Macbook pros and thermal dissipation - any engineers out there?

Discussion in 'MacBook Pro' started by Revmax, Oct 2, 2012.

  1. Revmax macrumors newbie

    Joined:
    Oct 2, 2012
    #1
    Hi,

    SO I was talking about this with my wife at dinner and realized neither of us could figure this one out so if there are any engineers out there, I'd love to have a definitive answer of some sort...

    Basically, I've been lurking/researching threads on various forums trying to figure out what would be my best option for a laptop cooling pad for my macbook pro

    Based on what I've absorbed, I've taken various steps to keep it cool, including:

    - Configured w. 512 GB SSD (I just did that cause it sounded neat but some folks say these run cooler)
    - don't play video games on it
    - turned off automatic graphics switching
    - installed iStat

    K, so, I did these things cause a friend's MBP recently died (logic board fried) and he swears it cause he ran it too hot, for too long

    This is the first laptop I've owned, so now I'm geeking out on trying to figure out what all the variables are for this

    First thought was to get one of those "laptop cooler" things with the fans, so I got a Zalman 2000 off of amazon.

    It does seem to keep both ambient temp and CPU about 4 degrees lower (celsius) when surfing the net - 57 degrees CPU rather than 61

    Now, I realize that NEITHER of these temps are anything to worry about I just am curious about the following:

    So, obviously most of the laptop coolers on the market are made for PCs, which have vents on the bottom, wheras macs dissipate heat through the hinges

    I picked up my MBP and sure enough the zalman is basically just blowing cold air at the flat surface of the bottom - NO air is getting inside the machine at all, so how effective can that be (already answered that - seems to be about 4 degrees C less than when off)

    But assumin I want to really understand the physics of this and the MBP is already engineered to cool itself admirably without extra fans blowing at its bottomside - lets just take that as a given - then it seems a passive cooling device would make more sense

    So, of those, some folks say that something like the mstand works as an effective heatsink since aluminum conducts heat so effectively

    http://www.amazon.com/Rain-Design-10032-mStand-Laptop/dp/B000OOYECC

    OK, makes sense, if the aluminum case of the mac itself is designed to dissipate heat then something like that would effectively increase the surface area of the case and so dissipate heat at a much greater rate

    This looked good too, and similar claims are made for it (the omnistand):

    http://www.radtech.us/Products/omnistand/

    BUT, in neither case is the aluminum of the MPB case actually in contact with the aluminum of either stand - they both have rubber pads which prevent metal/metal contact (and thus, scratching)

    So, theres at least a thin layer of air between the two aluminum surfaces - so can either stand really act as a "heat sink" since air is such a terrible conductor? I do not understand the physics of that. Wouldn't they function as INSULATING layers instead?

    If so, then wouldn't it make much more sense to just expose as much of the case to the air as directly as possible with something like the incline pro:

    http://www.koyono.com/Inclinepro-Portable-Ergonomic-Laptop-Cooling-Stand-p/inclinepro.htm

    or the "Opteka X-Stand Ergonomic Portable Natural Airflow Cooling Stand"

    http://www.amazon.com/gp/product/B004ARHYZS/ref=oh_details_o00_s00_i00

    or the bookarc:

    http://twelvesouth.com/products/bookarc/

    So that's an engineering question - if the aluminum case is already so effective at dissipating heat, and since these aluminum stands etc don't actually have metal to metal contact - then would they NOT actually effectively increase the surface area? WOuldn't they actually function as INSULATORS?

    Wouldn't it be BETTER to chose some alterate means of exposing as much of the case to the air as possible, either by lifting it off the desk or else truning it on its side?

    Is this whole "stand as heatsink" thing just a scam based on a misunderstanding of thermodynamics?

    Or is there something about "heatsinks" and how they work I'm not just getting here?

    Is the case itself an effective enough dissipating device that all it needs is adequate airflow, or would it actually be able to dissipate heat more effectively if it had a greater surface area?

    Thanks!
     
  2. zwodubber, Oct 2, 2012
    Last edited: Oct 2, 2012

    zwodubber macrumors 6502a

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    #2
    Short reply to a long question and just my personal experience. I keep mine on an Mstand mostly because it keeps it more inline with my displays and looks like an apple product. As you stated it does not noticeably help as a heatsink as the rubber prevents aluminum to aluminum contact. I did some thermal scans to prove this.

    The cooling pads are pretty ineffective also and once again as you pointed out MBP's vent through the hinge and dissipate heat through the aluminum. I got the laptop for portability, not to use on my lap so heat issues aren't really an issue for me.

