Question

The inner and outer panes of a double-glazed window of dimensions 2 m x 2 m and 0.6 cm thick, the temperature is 18 ° C and 6 ° C, respectively. If the 1 cm gap between the two panes is filled with still air, determine the rate of heat transfer through the conduction air layer in kW and the temperatures at the air-glass interfaces. K air = 0.026 ? / ?.? and K glass = 0.85 ? / ?.k

Answer 1

The rate of heat transfer is given by

Where d is the thickness and A is the area of the plates.

Here, we have 3 layes.

We have to find H and the temperature between the layers.

Let Ta be the temperature between the layer 1 and the air

So,

Here,

A = 2m*2m = 4 m^2

d glass = 0.6 cm = 0.006 m

T2 = 18 C

The heat reansfered through air is

HWere Tb is the temperature after the layer of air

d air = 1 cm = 0.01 m

For the last layer of glass

T1 = 6 C

Since energy must be conserved, all these heat values must be equal.

So,

Applying the values,

Solving the equations we get

and