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oai:www.ideals.illinois.edu:2142/20421 2023-07-10 col_2142_5131 col_2142_14787 com_2142_5130 com_2142_9630 com_2142_234

Dunn, William E. Heun, Matthew Kuperus 2011-05-07T12:38:43Z 2011-05-07T12:38:43Z 10000-01-01 1995 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. Made available in DSpace on 2011-05-07T12:38:43Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9624362.pdf: 9687386 bytes, checksum: ecd1293fd0d9961ebb4271ccfa2e7430 (MD5) Previous issue date: 1995 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:43:47Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:19:12-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9624362 (UMI)AAI9624362 http://hdl.handle.net/2142/20421 eng Copyright 1995 Heun, Matthew Kuperus Engineering, Mechanical Performance and optimization of microchannel condensers text Mechanical Science and Engineering Mechanical Engineering University of Illinois at Urbana-Champaign Dissertation Ph.D.