Land–atmosphere coupling and sea surface temperature(SST)anomalies both have essential impacts on weather and climate extremes.Based on the ERA5 reanalysis dataset and the CESM1.2.2 model,this study investigates the ...Land–atmosphere coupling and sea surface temperature(SST)anomalies both have essential impacts on weather and climate extremes.Based on the ERA5 reanalysis dataset and the CESM1.2.2 model,this study investigates the influence of land–atmosphere coupling on summer extreme hot-humid events(EHHE)over southern Eurasia under different SST backgrounds.The results suggest that coupling causes near-surface air temperature increases that exceed 0.5℃.From 1961 to 2020,the frequency of EHHE has continuously increased,and is closely related to soil moisture anomalies in the northern Indian Peninsula(IDP)and the middle and lower reaches of the Yangtze River(YRB).Numerical simulations further demonstrate that land–atmosphere coupling raises the risk of EHHE by 25.4%.In a typical El Niño SST background state,intensified land–atmosphere coupling tends to produce notable increases in the frequency of EHHE.The dominant processes that land–atmosphere coupling affects the EHHE variations are evidently different between these two regions.Land surface thermal anomalies predominate in the IDP,while moisture conditions are more critical in the YRB.When warm SST anomalies exist,dry soil anomalies in the IDP are prominent,and evaporation is constrained,increasing sensible heat flux.Positive geopotential height anomalies are significant,combined with adiabatic warming induced by descending motion and a noticeable warm center in the near-surface atmosphere.The southward shift of the westerly jet enhances divergence over YRB.The anticyclonic circulation anomalies over the western Pacific are conducive to guiding moisture transport to the YRB,providing a favorable circulation background for the development of summer EHHE.展开更多
Heat strain experienced by individuals wearing chemical protective clothing(CPC)is severe and dangerous especially in hot-humid environment.The development of material science and interdisciplinary studies including e...Heat strain experienced by individuals wearing chemical protective clothing(CPC)is severe and dangerous especially in hot-humid environment.The development of material science and interdisciplinary studies including ergonomics,physiology and heat transfer is urgently required for the reduction of heat strain.The aim of this paper was to study the relationship among clothing thermal properties,physiological responses and environmental conditions.Three kinds of CPC were selected.Eight participants wore CPC and walked(4 km/h,two slopes with 5%and 10%)on a treadmill in an environment with(35±0.5)℃ and RH of(60±5)%.Core temperature,mean skin temperature,heart rate,heat storage and tolerance time were recorded and analyzed.Physiological responses were significantly affected by the clothing thermal properties and activity intensity in hot-humid environment.The obtained results can help further development of heat strain model.New materials with lower evaporative resistance and less weight are necessary to release the heat strain in hot-humid environments.展开更多
The current ventilation condition of the hot and humid regions was analyzed through on-site investigation. It is found that residents in this region expect to improve indoor thermal environment through natural ventila...The current ventilation condition of the hot and humid regions was analyzed through on-site investigation. It is found that residents in this region expect to improve indoor thermal environment through natural ventilation as much as possible. Then,it comes to a conclusion by the field test that natural ventilation has certain practical effect on improving indoor thermal environment. CFD simulation software is employed to verify the test result. Based on PMV modified model,and according to norms,geography and climate combined with the measured and simulated results,the application of the time and effectiveness of natural ventilation in hot and humid region were analyzed,to some extent,providing a basis for reducing the air-conditioner's runtime with natural ventilation.展开更多
The effect of hot-humid exposure(i.e., 40 C and 98% R.H.) on the quasi-static strength of the adhesive-bonded aluminum alloys was studied. Test results show that the hot-humid exposure leads to the significant decreas...The effect of hot-humid exposure(i.e., 40 C and 98% R.H.) on the quasi-static strength of the adhesive-bonded aluminum alloys was studied. Test results show that the hot-humid exposure leads to the significant decrease in the joint strength and the change of the failure mode from a mixed cohesive and adhesive failure with cohesive failure being dominant to adhesive failure being dominant. Careful analyses of the results reveal that the physical bond is likely responsible for the bond adhesion between L adhesive and aluminum substrates. The reduction in joint strength and the change of the failure mode resulted from the degradation in bond adhesion, which was primarily attributed to the corrosion of aluminum substrate. In addition, the elevated temperature exposure significantly accelerated the corrosion reaction of aluminum, which accelerated the degradation in joint strength.展开更多
