Pub Date : 2023-12-29DOI: 10.1177/17442591231207968
Wenjie Zhang, Juan Zhao, Botao Zhou, Liang Wang, Yongcai Li, Xinhui Lv, Chuang Liu
To determine the optimal heating method for gymnasiums, this study focuses on a specific gymnasium. The heat load of the gymnasium is analyzed by importing the meteorological data of Xi’an, and energy consumption simulation models for four heating systems are developed using the TRNSYS simulation software. The economic evaluation of these systems is conducted using the annual cost value method, and the optimal solar collector area is proposed. Additionally, the study examines the impact of different electricity prices on the annual cost value of the heating systems, as well as the optimal heating system configuration and its effect on the annual cost value under varying electricity prices. The main conclusions are as follows: (1) The density of people in the competition hall is much higher than that in the practice area, and the competition hall is located in the inner area with no external heat transfer protection structure, only the roof is used for heat exchange. The heat load in the competition hall (14.43 W/m2) is lower than that in the practice area (81.41 W/m2); (2) Through the economic analysis of two solar composite heating systems with different heat collection areas. The optimal heat collection area of the solar coupled electric boiler system and the solar coupled air source heat pump are 3024 and 2394 m2, respectively, and the minimum annual cost are 1,132,300 and 699,200 CNY, respectively; and (3) An economic analysis is conducted on the four heating systems at different electricity prices. When the electricity price is between 0.5 and 1.0 CNY/kWh, the air-source heat pump coupled with electric boiler system has the lowest annual cost value. However, when the electricity price is between 1.1 and 1.5 CNY/kWh, the solar energy coupled with air-source heat pump system has the lowest annual cost value.
{"title":"Optimization and economic analysis of heating scheme of a gymnasium","authors":"Wenjie Zhang, Juan Zhao, Botao Zhou, Liang Wang, Yongcai Li, Xinhui Lv, Chuang Liu","doi":"10.1177/17442591231207968","DOIUrl":"https://doi.org/10.1177/17442591231207968","url":null,"abstract":"To determine the optimal heating method for gymnasiums, this study focuses on a specific gymnasium. The heat load of the gymnasium is analyzed by importing the meteorological data of Xi’an, and energy consumption simulation models for four heating systems are developed using the TRNSYS simulation software. The economic evaluation of these systems is conducted using the annual cost value method, and the optimal solar collector area is proposed. Additionally, the study examines the impact of different electricity prices on the annual cost value of the heating systems, as well as the optimal heating system configuration and its effect on the annual cost value under varying electricity prices. The main conclusions are as follows: (1) The density of people in the competition hall is much higher than that in the practice area, and the competition hall is located in the inner area with no external heat transfer protection structure, only the roof is used for heat exchange. The heat load in the competition hall (14.43 W/m2) is lower than that in the practice area (81.41 W/m2); (2) Through the economic analysis of two solar composite heating systems with different heat collection areas. The optimal heat collection area of the solar coupled electric boiler system and the solar coupled air source heat pump are 3024 and 2394 m2, respectively, and the minimum annual cost are 1,132,300 and 699,200 CNY, respectively; and (3) An economic analysis is conducted on the four heating systems at different electricity prices. When the electricity price is between 0.5 and 1.0 CNY/kWh, the air-source heat pump coupled with electric boiler system has the lowest annual cost value. However, when the electricity price is between 1.1 and 1.5 CNY/kWh, the solar energy coupled with air-source heat pump system has the lowest annual cost value.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"95 2","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139146330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-24DOI: 10.1177/17442591231208362
Mauricio Aguilar Cardenas, Christopher Kendrick, Martin Heywood, S. Resalati
