Thermodynamic properties such as density, heat capacities, speed of sound, enthalpy, entropy, and other properties, can be calculated from a single thermodynamic equation of state in the case of pure fluids. Equation of state representing Helmholtz free energy provides those property values accurately in wide gaseous, liquid, and supercritical phases even at high temperatures and pressures by only differential procedures, which is sometimes called as fundamental equation of state. For many important fluids like water, air, carbon dioxide, ammonia, methane, isobutane, methanol, and hydrofluorocarbons (HFCs), the fundamental equations of state have already been established. This article introduces these fundamental equations of state and the background of them. Some latest aspects obtained in our group on thermodynamic equations of state are also introduced.
PρT property data for working fluids and other functional fluids are fundamental to estimate the compressibility and/or enthalpies for their safety and significant applications. The present paper was to review the developments in the techniques for PρT property measurements of fluids in a single phase region. Many earlier or new innovations for direct or indirect precise measurements of volume or density changes were described. Moreover, it could be also expected that a large enough number of reliable experimental PρT property data in wider ranges of temperatures and pressures for accepted HC refrigerants will be accumulated in the near future.
Recently, the necessity of measurements for thermodynamic properties of high pressure fluids is growing for the purpose of protecting global environmental needs in industry. This report shows not only the method of experimental study for isobaric heat capacity but an example of apparatus in detail. Furthermore, it explains a development of correlations for isobaric heat capacity and their applicability to alternatives for chlorofluorocarbons.
In order to develop a reliable equation of state for a fluid, various thermodynamic property measurements of the fluid are required. Among them, isochoric heat capacities (cv) measurements provide a very useful check for calculations of the second derivative of the pressure with respect to temperature which is challenging to measure accurately. This paper briefly explains principles and problems to measure cv, especially experimental requirements for high pressure fluids. Under high pressures, specialized electronic measuring and control techniques as well as data processing are required. Major adiabatic calorimeters and their constructions are described in accordance with this aspect. Among them, a newly-developed twin-cell adiabatic calorimeter is selected and described in detail. Also, their measurement results which show some interesting behavior of cv are introduced.
In this paper, the simple and useful procedures of the surface tension measurement are reported. The principles and calculation methods as well as the experimental technique are also represented with respect to the typical methods, i.e., Wilhelmy method, ring method, capillary rise method, and so on. Especially, the differential capillary rise method, which is adopted by the author for the surface tension measurements under high pressures are explained in detail.
Here is reviewed our recent research on the title subject that has led to the Award of The Japan Society of High Pressure Science and Technology, 2004. In particular, we focus on the explanation of motivations and backgrounds for selecting the research subject as well as the scientific contents. First we show what has been thought to carry out experimental and theoretical investigations of the dynamic behaviors of electrolytes in water at high pressures. Second it is described how the high-pressure solution NMR probe has been developed to attain high resolution and sensitivity required for the study of very dilute aqueous solutions at high pressures. The newly developed high-pressure probe has enabled us to examine the dynamics of water in benzene and benzene in water; in solubility they hate each other. Third it is illustrated how our recent studies have been performed on the structure, dynamics, and reactions of supercritical water. Issues discussed here are related to the environmental and energy problems to be solved to make our life and earth sustainable in the 21st century.
Residual effects in solid materials produced by intense shock wave are examined by transmission electron microscopy. Several characteristic textures induced by shock compression are shown. Examination of shock-induced phases of Nb2O5, TiO2, MnF2 and mullite provides important information on the mechanism of the shock-induced phase transitions. Shock metamorphism of Bi2Sr2CaCu2O8 and quartz is presented. Various microscopic textures caused by chemical reactions under shock process are demonstrated for the case of decomposition reaction in SiO and ZrSiO4, and redox reaction between SiO2 and the 5 group metals (Ta, Nb).
The discovery and the most recent developments of the hydrogen clathrate hydrate are reviewed with the consideration of characteristic properties of gas hydrates. The practical use for hydrogen storage requires to maintain the stability of hydrogen hydrate at lower pressures and higher temperatures. We present and explain some studies made for approaching toward its goal.