Journal
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
Volume 62, Issue -, Pages 124-134Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijheatmasstransfer.2013.02.068
Keywords
Two-phase flow; Refrigerant distribution; Vertical header; Microchannel heat exchanger
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Funding
- Air Conditioning and Refrigeration Center at the University of Illinois at Urbana-Champaign
- Creative Thermal Solutions
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R134a upward flow in four different vertical headers and its effect on R134a distribution into parallel microchannel tubes were investigated experimentally. R134a was provided into the header by (5 or 10) tubes in the bottom pass and exits through the (5 or 10) tubes in the top pass representing the flow in the heat pump mode of reversible systems. The inlet quality was varied from 0.2 to 0.8, and the mass flux from 92.26 to 276.79 kg m(-2) s(-1) per tube. The best distribution was at high flux and low quality. Experiment and visualization reveals the flow pattern effect in terms of homogeneity and momentum: churn flow has better distribution than separated flow since the two-phase mixture is more homogeneous; distribution is better at high mass flux in the header (by increasing mass flow rate, tubes number and/or tubes protrusion) because the higher momentum liquid can reach the top exit tube. (C) 2013 Elsevier Ltd. All rights reserved.
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