Concept of heat:

Heat is one of the forms of energy that expresses the level of movement of the elements that make up objects, and that can be transferred from one body to another. Heat is transferred automatically from objects that have a high temperature to bodies that have a low temperature to reach a state of balance between them.

heat transfer:

Heat transfer is a branch of thermal engineering that is concerned with the generation, utilization, conversion and exchange of thermal energy between physical systems. Heat is transferred in various ways such as thermal conduction, convection currents, and thermal radiation.

Heat transfer methods:

1) Transportation: It is the mechanism of moving a fluid from one place to another, and it is related to the movement and momentum of this fluid.

2) Conduction or diffusion: the transfer of heat between objects that are physically in contact.

3) Convection currents: the transfer of energy between an object and its surrounding medium, due to the movement of the fluid.

4) Radiation: the transmission of energy by the emission of electromagnetic radiation.

Thermal conductivity:

It is the transfer of heat through solid bodies as a result of the movement of atoms and molecules in an object; Which leads to the transfer of part of its thermal energy to the atoms and molecules adjacent to it, the ability of materials to transfer heat depends on the degree of its conductivity of heat and it is called thermal conductivity, so the more the thermal conductivity of the material increases its efficiency in thermal conductivity, and metals are considered from the materials with high thermal conductivity, and the conductivity is proportional The thermal conductivity values ​​of the materials are very important in the field of building thermally insulated buildings.

Convection currents:

It is the simultaneous transfer of heat and mass in fluids; As a result of the difference in the temperature of the material, and thus its density, there are two types of convection:

Free convection: are the convection currents that arise from the buoyancy of liquids as a result of their temperature and different densities without the interference of external forces.

Forced convection: In which the liquid particles are transferred due to the presence of forced currents generated by external forces. It also occurs when food is heated in an oven equipped with a fan that conveys hot air faster.

Thermal radiation:

It is the transfer of thermal energy in the form of electromagnetic radiation that travels at the speed of light in all directions without the need for a physical medium to carry it. An example is the transmission of the sun's heat to the Earth. The amount of energy carried by radiation depends on the nature and temperature of the emitting surface.