Multiple size group (MUSIG) model combined with a three-dimensional two-fluid model were employed to predict subcooled boiling flow of liquid nitrogen in a vertical upward tube. Based on the mechanism of boiling heat transfer, some important bubble model parameters were amended to be applicable to the modeling of liquid nitrogen. The distribution of different discrete bubble classes was demonstrated numerically and the distribution patterns of void fraction in the wall-heated tube were analyzed. It was found that the average void fraction increases nonlinearly along the axial direction with wall heat flux and it decreases with inlet mass flow rate and subcooled temperature. The local void fraction exhibited a U-shape distribution in the radial direction. The partition of the wall heat flux along the tube was obtained. The results showed that heat flux consumed on evaporation is the leading part of surface heat transfer at the rear region of subcooled boiling. The turning point in the pressure drop curve reflects the instability of bubbly flow. Good agreement was achieved on the local heat transfer coefficient against experimental measurements, which demonstrated the accuracy of the numerical model.

In many gas-liquid processes, the initial bubble size is determined by a series of operation parameters along with the sparger design and gas-liquid flow pattern. Bubble formation models for variant gas-liquid flow patterns have been developed based on force balance. The effects of the orientation of gas-liquid flow, gas velocity, liquid velocity and orifice diameter on the initial bubble size have been clarified. In ambient air-water system, the suitable gas-liquid flow pattern is important to obtain smaller bubbles under the low velocity liquid cross-flow conditions with stainless steel spargers. Among the four types of gas-liquid flow patterns discussed, the horizontal orifice in a vertically upward liquid flow produces the smallest initial bubbles. However the orientation effects of gas and liquid flow are found to be insignificant when liquid velocity is higher than 3.2 m·s^-1 or the orifice diameter is small enough.

This work is focused on the theoretical investigation of internal leakage of a newly developed pilot-scale fluid switcher-energy recovery device (FS-ERD) for reverse osmosis (RO) system. For the purpose of increasing FS-ERD efficiency and reducing the operating cost of RO, it is required to control the internal leakage in a low level. In this work, the internal leakage rates at different leakage gaps and retentate brine pressures are investigated by computational fluid dynamics (CFD) method and validating experiments. It is found that the internal leakage has a linear relationship with the retentate brine pressure and a polynomial relationship with the scale of leakage gap. The results of the present work imply that low internal leakage and high retentate brine pressure bring benefits to achieve high FS-ERD efficiency.

Laminar flow and heat transfer characteristics of jacketed vessel with triangular flow channels were numerically studied under hydrodynamically and thermally fully developed conditions. Constant heat flux at the heated wall was assumed. The numerical program code in terms of vorticity, stream function, axial velocity component and energy equations was written based on a finite volume method. Based on the numerical results, the flow and temperature field were given, and the effects of Dean and Prandtl numbers on flow and heat transfer were examined, and the correlations of flow resistance and mean Nusselt number were developed for the jacket. The results show that the structure of secondary flow is steady two vortices in the investigated range of dimensionless curvature ratio and Reynolds number. Two peaks of local Nusselt number increase significantly with Prandtl and Dean number increasing, but the local Nusselt numbers near two ends and at the center of the heated wall increase only slightly. The center and two ends of heated wall are the poor positions for heat transfer in the jacket. Compared with the outer half coil jacket at the same area of heated wall, curvature radius, Reynolds number and Prandtl number, the jacket of triangular flow channel has lower flow resistance and less mean Nusselt number.

This paper presents the heat transfer characteristics of Al₂O₃-water nanofluid in a coiled agitated vessel with propeller agitator. The experimental study was conducted using 0.10%, 0.20% and 0.30% volume concentration of Al₂O₃-water nanofluids. The results showed considerable enhancement of convective heat transfer using the nanofluids. The empirical correlations developed for Nusselt number in terms of Reynolds number, Prandtl number, viscosity ratio and volume concentration fit with the experimental data within ±10%. The heat transfer characteristics were also simulated using computational fluid dynamics using FLUENT software with the standard k-ε model and multiple reference frame were adopted. The computational fluid dynamics (CFD) predicted Nusselt number agrees well with the experimental value and the discrepancy is found to be less than ±8%.

