The tube in a heat exchanger has a 2-in. inner diameter and a 3-in. outer diameter. the thermal conductivity of the tube material is 0.54 btu/h∙ft∙℉, while the inner surface heat transfer coefficient is 50 btu/h∙ft2∙℉ and the outer surface heat transfer coefficient is 10 btu/h∙ft2∙℉. determine the overall heat transfer coefficients based on the outer and inner surfaces.

Asolid cylinder is concentric with a straight pipe. the cylinder is 0.5 m long and has an outside diameter of 8 cm. the pipe has an inside diameter of 8.5 cm. the annulus between the cylinder ad the pipe contains stationary oil. the oil has a specific gravity of 0.92 and a kinematic viscosity of 5.57 x 10-4 m2/s. most nearly, what is the force needed to move the cylinder along the pipe at a constant velocity of 1 m/s?