Separate experiments with a condenser and an evaporator showed that changes in refrigerant-side heat transfer coefficients produced variations in overall heat transfer resistance of up to 20% over a wide range of operating conditions. An extensively instrumented refrigerator was used to gather air- and refrigerant-side temperature, pressure, power, and refrigerant mass flow measurements to provide in situ colorimetry for 95 operating conditions. These operating conditions included three different refrigerator charges that provide a variety of evaporator and condenser outlet conditions. Accounting for the variation in refrigerant-side heat transfer coefficients produced better results than assuming that the heat transfer coefficients were constant. The variable conductance models developed can be used to predict changes in performance resulting from the use of alternative refrigerants and different heat exchanger tube dimensions.

KEYWORDS: year 1995, experiment, validating, heat exchangers, refrigerators, freezers, condensers, evaporators, heat transfer coefficient, heat flow, operations, temperature, pressure, refrigerants, fluid flow, climate chambers, calorimeters, calculating, performance, replacing