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  • 1. Alsved, M.
    et al.
    Civilis, A.
    Ekolind, P.
    Tammelin, A.
    Andersson, A. Erichsen
    Jakobsson, J.
    Svensson, T.
    Ramstorp, M.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Lawrence Berkeley Natl Lab, Berkeley, CA USA.
    Larsson, P-A
    Bohgard, M.
    Santl-Temkiv, T.
    Londahl, J.
    Temperature-controlled airflow ventilation in operating rooms compared with laminar airflow and turbulent mixed airflow2018In: Journal of Hospital Infection, ISSN 0195-6701, E-ISSN 1532-2939, Vol. 98, no 2, p. 181-190Article in journal (Refereed)
    Abstract [en]

    Aim: To evaluate three types of ventilation systems for operating rooms with respect to air cleanliness [in colony-forming units (cfu/m(3))], energy consumption and comfort of working environment (noise and draught) as reported by surgical team members. Methods: Two commonly used ventilation systems, vertical laminar airflow (LAF) and turbulent mixed airflow (TMA), were compared with a newly developed ventilation technique, temperature-controlled airflow (T(c)AF). The cfu concentrations were measured at three locations in an operating room during 45 orthopaedic procedures: close to the wound (<40 cm), at the instrument table and peripherally in the room. The operating team evaluated the comfort of the working environment by answering a questionnaire. Findings: LAF and T(c)AF, but not TMA, resulted in less than 10 cfu/m(3) at all measurement locations in the room during surgery. Median values of cfu/m(3) close to the wound (250 samples) were 0 for LAF, 1 for T(c)AF and 10 for TMA. Peripherally in the room, the cfu concentrations were lowest for T(c)AF. The cfu concentrations did not scale proportionally with airflow rates. Compared with LAF, the power consumption of T(c)AF was 28% lower and there was significantly less disturbance from noise and draught. Conclusion: T(c)AF and LAF remove bacteria more efficiently from the air than TMA, especially close to the wound and at the instrument table. Like LAF, the new T(c)AF ventilation system maintained very low levels of cfu in the air, but T(c)AF used substantially less energy and provided a more comfortable working environment than LAF. This enables energy savings with preserved air quality.

  • 2. Alsved, Malin
    et al.
    Wang, Cong
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Civilis, Anette
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ekolind, Peter
    Skredsvik, Henrik
    Höjerback, Peter
    Jakobsson, Jonas
    Löndahl, Jakob
    Experimental and computational evaluation of airborne bacteria in hospital operating rooms with high airflows2018In: Proceedings of The 5th Working & Indoor Aerosols Conference 18-20 April 2018; Cassino, Italy, 2018Conference paper (Refereed)
    Abstract [en]

    Post-operative infections after surgery can be decreased by the use of efficient ventilation with clean air. In this study, we investigated three types of operating room ventilation: turbulent mixed airflow(TMA), laminar airflow (LAF) and a new type of ventilation named temperature controlled airflow(TcAF). Measurements of airborne bacteria were made during surgery and compared with values calculated by computational fluid dynamics (CFD). The results show that LAF and TcAF are most efficient in removing bacteria around the patient. With LAF, there are large differences in bacterial loads, depending on location in the room.

  • 3. Enze, Tian
    et al.
    Yulong, Chang
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Jinhan, Mo
    Afshari, Alireza
    Airborne Particles removal by Negative Ions Generated in Ambient Air and Inert Gas2017In: In: Proceedings of the 10th International Symposium on Heating, Ventilation and Air Conditioning – ISHVAC 2017. 19-22 2017; Jinan, China, 2017Conference paper (Refereed)
    Abstract [en]

    Airborne particles can be removed by air ions in enclosed environment, but the main drawback of this method is the formation of harmful by-products such as ozone (O3). In this study, we use ambient air and inert gas, including argon (Ar) and Nitrogen (N2) to generate negative ions respectively, and then release those ions into an enclosed chamber with ambient air. We then investigated the particle concentration decay rates and O3 concentration increase in the chamber. We found that the particle concentration decay rates were 0.343 min-1, 0.209 min-1 and 0.274 min-1 when ions were generated in ambient air, Ar and N2 respectively. The ozone concentration does not show a marked increase when using either ambient air or inert gas (Ar and N2) to generate ions. Since the temperature and humidity of ambient air may influence the ozone generation during ionizing, further study should be investigated.

  • 4. 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.

  • 5.
    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.

