View Full Version : Building a shroud what's optimum fan gap 4 me
05-13-07, 04:58 PM
getting the urge to build a shroud after seeing some blind spots on my rad( from the dust traces).
I'm running with :-
3xYateLoon D12SH-12 150 m³/h @ 12v*
*Controlled by Mcubed t-balance Idle= 32% 6.8v 751rpm
Black Ice GT Stealth III
Now my radiator is pretty dense i know, am wondering what would be the best gap between fan & rad.
are there any formulae, physics i can apply or be aware of.
Most shrouds I have seen have about a 1 inch spacer.
05-13-07, 05:23 PM
that's part of my raeson for asking, have seen various 1" as u say to ThermoChill PS120.x (http://www.thermochill.com/ps120.php) which comes in at 40mm just over 1.5"
I like to try to keep a fan-height distance between any rad and fan, but i add more if the rad is larger than the fan, like most heatercores. for 120x25 mm, a 25mm spacer is optimal were if your running a 120x38, you might add more, about 35mm of space.
there is a 5mm spacer there from the chamber anyway. its too bad the channels arent removable for custom shroud mounting. just adds turbulence on the exaust which leads to more noise.
05-13-07, 08:20 PM
Can you just use washers to give the "space" between the fan and the rad?
Have you checked out this Shroud Building Thread (http://www.ocforums.com/showthread.php?t=308900) in the OCForums sticky section>? It helped me out a lot when I built my shroud.
05-13-07, 10:28 PM
Can you just use washers to give the "space" between the fan and the rad?
you need to trap the air in or you'll get alot of wash out through the opening rather than directing the flow through the rad.
going off no supporting evidence at all, I thought I remembered to get optimal diffusion of air from a shroud you needed like 8" or something retarded. maybe Im making it up, or maybe whoever it is that Im vaguely remembering said it made it up.
I dont have 2mm for a shroud in my case, and Im not willing to have one outside the case, so owell right?
05-14-07, 02:13 AM
You could use spacers but you'd have to create a funnel using tape or something like that. It would look pretty ghetto unless you're pretty 1337 with tape.
05-14-07, 05:16 AM
Anything bigger than 20mm is "enough"... beyond that, difference in performance is immeasurable (ie: miniscule). With fans above 40cfm, performance difference tends to be immeasurable also...
05-14-07, 06:32 AM
Thanks for answers think i'll follow Valk & Marci's advice & go for 20mm shroud which will be just under 25mm gap taking in the gab on the rad between mounting & radiator.
If your worried about cost or workability, card and duct-tape do wonders for shroud making. I used mattboard my first few times.
I asked a similar question a while back, and my recollection is similar to ares350, in that someone whipped out some math and came up with a distance that was really unreasonable (I remember 4", but no matter, I digress). So anywho, I figure about a fan's width is reasonable.
05-14-07, 10:47 AM
If your worried about cost or workabilityno thanks m8, got some aluminium sheet on it's way just want to make sure shroud design incorporates best gapo for my bits
@ARCJr yep that's where i was coming from have seem some smart applied maths used elswhere was wondering if there was something similar for this, or others experiences, 20~25mm seems to be coming out favourite
05-14-07, 05:08 PM
This is plan shroud i'm to put together:-
Design Plan (http://homepages.nildram.co.uk/~chsmith/AsusBuild/WC/shroud.png) have a small bending brake so can fold edges. Idea is verical pieces centre top & bottom can be mounted on the rad using short screws, thus i can visualy confirm screw clearance. Fans can be fitted onto the top using somethinhg like 30mm m4s. the top cabn then be screwed on & the ends plugged in.
shroud side is 45mm less fan = 20mm gap probably 25ish including rad gap.
will be mounted on:-
The base has been expanded to 2xblowholes using empty 120mm fan frames. I may do a 2x shroud to go between rad & case. I have some neophane on the way to use as gaskets.
05-16-07, 05:37 AM
If you read a couple of Weapon's posts he recommends 2" as optimum shroud spacing.
