insulation is reported to be \(k = 0.029 \text{ W/m\cdot K}\). The
measured temperature difference across a 20-mm-thick
sheet of the material is \(T_1 - T_2 = 10^{\circ}C\).
(a) What is the heat flux through a 2 m \(\times\) 2 m sheet of
the insulation?
(b) What is the rate of heat transfer through the sheet
of insulation?
1.2 The heat flux that is applied to the left face of a plane
wall is \(q'' = 20 \text{ W/m}^2\). The wall is of thickness \(L = 10\
mm\) and of thermal conductivity \(k = 12 \text{ W/m\cdot K}\). If the
surface temperatures of the wall are measured to be
\(50^{\circ}C\) on the left side and \(30^{\circ}C\) on the right side, do
steady-state conditions exist?
1.3 A concrete wall, which has a surface area of \(20 \text{ m}^2\) and
is 0.30 m thick, separates conditioned room air from
ambient air. The temperature of the inner surface of the
wall is maintained at \(25^{\circ}C\), and the thermal conductiv-
ity of the concrete is \(1 \text{ W/m\cdot K}\).
(a) Determine the heat loss through the wall for outer
surface temperatures ranging from \(-15^{\circ}C\) to \(38^{\circ}C\),
which correspond to winter and summer extremes,
respectively. Display your results graphically.
(b) On your graph, also plot the heat loss as a function of
the outer surface temperature for wall materials hav-
ing thermal conductivities of 0.75 and 1.25 \(\text{W/m\cdot K}\).
Explain the family of curves you have obtained.