    [​IMG]

    Bottom


    [​IMG]


    [​IMG]
     
  3. Mrbobb macrumors 601

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    Aug 27, 2012
    #3
    Ur having an O.C.D. episode for first time owners. Before u know it, ur gonna get ketchup on that thing.

    Computers, like car engines are designed to run hot without damage. It has built-in mechanisms to slow/shut things down before damage occur.

    Ur "friend's" anecdote is 1 person experience which should not be extrapolated to the whole population.
     
  4. Revmax thread starter macrumors newbie

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    Oct 2, 2012
    #4
    Hi thanks for your reply, I've been using Apple computers since 1987, so this is probably my 7th or 8th Apple, its just my first laptop

    ANd yes I am slightly OCD, I am just genuinely curious about how heatsinks work - I see an enormous amount of speculation on these boards but zero empirical data to back it up

    As I said, since the MBPs dissipate heat through the hinge, the standard coolers don't make sense

    IN addition, stands touted as heatsinks have rubber pads, thus it would seem to me that they can't actually function as heatsinks, if anything they would seem to provide an insulating layer of air, unless there is just something about the physics of this I don't understand, e.g., convection currents or whatnot

    It would seem to me that the best approach, particularly if you're operating in clamshell mode (which I am) would be to aircool the MBP via something designed to expose the entire device to the air, e.g, the bookarc, etc

    ----------


    Thank you this is fascinating! I have wanted to see thermal imagery of an MBP, this helps
     
  5. snaky69 macrumors 603

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    Mar 14, 2008
    #5
    Aluminum is an excellent heat conductor, though none of the electronic components actually touch the case itself. Nearly all heat that is transferred to the casing of the macbook pro is transferred by convection and radiance.

    The macbook pro uses heatpipes as seen in the picture I lifted from ifixit.com(the person's hand is holding the heatpipes and cooling fins.)
    [​IMG]

    Those pipes carry heat to the copper heat sinks at each end. A heat sink is usually a good conductor with a large surface area, hence the fins. Fins increase surface area greatly and are generally very effective when correctly designed and used.

    Once heat is transferred to the fins by conduction through the heatpipes, air is blown across them by the fans to cool them through convection. Since heat flows from hot to cold, the heat coming from the computer replaces the one that has been dissipated and the cycles goes on and on...

    As far as cooling using stand or fans, the only way I can see it helping is by allow more airflow along the various surfaces of the casing. A colder casing will be able to absorb more heat faster, which is why you saw a slight decreased in temps using your fan on the bottom.

    Another way which isn't currently doable with stands is to increase the amount of air the fans can intake and increase the flow along the cooling fins. This in turn increases convection around the fins, making them dissipate heat faster.

    Or, one could attempt to lower the temperature of the air being taken in by the fans to be blown through the fins.

    All in all, in my humble, nearly graduated mechanical engineering opinion, the MacBook Pro is quite capable of cooling itself, the cooling system is about as well designed as it can be considering the size constraints it has due to the amount of space available in the casing. The aluminum enclosure helps cooling as a side effect, but I feel most of the heat comes out the exhausts.
     
  6. thermodynamic Suspended

    thermodynamic

    Joined:
    May 3, 2009
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    USA
    #6
    Only if the metal is touching (e.g. a heatsink).

    Otherwise the chassis acts like a container.

    The MacBook casing is NOT designed to dissipate.

    "aluminum vs plastic insulation" might help in a web search, but plastic is more porous - air can seep through and, thus, cool faster.
     
  7. Pentad macrumors 6502a

    Pentad

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    Nov 26, 2003
    Location:
    Indiana
    #7

    This is not correct. There was an article with Bob Mansfield, Dan Riccio and Jonathan Ivy talking about the MBP and the move to aluminum (this was some time ago) and all stated that aluminum allowed a greater heat dissipation rate than what they saw with other materials.

    In fact, they talked at length about the different materials they looked at (for strength, durability, etc) and lessons they learned in the past (plastics, Titanium, etc). In the end, they found aluminum to be the best at serving all of their needs.

    To be honest, I accidentally ended up in this thread so I don't really care, but this is just an FYI. If you do a search on Google I'm sure you can find the article.


    -P


    People don't realize it because Steve and Jonathan usually got/get the media attention but Bob and Dan are very smart.
     
  8. Revmax thread starter macrumors newbie

    Joined:
    Oct 2, 2012
    #8

    Interesting thank you for the overview. SO to recap, it sounds like the heat that is dissipated through the aluminum casing occurs through internal convection. So just keeping the case itself cool (via airflow) is a sound practice in that it facilitates heat dissipating from the entire device

    That said, most of the heat dissipation (if I'm understanding you correctly) takes place via internal fans circulating air over the internal cooling fins and out the exhaust.

