I am currently a senior ChemE on internship and one of my assignments is to calculate the evaporation rate of water in an ultrasonic cleaning station.
The knowns are:
- Dimensions of the water basin
- The relative humidity of air blowing across the basin
- The temperature of the air (assumed to be ambient)
- The flow rate of air over the basin
- the temperature of the water bath
my first thought was to use a mass transfer/diffusion method assuming that the basins were flat plates and accounting for the transition from laminar to turbulent flow.
In this case the mean mass transfer coefficient would be
Kc=(0.664(Dab)(Ret)1/2Sc1/3+0.0365(Dab)Sc1/3(ReL4/5-Ret4/5))/L
and the average flux would be
WA=Kc(P*A-PAbulk)
Where
- Kc=mean mass transfer coeff
- Dab=diffusion coefficent
- Ret = the transition Reynolds number
- ReL=the Reynolds number at the end of the pan
- L=critical length of basin
- Wa= average flux leaving the surface
- P*A=vapor pressure of water at the basin temperature
- PAbulk = partial pressure of water in Air
However as I thought about it more I realized that the mass transfer correlation would most likely not hold up under the ultrasonic conditions since the "wavy" motion of the water would greatly enhance the mass transfer for a number of reasons (in my mind there would be more surface area, more energy supplied to the water, and I guess more turbulence at the interface of air/water).
I was wondering if someone could point me a the right direction for either a better mass transfer coefficient correlation that would apply to ultrasonic flow over a flat plate, or a better method that I sound be using.
Thanks a lot for all your help