A Multi-Substance Add-in for the Analyses of Thermo-fluid Systems using Microsoft Excel

Mohamed M. El-Awad

Analyses of thermo-fluid systems require the thermo-physical properties of the working fluids to be repetitively determined at different conditions of pressure and or temperature. However, relevant computer applications may not be available to many engineering students and practicing engineers particularly in developing countries. This paper presents an add-in that determines these properties for various fluids by using Microsoft Excel. Developed with Microsoft VBA, the add-in provides property functions for ideal gases, saturated and superheated water, saturated and superheated refrigerants for vapour-compression (VC) systems, binary solutions of ammonia-water and water-lithium bromide for vapour-absorption (VA) refrigeration systems, reacting mixtures, and atmospheric air. With its comprehensive library of functions, the add-in enables Microsoft Excel to be used as a modelling platform for conducting parametric and optimisation analyses of advanced power generation and refrigeration cycles, air-conditioning systems, and combustion processes. The present paper highlights the general features of the add-in before focussing on the set of functions that deal with the analyses of VC and VA refrigeration cycles. For the analyses of VC systems, the add-in currently supports ten synthetic and natural refrigerants (R12, R22, R32, R123, R134a, R152a, R717, R290, R600, R600a). The paper verifies the add-in functions for VC analyses by comparing its results with those obtained from relevant published research that used the well recognised REFPROP software. Similarly, the paper verifies the add-in functions for both ammonia-water and water-lithium bromide VA systems. The results obtained for both VC and VA cycles show that the add-in gives reasonably accurate estimations.