Asia-Pacific Journal of Chemical Engineering最新文献

This work presents the results of studies on obtaining biodegradable materials based on PLA/OLA-g-cellulose/bentonite/kaolin. It was shown that bioplastic materials can be obtained by adding up to 15% by weight bentonite, kaolin, and their mixtures in equal amounts to PLA/OLA-g-cellulose 80:20 samples. The physicochemical properties of the samples were studied by FTIR, XRD, SEM, TGA, and DSC methods. Their hydrophilic properties were checked by optical determination of contact angles. The results of FTIR analysis revealed that strong interactions between polymer macromolecules and the mineral component occurred in PLA/OLA-g-cell composite materials. The results of thermal analysis showed that the addition of kaolin mineral facilitated the decomposition of the samples, and the components in the kaolin mineral played a catalytic role in this process. The DSC method revealed that the materials obtained by adding 10% kaolin to the samples, as well as 5% bentonite + 5% kaolin, have a higher proportion of free space, and the glass transition temperature is 25°С lower than that of other samples. When examining the textural and other physicochemical properties of the materials, it was found that the introduction of minerals in their composition in an amount of 10% or more leads to a deterioration in the textural properties, that is, to a deterioration in the mutual adhesion of the components. It was shown that the introduction of minerals into the composition of the materials increases their hydrophilicity. These bioplastic materials can be used as secondary packaging materials for medicines, primary packaging materials for agricultural products, as they are biocompatible.

In this research, optimization of the solution chemicals used in wet wipes was carried out with response surface methodology (RSM). Surface-active chemicals such as monopropylene glycol (MPG) and cocamidopropyl betaine, protective mixture such as phenoxyethanol–benzoic acid–dehydroacetic acid chemicals, and ethylenediaminetetraacetic acid (EDTA) were selected independent variables, and pH values were used as response. Experimental design was created with the Design Expert program, and central composite design (CCD), which is part of RSM, was applied to determine the optimum conditions. Wet wipes samples were prepared with different concentrations of chemical solutions, which were applied to dry fabrics by drip method. pH measurements and microbiological analyses of prepared wet wipes were carried out, and the results were evaluated for the level to be supplied to the market. The measured pH values of wet wipes were processed in the program, and the created three-dimensional (3D) figures were interpreted. The analysis of variance (ANOVA) analysis examined the interaction between response and independent variables with the program. pH values calculated with the optimization solutions and experimentally measured were compared, and differences between pH values were less than 5%. The optimum concentrations of solution chemicals (g/mL), PBD conc. (X₁), EDTA conc. (X₂), MPG conc. (X₃), and betaine conc. (X₄) of wet wipes were determined as 0.823, 0.197, 0.122, and 0.949, respectively. The results showed that RSM is a suitable method for the optimization of solution chemicals used in wet wipes. It was observed that there was growth in the dry fabrics without adding any solution, but no microorganisms were detected on wet wipes samples prepared for optimization, which were suitable for the market because the amount of protective mixture in microbiological cultivation provided full protection.

Twisted-tape inserts are widely used as passive heat transfer enhancement techniques, but their high flow resistance limits engineering applications. This study proposes a single-pitch hollow twisted-tape structure that reduces pressure drop by decreasing fluid contact area while enhancing heat transfer via vortex hysteresis effects. Numerical simulations were systematically conducted to investigate the flow and heat transfer characteristics under laminar conditions. Local parameters including wall heat flux, radial velocity field, temperature distribution, and synergy angle were analyzed based on field synergy theory. Results demonstrate that at Re = 800, the 15-mm hollow-width tape enhances wall heat flux by 414.2% compared with plain tubes, with near-wall synergy angle reduced to 23°, indicating remarkable heat transfer enhancement. The 12-mm hollow-width tape exhibits optimal vortex hysteresis effects, achieving local Nusselt numbers 1.21 times the peak value in the insert section. Comparative analysis of global parameters reveals the 12-mm structure achieves optimal overall performance (PEC = 1.13–1.6) within Re = 200–1800, with maximum Nusselt number reaching 2.02 times that of plain tubes.

This research determines the thermal performance factor (TPF) in a double-pipe heat exchanger (DPHE) and establishes a correlation between the parameters. In this study, the effect of dimpled twisted tape (TT) is characterized by a front surface that protrudes and perforations that extend along a tube length of 1500 mm that is investigated using SiO₂ as a medium over a range of dimple diameters (D₁) and diameter-to-depth ratios (D₁/H₁) while maintaining a constant twist ratio (TR) of 5.5. This investigation includes six different dimpled TT layouts. The results reveal that the optimum Nusselt number (N_u) is found to be at 3.0 and 4 mm for D₁/H₁. The optimal friction factor (f) is reached when D₁/H₁ equals 4.5 and D₁ is equal to 2 mm. For a diameter of 4 mm, the best TPF is found at D₁/H₁ = 4.5. The mixing of the SiO₂ nanofluid improved the heat transfer in the dimpled tube inserts because of its radiative characteristics. A contribution to the optimization of heat exchanger design and efficiency is made in the study. The validation of experimental results is accomplished by establishing correlations, which in turn provides insights into the efficiency of heat transport and frictional losses.

