Mass Transfer Characteristics Research Articles

Impact of Reverse Buoyancy on Heat and Mass Transfer in MHD Flow of PbLi Within a Poloidal Duct in a Typical DCLL Liquid Breeder Blanket

The typical dual-coolant lead-lithium (PbLi) design of a liquid breeder blanket in a magnetic confinement fusion reactor involves the utilization of PbLi as the working fluid to effectively remove neutron heat. However, the nonuniform heating of neutrons with a significant radial gradient induces a buoyancy effect, resulting in the formation of vortexes ices within the downward flow duct. These vortexes have an adverse impact on the heat and mass transfer characteristics of the magnetohydrodynamic (MHD) flow of PbLi. The simulations in this work employed a MHD buoyant mixed-convection solver to resolve the characteristics of PbLi flow and a one-way coupled Lagrangian method to analyze the qualitative characteristics of tritium transport in PbLi flow. The results indicate that buoyant reverse flow can create vortexes that contain hot spots in the PbLi fluid, which can significantly impede heat transport. Additionally, the vortex causes tritium recirculation in the flow field and retention, resulting in adverse effects on tritium transport.

A Review on the Heat-Source Tower Heat Pump Systems in China

Based on air-, water-, and ground-source heat pump systems, a novel type of heat pump system, named the heat-source tower heat pump system (HSTHPS), has recently been developed in the southern area of China. The HSTHPS overcomes the evaporator frosting problems of the air-source heat pump system (ASHPS) when the ambient temperature is lower, and it avoids the geological condition constraints of the water- and ground-source heat pump systems. However, studies on the HSTHPS are insufficient, thereby limiting its development and applications. Thus, the present review provides a detailed literature review on the advancements of HSTHPSs in China, including the HSTHPS operation principle, heat-source tower (HST) structure, heat and mass transfer characteristics, HSTHPS performance, antifreeze solution use, and antifreeze solution regeneration. Studies on the heat and mass transfer characteristics of HSTs are sufficient for guiding the application. Regarding open systems, the solution drifting to the air needs to resolved, and future studies need to focus on structure optimization for heat exchangers in closed systems. Moreover, advanced defrosting technology should be applied to closed-type HSTs, and a suitable operation strategy for HSTHPSs should be developed. Future priorities should involve integrating HSTHPSs with additional renewable energy in order to achieve continuous, stable, and efficient heating in winter based on the characteristics of local climate and renewable energy.

Theory-based cryopreservation mode of mesenchymal stromal cell spheroids

Cryopreservation of spheroids requires development of new improved methods. The plasma membranes permeability coefficients for water and cryoprotectants determine time characteristics of mass transfer through the cell membranes, and therefore the optimal modes of cells cryopreservation. Here we proposed an approach to cryopreservation of multicellular spheroids which considers their generalised characteristics as analogues of the membranes' permeability coefficients of the individual cells. We have determined such integral characteristics of spheroids from mesenchymal stromal cells (MSCs) as osmotically inactive volume; permeability coefficients for water and Me2SO molecules and the activation energy of their penetration. Based on these characteristics, we calculated the osmotic behaviour of multicellular spheroids under cooling conditions to select the optimal cooling rate. We also determined the optimal cooling rate of spheroids using the probabilistic model developed based on the two-factor theory of cryodamage. From the calculation it follows that the optimal cooling rate of the MSC-based spheroids is 0.75 °С/min. To verify the obtained theoretical estimates, we conducted experiments on freezing MSC-based spheroids under different modes. The obtained results of primary viability screening indicate that freezing at a constant linear cooling rate of 0.75 - 1.0 °С/min gives a good result. Theoretical prediction of the spheroid osmotic behaviour during cooling provided the basis for experimental verification of varying the temperature to which slow cooling should be carried out before immersion in liquid nitrogen. Slow freezing of spheroids to -40 °C followed by immersion in liquid nitrogen was shown to preserve cells better than slow freezing to -80 °C. Obtained data allow more effective use of MSC-based spheroids in drug screening and regenerative medicine.

