Numerical simulation of solar parabolic trough collector with arc-plug insertion

Abstract

ABSTRACT This paper investigates the effect of insertion of arc-plug within the absorber tube for the thermal improvement of the solar parabolic trough collector (PTC). In order to check the optimized dimension of the arc-plug, eleven different cases have been compared. Ansys-Discovery-Aim 2019 R1 has been used for the evaluation of required thermodynamic and hydraulic properties for these distinct cases of the modified PTC (MPTC). SOLTRACE-7.9 is used for the evaluation of heat flux boundary condition need in the Ansys physics condition. The arc-plug with eleven factor R values that are taken into consideration are 0.394, 0.515, 0.636, 0.757, 0.879, 1, 1.121, 1.242, 1.364, 1.485, and 1.6060. Under the usual sets of operating conditions, the thermal efficiency (η) for factor R = 1 and R = 1.6060 are seen to be varying from 73.09% to 67.55% and 67.78% to 65.37% respectively. Whereas, under the same sets of operating conditions, the highest thermal enhancement index (TEI) for factor R = 1 and R = 1.6060 are observed to be 1.1039 and 1.3016 respectively. The arc-plug can be considered as a triangular fin with its base attached to the high thermal flux region within the absorber tube. Therefore, it cannot be taken as granted that high TEI leads to high thermal efficiency; there may occur that the fins or obstructions may act as insulators at some point of operation. It is observed that for arc-plug with factor R = 1 and R = 0.879; the PTC shows the highest thermal efficiency. Whereas, for the arc-plug with factor R = 1.6060; the PTC shows the highest heat transfer performance. Abbreviations: CFD: Computational fluid dynamics; CPTC: Concentrated parabolic trough collector; MPTC: Modified parabolic trough collector; NUHF: nonuniform heat flux; PFAI-PTC: Pin fin array inserts parabolic trough collector; PTC: Parabolic trough collector; PTR: Parabolic trough receiver; SAT: Smooth absorber tube; SPTC: Smooth parabolic trough collector; SNL: Sandia national laboratory; TEI: Thermal enhancement index; UHF: Uniform heat flux; UMLVE: Unilateral milt-longitudinal vortexes enhanced; USR:Unilateral spiral ribbed