Effect of Thermophysical Property Variation on Entropy Generation towards Micro-Scale

Abstract

AbstractIn this work, the effect of temperature-dependent thermal conductivity (k(T)) and viscosity (\mu (T)) variation on entropy generation in circular channels with an approach from macro- to micro-scale is numerically investigated. Thermally as well as hydrodynamically fully developed flow of water through the fixed length channels with constant total heat flow rate and total mass flow rate is considered. The effects of k(T) variation and \mu (T) variation on entropy generation are analyzed individually as well as collectively. It is observed that in the case of Constant Property Solutions (CPS) {S_{\mathit{gen},\mathit{tot}}} is maximum at the macro-level; however, in the case of combined k(T) and \mu (T) variations it is maximum at the micro-level. The Bejan number (\mathit{Be}) and irreversibility distribution ratio (φ) are also calculated for asserting the dominance of frictional irreversibility and conduction heat transfer irreversibility. Additionally, the optimum diameter ({D^{\ast }}) corresponding to the optimum number of channels is calculated at minimum total entropy generation. It is observed that {D^{\ast }} is minimum for k(T) variation followed by CPS, \mu (T) variation, and combined k(T) and \mu (T) variations.