Innovative method to reduce frost formation in liquid-to-air membrane energy exchangers (LAMEE) based on 3D CFD simulation

Abstract

Frost formation is an important and challenging problem in the proper operation of ventilation systems. In this study, a novel model is developed to predict the amount of frost formation in a Liquid-to-Air Membrane Energy Exchanger (LAMEE) based on the 3-Dimensional Computational Fluid Dynamics (CFD) technique. This model can be a robust way to find and analyze different proposed methods to combat frost. The results show that the presence of the membrane reduces the mass of frost compared to the impermeable surface by approximately 60% due to the mass transfer phenomenon. Moreover, the variations of air temperature along the LAMEE are sharper than the changes in humidity ratio, which is an important reason for more frost forming. Condensed Humidity Ratio (CHR) is presented as a valid criterion for analyzing the distribution of frost formation in heat and energy exchangers. Furthermore, an innovative method is proposed based on 3-fluid LAMEE to reduce frost formation. In the proposed method, the solution temperature is controlled with another fluid that flows in tubes located in the solution channel. Therefore, this model control heat transfer between air and solution flows in different parts and moderate air temperature variations for vapor reach the saturation line in a low humidity ratio. The developed CFD model predicts that the frost formation in the proposed LAMEE is around 25–28% saturation less than the typical LAMEE at an equal sensible cooling capacity.