Tubular light pipes （i.e., solar tubes） are modern daylighting devices, which are designed to let confined interior spaces benefit from natural lighting. In tropical country, the use of sunlight for lighting is a ma...Tubular light pipes （i.e., solar tubes） are modern daylighting devices, which are designed to let confined interior spaces benefit from natural lighting. In tropical country, the use of sunlight for lighting is a major concern due to the heat associated with sunlight, which has the potential to increase the cost of cooling, thereby reducing the energy savings from the reduction in lighting load. To investigate the thermal and lighting performance of light pipes, a case study for a seminar room, in which light pipes are installed, is presented. Temperatures for the solar tube （dome and diffuser）, window and room were monitored continuously for 24 h periods. Results from the study indicate that the diffuser was on average 6.68 ~C higher than room temperature on a clear day between 7：00 a.m. and 4：00 p.m., while dome temperature was on average 4.45 ~C higher than diffuser＇s temperature during the same period. This large thermal gradient in the day between dome, diffuser and room can significantly increase the cost of maintaining thermal comfort of 25 ~C, in the room. Another finding was the phenomenon of light pipes acting as a heat pumping the night, because it extracts heat from the room during the night between 7：00 p.m. and 4：00 a.m. This occurred because dome temperature is always smaller than diffuser and room temperature in the night. Therefore, for energy savings to be realized from light pipes, thermal performance must be taken into consideration in the analysis of energy savings from light pipes.展开更多
Daylight is one of the essential criteria for decent housing.However,in an urban kampung,access to daylight is limited due to the high-density population in urban Kampung Kota.This study aims to improve the visual and...Daylight is one of the essential criteria for decent housing.However,in an urban kampung,access to daylight is limited due to the high-density population in urban Kampung Kota.This study aims to improve the visual and thermal conditions by modifying the aperture of the light pipe based on visual daylight distribution,illuminance level,and thermal conditions in multi-storey houses in hot-humid climates.Light pipe was developed experi-mentally through the simulation model to investigate the performance and impact on the visual and thermal conditions like operational temperature and RH in densely populated Kampung Kota without vertical apertures.According to the results,the two-aperture light pipe residential space enhanced the current situation but did not fulfill the standards.The two aperture light pipe visually improved daylight distribution by 1.05%-31.36%and illumination level by 8.4%-14.8%.We also found that light pipe also impacts thermal conditions with a 10.92%RH reduction while at the same time increasing temperature up to 10.57%.Therefore,it can be concluded that a two-aperture light pipe has the potential to be applied to actual conditions in hot-humid climates.展开更多
The even and transparent nanometer TiO2 thin films named DegussaP25 as photocatalysis deposited on the surface of diffusers of solar light pipe were prepared by sol-gel processing.The rugged side of the diffusers of s...The even and transparent nanometer TiO2 thin films named DegussaP25 as photocatalysis deposited on the surface of diffusers of solar light pipe were prepared by sol-gel processing.The rugged side of the diffusers of solar light pipe was coated evenly with DegussaP25 solution for the quality of 1.75 g.The experiments had showed that when the coated side was away from the sun the lighting degree may be reduced compared with that facing the sun.The average reduction was only 3.03%,which would not have a significant impact on lighting.Diffusers are important parts of a light pipe which can diffuse light evenly to the place needed to be illuminated.The experiments showed that in a sunny summer day under the direct sunlight,the solar light pipe combined with photocatalysis could reduce the formaldehyde volume fraction in a box of 0.1 m3 from 1.0×10-6 to 0.16×10-6.After 1 h of photodegradation the formaldehyde volume changed from 1.0×10-6 down to 0.1×10-6 with faster and more complete degradation of formaldehyde.The rate of degradation under cloudy and partly cloudy conditions was slower than that under sunny conditions.It was slower in winter than in summer under sunny conditions.The experimental results also showed that the performance of photocatalysis combined with diffusers of light pipe had better effect in a small space.The performance in large space,such as open space,will be the next work in the future,which will be a great challenge.展开更多
The following article has been retracted due to the fact that it cannot be accepted as Duplicate Publication. The Editorial Board takes a very strong respect to the author’s situation on this matter. This paper publi...The following article has been retracted due to the fact that it cannot be accepted as Duplicate Publication. The Editorial Board takes a very strong respect to the author’s situation on this matter. This paper published in Journal of Power and Energy Engineering Vol.3 No.4, April 2015, has been removed from this site.展开更多
This work aims to improve the thermal performance of a light emitting diode(LED) module by employing a novelly assembled heat pipe heat sink. The heat pipe was embedded into the heat sink by a phase change expansion a...This work aims to improve the thermal performance of a light emitting diode(LED) module by employing a novelly assembled heat pipe heat sink. The heat pipe was embedded into the heat sink by a phase change expansion assembly(PCEA) process, which was developed by both finite element(FE) analysis and experiments. Heat transfer performance and optical performance of the LED modules were experimentally investigated and discussed. Compared to the LED module with a traditionally assembled heat pipe heat sink, the LED module employing the PCEA process exhibits about 20% decrease in the thermal resistance from the MCPCB to the heat pipe. The junction temperature is 4% lower and the luminous flux is 2% higher. The improvement in the thermal and optical performance is important to the high power LED applications.展开更多
随着LCOS(Liquid Crystal on Silicon)技术的发展,投影仪趋于微型化,传统的UHP(Ultra High Performance)光源已经不适合作为微投系统的光源。使用LED阵列作为微投系统的光源,分别采用CPC(Compound Parabolic Con-centrator)集光器和锥...随着LCOS(Liquid Crystal on Silicon)技术的发展,投影仪趋于微型化,传统的UHP(Ultra High Performance)光源已经不适合作为微投系统的光源。使用LED阵列作为微投系统的光源,分别采用CPC(Compound Parabolic Con-centrator)集光器和锥形光棒来耦合光束,使光源发出的光束会聚在LCOS上。分析结果表明,这两种照明系统都具有很好的调节光束角度和收集光束的能力,并在微型投影仪中实现高效的均匀照明。展开更多
文摘Tubular light pipes （i.e., solar tubes） are modern daylighting devices, which are designed to let confined interior spaces benefit from natural lighting. In tropical country, the use of sunlight for lighting is a major concern due to the heat associated with sunlight, which has the potential to increase the cost of cooling, thereby reducing the energy savings from the reduction in lighting load. To investigate the thermal and lighting performance of light pipes, a case study for a seminar room, in which light pipes are installed, is presented. Temperatures for the solar tube （dome and diffuser）, window and room were monitored continuously for 24 h periods. Results from the study indicate that the diffuser was on average 6.68 ~C higher than room temperature on a clear day between 7：00 a.m. and 4：00 p.m., while dome temperature was on average 4.45 ~C higher than diffuser＇s temperature during the same period. This large thermal gradient in the day between dome, diffuser and room can significantly increase the cost of maintaining thermal comfort of 25 ~C, in the room. Another finding was the phenomenon of light pipes acting as a heat pumping the night, because it extracts heat from the room during the night between 7：00 p.m. and 4：00 a.m. This occurred because dome temperature is always smaller than diffuser and room temperature in the night. Therefore, for energy savings to be realized from light pipes, thermal performance must be taken into consideration in the analysis of energy savings from light pipes.
