Effectiveness Correlations for Heat and Moisture Transfer Processes in an Enthalpy Exchanger With Membrane Cores

Abstract

The performance correlations for the effectiveness of heat and moisture transfer processes in an enthalpy exchanger with membrane cores are presented. The physical phenomena relevant to the heat and moisture transfer in these devices have been used to develop a novel set of correlations based on the relevant dimensionless parameters. The total enthalpy effectiveness can be calculated from sensible effectiveness, latent effectiveness, and the ratio of latent to sensible energy differences across the unit. Studies show that the sensible effectiveness is a function of NTU, the number of transfer units for heat; while the latent effectiveness is a function of NTUL, the number of transfer units for moisture. The relations between NTUL and NTU are derived and studied with the proper separation of moisture resistance for membranes. This newly developed dimensionless parameter, NTUL, is to summarize the sorption characteristics of membrane material, the exchanger configurations, as well as the operating conditions. A number of experimental results on an enthalpy exchanger with novel hydrophilic membrane cores has been used to valid these correlations.