Experimental study of a series-connected two-evaporator refrigerating system with propane (R-290) as the refrigerant

The performance of a refrigerating system with an environment-friendly refrigerant, propane (R-290) as the refrigerant, was experimentally studied. There were two evaporators connected in series within the system under study. The results show that with both lengths of the two capillary tubes fixed, both the mass flow rate of the refrigerant and the suction pressure of the system increase with the condensing pressure. In addition, the cooling capacity of the high-temperature evaporator decreases, but that of the low-temperature evaporator increases. As the condensing pressure is fixed and the length of the capillary tube for the high-temperature evaporator is increased while that for the low-temperature evaporator is fixed, the cooling capacity of the high-temperature evaporator increases while that of the low-temperature evaporator decreases. On the other hand, as the capillary tube for the low-temperature evaporator is lengthened while that for the high-temperature evaporator is fixed, the variations in the cooling capacity of these two evaporators reverse. The enthalpy changes of the refrigerant within the evaporators are strongly affected by the length of the high-temperature capillary tube, while the evaporating pressures are influenced mainly by the length of the low-temperature capillary tube.