Evaluation of the influence of air maldistribution on the refrigerant charge in a finned tube heat exchanger
Most of the refrigerant fluids with low Global Warming Potential has as a drawback the fact that they are flammable. This fact has made charge minimization and therefore the analysis of the refrigerant charge required in a heat pump a very relevant topic nowadays. Nevertheless, the theoretical estimation of the charge in a heat pump is not a solved problem as it is affected by several factors like the knowledge of internal volumes, the precise determination of the refrigerant flow conditions, the refrigerant-oil solubility or the maldistribution of refrigerant among the different circuits of the system. In this paper we analyze the influence of air maldistribution in the estimation of the refrigerant charge of an air to water heat pump. This factor usually is not considered in this kind of system but could be important as this maldistribution could be originated by the system design itself but can be introduced also during the operation of the system because of some fouling on it. Findings reveal that air maldistribution could significantly affect refrigerant distribution in finned tube evaporators with several circuits leading to important variations in the refrigerant charge demanded by the heat exchanger. This fact could introduce relevant performance degradation especially in systems without liquid receivers, in which the minimization of charge could be an objective.