Question

A house has a composite wall of wood, fiberglass insulation, and plaster board, as indicated in the sketch. On a cold day, the temperature and the convection heat transfer coefficients are T∞,i =20°C, hi =30 W/m2K and T∞,o=−15°C, ho =60 W/m2K. The wall surface area is 350 m2. Determine the total heat loss through the wall. Conductivities are given as b k =0.038 W/m.K, s k =0.012 W/m.K, p k =0.17 W/m.K

Glass fiber blanket (28 kg/m3), kn Plaster board, kp Plywood siding, kg Toy, Tosho 10mm + 100mm-20mm

Answer 1

Solution :- The expression for the total thermal resistance of the house wall is given by as follows: Lp Lb Ls hia KpA Kb. A Ki A hoa immine ww Mhhuhh To,o=156 Tooi 1 = 20c :. R total 1 1 = ER= + Lp ke:A + Lb KoA Ls ks. A + hi A boia 1 Ls 1 Rtotal = 1 А. + Lp ke + Lb Kb + + hi Ks ho 1 0.01 0.10 0.02 1 + + 1 350 + + - 30 0.17 0.038 0.012 60 Riotal = 0.012592 °C 1 watt AT The heat loss loss then ; q = R total q 20-(-15) 2779.54 Calatl 0.012592 q = 2.78 kcal