Chapter 8, Problem 8.38P

An air heater for an industrial application consists of an insulated, concentric tube annulus, for which air flows through a thin-walled inner tube. Saturated steam flows through the outer annulus, and condensation of the steam maintains a uniform temperature $T_s$ on the tube surface.

Consider conditions for which air enters a 50-mm-diameter tube at a pressure of 5 atm, a temperature of $T_{m,i}=17°C$ , and a flow rate of $\stackrel{\dot{}}{m}=0.03\text{kg/s}$ , while saturated steam at 2.455 bars condenses on the outersurface of the tube. If the length of the annulus is $L=5\text{m}$ , what are the outlet temperature $T_{m,o}$ , and pressure $p_o$ of the air? What is the mass rate at which condensate leaves the annulus?