A. Horibe

Surface tension of low-temperature aqueous solutions

Measurements of the surface tension have been carried out to determine the effects of both temperature and concentration on the surface tension of aqueous solutions of sodium chloride, propylene glycol, and ethylene glycol. A differential capillary-rise method was employed for the measurements. The results show that the surface tension of the ethylene glycol solution and the propylene glycol solution increases as the concentration of the solution decreases, while for the sodium chloride solution the surface tension increases monotonically as the concentration increases. The surface tension of the liquids was found to be an almost-linear function of temperature from 20°C to just above the freezing temperature. Equations for the surface tension of the three binary aqueous solutions as a function of temperature and concentration are presented.

Melting point and supercooling characteristics of molten salt

Abstract Melting points of some kinds of molten salts have been determined, and also supercooling characteristics of potassium thiocyanate KSCN and calcium chloride CaCl2 have been investigated. Molten salt has been utilized as a thermal storage material, cooling material for the nuclear reactor, refinement of the petroleum, fuel battery, molten-salt reactor because of its excellent thermal characteristics and chemical stability. Therefore, it is important for its utilization to store the data of thermophysical properties to control both the melting and solidification processes. The sample of molten salt is both heated and cooled depending on the prescribed heating-cooling temperature curves in the electric furnace with a controller. The melting points were determined as the constant temperatures which can be observed for some period in the cooling process. Furthermore, the supercooling characteristics were investigated under various sample masses and cooling rates as parameters. It was found that the degree of supercooling depended closely on both the cooling rate and the sample mass.

Ice accretion characteristics along a circular cylinder immersed in a cold air stream with seawater spray

Abstract An experimental investigation has been conducted to determine the characteristics of marine icing on a horizontal circular cylinder immersed in a cold airstream accompanied by seawater spray. Extensive measurements were made for a variety of conditions including airstream velocity, air temperature, droplet diameter, initial droplet temperature, and mass flow rate of droplets. The salt content distribution within an ice layer accumulated on the cylinder was successfully determined. It was distinctly observed that the morphology of the ice accretion depended mainly upon both airstream velocity and droplet size, while the surface features of the ice layer varied markedly with both droplet diameter and droplet temperature.

Freezing Characteristics Along a Horizontal Cooled Tube Immersed in Aqueous Binary Solution With Main Flow

An experimental study has been performed to investigate the freezing characteristics of an aqueous binary solution along a horizontal cooled tube. A copper coaxial cooling tube was set horizontally in a flow duct which has cross-sectional dimensions of 120 mm [times] 200 mm. Ethylene-glycol solution was utilized as a test solution. Observation of frozen layer, measurement of heat-transfer coefficient, and visualization of flow pattern were extensively carried out under a variety of concentration of the solution, initial temperature, cooling temperature, and flow velocity as parameters. It was found that the characteristics of the frozen layer could be well grouped using both the Reynolds number and the cooling temperature ratio, and that the flow field had a considerable effect on the characteristics of the frozen layer. The correlations of the averaged frozen-layer thickness at the steady state were determined. This is applicable to thermal storage systems for air conditioning.

An experimental study of ice-layer transition phenomena in a rectangular duct containing water flow

Measurements of both the velocity and turbulence-intensity distributions above an ice-layer surface along flow direction have been performed to clarify the ice-layer transition phenomena observed in a rectangular duct. The test duct which has a lower cooled wall kept less than the freezing temperature of water with cross-sectional dimension of 50 mm by 19 mm was used in the present measurements. The velocity and turbulence-intensity distributions in the test duct were measured using Laser Doppler Velocimeter set up on the two-dimensional traversing table. The freezing experiments were carried out under the condition of uniform water-flow rate even after the ice layer has developed in the test duct. It was found that inlet water flow tended to be laminarized under an influence of developing ice layer, and that onset of the ice-layer transition phenomena might be closely related to an increase in turbulence intensity in the water flow above the developing ice-layer surface.ZusammenfassungZur Klärung der Umschlagerscheinungen, welche an der sich ausbildenden Eisschicht innerhalb eines wasserdurchströmten rechteckigen Kühlkanals beobachtet wurden, erfolgte die Gewinnung der Geschwindigkeits- und Turbulenzgradverteilung in Strömungsrichtung. Beim Versuchskanal mit den Abmessungen 50 × 19 mm2 war die Unterseite als Kühlplatte ausgebildet, deren Temperatur unter dem Gefrierpunkt von Wasser lag. Geschwindigkeits- und Turbulenzgradmessungen im Kanal wurden mittels eines auf einem Zweikomponenten-Meßtisch angeordneten Laser-Doppler-Anemometers vorgenommen. Bei allen Messungen — also auch bei Eisbildung — blieb der Wasserstrom gleich. Es zeigte sich, daß die anwachsende Eisschicht einer Laminarisierung des zulaufenden Wasserstroms bewirkt, woraus vermutet werden kann, daß das Einsetzen der Umschlagphänomene engstens mit einem Anstieg des Turbulenzgrades im Wasserstrom über der sich bildenden Eisschicht in Beziehung steht.