Super-insulation materials have become more commonplace as highly insulated building envelopes are required to reduce the energy demand of buildings aligned with the net zero targets. While several super insulation materials are available, their environmental impacts and practical on-site limitations hindered their large-scale adoption. The following paper investigates the feasibility of developing hollow-core vacuum insulated panels supported by an internal structural array with different configurations. The designed panel was simulated and measured to evaluate its performance as a thermal insulator for building applications. Panel samples were manufactured from polished stainless-steel plates separated by a PTFE structural array. The change in temperature and heat flux through the sample was measured in a vacuum chamber at a pressure of 0.01 Pa. Thermal conductance was obtained from gradual measurements of heat flux and temperature across the sample after a rapid increase in temperature. Numerical methods that combine molecular and macroscopic solvers were used to model unsteady behaviour recorded in empirical tests. Direct Simulation Monte Carlo (DSMC) was used to calculate the thermal conductivity of the rarefied gas, which was then used to solve the enthalpy equation for the multi-region model. Thermal resistance from empirical tests and numerical methods are in agreement within error bands, the greatest accuracy observed in high conductance models. Thermal resistance as low as 0.17 [Formula: see text] and as high as 4.75[Formula: see text] was measured. Low conductance sample configurations were sensitive to thermal contact conductance from the structural array contact interfaces, accounting for at least 40% of transferred energy. Gas conduction at a pressure of 0.01 Pa transfers up to 4% of energy in low emissivity sample configurations. Radiative energy transfer in high conductance configurations was responsible for up to 95% of transferred energy. The paper provides a comprehensive feasibility study, providing a solid foundation for further design optimization of the technology.
由于需要高度隔热的建筑围护结构来减少建筑物对能源的需求，以实现净零目标，因此超级隔热材料变得越来越普遍。虽然目前已有几种超级隔热材料，但它们对环境的影响和现场的实际限制阻碍了它们的大规模应用。以下论文研究了开发由不同配置的内部结构阵列支撑的空心真空绝热板的可行性。对所设计的面板进行了模拟和测量，以评估其作为建筑用隔热材料的性能。面板样品由抛光不锈钢板制成，并由聚四氟乙烯结构阵列隔开。在压力为 0.01 Pa 的真空室中测量了样品的温度变化和热通量。热导率是在温度快速升高后，通过逐步测量穿过样品的热通量和温度得到的。结合分子和宏观求解器的数值方法用于模拟经验测试中记录的不稳定行为。直接模拟蒙特卡罗（DSMC）用于计算稀薄气体的热导率，然后用于求解多区域模型的焓方程。经验测试和数值方法得出的热阻在误差范围内是一致的，在高导模型中观察到的热阻精度最高。测得的热阻最低为 0.17[计算公式：见正文]，最高为 4.75[计算公式：见正文]。低传导样品配置对来自结构阵列接触界面的热接触传导非常敏感，至少占传递能量的 40%。在低发射率样品配置中，0.01 Pa 压力下的气体传导最多可传递 4% 的能量。在高传导率配置中，辐射能量传递占传递能量的 95%。本文提供了一项全面的可行性研究，为进一步优化该技术的设计奠定了坚实的基础。
{"title":"Feasibility study of developing hollow-core vacuum insulated panels","authors":"Mauricio Aguilar Cardenas, Christopher Kendrick, Martin Heywood, S. Resalati","doi":"10.1177/17442591231208362","DOIUrl":"https://doi.org/10.1177/17442591231208362","url":null,"abstract":"Super-insulation materials have become more commonplace as highly insulated building envelopes are required to reduce the energy demand of buildings aligned with the net zero targets. While several super insulation materials are available, their environmental impacts and practical on-site limitations hindered their large-scale adoption. The following paper investigates the feasibility of developing hollow-core vacuum insulated panels supported by an internal structural array with different configurations. The designed panel was simulated and measured to evaluate its performance as a thermal insulator for building applications. Panel samples were manufactured from polished stainless-steel plates separated by a PTFE structural array. The change in temperature and heat flux through the sample was measured in a vacuum chamber at a pressure of 0.01 Pa. Thermal conductance was obtained from gradual measurements of heat flux and temperature across the sample after a rapid increase in temperature. Numerical methods that combine molecular and macroscopic solvers were used to model unsteady behaviour recorded in empirical tests. Direct Simulation Monte Carlo (DSMC) was used to calculate the thermal conductivity of the rarefied gas, which was then used to solve the enthalpy equation for the multi-region model. Thermal resistance from empirical tests and numerical methods are in agreement within error bands, the greatest accuracy observed in high conductance models. Thermal resistance as low as 0.17 [Formula: see text] and as high as 4.75[Formula: see text] was measured. Low conductance sample configurations were sensitive to thermal contact conductance from the structural array contact interfaces, accounting for at least 40% of transferred energy. Gas conduction at a pressure of 0.01 Pa transfers up to 4% of energy in low emissivity sample configurations. Radiative energy transfer in high conductance configurations was responsible for up to 95% of transferred energy. The paper provides a comprehensive feasibility study, providing a solid foundation for further design optimization of the technology.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"2003 8","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139239286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-08DOI: 10.1177/17442591231204360
