Heat and Thermodynamics

4.12 Thermal Transpiration

Let us consider a gas enclosed in two vessels A and B at different temperatures T₁ and T₂, T₁ >T₂. The two vessels are separated by a heat-insulated porous plug (Fig. 4.33). Initially, the pressures are the same in both the vessels.

 

 

Fig. 4.33 Illustrating thermal transpiration

 

Let υ₁ and υ₂ be the densities of gas in the vessels. From the gas law p = υkT, we have υ₁/υ₂ = T₂/T₁.

The molecules from the vessel A moving to the vessel B are 1/4 υ₁ and the molecules moving from the vessel B to the vessel A are 1/4 υ ...