An experimental investigation on compound heat transfer enhancement by a combination of ribbed tubes with wire coil inserts was performed. Two wire coils with different geometries were inserted in smoothed, straight ribbed and helically ribbed tubes to make six variations of enhanced tube, and the effects of heat transfer enhancement were examined. The heat transfer coefficient was obtained for Reynolds numbers ranging from 300 to 30,000 by means of Wilson’s method. The friction factor was also obtained from the measurement of pressure drop between both ends of the tube. Moreover, the performance of enhanced tubes were evaluated by comparing the heat transfer coefficient with that of the smoothed tube under the condition of the same pumping power. All enhanced tubes exhibit higher performance in the laminar region than in the turbulent region. The highest performance is accomplished by the helically ribbed tube with a wire coil having a pitch ratio P/e = 10.0 and a clearance NDC = 0.04 due to much higher heat transfer enhancement in comparison to the other five enhanced tubes and the smaller friction factor increase in comparison to the straight ribbed tubes.
The mixing performance of reciprocal shake mixing was extremely different from that of rotationally shake mixing. The mixing time did not decrease monotonously with increasing the shaking frequency. The transition of a flow pattern from a progressive wave type to a rotational wave type was quite complicated. The frequency, at which the steady rotational flow gives the optimum operation for mixing, is directly proportional to the natural frequency of the cylindrical vessel. This frequency can also be correlated only with the Froude number, and it did not depend on the shaking width. The mixing time decreased monotonously with increasing the power consumption per unit volume.
A mathematical model for the leveling process of a polymer/solvent film coated on a flat substrate was constructed by employing a two-dimensional finite element analysis, in which the film thinning due to solvent evaporation was taken into account in addition to the spatial and temporal variations of the physical properties. Then, the effects of the solvent evaporation rate, the wavelength, and amplitude of disturbances on the leveling behavior were numerically investigated. As a result, the critical value of the Biot number, beyond which the coated film with irregular surface geometry is frozen due to the completion of solvent evaporation before the film surface becomes uniform by leveling, decreased with increasing wavelength of disturbances. Also, the leveling time at which the film becomes flat by leveling increases rapidly with the Biot number, and then the shortest drying time could be found as the time at which the leveling time coincides with the time of complete solvent evaporation.
In this work, permeation of air through immobile surfactant monolayers has been studied by measuring the rate of shrinkage of an air bubble pressed to the horizontal air–water interface by gravity. The thin liquid film has been made of an ionic surfactant and an inorganic electrolyte. With an increase in temperature, the rate of permeation has been found to increase. A model has been developed to describe the rate of reduction in the size of the bubble with time. The model fits to the experimental data well. From the variation of the permeability constant with temperature, the validity of the energy barrier theory for gas permeation has been examined.
Preparation of the plate-type catalyst is important in constructing a wall reactor system that has an effective exchange of heat energy and a quick load response. In the preparation of the plate-type catalyst by electroless plating consisting of the displacement of aluminum by zinc and the deposition of nickel by chemical reduction, this study identified the effect of different plating conditions on the catalytic properties of the prepared plate-type catalysts, for preparing a suitable plate-type catalyst for decomposition of methanol. Using an alkaline bath in chemical reduction plating or immersing the prepared catalyst in an alkaline solution after plating improved the activity of decomposing methanol but decreased the selectivity of products. The results show that preparing conditions had significant effects on catalytic properties of plate-type catalyst. Furthermore, in preparing a catalyst with high decomposition performance that was prepared using an alkaline zinc plating bath and a neutral nickel plating bath, an experiment was performed to examine in detail the effect of zinc plating conditions, such as a bath temperature and an added amount of sodium hydroxide, on the decomposition property of the catalyst. The results show that the catalyst had the greatest decomposition performance when it was prepared at a bath temperature of 293 K and with an addition of 90 g·l–1 of sodium hydroxide.
The solubility of magnesite ore in citric acid, an environmentally friend and natural reagent, was investigated. The effects of reaction temperature, particle size and acid concentration were examined. The leaching rate increased with decreasing particle size and with increasing temperature. The dissolution in terms of acid concentration increased initially and then fell with increasing concentration. By testing shrinking core models for fluid-solid systems, it was observed that the dissolution of magnesite was controlled by chemical reaction. The following semi-empirical model was developed: 1 – (1 – x)1/3 = 6.4 × 107(D)–017(C)0.11e–61.35/RTt, where D is the particle size, C the acid concentration, T the reaction temperature and t the reaction time. The activation energy of the process was 61.35 kJ·mol–1.
