Abstract

Boiling is an efficacious mode of heat transfer and is utilized in various energy conversions, heat exchange systems and in cooling of high energy density electronic components. Fundamental pool boiling mechanisms suggest that liquid rewetting on a heated surface is a key factor in delaying critical heat flux (CHF) for enhancing pool boiling performance. In this study, pool boiling enhancement is achieved by providing improved liquid supply pathways to nucleation sites in open microchannels.

A two part study is conducted to enhance pool boiling performance of open microchannels. Micromachined and porous surfaces are identified as enhancement techniques in Part-I and Part-II respectively. The results obtained in part-I showed significant improvement in the pool boiling performance when tested with water and FC-87. In part-II of the study, porous coatings are deposited on the boiling surface of an open parallel microchannel fin tops, channel bottoms and both, and individually investigated for their pool boiling performance. The best performing surface was with porous coatings throughout the geometry and had a CHF of 313 W/cm2 at a wall superheat of 7.5 °C. High speed images for the three surfaces show that bubble nucleation occurred at the location of porous deposits. Furthermore, additional nucleation sites are identified as the main contributing factor in the best performing surface which had an enhancement of 150% in CHF when compared to a plain surface. Efficient liquid recirculation provided by open microchannels also contributed to improved microconvection in the channels.

Library of Congress Subject Headings

Heat sinks (Electronics); Heat exchangers--Fluid dynamics; Ebullition; Microfluidics

Publication Date

11-2014

Document Type

Thesis

Student Type

Graduate

Degree Name

Mechanical Engineering (MS)

Department, Program, or Center

Mechanical Engineering (KGCOE)

Advisor

Satish G. Kandlikar

Advisor/Committee Member

Michael Schertzer

Advisor/Committee Member

Surendra Gupta

Comments

Physical copy available from RIT's Wallace Library at TP363 .J34 2014

Campus

RIT – Main Campus

Plan Codes

MECE-MS

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