning of a hydronic baseboard heating system with integrated air supply was analyzed. The aim was to investigate thermal performance of the system when cold outdoor (ventilation) airflow was forced through the baseboard heater. The performance of the system was evaluated for different ventilation rates at typical outdoor temperatures during the Swedish winter season. Three different analytical models and Computational Fluid Dynamics (CFD) were used to predict the temperature rise of the airflow inside the baseboard heater. Good agreement between numerical (CFD) and analytical calculations was obtained. Calculations showed that it was fully possible to pre-heat the incoming airflow to the indoor temperature and to cover transmission losses, using 45 degrees C supply water flow. The analytical calculations also showed that the airflow per supply opening in the baseboard heater needed to be limited to 7.0 l/s due to pressure losses inside the channel. At this ventilation rate, the integrated system with one air supply gave about 2.1 more heat output than a conventional baseboard heating system. CFD simulations also showed that the integrated system was capable of countering downdraught created by 2.0 m high glazed areas and a cold outdoor environment. Draught discomfort in the case with the conventional system was slightly above the recommended upper limit, but heat distribution across whole analyzed office space was uniform for both heating systems. It was concluded that low-temperature baseboard heating systems with integrated air supply can meet both international comfort requirements, and lead to energy savings in cold climates.

  • 50.
    Polak, Joanna
    et al.
    Aalborg Univ, Danish Bldg Res Inst, AC Meyers Vaenge 15, DK-2450 Copenhagen SV, Denmark..
    Afshari, Alireza
    Aalborg Univ, Danish Bldg Res Inst, AC Meyers Vaenge 15, DK-2450 Copenhagen SV, Denmark..
    Sadeghian, Parastoo
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Wang, Cong
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Improving the performance of heat valve ventilation system: A study on the provided thermal environment2019In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 164, article id UNSP 106338Article in journal (Refereed)
    Abstract [en]

    The current study presents and evaluates the performance of two types of supply air terminal devices applied in a heat valve ventilation (HVV) system with regard to the provided thermal environment in a room heated and ventilated by the HVV system. To that end, air temperature and air velocity patterns and local thermal discomfort due to draught were studied both experimentally and numerically. Using numerical simulations, parametric analysis was carried out for investigating the provided indoor thermal environment for a wider range of boundary conditions. The considered parameters included the influence of cold vertical surfaces, supply airflow rate and temperature, and room heating energy demand. The results showed that both of the applied air terminal devices could avoid temperature stratification within the occupied zone. The maximum air temperature difference between 0.1 and 1.8 m above the floor was 2.1 degrees C when using a circular valve placed in the external wall below the window and 2.6 degrees C in the case when the air was supplied through three nozzles located in the wall opposite to the window in the upper part of the room. In general, placing the air terminal device below the window provided more uniform air temperature distribution and contributed to the prevention of downdraught caused by a cold window surface. The outcomes of this study are relevant to selecting and designing ventilation and air heating systems for low-energy buildings.

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