Heat and mass transfer analysis of a helical coil rectifier in an ammonia–water absorption system

Abstract

This paper presents a detailed study on the ammonia–water vapour rectification process in absorption systems using a helical coil rectifier. A differential mathematical model has been developed on the basis of mass and energy balances and heat and mass transfer equations. The differential volume has been defined in each coil turn by a differential angle on the turn and a second differential angle on the coiled tube cross section. It contains the corresponding differential portion of coolant, coiled tube wall, condensate film and vapour. Simultaneous heat and mass transfer processes have been taken into account in the vapour and liquid phases. The model equations have been solved using the finite-difference method. Results have been obtained for characteristic data from an ammonia–water absorption refrigeration system. Most significant calculated variable profiles along the coil height as well as in the coiled tube cross section are presented and discussed. The influence of the heat and mass transfer coefficients on the rectifier performance has also been considered.