Watercooling Experts Wanted

[Indybird]

Just to let you know, I'm not actually planning on buying watercooling just yet...

I have been thinking about getting my computer water-cooled in the future (maybe for christmas :p ) and I would really appreciate it if someone could give my a list of Danger Den water-cooling parts that I would need for my computer (check my sig). I want Danger Den because they are high quality, but not too expensive and they are the only people who make watercoolers for the Geforce 7950GX2...

Thanks, Indybird

[jreffy]

I wouldn't say I'm an expert, but I'm currently in the process of building a computer that is almost identical to yours (going with an E6600). While not an expert, I have been researching parts, including water-cooling for the last 2 months, so I'm probably just a few steps ahead of you. A few things;

Currently there is no waterblock for the 7950. There are a couple in development, but none have been released yet. The only thing I've seen is a 7950 card that comes with a waterblock already attached, but I wasn't crazy about it. I decided instead to go to a 7900. This way I don't have to wait for a 7950 Waterblock, plus I'll just be replacing that 7900 in a year when dx10 games are more prevalent.

As far as the rest of you watercooling setup, it's just a matter of answering a couple questions.

1) External or Internal water cooling?
**I'm using the Lian-Li PC-70 case, which is a monster, so I have a ton of room. Definitely want to keep everything contained inside the case, so I'm goign with internal.

2) DC or AC pump?
**I don't want more plugs going into my surge protector than I already have, in addition, I don't want to have to turn on my water pump seprately from my PC. I know I could wire a switch up to do this, but I still don't want the extra plug coming out of my PC.

Those are really the only "big" questions. Which waterblock to use and what hose size are all relative. I'm doing 1/2" personally, and going with a quality socket 775 waterblock for my CPU. Here is what I'm looking at right now. I didn't include a resivoir because it's not that critical, and I think I'm going to be making my own.

Pump: Swiftech MCP350 (http://www.subzeropcs.com/swiftech_mcp350_water_pump.html)

Radiator:DangerDen Black Ice II Pro (http://www.dangerdenstore.com/product.php?productid=193&cat=73&page=1) (need to do some final measurements to make sure it will fit) Cross-flow and more FPI (fins per inch) are always better.

CPU:DangerDen Silver TDX (http://www.dangerdenstore.com/product.php?productid=186&cat=61&page=1) (bit expensive though)

GPU: DangerDen Koosah (http://www.dangerdenstore.com/product.php?productid=231&cat=48&page=1) (for the 7900, NOT 7950)

[Silenced_Coyote]

I'm not sure if cross-flow is always better. Isn't water velocity in a single-pass half of what it is in a dual pass radiator? Increased water velocity should mean increased heat transfer.

Single Pass vs. Dual Pass (http://forums.bit-tech.net/showthread.php?t=100862)

[meticoeus]

I'm by no means an expert but I can hopefully still help.

The more fins per inch, the more cubic feet per minute (air) you need to puch/pull through for efficient noise which roughly translates into more noise, so it depends if you are going performance cooling (for overclocking) or ~silent cooling in noise bugs you.

Silver blocks do not have a significantly greater heat transfer and doesn't justify the price in that regard, but they are silver so I hope people don't buy them for performance gains anyway ;p.

Since you are alreaddy overclocking your system you'll probably want a high flow system (1/2" tubing, inpingement cpu block). I think both the RDX and The TDX can use impingement jets. For a high flow system you'll need high volume cooling so probably a 360mm rad. Ask other for advice for the rads for this though.

Make sure you get a powerful enough pump for the system you build, probably just a D5 for the 1/2" inpingement, though if you have too many blocks/radiators/etc in your system you may need to use two pumps to keep the flow high.

hth and good luck.

[Silenced_Coyote]

You mentioned that you didn't want it to be too expensive. What is your budget?

[jreffy]

I'm not sure if cross-flow is always better. Isn't water velocity in a single-pass half of what it is in a dual pass radiator? Increased water velocity should mean increased heat transfer.

