Additional Baffles Research Articles

Catalytic oxidation of n-hexane in a fluidized bed with modified flow

The results of the n-hexane oxidation process in a fluidized bed reactor with a catalytic bed are presented. Additional baffles were located in the fluidized bed reactor, the purpose of which was to modify the flow in a way to increase the efficiency of the process, while maintaining constant values of the residence time of the reactants in the fluidized bed. The characteristics of a reactor without flow modifications and those of reactors using three types of baffles, two vertical and one of horizontal were compared. It turned out that the best results were achieved by a reactor using horizontal elements in the form of grids. Thanks to the use of a set of 3 meshes, it was possible to significantly improve the conversion of n-hexane to carbon dioxide. For example, at 350 °C it is possible to improve the full conversion of hexane from 85 to 97%. The oxidation efficiency is improved by reducing the size of the bubbles, which was visually confirmed. Additionally, the analysis of recorded pressure fluctuations was used to analyze flow of bubbles in the nonmodified and modified fluidized bed reactors. A relation between the recorded values of pressure fluctuations and chemical effects in the form of emissions of incomplete combustion products was shown. Baffles that improve n-hexane conversions also reduce the amplitudes of pressure fluctuations. In addition, the calculated values of bubble sizes in the reactor without modification and in the reactor modified with elements in a horizontal system are shown.

Numerical investigation of the flow inside a precession-driven cylindrical cavity with additional baffles using an immersed boundary method

In this paper, we present a numerical approach to solve the Navier–Stokes equations for arbitrary vessel geometries by combining a Fourier-spectral method with a direct-forcing immersed boundary method, which one allows to consider solid–fluid interactions. The approach is applied to a paradigmatic setup motivated by the precession dynamo experiment currently under construction at Helmholtz–Zentrum Dresden–Rossendorf. The experiment consists of a fluid-filled cylinder rotating about two axes, which induces a precession-driven flow inside the cavity. The cylinder is also equipped with baffles at the end caps with adjustable penetration depth to impact the flow. The numerical details and simulation results for the spin-up and precession-driven flow in a circular cylinder with additional baffles are presented. The results provide a first confirmation that the use of such baffles in the precession dynamo experiment is a useful way of influencing the flow, allowing more efficient driving without changing the known flow structure too much.

Experimental Study on the Impact Dynamics of Cylindrical Baffles with a Rigid Barrier against Debris Flows

The use of baffle arrays behind a rigid barrier is an effective method to reduce impact force by dissipating flow energy with filtering boulders from debris flows. To prevent structural damage of the rigid barrier, appropriate configurations of the baffle arrays are needed; however, design guidelines for the geometric construction of baffle arrays have not yet been proposed. One of the major challenges in designing multiple structures (baffles and a rigid barrier, etc.) is to set up a framework for a safe and economical design. The flow–structure interaction and impact force of debris flows on a rigid barrier are affected by the configuration of baffles installed behind the rigid barrier. In this study, to evaluate the flow behavior and the dynamic impact force on the terminal barrier after the flow has passed through the baffle arrays, we conducted a series of small-scale flume tests under various baffle heights and a number of rows. The test results revealed that the installation of baffles reduced the run-up height and the impact force on the terminal rigid barrier. The flow impedance induced by baffles had a significant influence on the dissipation of the kinetic energy of debris flows. Moreover, additional baffle rows produced a greater reduction in the run-up and impact force by decreasing debris flow and boulder mobility.

Experimental analysis of an improved cascade solar desalination still with modified absorber plate

Solar desalination is becoming more reliable and common especially in developing countries where receive sufficient sunshine throughout the year. In addition, solar still devices are considered as one of the cheapest and simplest desalination methods depends on solar energy, but suffer from low productivity. This work presents an experimental analysis of the performance and productivity of novel cascade solar still with a modified absorber plate with additional baffles on the slope surfaces as a new attempt to enhance the productivity of solar stills. The solar intensity was taken as input and the productivity as output are considered for evaluating the solar still in order to examine the effect of the modified absorber plate on the performance and productivity of novel cascade solar still.

Improving the Cascade Solar Still Performance Using Baffles Fixed on the Absorber Plate: Experimental Study

This work presents an experimental study of novel cascade solar still with baffles. Cascade solar still has been fabricated and tested experimentally, then modified by fixing additional baffles to sloped absorber surfaces. This modification enhances the evaporative surface area and the solar energy receiving area, resulting in an increase in the productivity of the still. The influence of solar radiation, glass cover temperature, basin water temperature, hourly and the daily productivity of cascade solar stills with baffles and without baffles have been studied. Experimentation has been conducted to compare the performance of the cascade solar still with baffles and cascade solar still without baffles. The experimental results have showed that the cascade solar still with baffles has produced higher distillate output in comparison to the cascade solar still without baffles. Furthermore, the cascade solar still with baffles has enhanced the productivity by 46% compared to the cascade solar still without baffles. The higher daily productivity obtained during the experimentation of both cascade solar stills with baffles and without baffles has been about 2.443 kg/m2 day, 1.732 kg/m2 day, respectively. Whereas, the thermal efficiency of cascade solar still with baffles has been 40% and the one of the cascade solar still without baffles has been 30.43%.

