Chapter 14, Problem 25Q

Part (a):

To determine

The mechanism of heat loss through glass panes, through metal frame and ventilation around edges.

Explanation of Solution

Introduction:

Heat is transferred from one place to another in three different ways: conduction, convection and radiation.

In conduction, energy is transferred through a substance when hot and faster molecules collide with slower moving neighbours.

In convection, the energy is transferred by the mass movement of molecules even a considerable distance.

Radiation does not require the presence of matter. All objects radiate energy which depends on the temperature and nature of the surface.

Heat loss through glass panes is due to conduction and radiation.

Heat loss through metal frame is due to conduction

Ventilation around the edges is heat loss by convection.

Part (b):

To determine

The type heat loss reduced by heavy curtains.

Answer to Problem 25Q

Solution:

Heavy curtains reduce all three types of heat loss.

Explanation of Solution

Heavy curtains can reduce all three heat losses. The curtains will prevent air circulation around the edges of the windows, thus reducing the convection cooling. The curtains are opaquer than the glass, preventing radiation heat transfer from reaching the glass. These curtains also provide another layer of insulation between the outdoors and the warm interior of the room, lowering the rate of conduction.