Helium thermodynamic properties

Table 1. Physical and Thermodynamic Properties of Helium-Group Gas Fluorides, Oxofluorides, and Oxides...

There are presently several database programs of thermodynamic properties data developed specifically for fluids commonly associated with low temperature processing including helium, hydrogen, neon. 

Homogeneous Liquids. The physical properties important in determining the suitability of a liquid for propellant application are the freezing point, vapor pressure, density, and viscosity. To a lesser extent, other physical properties are important such as the critical temperature and pressure, thermal conductivity, ability to dissolve nitrogen or helium (since gas pressurization is frequently used to expel propellants) and electrical conductivity. Also required are certain thermodynamic properties such as the heat of formation and the heat capacity of the material. The heat of formation is required for performing theoretical calculations on the candidate, and the heat capacity is desired for calculations related to regenerative cooling needs. 

L. V. Gurvich, I. V. Veyts, and C. B. Alcock, Thermodynamic Properties of Individual Substances, Vol. 1 Elements Oxygen, Hydrogen (Deuterium, Tritium), Fluorine, Chlorine, Bromine, Iodine, Helium, Neon, Argon, Krypton, Xenon, Radon, Sulfur, Nitrogen, Phosphorus, and Their Compounds, Pt. 1 Methods and Computation, Hemisphere, New York, 1989. 

There are several reports in the literature that measure binary adsorption equilibria using gas chromatography [4,S,6]. In GC techniques the adsorbent is equilibrated with a continuous flow of carrier gas (gas 1). Then a pulse of gas 2 is injected at the column inlet. A peak of the gas 2 is eluted at the exit of the column after some time. Net retention time (or volume) is calculated from the first moment of the peak after correcting for void volume (by measuring the retention time of a non-adsorbing species). If the carrier gas is inert (i.e. helium) the net retention time is related to the pure component Henry s constant. Typical binary measurements reported so r use a mixture of the two gases as carrier and introduce a small perturbation in composition. The net retention volume is related to the thermodynamic properties by [4]... 

The Blume-Emery-Griffiths (BEG) model is one of the well-known spin lattice models in equilibrium statistical mechanics. It was originally introduced with the aim to account for phase separation in helium mixtures [30]. Besides various thermodynamic properties, the model has been extended to study the structural phase transitions in many bulk systems. By... 

The values in these tables were generated from the NIST REFPROP software (Lemmon, E.W., McLinden, M.O., and Huber, M.L., NIST Standard Reference Database 23 Reference Fluid Thermodynamic and Transport Properties—REFPROP, National Institute of Standards and Technology, Standard Reference Data Program, Gaithersburg, Md., 2002, Version 7.1). The primary source for the thermodynamic properties is McCarty, R.D., and Arp, V D., A New Wide Range Equation of State for Helium, Ado. Cryo. Eng. 35 1465-1475,1990. The source for viscosity is Arp, V. D., McCarty, R. D., and Friend, D. G., Thermophysical Properties of Helium-4 from 0.8 to 1500 K with Pressures to 2000 MPa, NIST Technical Note 1334, Boulder, Colo., 1998. The source for thermal conductivity is Hands, B. A., and Arp, V. D., A Correlation of Thermal Conductivity Data for Helium, Cryogenics, 21(12) 697-703,1981. 

Note Liquid helium has unique thermodynamic properties too complex to be adequately described here. Liquid He I has refr index 1.026,dO.l 25, and is called a quantum fluid because it exhibits atomic properties on a macroscopic scale. Its bp is near absolute zero and viscosity is 25 micropoises (water = 10,000). He II, formed on cooling He I below its transition point, has the unusual property of superfluidity, extremely high thermal conductivity, and viscosity approaching zero. 

McCarty, R. D., Thermodynamic Properties of Helium, /. Phys. Chem. 

Douglas B. Mann, The Thermodynamic Properties of Helium from 3 to 300°K Between 0.5 and 100 Atmospheres, National Bureau of Standards Technical Note 154, U.S. Government Printing Office, Washington, D.C., 1962,95 pp. 

Operating data for the 1-kw refrigerator indicate a value of i , the work input per unit of refrigeration, of 70 with a conventional nonlubricated compressor. The average refrigeration effect per pound of circulated gas, J5, is 12.0. This compares to calculated values of 58 and 16 for E and B, respectively. These differences in the theoretical and measured parameters are due to reduced performance by the compressor, expander, and heat exchanger. The comparison is also affected by the values assumed for the thermodynamic properties of the helium. 

In summary, to obtain similar thermod5mamic efficiency, it appears that nitrogen-based systems will have somewhere around 40% larger volume than helium-based systems. Their capital cost will be higher because of the less optimal thermodynamic properties of nitrogen compared with helium. However, the nitrogen-based Brayton cycle is expected to be less expensive than the equivalent Rankine steam cycle because of the low-pressure steam components and the moisture separator components required for the Rankine cycle. 

Thermodynamic parameters, excluding the highly precise parameters, of a chromatographic process may be determined if helium, whose properties are those of a perfect gas, is employed as the carrier gas. 

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