Help me theoretically determine SW evaporation rate

[SoFloReefer]

I am trying to determine the saltwater evaporation rate from a known surface area based on the temperature of the water, the ambient air temperature, the ambient humidity, with negligible surface air convection taking place. I would also like to account for surface air convection from a fan in a second equation. I have searched all over the internet and in my heat transfer book and I'm coming up short. Maybe Randy can answer this. Thanks!

 

[disc1]

All I can say is good luck. I don't know that it can be done without modelling the airflow. If airflow was zero I could get you to the equilibrium partial pressure of the water in the air and you could calculate the amount that had evaporated from there but that would assume a sealed container. With an open system you'll have to model the airflow and the diffusion rates of water from the air right above the tank into the air in the rest of the room. Definitely not a trivial exercise.

 

[SoFloReefer]

I wonder if ANSYS can model mass flow rate problems?

 

[Ron Reefman]

May I ask why you feel the need to model the evaporation rate?

I suspect you are going to find it close to impossible. And even if you find such a formula it's only going to approximate the rate. You would probably have just as good a chance of giving out the parameters here and let those of us with some similar experience give you our best estimates based on real world experiences.

Good luck.

 

[Chemistry Guy]

This is a case where experimentation is going to be far simpler than computation.

Set up a bucket with saltwater/heater to simulate your tank. Put it on a bathroom scale and record the loss in weight (mass) over a period of time. Add whatever powerheads/fans you want to change water and air flows.

 

[Maivortex]

Like chem guy said, use experimentation. This is done using pan evaporation.

 

[ReefKeeper64]

With so many variables your results will vary. A fan generating a slight breeze to help keep the water temp down can easily double your evaporation rate over the course of a week.

Fill a 5 gallon container of RO water up with your tank topped off at the beginning of the week. Keep a lid on your container. When you need to add water from evaporation out of your 40 breeder, you get it from your 5 gal container. At the end of the week you can measure exactly how water you have remaining in your 5 gal container. What is gone is what evaporated out of your tank.

 

[billsreef]

Also keep in mind, the only part of SW that evaporates is the FW I'd expect you could find some existing data for that.

 

[disc1]

Also keep in mind, the only part of SW that evaporates is the FW I'd expect you could find some existing data for that.

And as it evaporates the salinity goes up which then decreases the rate of evaporation. So even if you get it worked out it wouldn't be constant.

 

[DrPat]

Fill a 5 gallon container of RO water up with your tank topped off at the beginning of the week. Keep a lid on your container. When you need to add water from evaporation out of your 40 breeder, you get it from your 5 gal container. At the end of the week you can measure exactly how water you have remaining in your 5 gal container. What is gone is what evaporated out of your tank.

jUST USE A ATO PUMP and follow reefkeepers sugestion
your data will be accurate for the study tank only and will change. so its a lot of effort for inconclusive results . just a point would nt you have to consider the effects of barometric pressure as well

 

[DrPat]

Fill a 5 gallon container of RO water up with your tank topped off at the beginning of the week. Keep a lid on your container. When you need to add water from evaporation out of your 40 breeder, you get it from your 5 gal container. At the end of the week you can measure exactly how water you have remaining in your 5 gal container. What is gone is what evaporated out of your tank.

jUST USE A ATO PUMP and follow reefkeepers sugestion
your data will be accurate for the study tank only and will change. so its a lot of effort for inconclusive results . just a point would nt you have to consider the effects of barometric pressure as well

 

[DrPat]

it post 2x