Quantifying Water Vapor Diffusion across Elastomer Pressure Sensor Seals
Water vapor diffusion across elastomer seals causes reference cavity pressurization and dielectric drift, requiring coulometric ISO 15105-2 verification.
Desiccant Sorption
Moisture Removal
A thermodynamic process involves the capture and retention of water molecules by a solid or liquid medium through physical or chemical attraction. Effective desiccant sorption occurs when the vapour pressure of the moisture in the desiccant is lower than the partial pressure of water in the surrounding gas. This gradient drives the transfer of moisture until equilibrium is reached at the surface of the material.
The efficiency of the process depends on the pore size and surface area of the specific media used.
Uptake Mechanism
Porous solids like molecular sieves or silica gels trap water molecules within their internal structure through van der Waals forces. During desiccant sorption, the material releases latent heat as the gaseous water transitions to a condensed phase on the surface. This release can reduce bed capacity if the heat is not dissipated through the gas flow.
High pressure environments typically enhance the rate of moisture capture by increasing the collision frequency between molecules and the desiccant surface.
Regeneration Cycle
Saturated media must undergo a thermal or pressure swing process to release the trapped moisture and restore capacity. Increasing the temperature provides the energy required to overcome the binding forces of desiccant sorption and allows the water to evaporate.
Performance Decay
Repeated cycling leads to a gradual loss of adsorption sites due to thermal stress or the accumulation of heavy hydrocarbons. If the desiccant material fractures into fine particles, the resulting pressure drop across the bed increases and reduces the overall system efficiency. Verification of the remaining capacity involves measuring the dew point at the outlet under maximum load conditions.