Development of high efficiency cycles for domestic refrigerator-freezer application

•It is recommended that evaporators be connected in series while compressors be in parallel.•Advanced cycle named “two-circuit cycle with evaporating subcooler” is newly developed.•The most important parameter for performance improvement is the freezing load ratio.•The degree of subcooling gives the most significant effect on the total refrigerant flow rate.•The refrigerant pair of (R/F) = (R152a/R600a) is the best candidate for the two-circuit cycle.

High efficiency 2-stage vapor compression cycles are developed for domestic refrigerator-freezer application. From the parametric analysis of the newly developed cycles, it is recommended that evaporators be connected in series while compressors be connected in parallel to obtain the highest COP (coefficient of performance) in domestic refrigerator-freezer systems. It is found that the most important parameter for performance improvement is the freezing load ratio (RQ˙F=Q˙F/Q˙total). It is also found that the degree of subcooling by the heat exchanger (ΔTsub=T2−T3ΔTsub=T2−T3) gives the most significant effect on m˙total. However, there are some difficulties in operating the newly developed cycle such as difficult individual operation of the evaporators. Therefore, this study proposes an advanced novel cycle with the evaporators connected in parallel and without the separator, which is named “two-circuit cycle with evaporating subcooler”. It is finally concluded that the refrigerants pair of (R/F) = (R152a/R600a) be the best candidate with the highest COP of 3.758 for the two-circuit cycle with evaporating subcooler.