An open wall consist in succession layer of fire bricks (Kf=1.21j/m²°C) a layer of lagging bricks(Kl=0.08j/m²°C) and a layer of bricks (Kb=0.6m²°C)each layer is 10cm thick, the temperature in the inside of the wall is 872°C ,on the outside 32°C. calculate the following (a)heat lost by conduction every 12 hours if the surface area of the wall is 20 m² (b) temperature in the middle of the layer of lagging bricks (c)overall heat transfer coefficient

The filament of an incandescent lamp has a temperature of 2000k. calculate the fraction of radiation emitted in the visible light band if the filament is approximated as blackbody

At 12 noon, the count in a bacteria culture was 400; at 4: 00 pm the count was 1200 let p(t) denote the bacteria cou population growth law. find: (a) an expression for the bacteria count at any time t (b) the bacteria count at 10 am. (c) the time required for the bacteria count to reach 1800.

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.