Computer Ed Radio

Turning Geek speak into street speak

Liquid vs. Air: Cooling Your CPU


noctua_nh_d14_1Cooling of the CPU has evolved a lot over the years, we have moved from a simple heatsink sitting on a fan to large towers of fins with heatpipes rising from the cooler plate resting on our CPU. The need for this was driven by the ever increasing temperatures of CPUs as we asked for more speed.

While the smaller, basic coolers are still in use you will be hard pressed to find a DIYer that will build a system using the stock cooler. They tend to be noisy and do not provide much besides the most basic of heat removal from the system. They get the job done, but lets face it, if we take the time to build our PC we do not want to settle for just good enough.

The tower style heatsink, as seen in the picture is pretty much the standard design now in use today for traditional air cooling. The method is simple, the heat pipes transfer the heat from the CPU up into the heatsink where fans blow air across the cooling fins, removing the heat from the heat pipes.

This style of cooler comes in many sizes and shapes with setups having anywhere from one to three fans on some of the higher performance models. The basic design however remains the same throughout with only minor modifications based on the shape of the heatsink, number of heatpipes and so on.

Because the basic design remains the same they all share the same limitation as well, the size and shape can make these difficult to install and the scan interfere with the ability to add RAM on some boards. The size also creates issues with some smaller cases forcing you to be very particular on the models you can select from. Another draw back is the fact that the heat removed from the heatsink is re-introduced into the cases air. This can potentially cause a small temperature rise within the case and thus could contribute to heat of other components.

On the plus side these units are usually very cost effective for the more basic models, cool much more effectively than stock coolers and despite having more fans they can actually be much quieter than a stock CPU cooler.

RTS2011LC-Product-Brief

The new kid on the block is the self contained liquid cooler. The principles for this are based off the same principles that cool your cars motor. A small pump moves fluid through a cooling block that is on the CPU, the heated liquid is pumped into a radiator and air is forced through the radiator by a fan, cooling the fluid.

While the use of a liquid cooling system for a computer has been around for a while now the original method was to put together a kit with a number of parts. This was a scary task for many people as you where introducing a liquid into a system and assembling the various fluid path connections on the spot. You had to learn how to bleed the system of air as well as monitor the system for low fluid or leaks.

The new self contained units come preassembled and filled. The unit is completely sealed from the factory and the only assembly is the mounting of the unit. You do not have to worry about bleeding the air or the fluid levels and these units come with guarantees against leakages.

While the traditional air cooler has only a single mounting point, at the CPU, the liquid system must be mounted at the CPU and the back or top of the case for the radiator. While this might sound like more work it is often a much easier install than many of the more advanced air cooler. The smaller area on the CPU means the cooler is easier to work with and opens the space on the motherboard meaning there is no interference with RAM. The radiator traditionally replaces the rear exhaust fan on your case and is easy to mount, requiring just 4 screws to hold it and the exhaust fan in place.

These coolers provide really good cooling and do so with less fans, which means less noise. Now the less fans is something people overlook but think about it for a moment. A single fan tower heatsink cooler adds a second fan to the case, the fan for the cooler and you still have the exhaust fan. The liquid model replaces the rear exhaust fan with one of it’s own and adds no other fan. This means the liquid cooler will normally be quieter than the air cooling methods. The down side is that while the liquid cooler is very effective it will often not quite match the pure cooling potential of the larger, multi-fan, air coolers.

The radiator design however offers a neat benefit, the system evacuates all of the CPU heat from the case directly. By locating it as an exhaust from the case, all of the heat it has pulled from the CPU actually leaves the case straight from the radiator. This has the benefit of actually helping to lower the overall air temperature within the case. The amount this will help the air temperature is dependent on the cases air flow and your results will vary with different case designs.

The real drawback to the liquid solution is the cost. You can often find air coolers that can provide as much cooler for the CPU for less money. A good air cooler can often be found for as little as $30 but the liquid solutions are seldom seen on sales for less than $50.

When looking at these two coolers it is easy to get caught up purely in the idea of the CPU temperatures, that is their job after all. However I personally feel that this is a limited view. True the higher end air coolers can run the CPU cooler than liquid cooling solutions for less cost. However the difference we are talking about is usually only 2C to 5C in the extreme cases. These numbers might sound like a lot to some DIYers but they are not. In even the extreme case we are not talking about numbers where the CPU is going to have an issue. While the air coolers might offer a better temp to cost ratio, both systems are more than capable of adequately cooling the CPU.

