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we just can't convince you guys sometimes after our video debunking a

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Corsair rep's claim that stacking radiators is ineffective for improving

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cooling you guys told us just how inadequate you felt our test methodology

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was you know what okay fine you guys want science we're going to

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bring you the science colin here spent two bloody weeks making our own data

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logger from scratch and built this behemoth of

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a radiator stack along with this wind tunnel just peppered with

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sensors to find the definitive final

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answer to exactly what effect stacking

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radiators has on water temperature tang wants to help

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you save money by helping you pay for only the mobile data that you use stick

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around until the end of the video to hear about their giveaway or click the link in the video description

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for a quick recap back in the day Corsair called us out for the apparently

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ineffective way that we were recycling the hot air or stacking the radiators in

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our hacc pro now this individual went as far as to

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send us images of their flow simulation data to prove their point our logical

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answer then was to just build a similarly configured system to prove

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that more rads definitely equals more better so we did

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and it did but while some of your complaints can be

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chalked up to frankly not paying enough attention to the video i get it happens

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others seemed to have some merit you guys still

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weren't satisfied and so i greenlit a

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project to go full crazy on a test rig to isolate the variables that we had

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kind of hand waved away last time we started out by reaching out to our

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friends at alphacool for seven of their

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240 millimeter cross flow rads and

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thermistor type temperature probes performance pc also threw some low

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profile fittings our way for stacking them together like this so with a little

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bit of fabrication and some 3d printed end caps here a wind tunnel was slapped

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together from clear acrylic these cross flow rads were specifically chosen

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because they give us some really interesting flow options that we may

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explore down the line so get subscribed if you want to see more from this test

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rig here for this video though we're sticking to serial flow in one out and

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then into the next and so on and so forth because that's how most people

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would configure a water cooling system if they had multiple radiators at every

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single radiator inlet and outlet we've got temperature probes see these puppies

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right here these are going to tell us the difference in temperature or delta t

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from when the water enters the radiator to when it exits but

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we had a problem how do you go about calibrating and

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recording the data from all of these sensors colin never content to just take

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the easy path decided to create this

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this right here with a little bit of code and arduino due chosen for its

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large array of analog inputs gives us full control over our data stream oh

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yeah and don't forget the absolute beauty of a breadboard right

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here that's important the 32-bit atmel processor in here can actually sample

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data much faster than we need but we settled on pulling the sensors every 250

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milliseconds or four times per sensor long story short the arduino does a

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little bit of math and converts the resistance of the thermistor sensor

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embedded in each of these fittings into degrees celsius using the steinhart

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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

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arduino code that we used and a good starting place for some reading now

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due to the varying resistance of the sensors themselves

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as well as the actual wire connecting them even

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the raw output that the arduino sees isn't accurate enough for our purposes

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so we added these trim pots right here

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numbered zero to eight to allow us to calibrate each sensor to

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a known temperature using a water bath once all the sensors were reading within

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half a degree of each other the data is pushed out via a serial connection to

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this surface laptop running putty an open source serial monitor which can

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output all the data to a convenient text file for later processing a relatively

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convenient text file okay so now's a good time to take a break from line of

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science tips here and hydrate lttstore.com before we get into our heat

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source on this test bench right here we've paired a 32 core Threadripper

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3970x furnace of a CPU with an NVIDIA

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titan v which combined should dump about 500 watts of heat into

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our system on the water side of things it's a fairly simple affair with a d5

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pump with a custom top as well as a no-name reservoir

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so that's the setup let's dive into how everything performed

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for our first two tests each radiator was paired with Noctua nff12 fans and we

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used our full assembly of seven radiators stacked one after the other

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down our wind tunnel air flows over the rads from sensor 0 to sensor 7. kind of

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like if our stack was mounted as a front intake on a super weird case that's like

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really deep with water flowing from sensor 0 to sensor 7 the radiator with

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the hottest water inside it is the one at the very front of the case and off

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the hop we can see that most of the cooling happens in this first radiator

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represented by the red line this makes sense because it's getting

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both the coldest air and the hottest

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water coming straight off of our system here the second radiator is orange and then

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yellow and then so on with each successive rad doing less and less of

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the actual work we hit a point of basically negligible returns at about

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radiator six now if we focus in on the initial start of load the first two

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minutes we can see here that each radiator gets progressively hotter in