Charles Berville, Florin Bode, Cristiana Croitoru, Razvan Calota, Ilinca Nastase
To improve building energy efficiency and address thermal storage challenges during periods without a heat source, such as cloudy weather or night-time, a range of solutions is required. Innovative technologies and sustainable practices are essential for combating climate change and reducing carbon emissions. This study primarily focuses on Thermal Energy Storage (TES) systems, specifically those using Phase Change Materials (PCMs), to increase energy efficiency for Transpired Solar Collectors used in buildings applications. During the last 30 years Transpired Solar Collectors (TSC) have been extensively investigated. However, a primary concern still exists regarding thermal storage when the heat source is unavailable, such as during periods of cloudy weather or at night. Thus, a Thermal Energy Storage (TES) system coupled with the TSC is a potential solution. In this study we are investigating using numerical simulation the arrangement of encapsulation for TES, integrating phase change materials (PCM) in spherical elements when compared with plate encapsulation elements. The model reproduces a part of a real scale thermal energy storage inserted in a Double Skin TSC. The model consists of a Plexiglas duct in which four different arrangements for the spherical encapsulated PCM were studied. For each of the arrangements the heat transfer between the TES elements and the air passing through the collector was analyzed. The primary finding of the study indicates that the hexagonal arrangement offers better passive airflow control, thus enhancing the heat transfer up to 12.3% compared to the rectangular arrangements
{"title":"Enhancing solar façade thermal performance with PCM spheres: A CFD investigation","authors":"Charles Berville, Florin Bode, Cristiana Croitoru, Razvan Calota, Ilinca Nastase","doi":"10.1177/17442591231204360","DOIUrl":"https://doi.org/10.1177/17442591231204360","url":null,"abstract":"To improve building energy efficiency and address thermal storage challenges during periods without a heat source, such as cloudy weather or night-time, a range of solutions is required. Innovative technologies and sustainable practices are essential for combating climate change and reducing carbon emissions. This study primarily focuses on Thermal Energy Storage (TES) systems, specifically those using Phase Change Materials (PCMs), to increase energy efficiency for Transpired Solar Collectors used in buildings applications. During the last 30 years Transpired Solar Collectors (TSC) have been extensively investigated. However, a primary concern still exists regarding thermal storage when the heat source is unavailable, such as during periods of cloudy weather or at night. Thus, a Thermal Energy Storage (TES) system coupled with the TSC is a potential solution. In this study we are investigating using numerical simulation the arrangement of encapsulation for TES, integrating phase change materials (PCM) in spherical elements when compared with plate encapsulation elements. The model reproduces a part of a real scale thermal energy storage inserted in a Double Skin TSC. The model consists of a Plexiglas duct in which four different arrangements for the spherical encapsulated PCM were studied. For each of the arrangements the heat transfer between the TES elements and the air passing through the collector was analyzed. The primary finding of the study indicates that the hexagonal arrangement offers better passive airflow control, thus enhancing the heat transfer up to 12.3% compared to the rectangular arrangements","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"4 15","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135390589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1177/17442591231195639
Diane Bastien, Martin Winther-Gaasvig, Jeppe Zhang Andersson, Zhe Xiao, Hua Ge
This contribution presents temperature and relative humidity data monitored over nearly two years for a case study building made of natural building materials. The case study building is a single-family house located in Denmark made of wood fiber insulation, wood fiber boards and indoor clay plaster without any membranes. Three different types of cladding systems have been tested: 1) mineral plaster rendering; 2) wood cladding applied directly over wood fiberboards; 3) wood cladding with a ventilated cavity. Monitored data is provided and compared with simulations performed with a commercial hygrothermal software. The moisture content and mold growth index are calculated from monitored data. The data indicates that the hygrothermal performance of the roof is excellent (RH < 70%); the hygrothermal performance of the walls