Chitosan gel particles were prepared by the suspension evaporation method in which various gelation conditions, such as acid media to dissolve the chitosan flake, gelation temperature and crosslinking degree were controlled. The gelation of the chitosan solution of strongly acidic (hydrochloric acid) media could not be observed at any gelation temperature. On the other hand, in the chitosan solution of weakly acidic media such as acetic and adipic acid, the gelation occurred at a temperature between 348 and 358 K. The amount and pKa values of amino groups in the gel particles were analyzed by an acid-base titration method and dissociation property of the amino groups was evaluated. The pKa of the amino groups in the chitosan gel particles was low compared with that of the original chitosan polymer. It was demonstrated that dissociation curves of the gel particles shifted toward a much lower pH region increasing their crosslinking degree, that is, the formation of three-dimensional polymer networks.
Electroosmotic dewatering has been tested in laboratory cells on four different porous materials: chalk sludge, iron hydroxide sludge, wet fly ash and biomass sludge from enzyme production. In all cases it was possible to remove water when passing electric DC current through the material. Casagrande’s coefficients were determined for the four materials at different water contents. The experiments in this work showed that chalk could be dewatered from 40% to 79% DM (dry matter), fly ash from 75 to 82% DM, iron hydroxide sludge from 2.7 to 19% DM and biomass from 3 to 33% DM by electroosmosis. The process was not optimised indicating that higher dry matter contents could be achieved by electroosmosis. It was possible to relate Casagrande’s coefficient directly to the electroosmotic coefficient obtained by dewatering experiments.
The removal of trace carbon dioxide from air was carried out in a two-bed pressure swing adsorption (PSA) packed with 1/16” MS13X zeolite as adsorbent in the depth of L = 0.79 m to find systematically the effect of design and operating variables on the product concentration Ca1 and the mass exchange efficiency ηa defined by ηa = (Ca0 – Ca1)/(Ca0 – Ca1Pd/Pa) for the feed concentration. The operation with a shorter cycle time resulted in a higher performance which approached a limiting value at a half cycle time of shorter than 20 min. The individual superficial velocities, Ua and Ud in the adsorption and desorption steps, and the velocity ratio Ud/Ua had a great effect on the product concentration Ca1. On the other hand, pressure in the desorption step Pd had little effect on the removal performance expressed in terms of the mass exchange efficiency ηa while higher pressure in the adsorption step Pa decreased the removal efficiency. This effect of pressure was explained by the decrease in the adsorption coefficient m and intraparticle diffusivity with an increasing pressure Pa. The experimental result agreed well with a simplified model called short cycle time approximation previously proposed by authors when it was applied to a linear isotherm of adsorption and a half cycle time shorter than 20 min. The model provides a distinctive relation between the product gas concentration Ca1 and operating and design parameters by the following equation
(1 – ηaUa/Ud)/(1 – ηa) = exp[KFOa(L/Ua – L/Ud)]
in which KFOa is the unified volumetric mass transfer coefficient based on gas phase driving force and inversely proportional to the sum of column pressure (Pa + Pd).
Indium is one of the most important strategic metal which has got wide application in advanced technology areas. The selectivity of indium extraction from various waste materials is the challenging work, where solvent extraction is one of the useful techniques that should be explored. The present investigation is based on the use of p-tolyl-α-thiopicolinamide for extraction of indium from alkaline media. The extraction system is investigated as a function of various parameters such as reagent concentration, variation of pH and temperature. Experimental data have been analyzed graphically and numerically, to determine the stoichiometry of extracted species. The effect of aqueous ionic strength on indium(III) extraction has also been studied. Another important feature of the proposed method is that extraction of indium with 0.35 M p-tolyl-α-thiopicolinamide and 10 vol% of n-decanol in xylene has resulted in 99% recovery in alkaline medium, in 5 minutes. The different thermodynamic functions—enthalpy (ΔH), entropy (ΔS) and free energy (ΔG), have been evaluated.
The effect of a porous structure formed after dissolution of fine particles dispersed in a coating layer was investigated on the release rate of core particle by random walk simulation. As a result, the release rate was described by the structure coefficient which increases with the ratio of contact to the surface area. The ratio was independent of the average size of soluble particles and it increased with an increasing volume fraction of soluble particles, with an increasing geometric standard deviation of particle size at the low volume fraction, and with a decreasing standard deviation at the high fraction. Then, the simple correlation was established between the structure coefficient and porous-structure parameters, which should be useful for the design of the release pattern.
