For the silicon chip of Example 3.5, determine the rate of entropy production, in kW/K. What is the cause of entropy production in this case? 7.43 At steady state, a 15-W curling iron has an outer surface temperature of 90°C. For the curling iron, determine the rate of heat transfer, in kW, and the rate of entropy production, in kW/K.
Example 3.5:
A silicon chip measuring 5 mm on a side and 1 mm in thickness is embedded in a ceramic substrate. At steady state, the chip has an electrical power input of 0.225 W. The top surface of the chip is exposed to a coolant whose temperature is 20°C. The rate of energy transfer by heat between the chip and the coolant is given by Q = -hA(Tb - Tf), where Tb and Tf are the surface and coolant temperatures, respectively, A is the surface area, and If heat transfer between the chip and the substrate is negligible, determine the surface temperature of the chip, in °C.