Heat of adsorption and its effects on transmembrane heat transfer

Adsorption heat is an important factor affecting the heat transfer characteristics during the heat and mass transfer across a membrane. The mass transfer affects the heat transfer because it affects the adsorption capacity, which influences the adsorption heat. In this research, formula for calculating the adsorption heat was obtained based on the D-A adsorption equation and mathematical model describing the transmembrane heat and mass transfer was established. The effects of various parameters including the adsorption capacity, adsorption characteristic constants, and system temperature on the adsorption heat were first studied and the effects of the mass transfer on the membrane surface temperatures and transmembrane heat fluxes were then investigated. The uniqueness of this research is to take into account the dependence of the adsorption heat on the adsorption capacity when analyzing the effects of the mass transfer on the heat transfer. When the heat of adsorption is treated as constant as in the previous studies, the membrane surface temperatures and the transmembrane convective and adsorptive heat fluxes all vary linearly with the mass flux. When the heat of adsorption is treated as adsorption capacity dependent, more complicated variations are observed for all those temperatures and heat fluxes. Furthermore, the membrane surface temperatures and transmembrane heat fluxes for variable heat of adsorption are close to those for constant heat of adsorption for a small mass flux but they deviate more from those for constant heat of adsorption for larger mass fluxes. (C) 2012 Elsevier B.V. All rights reserved.