Mass Transfer Technique Research Articles

Flow characteristics in a semi-confined circular-pipe impinging jet

The impinging jet is a complex heat and mass transfer technique that involves several process variables, such as the jet Reynolds number, impingement distance, and jet configuration. In this study, the flow characteristics of a semi-confined circular-pipe impinging jet over different Reynolds numbers and impingement distances were experimentally investigated using a two-dimensional particle image velocimetry technique. The confinement was achieved by positioning a plate parallel to the impinging plate at the nozzle exit. The time-averaged velocity field exhibited a recirculation structure that gradually shifted downstream with increasing Reynolds numbers or impingement distances. Notably, at H/d = 2, this downstream shift of the structure was accompanied by an increase in the vortex intensity. Moreover, the confined plate induced alterations in the overall flow pattern within the confined region, significantly reducing the wall jet decay rate compared with both unconfined and confined radial wall jets for H/d ≥ 3. Conversely, the confinement did not affect the expansion of the wall jet. Unlike the free (unconfined) impinging jets, the semi-confined circular-pipe impinging jet did not exhibit self-similar behavior in the conventional outer-scaled coordinates, particularly concerning the turbulence intensity and Reynolds shear stress. Finally, self-similarity in the time-averaged velocity and various turbulence parameters was achieved using the parameter scale proposed in this study, thereby obtaining the corresponding scaling laws in the wall jet region. Our study results can deepen the current understanding of the flow characteristics of semi-confined circular-pipe impinging jets and are significant for optimizing the performance and efficiency of compact electronic packaging equipment.

Adsorptive Recovery of Heavy Metal Ions from Aquatic Systems Using Metal‐Organic Frameworks: A Perspective in the Sustainable Development of Nanomaterials

AbstractRapid industrialization in the developing countries has facilitated the unwanted mixing of wastes into the already depleting sources of potable, domestic and industrial water. In particular, the mixing of toxic heavy metal wastes into the aquatic resources have not only increased the scarcity of water at the different levels of usage but also hygiene of the ecosystem is further threatened by the presence of abysmal quality of aquatic environment around the living world. Thus, it has become quite imperative to mitigate such problems through the removal of such water contaminants at the sources before supplied for a specific purpose. In this direction, among the other available mass transfer techniques, specific and efficient adsorption of heavy metal species on the nanomaterials such as metal‐organic frameworks (MOFs) are found to be a promising method of heavy metal ions recovery. This reports targets to provide a new perspective into heavy metal ions removal from wastewater as a rationale for sustainable nanomaterial engineering through the recycling of toxic metal species as precious precursors in the synthesis of nanomaterials. Decades of exploring materials sciences led to the generation of groundbreaking materials of nanoscale regime, which has advanced myriad avenues of science and technology, viz. electronic, energy, biomedical, environmental, agriculture applications, and more. In this regard, nanotechnology has had a global impact by several folds, which can be observed in all day‐to‐day facilities. This perspective aims to conceptualize a strategy of wastewater decontamination through the adsorptive retrieval of heavy metal species to be subsequently recycled in the design of smart nanomaterials.

Research Progress on Process-Intensified Water Treatment Applications

Process intensification (PI) is aimed towards essentially smaller, cleaner, safer, energy-efficient sustainable technologies involving the application of a number of strategies, including reducing the number of devices, miniaturization, process integration, improving mass and heat transfer, novel energy and separation techniques and combined optimization and control methodologies. Over the recent years, PI has attracted attention in the domain of aqueous medium adsorptive separations and wastewater treatment as well. Thus far, a limited number of investigations have appeared in the literature; in addition, there is yet a lack of published methods to follow the intensified solutions for processes in wastewater treatment. In this connection, this article aims to present an overview of the recent applications and advances in process-intensified decolorization of dyes; removal of aromatic hydrocarbons from wastewaters; and recovery of proteins, heavy metals and rare earth elements from aqueous media. Selected applications have been identified in terms of the PI techniques, and the corresponding process improvements have been discussed for a variety of examples with the aim of contributing to the future progress of applications. It has been confirmed that considerable process improvements could be possible, such as intensified process efficiency, improved adsorption and separation performance, and minimized sorbent requirement and processing time. Even though there have been considerable developments in the field, there is still a need for further developments for the enhancement of the technologies in adsorption wastewater treatment using a systems approach.

