Question

2). A hydrocarbon fluid is to be cooled from 90 to 15 C at a rate of 9.72 ton per hr. pass shell and tube heat exchanger with the following specification is available A single- Number of tubes 250 1.0 m 23.5 mm 25 mm 15 W m- K-I Tube length Internal tube diameter External tube diameter Thermal conductivity of tube wall Chilled water is supplied at 4C and is normally discharged at 10 C. From experience it is assumed that the film heat transfer coefficients for the tube side (water) and the shell side will be 2500 and 3000 W m2 K1, respectively. Is the exchanger adequate? (Estimate for both co- current and counter-current flows.) After some time of operation, the tubes become scaled and a fouling factor of 2 x 104 m2K W-1 can be assumed. What is the new overall heat transfer coefficient and, assuming that the inlet and outlet temperatures remain unchanged, what is the reduction on capacity of the heat exchanger? Take the mean heat capacity of the hydrocarbon fluid to be 3.90 kJ kg"K. mos Re

Answer 1

"us +끝ト(#)+.liqu U Ui K 200o s U 12 33.12 Wm do 1f Uf Uclean 1233.92

an widl be Thas y dhe mas flois hate will become 675,3 _ _ 2.31 Cp A1 37x(30-15) %Reduction-2-88-231 X 100=17.8% 2.89