Bubble pressure filter pore size analyzer basic principle - Database & Sql Blog Articles

Fundamental: The method involves using a specific membrane material that is fully wetted with a liquid capable of penetrating it. The liquid becomes trapped in the pores due to surface tension. A gradually increasing gas pressure is applied on one side of the membrane. When the gas pressure exceeds the surface tension of the liquid in a particular pore, the liquid is expelled by the gas. Smaller pores require higher pressure to push out the liquid because the surface tension effect is stronger at smaller diameters. As pressure increases, the largest pores open first, allowing gas to pass through. Then, as pressure continues to rise, progressively smaller pores open in sequence until all pores are clear, matching the transmittance of the dry film. The pressure at which the first pore opens is called the bubble point pressure, and the corresponding pore size is the largest. During this process, both pressure and flow rate are recorded in real-time to generate a pressure-flow curve. This curve provides information about pore size distribution and the number of pores at different sizes. By testing the dry film's pressure-flow curve, we can calculate key parameters such as maximum pore size, average pore diameter, minimum pore size, pore size distribution, and overall transmittance using specific formulas. The relationship between pore size and pressure follows the Washburn equation: **D = 4γCosθ / P** Where: - D = pore diameter - γ = surface tension of the liquid - θ = contact angle - P = pressure difference Pore size distribution is calculated using: **f(D) = -d[(Fw/Fd) × 100]/dD** Where: - Fw = flow rate of the wet sample - Fd = flow rate of the dry sample This technique allows for accurate characterization of membrane structure, making it essential in filtration, separation, and material science applications.

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