Answer:
Heat transfer occurs due to a temperature gradient and may occur by conduction, convection or radiation.
Conduction heat transmission - it is the transmission of heat molecule by molecule, consequently requiring a material medium, always occurring from a point of higher energy potential (higher temperature) to lower potential (lower temperature). Example: Heating a metal bar ; Warming a metal spoon perched on a pan.
Convection heat transmission - This is the heat transmission that occurs between a solid body and a moving fluid, the fluid body being either liquid or gaseous. Convection may be natural or forced. Convection is said to be natural when fluid movement occurs solely due to variations in its specific weight (density). In forced convection fluid movement is caused by a pump in the case of a liquid or a fan in the case of a gaseous fluid. Example: Air conditioning ; Heaters; Atmospheric air currents.
Radiation Heat Transmission - All bodies being at a specified temperature above 0 K (-273 C), consequently, having molecular and atomic motion, emit electromagnetic radiation. This radiation must be analyzed from quality and quantity because its characteristics, behavior, and interaction with elements depending heavily on electromagnetic radiation properties. Quality of electromagnetic radiation - For the transmission of radiant energy to occur, a transparent medium must exist for this wave. Electromagnetic waves propagate in a vacuum at a constant speed of 300,000 km / s, and their velocity in the air of the earth's atmosphere is slightly lower. Amount of electromagnetic radiation The amount of radiant energy emitted per m2 by a body depends on the fourth power of its absolute temperature (Stephan Boltzmann's Law) and the emissivity characteristics of its surface. Example: Solar energy ; Solar boards.
