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  2. Second law of thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Second_law_of_thermodynamics

    For isolated systems, no energy is provided by the surroundings and the second law requires that the entropy of the system alone must increase: ΔS > 0. Examples of spontaneous physical processes in isolated systems include the following: 1) Heat can be transferred from a region of higher temperature to a lower temperature (but not the reverse).

  3. Heat equation - Wikipedia

    en.wikipedia.org/wiki/Heat_equation

    Certain solutions of the heat equation known as heat kernels provide subtle information about the region on which they are defined, as exemplified through their application to the Atiyah–Singer index theorem. [8] The heat equation, along with variants thereof, is also important in many fields of science and applied mathematics.

  4. Heat sink - Wikipedia

    en.wikipedia.org/wiki/Heat_sink

    Experimental tests are one of the more popular ways to determine the heat sink thermal performance. In order to determine the heat sink thermal resistance, the flow rate, input power, inlet air temperature and heat sink base temperature need to be known. Vendor-supplied data is commonly provided for ducted test results. [29]

  5. Laws of thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Laws_of_thermodynamics

    At absolute zero temperature, the system is in the state with the minimum thermal energy, the ground state. The constant value (not necessarily zero) of entropy at this point is called the residual entropy of the system. With the exception of non-crystalline solids (e.g. glass) the residual entropy of a system is typically close to zero. [2]

  6. Entropy (classical thermodynamics) - Wikipedia

    en.wikipedia.org/wiki/Entropy_(classical...

    The same is true for its entropy, so the entropy increase S 2 − S 1 of our system after one cycle is given by the reduction of entropy of the hot source and the increase of the cold sink. The entropy increase of the total system S 2 - S 1 is equal to the entropy production S i due to irreversible processes in the engine so = +. The Second law ...

  7. Heat pump and refrigeration cycle - Wikipedia

    en.wikipedia.org/wiki/Heat_pump_and...

    A heat pump is a mechanical system that transmits heat from one location (the "source") at a certain temperature to another location (the "sink" or "heat sink") at a higher temperature. [2] Thus a heat pump may be thought of as a "heater" if the objective is to warm the heat sink (as when warming the inside of a home on a cold day), or a ...

  8. Fin (extended surface) - Wikipedia

    en.wikipedia.org/wiki/Fin_(extended_surface)

    A similar approach can be used to find the constants of integration for the remaining cases. For the second case, the tip is assumed to be insulated, or in other words to have a heat flux of zero. Therefore, | = = For the third case, the temperature at the tip is held constant.

  9. Newton's law of cooling - Wikipedia

    en.wikipedia.org/wiki/Newton's_law_of_cooling

    [1] [2] Newton did not originally state his law in the above form in 1701. Rather, using today's terms, Newton noted after some mathematical manipulation that the rate of temperature change of a body is proportional to the difference in temperatures between the body and its surroundings. This final simplest version of the law, given by Newton ...