The shape and rising velocity, pressure variation of a bubble and pressure spectrum from the pressure variation due to the rise of a bubble in water have been studied for bubble volumes from 1 × 10–6 to 5 × 10–5 m3. The vertical bubble length and radius of curvature are found to be 0.393 and 1.21 times the equivalent bubble diameter, respectively. The mean frequency of the pressure spectrum decreases with increase in bubble size. The dynamic minimum pressure is related to the radius of curvature and the maximum pressure to the vertical bubble length. The pressure spectrum is correlated with the bubble properties. The energy dissipation rate was determined from the pressure spectrum and was found to increase with increase in the bubble radius of curvature.
A new type of absorption heat pump is proposed, in which a rectification column (fractional distillation column) and a “reverse-rectification” column are combined. The two components of a working pair are separated in the first column and re-mixed in the second. The heat-pump effect is due to upgrading the heat flux supplied to the evaporator and extracted, at a higher temperature, from the heat exchanger incorporated into the reverse-rectification column. This new absorption heat pump can operate as a type I, a type II, or a refrigerator. It can use any mixture, even an ideal mixture, as the working pair. The paper presents an example of type II-AHP (=heat transformer) working with the pair pentane + octane for upgrading heat from about 413.2 K (140°C) to about 493.2 K (220°C). The AHP is modelled with graphical methods derived from the classical methods of McCabe–Thiele and Ponchon–Savarit, commonly used for distillation columns.
In a “reverse-rectification system,” a volatile liquid (water) is injected into the evaporator placed at the bottom of a packed column. A less-volatile liquid (ethylene glycol) is injected into the head of the column. In the column, vapor and liquid are contacted in countercurrent flow (glycol downfiow, water-vapor upflow). Some heat is evolved by the vapor-liquid absorption, and is extracted through a heat exchanger incorporated in the column. Three different structures of the system are modelled and compared, by using the Ponchon diagram. A lab-scale reverse-rectification column with an integrated glycol preheater was constructed and operated under atmospheric pressure. The measured performance criteria are: the temperature lift, which is the difference between the temperature of the upgraded heat flux extracted from the column and that of the heat flux supplied to the evaporator, and the heal efficiency, which is the ratio of these two heat fluxes. The temperature lift and the heat efficiency were studied as functions of the flow rates of the liquids injected at the top and the bottom of the system.
The extended Brinkman model for flocculated dispersion is presented. This model can describe fluid flow relative to a swarm of flocs over a wide concentration range. The theoretical floc density function is derived by combining the model with the permeability data in a concentrated region where individual flocs contact each other. For flocculated polystyrenes consisting of non-porous, impermeable, and spherical particles of submicron size, the density, the aggregation number, and the projected area diameter of a floc were determined by the sedimentation method, the drying method, and the photographic method, respectively. The permeability data in dilute and concentrated regions were obtained by the sedimentation test and the constant-rate expression method, respectively. Agreement between the theoretical floc density function and experimental floc characteristics was satisfactory. The floc morphology was strongly reflected in the permeability characteristic in a concentrated region. It was found that the overall solidosity when complete floc breakage occurs is approximately equal to that of the loosest packing structure if a sphere bed.
The effects of multiple inclined blades on the flow and mixing characteristics of a high-viscosity fluid were investigated in an agitated thin-film evaporator under isothermal conditions. The residence time distribution, mean residence time, material exchange-rate and power consumption were measured, and the effects of the inclined blades on the measured quantities were examined by comparison with the measurements in a vertical-blade evaporator. The results show that the flow and mixing characteristics in the axial direction are almost the same in the inclined-blade evaporator as in the vertical-blade evaporator, and that the mean residence time can be controlled by using inclined blades. Multiple inclined blades can provide almost the same material exchange rate as multiple vertical blades, even when the distance between upper and lower inclined blades is reduced to about half that between vertical blades. The results further show that the power consumption of inclined blades can be reduced to about half that of vertical blades.
Pressure fluctuations were measured in a two-dimensional gas-solid fluidized bed at temperatures ranging from 13 to 270°C. The random pressure fluctuation signals were studied on-line by the statistical method. The results indicate that the frequency spectrum, major frequency, and mean pressure amplitude depend considerably on the gas excess velocity and temperature. A probability density function of pressure fluctuations with two peaks was observed in the upper portion of the bed, indicating bubble eruption behavior at room temperature. The two peaks in the p.d.f. are transformed into a single peak at higher temperature, and the location of maximum amplitude also changes at higher temperature. Both measurements of pressure drop fluctuations and differential pressure fluctuations were used in this study, and the latter were found to be superior in the study of bubble behavior.
