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  • 1.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Bourdakis, Eleftherios
    Ploskic, Adnan
    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.
    Experimental study of energy performance in low-temperature hydronic heating systems2015In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 109, p. 108-114Article in journal (Refereed)
    Abstract [en]

    Energy consumption, thermal environment and environmental impacts were analytically and experimentally studied for different types of heat emitters. The heat emitters studied were conventional radiator, ventilation radiator, and floor heating with medium-, low-, and very-low-temperature supply, respectively. The ventilation system in the lab room was a mechanical exhaust ventilation system that provided one air change per hour of fresh air through the opening in the external wall with a constant temperature of 5 °C, which is the mean winter temperature in Copenhagen. The parameters studied in the climate chamber were supply and return water temperature from the heat emitters, indoor temperature, and heat emitter surface temperature. Experiments showed that the mean supply water temperature for floor heating was the lowest, i.e. 30 °C, but it was close to the ventilation radiator, i.e. 33 °C. The supply water temperature in all measurements for conventional radiator was significantly higher than ventilation radiator and floor heating; namely, 45 °C. Experimental results indicated that the mean indoor temperature was close to the acceptable level of 22 °C in all cases. For energy calculations, it was assumed that all heat emitters were connected to a ground-source heat pump. Analytical calculations showed that using ventilation radiator and floor heating instead of conventional radiator resulted in a saving of 17% and 22% in heat pump's electricity consumption, respectively. This would reduce the CO2 emission from the building's heating system by 21 % for the floor heating and by 18% for the ventilation radiator compared to the conventional radiator.

  • 2.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ploskic, Adnan
    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.
    Integrating Low-temperature Heating Systems into Energy Efficient Buildings2015In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 78, p. 3043-3048Article in journal (Refereed)
    Abstract [en]

    Energy requirements for space heating and domestic hot water supplies in the Swedish building sector are responsible for almost 60 % of the total energy used. To decrease this enormous figure, energy saving measures are required, as well as opportunities to use low-temperature heating systems for increase sustainability. The present paper studies low-temperature heating systems, including heat production units (district heating or heat pumps) and heat emitting units in the room. The aim was to find an answer to the question of whether or not low-temperature heating systems are energy efficient and sustainable compared with conventional heating systems. To answer this question, we considered different efficiency aspects related to energy and exergy. The analysis showed that low-temperature heating systems are more energy efficient and environmentally friendly than conventional heating systems. This was attributed to heat pumps and district heating systems with lower temperature heat emitters using a greater share of renewable resources and less auxiliary fuels. This report discusses the pros and cons of different types of low-temperature heat emitters.

  • 3.
    Holmberg, Sture
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Myhren, Jonn Are
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Low-temperature heat emission with integrated ventilation air supply2010In: Proceedings of International Conference Clima 2010, 2010Conference paper (Refereed)
  • 4.
    Härer, Simon
    et al.
    Faculty of Engineering, Reutlingen University, Reutlingen, Germany.
    Nourozi, Behrouz
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. Uponor AB, Västerås, Sweden.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. Bravida Holding AB, Hägersten, Sweden.
    Frost reduction in mechanical balanced ventilation by efficient means of preheating cold supply air2019Conference paper (Refereed)
    Abstract [en]

    This study has focused on evaluating the financial potential of wastewater and geothermal heat recovery systems in a multi-family building. The recovered heat was used to improve the performance of mechanical ventilation with heat recovery (MVHR) system during the coldest days in central Sweden. The main issue, which was targeted with these solutions, was to reduce frost formation in the system and hence increase its thermal efficiency. By looking at the life cycle cost over a lifespan of 20 years, the observed systems were being evaluated economically. Furthermore, statistical analyses were carried-out to counter the uncertainty that comes with the calculation. It was found that the studied wastewater systems have a high possibility of generating savings in this period, while the one fed by geothermal energy is less likely to compensate for its high initial cost. All designed systems however, managed to reduce operational cost by 35-45% due to lower energy usage.

