A3-mm-diameter electrical wire is insulated by a 2-mm-thick rubberized sheath (k = 0.13 w/m·k), and the wire/sheath interface is characterized by a thermal contact resistance of r, e=3x1 convection heat transfer coefficient at the outer surface of the sheath is 15 w/m2 . k, and the temperature of the ambient air is 20°c. if the temperature of the insula- 0-4m2. k/w. the tion may not exceed 50'c, what is the maxtimun allow- able electrical power that may be dissipated per unit length of the conductor? what is the critical radius of the insulation?

Steel is coated with a thin layer of ceramic to protect against corrosion. what do you expect to happen to the coating when the temperature of the steel is increased significantly? explain.

An air conditioning system consist of a 5 cm diameter pipe, operating at a pressure of 200 kpa. the air initially enters the pipe at 15°c with a velocity of 20 m/s and relative humidity of 80%. if the heat supply throughout the process is 960 w, determine the relative humidity and the temperature at the outlet

Along 8-cm diameter steam pipe whose external surface temperature is 900c connects two buildings. the pipe is exposed to ambient air at 70c with a wind speed of 50 km/hr blowing across the pipe. determine the heat loss from the pipe per unit length. (b) air at 500c enters a section of a rectangular duct (15 cm x 20 cm) at an average velocity of 7 m/s. if the walls of the duct are maintained at 100c. a) the length of the tube for an exit temperature of the air to be 40 0c. b)the rate of heat transfer from the air. c) the fan power needed to overcome the pressure drop in this section of the duct.