Flow Distributor Research Articles

Analysis of a horizontal flow closed loop thermal energy storage system in pilot scale for high temperature applications – Part II: Numerical investigation

The storage system investigated in this work, namely the CellFlux system, consists of a regenerator type thermal energy storage volume which is coupled to a heat exchanger by a circulating intermediate working fluid. The numerical simulations in this work are based on experiments conducted with a large scale pilot plant having a bed length of more than 10 m. The storage volume is of a novel design with horizontal flow direction and is filled with hollow bricks as sensible heat storage material. So far, most publications focus on packed bed storage systems, often with molten salt or oil, only few consider regularly shaped channels with gaseous flow. For the investigation in this part of the publication, a one-dimensional dispersion concentric model for channel flow is implemented in MATLAB/Simulink.The analysis in part I of this publication has revealed a radial flow maldistribution, which can be predicted by a correction function correlated beforehand. The commonly used assumption of plug flow, however, will be afflicted with an error. Thus, the aim of this work is to determine the accuracy of the model both under the plug flow assumption and the application of aforementioned correction function. Three single blow experiments, where the storage is charged or discharged from a uniform initial temperature, are compared to the numerical model. The average temperature deviation between experiment and simulation reaches up to 10% without the correction function, but improves significantly through its application and then ranges between 0.4% and 4.8%.Moreover, studies based on larger experiments have either not observed or generally not addressed the effect of a flow maldistribution. This appears to be an issue for small scale experiments where typically more sophisticated models are applied. If it was possible to model the entire storage volume with the present 1D model, the flow maldistribution effects could average out. Also, computing effort would be low and allow simulations on system level. This approach was taken only by few authors so far, particularly for packed bed systems and was also not experimentally verified. In order to correctly depict the experimental set up, the model considers the different composition of the interior, such as flow distributors and inlet/outlet cones as well as the thermal heat capacity of the walls and losses to the environment. As a result the model shows good agreement with the experiments: the mean temperature difference of the exit temperature between experiment and simulation during cyclic operation remained below 5%.

Three-dimensional simulation of solid oxide fuel cell with metal foam as cathode flow distributor

In this study, the use of metal foam as a flow distributor at cathode is evaluated numerically by a comprehensive three-dimensional solid oxide fuel cell (SOFC) model. The results show that the adoption of metal foam improves the power density by 13.74% at current density of 5000 A m−2 in comparison with conventional straight channel design. It is found that electronic overpotential, oxygen concentration and reaction rates distribute more uniformly without the restriction of ribs. The effects of cathode thickness on the two different flow distributors are compared. Compared with conventional straight channel, the metal foam is found to be more suitable as a distributor for anode supported SOFC with thin cathode gas diffusion layer. Moreover, when metal foam is applied to the fuel cell with a larger reaction area, a more uniform velocity distribution and a lower temperature distribution can be achieved. It is also found that an appropriate permeability coefficient should offer a reasonable pressure drop, which is beneficial for the fuel cell system performance improvement.

An additive manufacturing approach to bioreactor design for mesenchymal stem cell culture

Bioreactor design is a challenging endeavour that aims to provide the most ideal environment in which cells can grow and biological reactions can occur. The emergence of regenerative medicine and stem cell therapies has led to the need for more diverse environmental requirements in the bioreactor design space.The study presented uses an additive manufacturing approach for the initial design phase of a packed/fluidized bed bioreactor for mesenchymal stem cell expansion. Combining 3D-printing with CFD for precision control over the bioreactor flow dynamics. Novel flow distributors were developed to engender swirling particle fluidization. The design was simulated and optimised using CFD, demonstrating an increase from 0.01 m/s to 0.02 m/s in the radial velocity of 3.0 mm macrocarriers (1080 kg/m3) at the minimum fluidization velocity. An autoclavable prototype was constructed to illustrate proof-of-concept in the use of swirling flow distribution to enhance cell attachment efficiency (compared to static culture system). Commercial Cytodex 1 carriers were tested: an improvement in attachment efficiency after 24 h from 50 % to 95 % was induced by the swirling flow distributor, with subsequent expansion of 2.4-fold after 6 days of culture.The computational design, modelling and 3D-printing of complex geometric architecture that control the flow dynamics within a bioreactor, provides a novel approach to bioprocess unit operation development for manufacturing novel ATMPs.

