A power amplifier an example of which is shown in the figure

A power amplifier, an example of which is shown in the figure below, is a semiconductor device used to amplify an input electronic signal and is commonly found in integrated circuits. For this problem we will be analyzing a power amplifier that is surrounded by air at 25 degree C while the case, which is constructed out of anodized aluminum, is at 125 degree C. The case has a surface area of about 3800 mm^2 and a height of 40 mm. Assuming that the amplifier is mounted vertically, determine the mean heat transfer coefficient for natural convection. If heat transfer occurs due to both natural convection and radiation, estimate the power dissipation from the unit and the relative magnitude of the radiation and convective heat transfer. Use emissivity = 1. Calculate the heat transfer coefficient due to natural convection if the amplifier is mounted horizontally instead. Compare the scenarios when the amplifier is mounted with the hot surface facing down and when the hot surface is facing up. Provide a physical explanation for the differences in the heat transfer coefficients.

Solution

A) qcon=h*A*( T1-T2)

=40*3800*(125-25)

=40*3800*100

152*10^5

qrad=A*e*5.676*10^-8*T^4

=3800*1*5.676*10^-8*125^4

=52658.2

q= qrad+qcon

=15.2*10^6

This is for the vertical .