Heat transfer is the movement of thermal energy from one object or material to another. Heat flows from areas of higher temperature to areas of lower temperature. The greater the temperature difference, the faster the flow of heat from one object to another. The three types of heat transfer are conduction, convection, and radiation.
What is Heat Transfer?
What do you think is the most important factor when it comes to heat transfer?
- Conductivity of materials
- Surface area of materials
- Temperature difference between materials
The transfer of heat energy through direct contact between objects. Example: Holding an ice block in your hands will cause your hands to get cold. This is because your hands are at a higher temperature than the ice, causing heat to flow from your hands to the block of ice (lower temperature). This will also cause the block to start melting.
The transfer of heat energy through the movement of a fluid or gas. Imagine you're sitting near a cosy bonfire on a chilly evening. As the fire burns, the air above it gets heated. This heat energy makes the tiny particles in the air gain energy and start moving faster.
As a result, these energetic particles spread out and become more spaced apart. The hot air that forms above the fire is lighter and less dense compared to the surrounding cool air. It's like a never-ending cycle: as the hot air rises, it cools down and eventually starts sinking again.
This creates a continuous flow, with the cool air moving in to take the place of the rising hot air. And this process keeps repeating, creating what we call a
What are some examples of heat transfer by convection in everyday life?
Radiation is the transfer of heat energy through electromagnetic waves, such as sunlight warming your face on a sunny day. Example: When you go outside into the sunlight, you can feel the heat from the Sun on your skin. Heat has travelled through empty space between the Sun and the Earth to reach you. It cannot travel through convection or conduction because there is no particles to vibrate or flow in the vacuum of space.
Often radiation will be partially absorbed, reflected or transmitted according to the material and its colour. Example: A dark-coloured car heats up more quickly in sunlight than in lighter-coloured cars. This happens because dark-coloured objects absorb most of the radiation, whereas lighter-coloured objects reflect radiation.
What are some everyday situations where heat transfer occurs through radiation?
What are the primary differences between conduction, convection, and radiation?