Radiator Thermal Test Bench Progress

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Originally Posted by bobo5195

I'm not sure that is possible from a thermodynamics POV given the conditions of the test.

Higher air speed would remove heat from the sensor faster if it was being warmed up though.

I have also never heard or seen it mentioned in textbooks or such. Good old Prof Kaynes would have brought it up.

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Thanks and thanks for the equations, you're always making me dig my old reference manuals out and keep an eye on the equations.:)

First up I'm trying a few repeatability tests just to see that, then I'll play around with some other data concepts. The data is all there, I've been capturing with each test about 2,000 rows with 14 column of temperature data (logged every second) along with a timestamp and RPM), so there are plenty of numbers to play with.

Here is a sample of 40 or so rows of the 2000 or so I'm collecting in just one run:
http://img519.imageshack.us/img519/6...prelim8qu2.png



Yeah the colder inlet vs ambient doesn't make sense to me either either, it was probably just error in the thermometers. If anything I've usually measured warmer temperatures at the inlet that's caused by recirculation of the exhaust. This is a big issue with alot of rear and top case mounted setups, my own system I was able to cut about 3C off by simply channeling air to exit and keep away from the inlet. In the end I don't find value in ambient, if the setup is done right ambient will equal Air In. Air in is what matters for heat exchange.

Even though I'm pretty impressed with these Dallas sensors, I still don't trust them for more than a few tenths of a degree and it's not uncommon for two sensors only a few inches apart to read as much as 1 degree difference. It's really amazing how much air temperature changes in such a small amount of space. After all air is considered and insulator, so it's not like measuring water and it's very high specific heat capabilities. Lots of sensors and logging for very long periods of time are the key to accurate air measurements is what I'm finding.

Also on the shroud vs. no shroud, I plan to do some controlled experiments to see if I can extract some good correction factors for a shroud vs. no shroud. I'm thinking on correction for 40mm hubs (25mm fans) and one for 55mm hubs (38mm fans) should be adequate, then you could adjust results for either shroud or no shroud.

If folks have the opportunity to see what those shroud performance results are, then they can decide for themselves if the effort is worth the hassle.

To keep the shroud design concept simple and easy for just about anyone, I'm thinking I'll try evaluating the effects of a shroud made from old 25mm fans with the motors snipped out of them. I could also play around with pull/pull, push/pull, etc. All of those difference scenarios where a flow chamber would only evaluate a shroud like condition, so it's not as flexible.

I think the equation goes PV=kT or something like that. P goes down, V is constant.

You can trivially make a shroud with a spacer ($10 for a bag of 50 from McMasterCarr) and some duct tape. No harder than attaching the fan with a longer screw.

Just because some people who fasten the fan directly against the radiator in push is no reason to test that way. Those people are already giving up 50% of their cooling capacity...what difference does the radiator curve mean to them? They could improve their systems significantly by spending 30 minutes with $10 of hardware.

Update:
A better comparison would be: is it better to add a two stage fan-set to a 2-fan radiator in pull with a shroud than to go to a 3-fan radiator?

And here is a picture of an actual plumbed and running test in progress, sorry for the mess...
http://img519.imageshack.us/img519/5...rbench8ip1.jpg

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Originally Posted by DavidNJ

I think the equation goes PV=kT or something like that. P goes down, V is constant.

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yep its nR but thats about right the equation for an ideal gas law. There are some mods to account for compressibility given the complexness of air you better off using tables and charts as ideal gas is not a useful approximation.

too much to say on Martins post as im off down the pub to talk about Ammonia fuel cells. hint NH3 holds alot more hydrogen than methanol CH3OH

The frame maybe two close to the inlet for the radiator, affecting (to a small degree) the numbers.

Question: why didn't you mount the radiator vertically? It would has worked with two vertical posts and some clamps.

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Originally Posted by DavidNJ

The frame maybe two close to the inlet for the radiator, affecting (to a small degree) the numbers.

Question: why didn't you mount the radiator vertically? It would has worked with two vertical posts and some clamps.

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Beacuse there is alot more differential between sensors that way, I get over 1 degree with my computer and the sensors are only aboug 6" apart, you'd probably have 3 degrees or more over a triple or quad rad mounted vertically.

The testing bench frame has 110mm opening, so there is no restriction. The radiator just barely sits on it's edges there, even on the PA which is wider than most. The only one I'll have to watch is the heatercore for that.

Curious, why did the Air In numbers vary so much?

Input Average Std Dev
AirIn1 25.76 0.03
Airln6 25.98 0.09
Airln4 26.33 0.04
Airln3 27.01 0.07
AirIn8 27.31 0.04
Airln5 27.40 0.04
Airln2 29.58 0.03
AirIn7 34.35 0.04

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Originally Posted by DavidNJ

Curious, why did the Air In numbers vary so much?