基金funded by the Directorate of Research and De-velopment,Universitas Indonesia under Hibah PUTI 2022 (grant no.NKB-332/UN2.RST/HKP.05.00/2022).
文摘Daylight is one of the essential criteria for decent housing.However,in an urban kampung,access to daylight is limited due to the high-density population in urban Kampung Kota.This study aims to improve the visual and thermal conditions by modifying the aperture of the light pipe based on visual daylight distribution,illuminance level,and thermal conditions in multi-storey houses in hot-humid climates.Light pipe was developed experi-mentally through the simulation model to investigate the performance and impact on the visual and thermal conditions like operational temperature and RH in densely populated Kampung Kota without vertical apertures.According to the results,the two-aperture light pipe residential space enhanced the current situation but did not fulfill the standards.The two aperture light pipe visually improved daylight distribution by 1.05%-31.36%and illumination level by 8.4%-14.8%.We also found that light pipe also impacts thermal conditions with a 10.92%RH reduction while at the same time increasing temperature up to 10.57%.Therefore,it can be concluded that a two-aperture light pipe has the potential to be applied to actual conditions in hot-humid climates.
基金supported by the National Natural Science Foundation of China (Grant No.50476036)
文摘The even and transparent nanometer TiO2 thin films named DegussaP25 as photocatalysis deposited on the surface of diffusers of solar light pipe were prepared by sol-gel processing.The rugged side of the diffusers of solar light pipe was coated evenly with DegussaP25 solution for the quality of 1.75 g.The experiments had showed that when the coated side was away from the sun the lighting degree may be reduced compared with that facing the sun.The average reduction was only 3.03%,which would not have a significant impact on lighting.Diffusers are important parts of a light pipe which can diffuse light evenly to the place needed to be illuminated.The experiments showed that in a sunny summer day under the direct sunlight,the solar light pipe combined with photocatalysis could reduce the formaldehyde volume fraction in a box of 0.1 m3 from 1.0×10-6 to 0.16×10-6.After 1 h of photodegradation the formaldehyde volume changed from 1.0×10-6 down to 0.1×10-6 with faster and more complete degradation of formaldehyde.The rate of degradation under cloudy and partly cloudy conditions was slower than that under sunny conditions.It was slower in winter than in summer under sunny conditions.The experimental results also showed that the performance of photocatalysis combined with diffusers of light pipe had better effect in a small space.The performance in large space,such as open space,will be the next work in the future,which will be a great challenge.
文摘The following article has been retracted due to the fact that it cannot be accepted as Duplicate Publication. The Editorial Board takes a very strong respect to the author’s situation on this matter. This paper published in Journal of Power and Energy Engineering Vol.3 No.4, April 2015, has been removed from this site.
基金Projects(51375177,U1401249,51405161)supported by the National Natural Science Foundation of ChinaProject(2014M560659)supported by the Postdoctoral Science Foundation of ChinaProject(2014B090901065)supported by the Science and Technology Planning Project for Industry-University-Research Cooperation in Guangdong Province,China
文摘This work aims to improve the thermal performance of a light emitting diode(LED) module by employing a novelly assembled heat pipe heat sink. The heat pipe was embedded into the heat sink by a phase change expansion assembly(PCEA) process, which was developed by both finite element(FE) analysis and experiments. Heat transfer performance and optical performance of the LED modules were experimentally investigated and discussed. Compared to the LED module with a traditionally assembled heat pipe heat sink, the LED module employing the PCEA process exhibits about 20% decrease in the thermal resistance from the MCPCB to the heat pipe. The junction temperature is 4% lower and the luminous flux is 2% higher. The improvement in the thermal and optical performance is important to the high power LED applications.
文摘随着LCOS(Liquid Crystal on Silicon)技术的发展,投影仪趋于微型化,传统的UHP(Ultra High Performance)光源已经不适合作为微投系统的光源。使用LED阵列作为微投系统的光源,分别采用CPC(Compound Parabolic Con-centrator)集光器和锥形光棒来耦合光束,使光源发出的光束会聚在LCOS上。分析结果表明,这两种照明系统都具有很好的调节光束角度和收集光束的能力,并在微型投影仪中实现高效的均匀照明。
