Numerical and experimental investigation of scheffler concentrator receivers for steam generation rate under different operating conditions

Concentrated Solar Technology (CST) is a device which can concentrate solar radiation using mirrors or lenses to produce temperatures in the range of 100 0 C to 450 0 C or more. Scheffler solar concentrator with fixed focus is one such important CST system. Receiver which contains a working fluid like water is placed at the fixed focus of Scheffler concentrator to receive solar radiations. Significant efforts are being made to analyse, characterise and improve performance of receivers since they have significant impact on overall efficiency of the system. In the subject work Scheffler solar concentrator of 2.7m 2 area with receivers of Cylindrical and Conical shape having 8 litres capacity were chosen. The scope of study was to map performance of both the receivers under General operating condition, with pre heated water to reduce thermal inertia and introducing a tilt or inclination to the receiver. The special emphasis was on studying influence of these conditions on temperature distribution in the focus region and steam generation rate which finally influence efficiency. Numerical analysis using Fluent-15 CFD package and experimental investigation were performed. Numerical analysis using CFD has helped to map changing temperature regions on the receiver under different conditions and thus provide rationale for influence on efficiency. Cylindrical receiver performed better in General operating condition and Pre heated water, While Tilt improved steam generation rate in conical. Preheating of water gave maximum impact on steam generation rate. The result shows good agreement between numerical and experimental values of mass flow rate of steam with maximum deviation 9 % and 10.21 % for cylindrical and conical receiver respectively and thus validating Numerical method. While CFD FLUENT package has been utilised by other researchers for computing Convective losses, the subject work is directed to mapping temperature distribution and Steam generation rate and hence directly the overall output parameter of solar system and thus easy link to efficiency. For any design of end application of solar system such as process heating its important to know steam generation rate rather than losses and hence the subject work has more practical utility. Besides it creates basis for further efficiency improvements by more changes and estimating their implication. © Renewable Energy Research, 2017.