Author Topic: Understanding Boat Refrigerator Plates  (Read 245 times)

Richard

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Understanding Boat Refrigerator Plates
« on: April 02, 2018, 11:46:48 am »
Thermo plates, Power plates and holding plates are all evaporator plates. The evaporator in a refrigerator is where liquid refrigerant is converted to as gaseous form of vapor absorbing heat as it changes. If a compressor has available surplus energy holding plates are sometimes used to store that surplus energy for use later. Power and Thermo plates store only small amounts of energy. Of all the different types of evaporators the standard evaporator maintains the best even control over box temperature.

Power and thermo plates help to smooth out the compressor stop and start run times but store very little Btu energy.. These small 12/24 volt compressors generally do not produce surplus Btu to store in holding plates unless boat is equipped with alternative sources of power from Solar or wind generation systems.

As far as a blue-water sailor is concerned it is only on the first day when refrigerator system is turned on will you see a difference in the different evaporator types. The standard evaporator begins to collect a very thin layer of frost after 15 minutes compressor running time. Thermo and power plates will take a longer running time to develop a frost cover. Holding holdover plates designed for freezing temperatures with cap tube flow control will take from 2 to 24 hours to freeze all of the eutectic solution, for this reason large holding plate systems use Thermo Expansion Valves instead of cap tubes.

In my thirty six years experience with manufacturing testing eutectic holding plates leads me to believe only a few plate designs would  have the COP as high as a roll bond thin aluminum evaporator plate. I have opened eutectic plates to inspect them from Frigoboat, Glacier Bay, Technautics, SeaFrost and Dole. Dole has probably built more pleasure boat refrigerator holding plates than any other company in the US. Dole I believe to have the most efficient plates for these reasons; True eutectic brine corrosion resistant mix solutions, Two independent evaporator coils mechanically attached  to exterior steel cold galvanized tank for quick thermo heat conduction between steel refrigerant evaporator tube assembly and warm products inside  refrigerated box. The solution in a Dole plate does not need to be frozen solid for heat to be extracted from box.

Most companies holding plates are designed to allow solution to freeze first on evaporator coils. Ice continuing to form around and away from coil reduces the rate of heat removed from area to be refrigerated. Companies that experiment with so called Super Eutectic Solution have problems. The companies that use Glycol and water eutectic mixtures eventually find poor plate performance because over time Glycol will separate from water and settle to the bottom as a jell substance.