Enhanced capillary performance in axially grooved aluminium wicks by alkaline corrosion treatment

This paper presents an alkaline corrosion treatment for axially grooved aluminium wicks, which significantly enhances the capillary performance of these wicks and increases the applicability of axially grooved aluminium heat pipes in space or in a horizontal direction. The effect of corrosion parameters (molar concentration and reaction time) on the capillary performance was investigated. An IR camera was used to build a capillary rate-of-rise test apparatus to measure the capillary performance of corroded wicks. Experimental results indicate that the corroded-aluminium grooved wicks always present higher capillary pressures than non-corroded ones. However, care should be taken to control the molar concentration and reaction time such that the best capillary performance can be achieved. In this study, the optimal corrosion parameters were found to be 1.25 mol/L NaOH for 10 min (noted as N1.25-10), which resulted in the best capillary performance parameter (Delta P-cap.K) of 8.97 +/- 0,38 x 10(-7) N. This finding demonstrated an enhancement of 155% compared with the value of 3.51 +/- 0.1 x 10(-7) N for the non corroded wicks. Furthermore, a novel prediction method was proposed to calculate.the capillary heat transfer limit of heat pipes based on IR rate-of-rise tests on wicks. The calculated corresponding heat pipe capillary limit (Q(C), max) of the sample N1.25-10 reached the maximum value of 9.00 W +/- 4.25%, far exceeding the value of 3.52 W +/- 1.5% for the non-corroded wicks. The underlying mechanism of the enhancement is associated with the micro-coarse-structured morphology and improved hydrophilicity of the corroded aluminium surface. This study demonstrates that alkaline corrosion treatment is an easy and effective way to improve the capillary performance of grooved aluminium wicks and the capillary heat transfer limit of grooved aluminium heat pipes. (C) 2016 Elsevier Inc. All rights reserved.