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The behavior of a thermodynamic system is summarized in the laws of Thermodynamics, which concisely are: . Zeroth law of thermodynamics; If A, B, C are thermodynamic systems such that A is in thermal equilibrium with B and B is in thermal equilibrium with C, then A is in thermal equilibrium with C.
For quasi-static and reversible processes, the first law of thermodynamics is: d U = δ Q − δ W {\displaystyle dU=\delta Q-\delta W} where δQ is the heat supplied to the system and δW is the work done by the system.
The first established thermodynamic principle, which eventually became the second law of thermodynamics, was formulated by Sadi Carnot in 1824 in his book Reflections on the Motive Power of Fire. By 1860, as formalized in the works of scientists such as Rudolf Clausius and William Thomson , what are now known as the first and second laws were ...
An isochoric process is described by the equation Q = ΔU. It would be convenient to have a similar equation for isobaric processes. Substituting the second equation into the first yields = + = (+) The quantity U + pV is a state function so that it can be given a name.
If the walls of a system are not adiabatic, and energy is transferred in as heat, entropy is transferred into the system with the heat. Such a process is neither adiabatic nor isentropic, having Q > 0, and ΔS > 0 according to the second law of thermodynamics. Naturally occurring adiabatic processes are irreversible (entropy is produced).
q = 1 / 2 ρv 2 is dynamic pressure, h = z + p / ρg is the piezometric head or hydraulic head (the sum of the elevation z and the pressure head) [11] [12] and; p 0 = p + q is the stagnation pressure (the sum of the static pressure p and dynamic pressure q). [13] The constant in the Bernoulli equation can be normalized.
The above derivation uses the first and second laws of thermodynamics. The first law of thermodynamics is essentially a definition of heat, i.e. heat is the change in the internal energy of a system that is not caused by a change of the external parameters of the system. However, the second law of thermodynamics is not a defining relation for ...
Volumetric flow rate should not be confused with volumetric flux, as defined by Darcy's law and represented by the symbol q, with units of m 3 /(m 2 ·s), that is, m·s −1. The integration of a flux over an area gives the volumetric flow rate. The SI unit is cubic metres per second (m 3 /s). Another unit used is standard cubic centimetres per ...