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Title:Performance and optimization of microchannel condensers
Author(s):Heun, Matthew Kuperus
Doctoral Committee Chair(s):Dunn, William E.
Department / Program:Mechanical Science and Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Engineering, Mechanical
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 shape on microchannel tube performance. Furthermore, this study is the first to suggest methods for improving microchannel heat exchanger designs.
We collected experimental data for flat, multiport tubes with hydraulic diameters in the range of 0.6 mm $\leq\rm D\sb{h}\leq$ 1.5 mm. The port shapes considered were circles, squares, triangles, enhanced squares, and small squares. We found that established relationships describe single-phase circular-tube heat transfer and pressure drop behavior in microchannel tubes. Circular-tube correlations are 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 Dobson (1994) annual 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 designs. 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
Type:Text
Language:English
URI:http://hdl.handle.net/2142/20421
Rights Information:Copyright 1995 Heun, Matthew Kuperus
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9624362
OCLC Identifier:(UMI)AAI9624362


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