with the three different cladding systems is good; one out of two sensor groups in the floor exhibits a moisture content up to 18% at the cold side of the insulation during summer and fall. Securing sufficient and evenly distributed crawlspace ventilation is recommended for eliminating concerns of eventual mold growth. Measurements show that materials employed in this house respond quickly to moisture changes, more quickly that simulated data. This work highlights the need for validating and adjusting WUFI simulation results with measured data to provide reliable results for building envelopes composed of highly hygroscopic plant-based materials. For these assemblies in these conditions, including a vapor retarder is not needed for achieving a satisfactory hygrothermal behavior.
{"title":"Hygrothermal performance of natural building materials: Simulations and field monitoring of a case study home made of wood fiber insulation and clay","authors":"Diane Bastien, Martin Winther-Gaasvig, Jeppe Zhang Andersson, Zhe Xiao, Hua Ge","doi":"10.1177/17442591231195639","DOIUrl":"https://doi.org/10.1177/17442591231195639","url":null,"abstract":"This contribution presents temperature and relative humidity data monitored over nearly two years for a case study building made of natural building materials. The case study building is a single-family house located in Denmark made of wood fiber insulation, wood fiber boards and indoor clay plaster without any membranes. Three different types of cladding systems have been tested: 1) mineral plaster rendering; 2) wood cladding applied directly over wood fiberboards; 3) wood cladding with a ventilated cavity. Monitored data is provided and compared with simulations performed with a commercial hygrothermal software. The moisture content and mold growth index are calculated from monitored data. The data indicates that the hygrothermal performance of the roof is excellent (RH < 70%); the hygrothermal performance of the walls with the three different cladding systems is good; one out of two sensor groups in the floor exhibits a moisture content up to 18% at the cold side of the insulation during summer and fall. Securing sufficient and evenly distributed crawlspace ventilation is recommended for eliminating concerns of eventual mold growth. Measurements show that materials employed in this house respond quickly to moisture changes, more quickly that simulated data. This work highlights the need for validating and adjusting WUFI simulation results with measured data to provide reliable results for building envelopes composed of highly hygroscopic plant-based materials. For these assemblies in these conditions, including a vapor retarder is not needed for achieving a satisfactory hygrothermal behavior.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"76 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135565278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lightweight eco-materials are in high demand in many sectors, such as aerospace, industry, and building due to their several characteristics. The present paper is an experimental investigation of the thermal characteristics of novel sandwich panels made with local and ecological materials namely agglomerated cork for the core and bio-composite materials for the skin. Three configurations (symmetric, asymmetric, and two layers) were studied with different cork core thicknesses. Density values have been measured and compared. Thermal characterization consists of determining thermal conductivity and specific heat using a HFM apparatus; whilst thermal diffusivity and thermal effusivity have been calculated using the experimental findings. The panels are lightweight and thermally insulating. The values of thermal conductivity are in the range 0.071 and 0.102 W.m−1.K−1. The comparison between experimental results of thermal conductivity to theoretical values highlights the accuracy of method for multi-layer thermal characterization and the good adhesion between layers. Finally, a life cycle assessment of the new sandwich panels has been carried out and compared with common insulation materials. The sandwich panels are efficient in terms of embodied energy and CO2 emissions compared to commercialized insulators and some insulators based on recycled or natural materials, the embodied energy for symmetric configuration with 4 cm cork core are 79.73, 94.75, and 89.35 MJ/FU corresponding to an embodied carbon 5.33, 6.32, and 6.01 CO2/FU respectively. They can be classified in the middle between synthetic and natural insulators. Based on the findings, it was concluded that utilizing these sandwich panels as construction materials for interior paneling or partition walls could offer benefits in terms of being environmentally sustainable and cost-efficient.
