Heat energy (also caloric energy or thermal energy) is the manifestation of energy in the form of heat. In all materials the atoms that make up their molecules are in continuous motion either moving or vibrating. This movement implies that the atoms have a certain kinetic energy which we call heat, heat energy or heat energy. In a way, calorific energy is the internal energy of a body.
The internal energy of a thermodynamic system can be changed in two ways: by performing work on the system and by exchanging heat with the environment. The energy that the body receives or loses in the process of exchanging heat with the environment is called the amount of heat or simply heat.
Heat energy transmission
Heatenergy can be transmitted from one body to another following the laws of thermodynamics in three different ways:
- Radiation heat transmission.
- Thermal energy transmission by conduction.
- Transmission of heat energy by convection.
Thermal radiation energy is transmitted through electromagnetic waves. It is the way in which thermal energy comes from the Sun. The main example of this case is found in solar thermal energy facilities, which take advantage of solar radiation to heat water. The hot water obtained from these solar installations is usually used for heating and for use as sanitary hot water.
The transmission of heat energy by conduction is experienced when a hot body is in physical contact with another colder body. Energy is always transmitted from the hot body to the cold body. If both bodies are at the same temperature there is no energy transfer. When we touch a piece of ice with the hand part of the thermal energy of our hand is transferred to the ice, so we feel cold.
The transmission of thermal energy by convection occurs when hot molecules are moved from side to side. It would be the case of wind, capable of moving molecules with certain heat energy from one side to another.
Unit of measurement of heat energy
The units for measuring heat energy are the same units that are used to measure energy since it is still a form of energy.
Energy is measured in Joules (J) according to the international system. Although when it comes to heat energy, calories (lime) are also used. A calorie is the amount of energy that is needed to raise a centigrade one gram of water. One calorie equals 4.18 joules.
The heat in the phase changes
If a body is supplied with thermal energy, increase its temperature. On the other hand, if it yields heat energy to the outside, it cools. This happens as long as this body is not changing phase. That is, during the transformation from solid to liquid, from liquid to gas and vice versa the variation of heat does not imply a change in temperature until the transformation is completed.
An example of this phenomenon can be observed with water. If liquid water is supplied with heat, it increases the temperature to 100 degrees Celsius, which boils. From this temperature all the heat supplied is used to change the liquid state to gas (water vapor). At this time the temperature will remain constant until all the water is steam. When all the water is steam, the temperature can continue to rise.
The energy required for the phase transition of a unit of mass of a substance is called the specific heat of the phase transformation. According to the physical process that occurs during the phase transformation, they can release the heat of fusion, heat of evaporation, heat of sublimation (sublimation), heat of recrystallization, etc. Phase transformations occur with an abrupt change in entropy, which is accompanied by the release or absorption of heat, despite temperature constancy.
Importance of heat energy in nuclear energy
In the process of nuclear fission of uranium atoms a large amount of energy is released in the form of heat. Thanks to the properties discussed above, this energy can be harnessed by performing different energy transformations. There are types of reactors, for example, boiling water reactors that take advantage of heat to perform a phase transformation and obtain steam from a secondary water circuit. With the steam, a steam turbine will then be activated to obtain electricity.
- Basic Principles of Classical and Statistical Thermodynamics (PDF)
- Thermal energy in the British Encyclopedia
Last review: February 3, 2020