heat & mass transfer

Do you Google?

If not, please tell us a little bit about the application. Is this a heat sink for a chip? Or the side of a power transformer? Is it free convection? Ambient? Temperature drop you're looking for? etc, etc.

actually, i m working on a study project of pin fins .

so i need all the info about it like types of fins, types of convection ,heat reduction furmulae. give me website name or any e-book names by which i can get it . and provide me as much u know.

You are talking about convection specifically? Or just getting rid of excess heat?

For convection, you want fin designs that will allow air to flow past them easily. That usually means parallel fins, arrayed vertically, so that heated air can rise through them without too much aerodynamic drag. How closely they should be spaced is probably a fairly complex calculation (balancing drag vs heat conduction to the air.)

OTOH, you can also force air past the fins with a fan. Fans are simple and cheap to run. No need to rely on simple convection.

All heatsink fans should be made of some material with high heat conductance, such as aluminum or copper. Thinner is better, for simple materials efficiency. No need to use more copper than you have to.

Not much else we can say, without details.

"Thinner is better . . . . "

I do not agree. There is a relationship of calculating fin efficiency and that depends a lot on thickness of the fin.

Thinner does not mean better, unless you are speaking in the context of adding additional fins due to a reduction in thickness. Technically speaking, you want to fit as many fins as you can, as thin as you can, with the largest surface area. The Miracle Thaw is the perfect example of this. Using natural convection, the Miracle Thaw absorbs the heat from the air to thaw the food. It has a large surface area, and is relatively thin. Furthermore, it is made of aluminum, which leads me to my next point - the material is very important as well. Using a highly conductive material is paramount to a fin.

actually, i m working on a study project of pin fins .

so i need all the info about it like types of fins, types of convection ,heat reduction furmulae. give me website name or any e-book names by which i can get it . and provide me as much u know.

Provide some more details of application.

With best regards,

Prasad

African elephants have larger ears than Indian elephants for this very reason.

Go back to your basic Physics thermodynamic equations. There you'll find that heat gets passively transferred by three techniques, conduction, radiation and convection. The materials and contact area between source and sink will set the maximum thermal transfer rate for the most part. Knowing this one can then consider your question about fins. The surface area of the fins will establish both the amount transferred by radiation (a small percentage but always present) and the conduction to the air adjacent to the heat sink surface. Up until this point, there's little difference in thermal transfer response from fin topology. But now, the air that this heat sink has heated must be permitted to move away from the heat sink and take this heat away. If the air is being driven by a fan this topology is less critical. If not then fin patterns should not block the normal rising of hot air. Staggered fin patterns increase the volume of air rising in this chimney like arrangement. Like all engineering considerations though, frequently other concerns get in the way. Often available space is limited so less than ideal heat sink topologies must be used.

Now that I've covered the details, there is no classifications of heatsink types that I know of. Frequently different manufacturers have similar patterns because the easiest manufacturing techniques do produce similar products. (Why do precision machining if an extrusion of stamping of sheet metal will do.)

thanks for details

can u suggest any book for this topic or ant website from which i can have the complete details?

I like the Halliday and Resnick textbook Physics Part I chapter 22 (particularly the three pages of 22.4) for understanding heat transfer. (I am an old f%*t) But you should have a good grasp of the previous chapter on temperature to understand what's going on. Differential equations would be good to also understand. I don't know if J. Wiley still publishes this textbook. They should, it's a good one.

After that any heat sink manufacturer should have some useful application notes. Check Thermalloy for a nice place to start.