Mass Transfer Correlations Research Articles

Mass and Heat Transfer Coefficients in Automotive Exhaust Catalytic Converter Channels

Mass and heat transfer coefficients (MTC and HTC) in automotive exhaust catalytic monolith channels are estimated and correlated for a wide range of gas velocities and prevailing conditions of small up to real size converters. The coefficient estimation is based on a two dimensional computational fluid dynamic (2-D CFD) model developed in Comsol Multiphysics, taking into account catalytic rates of a real catalytic converter. The effect of channel size and reaction rates on mass and heat transfer coefficients and the applicability of the proposed correlations at different conditions are discussed. The correlations proposed predict very satisfactorily the mass and heat transfer coefficients calculated from the 2-D CFD model along the channel length. The use of a one dimensional (1-D) simplified model that couples a plug flow reactor (PFR) with mass transport and heat transport effects using the mass and heat transfer correlations of this study is proved to be appropriate for the simulation of the monolith channel operation.

An enhanced correlation for gas-particle heat and mass transfer in packed and fluidized bed reactors

Particle-resolved (PR) high-fidelity simulations, e.g., direct numerical simulation (DNS), have emerged as a powerful tool to precisely capture the full details of complex fluid-particle heat and mass transfer behaviors. The captured information can be used to constitute closures for unresolved conservation equations. However, such simulations are commonly performed under a specific variety of operating conditions. To broaden the range of closure model applicability, this fundamental study develops an enhanced correlation for the gas-particle transport rate in terms of Nusselt (Sherwood) number via collecting data points (ε = [0.35, 1], Rep = [0, 550]) from open sources. The collected data are predicted with a mean relative error of 9.3%. The extended correlation is then systematically validated by comparison with experimental data and PR-DNS results. Finally, the correlation is applied to integrate with a macroscopic computational fluid dynamics (CFD) reactor model. Validation results reveal an enhanced improvement in mass and heat transfer predictions. Moreover, the overall thermal and reactive behaviors computed from the coupled reactor model achieve reasonably good accordance with PR-DNS predictions over various process conditions. The developed correlation is hopeful to improve the accuracy of coarse-grained simulation of interphase heat and mass transfer accompanied by heterogeneously catalyzed chemical reaction.

Development of heat and mass transfer correlations and recovery calculation for HCl–water azeotropic separation using air gap membrane distillation

In the present work, the air gap membrane distillation (AGMD) process has been experimentally studied for the separation of aqueous HCl azeotropic (20.2 wt% HCl) mixture. A test cell AGMD module equipped with polytetrafluoroethylene flat sheet membrane of 0.22 µm pore size was used to perform different experiments. The effect of operating parameters, mainly feed bulk temperature and air gap widths on the total permeate flux, selectivity and HCl concentration on permeate and retentate, was analyzed. Heat transfer correlation was developed from experimental data of heat transfer coefficient. Also, the effect of operating time on membrane morphology was investigated by FESEM (field emission scanning electron microscopy) and AFM (atomic force microscopy) analysis. The SEM image was further studied to determine the pore size distribution. A recovery model was developed to assess HCl recovery at several temperatures in the range of 40–50 °C. At 45 °C of feed temperature, 42% recovery was achieved by recycling the retentate to the feed tank resulting in 31 wt% of HCl in the feed tank for 80 h of continuous operation. The experimental results show that total permeate flux increases from 12.35 to 25.89 kg/m2 h on decreasing air gap thickness from 11 to 3 mm at 1 lpm of feed flow rate. Also, it increases from 7.35 to 35 kg/m2 h on increasing temperature from 30 to 50 °C at 3 mm air gap thickness. The maximum concentration of HCl in the permeate and retentate was found to be 16.09 wt% and 31 wt%, respectively. The HCl selectivity in the permeate was found to be lower than one, which reflects the high HCl concentration in the retentate as compared to the permeate.

