HEAT TRANSFER in AMMONIA COMPACT HEAT EXCHANGERS

This paper reports a review on ammonia heat transfer in plate heat exchangers, from both theoretical and experimental points of view. It also addresses the current ecological aspect implied by refrigerants, by choosing ammonia, which is a natural refrigerant, known for its zero ozone depleting potential and for its low global warming effect. The theoretical study presents the modeling of the convective ammonia heat transfer coefficient in narrow spaces by several correlations, currently available in the open literature and valid for the case under consideration. The experimental study was carried out on specially designed set-ups that allowed both measuring and acquisition of data. The experimental values were further used in order to validate the correlations, under specific geometrical configuration of the plate heat exchanger used and specific operating conditions. The paper concluded all correlations under study describe, more or less accurately, the process of convective evaporation of ammonia in plate heat exchangers and determined a hierarchy among them, based on deviation shown with respect to the experimental values.