Sand blasting. Any benefit?
 

Does anyone know for certain whether sandblasting the channels in a maze design improves cooling?

You refering to bead blasting???
well, it does increase turbulance,surface area....and more turbulance means a thinner boundary layer and less laminar flow.

So ,yes. It has to increase cooling efficiency in the same design.
But your mileage may vary.
A systems performance is not measured by the heat exchanger alone.
The pump, rad , and tubing all play a major part in the system performance also.
The key is finding the correct mates to acheive the maximum cooling capability of a given setup.

I hope this answers your ?

Well, even if it did very little for your performance, it would get rid of any corrosion inside the WB. I know that's why I sandblasted mine.

het koslov

queation for ya... did u re attach the top of ur maze or did u make an acrylic top for it? and if u used the old top, did u run into any problemz puttin it back on? i got 2 maze1 and i still have not got the crap out of them yet... ive done everything to clean them so far and they r still a mess inside

try soaking it in a 5% lyme solution(farm supply).......just make sure you watch it cause it WILL eat it up quickly

Well, also.......you have to consider that anything that creates more turbulance, creates more flow restriction, because the water is not travelling in a straight path anymore....its bumping all against itself as it exits.. So maybe a bigger pump is a good idea.
The Tim The Toolman urge always gets me when I pick out a pump.Besides if it proves to be too much, you can always restrict the flow down to your sweet spot.

Bead blasting can increase your surface area 2 fold.
It works for me:dome:

So, how do you know that the bead blasted surface doesn't 'hold' a layer of slow moving water in place?

Anyone know of a link to any scientific studies done on this?

i never thought of using lyme, ive bin using CLR right now...

Since87
promotes mixing normal to the face
heat 'sheding' at tips, where the action is
google a bit, stuff all over

Been doing a lot of googling using various combinations of:

blasting
sandblasting
sandblasted
sand
bead
convection
heat exchanger
turbulence
boundary layer

Found nothing so far. Any pointers?

be more general
perhaps
surface texture + heat convection (rate)

or so

anything interesting, post it eh ?
- there are even specific shapes that are better (inclined chevrons)

Yeah, I was planning on making an acrylic top, but I can't get any cheap enough. The local plastics supplier quoted me $66 for a 4' x 2' piece of 1/2" thick clear acrylic, the smallest piece they can sell in 1/2". I have plenty of 1/4" acrylic lying around, but I am afraid the barb thread won't be secure. I also wanted the extra thickness so I could experiment with nozzles.

BTW: My block is a Z4, so there's no way I am putting the unanodized aluminum top back on. Both the exposed copper and alu were black when I took it off.

Who knows, maybe I'll buy the big piece and try to sell smaller pieces on the forums. PM me if anyone is interested.

Edit: Oops, got the quotes mixed up. $66 for 1/2", and $50 for 3/8".

I opened a block that I made using an AL top, with an Oring as a gasket...and when I finally got it pred off,galvanic corrosion ate the Al about the size of an oring 3 times the original size in the surface, and had to mill a new top. I should have made the AL and Cu touch, and it wouldnt have done that much damage in 2 weeks! DOH!

I would stay away from acrylic, unless of coarse you are using nylon hose barbs.
Use lexan...costs more but very very strong stuff if youre going to use it for a WB top.

Yes, I have nylon hose barbs, from Home Depot. I would use Lexan, but I can barely afford the acrylic.

I use 1/4" acrylic for my tops. Hell I used 1/8" acrylic before. Allways use brass barbs to boot! Never a problem. :shrug:

I have some 3/8" acrylic and 1/4" acrylic at work. I can laser cut a couple peices to size for you and ship them. Be about $6 - $7.00 shipped.

I didnt say there was a problem with acrylic, just that "I" would stay away from it....I dont know about you guys, but I got alot of time invested in my PC to trust it to the structurial properties of Acrylic! One wrong shift of the tubing and............. BAM....your top springs a leak all over your $hit!
Not something I want to do again!!!

Maybe there is a flaw in yout teqnique? :p I can pick the mobo up by the brass barbs on the acrylic top and swing it around! (Only do this on a mobo with a dead CPU!, it is how I test the strengh of my stuff :)) if you thread the holes properly it is very strong, even with metal barbs. I havn't had any problems with it. Not to say that I won't though! I will check the prices on Lexan one of these days. We only pay about $15 for 4ft X 8ft sheet of 1/4" acrylic. :p

I've been googling till my brain is raw. I've found stuff discussing surface roughness from the scale of mountains down to about 3mm. Nothing discussing surface roughness on the scale of a sandblasted surface. (0.2-0.3mm RMS at a guess?)

Found a fair amount on flat plate heat exchangers when I threw "chevron" into the mix, but again, feature size was much greater than a sandblasted surface.

I don't know how this stuff scales, so I don't know if there is much relevance to the data on larger scale textures.

I would suspect it is directly related to the surface 'friction' (drag)
as it is the same mechanism that is effecting both

I'll try digging a bit also when I get some slack time, bit pressed right now

Koslov

I have some 1/2" Lexan on hand. I don't have a lot, largest chunk is roughly 5" x 6" rough edges but is pretty well square.

Still has most of the paper still on it, but may have just a few scratches. Not enough to allow a great deal of testing, but should sure enough do for one block. I'll ship it to you no charge, as I got it for the same price.;) :D

I know that in some cases texture can reduce drag. (Dimples on golf ball. Size of turbulent wake is reduced.)


I don't know if that has any relevance to the walls and base of a maze block though. Seems to be more of an issue with fluid flowing into the gap 'behind' an obstacle.

Sandblasting a pin fin block might reduce turbulence?

bit of a stretch to extrapolate from impingement to parallel flow,
but my 462B results were quite clear

not too sure that the MUCH lesser roughness due to blasting would be discernable,
but it would have to be in the right direction

good for marketing anyway

koslov;

you can glue mulitple layers of plexi together to get a thicker peice(using the correct adhesive)

I've done that with all of my plexi based blocks so far. my micropin block is 2 peices glued together.

About sandblasted surface: i've been thinking about that for a long time... I think that there's a limit under which surface features act by 'stopping' water molecules, and not 'throwing them around' as a bigger feature does.
I think there's a limit dictated by water viscosity, or surface tension, or both. Under this limit, surface features would only thicken the boundary layer, thus reducing the heat transfer.

(personal experience): in ultra-vacuum chambers one heats the chamber walls to make them reject water & gases molecules trapped by adsorption. (Try a google on 'adsorption' to know what it's about). Because any surface is not perfect, its surface features would trap other materials molecules that come into contact.
I tend to link that 'trapping' effect to the boundary layer between a solid and a fluid in motion. Maybe i'm wrong, it's just pure speculation.
If i'm right, then mirror finished waterblock transfer surfaces would perform better than sandblasted (or rough) ones.

The limit in surface feature size would be in accordance to the minimum radius of a water drop against that surface. Does that make sense ?