Objective This study was aimed to explore the physiological changes and the effect of heat acclimation training via a randomized control trial study.Methods Forty healthy male volunteers were chosen and divided into e...Objective This study was aimed to explore the physiological changes and the effect of heat acclimation training via a randomized control trial study.Methods Forty healthy male volunteers were chosen and divided into experimental group and control group randomly.Those in experimental group received heat acclimation training including but not limited to meditation,unarmed run,yoga,and stepping in hot lab environment.And then,subjective feeling,rectal temperature,average skin temperature,and sweat electrolytes concentration were detected in order to describe their physiological changes.Before and after the training,both groups received some tests and their 3 000 m run-race time,nervous reaction time and subjective perception scores were recorded to evaluate the effect of acclimation training.Results(1) There was no difference in 3 000 m between the 2 groups in the same environment.Subjects' 3 000 m race time in experimental group was obviously shortened than that in control group in room temperature environment(t=2.326,P<0.05).And subjects' 3 000 m race time in experimental group was obviously shortened than that in control group in hot-humid environment(t=4.518,P<0.01).(2) Subjects' reaction time(RT) in experimental group was shortened than that in control group in room temperature environment(Z=11.258,P<0.05).And Subjects' RT in experimental group was sharply shortened than that in control group in hot-humid environment(Z=6.519,P<0.01).(3) No difference between the experimental and control groups was observed in subjective perception score(SPS) in room temperature environment.But subjects' SPS in experimental group was obviously lowered than that in control group and in hot-humid environment(t=17.958,P<0.01).(4)Anal temperature(AT) was lowered during training,while the change of mean skin temperature(MST) was not significant.Sweat sodium concentration(SSC) was lowered during training.SPS continued to decrease and entered plateau on the 13 th day after training.(5) After acclimation training,the working capacity of the experimental group in hot-humid environment was over 85%of that in room temperature environment.While subjects' working capacity in control group in hot-humid environment was about 80%of that in room temperature environment.Conclusion Hot-humid environment acclimation training improved the working capacity.After training,subjects' working capacity in hot-humid environment remained over 85%of that in room temperature environment,which was higher than that of those subjects who did not take part in training.展开更多
When sudden disasters such as earthquakes and tsunamis culminate in the outage of control systems in nuclear power plants,the operators may be exposed to extremely hot-humid environmental conditions while still facing...When sudden disasters such as earthquakes and tsunamis culminate in the outage of control systems in nuclear power plants,the operators may be exposed to extremely hot-humid environmental conditions while still facing demanding cognitive tasks.To investigate how their cognitive performance is related to their heart rate variability(HRV),we exposed nuclear power plant operators to four high temperature and humidity environments and measured their HRV during seven different cognitive tasks for 30 min.Generalized linear mixed-effects models(GLMMs)are used to analyze the relationship between HRV and operators'cognitive performance.Studies have shown that all indicators of HRV have a significant impact on the cognitive ability of operators.In both the low frequency(LF)and high frequency(HF),especially in the very low frequency(VLF)domain,HRV significantly correlates with the operator's cognition.Although the cognitive performance aggravates slightly within 30 min,increasing the humidity under fixed high temperatures does not exhibit an overall effect on cognitive performance.Henceforth,this study provides a guidance for safety limits of the operator's working duration.Moreover,VLF,LF,and HF domains might be potential physiological indicators to monitor the cognitive ability of operators.展开更多