Local heat/mass transfer distributions on the bottom surface of a cavity exposed to an approaching turbulent boundary layer: Aspect ratio effects

We investigate convective transport from the bottom surface of rectangular cavities of depth d exposed to an oncoming boundary layer flow, using experimental and numerical techniques. The effects of cavity width W are explored for cavities with different lengths L in the downstream direction. Depending on the value of L/d (0.52≤L/d≤10), the approaching boundary layer separates and reattach on the bottom surface and establish a new boundary layer, or skims past the open face of the cavity. This results in significantly different convective transport coefficient distributions on the bottom surface. As cavity width is reduced, three-dimensional effects arise, with interaction of vortex systems on the cavity floor. Detailed spatial distributions of the transport coefficient are captured using a mass transfer technique based on naphthalene sublimation. Further insight into the flow structure responsible for the observed distributions is gained through numerical simulations using a k−ω SST model that is first validated using the experimental results by using a heat/mass transfer analogy factor. Flow streamlines from the computations are used to explain how the time averaged streamlines affect the heat transfer at the bottom surface.

Numerical Simulation of the Cleaning Performance of a Venturi Scrubber

Industrial applications need to use different systems for the problem of gas cleaning. A lot of processes have been developed, such as the use of a venturi for gas cleaning and pollution reduction. Additionally, several studies have been developed especially in terms of pressure drop because it is one of the main parameters to determine its efficiency. While the phenomenon of mass transfer in a venturi scrubber has not found much attention, in the present study, a mass transfer two-dimensional simulation is developed for gasification gas cleaning through a venturi scrubber with boundary conditions represented in air inlet velocities of 10, 15, and 20 m/s and water inlet mass flow of 0.02, 0.04 and 0.06 kg/s. In this work, Navier–Stokes equations are solved numerically and the mass transfer technique is treated by the volume of fluid (VOF) model, using CFD software. The obtained results were analyzed by presenting the mass fraction, velocity and pressure contours, and profiles. The probability density function (PDF) of mass transfer is studied too, showing how the removal efficiency of the venturi scrubber increases with a decrease in the liquid flow rate and an increase in the gas velocity. Therefore, the results show that the proposed venturi has the best mass transfer performance with a PDF that reaches 97.6 for velocity liquid of 20 m/s and the removal efficiency showed higher values at low liquid flow rates.

MHD dissipative Casson nanofluid liquid film flow due to an unsteady stretching sheet with radiation influence and slip velocity phenomenon

Abstract The problem of non-Newtonian Casson thin film flow of an electrically conducting fluid on a horizontal elastic sheet was studied using suitable dimensionless transformations on equations representing the problem. The thin film flow and heat mechanism coupled with mass transfer characteristics are basically governed by the slip velocity, magnetic field, and the dissipation phenomenon. The present numerical analysis by the shooting method was carried out to study the detailed, fully developed heat and mass transfer techniques in the laminar thin film layer by solving the competent controlling equations with eight dominant parameters for the thin liquid film. Additionally, the predicted drag force via skin-friction coefficient and Nusselt and Sherwood numbers were correlated. In view of the present study, a smaller magnetic parameter or a smaller slip velocity parameter exerts very good influence on the development of the liquid film thickness for the non-Newtonian Casson model. Furthermore, a boost in the parameter of unsteadiness causes an increase in both velocity distribution and concentration distribution in thin film layer while an increase in the same parameter causes a reduction in the film thickness. Likewise, the present results are observed to be in an excellent agreement with those offered previously by other authors. Finally, some of the physical parameters in this study, which can serve as improvement factors for heat mass transfer and thermophysical characteristics, make nanofluids premium candidates for important future engineering applications.

