3. Radiator / Fans
The radiator is an essential part of a watercooling system, as it removes the heat in the water deposited form the waterblocks and the pump. Without it the system would overheat in a matter of seconds. Radiators come in many different shapes and sizes. Some are better than others, but it all depends on application and the fans chosen. There are two types of radiators that are commonly used in watercooling setups. The first are the purpose built radiators that are designed to accommodate 120mm fans (some also use 80mm fans) and have different types of hose barbs for a myriad of applications. The second are heatercores. Heatercores are the heating elements used in car heating systems. There are plus and minus’ to both solutions that I will discuss.
Before I continue with explaining the types of radiators there are a few basic terms used to describe radiators that should be explained. The first commonly used term that is often confused or misunderstood is "passes". All radiators can be described in terms of passes. Passes are essentially how many directions the water goes in the radiator while being cooled. Generally watercooling radiators are 1 or 2 passes. The higher the number of passes the more restriction due to having the water change flow direction and that generally the area the water has to flow (per pass) in higher pass radiators is smaller. For a graphical explanation of "Passes" take a look at
THIS picture.
The second bit of terminology is "Rows". Rows refer to the number of flow tubes the radiator has, with regards to depth. By depth I am referring to the thickness of the radiator in the direction of the airflow, and not the water channels. The picture
HERE shows a CoolRad 12-T which is dual row. Each row looks like a column of elliptical holes. A single row radiator would be one column of those holes, and would be accordingly about 50% the thickness.
Now back to the radiator types.
The purpose built radiators have their plus’, and their minus’. They are a good choice for their ease of use and good performance, but they do not provide the absolute maximum performance. There are a few reasons for this. Mainly it is due to their basic design. Because they are purpose built there is not the essential equipment to build the radiators as they are made in car radiators. The way that they are designed causes two pitfalls. The first is that they are a bit more restrictive, and the second is that they are not as efficient at heat transfer. A dual 120mm (uses 2 120mm case fans on each side) version will run anywhere from 45 to 100 dollars. Now you may wonder why you would want one of these radiators after hearing what I said, but do not be worried. These radiators will perform admirably in near any system if used correctly. They are great for the user who wants a very clean looking system and doesn’t want to hassle with having to modify a radiator to get it to work in their rig. The purpose built radiators come in two general styles. “Low Noise” and “High Noise”. The low noise fans are optimized for fans like the Yate-Loon D12SL-12 and other quiet, 25mm thick fans. These radiators are either thin, like the Black Ice Pro’s from HWLabs or have a lowered fin count (~12 Fins Per Inch) to reduce the airflow restriction. The reduced airflow restriction allows the quieter fans to be used without suffering great performance losses. Conversely, the “high noise” radiators are designed for fans around 100CFM and 38mm thick. These fans can cope with the higher fin count (17-25 FPI). The high noise radiators do have a higher maximum performance potential, but at a sacrifice of noise. If noise does not bother you, then a high noise radiator is the way to go, otherwise stick with the low noise radiators. For a complete listing of these radiators check out my Parts guide
HERE.
The big difference between the “high noise” and “low noise” radiators is the fin density which I mentioned earlier. Here is a simple image demonstrating the difference in fin density between the two styles.
”High Noise” – High Fins Per Inch
”Low Noise” – Low Fins PerInch
The radiators come in 7 different sizes; Single 80mm, Dual 80mm, Single 90mm, Dual 90mm, Single 120mm, Dual 120mm and Triple 120mm. (Thermochill came out with a 160mm radiator for 120mm fans as of May 205. It performs slightly worse than a dual 120mm radiator) The mm sizing refers to the fan that is being used and the single, dual and triple refers to the number of fans that can be attached to each side of the radiators face. I should mention that anyone building a system that is either overclocked or uses both a GPU and a CPU waterblock will want to stay away from the 80mm sized radiators. They do not dissipate a great deal of heat and would give abnormally high temperatures for a watercooling system. I would suggest a single 120mm as the minimum for a single CPU setup, a dual 120mm for a CPU and GPU setup, and a triple 120mm for those who want the absolute maximum performance that these types of radiators can provide.
UPDATE: As of October 2005 Thermochill has released the PA series purpose built radiator and for fans below 100CFM they are the pinnacle of performance, surpassing all other radiators including heatercores in sub 100CFM (per fan) applications.
