Answer to Question #291970 in Physics for kiana

Question

1. a) What is the rate of energy loss in watts per square meter through a glass window 1.8 mm thick if the outside temperature is -16°F and the inside temperature is +76°F? (b) A storm window having the same thickness of glass is installed parallel to the first window, with an air gap of 5.3 cm between the two windows. What now is the rate of energy loss if conduction is the only important energy-loss mechanism? (The thermal conductivity of window glass is 1.0 W/m·K, and of air is 0.026 W/m·K.)
2. Consider a slab of face area A and thickness L. Suppose that L = 34 cm, A = 63 cm², and the material is copper. If the faces of the slab are maintained at temperatures T_H = 199°C and T_C = 21°C, and a steady state is reached, find the conduction rate through the slab. The thermal conductivity of copper is 401 W/m·K.

Answer 1

(a) The rate of energy loss in watts per square meter is

$$q=k\Delta T/t=28.4\text{ kW/m}^2.$$