Identifier

etd-08242015-141926

Degree

Master of Science (MS)

Department

Mechanical Engineering

Document Type

Thesis

Abstract

Conjugate heat transfer in a porous media is investigated with a temperature jump condition obtained from kinetic gas theory. The temperature jump appears alongside flow boundary condition when the pressure is low, and considered to be in non-continuum regime. This investigation focuses on both one-dimensional and two-dimensional porous media models. The length scale of the pores is 100 microns. The temperature is ambient, and the pressure is low enough to reach the slip-flow regime. The thermal behavior of porous media is investigated using a slot model with a gas trapped between two solid blocks. Aluminum oxide and air are considered as a baseline combination. The steady-state results show the change in the temperature jump and net heat flux as a function of Knudsen number for gas-solid systems. For unsteady cases, a change in the amplitude and phase of the heat flux is shown over the range of frequencies between 10 Hz and 10 kHz. The effects of different solid-gas combinations are also investigated. The results show that the properties of the gas has a significantly larger impact than those of the solid. Steady-state heat transfer in two-dimensional porous media is also investigated using a brick model with a rectangular cavity of 90% void fraction. The results show the effects of pressure, void fraction and solid-gas combinations on the effective thermal conductivity of the porous media model. A multi-cell structure is also investigated to study the effective thermal conductivity and edge effects when low number of cells are considered. Pressure dependent thermal properties of the gases and silica based solid non-porous materials are also investigated due to their very low thermal conductivity.

Date

2015

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Martin, Michael J.

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