Two dual-evaporator natural convection refrigerators, one operating with a Lorenz-Meutzner cycle and the other with a modified Lorenz-Meutzner cycle, were tested with a control scheme to provide independent temperature control of the freezer and fresh food compartments. A solenoid valve is used to switch the refrigerant flow either to a path that passes through both the freezer and food evaporators or to a path passing through only one of the evaporators. It was found that the solenoid valve, together with the temperature glide of the zeotropic hydrocarbon mixture and the additional refrigerant path, provided the desired level of temperature control in the compartments of the refrigerators. With the additional control devices, the daily power consumption increased by 10.4% for the basic Lorenz-Meutzner (LM) cycle and by 5.6% for the modified Lorenz-Meutzner (MLM) cycle. Even though this energy penalty offsets the LM cycle savings, the MLM cycle still showed a net 6.5% CFC-free energy savings potential with respect to the conventional CFC-based Rankine cycle. Higher power consumption will result as the operating time of the additional refrigerant path increases.

KEYWORDS: year 1996, refrigerators, freezers, temperature control, cyclic, refrigerants, mixtures, propane, butane, fluorocarbons, energy consumption, refrigeration, testing, solenoid operating devices, temperature lift, comparing