(b) The heat flux q is the quantity of heat flowing through a unit area of material per unit time. It can be computed using Fourier's law,
J = -k dT/dx
where J (W/m^2) and k = coefficient of thermal conductivity that parameterizes the heat-conducting properties of the material (W/°C m), T = temperature (°C) and x = distance (m) along the path of the heat flow. The following temperatures are measured from the surface (x = 0) into a stone wall:
x, m 0 0.08 0.20
T, °C 20 17 15
If the flux at x = 0 is 60 W/m^2, compute k.
