The rheological behavior of products made by the liquefaction of Wandoan coal with hydrogenated anthracene oil at high temperatures for a short contact time was studied. The products were separated into filtrates, benzene-soluble fractions and n-hexane-soluble fractions. and the viscosity of each fraction was then measured in the shear rate range from 5 to 500S-1 by use of a rotating rheometer. The slurries were pseudoplastic fluids with a yield point, and their apparent viscosities at 100°C decreased with increasing liquefaction temperature. The filtrates were pseudoplastic fluids with no yield point, and their preasphaltene content had strong effects on the viscosity. The benzene-soluble fractions were Newtonian fluids and their viscosities increased with increasing asphaltene content and rising liquefaction temperature. The n-hexane-soluble fractions were also Newtonian fluids and their viscosities were constant at all liquefaction temperatures. Remarkable thixotropic behavior was observed at a temperature below 100°C for the slurries and the filtrates from lower liquefaction temperature. It seems that the thixotropy occurs by the formation of a sort of network structure due to the deposition of an intermediate product such as preasphaltene at lower temperature.
Experimental measurements were made of the behavior of a horizontal gas jet in a powder bed under various aeration conditions. Data on particle velocity in a jet and the relationship between jet penetration length and various operating conditions are illustrated in this paper. Among the factors affecting the jet length, momentum of injected gas and powder pressure at the level of jet axis are found to be most important. A mechanistic model is presented and solved approximately to give a correlation for horizontal jet length. Predictions from the correlation are compared with experimental data including those by previous investigators. Prediction with an accuracy of 30% can be obtained by the present correlation for a wide range of operating conditions covering blast furnaces, fixed beds and fluidized beds.
Static pressure fluctuations were measured in a turbulent jet region of jet mixing by a probe which consisted of electrodes for measuring velocity and a small pressure transducer. Experimental results about the root-mean-square value of static pressure fluctuations p′ were newly obtained, and the relation between p′ and velocity fluctuations u′ was quantitatively investigated by using the turbulent Euler number Eu, which was defined as the ratio of p′ to the representative turbulent kinetic energy ρu′2. The value of Eu was constant in the jet region of fully-developed turbulent conditions near the nozzle exit at large Reynolds numbers. On the other hand, with decreasing Reynolds number Re or with greater distance of the measured point from the nozzle exit, the value of Eu showed a tendency to increase. The distribution of Eu along the jet axis was correlated with Re·d/ (z+a) ((z+a) /d: dimensionless distance from the virtual source of the jet) and a critical value of Re·d/ (z+a) for the turbulent condition in the jet region was found.
Numerical calculations were carried out to investigate the behavior of the thermal plasma flow in a water-cooled pipe, assuming three states: thermal equilibrium, frozen and approximately real state. From these results, it was found that the velocity and energy profiles are different from an ordinary pipe flow and vary characteristically depending on the state in a pipe and the initial condition. For example, center-line velocity increases and then decreases, bulk temperature and total enthalpy do not change in a similar manner, and the pressure decreases and then increases. With regard to heat flux to the pipe wall, the Nusselt number, Nu, was calculated according to the ordinary method and this result is discussed.
Batch experiments with respect to transient heat transfer were done by using a rotary drum, externally heated by a sheathed heater, in order to obtain overall heat transfer coefficients from the drum wall to the particles bed. It was found that the heat transfer resistance near the wall, which could be neglected in the previous reports, must be taken into account. An empirical equation for estimating the overall heat transfer coefficient is presented semi-theoretically.
The effect of buoyant force on laminar forced convective heat transfer in the entrance region of horizontal parallel plates was studied by a numerical method for the case of twodimensional flow under two thermal conditions of uniform wall temperature and of uniform heat flux. The complete set of Navier-Stokes and energy equations were solved under the Boussinesq approximation for the three constitutions of parallel plates: both walls heated in the same uniform states; upper wall heated and lower wall insulated; and lower wall heated and upper wall insulated. The velocity and temperature profiles were assumed to be uniform at the inlet, and the entering flow here was considered to be irrotational again (u0′=const., v′=0, ω′=0, t0′=const. at x′=0). Numerical results were obtained for the following ranges of parameter values: 30≤Re0≤300; Pr=0.71: 0≤Ra≤1800. The results are illustrated for the developing velocity profiles, pressure gradient, wall shear stress, developing temperature profiles and local Nusselt number with figures, revealing how the developing velocity and temperature fields in the entrance region were influenced by the buoyant force.
