A 15cm diameter, 2cm thick sight glass installed in the wall of a glass fired boiler allows the operator to observe conditions inside the boiler during operation. During normal boiler operation,the inside surface of the sight glass is 130C. Due to natural convection current in the warm boiler room, air at 35C flows vertically across the outside surface of the sight glass, giving the heat transfer coefficient of 25 W/m² K. The sight glass is made of soda lime glass with a thermal conductivity of 1.4 W/mK. Find the temperature of the outside of the sight glass and the heat transfer through the sight glass.

Fig: 1