A CPU chip with a footprint of 2.5 cm by 2 cm is mounted on a circuit board. The chip rejects heat to the environment at 28oC by convection and radiation. The outer casing of the chip has an emissivity of 0.88 and the heat transfer coefficient is 40 W/m2·K. If the chip temperature is 82 oC, calculate the heat transfer rate at the outer surface of the chip. Neglect the thickness of the chip and any conduction into the circuit board

The heat transfer rate is 0.9504 W

Explanation:

Heat transfer rate (Q) = ekA∆T

e is emissivity of the chip = 0.88

k is heat transfer coefficient = 40 W/m^2.K

A is surface area of chip = 2.5 cm × 2 cm = 5 cm^2 = 5/10000 = 5×10^-4 m^2

∆T is change in temperature = 355 - 301 = 54 K

Q = 0.88 × 40 × 5×10^-4 × 54 = 0.9504 W

the equation above shows how temperature f, measured in degrees fahrenheit, relates to a temperature c, measured in degrees celsius. based on the equation, which of the following must be true?

a temperature increase of 1 degree fahrenheit is equivalent to a temperature increase of

5

9

degree celsius.

a temperature increase of 1 degree celsius is equivalent to a temperature increase of 1.8 degrees fahrenheit.

a temperature increase of

5

9

degree fahrenheit is equivalent to a temperature increase of 1 degree celsius.

a) i only

b) ii only

c) iii only

d) i and ii only