This article discusses about examples of heat transfer. Heat transfer is a branch of thermal engineering that concerns with generation, use and exchange of heat energy from one system to another.
Heat can be transferred by many ways. Most commonly known methods are conduction, convection and radiation. This article discusses about different modes of heat transfer and then we will discuss about examples of heat transfer that we see in our daily lives.
- Our skin gets warm after going out in sunlight
- Boiling water
- We get burned after touching hot pan
- Water gets warm after leaving under hot sun
- Food gets warm after heating it in microwave
- Food gets cold when left in room
- Tea cup gets hot after tea is poured in the cup
- Phone gets hot when its battery gets hot
- Phone charger gets hot when the wires inside get hot
- TV gets hot after its coil gets hot after excessive usage
- Forest fire
- Ice melts after being dipped in a warm drink
What is heat transfer?
As discussed above, heat transfer is the branch of thermal engineering which deals with generation of heat, use of heat and transfer of heat through various physical systems.
Heat does not necessarily need a medium to get transferred from one system to another. These systems are at different temperatures. The heat will flow from a system with high temperature to a system that is at lower temperature. We shall study about its types in the later sections of this article.
Modes of heat transfer
The heat can be transferred from one system to another by many ways. Some methods need a medium whereas some methods like radiation don’t need any medium for heat transfer to take place.
The different methods of heat transfer are given below as follows-
- Conduction – Conduction is a mode of heat transfer where the heat s transferred through systems when they are in contact with each other. The molecules of these systems vibrate and transfer energy through these vibrations. The vibrations although fade away as the distance becomes larger proving that conduction is inversely proportional to the length of the systems.
- Convection – Convection is the process of heat transfer with the help of moving fluids. When we pour warm water on our body and our muscles get relaxed, this is due to convection of heat from water to our skin.
- Radiation – Radiation is a process of heat transfer in which the heat is transferred without the help of any medium or physical contact between the systems.
Examples of heat transfer
Heat transfer takes place almost everywhere around us in daily lives. The most commonly seen examples of heat transfer are given below-
Our skin gets warm after going out in sunlight
The heat emitted by the Sun gets radiated towards Earth. This radiated heat is absorbed by our skin and hence we feel warm when we go outside in sunlight. Long exposures may even burn the skin (tanning is an example).
The steel spoon gets warm after coming in contact with hot container
When the steel spoon is kept in touch with a hot container, the steel spoon gets warm due to heat transfer by conduction. As the steel spoon is a good conductor of heat, the heat gets easily transferred to steel making the steel spoon’s temperature higher.
The water is boiled due to convection and conduction both. The vessel inside which the water is kept becomes hot first. This is due to conduction heat transfer. Then the water gets heated as a result of heat transfer between the water surface and the hot vessel. The remaining water gets hot by the process of convection.
In thermometer, the level of Mercury rises when the heat from body is transferred to it. The rise in Mercury is used to determine the temperature of our body.
We get burned after touching hot pan
When the pan is hot and we touch it, we feel hot or burn our hands sometimes. This is due to heat transfer taking place due to conduction. The heat from hot pan is transferred to our skin as we make contact to the pan.
Water gets warm after leaving under hot sun
When we leave water under hot sun, the heat radiated by the Sun makes the water warm. This happens so because the water absorbs the radiated heat which in turn makes it warm. This is the same reason why we feel hot after stepping outside the house under scorching heat.
Food gets warm after heating it in microwave
Microwave is used for warming the food. The microwave sends out waves which makes the food warm. This entire heat transfer process takes place in the form of radiation.
Food gets cold when left in room
When we leave the food untouched in our room, then the food tries to make thermal equilibrium with the surroundings which happens by lowering the temperature of food. As the food gets colder, thermal equilibrium is established. This is also an example of heat transfer as heat is transferred from the food to surroundings.
Tea cup gets hot after tea is poured in the cup
After tea is poured in the cup, conduction takes place between the outermost layer of tea and the surface of the cup. This way the heat is transferred from tea to the cup as a result of which the cup becomes hot.
Phone gets hot when its battery gets hot
When the battery gets hot due to longer operation of phone, the phone also gets hot. This is because the battery is in contact with the mobile phone. The heat is transferred from battery to the phone with the help of conduction.
Phone charger gets hot when the wires inside get hot
The wires inside a charger adaptor get hot due to excessive charging. These wires are in contact with the adaptor from inside, this way heat transfer due to conduction takes place and adaptor in turn also becomes hot.
TV gets hot after its coil gets hot after excessive usage
After excessive usage, the coils inside TV get hot. The coil being in contact with the inside of TV, makes the tv also hot. This is why it is recommended to watch television under control.
When the heat from sun is very strong, the dry leaves may catch fire due to excessive heat. This is an example of radiation heat transfer. It is important to note that radiation can cause fire too!
Ice melts after being dipped in a warm drink
After dipping the ice in a warm drink, convection takes place between ice and the drink which makes the temperature of ice higher. This result in melting of ice.
Steamer is a device that emits out steam. This steam is used for getting rid of cold or skin treatment etc. The heat from the steam is transferred to our skin with the help of convection. The steam carries the heat with it and transfers it to the skin when in contact with it.
Examples of heat transfer by radiation
Radiation heat transfer does not physical contact of both the systems nor it needs a medium to get the heat transferred from one system to another. Let us see some of the examples of radiation heat transfer given below-
- Hot metal rod transferring heat to surroundings – When a metal rod is heated, it emits out heat to its surroundings, this heat transfer takes place with the help of radiation. If we put our hand near the metal rod, we will feel hot even without touching it.
- Microwave – Food is warmed inside a microwave by the action of heat transfer by radiation. The microwaves inside the microwave make the food warm with the help of radiation.
- Solar UV radiation – Solar UV radiation is the radiation emitted by the sun. This radiation can be used for generating electricity using solar panels. Even our skin gets warm due to the action of UV radiation. This is solely due to heat transfer by radiation.
- Emission of Gamma rays – Gamma rays are a type of em wave. These waves move by the principle of radiation after being emitted.
- Light being emitted by incandescent lamp -Light from incandescent lamp is an example of radiation as we feel warm while standing beside the lamp even without touching it.
- Heat coming out from bonfire – Bonfire is a small controlled fire used to make ourselves feel warm during cold weather. The heat transfer takes place with the help of radiation. We do not touch the fire of bonfire but still feel the heat being emitted by it.
- Heat emitted by a radiator – A radiator in vehicle becomes hot when the vehicle has travelled too much. The heat emitted from the radiator can be felt by us. This is due to radiation heat transfer. We do not physically touch the radiator but still feel the heat.