Generation of entropy in micro thermofluidic and thermochemical energy systems-A critical review

Micro energy systems have progressed significantly over the last two decades, as has the utilization of micro thermofluidic and thermochemical systems. Several studies were conducted to analyze the thermophysical and chemical characteristics of these systems. In general, the large rates of heat and mass transfer typically encountered in these microsystems make them susceptible to significant irreversibilities and as a result, poor second-law performances. Although the understanding and modelling of entropy generation rate in microsystems is an inevitable part of their performance analyses, no reviews were found on the second law analysis, and more specifically on the entropy generation rate of micro thermal and thermochemical systems. To address this shortcoming, the current review explores the mechanisms of entropy generation rate in these micro energy systems and identifies the possible future avenues of research in this field. The existing literature on entropy generation rate in micro single and multiphase thermofluidic systems, with the inclusion of various effects such as magnetic and electric fields, nanopartides and thermochemical reactions are reviewed in detail. The unexplored and less investigated areas such as second law analysis of micro porous systems using pore-scale modeling and entropy generation rate of airflow through microchannels with inserts are identified, and recommendations are made for future research. (C) 2020 Elsevier Ltd. All rights reserved.