In this study, poly(γ-glutamic acid)-coated Fe₃O₄ magnetic nanoparticles (γ-PGA/Fe₃O₄ MNPs) were successfully fabricated using the co-precipitation method. Fe₃O₄ MNPs were also prepared for comparison. The average size and specific surface area results reveal that γ-PGA/Fe₃O₄ MNPs (52.4 nm, 88.41 m²·g^-1) have smaller particle size and larger specific surface area than Fe₃O₄ MNPs (62.0 nm, 76.83 m²·g^-1). The γ-PGA/Fe₃O₄ MNPs can remove over 99% of Cr³⁺, Cu²⁺ and Pb²⁺, and over 77% of Ni²⁺ in deionized water, much higher than γ-PGA and Fe₃O₄ MNPs, attributed to the larger specific surface area of γ-PGA/Fe₃O₄ MNPs. With the solution pH higher than 6.0, γ-PGA/Fe₃O₄ MNPs demonstrate better removal activity. The adsorption isotherm of γ-PGA/Fe₃O₄ MNPs for Cr³⁺ fits the Freundlich model well, with the adsorption capacity of 24.60 mg·g^-1. γ-PGA/Fe₃O₄ MNPs are strongly attracted by permanent magnet, so it is easy to separate them completely from water. With their high efficiency for heavy metal removal and easier separation, γ-PGA/Fe₃O₄ MNPs have great potential applications in water treatment.

In this paper, fouling mechanisms of mullite ceramic membranes for treatment of oily wastewaters in hybrid coagulation-microfiltration (MF) process presented. Hermia's models for cross flow filtration were used to investigate the fouling mechanisms of membranes with various coagulating chemicals concentrations. Four coagulating chemicals (FeCl₂·4H₂O, FeSO₄·7H₂O, AlCl₃·6H₂O and Al₂(SO₄)₃·18H₂O) plus Ca(OH)₂ of the same concentration were evaluated in the coagulation-MF hybrid process with different concentrations (0, 50 mg·L^-1, 100 mg·L^-1 and 200 mg·L^-1). To determine whether the data agree with models under consideration, the coefficients of determination (R²) of all models were compared with one another. In addition, average prediction errors of models were calculated. The results showed that cake filtration model can be applied for prediction of permeation flux decline for MF and coagulation-(MF) hybrid process with the best average error equal to 0.09%. Results indicated that pore blocking behavior changes as time of filtration increases, and one model cannot predict pore blocking behavior in all filtration time with very good precision.

Modified peanut shell (MPS) was prepared by amination reaction with peanut shell (PS) as the starting material. The sorption of Cr(Ⅵ) oxyanions on MPS in static and column tests were investigated. In addition, the sorption isotherm and kinetic models were applied to confirm the sorption capacity and the sorption mechanisms. BET surface area analysis showed the physicochemical characteristics of the samples. The results of zeta potential, Fourier transform infrared (FT-IR) and Raman spectra analysis illustrated that chemical adsorption and ion exchange are the potential sorption mechanism. The static sorption test showed that the maximum sorption capacity (q_max) of MPS for Cr(Ⅵ) increased with temperature, which indicated that the Cr(Ⅵ) sorption process was endothermic. The saturated sorption capacity of Cr(Ⅵ) in the column sorption test was 138.34 mg·g^-1, which accounted for 93.9% of the q_max at 25 ℃. The regeneration capacity of MPS was evaluated using HCl solution as an eluent. The high regeneration efficiency (82.6%) validated the dominance of the ion exchange mechanism in the Cr(Ⅵ) sorption process with Cl^- ions displacing Cr(Ⅵ) oxyanion on MPS. The Langmuir isotherm model showed a higher correlation coefficient than the other adsorption isotherm models. And in the kinetic study, a pseudo-second-order model fit the data best.

Soot formation was investigated numerically with CO₂ addition in a jet-stirred/plug-flow reactor (JSR/PFR) C₂H₄/O₂/N₂ reactor (C/O ratio of 2.2) at atmospheric pressure. An updated Kazakov mechanism emphasizes the effect of the O₂/CO₂ atmosphere instead of an O₂/N₂ one in the premixed flame. The soot formation was taken into account in the JSR/PFR for C₂H₄/O₂/N₂. The effects of CO₂ addition on soot formation in different C₂H₄/O₂/CO₂/N₂ atmospheres were studied, with special emphasis on the chemical effect. The simulation shows that the endothermic reaction CO₂ + H1269CO + OH is responsible of the reduction of hydrocarbon intermediates in the CO₂ added combustion through the supplementary formation of hydroxyl radicals. The competition of CO₂ for H radical through the above forward reaction with the single most important chain branching reaction H + O₂1269O + OH reduces significantly the fuel burning rate. The chemical effects of CO₂ cause a significant increase in residence time and mole fractions of CO and OH, significant decreases in some intermediates (H, C₂H₂), polycyclic aromatic hydrocarbons (PAHs, C₆H₆ and C₁₆H₁₀, etc.) and soot volume fraction. The CO₂ addition will leads to a decrease by only about 5% to 20% of the maximum mole fractions of some C₃ to C₁₀ hydrocarbon intermediates. The sensitivity analysis and reaction-path analysis results show that C₂H₄ reaction path and products are altered due to the CO₂ addition.

