Abstract

Miniaturization in microelectronics demands effective thermal management from high energy density devices. While current cooling solutions employ single-phase heat transfer, they are often limited by high fluid temperature differences and pressure drops. Alternatively, two-phase cooling schemes offers attractive solutions to dissipate high heat fluxes at small temperature differences. Specifically, pool boiling has the potential to dissipate high heat fluxes without using pumps and other complex header configurations.

Two performance criterion that govern the heat transfer in pool boiling systems are the (i) Critical Heat Flux (CHF), and the (ii) Heat Transfer Coefficient. The CHF is the upper limit in nucleate boiling, while the Heat Transfer Coefficient dictates the efficiency of the process. The current thesis work relates to increasing the aforementioned parameters through copper porous coatings. In this work, copper substrates were coated with 3M copper powders using a drop coating and screen printing technique. Substrate bonding was achieved by sintering at elevated temperatures. The coated substrates were characterized using Scanning Electron Microscopy and Laser Confocal Microscopy which revealed the different geometrical parameters (pore sizes and coating thickness etc.) associated with the coatings. Pool boiling tests were conducted with distilled and degassed water at atmospheric pressure. A highest Critical Heat Flux (CHF) of 303 W/cm2 was obtained on a test sample corresponding to a coating thickness of 447 µm. This translated to a CHF enhancement of ~135 % when compared to a plain copper surface. The effect of coating thickness on pool boiling performance was studied. High speed visualization was conducted on the test samples to identify underlying boiling mechanisms. The effect of additional nucleation sites, and wickability were evaluated in this study. The experimental observations were supplemented with analytical equations available in literature to identify driving mechanisms with the thin and thick porous coatings.

Library of Congress Subject Headings

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

Publication Date

12-2016

Document Type

Thesis

Student Type

Graduate

Degree Name

Mechanical Engineering (MS)

Department, Program, or Center

Mechanical Engineering (KGCOE)

Advisor

Satish Kandlikar

Advisor/Committee Member

Agamemnon Crassidis

Advisor/Committee Member

Michael Schrlau

Comments

Physical copy available from RIT's Wallace Library at TK7872.H4 L48 2016

Campus

RIT – Main Campus

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