Why measure flow???

[Dix Dogfight]

Can anybody tell me why the measurement of the waterflow is of great importance when you try to compare different WB's.

If I have read all the threads conserning WB-design etc correctly I've come to understand that more flow is allways better, yes?
If so, then comparing two different blocks require that I use the same flow/presssure-generating device and that the rest of the setup is the same.
(I know that a bigger pump generates more heat and so on. Thats why I wrote DEVICE. The pump can easily be replaced with a watertower and then the added pumpheat will be ZERO and preassure on the WB-inlet the same, so no pump arguments pleace).

The reason I ask this question is:
A few WB/HW-reviewers say that measuring the flow is a must to determine which block is better.
The blocks capacity to remove heat is of course a function of the flow and therefore the calibratiion and accuracy of the flowmeter is of great importace. BUT better (in my world) means lower temp.
So why not concentrat on measuring temp and forget the flow.
Maybe measure its flowrestriction/preassuredrop instead?

It would be much easier for the buyer to read a review if it says something like. Block A is producing this deltaT and this is probably because it has a lower flowrestriction than the other blocks so it will perform good with all kinds of pumps..........
(ok so i wrote the "pump" word, but disregard that )

I would prefer if comments like "try and measure a few blocks your self and see how hard it is......." where kept out of this thread OK.

Any informative/intelligent/constructive answer will do just fine.

Thanx for reading so far

[MadDogMe]

Flow through diferent blocks are (nearly) always different. when tring to compare two things differences have to be taken into consideration. and seeing as flow makes such a big difference to performance, it's very important. it's the biggest variable there is....

Compare two blocks with a Eheim 1250:

Block 'A' might run 3degC hotter than pump 'B'. you'd be inclined to call pump 'A' shite, but if you ran both blocks with a 1060, block 'A' could run cooler than (the previuos best) block 'B'. the 1060's flow could make all the difference...

So would it be a safe bet for a reveiwer to tout block 'A' as shite?. considering not everyone(though nearly ) runs a 1250 Eheim?...

That's one reason, bet your ass there are more ...

Basicly to be comparable they have to have the same amount of flow through each.
I kinda know what you're thinking( I think!!). the flow through is part of the design and therefore should be taken as such and ignored. that would be OK if flow was'nt so bloody variable from pump to pump, and a reveiwer is trying to cover ALL bases ...
***********************************************

Disclaimer: This is just My take on this, and as such anything I say is subject to altered reality, and so can be retracted, denied or hipocrosised as I see fit. Also it is not to be taken as gospel unless St Paul appears in front of you as you read my words ...

[MadDogMe]

Maybe measure its flowrestriction/preassuredrop instead?

I think the Ideal review needs to state what the flow restriction is[at flows that corospond with flows used for testing](measure flow with then without block), as well as what the particular flow was at testing.
A 'graphed' chart of 'performance to measured flow' would be needed as well, so you could asertain performance for your own flow/pump.

Before and after water temps are good. the Rad does'nt really come into it,in fact I think it can only confuse the readings. so I would have a large res' of 'sustained temperature' water, and conduct all tests from this water temp.

I'm sure there's more but I've never realy thought about this till now...

[Dix Dogfight]

MadDogMe thanks for the fast reply

OK so we are back to squre one then. Test all combinations of blocks and pumps?? That would render to much work for any reviewer. So I would say it's a no go.

Why not connect the WB to the tapwater then? That way you have a "constant" pressure device, with a constant temp, that has a higher pressure than any reasonable cooling pump out there can deliver. And it will not add any pump heat. One variable less to be concered about OR?

cheers

Edit: Damn spelling errors just won't quit on me

[myv65]

There are many factors that make evaluation of any block a difficult task, at best. All blocks will be affected by flow rate and power input from the CPU. Obtaining even two data points for different flow rates on a given CPU only begins to hint at the block's performance at all possible conditions. Trying to get accurate data at multiple flow/power combinations quickly adds up to a lot of work for a reviewer. On top of all this, everyone's systems are different and there is no easy way to predict how much flow you'll get from a given setup unless it precisely matches a review somewhere.

IMHO, I'd like to see four measurements made for a block. High vs low flow and high vs low power. Sounds simple enough, but even here folks would argue about the definition of "high" and "low".

Then there's the perspective of people that are interested in overall system performance as opposed to a piece-meal evaluation of components. A great block is no good if the radiator or fans are not up to the task. Sure, lots of people piece together systems on their own, but lots simply want a complete kit.

You'll never please everyone no matter how you review.

[bigben2k]

Testing WBs is difficult, and it does involve a fair amount of work, any way you look at it.

About the flow rate test: It is important to know the flow restriction of a waterblock. The less restrictive it is, the more flow it can handle, which could be supplied by a less powerfull pump. Now I know that even that's not clear enough... You also have to factor in the rad, seperately, since more heat will cause the rad to be more efficient, but will still cause the water temp to be higher, something to be avoided, if possible.

The water tap idea may not work, because it may not achieve the desired flow rate, plus you really can't be sure that it's steady pressure or temp, for that matter.

I thought that it might be best to use a big pump, and just put a restriction on it (valve), to reduce the flow rate to the desired level, but that big pump would induce a fair amount of heat, so it's only good for flow testing.

