Oil is heated from 22°C to 56°C by passing through a tube of 4 cm in diameter. Find out the length of the tube required, for an oil flow rate of 60 kg/min if the surface temperature of the tube wall is maintained at 100°C. Assume the following properties of oil at mean temperatures; $\rho$ = 895 kg/m3; cp = 0.52 kcal/kg-0C, K = 0.13 kcal/hr-m-0C, v = 0.4´10-6 m2/sec.