Problem 1
A horizontal steel pipe having a diameter of 5 cm is maintained at a temperature of 50°C in a large room where the air and wall temperatures are 20°C. The surface emissivity of the pipe is 0.8.
(a) Estimate a value for the convective coefficient, h, with the basis of your estimate
(b) Show a diagram with the energy fluxes on the pipe
(a) Estimate the heat loss of the pipe per unit length
Problem 2
A 60 cm long steel rod with diameter = 3 cm is welded to a furnace wall and passes through 20 cm of insulation before emerging into the surrounding air. The furnace is kept at 300°C. The air temperature is 20°C. Estimate the temperature of the steel rod's tip if the convective coefficient is 13 W/m2 K.
Problem 3
A cylindrical billet of steel, 50 cm long with an outside diameter of 3 cm is initially held at 500°C. The billet is plunged into an oil bath at 100°C. The average convective coefficient, h, between the oil and the steel is 500 W/m2 K. Find the time it takes to cool the center of the billet to a temperature of 250°C, assuming:
(a) Lumped Capacitance
(b) Billet is not lumped.