In winter, a pipe is used to deliver hot water at the temperature of 88 C. This 60 m long pipe has an internal diameter and external diameter of 0.14 m and 0.26 m, respectively. A protective insulation layer with uniform thickness is applied on the pipe's external surface to control the maximum heat loss to the surrounding air at 10 C to below 1000 W. Some useful information is provided: Thermal conductivity of pipe (kp) = 1.6 W/mK Thermal conductivity of thermal insulation layer (k/) = 0.03 W/mK Convection heat transfer coefficient at the air-side external surface (ha) = 4 W/mK Convection heat transfer coefficient at the water-side internal surface (hw) = 20 W/mK Solve the followings by assuming negligible radiation: (a) Estimate the minimum thickness of the thermal insulant. (b) Determine the surface temperature of the applied thermal insulant. Given: Thermal resistance of convection: R = Thermal resistance of cylinder: R - 1 hA In(2) 2m1.2