Experimental evaluation on heat/mass transfer and pressure drop of a microchannel membrane‐based desorber for compact and efficient H2O/LiBr absorption refrigeration

Abstract

• Microchannel membrane-based desorber using H 2 O/LiBr is experimentally studied. • The lower channel performs better in heat/mass transfer but worse in pressure drop. • Nu and Sh increase with Re and inlet temperature but decrease with concentration. • f increases with inlet concentration but decreases with Re and inlet temperature. • Prediction accuracies of Nu, Sh , and f are improved by 38.83%, 62.76%, and 78.18%. Microchannel membrane-based desorber plays a vital role in compact and efficient absorption refrigeration systems to utilize renewable and waste energy. However, its existing models have certain errors because they are based on the empirical correlations that developed for other processes. In this study, experiments are carried out to evaluate the heat/mass transfer and solution pressure drop characteristics of a H 2 O/LiBr microchannel membrane-based desorber (1 mm width, 250 mm length, 0.15 and 1 mm height, and 100 channel numbers) with mass concentration ranging between 50 and 60 wt% and inlet temperature between 65 and 85 °C. The desorber with a lower channel height has a higher overall heat transfer coefficient, a higher desorption rate, and a greater pressure drop. But when the inlet temperature reaches 85 °C, the higher channel yields an unexpected higher desorption rate (0.00645 kg/(m 2 ⋅s)) than the lower channel (0.00615 kg/(m 2 ·s)). The experimental results show that both heat and mass transfer processes are strengthened by a higher solution flow rate, higher inlet temperature, and lower concentration, while the solution pressure drop is significantly reduced by a lower flow rate, lower concentration, and higher inlet temperature. Based on the experimental data, empirical correlations for Nusselt number, Sherwood number, and friction factor are obtained with errors of ± 40%, ± 20%, and ± 25% with prediction accuracies improvement of 38.83%, 62.76% and 78.18% compared to the correlations from the literature, facilitating the evaluation and design of compact and efficient absorption refrigeration systems.