Optimization of solution concentration in liquid desiccant air-conditioning system driven by heat pump

Abstract

The heat pump driven liquid-desiccant air-conditioning (HPLDAC) system becomes increasingly popular in buildings, because of its compact size and energy-efficient performance. Although numerous efforts have been made in previous studies to save energy in the HPLDAC system, it has not been fully revealed from the perspective of desiccant solution concentration. In this study, two crucial issues concerning about the solution concentration are discussed for performance optimization of the HPLDAC system: (i) for only dehumidification, the optimal solution concentration for achieving the minimum energy consumption of the compressor; (ii) for both cooling and dehumidification, an energy-efficient strategy for realizing a required solution concentration. First, the simulation results reveal that the optimal desiccant solution concentration occurs when all of the condensing heat is used to heat the desiccant solution, with no condensing heat exhausted to outdoors. Second, two strategies for achieving the required solution concentration are compared, i.e., replenishing water to the solution (strategy I) and adding an auxiliary condenser to exhaust the redundant condensing heat to outdoors (strategy II). By model simulation, it is revealed that COP of the system in strategy II is 23.5% higher than that in strategy I under basic conditions. During the entire cooling season in Beijing, the running cost of the system in strategy II is 19.3% lower than that in strategy I.