heat transfer help!!!!!?

Question

i want to evaluate the optimum thickness of insulation for a 2-in (nominal) diameter copper pipe carrying hot water at 70 °C with a heat transfer coefficient, hi, of 100 W/m2°C and subjected to a surroundings of air at 20°C with ho=10 W/m2°C....

Answer 1

The optimum thickness is infinity. You need to factor in the cost for various thicknesses and weigh that against how much heat you are willing to lose.