A Semi-Empirical Method for Representing Domestic Refrigerator/Freezer Compressor Calorimeter Test Data
by Dagmar Jähnig, Douglas Reindl, Sanford Klein
Title: A Semi-Empirical Method for Representing Domestic Refrigerator/Freezer Compressor Calorimeter Test Data
Author(s): Dagmar Jähnig
Mass flow rate and power calorimeter test data for domestic refrigerator/freezer fully hermetic compressors have been collected on compressors from three manufacturers. The calorimeter test data were taken by 10 different organizations. These test data are commonly correlated with 10-coefficient polynomials (using the method presented in ARI Standard 540-91) as a function of the saturated evaporator and condenser temperatures. In general, these polynomial representations accurately represent the experimental data but do not necessarily provide reliable interpolations or extrapolations for conditions not represented in the compressor calorimeter tests. A semi-empirical model to represent compressor performance has been investigated. The model is based on the concept of volumetric efficiency and assumes a polytropic compression process. The model has five parameters that must be determined by fitting experimental data. Four or more measurements of refrigerant flow rate and compressor power were found to be sufficient to determine the model parameters, thereby allowing the generation of accurate compressor maps with the model. The model has been found to extrapolate within 5% error with condensing and evaporating temperatures that extend beyond the measured data by 10°C (18°F). A small set of available data for suction temperatures other than 32.2°C (90°F) were investigated. The results indicate that the model can accurately model the effect of changes in the suction temperature.