The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
J L Bhagoria - One of the best experts on this subject based on the ideXlab platform.
-
Heat Loss study of trapezoidal cavity absorbers for linear solar concentrating collector
Energy Conversion and Management, 2010Co-Authors: Panna Lal Singh, R M Sarviya, J L BhagoriaAbstract:Abstract There should be minimum Heat Loss from the absorber to achieve better efficiency of the solar collector. Overall Heat Loss coefficients of the trapezoidal cavity absorber with rectangular and round pipe were studied in the laboratory. Two identical rectangular pipe absorbers (section size: 100 × 23 mm, thickness: 2.5 mm and length 2170 mm) and two round pipe absorbers (a set of six mild steel round tubes of 16 mm diameter and 2.5 mm thickness brazed together in single layer making 100 mm width) were fabricated. A rectangular and a round pipe were painted with ordinary mat black paint (emissivity at 100 °C = 0.91) and one pipe of each type was coated with black nickel selective surface (emissivity at 100 °C = 0.17). Overall Heat Loss coefficient of the absorber was studied by circulating hot oil through it at different temperatures. The Heat Loss coefficient was increased with the absorber temperature. The Heat Loss coefficients for ordinary black coated and selective surface coated round pipe absorbers were varied from 3.5 to 7.5 W/m 2 /°C and 2.7–5.8 W/m 2 /°C respectively. The rectangular pipe section has marginally higher Heat Loss coefficients as compared to round pipe absorber. Selective surface coating on the absorbers reduced Heat Loss coefficient significantly by 20–30% as compared to ordinary black coating. The double glass cover also reduced Heat Loss coefficient by 10–15% as compared to single glass cover. The overall Heat Loss coefficients were also estimated analytically by parallel plate correlation and cavity correlations. The trend of variation of estimated Heat Loss coefficients by both methods was similar to experimental values. However, estimated values by cavity correlation were closure and uniformly distributed at all temperature range.
Zuguo Shen - One of the best experts on this subject based on the ideXlab platform.
-
experimental investigation on Heat Loss of a fully open cylindrical cavity with different boundary conditions
Experimental Thermal and Fluid Science, 2013Co-Authors: Jingyu Guan, Lan Xiao, Zuguo ShenAbstract:Abstract An experimental investigation using electrically Heating method was carried out to explore the effects of surface boundary condition, tilt angle and Heat flux on Heat Loss of a fully open cylindrical cavity. Three cases were examined: (i) only the bottom surface Heated, (ii) only the side surface Heated, and (iii) all surfaces Heated. For all cases, the surfaces were Heated with constant Heat flux and the cavity rotates from 0° (the opening facing horizontally) to 90° (the opening facing vertically downwards) at intervals of 30° in addition to 45°. From the three cases, it is concluded that temperatures of bottom surface fluctuate in a small region, and side surface temperatures decrease with increasing position departure from bottom surface. The natural convection Heat Loss is sensitive to the tilt angle in comparison with the radiation and conduction Heat Losses. The Heat Loss characteristics are also dependent on the surface boundary conditions to some extent. When the total Heat flux keeps constant, Nusselt numbers for determining the natural convection Heat Loss and the total Heat Loss reduce with increasing inclination. However, the inclination has little effect on the Nusselt number for determining the radiation Heat Loss. In addition, the empirical correlations of the natural convection, radiation and total Heat Loss Nusselt numbers versus the Grashof number, tilt angle and ambient temperature were proposed.
Simon Furbo - One of the best experts on this subject based on the ideXlab platform.
