Shuya Kamei

Condensing phenomena of a single vapor bubble into subcooled water

Abstract Experiments have been carried out to investigate direct contact condensation of saturated vapor bubbles introduced into a quiescent subcooled water environment. The experiments were performed for a range of pressures from atmospheric to 1 MPa, for subcooling from 10 to 70 K, and for initial bubble diameters of about 10 mm. Flow visualization by highspeed motion pictures was based on a frame-by-frame analysis. The photographs show that the successive shapes of the bubbles during their collapse histories proceeded from a sphere to a hemisphere, to an ellipsoid, to a sphere, and finally to collapse. Two-dimensional photographs clearly show that the cavities of the bubbles during their collapse histories proceeded from the bottom to the top. The time to collapse increased with increasing pressure difference. The rising velocities of the bubbles were essentially constant, with an overall range of 20–25 cm/s.

Visual measurement of flow rates for falling droplets from a capillary tube

The paper deals with the flow control and measurement of liquids that form droplets. An experimental investigation on the mass of the falling droplet from capillary tubes was carried out. Examples where the present study is considered useful are in the measurement of injection flow rates of fuel in a diesel engine and for flow measurement of drops from capillary tubes in medicine. In this investigation the capillary tubes used were made of brass and Bakelite material. The inner diameter of each tubes was kept constant at 1 mm and outer diameter tubes were changed from 2 mm to 5 mm in accordance with the variation in the liquid surface tension. Experiments on falling droplet of distilled water and methyl alcohol were also carried out, as the surface tension of these liquids are so very different. The experiments were performed using a visualization technique. The present paper discusses the effect of tube diameter, droplet size and physical property of liquid on the phenomena of a falling droplet.

Boiling phenomena due to periodically moving the heated surface in pure water pool

For the purpose of explaining the correlation of the heat transfer characteristics and the steam bubble behavior, the boiling phenomena were observed. The heating surface was the horizontal Pt-wire, and shaken periodically for the normal direction to the axial direction in the saturated distilled water. Also, this was a continuous and smooth motion. The experimental condition was performed for atmospheric pressure. The observations were using shadow-graphy with a high speed video camera and a still camera. In the consequence of the present experiments, the high burn-out heat flux and the high average heat transfer coefficient were obtained by the comparison with the still heated surface. Also, by the visualization of the quantity of the bubble population on the shaking surface, it was observed that the quantity decreased by the comparison with the still heated surface. It was conjectured that the present phenomena were caused by tearing the overheated liquid, and by promoting of departing of steam bubble on the heating surface. The detailed research of the generating and departing of bubble with periodically moving heated surface is expected. Also, the research of the boiling characteristics by changing the frequency of the motion is expected.

Control of oscillation noise caused by condensing vapor in subcooled water

Experimental considerations for control of the oscillation noise were performed for results of various steam vapor injecting visualization as in previous reports. These phenomena were observed by means of shadowgraphy using a high speed video camera and a still camera. These injecting patterns of the steam bubble were analyzed through the photographs selected from each picture film. Peak frequency and amount of the oscillation noise caused by the condensing vapor were dependent on subcooling and amount of the mixing ratio for injecting gas. These experiments were performed for atmospheric pressure, and for temperature differences between the saturated steam and water for subcooling 20-70. The present investigation was clarified that the condensing oscillation noise would have significant relationships for a quantity of thermal layer near the orifice surface. Temperature distribution on the orifice and S.P.L. of the condensing noise predicted for some visualized results had so much correlations. The effect of bulk temperature in a water tank and difference among a single orifice and the other orifice were discussed and good predictive results for the flow visualization in subcooled water.

Visualization study on pool boiling heat transfer

The visualized boiling phenomena were observed by means of high speed photographic shadowgraphy using a rotating prism camera (nac HIGH SPEED CAMERA model-16HD) with the speed of about 3500 frames per second. The photographs show that pool boiling heat transfer phenomena are varied for the boiling curve based on the experiments. Experiments have been carried out to investigate pool boiling heat transfer phenomena on a horizontal thin filament in subcooled and saturated distilled water. The experiments were performed for atmospheric pressure,for filament diameters of about 0.3 mm, for region of natural convection to film boiling. The color-film made by high speed movie camera are converted to high speed color video-tape. It is convenient to edit and show the tape for visualization with teaching the students. The high speed color video showed that the successive motion and shape of bubbles during their process of detachment varied with increasing heat flux on the heated surface of a filament. From these results, it was confirmed that the high speed phenomena of boiling by the slow motion video pictures could be estimated clearly.

Observational Study On Thermal Flow And Condensation Of Injecting Steam From Various Submerged Orifices

It has been recognized that the steam accumulator plays an important role as one of thermal energy storage system and was used at hospitals, hotels and food factories in recent years. Experiments have been carried out to investigate direct contact condensation of saturated steam into a quiescent subcooled water environment. They were performed for subcooling from 20 - 70°C, for atmospheric pressure, and for various type of orifice ( single-orifice, multi-orifice and porous-disc-orifice ). The phenomena were observed by means of high speed shadowgraphy using a rotating prism camera. The phenomena were also visualized by techniques of liquid crystal using a still camera. The effect of bulk temperature in a water tank and the difference among a single-orifice, a multi-orifice and porous-disc-orifice were discussed and good predictive results for the visualization of thermal flow in a quiescent subcooled water environment were obtained.

High Speed Photographic Study On The Oscillation Noise By The Condensation Of Injecting Steam From A Submerged Orifice

Frequency Analysis was carried out for the oscillation noise due to the condensation of steam injected from a submerged orifice into the subcooled liquid. The phenomena were also observed by means of high speed photographic shadowgraphy using a rotating prism camera with the speed of 3500 frames per second. Operations were conducted at atmospheric pressure, and water temperature varied in the range from 30°C to 80°C. The steam flow rate was varied from about 0.06 g/sec to about 3 g/sec. The present study has clarified that the condensation process arising from the steam-water transformation plays a most signifcant role for producing the oscillation noise of steam bubbles.