  • 5.
    Nourozi, Behrouz
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Härer, Simon
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. Uponor AB.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. Bravida AB.
    Life cycle cost analysis of air preheating systems using wastewater and geothermal energy2019In: The REHVA European HVAC Journal, ISSN 1307-3729, Vol. 56, no 1, p. 47-51Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Frosting is a common problem in air handling units in buildings in cold climates. Tacklingthis problem is so far achieved by using considerable amount of energy while during thisprocess, the indoor air quality is compromised. This article presents the Life Cycle Cost(LCC) assessment of a preventive solution for frosting using two renewable heat sources.

  • 6.
    Nourozi, Behrouz
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Uponor AB, Hackstavägen 1, S-72132 Västerås, Sweden..
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Bravida Holding AB, Mikrofonvägen 28, S-12637 Hägersten, Sweden..
    Energy and defrosting contributions of preheating cold supply air in buildings with balanced ventilation2019In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 146, p. 180-189Article in journal (Refereed)
    Abstract [en]

    Residential wastewater is a constant and available source for saving energy. This paper mainly investigated the possibility of utilizing wastewater heat to reduce ventilation heat load. Swedish residential buildings are to a significant extent served by mechanical ventilation with heat recovery (MVHR) systems. MVHR in airtight buildings has greatly reduced ventilation heat loads, especially in cold climate countries such as Sweden. However, cold outdoor air might lead to frost formation in heat recovery exchangers which increases the energy use. Therefore, this study focused on reducing the defrosting need by preheating the incoming cold outdoor air to MVHR during the coldest days. The effects of preheating the incoming air to MVHR on ventilation heat load and annual ventilation heating demand were also studied. It was found that the heat recovery efficiency of MVHR is the most decisive factor in rating the performance of the combined system with an air preheater. Contributions of the studied air preheater to annual energy savings were negligible. On the other hand, the reduction of the initial defrosting need was significant. The obtained results showed that the defrosting need in a building located in central Sweden in two cases of an MVHR system equipped with a rotary heat exchanger/plate heat exchanger was eliminated/reduced to one-third. The defrosting need was reduced by 50% in northern Sweden for both cases.

  • 7.
    Nourozi, Behrouz
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Uponor AB.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Bravida Holding AB.
    Identifying frost threshold in a balanced mechanical ventilation system by inlet and exhaust air temperature control2019Conference paper (Refereed)
    Abstract [en]

    Frosting is a common issue in air-to-air heat recovery exchangers installed in buildings in cold climate countries. Further to the developed defrosting methods, frost prevention by preheating the outdoor air can reduce the energy usage in buildings. In this study, residential wastewater as a renewable heat source is used to preheat the outdoor air. Due to limited wastewater hourly flowrate and the impact of preheated air temperature on the efficiency of heat exchanger, controlling the preheating temperature is of utmost importance. In this investigation, preheated and exhaust air temperatures are monitored to generate an operational signal to the wastewater circulation pump. The cold surface at the heat exchanger and the dew point of the return air are analyzed to comprehend the condensation and frosting temperatures. The results show that in case of 30% relative humidity in the return air, the frosting threshold is at preheated and exhaust air temperatures below -2.2°C and 2.1°C, respectively. Using these temperatures as controlling parameters, the frosting period has decreased by 23%.

  • 8.
    Nourozi, Behrouz
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Wang, Qian
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Ploskic, Adnan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Maximizing thermal performance of building ventilation using geothermal and wastewater heat2019In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 143, p. 90-98Article in journal (Refereed)
    Abstract [en]

    An efficient use of waste heat recovery and geothermal heat can play an important role in lowering the overall energy use of buildings. This study evaluated the potential of geothermal energy and heat recovery from residential wastewater to reduce the energy need of building-ventilation in cold climates. The performance of the mechanical ventilation with heat recovery (MVHR) system in a multi-family building located in central Sweden was studied. The focus of the investigation was on reduction of frosting in the air handling unit during the coldest months. Three configurations of one air preheating system fed by two renewable heat sources, wastewater and geothermal energy, were studied. It was found that compared to building without an air preheating system, the suggested air preheating systems reduced the defrosting time to 25%. By controlling and maintaining the preheated air temperature to slightly above the defrosting start, air heat recovery efficiency of MVHR above 80% was achieved for 90% of the studied time during heating season when frosting occurs. The energy need for the circulation pumps in the suggested air preheating systems was 5% of the recovered thermal energy from wastewater. The simulation results suggested that the air preheating system using wastewater heat recovery with a temperature-stratified storage tank was the most efficient one among the studied systems.

