For this problem we will be analyzing a power amplier that is surrounded by air at 25C while the case, which is constructed out of anodized aluminum, is at 125C. The case has a surface area of about 3800 mm2 and a height of 40 mm.
(a) Assuming that the amplier is mounted vertically, determine the mean heat transfer coefficient for natural convection. If heat transfer occurs due to natural convection and radiation, estimate the power dissipation from the unit and the relative magnitude of the radiation and convective heat transfer.
(b) Calculate the heat transfer coeffcient due to natural convection if the amplifer is mounted horizontally instead with the heated surface facing up. Provide a physical explanation for the dierence in heat transfer coecients you would observe if the amplier was mounted with the heated surface facing down.