  • 6. Rahnama, S.
    et al.
    Afshari, A.
    Bergsøe, N. C.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Aalborg University, Denmark.
    Experimental study of the pressure reset control strategy for energy-efficient fan operation: Part 1: Variable air volume ventilation system with dampers2017In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 139, p. 72-77Article in journal (Refereed)
    Abstract [en]

    This paper is the first part of a two-part series which investigate the energy saving potentials in a novel mechanical ventilation system by replacing terminal dampers with decentralized fans. In Part 1, a conventional variable air volume (VAV) ventilation system with dampers is studied as a reference for comparison with the novel ventilation system in Part 2. The present study (Part 1) proposes a new method to implement the pressure reset strategy in practice. A common strategy to control the supply fan speed in a VAV system is to install a pressure sensor in the supply duct system. Then the fan speed is controlled such that a constant static pressure is maintained at the sensor location. Further energy saving can be obtained by resetting the pressure setpoint to a lower value at partial load conditions. This strategy is known as pressure reset control or critical zone reset strategy in the literature. The proposed method has been evaluated through an experimental mock-up in a laboratory environment. Experimental results show a minimum reduction of about 20% in fan power demand with applying the reset strategy compared to a constant static pressure setpoint.

  • 7.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Application of computational fluid dynamics in hospital operating theatre2016In: Proceedings of the 47th R3 NORDIC SYMPOSIUM with EXHIBITION Scandic Sydhavnen, Copenhagen, 5-6 September 2016, 2016Conference paper (Refereed)
  • 8.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Design of Hospital Operating Room Ventilation using Computational Fluid Dynamics2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The history of surgery is nearly as old as the human race. Control of wound infection has always been an essential part of any surgical procedure, and is still an important challenge in hospital operating rooms today. For patients undergoing surgery there is always a risk that they will develop some kind of postoperative complication.

    It is widely accepted that airborne bacteria reaching a surgical site are mainly staphylococci released from the skin flora of the surgical staff in the operating room and that even a small fraction of those particles can initiate a severe infection at the surgical site.  Wound infections not only impose a tremendous burden on healthcare resources but also pose a major threat to the patient. Hospital-acquired infection ranks amongst the leading causes of death within the surgical patient population. A broad knowledge and understanding of sources and transport mechanisms of infectious particles may provide valuable possibilities to control and minimize postoperative infections.

    This thesis contributes to finding solutions, through analysis of such mechanisms for a range of ventilation designs together with investigation of other factors that can influence spread of infection in hospitals, particularly in operating rooms.

    The aim of this work is to apply the techniques of computational fluid dynamics in order to provide better understanding of air distribution strategies that may contribute to infection control in operating room and ward environments of hospitals, so that levels of bacteria-carrying particles in the air can be reduced while thermal comfort and air quality are improved.

     A range of airflow ventilation principles including fully mixed, laminar and hybrid strategies were studied. Airflow, particle and tracer gas simulations were performed to examine contaminant removal and air change effectiveness. A number of further influential parameters on the performance of airflow ventilation systems in operating rooms were examined and relevant measures for improvement were identified.

    It was found that airflow patterns within operating room environments ranged from laminar to transitional to turbulent flows. Regardless of ventilation system used, a combination of all airflow regimes under transient conditions could exist within the operating room area. This showed that applying a general model to map airflow field and contaminant distribution may result in substantial error and should be avoided.

    It was also shown that the amount of bacteria generated in an operating room could be minimized by reducing the number of personnel present. Infection-prone surgeries should be performed with as few personnel as possible. The initial source strength (amount of colony forming units that a person emits per unit time) of staff members can also be substantially reduced, by using clothing systems with high protective capacity.

    Results indicated that horizontal laminar airflow could be a good alternative to the frequently used vertical system. The horizontal airflow system is less sensitive to thermal plumes, easy to install and maintain, relatively cost-efficient and does not require modification of existing lighting systems. Above all, horizontal laminar airflow ventilation does not hinder surgeons who need to bend over the surgical site to get a good view of the operative field.

    The addition of a mobile ultra-clean exponential laminar airflow screen was also investigated as a complement to the main ventilation system in the operating room. It was concluded that this system could reduce the count of airborne particles carrying microorganisms if proper work practices were maintained by the surgical staff.

    A close collaboration and mutual understanding between ventilation experts and surgical staff would be a key factor in reducing infection rates. In addition, effective and frequent evaluation of bacteria levels for both new and existing ventilation systems would also be important.

