(50 Marks\} Define Nusseit Number and explain its ugnificance in terms of the conduction and comvection modes of heat transfer- [Marks 10) During a cold winter nohh, a room is heated by initiatirg fire at the fireplace as shown in the figure. The fireplace is separated from the room air by the use of a glass screen of length (height) 70cm and width of 120cm, if the room al temperature is 20C and the surface temperafure (room side) attained by the glass is 180 " C. Considering one dimensianal condition, caiculate the free convection heat transfer rate from the glass surface into the roam. Assume the glass surface to be a vertical flat plate. Solution; (Marks 40)