Handling Humidity in CFX

sunilpatil · October 17, 2013, 05:53

Hello everyone,
I successfully simulated effect of outdoor conditions on room temperature by considering air as Dry (Air at 25 C). now i want to simulate the same by considering humidity (i.e RH = 30%, 40%, 50%, 60%) how to add humidity effect in CFX

Thank you

behrouz · January 1, 2017, 05:02

hi Sunil
did you find how model the humidity in cfx???

ghorrocks · January 1, 2017, 05:58

The obvious thing to do is to use a multi-component mixture (NOT multiphase) to model the water mass fraction.

behrouz · January 1, 2017, 06:35

thank you Glenn,
as alwase responsible and helpfull.

sunilpatil · January 4, 2017, 04:19

Hi behrouz,
I am unable to model humidity effects, still I m trying
Thanks

Sent from my MI 4W using CFD Online Forum mobile app

ghorrocks · January 4, 2017, 17:15

Have you looked at the CFX tutorial examples? They are available on the ANSYS customer webpage. There are a few examples which use multi-component mixtures so I recommend you have a look at them.

If you just want a simple humidity model then define a multicomponent mixture, with the components being dry air and water vapour. If you use simple equations of state like constant properties or ideal gas then it should be pretty numerically robust. Then define your mass fractions at initial condition and boundaries. If you want parameters like relative humidity or wet bulb temperature then you will need to define a expression to evaluate this from the mass fractions.

CFD Engineer · January 14, 2020, 09:07

Mr Ghorrocks. Yes you are correct, Multi component needs to be used but how to get Wet Bulb Temp and Relative humidity as Output

Thanks

ghorrocks · January 19, 2020, 03:25

Define CEL expressions to calculate it from the mass fractions.

October 17, 2013, 05:53	Handling Humidity in CFX	#1
sunilpatil Senior Member sunil Join Date: Jul 2012 Location: Bangalore Posts: 179 Rep Power: 13	Hello everyone, I successfully simulated effect of outdoor conditions on room temperature by considering air as Dry (Air at 25 C). now i want to simulate the same by considering humidity (i.e RH = 30%, 40%, 50%, 60%) how to add humidity effect in CFX Thank you

January 1, 2017, 05:02	did you find the answer??	#2
behrouz Member behrouz Join Date: Mar 2015 Posts: 34 Rep Power: 11	hi Sunil did you find how model the humidity in cfx???

January 4, 2017, 04:19		#5
sunilpatil Senior Member sunil Join Date: Jul 2012 Location: Bangalore Posts: 179 Rep Power: 13	Hi behrouz, I am unable to model humidity effects, still I m trying Thanks Sent from my MI 4W using CFD Online Forum mobile app __________________ Regards, Sunil

January 19, 2020, 03:25		#8
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Define CEL expressions to calculate it from the mass fractions. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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January 1, 2017, 05:58		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	The obvious thing to do is to use a multi-component mixture (NOT multiphase) to model the water mass fraction.

January 1, 2017, 06:35		#4
behrouz Member behrouz Join Date: Mar 2015 Posts: 34 Rep Power: 11	thank you Glenn, as alwase responsible and helpfull.

January 4, 2017, 17:15		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Have you looked at the CFX tutorial examples? They are available on the ANSYS customer webpage. There are a few examples which use multi-component mixtures so I recommend you have a look at them. If you just want a simple humidity model then define a multicomponent mixture, with the components being dry air and water vapour. If you use simple equations of state like constant properties or ideal gas then it should be pretty numerically robust. Then define your mass fractions at initial condition and boundaries. If you want parameters like relative humidity or wet bulb temperature then you will need to define a expression to evaluate this from the mass fractions.

January 14, 2020, 09:07		#7
CFD Engineer New Member Join Date: Mar 2015 Posts: 12 Rep Power: 11	Mr Ghorrocks. Yes you are correct, Multi component needs to be used but how to get Wet Bulb Temp and Relative humidity as Output Thanks