Penetrant gas

The models described in the following use only one parameter for the cleaning efficiency, which is thus a simplification that must be kept in mind when using these models. This works quite well as long as the efficiency value is the smallest one—e.g., the efficiency for the most penetrating particle size or the efficiency for the most penetrating gas concentration. 

A degasser is installed on the mud line to remove gas from drilling fluid while penetrating gas bearing formations. Samples of gas are analyzed using the gas chromatograph. 

Bubble Point Large areas of microfiltration membrane can be tested and verified by a bubble test. Pores of the membrane are filled with liquid, then a gas is forced against the face of the membrane. The Young-Laplace equation, AF = (4y cos Q)/d, relates the pressure required to force a bubble through a pore to its radius, and the interfacial surface tension between the penetrating gas and the liquid in the membrane pore, y is the surface tension (N/m), d is the pore diameter (m), and P is transmembrane pressure (Pa). 0 is the liquid-solid contact angle. For a fluid wetting the membrane perfectly, cos 0 = 1. 

Fig. 5. Correlation between experimental D.Di values with the Lennard-Jones parameter of the penetrant gas for four glassy polymers2S) O a copolyester 26i A a polysulphone 23 PC A PPO...

The rate of permeation for the case shown schematically in Fig. 2.57 is defined as the mass of penetrating gas or liquid that passes through a polymer membrane per unit time. The rate of permeation, m, can be defined using Fick s first law of diffusion as... 

Koelling et al. (70) conducted nonisothermal, pressurized gas-bubble Newtonian fluid-displacement experiments. The fluid used was PB H-300. It was injected into a capillary tube maintained at 60°C. The tube was then transferred in a different temperature bath at 0°C. The penetrating gas was then injected after different delay times, t. The longer the delay time, the deeper the cooling penetration thickness will be, since it is dependent on the Fourier number,... 

The factors affecting the selectivity and permeability of polymer membranes to different gases are best discussed on the basis of Eqs. (12) and (14). As noted in Eq. (12), the permeability coefficient, P, of a penetrant gas in a polymer membrane is the product of a (concentration-averaged) diffusion coefficient, D, and of a solubility coefficient,... 

S. The diffusion coefficients of gases in glassy polymer membranes are strong functions of the penetrant gas concentration in the membranes (or of the gas pressure), and depend also on polymer morphology (crystallinity, orientation), crosslinking, and chain mobility. The chain mobility depends, in turn, on the polymer free volume, the... 

The permeation of a gas through a porous polymer is generally described by equations based on the kinetic theory of gases. The sorption isotherm described by Eq. 1 is concave to the pressure axis and is commonly observed for a penetrant gas in a glassy polymer. It is composed of Henry s law and Langmuir-terms [20] ... 

With coal-gas as external atmosphere Graham found that the penetration began at about the same temperature, but the penetrating gas appeared to be perfectly pure hydrogen, and contained no trace of hydrocarbons. This was confirmed by Ramsay.12 Clearly it should be... 

Figure 169. Bubble formation from bed-penetrating gas jets at the grid points ...

Integration of Equation 1 for the desired geometry and boundary conditions yields the total rate of diffusion of the penetrant gas through the polymer. Integration of Equation 2 yields information on the temporal evolution of the penetrant concentration profile in the polymer Equation 2 must be augmented by the desired initial and boundary conditions of interest. The above relations apply to homogeneous and isotropic polymers. 

The equilibrium concentration (solubility), c, of a penetrant gas dissolved in a polymer can be related to the pressure, p, of the penetrant by the isothermal relation ... 

The mechanisms of gas diffusion are very different at temperatures above and below the glass-transition temperature, T, of the polymers, i.e., when the polymers are in their "rubbery" or "glassy" state, respectively (1,3-8). The difference in these mechanisms is reflected in the significant differences observed in the dependence of the diffusion coefficient, as well as of the permeability and solubility coefficients, on the penetrant gas pressure or concentration in polymers and on the temperature. 

It has been observed recently that some penetrant gas/polymer... 

Toxic smoke, usually an arsenical compound, could penetrate gas masks— which were quite effective by 1918 because smoke is not a gas and the smoke particles would not be absorbed by the charcoal or lime in the mask canisters. Moreover, America had developed a thick felt that would filter out the smoke particles even with Brownian motion operating. This felt was simply wrapped around existing mask canisters. Also, the small size of bombs and projectiles made candles and smoke generators particularly attractive. 

Gas-Permeability Coefficient A measure of gas permeability of a barrier wall such as plastic film. Gas permeability coefficient, P, is a coelficient in Pick s first law that states that the volume (V) of a substance that penetrates a barrier wall is directly proportional to the area (A) of the wall, partial pressure differential (p) of the penetrant, and time (t) and inversely proportional to the wall thickness (s), if the wall is homogeneous in the direction of penetration. Gas permeability coefficient depends on the test temperature. 

It can be shown that the mean permeability coefficient P is a product of a mean diffusion coefficient, D, and a function 5 related to the solubility of the penetrant gas in the polymer [1-9] ... 

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