Consider a pipe-in-pipe configuration consisting of concentric steel tubes with an intervening insulating material. The inner tube is used to transport warm crude oil through cold ocean water.The inner steel pipe (k = 35 W/mK) has an inside diameter of D = 150 mm and wall thickness t₁ = 20 mm. The outer steel pipe has an inside diameter of D = 250 mm and wall thickness t₂. Determine the maximum allowable crude oil temperature to ensure the polyurethane foam insulation (k = 0.0675 W/mK) between the two pipes does not exceed its maximum service temperature of 20°C. The ocean water is at θ[infinity] and provides an external convection heat transfer coefficient h = h[infinity]. The convection coefficient associated with the flowing crude oil is hₒ = 450 W/m²K.