Method for defrosting heat exchangers using an air-particle jet

We report test results on a method for defrosting heat exchangers in which solid particles accelerated by an air jet impinge on heat exchange surfaces. This study was motivated by the development of a cryogenic heat exchanger for a hypersonic aircraft engine. We conducted experiments to remove frost from a single-row heat exchanger cooled with liquid nitrogen as the refrigerant. In the experiments, particle-jet defrosting was conducted for 1 s at intervals of 50-300 s over total experimental durations of 600 s. The experiments were performed using different intervals between defrost cycles, different particle diameters, and different numbers of particles. The effects of these parameters on the performance of the heat exchanger were evaluated by measuring pressure losses and heat transfer rates. The results show that the method prevents buildup of frost and is more effective than defrosting with only an air jet. (C) 2015 Elsevier Ltd and International Institute of Refrigeration. All rights reserved.