Looking for input on fin lengths on DIY waterblock

**Dr_Swizz** · 01-26-2011, 10:18 AM

Hi!

I am looking for input on how long I should make the fins on a GPU waterblock that I am going to make.
I am using the copper base from an old Pentium 4 cooler (see attached image) and I am going to try to mimic the design of a modern high flow block.

How much should I cut the fins? Should I make them 1mm? longer/shorter?

**relttem** · 01-26-2011, 10:38 AM

you are wanting to pass water thru the fins? You need to make sure that the water is going to go thru the fins and not find another path of least resistance - basically going to have to cap it and then worry about the pressure drop across it. You can crunch out the numbers, since you pretty much know everything.

**Dr_Swizz** · 01-26-2011, 12:39 PM

Originally Posted by relttem

you are wanting to pass water thru the fins? You need to make sure that the water is going to go thru the fins and not find another path of least resistance - basically going to have to cap it and then worry about the pressure drop across it.

Yes, I was thinking of trying a basic desing at first with inlet/outlet at opposite ends of the block and a "bulge"/restriction in the middle that it is close to the fins.
If it doesn't work so well I was thinking of making a different top with the inlet in the middle and a nozzle plate to restrict the water flow.

Originally Posted by relttem

You can crunch out the numbers, since you pretty much know everything.

I have no idea how to that, care to elaborate?

**Church** · 01-26-2011, 02:11 PM

Imho simplest is to copy-cat some of leading blocks, eg. EK Supreme HF. 1.9-2mm deep 49 thin channels (but probably the thinner/more channels you can cut, the better). IIRC Old supreme block and HK 3.0 had shallower, about 1.5mm, which resulted in more flow restriction. No sense in making channels much deeper too, as further from base of block/from cooled CPU, less heat is conducted from it to top ends of fins. Couldn't find though how wide those channels & fins are and how thick is base of HF. Base of waterblock should be thin as possible for better heat conductivity (and lacking resulting rigidity should be compensated by top pushing through O-ring on waterblock's base with channels.

**Dr_Swizz** · 01-26-2011, 05:10 PM

Originally Posted by churchy

Imho simplest is to copy-cat some of leading blocks, eg. EK Supreme HF. 1.9-2mm deep 49 thin channels (but probably the thinner/more channels you can cut, the better). IIRC Old supreme block and HK 3.0 had shallower, about 1.5mm, which resulted in more flow restriction. No sense in making channels much deeper too, as further from base of block/from cooled CPU, less heat is conducted from it to top ends of fins. Couldn't find though how wide those channels & fins are and how thick is base of HF. Base of waterblock should be thin as possible for better heat conductivity (and lacking resulting rigidity should be compensated by top pushing through O-ring on waterblock's base with channels.

That was very helpful; thank you!
I'll go for 2mm fin length then.

I'm thinking of making the base 1.5 mm thick (I don't think I'll dare making it thinner than that.