Single Pass vs. Dual Pass (http://forums.bit-tech.net/showthread.php?t=100862)


Ah, I was assuming only single-pass rads. That article is correct, 2-pass is better than single-pass.

I think I messed up because Modine was automotive, they usually don't have the inlet and the outlet on both sides of the radiator in a car :). I got stuck in gear-head mode haha.

[Slug Toy]

I'm not sure if cross-flow is always better. Isn't water velocity in a single-pass half of what it is in a dual pass radiator? Increased water velocity should mean increased heat transfer.

not always true.

ok... single pass velocity being half of double pass velocity? i think you mean the other way around. adding another radiator or another pass means adding more resistance or potential for it... meaning a general drop in velocity. so single pass in theory should be double the velocity of a double pass system... if you dont take into account the tubing and waterblocks.

crossflow is generally accepted as an efficient way to strip heat off a surface. dont ask me why, because that means getting into math that even i dont have a firm grasp on. just try this:

1. hold your hand so your fingers are pointing upwards, palm facing you. blow on your fingers. this is crossflow.

2. hold your hand with your fingers pointing away from you, palm can facing the ground (parallel). blow on your wrist towards your fingers. this is not crossflow.

note that the crossflow feels cooler in this test. nifty huh?


and finally. increased velocity doesnt always mean increased heat transfer. you can go too fast, and not give enough time for the water to take up heat. in terms or what current water pumps can put out... thats not too fast. its actually probably not fast enough. again... i would have to get into some math that i really dont want to... but there is a threshold that would be ideal, actually there are two thresholds. one is the velocity at which water has enough time to soak up a lot of heat, almost to the point where it "shows" worse efficiency than air cooling, and then you need two or three passes in a radiator. the other threshold is at the velocity where water is no longer performing effiiciently. it gets complicated very fast, but lets just keep it at this: any water pump you buy will put out a velocity that is between the two thresholds, and is completely fine.

[jreffy]

ok... single pass velocity being half of double pass velocity? i think you mean the other way around. adding another radiator or another pass means adding more resistance or potential for it... meaning a general drop in velocity. so single pass in theory should be double the velocity of a double pass system... if you dont take into account the tubing and waterblocks.

The thing you are forgetting is that the single-pass and double-pass radiators are the exact same size, with the same number of tubes. The difference in the double-pass and the single-pass is the number of tubes that the fluid goes through each pass. For example;

Single-pass radiator (32 tubes) - all the fluid goes through all 32 tubes at once, and exits the radiator

Double-pass radiator (32 tubes) - all the fluid goes through 16 tubes, hits the other end of the radiator, does a U-turn, and passes thruogh the other 16 tubes, and exits the rad on the same side it entered on. (pic;http://www.scr03.com/radichevy_001.jpg)

So the velocity INCREASES. Why? Because you are taking the same volume of fluid, but passing it through FEWER tubes.


crossflow is generally accepted as an efficient way to strip heat off a surface. dont ask me why, because that means getting into math that even i dont have a firm grasp on. just try this:

1. hold your hand so your fingers are pointing upwards, palm facing you. blow on your fingers. this is crossflow.

2. hold your hand with your fingers pointing away from you, palm can facing the ground (parallel). blow on your wrist towards your fingers. this is not crossflow.

When talking about radiators, crossflow does not refer to the passage of air across the tubes. By your definition, EVERY radiator would be a crossflow radiator, because in every rad, the air blows perpendicular to the tubes.

Crossflow in the world of radiators (typically only single-pass rads) refers to the location of the input and output for the coolant. Notice the difference

Upright Radiator; http://www.speedpartz.com/foz_rad_minisprint_diagonal_1.jpg
Crossflow Radiator; http://www.sprintcarexchange.com/part_pics/web%20crossflow.jpg

As far as velocity is concerned, in a water-cooling system for your computer, you really don't have to worry about the fluid moving TOO fast. The only concern with speed in a PC cooling system is that you want to make sure your fluid is moving fast enough through the radiator to cause turbulant flow rather than laminar flow. Turbulant flow mixes up the water molecules ensuring better heat absorption in the the tubes.

