Boiling heat transfer enhancement by a pair of elastic plates

Abstract

Boiling heat transfer enhancement is essential for energy utilization. Traditional passive boiling enhancement methods aiming at bubble departure promotion usually depend on the modulation of surface tension force by surface modification. However, the limited driven force which benefits bubble departure cannot help the further improvement of heat transfer performance facing the increased heat dissipation amounts. In this paper, a novel boiling enhancement method using a pair of elastic plates (i.e., flexible parallel plates made of stainless steel) which promotes bubble departure by its swing effect for boiling on Pt wire in confined space is proposed and investigated. Compared to boiling with a pair of rigid plates (the thickness of 0.5 mm and the length of 12 mm), the heat transfer coefficient (HTC) is improved by 55.8% of those with elastic plates (the thickness of 0.01 mm and the length of 12 mm).Periodic expansion and recovery process of plates coupling bubble dynamics is observed and studied. Experimental results indicate that elastic plates enhance boiling heat transfer performance significantly by smaller bubble departure diameter and lower wall superheat at the same wall heat flux. A correlation for bubble departure diameter prediction in elastic channel is proposed which matches well with experimental results. It is found that the stronger pumping effect induced by higher swing rate of plates enhance HTC significantly. The mechanism where expansion process of plates promotes bubble departure while its subsequent recovery process benefits the supply of the cold liquid is verified by simulation. This study proposes a new approach for boiling heat transfer enhancement by inducing the energy exchange between bubbles and elastic plates, and provides theoretical and technical support for boiling study based on flexible materials.