Alright, my current setup is a asetek modified setup with 1/2 tubing and a L35 pump, with a custom reservoir and 240x120 radiator. My dad insists that if you add a restrictor at the outlet of the pump to slow down the output flow, temps will go down because the water is spending more time at the blocks, absorbing more heat.

I can see where hes getting at, except that he wants me to go from 1/2" to things like 3/16", 1/8" or 1/4". the 1/4" sounds reasonable, but something tells me im not gonna get squat since the pump is a high flow one, which I think would have more than enough power to not even notice the restriction. Hes willing to bet his theory on a completely new setup of any parts I want if hes wrong. Seeing that i have nothing to lose, im going to test out his theory after i get my new rig setup. Anyone have any comments on this?

Quote: Originally Posted by CommanderZero Alright, my current setup is a asetek modified setup with 1/2 tubing and a L35 pump, with a custom reservoir and 240x120 radiator. My dad insists that if you add a restrictor at the outlet of the pump to slow down the output flow, temps will go down because the water is spending more time at the blocks, absorbing more heat. I can see where hes getting at, except that he wants me to go from 1/2" to things like 3/16", 1/8" or 1/4". the 1/4" sounds reasonable, but something tells me im not gonna get squat since the pump is a high flow one, which I think would have more than enough power to not even notice the restriction. Hes willing to bet his theory on a completely new setup of any parts I want if hes wrong. Seeing that i have nothing to lose, im going to test out his theory after i get my new rig setup. Anyone have any comments on this?

While your father's logic is, well, logical, it is flawed. Let's use an analogy to see what the flaw is. Here is the setup, the NY GIants just won the Superbowl and 70,000 fans (aka the heat) are trying to leave the stadium (the CPU). There is only one area where they can get picked up by their cars (surface area for heat transfer), and only 20 cars can pull up at a time. The cars (the water) can each hold 4 people.

So we want to transfer the people (heat) from the stadium (cpu) to the cars (water) via the surface area (CPU block). Now, the flow rate will be equal to the amount of time the cars wait for people to get in. For every 5 seconds that the car waits, another person can get in.

So the optimal "flow rate" is 3 cars per minute (one every 20 seconds). That would mean that each "spot" would move 12 people per minute. Now, if the flow rate is slower, it doesn't help because the cars are full. So let's look at a faster flow rate:

At 10 seconds, 2 people can get in a car and 6 cars per minute = 12 people per minute.
At 5 seconds 1 person can get in a car and 12 cars per minute = 12 people per minute
At 15 seconds 3 people can get in the car and 4 cars per minute = 12 people per minute

Wait, so no matter what the flow rate you get the same amount of thermal transfer? Assuming everything else stays the same, yes. However, when you change the flow rate you change the pressure. Changing the pressure may mean that more (or less) cars can pull up to pick people up, depending upon the design of the block.

So while your father may be right, it is not for the reasons he is thinking. If more high pressure/low flow works better, it is because of the way your block is designed and the pressure of the water, not the flow rate.

At least that is my 2 cents and understanding of how this stuff works, and while I am somewhat of an "expert" on water cooling, I am far from anything resembling capable at thermodynamics.

Let's see if this works THIS time . . . Tried posting something earlier and the 'Intertubes' ate it.

If you restrict flow, as in slowing down the flow (usually, restricting the flow by adding a smaller fitting increases pressure which makes more turbulence . . . Same amount of water through a tighter space . . . it's like blocking a faucet or garden hose with your thumb to make it spray farther . . . But that's another thing) like your father suggests, is BAD for water cooling.

What makes water cooling work is having a constant fresh supply of cool water removing the heat from the blocks and into the heat exchanger(radiator) to be cooled off again.

If you leave the water in the waterblock, it's going to remove heat to a certain point, then the heat will just build up in the metal.

If you want a hands on demonstration, fill a heavy sauce pan with cold water, put it on the stove and turn the heat on low. Reach into the pan and touch the bottom with your fingers, and when you feel the heat come through, move your fingers up to the side of the pan. Notice how the metal is still cold on the side. If you wait a few minutes, however (Don't wait so long that you will be burned by the hot water, mind) and touch the side of the pan, the metal is the same temp as the water, because it's no longer being cooled.

I'm not a genius in WC, that title belongs to others here, but I DO know the three things needed for good water cooling - Good flow(not too fast and not too slow), turbulence through the system (increases the amount of 'cool' water contacting the water blocks, prevents dissolved air from releasing into the tubs, causing a vapor lock and increases the effectiveness of the heat exchange/radiator) and a good radiator or two (depends on both how many surfaces you are cooling and how good of a pump you have, as too many radiators will kill your flow).

