SEMINAR

DEPARTMENT OF MECHANICAL ENGINEERING

Pool Boiling in Low Gravity: The Role of Wall Superheat and Liquid Subcooling

Prof. Amir Riaz Mechanical Engineering University of Maryland, College Park

Abstract

Effects of gravity on the efficiency of boiling heat transfer are important for two phase cooling systems onboard spacecraft and satellites. Experimental investigations of nucleate boiling over a range of gravity conditions reveal two distinct boiling regimes; dominated by buoyancy (BDB) in high gravity and surface tension (SDB) in low gravity. These regimes are separated by a sudden transition from a finite to extremely low heat flux with decreasing gravity. Experimental observations further reveal the dependence of such behaviors on the degree of wall superheat and fluid subcooling. We use high fidelity simulation of the dynamics of nucleate bubbles in 3-D to understand the relevant underlying physical mechanisms. This talk will first describe experimental observations and results, followed by a description of the numerical methods for resolving phase change, dynamic contact line and thin thermal boundary layers. We will then discuss some relevant physical mechanisms and bubble statistics related to the scaling of heat flux in BDB, SDB and transition regimes.

Biography

Amir Riaz is an Associate Professor of Mechanical Engineering and Applied Mathematics at the University of Maryland, College Park. He received his Ph.D. from the University of California at Santa Barbara and was a postdoctoral researcher at Stanford University. His work focuses on theoretical and computational fluid dynamics, with an emphasis on hydrodynamic instabilities, multiphase flow, phase change and flow through porous media.