Chapter 11, Problem 11.7P

The condenser of a steam power plant containsN=1000 brass tubes $\left(k_t=110\text{ W/m}\cdot \text{K}\right)$ ,each of
inner and outer diameters, $D_t=25$ mm and $D_o=28$ mm, respectively. Steam condensation on the outersurfaces of the tubes is characterized by a convectioncoefficient of $\left(h_o=10,000{\text{ W/m}}^2\cdot \text{K}\right)$ .
(a) If cooling water from a large lake is pumpedthrough the condenser tubes at ${\stackrel{\dot{}}{m}}_c=400\text{ kg/s}$ , whatis the overall heat transfer coefficient $U_o$ , basedon the outer surface area of a tube? Properties ofthe water may be approximated as $\mu =9.60\times {10}^{-4}N\cdot s/m^2$ , $k=0.60\text{ W/m}\cdot \text{K}$ and $Pr=6.6$ .
(b) If, after extended operation, fouling provides aresistance of $R_{f,i}^n={10}^{-4}{m}^2\cdot \text{K/W}$ , at the inner
surface, what is the value of $U_o$ ?
(c) If water is extracted from the lake at $\text{15}°\text{C}$ and $10\text{ Kg/s}$ of steam at $0.0622$ bars are to be condensed, what is the corresponding temperature ofthe Water leaving the condenser? The specific heatof the water is $4180\text{J/kg}\cdot \text{K}$ .