[Slug Toy]

ok, i see what you're talking about now. evidently im not up on all the terminology, because i dont call double pass radiators double pass, i call them a bad idea in general.

as for the water velocity... if we look at it in these new circumstances... velociy stays the same because the water is ultimately passing through the same length of pipe. whether it be a straight shot through 32 pipes, or two shots through 16 pipes... it works out to 32.

and the crossflow thing... i dont want to get further into that. lets just say the radiator business is ruining physics.

[Silenced_Coyote]

So lets drop the terminology and physics and come to a decision. Buy single pass or double pass radiator?

If you want to keep explaining the differences, feel free!

[Slug Toy]

well, i would suggest single pass.

double pass doesnt sit right with me. it means cooling water in one direction, and bringing it back up to the top again... where the hot water is going in. maybe not directly beside the hot water, but it means you're weaving cold water between hot water. i highly doubt that double pass is as efficient because there is plenty of time for heat to be conducted back into the cold water... not much, but the fact still remains.

[Silenced_Coyote]

What do you mean by weaving cold water between hot water?

I'm not sure if this is right. But this is what I am thinking. Water gradually cools so the longer it stays in the radiator, the cooler it should get. So even if it does transfer some heat, the effects should be very minimized or has no effect at all. I think I heard that if you add a row of fans on the top and bottom of the radiator, it will give you about a 1-2% decrease in temps. So you got one of the "hot" side and the other on the "cold" side.

I think I just confused myself... lol. If only someone had 2 radiators that are exactly the same, but one single pass and the other double pass......

[Slug Toy]

actually, im confusing myself too. seeming as all the terminology ive been using just got turned upside down... things are getting me messed up.

lets see if i can put this in terms that make sense without having to understand anything about radiators.

it would make more sense to have water pass through in one straight line, so you have a set heat gradient. having water go through and then make a 180 and go back the way it came means you are passing cooler water next to warmer water, which as i said creates the potential for heat transfer within the radiator. however small that transfer might be, it still means that having the water doing a 180 is less efficient.

basically... look for a radiator with the holes on opposite sides, and not on the same side.

[silverdemon]

I believe slug is trying to tell that you blow air over the "hot" tubes, and then over the colder tubes... which means that the air that went over the hot tubes is slightly warmer and thus doesn't cool the cold tubes as good as it would do when the air was "fresh"...
http://i79.photobucket.com/albums/j139/rstakelbeek/rad.png

[Slug Toy]

yes, thats part of what i was getting at. there are a couple other problems associated with it... but you can extract examples of them from this airflow example. the conduction issue is practically the same issue... look at how close the cold and hot sides are together and you can see why it isnt an efficient design.

[dgrmkrp]

ok.. these are 2 radiators.. i don't really know what u are arguing, but the previous post(silverdemon) makes sense.. this is interesting...

x-flow (http://www.performance-pcs.com/catalog/index.php?main_page=product_info&cPath=200&products_id=3891&zenid=45fb27bc0efa6139aee33eac73289d08) normal? (http://www.performance-pcs.com/catalog/index.php?main_page=product_info&cPath=200&products_id=3123&zenid=45fb27bc0efa6139aee33eac73289d08)

[jreffy]

Ok, there seems to be a lot of confusion here, lol.

SINGLE-PASS; your fluid enters the side-tank of the radiator, passes through all the tubes, flows into the other side-tank of the rad, and then goes through the outlet.

DOUBLE-PASS; fluid enters the side-tank (usually in the top-corner), the side-tank is divided in half so that the fluid only enters the top half of the radiator. So if you have a 32 tube rad, the fluid enters the first 16 tubes on one half of the radiator. It then passes to the other side-tank and the through the bottom 16 tubes of the radiator, back to the other half of the first side tank, and passes through the outlet.