{"title":"Thermal properties and Life Cycle Assessment of new eco-sandwich panel for building thermal insulation","authors":"Hafida Er-rradi, Mohamed Oualid Mghazli, Abdelilah Jilbab, Chakib Bojji, Rachida Idchabani","doi":"10.1177/17442591231208360","DOIUrl":"https://doi.org/10.1177/17442591231208360","url":null,"abstract":"Lightweight eco-materials are in high demand in many sectors, such as aerospace, industry, and building due to their several characteristics. The present paper is an experimental investigation of the thermal characteristics of novel sandwich panels made with local and ecological materials namely agglomerated cork for the core and bio-composite materials for the skin. Three configurations (symmetric, asymmetric, and two layers) were studied with different cork core thicknesses. Density values have been measured and compared. Thermal characterization consists of determining thermal conductivity and specific heat using a HFM apparatus; whilst thermal diffusivity and thermal effusivity have been calculated using the experimental findings. The panels are lightweight and thermally insulating. The values of thermal conductivity are in the range 0.071 and 0.102 W.m−1.K−1. The comparison between experimental results of thermal conductivity to theoretical values highlights the accuracy of method for multi-layer thermal characterization and the good adhesion between layers. Finally, a life cycle assessment of the new sandwich panels has been carried out and compared with common insulation materials. The sandwich panels are efficient in terms of embodied energy and CO2 emissions compared to commercialized insulators and some insulators based on recycled or natural materials, the embodied energy for symmetric configuration with 4 cm cork core are 79.73, 94.75, and 89.35 MJ/FU corresponding to an embodied carbon 5.33, 6.32, and 6.01 CO2/FU respectively. They can be classified in the middle between synthetic and natural insulators. Based on the findings, it was concluded that utilizing these sandwich panels as construction materials for interior paneling or partition walls could offer benefits in terms of being environmentally sustainable and cost-efficient.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"94 12","pages":"332 - 352"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135515779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-25DOI: 10.1177/17442591231203245
Ibrahima Diaw, Mactar Faye, Stéphane Hans, Frédéric Sallet, Vincent Sambou
The reduction of energy consumption in the building sector is an important consideration for the protection of environment and availability of fossil resources. Therefore, plant-based concretes are increasingly developed to insulate buildings and reduce the contribution of the construction sector to energy consumption. In this study, concrete made of typha with a cementitious matrix was elaborated. The mechanical performances (compressive strength and apparent elastic module) are evaluated. The variability of these performances according to the water/binder ratio, the curing conditions, and the class of cement were studied. The results show that mechanical performances of Typha cement concretes are in accordance with the values recommended in the French professional rules for hemp construction. The apparent elastic module obtained range from 15 to 35 MPa. The stress at 10% strain decreases from 0.52 to 0.30 MPa with increasing water content. The water/binder ratio of 0.7 conducted to the best mechanical performance.
