MacBook Pro Heat, Lid Down, External Monitor

OK, this may sound silly but it works really well:

1) Put down something soft for your MBP to sit on. A magazine can work in a pinch.
2) Place the MBP, lid closed, upside down on the soft surface.
3) Put a piece of paper on the upward facing underside of the MBP.
4) Put a heavy piece of aluminum on the piece of paper. I have used an aluminum baking dish for this. Make sure the aluminum pan, or whatever, is sitting on the paper and not on the rubber feet of the MBP.

This works amazingly well at pulling heat out of the notebook and letting it run all day at low temperature without the fan coming on at all. If you really want to go overboard you can keep a gel ice bag in the refrigerator (not the freezer) and throw the gel pad in the aluminum pan. Use two in rotation, keeping one in the fridge at all times. Your very own cryogenic cooling system made from common items found around the house ;o)

I run my MBP for weeks at a time in "clamshell" mode. It sits on a shelf below my desk. It doesn't seem unusually hot -- maybe a little warmer than my G4 Powerbook was, running the same way. CPU temperature runs 3-4 degrees Celsius warmer than the G4. But I don't load up the processor much, so your situation may be different.

I bought a slim laptop cooling pad that has two small fans in it, powered by the USB bus, for when I have my machine docked to my 30" display & other peripherals. Works quite well at keeping the machine cool.

Use mine like that all day everyday for 3 months. No issues at all.
I don't fuss with pads, fans etc, it just sits on my desk.

Ive been using mine lid closed for many hours at a time since i got it.. only problem ive had is that i cant use the iSight camera! 🙂

Ill admit i do check it for heat etc and of course make sure its on a hard surface and nothing is obstructing the air vent etc. Ive had no problems.

I use mine extensively this way and have ended up with a "warped screen". I am on the way to the Apple store today to "hopefully" get this repaired.

I've used my MBP every day, in the office, lid closed, for the last two months, 10-11 hours each day, no problems at all. At the end of the day, it is a bit warm, but nothing alarming. And no problems so far.
But BSteely does give me the idea that, if you're concerned about heat buildup, there's no reason not to turn your MBP upside down, hot side up, as long as you are going to use it lid closed on your desk.

Dave