Hollow fiber gas membrane-based removal and recovery of ammonia from water in three different scales and types of modules

Ammonia present in many industrial process streams and effluent streams is beginning to be recovered by means of microporous hydrophobic hollow fiber-based membrane contactor devices with gas-filled pores; the process is often characterized as supported gas membrane (SGM) process. Ammonium sulfate is usually obtained in a sulfuric acid stream on the other side of the membrane. It is useful to develop a quantitative basis for the extent of ammonia removal in such devices. Unlike deoxygenation of aqueous streams in such devices, membrane resistance is quite important for ammonia transport. Ammonia transport modeling in such devices is hampered by the complexity of feed liquid flow in the shell side of commercially used devices and lack of information on membrane resistance where membrane tortuosity introduces considerable uncertainty. The approach adopted here involves studying ammonia transport with the feed solution flowing through the hollow fiber bore where the fluid mechanics is simpler than shell-side flows. Comparison of model-based predictions of overall mass transfer coefficient (ko) with experimentally observed values allows estimation of the membrane mass transfer coefficient (km). One can use such estimates of km to model the observed ammonia transport in small crossflow devices and develop an empirical guidance of the dependences of the shell side mass transfer correlations. Guided by such information and deoxygenation SGM literature, a model was developed for large modules used for ammonia recovery via SGM. Model predictions of performances of the large modules are likely to be useful for various process considerations including the effect of temperature and feed flow rate variations on ammonia removal.

Validation of mass transfer and liquid holdup correlations for CO2 absorption process with methyldiethanolamine Solvent and piperazine as an activator

In the present study, 24 data sets regarding CO2 absorption by the piperazine (PZ) activated aqueous methyldiethanolamine (MDEA) solution (30% wt) have been obtained from Khan et al.’s work and have been investigated using rate base model. Hence, mass transfer correlations such as Onda’s, Bravo-Fair’s, Billet-Schultes’ correlations and liquid hold-up correlations of Billet-Schultes and Stichlmair have been studies in the current paper. In addition, important parameters like CO2 absorption (%), liquid temperature and rich solvent’s loading have been compared in different mass transfer and liquid hold-up correlations. The results of using the rate-base model in the mass transfer and liquid hold-up correlations in 24 different experimental conditions indicate that the Bravo-Fair mass transfer correlations have higher accuracy compared to other mass transfer correlations. This comparison has been carried out based on CO2 absorption (%) and the rich solvent’s loading. Moreover, studying mass transfer correlations give the following amounts for the average error of Onda’s, Bravo-Fair’s and Billet-Schultes’ mass transfer correlations respectively for CO2 absorption (%) calculation in 16 different experimental conditions: 23.45, 14.63 and 38.59 (%). In the last part of the paper, rich solvent’s loading is compared with real amounts in 12 different experimental conditions. The comparison shows that the average errors of Onda’s, Bravo-Fair’s and Billet-Schultes’ mass transfer correlations are 14.80, 9.70 and 21.75 (%) respectively. Investigating liquid hold-up correlations indicates that Billet-Schultes’ and Stichlmair’s correlations give the same results regarding rich solvent’s temperature, solvent’s temperature profile along the absorption column, CO2 absorption (%) and rich solvent’s loading.

Determination of gas film mass transfer coefficient in a packed bed reactor for the catalytic combustion of hydrogen

The overall kinetics of catalytic combustion of hydrogen in air is decided by the contribution of the different resistances offered in individual steps such as external diffusion, internal diffusion and surface reaction. To estimate the contribution of external mass transfer resistance, empirical correlations in terms of dimensionless numbers viz., Sherwood number, particle Reynold's number, and Schmidt number are used in general. The Schmidt number for hydrogen in air is approximately 0.2 and most of the mass transfer correlations in packed bed reactors are valid for Schmidt number higher than 0.6, which corresponds to that of water vapour in the air. The external mass transfer correlations applicable for hydrogen-air system are scarce. In the present study, the external mass transfer effects were decoupled from internal diffusion and intrinsic reaction by conducting experiments with different particle Reynolds numbers in a packed bed batch reactor with complete recycle. Further, the system is theoretically modeled and the external film mass transfer coefficients were estimated at different particle Reynold's numbers using experimental data. Based on the experimental data, a new mass transfer correlation has been proposed to determine the gas film mass transfer coefficient of hydrogen in the air in packed bed reactors, in terms of conventional dimensionless numbers i.e., Sherwood number, Schmidt number, and particle Reynolds number. Further, the contribution of external mass transfer resistance on the overall reaction kinetics was also estimated.

