Correlating Gas Leakage Rates to Fluid Ingress in Sensor Seals
Correlating gas leakage rates to liquid ingress requires deriving equivalent pore radius to confirm capillary entry pressure exceeds target hydrostatic head.
Young Laplace Equation
Interface Physics
Mathematical descriptions of the capillary pressure across the interface between two static fluids define the relationship between the pressure jump and the surface curvature. This young laplace equation calculates the force required to move a liquid through a pore. It identifies the tension at the boundary and the two principal radii of curvature that describe the shape of the meniscus.
Pressure Calculation
Internal pressure of a spherical droplet is higher than the outside pressure by a factor of twice the surface tension divided by the radius. As the radius decreases, the pressure needed to maintain the interface grows. This explains why smaller pores in a filtration membrane provide better resistance to liquid penetration.
Drop Shape
Instrumentation for surface energy measurement uses this formula to determine the tension of a liquid from the profile of a pendant or sessile drop. By measuring the coordinates of the drop edge, the software calculates the curvature and solves for the tension. This provides a way to verify the purity of a liquid or the cleanliness of a surface.
Physical Assumption
Precision depends on the system being in a state of static equilibrium where no external flow or vibration is present. The equation assumes the surface is smooth and the fluid properties are uniform throughout the volume. It fails when the dimensions reach the molecular scale or when the liquid is moving rapidly, as dynamic effects and viscosity begin to dominate the behavior of the interface.