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Thermal conduction is the diffusion of thermal energy (heat) within one material or between materials in contact. The higher temperature object has molecules with more kinetic energy; collisions between molecules distributes this kinetic energy until an object has the same kinetic energy throughout.
The thermal conductivity of a material is a measure of its ability to conduct heat.It is commonly denoted by , , or and is measured in W·m −1 ·K −1.. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity.
Thermal contact resistance is significant and may dominate for good heat conductors such as metals but can be neglected for poor heat conductors such as insulators. [2] Thermal contact conductance is an important factor in a variety of applications, largely because many physical systems contain a mechanical combination of two materials.
It quantifies how effectively a material can resist the transfer of heat through conduction, convection, and radiation. It has the units square metre kelvins per watt (m 2 ⋅K/W) in SI units or square foot degree Fahrenheit–hours per British thermal unit (ft 2 ⋅°F⋅h/Btu) in imperial units. The higher the thermal insulance, the better a ...
The process of heat transfer from one place to another place without the movement of particles is called conduction, such as when placing a hand on a cold glass of water—heat is conducted from the warm skin to the cold glass, but if the hand is held a few inches from the glass, little conduction would occur since air is a poor conductor of heat.
The first case is when natural convection aids forced convection. This is seen when the buoyant motion is in the same direction as the forced motion, thus accelerating the boundary layer and enhancing the heat transfer. [5] Transition to turbulence, however, can be delayed. [6] An example of this would be a fan blowing upward on a hot plate.
Thermal equilibrium - When two objects A and B are in thermal contact and there is no net transfer of thermal energy from A to B or from B to A, they are said to be in thermal equilibrium. The majority of objects experiencing thermal equilibrium still do exchange thermal energy but do so equally so that the net heat transfer is zero.
The statement of Newton's law used in the heat transfer literature puts into mathematics the idea that the rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings. For a temperature-independent heat transfer coefficient, the statement is: