| Summary: | The paper deals with the development and verification of an educational add-in for Microsoft Excel that determines the thermo-physical properties of various synthetic and natural refrigerants used in vapour-compression refrigeration (VCR) systems. To determine the properties of saturated and compressed liquid refrigerants, the add-in uses a linear interpolation function to interpolate the data published by ASHRAE. For superheated refrigerants, the add-in determines the enthalpy and entropy by adopting ideal-gas relationships in which the specific heat is also taken from ASHRAE data, but at a reduced pressure. The paper tests the accuracy of these relationships with different options for evaluating the reduced pressure by comparing their estimates against ASHRAE data for refrigerant R134a. The paper then shows how the add-in can be used to analyse a two-stage compression VCR system and compares the results with those obtained by using another Excel add-in for R134a developed at the University of Alabama. Finally, the paper shows how the add-in can be used with Solver to perform optimisation analyses of a three-stage compression VCR system also using R134a.
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