Local heat/mass transfer distributions on the bottom surface of a cavity exposed to an approaching turbulent boundary layer

Heat/mass transfer on the bottom surface of a rectangular cavity in an incompressible turbulent boundary layer flow is investigated, with emphasis on the effects of cavity width (W) to depth (d) ratio, for a cavity with aspect ratio L/d (length L to depth) of 6. For a wide cavity, this value of L/d is known to establish a flow structure in which the streamwise flow does not reattach on the bottom surface of the cavity, and instead shears past the entire open surface of the cavity, impinging on the downstream wall. A naphthalene sublimation mass transfer technique is used to evaluate local (mass) Stanton numbers at the cavity bottom surface for W/d ranging from 0.51 to 10, and two Reynolds numbers of 8100 and 12,800 defined using the cavity depth and freestream velocity. For W/d>2, the area-averaged mass transfer Stanton number asymptotes to a constant value. Despite the nominal two-dimensional behavior implied by the area-averaged Stanton number for W/d > 2, the details of the local mass transfer distributions show the effects of a system of multiple vortices that remain influential beyond W/d>2 and cause strong spatial variations in transport on the bottom surface. For W/d<2, the area-averaged Stanton number decreases as width is reduced, scaling as a power law with W/d, and appears to be independent of Reynolds number. Computations using the SST k−ω RANS model are able to predict the measured heat/mass transfer at the bottom surface well for W/d>3. For 0.8<W/d<3, the computations are able to capture the trends only qualitatively. For W/d<0.8, computations fail to predict the observed distributions and significantly under-perform.

Review—Progress in High Performance III-Nitride Micro-Light-Emitting Diodes

The developments of high performance InGaN based micro-light-emitting diodes (μLEDs) are discussed. We first review the early demonstrations of μLEDs and the state-of-the-art outstanding achievements on the emerging high-quality display and visible-light communication applications. Due to the miniature dimensions of μLEDs, the key understandings and the significant device advancements to achieve excellent energy efficiency are addressed. Lastly, two other critical challenges of μLEDs, namely full-color scheme and mass transfer technique, and their potential solutions are explored for future investigations.

Concept Inventories for Electrochemistry and Electrochemical Engineering

Conceptual understanding is essential to the development of competence and confidence in a particular field. Mastering concepts also plays a critical role in organizing material for recall and later use. Concept inventories are research-based assessment instruments that probe conceptual understanding. These inventories have been used in physics, thermal sciences, and other fields of science, engineering, and mathematics; however, no application to electrochemical systems was found. Rather than a means of presenting the course content, the concept inventory is used to assess the effectiveness of teaching and to reveal where students are missing key ideas and principles. Although some studies of misunderstandings related to electrochemistry are available, these tend to focus on a few narrow topics, often at the high school or freshman chemistry level, and do not explore more advanced topics, such as current distributions or the effect of mass transfer on cyclic voltammetry. Six concept inventories that cover electrochemical fundamentals (e.g., Faraday’s law), thermodynamics, electro-kinetics, mass transfer, porous electrodes, and electroanalytical techniques were developed and given to students at the Georgia Institute of Technology and Brigham Young University. These consisted primarily of multiple choice questions, with one correct answer and several distractors, which are intended to probe conceptual understanding. Student performance has been compiled and will be discussed in relation to the desired conceptual understanding. As expected, the inventories clearly showed deficiencies in student understanding of important concepts. The presentation includes a discussion of common concepts that prove difficult for students, possible sources of these misunderstandings, and suggestions for changing instructional approaches. In addition, the effectiveness of the questions was also evaluated. This evaluation included determination of a discrimination index for each question, which was calculated automatically by the Canvas learning management system. This metric provides a measure of how well a single question can tell the difference (or discriminate) between students who do well on a test and those who do not. It divides students into groups based on their score on the entire concept inventory and examines the correlation between performance on the specific question and the performance of the group on the complete exam. Second, based on the frequency that a wrong answer was selected, the effectiveness of the distractors was assessed. The distractors are intended to provide instructors with insight into the misunderstandings held by the students. However, if students rarely or never pick a particular incorrect answer, then it is not useful as a distractor and should be eliminated. The concept inventory continues to be developed beyond the first generation reported here. Within Canvas, a “sandbox” has been established that allows educators from different institutions to access these concept inventories. Sets of questions can then be transferred to instructor’s home institution for use with their students. We also look to the community for help in adding new content and refining questions in order to enhance the education of students in this important field.