Hydrate Formation and Methane Mass Transfer Characteristics in Static Systems of Pure Water and Saline Water with Varied Initial Dissolved Methane Concentrations

Hydrate Formation and Methane Mass Transfer Characteristics in Static Systems of Pure Water and Saline Water with Varied Initial Dissolved Methane Concentrations

Investigation of conjugate heat and mass transfer in a sleeve-type hollow fiber membrane for liquid desiccant dehumidification

In adiabatic conditions, the dehumidification capacity of hollow fibre membranes decreases as solution temperature rises. To address this limitation, this study proposed a novel approach based on sleeve-type hollow fibre membranes. The study focused on three distinct fluid streams and the sleeve-type hollow fibre membrane tube. A three-dimensional model of the dehumidifier was created, and the dehumidifier's heat transfer, mass transfer, and fluid flow characteristics were thoroughly analyzed and experimentally validated. The results showed that the average values of the Sherwood number and Nusselt number on the air side are significantly influenced by the Reynolds number. On the solution side of the sleeve-type hollow membrane, the average Nusselt number and Sherwood number are approximately 4.0 and 4.6, respectively. According to the research, 76 % of the resistance is accounted for by the mass transfer resistance on the membrane side. The study's conclusions provide insightful information for improving the design of sleeve-type hollow fibre membrane dehumidifiers.

Characterization of liquid-liquid two-phase flow patterns and mass transfer coefficients in Human-shaped microchannels

Based on the principle of splitting and recombining, this study designed and fabricated millimeter-scale Human-shaped microchannels. The research focused on investigating the flow patterns and mass transfer characteristics of liquid-liquid two-phase flow within the Human-shaped microchannels. The experiment utilized a water and n-butanol system to investigate the flow behavior of liquid-liquid two-phase in the channel with a flow rate ratio of 1. When the total volumetric flow rate increases from 120 µl/min to 2400 µl/min, the flow pattern experiences slug flow, slug-droplet flow, parallel flow and non-steady flow patterns respectively. The study investigated the impact of factors including total flow rate, feed method, angle, curvature, channel width, phase ration extraction efficiency and mass transfer coefficients. The Human-shaped channel exhibited superior mass transfer performance compared to conventional microchannels due to its advantageous configuration. The higher the included angle is, the stabler the flow pattern within the channel, resulting in a better mass transfer performance. Furthermore, the absence of curvature is more favorable for achieving higher mass transfer efficiency. In the experiments, the overall volume mass transfer coefficient ranged from 0.007 to 0.1742 s−1. This study can provide insights for the development and structural optimization of microchannels based on the split-recombine principle.

A Novel Numerical Model Considering Unsaturated Soil Properties and Computational Study on Heat and Moisture Transfer Characteristics of Helix Ground Heat Exchanger

Abstract A novel three-dimensional numerical simulation model for the helix ground heat exchanger was proposed in this paper, which takes into account unsaturated soil properties. This model is more suitable for real working conditions. To validate its accuracy, a miniature model heat transfer experimental platform was constructed. Additionally, the study conducted simulation research using three types of soil with significantly different thermal and moisture characteristics. Moreover, the comprehensive thermal conductivity and water diffusion coefficient of these three soil types were determined by relevant literature and experimental tests. The aim was to comprehensively explore the impact of different soil types on the heat and mass transfer of the helix ground heat exchanger. The results indicate that the numerical model developed in this paper accurately captures the heat and mass transfer characteristics of the helix ground heat exchanger to a certain extent. Increasing the comprehensive thermal conductivity and water diffusion coefficient of the soil can significantly enhance the heat exchange capacity of the exchanger. For instance, under sandy loam conditions, the heat exchange capacity is approximately 20.73% higher compared to clay loam conditions. The study also identifies two distinct areas around the helix ground heat exchanger: the severe change region and the soft change region. In the severe change region, there is a notable decrease in soil water content near the exchanger, which inevitably weakens the thermal conductivity of the soil. It is advised to minimize this effect through measures like active water spraying.