  • 9.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Indoor Air quality, thermal comfort and infection control in hospital environments: experiment and numerical approaches2016In: Proceedings of 9th International Conference on Indoor Air Quality Ventilation & Energy Conservation In Buildings. October 23-26, 2016; Seoul, Republic of Korea, 2016, p. 11-11Conference paper (Refereed)
  • 10.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Afshari, Alireza
    Iqbal, Ahsan
    A numerical analysis of diffuse ceiling ventilation performance in a school classroom and auditorium under different operating conditions2017In: In: Proceedings of Healthy Buildings 2017 Europe. July 2-5 2017; Lublin - Poland, 2017Conference paper (Refereed)
  • 11.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Afshari, Alireza
    Karimipanah, Taghi
    Hakansson, Ulf
    Nielsen, Peter V.
    Numerical simulation of the impact of surgeon posture on airborne particle distribution in a turbulent mixing operating theatre2016In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 110, p. 140-147Article in journal (Refereed)
    Abstract [en]

    Airborne particles released from surgical team members are major sources of surgical site infections. To reduce the risk of such infections, ultraclean-zoned ventilation systems have been widely applied, as a complement to the ventilation of the main operating theatre. The function of ventilation in an operating theatre is usually determined without considering the influence of the staff members' posture and movements. The question of whether the surgeon's posture during an on-going operation will influence particle distribution within the surgical area has not yet been explored in depth or well documented. In the present study we analysed data from investigation of two positions (bending and straightened up), which represent the most common surgeon and staff-member postures. The investigation was performed by applying the computational fluid dynamics methodology to solve the governing equations for airflow and airborne particle dispersion. Ultraclean-zoned ventilation systems were examined as an addition to the conventional operating theatre. We examined three distinct source strengths (mean value of pathogens emitted from one person per second) due to the variety of staff clothing systems. In the upright posture, the screen units reduced the mean air counts of bacteria and the mean counts of sedimenting bacteria to a standard level for infection-prone surgeries in the surgical area. However, the performance of this system could be reduced drastically by improper Work experience. Surgical garments with a high protective capacity result in lower source strength and thus reduces the particle concentration within the surgical area. These results are useful for developing best practices to prevent or at least reduce the infection rate during a surgical intervention.

  • 12.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ekolind, Peter
    A new principle of ventilation system for operating rooms: Temperature-Controlled Air Flow2016In: Proceedings of 12th REHVA world congress, CLIMA Conference. May 22-25, 2016; Aalborg - Denmark, 2016Conference paper (Refereed)
  • 13.
    Sadrizadeh, Sasan
    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.
    Comparison of different ventilation principles in an operating suite2014In: Proceedings of 13th SCANVAC International Conference on Air Distribution in Rooms, 19-22 October,2014, São Paulo-Brazil, 2014Conference paper (Refereed)
  • 14.
    Sadrizadeh, Sasan
    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.
    Cross-infection in a hospital wardroom with individual return openings2015In: Proceedings of International Conference on Healthy Buildings 2015 Europe. May 18-20th 2015 – Eindhoven – The Netherlands., 2015Conference paper (Refereed)
    Abstract [en]

    This article considers the role of individual return openings in controlling the spread of infection in a two-bed hospital ward. It proposes a simple and economical ventilation design capable of reducing cross-infection risk. A two-bed hospital ward ventilated by a ceiling-level low velocity diffuser was considered. Computational fluid dynamics analysis was used to simulate and compare particle removal efficiency of return openings. Different particle sizes were considered for simulating pathogenic contaminants and their concentration was calculated in patient breathing zones. A range of return opening velocities was tested. According to the results, boosting local individual return opening air velocity could effectively increase ventilation performance and particle removal efficiency could be significantly improved. The proposed personal exhaust opening system can be potentially applied in retrofitting practice in existing hospital wards with high cost effectiveness as compared to a full-scale renovation.

