Control of nano-micro particulate flow processes in plasma spraying, cold spray and fine particle synthesis using plasma flows is described by integrating numerical simulation and experiment. These processes can be regarded as particle laden plasma flows with complex interactions and phase changes. The in-flight particle heating can be effectively enhanced by Joule heating with applying RF electromagnetic field in plasma spraying to control the coating thickness distribution. Furthermore, the impact particle velocity can be effectively accelerated by electrostatic force with applying corona discharge in cold spray process to increase deposition efficiency. Finally particle size distribution and particle morphology can be changed by phase change control with various kinds of inlet gas flow rates, downstream quench gas and operating pressure in fine particle synthesis using RF induction plasma flow and DC-RF hybrid plasma flow system. It is clearly shown that control of dynamic behavior and phase change of in-flight nano-micro particles in plasma flows can be achieved by using electromagnetic field, discharge mode, inlet flow rates and operating pressure for coating process and fine particle synthesis.

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As semiconductor-devices become more highly integrated and their geometry continues to shrink, conventional aqueous (or liquid-phase) cleaning/drying tends to collapse high-aspect-ratio fragile LSI (large-scale integrated circuit) structures due to the high surface tension of aqueous chemicals and water. The use of physical cleaning aids such as ultrasonic agitation can also cause damage to the fragile nano-structures. The process window for damage-free cleaning is becoming narrower as the device geometry shrinks every year. This makes the development of novel damage-free cleaning methods a high priority, with preferably less chemical/water consumption. In this paper, the problems of aqueous cleaning of the semiconductor surfaces are briefly reviewed and then various alternative cleaning techniques to employ multiphase flows are described and discussed which include gas-injected megasonic cleaning, high-pressure atomizing jet spray cleaning, and cryogenic aerosol cleaning. There will be more research challenges and business opportunities in the environmentally-benign multi-phase flow technologies in the near future.

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The alternative and natural refrigerants presently used to address global warming problem yield low coefficient of performance and should be studied further. Recently, new technique using two-phase ejector flow model is developed. This paper shows the theoretical analysis of energy conversion efficiency of ejector from the thermodynamic and fluid dynamics point of view. Also, two-phase flow shockwaves appearing in the nozzle of ejector are shown based on experimental results. These shockwaves are categorized into two types; one is pseudo shockwave and the other is dispersed shockwave. The theoretical analysis with momentum relaxation given in this paper provided a good representation of these shockwaves.

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In the present study, a novel gas-liquid separator using surface tension force is proposed and its performance is evaluated. The gas bubbles are forced out from the liquid flow at the expanding section by the minimization effect of excess gas-liquid interface free energy, while the liquid phase remains confined inside the micro grooves. Two major gas-liquid separation limits, i.e., (1) flooding limit at high liquid flow rate, and (2) entrainment limit at high gas flow rate are observed and investigated by air-water experiment. Dimensionless correlation for predicting gas-liquid separation limits is proposed. Based on the knowledge from the air-water experiment, a compact gas-liquid separator for R-410A system is developed and the basic characteristics of the separator in refrigerant cycle are investigated. The volume of the present separator is 1/7 compared to that of the conventional separators. Pressure drop reduction in an evaporator is confirmed by bypassing the gas from the evaporator. Finally, a series of 4-16kW capacity gas-liquid separators for practical use is developed.

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For the purpose of developing microactuators driven by liquid crystals, transient behaviors of a nematic liquid crystal between two parallel plates under an electric field are investigated on the basis of continuum mechanics and molecular dynamics. Imposition of an electric field on the liquid crystal induces flow, called backflow, whose profile and magnitude depend strongly on the twist angle of the director; that is, the velocity profile between plates is S-shaped when the twist angle is 0 deg, and unidirectional flow is generated when the twist angle is 180 deg. It is confirmed from the molecular dynamics simulation that the rotation and rearrangement of molecules during the reorientation process generate a local bulk velocity gradient. Furthermore, we have visualized the backflow induced between parallel plates to confirm qualitatively the predictions obtained numerically. As an example of liquid crystalline microactuators, we have manufactured micromotors and examined the revolution speed as a function of the frequency of an electric field.

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This paper reviews the principle of cosmic-ray muon radiography (muography) and its application to the analysis of gas-liquid two-phase flow in a conduit during volcanic eruption. Muography is a useful technique for imaging internal density distribution of a big object (e.g., a volcano, a blast furnace, etc.). By measuring muon path lengths and absorption along different paths through the object, one can deduce average density along the path inside the object. According to numerical modeling of gas-liquid two-phase flow in the volcanic conduit during a dome-forming eruption, magma porosity (i.e., density) inside the conduit largely changes depending on magma flux even if the porosity at the surface is kept low. The increase in the porosity inside the conduit may induce the transition to explosive eruption. This implies that high-resolution measurement of the porosity distribution inside the conduit is essential for predicting the transition of eruption styles. Recent progress in a muon detector system enables us to perform this measurement, such as in Mt. Iwodake of Satsuma-Iwojima Volcano, Japan. Spatial resolution of muography is adequate for detecting the variation of the porosity inside the conduit. Applications to industrial plant monitoring are also discussed.

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Water flow in a cylindrical bath under mechanical offset agitation is investigated by PIV measurement from two directions. Velocity vectors in the vertical and horizontal cross-sections are presented. An inclined-vortex forms under certain conditions in this agitation method. A fast flow toward impeller blades is observed above the impeller. A radial flow is observed below the impeller. Low-density particles widely disperse into the bath through the effects of these two kinds of flows.

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Dropwise condensation heat transfer coefficients can be calculated from the density of drop-size distribution and the growth rate of drops. In the case of steam including non-condensable gases the heat transfer coefficient can be calculated. The purpose of this study is to investigate the effect of pressure and non-condensable gas concentration for dropwise condensation heat transfer. Furthermore, the validity of the density of drop-size distribution formula in the presence of non-condensable gases proposed by Tanaka is evaluated. Heat transfer coefficients are measured in the air mole fraction range between 1 % and 25 % and in the pressure range between 0.1 MPa and 0.4 MPa. And drop diameters and drop numbers are measured using image analysis. As a result, the theoretical formula proposed by Tanaka is applicable when non-condensable gas concentration is 25 % or less.

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This study is concerned with a siphonage with a sliding outer tube, aiming at the collection of sediments, causing a decrease in pondage as well as water pollution in dams. Experiments were performed using siphon pipes of 20 mm and 30 mm I.D. and five kinds of particles with different densities and dimensions. Measured parameters are the volume fraction of the particle in the siphon pipe, the flow rates of water and the particle. The effects of particle diameter and density and the level difference from water surface to siphon exit were investigated. In addition, a performance prediction model is proposed and tested to know its applicability as a design tool of actual large scale systems.

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