Building a PC: Air vs Liquid Cooling

Prologue

The use of liquid cooling within a computer system can trace its roots all the way back to the Cray-2 supercomputer, which had a very unusual cooling system. The circuit boards were completely immersed in a non-conductive fluid called Fluorinert™ which was cleverly re-circulated throughout the entire system. That is quite groundbreaking, especially when you consider that the development of that system began around 1982. It was not until the 1990’s that liquid cooling began to trickle –pardon the pun- into personal computers, but back then it was reserved for only the most extreme individuals or enthusiasts out there. These were the type of people who were always pushing the limits of case modifications and overclocking, and it is thanks to these pioneers that we are no longer stuck with the boring beige boxes of yesteryear.

Fast-forward to 2018 and liquid cooling has become relatively mainstream. Several manufacturers offer AIO (all-in-one) kits which are pre-filled and sealed, and merely require the end-user to physically install them into their PC. These systems are fairly simple to configure, and a user can even buy video cards nowadays that come with their own dedicated liquid cooling setup. On the other end of the spectrum however, an enthusiast can choose to make a ‘custom loop’, which is is basically a bespoke liquid cooling system; allowing the individual selection of all the various components required to cool a modern Gaming Rig.

There is no denying that a liquid-cooled computer can look absolutely epic, and there are certainly some noticeable benefits to liquid cooling; but I can’t help but think about a question that people ask me all the time:

‘Which is better, Air or Liquid Cooling?’ 

My usual response of ‘Well that depends…’ does not usually go down too well with them, but it really does depend on a lot of variables as well as your use-case scenario. Let me try to elaborate on that a little.

Air Cooling

In a previous brief article, I mentioned the first law of thermodynamics and why the components of a PC get hot in the first place. Regardless of whether you intend to cool your system with strictly air, strictly liquid, or a combination of the two, I recommend giving it a quick read to familiarize yourself with case pressure. In other words, that box has already been ticked elsewhere and I will try my best not to introduce that debate into this article.

Air cooling is relatively simple to understand, if you live in a warm climate then you most likely use fans in your house (or air-conditioning) to keep yourself comfortable. You are probably familiar with the sensation that the faster the air is moving, the colder it is. What you may not realize is that this is not actually the case, regardless of the speed at which the air travels, the temperature of it remains the same. What you feel as ‘colder’ air is actually how your skin –ergo your nervous system– interprets convective heat transfer. Usually the ambient temperature will be lower than your body temperature, so the faster the ambient air travels across your skin, the colder it feels. This is also true if the ambient temperature is higher than your body temperature, the faster this hot air is blown across your skin, the hotter it will feel. This is what air cooling is all about, transferring the heat from your component through the use of ambient air with the assistance of fans.

When I first started seriously tweaking my own systems (I used to chase the leader boards of popular bench-marking tool 3DMark, at one point even ranking 3rd worldwide for my particular setup), the common solution was to install as many fans as the case would physically allow. Back then I was using an Antec SX1040B, which was a respectable case back then; but since it made use of 80mm fans, the thing sounded like a Jumbo Jet when it was turned on. It did keep everything extremely cool though, and I usually played my games at high volumes so it did not bother me too much. I wish I had a photograph of this old system, as I had painted the interior red (although it came out more of a burnt sienna) and was quite proud of it at the time. Whilst I do not have any images of that particular computer, I was able to find some from another build that I put together over a decade ago, which is pictured above and below. This system was considerably quieter, thanks in part to using 120mm fans and also by adjusting the fan curves so they were not always blasting away at 100%.

Air cooling has some distinct advantages, one of which of course is price. Fans of high quality and more importantly high reliability can be purchased relatively inexpensively these days, well unless you of course want a bit more style. Fans of course come available in many different sizes, but there also different fans for specific uses. When you are shopping for fans be sure to pay attention to whether they are designed for High Airflow or for Static Pressure, most reputable manufacturers will incorporate this into their naming convention (e.g. Corsair AF120,  Cooler Master Pro 120 Air Pressure) or certainly within their product description. High Airflow fans are designed to move as much air as they physically can, as long as there is nothing impeding them. This usually means that fans which favor airflow are usually a good choice to be used as either intake or exhaust fans for your case, key word is usually. If however we need to either push or pull air through some sort of obstruction (a CPU heat sink or a poorly designed front panel), then Static Pressure fans are preferred as they deal with the resistance much more efficiently than High Airflow fans do.

