Radiators & Airflow
 

120:3 rad
3 x Xinrullian pushing 92 CFM
MCP600 @ 13.6V
Swiffy 6002
Fusion HL
All 1/2" (a little shy of 10ft of tubing all in)

running ... Res > Pump > Rad > CPC quick Connect > 6002 > HL > CPC quick connect > Res

The reason I mention the CPC connectors are because they are self sealing and so inhibit flow somewhat, don't know if thats a factor here or not...Anyway, onto the questions...

Running the fans at roughly half speed on my fan controller, is it fair to assume that half speed = half the rated airflow??

Either way, airflow is much reduced but when turning the fans up to full, the temps do not improve any, not even by a degree.
Now, I guess there must be a point at which no matter how much air you throw at a rad it won't go any lower, so am I at that point with the fans on the low setting??

I'm sure that flow rate, ambient temps and many other factors will affect that, I guess I'm also after an idiots explaination as to the relationships between these things, or a pointer to some articles.
Or am I missing something more fundamental here? Even my humble exos can dent the temps by 1 degree by turning the fans up to full.

there is a temperature change from having your fans at 1/2 speed to full speed but the diffrence is minimal.
smaller then what you can acurately measure I'm guessing.
my 2¢

Roughly speaking, half the voltage does usually end up being half the airflow. That relationship usually falls apart below half voltage though. If increasing airflow does not decrease operating temps, that means the cooling bottleneck in your system is not the radiator. In other words, regardless of airflow, the radiator has reached a plateau in efficiency given the current system components.

So, I've either hit the sweet spot for my gear first time, or theres improvements to be made elsewhere in the set up.
Interesting. I'd suspect flow rates are being hit by the CPC connectors, I'd hoped to compensate for that a little by running at the higher voltage. Gives me something else to play with for a while :)

any pictures?

On the test bench...3/4 rear shot

http://homepage.ntlworld.com/sam.nurse/Radbox4.jpg


In situ and running...

http://homepage.ntlworld.com/sam.nurse/Radbox5.jpg


The side mounted LCD gives me a temps readout from MBM5 :)

Looks good... :)

Yes, many variables affect final temp - radiator airflow is only one. IMHO, if you are not seeing any measurable change in temps when slowing the raddy fans down by roughly half, then the radiator system is not the limiting factor in your cooling system. Something else, such as overall flow rate, is holding you back.

Try measuring your system flow rate: connect a large (constantly filling reservoir to mainatain constant level), disconnect your return line and measure how long it takes to fill a 1 gallon (or 5 gallon) bottle => GPM or GPH (or liters if you prefer)

That's a nice setup, very clean and functional. What CPU, video card etc are you running? You may not be dumping enough heat into the system to really tax it. If I had to guess, I would say you're running near the peak efficiency of your waterblock, which puts you in the flat part of the curve in this graph:


Your pump can push over 2.9 GPM with no head, so even if we figure you have enough resistance to drop your flow rate to 1.5 GPM, for instance, you still wouldn't see much of a difference (less than .5 degree). Thus I don't think the pump is the problem, and the rad probably isn't either, given your results with fan speed changes.

That means that given the amount of heat your hardware is producing, the bottleneck in your system is probably the MCW6002, which is a pretty good bottleneck to have, given its performance numbers.

What's your dT air/water at load?

Keep in mind, you will Not get those delta T results with an A64 if that is what you have for a CPU. About the best you'll get will be in the area of 21-22C inlet water to core ratios.

Hoot

and I would note that Hoot has a very temperature stable room in which he tests
got to have a baseline

I was thinking along the lines of water temp in his circuit vs ambient air. Isn't water temp at any point in a circuit the same (within .5C) regardless of where it is measured?

I'd speculate that is true for the most part with systems having a reasonable flow rate. Something in the .5-1.0C range. I just ran downstairs and checked mine with my Fluke and Type K sensors and they're running 22.0C out of the Radiator and 22.8C into it. That's using the setup in my sig and running Prime95 Torture In-Place Large FFTs fixed at 896k. FWIW, the core is reading 43C.

BTW, nice workmanship on the external heat exchanger.

Hoot

Current spec is...

XP-M2500 217 x 12 = 2604 @ 1.75V
9800Pro @ 433/370

I can't really give you any figures for dt or even ambient tbh, ambient tends to jump about a bit in this room.

However, had a little scare this morning. Just browsing forums and had a reboot, a quick glance at the temp display showed 45c....not too alarming but curious as I had been at a steady 38c. Another glance at the radbox showed the pump power had cut off! 1 quick shutdown later and it was back to the bench for some investigation.

To cut a long story short, the PSU I filched out of work was duff :rolleyes: The upshot being the pump may have been running at below 12V, so it was back to the workshop to aquire another. A bit of testing/refitting later and it's back on.

I'm just waiting for it to get a good warm up before I try the fans again.

Update...

The pump is now running at 13.8V ok. Temps have remained the same as before at 38/39 idle, 42/43 load as measured by MBM5. Turning the fans to full did decrease the temp by 1c but it took a fair few minutes to filter through. I'm not unhappy with those temps but I did expect them to be better. Maybe my expectations were too high.

The only other thing I can try is run without the CPC connectors to increase my flow. Here's a chart of thier pressure drop, maybe someone with better knowledge can interpret it and let me know if it's doing more harm than good??

http://homepage.ntlworld.com/sam.nurse/L179501-01.gif

Another FWIW: Air coming out of my radiator is 3C warmer than the air going into it, as measured with the Fluke under the above conditions.

Hoot

Nice setup there, still got the same?

those quick-disconnects look pretty nice. what do they do to flow/where did you get them?

http://www.omega.com/pdf/tubing/coup...fc12series.asp

I was trolling and knew the source.
The spec pictured is for the 3/8" ones. I use the 3/4" W 1/2" ID Tygon R3603.
I installed them as TBirdX did. I don't have to drain the system or have two people to move it. They are fairly restrictive, but I think they can be modded to be better although I havn't had time to try. In a system with an Eheim 1048 they reduced flows from 0.91GPM to 0.78GPM.

Can you please post more pictures of your rad box. It looks like one that I want to make. Thanks