Niobium capacitor uses electrolytic Nb2O5 as dielectric layer formed on surface of porous niobium anode through electrolytic reaction. Analysis of Scanning Electronics Microscope (SEM) combined with X-ray Photoemissio...Niobium capacitor uses electrolytic Nb2O5 as dielectric layer formed on surface of porous niobium anode through electrolytic reaction. Analysis of Scanning Electronics Microscope (SEM) combined with X-ray Photoemission Spectrum(XPS) shows that the formed niobium oxide dielectric consists of not only Nb2O5, but also two kinds of low valence niobium NbO2 and NbO oxide. When using different electrolytic reaction conditions, different valence niobium oxide shows different relative content. The fact provides an important basis for analyzing and improving performances of niobium capacitor.展开更多
For three weeks in October 2009, the U.S. Department of Energy hosted the Solar Decathlon Competition in which 20 teams of college and university students competed to design, build, and operate their own version of a ...For three weeks in October 2009, the U.S. Department of Energy hosted the Solar Decathlon Competition in which 20 teams of college and university students competed to design, build, and operate their own version of a solar-powered house. Team North＇s mission was to deliver North House, a compelling, marketable solar powered home for people with active lifestyles, while building Canada＇s next generation of leaders in sustainable engineering, business and design. This paper deals with a solar-assisted space heating system that was studied as a potential design for the competition. Among several other conclusions, it was found that using a solar-assisted in-floor heating system can decrease the energy consumption to only 8% of the case without the in-floor loop.展开更多
The Iraqi climate is extremely hot and arid zone covers a belt between latitude （29°N to 36°N）. The energy required for air conditioning of Iraqi buildings is about 60% of the entire energy consumption in ...The Iraqi climate is extremely hot and arid zone covers a belt between latitude （29°N to 36°N）. The energy required for air conditioning of Iraqi buildings is about 60% of the entire energy consumption in buildings. This research deals with the possibility of using different technics for the reducing energy consumption in buildings by blocking or eliminates the effect of direct solar radiation in summer season. This study deals with different local insulation materials which were added to the south face of walls surface of Iraqi buildings, as well as built water spray system upon the exterior roof surface to minimize the effect of incident solar radiation upon the roofs and wall surfaces. The results showed that thermal conductivity of local insulation materials （papyrus） are very low, also the results showed that when using water spray roof system, gives good indication to use this method in hot arid rejoins.展开更多
We experimentally evaluate and optimize the time constant of solar irradiance absolute radiometer(SIAR). The systemic error introduced by variable time constant is studied by a finite element method. The results shown...We experimentally evaluate and optimize the time constant of solar irradiance absolute radiometer(SIAR). The systemic error introduced by variable time constant is studied by a finite element method. The results shown that, with a classic time constant of 30 s for SIAR, the systemic errors are 0.06% in the midday and 0.275% in the morning and afternoon. The uncertainty level which can be considered negligible for SIAR is also investigated, and it is suggested that the uncertainty level has to be less than 0.02%. Then, combining the requirement of international comparison with these two conclusions, we conclude that the suitable time constant for SIAR is 20 s.展开更多
According to the requirements of a solar dish-Brayton system,a centrifugal compressor stage with a minimum total pressure ratio of 5,an adiabatic efficiency above 75% and a surge margin more than 12% needs to be desig...According to the requirements of a solar dish-Brayton system,a centrifugal compressor stage with a minimum total pressure ratio of 5,an adiabatic efficiency above 75% and a surge margin more than 12% needs to be designed.A single stage,which consists of impeller,radial vaned diffuser,90° crossover and two rows of axial stators,was chosen to satisfy this system.To achieve the stage performance,an impeller with a 6:1 total pressure ratio and an adiabatic efficiency of 90% was designed and its preliminary geometry came from an in-house one-dimensional program.Radial vaned diffuser was applied downstream of the impeller.Two rows of axial stators after 90° crossover were added to guide the flow into axial direction.Since jet-wake flow,shockwave and boundary layer separation coexisted in the impeller-diffuser region,optimization on the radius ratio of radial diffuser vane inlet to impeller exit,diffuser vane inlet blade angle and number of diffuser vanes was carried out at design point.Finally,an optimized centrifugal compressor stage fulfilled the high expectations and presented proper performance.Numerical simulation showed that at design point the stage adiabatic efficiency was 79.93% and the total pressure ratio was 5.6.The surge margin was 15%.The performance map including 80%,90% and 100% design speed was also presented.展开更多
文摘Niobium capacitor uses electrolytic Nb2O5 as dielectric layer formed on surface of porous niobium anode through electrolytic reaction. Analysis of Scanning Electronics Microscope (SEM) combined with X-ray Photoemission Spectrum(XPS) shows that the formed niobium oxide dielectric consists of not only Nb2O5, but also two kinds of low valence niobium NbO2 and NbO oxide. When using different electrolytic reaction conditions, different valence niobium oxide shows different relative content. The fact provides an important basis for analyzing and improving performances of niobium capacitor.
