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Technical Deep-Dive: Closed-Loop Liquid Cooling

2017-05-26
although the basics of a liquid cooler are pretty simple it's really not that different from your car radiator the inner workings of it are somewhat interesting and we have a lot of those details for you today and besides NZXT would not stop sending me these things until we did one of these videos on liquid cooler specifically before we get to the detail on permeation stators impellers and chemical composition of the coolant this video is brought to you by NZ FD and their Kraken series of liquid coolers our in-house 3d animation that will be shown in this video was actually based off of a Kraken x52 which you can find in the link in the description below we've torn apart a lot of liquid coolers and they're more or less the same when it comes to implementation of how they're cooling a CPU but they differ in terms of execution so that would be the design and how the cooler actually comes out of the factory when it's done because there are a few differences that are key to note a few cooling products for an example will relocate the pump to be somewhere else in the system so on some of the old Antec dino tron made products they have the pump located on the fan near the radiator or attach the radiator on a lot of these products from NZ ft from Corsair from EVGA really for most vendors the pump is located on the CPU block itself and then a couple folks like deep cool do some really interesting stuff where they position the pump kind of on the block but not quite for legal reasons so there are a lot of different executions of the core function which is to get a pump in the loop somewhere but the difference is just how that's pulled off liquid coolers are mostly made by a few companies one of them would be ASA tag to make the NZXT products including the kraken line the corsair products or some of them anyway Eva J products and Thermaltake C LTS cool it's or quality isn't known for Corsair some of their products and for data center cooling Coolermaster makes their own which is a bit different and you may be interested to know that Kula master o am the most of the intel and and the stock coolers as well including the air coolers while AC tech OMS many of the stock liquid coolers and then there are a couple of smaller companies that also exist in the space largely consisting the appall tech known for enter max and leopard coolers and Dino Tron known for some of an tech schoolers we have an older content piece about who makes your CLC if you're curious to learn more about that aspect of it but let's start by getting a foundational understanding we can look at the torn down a crack and x42 that we previously disassembled on camera and start at the cpu block then work our way around the basics remain the same as our air cooler animation heat from the CPU is conducted through Tim or solder into the IHS which then transfers through another layer of Tim to the cold plate that thermal interface helps deal with microscopic imperfections in the service of the IHS or the cold plate but is otherwise undesirable it's got worse thermal conductivity compared to the flanking copper interfaces these days the most CLC cold plates are circular and smooth though there are older models that use the tree like ringed cold plate and this is largely a manufacturing and production improvement in the die casting process to make those cold plates because there are only a few cold plates of pliers just like there are only a few pump suppliers and so forth most plates aren't now smooth instead of that rain design some cold plate suppliers make the cold plate service concave to better match the CPU IHS with GPU cooling plates remaining generally flat these days again with the most current generation of enthusiast grades liquid coolers that like the kraken X 52 that we've modelled for this video those cold plates are now flat generally the manufacturing complexity of the concave indent was not worth the efforts based on the cochlea spoken to in the industry and going with a flatter smoother service generally seems to have an overall equivalent or superior performance gain anyway the copper itself is thin by design with the side internal to the pump housing terminating in dense and micro fins the density of the fins allows for greater surface area for heat spreading with heat being whisked away by a straight flow or split flow liquid design surface area is critical but so is flow impedance fin density and fin pitch impact flow rate which is directly controlled by pump speed radiator design or heat exchanger design if you prefer and manufacturer spec it's up to the manufacturers so that the folks like NZXT and their suppliers to work together on a custom solution for the product the because a one-size-fits-all model while deployable doesn't mean it will be the best performance out of box some coolers but not all will use a rubber gasket for split flow circulation this sits between the housing and the cold plate and directs liquid down the center channel split flow minimizes dead zones on cold plates though straight flow is an alternative that is also commonly used as for liquid movement that's pushed around by an impeller the coolers we've dismantled lately I'll use an 8 pole impeller design including the NZXT kraken series the coarser h100 ib2 and 115 i v2 and the EVGA CLC products as an aside this also means that your bios readings of pomp RPM will be incorrect since bios is expecting a 4-pole fan pwm but receiving 8 the maximum 12-volt pump rpm