Editing Heat transfer (section)

===Conduction===
{{main|Thermal conduction}}
On a microscopic scale, heat conduction occurs as hot, rapidly moving or vibrating atoms and molecules interact with neighboring atoms and molecules, transferring some of their energy (heat) to these neighboring particles. In other words, heat is transferred by conduction when adjacent atoms vibrate against one another, or as electrons move from one atom to another. Conduction is the most significant means of heat transfer within a solid or between solid objects in [[thermal contact]]. Fluids—especially gases—are less conductive. [[Thermal contact conductance]] is the study of heat conduction between solid bodies in contact.<ref name=Abbott>{{cite book |last1=Abbott |first1=J.M. |last2=Smith |first2=H.C. |last3=Van Ness |first3=M.M. |title=Introduction to Chemical Engineering Thermodynamics |year=2005 |publisher=McGraw-Hill |location=Boston, Montreal |isbn=0-07-310445-0 |edition=7th}}</ref> 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. Steady-state conduction is an idealized model of conduction that happens when the temperature difference driving the conduction is constant so that after a time, the spatial distribution of temperatures in the conducting object does not change any further (see [[Fourier's law]]).<ref>{{cite web |title=Heat conduction |url=https://www.thermalfluidscentral.org/encyclopedia/index.php/Heat_Conduction |work=Thermal-FluidsPedia |publisher=Thermal Fluids Central}}</ref> In steady state conduction, the amount of heat entering a section is equal to amount of heat coming out, since the temperature change (a measure of heat energy) is zero.<ref name="Abbott"/> An example of steady state conduction is the heat flow through walls of a warm house on a cold day—inside the house is maintained at a high temperature and, outside, the temperature stays low, so the transfer of heat per unit time stays near a constant rate determined by the insulation in the wall and the spatial distribution of temperature in the walls will be approximately constant over time.

''Transient conduction'' (see [[Heat equation]]) occurs when the temperature within an object changes as a function of time. Analysis of transient systems is more complex, and analytic solutions of the heat equation are only valid for idealized model systems. Practical applications are generally investigated using numerical methods, approximation techniques, or empirical study.<ref name="Abbott"/>