文摘For three weeks in October 2009, the U.S. Department of Energy hosted the Solar Decathlon Competition in which 20 teams of college and university students competed to design, build, and operate their own version of a solar-powered house. Team North＇s mission was to deliver North House, a compelling, marketable solar powered home for people with active lifestyles, while building Canada＇s next generation of leaders in sustainable engineering, business and design. This paper deals with a solar-assisted space heating system that was studied as a potential design for the competition. Among several other conclusions, it was found that using a solar-assisted in-floor heating system can decrease the energy consumption to only 8% of the case without the in-floor loop.
文摘The Iraqi climate is extremely hot and arid zone covers a belt between latitude （29°N to 36°N）. The energy required for air conditioning of Iraqi buildings is about 60% of the entire energy consumption in buildings. This research deals with the possibility of using different technics for the reducing energy consumption in buildings by blocking or eliminates the effect of direct solar radiation in summer season. This study deals with different local insulation materials which were added to the south face of walls surface of Iraqi buildings, as well as built water spray system upon the exterior roof surface to minimize the effect of incident solar radiation upon the roofs and wall surfaces. The results showed that thermal conductivity of local insulation materials （papyrus） are very low, also the results showed that when using water spray roof system, gives good indication to use this method in hot arid rejoins.
基金supported by the National Natural Science Foundation of China(No.41474161)the National High Technology Research and Development Program of China(No.2015AA123703)
文摘We experimentally evaluate and optimize the time constant of solar irradiance absolute radiometer(SIAR). The systemic error introduced by variable time constant is studied by a finite element method. The results shown that, with a classic time constant of 30 s for SIAR, the systemic errors are 0.06% in the midday and 0.275% in the morning and afternoon. The uncertainty level which can be considered negligible for SIAR is also investigated, and it is suggested that the uncertainty level has to be less than 0.02%. Then, combining the requirement of international comparison with these two conclusions, we conclude that the suitable time constant for SIAR is 20 s.
基金supported by the National Natural Science Foundation of China(Grant No.51010007)China Scholarship Council(CSC)
文摘According to the requirements of a solar dish-Brayton system,a centrifugal compressor stage with a minimum total pressure ratio of 5,an adiabatic efficiency above 75% and a surge margin more than 12% needs to be designed.A single stage,which consists of impeller,radial vaned diffuser,90° crossover and two rows of axial stators,was chosen to satisfy this system.To achieve the stage performance,an impeller with a 6:1 total pressure ratio and an adiabatic efficiency of 90% was designed and its preliminary geometry came from an in-house one-dimensional program.Radial vaned diffuser was applied downstream of the impeller.Two rows of axial stators after 90° crossover were added to guide the flow into axial direction.Since jet-wake flow,shockwave and boundary layer separation coexisted in the impeller-diffuser region,optimization on the radius ratio of radial diffuser vane inlet to impeller exit,diffuser vane inlet blade angle and number of diffuser vanes was carried out at design point.Finally,an optimized centrifugal compressor stage fulfilled the high expectations and presented proper performance.Numerical simulation showed that at design point the stage adiabatic efficiency was 79.93% and the total pressure ratio was 5.6.The surge margin was 15%.The performance map including 80%,90% and 100% design speed was also presented.
