The present subject matter relates generally to systems and methods for defrosting eutectic plates of a refrigeration system.
Refrigeration plates for maintaining a low temperature in a storage area are well known. For example, trucks with refrigerated storage areas are commonly used for transporting frozen or perishable foods. In a typical storage area, a refrigeration unit comprises a plurality of metal plates. Each metal plate has a cavity filled with an amount of freezable fluid or eutectic solution and a conduit immersed in the eutectic solution. The conduit winds back and forth through the interior of the plate, with the two ends of the conduit communicating with the outside of the plate. An exemplary refrigeration plate is described in U.S. Pat. No. 3,756,037, the disclosure of which is hereby incorporated herein by reference.
The ends of the conduit are connected in line with a refrigeration circuit including, among other things, a condenser, a compressor, and a volatile refrigerant that flows through the circuit. An exemplary refrigeration circuit is described in U.S. Pat. No. 4,043,144, the disclosure of which is hereby incorporated herein by reference. A “freezing cycle” is implemented to freeze the eutectic solution during a period of non-use of the refrigerated storage area. Once the eutectic solution has frozen and the plates have reached a sufficiently low temperature, the freezing cycle is terminated and the storage area may be returned to use during an operating period. During the operating period, air is blown across the plates to cool the storage area while the truck is used to deliver the cargo to its destination.
Over the course of the operating period, frost may accumulate on the surface of the plates due to moisture in the air. Since frost acts as a thermal insulator, the presence of frost on the plates and between adjacent plates reduces their cooling efficiency, so the plates must be periodically defrosted.
There are several known methods for defrosting the plates. For example, U.S. Pat. No. 3,727,422 describes a method of applying water to the surfaces of the plates to remove frost. In another system, which is described in U.S. Pat. No. 4,043,144, a defrost coil is positioned against the outer surfaces of the plates and hot gas is run therethrough to defrost the plates. U.S. Pat. No. 6,595,019 describes yet another system, which employs vertical scrapers that are moved across the outer surfaces of the plates to remove frost. All of these patents are hereby incorporated herein by reference.
All of these methods have certain disadvantages. For example, using water to defrost the plates requires an operator to connect a water hose to a water dispersal or spray system to begin the defrosting process by running relatively warm water over the frost. Then the water falling off of the plates has to be collected and disposed of. And finally the operator has to disconnect the hose when the defrosting process is completed.
In view of the foregoing, there is a need for a defrost system and method which are not only effective, but which also eliminate the need for human intervention for defrosting control.