Joule-Thompson coefficient

Buckingham R A and Corner J 1947 Tables of second virial and low-pressure Joule-Thompson coefficients for intermolecular potentials with exponential repulsion Proc. R. Soc. A 189 118... 

Joule-Thompson Coefficient for Real Gases. This expresses the change in temperature with respect to change in pressure at constant enthalpy ... 

For a compressible fluid that undergoes exansion through a valve or an orifice, the Joule-Thompson coefficient is defined as ... 

U = Heat transfer coefficient for transfer between the pipeline and surrounding ground, Btu/hr-ft -°F X = Distance from origin, ft Z = Distance above datum, ft = Joule-Thompson coefficient 6 = Incremental amount of a variable... 

Consideration shall be given to the temperature increase of hydrogen during depressurization when designing a system (negative Joule-Thompson coefficient). Refer to CGA G5.5 for additional guidance. 

The Joule-Thompson coefficient measures the temperature change when a gas ... 

A throttle does not change the enthalpy of the fluid throttling is an isenthalpic process. For a given input state and a specified outlet pressure, one finds the outlet temperature by conducting a one-dimensional search for a temperature at which the enthalpy is equal to the input enthalpy. An enthalpy chart provides a convenient means for the search. Another method of solution is to apply the Joule-Thompson coefficient, defined by... 

To investigate the variation of temperature during an isenthalpic change of pressure, one is naturally interested in the derivative (dT/dP)H, called the Joule-Thompson coefficient, / jj. An easy way to derive an expression for this quantity is to use Table 2.1. From Table 2.1, 3T)h = —V + T dV/dT)p, and (3P)h = Cp. Then... 

Where they have a positive slope, water cools on adiabatic expansion and warms if adiabatically compressed, and the two regions are separated by the Joule-Thompson inversion curve. Much the same information is contained in the enthalpy-pressure diagram (Figure 8.6), where it can be seen that constant enthalpy changes in pressure lead to increases in temperature in one region and decreases in another. The effect of dissolved NaCl on the Joule-Thompson coefficient has been calculated by Wood and Spera (1984), and the effect will be similar for other electrolytes. Because the addition of most electrolytes to water results in a decrease in V and in a, fijT is smaller, and the net effect is to move the inversion curve to higher temperatures, as shown in Figure 8.5. 

As an example of how the Joule-Thompson coefficient might be used, consider some hot spring fluids (approximated by pure water) rising vertically in the crust. When boiling begins, the pressure is 165 bars and the temperature is 350°C. At this point, VhjO = 31.35 cm mol = 0.7493 calbar mol , a = 0.01037 and C° = 43.60 calK moP, and... 

Figure 6.4 Isotherms on logP versus enthalpy in kJ moh for water. Dashed contours are the Joule-Thompson coefficient, The contour for /ajj = 0 is the Joule-Thompson inversion curve. Data from the program steam of Harvey et al. (2000).

The effect of dissolved NaCl on the Joule-Thompson coefficient has been calculated by Wood and Spera (1984), and the effect will be similar for other electrolytes. Because the addition of most electrolytes to water results in a decrease in V and in a, is smaller, and the net effect is to move the inversion curve to higher temperatures and lower pressures. 

Obviously every industrial application of equations of state can not be covered in this section of the paper. Thus, for example, calculation of Joule-Thompson coefficients, heats of mixing, and the velocity of sound, and obtaining various other parameters required in compressor calculations, which are an integral part of industrial design, will not be discussed. 

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