The Experts below are selected from a list of 201 Experts worldwide ranked by ideXlab platform

Matthew Boyd - One of the best experts on this subject based on the ideXlab platform.

  • analytical model for solar irradiance near a planar vertical Diffuse Reflector formulation validation and simulations
    Solar Energy, 2013
    Co-Authors: Matthew Boyd
    Abstract:

    Abstract An analytical model is formulated for the irradiance on a surface (collector) with a rear (opposite the sun) planar vertical Diffuse Reflector, as is common for a lower roof on a multi-story building. The vast majority of research on solar Reflectors has been for specular, or mirror, Reflectors, with any Diffuse reflections modeled about the specular reflection angle. This model is capable of calculating incident and reflected direct, Diffuse, and ground-reflected radiation using components borrowed from the Hay, Davies, Klucher, Reindl (HDKR) irradiance model, and is easily implemented in any computation programming software capable of numeric integration. The model accounts for Reflector edge effects and shading of Diffuse and ground-reflected radiation by the Reflector, but it does not account for shading of beam radiation by the Reflector. The model shows good overall agreement with experimental tests, and is three percentage points more accurate than a standard radiation model for tilted surfaces. The model indicates that a planar vertical Diffuse Reflector increases the irradiance at high clearness indices and low Reflector incidence angles, and decreases the irradiance otherwise. Increasing the Reflector height and decreasing the collector pitch and distance between the collector and Reflector increases the irradiance during clear periods, but decreases the irradiance, to a lesser absolute extent, during cloudy periods. Annual simulations show a gain in winter insolation and a loss in summer insolation for an average collector/Reflector, with an increase in annual insolation for collectors near high albedo Reflectors.

  • Analytical model for solar irradiance near a planar vertical Diffuse Reflector – Formulation, validation, and simulations
    Solar Energy, 2013
    Co-Authors: Matthew Boyd
    Abstract:

    Abstract An analytical model is formulated for the irradiance on a surface (collector) with a rear (opposite the sun) planar vertical Diffuse Reflector, as is common for a lower roof on a multi-story building. The vast majority of research on solar Reflectors has been for specular, or mirror, Reflectors, with any Diffuse reflections modeled about the specular reflection angle. This model is capable of calculating incident and reflected direct, Diffuse, and ground-reflected radiation using components borrowed from the Hay, Davies, Klucher, Reindl (HDKR) irradiance model, and is easily implemented in any computation programming software capable of numeric integration. The model accounts for Reflector edge effects and shading of Diffuse and ground-reflected radiation by the Reflector, but it does not account for shading of beam radiation by the Reflector. The model shows good overall agreement with experimental tests, and is three percentage points more accurate than a standard radiation model for tilted surfaces. The model indicates that a planar vertical Diffuse Reflector increases the irradiance at high clearness indices and low Reflector incidence angles, and decreases the irradiance otherwise. Increasing the Reflector height and decreasing the collector pitch and distance between the collector and Reflector increases the irradiance during clear periods, but decreases the irradiance, to a lesser absolute extent, during cloudy periods. Annual simulations show a gain in winter insolation and a loss in summer insolation for an average collector/Reflector, with an increase in annual insolation for collectors near high albedo Reflectors.

Yongjo Park - One of the best experts on this subject based on the ideXlab platform.

Tae Geun Kim - One of the best experts on this subject based on the ideXlab platform.

  • al2o3 aln al based backside Diffuse Reflector for high brightness 370 nm algan ultraviolet light emitting diodes
    Journal of Alloys and Compounds, 2019
    Co-Authors: Tae Hoon Park, Tae Ho Lee, Tae Geun Kim
    Abstract:

    Abstract We report an Al2O3/AlN/Al-based backside Diffuse Reflector for near-ultraviolet light-emitting diodes (NUV LEDs), and its superiority compared with conventional Reflectors. After fabrication of LEDs, a sapphire (Al2O3) surface was UV-irradiated to utilize the Diffuse reflection effect by roughening the surface. Then, a thermally treated AlN layer was deposited on it, to obtain a mirror-like surface, before deposition of Al. The reflectance increased by 1.3% and 3.9% for these Al2O3/AlN/Al Reflectors without and with surface treatment, respectively, compared with an Al Reflector. These Reflectors were then used with 370 nm AlGaN NUV LEDs, and the performances of LEDs without and with an Al Reflector were compared. As a result, the NUV LED with both thermally and UV-treated AlN/Al Reflector exhibited the best performance, and its output power and electroluminescence intensity were higher by 82.7% and 41.9%, respectively, than those of the LED without a Reflector.

  • Al2O3/AlN/Al-based backside Diffuse Reflector for high-brightness 370-nm AlGaN ultraviolet light-emitting diodes
    Journal of Alloys and Compounds, 2019
    Co-Authors: Tae Hoon Park, Tae Ho Lee, Tae Geun Kim
    Abstract:

    Abstract We report an Al2O3/AlN/Al-based backside Diffuse Reflector for near-ultraviolet light-emitting diodes (NUV LEDs), and its superiority compared with conventional Reflectors. After fabrication of LEDs, a sapphire (Al2O3) surface was UV-irradiated to utilize the Diffuse reflection effect by roughening the surface. Then, a thermally treated AlN layer was deposited on it, to obtain a mirror-like surface, before deposition of Al. The reflectance increased by 1.3% and 3.9% for these Al2O3/AlN/Al Reflectors without and with surface treatment, respectively, compared with an Al Reflector. These Reflectors were then used with 370 nm AlGaN NUV LEDs, and the performances of LEDs without and with an Al Reflector were compared. As a result, the NUV LED with both thermally and UV-treated AlN/Al Reflector exhibited the best performance, and its output power and electroluminescence intensity were higher by 82.7% and 41.9%, respectively, than those of the LED without a Reflector.

Hong Luo - One of the best experts on this subject based on the ideXlab platform.

Masud Behnia - One of the best experts on this subject based on the ideXlab platform.

  • Natural circulation flow through water-in-glass evacuated tube solar collectors
    Solar Energy, 2007
    Co-Authors: I. Budihardjo, Graham Morrison, Masud Behnia
    Abstract:

    Experimental and numerical investigations were undertaken to develop a correlation for natural circulation flow rate through single-ended water-in-glass evacuated tubes mounted over a Diffuse Reflector. The circulation flow rate was correlated in terms of solar input, tank temperature, collector inclination and tube aspect ratio. The sensitivity of the flow rate correlation to the variation in circumferential heat flux distribution was also investigated.

  • measurement and simulation of flow rate in a water in glass evacuated tube solar water heater
    Solar Energy, 2005
    Co-Authors: G L Morrison, I. Budihardjo, Masud Behnia
    Abstract:

    Abstract This paper evaluates the characteristics of water-in-glass evacuated tube solar water heaters including assessment of the circulation rate through single ended tubes. A numerical model of the heat transfer and fluid flow inside a single-ended evacuated tube has been developed assuming no interaction between adjacent tubes in the collector array. Flow measurement using Particle Image Velocimetry (PIV) has been undertaken to validate the numerical model. The experimental rig consists of a single full-scale tube coupled to a storage tank. A non-dimensional correlation has been developed of the circulation rate through a single evacuated tube mounted at 45° inclination over a Diffuse Reflector. Simulation results show that the natural convection flow rate in the tube is high enough to disturb the tank’s stratification and that the tank temperature strongly affects the circulation flow rate through the tubes. Circumferential heat distribution was found to be an important parameter influencing the flow structure and circulation rate through the tube, hence a separate correlation needs to be developed if a concentrating Reflector is incorporated into the collector.