A 20-km insulated standard steel pipeline of nominal size 200mm (XS-80) is carrying oil at an average temperature of 27C. The ambient temperature is 10C and the outer wall of the insulation is assumed to be at this temperature (negligible heat transfer coefficient between insulation and the ambient). The maximum allowable rate of heat loss from the line is to be 500 kW to ensure flow assurance. Consider separately the three materials, polyethylene, polypropylene and polyurethane as insulation material. The thermal properties of these materials are given in table 1. Determine the minimum thickness of insulation required in each case. State all the assumptions