International Journal of Heat and Mass Transfer, Vol.133, 435-444, 2019
Evaluation of the frost properties on a semipermeable membrane
The onset of the formation of frost on a semipermeable membrane, which allows both heat and moisture transfer through it, can be delayed, due to the moisture transfer through the membrane however, at severe conditions, frost formation cannot be avoided completely. In this paper, the formation of frost on a semipermeable membrane is evaluated both visually and quantitatively. The frost thickness and mass, and the area of the surface covered with frost are measured for a semipermeable membrane and compared with those on an impermeable plastic surface. Moreover, the effect of operating conditions (air humidity ratio, air mass flow rate, liquid desiccant temperature and salt concentration) on the properties of the accumulated frost, on the semipermeable membrane, are investigated. The results show a 30-60 min delay in frost deposition and also the formation of a thinner, lighter frost layer on the semipermeable membrane compared to the impermeable surface. Also, results show that increasing the moisture transfer through the semipermeable membrane, by decreasing the humidity ratio of the cold liquid desiccant, can lead to frost that is less thick; however, increasing the humidity ratio of the humid air leads to a higher rate of frost formation. Increasing the air mass flow rate or decreasing the surface temperature increases the thickness of the frost layer on the semipermeable membrane. (C) 2019 Elsevier Ltd. All rights reserved.