Performance of the proton exchange membrane fuel cell(PEMFC)is appreciably affected by the channel geometry.The branching structure of a plant leaf and human lung is an efficient network to distribute the nutrients in...Performance of the proton exchange membrane fuel cell(PEMFC)is appreciably affected by the channel geometry.The branching structure of a plant leaf and human lung is an efficient network to distribute the nutrients in the respective systems.The same nutrient transport system can be mimicked in the flow channel design of a PEMFC,to aid even reactant distribution and better water management.In this work,the effect of bio-inspired flow field designs such as lung and leaf channel design bipolar plates,on the performance of a PEMFC was examined experimentally at various operating conditions.A PEMFC of 49 cm2 area,with a Nafion 212 membrane with a 40%catalyst loading of 0.4 mg·cm-2 on the anode side and also 0.6 mg·cm-2 on the cathode side is assembled by incorporating the bio-inspired channel bipolar plate,and was tested on a programmable fuel-cell test station.The impact of the working parameters like reactants’relative humidity(RH),back pressure and fuel cell temperature on the performance of the fuel cell was examined;the operating pressure remains constant at 0.1 MPa.It was observed that the best performance was attained at a back pressure of 0.3 MPa,75°C operating temperature and 100%RH.The three flow channels were also compared at different operating pressures ranging from 0.1 MPa to 0.3 MPa,and the other parameters such as operating temperature,RH and back pressure were set as 75°C,100%and 0.3 MPa.The experimental outcomes of the PEMFC with bio-inspired channels were compared with the experimental results of a conventional triple serpentine flow field.It was observed that among the different flow channel designs considered,the leaf channel design gives the best output in terms of power density.Further,the experimental results of the leaf channel design were compared with those of the interdigitated leaf channel design.The PEMFC with the interdigitated leaf channel design was found to generate 6.72%more power density than the non-interdigitated leaf channel design.The fuel cell with interdigitated leaf channel design generated5.58%more net power density than the fuel cell with non-interdigitated leaf channel design after considering the parasitic losses.展开更多
In this study, indoor quality and environmental comfort were investigated in secondaiy school buildings located in the State of Kuwait. Comfort variables such as temperature and relative humidity (thermal comfort), no...In this study, indoor quality and environmental comfort were investigated in secondaiy school buildings located in the State of Kuwait. Comfort variables such as temperature and relative humidity (thermal comfort), noise (acoustic comfort), illumination (visual comfort), as well as allocated classroom floor area per student (spatial comfort) were measured. Data was collected over a 7-month period on a spot basis during school hours in student-occupied classrooms at 46 selected schools. The measured data was then compared to international guidelines and standards related to indoor environment quality. The data for noise and allocated space were shown to be in the comfort ranges in all the schools. However, 11% of the schools are not adequately illuminated, 33% had temperatures not within the recommended limits, and 22% of the schools had humidity levels either higher or lower than the recommended levels. Also, 9% of the schools had low illummation readings. In addition, during the data monitoring, a survey was conducted by which the student occupants completed a questionnaire so that subjective and objective evaluations could be compared. The findings of the questionnaire displayed significant correlations between the measured data and some ailments and other corr^laints experienced by the students. Ultimately, the results found in this research will provide a baseHne for comparison with future indoor environment quality assessments in buildings. Furthermore, recommendations are suggested in order to improve the environmental quality problems encountered in some of the schools, which may be beneficial for policymakers, facilities managers, and design engineers.展开更多
Air pollution surveys of formaldehyde（HCHO） were conducted in 2324 rooms decorated within one year in 2007-2009 in Hangzhou,China.The mean HCHO concentration（C HCHO） was 0.107 ± 0.095 mg/m 3,and 38.9% of samp...Air pollution surveys of formaldehyde（HCHO） were conducted in 2324 rooms decorated within one year in 2007-2009 in Hangzhou,China.The mean HCHO concentration（C HCHO） was 0.107 ± 0.095 mg/m 3,and 38.9% of samples exceeded the Chinese National Standard GB 50325-2010.Over the past 3 years,the C HCHO decreased with time（p 〈 0.05）.Relationships of potential factors to indoor C HCHO were also evaluated.C HCHO was related to temperature（T）,relative humidity（RH）,time duration of the windows and doors being closed before sampling（DC）,time duration from the end of decoration to sampling（DR） and source characteristics（d）.A model to relate indoor C HCHO to these five factors（T,RH,DC,DR,d） was established based on 298 samples（R 2 = 0.87）.Various factors contributed to C HCHO in the following order：T,43.7%;d,31.0%;DC,10.2%;DR,8.0%;RH,7.0%;specifically,meteorological conditions（i.e.,RH plus T） accounted for 50.7%.The coefficient of T and RH,R TH,was proposed to describe their combined influence on HCHO emission,which also had a linear relationship（R 2 = 0.9387） with HCHO release in a simulation chamber test.In addition,experiments confirm that it is a synergistic action as T and RH accelerate the release of HCHO,and that is a significant factor influencing indoor HCHO pollution.These achievements could lead to reference values of measures for the efficient reduction of indoor HCHO pollution.展开更多
