Comparative study of the parameters affecting the performance of microchannels' heat exchangers: Latest advances review

INTRODUCTION

For the extraction of heat from hot surfaces, energy conversion, waste heat recovery, and energy conservation heat exchangers play an important role and are considered essential equipment. In heat exchangers, fluid flow is separated by a thin wall. Initially, the heat is exchanged from the hot side fluid to the adjacent wall, from where it is transferred to the cold side fluid. To improve the heat-transfer process of a heat exchanger, improvements can be made in the heat-transfer section of the exchanger. In a direct transfer heat exchanger (recuperator), heat is transiently transferred between fluids through a separating wall.¹ Liang et al. worked on the investigation of the significant parameters to enhance the performance of the ground-type heat exchangers with an aim to enhance the overall efficiency.² A membrane-based microchannel refrigeration system powered by three different sources of energy was studied by Chong Zhai and Wei Wu for energy, exergy, environmental and economic analysis. The results show that the microchannel membrane absorption refrigeration system can be used to achieve good performance with carbon neutrality.³ Two processes occur in the heat exchangers: one is the working fluid flowing in the tubes and the second one is the heat transfer across the cold and hot fluids through the walls. The effectiveness of the heat exchangers might also be enhanced by examining various parameters that affect their performance. Experimental studies have shown that microchannel heat exchangers have distinct features apart from conventional heat exchangers such as a capability to yield small heat-transfer coefficients, having compact size as well as small volume per heat load, with a requirement for less coolant.^4,5

The growth of mini- and microchannel heat exchangers is materialized out by research of Tuckerman, who discovered that the reduced diameters of the tubes enhance the heat-transfer coefficient.^6,7 In addition, it is uncovered that the Nusselt number remains the same for the constant surface temperature in a fully developed region of Nu = 3.657 as presented in Equation (1). [Image Omitted. See PDF] [Image Omitted. See PDF]

Equation (2) indicates that decreasing the channel diameter of the microchannel exchangers enhances the heat-transfer rate. The compactness of modern devices and technological advances have made microchannel heat exchangers an important...