Fluid Distributor Research Articles

Processing and surface modification of titanium open cell porous structures for PEM fuel cell bipolar plates

Bipolar plate (BP) and porous transport layer (PTL) materials and designs are critical for the performance of a proton exchange membrane fuel cell (PEMFC) and electrolyser (PEMEC) due to their role as fluid distributor and electron transporter between cells. Designs based on open cell porous structures require a good control on the porosity features. The aim of this work is to use powder metallurgy to manufacture titanium porous structures and the use of suitable surface modification techniques that can improve the performance of the PEM systems, focusing on fuel cells. Using the space holder method, porous structures of up to 63% porosity and controlled pore size can be processed to tailor the characteristics for an optimal design and, through a simple gas nitriding treatment, the performance of the material in terms of interfacial contact resistance (below 10 mΩcm2 after corrosion) and corrosion resistance (below 1 μAcm−2) are improved for both dense and porous structures.

Study of the Hydrodynamic Performance of a Compact and Intensified G/L Contactor: The RPB

Modern process equipment needed for safe and economically viable chemical and biological processes requires flexibility, compactness, and a great potential for enhancing mass transfer. Centrifugal process intensification equipment such as the rotating packed bed (RPB) satisfies the above mentioned requirements in addition to zero sensitivity to changes caused by gravity. The fundamental principles of RPBs are yet to be fully established due to difficulty in predicting their behavior which has necessitated the need for treating their design, modeling, and optimization on a case-to-case basis. This study focused on the hydrodynamics (pressure drops) of a pilot-scale RPB equipped with a stainless steel wire mesh packing. The effects of three operational parameters: average high gravity factor, integrated gas capacity factor, and liquid load, as well as a design parameter, the fluid distributor type were investigated. The maximum value of the average gravity factor used was 452. Also, a combined gas capacity factor of 2.6Pa0.5, and a liquid load of up to 20m3m-2h-1 were explored. Additionally, the influence of liquid distributor type on the pressure drop of RPBs was investigated.

Improved thermocline initialization through optimized inlet design for single-tank thermal energy storage systems

Single tank thermal energy storage systems based on the thermocline concept have attracted large interest in the last years at both, scientific and industrial levels, as cost-effective alternative to the commercially available and proven molten salt double tank storage system. Recently, many experimental and modeling results of these systems validating the technology and addressing guidelines to optimize its thermal performance have been reported. However, high cyclic efficiencies predicted in simulation have not been reported to be achieved experimentally. This paper addresses one of the reasons for this discrepancy, i.e., the fact that the additional temperature stratification volume generated by the fluid distribution at the tank's inlet is typically not considered in theoretical models. This paper demonstrates that assuming idealized flow distribution in the tank's cross-section will not represent reality adequately. Using this approach, the thermocline thickness at the beginning of the charge operation can be misestimated by more than 50%. Furthermore, a sensitivity analysis of the geometric characteristics of a specific radial fluid distributor type is included in this work. A theoretical model is developed for this purpose and validated with experimental data. The results of the analysis show that the fluid distributor should always be located in the upper-most part of the tank to minimize the initial thermocline thickness. Besides, the analysis of the cross-sectional area occupied by the distributor has been analyzed. It is shown that an optimal value exists for this parameter in order not to inhibit thermal stratification and to create further temperature gradients by subdividing the tank and thereby creating fluid-dead volumes.

Derivative-free level-set-based multi-objective topology optimization of flow channel designs using lattice Boltzmann method

A derivative-free level-set-based topology optimization method (DFLS-TO) was proposed and was used for channel structure design. Unlike in a conventional level-set method, quantum-behaved particle swarm optimization (QPSO) was used in DFLS-TO to optimize the level-set values at the knot points. The values at the non-knot points were interpolated by solving the Laplace equation. QPSO was combined with the Tchebycheff decomposition method to search for optimal level-set values in multi-objective problems. The channel boundary was represented by an iso-contour of the level-set function, and the B-spline method was used to convert the zigzag-like boundary into a smooth boundary. The lattice Boltzmann method (LBM) was integrated with the immersed boundary method to simulate the fluid flow. The Spalart–Allmaras model was incorporated with the LBM during the simulation of turbulent flows. To demonstrate the applicability of DFLS-TO, optimization of a pipe bend and a fluid distributor were performed.