  • 9.
    Nourozi, Behrouz
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Uponor AB.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Bravida Holdings AB.
    Preheating Cold Supply Air to Mechanical Balanced Ventilation using Wastewater or Passive Geothermal Energy2019Conference paper (Refereed)
    Abstract [en]

    This study investigated the thermal potential of two renewable heat sources, residential wastewater and geothermal energy, for preheating the incoming air to the air-handling unit (AHU) in a multi-family building. The main purpose of preheating the inlet air was to avoid the frost formation inside AHU due to low outdoor temperatures during winter. Wastewater extraction flowrate and temperature, as two design parameters, were studied in detail by employing two types of wastewater storage tanks.The suggested outdoor air preheating systems equally reduced the defrosting period to 26% compared to the mechanical ventilation with heat recovery system (MVHR) without air preheating. The system that utilized a temperature stratified wastewater storage tank provided a higher ratio of heat output to electricity input. The other outdoor air preheating system, which was equipped with an unstratified wastewater storage tank, provided a lower ratio of heat output to pumping power. However, this ratio was not disturbed by variations in outdoor air temperature.

  • 10.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Bra inneklimat ger hälsa och sparar pengar2019Report (Other (popular science, discussion, etc.))
  • 11.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    ENERGISNÅLA RADIATORSYSTEM FÖR EFFEKTIV LÅGTEMPERATURUPPVÄRMNING OCH GOTT INOMHUSKLIMAT I SMÅHUS2019Report (Other (popular science, discussion, etc.))
  • 12.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Framledningstemperaturenbestäms av värmebehovet2016Report (Other (popular science, discussion, etc.))
  • 13.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Low - Temperature Basedboard Heaters in Built Environments2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The European Union has adopted a plan to decrease 20 % of total energy consumption through improved energy efficiency by 2020. One way of achieving this challenging goal may be to use efficient water-based heating systems supplied by heat pumps or othersustainable systems. The goal of this research was to analyze and improve the thermalperformance of water-based baseboard heaters at low-temperature water supply. Both numerical (CFD) and analytical simulations were used to investigate the heat efficiency of the system. An additional objective of this work was to ensure that the indoor thermal comfort was satisfied in spaces served by such a low-temperature heating system.

    Analyses showed that it was fully possible to cover both transmission and ventilation heatl osses using baseboard heaters supplied by 45 °C water flow. The conventional baseboards, however, showed problems in suppressing the cold air down-flow created by 2.0 m high glazing and an outdoor temperature of – 12 °C. The draught discomfort at ankle level was slightly above the upper limit recommended by international and national standards. On the other hand, thermal baseboards with integrated ventilation air supply showed better ability to neutralize cold downdraught at the same height and conditions. Calculations also showed that the heat output from the integrated system with one ventilation inlet was approximately twiceas high as that of the conventional one. The general conclusion from this work was that low-temperature baseboards, especially with integrated ventilation air supply, are an efficient heating system and able to be combined with devices that utilize the low-quality sustainable energy sources such as heat pumps.

  • 14.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Spillvatten är en hållbar resurs2017Report (Other (popular science, discussion, etc.))
  • 15.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Technical solutions for low-temperature heat emission in buildings2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The European Union is planning to greatly decrease energy consumption during the coming decades. The ultimate goal is to create sustainable communities that are energy neutral. One way of achieving this challenging goal may be to use efficient hydronic (water-based) heating systems supported by heat pumps.

