Modeling of the rectifier of a mini absorption cooling device using ceramic hollow fiber membranes

Miniaturized and mobile absorption cooling devices may be used in many applications, but effective and small size heat and mass exchangers are required. Ceramic hollow fiber membranes are thermally stable so that they can be used for the rectification of ammonia in an absorption cooling device. In this paper the simultaneous heat and mass transfer between the ammonia-water vapor and the reflux liquid is modeled in a rectifier with hydrophobic ceramic hollow fiber membranes. A similar model is used to simulate the same process in another rectifier with random packing. The stagnant film model is used to calculate the heat and mass fluxes. The rectifier is divided into segments and the equations for all segments are solved simultaneously. The model is verified by comparing the results with the literature. The effects of the packing density, effective porosity, pore radius and heat and mass transfer coefficients on the distillate concentration and the flow rate are discussed. The sensitivity of the concentration profiles to the grid refinement is shown. The hollow fiber membrane module results in a higher ammonia concentration and higher mass flow rate at the outlet compared to the random packing because it provides higher vapor-liquid interfacial area