Reg: simulation of refrigerator condenser

[Anonymous]

Hello,

I have to perform simulation of refrigerant inside condenser tubes with air as an environment outside the tubes.

• do I need to create external fluid volume for convection effect to air? 
• I have taken these BC conditions right now:--- inlet: quality=1, pressure=12bar gauge total, velocity: 5m/s, temperature: 60 Celsius. Outlet: unkown. 

So, please help me! 

regards,

Akshay Kumar

[Anonymous]

Hello Sir,

I have attached my simple model here. As I don't know much about thermal analysis. I have to see the pressure drop across the tube and heat transfer from the condensing fluid to copper tube.  

Please help me if anybody can help me in setting appropriate boundary conditions and parameters.

regards,

Akshay Kumar

[Xiaojin.Zhang]

Hi Akshay,

You don't need to create external fluid volume for convection effect to air. 

Using film coefficient at the exterior surface as you did in your model simulates heat transfer to external flow.

It seems that you would like to run a compressible analysis. Compressible flows are usually high speed flows with Mach numbers greater than about 0.3.

If the inlet velocity is 5m/s. It should be an incomressible flow. Please refer to the link below to assign the boundary condition:

http://help.autodesk.com/view/SCDSE/2018/ENU/?guid=GUID-6F2E3547-E76A-4F13-8A7D-44A9BC971C53

Thank you!

Xiaojin

[Anonymous]

Hello,

Thanks for your suggestions, as I am running incompressible now but still the result is same No fluid is moving into the pipe and no heat transfer is taking place. only at the inlet of the pipe something is happening. but whole pipe remains same. no change in either parameters.

I am attaching the screenshots of the results.

regards,

Akshay Kumar

[Xiaojin.Zhang]

Hi Akshay,

I guess you didn't change the boundary condition for incompressible flow.

The best way to assign the boundary condition for your model I believe is:

Inlet: Velocity, temperature, quality

Outlet: P=0

Please make sure heat transfer is also enabled.

Thanks!

Xiaojin

[Anonymous]

Hi @Xiaojin.Zhang,

thank you for your suggestions. I have some more doubts.

• Do I need to on auto forced convection mode?
• what are the effects of gravity direction?
• And I am using film coefficient value for r134a refrigerant 2000 W/m^2/K is it okay?

thanking you,

Akshay Kumar

[Xiaojin.Zhang · Accepted solution]

Hello Akshay,

I don't think you need to enable auto forced convection or gravity direction.

Link below explains what is forced convection and gravity direction is checked for natural convection analysis.

http://help.autodesk.com/view/SCDSE/2018/ENU/?guid=GUID-5DE738D2-BE39-4310-88BF-593451F54588

Thanks!

Xiaojin

[Anonymous]

Thank you so much! 

I will try all these first.

regards,
Akshay Kumar