    The main objective of the research reported in this work was to improve the thermal performance of wall-mounted hydronic space heaters (radiators). By improving the thermal efficiency of the radiators, their operating temperatures can be lowered without decreasing their thermal outputs. This would significantly improve efficiency of the heat pumps, and thereby most probably also reduce the emissions of greenhouse gases. Thus, by improving the efficiency of radiators, energy sustainability of our society would also increase. The objective was also to investigate how much the temperature of the supply water to the radiators could be lowered without decreasing human thermal comfort.

    Both numerical and analytical modeling was used to map and improve the thermal efficiency of the analyzed radiator system. Analyses have shown that it is possible to cover space heat losses at low outdoor temperatures with the proposed heating-ventilation systems using low-temperature supplies. The proposed systems were able to give the same heat output as conventional radiator systems but at considerably lower supply water temperature. Accordingly, the heat pump efficiency in the proposed systems was in the same proportion higher than in conventional radiator systems.

    The human thermal comfort could also be maintained at acceptable level at low-temperature supplies with the proposed systems. In order to avoid possible draught discomfort in spaces served by these systems, it was suggested to direct the pre-heated ventilation air towards cold glazed areas. By doing so the draught discomfort could be efficiently neutralized.    

    Results presented in this work clearly highlight the advantage of forced convection and high temperature gradients inside and alongside radiators - especially for low-temperature supplies. Thus by a proper combination of incoming air supply and existing radiators a significant decrease in supply water temperature could be achieved without decreasing the thermal output from the system. This was confirmed in several studies in this work. It was also shown that existing radiator systems could successfully be combined with efficient air heaters. This also allowed a considerable reduction in supply water temperature without lowering the heat output of the systems. Thus, by employing the proposed methods, a significant improvement of thermal efficiency of existing radiator systems could be accomplished. A wider use of such combined systems in our society would reduce the distribution heat losses from district heating networks, improve heat pump efficiency and thereby most probably also lower carbon dioxide emissions.  

  • 16.
    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.

  • 17.
    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 boards: An analytical investigation2009In: FIFTH INTERNATIONAL WORKSHOP ON ENERGY AND ENVIRONMENT OF RESIDENTIAL BUILDINGS AND THIRD INTERNATIONAL CONFERENCE ON BUILT ENVIRONMENT AND PUBLIC HEALTH, VOL I AND II, PROCEEDINGS / [ed] Zhang Q; Leung M; Wang XK; Liu YJ; Mo JH, HUNAN: HUNAN UNIV, COLLEGE CIVIL ENGINEERING , 2009, p. 1354-1361Conference paper (Refereed)
    Abstract [en]

    Thermal insulation of buildings has greatly improved over past decades and thermal power needed to cover heat losses through the building envelope has markedly decreased. This means that powerful heating appliances are not always needed in modern buildings. Low-temperature thermal emitters can often replace conventional heating devices. Different studies have shown that people living in buildings with low-temperature heating systems were very satisfied with ambient indoor conditions. In particular; thermal comfort levels were considered to be higher than in buildings with a traditional heating system. Low-temperature heating systems distribute mainly radiant heat with small temperature differences and minimal air movement. This means less spread of allergens and pollutants in the room air and a healthier indoor environment. The general conclusion from this research is that low-temperature heating systems give not just energy savings but may also improve indoor conditions. A combination of low-temperature heating systems and low-valued energy sources, such as heat pumps, give a higher coefficient of performance (COP). This means an environmentally friendly alternative.

  • 18.
    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.