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sequence which is to be expected however if we look at just the section

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where the load is stopped the results get much more interesting

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check this out when firmark is closed the first radiator stays the hottest

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which we expect but see how these lines cross over subsequent radiators

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this is actually a really cool visual representation of heat soak

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so the preheated radiators farther down the line are actually reheating the

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water coming from that front rad which as you guys remember is doing most of

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the work as it passes through the dark blue line here is the exit water

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temperature and it actually comes out hotter than the other rads in the series

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zooming out a little bit more shows the middle radiators eventually equalize and

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fall into order once again so seeing heat soak right here in the data is

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super cool well more like 39.5 degrees not that cool but

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hey who's counting got him of course one way to counteract

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this reliance on the front radiator is to run the water the other way as many

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of our viewers recommended last time around that puts the freshest air into

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the last radiator for the water to flow through

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so the only variable between test one and test two is that we reversed the

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water flow direction in the loop this is

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generally considered to be the better way to stack and according to our

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testing that checks out by flipping the flow all the rads come up to temperature

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more slowly as the stack gets progressively hotter and if we overlay

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the two water exit temps and offset to account for the ambient slash idle

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temperature of the system the outlet temperature does show minor improvements

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versus test one's flow direction cool quick takeaways then it appears that for

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this combination of CPU and GPU at least

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by the time the water reaches the six radiator we've imparted as much heat

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into the air as we're going to at the highest water temp we were seeing a

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delta t of about four degrees from the first rad to the sixth the last one that

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was actually making a difference give or take a half a degree

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and we also see that the majority of the work is being done by the first radiator

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so our Corsair representatives point about the small gains from stacking

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being offset by the reduction in airflow that comes from adding more restriction

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and more fins does seem to be fair

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but it's also true that there is still performance to be gained so

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for our third scenario we moved on to a more sensible setup right here you're

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looking at one bank of fans and two radiators and

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here there's definitely less volume in the

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loop so we see the temperatures rise much quicker overall we hit a peak temp

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of 38 and a half degrees after 10 minutes of load

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but when we ran the same test with a single radiator we also hit

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38.5 degrees here's where it gets really interesting

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for a sanity check we charted the change

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in temperature from the inlet to outlet side of both the single and the dual

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tests so a higher delta t on one system

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would mean that that particular one is more effective now the data is a bit

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noisy for one of the tests but regardless they look pretty well aligned

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so in my eyes that's pretty definitive when

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it comes to one rad versus two assuming you've only got one set of fans

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a second radiator isn't really going to do anything for you besides add some

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thermal capacity in the form of metal and water mass so i can't believe i'm

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saying it but i was wrong i've been saying that a lot

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lately at least i was wrong for this test now

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as i alluded to earlier a lot of you missed this but the minecraft server did

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perform better with three versus two radiators under full load and for that

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matter so did the hack pro we believe this comes down to either having enough

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airflow to utilize the extra surface area or having a mix of preheated air

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and ambient air mixed in because a typical computer case is not actually a

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sealed system but we still learned a lot here first is that more rads does not

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always mean more better in the case of our one rad versus two in the wind

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tunnel it appears that Corsair is right in that adding a second radiator doesn't

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do anything the data we gathered proves this and this is with a bank of static

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pressure optimized fans these are not like pinner crappy fans second some of

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the perceived gains from radiator stacking could simply come down to

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flawed tests where the system is not allowed to reach equilibrium making it

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seem like it's running cooler but if they had just left it for longer that

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water would have eventually heated up that's an easy mistake to make because

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the increase in thermal mass of the radiators themselves as well as their

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water capacity can make this kind of testing take a really

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long time third and finally you can still get

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a benefit from stacking but only with a correctly configured system that moves

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the air fast enough to maintain a meaningful difference in temperature

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between the air and the water in the last radiator in the stack

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so i really wanted to come out and say boom headshot

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gotcha Corsair but when we isolated

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everything down like this the results didn't quite match up with

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that this is not what i expected but in a way that's kind of great too and i

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learned something today kind of great like our sponsor ting does

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link in the video description you'll find the full details and when it ends

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down below so thanks for watching guys i want to throw you guys over to the hack pro

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series which actually inspired this whole experiment you can check out how

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difficult it was to jam water cooling into that case however effective or

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ineffective it ended up being