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ACRC Technical Report 81PDF

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Title:Performance and Optimization of Microchannel Condensers
Author(s):Heun, Matthew Kuperus; Dunn, W.E.
Subject(s):microchannel condenser tubes
Abstract:This study is the first to document the condensation heat transfer performance of small diameter, microchannel tubes in crossflow heat exchange, and this study provides the fIrSt systematic evaluation of the effect of port ~hape on microchannel tube performance. Furthermore, this study is the flI'St to suggest methods for improving microchannel heat exchanger designs. We collected experimental data for flat, multiport tubes with hydraulic diameters in the range 0.6 mm S Db S 1.5 mm. The port shapes considered were circles, squares, triangles, enhanced squares, and small squares. We found that established relationships describe singlephase circular-tube heat transfer and pressure drop behavior in microchannel tubes. Circular-tube correlations are appropriate for noncircular tubes if dimensionless numbers are formed with appropriate length scales. The wavy flow correlation of Dobson [1994] was found to predict accurately condensing heat transfer in flows predicted to wavy. A slightly modified form of the Dob~n [1994] annular flow correlation was found to predict accurately condensing heat transfer in flows predicted to be annular. An analytical study·of methods to improve microchannel condenser design was performed. We found that volume minimization is a comprehensive and reasonable objective for. the suboptimization analysis. As condenser volume is reduced, system charge, condenser mass, and material costs all decrease • . ' . Refrigerant-side circuiting flexibility is the key that unlocks the potential of the microchannel technology. With unconstrained refrigerant circuiting, smaller port diameters always lead to reduced condenser volume. However, the pressure-drop effect drives optimal condenser designs toward many tubes of short length, and the crossflow-heat-exchanger effect drives optimal condenser designs toward many tubes of short length and few ports. We found that port shape significantly impacts condenser design. To achieve reduced internal volume, the order of preference for port shapes is circle, square, and triangle. To achieve minimized external volume, the order of preference for port shapes is triangle, square, and circle.
Issue Date:1995-07
Publisher:Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Series/Report:Air Conditioning and Refrigeration Center TR-81
Genre:Technical Report
Type:Text
Language:English
URI:http://hdl.handle.net/2142/11041
Sponsor:Air Conditioning and Refrigeration Center Project 48
Date Available in IDEALS:2009-04-17


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