Gaseous thermal conductivity of HFC-32, HFC-125 and their mixtures has been measured by a transient hot-wire method at temperatures from 283 to 333K and pressures up to saturation. The uncertainty of the experimental data obtained is estimated to be within 1%. A simple correlation equation was developed to reproduce the experimantal thermal conductivity as a function of temperature, pressure and composition. Generalization of the residual thermal conductivity has been also undertaken by means of the law of corresponding states.
Measurements of thermophysical properties are sometimes required on samples having anomalous shape. For example, values of thermal conductivity of the cladding material for nuclear fuel of water-cooled reactor, in a form of tubing -8mm in diameter, are essential for the safety design of the reactor. The present study aims to investigate the effectiveness of the logarithmic method for the cases of (1) thin samples, (2) local heating by the use of small aperture, (3) samples small in diameter, and (4) samples having a cylindrical shape. The adoptability of the logarithmic method for analyzing laser-flash data on such samples of anomalous shape was tested and it was concluded that the measurements can be made with the possible error within 5%.
Molecular dynamics simulation by using NPT algorithm was performed to estimate selfdiffusion constant of molten silicon. The estimated value shows monotonous increase with increase in temperature. Absolute value of the constant is estimated to be about 1×10-4cm2/s. More than one thousand of atoms are requested to obtain macroscopic thermophysical properties.
A transient heating technique that is an improved technique of a constant-rate-heating technique is proposed for thermal diffusivity measurements of metals. An equation used for determining thermal diffusivity of metals is derived, and then a principle of the present technique by a transient heating technique is described. Additionally, an analysis is made to satisfy a condition involved in the principle with the radiative thermal insulation at the end of the spcimen used in this study. To verify the validity of the technique, the thermal diffusivity of iron, whose thermophysical properties have been well known, has been measured with the same apparatus as used in our previous work and the experimental results have been discussed. Moreover the thermal diffusivity of constantan is measured using the present technique.
The authors have studied the solidification and melting processes of water containing conductive solids in order to improve the phase change characteristics [1-3]. In the previous report , experiments for promoting the phase change rate were performed for the tube with aluminum spain fins. In the present study, experiments are carried out for the solidification and melting processes of water around the copper tube with strip copper fins settled at regular distance. The relation between the fin volume and the solidification or melting rate, the temperature distribution and the heat flux change are measured. On the other hand, the influence of the natural convection in the water is investigated by considering the Nusselt number and Rayleigh number, and the shape of the ice-water interface is observed visually.
The snow-room is a natural ice box utilized snow. It had been thought out in a life of snowy country. This paper begins with descriptions of snow-room, effectivity, economics and problem. It has been proposed a new utilization that is combine a snow-room and a system utilizing an aquifer.
The hydraulic conveying of snow and ice has promising applications, e.g. in a district cooling system, because the pressure drop through pipes, as well as pipeline elements such as elbows, valves and pipe junctions, increases insignificantly with mixing snow and/or ice into water with a fraction up to 25%. From a practical point of view, it is neccessary to develop a technique to prevent the blockage due to compressed snow.
Crystal structures and physical properties of ice Ih were discussed with special reference to its thermal properties. Structures of snow, which is a mixture of ice and air, were also discussed on the basis of the sintering mechanism together with various modes of thermal transport in snow.
The existence of supercooling state of water in a latent heat thermal storage system reduces COP. Therefore it is important to clarify the freezing phenomenon of supercooled water. In this report, ice appearing process on a solid surface was considered, and the effect of the characteristics of the surface on the freezing of supercooled water was clarified. Furthermore, prediction and controlling method of the initiation of the ice on the surface was introduced.
The mixture of fine ice particles and liquids has been increasingly utilized for cold-thermal energy storage material in the ice-thermal storage system. The sherbetlike ice is called “liquid ice” due to its fluidity and shows some suitable properties for thermal storage system. In this article, the characteristics and properties of liquid ice are summerized and recent researches on the production and utilization of sherbet-like ice systems are reviewed.
A freezing of a porous medium saturated with an aqueous solution is such a complex phenomenon where the freezing progresses with interaction of effects of a permiability in a mushy region, mass diffusion and a double-diffusive convection. In this report, a simple transient measurement method of a permeability in a mushy region offered by authors to investigate physical parameters on which the permeability depends, and the measurement results are stated. Then, the results of experiments and analyses for two types of models of the freezing which have been done by authors are stated.