Investigations of evaporation from pans

Abstract

The analogy between heat transfer and evaporation yields theoretical equations for evaporation from pans into still air and into moving air under turbulent and laminar boundary conditions. It is found that empirical equations obtained in a wind tunnel (using a water surface covered by blotting paper to prevent spraying) agree well with these theoretical results. The change between laminar and turbulent flow takes place suddenly and without any noticeable transition at a certain critical Reynolds Number. If the usual evaporation pan is used, however, as in Millar's experiments, the water surface becomes turbulent even for small Reynolds numbers and the empirical formula for evaporation is slightly different.