Mass flow rate and permeability measurements in microporous media

Abstract

The transient method of the mass flow rate measurements through a microporous media is developed and analyzed. This method is based on the constant volume technique and the exponential fit of the pressure evolution in each tank which allows calculating the permeability directly. The pressure relaxation time, a single fitting parameter, is introduced and its behaviors are analyzed in a large pressure range. By measuring the pressure relaxation time for one gas, the permeability of a microporous sample can be derived for the other gases. With the actual experimental setup, we measured the mass flow rate through the microporous media in the range 5 • 10 −7 − 5 • 10 −12 [kg s −1 ] and the permeability in the range 10 −14 − 10 −11 [m 2 ].

Determination of an effective pore dimension for microporous media

“…The experimental methodology, applied in this article, is described in details in Ref. [11]. We present here only the summary of this technique, essential to understand the data treatment.…”

“…The constant volume technique [17], [18] and the methodology, analogous to the pulse decay method [19], [11], are implemented here to measure the mass flow rate through samples of a microporous ceramic medium. The applied experimental technique allows us to deduce the mass flow rate and also the permeability from the pressure variation in time in both tanks.…”

“…Ref. [11]. Therefore, if the temperature variations during the experimental time are small compared to the pressure variations we can calculate the mass flow rate from the pressure variation in each tank as following:…”

“…To measure the mass flow rate, first, the initial pressure difference is settled between the tanks, then the gas starts to flow from higher to lower pressure tank up to the same final pressure p f is reached, see Fig. 2 in [11]. During the experiments the pressure variations over time in each tank are recorded, then, their difference is fitted by using the exponential fitting function [19], [11]:…”

“…We propose here a simple approach for the non-destructive porous sample characterization by measuring the pressure variation in the inlet and outlet tanks (or just the pressure difference between them). The experimental methodology, based on the constant volume technique, was initially developed for the isothermal and non-isothermal measurements of the mass flow rate through the microchannels [10] and has been recently adapted for the analysis of porous samples [11]. The gas permeability of the porous sample can be easily obtained directly from the pressure evolution in time without calculation of the mass flow rate.…”