Production tests of the experimental sample of the universal flow distributor of stem materials from rolls on the basis of the KTU 10A feed distributor

Annotation Purpose. Improving the efficiency of the technological process of distribution of stem roll materials for feed and bedding on cattle farms with the use of universal technical means based on the feeder type KTU-10. Methods. Analysis of technological processes of distribution of stem materials for feed and litter for cattle. Experimental planning method and experimental calculation method. Results. In ZRCML NSC “IAEE” together with LLC “Orikhivsilmash” made an experimental sample on the basis of the feeder type KTU-10 with new working bodies of the current principle of action for small-volume separation and delivery of rolled stem forage and litter materials. It was tested on an existing dairy farm for 356 dairy cows with loose-box technology of keeping animals of LLC “40 years of Agro” in the village Smyrnove, Bilmatskyi district, Zaporizhia region. The use of a universal distributor based on KTU-10A on a farm for 350 cows in comparison with the Siloking Compakt mixer (10 m3) will reduce capital investment by 76.9%, specific fuel costs by 28.5%, specific operating costs by 29.5%. The estimated annual economic effect from the use of a streaming distributor when servicing 100 cows is UAH 121.3 thousand. Keywords: rotary and bitters working bodies, streaming distribution, forages, bedding, rolls, bales

바이오의약품 정제용 크로마토그래피 컬럼의 고효율 흐름 분배기 개발

We developed a flow distributor for high-performance chromatographic processes during the purification of biopharmaceuticals. Twelve distributor candidates are provided, including four types of distributors with different-shaped holes, and three sub-types with different number of holes. We evaluated the flow distributor candidates by spreading bromophenol blue dye on the membrane , and selected the most suitable distributor Arc 45 deg. type. Using 10 ml columns with three different length-to-diamter (L/D) ratios (4.33, 0.92, and 0.34) of column, we measured peak asymmetry (As) values. The 10 ml column with 0.92 L/D ratio showed best As value. We also carried out flow experiments on the three sub-types of Arc 45 deg. distributors on the 0.92 L/D ratio 50 ml column and Arc 45 deg. 1:8 distributor showed best performance. The As values of this optimal flow distributor are 1.2 or less. In summary, this study provides optimal distributor values for chromatographic purification of biopharmaceuticals.

Numerical investigation to optimize the inlet flow distributor of the intermediate heat exchanger in an HTGR

The intermediate heat exchanger (IHX) is a key part of the high-temperature gas-cooled reactor (HTGR). The inlet flow uniformity then strongly impacts the heat transfer in the IHX. The inlet passage design is the main cause of flow nonuniformities and an inlet flow distributor has been shown to effectively reduce these nonuniformities. This study numerically optimized the flow distributor structure by improving the flow uniformity. The structural optimization varied the installation height, distributor length and distributor area. The results show that the distributor length has an optimal value and the distributor area has two opposing effects on the velocity uniformity with both coupled to the installation height. The flow field analysis indicates that the ratio of the flow directly into the distributor and that guided into the distributor that had opposing transverse velocities is the key factor determining the velocity uniformity and the optimization effect can be intuitively reflected by the magnitude of the swirling strength. The optimization shows that the narrow structure at the 350 mm installation height gives the best velocity uniformity of 0.974.

