 Welcome to Linus Tech Tips. Today's video is all about building and using a 6 foot tall evaporative cooler to cool down a Core i7 Extreme Edition processor. This is colloquially known as bong cooling. So sit back, relax, get real relaxed, and enjoy. TunnelBear is the easy to use VPN service that lets you use the web as though you're in one of 20 different countries. Learn more and try TunnelBear for free at the link in the video description. So some of you are probably asking yourselves, is he serious right now? And the answer is yes. Let's begin then with some theory. Traditional PC coolers like heat sinks and closed loop water cooling systems, and even fully custom water coolers, can deliver fantastic results for overclockers and silent enthusiasts. But sadly, videos like this, showing minus 10 to minus 20 degree CPU temperatures with a bunch of fans on a radiator, will always be, shockingly effectively however, epic trolls. Through the miracle of video editing, TTL, who legitimately has plenty of gear capable of reaching those temps, swapped in some screen cap of a different cooling system. And we know this because, three cheers for science and the laws of thermodynamics, heat, just like water or nutrients across the membrane of a cell, naturally flows from an area of higher temperature, one with a higher average kinetic energy of its molecules and atoms, to one of lower temperature. So as air, let's say it's 22 degrees Celsius, passes over a heat sink, that's sitting at around 50 degrees Celsius due to its absorption of thermal energy from a CPU underneath, that thermal energy naturally transfers from the hot heat sink to the cooler surrounding air, where it can be blown out a window or whatever. And the wider the difference in temperature between the heat sink and the air, the faster this transfer takes place, which is why you'll reach a maximum load temperature while running a game for 15 to 30 minutes, instead of it just continuing to rise. Cool, right? Sure it is, but, all cooling systems that rely on these principles inherently share a hard performance limit. That is to say that no matter how many heat pipes, radiators or cooling fans you add, you can never get below the temperature of the air around you. Well hold on a second Linus, what about wind chill? When I put my arm out the window of my car, it feels a whole hell of a lot cooler cruising down the highway than sitting at a red light, even when it's really hot outside. Well that is because you are made of water. The effect that you're feeling is called evaporative cooling, and it works thanks to a neat little concept called, stick with me here, we're almost done, the enthalpy of vaporization. In simple terms, for a given mass of fluid to change phases, for example from liquid to gas, energy must be either absorbed or released. Ice can be colder than zero degrees, fun fact, and water vapor can be hot enough to burn you or hot enough to freaking cook you. But not while it is in the midst of a phase change. That's why the mixture of ice and water in your glass stays at exactly zero degrees Celsius until all of the ice is melted, and that's why your boiling pot of water on the stove stays at exactly 100 degrees until all the water evaporates and then you need to buy a new piece of cookware. The heat energy being added by the sun or the cooking element is being used to break hydrogen bonds between H2O molecules before the new phase can continue to heat up. So as long as you keep adding ice or water to that two-phase mixture, the temperature remains constant. Okay then, so, bomb cooling. You don't have to put water on a stove for it to evaporate. Otherwise, I mean, how would the glass of water you spill on the carpet ever dry? More heat just speeds up this process, and if you've ever tried to clean up a spill before mom notices it, you probably also know that more airflow, maybe in the form of a fan, makes this happen faster too. So in a nutshell, a bomb cooler works by first creating small droplets of water with a shower head. This gives the falling water more surface area, making it easier to evaporate, then dropping these water droplets down a cooling tower, which causes the water molecules on the surface of the droplets to change phase to gas, absorbing heat energy from the liquid water that remains in the falling droplet, effectively cooling it. We use fans then to blow air from the bottom of the cooling tower to the top to accelerate this process. This allows us to potentially reach sub-ambient temperatures, assuming enough airflow, big enough towers, and favorable humidity and atmospheric pressure conditions. This is at the cost, however, of losing to the room around us some of that liquid water. So let's build it then, shall we? Darius will be assisting me since I'll be in another country by the time this is being filmed. Here's what you'll need. We took a lot of cues from this awesome build log over on overclock.net. 4-inch diameter PVC piping, PVC joiners, two 120-millimeter fans with a power adapter for them, as many shower heads as you will have cooling towers, some wood, a PVC Y, one per tower, a powerful pump to get water to the top of the shower heads, half-inch clear flexible tubing, some miscellaneous 5-eighths inch PVC fittings to join our tubing runs together, and a normal CPU water block. Which leads us then to moment of truth time. And here are the results. The advantage of bong cooling here is that it's not as hot as the other ones. It's a lot colder than the other ones, and it's a lot more comfortable. So let's go back to the moment of truth time. And here are the results. The advantage of bong cooling here is that we were able to beat the performance of a traditional ambient CPU cooler without adding a significant electrical cost. Thermoelectric or Peltier cooling, air conditioning or phase change would incur these penalties. And the more environment desert dwellers rejoice, the more effective this would be. But there are some disadvantages as well. It's kind of loud if you're not into the whole falling water relaxation thing. It increases the humidity of the room it occupies. It's large if you want it to work well. And finally, unless you were to rig up some kind of water level meter and an automated top-up mechanism connected to your house plumbing, which is possible, mind you, you need to constantly top it up with water, which is why most people don't build them. But hey, that's never stopped us before, has it? Speaking of not being able to stop us, you can't stop us from talking about Crunchyroll. Crunchyroll is the site created by anime fans for anime fans. They offer the most current episodes of new shows straight from Japan with a huge collection of the most popular anime series. Their featured content for spring of this year is Twinstar Exorcists, Ace Attorney, Re Zero, and Kiznaver. And all the content on their site is professionally subtitled. So head over to crunchyroll.com slash Linus for a special surprise. You can sign up for a 30-day free trial of Crunchyroll Premium. Yes, 30 days of all the anime you can eat. Our link gives you all of the content on the site completely ad-free. And if you enjoy the many benefits of premium, like 1080p streaming, getting new episodes of shows straight from Japan within an hour of their premiere, and being able to stream anywhere, anytime from a variety of devices like your tablet, game console, or mobile phone, you can continue your premium membership for only $6.95 per month. So head over to crunchyroll.com slash Linus and start rolling your crunchies today, as the kids say. They don't say that, do they? So thanks for watching, guys. If this video sucked, you know what to do. But if it was awesome, get subscribed, hit that like button, or even consider supporting us directly by using our affiliate code to shop on Amazon, instructions up there, by buying a cool t-shirt like this one at the link in the video description, or by joining our community forum where you can ask questions, answer questions, and basically just talk tech. Now that you're done doing all that stuff, you're probably wondering what to watch next, so check out that little button in the top right corner to check out our latest video over on Channel Superfun. It's worth subscribing over there. Go ahead, do it.