Steady State or Open Testing for Waterblocks

[Bignuts]

With all the hoopla in the forums lately I wanted to post a question for us all to consider.


Why doesn't anyone test waterblocks witha rig that cycles water through the block only once? This would allow us to see the effects on the blocks ability to remove heat from the core ONLY.



1. Such a setup would have a large holding tank, or would use a constantly repenished source of water at a constant temperature.



1A. The large holding tank has some issues with affecting flow rate.


1A1. The pressure at the pick up point in the tank will change as the water level in the tank is depleted.

1A2. Hard to insulate against effects of room tempurature.



1B. A constantly replenished source of water at a constant temperature can be had by locating the test rig near the spigot closest to the incoming water line for the testing facility.



1C. Water table temps in any particular area will remain constant at any testing area.



1D. Incoming water temps can be affected by testing area constraints.


1D1. Cycling well pumps.

1D2. Long interior piping runs to the test area.

1D3. Storage capacity of the well presurization tank.

1D4. Insulation of the incoming lines. piping, and holding tanks.



1E. Water temps can be stabilized prior to testing.


1E1. Run water through the spigot at a higher flow rate than the testing will occur at.

1E2. Allow the test rig to run with CPU heating software for a period prior to actual testing.



2. Tests should be recorded at different flow rates that encompass a range normally found in typical systems.



A. Apendix



ZZ. Errata

[bigben2k]

Actually, I suggested that... One could use those special faucets that they use in photo labs, that spurt out water at a constant temp. The problem is the holding tank, if you're gonna hold on to the water.

The problem is that in a block roundup, there's gonna be a lot of water used, and I mean a lot, simply because the block has to be allowed to stabilize it's own temp.

Also, since we'd want to test a block at different flow rates, then we're talking about a humongous amount of water, so unless you've got a water tower in your backyard, it's out.

The theory still stands though. The application is just not easily attained. A water chiller would be best, but they can be expensive.

[myv65]

Probably because it doesn't matter. Anytime you test a block you have to deal with measurement errors. The most obvious ones involve temperature, but you also have power measurements (for the CPU, pump, and all the other stuff generating heat), flow measurements, etc.

In terms of a block's performance, you really only need to know an inlet temperature (or outlet temperature) and flowrate to go along with CPU wattage. Fluid properties dictate, and I really mean DICTATE how much the fluid temperature will change. So long as your system is operating at steady-state, who cares if the water comes from an "infinite reservoir" or gets recirculated, it's still entering the block at a known condition (within our measurement error, that is).

It really is not that complicated to conduct a test. The real trick lies in how well you can control and measure your test conditions. Drawing fluid from a very, very large reservoir offers no inherent advantage over recirculating fluid once you reach steady-state. And make no mistake, even when drawing from a large reservoir you STILL need to wait for the block to reach a steady-state condition.

Personally I prefer an all inclusive test of a real world system. Unfortunately, the range of complete kits available isn't very extensive so we're left cobbling together bits and pieces from multiple sources. This makes gaging performance before assembly is complete rather a difficult task. Yeah, individual reviews can help in this area, but you still won't know how everything will work together as a group until you actually put it together and run it.

[Bignuts]

myv65:

"It really is not that complicated to conduct a test. The real trick lies in how well you can control and measure your test conditions. Drawing fluid from a very, very large reservoir offers no inherent advantage over recirculating fluid once you reach steady-state. And make no mistake, even when drawing from a large reservoir you STILL need to wait for the block to reach a steady-state condition."-

Wouldn't it take less time to perform the test because you wouldn't need to wait for the entire system with a radiator and all that extra mass of fluid to reach stabilization?


myv65:

"Personally I prefer an all inclusive test of a real world system. ...
...but you still won't know how everything will work together as a group until you actually put it together and run it."-

But will the test data collected from the intitial post still be relevant for any system, irregardless of the other equipment used? If not, what changes would need to be made to the test procedure?

[myv65]

There are trade-offs either way you go. With a complete system you are correct, you must wait for all of it to hit steady-state. In closed-loop systems though, this isn't very long. If you've got a reservoir of even a couple liters, it'll add considerable time.

Any data taken under properly controlled conditions is relevent. It's knowing the error bands associated with all your miscellaneous measurement equipment that is almost universally overlooked.

The other point I was making is that while your test conditions would display block performance, end users could still be disappointed because their complete package:

1) Couldn't meet the flowrates that you used (multiple tests over a very wide range address this)
2) Didn't know where their flowrate would fall and find out it's lower than they thought it would be
3) Don't have the ventilation/radiator area/ambient temperature to match the fluid temperature you tested (multiple tests over a wide water temp range address this)
4) Didn't know what their fluid temperature would be based on their radiator setup and it's higher than they thought it would be.

Where I'm going is that you could invest literally hundreds of hours to test a single block over a wide range of realistic flows and temperatures (not to mention power ratings, but I'll let you fill them in as points 5 and 6 in the list ). In spite of all this, folks would have a hard time correlating the data to a completed system.

Sure, they may know that block "A" did better across the board than block "B". But you don't need hundreds of testing hours to determine this. It's an interesting debate topic that has no single right answer.

In the end you'll never satisfy everyone with testing. Some want precisely what you've outlined. Others want to see systems tested. Many (most?) haven't a clue about what "controlled conditions" means (including most reviewers). Discussions such as this one will hopefully change this last fact.

[airspirit]

Agreed. There are so many variables that go into a WC system that it would be impossible for an end user to use the data in reference to their own design.

You can say that when using a XP@1.95V at 12.5x and 150FSB (AGOIA steping) on a KT3Ultra2 with a Altec 480W PSU (list all voltage values) with a total of 7.4ft 1/2" tygon tubing running a BIX with Xcfm of air @ X degrees Celsius when the blah blah blah with my girlfriend's jugs dangling 14.3 inches over (68 degree angle of declination) the blah blah blah 13 Fat Tires later (12 ounce bottles) and blah blah 14.2 minutes of pr0n dloading blah blah ... you get a stable temperature of X.

To an end user this translates to: um ... spir@ls look k3wl, i wanna buy 1.

You can do simple tests on a block similar to what Webmedic is doing and get more meaningful results. All you need to do is use a standard setup for all tests, plug the block in and let it run for an hour. Take your measurements, and go onto the next block. All this silliness about increasing the accuracy of the test serves no purpose but to make the test more meaningless to the end user. Sorry, guy.