Development of a stable Boehmite layer on aluminum surfaces for improved pool boiling heat transfer in water

Abstract

Oxidation layers that develop on an aluminum surface can cause changes in the surface wettability. When the aluminum surface is used as a heating surface, these changes result in inconsistencies in the nucleate boiling heat transfer performance and critical heat flux (CHF). Data is presented in this paper to define a “Boehmite treatment,” which is developed by placing the aluminum surface in boiling water for 180 min. The Boehmite treatment results in a favorable and stable oxidation layer. The layer is found to cause a reduction in the water contact angle from 55° to a sustainable range of 12–13°. Successive pool boiling tests, using this aluminum surface as a horizontal flat heater, are used to demonstrate the stability of the Boehmite layer. Comparisons are made against pool boiling results using a copper surface. The CHF for a Boehmite treated aluminum surface is 80% higher than that for a copper surface with similar surface roughness due to the highly wettable Boehmite layer on the aluminum surface. This work is performed using distilled saturated water at atmospheric pressure.