Experimental measurements of the permeability of fibrous carbon at high temperature

TL;DR

This study experimentally measures the permeability of FiberForm carbon preform at high temperatures, analyzing how temperature, pressure, and microstructure influence gas flow and proposing a model for effective permeability.

Contribution

It provides new experimental data on FiberForm's permeability at high temperatures and introduces a model linking permeability to microstructure, temperature, and gas type.

Findings

Intrinsic permeability evaluated at 5.57e-11 m^2

Klinkenberg correction parameter determined as 2.51e5 m^{-1}

Permeability depends on microstructure and gas conditions

Abstract

A series of experiments was performed to obtain permeability data on FiberForm(R), a commercial carbon preform used for manufacturing thermal protection systems. A porous sample was placed in a quartz flow-tube heated by an isothermal furnace. The setup was instrumented to measure mass flow through and pressure drop across the sample. The intrinsic permeability and the Klinkenberg correction, which accounts for rarefied effects, were computed from the experimental data. The role of the gas temperature and pressure on the effective permeability is shown, and it is demonstrated that with proper data reduction, the intrinsic permeability is strictly a function of the micro-structure of the material. A function for the effective permeability of FiberForm, dependent on temperature, pressure, pore geometry, and type of gas is proposed. The intrinsic permeability was evaluated at $K_0 = 5.57 \times 10^{-11}$ m$^2$, with a Klinkenberg parameter of $8c/d_p = 2.51 \times 10^5$ m$^{-1}$ and a reference porosity of $\phi^\dagger = 0.87$.