Isothermal Joule-Thomson coefficient

It is also possible to measure (dH/dP)T, the isothermal Joule-Thomson coefficient directly, which is a quantity more diiectly related to deviations from ideality [14]. 

There are two variations of the basic set-up of the Joule-Thomson experiment which both yield practical information. In the isothermal Joule-Thomson experiment the temperature is held constant with a downstream heater, and the resultant heat input for the pressure decrease permits an experimental evaluation of (8H/8P)T, the isothermal Joule-Thomson coefficient. In the other variation there is no throttling device used, and the pressure is held constant. For the steady-state flow of gas the temperature change is measured for measurable inputs of heat. This experiment, of course, yields (8H/8T)P, or CP. Thus, the variations of this constant-flow experiment can yield all three of the important terms in Equation (7.46). 

Flow calorimetric measurements of the isothermal Joule-Thomson coefficient of a vapour also provide information on gas non-ideality which is fiee from adsorption errors. Basically, all that is required is a fixed-throttle flow calorimeter, free of heat leaks, fitted with an electric heater as shown in Figure 9 so that isothermal measurements can be made [77-alb/wor]. 

Calorimetric Measurements.— The relation between the equation of state and the isothermal Joule-Thomson coefficient ft = (dHjdp)j. can be obtained from equation (16b). In the low pressure limit it is simply... 

A flow calorimeter for measurement of the isothermal Joule-Thomson coefficient of vapours has been described by Francis, McGlashan, and Wormald and an apparatus said to be useful for studies on mixtures has been described by Dawe and Snowdon, but very few measurements of ft for mixtures have been... 

Use eqn 17.45 to compute the limiting isothermal Joule-Thomson coefficient dB... 

Joule-Thomson Effect, Francis, McGlashan, and Wormald have measured the isothermal Joule-Thomson coefficient... 

Heat capacity, molar Heat capacity at constant pressure Heat capacity at constant volume Helmholtz energy Internal energy Isothermal compressibility Joule-Thomson coefficient Pressure, osmotic Pressure coefficient Specific heat capacity Surface tension Temperature Celsius... 

Temperature, pressure, volume, amount, energy, enthalpy, heat capacity, expansion coefficient, isothermal compressibility, and Joule-Thomson coefficient. 

If this coefficient is constant in an isothermal Joule-Thomson experiment, then the heat which must be supplied to maintain constant temperature is AH in the following relationship... 

THERMAL PROPERTIES OF PROPANE. HEAT CAPACITY, JOULE-THOMSON COEFFICIENT, ISOTHERMAL THROTTLING COEFFICIENT, AND LATENT HEAT OF VAPORIZATION. FROM PROCEEDINGS OF THE 4TH SYMPOSIUM ON THERMOPHYSICAL PROPERTIES, UNIV. MARYLAND COLLEGE PARK, MD. 

Derive expressions for the coefficient of thermal expansion (3, the isothermal compressibility k, the Joule—Thomson coefficient fi, and the difference Cp — Cy for a gas that obeys the van der Waals equation of state. 

NIST/ASME Steam Properties Database versiou 2.21 http //www.nist.gov/srd/nistlO.cfm (accessed November 10, 2010) (purchase required). Thermophysical properties include in the STEAM Database temperature, Helmholtz energy, thermodynamic derivatives, pressure, Gibbs energy, density, fugacity, thermal conductivity, volume, isothermal compressibility, viscosity, dielectric constant, enthalpy, volume expansivity, dielectric derivatives, internal energy, speed of sound, Debye-Hlickel slopes, entropy, Joule-Thomson coefficient, refractive index, heat capacity, surface tension. The STEAM database generates tables and plots of property values. Vapor-liquid-solid saturation calculations with either temperature or pressure specified are available. 

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... 

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