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-   -   Can FLUENT model flashing liquids? (https://www.cfd-online.com/Forums/fluent/38907-can-fluent-model-flashing-liquids.html)

SWK December 12, 2005 12:55

Can FLUENT model flashing liquids?
 
hi,

I want to model flashing liquid inside a control valve. For FLUENT 6.2, i know that there is two models available for modelling mass transfer which is the cavitation model and the unidirectional mass tranfer model. At first i thought i can do it with cavitation model but it seems that the pressure profile is not really correct as the outlet pressure cannot go below the vapor pressure as it should be for flashing service.

Anyone out there can give me a help? Btw anyone know where to download Fluent 6.2 User Guide?

Thank you in advance.

Regards,

SWK

Alec Eiffel December 12, 2005 14:14

Re: Can FLUENT model flashing liquids?
 
hi

Our research group developed a flashing flow model using UDFs and UDS equations for FLUENT. Unfortunately its under a confidentiality agreement so cant share the code. You will need to write your own code for FLUENT to model flashing liquid as FLUENTs cavitation model is not suitable as you have said.

best of luck!

SWK December 12, 2005 20:24

Re: Can FLUENT model flashing liquids?
 
Thank you Alec.

I try to use the UDF but when i try to interpreted it, it show parse error. Anything i can do for this in order to proceed? Btw when it show line 1: parse error, from which line we start to count from the code? start from DEFINE ...?

Regards,

SWK

Alec Eiffel December 13, 2005 12:57

Re: Can FLUENT model flashing liquids?
 
It counts from the very first line of the c file. Have you included the #include "udf.h" line at start of UDF?

SWK December 13, 2005 22:55

Re: Can FLUENT model flashing liquids?
 
yup... i have that line. you mean start to count from include udf.h?

khaledhussain June 17, 2017 01:21

Hi .. could anyone send me the UDF for flashing, I am trying to use fluent to expect fluid flashing on CD nozzle, please I need your help, I tried the euilerian evaporation condensation model and the real gas model but I couldnt find any realistic results in terms of pressure and velocity profiles.

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lihongyang0 June 20, 2017 13:04

I think you could simply your case. What the saturation do you want to simulate?

khaledhussain June 21, 2017 19:01

Thanks for your reply ! simulation is aimed to expand the compressed liquid water from 50 C (4 degrees below saturation temp) down to 6 C at saturation condition. The eulerian evap.cond. model gave me a result for flashing (as the water is successfully evaporated) but not accurate as the mixure velocity supposed to increase at diversion section after nozzle thoat because of supersonic cond. but this wasnt happen. also the pressure profile is totally different than experimental resuls. Please advise !

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lihongyang0 June 21, 2017 21:45

I am using cavitation model to simulate flashing. In some nozzles, the results agrees well with the experiment. How about changing your software? Use 17.0 or higher?

khaledhussain June 22, 2017 01:17

I tryed the cavitation model but the problem that the pressure at diversion section is increased above saturation regardless of the pressure ratio, so bubells are getting collapse and condesate back (it make sense for cavitation). I am using 16.2 and didnt check the higher ver., do you think the problem of flashing is resolved in 17 ?!

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