Liquid Cooling 101 - Needs Updating

Discussion in 'Computer Cases, Power Supplies and Cooling' started by Geoff, Feb 2, 2006.

  1. Geoff

    Geoff VIP Member

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    Why Liquid?

    Multiple components within a computer generate excessive amounts of thermal energy, which must be removed to prevent damage. Items such as processor, video card's GPU/RAM, motherboard's chipset, memory, or hard drive are all generally dependent on air cooling mechanisms to remove this heat. These components are attached to a metal object (heatsink) with high thermal affinity and high surface area which conducts the heat away from the source and dissipates it into the air, often with the aid of a fan (active cooling) but occasionally fanless (passive cooling). An common example is that of the cpu, which is illustrated below. Note that the use of a fan is normally essential for a high thermal output device such as a cpu.

    [​IMG]

    While altering a heat sink's size and makeup can improve the effectiveness, it is still limited because air absorbs and transfers heat very slowly. To help counteract this, the fan can be run at a higher speed, but most people know what that means.. high performance usually comes with high noise. As systems continue to be upgraded, they require larger heatsink, and faster fans to help dissipate the increase in TDP (Thermal Design Power).


    Many people ask the question "why liquid?". Now liquid cooling isn't for everyone, as it poses many risks, however as processors and video cards advance, they require more power to run, and more power means more heat. Heatsinks and fans have been able to compensate for the increase in heat, with the introduction of more efficient heatsink designs and more powerful fans. However liquid cooling has a significant advantage over traditional air cooling - being that it can transfer heat away from the component much more quickly and efficiently. For the average to moderate computer user, air cooling will suffice their needs, however when you get into the high-end gamers and computer guru's who have all the latest and greatest technology, the need for better cooling becomes realized very quickly. In addition to being a high-end gamer, many people use liquid cooling to extend the limits of their components - by overclocking.

    I wont get into the details of overclocking, but if you wish to learn more, head over to OC101. As you overclock and start increasing the voltages, you cause the component to use up more power, which again means more heat. Overclocking on air cooling poses a severe bottleneck once you get to a certain point, whereas liquid cooling will allow you to keep the temperatures down, allowing you to overclock further. Although even water cooling becomes an issue as you reach a certain point, and thats where thermoelectric coolers and phase-change cooling come into play.

    Here we have one of the most common types of liquid cooling setups, which cools both the processor and video card:
    [​IMG]


    • Now before I get started on how exactly water cooling works, first you should know some of the basics, such as why we use certain liquids and not others, and then some scientific facts.



    Types of liquid:

    You may be asking yourself, "Why do they use water?". The answer is because when it comes to transferring heat, water is very efficient when compared to other liquids. Now the reason for water instead of mercury is simple - water is much easier and cheaper to obtain, and much safer to deal with.

    Although using distilled water is very cheap and effective, it's not recommended to use only 100% distilled water. The reason being that distilled water wants to maintain an equilibrium, and will take them from any source - such as the water blocks. So in other words, using 100% distilled water will eventually "attack" metallic sources, especially aluminum. Because of this many prefer specialized coolants for their system, which are made primarily out of water, but contain additives to help keep the system clean, corrosion free, and some add colors for a higher appeal.

    Water (after mercury) conducts heat the fastest. It's thermal conductivity is about 30 times greater than that of air. In addition, water can hold a lot more heat. Did you know that it takes over 4 times as much heat to raise the temperature of water as it does air?

    Because of these basic physical attributes, liquid cooling has considerable advantages of air cooling.



    Thermal Conductivity

    Thermal Conductivity is the amount of heat a particular substance can carry through it in unit time.
    No matter how flawless a surface may appear, it is highly irregular on a microscopic level. In fact, a CPU and heat sink may only touch at 0.01% of their total surface areas. Because the rest of the surfaces are separated by air, many high-heat sources would fail without a thermal compound/paste.
    [​IMG]
    [​IMG]

    The best thermal interface compounds contain elements with high thermal conductivity. These are generally more expensive, and so most stock heat sinks use cheaper graphite (gray/black pads) or silicon/zinc oxide (white paste) compounds.

