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# Are there pulsatile pumps?

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February 28, 2013 2:32:10 PM

I am designing a liquid cooling system that will function not necessarily in the most efficient way, but rather in the most awesome way. I am planing on machining any unique parts I need, but would like to avoid building a pump from scratch. I want a pump that ideally can provide a positive and negative pressure (such that the liquid would move back and forth) and then I will use a one way valve to create a net forward motion. This will cause a back pressure. Basically something that mimics a human heart. There are laboratory pumps such as this, but they cost several times more than my entire rig.

If there is nothing, then I will have to build a rotary motion to linear motion conversion, and use that to drive a cylinder.

a b K Overclocking
February 28, 2013 9:31:29 PM

I have no idea if those exist, but my guess would be that they are not consumer-level products (i.e. something you can buy off a store shelf).

I'd also be somewhat concerned using that for cooling. If it pulsed at the equivalent of ~100 BPM, there wouldn't be enough flow to provide great cooling. You'd need to really over-rad the loop to cool even a CPU.

I'm not trying to shoot down your idea, but it's a little more complex than just assembling a normal loop. The pulsating function of the loop would require a bit more in-depth thermal analysis.
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a b K Overclocking
February 28, 2013 9:43:47 PM

if the pump is DC then a switch that can reverse the current flow would do the trick. all though I don't know how long a pump could withstand the pressure of being swapped on and off along with backwards and forwards.
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February 28, 2013 10:12:01 PM

The equation for flow I got is this, assuming a 20mL stroke volume
Q=(0.02L)(BPM)(0.26gal/L)

So at 100 BPM that's 0.52 gal/min
and at 600 BPM that's 0.32 gal/min

600BPM is easily doable, the problem would be noise and maybe voltage.

I will be cooling about 365 TDP at max. (About half of that 90% of the time).

I did a quick block diagram sketch
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a b K Overclocking
February 28, 2013 10:32:05 PM

get a chemical sump pump it has a piston drive system.
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a c 330 K Overclocking
March 1, 2013 1:20:01 AM

Is this a 'what if' kind of exploratory project or why not use a typical magnetic motor driven circulation pump you'd normally use in watercooling?
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March 1, 2013 2:27:51 AM

rubix_1011 said:
Is this a 'what if' kind of exploratory project or why not use a typical magnetic motor driven circulation pump you'd normally use in watercooling?

Yes, it seems like a very fun project. At the worst I'll just buy a regular pump, keep the rest of the system, and have a standard loop.

Also, I was given one of these, and would love to incorporate it into my computer.
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a c 239 K Overclocking
March 1, 2013 9:07:32 AM

The human body is actually cooled by the evaporation of perspiration, how the circulation of the heart moving that cooling effect through the body could be related to cooling a computer will probably be the most expensive cooling ever conceived.

What makes you think alternating pump flow is going to increase cooling performance of a heat generated CPU, or successfully deal with it at all, much less adding the GPU and N/B to the mix?

The heat needs to be removed as soon as possible not transferred back and forth across the heating elements and eventually cycled away, I understand the concept, I just don't think it is a viable cooling solution.

Your diagram won't work as the first T-junction split will equalize the pump pressure making your valve useless, it would possibly take 2 opposed valves to make it work one before as you've shown and one in the return to pump line.

Meaning the return line valve closes when pump pressure hits it causing the feed line pressure to open the feed valve, then when the pump is on it's draw stroke it closes the feed valve and opens the return valve, pulling water through.

One possible benefit would be the water would stay in the heat exchanger longer, but it still is at the mercy of ambient room temperature, just like a normal water cooling loop.

A serious negative would be the hardware at the end of the cooling chain would be cooled by preheated water.

Don't take me wrong as one of the crazy ones here I'm all for improving cooling solutions, I just think this will turn out as a novelty hobby maybe and not a viable solution, but by all means go for it.
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a c 177 K Overclocking
March 1, 2013 9:51:10 AM

Since what your after is a visual effect rather than an experiment or testing, you could cheat a little. Have LED lighting on the tubing/reservoir and have it pulse regularly, combine that with Mayhems Aurora and I bet it'l look pretty good.

It seems having the water move back and forward isn't really a viable solution, as you will be drawing hot water back and forth over the CPU/GPU and the heat wouldn't go anywhere quickly. A better solution to get the pulse effect in the water would be to attach a 2nd pump that only runs for short bursts. That way you get a sudden increase in flow, which would be visible in water if you use aforementioned Aurora. So you have your constant flow of water to keep things cool, with the water still "beating". Could probably do the same with a PWM or voltage controlled pump, maybe a D5 Vario and a bit of custom software?

Sync the pump and LED's, very neat effect I think  .

Inb4 Mayhems Aurora flaming
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March 1, 2013 12:01:03 PM

4Ryan6 said:
The human body is actually cooled by the evaporation of perspiration, how the circulation of the heart moving that cooling effect through the body could be related to cooling a computer will probably be the most expensive cooling ever conceived.

In this analogy, the heart is the pump and the skin is the heat exchanger. The pump does not get rid of heat itself, it just equalizes it equally among the system.

4Ryan6 said:
Your diagram won't work as the first T-junction split will equalize the pump pressure making your valve useless

I've seen that handled by restricting the area of the open path. On the "power stroke" it will be much easier for the water to go back through the valve rather than the small diameter. The point of doing this rather than having two one way valves is to create a negative pressure which the valve counters. Although this creates a soft clicking sound.

4Ryan6 said:
A serious negative would be the hardware at the end of the cooling chain would be cooled by preheated water.