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The impact of tubing sizes

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Mycobacteria said:
Does a system with large tubes hold more water compared to a system that used small tubes?

Would this difference in volume influence the temperature in any way?

I would say yes to both. Even if it was minuscule, it take does take longer to heat up a bigger volume of water.
 
Mycobacteria said:
Does a system with large tubes hold more water compared to a system that used small tubes?

Would this difference in volume influence the temperature in any way?

It doesn't affect the final temperature that is reached, it just influences how quickly it takes to reach the final temperature.
 
Great post, Cathar! :thup:



As far as temps go I doubt a "normal" loop would be big enough to have much effect. However, a serious gamer could create an over-large res to act as a heat-sink for those video intensive moments during a game, thereby increasing the time required to reach max temp. If the sink is large enough the system should still be below max temp by the time the CPU/GPU load decreases in the game (those "quiet" moments before and after a battle or race). The size of the heat-sink/res needed would vary a lot by the game being played.

Of course the heat-sink wouldn't do SETI and Folding rigs any good since they run 24/7 at a constant, high load ...
 
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QuietIce said:
Great post, Cathar! :thup:



As far as temps go I doubt a "normal" loop would be big enough to have much effect. However, a serious gamer could create an over-large res to act as a heat-sink for those video intensive moments during a game, thereby increasing the time required to reach max temp. If the sink is large enough the system should still be below max temp by the time the CPU/GPU load decreases in the game (those "quiet" moments before and after a battle or race). The size of the heat-sink/res needed would vary a lot by the game being played.

Of course the heat-sink wouldn't do SETI and Folding rigs any good since they run 24/7 at a constant, high load ...

In that case, the serious gamer would get more radiators, and high RPM fans. Extra large rads will pwn extra large reservoirs, any day of the week (except for maybe mondays because mondays suck).

Edit: Brain fart typo.
 
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jrafael said:
Glad to see there is almost no difference within 7/16 and 1/2

Something I dont seem to understand with his post and this statement;

The op used the same sized connectors for both the 1/2" and 7/16" ID tubing, which was a 10.5mm ID connector. Wouldnt this be the reason for the little difference between the 2 different ID tubings? Or did I read something wrong?:shrug:
 
I went to 1/2 inch from 3/8 a while back because of all the hype. I really did not notice a change in temp. It did make it more difficult to route through my case though. I can live with a .25 increase in temps to get a better, cleaner setup.
 
Mpegger said:
Something I dont seem to understand with his post and this statement;

The op used the same sized connectors for both the 1/2" and 7/16" ID tubing, which was a 10.5mm ID connector. Wouldnt this be the reason for the little difference between the 2 different ID tubings? Or did I read something wrong?:shrug:

Most people use 7/16 on half inch barbs, its a tight fit but it works, really this accentuates the difference in the tubing size since it eliminates the barb size variable, and clearly the tubing size is of little impact to performance between those two sizes. I'm glad to see the 7/16ths on my video card (the MCW60 is too close to the ramsinks to stay with 1/2" tygon like the rest of my loop) isn't strangling my system. Great post as always Cathar.
 
Maviryk said:
In that case, the serious gamer would get more radiators, and high RPM fans. Extra large rads will pwn extra large radiators, any day of the week (except for maybe mondays because mondays suck).
Agreed - but the extra fans will make more noise ... ;)
 
Maviryk said:
In that case, the serious gamer would get more radiators, and high RPM fans. Extra large rads will pwn extra large radiators, any day of the week (except for maybe mondays because mondays suck).


Hmm... I am not getting your logic ;) Maybe since radiator is a bigger word than rad, haha?


Oh, BTW.... awesome write up! I would not have thought that there was that small of a difference in high and low flow but it does make sense now that I think of it...

Hotter water at the inlet of the rad in a lower flow will result in nearly the same outlet water temperature as a high flow setup with a lower intake temperature.
 
