 We just can't convince you guys sometimes. After our video debunking a Corsair reps 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. 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, 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 Alpha Cool 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 wanna 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 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 an 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 Steinhardt-Hart equation. If you wanna 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 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 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 the 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 NFF 12 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 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 the section where the load is stopped, the results get much more interesting. Check this out. When firm arc 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 and a half degrees, not that cool, but hey, who's counting? Hey, got him. Of course, one way to counteract this reliance on the front radiator is to round 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 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 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 gonna 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 coarser 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 coarser. 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. Kind of great, like our sponsor. Ting does mobile phone service differently. There's no contracts, overage fees, or any other carrier tricks. You just pay a fair price for the talk, text, and data that you use each month. 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You can check out how difficult it was to jam water cooling into that case, however effective or ineffective it ended up being.