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ACRC Technical Report 68PDF


Title:Refrigerant-Oil Mixtures and Local Composition Modeling
Author(s):Martz, W.L.; Jacobi, A.M.
Subject(s):refrigerant-oil combinations
saturation pressure-temperature relationships
Abstract:The solubility and miscibility refrigerant-oil mixtures are important in understanding the performance of refrigeration and air-conditioning systems. The objective of this study was to provide useful information on the thennophysical properties of new refrigerant-oil mixtures and to evaluate candidate mixture models. In this report, the effect of a polyol ester lubricant on equilibrium pressure, liquid density, and viscosity is presented for R-22, R-125, R-134a, and AZ20 (50% R-125, 50% R-32) at varying temperatures and concentrations. Deviations from ideal mixture behavior are interpreted using activity coefficients and may be manifested in three ways: positive, negative, or mixed deviations from Raoult's law. The departure from Raoult's law is related to molecular size differences and intennolecular forces in the mixture. Six different models are used to correlate the experimental data: Wilson's relation, the Heil equation, the Non-Random Two Liquid (NRTL) model, the Universal Quasi-Chemical (UNIQUAC) theory, and two different extensions of Wilson's relation. Interaction parameters for all six models are developed from the experimental data (and data from a previous ACRC research project). A comparison of the pressure predictions (activity coefficients) for each model over a wide range of mixture compositions and temperatures shows that the Heil equation has the best overall penonnance. The Heil equation correlates the saturation behavior of these mixtures with an average error less than 6%. The report is organized as follows: Chapters 1 & 2: Background material and research objectives. Chapter 3: A detailed description of the apparatus and test procedure. A comparison of measurements from this apparatus to ASHRAE data. Chapter 4: Experimental data: mixture pressure as a function of liquid mass fraction and temperature; liquid density as a function of liquid mass fraction and temperature; viscosity as a function of temperature and liquid mass fraction. Oil density data and limited miscibility results (see also Appendix D). Chapter 5: Data analysis background (see also Appendix A). Chapter 6: Mixture modeling background (see also Appendices B, C, &E). Chapter 7: Interaction parameters for all mixtures and models are provided, and a detailed comparison of model performance is given. Chapter 8: A very brief summary of conclusions and recommendations.
Issue Date:1994-10
Publisher:Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report:Air Conditioning and Refrigeration Center TR-68
Genre:Technical Report
Sponsor:Air Conditioning and Refrigeration Center Project 17
Date Available in IDEALS:2009-04-17
Identifier in Online Catalog:3830670

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