Radiator 'stacking' and pump flow rate

Hi guys,

I'm in the planning stages of a watercooling loop for a Mac G5 conversion I have in the pipeline. The components I plan on cooling are the CPU and GPU only at this stage, and due to size constraints inside a G5, I am limited to using 240mm radiators.

I don't think a single 240 radiator is going to sufficiently cool a Haswell CPU and a *probably* high-end GPU. So I'll need more to shift the heat. I can add a second 240 radiator, but the only way I can think of mounting it is as an exhaust, adjacent to the intake for the first radiator. Whilst this is not strictly 'stacking' the radiators, but it's close enough. I know that radiator stacking for dual loops is a no-no, but for a single loop with two radiators, is this more acceptable?

I made a drawing to show what I'm on about. It's not to scale, and is a top-down view:



The proposed order for the loop is as follows:
Pump -> CPU -> Radiator 1 -> GPU -> Radiator 2 -> Reservoir -> Back to Pump

I wanted to make sure a radiator was in between the CPU and the GPU, so that some of the heat from the CPU is shifted before it gets to the GPU. Because of the positioning of the radiators, which are in the front of the case, there will be a lot of tubing. With this in mind, would something like an 18W DDC do the trick, or do I need something beefier, or even two pumps in series?

 

I wouldn't bother going that route to be honest, loop order after the res>>pump part is basically meaningless. The whole loop will eventually warm up to a similar temperature with the variance between blocks being so minuscule it basically doesn't affect the temperature gradient.

Just stick in a D5 pump of sorts, then connect up using the route that either looks nicest or is simplest (often are the same thing). So using your example:

Pump -> CPU -> GPU -> Radiator 1 -> Radiator 2 -> Reservoir -> Back to Pump

Or something similar to that effect.

 

Good to know, that means that I don't have to worry about loads of tubing all over the place, so thanks!

As far as the radiator is concerned then, would it be a problem using the method I suggested, or would a single extra thick 'monsta' rad be a suitable alternative?

It's going to be difficult to tell without knowing which parts I'm using, and I can't seem to find the maximum heat dissipation for the Alphacool Monsta radiators. If I can get away with using one of them with 4 fans in push/pull, that will make life infinitely easier.

 

Radiators will be absolutely fine. The difference in temperature between air coming in and exiting a radiator is a few degrees at most. So your second rad still gets plenty of cool air.

 

No,it doesnt work like that,rebreathing exhaust from rads thru other rads can really reduce the performance of the second rad,you really dont want to do that.

All intaking gives the best performance

Martin and HES did some testing on it.



Keep the loop simple with the shortest tube runs you can get,loop order,as mentioned already,has no RL difference...until you get into quadfire/sli and 2P/4P for folding.

 

Looking at the image in Post #1 it doesn't look as though the rads are actually stacked. I'd have them both as intakes though although there's only likely to be a couple of degrees difference at most between both intake and one intake and one exhaust.

 

Exactly. When you sandwich rads you have to take into account the cumulative restriction in airflow. Air passing through the second rad will be less than that passing through the first. Stuartwood89's setup will be more like scenario 3, where the radiators are separated and thus each have relatively unrestricted airflow.

 

Unrestricted,Yes.

Greatly reduced thermal carrying capacity? Yes.

While im not saying it will be crippled or worthless,I am saying that the component is not working at its best. The whole effectiveness of a loop is measured in 2-3c differences,why lose that advantage of a free few c in temp reduction?

 

When you try and cram it all into a case, compromises have to be inevitably made. Exhaust radiators drawing warmer air from inside the case are always a compromise. The benefit of adding a radiator will far outweigh its less than ideal placement though.

 

Thanks for the comments guys.

So based on what I've seen, are we saying that two radiators arranged in the formation in the OP is going to be better than a single extra thick radiator in push/pull?

My main concern with having both radiators as intakes was that the air would have to go somewhere, and with only room for two 92mm fans at the back, I'm not sure it will be able to shift that much heat built up into the case.

 

Which i why I recommend all intaking.
Im not saying remove the rad,just flip the fans..this isnt a placement issue,its an airflow issue.

You will make your case positive pressure,the case temp will go up 4-6c but,as everything is likely to be watercooled, the temp of air inside the case is much less of an issue.

 

Changing he side fan to intake air is no big deal. I just remembered that the PSU will also help in exhausting some of the heat, so that's not so bad.

I did a bit more digging on the Monsta 240, and based on discussions it isn't recommended for a CPU and GPU (for that they recommend at least a 360 radiator). By having two 240s in series, I'll basically have a 480 in total. It will be a pain to fit/maintain compared to a single chunky radiator though.

 

People tend to overestimate the size of radiator needed. I'm running a dual Opteron 250 (2x89W) and ATi Radeon 1650XT (44W): a total of 222W on a single Black Ice Xtreme.

 

I use the standard of 240 for a CPU and add 120 for each heat source in the loop,mobo and ram dont count in this.

OC'ed components are not in the same league as your setup,if a modern CPU can overwhelm a h80/100 then a single 120 will not cut it.

I do agree that some go stupid with 3 480s for a CPU and GPU for example but more rad face=lower fan speeds.

 

A CPU does not need more than a single 120mm rad (although, as you say, if you want to run very silent, why not?). GPUs are the big heat sources, twice the wattage of a CPU, but even then you can add a 120 per card. If you intend to maniacally overclock, add another 120 to be sure.

 

If I can get the maximum heat dissipation of the NexXxoS 240, then I can work it out. Unfortunately the Alphacool website doesn't have that information, and I can't seem to find the dissipation for any radiator I've seen so far

So according to Wikipedia, the TDP of a 780Ti is 250W, an Intel i7 4770K (Haswell) chip has a TDP of 84W, meaning a combined output of 334W of heat. I'll need a system that could handle that.

To be clear, I don't actually plan on going for this hardware, however seeing as these are considered top-end in the current market, I'd prefer to overestimate the heat output than fry my rig.

 

Thanks for the diagram, helped me make my mind up

 

GPU's are not the thermally limited component,tailor the loop to the CPU.

GPU's also dont emit as much heat as you think,the average TDP for a GPU is 250-300w for a high end card.
The problem is this,GPU TDPs are a whole card value,not just the chip like a CPU. Intel further muddy the waters by publishing TDP's that are the throttled value,not the max or sustained value.

Case in point.



My trusty 95w x5650's......not 95w at all.

Why do you think that most watercooled cards are around 40c max temp with all the added input from the VRM and VRAM while the CPU can push double and then some? Even with the benefit of impingement blocks over the GPU microfin design.

Also worth mentioning is this.



Dual 7970 cooled by a single no doubt cheap 120 rad,not something to try with a CPU....

We have debated this on OCN hard,TDP as a value is nigh on worthless,a meter at the plug is the only real guide.

 

So do you think an extra thick 240 radiator with push/pull fans would do the job, or would I really need two standard thickness radiators in series, in the formation shown above?

I think the answer is going to be two radiators in series, but I'm struggling with a way in which they can be taken out and maintained in such a small confined space. They'll need filters, so those will need to be accessible for cleaning etc.

 

Thickness of a rad doesnt matter nowhere as much as actual rad face. 2 240s will net you a much larger gain than splurging on a Monsta...

Have the fans on the back side of the rad then the front face can just be brushed off easily.
Demicflex make good filters but they are no lookers.