{"title":"Variability of mechanical performance of cement-typha insulation materials","authors":"Ibrahima Diaw, Mactar Faye, Stéphane Hans, Frédéric Sallet, Vincent Sambou","doi":"10.1177/17442591231203245","DOIUrl":"https://doi.org/10.1177/17442591231203245","url":null,"abstract":"The reduction of energy consumption in the building sector is an important consideration for the protection of environment and availability of fossil resources. Therefore, plant-based concretes are increasingly developed to insulate buildings and reduce the contribution of the construction sector to energy consumption. In this study, concrete made of typha with a cementitious matrix was elaborated. The mechanical performances (compressive strength and apparent elastic module) are evaluated. The variability of these performances according to the water/binder ratio, the curing conditions, and the class of cement were studied. The results show that mechanical performances of Typha cement concretes are in accordance with the values recommended in the French professional rules for hemp construction. The apparent elastic module obtained range from 15 to 35 MPa. The stress at 10% strain decreases from 0.52 to 0.30 MPa with increasing water content. The water/binder ratio of 0.7 conducted to the best mechanical performance.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"32 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135217365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-30DOI: 10.1177/17442591231182330
Sarah B. Fahmy, M. Zamzam, T. Khalil, Yasmine Abdalla, Thomas Loeffler, S. Ahmed, M. Abd-Elhady
The objective of the research is to improve space heating of green buildings by examining experimentally the influence of the heating medium mass flow rate on thermal performance. A green building was built in Cairo, Egypt, that consists of two similar rooms: one is the heated room and the other is a reference for comparison. A photovoltaic thermal (PV/T) collector is used to heat up water in a storage tank, and the hot water in the tank is circulated in the radiant floor of the examined green building. The hot water mass flow rate was varied between 0.04 and 0.08 kg/s. It was found that decreasing the water mass flow rate improves the heating of the radiant floor. The percentage improvement in floor temperature due to heating over the reference room, reaches about 17% and 6% at mass flow rates of 0.04 and 0.08 kg/s, respectively. Engineering Equation Solver (EES) was used to solve the equations for the heat transfer process between the heating water and the floor. It was found that decreasing the mass flow rate increases the residence time of the heating water in the radiant floor, consequently, increases the heat energy transfer and the floor temperature. Increasing the heating fluid mass flow rate in green buildings could have a negative effect on the heat transfer, such that the appropriate heating fluid mass flow rate should be calculated based on the green building massive material as well as the operating conditions, for example, ambient temperature and wind speed.
{"title":"Influence of the hot water mass flow rate on heating of radiant floors of green buildings","authors":"Sarah B. Fahmy, M. Zamzam, T. Khalil, Yasmine Abdalla, Thomas Loeffler, S. Ahmed, M. Abd-Elhady","doi":"10.1177/17442591231182330","DOIUrl":"https://doi.org/10.1177/17442591231182330","url":null,"abstract":"The objective of the research is to improve space heating of green buildings by examining experimentally the influence of the heating medium mass flow rate on thermal performance. A green building was built in Cairo, Egypt, that consists of two similar rooms: one is the heated room and the other is a reference for comparison. A photovoltaic thermal (PV/T) collector is used to heat up water in a storage tank, and the hot water in the tank is circulated in the radiant floor of the examined green building. The hot water mass flow rate was varied between 0.04 and 0.08 kg/s. It was found that decreasing the water mass flow rate improves the heating of the radiant floor. The percentage improvement in floor temperature due to heating over the reference room, reaches about 17% and 6% at mass flow rates of 0.04 and 0.08 kg/s, respectively. Engineering Equation Solver (EES) was used to solve the equations for the heat transfer process between the heating water and the floor. It was found that decreasing the mass flow rate increases the residence time of the heating water in the radiant floor, consequently, increases the heat energy transfer and the floor temperature. Increasing the heating fluid mass flow rate in green buildings could have a negative effect on the heat transfer, such that the appropriate heating fluid mass flow rate should be calculated based on the green building massive material as well as the operating conditions, for example, ambient temperature and wind speed.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"163 1","pages":"182 - 203"},"PeriodicalIF":2.0,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90680458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-29DOI: 10.1177/17442591231177429
Hakan Baş, İlknur Türkseven Doğrusoy, S. Reiter
High-speed wind flow in urban areas poses a risk of pedestrian wind discomfort. Coastal cities, particularly, are at risk of wind discomfort as they are exposed to strong sea breezes. To improve the wind climate in coastal cities, we redesigned a standard coastal urban fabric by placing a new building at its center. Then we investigated the effect of critical variables, the central building’s location (x/L ratio) and dimensions (height, width, length) on wind conditions with a parametric design approach based on the computational fluid dynamics (CFD) method validated by experimental data. We found that an optimum combination of x/L ratio and central building height (H) can reduce the corner and double corner effect between two parallel buildings by up to 45% and minimize the risk of wind discomfort. The findings can be applied to newly-designed coastal settlements where wind shelter is required and can help urban policymakers and designers.
