- We just can't convince
you guys sometimes. After our video debunking
a Corsair rep's claim that stacking radiators is ineffective for improving cooling, you guys told us just how inadequate you felt our test methodology was. You know what? Okay, fine. You guys want science? We're gonna bring you the science. Colin here spent two bloody weeks making our own data logger from scratch and built this behemoth
of a radiator stack, along with this wind tunnel
just peppered with sensors, to find the definitive,
final answer to exactly what effect stacking radiators
has on water temperature. Ting wants to help you save money by helping you pay for only
the mobile data that you use. Stick around until the end of the video to hear about their giveaway, or click the link in
the video description. (upbeat electronic music) For a quick recap: back in the day, Corsair called us out for the apparently ineffective way that we were recycling the hot air, or stacking the radiators in our Hack Pro. Now this individual went as far as to send us images of
their flow simulation data to prove their point. Our logical answer then, was to just build a similarly configured system to prove that more rads definitely
equals more better. So we did, and it did. But, while some of your complaints can be chalked up to frankly not paying enough attention to
the video, I get it, happens; others seemed to have some merit. You guys still weren't satisfied, and so I green-lit a
project to go full-crazy on a test rig to isolate the variables that we had kind of
hand-waved away last time. We started out by reaching
out to our friends at Alphacool for seven of
their 240MM crossflow rads and thermistor-type temperature probes. Performance PC also threw
some low-profile fittings our way for stacking
them together like this. So with a little bit of fabrication, and some 3-D printed end caps here, a wind tunnel was slapped
together from clear acrylic. These crossflow rads
were specifically chosen because they give us some
really interesting flow options that we may explore down the line. So get subscribed if you want to see more from this test rig here. For this video, though, we're
sticking to serial flow. In one, out, and then into the next, and so on, and so forth. Because that's how most people would configure a water cooling system if they had multiple radiators. At every single radiator inlet and outlet, we've got temperature probes. See these puppies right here? These are gonna tell us the
difference in temperature, or delta T, for when the
water enters the radiator, to when it exits. But we had a problem. How do you go about calibrating
and recording the data from all of these sensors? Colin, never content to
just take the easy path, decided to create this. This right here, with a little bit of code and Arduino Due, chosen for it's large
array of analog inputs, gives us full control over our datastream. Oh yeah, and don't forget
the absolute beauty of a breadboard right here. That's important. The 32-bit Atmel processor in here can actually sample data
much faster than we need, but we settled on pulling the sensors every 250 milliseconds,
or four times per sensor. Long story short, the Arduino
does a little bit of math and converts the resistance
of the thermistor sensor embedded in each of these
fittings into degrees celsius using the Steinhart-Hart equation. If you want to give this a shot yourself by the way, we're gonna have a link in the description to the
Arduino code that we used, and a starting good
place for some reading. Now due to the varying resistance of the sensors themselves, as well as the actual wire
connecting them, even, (groans) the raw output that the Arduino sees isn't accurate enough for our purposes. So, we added these trimpods. Right here, numbered zero to eight, to allow us to calibrate each sensor to a known temperature using a water bath. Once all the sensors are reading within half a 'gree of each other, the data is pushed out
via a serial connection to this Surface laptop running PuTTy, an open-source serial monitor which can output all of the data to a convenient text file
for later processing. A relatively convenient text file. Okay, so now's a good time to take a break from Linus Science Tips here and hydrate Https://www.lttstore.com/ before we get into our heat source. On this test bench right here, we've paired a 32-core
Threadripper 3970x furnace of a CPU with a Nvidia Titan V, which combined should dump
about 500 watts of heat into our system. On the water side of things, it's a fairly simple affair with a D5 pump with a custom top, as well
as a no-name reservoir. So that's the setup. Let's dive into how everything performed. For our first two tests, each radiator was paired
with Noctua NF-F12 fans, and we used our full
assembly of seven radiators, stacked one after the
other, down our windtunnel. Air flows over the rads from sensor zero to sensor seven, kind of like if our stack was mounted as a front intake on a super weird case
that's like, really deep. With water flowing from
sensor zero to sensor seven, the radiator with the
hottest water inside it is the one at the very front of the case. And off the hop, we can see that most of the cooling happens
in this first radiator, represented by the red line. This makes sense because it's getting both the coldest air and the hottest water coming straight off of our system here. The second radiator is orange, and then yellow, and then so on, with each successive
rad doing less and less of the actual work. We hit a point of basically
negligible returns at about radiator six. Now if we focus in on the
initial start of load, the first two minutes. We can see here that each radiator gets progressively hotter in sequence, which is to be expected. However, if we look at just at the section where the load has stopped, the results get much more interesting. Check this out. When FurMark is closed, the first radiator stays the hottest, which we expect. But see how these lines cross