-
thermal stratification in a hot water tank established by Heat Loss from the tank
Solar Energy, 2012Co-Authors: Jianhua Fan, Simon FurboAbstract:Abstract This paper presents numerical investigations of thermal stratification in a vertical cylindrical hot water tank established by standby Heat Loss from the tank. The transient fluid flow and Heat transfer in the tank during cooling caused by standby Heat Loss are calculated by means of validated computational fluid dynamics (CFD) models. The measured Heat Loss coefficient for the different parts of the tank is used as input to the CFD model. Parametric studies are carried out using the validated models to investigate the influence on thermal stratification of the tank by the downward flow and the corresponding upward flow in the central parts of the tank. Tank design parameters such as tank volume, height to diameter ratio and insulation and different initial conditions of the tank are investigated. It is elucidated how thermal stratification in the tank is influenced by the natural convection and how the Heat Loss from the tank sides will be distributed at different levels of the tank at different thermal conditions. The results show that 20–55% of the side Heat Loss drops to layers below in the part of the tank without the presence of thermal stratification. A Heat Loss removal factor is introduced to characterize the effect of the buoyancy driven flow on exchange of Heat Loss between tank layers by natural convection. Based on results of the parametric studies, a generalized equation for the Heat Loss removal factor is obtained by regression which takes into account the influences of tank volume, height to diameter ratio, tank insulation and initial conditions of the tank. The equation is validated for a 150–500 l tank insulated with 0–7 cm mineral wool and a tank height to diameter ratio of 1–5. The equation will be implemented in an existing tank optimization and design program for calculation of thermal performance of a hot water tank.
Panna Lal Singh - One of the best experts on this subject based on the ideXlab platform.
-
Heat Loss study of trapezoidal cavity absorbers for linear solar concentrating collector
Energy Conversion and Management, 2010Co-Authors: Panna Lal Singh, R M Sarviya, J L BhagoriaAbstract:Abstract There should be minimum Heat Loss from the absorber to achieve better efficiency of the solar collector. Overall Heat Loss coefficients of the trapezoidal cavity absorber with rectangular and round pipe were studied in the laboratory. Two identical rectangular pipe absorbers (section size: 100 × 23 mm, thickness: 2.5 mm and length 2170 mm) and two round pipe absorbers (a set of six mild steel round tubes of 16 mm diameter and 2.5 mm thickness brazed together in single layer making 100 mm width) were fabricated. A rectangular and a round pipe were painted with ordinary mat black paint (emissivity at 100 °C = 0.91) and one pipe of each type was coated with black nickel selective surface (emissivity at 100 °C = 0.17). Overall Heat Loss coefficient of the absorber was studied by circulating hot oil through it at different temperatures. The Heat Loss coefficient was increased with the absorber temperature. The Heat Loss coefficients for ordinary black coated and selective surface coated round pipe absorbers were varied from 3.5 to 7.5 W/m 2 /°C and 2.7–5.8 W/m 2 /°C respectively. The rectangular pipe section has marginally higher Heat Loss coefficients as compared to round pipe absorber. Selective surface coating on the absorbers reduced Heat Loss coefficient significantly by 20–30% as compared to ordinary black coating. The double glass cover also reduced Heat Loss coefficient by 10–15% as compared to single glass cover. The overall Heat Loss coefficients were also estimated analytically by parallel plate correlation and cavity correlations. The trend of variation of estimated Heat Loss coefficients by both methods was similar to experimental values. However, estimated values by cavity correlation were closure and uniformly distributed at all temperature range.
Jingyu Guan - One of the best experts on this subject based on the ideXlab platform.
-
experimental investigation on Heat Loss of a fully open cylindrical cavity with different boundary conditions
Experimental Thermal and Fluid Science, 2013Co-Authors: Jingyu Guan, Lan Xiao, Zuguo ShenAbstract:Abstract An experimental investigation using electrically Heating method was carried out to explore the effects of surface boundary condition, tilt angle and Heat flux on Heat Loss of a fully open cylindrical cavity. Three cases were examined: (i) only the bottom surface Heated, (ii) only the side surface Heated, and (iii) all surfaces Heated. For all cases, the surfaces were Heated with constant Heat flux and the cavity rotates from 0° (the opening facing horizontally) to 90° (the opening facing vertically downwards) at intervals of 30° in addition to 45°. From the three cases, it is concluded that temperatures of bottom surface fluctuate in a small region, and side surface temperatures decrease with increasing position departure from bottom surface. The natural convection Heat Loss is sensitive to the tilt angle in comparison with the radiation and conduction Heat Losses. The Heat Loss characteristics are also dependent on the surface boundary conditions to some extent. When the total Heat flux keeps constant, Nusselt numbers for determining the natural convection Heat Loss and the total Heat Loss reduce with increasing inclination. However, the inclination has little effect on the Nusselt number for determining the radiation Heat Loss. In addition, the empirical correlations of the natural convection, radiation and total Heat Loss Nusselt numbers versus the Grashof number, tilt angle and ambient temperature were proposed.
