| 摘要 |
An auxiliary outside air refrigeration mechanism for a refrigerated storage room comprises an air-to-air heat exchanger wherein the two air supplies are sealed from each other by a physical seal and by a positive pressure air differential between the air supplies. An inlet and outlet for one air supply is connected to receive and return storage room air and an inlet and outlet for the other air supply is connected to receive and circulate outside air. A control mechanism automatically renders the auxiliary refrigerating mechanism operational when the outside temperature is a predetermined temperature below the upper temperature limit in the storage room. The control mechanism actuates the auxiliary refrigerating mechanism at a temperature below the temperature at which the conventional mechanical refrigerating unit is actuated, thus supplementing the conventional refrigerating unit when the outside temperature is cold. The control mechanism automatically switches off the outside air circulation when condensate in the heat exchanger freezes, and the unit self defrosts and drains the water through an inclined opening. The heat exchanger employs a special tube bundle formed of thin-walled thermoplastic tubes heat welded in openings in thermoplastic traverse mounting plates at opposite ends of the tube bundle.
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