Kinetics and Heat Exchanger Design for Catalytic Ortho‐Para Hydrogen Conversion during Liquefaction

AbstractA major challenge for hydrogen liquefaction is the required catalytic ortho‐para hydrogen conversion. Efficient liquefaction plants use catalyst‐filled plate‐fin heat exchangers for the conversion. Kinetics of the allotropic reaction are determined using raw literature data on common first‐order and a Langmuir‐Hinshelwood kinetics, including temperature and molar concentration dependencies. Evaluation and comparison of the obtained kinetics results in the first‐order approach as the most stable model. A one‐dimensional continuum reactor model of the counterflow‐cooled, catalyst‐filled plate‐fin heat exchanger is developed and tested combining correlations for heat, mass, and momentum transfer as well as a state‐of‐the‐art equation‐of‐state.

Kinetic modelling of Prileschajew epoxidation of oleic acid under conventional heating and microwave irradiation

Epoxidation of oleic acid by peracetic acid (PAA) was studied in a recycled reactor system under conventional heating and microwave irradiation. This reaction system consists of several steps. Thus, a kinetic modelling strategy to diminish the number of parameters to be estimated was developed by investigating each reaction step: PAA synthesis and decomposition, epoxidation and ring-opening. The energy balance for microwave heating was correlated with the concentration of the microwave-absorbent species and the total input power of the microwaves. The epoxidation reaction was conducted in the vigorously stirred tank reactor under isothermal conditions within a temperature range of 50–70 °C. The organic phase content was 32–45% v/v. The interfacial mass transfer was supposed to be faster than the intrinsic reaction kinetics suppressing the use of mass transfer correlations. Nonlinear regression was used to estimate the kinetic parameters. Two models were developed for microwave and conventional heating respectively. The perhydrolysis showed to be the slowest reaction, followed by the epoxidation and the ring-opening. The use of microwave irradiation resulted in considerable process intensification for the epoxidation process. By employing microwave heating, the perhydrolysis step in the aqueous phase was enhanced, and the reaction time was reduced by 50% in best cases, which implies that the reactor size can be diminished by microwave technology.

A comparative study of different mass transfer and liquid hold-up correlations in modeling CO2 absorption with MEA

Although CO2 absorption processes have been widely studied in both laboratory and industrial scales, the viability of different relations for the estimation of mass transfer coefficients has not been studied for industrial units. In this paper, the accuracy of different various equations for the estimation of mass transfer coefficients were are evaluated and compared, on the basis of according to the results of an industrial CO2 absorption unit. Therefore, the relations proposed by Onda, Bravo and Billet-Schules were are selected. Also, in some parts of the column pall ring packing was is used. in these parts the Hanley mass transfer coefficients were also used. In addition, Hanley mass transfer coefficients are used for those parts of the column in which pall ring packing is used. Based on the results of rate-based modeling of the column, obtained results show that the Onda equations show have higher accuracy compared to the other mass transfer equations. The comparison was is carried out based on CO2 absorption capacity, temperature profile and rich solvent concentration. The average errors of Onda's mass transfer correlations and Billet & Schultes's liquid holdup correlations in estimating CO2 absorption (%), temperature of rich solvent's temperature, temperature of outlet water's temperature and loading of rich solvent's loading were are 1.153, 2.923, 6.99 and 1.163% respectively. Onda and Billet & Schultes correlations exhibited the most accurate results. Also additionally, liquid film discretization shows indicates that the reaction occurs almost rather instantaneously at liquid-vapor interface and diffusion is the controlling step in the absorption process.

