Performance of a mass recovery microchannel membrane-based heat/mass exchanger in an absorption chiller

Abstract

Solution heat exchanger plays a vital role to recover the heat and improve the system coefficient of performance (COP) in absorption chiller. This study introduces an innovative microchannel membrane-based heat/mass exchanger (MMHX), aiming at replacing conventional heat exchangers. The MMHX notably increases the solution concentration difference between absorber and desorber, leading to an improved COP. This research comprehensively analyzes the heat and mass transfer performance, along with the solution pressure drop characteristics of the MMHX, in both co-current and counter-current flows, comparing these with a traditional microchannel heat exchanger (MicroHX). Due to the lower thermal conductivity of the porous membrane, the MMHX demonstrates a heat transfer capacity that is 3.5 times and 2.1 times lower than the MicroHX in the respective flow directions. However, the absorption chillers equipped with the MMHX outperform those with MicroHX at solution flow rate above 0.03 kg/s, with average improvement in COP of 15.76 %. While introducing a gap between strong and weak solution channels in the MMHX aids mass transfer, it also reduces heat recovery efficiency, impacting the COP negatively. Consequently, a gap-less MMHX is identified as an optimal solution, enhancing COP and advancing the development of efficient, compact absorption chillers for future space cooling.