The objective of this study was to develop an adaptive thermal comfort equation for naturally ventilated buildings in hot-humid climates. The study employed statistical meta-analysis of the American Society of Heating...The objective of this study was to develop an adaptive thermal comfort equation for naturally ventilated buildings in hot-humid climates. The study employed statistical meta-analysis of the American Society of Heating, Refrigerating and Air-Conditioning Engineers （ASHRAE） RP-884 database, which covered several climatic zones. The data were carefully sorted into three climate groups including hot-humid, hot-dry, and moderate and were analyzed separately. The results revealed that the adaptive equations for hot-humid and hot-dry climates were analogous with approximate regression coefficients of 0.6, which were nearly twice those of ASHRAE and European standards 55 and EN15251, respectively. The equation using the daily mean outdoor air temperature had the highest coefficient of determination for hot-humid climate, compared with other mean temperatures that considered acclimatization of previous days. Acceptable comfort ranges showed asymmetry and leaned toward operative temperatures below thermal neutrality for all climates. In the hot-humid climate, a lower comfort limit was not observed for naturally ventilated buitdings, and the adaptive equation was influenced by indoor air speed rather than indoor relative humidity. The new equation developed in this study can be applied to tropical climates and hot humid summer seasons of temperate climates.展开更多
Public buildings such as libraries consume a vast amount of cooling energy for maintaining a comfortable and stable indoor environment in summer,especially in the hot-humid climate.This study used a case study approac...Public buildings such as libraries consume a vast amount of cooling energy for maintaining a comfortable and stable indoor environment in summer,especially in the hot-humid climate.This study used a case study approach to discuss the effect of low-energy strategies that can be applied to improve indoor thermal environment and cooling energy consumption of library buildings in hot and humid cities like Nanning City(a southern city,China).The use of cooling window shutters(a shutter with the effects of shading and evaporative cooling)and ceiling fans for generating airflow was considered as applicable energy-saving measures in this study,and a university library was selected as the study building in which the two energy-saving measures were employed.The SET*and annual cooling load before and after the adoption of the proposed measures were quantitatively investigated with a building energy consumption simulation software(DesignBuilder).Simulation results showed that the daytime SET*values can be reduced by 3.0℃and 4.5℃respectively on a typical summer day after the use of the cooling shutters and ceiling fans.Moreover,the cooling loads can also be decreased by 8.4%and 16.6%respectively.Particularly,the combination of these two measures enabled the daytime SET*value and annual cooling load lower by 7.0℃and 60.8%respectively.展开更多
In hot-humid climates,particularly in sub-Saharan Africa(SSA),ambient temperatures and relative humidity are as high as 35°C and 84%,respectively,requiring the use of mechanical cooling systems for indoor thermal...In hot-humid climates,particularly in sub-Saharan Africa(SSA),ambient temperatures and relative humidity are as high as 35°C and 84%,respectively,requiring the use of mechanical cooling systems for indoor thermal comfort.Split-type vapor-compression air-conditioners(SVAC)are mainly used for space cooling in SSA and consume 60-80%of total energy consumption in commercial and public buildings.Appropriate control strategy of the indoor set-point temperature of SVAC can result in significant energy savings in these buildings.In this study,modeling and dynamic simulation have been conducted using EnergyPlus to predict the energy saving potential and indoor thermal comfort of buildings in hot-humid climates by controlling set-point temperature of the SVAC.In a case study,climatic data for Ghana,was used to predict the energy saving potential and indoor thermal comfort.The study results revealed that,to ensure indoor thermal comfort at high outdoor temperature condition of 35°C,the least and optimum set-point temperatures of the SVAC should be 21°C and 25°C,respectively.On the other hand,for low outdoor temperature condition,the least and optimum set-point temperatures were 22°C and 26°C,respectively.Considering 1-star and 2-star rated SVACs which are dominantly used in Ghana,operating at 21-25°C in the case of high outdoor conditions,and 22-26°C for low outdoor conditions relative to the least temperatures resulted in energy savings of 8-33%and 12-44%,respectively.展开更多