Anyway, that's how I see it . . . I may be totally off base, and if so, welcome the correction from our WC guru's!

d

Don't take my word for it my first W/C setup is currently waiting to be set up but;
if you heat up the water you have to cool it,
so the more time its absorbing heat, the more time it has to spend cooling.
From my knoweldge the bigger the temp difference between two substances the quicker the temperture exchange will occure (example putting hot water into an ice cube tray vs room temp or cold)

I'm sure every setup has its own optimal settings.

I'd say you don't need to change fittings to experament with efficency, an variable speed pump would be best possibly.

I'm still considering myself a green horn in W/C just thought I'd share my mental hypothasys going into W/C.

By the way very interesting analogy DickNervous.

Everyone that's posted has explained it well already, but putting together what has previously been stated, this is how I see it. As DN explained, the flow rate isn't a significant issue when heat transfer remains constant, and as Spatha explained, the greater the difference between temperatures, the faster the change.

The trick is getting a larger amount of water to pass over the block in a given moment, or the volume per unit of time. This is why the water cooling market worked its way from 1/4" tubing up to the 1/2" tubing you see today.

To relate back to DN's analog, if more cars are able to arrive and pick up people at the same time, a greater volume of people can leave the stadium during a shorter period.

Ah, yes Jobistopper, but 1/2" inch is not always better than 1/4". It all depends upon the design of the block, all other things being equal.

And thanks Spatha, I was trying to think of a good analogy for a while and actually impressed myself with that one.

The bottom line , as anyone who has researched water cooling will tell you, when asked if this setup will cool better than that setup is that "it depends".

If you could reliably change just one variable, you could isolate the impact each has on a specific setup. However, you can not separate flow rate from pressure. When you change one, you change the other. And when you change a component in the system, you impact both flow rate and pressure. Hell, if you and I setup identical systems and put them in the same room, we will get different results with if one of my tubes is an inch longer than one of yours. It may be a minuscule difference, but it will be there. This is why when a reviewer says something like "Block A will always trounce Block B in performance" I want to reach out and beat them on the head. Yes, in your test environment that may be true, but not in mine.

There were two sites that are now somewhat defunct, but still around, SystemCooling and ProCooling that did very scientific reviews of water blocks. They would measure the heat transfer across the block and rate them based upon that, which is the most accurate way of doing it. It also required a great deal of scientific knowledge and pretty sophisticated setup.

But back on topic......

Some blocks are optimized for high pressure/high turbulance setups, like the Danger Den TDX, Swiftech Storm, or any other block that uses "jets" or "nozzles". Some are optimazed for high flow, such as the PolarFLO TT and Whitewater. So the design of the block will determine if low flow/high pressure or high flow/low pressure works best. And the only accurate way to figure it out is to test it.

Thanks for clarifying DN

Quote: Originally Posted by CommanderZero My dad insists that if you add a restrictor at the outlet of the pump to slow down the output flow, temps will go down because the water is spending more time at the blocks, absorbing more heat.

No, adding a restriction somewhere in the loop (other than a heat exchanger) will only result in higher temperatures. What's important is the rate of heat transfer to the water, which is directly related to the mass flow rate. Sorry, no analogies, but I can prove it to you mathematically if you prefer.

Quote: Originally Posted by DickNervous While your father's logic is, well, logical, it is flawed. Let's use an analogy to see what the flaw is. Here is the setup, the NY GIants just won the Superbowl and 70,000 fans (aka the heat) are trying to leave the stadium (the CPU). There is only one area where they can get picked up by their cars (surface area for heat transfer), and only 20 cars can pull up at a time. The cars (the water) can each hold 4 people. So we want to transfer the people (heat) from the stadium (cpu) to the cars (water) via the surface area (CPU block). Now, the flow rate will be equal to the amount of time the cars wait for people to get in. For every 5 seconds that the car waits, another person can get in. So the optimal "flow rate" is 3 cars per minute (one every 20 seconds). That would mean that each "spot" would move 12 people per minute. Now, if the flow rate is slower, it doesn't help because the cars are full. So let's look at a faster flow rate: At 10 seconds, 2 people can get in a car and 6 cars per minute = 12 people per minute. At 5 seconds 1 person can get in a car and 12 cars per minute = 12 people per minute At 15 seconds 3 people can get in the car and 4 cars per minute = 12 people per minute Wait, so no matter what the flow rate you get the same amount of thermal transfer? Assuming everything else stays the same, yes. However, when you change the flow rate you change the pressure. Changing the pressure may mean that more (or less) cars can pull up to pick people up, depending upon the design of the block. So while your father may be right, it is not for the reasons he is thinking. If more high pressure/low flow works better, it is because of the way your block is designed and the pressure of the water, not the flow rate. At least that is my 2 cents and understanding of how this stuff works, and while I am somewhat of an "expert" on water cooling, I am far from anything resembling capable at thermodynamics.

