The three types of heat transfer are one of those pieces of knowledge that, as an aspiring firefighter, you’ll need to learn. Not only will it make you knowledgeable in all things fire-related, but it will also come in handy when facing an actual fire situation.
What types of heat transfer exist?
There are three types of heat transfer: conduction, convection, and radiation.
- Conduction: when heat transfers through conduction, it flows through solid elements or materials. As an example, imagine you place your hand on a cooking pot that has been on a stove, and you can feel its heat. Some elements are good heat conductors, while others are bad. A good conductor is, for example, sand and metal. A lousy conductor can be wood, plastic, or air.
- Convection: convection happens when heat transfers through gases or liquids. For example, when you’re boiling water, you can feel the heat from the vapor that emits and the hot water.
- Radiation: the last type is when heat transfers through electromagnetic waves. It’s called radiation. For example, when you stand outside and feel the sun’s warmth or near an open flame, you can feel its heat.
What is Heat Transfer?
If we go by the book definition, in thermodynamic systems, we can define heat transfer as:
“The movement of heat across the system’s border due to a difference in temperature between the system and its surroundings.”
Another thing to know is why heat transfer occurs. In physics, it’s due to the second law of thermodynamics.
In simpler terms, when you put two items at different temperatures together (in thermal contact), they will try to balance their thermal energy between them. Once they reach the same temperature, we say they are at thermal equilibrium.
In practice, what happens is that heat always flows from a hotter element to a colder one.
And while we refer to it as heat transfer, that doesn’t mean it’s hot. For example, suppose you mix a glass of cold water with a glass of water at room temperature. In that case, we are also referring to heat transfer, from a freezing liquid to a slightly hotter one. At some point, both elements will reach thermal equilibrium.
Conduction heat transfer examples:
- Ironing: heat transfers from the appliance to your clothes when ironing them.
- Melting ice cubes: when you grasp an ice cube with your hands, heat transfers between them until the ice melts away.
- Walking through sand: You can feel its heat if you walk through the sand. If it’s summer, do you too, having received energy from the sun.
Convection heat transfer examples:
- Blood circulation: In warm-blooded animals, blood circulation works by convection, which regulates the body’s temperature.
- Sea Currents: On the sea, some currents form because warm water travels towards the poles while cold water travels towards the equator.
- Boiling water: When you boil water, the denser molecules flow towards the bottom while the hotter ones go to the top of the pot.
Radiation heat transfer examples:
- Microwave / Oven cooking: A microwave or a conventional oven emits heat that cooks the food.
- UV sunlight: The rays of light from the sun travel through the air, yet you can feel the sun’s warmth on your skin.
- Fireplaces: you can feel the warmth of a lit fireplace, even though you don’t touch the flames.
As you’ll soon realize, understanding the different methods of heat transfer is essential for a firefighter in your theoretical classes and the field. You’ll be able to recognize, for example, when there is a fire in an adjacent room by feeling the heat without burning yourself. In addition, you learn about tricks and which materials are better conductors than others.
While it sounds easy, this knowledge may save your life in a blaze.
What are the 3 types of heat transfer?
They are conduction (solids), convection (gas or liquid), and radiation (electromagnetic waves).
Do I need to know this to become a firefighter?
In many jurisdictions, it will be part of your theoretical evaluation.
What are the top thermal conductive materials?
The top materials based on their thermal conductive properties, that is, the ability to transmit heat easily, are:
- Aluminum nitride
- Silicon carbide
These materials can transfer heat efficiently or absorb heat from their environment.
What are some of the worst thermal conductive materials?
Here’s a list of some of the worst thermal conductors:
- Vacuum (nothingness)
- Air (not a material)
- Polystyrene foam
- Fiberfax paper
- Foamed glass
These materials can barely transfer heat or are incredibly inefficient in doing so.
Do you need detailed data on a particular substance?
The Material Database at ThermTest has more than 1,000 materials listed if you want to learn about other substances. They include their respective thermal conductivity ratings, density, diffusion, and many other metrics.