Conduction of heat: A solid concrete wall 4.0 m by 2.4 m and 30 cm thick, with a thermal conductivity of 1.3 W/(m ∙ K), separates a basement at 18°C from the ground outside at 6°C. Under steady state conditions, how much heat flows through the wall in one hour?
A) 1.8 MJ
B) 1.8 kJ
C) 500 J
D) 5.0 MJ
E) 5.0 kJ

Question

Quizplus · Accepted Answer

The heat flow through the wall can be calculated using the formula $Q = \frac{kA(T_{hot} - T_{cold})t}{d}$, where $Q$ is the heat flow, $k$ is the thermal conductivity, $A$ is the area of the wall, $T_{hot} - T_{cold}$ is the temperature difference across the wall, $t$ is the time, and $d$ is the thickness of the wall. Plugging in the given values: $Q = \frac{1.3 \times 4.0 \times 2.4 \times (18 - 6) \times 3600}{0.3}$, which calculates to approximately 1.8 MJ.

Conduction of Heat: a Solid Concrete Wall 4