Kawaji, M.

KawajiB.A.Sc. (Toronto), M.S., Ph.D. (U. California, Berkeley), P. Eng., FCIC, FASME 

Room: WB357
Tel.: 416-978-3064 
Email: masahiro.kawaji@utoronto.ca 

Honours and Awards

Fellow, Chemical Institute of Canada/CSChE 
Fellow, American Society of Mechanical Engineers (ASME) 
Engineering Medal (R&D category), Professional Engineers Ontario, 2006 
Jules Stachiewicz Medal, CSChE, 2002 
Best Paper Award, Japan Multiphase Flow Society, 2000 


Canadian Society for Chemical Engineers (CSChE) 
American Institute of Chemical Engineers (AIChE) 
Director, Transport and Energy Processes Division, AIChE 
American Society of Mechanical Engineers (ASME) 
Heat Transfer Society of Japan (HTSJ) 
Japan Society of Multiphase Flow (JSMF) 
American Nuclear Society (ANS) 

Research Interests

Multiphase flow and phase change heat transfer, transport phenomena, microfluidics, micro-heat pipes, nuclear reactor thermal-hydraulics and safety analysis, microgravity fluid physics and transport phenomena, thermal diffusion, advanced instrumentation, numerical simulation of free surface problems, compact heat exchangers, thermal analysis of Kraft Recovery boilers and lime kilns, sustainable energy, biomass gasification, thermal energy storage, hydrogen production by electrolysis. 

Brief Descriptions of Recent Research Topics: 

(Recent publications are listed at the end.) 

(I) Transport phenomena in microchannels and micro heat pipes: In gas-liquid two-phase flow, surface tension effects are important due to the small radii of microchannel curvature. Our research has revealed significant differences in flow regimes, void fraction and friction pressure drop characteristics between channels of diameters above and below about 200 microns. In single-phase flow, our pressure drop measurements showed that the critical Reynolds number for laminar to turbulent flow transition is unchanged in a 100 micron diameter microchannel contrary to some previous studies. We have focused our efforts on the latest heat pipe technology called pulsating or oscillating heat pipes for advanced cooling of micro-electronics components such as CPU’s, although their flow and heat transport mechanisms are not yet fully known. The effects of heat pipe orientation and gravity on the heat transport mechanism and performance of pulsating heat pipes as well as wicked heat pipes were investigated by conducting experiments on the ground and under reduced gravity in a parabolic flight. The results suggested that the micro-pulsating heat pipes are an excellent device for microelectronics cooling applications on the ground and in space. 

(II) Fundamental Gas-Liquid Two-phase Flow Studies: For several two-phase flow regimes, the flow structures and mechanisms have been identified using the photochromic dye activation technique. Measurements of instantaneous liquid velocity profiles around a rising Taylor bubble and the drag force exerted on a solid model of a Taylor bubble by a flow were performed to understand how Taylor bubbles can accelerate and coalesce with one another in slug flow. The same technique was also used to clarify the flow structure of wavy falling films and the cause of countercurrent flooding. The motion of particles in a fluidized bed was also determined experimentally. 

(III) Nuclear Reactor Thermal-hydraulics and Safety: Several important gas-liquid two-phase flow and phase change heat transfer problems encountered in both light water reactors (LWR’s) and heavy water (CANDU) reactors have been investigated. High pressure steam-water two-phase flows in large diameter (30-50 cm I.D.) vertical and horizontal pipes under high pressure/temperature conditions were studied both experimentally and numerically. Using a full size nuclear reactor pump, the pump head degradation data were obtained under high-pressure steam-water two-phase flow conditions. The data were analyzed numerically which revealed important multidimensional effects. Two-phase cross flow, boiling heat transfer, and tube vibration phenomena in tube bundles used in steam generators of Pressurized Water Reactors and kettle reboilers were investigated to optimize tube bundle designs, reduce their size, fluid inventory and cost, and increase their energy efficiency. For CANDU reactors with a horizontal flow channel in the core, the mechanism of liquid transport in horizontal annular flow was investigated by measuring the liquid motion in disturbance waves. The liquid was shown to be carried upward towards the crown of the tube, replenishing the liquid film and preventing the liquid film from drying out during the passage of the disturbance waves. Countercurrent flooding in piping with elbows was also investigated experimentally for applications to both LWRs and CANDU reactors. In the near future, the liquid film dryout phenomena in horizontal fuel channels and intermittent buoyancy induced flow phenomena will be investigated experimentally and numerically for CANDU reactors. 

(IV) Microgravity fluid physics and heat transfer: The effects of small vibrations on fluid systems have also been investigated experimentally, theoretically and numerically. By collaborating with researchers in Russia, US, and Japan, experimental, theoretical and numerical analyses of vibration-induced motion of particles and bubbles in a fluid cell and the surface of a liquid bridge have been conducted to yield new insights. A study has also been conducted on thermocapillary or Marangoni convection involved in various material processing operations on the ground and in space. For semi-conductor crystal growth, the onset of oscillatory Marangoni convection in liquid bridges and liquid layers has been investigated experimentally. For protein crystal growth based on vapour diffusion in a hanging droplet method, the occurrence of concentration gradient-driven Marangoni convection was successfully investigated. For the liquid bridge, a three-dimensional level set code was developed to successfully predict the surface oscillations. Thermal diffusion in porous media has been extensively investigated numerically. 

(V) Efficient energy utilization and ice slurry: To improve the efficiency of energy systems and equipment for air conditioning applications, the use of ice slurries has been investigated in an NSERC-CRD project. The ice-slurry flow and heat transfer characteristics, which had not been studied in detail in the past, were systematically investigated. A complete test facility was developed and used to obtain detailed ice slurry flow and heat transfer data in rectangular heat exchanger channels. A compact ice slurry generator was also developed to demonstrate the feasibility of generating ice slurry in a rectangular and stackable, rather than a tubular scraped surface heat exchanger. Recently, a new project has been started on the use of phase change emulsions which would not require re-generation after melting and could be used for both cooling and heating applications by selecting the phase change material with a low or high phase change temperature. 

(VI) Heat transfer problems in boilers and heat exchangers: For optimized designs of kettle reboilers, two-phase flow and boiling heat transfer characteristics in tube bundles have been clarified in an extensive series of laboratory experiments. As part of an NSERC and industry funded research consortium project, laboratory and field experiments as well as numerical analyses have been conducted to investigate the heat transfer problems associated with temperature excursion and corrosion in air port and floor tubes of Kraft Recovery boilers, and accelerated char bed cooling following an Emergency Shutdown Procedure. Recently, a new project has been initiated to improve heat transfer in rotary lime kilns. 

(VII) Production of Renewable Fuels: Production of hydrogen is investigated by numerically simulating a high-pressure electrolyzer. A new project on biomass gasification for production of synthesis gas containing hydrogen and CO has been initiated. Using a bench-scale downdraft gasifier, the gasification of biomass such as wood wastes is investigated experimentally. 

(VIII) Recovery of Oil from Oil Sands: The phase and flow behaviour of a mixture of bitumen and hydrocarbon gases is investigated experimentally at high pressure and temperature with a goal to enhance in-situ oil recovery from oil sands in Alberta.