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  • 1. Cao, Z.
    et al.
    Lei, L.
    Wang, Qian
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik. KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Fransson, Torsten
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Comparison study of the development of ethanol fuels in China2010Ingår i: 6th Advanced Forum on Transportation of China (AFTC 2010), 2010, nr 573 CP, s. 150-154Konferensbidrag (Refereegranskat)
    Abstract [en]

    Based on the analysis of the producing principles of ethanol fuels for the vehicles and their development in the world,in the article the ethanol fuels is compared with conventional fuels in eight indicators covering economic, environment and producing technology by AHP model. The main objective of this research work is to study the difficulties and arising obstacles of promoting the ethanol fuel in Chinese market based on the calculation results, and finally propose appropriate solutions and new ideas to ease the energy crisis and traffic pollutions in China.

  • 2.
    Härer, Simon
    et al.
    Faculty of Engineering, Reutlingen University, Reutlingen, Germany.
    Nourozi, Behrouz
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Hållbara byggnader.
    Wang, Qian
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Hållbara byggnader. Uponor AB, Västerås, Sweden.
    Ploskic, Adnan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Hållbara byggnader. Bravida Holding AB, Hägersten, Sweden.
    Frost reduction in mechanical balanced ventilation by efficient means of preheating cold supply air2019Konferensbidrag (Refereegranskat)
    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.

  • 3.
    Nourozi, Behrouz
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Hållbara byggnader.
    Härer, Simon
    Wang, Qian
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Hållbara byggnader. Uponor AB.
    Ploskic, Adnan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Hållbara byggnader. Bravida AB.
    Life cycle cost analysis of air preheating systems using wastewater and geothermal energy2019Ingår i: The REHVA European HVAC Journal, ISSN 1307-3729, Vol. 56, nr 1, s. 47-51Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    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.

  • 4.
    Nourozi, Behrouz
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Wang, Qian
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik. Uponor AB, Hackstavägen 1, S-72132 Västerås, Sweden..
    Ploskic, Adnan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik. Bravida Holding AB, Mikrofonvägen 28, S-12637 Hägersten, Sweden..
    Energy and defrosting contributions of preheating cold supply air in buildings with balanced ventilation2019Ingår i: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 146, s. 180-189Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Nourozi, Behrouz
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Wang, Qian
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik. Uponor AB.
    Ploskic, Adnan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik. Bravida Holding AB.
    Identifying frost threshold in a balanced mechanical ventilation system by inlet and exhaust air temperature control2019Konferensbidrag (Refereegranskat)
    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%.

  • 6.
    Nourozi, Behrouz
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Energi och klimatstudier, ECS.
    Wang, Qian
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Energi och klimatstudier, ECS.
    Ploskic, Adnan
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Energi och klimatstudier, ECS.
    Maximizing thermal performance of building ventilation using geothermal and wastewater heat2019Ingår i: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 143, s. 90-98Artikel i tidskrift (Refereegranskat)
    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.

  • 7.
    Nourozi, Behrouz
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Wang, Qian
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik. Uponor AB.
    Ploskic, Adnan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik. Bravida Holdings AB.
    Preheating Cold Supply Air to Mechanical Balanced Ventilation using Wastewater or Passive Geothermal Energy2019Konferensbidrag (Refereegranskat)
    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.

  • 8.
    Ploskic, Adnan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Wang, Qian
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Evaluating the potential of reducing peak heating load of a multi-family house using novel heat recovery system2018Ingår i: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 130, s. 1182-1190Artikel i tidskrift (Refereegranskat)
    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.

  • 9.
    Ploskic, Adnan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Wang, Qian
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    Sadrizadeh, Sasan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap.
    A holistic performance evaluation of ventilation radiators – An assessment according to EN 442-2 using numerical simulations2019Ingår i: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 25, artikel-id 100818Artikel i tidskrift (Refereegranskat)
    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.

  • 10.
    Ploskic, Adnan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik. Bravida Holding AB, Mikrofonvagen 28, S-12637 Hagersten, Sweden..
    Wang, Qian
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik. Uponor AB, Hackstavagen 1, S-72132 Vasteras, Sweden..
    Sadrizadeh, Sasan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik. 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 Dwellings2018Ingår i: Applied Sciences, E-ISSN 2076-3417, Vol. 8, nr 10, artikel-id 1973Artikel i tidskrift (Refereegranskat)
    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.

