Mass Transfer Factor Research Articles

Investigation of the insoluble impurities' impact on flow boiling heat transfer in aluminum microchannel heat exchangers

Microchannel flat-tube heat exchangers are known for their high heat transfer efficiency and compact size. In practical applications, the predominantly adverse influence of insoluble impurities on the condensation process necessitates further exploration into the underlying mechanisms affecting the flow boiling process. The effect of common insoluble impurities on the flow boiling of R410A refrigerant in a microchannel flat-tube heat exchanger has been investigated, and variation of the impurity volume fraction on heat transfer, mass transfer, pressure drop, and bubble formation are analyzed. Additionally, an adaptive modification method for the mass transfer factor is proposed. The numerical model of flow boiling heat transfer in a microchannel is validated through experimental data and empirical correlations. Thermo-hydraulic performance evaluation incorporates efficiency index and area goodness ratio metrics. Results reveal that the presence of insoluble impurities complicates the boiling heat transfer mechanism by influencing bubble evolution and multiphase flow patterns. Air impurities at a volume fraction not exceeding 5% prove beneficial for enhancing flow boiling efficiency in microchannels; however, a 38.5% decrease in efficiency index is observed with 1% oil impurities present. Optimal thermo-hydraulic performance is achieved with approximately 2%–3% water impurities.

Methanogenesis kinetics of organic matter of the leachate in an up-flow anaerobic sludge blanket reactor

Understanding the treatment of leachate mediated by the development of anaerobic sludge makes it possible to create an effective design process of biodegradation technology. This study used an up-flow anaerobic sludge blanket (UASB) reactor equipped with a gas–liquid-solid separator to capture CH4 for treating landfill leachate to improve understanding of methanogenesis kinetics of organic matter. The performance of UASB was able to remove 154.75 g/L of chemical oxygen demand (COD) content of the leachate originally anticipated to emit 2.99 L of CH4 production into the atmosphere. The trend in the variation of internal mass transfer (IMT) factor was close to the global mass transfer factor; however, it was far higher than that of external mass transfer (EMT) factor. After 30 days of the experiment, methanogenesis kinetics of organic matter of the leachate were supported mainly by the breakdown of complex molecules. The rate-limiting step of CH4 desorption was controlled by IMT at the beginning and then by EMT after 30 days of the experiment. The strongly decreased EMT factor was counterbalanced by an increased value of the IMT factor at before 5 days of the experiment. It would be of interest to predict the methanogenesis kinetics of CH4 desorption using the Generalized Fulazzaky equations, which cannot be evaluated using other models. Analysis of the methanogenesis kinetics of organic matter of the leachate provides a new insight into the performance of UASB reactor, which may contribute to advanced treatment of landfill leachate in the future.

Mercury Capture Performance and Kinetics of CCl4-Adsorbed Activated Carbon Pretreated by the Mechanochemical Method.

In the present work, CCl4-adsorbed activated carbon pretreated by the mechanochemical method (CCl4-AC) was produced for gas-phase mercury capture. The physicochemical properties of the CCl4-AC sorbent were analyzed via N2 adsorption, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The mercury capture performance of the CCl4-AC sorbent under different flue gas components was investigated in a fixed-bed experimental device. The programmed temperature desorption of mercury was used to determine the mercury capture product of the spent CCl4-AC. Finally, the mass transfer factor model proposed by Fulazzaky was used to analyze mercury capture on the CCl4-AC for clarifying its characteristics. The results showed that the prepared CCl4-AC can be used as a mercury sorbent because of its high mercury capture performance. Mercury capture by the CCl4-AC was interfered by SO2 and promoted by O2 and H2O. Hg-temperature programmed desorption (Hg-TPD) analysis indicated that the main mercury capture products of the CCl4-AC were HgCl2 and HgO. Because of the presence of SO2 in flue gas, there was a little Hg2SO4 formation on the sorbent. XPS analysis showed that the functional group of C-Cl played the dominant role in Hg0 capture, and part of the C-Cl groups were converted into Cl- after mercury capture. The mercury desorption energy of the spent CCl4-AC was 50.49 kJ/mol and stronger compared with that of raw activated carbon. Mass transfer analysis displayed that surface adsorption was the main form at the beginning of mercury adsorption, and the external mass transfer was the mercury adsorption rate-controlling step. Then, mercury adsorption entered the second stage; internal diffusion adsorption stage with internal mass transfer became the adsorption rate control step.

