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ACRC Technical Report 61PDF


Title:Refrigerator/Freezer System Modeling
Author(s):Goodson, M.P.; Bullard, C.W.
Subject(s):cycling performance
Abstract:This report describes the development of a refrigerator/freezer model (RFSIM) that is capable of running in either design mode (user-specified superheat and subcooling) or full simulation mode. The primary purpose was to build on the foundation of an earlier version of the model, to make it refrigerant-independent, and to compare it to experimental data. First, a capillary tube-suction line heat exchanger (ct-sl hx) model, based on first principles, replaced a curve fit of experimental data that had previously calculated the mass flow rate through the capillary tube, in such a way that the speed and robustness of the model were not sacrificed. Second, a study of several void fraction correlations was also conducted to determine which one would most accurately calculate the refrigerant in the two-phase zones of the condenser and evaporator, and refrigerant inventory equations for the single-phase components and the lubrication oil were also included in the model. Lastly, several heat transfer and pressure drop correlations were added to allowed the calculation of the overall heat transfer coefficients and pressure drops in each zone of the evaporator and condenser. The predictions of the model in both design and simulation mode were then compared to experimental data. The results of the design mode analysis showed that the model predicted several system variables, including efficiency and evaporator capacity, very accurately. The accuracy of the design model could only be improved by using more accurate maps. The simulation model results reflected the errors in the ct-sl hx component model, which significantly underpredicts the mass flow rate. Simulation results using propane are consistent with these findings, but reflect additional errors associated with the lack of compressor map data obtained with propane.
Issue Date:1994-08
Publisher:Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report:Air Conditioning and Refrigeration Center TR-61
Genre:Technical Report
Sponsor:Air Conditioning and Refrigeration Center Project 30
Date Available in IDEALS:2009-04-06

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