BOILING OF MIXTURES IN A NARROW SPACE

Abstract

Nucleate pool boiling of binary mixtures composed of water and normal propyl alcohol (NPA) within a narrow space between heated and unheated horizontal-parallel surface has been investigated under atmospheric pressure. The electrically heated lower surface is made of a sheet of stainless steel 304 with the dimension of 145 x 22 x 0.05 mm and the unheated upper plate is a stainlesssieel cylinder with a diameter of 20 mm. The periphery of the confined space is open and the size of the gap can be varied from 0 to 10 mm. Experimental results show that the heat transfer coefficient of nucleate pool boiling of binary mixture in a narrow space is much greater than that of conventional nucleate pool boiling. It is due to the evaporation of a thin liquid film under the deformed bubble. Experimental results also show that mass diffusion effect is important in both nucleate pool boiling in a narrow space and in conventional nucleate pool boiling. Based on the experimental results, the microlayer evaporation, mass diffusion and the film flow driven by the gradient of the disjoining pressure and the Marangoni effect are discussed.

KEYWORDS:

• Nucleate boiling
• Narrow space
• Binary mixture
• Microlayer evaporation

Additional information

Notes on contributors

M. T. LEE

The author ot whom corrrespondence should be addressed.