Importance

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Abstract

A system and method for controlling the temperature of thermal loads which might be controlled by refrigeration at any temperature within a wide range from -40.degree. C. to +120.degree. C. employs a refrigeration loop with pressure and temperature sensitive shunt paths to provide stabilized refrigerant flow so that a thermal expansion valve can operate stably only with liquid refrigerant inputs. For efficiency, thermal energy is interchanged between refrigerant returning from thermal energy exchange with a thermal load such as a cluster tool used in semiconductor fabrication and counterflow pressurized liquid refrigerant that is to be expanded for heat exchange. If the input in a suction line to the compressor is too high in temperature, a portion of pressurized refrigerant for the thermal expansion valve that is being subcooled prior to feeding to the valve is diverted into counterflow relationship with the subcooling exchange. This diversion both lowers the temperature of the pressurized refrigerant, thereby eliminating the possibility of partial vaporization, and lowers the input temperature to the compressor, preventing overheating. The proportion of flow is sufficiently small not to interfere with the main function of controllably cooling the thermal load. Concurrently, if the pressure input to the compressor drops too low, hot gas from the compressor output is shunted back to the input through a hot gas valve in a second shunt path.

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First Claim