Lanthanum-doped chitosan-based polyacrylamide double network hydrogels for adsorption of phosphorus from wastewater.

Excessive phosphorus in aqueous solutions can cause eutrophication, which can harm aquatic organisms and pose a risk to the safety of drinking water for humans. The Chitosan/Polyacrylamide/Lanthanum (CS/PAM/La) hydrogel was designed to get rid of phosphate from aqueous solutions. La (III) was used to enhance the capacity of adsorption of CS. Polyacrylamide was used to enhance the mechanical properties of CS. The results showed that the adsorption capacity of CS/PAM/La hydrogel for phosphate was increased compared with that of CS. When pH of 5.0, the adsorption capacity was 80.07mg-P/g. In addition, after five adsorption and desorption cycles, the adsorption efficiency remained above 90%. The mechanism of phosphate adsorption on CS/PAM/La material was analyzed using a mass transfer factor model (MTF) and the possible structure of CS/PAM/La hydrogel was calculated by density functional theory calculation (DFT). The application of CS/PAM/La composite hydrogel for removal of phosphate from actual wastewater was investigated, and the results met the requirement of national standard.

Preparing high-performance microspheres based on the chitosan-assisted dispersion of reduced graphene oxide in aqueous solution for bilirubin removal

The removal of excess bilirubin from blood is of great clinical importance. Reduced graphene oxide (rGO) is often used to efficiently remove bilirubin. However, thin rGO pieces tend to aggregate in the aqueous phase because they are hydrophobic. In this context, we propose an effective strategy based on the chitosan-assisted (CS-assisted) dispersion of rGO to produce high-performance bilirubin-adsorbing microspheres. CS possesses a hydrophobic CH structure, which offers strong hydrophobic interactions with rGO that assist its dispersion, and the large number of hydrophilic sites of CS increases the hydrophilicity of rGO. CS serves as a dispersant in a surfactant-like manner to achieve a homogeneous and stable CS/rGO dispersion by simply and gently stirring CS and rGO in a LiOH/KOH/urea/H2O system. Subsequently, CS/rGO hybrid microspheres were prepared by emulsification. CS ensures blood compatibility as a base material, and the entrapped rGO contributes to mechanical strength and a high adsorption capacity. The CS/rGO microspheres exhibited a high bilirubin adsorption capacity (215.56 mg/g), which is significantly higher than those of the rGO and CS microspheres. The determined mass-transfer factors revealed that the rich pores of the CS/rGO microspheres promote mass transfer during bilirubin adsorption (equilibrium is almost achieved within 30 min). The CS/rGO microspheres are promising candidates for bilirubin removal owing to a combination of high strength, blood compatibility, and high adsorption capacity.

Mass transfer kinetics of polyethylene degradation by bacterial-fungal consortium

Understanding the biodegradation rate of polyethylene (PE) plastic waste mediated by bacterial-fungal consortium (BFC) is important to ensure effective design process of the bioremediation technology. The aims of this study were to scrutinize the behaviors of PE plastic degradation mediated by the BFC colonies numerically simulated the experimental data using the modified mass transfer factor models and to analyze the kinetics and mechanisms of internal, external and global mass transfer. The performance of rectangular reactor (RR) to biologically degrade the PE plastic increased up to 61.5% shows an increased efficiency of 55.9% stimulated by the presence of BFC colonies. Trend in the variation of internal mass transfer is almost the same with that of global mass transfer and is far higher than that of external mass transfer (EMT). The rate-limiting step of PE plastic degradation is dependent on the resistance of EMT. The application of BFC colonies aimed to improve the biodegradation rate of PE plastic waste contributes to advancing the future environmental engineering technologies.