  • 15.
    Sadrizadeh, Sasan
    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.
    Different unidirectional laminar airflow ventilation systems in an operating room2014In: Proceedings of 13th SCANVAC International Conference on Air Distribution in Rooms, 19-22 October,2014, São Paulo-Brazil, 2014Conference paper (Refereed)
  • 16.
    Sadrizadeh, Sasan
    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.
    Door opening and its effect on the performance of turbulent-mixing ventilation in an operating theater2014In: Proceedings of 13th SCANVAC International Conference on Air Distribution in Rooms, 19-22 October,2014, São Paulo-Brazil, 2014Conference paper (Refereed)
  • 17.
    Sadrizadeh, Sasan
    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.
    Effect of a mobile LAF screen on particle distribution in an operating room2014In: Proceedings of 13th International Conference on Indoor Air Quality and Climate. July 7-12, 2014, Hong-Kong., 2014, p. 772-776Conference paper (Refereed)
    Abstract [en]

    Prediction of bacteria-carrying particle dispersion and distribution released from personnel in an operating room has been simulated by means of computational fluid dynamics technique. This investigation is focused on the performance and influence of a local ultra-clean laminar ventilation system on the airflow field and the particle distribution in an operating room. A RNG k-ε turbulence model was used to map the airflow field. Particle movement was simulated using Lagrangian DRW particle tracking method. It is shown that, MLAF can play a key role in the microorganism transmission over the instrument and operating tables. Counts of particles reveal obvious declining trends as the MLAF airflow speed increased.

  • 18.
    Sadrizadeh, Sasan
    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.
    Effect of a portable ultra-clean exponential airflow unit on the particle distribution in an operating room2015In: Particuology, ISSN 1674-2001, E-ISSN 2210-4291, Vol. 18, p. 170-178Article in journal (Refereed)
    Abstract [en]

    The effects of a mobile laminar airflow unit on the concentration, deposition and distribution of bacteria-carrying particles in an operating room are investigated. The exploration is carried out using numerical calculation schemes (computational fluid dynamics approach). The model validation was performed through result comparisons with published measurement data from literature. Two types of mobile screen units were evaluated as an extension of turbulent-mixing operating-room ventilation. Airborne particle concentration/sedimentation was recorded with and without a screen unit on the operating table and two instrument tables. Both active and passive air sampling were examined and the results are compared. It was found that the additional mobile ultra-clean laminar airflow unit reduces the counts of airborne bacteria and surface contamination to a level acceptable for infection-prone surgeries.

  • 19.
    Sadrizadeh, Sasan
    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.
    Evaluation of various turbulence models for indoor airflow prediction: a comparison study with experimental data2016In: Proceedings of 9th International Conference on Indoor Air Quality Ventilation & Energy Conservation In Buildings. October 23-26, 2016; Seoul, Republic of Korea, 2016Conference paper (Refereed)
  • 20.
    Sadrizadeh, Sasan
    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.
    How safe is it to neglect thermal radiation in indoor environment modeling with high ventilation rates?2015In: Proceedings of 36th aivc-5th Tightvent & 3rd Venticool Conference. Sep 23-24, 2015; Madrid - Spain, 2015, p. 436-Conference paper (Refereed)
  • 21.
    Sadrizadeh, Sasan
    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.
    Impact of staff posture on airborne particle distribution in an operating theatre equipped with ultraclean-zoned ventilation2015In: Proceedings of 36th aivc-5th Tightvent & 3rd Venticool Conference. Sep 23-24, 2015; Madrid - Spain, 2015, p. 919-Conference paper (Refereed)
  • 22.
    Sadrizadeh, Sasan
    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.
    Optimal positioning of exhaust grills in an operating room based on recovery test2014In: Proceedings of 35th AIVC-4th Tightvent & 2nd Venticool Conference - 24-25 September 2014, Poznań-Poland, 2014Conference paper (Refereed)
  • 23.
    Sadrizadeh, Sasan
    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.
    Surgical clothing systems in laminar airflow operating room: A numerical assessment2014In: Journal of Infection and Public Health, ISSN 1876-0341, Vol. 7, no 6, p. 508-516Article in journal (Refereed)
    Abstract [en]

    This study compared two different laminar airflow distribution strategies - horizontal and vertical - and investigated the effectiveness of both ventilation systems in terms of reducing the sedimentation and distribution of bacteria-carrying particles. Three different staff clothing systems, which resulted in source strengths of 1.5, 4 and 5 CFU/s per person, were considered. The exploration was conducted numerically using a computational fluid dynamics technique. Active and passive air sampling methods were simulated in addition to recovery tests, and the results were compared. Model validation was performed through comparisons with measurement data from the published literature. The recovery test yielded a value of 8.1 min for the horizontal ventilation scenario and 11.9 min for the vertical ventilation system. Fewer particles were captured by the slit sampler and in sedimentation areas with the horizontal ventilation system. The simulated results revealed that under identical conditions in the examined operating room, the horizontal laminar ventilation system performed better than the vertical option. The internal constellation of lamps, the surgical team and objects could have a serious effect on the movement of infectious particles and therefore on postoperative surgical site infections.

