A 1.2 m high and 2 m wide glass window, whose thickness is 6 mm and has thermal conductivity of 0.78 W/m.K and emissivity ε = 0.9. The room and the walls which face the window are maintained at 22°C,...

A 1.2 m high and 2 m wide glass window, whose thickness is 6 mm and has thermal conductivity of 0.78 W/m.K and emissivity ε = 0.9. The room and the walls which face the window are maintained at 22°C, and the average temperature of the inner surface of the window is measured to be 4°C. If the temperature of the outdoor is – 6°C, calculate

(a) the convection heat transfer coefficient on the inner surface of the window

 (b) the rate of total heat transfer through the window

(c) the combined natural convection and radiation heat transfer coefficient on the outer surface of the window.