Adiabatic Curve

Adiabatic Curve

 

(also adiabat), a line depicting a stable adiabatic process (that is, a process in which no heat is exchanged with the surroundings) on a diagram of state. The simplest adiabatic curve is that for an ideal gas. For this case, the equation of the adiabatic curve is pvy - const, where ρ is the pressure exerted by the gas, ν is the specific volume of the gas, and y is the adiabatic index, which is constant for a given gas and is equal to the ratio of the specific heats of the gas at constant pressure cp and at constant volume cv : γ = cp /cv. For monatomic gases (argon, neon, etc.), γ = 1.67 at ordinary temperatures; for diatomic gases (hydrogen, nitrogen, oxygen, etc.), γ = 1.4. At very low temperatures (near absolute zero) and at high temperatures (above 1000°C), the slope of the curve is somewhat different, since y depends on both temperature and pressure.

For equilibrium (reversible) adiabatic processes the entropy is characteristically constant. For this reason the adiabatic curve can also be called an isoentropic curve.

References in periodicals archive ?
The point D (Figure 1) of a tangency of the Michelson-Rayleigh line ODS to a detonation branch 1 of adiabatic curve of energy release Q = const corresponds to minimum growth of an entropy [DELTA][S.sub.D] = min (isentropic curve is tangent to an adiabatic curve from below) in a comparison with any other points.
Point is that if the regime has a smaller velocity on a comparison with an ideal C-J velocity (regime of quasi-detonation), the point of contact of the Mikhelson line with an adiabatic curve of energy release at decreasing of DW velocity will be displaced in region of smaller P-V, and so pressure in such wave will be lower than pressure in ideal DW.

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