The Stefan number, St or Ste, is defined as the ratio of sensible heat

Sensible heat

Sensible heat is the energy exchanged by a thermodynamic system that has as its sole effect a change of temperature.The term is used in contrast to a latent heat, which is the amount of energy exchanged that is hidden, meaning it cannot be observed as a change of temperature...

 to latent heat

Latent heat

Latent heat is the heat released or absorbed by a chemical substance or a thermodynamic system during a process that occurs without a change in temperature. A typical example is a change of state of matter, meaning a phase transition such as the melting of ice or the boiling of water. The term was...

. It is given by the formula



where is the specific heat, is the temperature

Temperature

Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 difference between phases, and L is the latent heat of melting. It is a dimensionless parameter that is useful in analyzing a Stefan problem

Stefan problem

In mathematics and its applications, particularly to phase transitions in matter, a Stefan problem is a particular kind of boundary value problem for a partial differential equation , adapted to the case in which a phase boundary can move with time...

. The parameter was developed from Josef Stefan's calculations of the rate of phase change of water into ice on the polar ice caps.