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Thread: Passive Rads

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  2. #2
    Xtremely slow runner antipop's Avatar
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    There's no such thing as a passive rad unless they're HUGE, i think those are big but i don't know they perform
    However for the price i'd rather go with a heatercore a push pull and a baybus
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    Those rads are ok, but only if you are seeking a quiet system.. if you want to oc much, then theyre not good..
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    Xtreme Enthusiast Jabo's Avatar
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    antipop, long time no see mate! what's up?, you good?

    I love design and precision of manufacture.
    They look really sweet, specially the tower one.

    They may be good for TEC'ed system since passive rads work the best with substantial temp delta.

    They have one fundamental design mistake which I'll try to unearth in my 'Project codename: Medusa' write-up coming soon to forum near you
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    Xtremely slow runner antipop's Avatar
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    Yeah it's been a long time, the year has been rather busy for me and now my computer is down. However i hope to be back soon. I don't really have time to spend on comps but i'll still come here to help people and keep up to date

    I'm impatient to read your write-up
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    they will not dissipate the heat a TEC puts out.

    I guaruntee it.

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    Xtreme Enthusiast Jabo's Avatar
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    Originally posted by sandman
    they will not dissipate the heat a TEC puts out.

    I guaruntee it.
    Oh yes, very happily they will, water will be at around 45-50 degC mark and using MCW5000P-T as a example one could anticipate (based on my P42.0@2.4) CPU temps at around 6-10C idle depending on other factors.
    You see, the higher water temps the better they work, passive rads that is.

    Not this coming weekend but the following it should be posted right here with lots of tasty piccies and simple expalnation of idea. I wanted to patent it but then realized that for this kind of design there isn't going to be lots of commercial value. It is strictly for enthusiasts but dead simple to make and dirt cheap too compared to other solutions and especially these Innovatek rads linked here by Z-301 (great find mate! - don't buy them yet, wait for my write-up )
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    You still need a lot of airflow for passive cooling solutions - you just don't need as much pressure as say an automotive heatercore.

    I don't really see how the passive rads can be more efficient than a much smaller (and cheaper) active solution.

  9. #9
    Xtreme Enthusiast Jabo's Avatar
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    The statement on Innovatek's website is to say the least, doubtful, unless rad they allude to is complete krap.
    It's about air, not air flow in passive cooling solutions - convective heat transfer.
    You are right thinking that the more air flow the better, if you were to piont a normal room fan on Innovatek's beauty it would most certainly leave ALL the competition in it's wake!
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    why passive? just get a large rad and mount a couple of silent 120mm fans on it. to get the same temps with a passive rad it would have to be 2 times in size or even bigger...

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    Originally posted by Jabo
    It's about air, not air flow in passive cooling solutions - convective heat transfer.
    No, it's about air flow. Air is a low-mass insulator, making it a terrible medium for convective cooling. Heat transfer always benefits tremendously from mass transfer (in this case air flow), whether you try to label a device as convective or not.

    All passive indicates as regards a cooling device is that such a device doesn't have an integrated active mechanism. That doesn't mean it doesn't need mass transfer to work. For example, the primary driving force behind the BTX FF design is the ability to use passive cooling - which in turn is only made possible by airflow improvements in the BTX spec.

    There's nothing magical about passive cooling or convective transfer that eliminates the benefit and/or need for mass transfer.
    Last edited by shrae; 02-26-2004 at 04:01 PM.

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    convective cooling only works with soldi materials and some liquids. water and air are both good heat insulators! if you have a passive rad the atoms in the air will hit the atoms of the heatsink and take some heat from them away. but energized "hot" atoms dont hit "cold atoms" in the air and hand the heatenergy on like copper and other metals do. once air atoms heated up they move faster. the hot air expands and moves upwards making room for fresh cold air that can take heat away from the rad.

    so even a passive rads need airflow to work, the diference is that it only "lives" of the airflow the heat it carries creates itself.

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    The problem is that the rad only has 35cm (45cm for the big version) to work with. If we were talking about something much bigger, I could lend more credence to its efficiency through convection. The flow rate of water through the rad is also a big question.

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    wouldnt those work a whole lot better if they were copper?
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    Guys, it says right here:
    The MAXI version is huge, about twice the size of the standard version and offers about 1/3 more cooling power! Manufacturer testing reveals performance levels greater than the Dual 120mm fan radiator
    If it's printed on a website, it *has* to be true.

    Seriously though, they look like they have incredibly restrictive fittings. Probably cool if you want a totally silent computer with very *little* overclocking. I'll take a fan setup with a rheobus so I can have it quiet while I work and crank the fans while I game.

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    Xtreme Enthusiast Jabo's Avatar
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    share , saaya -> I agree with you guys 100%, thaat's exactly how it works.
    Without air movement or air flow or however you call it there is no cooling at all. Passive cooling uses economy of scale and is always HUGE compared to active solutions (Innovatek's is not and most probably will not work and defenetily will not outperform nor even get close to any active cooling setup unless made in such a way as to prove Innovatek's point, if you know what I mean here).
    The only thing I like with Innovatek's product is design, it is simply well designed from aesthetic point of view.


    Christ0f -> yes, copper would be much better choice but price would be 5 tiimes more
    Stock is never good enough!

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    Xtreme Addict kommando's Avatar
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    They're alright but would be better with alot more surface area.