Study on the impact of methanol steam reforming reactor channel structure on hydrogen production performance

The design and operation of embedded reactors involve chemical reaction efficiency issues, with the main consideration being heat and mass transfer characteristics. The contact area of the porous catalytic coating with methanol is affected by the reactor structure, to improve the hydrogen yield and reveal the mechanism of the channel structure on the hydrogen production performance, the hydrogen production performance of circle-triangle, circle-square, square-circle, square-square, and triangle-circle channels was investigated. The reasons for the differences in methanol conversion, hydrogen, and carbon monoxide selectivity were analyzed from the perspective of heat and mass transfer using a three-rate reaction mechanism. The results showed that the circle-triangle channel performed outstandingly in the hydrogen production from methanol steam reforming with 98.61 % methanol conversion, 88.74 % hydrogen selectivity, and 29.06 % CO selectivity. The shapes and sizes of the different channel structures affect the fluid flow pattern and velocity distribution, which in turn affect the mass transfer efficiency and lead to differences in hydrogen production performance. The circle-triangle channel exhibits superior heat transfer and material transport performance, which can improve the hydrogen production efficiency of methanol steam reforming and help provide an important reference for the embedded reactor design.

Hydrodynamic simulation-informed compartment modelling of an annular centrifugal contactor

Abstract The geometrical and hydraulic parameters have a great impact on the mass transfer characteristics of annular centrifugal contactors. The objective of this study is to evaluate the mass transfer performance of a single annular centrifugal contactor by applying the computational fluid dynamics informed compartment modelling approach. In the study, a steady state compartment model of an annular centrifugal contactor is developed in gProms general purpose process modeller by using the hydrodynamic parameters obtained from computational fluid dynamics simulations performed in OpenFOAM with the GEneralised Multifluid Modelling Approach (GEMMA). The mass transfer rate predicted by the developed compartment model is compared with data obtained from uranium extraction with Tributyl Phosphate experiments performed with a laboratory-scale annular centrifugal contactor. Uranium concentrations in the organic and aqueous outlets and the mass transfer rate evaluated by the developed compartmented contactor model are in good agreement with the experimental data. The results reveal that the use of a hydrodynamic-informed compartment modelling approach raises the possibility of designing full-scale annular centrifugal contactors without the need for detailed computational fluid dynamics simulations and the prediction of mass transfer performance of the whole system from laboratory scale experiments.

Two-dimensional hydrophilic imprinted resin–graphene oxide composite for selective extraction and rapid determination of gibberellin traces in licorice samples

This study presents novel methodologies and materials for selectively and sensitively determining gibberellin traces in licorice to address food safety concerns. A novel hydrophilic imprinted resin–graphene oxide composite (HMIR–GO) was developed with fast mass transfer, high adsorption capacity, and exceptional aqueous recognition performance for gibberellin. Leveraging the advantages of molecular imprinting, hydrophilic resin synthesis, and rapid mass transfer characteristics of GO, HMIR–GO was employed as an adsorbent, showing resistance to matrix interference. Coupled with HPLC, a rapid and selective method for determining gibberellin was established. Under optimal conditions, the method exhibited a wide linear range (0.02–5.00 μg g−1, r = 0.9999), low detection limits (3.3 ng g−1), and satisfactory recoveries (92.0–98.4%), enabling the accurate and rapid detection of gibberellin in licorice. This study introduces a pioneering strategy for the selective extraction and determination of trace gibberellin levels, offering insights for similar applications in functional foods.

Nonlinear heat radiation and mass transfer characteristics on MHD Walters’ B fluid flow through a porous medium over a stretching sheet

To handle the continuous thermal power supply is very important in thermal systems and industries, so magnetized heat transport with non-Newtonian fluid is an appropriate platform for thermal power energy. In view of this usefulness, this paper provides a numerical assessment of electrically conducting Walter's B fluid flow through nonlinear permeable stretching sheet subject to mixed convective, porous medium, and Newtonian heating phenomena. Thermophoresis and Brownian motion effects have been included in energy and species diffusion equations to account for the impacts of nonlinear thermal radiation, joule heating, heat source and chemical reaction. The system of governing equations has been reduced to dimensionless nonlinear coupled equations using similarity transformations. The bvp4c technique has been used to obtain the solution for velocity, temperature, and concentration distributions. We consider both regions of assisting and opposing flow and provide various tables and graphs to examine the impact of varying values of emerging factors. Heat source and thermal radiation characteristics are found to enhance the thermal boundary layer thickness, which may be used to dissipate heat. The magnetic parameter augmented the fluid temperature and decelerated the velocity field. The chemical reaction parameter accelerated the concentration distribution. Further, the Sherwood number, Nusselt number, and skin friction coefficient have been determined and compared well to prior research that has been published.

