8.20 engine oil flows through a 25‐mm‐diameter tube at a rate of 0.5 kg/s. the oil enters the tube at a temperature of 25°c, while the tube surface temperature is maintained at 100°c. determine the oil outlet temperature for a 5‐m and for a 100‐m long tube. for each case, compare the log mean temperature difference to the arithmetic mean temperature difference

Awall of 0.5m thickness is to be constructed from a material which has average thermal conductivity of 1.4 w/mk. the wall is to be insulated with a material having an average thermal conductivity of 0.35 w/mk so that heat loss per square meter shall not exceed 1450 w. assume inner wall surface temperature of 1200°c and outer surface temperature of the insulation to be 15°c. calculate the thickness of insulation required.

What is the heat treatment of metals? what is the benefit of it? why and how it's useful? answer in details, do not write by hand.

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.