Isothermal curves within a cylindrical specimen in which thermocouples were inserted with sheaths and whose surface was heated continuously or sinusoidally were calculated by the finite element method. The measurement error of thermal diffusivity was estimated as a function of the thermal property and the location of the probe (thermocouple and sheath). A thermal diffusivity of the probe higher than that of the specimen intensely affects the temperature field around it. The error increases with the ratio of the thermal diffusivity of the probe to that of the specimen. The preferred position of the porbe is found to be away from the specimen surface.
The effects of following four parameters on working fluid distribution within the wick of two shapes of heat pipe (rectangular and cylindrical) were examined experimentally: 1. wick material, 2. heat input, 3. fill charge of working fluid, 4. inclination of pipe In horizontal operation, saturation distribution, though its level depends on heat input and fill charge of working fluid, drops steeply in the heating section while it is uniformly distributed through the adiabatic and cooling sections. In bottom-heated mode operation, saturation decreases in the cooling section as well as the heating section, and increases a little in the heating section in comparison with horizontal operation by the effect of gravity. Top-heated mode operation, dry out of wick may be expected at a lower heat input than in horizontal operation by the effect of gravity.
When micropores can be approximated by the ink bottle model, pore distributions are described in two parameters, i. e. pore radius and pore narrow-neck radius. Distribution of pore radius can be calculated from an adsorption branch of the isotherm, while distribution of narrow-neck radius can be measured by the mercury penetration method. In this paper, calculation procedures for the distribution of narrow-neck radius are described on the basis of the nitrogen isotherm. Based on experimental results using active aluminas, it is apparent that the present method can be substituted for the mercury penetration method.
Preventive measures against potato juice spoilage and a chemical cleaning procedure for membrane foulant which cannot be cleaned out with spongeballs in the reverse osmosis plant were considered. Spoilage of potato juice occurs because the population of microorganisms increases logarithmically in the plant and spoilage is promoted by microorganism slime formed on inside walls of storage tanks or inside pipes within the plant. Periodic discharge of juice in the plant and complete disinfection are required to prevent the formation of slime. The storage tank, therefore, must be so constructed as to allow complete discharge of the juice. Disinfection with a germicide (NaClO solution) after cleaning the equipment with water and a chemical detergent (pH-9.7) is effective. This is because the germicide is not used for oxidization of the juice adhering in the plant. A small amount of membrane foulant is also removed by chemical cleaning. A suitable cleaning and disinfection frequency is once a day, and the time required is 90-120 minutes.
Seasonal changes in the quality of potato juice and changes in reverse osmosis performance accompanying the former were considered. Potato starch is produced annually from September to December. The concentration of potato juice is almost constant from late September to early October, but continues to rise through mid- October to December. When production ends, the concentration is almost 1.5 times that at the opening of the season. As the concentration starts to rise, membrane foulant degenerates to a substance that cannot be cleaned out with spongeballs. The membrane foulant after mid-October is protein containing melanin which is oxidized by protein including poly-phenol in the presence of oxygen. To prevent this degeneration, equipment should be constructed to exclude contact between juice and oxygen. Operation at low temperature (25°C) as well as high pH (6) is also effective in preventing oxidation of protein.
A new model reaction to investigate the behavior of fluid beds is proposed. This method utilizes the absorption of CO2 gas in ambient air into an alkaline solution that is supported on porous fine particles. Alumina particles of 60μm mean diameter, which fluidized smoothly in a polymethylmethacrylate bed of 0.10m in diameter, were first prepared by soaking aqueous NaOH solution. Reactivity of sample particles taken from the fluid bed was measured in a fixed bed and had a pseudo-first order reaction rate constant of around 10s-1.
Impulse responses of yeast physiological activities-the specific rate of glucose consumption, that of cellular growth and that of alcohol production-to successive additions of substrate were elucidated by experiments. These responses were expressed in terms of dimensionless characteristic curves. Both the maximum values of these specific rates and the dimensionless characteristic curves were compared with those obtained in the batch culture system. The following conclusions were drawn from these experiments and comparisons: Firstly, the dimensionless characteristic curves and the maximum values of the specific rates were independent of the frequency of substrate addition. Secondly, the characteristic curves coincided well with those obtained for the batch culture system. Thirdly, the maximum values of the specific rates in the fed-batch culture system were slightly different from those in the batch culture system. Based on the above-mentioned facts, the authors express functionally the successive fedbatch culture system in a block diagram. They simulated the fed-batch culture system and compared the calculated results with experimental data. The calculated and experimental results agree well with each other.