Abstract: An open loop, air refrigerant heat pump process is set forth for producing a refrigerated atmosphere inside an enclosed space, in particular the enclosed space of a food freezer. A key to the present invention is that it uses a portion of the cold expander discharge to cool the air feed to the expander, prior to using said portion as a regeneration gas for the front end, adsorbent-containing drier. This is key because it allows one to eliminate the prior art's need to recover refrigeration from the air exiting the enclosed space which, more importantly, allows one to eliminate the prior art need to remove any cryogenically generated ice that the air picks up inside the food freezer.