Evaluation of mass transfer correlations applying to cryogenic distillation process with non-equilibrium model

Reliable heat and mass transfer model plays a significant role on design and calculation of the distillation process. Since the cryogenic fluids of oxygen, nitrogen and argon have obviously different thermal physical properties compared to the room temperature ones, it is of great necessity to evaluate the feasibility of the existing heat and mass transfer models in the cryogenic distillation calculation. In this study, a non-equilibrium model (NEM) based on the FORTRAN compiler is implemented to investigate the actual cryogenic distillation process in a structured packing column (SPC) of the air separation unit (ASU) with capacity of 17,000 Nm3/h. The complete conservation equations for materials, mass and energy in the phases are numerically solved based on the Thomas algorithm. The commonly used mass transfer coefficient models with different diffusion coefficients, as well as the heat transfer model, are evaluated in the performance prediction of the cryogenic SPC. The multiple imports and exports of the model are validated by the limited available measurements, while the calculated distributions of the component molar fraction, temperature, pressure and flow rates along the column are compared with those from the Rate-based module of Aspen plus simulation. The comparisons verify the solving strategy and help to understand the reliability of the existing basic transfer correlations for future cryogenic distillation calculation.

Biodegradation of fluorene by neoteric LDPE immobilized Pseudomonas pseudoalcaligenes NRSS3 in a packed bed bioreactor and analysis of external mass transfer correlation

Abstract The main objective of this study was to analyze the effects of the external mass transfer on fluorene (polycyclic aromatic hydrocarbon) degradation with immobilized LDPE (low-density polyethylene) in a packed bed bioreactor (PBBR). A most effective bacterial species Pseudomonas pseudoalcaligenes NRSS3 (MF9921912) was isolated from petroleum contaminated soil and immobilized on LDPE. The effect of different flow rates (10, 20, 30, 40, and 50 mL/h) on the degradation of fluorene was studied in a continuous PBBR. The overall removal efficiency of fluorene was found to be 88.49% in PBBR. The rate constants were estimated at different flow rates. The effect of flow rates on external mass transfer was also studied and correlated with the obtained experimental data. A correlation between Reynolds number (NRe) and Colburn factor (JD) ( J D = K N R e ( n - 1 ) ) was used to study the mass transfer aspects. The model was tested with various values of K, and n and based on experimental data, a new correlation J D = 5.71 N R e - 0.2 was obtained to predict the removal of fluorene in PBBR. The intermediate metabolites of the degraded sample were also analyzed by GC–MS and found that 1,2-benzenedicarboxylic acid and catechol were formed during the biodegradation process.

Optimal Y-shaped constructs heat sinks under different size constraints

Losses due to irreversible processes accompanying the heat and fluid flows. This paper addresses the fundamental question of what the shape of parent and offspring branches should be, to minimize the total irreversibility. I explore how the delivery of fluid and heat influences both the optimal size of Y-assemblies of tubes and Y-shaped junctions of tubes filled with a packing material, that are used as an elemental unit to construct tree-shaped flow networks. The geometric features of these constructs are obtained from the global minimization of expenditure of power associated to fluid flow and heat transfer. The optimal step factors for tube diameters and for tube lengths, and the optimal angle between the branches are obtained under different size-limiting constraints (surface area and volume). Among other results, I show that the geometrical features of the construct may be influenced by the heat flux. Besides, it is crucial to include the size-limiting requirements in agreement with goal of the system.For similar geometries, the heat and mass transfer correlations are analogous. Then, optimal size ratios and optimal angles of branching obtained here are also valid for mass flux by replacing the heat transfer dimensionless numbers by the equivalent mass transfer numbers. The analytical expressions obtained here provide fundamental information for designers assemble the inserts that formed a tree-shaped flow network.

Mass Transfer Coefficient in Multi-Stage Reformer/Membrane Modules for Hydrogen Production.

Hydrogen is a promising energy carrier, and is exploitable to extract energy from fossil fuels, biomasses, and intermittent renewable energy sources and its generation from fossil fuels, with CO2 separation at the source being one of the most promising pathways for fossil fuels’ utilization. This work focuses on a particular configuration called the Reformer and Membrane Module (RMM), which alternates between stages of Steam Reforming (SR) reactions with H2 separation stages to overcome the thermodynamic limit of the conventional SR. The configuration has numerous advantages with respect to the more widely studied and tested membrane reactors, and has been tested during a pilot-scale research project. Although numerous modelling works appeared in the literature, the design features of the material exchanger (in the so-called RMM architecture) of different geometrical configurations have not been developed, and the mass transfer correlations, capable of providing design tools useful for such membrane modules, are not available. The purpose of this work is therefore to apply a physical-mathematical model of the mass transfer, in three different geometries, considering both concentration polarization and membrane permeation, in order to: (i) simulate the cited experimental results; (ii) estimate the scaling-up correlations for the “material exchange modules”; and (iii) identify the mass transfer limiting regime in relation to the gas mass flow rate.

