Tuesday, June 14, 2011

Phase Change Material for Marine Holdover Plates

Holdover plates, as defined by the Refrigeration Parts Solution, are stainless steel tanks which contain an evaporator coil surrounded by a Phase Change Material called propylene glycol .  As the compressor runs, this solution freezes.  Once the compressor turns off, the frozen solution continues to absorb heat from the refrigerated box thereby extending the "off" cycle of the compressor.  When incorporated into a properly designed system, holdover plates can significantly reduce average energy consumption.





Holdover Plate by myboatsgear
Marine Holdover Plates also known as Marine Refrigerator Holding Plates act like large blocks of ice and can maintain cold for long periods for refrigerators and freezers. These hold over plates are made out of Stainless Steel and Copper Tubing. Non-Toxic propylene glycol in different concentrations is used as a liquid to store the energy. 


Wikipedia notes the environmental safety for Propylene glycol. It is known to exert high levels of biochemical oxygen demand (BOD) during degradation in surface waters. This process can adversely affect aquatic life by consuming oxygen aquatic organisms need to survive. Large quantities of dissolved oxygen (DO) in the water column are consumed when microbial populations decompose propylene glycol. Sufficient DO levels in surface waters are critical for the survival of fish, macro invertebrates, and other aquatic organisms. 


Phase Change Material like savEnrg™ PCM23N can be an environmentally safe and economical replacement for 40% Propylene glycol solution . PCM23N is an inorganic salt hydrate that is safe for the environment, non toxic and non flammable. The product is compatible with stainless steel, copper and high density polyethylene however, corrosive to aluminum. This product features a melting point of  -22°C and freezing point of - 23°C. PCM23N has a latent heat storage capacity of 200 kJ/Kg and sensible heat storage of 0.83 kcal/kg.k. It's solid density is 1120 Kg/m3 and a liquid density of 1180 Kg/m3 featuring a low volumetric expansion during phase change. The product is recommended to be used for the freezer application and provides very effective temperature control for long duration's. 



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