  • 19.
    Ploskic, Adnan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Evaluating the potential of reducing peak heating load of a multi-family house using novel heat recovery system2018In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 130, p. 1182-1190Article in journal (Refereed)
    Abstract [en]

    The current study evaluated the potential of reducing ventilation heat load by using heat from waste water in mechanical ventilation with heat recovery (MVHR) served Swedish residential buildings. A typical Swedish low-energy, multi-family house locating at the northern part of Sweden was selected to present the analysis. The building was locating at the northern part of Sweden and was served by mechanical ventilation with heat recovery (MVHR). The data from on-site measurements and analytical model were applied to evaluate the reduction potential of the suggested heat recovery system. The study focused on the evaluation of benefit of using an air preheater in front of the existing MVHR system. Two different sizes of an air preheater design: Small air preheater with the size of 0.4 m x 0.4 m x 0.4 m (AP(0.4mx0.4 mx0.4 m)), feed with waste water flow of 0.15 kg/s (from storage tank to air preheater); and a large air preheater with the size of 0.8 m x 0.8 m x 0.4 m (AP(0.8 mx0.8 mx0.4 m)), feed with waste water flow of 0.2 kg/s. It was found that the heat recovery efficiency of MVHR is the core to determine the selection of air preheaters. In comparison to the MVHR without air preheater, maximum air supply temperature improvements of 25% and 41% were found from AP(0.4mx0.4 mx0.4 m) and AP(0.8 mx0.8 mx0.4 m), respectively. The studied system reached its highest contributions when the heat recovery efficiency of MVHR was between 80% and 85%. On average, AP(0.4mx0.4 mx0.4 m) can reduced the peak heat load up to 27%. AP(0.8 mx0.8 mx0.4 m) can reduce the peak heat load up to 40% in the studied climate.

  • 20.
    Ploskic, Adnan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Reducing the defrosting needs of air-handling units by using heat from wastewater in apartment buildings in cold climates2019In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 157, article id 113647Article in journal (Refereed)
    Abstract [en]

    This paper is the second part of a two-part series that investigates the energy-saving potentials of a novel wastewater heat recovery system connected to mechanical ventilation with heat recovery (MVHR). The main idea is to use the heat from stored wastewater to preheat the incoming cold outdoor airflow to the MVHR and thereby reduce the defrosting needs of the MVHR. The study evaluated the potential of two air preheaters, AP 0.4 m x 0.4 m x 0.4 m and AP 0.8 m x 0.8 m x 0.4 m , placed in front of the existing MVHR. Dynamic simulations in this study have shown that the smaller air preheater could lower the frost threshold temperature by 5 °C and the larger one could reduce it by 11 °C. Without an air preheater, the defrosting was needed during nearly two-thirds of January in the studied climate. By contrast, with the evaluated air preheaters in front of the MVHR, the defrosting was needed during 45% and 20% of the evaluation period, respectively. The results also showed that frost growth inside the heat exchanger could be reduced by 38% with AP 0.4 m x 0.4 m x 0.4 m and by 62% with AP 0.8 m x 0.8 m x 0.4 m during the peak load. The main conclusion is that the suggested heat recovery system has good potential for improving the overall performance of MVHR systems in cold climates. © 2019 Elsevier Ltd

  • 21.
    Ploskic, Adnan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    A holistic performance evaluation of ventilation radiators – An assessment according to EN 442-2 using numerical simulations2019In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 25, article id 100818Article in journal (Refereed)
    Abstract [en]

    This research explored the importance of airflow rate and convector plate design on the operational performance of heating radiators equipped with an air device (ventilation radiators). The radiator was analyzed according to European Norm EN 442-2 using numerical simulations. The largest benefit of using staggered convector plates was the more efficient preheating of the incoming outdoor air supply. With this plate design, the evaluated radiator increased the temperature of the incoming airflow of 10 l/s from -5 °C to 26 °C with water supply/return temperatures of 45 °C/35 °C. With these water temperatures, the radiator was able to cover a room heat loss of 34 W/m2 floor area. However, the design of the convector plate alone was found to have a limited impact on the heat output from the radiator. Neither did the plate design significantly affect the uniformity of heat distribution nor the vertical temperature stratification inside the room. The results also showed that ventilation radiators might cover a building heating load (kW) with a lower supply water temperature but not necessarily give a lower annual energy use (kWh) for the space heating of a building.

