Three fundamental modes of heat transfer

HEAT  TRANSFER is the exchange of thermal energy between physical systems. The rate o of heat transfer is dependent on the temperatures of the systems and the properties of the intervening medium through which the heat is transferred. 

The three fundamental modes of heat transfer are CONDUCTION,  CONVECTION  & RADIATION. 

✔Thermal conduction

Thermal conduction is the transfer of heat (internal energy ) by microscopic collisions of particles and movement of electrons within a body. The microscopically colliding objects, that include molecules, atoms, and electrons, transfer disorganized microscopic kinetic and potential energy, jointly known as internal energy. Conduction takes place in all phases of matter, such as solids, liquids, gases and plasmas. The rate at which energy is conducted as heat between two bodies is a function of the temperature difference (temperature gradient ) between the two bodies and the properties of the conductive medium through which the heat is transferred. Thermal conduction was originally called diffusion.

✔Convection 

Convection is the movement of groups of molecules within fluids such as liquids or gases, and within rheids. Convection takes place through advection, diffusion or both.

Convection cannot take place in solids because neither bulk current flows nor significant diffusion can take place in solids. Diffusion of heat can take place in solids, but that is called heat conduction.

Convection can be demonstrated by placing a heat source (e.g. a Bunsen burner) at the side of a glass full of a liquid, and observing the changes in temperature in the glass caused by the warmer ghost fluid moving into cooler areas.

✔Radiation 

In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium.This includes:

• electromagnetic radiation, such as heat,radio waves, visible light, x-rays, and gamma radiation (γ)
• particle radiation, such as alpha radiation (α), beta radiation (β), and neutron radiation(particles of non-zero rest energy)
• acoustic radiation, such as ultrasound,sound, and seismic waves (dependent on a physical transmission medium)
• gravitational radiation , radiation that takes the form of gravitational waves, or ripples in the curvature of spacetime.