Mass transfer in fibrous media with varying anisotropy for flow battery electrodes: Direct numerical simulations with 3D X-ray computed tomography

A numerical method for calculating the mass transfer coefficient in fibrous media is presented. First, pressure driven flow was modelled using the Lattice Boltzmann Method. The advection-diffusion equation was solved for convective-reacting porous media flow, and the method is contrasted with experimental methods such as the limiting current diffusion technique, for its ability to determine and simulate mass transfer systems that are operating at low Reynolds number flows. A series of simulations were performed on three materials; specifically, commercially available carbon felts, electrospun carbon fibers and electrospun carbon fibers with anisotropy introduced to the microstructure. Simulations were performed in each principal direction (x,y,z) for each material in order to determine the effects of anisotropy on the mass transfer coefficient. In addition, the simulations spanned multiple Reynolds and Péclet numbers, to fully represent highly advective and highly diffusive systems. The resulting mass transfer coefficients were compared with values predicted by common correlations and a good agreement was found at high Reynolds numbers, but less so at lower Reynolds number typical of cell operation, reinforcing the utility of the numerical approach. Dimensionless mass transfer correlations were determined for each material and each direction in terms of the Sherwood number. These correlations were analyzed with respect to each materials’ permeability tensor. It was found that as the permeability of the system increases, the expected mass transfer coefficient decreases. Two general mass transfer correlations are presented, one correlation for isotropic fibrous media and the other for through-plane flow in planar fibrous materials such as electrospun media and carbon paper. The correlations are Sh = 0.879 Re0.402 Sc0.390 and Sh = 0.906 Re0.432 Sc0.432 respectively.

An empirical model for the evaluation of the dissolution rate from a DNAPL-contaminated area.

This paper investigates dynamic variation in the morphologic distribution of dense non-aqueous phase liquids (DNAPLs), which take into account the coupled mass transfer. Experiments were carried out in a 2D tank representing a reconstructed aquifer model. DNAPL dissolution rates were investigated over a wide range of DNAPL saturations, several source configurations, and different hydraulic conditions. Morphometric indexes are presented that take into consideration further factors affecting the dissolution process. Local information regarding transport parameters related to the characteristics of the medium was obtained through a neural network and an optimization algorithm applied to experimental tracer tests. The history of DNAPL source architecture, in terms of saturation, indentation grade, and orientation, was determined by image analysis. Dissolved concentrations were registered and mass transfer rate coefficients were obtained for a wide range of source-zone configurations. A statistical analysis was performed to develop a constitutive equation that is descriptive of the mass transfer rate as a function of source-zone metric characteristics. A new empirical dissolution model using the proposed morphometric parameters is presented and compared with other models. The mass transfer correlation reported incorporates morphometric parameters and considers the complex and variable architecture of non-miscible contaminants. The proposed correlation can be used for an initial assessment of non-aqueous phase liquid (NAPL) dissolution rates over a wide range of saturation (residual and non-residual) conditions and different aqueous phase velocities within the NAPL source zone.

Mass Transfer Rate Parameters of Sulzer EX Laboratory Scale Gauze Structured Packing

Sulzer EX packing is widely used in lab-scale separation studies owing to its high efficiency, low theoretical stage height and small pressure drop. In this work the three fundamental characteristic mass transfer parameters of this packing, effective gas-liquid contact area (ae) gas-film and liquid-film mass transfer coefficient (kG) and (kL) are measured in a 0.19 mm ID counter-flow absorption column using aqueous liquids. With end effects removed, the results show that the effective gas liquid contact area is independent of gas and liquid loads and reaches about 90 % of the geometric area of the packing. Correlations of the dimensionless gas and liquid phase mass transfer parameters are determined as ??hG = 0.048 ????G1.0 ????G0.33 and ??h L = 0.050 ????L0.4????L0.5.

