A 5 cm diameter cylinder is maintained at a constant temperature of 200°C and it is "completely enclosed" by a wind tunnel test chamber, walls of which are at 10°C. Air at 350K is forced across the cylinder at a velocity of 50 m/s (h=180 W/m°C). If the surface emissivity of the cylinder is 0.7, determine the total (convective and radiative) heat transfer from the cylinder(W per meter length). A. 13 B. 272 C. 3750 D. 985

Steel pipe (outer diameter 100 mm) is covered with two layers of insulation. The inner layer, 40 mm thick, has a thermal conductivity of 0.07 W / (m K). The outer layer, 20 mm thick, has a thermal conductivity of 0.15 W / (m K). Pipes are used to deliver steam with a pressure of 700 kPa. The temperature on the outer insulation surface is 24 ° C. If the pipe is 10 m long, determine the following: (assuming that the conduction heat transfer resistance of the steel pipe and the vapor convection resistance are negligible). a. Heat loss per hour. = AnswerkJ / hour. b. Temperature between insulation layers. = Answer° C.

A large slab of aluminum has a thickness of 10 cm and is initially uniform in temperatureat 400◦C. It is then suddenly exposed to a convection environment at 90◦Cwith h=1400 W/m2 · ◦C. How long does it take the center to cool to 180◦C?

Please answer A