    Ripping it up on old technology
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    Xtreme Member Jimbo Mahoney's Avatar
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    Just to add some more opinions to the mix:

    What about a hybrid copper / aluminium rad? ie Copper pipes with aluminium fins? Copper is a better conductor of heat, aluminium is a better radiator / convector of heat. This is the principle utilised by HSF manufacturers and I have found it to be true in low airflow situations. A solid copper sink was TERRIBLE in my quiet / low CFM aircooling setup, but a hybrid copper-base / alu fin sink was much better.

    In addition, merging the theories mentioned (more airflow is better and higher delta T is better for passive) - these two go hand-on-hand. With a higher delta T, hotter air will be produced in the vicinity of the rad, causing a greater airflow to be established by the decrease in air density. Get me?

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    Registered User 8-ball's Avatar
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    Originally posted by Jimbo Mahoney
    Just to add some more opinions to the mix:

    What about a hybrid copper / aluminium rad? ie Copper pipes with aluminium fins? Copper is a better conductor of heat, aluminium is a better radiator / convector of heat. This is the principle utilised by HSF manufacturers and I have found it to be true in low airflow situations. A solid copper sink was TERRIBLE in my quiet / low CFM aircooling setup, but a hybrid copper-base / alu fin sink was much better.

    In addition, merging the theories mentioned (more airflow is better and higher delta T is better for passive) - these two go hand-on-hand. With a higher delta T, hotter air will be produced in the vicinity of the rad, causing a greater airflow to be established by the decrease in air density. Get me?
    When will people learn that HSF manufacturers only use aluminium because it is:

    cheaper
    lighter
    cheaper
    easier to manufacturer
    cheaper

    and did I mention cheaper.

    I will concede that aluminium DOES radiate thermal energy better than copper. However, raidation is simply not a significant mode of heat dissipation unless you are cooling something in a vacuum. It also needs to be significantly hotter than the surroundings to get a reasonable amount of heat dissipation.

    As for convection.

    Convective heat transfer, the process by which thermal energy is transferred from a solid into a moving body of fluid, such as water in your water block, or air flowing through a rad, is INDEPENDENT of the material of which the rad/block is manufactured.

    The only bearing the material has on the heat transfer is getting the thermal energy to the surface. Once it is at the surface, it may as well be glass for all I care. The only thing which determines how well the thermal energy is dissipated in to the air flow, is the physical properties of the liquid/gas, the flow regime, and the geometry of the transferring surface.

    8-ball

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    Xtreme Enthusiast Jabo's Avatar
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    Exatcly right with air thingie, that's how convective cooling works by creating a colmn of upward moving air.

    The same construction blocks/heatsinks but one all copper and other copper/alu and all copper leaves hybrid in the dust picking up it's teeth
    It simply because of thermal properties of these two metals.
    Where did you hear that alu is better radiator?
    Manufactirers use because is significantly cheaper to obtain and work with.
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  21. #21
    Registered User 8-ball's Avatar
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    Aluminium IS a better radiator, in that its radiating properties are closer to that of a black body than copper.

    However, as I said, radiation simply doesn't figure significantly enough for using aluminium to perform better than copper due to the performance hit associated with the conduction of thermal energy to the dissipating surface.

    Just about the only scenario where aluminium's better radiating (and let me point out, that it isn't that much better) properties justify it's use are in space, where ALL thermal energy must be dissipated by radiation due to the vacuum.

    As long as there is some medium to carry the heat away by convective heat transfer, then radiation properties are pretty irrelevent.

    8-ball

  22. #22
    Xtreme Enthusiast Jabo's Avatar
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    Again, naming things...
    I didn't men radiative energy dissipation...
    never mind
    Stock is never good enough!

    M E D U S A

  23. #23
    Registered User 8-ball's Avatar
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    Originally posted by Jabo
    Again, naming things...
    I didn't men radiative energy dissipation...
    never mind
    As i understand it, the myth that aluminium is a better radiator, (and a common myth) is down to the radiative properties of the materials. It is true that aluminium is a better radiator, but radiation doesn't playa big enough role for this fact to outweigh it's much poorer conductivity.

    As I alos said, and you correctly backed up, cost is the predominant factor in using aluminium over copper for thermal management applications, and maybe weight.

    8-ball

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    Xtreme Member Jimbo Mahoney's Avatar
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    Hmm.

    Interesting.

    8-ball, are you saying that a hybrid alu-copper sink exists purely due to cost, or is most of your argument focussed on radiators?

    I take on board your comments on radiator/passive/material performance, but I still find it hard to believe a solid copper sink will perform the same as a hybrid sink (given the same active airfllow).

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    Registered User 8-ball's Avatar
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    Originally posted by Jimbo Mahoney
    8-ball, are you saying that a hybrid alu-copper sink exists purely due to cost, or is most of your argument focussed on radiators?
    My argument apllies to both radiators AND heatsinks.

    Originally posted by Jimbo Mahoney
    but I still find it hard to believe a solid copper sink will perform the same as a hybrid sink (given the same active airfllow).
    To the contrary, an all copper heatsink will perform BETTER than a hybrid alu/copper heatsink in ALL cases, provided the same airflow.

    Almost ALL of the thermal energy is transferred to the air via convective heat transfer, a mode of transfer where the material from which the heat is being transferred is irrelevent. As such, a copper heatsink will always perform better than an identical one of mixed copper and alu, since the major performance factor is associated with conducting the thermal energy from the cpu to the dissipating surface of the fins. And since copper has a far superior conductivity that aluminium, there is no argument as to which performs better.

    8-ball

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