Effect of hybrid nanofluid on heat transfer performance of parabolic trough solar collector receiver

Abstract

In this study, three-dimensional heat transfer and flow characteristics of hybrid nanofluids under turbulent flow condition in a parabolic trough solar collector (PTC) receiver has been investigated. Ag–ZnO/Syltherm 800, Ag–TiO2/Syltherm 800, and Ag–MgO/Syltherm 800 hybrid nanofluids with 1.0%, 2.0%, 3.0%, and 4.0% nanoparticle volume fractions are used as working fluids. Reynolds number is between 10,000 and 80,000. The temperature of the fluid is taken as 500 K. The C++ homemade code has been written for the nonuniform heat flux boundary condition for the outer surface of the receiver. Variations of thermal efficiency, heat transfer coefficient, friction factor, PEC number, Nusselt number, and temperature distribution are presented for three different types of hybrid nanofluids and four different nanoparticle volume fractions with different Reynolds numbers. Also, the graphs of the average percent increase according to Syltherm 800 are given for the working parameters. According to the results of the study, all hybrid nanofluids are found to provide superiority over the base fluid (Syltherm 800) with respect to heat transfer and flow features. Heat transfer augments with the growth of Reynolds number and nanoparticle volume fraction. Thermal efficiency, which is one of the important parameters for PTC, decreases with increasing Reynolds number and increases with the increasing volume fraction of nanoparticle. It is obtained that the most efficient working fluid for the PTC receiver is the Ag–MgO/Syltherm 800 hybrid nanofluid with 4.0% nanoparticle volume fraction.