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Thermodynamic temperature is a quantity defined in thermodynamics as distinct from kinetic theory or statistical mechanics.. Historically, thermodynamic temperature was defined by Lord Kelvin in terms of a macroscopic relation between thermodynamic work and heat transfer as defined in thermodynamics, but the kelvin was redefined by international agreement in 2019 in terms of phenomena that are ...
For example, single-component graphs of temperature vs. specific entropy (T vs. s) for water/steam or for a refrigerant are commonly used to illustrate thermodynamic cycles such as a Carnot cycle, Rankine cycle, or vapor-compression refrigeration cycle. Any two thermodynamic quantities may be shown on the horizontal and vertical axes of a two ...
The easiest thermodynamic models, also known as equations of state, can come from simple correlations that relate different thermodynamic properties using a linear or second-order polynomial function of temperature and pressures. They are generally fitted using experimental data available for that specific properties.
Annotated color version of the original 1824 Carnot heat engine showing the hot body (boiler), working body (system, steam), and cold body (water), the letters labeled according to the stopping points in Carnot cycle. Thermodynamics is principally based on a set of four laws which are universally valid when applied to systems that fall within ...
If at every point in the cycle the system is in thermodynamic equilibrium, the cycle is reversible. Whether carried out reversible or irreversibly, the net entropy change of the system is zero, as entropy is a state function. During a closed cycle, the system returns to its original thermodynamic state of temperature and pressure.
The main feature of thermodynamic diagrams is the equivalence between the area in the diagram and energy. When air changes pressure and temperature during a process and prescribes a closed curve within the diagram the area enclosed by this curve is proportional to the energy which has been gained or released by the air.
The zeroth law of thermodynamics allows this definition to be used to measure the absolute or thermodynamic temperature of an arbitrary body of interest, by making the other heat reservoir have the same temperature as the body of interest. Kelvin's original work postulating absolute temperature was published in 1848.
internal energy and entropy of liquid water at the solid-liquid-gas triple point are zero, entropy and enthalpy of seawater are zero at S A (Absolute Salinity) = 35.16504 g/kg, T (Temperature) = 273.15 K, p (pressure) = 101325 Pa, entropy and enthalpy of dry air are zero at T (Temperature) = 273.15 K, p (pressure) = 101325 Pa. [6]