Input Average Std Dev
AirIn1 25.76 0.03
Airln6 25.98 0.09
Airln4 26.33 0.04
Airln3 27.01 0.07
AirIn8 27.31 0.04
Airln5 27.40 0.04
Airln2 29.58 0.03
AirIn7 34.35 0.04

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I've got a pump that only about a foot away that's probably influencing some of the temp sensors, and sensor 7 isn't being used right now, it's sitting there idle along wiht #8 only for quad rads.

This is why I was saying you need alot of sensors. The sensors themselves have some error and the air temperature is different all over the place, that's why I put all the effort to include so many sensors and log temperatures for so long. If the temperature was the same everywhere I wouldn't have bothered with all the effort.

Take a look at coolingmasters radiator test, they also plastered the run with sensors, one is not enough, it varies alot more than you would expect. And they don't just sit there idle, they bounce around.

Ok, I've made the change in removing my variac all together and just reading the actual watts the Kill-a-watt registers plus 15 watts for my pump. This seems to have straightend the curve right out for a nice linear relationship. So I obviously had some error in the power consumption of the variac which is eliminated now.

With this I think I'll just plan on testing at around 300 and again at 600 watts and plot the linear trendline.:up:

http://img528.imageshack.us/img528/2...prelim9xm3.png

Repeatability is really good too, I'd say within about .1C at 600 watts, so .1 of 12.12 is less than 1% error, so I'm happy with that. This should save a little time too.

Next up is a trial on measuring flow rate effects. I think I'll just do that at 600 watts at .5, 1.0, 2.0, Max Flow.

I doubt fluid flow will have more than a 10% influence, if that. Much more interesting would be adding a shroud. Based on Ira's tests, that may drop your tests that may drop your 300-330 number to under 5C.

And maybe those Panaflos which probably have 50% more pressure at zero flow. Based on existing Thermochill stuff, the M, and virtually certainly the H, would drop you peak number under 10C.

When testing denser finned radiators like the GTX, I imagine they will be more sensitive to more pressure being developed (or less pressure in a pull :) )

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Originally Posted by Martinm210

I've got a pump that only about a foot away that's probably influencing some of the temp sensors, and sensor 7 isn't being used right now, it's sitting there idle along wiht #8 only for quad rads.

This is why I was saying you need alot of sensors. The sensors themselves have some error and the air temperature is different all over the place, that's why I put all the effort to include so many sensors and log temperatures for so long. If the temperature was the same everywhere I wouldn't have bothered with all the effort.

Take a look at coolingmasters radiator test, they also plastered the run with sensors, one is not enough, it varies alot more than you would expect. And they don't just sit there idle, they bounce around.

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Could some of the temperature anomolies also be the result of fan effects exaggerated by not using a shroud and my affects of the base (its supporting corners) and proximity to the table? Would standing the radiator upright (and using a shroud) eliminate the descrepencies?

First, let me thank you again, Martin, for all your testing and work you've done and are doing. It's great to have all this empirical data available to us "grunts" down here in the WC'ing trenches.

Second, David, let the shroud thing rest a bit. All I read in your posts is shroud, shroud, shroud. Honestly, you've become something of a broken record about that. Give it a rest for a bit.

I say that because of a few things. The vast majority using WC'ing don't use a shroud, for whatever reason. In my situation, a shroud is impratical, no matter how great one may be in actual use.....which I am ambivalent about, anyway. Space is my concern.....I've got my TC 120.3 top mounted in my case and with the rad and fans mounted, I've got less than a 1/2" of space between the rad's bottom and the motherboard's MOSFET heatsinks.....sinks that would definitely interfere with any attempt to mount a shroud.

I'd imagine that I'm not the only one with that sort of problem, too. While a shroud may be useful, it's not practical in my case and probably not in a lot of other situations, either. So, why test for something the majority choose not to use or cannot use, in any event.

Instead, more valuable information would be fan choice, radiator choice, and flow rates through the individual radiators. Those are factors that all WC'ing enthusiasts can use.....we all use rads, fans, and pumps with flow rates. So that info would be applicable to all of us.....


And just one more point.......my particular setup consists of a Q6600-G0 stepping, a Thermochill PA 120.3 radiator w/3 Scythe S-Flex "F" fans running at 7-8V, a Laing DDC2 pump (the original DDC2 18W pump, not the newer 3.2 version) with an XSPC top, a D-Tek cpu block with washer and quad nozzle, an EK S-Max NB block and all 3/8" tubing.

I've got an OC on the Q6600 of 3.6GHz at 1.35V.....and with the above setup, running OCCT hour after hour gives me max load temps of 56C on my "hotter" of pairs of cores in my cpu. (Ambient, or air in temps are at 24-25C.) Now, you're telling me I'm losing upwards of 50% of my cooling capacity because I'm running in push w/o a shroud?

I just really find that hard to believe. But then again, I'm just a 53 yo gent who is into WC'ing as a hobby.....and it's not my life. My temps are quite acceptable to me.....and wll below any I'd expect to see from decent air cooling......