    One of the best thermal compounds available for a decent price, is Arctic Silver 5. Silver is the second best conductor of heat (behind diamond), because of this, Arctic Silver 5 is rated one of the best thermal compounds (in it's class), available.


    Below is a table comparing the thermal conductivity of a variety of solids, liquids, and gases. The higher the number, the more heat it can obtain and transfer.

    [​IMG]



    Heat Capacity

    Heat Capacity is the amount of heat a particular substance can hold.

    The rate depicts how many kilojoules of energy are required to change the temperature of one kilogram of said substance by one Kelvin.

    [​IMG]


    What do all of these numbers mean?

    The above thermal conductivity shows why copper is the preferred cold plate material for cooling systems. It is extremely close to silver in performance, but only 1/6 the cost. Like most metals however, copper doesn't hold heat for very long, it needs to be absorbed by something else such as water or air.

    The specific heat capacities show water to be the best liquid for holding heat. Practically, it is also the best for transferring it.

    This would indicate the ideal configuration is to use copper to transfer heat from the processor (as well as other heat-generating parts), and to use water to absorb and move away the heat. Although there are many other factors involved, here you have the basic understanding of a liquid cooling system.



    Liquid Cooling Design


    At first glance, liquid cooling looks simple. Liquid is pumped through a cooler, it absorbs heat, and it's cooled back down with a radiator. But because you're working with liquid, the design principles become more complic
    ated.

    Most users are turned off by the idea of liquid cooling because they are afraid it will leak, and thereby destroy their expensive computer. Although this is one of the biggest risks, it's not all that common. Most professional systems have been tested for leaks before they are produced and shipped to customers, so as long as you follow the directions and make sure all the hoses are clamped down, you should be all set.

    However, even though liquid cooling kits shouldn't leak, you should always do a test run, by connecting everything outside of your computer, and let it run for a while to ensure that nothing is malfunctioning and/or leaking.

    Pump Reliability:
    The pump is a liquid cooling system's "heart". If the pump fails, its like the heart failing. This doesn't mean it is necessary for a liquid cooling system to use a $200 pump, although some pumps will work that are not designed for PC water cooling, it is recommended that you use one specially designed for water cooling.


    [​IMG]



    Corrosion:
    There are multiple types of chemical reactions that can be present in a cooling system that uses liquid. The most common is galvanic corrosion, caused by different metals in an electrolyte (in most cases, water). These varying electrode potentials can create a "battery" effect, damaging the metal.

    The worst situation in which corrosion might occur is by using regular tap water in a liquid cooling system. Tap water contains numerous trace elements that can accelerate galvanic corrosion. This is the reason distilled water should be used (not to be confused with drinking water).

    In addition to corrosion, tap water poses a significant risk in the formation of algae, especially if the system is turned off for a significant amount of time. When algae forms, it will cause certain parts to become clogged, and thereby causing the system to potentially become severely restricted.

    NOTE: Common cooling additives, such as antifreeze and Water Wetter, in addition to lowering the heat conduction of water, can degrade some polymers and are not recommended.


    Radiators
    By far, most computer liquid cooling systems use a "tube and fin" style radiator, typically a copper tube which snakes among multiple aluminum or copper fins. The tube and fin is popular for a good reason: it is cheap and easy to produce. Unfortunately, the benefits end there.

    Since copper and aluminum can not be fused together, and thin strips of copper can not be welded without melting, the actual liquid tube simply sits between its fins. These poor junctions drastically reduce heat conduction.

    As a base metal, copper can begin with a higher performance than aluminum in a radiator. Tube and fin radiators are generally made of copper because it can be easily shaped. But after prolonged use (beyond 3-6 months), heated water stains copper, resulting in a darkened internal coating which can lower heat transfer to below that of aluminum.


