Tuesday, December 16, 2014

Nucleate Boiling and More, Subcooled

For the record, more sometime.  Left click to see the show.

Sunday, December 14, 2014

Bunk from academia regarding nucleate boiling on small wires

Here is an "informative" link from the 1970's.

I've copied the following and added some highlights (bold).


NANIK BAKHRU IBM Corporation, Hopewell Junction, New York 12533, U.S.A .
.JOHN H. LIENHARD  Dept. of Mechanical Engineering, University of Kentucky, Lexington, Kentucky 40506, U.S.A.
(Received 27 Seprember 1971)

Abstract-Heat transfer is observed as a function of temperature on small horizontal wires in water and four organic liquids. When the wire radius is sufficiently small, the hydrodynamic transitions in the boiling curve disappear and the curve becomes monotonic. Three modes of heat removal are identified for the monotonic curve and described analytically: a natural convection mode, a mixed film boiling and natural convection mode, and a pure film boiling mode. Nucleate boiling does not occur on the small wires.

In the text you will find:

Since the wires would melt during atmospheric runs in water,  the water runs were all made at pressures in the neighborhood of 3 in. Hg abs.

It is absurd to operate at reduced pressure in order to avoid burnout.  Think about it.

Nucleate boiling was averted by operating at reduced pressure.  Burnout was avoided by limiting the maximum power.  Burnout could likewise have been avoided at atmospheric pressure.
Nucleate boiling will occur on the "small cylinders" at higher pressures. Below are four runs with 0.0003 inch platinum "cylinders" and nucleate boiling (phase change heat transfer) is evident.  Right click on "view image" to view the entire plots.  No, I give up.  Left click on the lower image to enlarge and to return here click on the reload (circular) arrow.