tube length vs flow rate

I was curious - i just put a water cooling setup in my system and i wanted to avoid using 90 bends etc as they reduce the flow rate. So in order to avoid 90's I had to use longer lengths of tubing to make the same bend and not kink.

question is what is more detrimental to overall performance - the reduced flow of a 90 bend (there would be a lot of 90's used) or long sweeping bends that make the pump have to pump further??

Any comments??

My particular setup is cooling the cpu-gpu -nb and the rad is on the outside of the case the tubing has to enter and exit the case - adding to the overall length as well !!

Im curious about this myself but I wonder if using oversized 90° Elbows would make a difference. Something like 5/8"ID or 3/4"ID on a 1/2"ID tube. Fittings cause resistance but I wonder if larger fittings would prevent this.

JT

Tubing length does decrease your flow, but not nearly as much as 90 degree fittings. Think of a car. You can't maintain your speed going through a 90 degree turn, and everyone behind you gets backed up too. Same thing with water. 90 degree turns kill flow rate.

i bet i could reduce the the overall length of tubing in my system by at least 2 feet if i used 90's....

i think my total system length is 12 feet (adds up quick)!!

Alacritan said:

Tubing length does decrease your flow, but not nearly as much as 90 degree fittings. Think of a car. You can't maintain your speed going through a 90 degree turn, and everyone behind you gets backed up too. Same thing with water. 90 degree turns kill flow rate.

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Has anyone ever measured (or tried to measure) the effect of a 90 degree turn? I mean, with a powerful pump, a single 90 degree turn may not hurt overall performance?

Its a simplified example of course, and many factors should be added, but I'm just trying to get an overall "feel" of how bad 90 degree turns are.

I'm using an Antec Sonata, and a few (1-2) 90 degree turns would really make adding an extra radiator a lot easier.

i was thinking using oversized 90's so that at the bend it doesnt go below 1/2"....

arctic-k20 said:

i was thinking using oversized 90's so that at the bend it doesnt go below 1/2"....

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My thought exactly!

Of course, a 90 degree turn is still a 90 degree turn, but with the right pump....I would say an DD D4 should be able to supply decent flow in a system with a TDX/Maze4 (cpu/gpu) combo? (with a few 90 degree turns)?

I havent been able to locate them yet but I have seen some really cool 90 degree bends. These were not the traditionl sharp 90 degree angle, they instead were short bent curves with a radius of around 2-1/2". If a person was to use these I dont think that it would effect the flow nearly as much, unfortunately as I stated earlier I am still in search for them. They were gray in color and appeared to be a plastic/nylon type.

If a person used these type fittings with an ID of the same size as the tubing (yep, it would be some work getting the tubing over the fitting barbs but certainly doable) I see very little reason they would decrease flow nearly as much as the standard sharp turns. Stack on top of that the reduction in turbulence due to having the same ID as the tubing and I think it might be a winner. If anyone locates them (I have seen pics on this forum of them before so they do exist) please post a link.

Why not boil the tubeing and bend it to the nessacary bend radius. If it still kinks, add wire ties. And as I said before, each one of those you add, you get 2 more possable points for a leak.

http://www.swiftnets.com/
go to Liquid Cooling Products then click on Coolsleeves Coils
that should help.

I don't know if this is a good idea, but its a thought. How about putting two 45 degree fittings together instead of a 90. It would be a little less sharp of a bend. Just an idea. Maybe also put a small length of tubing between the 45's to conserve flow.

instead of using plastic 90s, go to a hardware store and get some of the copper plumbing 90s, they have much gentler curves

Don K said:

Has anyone ever measured (or tried to measure) the effect of a 90 degree turn? I mean, with a powerful pump, a single 90 degree turn may not hurt overall performance?

Its a simplified example of course, and many factors should be added, but I'm just trying to get an overall "feel" of how bad 90 degree turns are.

I'm using an Antec Sonata, and a few (1-2) 90 degree turns would really make adding an extra radiator a lot easier.

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A couple 90 degree bends won't make your system unusable but they do seriously decrease flow. The more powerful the pump, the more noticable it will be.

pirred908 said:

I don't know if this is a good idea, but its a thought. How about putting two 45 degree fittings together instead of a 90. It would be a little less sharp of a bend. Just an idea. Maybe also put a small length of tubing between the 45's to conserve flow.

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Why bother? 1/8" sidewalled Tygon tubing can make sharper than 90 degree turns, just with a wider radius. Buy better tubing that doesn't kink as easily and you should have no need for 90 degree fittings.