Refrigeration system using liquid-to-liquid heat transfer for warm liquid defrost

A warm liquid defrost refrigeration system comprising:

• a primary refrigeration loop including a compressor, a condenser, a receiver an expansion device, and a first side of a chiller;
• a secondary refrigeration loop including a pump, a second side of said chiller, and a refrigerated space heat exchanger, wherein said secondary refrigeration loop is in thermal communication with said primary refrigeration loop through said chiller;
• a defrost heat exchanger having a hot side and a cold side, said hot side of said defrost heat exchanger being connected to said primary refrigeration loop between said receiver and said expansion device such that liquid refrigerant can flow from said receiver through said hot side of said defrost heat exchanger;
• a coolant supply line having first and second ends, said first end of said coolant supply line being connected to said secondary refrigeration loop at a point downstream of said pump and said second end of said coolant supply line being connected to said cold side of said defrost heat exchanger;
• and
• a warm liquid supply line having first and second ends, said first end of said warm liquid supply line being connected to said cold side of said defrost heat exchanger and said second end of said warm liquid supply line being connected to said refrigerated space heat exchanger;
• wherein when a defrost cycle is operated, coolant from the secondary refrigeration system flows through said cold side of said defrost heat exchanger, is heated by the liquid refrigerant flowing through said hot side of said defrost heat exchanger, and then is transported to said refrigerated space heat exchanger to melt any frost formed on said refrigerated space heat exchanger.

A method for warming coolant for warm liquid defrost in a secondary coolant refrigeration system comprising a primary refrigeration loop including a compressor, a condenser, a receiver and the first side of a chiller, and a secondary refrigeration loop including a pump, the second side of the chiller and a refrigerated space heat exchanger, said method comprising the steps of:

• providing a defrost heat exchanger having a hot side and a cold side;
• transporting high temperature liquid refrigerant from the receiver through the hot side of the defrost heat exchanger while simultaneously transporting low temperature coolant from the pump through the cold side of the defrost heat exchanger such that the coolant is heated by the liquid refrigerant;
• and
• transporting the heated coolant from the cold side of the defrost heat exchanger to the refrigerated space heat exchanger to melt any frost formed on the refrigerated space heat exchanger.