Thermal energy analysis on liquid desiccant air conditioning system at different desiccant solution parameters

Abstract

Selection of suitable liquid desiccant operating parameters plays a significant role in the design of energy efficient liquid desiccant air conditioning system. To achieve same dehumidification rate from ambient air, different combinations of solution parameters (heat capacity ratio, concentration, and vapor pressure) could be employed in the system. Considering dehumidifier air inlet condition and dehumidification rates are fixed, an analytical study is carried out on the thermal energy analysis of the system at different solution operating parameters. Operating parameters considered in this study are solution concentrations (C_s = 0.25, 0.3, 0.35 and 0.40) and heat capacity ratios ( $C_r^{*}$ = 2.5, 3, 4 and 5). Control volume which includes a pair of air and solution channels (half width channels) of full scale liquid-to-air membrane energy exchangers (LAMEE) has been chosen to analyze the energy transfer between air and solution. The results indicate system requires lesser chiller load (Q_chiller) at high concentration and low heat capacity ratio (C_s = 0.40 and $C_r^{*}$ = 2.5) which is 0.29 kW to achieve 0.61 kW cooling load. This is 99% lesser than the Q_chiller at high concentration and high heat capacity ratio (C_s = 0.40 and $C_r^{*}$ = 5) and 30% lesser than the Q_chiller at low concentration and low heat capacity ratio (C_s = 0.25 and $C_r^{*}$ = 2.5). Solution heat addition rate (Q_add) per kW cooling capacity (Q_cc) at this solution condition is found as 0.85 kW.