Manual (non-FEA and non-FDM) Solution for Finned Heat Sink 4

[Tunalover]

We have a recurring need to analyze a plate-fin heat sink with forced-air convection but I have not been able to find a manual (or spreadsheet) solution for this seemingly simple problem. The heat sink is basically a constant-cross-section rectangular duct with internal, constant-pitch parallel fins extending from the base to the opposite surface. The heat sink is mounted to a heat source in such a way that it can be assumed that the heat/unit area entering the base is constant. The fins are normal to the base and are of uniform material and thickness. The fins are on the order of .02" thick, the rectangular cross-section on the order of 1" high by 4" wide. The pitch of the fins is on the order of .19". The length is on the order of 6". A fan either pushes air in or pulls it out. I'd be happy to assume that the entrance and exit are hollow ducts with the same cross-section as the heat sink and of sufficient length to provide full-developed flow before and after the heat sink.

We have about 150Watts to reject from the base to the air stream. Am I oversimplifying this or is this harder than it looks? It is surprising that there is no handbook solution available for this exceeding common problem. Thanks in advance for you valuable comments and remarks!


Tunalover

 

[ko99]

Tunalover,

The method described in the paper below is for plate-fin sinks but not covered as you described. However, since your flow is fully ducted and your heat source is ~uniform, you can account for the effects of your cover simply by adding the surface area.

You should also include fin efficiency and, depending on how your airflow is delivered, you may also need to calculate pressure drop. Let me know if you need references for these.

Teertstra, P., Yovanovich, M.M., and Culham,J.R.
"Analytical Forced Convection Modeling of Plate Fin Heat Sinks"

http://www.engr.mun.ca/~yuri/PAPERS... Plate Fin heat Sinks - 2001 IEEE Journal.pdf

ko (

http://www.ecooling.biz)

 

[Tunalover]

ko99-
Did you solve any problems using the method described in the article? If so, did you compare the solution with test results? I'm just fishing for more background here.


Tunalover

 

[ko99]

Yes, I use this method as a nice short-cut calculation. I've compared it with test data and CFD simulations and results are excellent within the Re Number range noted in the paper.

Again, it's important that the air is fully ducted (no bypass) and the heat source is uniform.

ko (

http://www.ecooling.biz)

 

[fallibleone]

We use a software tool - nonFEA, nonFDA - for heat sinks that has proven to be quite accurate (

http://www.heatsinkdesigner.com).

It's only a few hundred bucks (request a discount) and does a lot more than a spreadsheet.

 

[unclesyd]

Here is good reference to fins, especially tubes, but has some good information on fins in general. There are three chapters on fins.

http://www.wlv.com/products/databook/ch1_5.pdf

 

[ko99]

tunalover,

fallibleone has a good point: HeatSinkDesigner will do exactly what you want and it probably makes more sense than developing your own spreadsheet

ko (

http://www.ecooling.biz)

 

[mecheng66]

I've been through this before and developed a little spreadsheet with some success, but now I use heatsink designer instead -- it's simple but I like the way it draws the sink for you and you can learn a lot simply by trying different materials and sizes and running optimizations.