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
Optical surface scattering analyses based on diffractive optics (DO) are typically applied to one surface;however, there is a need for simulating surface scattering losses for devices having many surface interactions ...Optical surface scattering analyses based on diffractive optics (DO) are typically applied to one surface;however, there is a need for simulating surface scattering losses for devices having many surface interactions such as light pipes. Light pipes are often simulated with geometric optics (GO) using ray tracing, where surface scattering is driven by the surface slope distribution. In the DO case, surface scattering analyses depend on the spatial frequency distribution and amplitude as well as wavelength, with the sinusoidal grating as a fundamental basis. A better understanding of the link, or transition, between DO and GO scattering domains would be helpful for efficiently incorporating scattering loss analyses into ray trace simulations. A formula for the root-mean-square (rms) scattered angle width of a sinusoidal reflection grating that depends only on the surface rms slope is derived from the nonparaxial scalar diffraction theory, thereby linking it to GO. The scatter angle’s mean and rms width are evaluated over a range of grating amplitudes and periods using scalar theory and full vector simulations from the COMSOL® wave optic module for a sinusoidal reflection grating. The conditions under which the diffraction-based solution closely approximates the GO solution, as predicted by the rms slope, are identified. Close agreement is shown between the DO and GO solutions for the same surface rms slope scattering loss due to angular filtering near the critical angle of a total internal reflection (TIR) glass-to-air interface.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
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.
文摘Optical surface scattering analyses based on diffractive optics (DO) are typically applied to one surface;however, there is a need for simulating surface scattering losses for devices having many surface interactions such as light pipes. Light pipes are often simulated with geometric optics (GO) using ray tracing, where surface scattering is driven by the surface slope distribution. In the DO case, surface scattering analyses depend on the spatial frequency distribution and amplitude as well as wavelength, with the sinusoidal grating as a fundamental basis. A better understanding of the link, or transition, between DO and GO scattering domains would be helpful for efficiently incorporating scattering loss analyses into ray trace simulations. A formula for the root-mean-square (rms) scattered angle width of a sinusoidal reflection grating that depends only on the surface rms slope is derived from the nonparaxial scalar diffraction theory, thereby linking it to GO. The scatter angle’s mean and rms width are evaluated over a range of grating amplitudes and periods using scalar theory and full vector simulations from the COMSOL® wave optic module for a sinusoidal reflection grating. The conditions under which the diffraction-based solution closely approximates the GO solution, as predicted by the rms slope, are identified. Close agreement is shown between the DO and GO solutions for the same surface rms slope scattering loss due to angular filtering near the critical angle of a total internal reflection (TIR) glass-to-air interface.
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.