{"title":"A proposal of urban coastal pattern for improving pedestrian wind comfort in coastal cities","authors":"Hakan Baş, İlknur Türkseven Doğrusoy, S. Reiter","doi":"10.1177/17442591231177429","DOIUrl":"https://doi.org/10.1177/17442591231177429","url":null,"abstract":"High-speed wind flow in urban areas poses a risk of pedestrian wind discomfort. Coastal cities, particularly, are at risk of wind discomfort as they are exposed to strong sea breezes. To improve the wind climate in coastal cities, we redesigned a standard coastal urban fabric by placing a new building at its center. Then we investigated the effect of critical variables, the central building’s location (x/L ratio) and dimensions (height, width, length) on wind conditions with a parametric design approach based on the computational fluid dynamics (CFD) method validated by experimental data. We found that an optimum combination of x/L ratio and central building height (H) can reduce the corner and double corner effect between two parallel buildings by up to 45% and minimize the risk of wind discomfort. The findings can be applied to newly-designed coastal settlements where wind shelter is required and can help urban policymakers and designers.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"61 4","pages":"151 - 181"},"PeriodicalIF":2.0,"publicationDate":"2023-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72507099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-29DOI: 10.1177/17442591231177428
T. Vivek, K. Balaji
Several alternatives have been introduced in recent years to enhance the thermal comfort levels within buildings. Thermally Activated Building Systems (TABS), one of the above alternatives, have gained interest because of the huge benefits this technology offers the building sector. This type of system consists of encapsulated pipes within the building structure to control the surface temperature. This study explores the thermal behavior of the cooling surface and fluctuations in indoor air temperature (IAT) of TABS under various cooling scenarios. Only limited number of investigations has been carried out to study the heat transfer behavior of TABS. Hence, the building indoor thermal properties such as air temperature, surface temperature and rate of heat transfer between the indoor air and inner surface of the TABS has been evaluated experimentally by enhancing the cooling surface area. Moreover the results were compared with the conventional building (no cooling provides). The thermal energy stored in the TABS is significantly removed by the increase in cooling surface area, resulting in a 2°C decrease in the average indoor air temperature. The average heat gain of all wall surfaces in the case of no cooling (WOC) ranges from −3 to 13 W/m2. The amount of heat gain on the walls was not significantly affected by only roof and floor cooling (R+F) activities. Moreover, it ranged from −2 to 24 W/m2 in all surface cooling (ASC) scenarios. As a result, there was additional surface cooling, which increased surface heat gain and indoor cooling capacity.