  • 22.
    Ploskic, Adnan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Bravida Holding AB, Mikrofonvagen 28, S-12637 Hagersten, Sweden..
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Uponor AB, Hackstavagen 1, S-72132 Vasteras, Sweden..
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Univ Calif Berkeley, Dept Architecture, Ctr Built Environm, Berkeley, CA 94720 USA..
    Mapping Relevant Parameters for Efficient Operation of Low-Temperature Heating Systems in Nordic Single-Family Dwellings2018In: Applied Sciences, E-ISSN 2076-3417, Vol. 8, no 10, article id 1973Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to map the parameters that have the greatest impact on the environmental impact of heating systems usually used in Nordic single-family dwellings. The study focused on mapping the technical requirements for efficient operation of heating systems in a broader context. The results suggest that the ability of a heating system to be operated with a low-temperature water supply depends to a large extent on the heating demand of a building. It was shown that an increase in the water flow rate in hydronic circuits would significantly increase the thermal efficiency from analyzed heating systems. This increase would not increase the pumping power need, nor would it create noise problems in distribution network if the distribution pipes and thermostatic valves were properly selected. However, this increase in water flow rate improved the efficiency of considered closed-loop heat pump. It was further shown that the efficiency of the heat pump could be additionally improved by halving the energy needs for the domestic hot-water and circulators. The main conclusion from this study is that exergy usage, CO2 emission and thereby environmental impact are significantly lower for heating systems that are operated with small temperature drops.

  • 23.
    Ploskić, 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.
    Low-temperature ventilation pre-heater in combination with conventional room heaters2013In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 65, p. 248-259Article in journal (Refereed)
    Abstract [en]

    The main focus of the present study was to find design requirements for an air-heater that would be able to operate at low pressure loss and low-temperature water supply. The idea was to combine this low-temperature air-heater with existing radiator systems so that they can operate at similar low-temperature supply as used in floor heating systems. Results indicated that the proposed air-heater was able to lift the temperature of supply air at 10 l/s from -15 degrees C to 18.7 degrees C using 40 degrees C water supply. In addition, a thermal performance analysis showed that radiator systems equipped with the proposed air-heater could meet a space heat loss of 35.6 W per square meter floor area, using supply water of 40 degrees C. It was also shown that the heat pump efficiency in the hydronic system with proposed air-heater was 8-18% higher than in system without air-heater. All results in the present study were obtained by analytical (semi-empirical) and numerical (Computational Fluid Dynamics - CFD) calculations.

  • 24.
    Ploskić, 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.
    Performance evaluation of radiant baseboards (skirtings) for room heating - An analytical and experimental approach2014In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 62, no 2, p. 382-389Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate the thermal performance of the hydronic radiant baseboards currently used for space heating in built environments. The presently available equations for determination of heat outputs from these room heaters are valid for a certain height at a specific temperature range. This limitation needed to be addressed as radiant baseboards may be both energy and cost efficient option for space heating in the future. The main goal of this study was therefore to design an equation valid for all baseboard heights (100-200 mm) and excess temperatures (9-60 C) usually used in built environments. The proposed equation was created by curve fitting using the standard method of least squares together with data from previous laboratory measurements. It was shown that the predictions by the proposed equation were in close agreement with reported experimental data. Besides, it was also revealed that the mean heat transfer coefficient of the investigated radiant baseboards was about 50% higher than the mean heat transfer coefficient of five conventional panel radiators of different types. The proposed equation can easily be used or programed in energy simulation codes. Hopefully this will help engineers to quantify more accurately the energy consumption for space heating in buildings served by radiant baseboards.

  • 25.
    Ploskić, Adnan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Bravida Holding AB,.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Low-Temperature Heating with Heat Pumps in Single Family Houses: Design Requirements and Future PerspectivesManuscript (preprint) (Other academic)
    Abstract [en]

    This study explored the potential of low-temperature space heaters connected to a heat pump in single-family dwelling in a broader context. The aim was to map the parameters that have the greatest impact on the thermal performance of this type of heating systems and their CO2 emissions. The results suggest that the ability of a heating system to be operated with a low-temperature supply depends to a large extent on the heating demand of a building, and the size, type and efficiency of the space heaters.It was shown that an increase in the water flow rate from 0.01 to 0.05 kg/s would significantly increase the heat outputs from analyzed heating systems. Consequently, this would also improve the efficiency of closed-loop heat pumps connected to these systems. This change would not increase the pumping power need, nor would it create noise problems if the distribution pipes and thermostatic valves were properly selected. It was further demonstrated that the efficiency of the heat pumps could be additionally improved by halving the energy needs for the domestic hot-water and circulation pumps. The results also suggest that the exergy need is significantly lower in heating systems that are operated with small temperature drops.

