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1140

Dissipate heat from the back of the LCD; not the laptop's bottom

1140 points posted to Accessories (Keyboards, etc.), Monitors and Displays, Laptops by endolith 06/10/07

The name for these devices has been changed from "laptop" to "notebook", because the bottoms of these things get so hot they slow cook your legs if you try to hold them on your lap. I've been using mine with a big cloth pad underneath since I got it, and it still heats up my legs.

The problem is that the heat is designed to dissipate mostly from the bottom. That's why the modern Dell laptops have little rubber bumper feet, so that, theoretically, you'll use it on a table and the fan will draw air past the bottom surface of the laptop. Back in reality, everyone just uses them on their laps or couches and the little rubber feet break off and get lost.

What you should do instead is route the heat to fins on the back of the LCD, where it will easily be dissipated. (You know, the part that's almost vertical, prone to convection, and always exposed to the environment instead of legs?) The parts that contact the lap should then be thoroughly insulated.

Options for routing the heat into the LCD:

  • Actively liquid-cooled laptops with little pumps and such.
  • Passive liquid heat pipes using alcohol or other working fluid that condenses in the heatsink, drips back down by gravity into the main body of the laptop, is warmed and evaporated to flow back up and be cooled in the heat sink, etc.
  • Active air cooling with the normal laptop fan blowing air into open ducts that go up the LCD housing
  • Very passive cooling that just leaves open ducts for air to naturally convect up the LCD housing like a chimney.


For connecting the main body to the LCD:

  • Rotational coupling built into or coaxial with the LCD's hinges
  • Flexible hoses

jervis961
06/10/07		 It's a nice theory and something needs to be done about the problem but this isn't possible. All laptops connect to the LCD with a hinge, There is no route from the notebook to the LCD for air to flow never mind fluids.
jorge
06/11/07		 We did this same Idea just a couple weeks ago, agh the memories.
expatinasia
06/11/07		 It's obvious that you don't understand either thermal management or the design of notebook computers.
ayeohx
06/18/07		 Hey now! Be nice! ('Course I'm usually the jerk...)
Anyhow it's an interesting idea Endo but it wouldn't work too well. LCDs can be pretty sensitive to heat. That's why if you leave it in your car on a hot day you can get that permanent discoloration in the middle of the screen.
Many of the manufacturers are working on better heat management. Unfortunately for us power users the more powerful the machine the more heat it's going to produce. But low powered (ie weaksauce) computer are coming out and if you don't mind taking a step back in power you can grab one.
And Endo, get that thing off of your lap!!!!!! Besides cooking your goodies you're going to cause hardware failure since you're preventing proper ventilation.
jason701802
06/18/07		 its better than a MacBook, you cant keep one on your lap for more than 15 minutes.
endolith
06/21/07
It's obvious that you don't understand either thermal management or the design of notebook computers.


Haha. Yeah. I know nothing about it. Go look up heat pipes and thermosiphons. Creating a reliable hinge that doesn't leak the fluid over several years of use would be somewhat difficult, but not impossible.

But the reason heatsinks have fins is to enlarge the surface area for conduction of heat into the air, so that the air can convect the heat into the environment. Active fans help, but use up energy and waste some as heat themselves. Vertical fins and passive heat pipes would help a lot, without contributing to the problem, and would enable the bottom of the laptop to be insulated.
blackkitty
06/25/07		 I'm not an engineer, but a laptop design that gets rid of the heat without being hot on my legs is something I would definately seek out and buy. And I would happily pay more $$$ for this feature. $200 extra to not burn my legs (a truly "cool" laptop) would be money well spent.
jorge
06/25/07		 The best solution is to use the new ULV chips from Intel, using a Duo 2 Quad Core will probably fry your lap, table top and what ever else you set it on.
scotty750
06/28/07		 air comes in the bottom out the back on all models. And I do know what I'm talking about, I take them apart all day long.
chewd
06/29/07		 blackkitty: if it was cool because it was slow, would you buy it then?

Personally, id give up the blazing speeds in order to avoid blazing hot trousers.... Is it possible to under-clock current cpus to achieve this? or would it require a whole new chip design? If so, would any of the chip manufacturers be willing to produce a slow chip to suit this need?

I dont necessarly *need* a 4ghz 64-bit cpu just to run office apps.
jorge
06/29/07		 Have you tried tat.exe?

Info:
http://forumz.tomshardware.com/hardware/CPU-Temps-Intel-Thermal-Analysis-Tool...< here:
http://shintai.ambition.cz/files/tat.exe< at your own risk but I think its a nice tool to throttle down a Duo 2 Core CPU or throttle up if you are cold.
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