Karakteristik Unjuk Kerja 2 Pompa Sentrifugal Dengan Susunan Seri Sebagai Turbin Pat

The pump is a device used to move fluid from one place to another through a media pipe or channel. The energy in the fluid is produced from the impeller which converts the kinetic energy (velocity) of the liquid into potential (dynamic) energy. Besides being used to move fluid (fluid) at this time the pump can also be used as a turbine by changing the working principle of the pump by giving a drop of water at an altitude to rotate the impeller on the pump so that the pump can operate upside down or called a pump as turbine), in this study the impeller on the pump as a turbine is driven by a water flow or water pressure that is large enough, the water flow is sourced from two centrifugal pumps with a series arrangement that functions as a driving force or fluid distributor which is assumed to be a high water fall or head. The use of centrifugal pumps with a series arrangement is so as to produce a large head to get a high water fall or a maximum head for turning a pump as a turbine. This study uses an experimental method that is using two centrifugal pumps as a fluid distributor and one pump that is used as a turbine and uses a variation of 5 watt and 10 watt light bulb. From the calculation of the suction pump and pump as a turbine without using a light bulb pump speed namely 920.5 rpm and the specific speed of the turbine produced is 76.61 rpm. by using a 5 watt light bulb load the pump rotation speed is 553 rpm and the specific turbine speed produced is 44.24 rpm, using a 10 watt light bulb load the pump rotation speed is 335 rpm and the specific turbine speed produced is 26.8 rpm. The greater the value of the pump head, the resulting water discharge will be smaller and vice versa, the size and size of the pump head obtained is also influenced by the presence of load on theturbine.

Batch chromatography with recycle lag. II—Physical realization and experimental validation

This is the second of a two-part study in which we explore the concept of batch chromatography with recycle lag, concluding with the design, construction, and experimental validation of a prototype—an eluate recycling device (ERD)—that embodies the physical realization of this concept. The ERD implements an approximate “first in, first out” method of organizing and manipulating the to-be-recycled fractions of eluate collected from the chromatography column, where the oldest (first) amount fluid, or ‘head’ of the fraction, is the first to exit and be recycled back to the column. Moreover, the apparatus is simple to set up in particular in view of large-scale applications. Here we detail the construction of the ERD and assembly of a setup to interconnect the ERD and a chromatography column. Through the coordinated operation of two-way valves and two-position six-port switching valves it is possible to implement a diverse set of configurations or operating modes interconnecting the chromatography column and the ERD. The setup is validated experimentally with success using the separation of a nucleoside mixture by reversed phase chromatography as a model problem. It is also shown that by redesigning the fluid distributor using 3D printing technology the ERD performance can be improved.

Design and Manufacturing of a Uniform, Massively Parallel Fluid Distributor for Automated Cell Culture Bioreactor

In this study, we present a design methodology that enables the automation of cell culture using a fluidic bioreactor module in a uniform, massively parallel fashion. To demonstrate our proof-of-concept validation, we designed the channel lengths that can uniformly distribute the fluid from one inlet to two to the power of n outlets. In our experiments, the module was composed of four layers which can hold eight petri dishes on each layer. The channel outlets were connected to the petri dishes, respectively. Cells and media were distributed into each petri dish by compensating the channel lengths with different potential energy of each layer in a controlled manner. The results show that the module was well-designed for the parallel supply of medium in automatic cell culture. Overall, the process can be automated by controlling the on/off events temporally, such as injecting a new cell media and removing the waste.

Novel multi-scale parallel mini-channel contactor for monodisperse water-in-oil emulsification

This paper presents the development of a novel parallel minichannel contactor for monodisperse water-in-oil emulsification. The novel contactor having 16 Y-junctions in parallel equipped with multi-scale tree-like fluid distributor and collector was realized and experimentally tested. Oils with different physical properties and water were used as continuous phase and dispersed phase, respectively. Influences of different factors including the parallelization, the water/oil flow-rate ratio and two-phase physical properties on the two-phase flow characteristics and on the coefficient of variation were studied and discussed. Results showed that for water-pure oil flow, the novel parallel minichannel contactor is capable of producing monodisperse water-in-oil emulsions with high throughput and low energy consumption under our tested conditions. The Ohnesorge number (Oh) has a significant influence on the emulsion monodispersity and the capillary number (Ca) appears as a proper indicator for liquid-liquid break-up regimes. A predictive correlation for the Oh number was proposed by fitting the experimental data obtained in the study.

