Energetic efficiency of cooling circuit influences the amount of refrigerant, which is changing when refrigerants with high GWP are substituted by refrigerants with low GWP. Substitution of R404A for R449A or R448A was carried on experimental cooling box with own cooling circuit and original refrigerant R404A with air cooled condenser. Heating load was selected adequately to cooling output of evaporator, which was possible to regulate by speed of ventilators. Cooling circuit was tested by ClimaCheck. Measured were 2 pressures, 9 temperatures humidity of surroundings and inside the box. Parameters were measured in real time in chosen interval. Measurements were carried out with increasing and with decreasing charge of refrigerant. Optimizing of refrigerant charge was carried out in the range of very low and very high refrigerant charge due to installed collector in the liquid line. Deciding parameters for the evaluation of energetic efficiency before and after refrigerant substitution were superheating and subcooling under stabile function of cooling circuit. Measurements proved different results with compared refrigerants and the need for adjusting of thermostatic expansion valve after the retrofit.
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