3. in a very hot and dry workplace outside air can be drawn in through water spray, and the air is cooled by the heat removed to evaporate the water (evaporative cooling). the data taken before and after installation of such an evaporative cooling system are given below: before installation after installation td (0c) 32.8 29.4 tg (0c) 46.1 35.0 twb (0c) 24.2 24.4 calculate the wet bulb globe temperature before and after installation of the system. also explain why dry bulb temperature (td) and globe temperature (tg) decrease while wet bulb temperature (twb) remains almost unchanged.

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.

Modern high speed trains do not have perpendicular expansion gaps where rails are joined end-to-end any more they are mostly welded together but what might happen if there was a spell of particularly hot weather that causes inspection of the tracks?

The proportional limit is always greater than the yield strength for a material. a)-trune b)- false