Analytical Methodology of Monthly Residential Building Electricity Consumption Based on Data Mining Models

With the development of urbanization, the energy consumption of residential buildings is growing rapidly. Previous researches mainly focus on the daily profile of residential electricity consumption, while monthly electricity consumption profile is essential for the design and optimization of power system and energy storage system. With the advancement of smart meters as well as mass data storage and transfer techniques, the availability of building energy data is growing rapidly. Thus, data mining methods are becoming possible and effective in the analysis of monthly electricity consumption in residential buildings. This paper first reviews the current research of monthly energy consumption profiles in residential buildings, then proposes a new stochastic distribution method based on data-driven models. A case study of Jiangsu residential building electricity consumption is conducted to illustrate and verify the application of this method. Finally, this paper discussed the future promotion of this method and possible perspective of monthly energy profiles.

CFD Modeling on Hydrodynamic Characteristics of Multiphase Counter-Current Flow in a Structured Packed Bed for Post-Combustion CO2 Capture

Solvent-based post combustion CO2 capture is a promising technology for industrial application. Gas-liquid interfaces and interactions in the packed bed are considered one of the key factors affecting the overall CO2 absorption rate. Understanding the hydrodynamic characterizations within packed beds is essential to identify the appropriate enhanced mass transfer technique. However, multiphase counter-current flows in the structured packing typically used in these processes are complicated to visualize and optimize experimentally. In this paper, we aim to develop a comprehensive 3D multiphase, counter-current flow model to study the liquid/gas behavior on the surface of structured packing. The output from computational fluid dynamics (CFD) clearly visualized the hydrodynamic characterizations, such as the liquid distributions, wettability, and film thicknesses, in the confined packed bed. When the liquid We (Weber number) was greater than 2.21, the channel flow became insignificant and flow streams became more disorganized with more droplets at larger sizes. The portion of dead zones is decreased at higher liquid We, but it cannot be completely eliminated. Average film thickness was about 0.6–0.7 mm, however, its height varied significantly.

Flavor Retention and Release from Beverages: A Kinetic and Thermodynamic Perspective.

For the investigation of retention and release of flavor components, various methods are available, which are mostly used on a case-to-case basis depending on the raw material. These effects that originate from kinetics and thermodynamics could be put in a much wider perspective if these fields were taken as a starting point of investigation in combination with rigorous data analysis. In this Review, we give an overview of experimental techniques and data analysis methods, and predictive methods using mass transfer techniques are also discussed in detail. We use this as a foundation to discuss the interactions between volatile flavors and the matrix of liquid foods/beverages. Lipids present in the form of an emulsion are the strongest volatile retainers due to the lipophilic nature of most of the volatile flavors. Proteins also have flavor retention properties, whereas carbohydrates hardly have a retention effect in beverages. Smaller components, such as sugars and salts, can change the water activity, thereby facilitating flavor release. Alternatively, salts can also indirectly affect binding sites of proteins leading to release (e.g., NaCl and Na2SO4) or retention (NaCSN and Cl3CCOONa) of flavors. Furthermore, the effects of temperature and pH are discussed. The Review concludes with a critical section on determination of parameters relevant to flavor release. We highlight the importance of accurate determination of low concentrations when using linearization methods and also show that there is an intrinsic preference for nonlinear regression methods that are much less sensitive to measurement error.

Experimental Evaluation of Thermal and Mass Transfer Techniques to Measure Adiabatic Effectiveness With Various Coolant to Freestream Property Ratios

