The surface tensions of 1,1,1,2,2,3,3,4,4-nonafluorohexane (CF3CF2CF2CF2CH2CH3) and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoro-ethyl ether (CHF2CF2OCH2CF3), which are potential alternatives to HCFC solvents, were measured by the differential capillary-rise method. 20 data points for 1,1,1,2,2,3,3,4,4-nonafluorohexane and 17 data points for 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether were obtained in the temperature range of 289–348 K. The experimental uncertainties of temperature and surface tension measurements were estimated to be within 20 mK and 0.14 mN·m−1, respectively. Surface tension correlations for 1,1,1,2,2,3,3,4,4-nonafluorohexane and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether were formulated and were found to reproduce the present data within the limits of experimental uncertainty.
Air and particle motions in a 3-dimensional circulating fluidized bed which contains about 380 million particles (diameter, Dp=115 μm) were numerically simulated. A stochastic scheme based on the DSMC method was introduced into the calculation of particle collisions supposed to be two body collisions to treat a large number of particles. The locally averaged 3-dimensional Navier–Stokes equations and Lagrangian particle motion equations, in which the drag and the lift forces acting on particles, collision between particles and the mutual interaction between air and particles were taken into account, were simultaneously solved. The subgrid scale flows were modeled in Navier–Stokes equations using LES in which the effect of the particle existence on the subgrid scale flows were considered. The good agreement between the present calculated results and experimental data in the circulating fluidized bed shows the applicability of the present simulation method to various gas and particle flows for examples in particulate matter pneumatic conveyors, high particle concentration cyclone separators, high mass mixture gas–solid jets, etc. Calculated results clearly present the particle clusters of which shape and size were in good agreement with the experimental results. These indicate that the cluster formation mechanisms are the non-elastic collision among particles and the interaction between the air and particle flows. Calculated results of flow characteristics which agree with experimental results show that the existence of small particles remarkably enhances the turbulent motions of air and particles in a circulating fluidized bed.
Mixing performance at unsteady speed within a single revolution was studied. Because the location of the vortices centers varied, the centers of stagnant domains of doughnut shape that are formed in laminar flow disappeared and the mixing time decreased drastically. For conventional impellers operating in laminar flow, the unsteady speed mixing technique was found to be much more effective than the steady speed mixing. The study confirms that asymmetric impellers are very useful in laminar mixing vessels.
Fracture strength, one of the rheological characteristics of powder, entrainment flux and distribution of bulk density at free board were measured in systems of FCC (dp=65 μm)−calcium carbonate (dp=0.9 μm) and catalyst (dp=50 μm)−fumed silica (dp=0.04 μm) to clarify the effect on the entrainment flux and distribution of bulk density of adding ultrafine powder to the fluidized bed. Fracture strength was stronger, and entrainment flux and bulk density at free board were decreased by adding the ultrafine powder to these systems. The added ultrafine powder attached to the surface of the fine powder during fluidization, rather than remaining separate. This suggests that the ultrafine powder increased the interparticle force and caused the fracture strength to increase. The increase in interparticle force would also give rise to particle agglomeration, as a result of which the apparent agglomerated particle diameter and terminal velocity would increase, and the entrainment flux and bulk density at free board would decrease. The entrainment flux and bulk density at free board were correlated as a function of the fracture strength for the systems examined here. The results suggest that the entrainment flux and bulk density at free board can be controlled by changing the fracture strength through addition of ultrafine powder, and that this method may be effective for industrial use.
To understand the effect of radiative heat transfer on ignition of pulverized coal clouds, radiative heat transfer and combustion analysis in a turbulent pulverized coal fired furnace (coal feed 6 kg·h−1) was carried out. Pulverized coal combustion simulation was performed in consideration of radiation transfer of particles in the furnace. The first-order spherical harmonics approximation was used to model the radiative heat transfer equation. To confirm the accuracy of the simulated result, the temperature and unburned carbon profiles were measured and compared. Parametrical analyses were employed to evaluate the influence of the particle emissivity on the combustion simulation. The influence of the radiation appeared particularly as differences in the ignition position and the relaxation of a temperature gradient around the flame zone, because the preheating effect of coal particles near the burner nozzle is enhanced by the absorption of radiation energy propagated from the combustion area. The calculated temperatures agreed with measurements when the particle emissivity was assumed to be a function of unburned carbon. It was found that the accuracy of a pulverized coal combustion simulation especially in the ignition step depends on radiation heat transfer.
The effects of the geometric properties of the perforated plate used as a gas distributor on average gas holdup, φ, were experimentally investigated in a bubble column. The geometric properties of hole diameter, d, the number of holes, n, and the hole pitch, p, were varied as follows: d=0.5, 1.0 and 2.0 mm; n=22, 88, 352, 864 and 1766; and p=0.7, 1.0, 1.6, 2.0, 3.0 and 6.2 cm. The hole arrangement on the perforated plate was a regular triangle. The clear liquid height, Z0, was 0.64 and 1.92 m. For the entire range of superficial gas velocity, uG0, covered in this study, the highest values of φ were obtained with the perforated plates having d=0.5 mm, n=864, p=1.0 cm and d=0.5 mm, n=1766, p=0.7 cm at both values of Z0. The value of φ obtained with the perforated plate of d=0.5 mm, n=88, p=0.7 cm was the smallest at both values of Z0. An empirical correlation predicting the bubble free rising velocity was obtained by use of the dimensional parameter np/dDT2.
