What does it do? Light enables us to see, and heat keeps us from being cold. However, ultraviolet rays often carry the unfortunate circumstance of containing too much energy. For example, infrared rays create heat in much the same way as rubbing your hands together does.

The hot air and sand in Death Valley have a lot of thermal energy, or the kinetic energy of moving particles. But even cold objects have some thermal energy. That’s because the particles of all matter are in constant random motion.

Matter in its gas state has the most thermal energy than when it is a solid or a liquid. Because gasses have more thermal energy than others, they move differently than others.

Materials that are good conductors of thermal energy are called thermal conductors. Metals are very good thermal conductors. Materials that are poor conductors of thermal energy are called thermal insulators. Gases such as air and materials such as plastic and wood are thermal insulators.

Figure below explains how a refrigerator does its work. As a liquid, the refrigerant absorbs thermal energy from the cool air inside the refrigerator and changes to a gas. As a gas, it releases thermal energy to the warm air outside the refrigerator and changes back to a liquid.

The thermal energy is used to heat water, which is pumped through a system of pipes and radiators. A warm-air heating system burns fuel in a furnace to produce thermal energy. The thermal energy is used to heat air, which is forced through a system of ducts and registers. A thermostat controls a home heating system.

How does heat travel? One thing you’ve probably noticed about heat is that it doesn’t generally stay where you put it. Hot things get colder, cold things get hotter, and—given enough time—most things eventually end up the same temperature.

Principles of Heat Transfer Heat is transferred to and from objects — such as you and your home — via three processes: conduction, radiation, and convection. Conduction is heat traveling through a solid material. Infrared radiation will also carry the heat of your walls and ceiling directly to your body.

The air coming out should be 14 to 20 degrees cooler than the air flowing in. Move the thermometer to a vent in each room or area of your home. If any of the vents are much colder or warmer than another, there may be a problem with the ductwork, or the distance may be too great from the blower.

Defrost mode basically means your heat pump temporarily switches to cooling mode. This forces the outdoor coils to heat up, melting any frost or ice that has built up. And because the heat pump switched to cooling mode, it will blow cold air into your home for a few minutes.