CO2, Heat Pump Dryer, Gas Cooler, Modeling.
Heat pumps working with CO2 as a refrigerant have low energy consumptions if right application areas and operating conditions are selected. The use of CO2 in heat pump dryers is feasible if operating temperatures are appropriate. In heat pump dryers working with CO2 according to the transcritical cycle, one of the most important operating conditions is optimum gas cooler inlet pressure, which gives the maximum coefficient of performance (COP). In this study, a model was developed by using MATLAB software for heat pump tumble dryer working with CO2. The model was validated by experimental data taken from existing literature. Then, COP, moisture extraction rate (MER), and specific moisture extraction rate (SMER) were found by running the model at different gas cooler inlet pressures (80–140 bars). All results were calculated in the same geometry for evaporator, gas cooler, and compressor. Thus, effects on the results of variation of the geometrical features were eliminated. Optimum gas cooler inlet pressure was determined as 100 bars for the system with data input to the model. In the optimum gas cooler inlet pressure working condition, SMER increased 24% and 12% by comparison with 80 bars and 140 bars gas cooler inlet pressure, respectively.