4341 (RP-993) -- Improved Fluids for Naturally Stratified Chilled Water Storage Systems PDF

This paper concerns the research performed in a search for alternative fluids or additives for depressing the freezing point below 32°F (0°C) of water used in chilled water storage systems, shifting or eliminating the density maximum of the resulting fluid to or below that of the depressed freezing point. The shifting or elimination of the density maximum from 39.2°F (4°C) for plain water is required to ensure the thermal stratification of the modified water solution. For the additives for which the approximate cost, corrosion, safety, and thermophysical data were obtained, it appears that ammonia, potassium formate, potassium nitrite, potassium acetate, sodium formate, and sodium nitrite are possibilities. Ammonia has the least cost, but corrosion, safety, and thermophysical property characteristics of the additives need to be determined or verified by testing and/or site demonstrations before their use.

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