Thermal analysis of MHD casson-sutterby fluid flow over exponential stretching curved sheet

The two-dimensional flow of Sutterby-Casson fluid flow over an exponentially curved sheet is considered. Incompressible and steady flow is taken into account. The magnetic and electric fields are ignored due to the small Reynolds number in the flow assumptions. Magnetic and chemical dipoles are considered at stretchable curved sheet. Heat generation and slip phenomena have been considered in the present analysis. The governing models of the above assumptions are reduced by implementing the boundary layer approximations and gained nonlinear coupled differential equations. The couple differential equation system is reduced in a dimensionless system (ordinary differential equations) using appropriate transformations. The dimensionless system is solved through a numerical scheme due to finding the results involving physical factors. The results are highlighted in graphs and as well as tables. Concentration achieved higher values by enlargement in the Brownian factor. The movement of particles becomes faster due to the enlargement of the Brownian factor, ultimately increment in concentration. Energy activation factor values enlarged which gained lesser values of Nusselt factor and mass transfer factor while friction factor remains constant. The reaction of chemical factor impact on mass transfer, friction factor, and heat transfer have been debated.

Microstructural study of apple slices during hot air‐explosion puffing drying

AbstractIn order to reveal the change laws of microstructure in apple slices during hot air‐explosion puffing drying, the microstructure images and parameters of apple slices under different drying conditions were obtained by using paraffin sectioning, microscopic observation, and image processing techniques with apples as raw material and CO2 as drying medium. Subsequently, the changes in internal cell and pore structure of dried apple slices were analyzed, as well as the relationship between micro‐parameters of apple slices and macro‐measurement indicators was further obtained. Results indicated that the overall cross‐sectional area, cross‐sectional perimeter, equivalent diameter, and porosity of cells increased by explosion puffing drying, while the cell roundness and wall roughness factors changed relatively little. Meanwhile, macro–micro parameters of expanded apples were fitted and analyzed. Then, the obtained mathematical model showed a nonlinear correlation as experimental and predicted results exhibited good agreement, with determination coefficients R2 more significant than 0.8, which could better expect the macro–microparameters to change in the drying process. The results of this research could provide an essential reference for exploring the change laws of tissue microstructure parameters in apples dried by hot air‐explosion puffing drying, with expansion and rehydration ratios under different experimental conditions, as well as optimizing the puffing drying process and designing corresponding drying equipment.Practical ApplicationsFresh apples have high moisture content and are not easy to store, so drying is usually used to reduce the moisture content to extend shelf time and increase economic benefits. For the drying process of fruit and vegetable products, scholars mainly focused on the influence of microstructure parameters on moisture migration, drying rate, heat and mass transfer and other factors, but did not give a quantitative description of how microstructure parameters affect macroscopic parameters. In this article, the relationship between microstructural changes and macroscopic indicators was investigated by taking puffed apple slices as an example. Research could provide an essential reference for exploring the change laws of tissue microstructure parameters in apples dried by hot air‐explosion puffing drying, with expansion and rehydration ratios under different experimental conditions, as well as optimizing the puffing drying process and designing corresponding drying equipment.

Mass transfer kinetics of chemical oxygen demand removed from palm oil mill effluent in stirred cylinder batch reactor

Understanding the mechanisms and mass transfer kinetics of chemical oxygen demand (COD) removed from palm oil mill effluent (POME) could be one of the most important steps to achieve an effective design process of engineering acetogenic bacteria. The aim of this study was to evaluate the mass transfer kinetics of COD removed from POME in stirred cylinder batch reactor (SCBR) under an anaerobic environment using the modified mass transfer factor models. The performance of SCBR for the removal of COD increased with an electromagnetic field (EMF) exposure reaches 77.6% of its maximum efficiency when the operation of SCBR was set at the hydraulic retention time of 9 days. The variation of [kLa]d value has a trend of almost similar to that of [kLa]g value and is far higher than that of [kLa]f value to conclude that the resistance of mass transfer for the removal of COD from POME by the SCBR process depends on external mass transfer. The analysis of COD removal efficiency pursuant to the [kLa]d value provides a new insight on the performance of SCBR increased with an EMF exposure contributing to advanced treatment of COD from POME for achieving an effective process of engineering acetogenic bacteria.