Optimization of Open Pore Cellular Foams for PEM Fuel Cells

Open pore cellular foams (OPCF) have attracted substantial attention for use as flow-field plates in proton exchange membrane fuel cells due to their potential to enhance the performance [1]. Moreover, they could help to mitigate membrane degradation due to the hygrothermal stresses, which are generally observed in fuel cells that use bipolar plates with the channel-rib structure [2]. In order to optimize the structure and operating conditions of OPCF for use in proton exchange membrane fuel cells, we performed coupled numerical and experimental studies. The numerical studies used a 2-D model that solved mass and momentum conservation and species transport, and coupled them to an electrochemical model in the catalyst layers for the source terms. Parametric studies indicated that some OPCF’s properties like thickness, porosity and pore diameter highly impact the global performance of the cell, and that the optimal properties could considerably be influenced by current density, humidity, and cell dimensions. The results allowed for the design of optimized OPCF in different operating conditions, which were tested in fuel cells. It was observed that the optimized OPCF were very efficient in enhancing the performance of the cells at high currents, where mass transport limitations are generally observed. Promising solutions for heat and water management were explored. [1] Ahrae Jo and Hyunchul Ju, Numerical study on applicability of metal foam as flow distributor in polymer electrolyte fuel cells. Int. J. Hydrogen Energy 43, 2018. [2] Fredy Nandjou et al., Impact of heat and water management on proton exchange membrane fuel cells degradation in automotive application, J. Power Sources 326, 2016.

Air Jet Impingement Cooling of Electronic Devices Using Additively Manufactured Nozzles

This article reports the design, fabrication, and demonstration of additively manufactured air jet impingement coolers for the thermal management of high-power gallium nitride (GaN) transistors. The polymer jet coolers impinge high-speed airflow with a velocity of 42-195 m/s (Reynolds number between 1.87×104 and 8.77×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> ) onto working GaN devices mounted on a printed circuit board (PCB). The air jet provides cooling heat fluxes of up to 58.4 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , cooling rates of up to 6.6 °C/s, and convective heat transfer coefficient ranging from 5.2 to 17.0 kW/(m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ·K). The cooling performance is comparable to that of jet coolers made from other materials and manufacturing technologies. A key benefit of additive manufacturing (AM) is design freedom and geometric complexity, which we highlight by demonstrating three different packaging configurations, each enabled by a different jet cooler design that is customized for different types of packaging configurations: Cooler 1 directs two parallel impinging jets onto the top side of two devices; cooler 2 directs two air jets onto the front side and two air jets onto the back side of two devices; and cooler 3 directs air jets onto the front side of four devices mounted on parallel adjacent circuit boards. The second benefit of AM is the ability to consolidate multiple components into a single part, which we highlight by combining a nozzle, a fluidic delivery system, and a flow distributor within a volume of 80 mm × 80 mm × 100 mm. This work demonstrates the potential of AM to create complex, lightweight, fluidic delivery systems to achieve thermally and hydrodynamically optimized air jet cooling for high-power-density electronic devices.

Detection of Multiple Blockages in Parallelized Microreactors

AbstractIn a plant consisting of parallelized microreactors (MRs), the product quality is lowered because of a lack of flow uniformity among them when blockage occurs. It is not practical to install sensors in every MR from the viewpoint of cost when detecting the blocked MRs. In the previous study, the multiple blockage detection (MBD) method using a small number of sensors was proposed, but its performance became low when the number of sensors decreased. Here, the conventional algorithm for MBD is improved by considering the process behavior on blockage occurrence, and the effectiveness of the improved algorithm is demonstrated through a numerical case study. The effects of flow distributor types and sensor types on the MBD performance are numerically investigated.

Additively manufactured, highly-uniform flow distributor for process intensification

The ability of flow distributors to achieve high flow uniformity over multiple outlet channels is fundamental to the scalability of the synthesis of pharmaceuticals, polymers, fine chemicals, nanoparticles, and medical devices for drug delivery. Recent developments in the field of additive manufacturing (AM) have significantly increased the range of manufacturable geometries and materials, enabling the construction of high-performance flow distribution devices. Such devices can be manufactured at a wide range of scales (from microns to meters) and from a variety of metal and polymer materials. In this work, we describe a flow distribution system based on a fractal bifurcation scheme which achieves high outlet flow uniformity and packing density, while satisfying additive manufacturing constraints. Performance is predicted using an extensive numerical study and subsequently validated using experimental testing of additively manufactured prototypes. The experimental results confirm the predicted high flow uniformity. The resulting flow distribution system has the potential for use in a wide range of applications.

