Comparison of the effect of using helical strips and fines on the efficiency and thermal–hydraulic performance of parabolic solar collectors

Abstract

In the near future, the construction of a solar thermal power plant will be considered an important strategy for energy supply from the point of view of environmental compatibility and sustainable development. Therefore, improving the thermal performance of parabolic collectors in these power plants has become a necessity. One of the most effective methods in connection with increasing the efficiency of the parabolic collector absorber pipe is to place the fines and spiral strips inside the absorber pipe. In this study, the numerical simulation of the thermal hydraulic performance of a linear parabolic collector absorber pipe with rectangular fines and helical strips in a stable, three-dimensional state under a turbulent flow regime with the help of Ansys Fluent software. Also, in order to model the turbulent flow and discretize the governing equations, the K-epsilon turbulence model and the simple algorithm have been used, respectively. For this purpose, geometries including 4 and 8 fins with thicknesses of 2 and 4 mm and also helical strips with steps of 0.25 and 0.5 m and thicknesses of 2, 4 and 8 mm have been used. According to the results, the average Nusselt number and the efficiency of the solar collector are strongly influenced by rectangular fines and spiral strips. Furthermore, the addition of rectangular fines and spiral strips increases the thermal performance and efficiency of the solar collector significantly compared to when the solar collector is simple. Examining the evaluation criteria of thermal hydraulic performance in the case of using rectangular fins and helical strips, it was observed that the optimal conditions in Reynolds number are equal to 10,000 and respectively using 8 fins with a thickness of 2 mm and using a turbulator with a thickness of 4 mm and a step of 0.5 mm.