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ACRC Technical Report 05PDF


Title:The Intertube Falling-Film Modes: Transition, Hysteresis, and Effects on Heat Transfer
Alternative Title:Two-zone modeling of a mobile air conditioning plate-fin evaporator
Author(s):Siambekos, C.T.
Contributor(s):Crawford, R.R.
Subject(s):plate-fin evaporator
mobile air conditioning systems
Abstract:The objective of the CU1TeJ1t study was to simulate the steady-state performance of an automotive air conditioning plate-fin evaporator. A one-zone model was defined for conditions when the evaporator outlet refrigerant exited as a two-phase mixture. A two-zone model was defined for conditions when the evaporator outlet refrigerant exited in a sUperheated state. An intermediate state was defined where the refrigerant changes from a saturated to a superheated vapor. 'Ibis intermediate state devided the evaporator into an evaporating and superheating section (Le. a two-zone model). The models were based on basic refrigerant momentum equations, air-side enthalpy potential equations, and air-side mass transfer equations. Each of these equations were applied to each section of the models. In order to predict the surface temperature, a refrigerant-side thermal resistance was defined thus allowing the surface temperature to "float" between the air and refrigerant temperatures. Furthermore, the predicted surface temperature was used for calculations in the enthalpy potential and the mass transfer equations. Embedded into each equation are parameters which are specific to both the heat exchanger geometry and the two working fluids (air and R-134a). Correlations for each of these parameters were determined with a least-squares fit of experimental data. Equation forms for the correlations developed were based on correlations found in the literature. It was found that the one- and two-zone models were able to predict the evaporator energy transfer, refrigerant pressure drop, air humidity ratio change, and air temperature change within a small percentage of the measured values. Finally, it was found that the trends for the model correlations developed described the parameters well.
Issue Date:1991-10
Publisher:Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report:Air Conditioning and Refrigeration Center TR-05
Genre:Technical Report
Sponsor:Air Conditioning and Refrigeration Center Project 09
Date Available in IDEALS:2009-03-06
Identifier in Online Catalog:3383930

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