The condenser of a steam power plant contains N = 1000 brass tubes (kt = 110 W/m · K), each of inner and outer diameters, Di = 25 mm and Do = 28 mm. respectively. Steam condensation on the outer surfaces of the tubes is characterized by a convection coefficient of ho = 10,000 W/m2 · K.
(a) If cooling water from a large lake is pumped through the condenser tubes at mc = 400 kg/s, what is the overall heat transfer coefficient Uo based on the outer surface area of a tube? Properties of the water may be approximated as µ = 9.60 x 10-4 N · s/m2, k = 0.60 W/m · K. and Pr = 6.6.
(b) If, after extended operation, fouling provides a resistance of Rnf,i = 10-4 m2 · K/W, at the inner surface, what is the value of Uo?
(c) If water is extracted from the lake at 15°C and 10 kg/s of steam at 0.0622 bars are to be condensed, what is the corresponding temperature of the water leaving the condenser? The specific heat of the water is 4180 J/kg · K.