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  2. Second law of thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Second_law_of_thermodynamics

    Heat cannot spontaneously flow from cold regions to hot regions without external work being performed on the system, which is evident from ordinary experience of refrigeration, for example. In a refrigerator, heat is transferred from cold to hot, but only when forced by an external agent, the refrigeration system.

  3. Joule heating - Wikipedia

    en.wikipedia.org/wiki/Joule_heating

    Some food processing equipment may make use of Joule heating: running a current through food material (which behave as an electrical resistor) causes heat release inside the food. [2] The alternating electrical current coupled with the resistance of the food causes the generation of heat. [3] A higher resistance increases the heat generated.

  4. Convection (heat transfer) - Wikipedia

    en.wikipedia.org/wiki/Convection_(Heat_transfer)

    Hot areas are shown in red, cold areas are shown in blue. A hot, less-dense material at the bottom moves upwards, and likewise, cold material from the top moves downwards. Convection (or convective heat transfer) is the transfer of heat from one place to another due to the movement of fluid.

  5. Heat transfer - Wikipedia

    en.wikipedia.org/wiki/Heat_transfer

    A hot, less-dense lower boundary layer sends plumes of hot material upwards, and cold material from the top moves downwards. Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy between physical systems.

  6. Rate of heat flow - Wikipedia

    en.wikipedia.org/wiki/Rate_of_heat_flow

    The rate of heat flow is the amount of heat that is transferred per unit of time in some material, usually measured in watts (joules per second). Heat is the flow of thermal energy driven by thermal non-equilibrium, so the term 'heat flow' is a redundancy (i.e. a pleonasm). Heat must not be confused with stored thermal energy, and moving a hot ...

  7. Thermal conduction - Wikipedia

    en.wikipedia.org/wiki/Thermal_conduction

    Thermal conductivity, frequently represented by k, is a property that relates the rate of heat loss per unit area of a material to its rate of change of temperature. Essentially, it is a value that accounts for any property of the material that could change the way it conducts heat. [1]

  8. Convection - Wikipedia

    en.wikipedia.org/wiki/Convection

    This motion of heat takes place in three ways, which a common fire-place very well illustrates. If, for instance, we place a thermometer directly before a fire, it soon begins to rise, indicating an increase of temperature. In this case the heat has made its way through the space between the fire and the thermometer, by the process termed ...

  9. Heat transfer physics - Wikipedia

    en.wikipedia.org/wiki/Heat_transfer_physics

    The macroscopic energy equation for infinitesimal volume used in heat transfer analysis is [6] = +, ˙, where q is heat flux vector, −ρc p (∂T/∂t) is temporal change of internal energy (ρ is density, c p is specific heat capacity at constant pressure, T is temperature and t is time), and ˙ is the energy conversion to and from thermal ...