A concentric annulus tube has inner and outer diameters of 1 in. and 4 in., respectively. Liquid

Question:

A concentric annulus tube has inner and outer diameters of 1 in. and 4 in., respectively. Liquid water flows at a mass flow rate of 396 lbm/h through the annulus with the inlet and outlet mean temperatures of 68°F and 172°F, respectively. The inner tube wall is maintained with a constant surface temperature of 250°F, while the outer tube surface is insulated. Determine the length of the concentric annulus tube. Assume flow is fully developed.