and most enthusiasts grade TLC's tends to be in the range of 2800 to 3000 rpm plus or minus about 10 percent with the one standout difference being the gen 4.5 EVGA GPU cooler at 3600 RPM to help mitigate the noise impact from a high RPM at several Coulee and OEM use a layer of foam padding between the pump internals and the outer shell our torn down X 42 it shows a big foam block used for this aiding in vibration and noise reduction getting back to the basics liquid moves up one tube and into the water tank on the radiator which has a partition wall down the middle the tube mounts to the radiator on a barb which is generally either a three flange or single flange design the single flange designs I'll use most commonly in server and data center use cases with ASA Tech's leveraging piano wire to pinch the tube like a clamp this helps sustain higher pressure in failure events though three flange Barb's are still rated for several times the pressure of what would ever be experienced in an enthusiast desktop setup anyway so those tend to be more common for people in our audience as the warm to liquid from the CPU feeds into the radiator it travels down roughly half the channels and to the other side this is the cooling process aluminum fins within the radiator core conduct heat away from the channels then the radiator fans dissipate that heat from the fins you may also hear the phrase heat exchanger or hex it really means the same thing as radiator when we're this particular type of product at the end of the channel the liquid does a u-turn and travels back down to return to the other side it's even one more path of cooling from the fan and the heat dens and at this point the liquid it should be nearing its lowest temperature that tends to be around 26 to 32 Celsius for the liquid temp the pending on the chemical composition of the liquid and the heat of the CPU being cooled as for the liquid use the density mix of propylene glycol and distilled water some manufacturers will use a higher percentage of one or the other depending on what their goal is for example you might be targeting as a manufacturer support for something like a negative 40 C environment if that's the case you would probably run a higher percentage of propylene glycol or just glycol in the mix then distilled water most of the manufacturers tend to target around negative 20 C for their lowest technically within spec supported temperature and that is because of mostly shipping reasons shipping and storage they want to be able to support that that's fine to make sure it doesn't freeze when you put it on a plane and ship it but some folks do negative 40 C targets or greater or just around that area the mixture of the liquid used for cooling can be modified by the supplier to fit that spec and finally we have tubes which are generally made of either Fe P or EPDM rubber the more rigid tubes tend to be Fe T which has excellent reduction of permeation but it's a lot less flexible during installation tinking and FP p2 will result in cracking the inner PTFE or Teflon coating which results in permeation and pore cooling ability it's really a very bad thing when you crack that inner coating that inner coating is what makes FTP good EPDM rubber tubes have the opposite set of pros and cons they really won't get damaged if you bend them all a lot they're more flexible but it does require a bit of an expensive R&D process to get the compound to a point of resisting permeation in a way that is competitive in the market finally all these things tend to have some sort of PCB in them the simpler ones without all the crackin Stiles crazy RGB LEDs use a smaller PCB that really serves one function which is the host firmware of the liquid cooler while the more advanced models that would be again this or something like the EVGA CLC we looked at or anything really with RGB LEDs in it might have some sort of custom PCB generally that's made by ASA tech or the supplier though in some cases they do allow manufacturers to customize their own PCB as we talked about in our x42 tear down that PCB is more or less the brains of the system and then depending on the manufacturer depending on the unit you buy it's possible they have some memory chips on there as well some sort of storage to keep the profiles for pump speeds if the particular cooler allow is a manual tuning of the pump speed a lot of them don't that can be stored on the PCB in some sort of memory depending on which cool you buy so these things are actually fairly complex for what they do considering air coolers are basically a radiator which is just what a thin stack is and a fan although they do have some complexity with the copper heat pipes it's nothing near what a closed-loop cooler does now it's not the sense the most complex thing we look at something like a GPU of course would be far more complicated but for something that cools a CPU or GPU there's a lot going on here that's why we wanted to make a video about it because really there's a lot more under the hood of what's going on with these things then you might really realize when first looking at it though our tear downs do teach quite a bit primarily don't use a drill to take apart it liquid cooler and we'll go back together so that's all for this one check us out on patreon you go to patreon.com/scishow and Xanax ourselves that directly the website gamers next to scott net will have a full article for this if you're curious to learn more thank you for watching subscribe for more i'll see you all next time you
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