Itsuro Honda

Flow and heat transfer on cryogenic flow boiling during tube quenching under upward and downward flow

The gravity effects on quenching of tube by cryogenic fluids for the development of cryogenic fluid management on orbit are studied. In this paper, the effects of the tube diameter, the flow directions, and the mass velocity on the tube quenching using liquid nitrogen are investigated systematically in the terrestrial conditions. The experiments are performed by the mass velocity between 100–600 kg/m2s in downward and upward flow directions by using three difference inner diameters of the transparent heated tube (7, 10, 13.6 mm) for measuring fluid behavior observations and heat transfer measurements simultaneously. The results indicate that the difference between the minimum heat fluxes under downward and upward flow conditions increased as the mass velocity increased. These characteristics of heat transfer were caused by filamentary flow pattern that was found in only downward flow and high mass velocity conditions.

Theoretical and Experimental Analysis of the Nonlinear Characteristics of an Air Spring With an Orifice

We herein propose a simple but accurate method for calculating the dynamic properties of an air spring that uses an orifice to produce a damping force. Air springs are commonly used in rail, automotive, and vibration isolation applications. However, because this type of air spring has nonlinear flow characteristics, accurate approaches have not yet been proposed. The restoring and damping forces in an air spring with an orifice damper vary with the amplitude of the body. This amplitude dependency has not been considered in previous studies. We herein propose a simple model for calculating the air spring constant and damping coefficient. However, this requires iterative calculation due to the nonlinearity of the air spring. The theoretical and experimental results are found to agree well with each other. The theoretical equations provide an effective tool for air spring design.

Numerical Analysis of the Internal Flow in an Annular Flow Channel Type Oil Damper

The purpose of the present study is to clarify the fluid flow of an oil damper through numerical analysis in order to obtain an exact value of the damping coefficient of an oil damper. The finite difference method (FDM) was used to solve the governing equation of the fluid flow generated by a moving piston. Time steps evolved according to the fractional step method, and the arbitrary Lagrangian–Eulerian (ALE) method was adopted for the moving boundary. In order to stabilize the computation in the moving boundary problem, a masking method with a single block grid system was used. In other words, algebraic grid generation using a stretching function was used for the moving piston in the cylinder of the oil damper. The time-dependent coordinate system in the physical domain, which coincides with the contour of the moving boundary, is transformed into a fixed rectangular coordinate system in the computational domain. The computational results were compared with experimentally obtained results and the approximate analytical solution. The results of the present analysis exhibit good agreement with the experimental results over various widths of the annular flow channel between the piston and cylinder.

Convection and surface tension profiles for aqueous droplet under microwave radiation

Application of microwave irradiation for chemical processes, such as emulsification and polymerization, has been reported [1,2]. Surfactant free emulsion can be produced with the help of microwave irradiation. Surface tension is an important property for the industrial process such as foaming/defoaming, wetting/dewetting and flotation. Similarly, the interfacial tension plays crucial role in separation and mixing process of two immiscible liquids, which are important unit operations of the fundamental chemical engineering. In practice, surface and interfacial tensions are often altered by introducing surfactants. In our previous research [3,4], specific property for surface tension of water droplet with salt under microwave radiation was found. For example, lower surface tension after the radiation was measured. The formation of nano-bubble will explain this behavior. Normally, the surface tension of aqueous solution increases with the salt concentration because cation and anion collect water molecule more strongly as a solvation. However, the exact mechanism of surface tension reduction by microwave radiation is not clear. We tried not only measurement of surface tension but also convection in the droplet during microwave radiation. This study investigates the influence of microwave on surface tension of aqueous solution. Moreover, relation between the concentration, temperature and droplet shape, which are related with surface tension.

In-situ observation of convection in droplet under microwave radiation by PIV

In this study, microwave irradiation is applied to a liquid droplet and the surface tension, the circulation flow and temperature of water droplet are measured dynamically under the irradiation. The droplet was allowed to return to its original temperature after the irradiation, it was found that water surface tension remained well below its original value for an extended period of time. Surface tension reduction shown similar effect of ”impurity“ at molecular level during the microwave, and some “memory” after microwave, which might be caused by nano-bubble. On the other hand, microwave can introduce the circulation flow of higher rotation speed and will be expected to be applied for non-contact stirring method.

