Please help with fan and heat sink airflow simulation

[SandyLunch]

I’m not exactly sure how to set up this heat transfer problem.

I have a heat sink. The heat comes in via four heat pipes, and leaves by forced convection from a fan. I would like to simulate one single layer, between the middle two sheets of copper. I’m not quite sure of the best way to set up the airflow for the fan.

This is my simulation volume:

The four small circles are where heat is coming into the heatsink. The two small rectangles represent the fan, either side of its hub. I would like the air to flow into one side of the fan and out the other side.

This is one attempt I have made to set up the simulation: SimScale Login

I think it’s a good start. But one obvious problem is that the air coming out of the fan is cold. Really it should be the same temperature as the air entering the fan.

Also, do I have correct values for the rest of the simulation?

How can I measure how much power is being taken out of the copper by the air?

Many thanks in advance for any help or suggestions.

[Leo007]

From what I saw in your project, your flow region is not continuous. Air enters from the right at ambient temperature (293 K in this case) and gets heated, but then it leaves the flow region. When that happens, it’s as if it ceases to exist and a different air enters through the middle, also at 293 K, because there’s that gap in the middle of the flow region.

[SandyLunch]

Thanks Leo,

That’s correct. I’m not sure how to implement a fan another way. What is the best way to set up a fan in the middle of a volume. All of the examples I can find are about setting up a fan on the boundary of the volume.

[SandyLunch]

Also, is there a way I can calculate how much power is leaving the system due to heat being blown off by the fan?

[Leo007]

To implement a fan mid volume you should use a momentum source advanced concept. and to calculate the power leaving the system, if you reach a continuos state them all power generated is also leaving the system, so check the TDP (watts) you set up and how many of them and thats the heat leaving your system in a continuos state (make sure its in a continuos state, set up a temperature result control in a important face or volume and once it stabilizes it means you reached it)

[SandyLunch]

Hi Leo,

Thanks, that makes sense. How do I set up the volume for the fan? Do I add another ‘fan’ volume inside my ‘air’ volume? Like this:

Or should I carefully cut up my ‘Air’ volume into ‘Fan’ and ‘not fan’ volumes, like this:

Is there a tutorial for this available?

Many thanks

[Leo007]

You are going to use only one flow region, and you are going to set up 2 thin blocks inside of it to be the fans boundry condition ( i am assuming this is what you are trying to simulate) . use the edit geometry option to create the blocks and set them up!