Learning Forum

[malay1995]

Hello Everyone.

My name is Malay and I am fairly new user to ansys fluent.

I am trying to simulate heat exchanger in ansys fluent. Since last 10 days i have run more then 30 analysis on heat exchanger however, i am not getting any proper results. i have checked all the videos on internet read lot of ansys guides on the website but still i ccouldnt figure out the issue.

The first thing i checked in cfd post is the temperature change of hot fluid [Oil at 110C] which flows in shell and the water at 7C flows in coil. There is not much temperature change actually no heat transfer is occuring, although somehow i got some temperature change but i am not sure if thats correct.

Secondly the mass flow rate of oil which is 9kg/s and water is 4kg/s at inlet boundary conditions. The velocity streamline from oil inlet is almost zero and at water inlet there is some velocity, so i guess water flow is fine but oil flow is not correct. i am attaching the pictures of flow rates and temperature. please go through it and let me know what to do. 

Please feel free to ask any other details. The mesh is on default settings because if i generate fine mesh it takes lot of time and i dont have that kind of computing power. K-epsilon realizable model is selected with standard wall function. solution method is default. there are three domains in cell zone conditions, water domain, oil domain and copper coil.

I have attached the step file of geometry created in solidworks.

[Amine Ben Hadj Ali]

I assume oil and water domain are communicating via a wall/wall-shadow / Interface and it is set to coupled. Check this please and add a screenshot of the related boundary conditions / interface and report about the Fluxes as shown in the Flux Report in Fluent: start by mass and then total heat transfer rate. You can then focus at first on the water domain and then on the oil domain. Check also for convergence and if you ran the case for longer time.

 

[malay1995]

Thanks for the reply

Yes you are absolutely correct the oil, water and coil domain have wall/wall shadow interface and i changed it to coupled wall.

But is this boundary conditions correct ?

If yes why i am not getting proper flow rate on oil side. water flow is good but in oil the velocity is zero so it means there is no flow of oil i guess. i want to run for more iterations but it took around 1hour for just 20-30iterations.