Automated control system for the fluid distributor of a distillation column with a structured packing

An automated system of acquisition of raw experimental data and a control system for operation modes of an experimental large-scale separation column are described. The influence of a new method of irrigation of a structured packing on the separation column efficiency is studied. Based on the data obtained by the developed automated system, a 20–30% increase in the efficiency of mixture separation on a structured packing is expected.

Design and optimization of baffled fluid distributor for realizing target flow distribution in a tubular solar receiver

This paper presents an original study on the design and optimization of baffled fluid distributor for the realization of optimal fluid flow distribution in a tubular solar receiver. The basic idea is to install a perforated baffle in the inlet fluid distributor and to optimize the configuration of orifices on the baffle so as to approach the target flow distribution among downstream parallel tubes. A pressurized-air solar receiver comprising of 45 parallel tubes is used for study, with copper or Inconel 600 used as the filling material.Results show that the final fluid flow distributions realized by the geometrically optimized baffles are in good agreement with the target curves. The peak temperature of the receiver wall can be minimized accordingly with moderate increase in total pressure drop of the receiver system. It is shown that the insertion of a geometrically optimized baffle is generally a practical solution with various features: capable of realizing non-uniform target distribution; small pressure drop increase; compact geometry; flexible and adaptive; easy fabrication with a reasonable cost, etc.

A study on using metal foam as coolant fluid distributor in the polymer electrolyte membrane fuel cell

This paper deals with the usage of metal foams in coolant flow field of bipolar or cooling plates in PEMFC stack rather than conventional machined channel designs. A three-dimensional model is employed to simulate the fluid flow and heat transfer in cooling plates and the capabilities of four different coolant flow field designs, include one parallel, two serpentine and one metal foam porous media field, are investigated and compared based on the maximum surface temperature, uniformity of temperature and the pressure drop. The numerical results indicated that a model with the porous flow field made by metal foam is the best choice for reducing the surface temperature difference, maximum surface temperature and average surface temperature, among the studied models. Furthermore, due to its high permeable coefficient, the coolant pressure drop is very low in this model. Consequently, this model can be well-used as a coolant fluid distributor to improve the PEM fuel cell performance.

Numerical and experimental hydrodynamic study of a coolant distributor for grinding applications

ABSTRACTIn grinding, the high frictional energy is converted into heat, which may cause thermal damage and degradation of the wheel and the workpiece. Unwanted thermal effects must thus be reduced, often by external cooling using a curved-duct coolant distributor to match the wheel geometry. The performance of such a system depends strongly on the impinging jet flow properties to ensure efficient sprinkling of the hot spots. The fluid distributor, placed above the workpiece, is pierced with a certain number of identical nozzle fittings, providing multiple jets at the outlet of the nozzles. These jets sprinkle the solids over a given zone and remove the heat by convective transfer. The cooling is hence dependent on the flow structure, meaning the jet diameters, trajectories and velocities, determined up-flow by the distributor design. The present study is devoted to the hydrodynamics aspects of the fluid distributor, aiming to determine the flow-rate distribution at the different orifices and the flow-rate–pressure relationship, for a variety of nozzle diameters and feeding flow rates, under isothermal conditions. A simple hydraulic balance in the device was not able to predict with sufficient accuracy the actual measurements, even when the Venturi effect was accounted for. This discrepancy is due to the curvature of the distributor, inducing secondary flows in interaction with the nozzle outlets, which leads to a rather complex flow pattern. To overcome this issue, a computational fluid dynamics (CFD) tool was used and compared with in situ experiments – global flow rate and pressure measurements were additionally taken with particle image velocimetry (PIV) to gain insight into the local structure. Simulations were performed with a 3D turbulence model for Reynolds numbers up to 100,000. This model provides an efficient tool for coupling with the thermal study at a later step, allowing global sizing and energetic optimization of the grinding process.

