Helical conveyor freezer

A combination food freezer having mechanical and cryogenic cooling apparatus comprising:

• a source of cryogen;
• an insulated enclosure including a conveyor for conveying food products through said enclosure;
• refrigeration apparatus including a first heat exchanger receiving mechanically cooled refrigerant, said refrigerant having a composition different from said cryogen, and disposed within said enclosure and gas circulation means to circulate an atmosphere gas through said first heat exchanger and across said food products to cool said food products;
• said refrigeration apparatus including mechanical refrigeration connected to said first heat exchanger to circulate a mechanically-cooled refrigerant through said first heat exchanger, said refrigeration apparatus further including cryogenic cooling apparatus coupled to said source of cryogen and having means within said enclosure for spraying said cryogen across the food products on said conveyor;
• and
• a second heat exchanger connected between said mechanical refrigeration and said first heat exchanger, so as to receive said mechanically-cooled refrigerant and said second heat exchanger coupled to said source of cryogen to subcool said cryogen with the mechanically-cooled refrigerant prior to spraying said cryogen across said food products and prior to circulating the mechanically-cooled refrigerant through said first exchanger.