COMPARISON; For pure heat exchanging ability, the double-pass radiator is 10-20% (don't quote me) more efficent. However, this comes at a cost of a higher pressure drop. Remember that the inlet and outlet flows of your radiator must be equal, so in a double-pass radiator, the water molecules must travel the length of the radiator TWICE in the same amount of time. Think of it in terms of a race. Car 1 races on a track of 10 miles, Car 2 on a track of 20 miles, but both cars must finish in the same amount of time. Car 2 must travel twice as fast as Car 1 to acheive this. That should also answer the earlier question about why double-pass radiators cause the fluid to travel at a higher velocity inside the tubes.


However in the world of radiators this increase in speed comes at the cost of a higher pressure drop. The higher the pressure drop, the more powerful your pump has to be. Single-pass radiators, while not as efficient in heat exchange, do not requre as powerful a pump to force the water through the tubes. Less powerful pump = less noise.


PURCHASING A RADIATOR; Double pass is the way to go for more efficient cooling. However, whether you go with a double-pass or single-pass, your radiator will have an effect on your choice in a pump. While double-pass is more efficient, it will also require a stronger pump. I do not know exactly what is considered a "strong" pump, but just from doing a quick comparison, for the DC motors, the highest vertical head is about 10ft.

I hope this cleared everything up for everyone.

[Silenced_Coyote]

This topic is really interesting! But I don't think buying water cooling just for this experiment is a smart idea. Does anyone know of a way to maybe get a review site to do this experiment? Or is anyone here part of a review site?

If not, I guess I can upgrade to water cooling, but that might not be until next summer (if I decide to do it). I can buy each radiator and post the results. But as I said, that is a long time from now....

[jreffy]

This topic is really interesting! But I don't think buying water cooling just for this experiment is a smart idea. Does anyone know of a way to maybe get a review site to do this experiment? Or is anyone here part of a review site?

If not, I guess I can upgrade to water cooling, but that might not be until next summer (if I decide to do it). I can buy each radiator and post the results. But as I said, that is a long time from now....


Don't really need an experiment. Go google comparisons between single pass and double pass radiators. Double-pass rads are better for cooling, hands down.

[Slug Toy]

Double-pass rads are better for cooling, hands down.

but theres no extra surface area compared to a single pass with the same number of tubes.

things really arent making sense for me now.

gravity is another issue i can think of. in a single pass, you can have the inlet at the top, and the outlet at the bottom... no issues. in a double pass, it doesnt matter whether the inlet and outlet are at the bottom or top... you still need to force the water upwards on one pass no matter what... meaning you have to fight gravity in one direction.

you know what... if single pass radiators arent as good... they've been done wrong somehow. everything is telling me that single pass is a good dea. it just makes more sense to go through a radiator once and once only, and in one direction only. it makes physical sense, it makes thermal sense, it makes practical sense. something's wrong here.

[jreffy]

but theres no extra surface area compared to a single pass with the same number of tubes.

yes, there is. Think of the water molecules path through the radiator. The water molecule experiences contact with more of the surface in a double-pass than a single-pass. Granted this happens FASTER, but during turbulent flow, the heat is exchanged rather quickly.

I don't think the radiators are large enough for gravity to become a problem. It's fighting gravity for a few inches, not a few feet.


you know what... if single pass radiators arent as good... they've been done wrong somehow. everything is telling me that single pass is a good dea. it just makes more sense to go through a radiator once and once only, and in one direction only. it makes physical sense, it makes thermal sense, it makes practical sense. something's wrong here.

What makes more sense is to get exposed to as much surface area as you can, which is what double-pass does. The water just moves faster in double-pass in order to cover that extra area in the same amount of time. The heat exchange happens so quickly that the speed of the water passing through the radiator does not effect the efficiency of the exchange.

[Slug Toy]

that still doesnt make sense about the surface area.

using your example... a 32 pipe single pass versus and 16 a 16 pipe double pass. they are both going through 32 pipes in total. its not like there is any sort of magic going on in a double pass that increases surface area. no matter how you look at it, 32 pipes is 32 pipes, and it will always have the same amount of area unless you start changing the pipe size... but we're doing a comparison here so that isnt the case.

if i have to, ill break out the math to prove this. dont make me do that.

