A shell and tube heat exchanger with one shell pass and 15 tube passes uses hot water on the tube side to heat oil on the shell side. The single tube has a length per pass of 3m and a diameter 25 mm. The water (heat capacity =4184J/kgK ) enters at 85C at 0.15kg/s and leaves at 20C. Inlet and outlet temperatures of the oil are 5C and 30. Find the average convective heat transfer coefficient for the outer tube surface. The coefficient for the internal flow hi=3600W/m2K