Doctoral Dissertations

Abstract

"This study consisted primarily of a laboratory investigation involving nucleate and film boiling heat transfer from copper spheres with saturated liquid nitrogen at atmospheric pressure. An initial study was directed towards obtaining reproducible boiling heat flux versus ΔT curves in the nucleate boiling region from surface conditions created by single and/or multiple glass bead peenings. The variables of bead size, nozzle line operating pressure, and distance a copper surface should be placed from the nozzle outlet were checked. The results indicated that a final peening of the surface with 0.0017-0.0035 inch diameter glass beads, a nozzle line pressure of approximately 20 psig and the surface being peened placed approximately 2.0 inches from the nozzle outlet produced the most desirable surface condition. Based on the conclusions of the initial surface condition study, a series of boiling heat flux versus ΔT curves for nucleate and film boiling were obtained from a 2.25 inch O.D. hollow copper sphere. The transient technique was used to obtain the necessary data for these curves from a machined, single peened, sandblasted and multiple repeened surface. The resulting boiling heat flux versus ΔT curves indicated a high degree of reproducibility from the single peened and multiple glass bead repeened spherical surface. In the film boiling region, the results indicated that surface conditions affect the minimum boiling heat flux (Liedenfrost Point) and the corresponding ΔT at which it occurs . In general, the results indicated that a peened spherical surface yields a Liedenfrost Point comparable to a polished spherical surface. A peened 0. 75 inch O.D. solid copper sphere was oscillated with peak-to-peak amplitude-to-diameter ratios (X/d) of 2.40, 5.73 and 7.33 and at frequencies from 3.0 to 10.15 cps. More than 100 percent increase in film boiling heat flux was noted over a stationary condition when the sphere was oscillated with an X/d ratio of 7. 33 and a frequency of 6.03 cps. At the two larger X/d ratios, the boiling heat flux versus ΔT curves in the film boiling region indicated steeper curve slopes. Heat flux versus ΔT curves in the nucleate and film boiling regions were obtained from peened 0.25, 0.125, and 0.0625 inch diameter solid copper spheres. The boiling heat flux versus ΔT curves obtained from the spheres in the nucleate boiling region differed from those curves obtained from larger peened and polished spherical surfaces in both the magnitude of peak nucleate boiling heat flux and critical ΔT. Accordingly, the deviation of these characteristics between the three diameter spheres indicated that the critical ΔT decreases as the sphere diameter was decreased. The film boiling heat flux for the three spheres were found to increase as sphere diameter was decreased. In addition, the correlation equation presented by Frederking and Clark [1]* for the Nusselt number was not representative of these size spheres. Utilizing the steady state technique, boiling heat flux versus ΔT curves in the nucleate and film boiling regions were obtained from a peened 2.25 inch O.D. hollow copper sphere with an enclosed heater. The resulting boiling heat flux versus ΔT curves were found to be comparable to those obtained by the transient technique from the similar 2. 25 inch O.D. hollow copper sphere. *Numbers in brackets refer to listing in the Bibliography"--Abstract, pages ii-iii.

Advisor(s)

Rhea, L. G.

Committee Member(s)

Park, Efton
Oetting, R. B.
Flanigan, V. J.
Faucett, T. R.
Gillett, Billy E.

Department(s)

Mechanical and Aerospace Engineering

Degree Name

Ph. D. in Mechanical Engineering

Sponsor(s)

University of Missouri--Rolla. Faculty Research Grant

Publisher

University of Missouri--Rolla

Publication Date

1970

Pagination

xi, 139 pages

Note about bibliography

Includes bibliographical references (pages 123-125).

Rights

© 1970 William David Hardin, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Nucleate boilingHeat -- TransmissionHeat fluxCopper -- AnalysisNusselt number -- Models

Thesis Number

T 2383

Print OCLC #

6020283

Electronic OCLC #

856903077

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