Another great advantage of air cooling is ease of use. Point the fan in the direction you want the air to move, secure it with screws (or clips in the case of a CPU cooler), and plug in the cable to either a header on the motherboard or a via a connector on the power supply. If something is not working correctly, you can see quite clearly whether the fan is moving or not, and if you are not happy with your temperatures then you can try to add more fans or even faster fans to improve the cooling efficiency. When it comes to CPU air coolers, most modern aftermarket models from reputable vendors are of good quality. They come in all manner of shapes and designs, and as time has gone by they have definitely increased in size. If you are not going to tinker with your CPU, as in overclock it, then you will likely be fine with the stock cooler that came with your CPU. Most of them perform alright, but they are considerably less efficient than something like the Be quiet! Dark Rock Pro 3. There are plenty of options out there, and your choice will ultimately be dictated by how much you want to spend as well as what will physically fit within your system.

There are some disadvantages to air cooling however, but these are not necessarily deal breakers as they can usually be mitigated somehow. First off is noise. The faster a fan spins, the noisier it becomes, or rather the movement of air becomes significantly noisier at higher speeds. This is especially true with smaller fan sizes, as they need to spin faster in order to move the same amount of air as a larger fan. So if for example your case can use either 120mm or 140mm fans, opting for the larger ones will be much kinder on your ears. Likewise, adjusting the speeds of your fans or having your motherboard control the speed of your fans automatically can help dramatically as well. This can often result in your idle temperatures being a little higher, but your PC will be relatively quiet under light load; with the fans only ramping up when your components need that extra cooling. The other big downside can be the accumulation of dust, as more air travels into your case so does the likelihood of introducing foreign particles. This can be mitigated through the use of filters, as well as by utilizing positive pressure (yes, I know I said I’d try not to introduce that debate) when setting up your air cooling setup.

Liquid Cooling

So if Air Cooling is relatively simple, inexpensive, and its inherent disadvantages can be mitigated to an extent, then you may be considering why would anyone even bother with Liquid Cooling?  I can completely understand that point of view, as I felt the exact same way for years. I initially did not feel comfortable with the potential risks that were involved, who in their right mind would introduce the potential for their computer to spring a leak and kill of their expensive components in the process? This mindset is certainly a barrier for many these days, whether it is an intrinsic fear of the unknown or perhaps just a lack of understanding. Either way, there are countless reasons that prevent people from taking the plunge –yes, another pun– into the world of Liquid Cooling.

In fact, most average computer users –and even most gamers– really do not need to venture into the world of Liquid Cooling; but as someone that got their feet wet –I did it again- only a few years ago, I do not think that I could ever go back. Now please do not interpret that as me unequivocally proclaiming that Liquid Cooling is better, it is just better for me; but it may not be for you, and it may not be ideal for your setup, your usage, or even your environment.

There are two key benefits to Liquid Cooling. First and foremost is efficiency, as in how efficiently a Liquid Cooling system dissipates heat in a PC. To put this into perspective, per unit of volume, water has about 3200 times the specific heat capacity of dry air. For you true academics out there, you may point out that whilst I am correct, the difference is less impressive if we judge it by weight (isobaric mass); in which case the difference is only about four times. Regardless of which measuring stick you choose, there is no denying that water is more efficient at transferring heat than air is. We find evidence of this in many facets of modern life, most internal combustion engines these days use Liquid Cooling rather than Air Cooling; and in colder parts of the world, we utilize hot water heating systems and radiators to distribute heat throughout our homes. In the realm of the PC world, we use Liquid Cooling as a means to direct the heat from a component (such as your CPU) to a radiator. The radiator’s sole purpose is to dissipate the heat from the liquid, thereby keeping our components cool. In order to do this, the liquid needs to continually circulate within the system (between the CPU block and the radiator), and the radiator usually needs a little assistance dissipating the heat via the use of fans.

Whilst Liquid Cooling is still reliant on fans (yes I know passive systems exist, but just ignore those for now), the fan speed necessary to adequately dissipate the heat is significantly lower than that of a system that strictly uses Air Cooling. Now, this does not mean that every single Liquid Cooling system will outperform Air Cooling, as the efficiency of the system is reliant on several other factors such as radiator size and pump speed. For example, a small AIO system such as the Corsair H55 will perform much better than the stock cooler that came with a CPU; but a high-end aftermarket air cooler will likely outperform it. Just last year I upgraded my own system from a 240mm radiator to a 280mm radiator, and my temperatures dropped several degrees and my system is even quieter than it was before.