    The vast majority of automobiles no longer use copper tube-and-fin radiators due to these problems. The durability of aluminum is what makes it a preferred material in modern day heat exchangers.
    Between parallel liquid channels is a web foil (Louver fin) which provides exceptionally high heat dissipation. The entire assembly is tightly bound together through a process called brazing. Louver Fin heat exchangers provide the highest dissipation rate among radiator designs. Although more expensive to produce, the performance advantages are significant.

    [​IMG]


    The Water Block:
    Although the water block is a critical component in every system, it is not solely responsible for performance.
    Efficiency is relative to the entirecollection of components in a liquid cooling system, so altering something as little as air flow over the radiator can actually affect how well a CPU Liquid Cooler operates.
    [​IMG]
    Materials:
    Copper is the most practical metal to use in a liquid cooler cold plate. It provides a very high degree of thermal conductivity and is abundant at reasonable cost.


    Unlike a fan and heat sink, a liquid cooler does not need to be completely made of metal. Only the areas between the heat source (such as the CPU) and liquid pass significant amounts of heat. A liquid block made completely of metal is not only excessive, but will generally be heavier and more expensive.

    Size & Efficiency:
    The internal design of a CPU Cooler is everything. Poorly-designed liquid coolers will require a higher flow rate to maintain system efficiency. Like air-cooled heat sinks, they will also tend to be larger and heavier, which can place physical stress on the processor and motherboard.



    What Kit is Right for You?

    There are several types of liquid cooling setups out there to choose from, such as integrated, internal, and external liquid cooling kits.

    Many factors determine how well a certain liquid cooling kit will perform, ranging from the type of water block they use, down to the size piping. Manufacturers make budget kits available for under $100, that are only designed to cool one component (generally the CPU). However you should be careful when picking out a budget liquid cooling kit, because there are a few that are known to have issues such as leaks or poor pump reliability.

    Integrated Kits:
    Integrated kits are built into the computer case itself, which allows for easier setup and increased space inside the PC. The disadvantages would be that there aren't as many choices to choose from, and the ones that are available can be pricey - most range from around $250 up to $700 or more. Integrated kits would be ideal for users who do not want to have to gamble on kits, and then find out that the one they bought does not fit their case, and are also ideal for those who want a more professional appearance, without having components scattered among the case.

    The following two links are both 1KW units from Koolance.
    http://www.xoxide.com/koolance-pc4-1025bk-1kw-case.html
    http://www.xoxide.com/koolance-pc4-1036bk-1kw-case.html

    [​IMG]

    Internal Kits:
    Internal kits are one of the most popular liquid cooling solutions. It allows you to add liquid cooling to virtually any case, given that there is enough room for the pump, reservoir, radiator, and tubing. Unlike integrated kits, internal kits can be as cheap as $50 or even less, to several hundred dollars. These kits are for those who prefer to spend less money and install it into the case themselves, and there are far more internal kits available for purchase.

    As far as internal kits go, there are many factors that come into play when deciding on which one to get. Many people will lean towards the cheap versions just for that reason, they're cheap. While the lower priced kits will work, they arent designed for high end systems with a high thermal output. You will notice that many kits display a certain wattage, those dont determine how much power they use, it's how much power they are able to dissipate from the system while keeping the load temp at or below 55C, with an ambient temperature of 25C. So the higher it's rated, the closer it can become to ambient temp.

    An example of a high end internal kit would be the Swiftech H20-220 Apex Ultra. The 220 uses an APOPGEE Extreme Performance water block, MCW60 VGA water block, and an MCW30 chipset water block.
    http://www.xoxide.com/swiftech-h2o-apex-ultra-plus.html

    Going down towards the mid ranged kits, the Swiftech H20-120 Premium is similar to the 220, however only includes a water block for the CPU.
    http://www.xoxide.com/swiftech-h2o-120-premium.html

