Sunday, 31 December 2017

Evaporation 2: Stafford Services

Here's my mug of coffee on a cold day. You can just make out the cloud of visible water vapour. I know that the rate of heat transfer is greater when there is a bigger temperature difference between inside and outside. I think that applies to conduction: it's a variable in the thermal conductivity equation. I also know that hotter liquids evaporate faster because the particles have higher average kinetic energy and are thus more likely to escape through the surface tension. But does the outside temperature have any bearing on evaporation? Would there be more evaporation of a hot liquid if the air temperature around was colder? Colder air holds less water vapour so perhaps not (that's why I got the "steam") but perhaps colder air might be more conducive to the formation of convection currents which would transport water vapour away from the surface of the liquid. So it hinges on whether the temperature of air affects the formation of convection currents.