Thermodynamic Properties of Sodium.

Abstract

EVERY PRACTICAL source of energy useful to man, other than water power, needs to be transformed to work via a fluid when not used in internal combustion engines or for heat as such. I n the heat engines which make use of a motive fluid as a medium for the transformation of heat energy into work, the theoretical efficiency is higher if the motive fluid is condensable over the major portion of the cycle, and if the ratio of boiling to condensing temperature is high. Except for the binary mercury-steam power cycle, the fluid used in all such condensing power cycles so far has been water.The most common source of high temperatures for power production in any desired location a t moderate cost has been chemical reactions. The highest temperature obtainable economically in this manner is about 3600' F. from the combustion of coal. I n recent years, heat energy is becoming available from nuclear reactions. This heat can in principle be produced a t much higher temperatures than might be obtained from chemical reactions. Nuclear power plants are currently being developed to make use of this energy. Sodium is being considered as a motive fluid for several such high-temperature power cycleg. Its physical and thermodynamic characteristics together with its relative abundance and low cost make it comparable and in many respects superior to mercury as a motive fluid for high-temperature power cycles.To design engines to use sodium as a motive fluid, values of its thermodynamic properties should be available in the form of a chart or tables. A critical examination of the literature on the thermodynamic properties of sodium leads to the following conclusions.There are inconsistencies among the various correlating equations, in spite of a wealth of data on the vapor pressure of sodium. Moreover, the data do not extend to temperatures high enough to meet the practical operating conditions of a prospective power cycle. Actually, except for two measurements of the normal boiling point of sodium (13, 30) and the very recent data of Makansi, Muendel, and Selke (24), the experimental vapor pressure points extend only to 1113.1" K., corresponding to P = 0.635 atm. (29).The data on the specific heat, the enthalpy, and the entropy of liquid and solid sodium along the saturation curve (8) extend to 1173" K. and appear to be very accurate.Spectroscopic data indicate that sodium in the vapor phase consists of both monomer and dimer species. There exists, on the other hand, some evidence in the literature that sodium liquid does not contain any of the diatomic species. The amount of dimer in the vapor phase is determined by the reversible reaction:There is considerable discrepancy in the literature between the numerical values of the heat of dimerization for the above reaction. Values ranging from -16,559 to -20,000 cal. per gram mole of Naz for the heat of dimerization a t the ground state have been reported.Recent calculations of the thermodynamic functions of the two species of sodium vapor by the methods of statistical mechanics (14) wer...

Thermodynamic Aspects of the Flow of Sodium Vapor Through A Supersonic Nozzle.

“…In general, the experimental data were not of sufficient precision to determine these factors. However, thermodynamic consistency calculations of the type made by Makansi, Selke, and Bonilla (7) were made which essentially substantiate their conclusions that the Ditchburn-Gilmour vapor equation is adequate, and that the enthalpy of dimerization is about 16,800 cal/gram mole of Na2. The methods used for thermodynamic and flow calculations as well as a discussion of the experimental program are contained herein.…”

High Temperature Properties of Sodium.

“…There are a number of publications in which thermodynamic properties of sodium vapor have been calculated by estimating gas imperfections from spectroscopic data. The properties generated in this article from a PVT study were compared to those derived in recent publications by Makansi, Selke, and Bonilla (9) and Weatherford, Tyler, and Ku (13). If the NRL data are taken arbitrarily as a reference and the property changes from p, to 2.9 p.s.i.a.…”

“…DeSIGN STUDIES of high-temperature power-converters employing alkali metal vapors as working fluids require an improved knowledge of their thermodynamic properties. In response to this need, experimental PVT, vapor-pressure, and liquid density data for three metalssodium, potassium, and cesium-have been measured by Stone et al (9,10,11). From the data for two of the metals, sodium and potassium, the authors have generated and published consistent sets of thermodynamic properties (5,6).…”

“…TREATMENT OF PVT DATA Derivation of Virial Coefficients. Coefficients for the cesium equation of state in its volume expansion form (Equation 1) were derived from the experimental PVT data of Stone et al (9), which cover a temperature range in the superheat region from 1305°to 2550°F. They were obtained graphically as described for potassium (5) by plotting experimental functions along constant temperature lines.…”

Toward a theory of ball lightning

“…As the sodium vapor cools, a stage is reached in which condensation into solid or liquid material particles occurs. If it is assumed that there is no reaction with the oxygen of the air, this temperature would be 806 ø and 946øK for sodium vapor pressures of 0.01 and 0.1 atmosphere, respectively [Makansi et al, 1960]. Regardless of the form of the condensation into particulate material, when it does occur, there will be a marked increase in the rate of cooling at the position of the outer edge of the sodium, for then the particles will emit blackbody radiation over the whole spectrum.…”