Solidification of aqueous binary solution on a vertical cooled plate with main flow

An experimental study of the transient solidification of an aqueous binary solution from a vertical cooled plate is reported in this paper. A copper plate of the flow duct, which has 50 mm×70 mm in cross-sectional dimension and 500 mm in length, was cooled uniformly. Ethylene-glycol solution was adopted as a testing liquid. The dependence of the plate wall temperature, the flow rate, the entry-liquid concentration, and the entry-liquid temperature on the solidification characteristics were extensively determined. The data reveal that the characteristics of the frozen layer at both the onset and the steady state could be favorably classified as a function of Reynolds number and the cooling temperature ratio. The correlation of the averaged frozen-layer thickness at the steady state was determined.ZusammenfassungEs wird über eine experimentelle Untersuchung des transienten Erstarrungsvorgangs einer wäßrigen Binärlösung an einer senkrechten Kühlplatte berichtet. Eine Seite des Versuchskanals (Querschnitt 50×70 mm2, Länge 500 mm) ist als gleichtemperierte Kühlplatte gebildet; als Testfluid wird Ethylen-Glykol verwendet. Die Abhängigkeit der Plattentemperatur, des Massenstroms, der Flüssigkeits-Konzentration und-Temperatur am Eintritt von der Erstarrungscharakteristik wurde eingehend untersucht. Die Meßdaten belegen, daß die Charakteristik der Erstarrungsschicht sowohl im Anlauf-wie im Stationärbetrieb eindeutig als Funktion der Reynolds-Zahl und des Kühltemperaturverhältnisses bestimmt werden kann. Eine Korrelationsgleichung liefert die mittlere Gefrierschicht im Stationärzustand.

Forced convection freezing characteristics along the convex wall of a return bend with rectangular cross section

An experimental study was made of the forced convection freezing characteristics on the convex wall of a return bend with a rectangular cross section. Observations were carried out for duct heights of 17 and 30 mm, a duct width of 300 mm, and a radius of curvature of 159 mm. The convex wall temperature was uniformly maintained below the freezing temperature of water, and the concave wall was insulated. It was found that a stepwise ice layer forms on the convex wall of a return bend and that the step position at the steady-state condition is closely dependent on both the water flow velocity and the cooling temperature ratio.

Forced-convection freezing heat transfer characteristics in a return bend with a rectangular cross section

Experiments have been performed to investigate the freezing heat transfer characteristics in a return bend with a rectangular cross section. The experiments were carried out for two kinds of duct heights of 30 and 50 mm under the fixed size of 300 mm in duct width and 159 mm in curvature radius of convex wall. Both the convex and concave walls of a return bend were kept less than the freezing temperature of water. It was found that the freezing characteristics on the convex wall are markedly different from those on the concave wall of a return bend, and that the cooling temperature ratio is one of the most important parameters on the forced-convection freezing heat transfer in a return bend.ZussammenfassungEs wurden Experimente zu Untersuchung des Wärmeübergangsverhaltens bei Eisschichtbildung in einem Umkehrkrümmer von rechteckigem Querschnitt durchgeführt, und zwar für zwei Kanalhöhen ()30 und 50 mm) bei 300 mm Kanalbreite und 159 mm Krümmungsradius der konvexen Wand. Die Temperaturen der konvexen und der konkaven Wand des Umkehrkrümmers lagen unter der Gefriertemperatur von Wasser. Es zeigte sich, daß das Gefrierverhalten an der konvexen Wand sehr unterschiedlich von dem an der konkaven Wand ist, und daß das Kühltemperaturverhältnis einen der Haupteinflußparameter für den Wärmeübergang bei Eisbildung unter Zwangskonvektion in einem Umkehrkrümmer darstellt.