  • 11.
    Ploskić, Adnan
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik. Bravida Holding AB,.
    Wang, Qian
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Low-Temperature Heating with Heat Pumps in Single Family Houses: Design Requirements and Future PerspectivesManuskript (preprint) (Övrigt vetenskapligt)
    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.

  • 12.
    Wang, Qian
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Low-temperature Heating in Existing Swedish Residential Buildings: Toward Sustainable Retrofitting2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Den ökande relativa energianvändningen i bostadsbyggnader i stadsmiljö har lett till högre krav på energieffektivit och hållbar omvandling av redan existerande bostadsbyggnader. En viktig förutsättning för att genomföra en sådan omvandling är att först utveckla metoder för hur effektiva beslut om renovering ska ske, samt att utveckla teknik för hållbar renovering. Lågtemperatursuppvärmning (LTH) har visat sig ha fördelar som ett hållbart och energieffektivt alternativ i länder med kallt klimat som Sverige. Metoden bidra till ökad effektivitet för uppvärmning och minskade energibehov för byggnadskomplexet. Det saknas fortfarande flera steg för hur man ska utforma modelleringsverktyg och utveckla kostnadseffektiva metoder för beslutsfattning och implementering av LTH i redan existerande byggnader. Dessutom försvårar avsaknaden av dessa verktyg och metoder genomförandet av kritiska utvärderingar av renoveringsalternativ utifrån hållbarhets- och effektivitetssynpunkt med huvudfokus på energibesparingspotential, miljöpåverkan och nöjdhet hos de boende. Dessa frågor undersöks i denna avhandling i samband med renovering av existerande bostadsbyggnader i Sverige.

     

    Målet är att bidra till utvecklingen av metoder och modelleringsverktyg för hållbar renovering. Under arbetet utvecklades tre modelleringskoncept som integrerats med varandra och som svarar för olika steg i renoveringsmodelleringen. Huvudfokus i arbetet var att göra LTH till en del av vår renoveringspraxis. De renoveringsalternativ som studerats i arbetet inkluderar renovering av klimatskalet för att minska energibehovet samt implementering av LTH-radiatorer och där påvisa deras fördelar för valt primärenergisystem. Analysen omfattar även den sammantagna effekten av och de ömsesidiga beroenden som föreligger mellan olika renoveringsåtgärder. Här utvecklade metoder kan sägas följa en ”uppifrån och ner” strategi och stärker LTH som ett uppvärmningsalternativ som uppfyller hållbarhetskriterier.

     

    Avhandlingen visar att effektiv renovering av energisystem kan minska det slutliga energibehovet med 36-54 % i de studerade byggnadstyperna. Kombinationen av LTH-radiatorer med värmeåtervinning från ventilation gav de allra största positiva bidragen. LTH-radiatorerna (ventilationsradiatorer och värmelister) fungerade som lågtemperatursuppvärmning vid uppvärmningsbehov under 30 W/m2 (12 W/ m3) och som ultra-lågtemperaturuppvärmning vid uppvärmningsbehov under 10 W/m2 (4 W/ m3).

    De låga framledningstemperaturer som leds till LTH-radiatorer bidrar dessutom till att öka COP (värmefaktorn) för luftvärmepumpar med 12 – 18 %, jämfört med traditionella radiatorer med lika stor värmeavgivande area.

    Något konkret stöd fanns inte för att Typ 22-radiatorer (dubbel konvektionsplåt) skulle ha högre värmeeffektivitet än Typ 21-radiatorer (enkel konvektionsplåt) för svenska klimatetförhållanden. Ökat antal konvektorplåtar visade sig alltså inte nödvändigtvis leda till ökad värmeeffektivitet.

    Tröskelvärdet för när Typ 11-radiatorer (enkel panel) presterar sämre än den mest effektiva radiatortypen, Typ 21-radiatorer (dubbel panel) som även har bättre exergiprestanda, visade sig vara ett värmebehov av 480 W/rum.

    För att uppnå full potential för LTH-radiatorer som renoveringsalternativ visade det sig utöver mer effektiva radiatorer även behövas ett välutformat system av rör, pumpar och energitillförsel, anpassade till byggnadens värmebehov före renovering vid rådande klimat.

