Ryan M. King

Graduation Semester and Year

2011

Language

English

Document Type

Thesis

Degree Name

Master of Science in Aerospace Engineering

Department

Mechanical and Aerospace Engineering

First Advisor

Mun Seung You

Abstract

The effect of an aluminum microporous coating on evaporative cooling performance was studied using distilled water as the working fluid. The aluminum microporous coating was fabricated by brazing aluminum particles to an aluminum substrate. Microporous coating thicknesses of 175 µm ± 20 µm, 270 µm ± 20 µm, and 900 µm ± 90 µm, and average aluminum particle sizes of 27 µm, 70 µm and 114 µm were used in a parametric study to determine the optimum aluminum microporous coating. A hot water treatment maximized the wickability of the microporous coating. Wickability was measured by vertical dipping of the coating. Both a mass approach and a height approach were employed in a vertical dipping test and the results were compared to Washburn's equation. Evaporative cooling tests were then performed on both the microporous coated samples and a plain aluminum reference surface. The results of the evaporative testing were analyzed by plotting heat flux versus average temperature difference between the surface and water. Heat transfer coefficients were plotted versus heat flux. The microporous coating increased evaporation heat transfer by its capillary pumping ability to deliver a film of fluid to a large area. When the particle size was increased from 27 µm to 70 µm the wickability of the microporous coating was enhanced. This enhancement in the wickability of the microporous coating increased the heat transfer coefficient by up to 600 % when compared to the plain aluminum reference. However, as the particle size increased from 70 µm to 114 µm no significant further increase in wickability or heat transfer performance was observed. Additionally, as the thickness of the microporous coating was increased, a larger volume of fluid was delivered to the heated surface and the onset of dry-out was delayed to higher heat fluxes. The thickest coating, 900 µm ± 90 µm (70 µm particle size), increased the dry-out heat flux 16 times relative to the plain aluminum reference.

Disciplines

Aerospace Engineering | Engineering | Mechanical Engineering

Comments

Degree granted by The University of Texas at Arlington

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