Hydrothermal analysis of heat transfer and thermal performance characteristics in a parabolic trough solar collector with Turbulence-Inducing elements

In present survey, a numerical study of fluid flow and heat transfer in a solar parabolic trough collector containing turbulence-inducing elements on wall of collector has been performed. Elements have helical profile throughout the pipe. The three-dimensional numerical simulations have been done by finite volume method using a commercial CFD code. The spatial discretization of mass, momentum, turbulence kinetic energy, turbulence dissipation rate and energy equations has been achieved by a second-order upwind scheme. SIMPLE algorithm has been used for velocity-pressure coupling. To calculate gradients, Green-Gauss cell-based method has been utilized. Generally, obtained numerical results are presented in two sections. In first part, examinations have been done to indicate impact of number of elements on collector efficiency. Five models including two, four, six, and eight numbers of turbulence-inducing elements have been analyzed. The results indicated that at V-Inlet = 0.32 m/sec, thermal efficiencies of models with two to six number of elements are greater than plain PTC by 6.6, 13.2, 20.6, and 27.6%, respectively. In second section, various types of element cross-section including rectangular, triangular, trapezoidal, and quasi-triangular has been investigated. Results depicted that maximum thermal efficiency belongs to case with rectangular cross-section at V-Inlet = 0.2 m/sec by 29% improvement.