Modeling of vacuum evaporator

CFD-fellow · May 7, 2018, 06:45

Hi
One method of chilling water is to put it under high vacuum so that the liquid reaches its saturation pressure.The water starts boiling and the vapor gets latent heat of vaporization from remaining water. This causes the water to get cold. For example water enters the evaporator at 12 C and exits at 6 C.

Is it possible to model this process in CFX? Which multi phase model should I use?

*Its enough to model evaporator with just two phases (water and water vapor without air)

Gert-Jan · May 7, 2018, 14:25

Yes this is possible. You could use a so-called material H2Ovl (vapour-liquid system) which assumes local equilibrium conditions (i.e. inifinite mass transfer rate).

Multiphase system is a bit more difficult. It depends on where boiling starts.....

But, what question do you want to answer using CFD? In other words, what challenges do you encounter?

May 7, 2018, 06:45	Modeling of vacuum evaporator	#1
CFD-fellow Senior Member Behrooz Jamshidi Join Date: Apr 2013 Posts: 110 Rep Power: 13	Hi One method of chilling water is to put it under high vacuum so that the liquid reaches its saturation pressure.The water starts boiling and the vapor gets latent heat of vaporization from remaining water. This causes the water to get cold. For example water enters the evaporator at 12 C and exits at 6 C. Is it possible to model this process in CFX? Which multi phase model should I use? Its enough to model evaporator with just two phases (water and water vapor without air) Last edited by CFD-fellow; May 7, 2018 at 08:29.*

May 7, 2018, 14:25		#2
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,928 Rep Power: 28	Yes this is possible. You could use a so-called material H2Ovl (vapour-liquid system) which assumes local equilibrium conditions (i.e. inifinite mass transfer rate). Multiphase system is a bit more difficult. It depends on where boiling starts..... But, what question do you want to answer using CFD? In other words, what challenges do you encounter? Last edited by Gert-Jan; May 7, 2018 at 17:14.

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