In a hot-humid tropical climate,indoor thermal performance can be enhanced by comfort ventilation.Indoor venti-lation depends upon building opening size.But risks involved in providing openings include ingress of mosq...In a hot-humid tropical climate,indoor thermal performance can be enhanced by comfort ventilation.Indoor venti-lation depends upon building opening size.But risks involved in providing openings include ingress of mosquitoes and insects which thrive in the tropical climate.A practical and prevalent option to prevent insects in ventilated dwellings of the tropical,hot-humid city of Chennai,India is through the use offly screens.Fly screens,when used over open-ings,prevent a certain quantum of solar radiation and wind from entering inside the rooms.Reduced direct solar radiation prevents the indoors from heating up,while reduced wind movement prevents the cross ventilation.There-fore,it is important to know the indoor thermal performance of ventilated rooms in the presence offly screens with changing opening sizes.The criterion to evaluate indoor thermal performance in this paper is indoor air temperature.The aim of this research is to investigate the influence offly screens on openings with varying sizes,in a naturally ventilated dwelling in the hot-humid climate of Chennai,India,during the summer period.The results of the study show thatfly screens raise the indoor air temperature when openings are in the range of 100%to 35%of the roomfloor area.There is no significant change in the indoor air temperature when the opening sizes are less than 30%of the roomfloor area.展开更多
Mosques have intermittent operational schedules with short-term occupancy during the five daily prayers.The occupancy level of the daily prayers is a fraction compared to the mandatory Friday prayers with full occupan...Mosques have intermittent operational schedules with short-term occupancy during the five daily prayers.The occupancy level of the daily prayers is a fraction compared to the mandatory Friday prayers with full occupancy.Usually,the same thermal control mechanism is operated within the same large prayer hall to maintain the thermal comfort of the occupants.Yet,the comfort requirements are often not met due to the short span of operation during prayer times.Nevertheless,mosques have a very high energy usage as the same energyintensive system is operated even during minimal occupancy profiles.The current research aims at using a passive approach towards design to achieve the comfort conditions during the low occupancy daily prayer times without employing mechanical intervention.Numerical simulations are carried out on a validated model of the case study building to investigate the impact of the west-facing Qiblah wall as the congregation stands in proximity to this wall.The design alternatives are tested in conjunction with ventilation strategies to holistically assess the thermal comfort of the occupants.Results show that as much as 4-6℃reduction in indoor wall surface temperature can be achieved with a suitable Qiblah wall design,which reduces the mean radiant temperature of the occupants by 2-4℃.Combined with ventilation strategies,thermal comfort can be significantly improved by at least 40%for the prayers during the hottest times of the day,and as much as 80%for night-time prayers.Results suggest that suitable comfort conditions can be achieved without the need for air-conditioning for at least two or three of the five daily prayers.展开更多
基金supported by the National Science Foundation of China(Grant Nos.42088101 and 42275172).
文摘Land–atmosphere coupling and sea surface temperature(SST)anomalies both have essential impacts on weather and climate extremes.Based on the ERA5 reanalysis dataset and the CESM1.2.2 model,this study investigates the influence of land–atmosphere coupling on summer extreme hot-humid events(EHHE)over southern Eurasia under different SST backgrounds.The results suggest that coupling causes near-surface air temperature increases that exceed 0.5℃.From 1961 to 2020,the frequency of EHHE has continuously increased,and is closely related to soil moisture anomalies in the northern Indian Peninsula(IDP)and the middle and lower reaches of the Yangtze River(YRB).Numerical simulations further demonstrate that land–atmosphere coupling raises the risk of EHHE by 25.4%.In a typical El Niño SST background state,intensified land–atmosphere coupling tends to produce notable increases in the frequency of EHHE.The dominant processes that land–atmosphere coupling affects the EHHE variations are evidently different between these two regions.Land surface thermal anomalies predominate in the IDP,while moisture conditions are more critical in the YRB.When warm SST anomalies exist,dry soil anomalies in the IDP are prominent,and evaporation is constrained,increasing sensible heat flux.Positive geopotential height anomalies are significant,combined with adiabatic warming induced by descending motion and a noticeable warm center in the near-surface atmosphere.The southward shift of the westerly jet enhances divergence over YRB.The anticyclonic circulation anomalies over the western Pacific are conducive to guiding moisture transport to the YRB,providing a favorable circulation background for the development of summer EHHE.
