Changes in optimal distribution of heat exchanger area between the evaporator and suction gas heat exchanger when replacing R22 with R407C: Modifications de la répartition optimale des surfaces des échangeurs thermique entre l'évaporateur et l'échangeur liquide–vapeur lorsque le R22 est remplacé par le R407C

Abstract

An investigation was made on whether the optimal distribution of heat exchanger area between the evaporator and the suction gas heat exchanger, at a given cost, will change when R22 is replaced with the non-azeotropic mixture R407C. A comprehensive computer program was used to simulate a refrigeration plant, originally designed for R22, where the tube-and-shell evaporator is of dry-expansion type. The simulations show that for R22, the area distribution in the original design is optimal for every set of conditions simulated. For R407C it is, in most of the cases simulated, favourable to move some heat exchanger area from the evaporator to the suction gas heat exchanger. The improvement in COP can be up to 3.4%. Further, it was observed that the optimal area distribution for R407C corresponds to the maximum use of the glide in the evaporator, and for R22 to the minimum pressure drop in the evaporator. The superheat at the evaporator exit is an important parameter, especially for the non-azeotropic mixture.