The Adsorption of Cr(VI) from Synthetic Solution onto Mussel Shell Incorporated Polyethersulfone Flat Sheet Membranes: Application of the Mass Transfer Factor Models

The Adsorption of Cr(VI) from Synthetic Solution onto Mussel Shell Incorporated Polyethersulfone Flat Sheet Membranes: Application of the Mass Transfer Factor Models

Bioaugmentation and enhanced formation of biogranules for degradation of oil and grease: Start-up, kinetic and mass transfer studies

Biogranulation technology is an emerging biological process in treating various wastewater. However, the development of biogranules requires an extended period of time when treating wastewaters with high oil and grease (O&G) content. A study was therefore conducted to assess the formation of biogranules through bioaugmentation with the Serratia marcescens SA30 strain, in treating real anaerobically digested palm oil mill effluent (AD-POME), with O&G of about 4600 mg/L. The biogranules were developed in a lab-scale sequencing batch reactor (SBR) system under alternating anaerobic and aerobic conditions. The experimental data were assessed using the modified mass transfer factor (MMTF) models to understand the mechanisms of biosorption of O&G on the biogranules. The system was run with variable organic loading rates (OLR) of 0.69–9.90 kg/m3d and superficial air velocity (SAV) of 2 cm/s. After 60 days of being bioaugmented with the Serratia marcescens SA30 strain, the flocculent biomass transformed into biogranules with excellent settleability with improved treatment efficiency. The biogranules showed a compact structure and good settling ability with an average diameter of about 2 mm, a sludge volume index at 5 min (SVI5) of 43 mL/g, and a settling velocity (SV) of 81 m/h after 256 days of operation. The average removal efficiencies of O&G increased from 6 to 99.92%, respectively. The application of the MMTF model verified that the resistance to O&G biosorption is controlled via film mass transfer. This research indicates successful bioaugmentation of biogranules using the Serratia marcescens SA30 strain for enhanced biodegradation of O&G and is capable to treat real AD-POME.

Aligned porous Chitosan/Ti3C2 MXenes monolith as a high-performance fixed-bed separation medium toward globular albumin separation

Designing and tuning macropores into aligned structure is of considerable importance in promoting mass transfer, improving chromatographic performance and enhancing column efficiency. Herein, we have synthesized an innovative aligned porous Chitosan/Ti3C2 MXenes monolith via a facile, versatile and reproducible unidirectional “freeze-casting” method. Typically, the accumulation of Ti3C2 MXenes directs the formation of aligned structure during the unidirectional freezing process and thus aligned macropores are formed by a subsequent freeze-drying process. By various physical characterization, the distribution of aligned macropores, micropores and specific surface area are determined to be 21 μm, 2.53 nm and 103.09 m2·g−1, respectively. In addition, monolith bed permeability is calculated to be 1.94 × 10-12 m2, approximately 10 times than conventional monolith. Batch adsorptive experiments confirm that adsorptive capacities to bovine serum albumin and bovine hemoglobin are remarkably elevated on account of the high affinity of proteins onto those imbedding Ti3C2 MXenes. Meanwhile, continuous mass transfer equation describes the aligned macropores facilitate the film mass transfer factor ([kLa]f) in a separation process thus driving the global mass transfer factor ([kLa]g). It is expected that the aligned porous Chitosan/Ti3C2 MXenes monolith promises great potential for a continuous separation of proteins when a wholesale production is required.

