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ACRC Technical Report 78PDF


Title:Friction and Heat Transfer Characteristics for Single-Phase Flow in Microchannel Condenser Tubes
Author(s):Graham, T.P.
Contributor(s):Dunn, W.E.
Subject(s):microchannel condenser tubes
Abstract:An experimental study of friction and heat transfer characteristics for single-phase flow in microchannel condenser tubes was conducted. Data were collected for the adiabatic flow of nitrogen, and also for the diabatic flow of single-phase R134a w.ith air in cross-flow. The nitrogen data were analyzed to obtain friction factors in the Reynolds number range of 500-20000, and the R134a data were analyzed to obtain Nusselt numbers in the Reynolds number ranges of 1000-7000 and 10000-70000. Several types of microchannel tubes were considered, including those with circular, square, enhanced square, and equilateral triangular ports. For each tube geometry, friction factors in the laminar regime follow the known analytical solution, but the critical Reynolds numbers for the noncircular tubes are all smaller than the value of 2100 found for the circular-port tube. In the turbulent regime, microchannel tube friction. factors follow a correlation for smooth tubes given by Churchill. Accordingly, there is no evidence of surface roughness or small length scale effects. Finally, Nusselt numbers in the range of 10000-70000, obtained from superheated vapor data, are within 10% of the correlation given by Gnielinski. The heat transfer data in the range of 1000-7000, obtained from subcooled liquid, are inconclusive.
Issue Date:1995-06
Publisher:Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report:Air Conditioning and Refrigeration Center TR-78
Genre:Technical Report
Sponsor:Air Conditioning and Refrigeration Center Project 48
Date Available in IDEALS:2009-04-17
Identifier in Online Catalog:3902855

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