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This allows to take into account the effect of temperature on the viscosity of the fluid flowing though the porous medium and to address other fluids than pure water, e.g., concentrated brines, petroleum, or organic solvents. Given the value of hydraulic conductivity for a studied system, the permeability can be calculated as follows:
An MVTR result without specifying these conditions is almost meaningless. Certainly no two results should be compared unless the conditions are known. For example, the effect of temperature on the permeability can be as high as 10% per °C, making it possible that MVTR results achieved at 23°C and 37°C can differ by a factor 4.
Permeability depends on the temperature of the interaction as well as the characteristics of both the polymer and the permeant component. Through the process of sorption , molecules of the permeant can be either absorbed or desorbed at the interface.
The movement of a fluid through porous media is described by the combination of Darcy's law with the principle of conservation of mass in order to express the capillary force or fluid velocity as a function of various other parameters including the effective pore radius, liquid viscosity or permeability. [3]
The coefficient of permeability varies with the void ratio as e/sup>/(1+e). For a given soil, the greater the void ratio, the higher the value of the coefficient of permeability. Here 'e' is the void ratio. Based on other concepts it has been established that the permeability of a soil varies as e 2 or e 3 /(1+e). Whatever may be the exact ...
Above the Curie temperature, the atoms are excited, and the spin orientations become randomized [9] but can be realigned by an applied field, i.e., the material becomes paramagnetic. Below the Curie temperature, the intrinsic structure has undergone a phase transition, [16] the atoms are ordered, and the material is ferromagnetic. [12]
K is the permeability of the medium (SI units: m 2); d is the characteristic length, e.g. the diameter of the particle (SI units: m). [1] Alternative forms of this number do exist depending on the approach by which Darcy's Law is made dimensionless and the geometry of the system. [2] The Darcy number is commonly used in heat transfer through ...
At low rates, air permeability will be higher than brine permeability. This is because gas does not adhere to the pore walls as liquid does, and the slippage of gases along the pore walls gives rise to an apparent dependence of permeability on pressure. This is called the Klinkenberg effect, and it is especially important in low-permeable rocks.