Based on the two-step model, surface-integration coefficients of potassium alum crystals below 5 × 10–4 m grown in a well-suspended fluidized bed were found to decrease sharply with decreasing crystal size so that the growth process is controlled by surface integration for small crystals. The mass-transfer coefficient is independent of crystal size and solution velocity. The mass-transfer resistance becomes significant when crystal size increases, and finally the growth rates become constant since both mass-transfer and surface-integration coefficients are constant. For larger crystals, there is no dominating step in the growth process, both resistances being important. The crystal growth behavior of various systems other than potassium alum was also examined. Finally, an experimental method for estimating the order of surface-integration rate is suggested.
A method for testing membrane gas filters having very high collection efficiency has been developed. These filters have high pressure drop together with their high collection efficiency. As a test aerosol, NaCl and ZnCl2 particles generated by an evaporation-condensation type aerosol generator were used. They had a geometric standard deviation ranging from 1.1 to 1.4. These aerosols were supplied into pressurized clean air (about 3 × 104 Pa gauge) by use of an ejector to overcome the pressure of the filter. Because of extremely low aerosol concentrations at the filter outlet, a high-flow rate CNC (condensation nucleus counter: 1 to 2 l/mm) which can detect aerosols of very low concentration was used. Measurement of the filter performance showed that the penetration by particles depended upon the structure of the membrane, but not upon pressure drop. As an example, a penetration of about 2 × 10–10 for 0.02 μm diameter particles at a pressure drop of 3.1 × 104 Pa gauge and a filtering velocity of 0.68 m/s has been observed.
The swelling behavior of poly(acrylamide-co-acrylic acid and trimethyl-N-acryloyl-3-aminopropyl ammonium chloride) gel in electrolyte solutions of NaCl (uni-univalent) and MgCl2 (bi-univalent) was investigated over the whole range of pH. The swelling of gel was induced by the ionic pressure due to Na+ and/or Mg2+ ions in the acid region (pH = 4–7) as well as basic region, where Na+ or Mg2+ ions added in solution were exchanged with H+ ion supplied by the yet undissociated group, –COOH. in the region of pH = 1–4, Cl– ions generated the ionic pressure. In the case of bivalent cation, Mg2+ especially, it was observed that the interactions between the localized fixed charges and the bivalent cation, may result in formation of new weak cross-linking. The swelling and behavior of the ions in the gel were predicted fairly well using a simple model based on Donnan equilibrium theory.
This paper reports simulation and experimental studies of the energy efficiency and the separation performance of a wetted-wall distillation column with internal heat transfer from the rectifying section to the stripping section. In the simulation, a mathematical model was established on the basis of the interface mass transfer theory, and an operation-type simulator for a differential distillation column with internal heat integration was developed. in the experiments, a vertical concentric double-tube wetted-wall distillation column was used, and the separation of a binary system of ethanol–water was carried out. The close agreement between the simulation results and the experimental results suggests the applicability of the proposed model. Both the simulation and experimental results show extensive improvement of the energy efficiency and the separation performance of the wetted-wall distillation column when it is operated with internal heat integration.
The flow characteristics of a three-phase fluidized bed with draft tube were studied, using air, aqueous sodium sulfite solution, and nylon particles (2.5 mm in diameter) as gas, liquid, and solid, respectively. Gas holdup decreased with increasing concentration of solid. When the diameter ratio of draft tube to outer column was about 0.6, the maximum of liquid circulation flow rate was obtained. Further, when this ratio was fixed, gas holdup decreased with increasing concentration of solid and with decreasing diameter of outer column. Circulation flow rates of solid and gas depended strongly on that of liquid. The specific gas–liquid interfacial area was larger in the annular section than in the inner section. from the relation between gas holdup and gas–liquid interfacial area, it was found that, in the inner section, large bubbles were broken into small ones by the existence of solid particles.
Experimental studies of mass transfer in binary packed column distillation were made for the acetone–ethanol, acetone–methanol, methanol–ethanol and methanol–water systems under total reflux conditions for wide ranges of vapor flow rate and liquid concentration. Measurements of the wetted area of the packings were made and the data were compared with Onda’s correlation. Diffusion fluxes under low mass flux conditions with a short packed column were examined. The effect of condensation of mixed vapors or evaporation from liquids on the diffusion fluxes were studied. A new method for predicting the separation performance of binary packed column distillation was developed with correlations for the diffusion fluxes under high mass flux conditions with a short column and for the wetted area of the packings. Predicted axial distributions of reflux flow rates and liquid concentrations in a long packed column by the present method were compared with the observed values.
