A Theory of Heat Transfer Between Two Gases in a Mixture

Starting from the mechanics of collision between two perfectly elastic smooth spherical molecules, the following equation for the heat transfer rate per unit volume from a gas or vapor 2 to another gas 1 in a mixture is derived based on the kinetic theory of gases: Methods of estimating molecular diameters when experimental values are not available are indicated, and values for sodium and UO₂ vapor are estimated. For a set of typical values of the parameters, the time constant for the heat transfer is found to be of the order of 10⁻⁸ sec, which implies that for processes occurring in time periods greater than those of the order of 10⁻⁸ sec, the gases can be assumed to come to a thermal equilibrium at the instant they mix.