    THe cooling fins themselves draw heat from the cooling pipes which absorb heat from other components in the inside of the machine in a purely passive manner.

    So in summary - the MBP well engineered to cool itself. My takeaways are as follows:

    1) I'll note that there are apps which do let you increase the fan speed (e.g., to 4000) so it sounds like that would be the single most effective means (besides keeping it clean of dust, etc) of cooling the internals


    2) Sounds like it doesn't hurt to keep the case cool, primarily by allowing air circulation all around it, it sounds to me also like a simple stand which exposes as much of the case as possible to airflow would be just as effective as a "cooling pad" for this purpose

    THANKS!
     
  9. angelsguardian macrumors regular

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    Jun 11, 2012
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    North East Scotland
    #9
    Buy a 2012 machine, it runs much cooler than the 2011 I had before. Much, much cooler.
     
  10. snaky69 macrumors 603

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    Mar 14, 2008
    #10
    You did understand me correctly yes. I'm in no way, shape or form an expert and this pretty much sums up my knowledge on such things.
     
  11. Revmax, Oct 3, 2012
    Last edited: Oct 3, 2012

    Revmax thread starter macrumors newbie

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    Oct 2, 2012
    #11
    THanks, that's interesting~!
     
  12. sno1man macrumors regular

    Joined:
    Oct 24, 2011
    #12
    Speaking not as an expert in thermodynamics, but being responsible for about 500 macs and about an equal number of PC's i do want to clear up one misconception about SSD's

    While they can be cooler than regular hard drives under light to medium duty, in heavy use they can be hot or hotter than a conventional drive.

    Specifically if you have an app(apps) that do a lot of writing to the drive on a regular basis. Worst case examples are database servers or web servers

    But surprisingly Adobe (photoshop, illustrator, indesign) Quark and some of apples own apps (aperture, FCP) also write to the disk almost constantly especially with big projects.

    Long story short, the harder you work the machine the greater the heat regardless of drive type

    PS: again anecdotally, the toshiba based drives seem to run cooler than the samsungs
     
  13. brucethemoose, Oct 3, 2012
    Last edited: Oct 3, 2012

    brucethemoose macrumors newbie

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    Jan 2, 2012
    #13
    I'm an EE student, with alot of chem/thermodynamics and experience with CPUs.


    If you're really worried about heat, follow this guide (or the one for whatever macbook you have).

    http://www.ifixit.com/Guide/Reapplying-Thermal-Paste-to-the-CPU-and-GPU/9587/1

    But use shin etsu X23D thermal compund, or this one if you're feeling adventurous.
    http://indigo-xtreme.com/


    It may not feel much cooler, but your MPB will be significantly better at getting heat out of the case. Think 10C-15C+ cooler... more than any fan or stand would ever do. This is an extreme mod: it'll cool it down ALOT, but it ain't easy to do. Aside from replacing the heatsink altogether or using the computer in a fridge, this is probably the best thing you can possibly do.



    Otherwise, I'll chime in with other info... Alot of programs are bottlenecked by Disk I/O. a.k.a the hard drive/SSD is the slowest thing in your Mac. The Samsung SSDs tend to be the fastest in the rMPB, so they'll be less of a bottleneck, allowing the CPU to work faster and produce more heat.

    However, hard drives are the first thing that heat usually kills in laptops. SSDs, on the other hand, are basically indestructible. So don't go out and replace your SSD.


    Airflow around the case should help a little, but not much. Turing down your A/C would help some. If you can get a good contact, a metal table will be much more effective (I remember how my old PS2 ran alot cooler on a metal table). If you can't get a solid metal on metal contact, it's pretty much useless.



    If you don't mind something ugly, sticking a peltier cooler with a heatsink/table on one side and your mac's body on the other would cool it really well.
     
  14. Revmax thread starter macrumors newbie

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    Oct 2, 2012
    #14

    Hi, thanks so much! Really not worried, just curious... I plan on owning this for a long time, so all this info is getting filed away for some day I might actually need it - thank you!
     
  15. mgipe macrumors demi-god

    mgipe

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    CA
    #15
    Excellent summary. I think you've got it!
     
  16. TheRdungeon macrumors 6502

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    Jul 21, 2011
    #16
    I've got SMC set to 2400rpm on both fans when on power, which you can't hear at all but still gives good cooling
     
  17. SavMBP15 macrumors 6502

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    Mar 26, 2010
    #17
    Let OS X keep the fans running at whatever speed they deem to run at. Your friend's logic board did not get damaged from excess heat. There are protections built into the bios to prevent that.

