Second Law Analysis for Free Convection in an L-Shaped Cavity Filled with Nanofluid

Abstract

Natural convection heat transfer occurs in
engineering applications like solar thermal collectors, electronic
device cooling, nuclear reactors, etc. This paper aims to analyze
the heat transfer and entropy generation in free convection
laminar flow of nanofluid flowing through an L-shaped cavity
using different nanoparticles. The second law of thermodynamics
has been applied to investigate the effect of Prandtl number on
the average Nusselt number, total entropy generation and Bejan
number using water and, Cu-water, Ag-water and Al2O3-water
nanofluids. Isotherms, stream function and entropy generation
caused by heat transfer are also presented as a function of
Prandtl numbers for various nanoparticles. Using the penalty
finite element method with Galerkin’s weighted residual, the
governing equations are solved. Results show that Ag-water
nanofluid with the highest Prandtl number gives the highest
amount of irreversibility as well as rate of heat transfer. Cuwater and Ag-water nanofluid produce more irreversibilities
than Al2O3-water nanofluid and base fluid. Also, Nusselt number
and Bejan number increase with the increasing Prandtl number.
Therefore, Prandtl number is a central parameter for desired
heat transfer increment with decreasing entropy generation in
the given geometry.