  We discuss the physics of the pot-in-pot cooler. By balancing temperature
decrease due to evaporation and temperature increase due to heat exchange, we
find the equilibrium temperature of the pot. In this simplified model, the
cooling jug acts as a psychrometer, and the theoretical prediction of our model
is in a good agreement with psychrometric tables. Next, we study dynamics of
the jug cooling. The cooling rate is limited by water vapour diffusion through
air, heat conduction through air, and heat conduction through the body of the
jug. The derived rate of temperature decrease is in general agreement with the
result of our experiment. In the end, we discuss some additional factors, such
as capillary effects in the raw clay, water viscosity in the capillaries, and
impact of complex shape of the jug.
