why would you want 1/2'' Tubing?

I don't really have any opinion on this really, i was just wondering in my head a little bit. If you have a bigger stream of water for the pump to push, wouldn't this make the pump work harder than if it was only pushing a tube of 1/4'' tube filled with water?

Just wondering.

port-error said:

I don't really have any opinion on this really, i was just wondering in my head a little bit. If you have a bigger stream of water for the pump to push, wouldn't this make the pump work harder than if it was only pushing a tube of 1/4'' tube filled with water?

Just wondering.

Click to expand...

No. Pumps work best with the least amount of restriction (there may be instances to the contrary, but for the most part true). Do a search for 'head loss' or 'pressure drop'.

theres an equation for tube restriction which-a-ma-callit... circumference.... radius...length... something along those lines. i have seen it in another thread if you care to look it up, but it doesnt sound like you are that interested. im not either.

As a former high school science teacher, I won't let a lack of interest stop me from providing the overly-elaborate facts...

Poiseuille's Law: "In a cylindrical tube model, the mean linear velocity of laminar flow is directly proportional to the energy difference between the ends of the tube and the square of the radius, and is inversely proportional to the length of the tube and the viscosity of the fluid."
"Volume flow ...is equal to the product of the mean linear velocity and the cross-sectional area of the tube."
(From Zweibel, et.al., Introduction to Vascular Ultrasonography, 2nd Ed.)

Translated: The stronger the pump, the shorter the tubing circuit and the larger diameter of the tubing, the more flow velocity and water volume you will run through your system (and past your block).
This is intuitively sensible if you think about it.
The question is really not why would you want to run 1/2" tubing, but why wouldn't you?

o yeah, no doubt 1/2'' tubing will give you better flow of water, obviously. But if you were a pump -=), would you want to push a huge amount of water across a long series of tubing which is alot more weight, or would you want to push less water across the same distance? Its no doubt your going to get better results with more water, but thats not what i'm asking. I'm asking are you puting more stress on your pump?

It's actually more stressful on a particular pump to pump a given volume of water through smaller diameter tubing rather than larger.
As the vessel radius decreases, there is a marked decrease in flow (35% with a 10% radius decrease, and about 95% with a 50% decrease in radius!).
The relative surface area of the vessel walls, and therefore the friction effect, also increases exponentially with vessel diameter reduction.

Edit: Because I think I understand your question better now: you're saying that with a given system (equal tubing length), a smaller diameter tubing would give you a smaller volume of water to pump, and would therefore be easier on the pump.
That does make sense, but I think the issues of flow resistance would overcome the volume differences.

okay.

okay, so your basically using the rational that, if there is better flow and less friction than the pump should put out less effort? Even though your pushing about 2x more water?

Well, considering that volume increases exponentially with increased diameter just as it decreases with reduction, it wouldn't take too much hose diameter to arrive at a water volume that would be a burden to a pump.
One reason I used a reference from a vascular text, is that I like to think of these things in analogies to the human cardiovascular system. Flow restriction is not only a very bad thing for the affected body part, it's also very hard on the heart. But your argument about flow volume in a closed system reminded me that hypertension from increased blood volume is pretty darn hard on the heart as well.
I think that 1/2" tubing is probably a good happy medium between the issues of resistance and volume. If my original theory were completely correct, we would all be running 1" tubing .
Thanks for making me think....

no problem.

ha, no problem. Was alot of help. didn't mean for it to be an arguement, i'm not for the 1/4'' anyway. My systems going to be 1/2''. I was just looking for the rational behind, why we choose that size. your explaination was very helpful. thanks.

Thanks for the info everyone. I can now look forward to getting some 1/2 tygon rather than the 3/8 I was originally intending on purchasing.

true.

true, thanks for the info on the 1/2'' tubing. I think this is the only place on the net, where people actively talk about water cooling options -=). and are responsive and smart.