Benzene is cooled at a rate of 1000 kg/h from 80 C to 40 C in a countercurrent double-pipe heat exchanger. The effective length of the heat exchanger is 20 m. Water flowing through the inner tube, entering at 30 C and leaving at 40 C, is the coolant. Benzene flows through the annulus. (a) Calculate the heat duty (q) of the exchanger and the water flow rate. Points (5+5=10) (b) Calculate the individual film coefficients and the overall coefficient based on outside area. (c) Do you think the tubes have fouled? and if yes, estimate the fouling factor. Required info : Inner tube 25 mm OD & 21 mm ID Outer pipe: 48 mm OD & 41 mm ID Physical properties of benzene at the average T (62.5 C): Points 30 Points 10 Specific heat = 1.88 kJ/kg.C; viscosity = 0.37 cp; density = 860 kg/m ; thermal conductivity = 0.154 W/m C Physical properties of water at the average T (35 C): Specific heat = 4.187 kJ/kg.C; viscosity = 0.8 cp; density = 1000 kg/m ; thermal conductivity = 0.623 W/m C