A steel tube with a thermal conductivity of 55 W/mK carries a fluid at 175°C, with a convection heat transfer coefficient of 190 W/m 2 ./K. The tube has an external diameter of 5 cm, a wall thickness of 1 cm and a length of 1.5 m. The ambient air and surroundings are at 27°C, with a convection heat transfer coefficient of 20 W/m 2 .K. Neglecting the effects of radiation, determine: a) the resistance by conduction through the tube wall b) the convection resistance inside the tube c) The total rate of heat transfer d) The temperature of the outer surface of the tube e) The total resistance considering the effects of radiation only on the outside, with the coefficient h r = 2W/m 2 .K f) The new heat transfer rate, taking into account the effects of radiation, if an additional layer of 15 mm thick foam with a conductivity of 0.03 W/mK is added to the system. g) The critical insulation radius of the system after the addition of this insulating layer.
A steel tube with a thermal conductivity of 55 W/mK carries a fluid at 175°C, with a convection heat transfer coefficient of 190 W/m 2 ./K. The tube has an external diameter of 5 cm, a wall thickness of 1 cm and a length of 1.5 m. The ambient air and surroundings are at 27°C, with a convection heat transfer coefficient of 20 W/m 2 .K. Neglecting the effects of radiation, determine:
a) the resistance by conduction through the tube wall
b) the convection resistance inside the tube
c) The total rate of heat transfer
d) The temperature of the outer surface of the tube
e) The total resistance considering the effects of radiation only on the outside, with the coefficient h r = 2W/m 2 .K
f) The new heat transfer rate, taking into account the effects of radiation, if an additional layer of 15 mm thick foam with a conductivity of 0.03 W/mK is added to the system.
g) The critical insulation radius of the system after the addition of this insulating layer.
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