  • 24.
    Sadrizadeh, Sasan
    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.
    Thermal comfort of the surgical staff in an operating theatre: a numerical study on laminar and mixing ventilation systems2016In: Proceeding  the 14th international conference of indoor air quality and climate (Ghent, Belgium July 3-8 2016), 2016Conference paper (Refereed)
  • 25.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture K. M.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Traffic patterns effects on surgical site infection in the operating room2014In: Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate, 2014, p. 765-771Conference paper (Refereed)
    Abstract [en]

    Prediction of bacteria-carrying particle dispersion and distribution released from personnel in an operating room has been studied to decrease hospital related infections. It is focused on influence of foot traffic effect, specifically the number of personnel in the operating rooms, on the airflow field and the bacteria-carrying particle distribution. This was done by applying a numerical calculation to map the airflow field and Lagrangian DRW method for the particle phase. It is shown that, increasing number of staff persons within the OR disrupts the airflow pattern and enhances contamination in the area of open wound.

  • 26.
    Sadrizadeh, Sasan
    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.
    Peter V, Nielsen
    Three distinct surgical clothing systems in a turbulent mixing operating room equipped with mobile ultraclean laminar airflow screen: A numerical evaluation2016In: Science and Technology for the Built Environment, ISSN 2374-4731Article in journal (Refereed)
    Abstract [en]

    Two types of mobile screens producing ultraclean local laminar airflow were investigated as an addition to turbulent mixing operating room ventilation. The exploration was carried out numerically using computational fluid dynamics. Surface and volumetric particle counts were simulated on the operating and instrument tables with and without the additional mobile airflow screen. Three different source strengths (the mean bacteria-carrying particle value emitted from one person per second) due to staff clothing variety were considered. Model validation was performed through result comparisons with experimental data from the literature. Results confirmed that the mobile screen units reduced the airborne bacteria to an acceptable level for infection-prone surgeries. No significant particle concentration differences existed in the periphery of the operating room. Lower source strength resulting from a clothing system with high protective capacity reduced particle concentration.

  • 27.
    Sadrizadeh, Sasan
    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.
    Tammelin, Ann
    A numerical investigation of vertical and horizontal laminar airflow ventilation in an operating room2014In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 82, p. 517-525Article in journal (Refereed)
    Abstract [en]

    The effectiveness of vertical and horizontal ventilation systems in terms of reducing sedimentation and distribution of bacteria-carrying particles in an operating room is investigated. The exploration is carried out numerically using computational fluid dynamics. Both airborne particle concentration and sedimentation are simulated under different ventilation flow conditions. Model validation is performed through comparisons with experimental data from the literature. Achieved results reveal that the preferred selection between vertical and horizontal ventilation scenario in an operating room is highly depend on internal constellation of obstacles, work practice and supply airflow rate. Improper positioning of operating room personnel may remarkably reduce the ventilation efficiency. Increasing the airflow rate reduces particle concentration in the surgical zone. Efficient ventilation, however, is not only a matter of increasing airflow rate. Inappropriate airflow rates result in flow pattern transition from laminar to less efficient turbulent mixing. A laminar and well-organized (unidirectional) flow pattern is retired for a good result. Innovative further solutions are suggested to be found in cross-disciplinary collaboration.

  • 28.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Imani, Ramin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Guangyu, Cao
    Numerical simulation on airflow penetration through hinged and sliding doors of an operating room2017In: Proceedings of Healthy Buildings 2017 Europe, 2017Conference paper (Refereed)
  • 29.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ljungqvist, Bengt
    Reinmüller, Berit
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Does Release Position Of Bacteria-Carrying Particles Influence Contaminant Distribution In An Operating Room?2015In: Proceedings of International Conference on Healthy Buildings 2015 Europe. May 18-20th 2015 – Eindhoven – The Netherlands, 2015Conference paper (Refereed)
    Abstract [en]

    It is generally accepted that human skin is a source of bacterial dispersal and the most common cause of infection in sensitive indoor surgical environments such as operating rooms (ORs). Airborne particles carrying microorganisms are dispersed from the whole body, but with different release rates. Previous studies show that particle dispersal was occurring mainly from the lower part of the body, especially from the perineal area. Whether the release position influences particle distribution in the surgical area has not been well known.

