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 going to
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 tang 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
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 hacc 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 greenlit 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
240 millimeter cross flow 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 3d printed end caps here a wind tunnel was slapped
together from clear acrylic these cross flow 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 going to tell us the difference in temperature or delta t
from 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 its
large array of analog inputs gives us full control over our data stream 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
heart equation if you want to give this a shot yourself by the way we're going to have a link in the description to the
arduino code that we used and a good starting place for some reading now
due to the varying resistance of the sensors themselves
as well as the actual wire connecting them even
the raw output that the arduino sees isn't accurate enough for our purposes
so we added these trim pots 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 were reading within
half a degree 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 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 line of
science tips here and hydrate 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 an 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 nff12 fans and we
used our full assembly of seven radiators stacked one after the other
down our wind tunnel air flows over the rads from sensor 0 to sensor 7. 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 0 to sensor 7 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 the section
where the load is stopped the results get much more interesting
check this out when firmark 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 preheated radiators farther down the line are actually reheating 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 39.5 degrees not that cool but
hey who's counting got him 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 the rads come up to temperature
more slowly as the stack gets progressively hotter and if we overlay
the two water exit temps and offset to account for the ambient slash 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 for
this combination of CPU and GPU at least
by the time the water reaches the six 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 representatives point about the small gains from stacking
being offset by the reduction in airflow 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 38 and a half degrees after 10 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 is 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 going to do anything for you besides add some
thermal capacity in the form of metal and water mass so i can't 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 preheated 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 have 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
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down below so thanks for watching guys i want to 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