[jreffy]

that still doesnt make sense about the surface area.

using your example... a 32 pipe single pass versus and 16 a 16 pipe double pass. they are both going through 32 pipes in total. its not like there is any sort of magic going on in a double pass that increases surface area. no matter how you look at it, 32 pipes is 32 pipes, and it will always have the same amount of area unless you start changing the pipe size... but we're doing a comparison here so that isnt the case.

if i have to, ill break out the math to prove this. dont make me do that.


Yes, they have the same surface area when you look at it from the outside. You're thinking about the total surface area of the radiator. Yes they are equal, the radiators take up the same amount of space. However, you are cooling the water molecules, so you have to think about the surface area that the individual molecules are exposed to! Follow the PATH OF THE INDIVIDUAL WATER MOLECULES!!! Think of how one water molecule goes through a single-pass radiator compared to a double-pass radiator.

Single Pass; It enters the inlet, goes down a tube, exits the radiator

Double Pass; It enters the inlet, goes down a tube, turns around and goes down a SECOND tube, exits the radiator.


The water molecule in a double-pass rad travels the lenght of TWO TUBES before exiting, in a single-pass the molecules only are exposed to the length of one tube. That's TWICE the exposure to surface area.


A double-pass radiator takes the same amount of water, but passes it through the radiator TWICE. that's DOUBLE the area that the single-pass fluid is exposed to. Yes, both radiators have the same surface area, but in a double-pass you are cramming all the molecules into 16 tubes. The molecule travels the length of the tube, then travel the length of the tube AGAIN. That's TWICE the exposure! You're just cramming more fluid into the tubes, hence why the flowrate in double-pass is higher, and you need a more powerful pump to make it happen.

[Slug Toy]

ok i sort of see where you're going now. half the pipes but twice the length.

now here's whats got my head hurting. are the flow rates the same? is it better to have one amount of fluid being cooled for a given time, or twice the amount being cooled for half the time? this is where the math would come in because you have to take into account... oh boy does that mean some complex figuring.

things just still arent sitting right in my head. i dont know why. i guess i have to prove or disprove myself now... or else im going to be eternally tormented.

[Indybird]

I don't mean to interrupt your thinking, but I already got the list I need from you guys, ahh...whatever
thanks :D

[jreffy]

ok i sort of see where you're going now. half the pipes but twice the length.

That's exactly right! Haha, it's ok, I've actually been remembering a lot of my fluid dynamics from this. I'm enjoying it a lot, I love figuring stuff out and helping people learn, anyway, on with the mental exercises!!


now here's whats got my head hurting. are the flow rates the same?

Get the time thing out of your head for now, think of it purely in terms of fluid flowrates and the amount of water passing through the tubes and radiator.

Ok. You're thinking in the right direction. The flowrate at the inlet and the outlet are equal. Because think, the entire system has to be moving at the same speed all the time, you can't have one section moving faster than the other, EXCEPT...INSIDE the radiator. If you measure the flow at the inlet and outlet of the rad, they are equal, but what about inside the tubes?

In the double-pass radiator, in order to have equal flowrates at the inlet and outlet, but only pass through half the number of tubes, the fluid accelerates inside the tubes! Think about it.

Draw 2 lines about a mile apart on a 4 lane freeway, and an 8 lane freeway. Cars represent water molecules. You need the same amount of cars to pass through this zone in an equal amount of time.

Since the 4 lane freeway is half the size of the 8 lane freeway, the cars need to travel TWICE as fast on the 4 lane freeway to get the same number of cars through that zone. Follow? Here's a simple equation.

8(tubes)*1(speed)= 8 (flowrate)
4(tubes)*2(speed)= 8 (flowrate)

Equal flowrates at the inlet and outlet, but different speeds inside the tubes!

It's the same way in the double-pass radiator. The speed of the fluid inside the tubes is twice that of the fluid inside the single-pass. This is what causes the larger pressure drop in double-pass radiators, and why you need a more powerful pump.


is it better to have one amount of fluid being cooled for a given time, or twice the amount being cooled for half the time? this is where the math would come in because you have to take into account... oh boy does that mean some complex figuring.

