Meaning
Rate measurement compared to established leak flow equations quantifies the speed at which gas moves through a physical barrier. Engineers use pressure differential kinetics to evaluate the effectiveness of pouch laminates and polymer seals. This analysis focuses on the time required for a specific pressure drop to occur within a vacuum chamber.
Results indicate the long term moisture barrier performance of the cell housing.
Flow Rate
High sensitivity sensors track the change in pressure over milliseconds. Pressure differential kinetics describes how the gas velocity changes as the gradient between the inside and outside of the cell diminishes. If the flow follows a linear path, it suggests a physical hole or crack.
Non linear flow typically indicates diffusion through the molecular structure of the plastic.
Gradient Influence
Molecular size of the test gas impacts the speed of the measurement. Helium is often used because its small radius allows it to pass through tiny defects faster than nitrogen. When analyzing pressure differential kinetics, the technician must account for the temperature and the starting pressure.
These variables change the viscosity of the gas and its ability to penetrate the seal.
Barrier Efficiency
Accurate modeling of these movements allows for the prediction of battery shelf life. Pressure differential kinetics provides the empirical data needed to select the best foil thickness for pouch cells. A faster pressure drop correlates with a higher risk of electrolyte dry out.
Materials with low permeability values are selected to ensure a twenty year service life for stationary cells.
