Hi All,

Is Silicon Bronze good for casting heatsinks? Does it have good thermal conductivity?

better stick with copper or aluminum.
You can check out material properties at matweb.com

better stick with copper or aluminum.
You can check out material properties at matweb.com

I do want to use copper, but i thought Silicone Bronze was 95% copper?

I do want to use copper, but i thought Silicone Bronze was 95% copper?

It is but it is also a fairly high strength copper alloy not easy to machine and the melting temperature is much higher than aluminum. You may find it difficult to cast a heat sink with closely spaced thin fins and you will definitely find it difficult to machine deep fins in a block of silicon bronze. Given that the efficiency of a heatsink depends on both the thermal conductivity of the material and the fin surface area that is rejecting heat I think aluminum with many deep thin fins will be as effective as silicon bronze with fewer thicker fins.

It is but it is also a fairly high strength copper alloy not easy to machine and the melting temperature is much higher than aluminum. You may find it difficult to cast a heat sink with closely spaced thin fins and you will definitely find it difficult to machine deep fins in a block of silicon bronze. Given that the efficiency of a heatsink depends on both the thermal conductivity of the material and the fin surface area that is rejecting heat I think aluminum with many deep thin fins will be as effective as silicon bronze with fewer thicker fins.

Geof, Would it still work if i made the heatsink with medium size, but short fins, and still use the silicone bronze, as this would be a watercooled heatsink?

Geof, Would it still work if i made the heatsink with medium size, but short fins, and still use the silicone bronze, as this would be a watercooled heatsink?

I guess I should have asked the question is it an air cooled or water cooled heat sink. With water in the picture corrosion becomes a consideration so silicon bronze is a practical choice. Fins will only be necessary if you are rejecting the heat to the air, i.e. the water circulates through the heat source and then through an air cooled heat sink. If your heat is being carried away entirely by water in a flow through system fins will not be needed. For a circulating system I would use bronze for all the components that contact water and for the air cooled heat sink attach a regular heavily finned piece of aluminum heat sink.

Not to sidetrack the thread (it's sorta related), but how about using one of the commercial flood coolant additives instead of plain water in a recirculating system?

I'm not anywhere close to current but pretty much all used to have corrosion inhibitors and some do enhance thermal conductivity. Over kill, or some consideration(s) I'm missing?



Tiger

Not to sidetrack the thread (it's sorta related), but how about using one of the commercial flood coolant additives instead of plain water in a recirculating system?

I'm not anywhere close to current but pretty much all used to have corrosion inhibitors and some do enhance thermal conductivity. Over kill, or some consideration(s) I'm missing?

Tiger

Tiger, i have plans to use a prestone type mix, it would not only be anti-corrosive, but would be able to pull more heat away like in a vehicle. The setup that i'm designing, will have a small radiator to remove any leftover heat.

Why i would like to use silicone bronze, is because a casting friend of my only casts with that. I thought about milling them from a piece of copper, but it'd be quicker to made a wax master, cast it then make a rubber mold to produce more, more quickly.

Sounds like the way to go if you have that "at hand" means of getting the castings made. I was just curious about coolant additives, hence the doofus noob question ;)



Tiger

Tiger, i have plans to use a prestone type mix, it would not only be anti-corrosive, but would be able to pull more heat away like in a vehicle. The setup that i'm designing, will have a small radiator to remove any leftover heat.

Why i would like to use silicone bronze, is because a casting friend of my only casts with that. I thought about milling them from a piece of copper, but it'd be quicker to made a wax master, cast it then make a rubber mold to produce more, more quickly.

Okay, now we have the full story what you want to do is eminently sensible. If you are lost wax casting then the story is quite different because you can get very fine detail. Not that you need it really if your ultimate heat rejector is a radiator.

The automobile antifreeze for corrosion protection is worthwhile but it does not enhance the heat removal capacity or, more precisely, in your situation it is unlikely to make a difference. A mixture of ethylene glycol and water has a lower specific heat than pure water so for the same volume flow rate and temperature change between the heat source and heat sink less energy is carried by the mixture. However in an internal combustion engine the heat source can be well above the boiling point of pure water so localised vapor bubbles can interfere with the heat transfer from metal to water. This does not occur as readily with the mixture so the overall efficiency can be improved.