Question

. [Problem 11-5, p.689 in Bergman, et al.] The condenser of a steam power plant contains N = 1000 brass tubes (k = 110 W/m-K), each of inner and outer diameters, D1 = 25 mm and D2 = 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 ṁw = 400 g/s, what is the overall heat transfer coefficient Uo (based upon the outer surface of the tube)? Properties of the water may be approximated as μ = 9.60x10‒4 N-s/m2, k = 0.60 W/m-K, and Pr = 6.6. You may use eqn.(8.60): hi = 0.023 (k/D1) ReD4/5 Pr0.4. (b) If, after extended operation, fouling provides a resistance of Rf = 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 oC 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 water is 4.180 kJ/kg-K and the heat of vaporization of the steam is 2414 kJ/kg. You may assume that ReD for the water = 3400

Answer 1