Physics

Problem

A composite wall has three layers in series, all of cross-sectional area

0.20\,\text{m}^2

: • brick, thickness

4.0\,\text{cm}

k=0.80\,\text{W m}^{-1}\text{K}^{-1}

• air gap, thickness

1.0\,\text{cm}

k=0.025\,\text{W m}^{-1}\text{K}^{-1}

• insulating board, thickness

3.0\,\text{cm}

k=0.040\,\text{W m}^{-1}\text{K}^{-1}

The inner surface of the brick is at

60^\circ\text{C}

and the outer surface of the board is at

0^\circ\text{C}

. Assuming steady conduction, find the temperature (in

^\circ\text{C}

) at the interface between the brick and the air gap. a)

47.5

37.5

57.5

53.3