Entropy generation by nanofluid with variable thermal conductivity and viscosity in a flat plate solar collector

Abstract

The entropy generation by nanofluid with variable thermal conductivity and viscosity of assisted convective flow across a riser pipe of a horizontal flat plate solar collector is investigated numerically. The water based nanofluid with copper nanoparticles is used as the working fluid inside the fluid passing riser pipe. The governing partial differential equations with proper boundary conditions are solved by Finite Element Method using Galerkin’s weighted residual scheme with discretization by triangular mesh elements having six nodes. The effects of temperature dependent thermal conductivity and viscosity related to performance such as temperature, velocity and heat flux distributions, heat transfer rate, mean temperature and velocity, collector efficiency and mid-height temperature (dimensional), mean entropy generation and Bejan number of the nanofluid as well as base fluid are investigated systematically. The results show that the better performance of heat transfer through the collector is found by using the higher and lower values of variable thermal conductivity and viscosity respectively. Thermal efficiency improves about 8% using water/Cu nanofluid. Numerical result obtained from present study is validated with the result available in the literature.

Keywords: Entropy generation, assisted convection, nanofluid, finite element method, variable thermal conductivity and viscosity.