Moisture transfer resistance method for liquid desiccant dehumidification analysis and optimization

The concepts of entransy, entransy dissipation and transfer resistance are introduced into liquid desiccant dehumidification analysis to reveal the irreversibility and moisture transfer resistance between moist air and liquid desiccant. By analyzing a typical water (vapor) transfer process coupled with heat transfer, we define the concepts of mass entransy of water and its dissipation, derive the expression of moisture transfer resistance (MTR) that reflects the irreversibility of water transfer during dehumidification processes, and also point out the relationship between MTR and dehumidification performance. With these concepts, both adiabatic and internal cooling liquid desiccant dehumidification systems with various operation conditions are analyzed and optimized. It is found that for the adiabatic dehumidification system, increasing the mass transfer coefficient leads to the reduction of MTR, and consequently, the improvement of dehumidification performance. Meanwhile, for the dehumidification system with internal cooling, in order to reduce the MTR and improve the dehumidification performance, pre-cooling should be centralized ahead of the liquid desiccant inlet when the flow rates ratio of air to desiccant is small, whereas, uniform cooling should be applied when the flow rates ratio of air to desiccant is large.