文摘Performance of the proton exchange membrane fuel cell(PEMFC)is appreciably affected by the channel geometry.The branching structure of a plant leaf and human lung is an efficient network to distribute the nutrients in the respective systems.The same nutrient transport system can be mimicked in the flow channel design of a PEMFC,to aid even reactant distribution and better water management.In this work,the effect of bio-inspired flow field designs such as lung and leaf channel design bipolar plates,on the performance of a PEMFC was examined experimentally at various operating conditions.A PEMFC of 49 cm2 area,with a Nafion 212 membrane with a 40%catalyst loading of 0.4 mg·cm-2 on the anode side and also 0.6 mg·cm-2 on the cathode side is assembled by incorporating the bio-inspired channel bipolar plate,and was tested on a programmable fuel-cell test station.The impact of the working parameters like reactants’relative humidity(RH),back pressure and fuel cell temperature on the performance of the fuel cell was examined;the operating pressure remains constant at 0.1 MPa.It was observed that the best performance was attained at a back pressure of 0.3 MPa,75°C operating temperature and 100%RH.The three flow channels were also compared at different operating pressures ranging from 0.1 MPa to 0.3 MPa,and the other parameters such as operating temperature,RH and back pressure were set as 75°C,100%and 0.3 MPa.The experimental outcomes of the PEMFC with bio-inspired channels were compared with the experimental results of a conventional triple serpentine flow field.It was observed that among the different flow channel designs considered,the leaf channel design gives the best output in terms of power density.Further,the experimental results of the leaf channel design were compared with those of the interdigitated leaf channel design.The PEMFC with the interdigitated leaf channel design was found to generate 6.72%more power density than the non-interdigitated leaf channel design.The fuel cell with interdigitated leaf channel design generated5.58%more net power density than the fuel cell with non-interdigitated leaf channel design after considering the parasitic losses.
文摘In this study, indoor quality and environmental comfort were investigated in secondaiy school buildings located in the State of Kuwait. Comfort variables such as temperature and relative humidity (thermal comfort), noise (acoustic comfort), illumination (visual comfort), as well as allocated classroom floor area per student (spatial comfort) were measured. Data was collected over a 7-month period on a spot basis during school hours in student-occupied classrooms at 46 selected schools. The measured data was then compared to international guidelines and standards related to indoor environment quality. The data for noise and allocated space were shown to be in the comfort ranges in all the schools. However, 11% of the schools are not adequately illuminated, 33% had temperatures not within the recommended limits, and 22% of the schools had humidity levels either higher or lower than the recommended levels. Also, 9% of the schools had low illummation readings. In addition, during the data monitoring, a survey was conducted by which the student occupants completed a questionnaire so that subjective and objective evaluations could be compared. The findings of the questionnaire displayed significant correlations between the measured data and some ailments and other corr^laints experienced by the students. Ultimately, the results found in this research will provide a baseHne for comparison with future indoor environment quality assessments in buildings. Furthermore, recommendations are suggested in order to improve the environmental quality problems encountered in some of the schools, which may be beneficial for policymakers, facilities managers, and design engineers.
基金supported by the National Natural Science Foundation of China (No. 20890111,21137003,20977075)the National High-Tech Research and Development Program (863) of China (No. 2010AA064902)
文摘Air pollution surveys of formaldehyde（HCHO） were conducted in 2324 rooms decorated within one year in 2007-2009 in Hangzhou,China.The mean HCHO concentration（C HCHO） was 0.107 ± 0.095 mg/m 3,and 38.9% of samples exceeded the Chinese National Standard GB 50325-2010.Over the past 3 years,the C HCHO decreased with time（p 〈 0.05）.Relationships of potential factors to indoor C HCHO were also evaluated.C HCHO was related to temperature（T）,relative humidity（RH）,time duration of the windows and doors being closed before sampling（DC）,time duration from the end of decoration to sampling（DR） and source characteristics（d）.A model to relate indoor C HCHO to these five factors（T,RH,DC,DR,d） was established based on 298 samples（R 2 = 0.87）.Various factors contributed to C HCHO in the following order：T,43.7%;d,31.0%;DC,10.2%;DR,8.0%;RH,7.0%;specifically,meteorological conditions（i.e.,RH plus T） accounted for 50.7%.The coefficient of T and RH,R TH,was proposed to describe their combined influence on HCHO emission,which also had a linear relationship（R 2 = 0.9387） with HCHO release in a simulation chamber test.In addition,experiments confirm that it is a synergistic action as T and RH accelerate the release of HCHO,and that is a significant factor influencing indoor HCHO pollution.These achievements could lead to reference values of measures for the efficient reduction of indoor HCHO pollution.