  • 26.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE).
    On the boundary conditions of numerical particle simulation in indoor environment2016In: Proceedings of 14th International Conference on Indoor Air Quality and Climate. July 3-8, 2016; Ghent, Belgium, 2016Conference paper (Refereed)
  • 27.
    Wang, Qian
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ploskic, Adnan
    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.
    Low-temperature heating in existing Swedish multi-family houses: An assessment of the significance of radiator design and geometry2017In: Science and Technology for the Built Environment, ISSN 2374-4731, E-ISSN 2374-474X, Vol. 23, no 3, p. 500-511Article in journal (Refereed)
    Abstract [en]

    The current study evaluates the impacts of radiator designs and geometries. The aim was to map the thermal efficiency and performance differences of studied radiator types. A typical Swedish low-rise, multi-family house was selected to present the analysis. A Swedish climate was employed to evaluate the applicability. The on-site measurements, analytical model, and real-life performance data from radiator manufacturing were applied for the modeling work. Radiator Type 21 (1.2 x 0.4m) showed the highest exergy efficiency; Type 11 (1.2 x 0.45m), the lowest. There is no evidence that Type 22 (adding more convector plate) has a higher thermal efficiency than Type 21, from an engineering perspective, within the climate range of -20 degrees C to 15 degrees C. Baseboard radiators showed a 34% higher exergy performance than the most efficient conventional radiator, with the same surface area, at mean outdoor temperatures during an average heating season in Sweden (-1.3 degrees C). The results also suggest that Type 21 would have higher efficiency than Type 11 during 50% time of the heating season, in severe climate conditions. In the climate of Stockholm, this efficiency advantage was 20%. For the mild climate, Type 11 and Type 21 performed almost the same over the entire heating season.

  • 28.
    Wang, Qian
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ploskić, Adnan
    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.
    Performance analysis of low temperature heating in retrofitting practice of existing Swedish multifamily houses: An investigation including simulation and measurements2015Conference paper (Refereed)
    Abstract [en]

    Two types of low-temperature heating (LTH) radiators (ventilation/ baseboard radiators) are evaluated with respect to conventional radiator (high-temperature) based on simulation and measurements in retrofitting existing Swedish multi-family house. The flow temperature variations of LTH are found and the influences to COP of heat pump are quantified. The primary energy savings by retrofitting conventional to ventilation/baseboard radiators are 12.4 and 10.2 %, respectively. 

  • 29.
    Wang, Qian
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ploskić, Adnan
    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.
    Retrofitting with low-temperature heating to achieve energy-demand savings and thermal comfort2015In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 109, p. 217-229Article in journal (Refereed)
    Abstract [en]

    Low-temperature heating (LTH) has shown promising advantages and shortcuts to improve the thermal performance of radiators. An investigation on which renovation measures from the demand side, can cope with LTH or should be selected as ‘pre-retrofit’ to provide building performance improvements, were carried out in this study. IDA ICE was selected to perform the simulation of a typical Swedish multi-family archetype. Five common energy-demand retrofit options were analyzed. Thermal performance and operational energy savings before and retrofitting were in focus. The results showed that LTH with each of the energy-demand retrofit options can improve the thermal performance to an acceptable level. LTH-combined ventilation retrofitting showed the highest contribution in air temperature, predicted percentage of dissatisfied, and energy savings for space heating. Combining LTH with external wall retrofitting showed the highest effect in operative temperature and total operational energy savings. Combining LTH with all energy-demand retrofitting as a package can achieve 55.3% and 52.8% total delivered and primary energy savings, respectively. This research showed that the existing building can cope with LTH when any of the five energy-demand retrofit options from a thermal performance perspective. Optimal selection shall be based on their abilities to reduce operational energy.

