Evaluation of efficiency, thermohydraulic performance evaluation criterion, and field synergy principle improvement of the parabolic solar collector containing the hybrid nanofluid using spring turbulators

Abstract

In this paper, the study and simulation of turbulent flow inside a parabolic solar collector tube equipped with two spring insert samples with two different pitch ratios (P/D = 0.22, 0.44) and a specific cross-section are investigated. Heat transfer and properties of Cu–Fe3O4/Water hybrid nanofluid with volume fractions of φ = 1%, 3%, and 5% for the range of Reynolds numbers of 7000, 9000, and 11000 are selected and investigated using the single-phase method. The tube is used as the adsorbent pipe of a parabolic solar collector to investigate the performance of the parameters such as volume fraction, Nusselt number, pressure drop, parabolic solar collector efficiency, performance evaluation criterion, and field synergy principle. The results show that with decreasing the pitch ratio, Nu and solar collector efficiency increase. The maximum efficiency is 2.53 for a tube with P/D = 0.22 (Re = 7000, φ = 1%). The maximum efficiency is obtained under the same conditions in a tube containing the spring insert with P/D = 0.44 is equal to 2.39. At the same Reynolds numbers, the average of these velocities is significantly higher than a plain tube. Field Synergy Principle is a reliable criterion to investigate the mechanism of heat transfer increase that this coefficient value in the tube equipped with a spring insert is much higher than in a plain tube. This increase indicates the positive performance of the spring insert on the heat transfer rate and solar collector efficiency improvements. Therefore, spring inserts with a lower P/D are more desirable to achieve the highest efficiency of solar collectors as a source of renewable energy.