Methods and apparatus for operating a refrigeration system

A method of using a flash tank in a refrigeration system which has an economizer cycle, including a refrigerant circuit having a refrigerant compressor which includes a suction port, an intermediate pressure port, and a discharge port, a condenser, an evaporator, a liquid line between the condenser and evaporator, a main suction line between the evaporator and the suction port, an auxiliary suction line between the flash tank and the intermediate pressure port, and a hot gas line between the discharge port and condenser, comprising the steps of:

• providing a flash tank,
• providing a cooling cycle by directing refrigerant from the compressor and condenser to the evaporator via the flash tank,
• controlling the flow of refrigerant which enters the flash tank from the condenser with a liquid sub-cooling valve, which opens and closes to maintain a predetermined degree of sub-cooling in the refrigerant,
• controlling the flow of refrigerant which flows from the flash tank to the evaporator with a thermostatic expansion valve which has a temperature control bulb disposed in heat exchange relation with the main suction line,
• providing a heating condenser in heat exchange relation with the evaporator,
• providing a hot gas heating cycle for the refrigeration system by connecting the hot gas line to the heating condenser instead of the condenser, and
• providing an orifice which interconnects the heating condenser and the main suction line, to permit refrigerant trapped in the heating condenser after a heating cycle to enter a cooling cycle,
• whereby the need for a float valve in the flash tank to control refrigerant flow is eliminated.

A refrigeration system for cooling a served space which has an economizer cycle, including a refrigerant circuit having a compressor which includes a suction port, an intermediate pressure port, and a discharge port, a condenser, an evaporator, a liquid line between the condenser and evaporator, a main suction line between the evaporator and the suction port, and a hot gas line between the discharge port and condenser, comprising:

• a flash tank in the liquid line,
• said flash tank having liquid input and liquid output points, with the flash tank defining a storage space for refrigerant between said liquid input point and said liquid output point,
• an auxiliary suction line between the flash tank and the intermediate pressure port,
• a liquid sub-cooling valve disposed between the condenser and the liquid input point of said flash tank,
• said liquid sub-cooling valve controlling the flow of refrigerant which enters the liquid input point of said flash tank from the condenser by opening and closing to maintain a predetermined degree of sub-cooling in the refrigerant,
• and a thermostatic expansion valve disposed between the liquid output point of said flash tank and the evaporator,
• said thermostatic expansion valve having a temperature control bulb disposed in heat exchange relation with the main suction line,
• said thermostatic expansion valve controlling the flow of refrigerant from the liquid output point of said flash tank to the evaporator,
• whereby the need for a float valve in the flash tank to control refrigerant flow is eliminated.

A refrigeration system for cooling a served space which has an economizer cycle, including a refrigerant circuit having a compressor which includes a suction port, an intermediate pressure port, and a discharge port, a condenser, an evaporator, a liquid line between the condenser and evaporator, a main suction line between the evaporator and the suction port, and a hot gas line between the discharge port and condenser, comprising:

• a flash tank in the liquid line,
• an auxiliary suction line between the flash tank and the intermediate pressure port of the compressor,
• a liquid sub-cooling valve disposed between the condenser and the flash tank,
• said liquid sub-cooling valve controlling the flow of refrigerant which enters the flash tank from the condenser by opening and closing to maintain a predetermined degree of sub-cooling in the refrigerant,
• a thermostatic expansion valve disposed between the flash tank and the evaporator,
• said thermostatic expansion valve having a temperature control bulb disposed in heat exchange relation with the main suction line,
• said thermostatic expansion valve controlling the flow of refrigerant from the flash tank to the evaporator,
• means for providing a hot gas heating cycle to heat the served space or defrost the evaporator coil,
• said means for providing a hot gas heating cycle including a heating condenser and valve means,
• said heating condenser being disposed in heat exchange relation with the evaporator,
• said valve means being disposed in the hot gas line,
• said valve means connecting the compressor to the condenser during a cooling cycle,
• said valve means connecting the compressor to the heating condenser during a hot gas heating cycle,
• and an orifice disposed to interconnect the heating condenser and the main suction line, to permit refrigerant trapped in the heating condenser during a heating cycle, to enter a cooling cycle,
• whereby the need for a float valve in the flash tank to control refrigerant flow is eliminated.