High power cooling - Page 1
Forum section: electronics / projects

author: justinjja
author_rank: Regular Contributor
timestamp: May 09, 2018, 06:19:49 pm
content: I'm doing some thermal calculations and wondering if I'm even close to accurate.I'm installing 15KW worth of computers in a tent,and exhausting through a 12in duct that is 5ft long and has 1 90 degree elbow.I have a bunch of Delta AFC1212DE 150CFM fans that I would like to use.Max ambient temp would be 38C.My target max temp in the tent is about 49C.By my calculations I need about 2200 CFM.And it will take about 25x of those deta fans to get 2200CFM through the duct.Thoughts?

author: CopperCone
author_rank: Super Contributor
timestamp: May 09, 2018, 06:48:07 pm
content: If you have duct work setup and shit, I would recommend getting a over sized box fan to pull all that air through the duct, this way you can install nice filters and stuff too.Probably more energy efficient as well as its a large motor, single bearing, etc. Less maintenance then 25 fans also.

author: justinjja
author_rank: Regular Contributor
timestamp: May 09, 2018, 07:09:49 pm
content: Thanks, but I think box fans have very little static pressure,CFM wouldn't be nearly high enough if my calculations are right.Something like this is plan B:https://www.grainger.com/product/DAYTON-1-4-HP-24-Dia-115VACV-Shutter-1HLB2

author: ajb
author_rank: Super Contributor
timestamp: May 09, 2018, 07:57:29 pm
content: Yeah, a box fan is not going to deal with ducting well.Are your computers actually going to dissipate 15kW, or is that just the total rating of the power supplies? Typically computers don't draw anywhere near the total PSU rating in normal operation.

author: justinjja
author_rank: Regular Contributor
timestamp: May 09, 2018, 08:28:48 pm
content: Yep, 15KW continuous and that is only half of them.I have a $2,000 electric bill lol.

author: CopperCone
author_rank: Super Contributor
timestamp: May 09, 2018, 08:29:34 pm
content: i meant squirel cage connected to ouput

author: Gregg
author_rank: Super Contributor
timestamp: May 09, 2018, 09:37:28 pm
content: Fantec makes the quality duct fans with some of the best fan curves. It is important to look at the fan curves of any fan you may consider and estimate the back pressure etc. Fantec FKD series would be my first choice. I would also suggest something to shade your tent from solar heating if it going to be in any sun.

author: dmills
author_rank: Super Contributor
timestamp: May 10, 2018, 01:09:07 am
content: I second the sun shielding, it is potentially at least as big a deal as the direct heat load.At the CCCs 5 yearly camp a few years back (Which turned out to be during a major heatwave) those metalised mylar emergency blankets were found to make superior reflectors with which to cover the shipping container housing the 10Gb routing and switching gear on site. Cheap as chips and the silver ones were about equal to the gold ones, well worth investigating.Regards, Dan.

author: james_s
author_rank: Super Contributor
timestamp: May 26, 2018, 08:51:34 pm
content: For loads of airflow through ducts you'd typically use a squirrel cage blower. You can get them in sizes from tiny all the way up to gigantic industrial blowers that are hundreds of horsepower.

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: May 26, 2018, 11:01:18 pm
content: Quote from: justinjja on May 09, 2018, 06:19:49 pmSpec sheet to find the p-q curve..if you can't find the spec sheet (its not listed on delta-fan), then if you know the static pressure you can make a guess by estimating linear and add margin. 12" dia 5 foot duct with typical 90 degree bend @ 2200cfm, I get found .17 inh2o pressure using hvac tables. For a AFC1212D-F00 (101cfm, .348 inh20) [I can't find the spec sheet for your specific fan], .17 inh2o halves the cfm rating. Also the flow is mostly limited by the 90 degree bend (3x pressure drop vs without it there), so if you can remove it or improve it in someway..

author: justinjja
author_rank: Regular Contributor
timestamp: May 27, 2018, 01:36:43 am
content: Hooked up the fans,It's a few degrees warmer than I worked out,but it will be good enough for now.

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: May 27, 2018, 05:23:23 am
content: Nice. Have two exhausts?If there's anything gas fired (water heater etc) near the space, check that the pressure in the room can't get low enough to pull flue products back into the area. Anything you can do to keep pressure from dropping in the room will help anyway

author: justinjja
author_rank: Regular Contributor
timestamp: May 31, 2018, 06:36:25 pm
content: At the top of the foam board "Chimney" is a 12,000 CFM fan removing the tent exhaust and another 100,000 BTU from several ASIC computers.I was actually worried about the water heater in that room, but even with all this airflow it is still exhausting correctly.The room has a ~10 SQFT intake.

author: james_s
author_rank: Super Contributor
timestamp: May 31, 2018, 07:11:04 pm
content: If only you could harness that 15kW of heat and transfer it into the water, you wouldn't need to run the water heater.