Enthalpy Joule-Thomson

With the help of the binary parameters kn or g -model parameters now the phase equilibrium behavior, densities, enthalpies, Joule-Thomson coefficients, and so on, for binary, ternary and multicomponent systems can be calculated. For the calculation of the VLE behavior the procedure is demonstrated in the following example for the binary system nitrogen-methane using classical mixing rules. The same procedure can be applied to calculate the VLE behavior of multicomponent systems and with g -mixing rules as well. 

It frequently is necessary to express the Joule-Thomson coefficient in terms of other partial derivatives. Considering the enthalpy as a function of temperature and pressure H T, P), we can write the total differential... 

From Equation (5.68), we know that the pressure coefficient of the molar enthalpy of a gas is related to the Joule-Thomson coefficient p,j x by the equation... 

Because of this relationship between (TT — and p-j x.. the former quantity frequently is referred to as the Joule-Thomson enthalpy. The pressure coefficient of this Joule-Thomson enthalpy change can be calculated from the known values of the Joule-Thomson coefficient and the heat capacity of the gas. Similarly, as (H — is a derived function of the fugacity, knowledge of the temperature dependence of the latter can be used to calculate the Joule-Thomson coefficient. As the fugacity and the Joule-Thomson coefficient are both measures of the deviation of a gas from ideahty, it is not surprising that they are related. 

Joule Thomson coefficient m may be defined as the temperature change in degrees produced by a drop of one atmospheric pressure when the gas expands under conditions of constant enthalpy. It is expressed as... 

Energy and Enthalpy E(T) H(T) E(V) H(P) Determine Cv end Cp from data Determine AHvap and AHtu Internal Pressure Combine with Cp to get Joule-Thomson coefficient... 

From (3.63) and (3.64), we recognize that AU = — A(PV), i.e., that Joule-Thomson expansion occurs under conditions of constant enthalpy ... 

The measured Joule-Thomson coefficient /jljt provides valuable information about how the enthalpy of real gases depends on variables other than temperature. To obtain information about the P dependence of H, we can employ the Jacobi cyclic identity (1.14b) to rewrite the Joule-Thomson coefficient as... 

Analysis of the Joule-Thomson experiment (Section 3.6.3) requires evaluation of the derivative (dT/dP)H at constant enthalpy (H = U + PV). The differential expression for dH,... 

Cooling curves such as the two in Figure 8.7 were determined for constant enthalpy (or Joule-Thomson) expansions, obtained from the First Law of Thermodynamics for a system flowing at steady-state, neglecting kinetic and potential energy changes ... 

Thus, the initial and final states of a Joule-Thomson expansion he on a curve of constant enthalpy (isoenthalp) and the Joule-Thomson process occurs at constant enthalpy. The Joule-Thomson coefficient, pJT, is defined as... 

There is another mode of gaseous expansion called the Joule-Thomson expansion, in which the change in gas volume occurs at constant enthalpy AHW = 0 without any change in energy. The vector of the isenthalpic expansion then stands perpendicular to the abscissa on the ordinate and points in the negative direction (exergy consumption) as is shown in Fig. 11.10(b). 

The Joule-Thomson coefficient p,j-r describes the extent and direction of the temperature change for an isenthalpic change of state (constant enthalpy h) ... 

Dielectric and pressure virial coefficients of NzO have been measured at 6.5, 30.1, and 75.1 °C. The dipole moment, polarizability, and molecular quadrupole moment were determined to be 0.18 D, 3.03 x 1CT24 cm3, and 3.4 xlO 26 e.s.u. cm2, respectively.91 A lower limit of —0.15 0.1 eV has been calculated for the molecular electron affinity of N20, using molecular beam studies.92 The enthalpy-pressure behaviour for N20 along eleven isotherms in the vapour phase has been determined from measurements of the Joule-Thomson effect.91... 

Temperature Pressure Density Volume Int. energy Enthalpy Entropy c. Sound speed Joule- Thomson... 

Temperature K Pressure MPa Density moPdm Volume dmVmol Int. energy kj/mol Enthalpy kJ/mol Entropy kJ/(mol-K) kJ/(mol-K) Cp kJ/(mol-K) Sound speed m/s Joule- Thomson K/MPa Therm. cond. mW/(m-K) Viscosity )J,Pa-s... 

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