A gas-dissolving device was designed and connected to the falling-body viscometer, which was used to determine the viscosities of liquids in our lab before. The equipment can be used to determine the gas composition, the densities and viscosities of the solution at the same time. The densities and viscosities of [bmim][PF₆] + CO₂ binary system were determined in the temperature range of 313.2 to 413.2 K and pressure range of 5.0 to 25.0 MPa by the equipment. Then the viscosities of [bmim][PF₆] + CO₂ binary system at constant temperature, constant pressure, and different temperature and pressure were correlated, respectively. For the correlation at different temperature and different pressure for different concentration mixtures the average relative deviation ARD is 0.037.

5-Aminolevulinic acid (ALA) is a common precursor for tetrapyrrole compounds in all kinds of organisms and has wide applications in agriculture and medicines. In this study, a new strategy, i.e. short-term dissolved oxygen (DO) shock during aerobic fermentation, was introduced to produce 5-aminolevulinic acid with a recombinant E. coli. Effects of duration time of DO shock operation on plasmid concentration, intracellular ALA synthase (ALAS) activity and ALA production were investigated in Erlenmeyer shake flasks. The results indicated that both ALAS activity and ALA yield were enhanced in an anaerobic operation of 45 min in the early exponential phase during fermentation, while they decreased when the anaerobic operation time was further increased to 60 min. The DO shock protocol was confirmed with the fed-batch fermentation in a 15 L fermenter and the ALA production achieved 9.4 g·L^-1 (72 mmol·L^-1), which is the highest yield in the fermentation broth reported up to now.

Equilibrium sorption amount, desorption diffusion coefficients and sorption diffusion coefficients of CO₂ in poly(l-lactic acid) (PLLA) films at elevated pressures were determined by the gravimetric method, in which the Fick's diffusion model was applied to analyze both the desorption and sorption processes. The equilibrium sorption amount of CO₂ in PLLA increased with lowering temperature and elevating pressure at the temperature range from 40 to 60 ℃ and pressure from 10⁴ to 2×10⁴ kPa. Desorption diffusion coefficients were greatly influenced by the equilibrium sorption amount, and they were in the same order of magnitude as the sorption diffusion coefficients. The scan electron microscope (SEM) photos demonstrated that there was no foaming phenomenon of the PLLA film during desorption and sorption processes. The XRD spectra implied that the crystalline degree of PLLA film decreased after CO₂ processing. It was concluded that PLLA polymer could be well swollen and plasticized by supercritical CO₂.

The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater discharged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirring speed and the metal ions on the reactive crystallization process of calcium sulfate between sulfuric acid and lime were systematically investigated. The morphology of the precipitated crystals evolved from platelet-like and needle-like shape to rod-like shape when the temperature was increased from 25 to 70 ℃. An increase in the agglomeration of calcium sulfate was found with increasing lime concentration. Metal ions markedly retard the rate of crystallization of calcium sulfate dihydrate. The crystallization of gypsum was slowed with the existence of Mg²⁺ in the solution, and the morphology of gypsum was transformed from platelet-like shape to rod-like shape when Mg²⁺ concentration reached 0.08 mol·L^-1. The amorphous ferric hydroxide was coated on the calcium sulfate after the co-precipitation process while Zn²⁺ and Al³⁺ ions in the solution enhanced the agglomeration of the calcium sulfate by absorbing on the surface of the crystals. Comprehensive acidic wastewater containing heavy metals was efficiently purified by the two stage lime neutralization technology, and highly agglomerated gypsum precipitates with needle-like shape were obtained. The precipitates could be purified by sulfuric acid washing, and the metal ions were effectively separated from the calcium sulfate by-products.

Nano-assisted inclusion separation of alkali metals from basic solutions was reported by inclusion-facilitated emulsion liquid membrane process. The novelty of this study is application of nano-baskets of calixcrown in the selective and efficient separation of alkali metals as both the carrier and the surfactant. For this aim, four derivatives of diacid calix[4]-1,3-crowns-4,5 were synthesized, and their inclusion-extraction parameters were optimized including the calixcrown scaffold (4.4%, by mass) as the carrier/demulsifier, the commercial kerosene as diluent in membrane, sulphonic acid (0.2 mol·L^-1) and ammonium carbonate (0.4 mol·L^-1) as the strip and the feed phases, the phase and the treat ratios of 0.8 and 0.3, mixing speed (300 r·min^-1), and initial solute concentration (100 mg·L^-1). The selectivity of membrane over more than ten interfering cations was examined and the results reveled that under the optimized operating condition, the degree of inclusion-extraction of alkali metals was as high as 98%-99%.