CONVENTIONAL BASIC DESIGN FOR CONVECTION OR CONDUCTION DRYERS

The items to be considered prior to selection of dryers are explained, and a simple method for a rough estimation of dryer sizes was proposed based on data obtained from operating industrial dryers.

The equations of basic design for batch or continuous type dryers were derived. The heat was supplied to materials by convection and/or conduction. The equations were simplified to the case when the falling rate of drying is proportional to the moisture content of materials under the constant drying conditions. The heat transfer coefficient used in the equations can be determined based on the calculations or the data obtained from the experimental or industrial dryers. The equations are useful for estimating the scale-up effect of dryers.     

Modeling of soot particles growth in fuel-rich premixed flame

The soot formation process and the structure of a fuel-rich premixed flame stabilized in the downstream side of a porous medium have been investigated by experimental measurements and numerical analysis. In the numerical analysis, a modified Tesner's model for the reaction rate of soot formation has been introduced through a comparison between measured and calculated distributions of the temperature and the species mole fractions. Furthermore, a novel model for soot growth is developed, taking both surface and coalescence growths into account. On the basis of this model, the following results are obtained. Surface growth becomes dominant immediately after the beginning of soot formation. In the downstream side, the soot particle increases due to grow by the coalescence with smaller soot particles, and decrease as a result of collision with radicals and coalescence with larger soot particles.     

Metallic conductivity in perovskite-type compounds AMoO3 (A = Ba,Sr, Ca) down to 2.5K

The resistivities of perovskite-type compounds AMoO₃ (A = Ba, Sr, Ca) have been measured over the temperature range from room temperature to 2.5K. The metallic conductivity have been observed in these compounds. The order of resistivities of AMoO₃ is discussed from the viewpoint of overlap intergrals.     

Experimental study of fire growth in a reduced-scale compartment under different approaching external wind conditions

In order to clarify the fire growth process in compartments under external wind conditions, detailed fire tunnel experiments were conducted in a reduced-scale compartment. The approaching external wind velocity was set to 0.0, 1.5 and 3.0 m/s, and the location of the fire source was changed between the downwind corner, upwind corner and center of the compartment. The experiments considered the effect of wind on a through-ventilation situation. The temperatures of the air and the wall surfaces in the compartment and the temperatures of the flames ejected from the opening were measured. The fuel mass loss rate and the heat flux from the opening were also recorded. Different fire growth characteristics are shown under different wind and fire source conditions. The temperature rises faster and burnout time is reduced under windy conditions. It is found that external wind has two opposing effects. One is to promote combustion within the compartment and thus raise the temperature, the other is to blow away and dilute the combustible gases in the compartment and decrease the temperature, or hasten its extinction. When the approaching wind velocity is high, the external plume is greatly inclined to the downwind side, and the flame becomes larger, thus increasing the risk of the fire spreading to neighboring buildings. The dimensionless temperature of the external flame was a little lower than the results indicated by Yokoi's experiments without wind.     

Polyelectrolyte complex prepared from carboxymethylated and aminoacetalized derivatives of poly(vinyl alcohol)

Some physical and chemical properties of an ionic complex made from the weak polyelectrolytes carboxymethylated poly(vinyl alcohol) (PA) and aminoacetalized poly(vinyl alcohol) (PC) are investigated in comparison with those of another ionic complex made from the strong polyelectrolytes sulfated poly(vinyl alcohol) (PSA) and poly(vinyl alcohol) acetalized with diethoxyethyltrimethylammonium (PTC). It was found that when the complex PC–PA was heated at high temperatures, covalent amide bonding took place, whereas no significant change occurred in the case of the PTC–PSA complex. As a result of these structural changes, the degree of swelling of the PC–PA complex in water was markedly decreased, but that of the PTC–PSA complex was not changed by the treatment. The PC–PA complex was insoluble in water and in 1N HCI and 1N NaOH aqueous solutions even if not heat treated, but the PTC–PSA complex was soluble in such acidic and basic aqueous solutions but not in water if heat treated. The PC–PA and PTC–PSA films exhibited good mechanical properties.     

Mechanism by which an elevation of extracellular glucide concentration induces pigment aggregation in medaka melanophores

An increase in glucide concentration induces pigment aggregation in melanophores in the skin on scales isolated from the medaka, Oryzias latipes. In this study, hexoses (including the common D-isomers of glucose, galactose, fructose, and mannitol) were examined. Denervated melanophores were refractory to such stimuli. An alpha-adrenolytic agent, phentolamine, effectively blocked the responses of normally innervated melanophores. The pigment-aggregating action of glucide was inhibited by withdrawal of Ca(2+) and Mg(2+) ions from the medium. A specific blocker of voltage-dependent N-type Ca(2+) channels, the omega-conotoxin GVIA, also inhibited the glucide action. The conclusion derived is that an elevation of glucide levels acts to open Ca(2+) channels of presynaptic membranes of sympathetic postganglionic fibers, and the consequently released adrenergic transmitter acts on the effector cells to induce the aggregation of their pigmentary organelles.