Air side performance of fin-and-tube heat exchangers with a hydrophilic layer under low-temperature frost-free conditions

In this paper, to provide a reference for the application and thermal design of fin-and-tube heat exchangers (FTHEs) under low-temperature frost-free conditions (LTFFCs) and to improve the dehumidification performance of cooling dehumidifiers in greenhouse environments of low temperature and high humidity, the air side performance of FTHEs with a hydrophilic layer under LTFFCs was experimentally investigated. The experimental findings were compared with the results of ordinary temperature conditions (OTCs). The critical environmental conditions for frosting FTHEs were obtained. The applicability of existing performance prediction correlations under the LTFFCs was discussed and corrected. The findings show that at the same inlet temperature difference between air and refrigerant, the LTFFCs have smaller heat transfer rates than the OTCs. Varying inlet conditions showed that in the test conditions range, the test FTHEs are at risk of frosting when the inlet air relative humidity is 95 %, inlet air temperature is 281 K, frontal velocity is 1 m/s, and inlet refrigerant temperature is as low as 270 K. The data analysis revealed that existing correlations could not accurately predict the experimental data under LTFFCs. By adding the correction coefficients for temperature and relative humidity to existing correlations, the corrected correlations describe the experimental data for 90.6 % and 87.5 % of the heat transfer factor and mass transfer factor, respectively, within ± 20 %, and the deviation of all friction factors is within ± 10 %. The mean deviations of the heat transfer factor, mass transfer factor, and friction factor are 8.2 %, 10.8 %, and 4.8 %, respectively.

Time-Dependent Flow of Water-Based CoFe2O4-Mn-ZnFe2O4 Nanoparticles over a Shrinking Sheet with Mass Transfer Effect in Porous Media.

The use of hybrid nanoparticles to increase heat transfer is a favorable area of research, and therefore, numerous scientists, researchers, and scholars have expressed their appreciation for and interest in this field. Determining the dynamic role of nanofluids in the cooling of microscopic electronic gadgets, such as microchips and related devices, is also one of the fundamental tasks. With such interesting and useful applications of hybrid nanofluids in mind, the main objective is to deal with the analysis of the unsteady flow towards a shrinking sheet in a water-based hybrid ferrite nanoparticle in porous media, with heat sink/source effects. Moreover, the impact of these parameters on heat and mass transfers is also reported. Numerical results are obtained using MATLAB software. Non-unique solutions are determined for a certain shrinking strength, in addition to the unsteadiness parameter. The mass transfer and friction factor increase for the first solution due to the hybrid nanoparticles, but the heat transfer rate shows the opposite effect.

A readily available and efficient Pt/P25 (TiO2) catalyst for glycerol selective oxidation

AbstractIn this work, a commercial P25 (TiO2) with phase junctions between (101) and (110) faces supported Pt catalyst was prepared for glycerol selective oxidation, giving a decent 76.8% glyceric acid (GLYA) yield, and good stability. The kinetic experiments calculated apparent activation energy, turnover frequency (TOF), and reaction rates, demonstrating Pt/P25 could facilitate glyceraldehyde (GLYAD) formation and inhibit GLYA over‐oxidation. Series of structural techniques confirmed the 101/110 junctions in P25 contributed electronic effect on Pt through metal‐support interface, which improved the oxygen activation ability and optimized the GLYAD/GLYA adsorption modes. Furthermore, progressive scale‐up reactions were tested and the mass transfer limitations under different conditions were thoroughly studied. The obtained mass transfer factors suggested the gas–liquid and liquid–solid mass transfer were severely limited. Finally, through optimizing the conditions, Pt/P25 catalyst achieved 75.8% GLYA yield at 300 ml‐scale reaction, realizing equivalent magnification with the 5 ml‐scale experiment.

Kinetics of Lignin Separation during the Atmospheric Fractionation of Bagasse with p-Toluenesulfonic Acid.

As a green and efficient component separation technology, organic acid pretreatment has been widely studied in biomass refining. In particular, the efficient separation of lignin by p-toluenesulfonic acid (p-TsOH) pretreatment has been achieved. In this study, the mechanism of the atmospheric separation of bagasse lignin with p-TsOH was investigated. The separation kinetics of lignin was analyzed. A non-simple linear relationship was found between the separation yield of lignin and the concentration of p-TsOH, the temperature and the stirring speed. The shrinking nucleus model for the separation of lignin was established based on the introduction of mass transfer and diffusion factors. A general model of the total delignification rate was obtained. The results showed that the process of lignin separation occurred into two phases, i.e., a fast stage and a slow stage. The results provide a theoretical basis for the efficient separation of lignin by p-TsOH pretreatment.

