Optical and thermal analysis of a linear Fresnel reflector operating with thermal oil, molten salt and liquid sodium

Linear Fresnel collectors are promising technologies for the exploitation of solar irradiation in medium and high temperatures. In this study, a linear Fresnel collector with flat primary mirrors and a parabolic shape secondary reflector is investigated. The location of the secondary reflector is simply optimized and then the collector is investigated under different incident angles (transversal and longitudinal). The next step is the thermal analysis of the collector with three different working fluids: thermal oil, molten salt and liquid sodium. The analysis is performed for temperatures up to 900 K with liquid sodium in order to examine the collector up to its stagnation temperature. Both the optical and thermal analysis are conducted with SolidWorks Flow Simulation. According to the final results, the exergy performance of the collector is maximized at 700 K and it is 30.20% with liquid sodium and 30.05% with molten salt. Generally, liquid sodium was found to be the best candidate according to performance criteria, with molten salt and thermal oil to follow. The high heat transfer coefficient is the reason for the superior performance of the liquid sodium. Moreover, the pumping work is maximized for operation with molten salt.