Kelvin effect

The Kelvin equation describes the change in vapour pressure due to a curved liquid–vapor interface, such as the surface of a droplet. The vapor pressure at a convex curved surface is higher than that at a flat surface. The Kelvin equation is dependent upon thermodynamic principles and does not allude to special properties of materials. It is also used for determination of pore size distribution of a porous medium using adsorption porosimetry. The equation is named in honor of William Thomson, also known as Lord Kelvin.

The Kelvin equation may be written in the form

where ${\displaystyle p}$ is the actual vapour pressure, ${\displaystyle p_{0}}$ is the saturated vapour pressure, ${\displaystyle \gamma }$ is the surface tension, ${\displaystyle V_{\text{m}}}$ is the molar volume of the liquid, ${\displaystyle R}$ is the universal gas constant, ${\displaystyle r}$ is the radius of the droplet, and ${\displaystyle T}$ is temperature.

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