Do external cooling fans really make any difference?

Question

Do external cooling fans really make any difference?

As the title suggests, I'm wondering whether or not laptop cooling fans that are built into a lap rest really make any difference? I remember asking a Genius at the Genius Bar about this and he said that my Mac's internal fan is sufficient enough and that my Mac's designed to take heat. I agree with him, but I'm curious on if a laptop rest with dual cooling fans that I own is making any difference whatsoever to how cool my MacBook Pro keeps under normal use.

MacBook Pro, Mac OS X (10.6.6), 2.66 GHz Intel Core i7 Processor, 4 GB 1067 MHz DDR3 Memory, 15.4" Glossy Display

Posted on Feb 17, 2011 12:45 PM

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Answer 1

Network 23

Level 6

12,333 points

Feb 17, 2011 1:29 PM in response to Technologeek KMJ

This New York Times article says don't bother.
http://gadgetwise.blogs.nytimes.com/2010/07/20/cooling-your-laptop-or-your-lap/

I recognize the name of the author of the article: He's written for various Mac magazines for many years.

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Answer 2

Kappy

Level 10

361,741 points

Feb 17, 2011 1:31 PM in response to Technologeek KMJ

Of course cooling fans will make a difference. The question really is if they are needed. That depends on what you do on the computer.

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Answer 3

eww

Level 9

53,028 points

Feb 17, 2011 1:48 PM in response to Technologeek KMJ

A laptop cooler will certainly keep the bottom pan of your MBP cooler than resting it on your lap will. Your lap, in addition to being a pretty good insulator, as also pretty warm to begin with — certainly warmer than the ambient air temperature of any comfortable workspace. How much cooler a fan-cooled gizmo would keep the bottom pan than just resting it on a hard, flat board, perhaps slightly sloping, is less clear to me, but I would expect some difference.

If the MBP had cooling air intake vents on its underside, then a fan-equipped coolpad could provide an active, direct assist in cooling the machine. But there are no such vents, so a coolpad can't blow air at the places where the heat is actually generated. It can only help to dissipate the heat that is transmitted to the bottom case, i.e., it provides only indirect cooling of the really hot parts of the machine.

Since you already have a coolpad, you could do the following comparison test:

First, install iStat Menus and set it up to display your computer's temperature in the menu bar.

Start your MBP up from a cold shutdown, without the coolpad under it, resting it on a flat tabletop. Open the Terminal. Type "yes" at the prompt and hit Return. This will place a heavy load on the processor cores. Wait exactly ten minutes to give the machine time to heat up and reach a stable temperature. Do nothing with it during that time. Record the temperature indicated by iStat at the end of ten minutes, then shut the machine down for an hour or two.

Put the coolpad under it in the same location and repeat the test with the coolpad running. Compare the temperature at the end with the one you recorded the first time. Let us know what you find.

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Answer 4

Network 23

Level 6

12,333 points

Feb 17, 2011 4:56 PM in response to Technologeek KMJ

When I have to use my MacBook Pro on my lap, I make sure my legs are apart enough to leave a big gap in the middle for air to flow past the bottom of the laptop.

I'm wondering whether or not laptop cooling fans that are built into a lap rest

Since you talked about a lap rest, the issue depends on the top surface of that lap rest.

If the lap rest top is any kind of soft top or upholstery, like a pillow, that's bad. It would completely conform to the bottom of the laptop, blocking all airflow.

If the lap rest has a hard flat top, the same as a table, don't worry about it at all. A hard top should allow the laptop feet to maintain space between the surface and the laptop case bottom, allowing air to flow by, just like when you work on a desk or table.

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Answer 5

Feb 17, 2011 11:10 PM in response to Technologeek KMJ

No... simple.... no

The MBP was designed specifically to sit on a flat surface. The rubber feet raise the notebook high enough for air to pass underneath the computer. Why is this so important because the bottom of the computer is a heatsink. Most lap fans are not flat.

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Answer 6

eww

Level 9

53,028 points

Feb 18, 2011 5:50 AM in response to Technologeek KMJ

I addressed the problem of a hot laptop on my (relatively) hot lap many years ago, when I had a Wallstreet Powerbook G3 that was sometimes ungodly hot. I bought a rectangle of 3/16" Plexiglas a little smaller than the outline of the Powerbook, rounded all its edges and corners over with sandpaper so they weren't sharp, put four self-adhesive nonskid rubber furniture feet on one side of it for the Powerbook to rest on, and three strips of self-adhesive nubbly nonskid rubber bathtub tape across the underside so it can't slide around on my lap. The furniture feet on the top are high enough to create about a 3/16" airspace underneath the computer's whole bottom at all times. When I replaced the Wallstreet with a Titanium PB G4 several years later, I made a new one that was the right size for the Tibook, and that one is close enough to the size of my MBP that I've just continued to use it. The total cost was about $6, it uses no power from USB or elsewhere, and when I travel it just slides into my briefcase with the MBP, where its rigidity gives the underside of the machine extra protection against sharp dings.

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Answer 7

Kappy

Level 10

361,741 points

Feb 18, 2011 11:14 AM in response to Mac_Man_X

Actually much better to raise the rear of the computer to allow better ventilation underneath the computer. Lying flat is not the best idea for keeping the computer cool. The bottom of the computer may be part of the dissipation system, but the surface on which it sits is not.

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Answer 8

May 19, 2013 9:51 PM in response to eww

eww: how high are the rubber furniture feet you used on the plexiglass?

thanks!

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Answer 9

Feb 15, 2014 12:24 PM in response to eww

@eww I actually did an informal test using iStat while I was converting some videos. I had been converting some videos and saw my cpu was hovering around 193F with fans maxing out around 6000. I had a small desk fan so I decided to aim it at the bottom of my mac (it's on a open bottom stand) thinking I'd help out the fans a bit. It definitely did help the fans as they slowed down to around the 3000's. But here's the thing, my processor temp went UP to around 203F. Still safe, from what I understand, but definitely hotter which is not desirable. My theory is the fans are balanced in a way to keep all the components cooling at a rate set by apple. When I externally cooled the outer case some other components didn't need as much cooling which slowed down the fan. But other components, like my CPU, where heat is more concentrated and maybe not as affected as much by the external fan were allowed to get hotter as the internal fans slowed down.

After this experiment I would strongly suggest NOT using any kind of external cooling device as it actually messes with your Macbook's internal cooling and makes your CPU run hotter than it would when you rely on your machine's built in cooling system.

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Answer 10

Mar 6, 2014 8:48 AM in response to random1destiny

The findings about external cooling of Macbook unsettling the internal cooling, is of real interest. I have read alot about how the Macbook unibody is designed, but I can see how external cooling would be similar to adding extra fans to a tower case without planning the airflow ... in the case of the Macbook, I wonder if there is a way of planning a more efficient cooling flow without tampering inside afterall. Thanks for the thought ... I agree that it'd be best to leave cooling to the Macbook. Anybody else done similar tests?

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