Hi to all,

I am doing multiphase heat exchanger simulation. Hot fluid vapor is cooled into liquid by water. There is no mixing and reaction of fluids

Here which one i should take primary and secondary fluid. Initially there is 95% hot fluid vapor is there.

How to specify the phase change. Really i want to find the volume fraction of vapor and liquid at outlet.

I am new to multiphase problems. Give your valuable suggestions to guide me.

Thanks in advance

JSM

Hi,UDF should be used in your example.Maybe you could refrence the tutorial of "Heat and Mass Transfer with the Mixture Model". The c-code will tell you how to solve this problem and set the boundary to simulate multiphase flow.

i dont know exactly in your case, but i modeled a flue gas through heat exchanger. You can use NTU model if the auxiliary fluid which is the one inside the pipe of the heat exchanger is one phase. The primary fluid is the fluid which is flowing trough the heat exchanger. Last thing, you cannot use simple effectiveness model if your heat rejection is negative.

Hi,

Thanks for your comments. I saw that multiphase tutorial in fluent. My simulation is different.

That is refrigeration water condenser. Water is flowing over the pipe and hot fluid vapor and liquid is flowing inside the pipe.

How can i specify the latent heat condensation for hot fluid flowing in pipe(may be through UDF). But in udf manual, i cannot find the exact example.

There is any need to specify the slip velocity for water and hotfluid vapor and liquid.And initially, vapor is 95% by volume. How to specify the diameter for vapor.

Thanks in advance

cheers JSM

Hi;

I have also experiances with multiphase simulation in heat exchangers using VOF , mixture and eulerian model. I haven't access to tutorials.therefore, I am appreciated you as send tutorial to my email inbox: saimon_ph@yahoo.com . perhabs I could help further you.

Thanks

The latent heat be dealed with in the example I mentioned in the last post response. It has been defined through the mass and energy source items.

Hi Rikio,

Thanks for your help. I saw the another tutorial last time. Now i got it.

But that tutorial is dealing with boiling. In my case, it is condensation. I think that they used some correlations for the vapor formation. I dont know exactly. Then what about condensation. My flow fluid is freon gas.

Where can i get that correlations or properties for freon. please help me.

cheers JSM

For freon propeties,you can look up the chart of different freon,such as R134a,R410a,etc. For the correlations,in fact,condensation is a opposite process of evaporation.If the energy and temperature terms satisfy the certain conditions,mass transfer will be completed. So,the main course is the same as evaporation,but some arguments.

Hi Rikio,

Thank you for your guidelines. I will try check in data tables for freon properties.

with regards JSM

[lucio]

Originally Posted by JSM
;141769

Hi,

Thanks for your comments. I saw that multiphase tutorial in fluent. My simulation is different.

That is refrigeration water condenser. Water is flowing over the pipe and hot fluid vapor and liquid is flowing inside the pipe.

How can i specify the latent heat condensation for hot fluid flowing in pipe(may be through UDF). But in udf manual, i cannot find the exact example.

There is any need to specify the slip velocity for water and hotfluid vapor and liquid.And initially, vapor is 95% by volume. How to specify the diameter for vapor.

Thanks in advance

cheers JSM

hi,JSM.Have you solved this problem?

i also meet this issue,and i don't know how to set the latent heat of the auxiliary fluid.

Could you give me some advise? thanks

[lucio]

Can anybody else help me?

I don't know how to define the property of the auxiliary fluid by UDF.i found that the UDF have no effect.How can i activate it?

thanks first.