Question

For such aircraft application (Figure 3), a wall is made from insulation material (k-0.030 W/m.K) and the insulation material is mounted between four layers of carbon steel (2 mm thickness), the carbon layers are separated by a 2 mm air gap (kair-0.025 W/mK). Figure 3, the thermal conductivity of the carbon steel is (k-15.5 W/m.K). The temperature inside the wall is maintained at 6 °C. The environmental temperature is 24°C. The engineer would like to avoid condensation occurring at outer surface of the wall when the outer surface temperature drops below 21°C. If the convection heat transfer coefficient at the inner surface of wall is h 6 W/m·K and the convection heat transfer coefficient at the outer surface of the wall is h- 11 W/m2.K a) Draw a fully labelled sketch for the wall, show the thermal resistance. (5 marks) b) Calculate the rate of heat transfer per unit of area of wall surface. (5 marks) c) Calculate the thickness of insulation to avoid condensation. (10 marks) Air ir Inside Outside Insulation. Carbon steel Carbon steel Figure 3

Answer 1

Accordiny to ha given datn k ins= 0.03 Tnsida. owsida. in air - 0-025 0c 21℃ to ote u 24-21. 0.002 , 0.002 . 0.002 ki吗 003 | χ= 3.82 mm 21-6 ax[0.oo2.o.0o2 o.002