  • 30.
    Wang, Qian
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ploskić, Adnan
    KTH, School of Architecture and the Built Environment (ABE).
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Low-temperature heating in existing Swedish multifamily houses: an assessment of the significance of radiator design and geometryManuscript (preprint) (Other academic)
    Abstract [en]

    This study evaluated the impacts of radiator designs and geometries. The aim was to map the thermal  efficiency and performance differences of studied radiator types. A typical Swedish low-rise multifamily house was selected to present the analysis. Swedish climate was employed to evaluate the applicability. On-site measurements, analytical model and real-life performance data from radiator manufactures were applied for the modeling work.

    It was found that radiator Type 21 1.2m x 0.4m shows the highest exergy efficiency. Type 11 1.2m x 0.45m shows the lowest exergy efficiency. There is no evidence found that Type 22 (adding more convector plate) has higher thermal efficiency than Type 21, from an engineering perspective, under the climate range of -20  to 15 . Baseboard radiator showed 34 % higher exergy performance than the most efficient conventional radiator, with the same surface area, at mean outdoor temperature during an average heating season in Sweden (-1.3 ). The results also suggest that Type 21 would have higher efficiency compared to Type 11 during 50 % time of the heating season, in severe climate conditions. In the climate of Stockholm, this was 20 %. For the mild climate, Type 11 and Type 21 perform almost the same during the whole heating season. 

  • 31.
    Wang, Qian
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ploskić, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Song, Xingqiang
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology. The Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries and Economics, UiT The Arctic University of Norway.
    Holmberg, Sture
    Ventilation heat recovery jointed low-temperature heating in retrofitting: An investigation of energy conservation, environmental impacts and indoor air quality in Swedish multifamily houses2016In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 121, p. 250-264Article in journal (Refereed)
    Abstract [en]

    Sweden is actively engaged in accelerating the sustainable transformation of existing building and energy systems. Most traditional investigations of this subject have been based on final energy savings and CO2 emission analysis, while most existing evaluation methods for energy-retrofitting have not accurately taken into account the influences of flow temperature patterns of different low-temperature heating (LTH) radiators to operational energy. In addition, comprehensive environmental impact analyses by energy systems, as well as the contributions to indoor air quality (IAQ), have not been fully achieved. Moreover, critical mapping of the sustainability of energy-efficient retrofitting have not yet been done. This omission leads to inaccuracies and misleading estimates of the benefits of LTH retrofitting from system and primary energy perspective. In order to fill these knowledge gaps, the present study evaluated two types of LTH systems combined with ventilation retrofitting, namely heat recovery jointed ventilation radiators (VRs) and baseboard radiators (BRs). A typical Swedish multi-family house was selected for retrofitting practice. This study aims at evaluating ventilation heat recovery jointed low temperature heating (VJLTH) retrofitting on energy conservation, environmental impacts and indoor air quality (IAQ) in typical Swedish multifamily houses. The compatibility of building performance and sustainability contributions were critically analyzed by delivered/primary energy usage, life cycle assessment (LCA), and IAQ modeling. IDA ICE (indoor climate and energy simulation program), SimaPro (LCA environmental impact modeling program), analytical model and on-site measurement data provided by both radiator and heat pump manufactures were employed. The results showed that the studied VJLTH retrofitting can save up to 55% of the final energy. And the corresponding primary energy savings are more than 25%. Compared with conventional radiators, low-temperature heating radiators can improve the COP by 12 − 18% for air-source heat pumps. The studied retrofit can positively contribute 11 of 16 environmental indicators, 7 of which had environmental impacts reduced by more than 50%. However, neglecting the indicators with negative impacts will increase the risk of over-representing the environmental contributions. The sustainability improvements of retrofitting, particularly for future large-scale implementation, should be critically evaluated from a broader perspective than final energy savings.

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