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Spherical cavity receiver of solar concentrator is made up of copper tubing material having cavity diameter 385mm to analyse the different heat losses such as conduction, convection & radiation. As the convection loss plays major role in heat loss analysis of cavity receiver, the experimental analysis is carried out to study convective heat loss for the temperature range of 55 °C to 75 °C at 0°, 15°, 30°, 45°, 60°, & 90° inclination angle of downward facing cavity receiver. The numerical analysis is carried out to study convective heat loss for the low temperature range (55 °C to 75 °C) as well as high temperature range (150 °C to 300 °C) for no wind condition only. The experimental set up mainly consists of spherical cavity receiver which is insulated with glass wool insulation to reduce the heat losses from outside surface. The numerical analysis is carried out by using CFD software and the results are compared with the experimental results and found good agreement. The result shows that the convective loss increases with decrease in cavity inclination angle and decreases with decrease in mean cavity receiver temperature. The maximum losses are obtained at 0° inclination angle and the minimum losses are obtained at 90° inclination angle of cavity due to increase in stagnation zone in to the cavity from 0° to 90° inclination. The Nusselt number correlation is developed for the low temperature range 55 °C to 75 °C based on the experimental data. The analysis is also carried out to study the effect of wind speed and wind direction on convective heat losses. The convective heat losses are studied for two wind speeds (3 m/s & 5 m/s) and four wind directions [α is 0° (Side-on wind), 30°, 60°, 90° (Head-on wind)]. It is found that the convective heat losses for both wind speed are higher than the losses obtained by no wind test. The highest heat losses are found for wind direction α is 60° with respect to receiver stand and lowest heat losses are found for wind direction α is 0° (Side-on wind). The heat losses obtained for wind direction α is 30° condition are higher than the heat losses obtained for wind direction α is 0° (Side-on wind) condition, while the heat losses obtained by wind direction α is 90° (Head-on wind) condition are less than the heat losses obtained for wind direction α is 60° condition.
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