This is the second major benefit to Liquid Cooling, noise. I am sitting here typing this out and the only apparent noise is the clicking of the keys of my mechanical keyboard. At idle, my PC is practically silent and the CPU is sitting at a comfortable 24C. If however I am in the middle of rendering a video, then of course the fans will spin up and it becomes more evident that there is a PC underneath my desk. But for gaming and even streaming, the fans stay at a relatively low speed and the CPU temperature rarely rises above the mid 40s. Keep in mind I am also using an AIO that is effectively just a plug and play solution, if I built my own Custom Loop then the temperatures and the noise would most likely be even lower than what they currently are.

The benefits of Liquid Cooling become even more apparent when you opt to overclock your components. Thanks to the increased cooling efficiency, I can run my CPU considerably faster than stock whilst still running cooler than with base clocks and a stock cooler. It also helps that I live in a relatively cold part of the world, so between the heating keeping the house at a steady 20C during the winter, and the summers not raising the house temperature much more than that, I have a nice stable ambient temperature for my system. Your situation my be very different, if for example you live in a very hot part of the world with considerably higher ambient temperatures, then you need to make sure your case still has plenty of airflow. Even though my CPU in the picture above is being handled by Liquid Cooling, the VRMs (the red and black heat sinks to the left and above the CPU) as well as the PCH (not pictured) are completely reliant on the ambient air in order to dissipate heat.

Whether to choose Air or Liquid Cooling if you live in a considerably hot environment (imagine living in SE Asia without air conditioning) is still very much up for debate, and I personally had no issues with my Air Cooling setups when I lived in that part of the world. Liquid Cooling will likely give you more piece of mind, but after extended use you will most likely discover one of Liquid Cooling’s dirty little secrets: the system will slowly creep up in temperature. This is one of the lesser-known aspects of PC cooling. In an Air Cooling system, the temperatures are usually higher and the jump in temperatures when transitioning from idle to load are evident almost immediately. In a system using Liquid Cooling, we do not tend to see an immediate spike in temperatures during this transition, but rather a steady increase. Many users will run a benchmark for 10-20 minutes, and be astounded at how low their temperatures are. If however they ran the same benchmark for 24 hours, they would likely notice a significant increase in temperature.

Now that that does not mean that a PC using Liquid Cooling will continue to rise in temperature indefinitely until the fluid boils over, just that due to the differences in efficiency between Air and Liquid Cooling, it can sometimes take a while to realize the temperatures a system will reach when using Liquid Cooling. Whereas with Air Cooling, you tend to know where you stand almost immediately.

Closing Thoughts

With all of that being said, considering the respective advantages as well as the disadvantages of both Air Cooling and Liquid Cooling, is there honestly a clear answer to the original question of:

‘Which is better, Air or Liquid Cooling?’ 

Much like most things in life, utilizing black-and-white or all-or-nothing thinking when it comes to cooling your PC just does not work. Which approach is better for you will depend greatly on your individual situation. Before you grab your pitchforks and point a finger at ‘Mr Ambiguous’, just hear me out for a moment and I’ll clarify.

If you are a light PC user, as in you use your PC for typical everyday tasks and occasional gaming, then the stock Air Cooling setup will most likely be fine for you. The only exception would be if you live in an extremely hot climate, then you will most likely want to upgrade your cooling in some way.

If you consider yourself a PC Gamer, and that is the primary use for your PC, then Air Cooling (even stock setups) should be absolutely fine for you; but make sure your case has adequate fans, as many come pre-installed with a relatively Spartan setup. If you are hitting the thermal limits on your CPU, or are having stability issues, then you should likely consider stepping up to an aftermarket CPU cooler.

If you are a content creator, whether that is live-streaming or recording and rendering videos, then I would recommend using high-quality aftermarket Air Cooling components at a minimum. Likewise, if you are a hardcore PC Gamer that is beginning to overclock their system in an effort to maximize performance, then aftermarket Air Cooling solutions should fit your needs just fine.

If you want to heavily overclock your system, or want your PC to operate in a practically silent manner, then Liquid Cooling is likely the preferred option for you. An AIO solution from any of the big brands should fit your needs just fine, and keep in mind most of them offer substantial warranties (many of which will cover incidental damage to other components in the event of failure). Ideally you should aim to fit the largest radiator your case can handle, as size does most certainly matter.

If you want the most efficient and fabulous looking cooling solution, transforming your humble PC into a full blown #BattleStation, then a Liquid Cooling system utilizing a custom loop (as pictured above) is for you. Not only will your system function well and run significantly cooler than any other option, it could also be considered a work of art and will certainly be something to be proud of. Just keep in mind that putting a system like that will take a certain degree of skill and technical knowledge, and will require routine maintenance to keep everything flowing as it should.