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Big Mike said:
Most people use 7/16 on half inch barbs, its a tight fit but it works, really this accentuates the difference in the tubing size since it eliminates the barb size variable, and clearly the tubing size is of little impact to performance between those two sizes. I'm glad to see the 7/16ths on my video card (the MCW60 is too close to the ramsinks to stay with 1/2" tygon like the rest of my loop) isn't strangling my system. Great post as always Cathar.

What I meant to point out, was that because both the 7/16" and 1/2" ID tubing is using the same ID sized connector, that the results may be skewed.

From what I remember back when I took aircraft hydraulics (over a decade ago, so yes, I could be wrong...), when fluid travels from a large diamter tube, to a smaller diameter, the pressure increase, but the volume of fluid decreases. Likewise, going from a smaller diameter tubing to a large one, would decrease the pressure, but increase the volume of fluid. Isnt the volume of fluid the same as what most refer to as "flow rate"?

If so, then going from a smaller diameter tube (7/16") to a larger (the 10.5mm barb) would result in more flow. Going from a larger diameter tube (the 1/2") to a smaller (the 10.5mm barb) would result in less flow, or one can say, a restricted flow.

If you look, there are (relatively speaking) large differences on the flow rate chart between the two 8mm and 9.6mm ID tubing, when using a smaller ID barb, to the quick fit. I'm guessing the quick fit ID matches that of the tubing.
 
Maviryk said:
In that case, the serious gamer would get more radiators, and high RPM fans. Extra large rads will pwn extra large reservoirs, any day of the week (except for maybe mondays because mondays suck).

Edit: Brain fart typo.

Fixed. I had a brain fart concerning nouns.

Also, I think gamers tend to use headphones or excessively loud speakers, so noise is not much of an issue anyhow!
 
Excellent post! I was looking at a watercooled set-up on some French site which was using 1/4" tubing and it looked really neat and compact. I wondered how effective it might be.
 
Mpegger said:
What I meant to point out, was that because both the 7/16" and 1/2" ID tubing is using the same ID sized connector, that the results may be skewed.

From what I remember back when I took aircraft hydraulics (over a decade ago, so yes, I could be wrong...), when fluid travels from a large diamter tube, to a smaller diameter, the pressure increase, but the volume of fluid decreases. Likewise, going from a smaller diameter tubing to a large one, would decrease the pressure, but increase the volume of fluid. Isnt the volume of fluid the same as what most refer to as "flow rate"?

If so, then going from a smaller diameter tube (7/16") to a larger (the 10.5mm barb) would result in more flow. Going from a larger diameter tube (the 1/2") to a smaller (the 10.5mm barb) would result in less flow, or one can say, a restricted flow.

If you look, there are (relatively speaking) large differences on the flow rate chart between the two 8mm and 9.6mm ID tubing, when using a smaller ID barb, to the quick fit. I'm guessing the quick fit ID matches that of the tubing.

The smaller the piping the larger the head loss for a given flow rate, there are some oddities of pressure and volume changing at size transitions, but over longer runs typically they even back out for the most part by the end of the run. But really my point was just that 1/2 barb 7/16 hose is the "norm", most people dont use a smaller barb with 7/16 hose, so its applicable to what people actually do. If you had a 3/4 OD 1/2 ID quick connect that worked well with the 1/2" tube you'd probably get a greater advantage over 7/16, but in most reasonable water cooling systems you're already well past the "diminishing returns" point. The quick fit fittings flow much better because they seal to the face of the tube and outside wall so the diameter of the opening can be as large or larger than the tube, rather than the ID of the tube minus more for the material to make up a barb.
 
Mpegger said:
Something I dont seem to understand with his post and this statement;

The op used the same sized connectors for both the 1/2" and 7/16" ID tubing, which was a 10.5mm ID connector. Wouldnt this be the reason for the little difference between the 2 different ID tubings? Or did I read something wrong?:shrug:

This was a concept that I put forward some time back as a way to select a tubing size that has a lesser overall outer diameter. The tubing size that was suggested was 7/16"ID|5/8"OD, as opposed to 1/2"ID|3/4"OD that most were using.

