1. Air at 25°C flows over a 10-mm-diameter sphere with a velocity of 25 m/s, while the surface of the sphere is maintained at 75°C.
(a) What is the drag force on the sphere?
(b) What is the rate of heat transfer from the sphere?
(c) Generate a plot of the heat transfer from the sphere as a function of the air velocity for the range 1 to 25 m/s.
2. Consider a sphere with a diameter of 20 mm and a sur- face temperature of 60°C that is immersed in a fluid at a temperature of 30°C and a velocity of 2.5 m/s. Calculate the drag force and the heat rate when the fluid is
(a) water and (b) air at atmospheric pressure. Explain why the results for the two fluids are so different.