     

    Renovering som inkluderar alla möjliga alternativ leder inte alltid till högre långsiktig ekonomisk avkastning. Det är viktigt att finna en balans mellan kostnadseffektivitet och energibesparing för likande byggnadstyper, i stället för att utveckla en enda lösning som ska passa överallt. För traditionella renoveringsalternativ, så som isolering, var det nödvändigt att utvärdera den inbäddade energin under hela renoveringsprocessen. Stor risk för överskattad hållbarhet föreligger om man inte beaktar detta.

  • 13.
    Wang, Qian
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Holmberg, Sture
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Combined Retrofitting with Low Temperature Heating and Ventilation Energy Savings2015Ingår i: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 78, s. 1081-1086Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents the modeling results of combining low temperature heating (ventilation radiator) with ventilation energy- demand savings. Investigations on operational energy and thermal comfort are in focus.

    IDA ICE is employed to investigate the thermal performance and energy usage. The results show that low temperature heating can reduce mean air temperature fluctuations in the selected archetype. When combining low temperature heating with ventilation and air-tightness renovations, the thermal performance of the heating system can be largely improved to an acceptable level. The retrofitting strategy can save 41% of heating energy demand and 27% of total primary energy.

  • 14.
    Wang, Qian
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Ploskic, Adnan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Holmberg, Sture
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Low-temperature heating in existing Swedish multi-family houses: An assessment of the significance of radiator design and geometry2017Ingår i: Science and Technology for the Built Environment, ISSN 2374-4731, E-ISSN 2374-474X, Vol. 23, nr 3, s. 500-511Artikel i tidskrift (Refereegranskat)
    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.

  • 15.
    Wang, Qian
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Ploskić, Adnan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Holmberg, Sture
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Performance analysis of low temperature heating in retrofitting practice of existing Swedish multifamily houses: An investigation including simulation and measurements2015Konferensbidrag (Refereegranskat)
    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. 

  • 16.
    Wang, Qian
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Ploskić, Adnan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Holmberg, Sture
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Retrofitting with low-temperature heating to achieve energy-demand savings and thermal comfort2015Ingår i: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 109, s. 217-229Artikel i tidskrift (Refereegranskat)
    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.

  • 17.
    Wang, Qian
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Ploskić, Adnan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE).
    Sadrizadeh, Sasan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Low-temperature heating in existing Swedish multifamily houses: an assessment of the significance of radiator design and geometryManuskript (preprint) (Övrigt vetenskapligt)
    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. 

  • 18.
    Wang, Qian
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Ploskić, Adnan
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Strömnings- och klimatteknik.
    Song, Xingqiang
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Industriell ekologi. 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 houses2016Ingår i: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 121, s. 250-264Artikel i tidskrift (Refereegranskat)
    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.

  • 19.
    Xue, Yu
    et al.
    Dalian Univ Technol, Sch Civil Engn, Dalian 116024, Peoples R China..
    Liu, Wei
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Hållbara byggnader.
    Wang, Qian
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Hållbara byggnader. Uponor AB, Hackstavagen 1, S-72132 Vasteras, Sweden..
    Bu, Fang
    Beijing Aerosp Inst Metrol & Measurement Technol, Beijing 10000, Peoples R China..
    Development of an integrated approach for the inverse design of built environment by a fast fluid dynamics-based generic algorithm2019Ingår i: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 160, artikel-id 106205Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is essential to further design built environments with improved thermal comfort level, air quality, and reduced energy consumption of the HVAC system. The CFD-based GA was able to identify the global optimal design, but this method requires numbers of CFD simulations which is time consuming. Besides, there is no general rule in determining the critical parameters of GA, such as population size, mutation rate, and crossover rate. Therefore, this study adopted the FFD instead of CFD and developed the FFD-based GA in OpenFOAM. By testing the FFD-based GA in designing the thermal environment in an office with displacement ventilation, it was found that the FFD-based GA had the similar performance with that of the CFD-based GA and saved more than 75% computational effect. Making use of the efficiency of the FFD-based GA, this investigation tested the effect of population size, mutation rate, and crossover rate on the inverse design by GA. In the same design case, the appropriate population size was and mutation rate was m = 0.1, while the crossover rate had no general effect on the inverse design.

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