0.8kg/s of furnace oil is to be heated from 10C to 90C in a shell and tube heat exchanger. Heating is done by steam available at 120C. Oil is circulated through the tubes while steam is circulated in the shell Tubes of 16.5mm inside diameter and 19mm outside diameter are available. Length of tube =3.0m. The film coefficient of heat transfer for oil is 90W/m2K while the film coefficient of heat transfer for condensing steam is 7400W/m2K. Density of furnace oil =900kg/m3. Specific heat of furnace oil =1970J/kgK. Fouling resistance for furnace oil =0.0009m2K/w. Suggest a suitable design of the shell and tube heat exchanger. Maximum oil velocity that can be used is 0.05m/s. Estimate the number of passes on tube side required in a heat exchanger