Characteristics of a series-connected two-evaporator refrigerating system

Based on the Buckingham Pi theorem, this study derives the dimensionless correlations to characterize a series-connected two-evaporator refrigerating system with propane (R-290) as the refrigerant. Experimental data are substituted into the correlations to demonstrate the most relevant factors. Simplified correlations are then obtained. The analytical results show that the mass flow rate of refrigerant ( ) is primarily affected by the condensing pressure, length of the high-temperature capillary tube, and the subcooling of refrigerant, while the heat transfer coefficients of refrigerant in the evaporators (hcH and hcL) are affected by the condensing pressure and the logarithmic-mean temperature difference of the specific evaporator. However, hcH and hcL are also affected by the lengths of the low- and high-temperature capillary tube, respectively. Additionally, the ratio of the cooling capacity of the high-temperature evaporator to the total capacity (α) is primarily affected by the condensing pressure and the logarithmic-mean temperature difference of both evaporators. The differences between the calculated and experimental data are between −4% and +5%, −16% and +16%, −12% and +16%, and −10% and +10% for , hcH, hcL, and α, respectively.