BTW, 7/16"ID is 11.1mm ID. 1/2" is 12.7mmID. The barb orifice ID is 10.5mm ID. There's a restriction still for both tubing types.

The suggestion was to stretch the 7/16" tubing over the 1/2" OD barbs.

The reason why this works, and has no real impact on flow rates, is that yes, even though the tubing restriction for 7/16" ID tubing is higher than 1/2" ID tubing, for flow rates less than around 10LPM, the differences are fairly small.

The real clincher comes with the tubing->barb interface. Fluid mechanics study has found that we experience a greater flow resistance when the sudden contraction is mismatched by a larger amount. i.e. it's easier to push flow through the 7/16" tubing over a 1/2" barb (with a 10.5mm orifice) than it is to push flow through 1/2" tubing over a 1/2" barb.

The size of the barb interface difference actually almost wholly counter-balances the increased flow resistance of the 7/16"ID tubing, if tubing run lengths are kept to less than 3 meters. In fact, if we have 4 tubing->barb reductions (eg. pump inlet, cpu inlet, gpu inlet, radiator inlet), then there is actually no difference in the overall tubing&barb restriction between the two tubing types.

The study of this data is what prompted the suggestion by me that everyone who uses 1/2" tubing, and complained about the size of it, could in fact be using the slightly more slender 7/16" tubing instead, and not see any performance difference. The realities of this has been confirmed many times.
 
I will say, for the record, putting 7/16 tube on a 1/2 barb while definitely doable, is a pain in the you know where. I'm still debating whether or not to switch all the tubing out when I get a decent case for this spaghetti I call a loop, I did put a lot of cash in this 1/2" monster tygon...
 
I think the important take-away message is to just go with whatever takes your fancy, at least from 8mm ID with quick-fits, and upwards. If 1/2" ID makes you happier, do it.
 
Could the take home message be: "bigger tubes are better and will lower the temperature by as much as 1 deg c."

From my understanding the final temperatures that you have listed are kinda "predicted" and based on "calculations"....

Will you be be using a probes to take the "actual" temperatures in the near future just to verify the calculations?
 
Mycobacteria said:
Could the take home message be: "bigger tubes are better and will lower the temperature by as much as 1 deg c."

LOL. Still holding onto the dream I see. :p

That statement of yours would only be true if we're talking about the differences between 1/4" to 1/2". There's a whole range of tubing sizes between the two, as I showed, with far, far, less differences. I don't want to see people walking away and thinking that the differences between, say, 3/8" and 1/2" are anything like 1C. They simply are not. There's actually been plenty of people who have seen the same sort of thing over the years, where they changed to a 1/2" system, and saw no difference at all.

From my understanding the final temperatures that you have listed are kinda "predicted" and based on "calculations"....

Have conducted numerous tests in the past, by using a tap to choke the flow-rates and measuring the impact. The only thing I haven't tested is the actual flow-rates with various tubing types, but the engineering science for pressure drops and PQ curves for such is actually pretty solid. It's telling us that even if we double the restriction due to the tubing used, our flow rates only drop by ~25%. Mapping that back to my own tap-restriction tests, I can assure you that dropping the flow rates by 2-5% (eg. as between 3/8" with quick-fits and 1/2") truly has an extremely minimal impact on final temperatures. Heck, even dropping the flow rates by 10% (e.g. 5/16" with quick fits as compared to 1/2") will only have an impact that is barely registerable on most thermal diodes.

The important aspect here is to ensure that the pump choice is sound.

Will you be be using a probes to take the "actual" temperatures in the near future just to verify the calculations?

Like I said. Have done so. Not for the exact scenario as in the OP, but for other testbeds, yes. In all cases, the theory and the empirical results typically aligned themselves within 10% or so, and certainly within the margins of error for the temperature recording. I trust the rather simple theoretical aspects enough in this to be extremely confident in what I'm putting forwards.
 
Using a separate temp sensor to verify the readings probably isn't necessary as the same CPU was used for all the tests here. You only need to adjust if you're using different cpus of the same architecture (i.e. two different E6600s or two different X2 4400s).
 
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