Since the end user will buy an off-the-shelf pump, there is not only a limited range of flow rates that will end up being used, there are actually very specific flow rates that will be achieved, but since there is quite a large number of pumps out there, it becomes quite unreasonable to test every single model.

Also, the end user may end up using just about any rad, and that in itself is a large variable, for both flow and temps.

[pHaestus]

Look at some of Bill's data:



Note that if you shift along the X axis the relative performance changes. This means that any observations you make without measuring and equalizing flow for every block will be totally system dependent (same pump, same rad, same fans, same tubing size/length/routing) and not of much general use.

So you could say "in MY setup at this moment block A is best", but making any changes that affect flow rates will make this statement potentially false.

That is why flow rates should be measured for testing. If you know the pump/rad that you plan on using then you can choose a block more appropriately if pressure drop and performance curves as a function of flow rate are available.

[Dix Dogfight]

Note that if you shift along the X axis the relative performance changes.......

Yes and thats why I was thinking that if you use a higher flow than 3gpm (extrapolate the graph to the right). The performace change (CW/GPM) is so small that any missreading on the flowmeter or fluctuation in the flow is irrelevant.

However I made the misstake of thinking that the tapwater could produce a higer flow than 3gpm. I measured mine at home yeasterday after work and it was only slightly above 2gpm .

So I guess all you HW-reviewers out there got your work cut out for you

Thanks for all input/thoughts

cheers

[Can O' Beans]

I could be completely wrong with any of these, as I'm basically in a state of learning disability, but....


What I was thinking is to have a system, with WAY too many heatercores, say 2-3+ in parallel. I think this would take *most* of the heatercore's performance in the system out of the equation. This would reduce overall flow restriction through the HC part of system, and since the water would be flowign thru each HC a lot slower, it should have no problem cooling the water to room temperature(which would have to be kept constant).

I've seen " Y " bypass valves that switch flow from one side to the other. You could have one line going to the waterblock and the other side going to a bypass line that just goes through a 2nd block of the exact same brand/type with the same exact length of hose. This bypass line block wouldn't be hooked up to a heat load, it would only be there to keep the same flow resistance on the 2nd line. As you switch from one line to the other, the pump wouldn't see any difference in flow resistance. This would prevent fluctuations in the temperature generated from the pump itself. You would also need a "dummy" flow meter on this line as well, just to keep any flow restriction caused by a flowmeter equal on both lines.

Now, with any worries of cooling system inadequacies and pump temp fluctuations removed, you can focus on the block itself. You would now adjust the Y bypass valve to raise/lower the flowrate through the testing block with a constant heat load on it. Start off with low flow rate, and measure temps as you slowly sweep through to maximum flow rate, letting the system fully stabilize at each recorded point.

As for mounting the blocks, you could do either or both of the following:

1. Use the hardware included with the block, and follow manufacturers directions on mounting.

2. Mount all blocks with the exact same pressure on the cpu die. This would require a calibrated precision torque driver following proper torquing procedures to torque the 4 bolts to a set amount.

If I'm thinking correctly, all this would help isolate the performance of the system to the block design itself. You should be able to get somewhat accurate results of the performance of the block itself, then plot it for comparison to other blocks.
************************************************** *

Now if I'm missing something (which I probably am) I hope these ideas can at least be tweaked/improved upon for better results I'm not even going to try to get as detailed in procedures as BillA would as I'm just not as edumacated

[MadDogMe]

Test all combinations of blocks and pumps??

You'd only have to use a one high flow pump and 'throttle' it down to lower flows with a clamp on the pipe or some such, then do a graph at varying flows(say100 GPH to 300 @ 25GPH.still alot of work!). as long as you know the flow of your own pump you can compare.

[bigben2k]

Originally posted by MadDogMe
You'd only have to use a one high flow pump and 'throttle' it down to lower flows with a clamp on the pipe or some such, then do a graph at varying flows(say100 GPH to 300 @ 25GPH.still alot of work!). as long as you know the flow of your own pump you can compare.

Except that you still have the same pump heat, regardless of the flow rate, plus, at certain flow rates (low ones) you'd have to watch for cavitation.

[MadDogMe]

As long as you measure the water before block surely it can be calculated?. then drop the temp of the test water accordingly?, or just include it in the temp. change the temp of the 'test water' to include the 'calculated' pump heat?.....

but would'nt that be more relevant to a loop?. I'd have the water pass through once, from a large insulated(constant temp) resevoir,how large I don't know, it would depend on the lenght of test. the test would'nt have to be too long would it?. as long as the heat load is right?.
Also I'd have no rad to interfere with back pressure, ect.

Has anyone ever calculated how much (or if) pumps put into the water?. for inline and submerged?. I read somewhere that pumps introduce heat as kenetic energy (from the impellor) more, as opposed to radiated(inline).

How much heat does a 1048, 1250 & 1060 Eheim produce respectivly?.

[Dix Dogfight]

Has anyone ever calculated how much (or if) pumps put into the water

Yes Iv'e done it here:
http://forums.procooling.com/vbb/sho...=&threadid=533

Easiest way would be submerged pump in a alu tank and then put a pelt on the outside of the tank and cool it with the same amout of watts as the pump consumes = dumps into the water.