where q is the heat flux, k is the thermal conductivity, A is the area, and dT/dx is the temperature gradient.
A large plane wall of thickness 40 cm has a thermal conductivity of 1.2 W/m°C. One side of the wall is maintained at a temperature of 80°C, while the other side is maintained at 40°C. Determine the heat flux through the wall.
q = -1.2 * 1 * 100 = -120 W/m²
dT/dx = (80 - 40) / 0.4 = 100°C/m
q = (20 - 0) / 0.5625 = 35.56 W/m²