Energy stores, transfers and conservation

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Question 55

Easy

To reduce thermal energy transfers out of residential properties, double-glazed windows are installed. The rate of heat transfer per unit area through the window is measured by its $U$ -value.

Figure 1 shows how the $U$ -value of a double-glazed window changes with the width of the air gap between the two glass panes.

Graph of U-value against Air gap width

Figure 1

Air gap width ( $mm\text{mm}$ )	$U$ -value ( $W/(m2⋅K)\text{W}/(\text{m}^2\cdot\text{K})$ )
2	4.5
4	3.5
8	2.8
12	2.6
15	2.7
18	3.0

Using the data in Figure 1, describe how the $U$ -value of the double-glazed window changes with the width of the air gap.

[2]

Energy stores, transfers and conservation

Question 55

Figure 1

Energy stores, transfers and conservation Questions

Energy stores, transfers and conservation

Question 55

Figure 1

Energy stores, transfers and conservation Questions