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post #11 of 24
Yeah, water seeks its own level, like my setup here, as long as I keep the res filled over the inlet it is really a zero head system, the ID of the system is the limiter.
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post #12 of 24
Quote:
Originally Posted by atomicfission92 View Post
Yes that is it. but the thing is, with that much tubing, its a long distance, and and you lose pressure. unless its a totally closed loop with no res, where the pressure can stay the same.
I think he would be ok because as long as the res is sealed like it should it should act like a expansion chamber and then continue on. The incoming liquid would force the exiting liquid out at equal force. There would be a small pressure drop just in the res similar to a expansion chamber on a ac unit but over all I think its worth a shot. I can’t prove it will work but if it was me and I had the parts I'd test it out and see how far it went.

If he did, we would all know for sure and this would be a quick answer to people with similar ideas.
post #13 of 24
Quote:
Originally Posted by DigitrevX View Post
I think he would be ok because as long as the res is sealed like it should it should act like a expansion chamber and then continue on. The incoming liquid would force the exiting liquid out at equal force. There would be a small pressure drop just in the res similar to a expansion chamber on a ac unit but over all I think its worth a shot. I can’t prove it will work but if it was me and I had the parts I'd test it out and see how far it went.

If he did, we would all know for sure and this would be a quick answer to people with similar ideas.
true, he know what, try it, if it doesn't work put another pump in the loop wth right try it. Experiment and learn for your self.
    
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post #14 of 24
dude feel free to use up to like 20 ft of tubing

read my faq about it

just casue the pump has 10 feet of head dosent mean it can only pump 10 feet
    
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post #15 of 24
Actually now that I think about it theres some one on here with a Mozart case that said he had over 15ft of tube with 2xgpu blocks, cpu block,3x 120mm rad, T line res, and 4 elbows and he did it with a D5. Not sure on how the flow was but I saw the pix he posted and was running. I'll try to dig it up.

edit: I could only find the old thread. In these pics he only has a 2x120mm rad and cpu, chipset blocks. But he does have 15ft of tube and one D5. And note in the pics that alot of the tubing is pretty vertical. http://www.overclock.net/water-cooli...hlight=Motzart
post #16 of 24
The reason we keep hoses as short as possible is to reduce the head loss caused by water running through tubing.

Our PC water-cooling loops are considered closed systems. For a closed systems, the static head of the system is always 0 ft. Therefore, the vertical height of tubing doesn’t matter, but total length does. All the flow resistance against the pump is generated by friction alone.

Here are some head loss numbers:
The Friction Head of 4 ft of 1/2" tubing, at 2 GPM is 0.58 ft.
The Friction Head of 4 ft of 7/16" tubing, at 2 GPM is 1.141 ft.
The Friction Head of 4 ft of 3/8†tubing, at 2 GPM is 2.5 ft.
The Friction Head of 4 ft of 1/4†tubing, at 2 GPM is 20.58 ft.

In a typical water-cooling loop, the MCP-355/655 pumps usually operate between 1.5 and 2 GPM.

At 2 GPM, 4 ft of 3/8" tubing has the same head loss as over 17 ft of 1/2" tubing.

At 2 GPM, 3/8" tubing can rob nearly 24" of head from the pump. That represents a significant portion of head (20%) for a pump with 10ft of head. That’s why it’s important to use 1/2" tubing

The stress on a pump is caused by the drop in head across the pump. The longer the tubes, the greater the drop in head. When a pump is operating near zero flow, the lateral forces on the impeller are greatest. There are many stories of aquarium pumps with cracked impeller shafts. These pumps have high GPH ratings but could only develop a very low GPH rate in a water-cooling setup, hence their shafts are cracked by the high lateral loads. The specialty pumps we use today don’t have these problems because they are high-head and low-flow.

Adding a second or third pump to a highly restrictive loop will probably NOT reduce the stress on the first pump. You’ll just end up with three highly stressed pumps. The reason is that each pump has to work at nearly the same high-stress point as before to create greater flow. The better solution is to get a single that is suited to the pumping requirements. As much as possible, you want your pumps to operate within the range they were designed to operate in. That’s when the pump is most efficient and reliable.

Tubing and radiators CAN be stressed by pressure. Fortunately, the pumps we use don’t come anywhere near those pressure levels.
post #17 of 24
Dead on the money, it's all about the friction and head loss...Very well said...
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post #18 of 24
Do some research on Reynolds Number. As the length of the tube increases, so does viscosity. High levels of viscosity actually increase flow rate. I guess you have to find the balance between viscous flow benefit and the loss from friction.

Regardless, a D5 can easily pump water through a 20ft long loop.
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post #19 of 24
Quote:
Originally Posted by pauldovi View Post
Do some research on Reynolds Number. As the length of the tube increases, so does viscosity. High levels of viscosity actually increase flow rate. I guess you have to find the balance between viscous flow benefit and the loss from friction.

Regardless, a D5 can easily pump water through a 20ft long loop.
how exactly does the length of the tube change the viscosity of liquid? Over time any liquids viscosity will break down, but if I had a 3 foot tube in the right hand and a 20ft coil in the left hows it going to change viscosity when I fire the system up?
post #20 of 24
Quote:
Originally Posted by pauldovi View Post
Do some research on Reynolds Number. As the length of the tube increases, so does viscosity. High levels of viscosity actually increase flow rate. I guess you have to find the balance between viscous flow benefit and the loss from friction.
The Reynolds number is affected by Kinematic Viscosity, which is a ratio between Absolute Viscosity and Density. There is no accounting for tube length in the Reynolds number.

Neither does tube length affect viscosity. Viscosity changes with density and temperature.

Water is unique in that its hydrogen bonds create a sort of self-compression. From 1 PSI to 10,000 PSI, the change in the viscosity of water is insignificant.

I have yet to read about the effect you described, but it's clear that it could only occur at very high Reynolds numbers and with large changes in temperature and/or pressure...none of which occurs in the scenarios being discussed in this thread.
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