A new learning algorithm of ARTMAP using the ART2 network is proposed in order to apply ARTMAP to fault diagnosis for plant systems. Conventional ARTMAP using the ART2 network can be inadequate to categorize a complicated evaluation data set. To solve the problem,we propose a new architecture of ARTMAP which has a vigilance parameter for each category in ART2. The proposed ARTMAP can solve the problem and improve the performance of categorization of a complicated evaluation data set.
To estimate the temperature profiles in a granular-bed heat conduction process, it is important to know the thermal properties accurately. In this paper, online parameter identification of the thermal properties was carried out by using the Extended Kalman Filter. A state space model was derived from the mathematical model of the granular-bed process by use of finite integral transformation, and the Extended Kalman Filter was used to estimate state variables and parameters simultaneously. The proposed parameter-identification method was applied experimentally to a laboratory scale granular-bed process. By using a small number of temperature measurements as observed variables, the Extended Kalman Filter provided accurate parameter identification even in the presence of measurement and system noises.
Three slurries containing particles of different sizes were coated onto PET film. The rotation rate of the spin coating, which is known to control the structure of spherical particle sols, was varied in the range of 1000–5000 min−1. The coated films were then dried by conduction, radiation or convection. The appearance of the coated film was observed and haze was measured as an optical characteristic of the film. The appearance and haze of films coated with particles of 2 μm or more in diameter were not affected by the drying method, but were affected by the rotation rate. On the other hand, those of films coated with 100 nm particle were strongly influenced by the drying method. Consequently, according to the size of the particle, by selecting the rotation rate or drying method, haze can be controlled.
For effective regeneration of the adsorbent used in a desiccant humidity conditioner, the possibility of microwave irradiation for desorption of water from zeolite was studied. To investigate the effect of microwave irradiation on the water desorption rate from zeolite (0.69 mm), experiments were conducted in a N2 flow type adsorption column equipped with a microwave irradiator. Desorption of water from zeolite by microwave heating under conditions of N2 gas of 30°C with relative humidity 40%, gas flow rate of 0.053 m/s and microwave power of 200–800 W was compared with that for hot-air heating at 47°C. The following results were obtained. (1) The amount of water desorbed from zeolite was 1.6–2.0 times larger by microwave heating than by hot-air heating. This amount corresponded to that obtained by hot-air heating at 10–16°C higher than the zeolite bed temperature. It was found that the desorption amount with microwave irradiation was larger than that with hot-air heating, regardless of microwave power. (2) Maximum desorption rate was about 5 times faster by microwave heating at 800 W than that by hot-air heating.(3) Desorption rate with microwave irradiation increased with microwave power, and it decreased linearly with the increase in water adsorption ratio in zeolite.
An attempt was made to develop new phase change materials (PCMs) for cold heat storage at 278–293 K. The melting temperature and the latent heat of new PCMs composed of trimethylolethane (TME) trihydrate and 5–30 wt% of organic or inorganic additives were evaluated by differential scanning calorimetry. As the results, the following findings were obtained; 1. The melting temperature of TME trihydrate decreased with the increasing amount of additive, irrespective of the species of additive employed. 2. TME trihydrate with the addition of NaCl, KCl, CaCl2, NH4Cl, NaNO3, KNO3, CH3COONa and urea was considered as a potential PCM for cold heat storage at 286–300 K. The melting temperature of TME trihydrate with the addition of more than 15 wt% of urea was 17 K lower than that of TME trihydrate, with the decrease in the latent heat value of 27% less than that of TME trihydrate. 3. One of the PCMs whose melting temperature was lowered by urea, the mixture of TME/H2O/urea at the mixing weight ratio of 46.9/28.1/25.0, was found to be non-corrosive to aluminum and stainless steel.
Polluted groundwater containing organic compounds, CN− and chromium (Cr3+, Cr6+) was oxidized by use of ozone combined with ultraviolet (UV) radiation. In the UV-ozone processing, hydrogen peroxide was added to improve oxidation. The advantage of this oxidation process (AOP: Advanced Oxidation Process) is that there is no production of salts which should be removed before the treated water is reused. The treated water containing Cr6+(HCrO4−) after the oxidation process was purified by passing through a cation exchange resin column and then through an anion exchange resin column. Electric conductivity of effluent water from the anion exchange resin column was less than 20 μS/cm. This deionized water can be used in production processes. This combined process could be applied to reuse of polluted groundwater.
The reduction of lead sulfate by carbon was investigated in order to obtain fundamental data for developing an efficient recovery process of metallic lead from lead sulfate in a spent storage battery. Lead sulfate particles mixed with carbon were heated at terminal temperatures ranging from 773 to 1173 K in a nitrogen stream with a fixed bed reactor. Metallic lead was produced remarkably from 1073 K through the reaction of lead oxide and lead sulfide after the solid carbon had been consumed. There exists an optimum amount of solid carbon that should be added to produce metallic lead efficiently from lead sulfate.