Previously published solid-liquid fluidization data and new experimental data were correlated to develop an explicit expression for bed voidage, ε, in solid–liquid systems. Based on the observed deviation between the voidage predicted by the Richardson–Zaki18) equation (εRZ) and the actual voidage, this new correlation assumes the form
ε = εPK + (1 – εPK)εRZA exp(B(1 – εRZ)
where A = 2.2n + 8dP/D and B = 2.1n. εPK is the “packed” bed or the static bed voidage (i.e., ε when the superficial liquid veIocity, UL, is zero), n is the Richardson–Zaki18) exponent, and dP/D is the particle diameter-to-column diameter ratio. A total of 811 data points were correlated with Reynolds numbers based on terminal velocity, Ret, ranging from 0.7 to 3200. The correlation satisfactorily predicts voidage with a standard deviation of less than 5%.
In the transport equation of charged ulfrafiltralion and reverse osmosis membranes which we proposed previously, the effective charge density and the membrane structure, that is, membrane thickness, tortuosity and the water content, are important transport parameters. In this study, these two parameters as determined from ultrafiltration experiments by using the previously proposed transport equation were compared with those obtained from other experiments. The effective charge density was determined from measurement of the membrane potential. It was strongly affected by the feed concentration and agreed well with that obtained from the filtration experiments. Moreover, the membrane structural parameter determined from filtration experiments was compared with that obtained from diffusion experiments. The two values showed good agreement. The measurement of membrane potential and the diffusion experiments were found to be useful for predicting the transport parameters of charged ultrafiltration membranes.
Extraction equilibria of hydrochloric acid by toluene solution of a long-chain secondary alkyl amine, di(2-ethylhexyl) amine, and of palladium from aqueous hydrochloric acid by the toluene solution of the amine were studied under various experimental conditions. The results were analyzed by the following reaction model:
Water content and IR spectra for alkyl ammonium chloride salt solution equilibrated with aqueous palladium chloride solution were also measured to estimate the complexes formed by the reactions. The amine reacts with hydrochloric acid to form dimer of ion-paired ammonium chloride salt together with water as (BHCl)2(2/3)H2O. The results for the extraction equilibrium of palladium by the amine were interpreted by a reaction model in which two kinds of ion-paired species (BH)2PdCl4 and (BH)2PdCl4(BHCl)2 are formed. Water dissolved in the organic solution was confirmed not to take part in the formation of the complexes. The equilibrium constants for reactions (1) and (2) were determined as 1.0 × 102 and 2.6 × 104 m3/kmol respectively.
Recently, interest has increased in the practical application of solvent extraction technology for the mutual separation and purification of rare earth metals. 2-Ethylhexyl phosphonic acid mono-2-ethylhexyl ester (henceforth EHPNA) has recently been developed, and was found to have high capacity of lanthanoid extraction. This paper reports the extraction rate of praseodymium and neodymium with EHPNA in toluene from hydrochloric acid solution by use of a stirred transfer cell of Lewis type at 298 K. The experimental results suggested the existence of chemical reaction resistance at the interface at low extractant concentration and high pH value in the forward extraction, in addition to the film mass transfer resistances in the aqueous and the organic phases. The time course change of the extraction from mixed lanthanoid aqueous solution was satisfactorily predicted by the extraction model presented.
Isobaric vapor–liquid equilibrium data at two pressures (114.66 and 127.99 kPa) over the entire range of compositions were obtained by using a recirculating equilibrium still for the binary systems formed by methyl acetate and either ethanol or propan-1-ol. In all cases, the systems studied exhibit positive deviations from ideal solution behavior. Methyl acetate + ethanol system shows an azeotrope at 114.66 kPa of x = y = 0.954 and T = 333.4 K and x = y = 0.948 and T = 336.7 K at 127.99 kPa. Once thermodynamic consistency was verified, prediction of data by several methods was carried out. Good predictions were obtained for all systems by the UNIFAC and ASOG methods, with mean error of about 5% as expected, but the calculated values for activity coefficients using the modified UNIFAC showed higher deviations.
Measurement of the heat transfer coefficient at the vessel wall was made in a jet mixing vessel with rotating nozzle around the vessel axis. The observed heat transfer coefficient was correlated with power input per unit volume, and the resultant correlation equation at low nozzle rotation speed roughly agreed with that for an agitated vessel with anchor. The heat transfer coefficient at higher nozzle rotation speed decreased with increase of the nozzle rotation speed (i.e., the innerr shaft rotation speed) and approached that for coaxial rotating cylinders. Baffle plates in the jet mixing vessel did not improve the heat transfer coefficient.