文摘Heat strain experienced by individuals wearing chemical protective clothing(CPC)is severe and dangerous especially in hot-humid environment.The development of material science and interdisciplinary studies including ergonomics,physiology and heat transfer is urgently required for the reduction of heat strain.The aim of this paper was to study the relationship among clothing thermal properties,physiological responses and environmental conditions.Three kinds of CPC were selected.Eight participants wore CPC and walked(4 km/h,two slopes with 5%and 10%)on a treadmill in an environment with(35±0.5)℃ and RH of(60±5)%.Core temperature,mean skin temperature,heart rate,heat storage and tolerance time were recorded and analyzed.Physiological responses were significantly affected by the clothing thermal properties and activity intensity in hot-humid environment.The obtained results can help further development of heat strain model.New materials with lower evaporative resistance and less weight are necessary to release the heat strain in hot-humid environments.
基金Project(50838009) supported by the National Natural Science Foundation of ChinaProject(2006BAJ01A05) supported by the National Key Technologies R&D Program of ChinaProject(CSTC,2008AB7110) supported by Key Technologies R & D Program of Chongqing City,China
文摘The current ventilation condition of the hot and humid regions was analyzed through on-site investigation. It is found that residents in this region expect to improve indoor thermal environment through natural ventilation as much as possible. Then,it comes to a conclusion by the field test that natural ventilation has certain practical effect on improving indoor thermal environment. CFD simulation software is employed to verify the test result. Based on PMV modified model,and according to norms,geography and climate combined with the measured and simulated results,the application of the time and effectiveness of natural ventilation in hot and humid region were analyzed,to some extent,providing a basis for reducing the air-conditioner's runtime with natural ventilation.
基金funded by General Motors Global Research and Development Center(Grant No.:PS21025708)
文摘The effect of hot-humid exposure(i.e., 40 C and 98% R.H.) on the quasi-static strength of the adhesive-bonded aluminum alloys was studied. Test results show that the hot-humid exposure leads to the significant decrease in the joint strength and the change of the failure mode from a mixed cohesive and adhesive failure with cohesive failure being dominant to adhesive failure being dominant. Careful analyses of the results reveal that the physical bond is likely responsible for the bond adhesion between L adhesive and aluminum substrates. The reduction in joint strength and the change of the failure mode resulted from the degradation in bond adhesion, which was primarily attributed to the corrosion of aluminum substrate. In addition, the elevated temperature exposure significantly accelerated the corrosion reaction of aluminum, which accelerated the degradation in joint strength.
文摘Objective This study was aimed to explore the physiological changes and the effect of heat acclimation training via a randomized control trial study.Methods Forty healthy male volunteers were chosen and divided into experimental group and control group randomly.Those in experimental group received heat acclimation training including but not limited to meditation,unarmed run,yoga,and stepping in hot lab environment.And then,subjective feeling,rectal temperature,average skin temperature,and sweat electrolytes concentration were detected in order to describe their physiological changes.Before and after the training,both groups received some tests and their 3 000 m run-race time,nervous reaction time and subjective perception scores were recorded to evaluate the effect of acclimation training.Results(1) There was no difference in 3 000 m between the 2 groups in the same environment.Subjects' 3 000 m race time in experimental group was obviously shortened than that in control group in room temperature environment(t=2.326,P<0.05).And subjects' 3 000 m race time in experimental group was obviously shortened than that in control group in hot-humid environment(t=4.518,P<0.01).(2) Subjects' reaction time(RT) in experimental group was shortened than that in control group in room temperature environment(Z=11.258,P<0.05).And Subjects' RT in experimental group was sharply shortened than that in control group in hot-humid environment(Z=6.519,P<0.01).(3) No difference between the experimental and control groups was observed in subjective perception score(SPS) in room temperature environment.But subjects' SPS in experimental group was obviously lowered than that in control group and in hot-humid environment(t=17.958,P<0.01).(4)Anal temperature(AT) was lowered during training,while the change of mean skin temperature(MST) was not significant.Sweat sodium concentration(SSC) was lowered during training.SPS continued to decrease and entered plateau on the 13 th day after training.(5) After acclimation training,the working capacity of the experimental group in hot-humid environment was over 85%of that in room temperature environment.While subjects' working capacity in control group in hot-humid environment was about 80%of that in room temperature environment.Conclusion Hot-humid environment acclimation training improved the working capacity.After training,subjects' working capacity in hot-humid environment remained over 85%of that in room temperature environment,which was higher than that of those subjects who did not take part in training.
