Isao Ishihara

Natural convection in a vertical rectangular enclosure with symmetrically localized heating and cooling zones

Abstract Numerical and experimental studies of natural convection in a single-phase, closed thermosyphon were carried out, using a vertical, rectangular enclosure model. Two vertical plates, each 100×100 mm2 in dimension, and placed symmetrically play the role of heat transfer surfaces. These symmetrical heat transfer surfaces are separated into three horizontal zones of equal height; the top and bottom thirds of these surfaces are the zones of, respectively, cooling and heating, the intermediate section being an adiabatic zone. Silicon oil is used as the working fluid. Variable parameters are the distance, D, between the two heat transfer surfaces, and temperature difference, ΔT, between the heating and cooling zones. By changing both D and ΔT, three regimes of natural convection flow; steady, quasi-two-dimensional, steady, three-dimensional, and unsteady flows were found in experiment. Converged solutions obtained by numerical simulation agreed well with experimental results with regard to the temperature and velocity of the fluid as visualized by means of thermo-sensitive liquid crystal powders.

Automatic spatial fringe analysis method for two-dimensional fringes image including phase discontinuities by obstructions

Abstract A new two-dimensional (2D) automatic spatial fringe analysis method or analysing a fringe image including images of obstructions, such as a blade in an interferogram of pressure distribution around turbine blades, is proposed. In the analysis, first, the image of the obstruction is removed from the fringe image using the characteristics of spatial fringe analysis method. Second, the problem with respect to the phase discontinuities of the principal values of the inverse-trigonometric function is discussed. Then, the processing paths for the automatic phase-unwrapping processing are found using the concept of the directed graph. Third, fringe analysis of an image including noise is discussed by the new method. Finally, automatic 2D spatial fringe analysis can be realized with the calculation along processing paths. The experimental results show that the 2D fringe analysis for the image with obstructions can be performed accurately and automatically by the method proposed. In addition to the experi...

Mixing in microchannel by electroosmosis flow

Rapid mixing is essential on the micromixer in microfluidic systems. Mixing in microchannel relies mainly on molecular diffusion due to the laminar flow at low Reynolds number. In this study, the sequential switching of electroosmosis flow is applied to the mixing in microchannel. By switching of the electroosmosis flow sequentially to the T-junction microchannel, the mixing stream is segregated by the two inlet streams on and off, then the mixing process can be accelerated and controlled by increasing the contact surface of two liquids. The flow pattern was classified into two patterns, wavy flow pattern and segmented flow pattern, by Strouhal number. The mixing degrees can be expressed as a function of Strouhal number.

Development of Low-NOx DME Multi-Ports Burner

This study focuses on fundamental characteristics of DME combustion, aiming at the development of low-NOx multi-ports burner. Multi-ports burner consists of a fuel-port and surrounding multi-air-ports. The strong re-circulation flow is formed by the small air jets, thus the short flames form a cluster on every burner unit so that the thermal NOx generation is significantly suppressed to a very low level. The NOx emission of the DME from the co-axial diffusion burner was over 130ppm beyond the level of the other fuels. On the other hand; NOx emission of DME from the newly advanced multi-ports burner was reduced to 60ppm at 0% O2 . With the help of the low-NOx combustion system, referred to as the tube-nested combustion, NOx emission of DME was further reduced to 20ppm at 0% O2 .© 2005 ASME