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Research Papers

Representative Results for Condensation Measurements at Hydraulic Diameters 100Microns

[+] Author and Article Information
Akhil Agarwal

 Shell Global Solutions, Inc., Houston, TX 77210

Srinivas Garimella1

George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405srinivas.garimella@me.gatech.edu

1

Corresponding author.

J. Heat Transfer 132(4), 041010 (Feb 22, 2010) (12 pages) doi:10.1115/1.4000879 History: Received December 01, 2008; Revised April 28, 2009; Published February 22, 2010; Online February 22, 2010

Condensation pressure drops and heat transfer coefficients for refrigerant R134a flowing through rectangular microchannels with hydraulic diameters ranging from 100μm to 200μm are measured in small quality increments. The channels are fabricated on a copper substrate by electroforming copper onto a mask patterned by X-ray lithography and sealed by diffusion bonding. Subcooled liquid is electrically heated to the desired quality, followed by condensation in the test section. Downstream of the test section, another electric heater is used to heat the refrigerant to a superheated state. Energy balances on the preheaters and postheaters establish the refrigerant inlet and outlet states at the test section. Water at a high flow rate serves as the test-section coolant to ensure that the condensation side presents the governing thermal resistance. Heat transfer coefficients are measured for mass fluxes ranging from 200kg/m2s to 800kg/m2s for 0< quality <1 at several different saturation temperatures. Conjugate heat transfer analyses are conducted in conjunction with local pressure drop profiles to obtain accurate driving temperature differences and heat transfer coefficients. The effects of quality, mass flux, and saturation temperature on condensation pressure drops and heat transfer coefficients are illustrated through these experiments.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Microchannel layout

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Figure 2

Wafer layout for electroforming

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Figure 3

Assembled refrigerant channels

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Figure 4

Coolant channels, test-section subassembly

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Figure 5

Test facility schematic

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Figure 6

Test facility photograph

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Figure 7

Refrigerant flow path schematic for pressure drop analysis

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Figure 8

Pressure drop along the length of the test section for the representative case

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Figure 9

Segmental conjugate heat transfer analysis

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Figure 10

Temperature distribution for the representative case

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Figure 11

Variation in segment heat duty along channel length

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Figure 12

Frictional pressure drop for 200×100 μm channels

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Figure 13

Heat transfer results for 200×100 μm channels

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