Once we get over that pure CPU temp hump the differences become more apparent. The liquid solution offers easier installation, does not potentially limit RAM choices and is quieter. Add to this the fact that it could even provide a cooler overall environment to the PC and you can see why liquid is the choice I use in my personal builds.

Is one choice truly better than the other, I would say in the end no. Both have their pros and their cons. However I can say that I have found I am much happier with my builds using the liquid solutions.

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February 25, 2012 - Posted by | Editorial | , , , , , ,

4 Comments »

  1. Some other things that are good to know.
    1. Not all self-contained watercoolers are quieter than air coolers. The Noctua NH-D14 and Phanteks PH-TC14PE is quieter than the Antec Kuhler H20 620 and Corsair H70 that I’ve used (which have Noctua NF-P12 fans). Mostly because you can somewhat hear the pump and the noise from the airflow through the radiator. Not that big of a difference, really, but noticeable.
    2. Resale value is better for air coolers. I traded my Antec Kuhler H20 620 that I bought new for $50 for the Noctua NH-D14, which usually goes about $80 new. I also bought a slightly used Phanteks PH-TC14PE for $60. Self-contained watercoolers have an expiration date. That is, some day, the pump is going to stop working. One thing you won’t have to worry about for long term usage for air coolers.
    3. In high overclock situations, the top-of-the-line air coolers will perform better than self-contained watercoolers, unless it’s a 120.2 radiator.

    I agree with the slightly easier installation for self-contained watercoolers that have a 120.1 radiator, especially for small form factor builds. Some motherboards, particularly the EVGA ones, have heatsinks on their northbridges, which also cause installation issues on most of the top-tier air coolers where you can only use one fan instead of two.

    Comment by El_Capitan | February 25, 2012 | Reply

    • The sound issue you are referring to is something that a simple fan replacement can fix. I will agree that the liquid systems I mentioned seldom come with really quiet fans. However the noise level is not an issue until they get pushed. At lower speeds these fans are very quiet. As for hearing the pump, that is rare. There is an issue with liquid coolers than can throw someone the first time they hear it. On new coolers on ones that have sit for a long time unused there can be a gurgling sound heard for about 2 days. This is from air pockets building within the system and they need time to work their way out. I have spoken to people at Corsair, Coolit and Antec about this and it is normal and does not effect the performance of the cooler.

      The resale value is honestly something I never considered. Now that I have moved to these coolers I intend to use them until they fail and then buy another. In fact I seldom sold old air coolers. I do agree about the fact that an air cooler can technically not wear out. The fans can fail but the cooler should still be viable with new fans. However considering the life expectancy of these liquid solutions and the way technology changes I doubt most people would every hit the time that the system just wears out.

      Comment by Computer Ed | February 26, 2012 | Reply

  2. As an avid supporter of air cooling there is one fact where air cooling fail miserably. Weight. Bolting very large air coolers for supreme cooling performance in a traditional vertical motherboard mounting scheme is a risky business. Already large coolers crossed the line. One false move with big dual-heatsink air cooler can destroy motherboard. Of course nobody is dancing or jumping up and down when conducting the operation, but the fact still remains. Large air coolers with weight over 1kg are just as dangerous as very long VGA cards mounted without any support. It is frankly baffling why not one large volume case manufacturer haven’t noticed this problem. Of course there are HTPC/mITX but you can’t put much inside. For now people building powerful WS with air cooling which require horizontal motherboard tray are stuck in DIY department, going with server oriented 19″ rack (not a option with limited space) or adapting products from (e.g.) Mountain Mods or XSPC (prohibitive price if you want to ship that half-way across the world).

    Noise argument air vs liquid is rather pointless. LC can be much more louder than air and vice versa. Using fans delivered with with LC kit is bad idea unless you couldn’t care less about the noise.

    Comment by El Sid | February 27, 2012 | Reply

    • I will agree that the included fans are typically not the quietest fans but do not be so quick to replace them without some information before hand. These fans are typically chosen because they are able to maintain a high static pressure. Now this is not the same thing as move a lot of air, this is a very different effect and is not hardly mentioned on fan specs at all. If you are going to get replacement fans for a liquid cooling unit you NEED to make sure you get the higher static pressure to overcome the very dense fin layout of a radiator.

      That being said I have good news, we have almost finished the Computer Ed Radio Fan Test Rig, The system we have crated will allow an easy to see and understand way to look at the fans ability to maintain pressure as well as how much air it moves. Hopefully we will get this rolling in the next few weeks.

      Comment by Computer Ed | February 27, 2012 | Reply


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