glass each 4mm thick separated by a 23mm air gap. This window is a replacement for a single glazed unit. The double glazed unit is installed in the wall of a room in which the air temperature is maintained at 23 degreesC, the outer surface of the window is exposed to the atmospheric temperature which is 2 degreesC. The surface heat transfer coefficient of the room side glass is 5.7 W/m?K and 9.1 W/m?K on the outer surface of the window. The thermal conductivity of the glass is known to be 0.76 W/mK. i) On the assumption that the air gap between the layers may be regarded as a stationary layer of air of thermal conductivity 0.026 W/mK, calculate the heat transfer rate through the window and the temperature of the room side surface of the glass. ii) Calculate the heat transfer rate for the single glazed unit which has been replaced. The window was of the same dimensions consisting of a single pane of glass. It may be assumed that all of the remaining data are unchanged.

PROBLEM 1Consider an adult human standing in the centre of a closed room. The air and room’swalls, ceiling and floor surrounding the being are at a temperature of 25oC. Assume forthe adult body a temperature of 37oC, a surface area of 1.7m2, an emissivity of 0.95 andthe heat transfer coefficient of 6 W/m2K for natural convection between the air and thebody. Question:(a) Describe the modes of heat transfer between the adult human and theirsurroundings. What are some assumptions that must be made before calculatingthe heat transfer rates?(b) Determine the total rate of heat transfer from the adult into their surroundings.

A household oven door of 0.4 m height and 0.6 m width reaches an average surface temperature of 50°C during operation. Estimate the total heat loss to the room with ambient air at 22°C and convective heat transfer coefficient 5 W/m².K, if the door has an emissivity of 0.83 and the surroundings are also at 22°C.

1. (a)   Consider a room with a 1.8-m-high and 2.0-m-wide double-pane window consisting of two 4-mm-thick layers of glass separated by a 10-mm-wide stagnant air space. The convection heat transfer coefficients on the inner and outer surfaces of the window are 12 W/m2 K and 25 W/m2 K, respectively, while the average thermal conductivity of glass is 0.78 W/m K; and the air, 0.026 W/m K.   If the room is maintained at 22 oC, the outside temperature is -4 oC and heat transfer due to radiation can be neglected, determine:                 (i) Draw the sketch and thermal resistance network;                                                (ii) the total thermal resistance;                (iii) the steady rate of heat transfer through this double-pane window;                                                                              (iv) the temperature of the inner surface of the window.…