Question

A windowpane is half a centimeter thick and has an area of 1.0 m2. The temperature difference between the inside and outside surfaces of the pane is 15° C.
What is the rate of heat flow through this window? (Thermal conductivity for glass is 0.84 J/s⋅m⋅°C.)
a. 50 000 J/sb. 2 500 J/sc. 1 300 J/sd. 630 J/s

Answer 1

To solve this problem it is necessary to apply the concepts related to the heat flux rate expressed in energetic terms. The rate of heat flow is the amount of heat that is transferred per unit of time in some material. Mathematically it can be expressed as:

$\frac{Q}{t} = \frac{kA}{L} (T_H - T_C)$

Where

k = 0.84 J/s⋅m⋅°C (The thermal conductivity of the material)

$A = 1m^2$ Area

$L = 5*10^{-3}m$ Length

$T_H$= Temperature of the "hot"reservoir

$T_C$= Temperature of the "cold"reservoir

Replacing with our values we have that,

$\frac{Q}{t} = \frac{kA}{L} (T_H - T_C)$

$\frac{Q}{t} = \frac{(0.84)(1)}{0.005} (15)$

$\frac{Q}{t} = 2520J/s$

Therefore the correct answer is B.