Experimentally evaluating gas turbine cooling schemes is generally prohibitive at engine conditions. Thus, researchers conduct film cooling experiments near room temperature and attempt to scale the results to engine conditions. An increasingly popular method of evaluating adiabatic effectiveness employs pressure sensitive paint (PSP) and the heat–mass transfer analogy. The suitability of mass transfer methods as a substitute for thermal methods is of interest in the present work. Much scaling work has been dedicated to the influence of the coolant-to-freestream density ratio (DR), but other fluid properties also differ between experimental and engine conditions. Most notably in the context of an examination of the ability of PSP to serve as a proxy for thermal methods are the properties that directly influence thermal transport. That is, even with an adiabatic wall, there is still heat transfer between the freestream flow and the coolant plume, and the mass transfer analogy would not be expected to account for the specific heat or thermal conductivity distributions within the flow. Using various coolant gases (air, carbon dioxide, nitrogen, and argon) and comparing with thermal experiments, the efficacy of the PSP method as a direct substitute for thermal measurements was evaluated on a cylindrical leading edge model with compound coolant injection. The results thus allow examination of how the two methods respond to different property variations. Overall, the PSP technique was found to overpredict the adiabatic effectiveness when compared to the results obtained from infrared (IR) thermography, but still reveals valuable information regarding the coolant flow.

Waste heat recovery and denitrification of flue gases from gas-fired boilers

A waste heat recovery and denitrification system was developed for improving energy conservation and emissions control especially for control of PM2.5 particles and haze. The system uses enhanced heat and mass transfer techniques in a packed heat exchange tower with self-rotation and zero-pressure spraying, low temperature NO oxidation by ozone, and neutralization with an alkali solution. Operating data in a test project gave NO x in the exhaust flue gas of less than 30 mg/Nm3 with an ozone addition rate of 8 kg/h and spray water pH of 7.5–8, an average heat recovery of 3 MW, and an average heat supply of 7.2 MW.

Turbine Platform Cooling and Blade Suction Surface Phantom Cooling From Simulated Swirl Purge Flow

This paper presents the swirl purge flow on a platform and a modeled land-based turbine rotor blade suction surface. Pressure-sensitive paint (PSP) mass transfer technique provides detailed film-cooling effectiveness distribution on the platform and phantom cooling effectiveness on the blade suction surface. Experiments were conducted in a low-speed wind tunnel facility with a five-blade linear cascade. The inlet Reynolds number based on the chord length is 250,000. Swirl purge flow is simulated by coolant injection through 50 inclined cylindrical holes ahead of the blade leading edge row. Coolant injections from cylindrical holes pass through nozzle endwall and a dolphin nose axisymmetric contour before reaching the platform and blade suction surface. Different “coolant injection angles” and “coolant injection velocity to cascade inlet velocity” result in various swirl ratios to simulate real engine conditions. Simulated swirl purge flow uses coolant injection angles of 30 deg, 45 deg, and 60 deg to produce swirl ratios of 0.4, 0.6, and 0.8, respectively. Traditional purge flow has a coolant injection angle of 90 deg to generate swirl ratio of 1. Coolant to mainstream mass flow rate (MFR) ratio is 0.5%, 1.0%, and 1.5% for all the swirl ratios. Coolant to mainstream density ratio maintains at 1.5 to match engine conditions. Most of the swirl purge and purge coolant approach the platform; however, a small amount of the coolant migrates to the blade suction surface. Swirl ratio of 0.4 has the highest relative motion between rotor and coolant and severely decreases film cooling and phantom cooling effectiveness. Higher MFR of 1% and 1.5% cases suffers from apparent decrement of the effectiveness while increasing relative motion.

Influence of mainstream turbulence on turbine blade platform cooling from simulated swirl purge flow

The paper presents the combined effect of mainstream turbulence intensity and swirl ratio on the cooling performance of turbine blade platform and suction surface. Pressure sensitive paint (PSP) mass transfer technique provides detailed cooling effectiveness distribution on platform and suction surface. Experiments have been completed in a low speed wind tunnel facility with a five blade linear cascade. The inlet Reynolds number based on the chord length is 250,000. Coolant to mainstream density ratio maintains at 1.5 to match engine conditions. Detailed mainstream turbulence intensities for test are Tu (%) = 0.72, 3.1, 6, 8.2, and 13. Swirl ratios (S) of 1 presents without rotation effect but 0.4 simulates high relative motion between rotor and coolant to represent rotation effect. Coolant to mainstream mass flow rate ratios are MFR (%) = 0.5, 1.0 and 1.5. Results show that elevated mainstream turbulence intensity increases cooling effectiveness in general. Best cooling performance is observed for high mainstream turbulence intensity of 13% cases no matter with or without rotation effect. Rotation effect reduces coolant capability at higher MFR of 1% and 1.5% cases for tested mainstream turbulence intensities.

