OK Children. We assume the processor, the thermal reservoir transfers heat to the case by conduction through physical conductors leading through the frame to the case, by convection of the air around the processor and by radiation. Assuming equilibrium since it appears this is a thread full of liberal arts majors and calculus is out of the question the formula for conduction in a steady state heat flow condition after equilibrium is established and assuming the heat flow from the processor is not enough to change the temperature of the processor but rather keep it constant the formula for conduction is:
H = kA * DT/Dl where H is heat flow, k is the thermal conductivity constant of the case material and frame (keep it simple same material), A is the area perpendicular to the heat flow, DT is the delta of temperature between the processor, the thermal reservoir and the atmosphere while Dl is the length in line with heat flow. So assuming a comfortable DT, increasing the area allows a greater heat flow without DT increasing. Or you could increase the thermal conductivity of the material, ie. use magnesium instead of plastic.
Convective heat flow is:
H = hA * DT where h the convective coefficient of the air in the case is determined as a function of air velocity in the case. So to keep the same DT with increased heat flow you would increase the velocity of the air, ie. a fan or increase the surface area of the processor, ie. fins.
And radiation heat flow is:
H = Ae * o * T4 where A is the surface area of the radiating body ie the processor, e is the emissivity of the surface of the radiating body and T4 is the absolute temperature to the 4th. Oh, o is the Stefen-Bolzmann constant. Likewise you would increase the surface area of the radiating body, ie. fins.
Have we had enough. By the way IanBruce. Tell me again you connection to MHD drive - I thought you were a designer (liberal arts major) involved in Worldboard. I missed the part about you being a marine engineer or naval architect or perhaps your part was to make the engine room look cute - God knows they need it. Or perhaps you read Popular Mechanics too much. Rich |