Pressurized Ammonia and Syngas Planar Anode-Supported Solid Oxide Fuel Cells and Their Performance Stability Test

This paper reports a stability test comparison between ammonia- and syngas-fueled anode-supported cells (ASC). The planar (50 x 50 mm2) ASC is consisted of 400-mm-Ni-YSZ anode, 3-mm-YSZ electrolyte, and 12-mm-LSC-GDC cathode together with metallic frames and current collectors which are sandwiched by a pair of rib-channel flow distributors (interconnectors) with guide vanes on both anode and cathode sides to form a single-full-cell stack in a dual-chamber pressure/temperature-controlled facility. Pressurization enhances the power density noticeably for both ammonia- and syngas-fueled ASCs. Little degradation is observed for the pressurized ammonia-fueled ASC at 0.8 V at 700°C (power density and stability increase with increasing temperature). However, the syngas-fueled ASC can only remain stable at 1 atm and at higher temperature (≥ 800°C); after five hours stable operation, a rapid degradation is observed at 3 atm due to severe carbon deposition even at 850°C.

Neutronic/thermal‐hydraulic design features of an improved lead‐bismuth cooled small modular fast reactor

Lead-based fast reactors (LFRs) have unique advantages in the development of a SMR, which has attracted a lot of attention in recent years. In this paper, an optimized design for a lead-bismuth small modular reactor was studied on the basis of the design of SUPERSTAR. This paper aims to propose an improved LFR core scheme to enhance the neutronic performance as well as the thermal-hydraulic safety of the reference reactor. Advanced nitride fuel is adopted in which the plutonium is used as the driven fuel, while thorium is used as the fertile fuel. Subchannel analysis was performed in the assembly design using an in-house subchannel code, SUBAS, and an 11 × 11 scheme with a pitch-to-diameter (P/D) ratio of 1.4 was chosen. Using the modified assembly, the core was redesigned using the coupled code MCORE. The active core was divided into four zones with different enrichment of 239Pu to extend the core lifetime and flatten the power distribution. The main kinetic parameters and reactivity coefficients were obtained. Neutronic performance at different operation times was also studied. The maximum radial power peak factor was 1.28, while the maximum total power peak factor was 1.737. During the whole lifetime, the reactivity swing was 0.926$, which was below the limit of 1$. The subchannel study of the core flow distribution showed that a flow distributor is needed to further improve the flow distribution capability. The peaking cladding temperature was 508.7°C, and the maximum fuel center temperature was 723.4°C, both of which do not exceed the limit temperature. Compared with features of SUPERSTAR, the peaking cladding temperature was well improved and the lifetime extended.

Metal foam as a turbulent flow distributor in the cooling channels of a PEM fuel cell—a numerical study

Operating temperature is one of the most important parameters affecting the performance of polymer electrolyte membrane (PEM) fuel cells. The cooling system of a PEM fuel cell maintains the temperature of the fuel cell stack at a specific value and removes the heat generated in the cell. This paper presents 3D numerical simulation of a water-cooled PEM fuel cell cooling system, with a metal foam insert instead of traditional cooling channels. We explore the possibility of using metal foams for thermal management of fuel cells. We consider the turbulent flow of the coolant through the porous medium and investigate the effect of metal foam properties, including porosity and pore size, on the performance of the cooling system. The Brinkman–Darcy–Forchheimer equation is employed to analyze the flow field in the porous medium and the k − ε model is utilized for turbulence studies. The numerical results indicate that, at a specific Reynolds number, by increasing the porosity and the pore size of the metal foam, the pressure drop decreases, while the maximum temperature difference occurs in the cooling plate. The temperature uniformity index also increases. The latter result indicates that the temperature distribution in the cooling plate becomes more uniform. The obtained results of present study are in good agreement with available experimental and analytical data, confirming that the presented computational fluid dynamics modeling using the selected turbulence model can accurately predict the flow field parameters in the cooling channels of PEM fuel cells.

