Sonic velocity single phase

The calculation of two-phase isothermal and isentropic compressibilities, two-phase sonic velocity, single-phase sonic velocity, and cooling and heating due to expansions are presented in the second part of this chapter. Cubic equations of state facilitate all of these calculations. One basic assumption in the formulation for the two-phase compressibilities and two-phase sonic velocities is the equilibrium state. In the transition from single-phase to two-phase state, compressibilities and sonic velocity may have a sharp discontinuity, which implies lack of validity of averaging procedures. 

The ratio of the sonic velocity in a homogeneous two-phase mixture to that in a gas alone is cm/c = Pg/ePm = Vpl/ATO — ). This ratio can be much smaller than unity, so choking can occur in a two-phase mixture at a significantly higher downstream pressure than for single phase gas flow (i.e., at a lower pressure drop and a correspondingly lower mass flux). 

The isentropic compressibility and the thermodynamic sonic velocity are related to each other both in the single-phase and two-phase states. They are used in problems in the exploration and production of hydrocarbon reservoirs and in different disciplines. We should also make a comment on the thermodynamic sonic velocity, which is a purely thermodynamic property. The thermodynamic sonic velocity is equal to the true sonic velocity over a wide range of frequencies and amplitudes. 

The next section presents the sonic velocity and temperature changes due to expansion in the single-phase region. 

Single-phase sonic velocity and temperature change due to expansion... 

The sonic velocity and the thermal properties of fluids are related to their volumetric behavior. The basic equations for the single-phase state are derived in this section. 

Eq. (3.133) gives the sonic velocity of a single-phase fluid of constant composition in terras of the volumetric behavior and the Cp/Cy ratio. 

The major difficulty concerning ES for polar compounds is the lack of accurate, comprehensive data or, in most cases, the lack of any data. Steam is probably the only highly polar compound for which there is a large body of data for a variety of properties such as vapor pressure, critical constants, saturation densities, heats of vaporization, single-phase densities in both liquid and vapor, calorimetric. Joule-Thomson, sonic velocities and heat capacity measurements (Z>.8 Recent data (10) and compilation work (11) have Improved the picture for ammonia. There is also a reasonable body of data for methanol but it is not altogether thermodynamically consistent (12). 

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