The kinetics of nonisothermal crystallization in a novel microbial synthesis of a biodegradable block copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate), P(HB-co-HV), in which the mole fractions of 3HV units are 7 and 10 mol%, were studied by differential scanning calorimetry (DSC). The kinetics of the block copolymer under nonisothermal crystallization conditions was analyzed by Ozawa’s equation using three different methods. The comparison of nonisothermal crystallization of the block P(HB-co-HV) copolymer, homopolymer polyhydroxybutyrate, PHB, and random P(HB-co-HV) copolymer, in which the mole fractions of 3HV units are 6 and 12 mol%, was performed. It was found that the n values of the block P(HB-co-7% HV) and block P(HB-co-10% HV) are the same as that of PHB, and have been found to be close to 3. The n values of the random P(HB-co-6% HV) and random P(HB-co-12% HV) have been found to be close to 1. It was obvious that the nonisothermal crystallization rate of block polymers was faster than that of random polymers.
The elongating potentials of pak-bung hairy roots were characterized in terms of ATP contents in root tip parts using the heterotrophic (HT) and photoautotrophic (PT) roots. When the HT roots with an initial ATP content in tip parts of 8.1 × 10–5–3.6 × 10–4 mol/m were cultivated in a sucrose-free medium, root elongation was found to cease at an ATP content below about 2.0 × 10–4 mol/m. In the case of the PT roots cultivated under light irradiation, the occurrence of root elongation depended on the root length from the root tip (L0), i.e., the roots with L0 = 2.0 × 10–2 m did not elongate but the root with L0 = 5.0 × 10–2 m did. From the time profiles of root elongation and ATP contents, cell yield of elongating roots and maintenance energy on a ATP basis were estimated to be 1.1 × 104–1.2 × 104 m/mol and 2.4 × 10–6 mol/(h·m) for the HT roots, and 1.2 × 104 m/mol and 2.2 × 10–6 mol/(h·m) for the PT roots, respectively, coinciding closely with each other under the examined conditions.
The drying characteristics of porous materials immersed in the fluidized bed of fluidizing particles with superheated steam were examined. A B-1 brick ball, in which the gas diffusion was governed by Knudsen diffusion, was used as the drying sample and the glass beads (0.12 mm in diameter) were used as the fluidizing particles. N2 gas was also used as the drying gas for the comparison. N2 gas was the substitute of air. The temperature of the fluidized bed and the mass velocity of drying gas were changed, respectively. The theoretical analysis including the convective gas transfer in the sample and condensation of the steam in the sample was also preformed. There is a period when the temperature of the sample center is almost constant in the fluidized bed drying with superheated steam and with hot air. The temperature of the sample center in superheated steam is higher than that in hot air. In the case of superheated steam, the temperature during the period when the temperature of the sample center is almost constant is equal to the boiling point of water. When the mass transfer resistance in a sample is large, the temperature in the sample increases because of the increment of the pressure in the sample. This phenomenon was confirmed by the calculated pressure in the sample. The effect of the bed temperature on the drying characteristics is significant, while that of the mass velocity of drying gas is very slight.
The performance of the anaerobic treatment of palm oil mill effluent for organic acids production at a short retention time of less than 5 days was assessed by incorporating a sludge recycle system with no pH control except by adding calcium carbonate. The system could be operated successfully for a 3.5-day retention time at pH 5. The sludge solids in the treated effluent were separated by a freezing-thawing technique and it was partly recycled back to the reactor. The thawed clarified POME solution contained a low SS of 2,200–3,500 mg/L. The organic acids production with a concentration of 10–14 g/L was essentially similar to the treatment for a 5-day retention time without a sludge recycle. Hence by incorporating a sludge recycle system with the freezing-thawing method, the retention time for the treatment could be reduced without affecting the organic acids generation.
Cryptomeria japonica bark was extracted using the hot compressed method, at temperatures higher than 373 K in different solvents. The yields of the extracts were 0.8–3.6%, under conventional extraction at ambient pressure. When the hot compressed method was used for extraction, however, the yields increased (1.2–9.6%). Based on the GC-MS analysis, the main components of the extracts were terpenoids such as ferruginol 1, 6,7-dehydroferruginol 2, and phyllocladanol 3. This study demonstrates that terpenoids in bark can be extracted using the hot compressed method.