The cofiring of biomass and coal has garnered significant attention in reducing pollutant emissions in power plants recently. In this study, the cofiring of eucalyptus bark (EB) and coal in a wall-fired boiler is investigated through numerical simulation. The influence of the EB blending ratio, which is 0%–20%, and different EB cofiring positions on the combustion characteristics and pollutant emission of the boiler is analyzed. The cofiring characteristics and pollutant emission under different cofiring positions blended with 20% EB are further analyzed. The results indicate that the cofiring of EB and coal in the furnace reduces the flue gas temperature and pollutant emissions. Under a 20% EB blending ratio, the flue gas temperature, NO emission, and SO₂ content at the furnace outlet are 1433 K, 178.18 ppm, and 0.16%, respectively. The simulation results indicate that blending with EB at the first, second, and third burner positions reduces 4%, 2%, and 8% of the furnace's heat flux density compared with pure coal combustion. The lowest burnout rate of 93.46% for the blend with EB occurs in the first-layer burner, while the lowest NO emission of 178.18 ppm is obtained in the third burner. This study will provide theoretical guidance and a foundation for the feasibility of cofiring EB and coal in the boiler.

This work develops a novel thermal management structure with reversed parallel channels and inserts camber fins to keep the lithium-ion battery operating temperature within the acceptable range. Compared to related past literature, a new type of Π-shaped flow channel structure is proposed. An orthogonal analysis is used to improve the temperature uniformity of the battery cooling structure by studying the structure height (H), channel diameter (D), and number of fins (F), using the maximum temperature (T_max), temperature variation (ΔT), and pressure drop (ΔP) as indicators. Through the polar deviation technique, it is found that the distribution number of fins has the greatest influence on the thermal management performance, followed by the channel diameter, and, lastly, the structure height. Results demonstrate that the lowest T_max is 28.81°C, along with ΔT of 1.06°C and ΔP of 66.75 Pa when the structure height is 50 mm, channel diameter is 5 mm, and number of fins is 56, respectively. This represents a reduction in T_max and ΔP by 30.00% and 88.85%, respectively, compared to the baseline model. The maximum error between the experiment and simulation is 0.47 °C. In addition to these specific results, the design optimization technique based on the orthogonal experimental method used here may find applications in enhancing the property of other battery cooling techniques as well.

This paper presents a numerical simulation study of a two-stage embedded cyclone separator. By nesting an inner cyclone separator with a secondary inlet inside an outer cyclone separator, an additional outlet was designed at the hopper section of the inner cyclone to allow for two-stage multiphase separation. Using the Reynolds stress model (RSM) in conjunction with the discrete phase model (DPM), this study investigates the influence of key structural components, specifically the position of the baffle (its location and the ratio of baffle height to cylinder height), on the tangential velocity, pressure, and turbulent kinetic energy inside the two-stage embedded cyclone separator under a pressure of 8 MPa. The performance changes of the separator are analyzed and summarized. The results indicate that the position of the baffle significantly affects the separation performance. When the baffle is closer to the inlet of the inner cyclone, the tangential velocity distribution within the inner cyclone becomes more uniform, the low-pressure core region maintains higher intensity, and the pressure gradient exhibits clear symmetry. The low-pressure region becomes larger, which is more favorable for particle separation. However, the baffle-to-cylinder height ratio has a minimal effect on separation performance. The pressure drop increases with the height ratio, while the separation efficiency initially increases and then decreases, but the overall variation remains within 10%. The findings provide a reference for improving the separation performance of two-stage embedded cyclones and offer valuable guidance for their engineering applications.

Lithium-ion batteries have high internal resistance at low temperatures, which leads to a reduction in effective capacity. Those batteries need to be preheated before use. This study introduces a method for heating batteries at low temperatures through pulse charge–discharge. The method allows for both pulse-discharge heating and pulse charge–discharge heating. Initially, the experimental analysis is performed to assess switching frequencies, duty cycles, battery SOCs (state of charge), and pulsed charging–discharging mode on the rate of temperature increase in the battery. Subsequently, 200 tests of pulse heating cycles are carried out to examine the effects of pulse discharge heating and pulse charge–discharge heating on battery polarization and aging under various input voltages. It is found that the initial SOCs and duty cycles have a positive correlation with the rate of temperature increase, with the highest rate of temperature rise observed at a frequency of 0.1 Hz. The rate of temperature increase in the battery is largely independent of the input voltage. The findings suggest that, at the appropriate input voltage, the pulse charge–discharge heating method effectively minimizes battery aging and polarization, outperforming the heating achieved through pulse discharge alone.

Microalgae-synthesized lutein has been received considerable attention in scientific research community. Although several microalgae have recently identified as hyper-lutein accumulators, further discovery of new microalgae strain owning an outstanding capability in lutein production is necessarily for diversification of large-scale cultivations. In this work, critical factors, for example, carbon, nitrogen source, and light intensity affecting growth and lutein accumulation by a newly isolate microalgal Dictyosphaerium sp. HT3, were investigated. In particular, biomass and lutein production by Dictyosphaerium sp. HT3 under mixotrophic cultivation were optimized via a sequential process of single-factor investigation, followed by response surface methodology. The obtained results displayed that Dictyosphaerium sp. HT3 achieved the optimal growth under mixotrophic cultivation in BG-11 medium with glucose of 8.6–9.2 g/L, sodium nitrate of 1.63–2.1 g/L, light intensity of 240–290 μmol photons m⁻² s⁻¹, aeration rate of 0.1 vvm, and 25°C, achieving the maximal dry biomass of 4.25–4.67 g/L and the highest lutein content of 17.06–18.95 mg/g. The one-stage cultivation and optimization developed in this study are superior to two-stage processes for microalgal lutein production reported in the literature. Our trial investigation demonstrated that Dictyosphaerium sp. HT3 holds a promising potential for scaling-up production of both biomass and lutein via mixotrophic cultivation.