基金supported by the National Natural Science Foundation of China(No.72374118,72304165,72204136)the Beijing Natural Science Foundation(No.L243005)the assistance provided by the State Key Laboratory of Nuclear Power Safety Technology and Equipment,China Nuclear Power Engineering Co.,Ltd.(No.K-A2021.402).
文摘When sudden disasters such as earthquakes and tsunamis culminate in the outage of control systems in nuclear power plants,the operators may be exposed to extremely hot-humid environmental conditions while still facing demanding cognitive tasks.To investigate how their cognitive performance is related to their heart rate variability(HRV),we exposed nuclear power plant operators to four high temperature and humidity environments and measured their HRV during seven different cognitive tasks for 30 min.Generalized linear mixed-effects models(GLMMs)are used to analyze the relationship between HRV and operators'cognitive performance.Studies have shown that all indicators of HRV have a significant impact on the cognitive ability of operators.In both the low frequency(LF)and high frequency(HF),especially in the very low frequency(VLF)domain,HRV significantly correlates with the operator's cognition.Although the cognitive performance aggravates slightly within 30 min,increasing the humidity under fixed high temperatures does not exhibit an overall effect on cognitive performance.Henceforth,this study provides a guidance for safety limits of the operator's working duration.Moreover,VLF,LF,and HF domains might be potential physiological indicators to monitor the cognitive ability of operators.
文摘The objective of this study was to develop an adaptive thermal comfort equation for naturally ventilated buildings in hot-humid climates. The study employed statistical meta-analysis of the American Society of Heating, Refrigerating and Air-Conditioning Engineers （ASHRAE） RP-884 database, which covered several climatic zones. The data were carefully sorted into three climate groups including hot-humid, hot-dry, and moderate and were analyzed separately. The results revealed that the adaptive equations for hot-humid and hot-dry climates were analogous with approximate regression coefficients of 0.6, which were nearly twice those of ASHRAE and European standards 55 and EN15251, respectively. The equation using the daily mean outdoor air temperature had the highest coefficient of determination for hot-humid climate, compared with other mean temperatures that considered acclimatization of previous days. Acceptable comfort ranges showed asymmetry and leaned toward operative temperatures below thermal neutrality for all climates. In the hot-humid climate, a lower comfort limit was not observed for naturally ventilated buitdings, and the adaptive equation was influenced by indoor air speed rather than indoor relative humidity. The new equation developed in this study can be applied to tropical climates and hot humid summer seasons of temperate climates.
基金supported from the National Natural Science Foundation of China(No.51968003)the Guangxi Science and Technology Project(No.AB16380193).
文摘Public buildings such as libraries consume a vast amount of cooling energy for maintaining a comfortable and stable indoor environment in summer,especially in the hot-humid climate.This study used a case study approach to discuss the effect of low-energy strategies that can be applied to improve indoor thermal environment and cooling energy consumption of library buildings in hot and humid cities like Nanning City(a southern city,China).The use of cooling window shutters(a shutter with the effects of shading and evaporative cooling)and ceiling fans for generating airflow was considered as applicable energy-saving measures in this study,and a university library was selected as the study building in which the two energy-saving measures were employed.The SET*and annual cooling load before and after the adoption of the proposed measures were quantitatively investigated with a building energy consumption simulation software(DesignBuilder).Simulation results showed that the daytime SET*values can be reduced by 3.0℃and 4.5℃respectively on a typical summer day after the use of the cooling shutters and ceiling fans.Moreover,the cooling loads can also be decreased by 8.4%and 16.6%respectively.Particularly,the combination of these two measures enabled the daytime SET*value and annual cooling load lower by 7.0℃and 60.8%respectively.