Gas–Liquid Microchemical Oxidation for Continuous Synthesis Processes: A Short Review

AbstractGas–liquid oxidation processes, despite their wide application in the chemical industry, still pose considerable safety concerns. Microchemical technology has received high recognition for its intrinsic safety performance and process-intensification capability in hazardous reactions. This Short Review offers a comprehensive summary on how microchemical technology can be employed to achieve gas–liquid oxidation processes for continuous synthesis of chemicals in a safe, efficient, and controlled manner. Herein, we discuss the key aspects of gas–liquid dispersion and hydrodynamics, as well as mass transfer characteristics on microscale, and present representative gas–liquid oxidation cases in microflow reactors. Finally, the current challenges in industrial applications and potential academic research directions are presented.1 Introduction2 Microbubble Generation Technology for Gas–Liquid Oxidation Reactions3 Hydrodynamic and Mass-Transfer Characteristics of Gas–Liquid Oxidation Microreactors4 Gas–Liquid Oxidation Reactions in Microreactors5 Conclusion and Outlook

Performance optimization of adsorption hydrogen storage system via computation fluid dynamics and machine learning

Adsorption hydrogen storage paves an alternative way for reliable hydrogen storage. Here, impacts of dimensionless fin geometry configurations of the fin-tube metal hydride bed on the hydrogen storage performance are systematically investigated. Results show employing fins can strengthen the heat and mass transfer characteristics in the adsorbent bed and shorten the adsorption duration, especially at large fin numbers. Larger dimensionless fin thickness, height and width can lower the average bed temperature, which contributes to the adsorption kinetics and hydrogen fraction. At a small adsorption duration, larger dimensionless fin thickness, height and width improve the hydrogen storage amount due to obviously augmented hydrogen fraction. At a larger adsorption duration, there exist optimal dimensionless fin thickness, height and width leading to the maximum hydrogen storage amount originating from the compromise between the hydrogen fraction and adsorbent filled. Based on machine learning, the relationships between dimensionless fin geometry parameters and hydrogen storage amount have been obtained, and the optimal adsorption duration depended dimensionless fin configurations are obtained based on genetic algorithm. At a moderate adsorption duration, the optimized finned bed can significantly enhance the hydrogen storage amount. At the adsorption duration of 400s, the hydrogen storage amount is augmented by 12.8%.

Cattano Christov double diffusion model for third grade nanofluid flow over a stretching Riga plate with entropy generation analysis

The current investigation delves into the convective heat and mass transfer characteristics of third-grade radiative nanofluid flow within a porous medium over a Riga plate configuration. The Riga plate structure incorporates magnets and electrodes strategically arranged on a plate surface. To enhance the accuracy of energy and concentration expressions within the third-grade fluid flow, the Cattano Christov Double Diffusion model is employed. Entropy generation analysis is conducted by applying the second law of thermodynamics, and Darcy's model is employed to characterize the behavior of a porous medium. Appropriate similarity transformations have been used to convert the partial differential equations monitoring the fluid flow model into dimensionless ordinary differential equations. The Galerkin weighted residual method is employed to resolve these equations numerically. The findings contain detailed explanations of how relevant factors affect the temperature field, concentration field, velocity field, entropy generation, and Bejan number, in addition to graphic representations of the results. The findings indicate that the medium's porosity and Brinkman number promote entropy generation. The Bejan number and entropy production is affected by the thermal radiation parameter, which first rises and then declines after a certain distance.

