The technique of solar dish and Stirling engine combination is the most challenging and promising one. For the efficient conversion of the externally concentrated heat to the usable power, we studied ...the influences of the wall temperature, inclination angle, and open area ratio of the receiver on the Stirling engine power and efficiency. The theoretical analysis of the heat exchange element of the solar Stirling engine was performed, and the simulation model of the cavity absorber was built and analyzed. The temperature cloud and heat loss trends of the receiver under different wall temperatures, inclination angles, and opening ratios were illustrated. When the wall temperature of the absorber changes from 700 to 1000 K, the efficiency of the engine has increased by 8.8% from 21.34% to 30.11%. The higher the temperature, the higher the efficiency. As the inclination angle of the absorber increases from 0° to 60°, the efficiency of the engine is increased by 7.7% from 21.1% to 28.8%. With the increases of the aperture ratio, the engine output and efficiency reduced. The engine efficiency at the aperture ratio of 0.5 is 4% larger than that at the aperture ratio of 1.
Stirling engine operated by concentrated solar energy can be a great mean to generate power. Highly concentrated solar radiations with minimum heat loss from cavity receiver are required to operate ...the Stirling engine. Therefore, heat transfer study of the cavity receiver is required for the maximum utilization of solar energy with minimum heat losses for the efficient Stirling engine generator. In this study, experiments were performed to find the most suitable cavity receiver configuration for maximum solar radiation utilizations by an Advanced Stirling Engine Generator (ADSEG). Dimensionless parameter: aperture ration (AR=d/D) and aperture position (AP=H/D) were used to characterize the different configurations of cylindrical cavity receiver. Experimental heat loss analysis (Convection, radiation and total heat loss) as well as air film temperature profiles along the wall height (H) of the receiver for different configurations of the cavity receiver was performed in this experiment for its selection. Based on experimental results, among the four different configurations of cylindrical cavity receiver, Type IV (AR=0.5 AP=0.53) was found to be the most suitable receiver for the ADSEG system.
•Solar flux distribution is evaluated around receiver via Monte-Carlo ray tracing tool.•Heat losses are evaluated at different wind directions and wind velocities.•Combined heat transfer coefficient ...is evaluated and validated against published data.•Computed receiver thermal efficiency (71–77%) is validated against experimental data.
A receiver serves as a pivotal component in the solar power system as it is responsible for the light-heat conversion. Extensive research has been carried out on cavity receivers while external receivers have been neglected hitherto. Considering this imperative research gap, this work endeavours to narrow the gap by numerically analyzing the thermal performance of an external cylindrical receiver. A methodology is proposed to determine the efficiency of a cylindrical shaped receiver. A heliostat field is simulated using Monte-Carlo Ray Tracing tool to obtain heat flux distribution on the receiver. The peak heat flux obtained, i.e., 425 kW/m2 lies at the centre of the receiver’s front. By designing a tube layout and using boiling heat transfer correlations, temperature at the receiver’s surface and water are obtained. Numerical analysis and simulations are then carried out to evaluate receiver’s thermal efficiency in six different wind directions and four different wind velocities between 3 m/s and 12 m/s. Natural convection and radiation losses were also considered. Combined heat transfer coefficients obtained through numerical simulations are compared with the previous experimental data. The effect of wind in a single direction is precisely evaluated by dividing the cylinder into panels and evaluating heat losses on each panel individually. The thermal efficiency evaluated oscillates between 71% and 77% based on wind velocity, and the results are validated against the real power plants and experimental data for cylindrical solar receivers. A tube at receiver’s centre having the highest temperature gradient is then selected to evaluate thermal stresses. The equivalent stress obtained is less than the yield strength with safety factor > 2.5.
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