But I'll let him and Marci fight that one out - I'm no expert ... :)
05-16-07, 05:51 AM
The shroud stuff was all postulated and theorised and discussed betwixt myself, Cathar and a few others during the PA160 development, when the original shroud ended up HUGE...
Which led to...
Marci, been plugging through the calculations with a flow calculator and the shroud angle.
10-15 degrees shroud angle from the vertical is optimal for the 16x16 -> 12x12cm shroud, with a pressure drop of 1.9Pa given a 50CFM air-flow, for which 35-50CFM is about the sorts of air-flows we're targetting with the low-noise optimised design.
A 30 degree shroud angle (4cm shroud depth), yields just a 2.0 Pa pressure drop.
A 45 degree shroud angle (2cm shroud depth), yields a 2.1 Pa Pressure drop
Given that the sorts of low-noise fans we're talking about are generating 10Pa air pressures at the sorts of air-flow rates we're talking about, then the variation here is trivial at best. We'd only be talking about impacting air-flow rates by 1% by converting the shroud into a very convenient and compact 4cm depth device (fan mounted on outside), and by 2% from "optimal" if the shroud was an even more compact 2cm depth (fan on outside).
In fact, even moving to a super-compact 1cm depth yields just a 3% loss of air-flow from the "optimal" depth.
I would however suggest that 4cm (30 degree angle from vertical) would be a very nice shroud depth for both the blow and suck fan orientations, and still make for a very compact design.
05-16-07, 06:58 AM
Thanks very much for your input marci & QuietIce
found this How much does a shroud help (http://www.ocforums.com/showthread.php?t=389346&highlight=shroud) which weap[on contributed to.but around 1.5" of standoff is a good balance between performance and the amount of space it takes up inside the case. For the best overall performance and less noise, a shroud is a definite go which in proper money :D is near enough 40mm.
Think i'll go with a 40mm high shroud which will then give me the options of mounting outsider or inside.
btw i just got some neophane sheet to allow me to build some gaskets, what is the best adhesive to use to attach to aluminium??
05-16-07, 07:29 AM
Evostick Impact... red tube... B&Q have it on the shelf, as do most DIY places.
05-16-07, 07:35 AM
Got some from focus, was a bit of a laugh.
Didn't realise there were 2 varieties:-
Empty tins (solvent based):D £4.50
Full tins (solvent free) £5.50
Thought the cheaper one wasn't to be sinffed at:D so went for that only to find that they didn't have any at the checkout, woman went to warehouse but couldn't sniff one out.
i saw she had a tube rather than tin under the counter so ended up with that.
gave me a laugh anyway.
just waiting 4 aluminium now.
05-16-07, 09:42 PM
If you stck some silicone fan dampeners (the full ones not the silicone screws)
stacking 2 of them gives you about 1cm as a shroud and its quiet too.
05-27-07, 12:43 PM
Well finally got round to building the shrouds
Currently working as intakes to case top blowholes from shrouds.
Top shroud is 45mm high giving about 25mm gap to rad when mounted internally as shown.Lower shroud is 60mm which gives a range of around
Both shrouds are modular to allow simple/easy fitting
Shows top shroud sides fitted.
I find this an advantage as i can feel safe that i ain't putting screws through rad:cry:
05-27-07, 12:44 PM
Top shroud fan mount plate:-
Lower shroud assembles the same way
bottom shroud mounted to case & fan, showing fan gap
adding the 2 pull fans has lowered temps by about 2~3C. Noise is a bit more subjective but certainly seems quieter & smoother. All in all i'm pretty pleased & have the options to experiment when the mood takes me.
05-27-07, 04:05 PM
Looks very good! :thup:
You really should get some grommets for the wire holes though ...
05-27-07, 04:24 PM
thanks i'm not sure about
You really should get some grommets for the wire holes though ...??
do u mean the fan cables from the upper shroud then yep your right , will keep an eye open for some.
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