Experimental study on wavy fin desiccant coated heat exchanger for hybrid air conditioning systems

The desiccant-coated heat exchanger (DCHE) is an energy-efficient alternative dehumidification equipment for humidity control in air conditioning. It exhibits a higher dehumidification performance than other solid desiccant systems and can simultaneously handle both latent and sensible loads. Taking the clue of research outcomes from the alternative heat exchangers to enhance the performance, a wavy fin DCHE is designed, fabricated and tested. Objectives of the study are to (i) analyse the dynamic performance of DCHE, (ii) compare the heat and mass transfer characteristics of plain and wavy fin-type DCHEs, and (iii) examine the influence of different operating parameters on the performance. The experimental investigation shows that the dehumidification capacity and thermal coefficient of performance of the proposed wavy fin DCHE are 0.34 g/s and 1.041, respectively, which are 75 % and 60 % higher than the conventional plain fin type. In addition, the developed DCHE has an average cooling capacity of 0.85 kW, which is 42 % higher. Besides, the total quantity of moisture adsorbed also increased by 35 %. Furthermore, the sensitivity analysis of the parametric study identified air velocity, cold water temperature, and inlet humidity ratio as the most influential operating parameters on the performance of wavy fin DCHE.

Physics-based modeling of the effective gas transport properties of single jersey knitted fabrics based on images

Physics-based modeling of the effective gas transport properties of single jersey knitted fabrics based on images

Numerical Simulation of Mass Transfer Characteristics of Gas–Liquid Bubble Columns and an Improved Mass Transfer Model

Numerical Simulation of Mass Transfer Characteristics of Gas–Liquid Bubble Columns and an Improved Mass Transfer Model

Liquid – Solid mass transfer characteristics of a heterogeneous reactor made of separated horizontal woven screens impinged by a submerged jet

The mass transfer characteristics of a submerged liquid jet impinging on a stack of separated screens were investigated by the electrochemical limiting current technique. The effects of changing the jet velocity, the nozzle diameter, and the screens’ porosity were studied. The present mass transfer data were found to be much higher than the data obtained by previous studies on jet impinging on flat surfaces. The mass transfer data also revealed that using the impinging jet greatly enhanced the mass transfer at screen surfaces with respect to other conventional forced convection methods used in previous studies. The mass transfer data were correlated by the equation: ShR=0.253Sc0.33ReN0.66ε0.745 for the conditions: Sc=1898, 8071 ≤ ReN≤ 33631, 0.668≤ε≤ 0.809. The importance of the above equation in the scale up and design of electrochemical and catalytic reactors suitable for diffusion-controlled reactions was highlighted. The calculated high energy utilization efficiency (kA/e) of the reactor lends support to its use in practice in preference to reactors made of flat surfaces impinged by a submerged jet. By supporting catalyst on the screens, the reactor also can replace stirred slurry reactors usually used in conducting biochemical and photochemical reactions in order to eliminate the time consuming and the costly step of separating the final product from the catalyst particles.

Study on the heat and mass transfer characteristics of wet air and solution on the surface of corrugated packings at lower ambient pressure

Study on the heat and mass transfer characteristics of wet air and solution on the surface of corrugated packings at lower ambient pressure

Heat and mass transfer characteristics of non-equilibrium flash at start stage

Our experiments showed that a V shape pressure drop appeared at start stage of non-equilibrium flash. V shape pressure drop firstly denoted the generating of superheat degree, which should be the starting force driving the non-equilibrium flash. Then evaporated vapor made up the pressure drop. Finally, a dynamic equilibrium was reached between the flash rate and the outflow rate, and the pressure behaved decreasing gradually. However, few published references focus on this start stage of the non-equilibrium flash. In this paper, experiments of the flash were conducted to investigate the heat and mass characteristics during V shape start stage. Dimensionless flash conversion coefficient (FCC) was proposed to normalize the flash with different initial liquid mass at start stage. The effects of initial temperature and the valve opening degree on the heat and mass characteristics of flash during the V drop start stage were studied. The results showed that the pressure of the working fluid changed dramatically during the V drop start stage. The peak of instant liquid superheat was proportional to the opening degree of the valve, which controlled the outflow rate. The flash rate increased with increasing initial temperature and valve opening degree, which had an approximately linear relationship with the flash time. FCC increased with valve opening degree. It could be deduced that flash intensity or flash rate would be higher for an expander with larger outlet area or higher working temperature.