Effect of orientation of a flat heating surface on nucleate boiling heat transfer

by Githinji, Philip Mwangi

Abstract (Summary)
The object of this experimental investigation was to obtain some information on the effect of the orientation of a heating surface on boiling heat transfer and particularly on the "burnout point". This was achieved by electrically heating a chromax strip that was cemented to some refractory backing so as to limit the heat transfer to one surface of the strip. The heating unit could be rotated about the longitudinal axis, thus allowing tests to be carried out with the surface of the strip oriented upwards, downwards, and vertically. The experiments were performed in a pool of subcooled isopropyl alcohol at three bulk temperatures. The results were presented in a graphical form with the heat transfer per unit area as a function of the difference between the strip surface and the bulk fluid temperatures. The curves obtained with the strip facing upwards or in a vertical position were qualitatively similar to the characteristic boiling curve while the curve for the downward facing strip resembled one commonly associated with free convection without boiling. With the bulk temperature at 80[degrees]F, for example, the burnout heat flux for the strip facing upwards was found to be 0.31 Btu/in[superscript 2]-sec, while that for a downward facing strip was 0.62 Btu/in[superscript 2]-sec. These results indicate the necessity of considering the orientation of heating elements in the design of heat transfer equipment which is to operate in the nucleate boiling region.
Bibliographical Information:

Advisor:Rolf H. Sabersky

School:California Institute of Technology

School Location:USA - California

Source Type:Master's Thesis

Keywords:mechanical engineering


Date of Publication:01/01/1963

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