Actually, both fluids spend an equal amount of time inside the radiator, but inside the double-pass radiator, the fluid is exposed to more tube (remember twice the tube length?). We know that they spend an equal amount of time inside the radiator because the flowrates at the inlet and outlet are equal. However, because the double-pass radiator is essentially a longer "track", the fluid travels FASTER in the double-pass, but is inside the radiator for the same amount of time.

So in theory if you made a TRIPLE-PASS radiator, it would do an even more thorough job of cooling the fluid, however it would require MORE power in order to push the fluid even FASTER through the tubes. The reason you don't see many triple-pass rads is because there isn't much of an improvement in a triple-pass over a double-pass that would make it worth getting the extra powerful pump.

[Slug Toy]

ok now you're making me contradict myself. i dont know if i like that... because now i have to go back and check what i said and then decide what is more true.

i wonder if what i said about speed actually holds up in a real world situation. i was drawing upon my physics theory stuff for that one.

actually, i wonder if there is any turbulence in that sort of system. i would imagine that a radiator is just a bunch of tubes, nothing special. theres no real turbulence in tubes like that, especially smooth metal ones. in fact, there probably wouldnt be much turbulence in a lot of waterblocks out there either.

great. now im not even sure im real anymore. see what you've done to me? probably not a good idea to be thinking this hard at 1 in the morning.

[Silenced_Coyote]

Isn't there turbulance in the Swiftech Storm CPU waterblock?

Must be rough Slug_Toy thinking about this at 1 AM. Because I know my head is hurting just reading what you two have to say.

[jreffy]

ok now you're making me contradict myself. i dont know if i like that... because now i have to go back and check what i said and then decide what is more true.

i wonder if what i said about speed actually holds up in a real world situation. i was drawing upon my physics theory stuff for that one.

actually, i wonder if there is any turbulence in that sort of system. i would imagine that a radiator is just a bunch of tubes, nothing special. theres no real turbulence in tubes like that, especially smooth metal ones. in fact, there probably wouldnt be much turbulence in a lot of waterblocks out there either.

great. now im not even sure im real anymore. see what you've done to me? probably not a good idea to be thinking this hard at 1 in the morning.

Actually, remember how the double-pass radiator has a higher velocity? The reason why the increased velocity in the tubes is a good thing, is because it causes turbulent flow. In the world of cooling, you WANT turbulent flow. It makes sure that all the water molecules are mixed up and exposed to the aluminum so they give up their heat.

And yes, pretty much ALL waterblocks will be turbulent flow, usually through the use of small nozzles where the fluid enters the actual block. I saw a picture of either the Storm or the TDX somewhere and you could see the nozzles clearly.

[Silenced_Coyote]

Here is the little nozzles on the Storm.
http://www.systemcooling.com/images/reviews/LiquidCooling/Swiftech_Storm/image10.jpg

Here are the wells that the nozzles shoot into.
http://www.systemcooling.com/images/reviews/LiquidCooling/Swiftech_Storm/image8.jpg

[dgrmkrp]

actually, i wonder if there is any turbulence in that sort of system. i would imagine that a radiator is just a bunch of tubes, nothing special. theres no real turbulence in tubes like that, especially smooth metal ones. in fact, there probably wouldnt be much turbulence in a lot of waterblocks out there either.
..don't wanna butt in.. but if you have a louvered fin radiator.. or heater core, there is lots of turbulence inside.. only in heat exghanger-type radiators, with visible tubes and fins travelling across the radiator, the turbulence appears solely becasue of the speeding water.. in louvered fin radiators there is a complex design that makes water go crisscross really fast and then sends it back (usually these are double-pass) quickly in the same crsii-cross manner..

In the world of cooling, you WANT turbulent flow.
i totally agree.. look not only at waterblocks, but at swiftech's pinned heatsinks..also, the storm block is based on a jet impingemet system and i don't think there is anything more turbulent than this :) because u jam high pressure streams of water in a copper wall, with holes.. so that there is absolute surface contacts and 0.00001% laminary flow.. man it rocks! i want one :)