Forced air at 25C and 10m/s is used to cool chips on a circuit board. Consider a chip, 4mm x 4mm, located 120mm from the leading edge of the board. An empirical correlation has been established for the local Nusselt number:

Nu_x = 0.04 * Re_x^0.85 * Pr^(1/3)

Estimate the surface temperature of the chip if it is dissipating 30mW.

(Thermophysical properties of air at 25C are needed to solve this problem. Please state your reference source for this information.)

Thermal stresses are developed in a metal when its a) initial temperature is changed b) final temperature is changed c) density is changed d) thermal deformation is prevented e) expansion is prevented f) contraction is prevented

The higher the astm grain size number, the finer the gran is. a)-true b)-false

Ahot wire operates at a temperature of 200°c while the air temperature is 20°c. the hot wire element is a tungsten wire of 5 um diameter and 2 mm in length. plot using excel current, heat transfer and heat generated by the wire for air velocity varying from 1-10 m/s in steps of lm/s? matlab the sensor voltage output, resistance, or assume nu 0.989 re033pr13 take air properties at tr (200°c20°c)/2 = 110°c properties of tungsten: c 0.13 kj/kg.k 3 p 19250 kg/m k (thermal conductivity) = 174 w/m.k