We will look at how to reduce unwanted energy transfers by using thermal insulation and lubrication.
Most people like their homes to be warm and to achieve this, they would need to reduce the amount of heat energy that is released to the surroundings.
There are many features in buildings to reduce this:
With convection, heat energy is transferred through liquids and gases. So, if air is able to escape out of the house, there will be a loss of heat energy by convection.
To prevent this, we would need to seal the house, to reduce the amount of air that can escape. This can be done by:
This is why we have foam seals around our doors and windows and one of the reasons why we draw our curtains at night.
With conduction, heat energy is transferred through solids. So the loss of heat energy by conduction would involve direct heat loss through a solid. For example, this solid could be a wall or a window.
To reduce heat loss by convection, houses tend to have:
It is also common for houses to have cavity walls, which is where there are two layers of bricks with foam in between them. Foam is used instead of an air gap. This is because, although foam and air are bad thermal conductors, air only reduces conduction whereas foam reduces conduction and convection.
Also, the foam has isolated air bubbles, which means the gap between the bricks isn’t quite solid or gas.
Frictional forces are formed when two objects move against each other. The frictional forces resist the motion, making it harder for the objects to slide against each other. The problem with friction is that it reduces the efficiency of energy transfer, causing objects to heat up.
Lubrication is a substance (often a liquid) used to reduce friction and wear between moving objects or surfaces. This increases efficiency.