Question

1. A wall of a house has a size of 20 mx 2 m. It consists of 3 layers of materials: 6 cm wood, 10 cm fiber glass, and 6cm wood. The conduction coefficients of wood and fiber glass are 0.2 and 0.05, respectively. The radiation cannot be ignored, and the emissivity of everything is 0.9. The room temperature in the house is always 20 C and the convection coefficient inside is always 5 W/m²-K. In a summer day, the outside temperature is 35 C and the convection coefficient outside is always 20 W/m²-K. The energy of the sunlight absorbed by the exterior wall is 800 W/m². a.) What is the exterior temperature of the wall? b.) What is the the heat removal rate by AC to maintain the room temperature at 20 C ? c.) What would the exterior temperature and heat removal rate be if the fibreglass becomes 5 cm or 20 cm?

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