Performance assessment of a membrane liquid desiccant dehumidification cooling system based on experimental investigations

Abstract

A membrane-based liquid desiccant dehumidification cooling system is studied in this paper for energy efficient air conditioning with independent temperature and humidity controls. The system mainly consists of a dehumidifier, a regenerator, an evaporative cooler and an air-to-air heat exchanger. Its feasibility in the hot and humid region is assessed with calcium chloride solution, and the influences of operating variables on the dehumidifier, regenerator, evaporative cooler and overall system performances are investigated through experimental work. The experimental results indicate that the inlet air condition greatly affects the dehumidification and regeneration performances. The system regeneration temperature should be controlled appropriately for a high energy efficiency based on the operative solution concentration ratio. It is worth noting that the solution concentration ratio plays a considerable role in the system performance. The higher the solution concentration ratio, the better the dehumidification performance. However simultaneously more thermal input power is required for the solution regeneration, and a crystallization risk in the normal operating temperature range should be noted as well. The system mass balance between the dehumidifier and regenerator is crucial for the system steady operation. Under the investigated steady operating condition, the supply air temperature of 20.4°C and system COP of 0.70 are achieved at a solution concentration ratio of 36%.

Experimental analysis and performance optimization of a counter-flow enthalpy recovery device using liquid desiccant

“…Table 3 compares the ranges of current operating parameters with those of similar studies using LiBr as the desiccant in dehumidifiers or regenerators. [9][10][11][12][13][14][15] The desiccant concentrations used in the present study were lower than those of dehumidification and regeneration conditions in the previous studies, thereby demonstrating the characteristics of the enthalpy recovery condition. Furthermore, the desiccant temperatures were also different, especially for those in the regenerators.…”

“…22 The layer of air in equilibrium with the desiccant is analyzed, as shown in Figure 6. The energy transfer process and mass transfer process can be described by equations (10) and (11), respectively.…”

“…In order to reflect the actual performance of the system, the experiment results were used to accurately calculate NTU m in the equations (10) and (11). Furthermore, the mass transfer Figure 6.…”

“…Besides, various types of solution (such as LiBr, LiCl and CaCl 2 ) have been used in the cross-flow device. [9][10][11] From a theoretical view, Zhang et al 7 performed exergy analysis with numerical model on this cross-flow liquid desiccant enthalpy recovery device in order to improve its performance. Furthermore, Xie et al 12 applied a simulation model to analyze the performance of a counter-flow heat pumpdriven liquid desiccant dehumidification system, in which the indoor exhaust air was used for heat recovery.…”

Modeling and control of dehumidifier in distributed operating liquid desiccant dehumidification system

“…Wang et al [57] presented an experimental study on the performance of a counter flow liquid desiccant dehumidifier. Other improvements such as the cooling/heating approaches [58][59][60], multi-stage structures [61,62], systems with membrane [63][64][65][66] and ultrasonic atomization system [67,68] have all been employed into the LDDS fields these years.…”