Heuristic shape optimization of baffled fluid distributor for uniform flow distribution

This paper presents a CFD-based, heuristic evolutionary algorithm for shape design and optimization of baffled fluid distributor. In this algorithm, the baffle surface is firstly divided into numerous identical control areas (volumes), each control area having an orifice in the middle. Under the constraint of constant global porosity of the baffle, the algorithm adjusts the size distribution of orifices so as to approach identical mass flowrate passing through every control area. An automatic program is processed iteratively so that the baffle configuration evolves toward the optimized shape, providing a uniform flow distribution among parallel outlet channels.To illustrate the principles and procedure of this algorithm, a 2D example of baffled fluid distributor is introduced and tested. Numerical results show that this algorithm can successfully reach uniform flow distribution with a small pressure drop increase. Sensitivity analysis also shows that this algorithm is robust, effective, general and flexible compared to traditional arbitrary or empirical propositions. A parametric study of influencing design parameters on the performance of the algorithm is carried out in order to provide some design guidelines. Finally, the theoretical basis and essential steps for the extension of the current algorithm to tackle 3D problem are established. The easy implementation of this simply solution for the general fluid maldistribution problem demonstrates its promising application in real engineering field.

Experimental advances and preliminary mathematical modeling of the Swiss-roll mixed-reactant direct borohydride fuel cell

The Swiss-roll single-cell mixed reactant (SR-MRFC) borohydride – oxygen fuel cell equipped with Pt/carbon cloth 3D anode and either MnO2 or Ag gas-diffusion cathodes is investigated by a combination of experimental studies and preliminary mathematical modeling of the polarization curve. We investigate the effects of four variables: cathode side metallic mesh fluid distributor, separator type (Nafion 112® vs. Viledon®), cathode catalyst (MnO2 vs. Ag), and the hydrophilic pore volume fraction of the gas-diffusion cathode. Using a two-phase feed of alkaline borohydride solution (1 M NaBH4 – 2 M NaOH) and O2 gas in an SR-MRFC equipped with Pt/C 3D anode, MnO2 gas diffusion cathode, Viledon® porous diaphragm, expanded mesh cathode-side fluid distributor, the maximum superficial power density is 2230 W m−2 at 323 K and 105 kPa(abs). The latter superficial power density is almost 3.5 times higher than our previously reported superficial power density for the same catalyst combinations. Furthermore, with a Pt anode and Ag cathode catalyst combination, a superficial power density of 2500 W m−2 is achieved with superior performance durability compared to the MnO2 cathode. The fuel cell results are substantiated by impedance spectroscopy analysis and preliminary mathematical model predictions based on mixed potential theory.

Lattice Boltzmann method for shape optimization of fluid distributor

The shape optimization of a flat-type arborescent fluid distributor is studied for the purpose of process intensification, in which a shape optimization algorithm based on the lattice Boltzmann method (LBM) (Wang et al., 2010) is adopted with the objective of decreasing the flow resistance subject to the constraint of a constant fluid volume. Prototypes of the initial distributor as well as the optimized one are designed. Fluid distribution and hydraulic characteristics of these distributors are investigated numerically. Results show that the pressure drop of the optimized distributor is between 15.9% and 25.1% lower than that of the initial reference while keeping a uniform flow distribution, demonstrating the process intensification in fluid distributor, and suggesting the significance of the proposed optimization algorithm in engineering optimal design.

Three-dimensional multi-scale fluid distributor assembly minimizing total viscous dissipation

In this paper, a novel multi-scale transport network geometry has been addressed by means of constructal theory. The channel dimensions are given and justified with an engineering criterion into the design itself. The first stage of this work consists of assembly optimization, which is formulated as follows: find the distribution of channel radii and angle that minimizes total viscous dissipation (or pumping power, pressure drop) under the constraints of fixed total volume of channels and tube material consumed. Analytical resolutions of the problem of optimal channel size distribution for tree-like networks used as flow distributors are obtained. In the subsequent stages, a large number of flow configurations are constructed based on the optimal channel size. The resulting structure is an optimized multi-scale flow distributor. Furthermore, for such configuration, the equality of pressure drops ensuring flow rate uniformity at the outlet ports of the distributor is demonstrated theoretically. Finally, CFD simulations are employed to investigate fully developed smooth turbulent flow on different branch junctions. Numerical results are found to be in good agreement with predicted analytical results and support the relationship between the pressure drop and the liquid flow rate at the inlet port of the constructal liquid distributor.

