- 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.
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(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.
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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.