Secondary refrigerants for indirect systems on thermophysical properties

A ''Working group on Secondary Refrigerants'' met in August 1995 to agree on the material for an IIR-publication on secondary refrigerants. It was decided that the material in Handbook No 12 of the Swedish Society of Refrigeration should be updated for such an IIR-publication entitled ''Thermophysical Properties of Liquid Secondary Refrigerants''. Methods used for updating the material have been literature search, numerical analysis and laboratory measurements. The publication contains thermophysical properties for aqueous solutions and some non-aqueous heat transfer liquids and comparisons are made. Properly data from tables have been converted into uniform polynom equations and sets of coefficients that can be put into computer programs for various applications. This paper focus on comparisons of different secondary refrigerants for freezer applications. Water solutions of potassium acetate, the main ingredient in some new secondary refrigerants on the market, perform somewhat better than ethylene glycol (higher heat transfer coefficient and with laminar flow also somewhat lower pressure drop), much better than most other organic aqueous solutions but not as good as calcium chloride. Non-aqueous liquids, such as silicon oils, require 2.5 - 3 times higher volume flow. They give lower pressure drop but also lower heat transfer coefficient.