Blockage Detection and Diagnosis of Externally Parallelized Monolithic Microreactors

To realize stable operation of a microchemical system, it is necessary to develop a process monitoring method that can detect and diagnose blocked microreactors. In this study, a system composed of five monolithic microreactors and a split-and-recombine-type flow distributor (SRFD) was developed for Suzuki–Miyaura coupling. Firstly, the effects of operating conditions on the yield was examined by using a single microreactor. After that, an optimal design problem was formulated to maximize the blockage detection performance by adjusting the channel resistances of the SRFD and the sensor locations in the SRFD under the design constraints. To efficiently solve the problem, a pressure drop compartment model, which is analogous to electrical resistance networks, was used. The optimally designed system was experimentally evaluated from the viewpoint of the capability of continuous operation and the blockage detection and diagnosis performance. The evaluation results show that continuous operation was successfully carried out for one hour, and that the artificially generated blockage of each microreactor was accurately identified. The developed system minimized the process performance degradation due to blockage.

Experimental assessment of flow distributors for falling-films over horizontal tube banks

Flow distributors are designed to evenly spread fluid along the length of horizontal tube banks used in falling-film heat and mass transfer components. This study comparatively assesses the performance of eight distributor designs described in previous studies under uniform conditions: water at 20 °C and atmospheric pressure with a distribution length of 203 mm over a film Reynolds number range of 12–495. Flow regimes from the droplet to sheet regime were observed, and the levels of maldistribution were quantified using a simple segmented collection system. Droplet and jet characteristics were measured using image analysis of high-speed video, with droplet volumes ranging from 20 mm3 to 540 mm3 and jet diameters ranging from 1.2 mm to 4 mm. Overall, the box-based distributor designs outperformed the tube-based distributors, but maldistribution was significant (>50%) for some flow rates in all the tested designs.

3D printed micro-chemical plant for biodiesel synthesis in millireactors

A micro-chemical plant implies the production increment of a determined product using micro/millireactor disposed in parallel. The flow distributor is responsible for the uniform distribution through these parallel microdevices. A mal-distribution, resulted from inadequate flow distributors designs, decrease the micro-chemical plant performance. Hence, the main goal of this paper was to apply 3D printing in manufacturing micro-chemical plant parts and to obtain data on flow uniformity and reaction yield by experimental tests for the increase of biodiesel production. The methodology consisted of design, printing and assembly of the micro-chemical plant and experimental tests for flow rate and chemical reaction. The nonuniformity flow coefficient (Ф) values were obtained for ethanol, sunflower oil and ethanol-sunflower oil mixture. The conical distributor without obstacle with height of 26 mm (CD26) and the conical distributor with obstacle and height of 52 mm (CDO52) presented excellent performance (Ф < 1%) for ethanol and sunflower oil flow, respectively, being used in the biodiesel synthesis scale-up. In the microplant, the pipes used for oil and ethanol followed length/diameter ratios of 39 and 113, respectively, which offered low pressure drop. The flow uniformity deviation obtained in the microplant was 4.2%, and its global yield was 42%, close to a single millireactor operation (50.4%). Thereby, the biodiesel was produced at 126.4 mL min−1. The developed microplant employed an efficient strategy for biodiesel scale-up. Another advantage of the methodology described here is the sharing possibility of files or objects over the internet. A user anywhere around the world can access the microplant developed here and start producing the desired chemical using a 3D Printer.