The other type of radiator that is quickly gaining popularity is the heatercore. These, as I mentioned previously, are merely air conditioning heating elements which have hot water pumped into them and air pushed through them to give you warm air in your car. In our watercooling loops we are essentially doing the same thing, but with much lower water temperatures. These heatercores are excellent for watercooling as they are highly efficient and provide the absolute maximum cooling per size that you can get. They are also very low restriction which lends themselves well to our purposes. They come in various sizes, suitable for a single 120mm fan, dual 120mm fans, and quad 120mm fans. The other thing that is great about them is that they are DIRT cheap. You can pick a dual 120mm one up for less than 20 dollars at your local auto parts store. The most commonly used one is the 2-302 for the 77 Bonneville with AC. A variant of this is the 2-199, which is also for the 77 Bonneville, but is without AC. As good as they are, there are issues to be had with heatercores. First, they need to be modified for use in watercooling. They start out with large copper (sometimes brass) fittings which can either be hack sawed off to the desired length (if your tubing is the appropriate size), or if you’re in need of a different fitting size, you must take a blow torch and remove the tubes all together, and place your own fittings on. To do so requires copper soldering (brazing) knowledge. The other issue with them is that you cannot just mount the fans to the face of them. They need to be used with a shroud. What the shroud does is move the fans away from the face of the radiator, thus lowering turbulence and the large dead spot in the middle of the fan. This does two things. It increases airflow through the heatercore, and reduces noise. There are various manufactures of shrouds. The best of which is sold by the Xtreme Systems forum member “Weapon”. The shrouds are partially manufactured by our forum member "Malph", and the finishing job is done by "Weapon". They sell shrouds for the 2-302 and 2-199. I currently am using one of their 2-199 shrouds, and can attest to its superb quality. There are several other shrouds which can be had over at
www.dangerden.com and
www.vouyermods.com . I also have the dangerden shroud for the 2-199. It is nice, but is not nearly as effective as the “Weapon” shroud. As with the thicker purpose built radiators, the heatercores are incredibly thick, and thus provide very high airflow resistance. Because of this, more powerful fans are needed. 38mm fans are a must when dealing with heatercores. For most people a 38mm thick fan at 12volts is too noisy, so running them at 7 volts is a good option. Their high airflow restriction would classify the heatercores in the “high noise” category of radiators, because if low noise fans are used with them, performance will greatly suffer.
I mentioned earlier that there was also a quad 120mm heatercore. Craig and Weapon over at XS dubbed it the monstercore. This thing has 2x the performance of a 2-302 or 2-199 and anywhere from 2-3x the performance of a dual 120mm purpose built radiator. This item is not generally used by anyone, but Weapon does also make a shroud for it if anyone is interested. There are several places that heatercores can be purchased. As I mentioned earlier, you can get one at your local auto parts store, but it will be unmodified. Doing the necessary modifications is not something that excites most users who are new to watercooling.
Thankfully there is an alternative. There are several sites online that sell pre-modified heatercores. Among them are the aforementioned danger den, vouyermods, and other various sites. Weapon also sells modified 2-302 heatercores with 1/2inch and 5/8inch fittings in any color. Pricing on modified heatercores ranges from 35-50 dollars.
As of April 2006, Weapon is not currently producing heatercore style radiators, therefore anyone looking to buy a heatercore will have to purchase it through DangerDen or Vouyermods. More information about these companies is available in my stores guide located
HERE
A basic rule of thumb here. If you have warm air pumping out of your radiator that means that it is NOT up to spec and NEEDS to be upgraded and/or more powerful fans used.
3b. Radiators to Stay Away From
Now that I have gone over which of the radiators that would be suitable for watercooling, I feel that I should warn potential watercoolers of which radiators to stay away from. Several years ago, condenser style radiators, which are used for refrigeration systems, were popular when we did not know better. Since then, they have lost their popularity, but they still seem to be alive and kicking in certain parts of Europe due to incredibly strong misinformation on the part of manufactures. Their popularity is what motivated me to write this section of the guide.
Anyway, back on topic. To avoid these condenser style radiators we need to know a bit more about them. First off, they can easily be spotted by the numerous 180 degree bends of tubing on both ends. Secondly, you can spot them by their characteristic round tubes. The last common characteristic is their incredibly high fin density which is designed for VERY powerful fans. The prime example of these radiators is the
Mora2 which is pictured above. You can see the numerous 180 degree turns on it, which creates an incredible amount of restriction for the pump leading to VERY low flowrates. What you can also notice is the round tubes. The round tubes provide less than adequate cooling efficiency because less of the water is close to the walls of the tube, unlike the flat tube radiators which I described earlier. To better show how much more efficient flat tube radiators are, look at the picture below. The blue parts are the cooler water, being cooled by the sides of the tube, and the red is the warmer water, which is insulated from the cooling effect of the walls by the water closer to the tubing wall.
While I didn’t spend much time describing the condenser style radiators, I hope that I got the point across as to why they are so poor for watercooling use.
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