    But the best way to make sure nothing ever happens is to never use it.
     
  18. Queen6 macrumors 603

    Queen6

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    #18
    If you are concerned about temperature and want to reduce it elevation of the rear of the machine helps, as sitting flat on the desk only reflects the heat back to the base of the Mac. You can buy passive aluminium coolers like Rain Designs Mstand or iLap. Most powered coolers are designed for PC notebooks and don't work overly well with Mac`s if at all. One cooler that does work efficiently is the Moshi Zefyr 2, as it`s principle of cooling is specifically designed for Apple portables, by blowing the air horizontally across the base of the computer, however don't expect miracles.
    [​IMG][​IMG]
    [​IMG]

    Link: Moshi Zefyr 2
    A cheap USB fan can achieve the same if strategically placed, not as elegant mind, nor as easy to put in your notebooks case :p but they do help to reduce case temperatures.

    You can use software to override Apple`s own cooling algorithm by manually taking control of fan RPM and setting up power profile presets with SMC Fan Control 2.4, or here with UltraFan which allows you stipulate a preset temperature and the software will automatically raise and lower fan RPM`s to keep the system at the predefined temp, which i personally feel is a far more elegant solution. At the end of the day you want to control your system temperature, not your fan rpm`s. For me SMC is now pretty much redundant with the latest release of UltraFan having manual control of the fans RPM, and subsequently i am starting to uninstall it from my own Mac`s. SMC FC is a great app, however although it`s recently updated, functionality is limited compared to some newer apps, equally SMC Fan Control is rock steady stable and a finished product.

    Strictly speaking Apple`s own cooling algorithm works, albeit at sacrifice of increased temps for quieter operation. This has always been the Apple way and is really nothing detrimental to the system, i have one MBP from 2008 all original barring a recent fan change that has an uptime of over 30K hours. The latest MBP`s need less assistance in remaining cool; for some it`s simply disconcerting the heat generated and transferred to the case, although it`s perfectly normal as the aluminium acts as a heat-sync. i have to deal with elevated ambient temperature so at times a software solution is useful. Apart from the passive cooling the Mstands bring they also offer a very sound ergonomic solution. A passive cooler and UltraFan will maximise the cooling, there is little else you can do short of reducing the ambient temperature or the system load. If I know i am going to push a system i will close all apps that are not essential as this can and does make an impact to system temperature.

    High temperatures in general is not overly harmful to your systems, what is far more detrimental is thermal stress, where temperatures rapidly fluctuate by significant margins over a short period of time. Anyone striving for great longevity should look to minimise rapid temperature changes, here UltraFan is your best friend.

    Using a RainDesign Mstand, a Moshi Zefyr 2 and latest version of UltraFan I can reduce temperature by over 20C when transcoding an MKV video file, and that is something worth thinking about;

    • Apple default cooling algorithm 99C - 103C (still on Mstand) fans 4K and escalating :eek:
    • Mstand, Zefyr & UltraFan 79C - 82C fans at 5.8K :cool:

    The old adage still applies; it`s easier to keep a system cool, than cool-down an already hot machine. This being said it`s not strictly necessary, equally it`s nice to know that there are options for reducing temperature out there.
     
  19. Queen6 macrumors 603

    Queen6

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    #19
    The OP does indeed raise some interesting and complex questions; the Mstands work best with 15" & 17" MBP`s as there is far more of the base of the machine exposed to the ambient air, in comparison to a 13". Passive cooling via radiance is more efficient with an aluminium Mac.

    A MBP flat on the desk will definitely run hotter in time as the radiated heat will saturate the underlying area and ultimately reflect this energy back to the base of the MBP increasing temperatures, elevation is always beneficial for Mac portables.

    External powered coolers are very much a mixed bag with few if any having any significant effect on a Mac`s internal temperature. Unlike a Portable PC which has a well ventilated base, the MBP`s base needs a horizontal stream of air to be even close to being effective, the net result is by cooling the case it helps to reduce temperature build up internally, however not necessarily individual components.

    The Mac`s own powered cooling system as has already been stated, likely is optimal given the space constraints and production costs. You can give it a boost by using software solutions such as UltraFan allowing you the end user to dictate the temperature at which the fans will spool up at. Typically Mac portables fans don't begin to spin up until the 80C mark has been passed (90C for Retina) by decreasing these thresholds temperatures can be significantly reduced at the cost of greater fan activity. As with any such system a clean out every 2-3 years will help to bring back it`s cooling performance, blocked/chocked heat-syns become ineffective in quick time.