Topology optimization as a powerful tool to design advanced PEMFCs flow fields

This paper presents a thorough and affordable numerical framework to design the flow field of Proton Exchange Membrane Fuel Cells using topology optimization. No assumption is made about the layout of the channels, which freely evolves along the optimization process, resulting in non-trivial optimized geometries. The optimization problem is formulated to maximize both the power generation and homogeneity of current density distribution, in the spirit of reduced costs and increased durability. The evolution of the flow field geometry is computed with a gradient-based optimizer with gradients of the objective and constraints computed through the discrete adjoint method. At each optimization iteration, the incompressible Navier-Stokes, advection-diffusion, and Butler-Volmer equations are solved with a 2D finite element model that predicts the flow in the channels, transport of chemical species and electrochemical reactions. The 3D transport effects are accounted for in the 2D model through an original depth-averaging procedure. The results of the 2D prediction are verified against a full 3D model calibrated using numerical and experimental results. The developed design framework can be used to identify flow field layouts that outperform current industrial solutions, catch design trends and provide guidelines to technology practitioners. The topology-optimized designs yield significant power generation enhancements, an improved reactant distribution and a reduced pressure drop as compared to conventional flow fields. Increasing the inlet pressure leads to more and more intricate configurations with complex topologies and highly tortuous channels. However, the cell performance is found to be more sensitive to the topology of the flow distributor at low rather than at high inlet pressures. Considering a measure of the current density homogeneity in the optimization objective allows the identification of layouts in which the gas channels concentrate close to the outlets rather than close to the inlet. These design features slightly affect the amount of power generated, suggesting a viable route for future technological development.

Application of Carbon Felt as a Flow Distributor for Polymer Electrolyte Membrane Fuel Cells

In this work, carbon felt is employed as a flow distributor in polymer electrolyte membrane fuel cells and the fuel cell performance of this design is compared to that of a conventional graphite serpentine channel design and copper metal foam. Experimental results show that carbon felts as flow distributors offer advantages over other flow distributors in terms of enhanced rates of mass transfer due to their levels of high porosity and strong convective flow. As a result, fuel cells with carbon felt as flow distributors perform well and especially in high current regions. In addition, the effects of the hydrophilicity of carbon felt on fuel cell performance are evaluated. The hydrophobic surface of raw carbon felt is rendered hydrophilic via ozone treatment. Ozone-treated hydrophilic carbon felt helps remove water from the hydrophobic gas diffusion layer, decreasing mass transfer resistance. However, the formation of oxygen functional groups by ozone treatment increases the levels of ohmic resistance. Thus, it is necessary to develop highly conductive and hydrophilic carbon felt as a flow distributor for high performance of polymer electrolyte membrane fuel cell.

Investigation of flow kinematics in the structured multibed catalytic cartridge

The reduction of harmful substances emission into the atmosphere is very important to create compact, energy-efficient catalytic units for afterburning volatile organic compounds. A key component of such units is the catalyst cartridge. The efficiency of its operation is provided by the supply of a gas flow with a uniform velocity field. To solve the problem, the gas flow distributor and an aerodynamic stand for its testing were created. A set of air-flow blades was used to align the velocity profile before the catalyst cartridge. Also flow kinematics inside the cartridge was investigated via laser Doppler anemometry method.

A numbering-up metal microreactor for the high-throughput production of a commercial drug by copper catalysis.

Microreactors are emerging as an efficient, sustainable synthetic tool compared to conventional batch reactors. Here, we present a new numbering-up metal microreactor by integrating a flow distributor and a copper catalytic module for high productivity of a commercial synthetic drug. A flow distributor and an embedded baffle disc were manufactured by CNC machining and 3D printing of stainless steel (S/S), respectively, whereas a catalytic reaction module was composed of 25 copper coiled capillaries configured in parallel. Eventually, the numbering-up microreactor system assembled with functional modules showed uniform flow distribution and high mixing efficiency regardless of clogging, and achieved high-throughput synthesis of the drug "rufinamide", an anticonvulsant medicine, via a Cu(i)-catalyzed azide-alkyne cycloaddition reaction under optimized conditions.