Energy loss per day?

Question

an aluminum window frame has an area of 400 cm^2 and is 4.00 cm thick. find the energy loss per day due to conduction when the inside temperature is 20.0 degrees C and the outside is 0 degrees C.

How do I find the Energy Loss?

Answer 1

You find the heat conductivity of aluminum. One value I found was 221 W/degK-m. This parameter can be translated as the watts lost through an aluminum piece 1 m^2 in cross-section area and 1 m long with 1 deg K difference across it. So for the window frame you divide the area (0.04 m^2) by the thickness (0.04 m) and multiply by the temperature difference, then multiply by the constant (221). Note that this value (221 w) is the heat loss if the inside and outside surfaces of the window frame have this 20 C temperature difference. In actuality there will be a smaller temperature difference as the surfaces will not be at the ambient temperatures. (If we lived in an aquatic environment this would be less true.) Wind will bring the outside air and outside surface temperatures closer and increase the heat loss. Materials that impede airflow will minimize ths effect.