文摘In hot-humid climates,particularly in sub-Saharan Africa(SSA),ambient temperatures and relative humidity are as high as 35°C and 84%,respectively,requiring the use of mechanical cooling systems for indoor thermal comfort.Split-type vapor-compression air-conditioners(SVAC)are mainly used for space cooling in SSA and consume 60-80%of total energy consumption in commercial and public buildings.Appropriate control strategy of the indoor set-point temperature of SVAC can result in significant energy savings in these buildings.In this study,modeling and dynamic simulation have been conducted using EnergyPlus to predict the energy saving potential and indoor thermal comfort of buildings in hot-humid climates by controlling set-point temperature of the SVAC.In a case study,climatic data for Ghana,was used to predict the energy saving potential and indoor thermal comfort.The study results revealed that,to ensure indoor thermal comfort at high outdoor temperature condition of 35°C,the least and optimum set-point temperatures of the SVAC should be 21°C and 25°C,respectively.On the other hand,for low outdoor temperature condition,the least and optimum set-point temperatures were 22°C and 26°C,respectively.Considering 1-star and 2-star rated SVACs which are dominantly used in Ghana,operating at 21-25°C in the case of high outdoor conditions,and 22-26°C for low outdoor conditions relative to the least temperatures resulted in energy savings of 8-33%and 12-44%,respectively.
文摘In a hot-humid tropical climate,indoor thermal performance can be enhanced by comfort ventilation.Indoor venti-lation depends upon building opening size.But risks involved in providing openings include ingress of mosquitoes and insects which thrive in the tropical climate.A practical and prevalent option to prevent insects in ventilated dwellings of the tropical,hot-humid city of Chennai,India is through the use offly screens.Fly screens,when used over open-ings,prevent a certain quantum of solar radiation and wind from entering inside the rooms.Reduced direct solar radiation prevents the indoors from heating up,while reduced wind movement prevents the cross ventilation.There-fore,it is important to know the indoor thermal performance of ventilated rooms in the presence offly screens with changing opening sizes.The criterion to evaluate indoor thermal performance in this paper is indoor air temperature.The aim of this research is to investigate the influence offly screens on openings with varying sizes,in a naturally ventilated dwelling in the hot-humid climate of Chennai,India,during the summer period.The results of the study show thatfly screens raise the indoor air temperature when openings are in the range of 100%to 35%of the roomfloor area.There is no significant change in the indoor air temperature when the opening sizes are less than 30%of the roomfloor area.
文摘Mosques have intermittent operational schedules with short-term occupancy during the five daily prayers.The occupancy level of the daily prayers is a fraction compared to the mandatory Friday prayers with full occupancy.Usually,the same thermal control mechanism is operated within the same large prayer hall to maintain the thermal comfort of the occupants.Yet,the comfort requirements are often not met due to the short span of operation during prayer times.Nevertheless,mosques have a very high energy usage as the same energyintensive system is operated even during minimal occupancy profiles.The current research aims at using a passive approach towards design to achieve the comfort conditions during the low occupancy daily prayer times without employing mechanical intervention.Numerical simulations are carried out on a validated model of the case study building to investigate the impact of the west-facing Qiblah wall as the congregation stands in proximity to this wall.The design alternatives are tested in conjunction with ventilation strategies to holistically assess the thermal comfort of the occupants.Results show that as much as 4-6℃reduction in indoor wall surface temperature can be achieved with a suitable Qiblah wall design,which reduces the mean radiant temperature of the occupants by 2-4℃.Combined with ventilation strategies,thermal comfort can be significantly improved by at least 40%for the prayers during the hottest times of the day,and as much as 80%for night-time prayers.Results suggest that suitable comfort conditions can be achieved without the need for air-conditioning for at least two or three of the five daily prayers.
