BARRER rate equations

This equation predicts that at constant pressure head the flow rate through a capillary should be linear with average pressure in the capillary, the- slope of such a plot being Br and the intercept Ar. This linear relation appears to be approximately obeyed for both single eapillaries and for porous materials (Barrer, 19, pp. 63-69). 

The determination of the life of vacuum-insulated equipment, as limited by degassing, will now be discussed. The rate atwhicl gas leaves the metal has not been experimentally determined, and unfortunately few data related to this problem are available. Barrer [1] gives the following equation for the degassing of a plate ... 

The permeability (permeance) P is defined as the gas flow rate multiplied by the thickness of the membrane, divided by the area and by the pressure difference across the membrane (Equation 1). The permeability is given in the unit barrer or gas permeation unit (GPU) (Equations 2 and 3). 

The unit barrer is a non-SI unit in the cgs system for the gas permeability P of thin materials in honor of the New Zealand chemist Richard M. Barrer (1910 1996), who was a leader in research on the diffusion of gases. The permeability P of 1 barrer corresponds to the flow rate of 10 cubic centimeters per second (volume at standard temperature and pressure, 0 °C and 1 atm), times 1 cm of membrane thickness, per square centimeter of membrane area, and centimeter of mercury difference in pressure between both sides of the membrane. That is, a permeability of 1 barrer = 10 cm s cmHg" (Equation 2), or. 

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