An Approximate Formula to Calculate the Restoring and Damping Forces of an Air Spring With a Small Tube

This paper proposes a simple expression for calculating the restoring and damping forces of an air spring equipped with a small tube. Air springs are commonly used in railway vehicles, automobiles, and various vibration isolators. The air spring used in this study consists of two tanks connected by a long tube. Using a tube instead of an orifice enables flexibility in the arrangement of the two tanks. In addition, this makes it possible to manufacture a thin air spring. The oscillating system, which consists of a single mass supported by this type of air spring, is a single-degree-of-freedom (SDOF) system. However, it has two resonance points for a reason that had been unknown for a long period of time. In this paper, we explain why the SDOF system has two resonance points. After that, assuming that the vibration is small and the flow through the tube is laminar, we derive the spring constant and damping coefficient of an air spring subjected to a simple harmonic motion. Then, we calculate the frequency response curves for the system and compare the calculated results with the experimental values. According to the experiment, there is a remarkable amplitude dependency in this type of air spring, so the frequency response curves for the system change with the magnitude of the input amplitude. It becomes clear that the calculation results are in agreement with the limit value when the input amplitude approaches zero.Copyright

Flow boiling in transparent heated microtube

In the present study, a detailed investigation of flow boiling in a transparent heated microtube was performed. The transparent heated tube was made by electroless gold plating method. The enclosed gas-liquid interface could be clearly recognized through the tube wall, and the inner wall temperature measurement and direct heating of the film were simultaneously conducted by using the tube. The experimental conditions were: tube diameter 1 mm, mass velocity 100 kg/m2 s, inlet liquid sub-cooling 20 K and heat flux up to 384 kW/m2 in the open system. Flow fluctuation was minimized by employing a twin plunger pump. Among our experimental results, we observed a high-frequency fluctuation of the inner wall temperature and a sharp peak for the heat transfer coefficient with high heat flux conditions, which have not been reported in previous experiments. This abrupt increase in the heat transfer coefficient coincided with a slight rapid axial growth of an elongated bubble found in the observation of the flow behavior. Hence, in low heat flux conditions, the fluctuations of temperature and heat transfer coefficient are strongly suppressed except for the instances when there is no bubble in the tube.Copyright

Numerical Analysis of the Internal Flow in an Oil Damper (Analysis Based on the Two-Dimensional Cylindrical Coordinates to the Damper with Annular Cross-Sectional Flow Channel)

The purpose of this study is to know the fluid flow of an oil damper by a numerical analysis, so as to obtain the exact values of the damping coefficient of an oil damper. The Finite Difference Method (FDM) was used for solving the governing equation of the fluid caused by the moving piston. Each time step proceeded in the Fractional Step method, and the Arbitrary Lagrangian-Eulerian (ALE) method was adopted for the moving boundary. In order to stabilize the computation in the moving boundary problem, we employed the masking method with a single block grid system. That is, the algebraic grid generation using stretching function was used for the moving piston. The time dependent coordinate system in physical domain which coincides with a contour of moving boundary is transformed into a fixed rectangular coordinate system in computational domain. The computational results were compared with the experimental ones and the approximate analytical solution. The results of present analysis show good agreement with the experimental results over a wide range of piston diameter.

A microgravity experiment of the on-orbit fluid transfer technique using swirl flow.

Abstract:  The cryogenic fluid transfer technique will prove useful for flexible and low‐cost space activities by prolonging the life cycle of satellites, orbital transfer vehicles, and orbital telescopes that employ cryogenic fluids, such as reactants, coolants, and propellants. Although NASA has conducted extensive research on this technique to date, a complicated mechanism is required to control the pressure in the receiver tank and avoid a large liquid loss by vaporization. We have proposed a novel fluid transfer method by using swirl flow combined with vapor condensation facilitated by spray cooling. This technique enables gas–liquid separation in microgravity and effectively facilitates vapor condensation without any special device like a mixer. In addition, since the incoming liquid flows along the tank wall, the tank wall would be cooled effectively, thereby minimizing the liquid loss due to vaporization. In this paper, the influence of the number of inlet points, fluid velocity at the inlet, fluid type, and boiling condition on swirl flow under microgravity conditions is investigated experimentally. The results indicated that the new fluid transfer technique using the swirl flow proposed by us is effective for cryogenic fluids that generally exhibit low surface tension and good wettability. In addition, it is possible to apply this technique to the real system because the swirl flow conditions are determined by the Froude number, which is dimensionless. Thus, the fundamental technique of fluid transfer by using the swirl flow under microgravity conditions was established.