EFFECT OF OIL ON THE HEAT TRANSFER OF MIXED REFRIGERANT BOILING IN EVAPORATOR TUBES

The paper presents the results of an experimental study of the effect of oil on the heat transfer rate at boiling of mixed refrigerant R406A.Since the air conditionning system is not a pure refrigerant, but a mixture of oil with a concentration of up to 8%, such an amount of oil affects both hydrodynamics and heat exchange in the evaporators.The experimental work covers the entire range of regime parameters typical for these systems.There is shown the process of changing oil concentration in the pipe, as the working fluid boils, proving that most of the oil pipe does not im-pair the heat exchange in the course of two-phase flow boiling.Different modes of refrigerant R406A boiling dynamics have been defined, and each mode is given a quantitative assessment in terms of the effects of the oil and explaining of this effect on the fluid flow and heat transfer based on visual observations and the experiment results.The main factor of the effect is the freon-oil foam, which increases the proportion of the wetted surface in the wave and stratified modes and the heat transfer rate to 30%.