Numerical Simulation of Phase Transition in Porous Media

Nathaniel Morgan, Georgia Institute of Technology

Non-conducting porous materials are currently being used for structural support and multiphase cooling of heat-generating elements. The interconnect voids in the porous material permit extensive direct contact between the coolant and the heater surface while allowing for multi-dimensional liquid-vapor transport. Currently, little is understood about how the geometric characteristics of the interconnect voids in the porous material affect boiling. It would be advantageous to know what interconnected void geometric features will improve bubble growth and departure. In addition, for any given pore geometry there may exist a minimum length ratio based on the length and hydraulic diameter of the interconnected voids such that for longer voids the bubbles departing from the heater surface would preferentially travel along the voids, leading to the transition from pool boiling to flow boiling. The objective of this study is to numerically investigate how the geometric characteristics of the interconnected voids affect bubble nucleation and ebullition during boiling in porous media. The numerical simulation will be used to determine the heat flux from the surface of a heater as a function of the various geometric features including the length-to-hydraulic diameter ratio of the pores; and to identify the length-to-diameter ratio that corresponds to the transition from pool boiling to flow boiling.

Abstract Author(s): N. R. Morgan, M. K. Smith, C. N. Ammerman, and S. M. Ghiaasiaan