Makoto Akiyoshi

A NUMERICAL STUDY ON NATURAL CONVECTIVE HEAT TRANSFER OF PSEUDOPLASTIC FLUIDS IN A SQUARE CAVITY

The natural convective heat transfer of pseudoplastic fluids in a square cavity with a heated bottom and cooled top walls was examined by a direct numerical analysis using the Sutterby model. Consequently, it could be verified that the heat transfer rate of pseudoplastic fluids became larger than that of a Newtonian fluid under thermal conditions where stable vortex flows were formed. The reason is that fluid flows are easy to further develop particularly near the walls due to the decrease in the apparent viscosity by the shear-thinning effect. On the other hand, it was found that the locally larger change in viscosity had the potential of causing the formation of a complicated flow field when the non-Newtonian fluid was highly pseudoplastic and the Rayleigh number increased. The contribution of the shear-thinning effect depending on the non-Newtonian property and the thermal condition was clearly revealed.

CHARACTERISTICS OF HEAT TRANSFER FROM A SPHERICAL SOLID BODY UNDER PULSATING FORCED CONVECTION

Heat transfer from a solid sphere having a Biot number Bi ≪ 0.1 to a flow medium in a cooling process under pulsating forced convection is experimentally examined. In the experiment, two kinds of pulse modes, which are the type of pulsating forced convection with continuous feed and the feed type mixing forced and natural convection, are considered as a pulse feed technique. Initially, the evaluation method of the Nusselt number Nu is derived in the cooling process and the validity of that method is verified by comparison with the experimental results. With regard to the effect of pulsating feed, it is shown that the pulsating feed conditions have a great influence on the characteristics of the heat transfer. The enhancement of heat transfer under the condition of the forced convection pulsatively fed with continuous feed is recognized, and the characteristics of heat transfer for the pulsating feed including natural convective heat transfer region are aggravated. Besides, it is clear that the decrease in the heat transfer characteristics is dependent on the duration of the natural convective heat transfer. Furthermore, Ranz-Marshall correlations for each pulsating feed condition are presented.

Oxidation Treatment of Dilute Hydrogen Cyanide. On the Formation of Carbon Monoxide and Carbon Dioxide.

気法によるシアン含有廃水処理等に際して排出される含シアンガスを燃焼して無害化する試みが行われている.この場合, シアン化水素ガスは酸化されて二酸化炭素, 窒素, 水に分解されることが期待されているが, 条件によっては有害な一酸化炭素や窒素酸化物が生成する可能性もある.また, シアン化水素は酸化反応のほかに, アンモニアを生成する加水分解反応, ジシアンを生成する熱分解反応等によっても減少する.通気法による処理が特に有効と考えられる低濃度シアン含有廃水の通気ガス無害化の基礎研究として, 前報では, 6.69×10-3及び1.34×10-2mol・m-3 (150及び300ppm) のシアン化水素を含む空気を923～1123Kに加熱して, その減少速度について報告した.本報では, 希薄シアン化水素含有空気を加熱した際生成する一酸化炭素, 二酸化炭素濃度を実測し, 炭素の物質収支より, 最終生成物の一つは二酸化炭素であることを示した.また一酸化炭素の生成についても若干の知見を得た.

Classification of Particles of the Same Density in Liquid-Solid Fluidized Beds.

Glass beads and crushed glass particles of diameters ranging from 1.0 to 5.0 mm were fluidized with tap water. The bed was initially fluidized completely, and then the liquid velocity was gradually decreased to obtain a fixed bed. The relationships of relative particle diameter ratios with the relative heights of the sampling sections in the beds were obtained at 7 mm height intervals. With respect to binary systems of glass beads, good size classification was accomplished at the size ratio of 1.10. This size ratio is much smaller than the widely accepted critical size ratio of 1.30 for classification in liquid fluidization. For a multicomponent system of crushed glass, the continuous classification of various size ranges was observed.Inclination of the fluidized column had a great adverse effect of the size segregation.