# Thread: Rate of Evaporation in a mixture

1. Hey everybody I have a quick question. I am am wondering if anyone knows how to calculate how much water is evaporating per hour in a given solution.

I am on an rig and we are drilling a hole and i know i am lossing water to evaporation at surface and i would like to calculate an exact figure instead of guessing like i am told to do. So looking around at various websights i found a formula for the rate of evaporation

E=KA(Xs-X)
E= rate of evaportation kg/hr
K=evaporation coeffieceint of
A=surface area
Xs=humidity ratio in saturated air at same temp
x=humidity ratio

Now Since i Have a solution and in fact the water is incased in the mineral oil through the use of an emulisfier i dont think this equation will work. SO how do i calculate it. Right now I am using the change in ratio between the water and the oil. Ie with no additions of water or oil if the ratio of oil to water goes from 70% oil to 78% oil and the water goes from 30% to 22% then we are seeing an 8% decrese in water so therefore i take the system which is x number of gallons and times it by 8% and that should give me the amount of water I lost. is this correct is there a better way.

The solution is 78% mineral oil and water is 22% right now. Now the flow rate of this particular liquid is 732 gpm. The temperature of the solution where it is exposed to air is 150 F.  2.

3. Instead of trying to derive a formula, you might try to set up an empirical formula. Record either the water level or how much water you had to add at different times/temperatures/other variables. You can then feed that into a statistics program and get a formula that hides all sorts of complicated variables behind a best fit curve.  4. The problem with that is i am not under lab conditions i can not control any factor but the rate in which i add water to the mixture. But thanks for the adivce all the same  5. If you had a solution I'd guess the rate of evaporation would be reduced from the value calculated by your formula in proportion to the volume fraction of water (which will be smaller than the mass fraction). But you don't have a solution, you have said you have an emulsion and the mass transfer is more complex, so this would at best be a rough approximation.  6. Well thanks for all the help  Bookmarks
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