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ACRC Technical Report 202PDF


Title:Characterization of Two-Phase Flow in Microchannels
Author(s):Nino, V.G.; Hrnjak, P.S.; Newell, T.A.
Subject(s):void fraction
pressure drop
Abstract:Aluminum multi-port microchannel tubes are currently utilized in automotive air conditioners for refrigerant condensation. Recent research activities are directed toward developing other air conditioning and refrigeration systems with microchannel condensers and evaporators. Three parameters are necessary to analyze a heat exchanger performance: heat transfer, pressure drop, and void fraction. The purpose of this investigation is the experimental investigation of void fraction and frictional pressure drop in microchannels. A flow visualization analysis is another important goal for two-phase flow behavior understanding and experimental analysis. Experiments were performed with a 6-port and a 14-port microchannel with hydraulic diameters of 1.54 mm and 1.02 mm, respectively. Mass fluxes from 50 to 300 kg/s.m2 (range of most typical automotive applications) are operated, with quality ranging from 0% to 100% for two-phase flow experiments. R410A, R134a, and air-water mixtures are used as primary fluids. The results from the flow visualization studies indicate that several flow configurations may exist in multi-port microchannel tubes at the same time while constant mass flux and quality flow conditions are maintained. Flow mapping of the fluid regimes is accomplished by developing functions that describe the fraction of time or the probability that the fluid exists in an observed flow configuration. Experimental analysis and flow observations suggest that pressure drop and void fraction in microchannel is dependent on the most probable flow regime at which the two-phase mixture is flowing. In general, correlations for void fraction and pressure drop predictions are based in a separated flow model and do not predict the experimental results in the range of conditions investigated. A flow regime based model is developed for pressure drop and void fraction predictions in microchannels.
Issue Date:2002-10
Publisher:Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report:Air Conditioning and Refrigeration Center TR-202
Genre:Technical Report
Sponsor:Air Conditioning and Refrigeration Project 107
Date Available in IDEALS:2009-06-04

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