Originally Posted by **oz93666** Definitely adding the cream first .... I'm always thinking about these sort of questions ....
I haven't much use for mathematical modeling ... I think this tread illustrates the limitations ... an extraordinarily difficult problem to model , the way the humid air would rise from the fluid surface is impossible to model... |

It's not particularly difficult, but it requires knowledge of psychrometrics, which is usually taught in engineering rather than in physics. It's definitely not a one-line formula you can ad-hoc include into an existing model thermal model. If you hit the engineering references, there's plenty of mathematical models available that are not too crazy to implement.

I've been researching existing models of evaporative cooling. Cooling towers in particular use evaporation for the cooling of warm water for cooling systems (e.g. typically power stations and HVAC systems). There's several calculation methods. The two main ones are:

1. Merkel theory method

2. Effectiveness-NTU method

There's others too, but they're mainly to take into account the particulars of cooling tower engineering nuances rather than just evaporation in general.

I'll put some details down in another thread perhaps for anyone that's interested. However, I think it's safe to say that approximating thermal losses due to evaporation using a convection term is a reasonable assumption.