Turbine Blade Surface Phantom Cooling from Upstream Nozzle Trailing-Edge Ejection

This paper presents upstream nozzle trailing-edge coolant ejection on downstream uncooled blades. A pressure-sensitive paint mass transfer technique provides detailed phantom cooling effectiveness distribution on modeled land-based turbine rotor blade surfaces. Without cavity purge and tip leakage flows, a uniform blade inlet temperature is adopted in the current study. Experiments have been completed in a low-speed wind-tunnel facility with a five-blade linear cascade. The inlet Reynolds numbers based on chord length are 100,000 and 200,000. Nozzle trailing-edge coolant ejection on a rotor blade is simulated by a spoked-wheel-type rotating facility with 32 hollow rods equipped with coolant ejection from 128 holes per rod. Coolant to mainstream density ratio maintains at 1.5 to match engine conditions. Nozzle coolant discharge velocity to nozzle mainstream velocity ratio varies from 0.4 to 1.4. Velocity ratios from 0.4–0.6 are closest to typical engine conditions. Coolant to mainstream mass flow rate ratio effect is from 0.67 to 2.94%. Higher phantom cooling effectiveness occurs on suction and pressure surfaces at the velocity ratio of 0.4–0.6 and over 1.0, respectively. Velocity ratio effect impacts phantom cooling effectiveness distribution more than the mass flow rate ratio effect. Most of the trailing-edge coolant migrates toward blade inner and outer spans than the blade midspan.

Experimental Study on Local Mass Transfer of Structured Packing with the Method of Flow Visualization

A chromochemical reactive mass transfer technique has been employed to study local mass transfer characteristics of structured packing. This technology adopted by experiment is an Ammonia Adsorption Method (AAM) that yields the surface distribution of transferred mass by analyzing the color distribution on a filter paper with the results of the color chemical reaction. A digital image processing technology is applied for data visualization. The three-dimensional plot of the local mass transfer coefficients shows that there exist three peak values on different positions of a unit cell of structured packing. In order to improve mass transfer efficiency of the structured packing, one piece of baffle is added between packing sheets. As a result, the average mass transfer coefficient increases by (10-20)% and the pressure drop decreases by (15-55)%.

On-chip thermal management of hotspots using a perspiration nanopatch

A cooling mechanism based on evaporation from thin liquid films is utilized for thermal management of hotspots combining efficient heat and mass transfer techniques. Dissipation of large heat fluxes from small form-factor areas is made possible by minimizing the thermal resistance across the evaporating liquid film. This is achieved by maintaining a very thin film (∼15 µm) of coolant by capillary confinement using a nano-porous membrane (∼10 µm). At the same time, evaporation is promoted by using jet impingement of dry air on the membrane. Based on these underlying ideas, a MEMS device called a ‘perspiration nanopatch’ is presented. The design and fabrication process of this micro-fluidic device is described along with experimental performance characterization under different operating conditions. Dissipation of heat fluxes in excess of 600 W cm−2 is demonstrated with heat transfer coefficients approaching 0.1 MW m−2 K−1 for surface temperatures well below the saturation temperature of the working fluid.

Membrane bioreactors for regenerative medicine: an example of the bioartificial liver

AbstractLiver transplantation is the only established treatment for liver failure. Because of the organ scarsity, liver support strategies are being developed with the aim of either supporting patients with the borderline functional liver cell mass until the organ transplantation or liver regeneration. A bioartificial liver (BAL) consisting of functional liver cells supported by an artificial cell culture material could provide a vital temporary support to patients with liver failure, and could serve as a bridge to transplantation while awaiting a suitable donor. In this paper, we discuss the critical issues for the development of BAL such as bioreactor configuration, mass transfer, cell source and culture technique. The characteristics of membrane BAL systems in clinical, preclinical and in vitro tests are reviewed. Membrane bioreactors used for the generation of in vitro physiological model systems for studying biological mechanisms and testing the efficacy of potential therapies are also discussed. Copyright © 2009 Curtin University of Technology and John Wiley &amp; Sons, Ltd.