ScholarWorks@중앙대학교

초록

Refrigerant mixtures have been proposed as alternatives to traditional refrigerants to meet environmental regulations while offering favorable thermodynamic properties. When zeotropic mixtures are utilized in heat pump systems, local composition shift arises from differences in velocity and composition between the liquid and vapor phases in the two-phase region. This phenomenon leads to off-design operation, as the local composition varies along the system, deviating from the initial charge composition. Therefore, it is necessary to consider local composition shift when designing heat pump systems with refrigerant mixtures. In this study, local compositions of mixtures are numerically estimated throughout a heat pump system, and a system model is suggested reflecting these composition shifts. The estimation results indicate good agreement with the experimental data, with maximum root mean squared error (RMSE) of 1.46% for local compositions of R32/R1234yf mixtures. Furthermore, two system models, one considering and one not considering local composition shift, are compared under various operating conditions. The model with composition shift shows improved accuracy, decreasing the mean absolute percentage error (MAPE) of system parameters by up to 5.52%p. Based on this model, the effect of local composition shift on the system is analyzed. Simulation results reveal that composition shift leads to capacity reductions of 3.7% and 7.4% in cooling and heating modes, respectively, under standard conditions of this study. © 2025

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