over subsequent radiators? This is actually a really cool visual representation of heat soak. So the pre-heated radiators
farther down the line are actually re-heating the water coming from that front rad,
which as you guys remember, is doing most of the work
as it passes through. The dark blue line here is
the exit water temperature, and it actually comes out hotter than the other rads in the series. Zooming out a little bit more shows the middle radiators eventually equalize and fall into order once again. So seeing heat soak right here
in the data is super cool. Well, more like 39 and a
half degrees, not that cool, but hey who's counting. Aye, got 'em. Of course, one way to
counteract this reliance on the front radiator is to
run the water the other way, as many of our viewers
recommended last time around. That puts the freshest
air into the last radiator for the water to flow through. So the only variable between
test one and test two is that we reversed the water
flow direction in the loop. This is generally considered to be "the better way to stack," and according to our
testing, that checks out. By flipping the flow, all of
the rads come up to temperature more slowly as the stack
gets progressively hotter, and if we overlaid the
two water exit temps and offset to account for the ambiant/idle
temperature of the system, the outlet temperature does
show minor improvements versus test one's flow direction. Cool. Quick takeaways, then. It appears that this combination
of CPU and GPU laced, by the time the water
reaches the sixth radiator, we've imparted as much heat
into the air as we're going to. At the highest water temp, we were seeing a delta
T of about four degrees from the first rad to the sixth, the last one that was
actually making a difference, give or take a half a degree. And we also see that
the majority of the work is being done by the first radiator. So our Corsair representative's point about the small gains
from stacking being offset by the reduction in air flow that comes from adding more
restriction and more fins, does seem to be fair. But it's also true that there is still performance to be gained. So for our third scenario, we moved on to a more sensible setup. Right here, you're looking at one bank of fans and two radiators. And here, there's definitely
less volume in the loop. So we see the temperatures
rise much quicker overall. We hit a peak temp of
30 and a half degrees after ten minutes of load. But when we ran the same
test with a single radiator, we also hit 38.5 degrees. Here's where it gets really interesting. For a sanity check, we charted
the change in temperature from the inlet to outlet side of both the single and the dual tests. So a higher delta T on one system would mean that that particular
one is more effective. Now the data's a bit noisy
for one of the tests, but regardless, they
look pretty well aligned. So in my eyes, that's pretty definitive. When it comes to one rad versus two, assuming you've only got one set of fans, a second radiator isn't really
gonna do anything for you besides add some thermal capacity in the form of metal and water mass. So I cannot believe I'm
saying it, but I was wrong. I've been saying that a lot lately. At least I was wrong for this test. Now, as I alluded to earlier, a lot of you missed this, but the Minecraft server
did perform better with three versus two
radiators under full load, and for that matter, so did the Hack Pro. We believe this comes down to either having enough airflow to
utilize the extra surface area or having a mix of pre-heated
air and ambient air mixed in, because a typical computer case is not actually a sealed system. But we still learned a lot here. First is that more rads does
not always mean more better. In the case of our one rad
versus two in the wind tunnel, it appears that Corsair is right in that adding a second
radiator doesn't do anything. The data we gathered proves this. And this is with a bank of
static-pressure optimized fans. These are not like, pinner crappy fans. Second, some of the perceived
gains from radiator stacking could simply come down to flawed tests, where the system is not
allowed to reach equilibrium. Making it seem like it's running cooler, but if they had just left it for longer, that water would've eventually heated up. That's an easy mistake to make. Because the increase in thermal mass of the radiators themselves, as well as their water capacity, can make this kind of testing
take a really long time. Third, and finally, you can still get a benefit from stacking. But only with a correctly
configured system that moves the air fast enough to maintain a meaningful difference in temperature between the air and the water in the last radiator in the stack. So I really wanted to come out and say, "Boom! Headshot. Gotcha Corsair." But when we isolated
everything down like this, the results didn't quite
match up with that. This is not what I expected. But in a way, that's kind of great too, and I learned something today. Kinda great, like our sponsor. Ting does mobile phone
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and when it ends down below. So thanks for watching, guys. I wanna throw you guys
over to the Hack Pro series which actually inspired
this whole experiment. You can check out how difficult it was to jam water cooling into that case, however effective or
ineffective it ended up being.
Say what you want about clickbait, they put in the (jank) effort for content.
So basically:
If you have a set of fans for every rad, stacking rads will improve performance with significanlty diminishing returns after 5 or 6 stacks.
If you are just stacking rads without adding fans, you will not get any performance increase.
Do any rads with both ports on the same side enable countercurrent exchange, with the air flowing down one face and back on the opposite side?
Or are they striped, with half of the rad face out and the other half back, the full depth dedicated to one direction?
This is why I love Linus, the dude can take a hit and he loves learning so he never comes across like an ass. At least not for long.