Effect of Wall Heat Flux on Entropy Generation in Turbulent Mixed Convection Heat Transfer of a Pipe Flow With Highly Variable Properties

Abstract

There are many engineering systems with working fluids which have properties varying significantly with temperature. This causes the effect of the wall heat flux on the velocity and temperature fields to become larger with respect to the constant property flows. In this study the effect of the wall heat flux on the entropy generation in the mixed turbulent convection heat transfer of a fluid flow with high property variations has been investigated. The local and total entropy generation is calculated. In addition, the region in which the entropy production is larger has been determined. Furthermore, the contribution of each of the mechanisms of entropy production which is depended on the wall heat flux is determined. It should be noted that the implementation of different heat fluxes at the tube wall affects all mechanisms of entropy generation. The results show that the bulk entropy generation reaches a minimum value when the heat transfer coefficient has a maximum value. The wall heat flux also has an opposite effect on the heat transfer coefficient and entropy generation which is a favorable result.