    In this paper, two different particle launch positions, one from the head and neck and one from the perineum region and feet, were compared. Computational fluid dynamics (CFD) technique was employed to solve the governing equations for airflow and particle distribution.

    The results indicate that particles released from the lower part of the body might easily rise by buoyancy forces. Several vortices generated by the main OR ventilation system may also bring particles from the lower part of the OR to the surgical area and increase the risk of infection.

  • 30.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Loomans, M. G. L. C.
    Thermal comfort in Hospital and healthcare facilities – a literature review2016In: Proceedings of 9th International Conference on Indoor Air Quality Ventilation & Energy Conservation In Buildings. October 23-26, 2016; Seoul, Republic of Korea, 2016Conference paper (Refereed)
  • 31.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Nejad Ghafar, Ali
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Halilovic, Armin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Håkansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Numerical, Experimental and Analytical Studies on Fluid Flow through a Marsh Funnel2017In: Journal of Applied Fluid Mechanics, ISSN 1735-3572, E-ISSN 1735-3645, Vol. 10, no 6, p. 1501-1507Article in journal (Refereed)
    Abstract [en]

    This paper presents the application of computational fluid dynamics technique in civil and underground industries to evaluate fluid behaviour in a Marsh funnel. The numerical approach, based on computational fluid dynamics, simulated an incompressible two-phase Newtonian flow by means of the Volume-of-Fluid method. A complementary analytical proposed which provided a quick, field-ready method to assess the fluid field in the Marsh funnel. A supplemental experimental effort evaluated the results obtained from both the analytical calculation and numerical simulation. Results showed that the application of computational fluid dynamics technique gives the desired results in studying fluid flows in civil and underground industries. Proposed analytical solution is also capable of accurately predicting the fluid flow and thus can complement the experimental and numerical approaches. Further, the proposed analytical approach can be an alternative method for faster evaluation of fluid, although it needs to be calibrated with either the numerical or the experimental studies.

  • 32.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Nielsen, Peter V.
    CFD prediction of non-isothermal flow– How to minimize the user factor?2016In: Proceedings of 14th International Conference on Indoor Air Quality and Climate. July 3-8, 2016; Ghent, Belgium, IEEE, 2016Conference paper (Refereed)
  • 33.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Nielsen, Peter V
    Modelling of coughed droplets in a hospital ward2016In: Proceedings of 12th REHVA world congress, CLIMA Conference. May 22-25, 2016; Aalborg - Denmark, 2016Conference paper (Refereed)
  • 34.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Nielsen, Peter V
    Department of Civil Engineering, Aalborg University, Aalborg, Denmark.
    To Predict Low Turbulent Flow2015In: Proceedings of ISHVAC-COBEE 2015: 9th International Symposium On Heating, Ventilation And Air Conditioning (ISHVAC) And 3rd Conference On Building Energy And Environment (COBEE), 2015Conference paper (Refereed)
  • 35.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Peng, Shia-Hui
    Royal Institute of Technology.
    Sensitivity analysis in numerical simulation of indoor airflow: Boundary conditions2016In: Proceedings of 14th International Conference on Indoor Air Quality and Climate. July 3-8, 2016; Ghent, Belgium, 2016Conference paper (Refereed)
  • 36.
    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)
  • 37.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Rojas, Gabriel
    Clark, Jordan
    Walker, Iain
    Sherman, Max
    Validated numerical simulations of wall-mounted kitchen range hood pollutant capture and sensitivity tests to inform development of a method of test2018In: Proceedings of The 15th Conference of the International Society of Indoor Air Quality & Climate (ISIAQ). July 22-27, 2018; Philadelphia, PA, USA, 2018Conference paper (Refereed)
    Abstract [en]

    Cooking is one of the most important sources of indoor air pollution in most residences. Until recently, range hoods used to remove pollutants generated during cooking were rated by flow rate and noise criteria only in the United States. We sought to help inform a standardized method of test for range hoods which relates rating more directly to pollutant removal performance. To this end, a numerical model is first validated and then used to assess the effects of several parameters on apparent capture efficiency for a wall-mounted hood. Results show that some seemingly benign variables, such as the size of the test room, have large effects on simulated capture efficiency.