Not with a ten foot pole....

Quote: Originally Posted by drougnor If you restrict flow, as in slowing down the flow (usually, restricting the flow by adding a smaller fitting increases pressure which makes more turbulence . . . Same amount of water through a tighter space . . . it's like blocking a faucet or garden hose with your thumb to make it spray farther . . . But that's another thing) like your father suggests, is BAD for water cooling.

A restriction will actually lead to a drop in pressure and an increase in velocity through the restriction. This increases the "turbulence" of the flow. This is undesirable everywhere but the heat exchangers, which rely on localized turbulence and increased fluid velocity to increase the convective heat transfer coefficient. This coefficient is inversely related to the temperature difference.

Quote: Originally Posted by drougnor If you leave the water in the waterblock, it's going to remove heat to a certain point, then the heat will just build up in the metal. If you want a hands on demonstration, fill a heavy sauce pan with cold water, put it on the stove and turn the heat on low. Reach into the pan and touch the bottom with your fingers, and when you feel the heat come through, move your fingers up to the side of the pan. Notice how the metal is still cold on the side. If you wait a few minutes, however (Don't wait so long that you will be burned by the hot water, mind) and touch the side of the pan, the metal is the same temp as the water, because it's no longer being cooled.

Don't understand the point you're trying to make, but doubt it's relevant to the thread topic.

Quote: Originally Posted by Spatha From my knoweldge the bigger the temp difference between two substances the quicker the heat exchange will occure (example putting hot water into an ice cube tray vs room temp or cold)

The same idea applied above can be applied to the radiator. You want the fins to be as close to the water temperature as possible. Therefore, in both situations a higher flow rate (less restriction) is desirable throughout the rest of the loop.

So Anonymous, was my analogy completely wrong? If so please enlighten me since that is how it has been explained to me in the past. Well, not with the analogy, but those concepts.

Quote: Originally Posted by CommanderZero Alright, my current setup is a asetek modified setup with 1/2 tubing and a L35 pump, with a custom reservoir and 240x120 radiator. My dad insists that if you add a restrictor at the outlet of the pump to slow down the output flow, temps will go down because the water is spending more time at the blocks, absorbing more heat. I can see where hes getting at, except that he wants me to go from 1/2" to things like 3/16", 1/8" or 1/4". the 1/4" sounds reasonable, but something tells me im not gonna get squat since the pump is a high flow one, which I think would have more than enough power to not even notice the restriction. Hes willing to bet his theory on a completely new setup of any parts I want if hes wrong. Seeing that i have nothing to lose, im going to test out his theory after i get my new rig setup. Anyone have any comments on this?

The mission with water cooling should be to cool down components, not to heat water.

The water is not there to absorbe heat from the block, it's there to cool down the block, which in my way to see it, the water needs to be as cold as possible at the block...
and also going with smaller tubes and same push on the pump, you cause friction, friction causes heat, but hell, prove him wrong, let him buy you new rig.....

And post some results!

Quote: Originally Posted by BeetleMan The mission with water cooling should be to cool down components, not to heat water. The water is not there to absorbe heat from the block, it's there to cool down the block, which in my way to see it, the water needs to be as cold as possible at the block... and also going with smaller tubes and same push on the pump, you cause friction, friction causes heat, but hell, prove him wrong, let him buy you new rig..... And post some results!

He could always let Anon prove him worng, or just confuse the heck out of him.

I dare you to let your dad try to read one of Anon's post, I get confused, and i think i understand him.

Quote: Originally Posted by DickNervous So Anonymous, was my analogy completely wrong? If so please enlighten me since that is how it has been explained to me in the past. Well, not with the analogy, but those concepts.

No idea about the analogy. To me it's more confusing than the actual thing, so I glazed over.

Car analogies usually don't work with fluid / heat transfer, i.e. fluid mechanics usually aren't used to describe traffic patterns because traffic is highly discretized while macro-scale fluid flow is continuous. Thinking of individual water "packets" picking up a quantity of heat and moving along isn't a good foot to start off on.

Quote: Originally Posted by lAnonymousl No idea about the analogy. To me it's more confusing than the actual thing, so I glazed over. Car analogies usually don't work with fluid / heat transfer, i.e. fluid mechanics usually aren't used to describe traffic patterns because traffic is highly discretized while macro-scale fluid flow is continuous. Thinking of individual water "packets" picking up a quantity of heat and moving along isn't a good foot to start off on.

