Investigating the thermal-hydraulic performance of new refrigerant mixtures through numerical simulation of minichannel and microchannel evaporators

In this study, a finite volume, steady-state evaporator model that includes rectangular minichannel and microchannel tubes with louvered fins was developed and validated. The model was then used to compare the thermal-hydraulic performance of experimental ternary refrigerant mixtures to more traditional refrigerants — namely, R-125/R-143a/R-161 (45%/40%/15%) versus R-404a and R-125/R-32/R-161 (34%/15%/51%) versus R-22. R-125/R-143a/R-161 (45%/40%/15%) exhibited significantly higher heat transfer per unit area than R-404a with only a small accompanying increase in the refrigerant-side pressure drop for the cases studied. Similarly, R-125/R-32/R-161 (34%/15%/51%) exhibited significantly higher heat transfer per unit area than R-22 with a minimal difference in refrigerant-side pressure drop. Both refrigerant mixtures also possess lower global warming potentials (GWPs). Based on these criteria (i.e. increased thermal performance and reduced GWPs), both mixtures would serve as suitable replacements for R-404a and R-22 in applications where the slight flammability of these blends was not a concern.