Thermal and fluid dynamic analysis of Direct Steam Generation Parabolic Trough Collectors

Abstract Direct Steam Generation (DSG) has attracted considerable attention in comparison with conventional technologies based on Heat Transfer Fluids (HTF) for electricity generation due to its higher temperatures. In this context, a detailed numerical model has been developed, not only for comparison and assessment purposes but also for optimization analysis, in order to obtain an accurate comprehensive analysis of this type of systems. This paper explains in detail a numerical model developed to accurately predict the phase change and the heat transfer in the DSG Parabolic Trough Collector (PTC) system. The whole numerical model has been validated using experimental data of Direct Solar Steam (DISS) test facility from scientific literature. The model results have been compared also to the measurements of an experimental DSG PTC setup installed at Ecole Nationale d’Ingenieurs de Tunis (ENIT) running under different working and climate conditions. In all cases, both numerical results and experimental data present a reasonable agreement. The numerical code is used to perform a parametric study pointing out the influence of inlet conditions on the performance of DSG PTCs. Emphasis is placed on the determination of the optimal mass flow rate range leading to a maximum thermal efficiency of the solar collectors. Annual thermal performance of the solar collectors is featured including useful energy and thermal efficiency evaluated under Tunisian climatic conditions.