Abstract: A liquid/gas bypass line bypasses an expansion device of a refrigeration apparatus. An inlet of the bypass line is connected slightly above the bottom of a condenser so that it can pass either liquid refrigerant or vaporous refrigerant, depending on the level of liquid refrigerant in the condenser. The other end of the bypass line is connected to discharge into the evaporator, bypassing the expansion device. The bypass line functions as a conventional hot gas bypass during low load conditions when the level of liquid refrigerant is below the line's inlet. When the level rises above the inlet, often occurring when the condenser coolant temperature is low and the compressor is fully loaded, the bypass line returns excess accumulated liquid refrigerant to the evaporator. Maintaining the proper levels of liquid refrigerant in both the condenser and the evaporator not only provides the most effective use of their heat transfer surfaces, but also promotes the proper return of oil to the compressor.

Abstract: A lubricant composition with decreased solubility in a liquid refrigerant and increased foaming characteristics useful in refrigeration systems to promote oil return to a compressor. A lubricant composition comprises a base lubricant, synthetic paraffinic oil, and a foaming agent. These ingredients are blended in predetermined amounts, so that when the lubricant is used in the refrigeration system, an oil rich layer will form atop the liquid refrigerant in the system's flooded evaporator, and a thick, stable foam will form when vaporized refrigerant boils up through the oil rich layer. The oil foam is then drawn through a connection at the top of the flooded evaporator and returned to the compressor.

Abstract: An air conditioning system and method of operation for reducing cyclic losses due to non-steady state operation at the start of operating cycles are disclosed. A bi-flow expansion valve assembly is provided in the refrigerant line between the heat exchangers, and the valve assembly can meter refrigerant flow between the heat exchangers or can permit substantially unrestricted flow therethrough. At the start of a cycle, the valve assembly is adjusted to allow refrigerant to flood between the heat exchangers, thereby correcting mislocation of refrigerant caused by the migration of refrigerant to the evaporator during the off-cycle, or caused when heat exchanger functions are switched, as, for example, during a defrost cycle of a heat pump.

Abstract: A heat pump system and method, wherein the system may be operated in cascade fashion to heat water using heat extracted from relatively cold outdoor ambient air, or in non-cascade fashion to provide supplemental heating or cooling in a comfort zone. The system uses a first and a second refrigerant fluid with separate compression cycle loops passing in heat transfer relationship through a tri-fluid heat exchanger. In a first mode of operation, the first refrigerant fluid condensed while heating water is vaporized in the tri-fluid heat exchanger to cool air supplied to the comfort zone, and in a second mode the first refrigerant fluid is vaporized by heat rejected from condensing the second refrigerant fluid. In a third mode, wherein only the second refrigerant loop is operative, air passing through the tri-fluid heat exchanger to the comfort zone is heated by condensation of the compressed second refrigerant fluid.