{"title":"Influence of cooling surface area on indoor air and surface heat transfer characteristics of a thermally activated building system in warm and humid zones: An Experimental study","authors":"T. Vivek, K. Balaji","doi":"10.1177/17442591231177428","DOIUrl":"https://doi.org/10.1177/17442591231177428","url":null,"abstract":"Several alternatives have been introduced in recent years to enhance the thermal comfort levels within buildings. Thermally Activated Building Systems (TABS), one of the above alternatives, have gained interest because of the huge benefits this technology offers the building sector. This type of system consists of encapsulated pipes within the building structure to control the surface temperature. This study explores the thermal behavior of the cooling surface and fluctuations in indoor air temperature (IAT) of TABS under various cooling scenarios. Only limited number of investigations has been carried out to study the heat transfer behavior of TABS. Hence, the building indoor thermal properties such as air temperature, surface temperature and rate of heat transfer between the indoor air and inner surface of the TABS has been evaluated experimentally by enhancing the cooling surface area. Moreover the results were compared with the conventional building (no cooling provides). The thermal energy stored in the TABS is significantly removed by the increase in cooling surface area, resulting in a 2°C decrease in the average indoor air temperature. The average heat gain of all wall surfaces in the case of no cooling (WOC) ranges from −3 to 13 W/m2. The amount of heat gain on the walls was not significantly affected by only roof and floor cooling (R+F) activities. Moreover, it ranged from −2 to 24 W/m2 in all surface cooling (ASC) scenarios. As a result, there was additional surface cooling, which increased surface heat gain and indoor cooling capacity.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"9 1","pages":"204 - 229"},"PeriodicalIF":2.0,"publicationDate":"2023-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89497629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recycled aggregate concrete has great significance from the environmental protection perspective. However, the current research findings on its hygrothermal properties are sparse. In this study, the apparent density, thermal conductivity, mass moisture content, water vapor permeability coefficient, water absorption coefficient, and liquid water diffusion coefficient of recycled aggregate concrete were determined by experimental methods. The effect of temperature and humidity on thermal conductivity was also studied. Furthermore, the fitting relations of the thermal conductivity of recycled aggregate concrete with the two variables of temperature and relative humidity were presented. The isothermal moisture absorption curve and the fitting relationship of water vapor permeability coefficient with relative humidity were also developed. The results indicate that the thermal conductivity of the eight recycled concrete specimens in the dry state at 25°C ranges from 0.994 to 1.242 W/(m·K). The thermal conductivity increases with the increase in temperature. When the temperature rises from 25°C to 35°C, the thermal conductivity of recycled aggregate concrete increases by 3.8%–13.5%. With the increase of relative humidity, the thermal conductivity of recycled aggregate concrete shows an increasing trend, followed by a steady state, and finally the increasing trend, showing a cubic function relationship between them. When the relative humidity increases from 0% to 95%, the thermal conductivity increases by about 20%. The mass moisture content and the water vapor permeability coefficient increase with relative humidity. The results of this study can provide basic information for the study on the heat and moisture transfer of recycled aggregate concrete, and enhance the database of hygrothermal properties of building materials.
{"title":"Experimental study on hygrothermal properties of recycled aggregate concrete","authors":"Xuemin Sui, Haoran Cui, Pinggang Yang, Biao Xu, Hua Huang","doi":"10.1177/17442591231178777","DOIUrl":"https://doi.org/10.1177/17442591231178777","url":null,"abstract":"Recycled aggregate concrete has great significance from the environmental protection perspective. However, the current research findings on its hygrothermal properties are sparse. In this study, the apparent density, thermal conductivity, mass moisture content, water vapor permeability coefficient, water absorption coefficient, and liquid water diffusion coefficient of recycled aggregate concrete were determined by experimental methods. The effect of temperature and humidity on thermal conductivity was also studied. Furthermore, the fitting relations of the thermal conductivity of recycled aggregate concrete with the two variables of temperature and relative humidity were presented. The isothermal moisture absorption curve and the fitting relationship of water vapor permeability coefficient with relative humidity were also developed. The results indicate that the thermal conductivity of the eight recycled concrete specimens in the dry state at 25°C ranges from 0.994 to 1.242 W/(m·K). The thermal conductivity increases with the increase in temperature. When the temperature rises from 25°C to 35°C, the thermal conductivity of recycled aggregate concrete increases by 3.8%–13.5%. With the increase of relative humidity, the thermal conductivity of recycled aggregate concrete shows an increasing trend, followed by a steady state, and finally the increasing trend, showing a cubic function relationship between them. When the relative humidity increases from 0% to 95%, the thermal conductivity increases by about 20%. The mass moisture content and the water vapor permeability coefficient increase with relative humidity. The results of this study can provide basic information for the study on the heat and moisture transfer of recycled aggregate concrete, and enhance the database of hygrothermal properties of building materials.","PeriodicalId":50249,"journal":{"name":"Journal of Building Physics","volume":"75 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87838758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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