Effects of membrane characteristics on the evaporative cooling performance for hollow fiber membrane modules

The hollow fiber membrane-integrated evaporative cooler (MEC) is considered as a promising strategy for space air conditioning applications. For a counter-flow MEC, the appropriate fiber specification and flow configuration need to be identified to improve its comprehensive performance. A numerical model was developed to capture the coupled heat and mass transfer process, and its feasibility was verified by measured data. The influence of fiber specifications and flow configuration on its cooling, space-saving, energy and water conservation performance were investigated. The results revealed that a reasonable fiber specification required a packing fraction of about 0.1 and a length slightly longer than the air channel's entrance length, while the inner diameter and membrane thickness should be determined based on the priority index. The flow configuration of air flowing via shell-side and water going through tube-side was more suitable for counter-flow MEC, which was more energy efficient while maintaining cooling ability. In addition, the contribution of each component's resistance to the total heat and mass transfer resistance would fluctuate as the influencing factors changed. In general, the total heat transfer resistance was dominated by the air-side convective resistance, while the main contributor to the total mass transfer resistance was the membrane resistance.