    CoolIt Systems has designed a liquid cooling system for a CPU. This may sound like an ordinary system, however unlike most others the CoolIt Freezone uses a thermoelectric CPU water block. Basically a thermoelectric cooler transfers the heat from one side (near the CPU), to the other (top), using electricity. Therefor it can transfer heat quicker, and actually get below ambient temp. However some smaller TEC's aren't very powerful, so if your using a high-end or overclocked processor, most likely you wont see any major differences in the temperature then that of a traditional liquid cooling solution.
    http://www.xoxide.com/coolit-systems-tec-water-cooling.html

    [​IMG]










    Sources:
    www.tomshardware.com
    www.frozencpu.com
    www.koolance.com
    www.guru3d.com
    www.endpcnoise.com
    www.petrastechshop.com
    www.xoxide.com
    www.wikipedia.org
     
    Last edited: Jan 19, 2010
  2. Motoxrdude

    Motoxrdude Active Member

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    8,932
    nice post, i definity understand the fine tuning of water cooling now, thanks!
     
  3. bigsaucybob

    bigsaucybob New Member

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    3,903
    very nice, well done.
     
  4. MIK3daG33K

    MIK3daG33K New Member

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    565
    Very nice, i have had both water and air. I had water for about 6 months and it was my first time experimenting with it. Although i enjoyed the expierence i think you can get the same temps with good air cooling for half the price and hastle not to mention the clutter. Therefore i would reccomend air, but very nicely done.
     
  5. ckfordy

    ckfordy banned

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    2,732
    very nice. good job.
     
  6. 4W4K3

    4W4K3 VIP Member

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    Well done, very easy to understand and covered the basics throughly.
     
  7. xtechforum

    xtechforum banned

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    73
    Looks good, but aqaruim pumps are very reliable :rolleyes: Well if you take out penguin's that is, get a ehiem and it'll last decades.
     
  8. skidude

    skidude New Member

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    Way to go dude, nice work :)
     
  9. Geoff

    Geoff VIP Member

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    Thanks for the compliments guys :)

    I would really like some admin/moderator input on this thread if you wouldnt mind.
     
    Last edited: Feb 3, 2006
  10. Cromewell

    Cromewell Administrator Staff Member

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    15,387
    Indeed, they are almost completely silent (you can't hear it over the ambient noise) when you run them properly too.
     
  11. bigsaucybob

    bigsaucybob New Member

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    3,903
    it looks really good. but i was thinking that there shuld maybe be something about how watevercooling is somewhat of a waste of money if the person doesnt plan on heavy overclocking. i dunno maybe u were just trying to talk about parts of the watercooling, thought i wuld throw it out there.
     
  12. xtechforum

    xtechforum banned

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    73
    I think it IS a waist of money because i can cost over a hundred dollars when you could just buy the next rated CPU, unless you have the MAX in the first place. so i agree with bigsaucybob
     
  13. atomic

    atomic New Member

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    707
    Well fortunatly this is not, IS IT WORTH IT 101. Im sure it was a guide to liquid cooling, and to advice and teach people about liquid cooling, So if its worth it or not is not a topic here. :)
     
  14. Chris Chan

    Chris Chan New Member

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    509
    Nice work, deserves a sticky.
     
  15. Geoff

    Geoff VIP Member

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    What do you think praetor?
     
  16. ReturnToEmpire

    ReturnToEmpire New Member

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    421
    hes gonna say something like, calling out admins personally will get your thread ignored. just my guess. lol nice thread though. i like all the science behind it.
     
  17. dragon2309

    dragon2309 P.I Dragon

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    Lol, thats exactly what i was thinking lol.... and yeh, thsi should so be a sticky, nice work geoff, i can see that probably took you a darn long time to complete.
     
  18. helmie

    helmie New Member

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    1,205
    Yeah, thats a great guide. STICKY!!! NOW!!!
     
  19. ghost

    ghost Active Member

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    2,265
    yeah thats a gr8 bit of work there GEOFF, you blatenty deserve to be a MOD NOW :D:D:D
     
  20. Geoff

    Geoff VIP Member

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    37,673
    Praetor will be looking this over very soon (hopefully ;)). Thanks for the compliments guys.
     

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