MacBook Pro: The Thermal Paste Question
Subject:   Heat
Date:   2006-05-23 20:14:48
From:   duncan
Response to: Heat

Indeed. Heat transfer is the whole point of the game. You want heat to be transferred from the chip to the heat pipe system and then to the radiators attached to the heat pipe where the fans can blow it out. Heat transmitted through the case (and into your lap or through the keyboard) is heat that wasn't blown out of the system by the sophisticated heat pipe system. A cooler temperature on the case means that heat is being transferred to air via the heat pipe system to the fans and then to the outside air.

An IR thermometer isn't adequate to measure the amount of heat coming out the vents. It gives good readings of the temperature of solid bodies, but since air moves, the heat removed from the system cannot be determined by measuring the heat of the vents. It's hard to measure with the equipment at hand. And the more heat energy that is removed from the system via air, the less heat energy is being dissapated through the case which means the lower the surface temperature will be.

In other words, you're correct that heat doesn't magically disappear and that it is transferred. But without measuring the total heat of the system--including the total heat exchanged into air and vented, we can't balance the equation. A simple IR thermoter won't do it. We'd have to get a more sophisticated facility, probably one that mimic those used to test HVAC equipment, to be able to do that.

But all of this goes way beyond the point. 2F is not a big delta. Using the equipment available to me, and accepting the errors inherit in how this is done, the delta is certainly no indication that any net change was made by changing out the thermal paste. It certainly is a long way from the 10-20C (18-36F) delta that has been claimed elsewhere.