Investigating dehumidification performance of solar-assisted liquid desiccant dehumidifiers considering different surface properties

Solar-assisted liquid desiccant dehumidification is promising regarding its lower energy consumption. Surface properties of dehumidifiers critically influence the dehumidification performance. Therefore, this paper aims at investigating the influence of surface properties on dehumidification performance of falling film dehumidifiers. Three commonly-used plate dehumidifiers, i.e., Stainless steel plate dehumidifier, Titanium plate dehumidifier and Polytetrafluoroethylene plate dehumidifier, with distinctive surface properties were chosen for study. Surface free energy was measured to characterize the adhesion between liquid desiccant and solid surface. Then, the effect of surface properties on dehumidification performance was experimentally investigated. The experimental results indicated that surface wettability demonstrated positive effect on dehumidification performance by increasing wetting area and reducing falling film thickness. As surface free energy increased from 30.34 mJ/m2 to 50.61 mJ/m2, the moisture removal rate increased from 0.155 to 0.213 with the enhancing ratio of 37.4%. A novel mass transfer correlation was developed, among which surface free energy was introduced to consider the effect of surface properties on dehumidification performance. It is estimated that 9.6% of the energy consumption could be saved by improving surface wettability of falling film dehumidifiers. This research is also very useful to other falling film applications, such as evaporators, condensers and chemical columns.

Heat and mass transfer in microscale diabatic distillation columns for ammonia–water desorption and rectification

An experimental investigation of heat and mass transfer in novel desorber and rectifier components based on the diabatic distillation principle is conducted. Heat and mass transfer coefficients measured here are compared with predictions of correlations from the literature. Temperature profiles are compared with component-specific heat and mass transfer models. Good agreement between model predictions and experimental results is shown. While heat and mass transfer correlations from the literature provide reasonable prediction of the data, further improvement is achieved with proposed correlations for liquid mass transfer and binary mixture correction coefficients. The results from this study show the potential for these novel designs to be implemented in small-capacity ammonia–water absorption systems.

Correlation between pulse 300 series SS wire parameters

A centralized and extensive relationship linking arc characteristics is presented to explain the metal transfer phenomenon, electrode melting rate, metal transport and weld-solidification during the Pulse gas metal arc welding. The study details interpretation of numerous arc, heat and mass transfer correlations during molten stage of the electrode, initiation of droplet, growth, detachment, transfer and impingement into the weld-pool. An interactive coupling between pulse process parameters, temperature distribution and weld pool dynamics has been discussed. This review elucidates conditions of the pulse metal transfer in the arc column and into the weld pool on the basis of current waveform, magnitude of peak, base and pulse current for 300stainless steel wire.

Mass transfer performance and correlation for CO2 absorption into aqueous 1-Dimethylamino-2-propanol (1DMA2P) solution in a PTFE hollow fiber membrane contactor

1-Dimethylamino-2-propanol (1DMA2P), a tertiary amine, has been regarded as the promising absorbent with relative higher reaction rate and high capacity for CO2 capture. The CO2 absorption into aqueous 1-Dimethylamino-2-propanol (1DMA2P) solution in the polytetrafluoroethene (PTFE) hollow fiber membrane contactor (HFMC) was firstly studied experimentally in the present work. The CO2 absorption performance in terms of the CO2 absorption flux was comprehensively investigated by considering a series of operating parameters, including liquid velocity, gas velocity, liquid phase temperature, CO2 partial pressure, initial lean CO2 loading in the liquid phase, amine concentration and flow orientations. The experimental results indicated increasing liquid velocity can significantly enhance CO2 absorption performance over a reasonable range of liquid velocities while similar trends were observed by increasing gas velocity, liquid temperature, CO2 partial pressure and amine concentration properly. By contrast, there was a severe loss of CO2 absorption flux with increase in lean CO2 loading. Counter-current flow achieved the improvement of CO2 absorption performance compared to co-current flow. Besides, to predict the CO2 absorption performance at various operating parameters, satisfactory correlations of KG and JCO₂ were proposed for the 1DMA2P-CO2 system.