Yujiro Hayashi

Stereoselective total syntheses of uncommon sesquiterpenoids isolated from Jatropha neopauciflora.

The first total syntheses of two tricyclic sesquiterpenes 1 and 2, isolated from Jatropha neopauciflora, were completed from dimethyl D-tartrate in a stereoselective manner. The crucial steps in these syntheses involved not only the Rh(I)-catalyzed Pauson-Khand-type reaction of the allenene derivative leading to the exclusive formation of the bicyclo[4.3.0]nonenone framework possessing an angular methyl group but also a highly stereoselective construction of the isopropylcyclopropane ring.

Rh(I)-catalyzed intramolecular [2 + 2 + 1] cycloaddition of allenenes: Construction of bicyclo[4.3.0]nonenones with an angular methyl group and tricyclo[6.4.0.01,5]dodecenone

Summary The [RhCl(CO)dppp]2-catalyzed intramolecular carbonylative [2 + 2 + 1] cycloaddition of allenenes was developed to prepare bicyclo[4.3.0]nonenones possessing a methyl group at the ring junction, which is difficult to achieve by the Pauson–Khand reaction of the corresponding enynes. This method also provided a new procedure for the construction of the tricyclo[6.4.0.01,5]dodecenone framework in a satisfactory yield.

HEAT TRANSFER FROM TUBES IN MIST FLOWS

The present work has been undertaken to pursue the high performance of mist-cooled heat exchangers, Hrrt, mist-cooling experiments are conducted for staggered tubes having a fine surface structure in a vertical crossflow, and mist-cooling heat transfer is discussed including the effects of mutual interferences among the tubes. Next, mist-cooling heat transfer is analyzed for an arbitrary configuration of tubes, and design optimization for mist-cooled heat exchangers is developed upon applying the performance-evaluation criteria method of Bergles.

MICROSOLIDIFICATION PROCESS IN MULTICOMPONENT SYSTEM

In conventional solidification of multicomponent mixtures, a mushy zone appears between the pure solid and liquid regions and promotes stable solidification by accepting the rejected solute regionally. From the standpoint that the fineness of inhomogeneity influences the mechanical properties in material processing, the linking of macro heat transfer and microsolidification in the mushy zone was studied. First, the crystal growth and its accompanying concentration field near the advancing front of the mushy zone were observed precisely by using the light absorption method. It was clarified that the mushy zone consisted of the leading front in which the frame structure formed with an accompanying concentration boundary layer and a growing region where the solidification proceeds by fattening of the crystals. Second, the mechanism of side-branch evolution was studied in conjunction with interfacial instability due to constitutional supercooling and curvature supercooling around the primary arm surface. Summarizing these results, the microsolidification process is discussed quantitatively in relation to macro heat transfer.

Experimental investigation of the mode of phase dissociation in superheated liquid jets

Abstract The present paper gives an exclusive experimental coverage of the flashing process of pure and gas-associated solutions of water at low absolute pressures. The analyses include the phenomenon of bubble nucleation, growth and departure from the source, and the consequential properties of the flashing and disintegration of the liquid jet. The influence of dissolvable substances in the liquid on the bubble nucleation and altered liquid jet physical properties is also made clear. The outcome of the results also leads to the conclusion that, at high concentrations of the solute gas, dissociative bubble nucleation dominates the process and is associated with simultaneous bubble nucleation at the solid body-liquid interface and in the bulk of the liquid, especially at low liquid temperatures.

Prediction of Condensation Heat Transfer of Binary Vapors of Immiscible Liquids on Horizontal Tube Banks. Condensation Model.

This work was undertaken experimentally and analytically to acquire a better understanding of condensation heat transfer of binary vapors of immiscible liquids on horizontal tube banks. The characteristics of condensation heat transfer on lower tubes, which received condensates inundated at the upper tube banks, were clarified through detailed experiments using an azeotropic mixture of carbon tetrachloride and water as binary vapors. Due to the combination of the organic immutable behavior and the extreme behavior of water droplets, standing droplets and continuously detaching droplets on the surface, a model of condensation was developed taking into account the sweeping effect and the inundation effect. The predictions obtained using by this model agree well with the experimental results.

Condensation Heat Transfer of Binary Vapors of Immiscible Liquids on Horizontal Tubes.

In order to enhance the condensation heat transfer of binary vapors of immiscible liquids, detailed experiments have been conducted with regard to the condensation of an azeotropic mixiture of carbon tetrachloride and water on horizontal tubes with enhanced fins. The condensation mechanism of this kind of vapor on horizontal tubes is clarified through the measurement of droplet departure frequency and heat transfer rates. The experimental results indicate that finned tubes are more effective in the enhancement of condensation heat transfer of binary vapors of immiscible liquids, and that an optimum dimension of fins exists.

Study on Condensation Heat Transfer of Binary Vapors of Immiscible Liquids (Nonazeotropic Mixtures).

In order to clarify the condensation heat transfer mechanism of binary vapors of immiscible liquids, experimental and theoretical studies have been performed on condensation of a nonazeotropic mixture of R113 and water on a cooled vertical flat plate. The condensation rate and the dynamic characteristics of droplets of water, i. e., the critical diameter and frequency of departure droplets, were measured for several concentrations of mixture. Considering the diffusion layer developing along the liquid layer and the sweeping effect by falling drops, we proposed a heat transfer model. The predictions of this model agree well with the experimental results for the mixed condensation heat transfer phenomena consisting of the water adherent drop and the organic liquid film.

Study on latent heat thermal energy storage using aqueous solution as PCM.

The freezing of an aqueous solution, occurs over a range of temperatures, and is composed of the solid, solid-liquid and liquid states. In this paper, latent heat thermal energy storage using aqueous solution as PCM is proposed, to pursue the high performance of a storage unit. Heat transfer characteristics were clarified by the experimental and theoretical studies, and the efficient and optimum configurations of the unit were determined.

Development of wet type electrostatic precipitator using a mist formation.

A newly wet type electrostatic precipitator method is developed so as to collect small particles with sub-micron radius in high efficiency. In this method, heterogeneous mist formation around particles, which results in enlargement of electric force due to increase of radius, is carried out in the forced convective and corona-electric fields between parallel cooled plates. Collecting efficiency is clarified on thee basis of heat and mass transfer characteristics.