Consider a silicon wafer positioned in a furnace that is zone-heated on the top section and cooled on the lower section. The wafer is placed such that the top and bottom surfaces of the wafer exchange radiation with the hot and cold zones respectively of the furnace. The zone temperatures are Tsur,h = 800 K and Tsur,c = 330 K. The emissivity and thickness of the wafer are e = 0.65 and d = 0.78 mm, respectively. With the ambient gas at T, = 700 K, convection heat transfer coefficients at the upper and lower surfaces of the wafer are 8 and 4 W/m2-K. Find the steady-state temperature of the wafer, in K. K Tw i

A long, thin-walled horizontal tube 10.0cm in diameter with an emissivity of 0.80 is maintained at 120.0°C by the passage of pressurized steam inside the tube. To reduce radiation heat transfer losses, a round, tubular radiation shield with an emissivity of 0.10 is installed surrounding the heated tube, with a gap of 1.00cm between the outside of the tube and the radiation shield. At steady-state operating conditions, the temperature of the radiation shield is measured to be 35.0°C. Calculate the total heat transfer rate per meter length assuming that the gap between the pipe and heat shield is now filled with air at a pressure of 1.00 atm.

This experiment is conducted to determine the emissivity of a certain material. A long cylindrical rod of diameter D₁ = 0.01 m is coated with this new material and is placed in an evacuated long cylindrical enclosure of diameter D₂ = 0.1 m and emissivity 2 = 0.95, which is cooled externally and maintained at a temperature of 200 K at all times. The rod is heated by passing the electric current through it. When steady operating conditions are reached, it is observed that the rod is dissipating electric power at a rate of 16 W per unit of its length, and its surface temperature is 600 K. Based on these measurements, determine the emissivity of the coating on the rod. The emissivity of the coating on the rod is 0.1165

An opaque surface which is insulated at the back side has a total, hemispherical absorptivity a=0.8 for solar radiation and a total, hemispherical emissivity of e=0.2. A solar radiation flux of 800 W/m2 is incident on this surface. The surface is exposed to the ambient air at T 300 K and convective heat transfer coefficient is h=15 W/m2 K. Neglect the sky radiation. • Sketch the heat fluxes received and dissipated by this surface • Estimate the equilibrium temperature of the surface (assume the surface temperature is higher than the ambient air temperature). 1.= 300 K, h-15 W/m*K 800 W/m? a-0.8 , e-0.2