Reliability of the Mass Transfer Factor Models to Describe the Adsorption of NH4+ by Granular Activated Carbon

Reliability of the Mass Transfer Factor Models to Describe the Adsorption of NH4+ by Granular Activated Carbon

Mass transfer mechanisms of water pollutions adsorption mediated by different natural adsorbents

AbstractIn textile industries, residual dyes and heavy metals are usually released into environment via wastewater effluent. Because of their negative effects not only to environment but also to human health, these contaminants are required to be removed from water environment. To achieve the effective adsorption of dye and heavy metal, the adsorption mechanism needs to be understood clearly. In this study, the complexity of adsorption of Remazol brilliant blue R (RBBR), methyl orange (MO), copper (Cu) ions, and iron (Fe) ions onto numerous natural adsorbents was analyzed using the modified mass transfer factor model (MMTF). The secondary adsorption data were collected from various sources. The study found that MMTF has a superior adaptability for describing the mechanism of the adsorption of dyes and heavy metals both in solely and in multi solute.

High-capacity amino-functionalized walnut shell for efficient removal of toxic hexavalent chromium ions in batch and column mode

This research investigated the feasibility of removing hexavalent chromium (Cr(VI) (e.g., HCrO4−, CrO42− and Cr2O72− ions) from water using walnut shells functionalized with amino groups (ACWNS) in a batch and continuous adsorption mode. The characterization of ACWNS was carried out utilizing FTIR, XPS, SEM, and BET methods. Adsorption was investigated in terms of pH, dose, concentration, and contact duration. Furthermore, at different temperatures, the adsorption isotherms, kinetics, and thermodynamics were studied. The Langmuir model described the experimental batch and column modes, while the Thomas and pseudo-second-order kinetics models predicted continuous and batch adsorption, respectively. The maximum uptake quantity toward Cr(VI) was 236.8 mg g–1 in batch mode and 308.4 mg g–1 in column mode at 303 K. There is some selective adsorption for Cr (VI) with some dyes coexisting in solution. Electrostatic interactions and the reduction process mediated Cr(VI) adsorption by ACWNS. The mass transfer potential (B) and the affinity between ACWNS and Cr(VI) (β) were computed using the modified mass transfer factor model. Since the attraction of Cr (VI) to ACWNS is more robust, the B value increases as the concentration increases. Again, MTZ assessment reveals that as MTZ length rises, diffusion resistance increases, resulting in increased adsorption. The adsorbent demonstrated improved regeneration capacity and therefore showed potential for the uptake of Cr(VI) ions from wastewater. Availability of data and materialThe dataset produced and processed during this research is available upon reasonable request from the corresponding author.

Revealing the Effect of Mass Transfer on Direct Dehydrogenation of Ethylbenzene Catalyzed by Phosphorous‐doped Boron Nitride: Comparative Study

AbstractPhosphorous‐doped boron nitride (PBN) was previously confirmed to be an effective metal‐free catalyst for the challenging topic of ethylbenzene direct dehydrogenation (DDH) to styrene. Here, the effect of mass transfer factors including the porosity and surface exposure degree of mesoporous‐PBN (m‐PBN) on its performance over DDH was investigated by control experiments. The central pore size of m‐PBN was closely dependent on the thiourea amount and heating rate. The m‐PBN with optimal pore size delivered a significantly improved styrene production rate of 21.47 mmolST g−1 h−1 and styrene selectivity over 98 %. Further, when m‐PBN was in‐situ grown on cordierite, the activity and stability of catalyst could be further enhanced to 27.08 mmolST g−1 h−1 for 50 h stable run, which presented a promising industrial application prospect. This paper justified that the mass transfer factors involved in two‐dimensional metal‐free catalysts were crucial for DDH of ethylbenzene.