Performance comparison of different flow arrangements of 4-fluid internally-cooled liquid desiccant dehumidifiers

Abstract

In this study, the performance of 10 different flow arrangements of 4-fluid internally-cooled liquid desiccant dehumidifiers were compared. The four fluids are supply air, exhaust air, liquid desiccant, and water. The comparison was performed using a two-dimensional heat and mass transfer model of the dehumidifier that was solved numerically. The model's predictions of supply air outlet humidity ratio matched experimental measurements within 6.7%. The two-dimensional variation of the air temperature and humidity ratio in the supply channel showed the importance of using a two-dimensional heat and mass transfer model when at least one of the fluids is in cross-flow with the other fluids. Moreover, a sensitivity analysis was performed to evaluate the effect of nine input parameters (supply air temperature and humidity ratio, exhaust air temperature and humidity ratio, liquid desiccant temperature, concentration, and flow rate, supply air mass flow rate, and exhaust to supply air mass flow rate ratio) on the performance of the dehumidifiers. The results showed that the best performance, in terms of the supply air humidity ratio and enthalpy decrease, was obtained when the supply air was in counter-flow with the exhaust air, liquid desiccant, and water. While the poorest performance was obtained when the supply air was in parallel-flow with the exhaust air and in counter-flow with the liquid desiccant and water. The approximate difference between the best and poorest performing flow arrangements in terms of the decrease in supply air humidity ratio and enthalpy is 4.3% and 10.5%, respectively. The results of the sensitivity analysis showed that for the 10 flow arrangements, the liquid desiccant inlet temperature, and flow rate have the least effects on the performance of the dehumidifier.