  • 38.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Stensson, Sofia
    Walker, Iain
    Marashian, Shahrzad
    Holmberg, Sture
    Airborne bacteria inactivation in a hospital ward by ultraviolet irradiation2018In: In: Proceedings of the 4th International Conference on building Energy & Environment (COBEE 2018). February 5-9 2018; Melbourne, Australia, 2018Conference paper (Refereed)
    Abstract [en]

    This study considers numerical modelling based on the Computational Fluid Dynamics technique for a hospital ward with an upper-room ultraviolet germicidal irradiation fixture. A two-bed hospital ward equipped with a ceiling-level low-velocity ventilation diffuser was considered. The airflow field was considered steady state and ultraviolet distribution was treated as a scalar flux. Different particle sizes were simulated representing the pathogenic contaminants released from patients’ breathing zones. The results confirm the effectiveness of ultraviolet germicidal irradiation. However, an optimization study should be performed to enhance the disinfection efficiency of the system. Ultraviolet germicidal irradiation is an effective technique for airborne bacteria inactivation which potentially can be used to prevent the spread of certain infectious diseases.

  • 39.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Tammelin, A.
    Nielsen, P. V.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Does a mobile laminar airflow screen reduce bacterial contamination in the operating room?: A numerical study using computational fluid dynamics technique2014In: Patient Safety in Surgery, ISSN 1754-9493, E-ISSN 1754-9493, Vol. 8, no 1, article id 27Article in journal (Refereed)
    Abstract [en]

    Background: Air-borne bacteria in the operating room (OR) may contaminate the surgical wound, either by direct sedimentation from the air or indirectly, by contaminated sterile instruments. Reduced air contamination can be achieved with an efficient ventilation system. The current study assesses the additive effect of a mobile laminar airflow (MLAF) unit on the microbiological air quality in an OR supplied with turbulent-mixing air ventilation.Methods: A recently designed OR in NKS (Nya Karolinska Sjukhuset, Stockholm, Sweden) was the physical model for this study. Simulation was made with MLAF units adjacent to the operating table and the instrument tables, in addition to conventional turbulent-mixing ventilation. The evaluation used numerical calculation by computational fluid dynamics (CFD). Sedimentation rates (CFU/m2/h) were calculated above the operating table and two instrument tables, and in the periphery of the OR. Bacterial air contamination (CFU/m3) was simulated above the surgical and instrument tables with and without the MLAF unit.Results: The counts of airborne and sedimenting, bacteria-carrying particles downstream of the surgical team were reduced to an acceptable level for orthopedic/implant surgery when the MLAF units were added to conventional OR ventilation. No significant differences in mean sedimentation rates were found in the periphery of the OR.Conclusions: The MLAF screen unit can be a suitable option when the main OR ventilation system is unable to reduce the level of microbial contamination to an acceptable level for orthopedic implant surgery. However, MLAF effect is limited to an area within 1 m from the screen. Increasing air velocity from the MLAF above 0.4 m/s does not increase the impact area.

  • 40.
    Sadrizadeh, Sasan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Tammelin, Ann
    Ekolind, Peter
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Influence of staff number and internal constellation on surgical site infection in an operating room2014In: Particuology, ISSN 1674-2001, E-ISSN 2210-4291, Vol. 13, no 1, p. 42-51Article in journal (Refereed)
    Abstract [en]

    Prediction of bacteria-carrying particle (BCP) dispersion and particle distribution released from staff members in an operating room (OR) is very important for creating and sustaining a safe indoor environment. Postoperative wound infections cause significant morbidity and mortality, and contribute to increased hospitalization time. Increasing the number of personnel within the OR disrupts the ventilation airflow pattern and causes enhanced contamination risk in the area of an open wound. Whether the amount of staff within the OR influences the BCP distribution in the surgical zone has rarely been investigated. This study was conducted to explore the influence of the number of personnel in the OR on the airflow field and the BCP distribution. This was performed by applying a numerical calculation to map the airflow field and Lagrangian particle tracking (LPT) for the BCP phase. The results are reported both for active sampling and passive monitoring approaches. Not surprisingly, a growing trend in the BCP concentration (cfu/m(3)) was observed as the amount of staff in the OR increased. Passive sampling shows unpredictable results due to the sedimentation rate, especially for small particles (5-10 mu m). Risk factors for surgical site infections (SSIs) must be well understood to develop more effective prevention programs.

