Alfred Martin

2021-12-16

A picture window has dimensions of $1.40\text{}m\times 2.50\text{}m$ and is made of glass 5.20 mm thick. On a winter day, the temperature of the outside surface of the glass is $-{20.0}^{\circ}$ C, while the temperature of the inside surface is a comfortable
$19.5}^{\circ$ C. (a) At what rate is heat being lost through the window by conduction? (b) At what rate would heat be lost through the window if you covered it with a 0.750-mm-thick layer of paper (thermal conductivity $0.0500\frac{w}{m}\cdot k$

Debbie Moore

Beginner2021-12-17Added 43 answers

We can calcualte the thermal resistance via

$R=\frac{L}{K}$

$=\frac{0.52\times {10}^{-2}\text{}m}{0.8\text{}\frac{W}{m}\cdot K}$

$=6.5\times {10}^{-3}\frac{{m}^{2}}{\cdot}\frac{K}{W}$

The rate of heat loss can be determined from

$H=\frac{A}{R}[{T}_{H}-{T}_{C}]$

$=\frac{1.4\text{}m\times 2.5\text{}m\times [19.5-(-20)]K}{6.5\times {10}^{-3}{m}^{2}\cdot \frac{K}{W}}$

$=2.1\times {10}^{4}\text{}W$

The rate of heat loss can be determined from

Bertha Jordan

Beginner2021-12-18Added 37 answers

b.

After converting the window with paper there will be additional thermal resistance

for

To calculated the rate of heat loss, calculate

22+64

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