    Apple have always chosen the path of increased operating temperatures to achieve quieter operation, their machines look great, are thin and light, quiet, however one the trade of is elevated temperatures...
     
  20. AlexMason86 macrumors newbie

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    Jul 29, 2010
    #20
    this really

    The surface area of the chassis is quite small once you work out the surface area of those two heat sinks inside. Surface area is king. The chassis will of course have some heat transferred to it and in turn it will try to transfer it to the environment. But all the transfer processes there are " less efficient" shall we say compared to the heat transfer abilities of thermal paste and copper heat pipes. So most of the heat is going down that path of least resistance, improving that path further will give you better gains. I haven't clicked the links but assume the guide is on about removing the heatsinks, lapping the processor heat spreaders (if they are there) and applying higher grade thermal pastes (properly).

    Heat pipes are almost magical in my view. Their ability to transfer heat from one location to another is epic. Given the space constraints I would say the cooling system is pretty well designed.

    You may see a few deg cooler by buying an external fan to add some turbulent air flow around your case (turbulent air flow is best for carrying away heat from a surface). I have even wondered if you could do a sort of entrained flow thing by blowing air along the underside of the MBP to cause a depression at the rear that will draw air out of the MBP... much like how those Dyson bladeless fans work. Would probably need some good speed to it though so I dont know how nice that will be if you want quiet!
     
  21. makaveli559m macrumors 6502

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    Apr 30, 2012
    #21
    What type of MacBook Pro you have? I use something called The TILT 15, for 15 inch version. Its a cooling pad that snaps onto the MacBook Pro and you dont need to take if off the machine, they have two versions, one with passive cooling that has no built in fan. Another one that has active cooling and that has a fan that uses usb power. I could use the MacBook pro my lap with it :)
     
  22. Erasmus macrumors 68030

    Erasmus

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    #22
    Internal convection is unlikely, as it requires space for air to move freely inside. The heat is more likely to flow through the solid components via conduction to the case, or even directly radiating onto the inside of the case.

    This is correct.

    This is also correct, and is the easiest solution. However it is noisy.

    The typical passive cooling stands that are basically just an angled block of plastic or metal will provide a small amount of extra cooling. This is both from as you said the extra air around the case, but mostly there will be an induced flow of air between the computer and the stand due to heating and the incline (hot air rises). This would work with any material. You could therefore make yourself a perfectly functional passive cooling stand out of plywood or perspex, cheaply and easily.
     
  23. rtfmoz macrumors newbie

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    Feb 25, 2014
    #23
    I find this conversion very interesting. Since I own one of the new rMBP 15" cooling interests me. Whenever I run software which heavily utilises the Nvidia Geforce GT 750M GPU the temps climb so high the mac is hot to touch near the top of the chassis, in front of the screen. You could literally cook an egg on it.

    From what I have read from this thread you agree the airflow is the main cooling element. In this case would it not be a bad idea to provide cold air to the intake. Such cold air could be generated from a $15 peltier cooling element and heatsink run from a USB port. Or would it be better to extract the heat directly from the aluminium body again using a peltier cooling element with heatsink.

    I realise the body is not the main cooling piece but pulling the heat away near the heat pipes will certainly allow them to cool more effectively. If I can reduce case body temps 10-15c then I would be a very happy person. I realise this would not cool the GPU directly however it would help the Mac with its cooling I guess.

    Thoughts?
     
  24. thundersteele macrumors 68030

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    Oct 19, 2011
    Location:
    Switzerland
    #24
    The previous poster just mentioned providing cool air, which reminded me of something not mentioned yet here: Ambient temperature.

    I remember that in the summer, when using the MBP in 25C - 30C environments, the fans would spin up easily with the simplest tasks, while in the winter with cozy 20C I can do a lot of stuff without bringing up the fans, and the machine would cool down much faster if it was under load for a while.
    The simple physics explanation is that the amount of heat dissipation is proportional to the temperature difference (or the gradient if you want to be precise).
    So getting an AC might be an option :)

    My main advice regarding heat is A) keep the laptop on an even surface, don't cover the vents and B) don't worry about heat.
     
  25. Wuiffi macrumors 6502a

    Wuiffi

    Joined:
    Oct 6, 2011
    #25
    Nope, you can't. People have tried that and failed (I am serious, you can find videos on google)

    Other thoughts:
    1. your computer is supposed to be hot when it does some serious computing (more power means more heat)
    2. you could install and use gfxcardstatus to force the iGPU when you don't need the dGPU, this will keep the system cooler
    3. your computer has safety features. If it gets to hot it will downclock or even shut down. As long as this is not happening I don't see any reason to worry
    4. Again, your computer is made to do some heavy work
     

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