A horizontal copper pipe of inner radius 2.5 cm carries saturated steam at 150 °C
PHYSICS · Multi-part · CBSE · Physics · Thermal Properties of Matter · Thermal Properties of Matter
Problem
A horizontal copper pipe of inner radius 2.5 cm carries saturated steam at 150 °C. The pipe is covered first with a 2 cm thick layer of asbestos (thermal conductivity 0.10 W m⁻¹ K⁻¹) and then with a 1 cm thick layer of fibreglass (thermal conductivity 0.04 W m⁻¹ K⁻¹). The outer surface of the fibreglass is exposed to air at 25 °C such that the outer surface of the insulation settles at 45 °C in steady state.
(i) Starting from the definition of heat current, obtain a general expression for the steady-state heat flow per unit length through two concentric cylindrical layers of different materials.
(ii) Using your expression, calculate the heat loss per metre length of the insulated pipe under the given conditions.
(iii) Determine the temperature at the interface between the asbestos and fibreglass layers.