Notebook Thermal Design Challenges
Seeking for “Desktop” equivalent processor frequency and features.
Shrinking form factor ( < 35mm is the common design goal).
35 Watts Northwood in a 17.2 mm internal height.
24.5 watts Banias in a 13 mm internal height.
12 watts Banias LV in a 10.2 mm internal height.
Ergonomics(small,low noise,cool to touch).
More effective design cycles.
To achieve long life and more reliable .
How the CPU Heat Dissipation Takes Place
Conduction─Exchange of kinetic energy between molecules.
Radiation ─Heat is simply radiated away form the object through
electromagnetic waves.
Convection ─Heat transfer is driven by movement of a heated or
cooled substance.
Forced Convection
Free Convection
Dimensionless Numbers in Heat Transfer
Reynolds Number = inertia forces / viscous forces
Nusselt Number = convection / conduction
High value of this no. means the heat transfer is enhanced by
convection.
Prandtl Number = momentum diffusivity/ thermal diffusivity
if Pr > 1 means thermal profile develops more rapidly than velocity
profile. For air Pr=0.72 at moderate temperatures.
Grashof Number = buoyancy forces / viscous forces
In free convection the Grashof number plays the same role as
the Reynolds number in force convection.
Rayleigh number = Grashof number * Prandtl number
Nu = C *( Ra )**n
作者: xlt 时间: 2011-5-1 08:57
收下了!!
感謝!!
作者: 绿丝绦 时间: 2011-5-1 08:57
关于风机和热管的, 非常不错. 谢谢
作者: 玻璃杯里 时间: 2011-5-1 08:57
thanks very much.
略看了一下, 终于对"thanks very much"这一句话有了深刻的体会