A preheater involves the use of condensing steam at 100°C on the inside of a bank of tubes to heat air that enters at 1 atmosphere and 15°C. The air moves at 8 m/s in cross flow over the tubes. Each tube is 2 m long and has an outside diameter of 5 mm. The bank consists of 196 tubes in a square, aligned array in which the distance between tube centers is 15 mm. What is the temperature of the air after passing through the tubes. Also, what is the pressure drop associated with the air flow?

In the final stages of production, a pharmaceutical is sterilized by heating it from 25 to 75°C as it moves at 0.21 m/s through a straight thin-walled stainless steel tube of 12.7-mm diameter. A uniform heat flux is maintained by an electric resistance heater wrapped around the outer surface of the tube. If the tube is 10 m long, what is the required heat flux? If fluid enters the tube with a fully developed velocity profile and a uniform temperature profile, what is the surface temperature at the tube exit? Fluid properties may be approximated as p = 1000 kg/m³, c, = 4000 J/kg-K, µ = 2x 103 kg/s-m, k = 0.8 W/m-K, and Pr = 10. Determine the required heat flux, W/m². q! = i W/m? Determine the surface temperature at the tube exit, in °C. i °C S,0

Heat transfer

A large bare duct having a diameter of 25cm runs horizontally across a factory area having environmental conditions of 20.C and 1 atm. The length of the duct is 100 m. Inside the duct a low pressure steam flow maintains the duct wall temperature constant at 120.C. Calculate the total heat lost by convection from the duct to the room