Flow distribution property of the constructal distributor and heat transfer intensification in a mini heat exchanger

AbstractThis article reports a numerical and experimental study on flow maldistribution and heat transfer intensification in a mini heat exchanger with constructal distributor/collector integrated. The flow distribution characteristics of the constructal component functioning as a fluid distributor or as a fluid collector have been investigated and compared using computational fluid dynamics simulations. An experimental setup is designed and constructed for thermal and hydraulic performances tests. The effects of various assembly configurations on heat transfer characteristics and pressure drops are discussed. The results indicate that the integration of one constructal collector at the outlet of the heat exchanger can achieve almost uniform flow distribution and consequently better intensify the heat transfer. It is also the most advantageous configuration based on a balanced consideration of heat transfer intensification and pump power consumption under the investigation conditions. © 2008 American Institute of Chemical Engineers AIChE J, 2008

Critical evaluation and comparison of fluid distribution systems for industrial scale expanded bed adsorption chromatography columns

The hydrodynamic properties of an expanded bed contactor with 30 cm or 150 cm internal diameter, which employs a rotating or oscillating fluid distributor, were compared to prototype columns of 60 cm or 150 cm diameter employing local stirring (fixed wall nozzles plus central bottom mounted stirrer) for fluid distribution. Fluid introduction through a rotating fluid distributor was found to give superior hydrodynamic characteristics in the 30 cm and 150 cm diameter column compared to using the local stirrer in both the 60 cm and 150 cm diameter columns. The shortcomings of the local stirring distributor at large scale were apparent: dead zones were present which could not be removed by increasing rotation rates or flow rates, and such changes led to a deterioration in hydrodynamic properties. In contrast, during fluid introduction through a rotating distributor no dead zones were observed, and residence time distribution tests showed that plate numbers remained constant or increased slightly as flow rate was raised from 200 cm h −1 to 470 cm h −1. Under the conditions studied, oscillation of the rotating fluid distributor led to increased mixing and poorer performance than rotary movement. The results imply that further improvement in distributor design is needed and careful attention should be given to the trade off between turbulence and adequate fluid distribution.

Constructal approach and multi-scale components

The constructal approach, proposed by Bejan is an emergent notion which quickly develops at the international level and in a multi-disciplinary frame. It is a method of optimization of the conception of objects and “components” which allows finding the geometry of a multi-scale system in view of an optimal performance. The constructal concept, as the fractal concept, is a way of connecting the geometry of a microscopic world (the structures of an equipment or a material at the finest scales) with the macroscopic world in which it is immersed, through several intermediate scales. Essential differences with the fractal object are that the constructal object optimizes the passages from one scale to the other, that the geometry is not necessarily invariant from one scale to the other, and that there maybe some thermodynamic content to the optimization, such as minimizing entropy production. The present paper addresses these issues through several aspects: general introduction to the constructal approach; discussion of some examples of multi-scale components (heat exchanger, fluid distributor, coupling of fluid distributor to heat exchanger, mixer and its coupling to a micro reactor); manufacturing issues; perspectives for applications and for further scientific research.

Optimal distribution of viscous dissipation in a multi-scale branched fluid distributor

This paper examines some theoretical aspects of the optimal design of multi-scale fluid distributors or collectors, built on a binary or quaternary branching pattern of pores. The design aims to distribute uniformly a fluid flow over a specified square surface (uniform irrigation) while simultaneously minimizing the residence time, the residence-time distribution, the pressure drop and the viscous dissipation, leading to an optimization problem of the pore-size distribution, for both length and diameter. For the binary branching, the uniform distribution of outlet points requires a particular, non-monotonous scaling law for pore lengths, and this distinguishes the structure from fractal branching patterns that have been studied previously. The quaternary branching allows a fractal-type structure (constant scale ratios for both pore length and radius). An important general result is established: in the optimal pore-size distribution, the density of viscous dissipation power (W⋅m −3) is uniformly distributed over the volume at all scales.