  • 41.
    Wang, Cong
    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.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Numerical study of temperature-controlled airflow in comparison with turbulent mixing and laminar airflow for operating room ventilation2018In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 144, p. 45-56Article in journal (Refereed)
    Abstract [en]

    Operating room (OR) ventilation is crucial for reducing airborne bacteria-carrying particles (BCPs) concentration and thus preventing post-operative infections. A variety of ventilation schemes have been introduced to ORs. This study explores the effectiveness of a newly developed ventilation scheme, temperature-controlled airflow (TAF), with respect to reducing BCPs distribution and sedimentation in an OR. Comparisons are made with the conventional turbulent mixing and laminar airflow (LAF) ventilation. The study is conducted using Computational Fluid Dynamics (CFD) and Lagrangian particle tracking (LPT), with numerical models validated against literature data. The results reveal that TAF represents reliable and effective ventilation and can serve as an energy-efficient alternative to the LAF systems. The results also show that increasing ventilation rates alone will not always result in better control of BCPs distribution. Airflow patterns play an important role in removing and diluting airborne BCPs, so a specific analysis is necessary to each design of OR ventilation.

  • 42.
    Wang, Cong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Numerical Assessment of a Novel Ventilation Strategy for Operating Rooms in Comparison with Turbulent Mixing and Laminar Air Flow2018In: Proceedings of The 15th Conference of the International Society of Indoor Air Quality & Climate (ISIAQ). July 22-27, 2018; Philadelphia, PA, USA, 2018Conference paper (Refereed)
    Abstract [en]

    Infectious airborne particles can cause surgical site infections (SSIs). SSIs cause substantially increased morbidity and mortality as well as patients’ sufferings. A well-functioning ventila-tion system in an operating room (OR) plays an essential role in the prevention of SSIs. In this study, we applied Computational Fluid Dynamics (CFD) to evaluate the performance of a novel OR ventilation strategy – temperature controlled airflow (TAF) against two widely used OR ventilation systems: laminar airflow (LAF) and turbulent mixing airflow (TMA). The performance was measured in terms of airborne bacteria concentration. Simulation results confirmed the superiority of LAF and TAF to TMA in providing high air cleanliness and also showed that TAF can serve as an efficient alternative to LAF.

  • 43.
    Wang, Cong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Sadrizadeh, Sasan
    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.
    Application of open-source CFD software to the indoor airflow simulation2017In: In: Proceedings of 38th AIVC - 6th TightVent & 4th Venticool Conference, 2017. September 13-14 2017; University Of Nottingham, Nottingham  – UK, 2017Conference paper (Refereed)
    Abstract [en]

    The use of open-source CFD has been growing in both industry and academia. Open-source CFD saves users a considerable license cost and provides users with full transparency of implementation and maximum freedom of customization. However, it is often necessary to assess the performance of an open-source code before applying it to the practical use. This study applies one of the most popular open-source CFD codes – OpenFOAM to theindoor airflow and heat transfer prediction. The performance of OpenFOAM is evaluated and validated against awell-documented benchmark test. Various OpenFOAM built-in turbulent viscosity models are attempted withinthe framework of Reynolds Averaged Navier-Stokes Simulation (RANS) approach and the simulation results arecompared to the experimental data. Among all models, the 𝑘 − 𝜔 𝑆𝑆𝑇 model has shown the best overall performance, whereas the standard 𝑘 − 𝜀 model is the most robust one despite its deficiencies. The results of this study demonstrate the capability of OpenFOAM in the field of indoor air simulation and promote users confidence in using OpenFOAM in their research work.

  • 44.
    Wang, Cong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Sadrizadeh, Sasan
    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.
    Influence of the shape of surgical lamps on the airflow and particle distribution in operating rooms2018In: Proceedings of Roomvent & Ventilation 2018. June 02-05, 2018; Espoo, Finland, 2018Conference paper (Refereed)
    Abstract [en]

    Operating room ventilation plays a significant role in reducing bacteria carrying particles concentration and preventing post-operative infections. The ventilation airflow may be disturbed by objects and heat loads and their effectiveness in reducing bacteria concentration can be compromised. Surgical lamps are one of the major disturbances in an operating room. This study numerically investigated the influence of lamp shapes on airflow patterns and dispersion of airborne bacteria.

    Two different shapes of lamps were studied: a closed-shape and an open-shape lamp. The simulation was performed based on the physical configuration of two operating rooms ventilated respectively by laminar airflow and temperature controlled airflow. Results show that the closed-shape lamp severely obstructs the airflow and results in high bacteria concentration in the laminar airflow, whereas the open-shape lamp has a negligible impact on the particle dispersion. The temperature controlled airflow is less sensitive to obstructions and maintains a clean surgical site with both types of lamps.

  • 45.
    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. 

1 - 45 of 45
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