Sort of how I just glazed over reading Capt Planet's post about his new cascade.

The car analogy may not work at being accurate, but I think it gets the basic concepts across.

Quote: Originally Posted by lAnonymousl Don't understand the point you're trying to make, but doubt it's relevant to the thread topic.

Must've not been clear enough . . . Point was that cold water cools the metal of the block, therefore the chip it's attached to, better than hot water.

d

Wait so...... if a smaller piece of tubing in the loop would drop th pressure in the entire loop..... wouldnt there be a location in the loop just shy of the restriction that in turn would suffer an increase in pressure. For every action, there is an equal, or greater reaction.
Based on this theory, he could raise the pressure in the block, by installing a 1/4 barb on the outake port of his block, and run say 1/4 tubing for 1-2 inches. This would create a higher pressure inside the block, while also creating a rolling boiling cascade effect, possibly further eliminating laminar flow more, increasing the surface area new water molecules touch the block for heat transfer. I dont see this working very well with a sealed, fully filled system. however with a vented reservoir and a pusher pump (before the waterblock) I could see this working.

Quote: Originally Posted by Ace123 Wait so...... if a smaller piece of tubing in the loop would drop th pressure in the entire loop..... wouldnt there be a location in the loop just shy of the restriction that in turn would suffer an increase in pressure. For every action, there is an equal, or greater reaction. Based on this theory, he could raise the pressure in the block, by installing a 1/4 barb on the outake port of his block, and run say 1/4 tubing for 1-2 inches. This would create a higher pressure inside the block, while also creating a rolling boiling cascade effect, possibly further eliminating laminar flow more, increasing the surface area new water molecules touch the block for heat transfer. I dont see this working very well with a sealed, fully filled system. however with a vented reservoir and a pusher pump (before the waterblock) I could see this working.

No. Only pumps raise the pressure of a fluid.

Slightly off topic but...

A waterpump (or any pump for that matter ) ,should NEVER be restricted on the intake side!!!

Flow control is achieved through restricting the OUTPUT ONLY !!!

If you restrict input you'll end up with cavitation and pump damage.



On this subject of flow.
More flow Is allways better.(provided the pump itself doesnt add additional thermal load)
Because... the radiator will have more time to lose the thermal load applied to it from the added cycles per minute through the rad.

As for friction from increased flow its so small as to be immeasurable in this application.

Quote: Originally Posted by RBIEZE More flow Is allways better.

DING DING DING DING We have a winner.

Complicated analogies and explanations aside. With everything else being equal, higher flow will always cool better than a lower flow.

Outside of a "sweet spot" at very low flow rates for radiators this is always true in water cooling.

Forget for a moment about higher velocities working better in some block designs and turbulent flow working better for heat transfer. Forget about large temperature differences in block and radiator.

For the sake of argument lets say the block is 16 degrees Celsius and the radiator is 15 degrees celsius. One calorie is the unit of energy required to raise one gram of water one degree Celsius at 15 degrees. So each gram of water can absorb one calorie of energy at the block and move it to the radiator where it is cooled back to 15 degrees. For all intents and purposes in this scenario the rate of transfer is a constant.

What is the only way to change the rate of exchange without changing the temperature differential or redesigning the loop?

Rule number one of water cooling is, higher flow always cools better.

Rule number two is, see rule number one.

Once you have this concept down, then add the variables. Generally the only place you can restrict flow (increasing velocity) and see an improvement is at the inlet of the block. Even then rule number one still applies.

The only real caveat to rule number one, as stated earlier, is the additional heat generated by a more powerful pump. Higher pressure comes at the cost of diminishing returns. A 300 gph pump may cool 50% better than a 150 gph pump. But a 600 gph pump may cool only 5% better than a 300 gph pump. A 900 gph pump may actually dump more heat back into the loop than a 300 gph pump.

so in the end, would this attempt this raise my temps? or would it even matter.

See rule number one. It's not open for interpretation or argument. Independent of any other consideration, more flow cools better.

In your case restricting the flow at the pump outlet would have no effect on turbulence at the waterblock or radiator, so you'd achieve nothing but a lower flow rate by restricting the flow. You'd also force the pump to work harder and dump more heat in the loop.

Higher temps.

It's amazing how much time people spend on these discussions, when in the end changing tubing size, which in essence is the same as what your suggesting makes a very small difference in a loop. Moving from 3/8 to 1/2" tubing could improve temps by a single degree or so with the old low head pond pumps we used to use, and makes virtually no difference with the newer high head pumps we use now.

In modern kits with modern waterblocks and pumps, the only truly significant way to improve cooling is with larger more efficient radiators and/or more powerful fans attached to it.