Design Analysis and performance evaluation of 3D printed baffle path diverters in hydraulic noise suppressor

The pump in the hydraulic systems is the main source of noise in form of vibrations or pulsations while noise reduction is an important part of pump design still some ripples are produced by the pump termed as pulsations. Pulsations result in line vibrations which cause additional noise. How much ripple the pump produces cannot be changed, so other ways to an average of 50 dB(A) to 60 dB(A) level of noise is often considered to safe, although the noise levels resulting due to pulsations are seen to be in ranges as high as 130 t 0 150 dB(A) that result in hose and piping failures and also results in damage to components like seals and valves. Through the introduction of a compressible membrane in the path with additional baffles for muffling of the noise the proposed solution is in the form of hydraulic noise reducer that incorporates both the compressible membrane as well as the baffle path diverter. Objective of paper is carried out the performance evaluation of the hydraulic noise reducer with elastomer membrane for noise reduction mechanism in conjunction to baffle type path diverters to even out the fluid pulsations or ripple to minimal without much pressure drop across the device to achieve minim; pumping losses. The paper discusses the performance evaluation of the diverter. The has been tested to determine mass flow rate and pressure drop. Experimental has been manufactured and test has been conducted to evaluate reduction in noiselevelinwithandwithoutthe3-dprintedbaffle arrangement and comparison has been carried out.

FP-TES: A Fluidisation-Based Particle Thermal Energy Storage, Part I: Numerical Investigations and Bulk Heat Conductivity

Renewables should become more continuously available, reliable and cost-efficient to manage the challenges caused by the energy transition. Thus, analytic and numerical investigations for the layout of a pilot plant of a concept called Fluidisation-Based Particle Thermal Energy Storage (FP-TES)—a highly flexible, short- to long-term fluidised bed regenerative heat storage utilising a pressure gradient for hot powder transport, and thus enabling minimal losses, high energy densities, compact construction and countercurrent heat exchange—are presented in this article. Such devices in decentralised set-up—being included in energy- and especially heat-intensive industries, storing latent or sensible heat or power-to-heat to minimise losses and compensate fluctuations—can help to achieve the above-stated goals. Part I of this article is focused on geometrical and fluidic design via numerical investigations utilising Computational Particle Fluid Dynamics (CPFD). In the process a controlled transient simulation method called co-simulation of FP-TES is developed forming the basis for test bench design and execution of further co-simulation. Within this process an advanced design of rotational symmetric hoppers with additional baffles in the heat exchanger (HEX) and internal pipes to stabilise the particle mass flow is developed. Moreover, a contribution bulk heat conductivity is presented to demonstrate low thermal losses and limited needs for thermal insulation by taking into account the thermal insulation of the outer layer of the hopper.

A numerical analysis of heat transfer in a cross-current heat exchanger with controlled and newly designed air flows

AbstractSimulations of heat transfer between air and flue gases in a plate heat exchanger are presented. The device was designed for the heating of the air supplying a fluidised furnace for the combustion of wet sludge and wood crumbs. The locations of inlets and outlets and the geometry of the heat exchanger are determined by the construction of the furnace. The aim of the simulations was to increase effectiveness of heat transfer through the use of flow redirections with additional baffles placed in the air chamber. The results of the simulations showed that a substantial part of the heat exchanger without baffles is not used effectively. On the basis of a velocity profile, a temperature distribution and a wall heat flux, the geometry of the inter-plate space within the air chamber was modified by adding baffles. The unmodified exchangers had 77% efficiency in comparison to counter-current exchangers with the same heat transfer area. After the application of baffles, the efficiency increased to 83-91% depending on the construction used (one, two or three baffles). The best model variant of the exchanger with baffles led to the increase in the temperature of air supplying the fluidised bed by approximately 76 K in relation to the system without baffles . Unexpectedly, the presented modifications of the geometry of the system had very low influence of the flow resistance in the air chamber. The value of Δp for the system without baffles is almost the same as for the best model variant.

On the mechanism of pressure rise in vented explosions: A numerical study

Abstract Accidental gas explosions are a significant concern in process industries. In an explosion event, the promotion of flame acceleration due to turbulence generated from obstacles is responsible for many severe damages. This paper discusses the numerical evaluation and the mechanism of pressure rise in vented explosions in the presence of obstructions using computational fluid dynamics (CFD). The large eddy simulation (LES) technique is employed with a dynamic flame surface density (DFSD) in the combustion model to account for the filtered chemical source term. The experimental test case considered for the validation of simulations is a small-scale explosion chamber with removable baffle plates and obstacles. It is found that the maximum overpressure increases with the baffle plates moved downstream from the ignition source or when additional baffles are placed in sequence. Large separation between baffles and the central obstacle results in lower overpressure due to the relaminarisation of the flame front. The trend of explosion overpressure is related to the competition between the strength of venting and expansion in the explosion chamber. Extensive interactions between the flame and the obstruction-generated turbulence are found to wrinkle the flame front and increase the burning rate. Satisfactory agreements have been obtained between LES and the experimental data. This confirms the capability of the developed model in predicting essential safety-related parameters in vented explosions. Results reveal the potential of using LES in the selection of design aspects for loss prevention, such as the area of vents and distance between congested regions in chemical processing plants.

Effect of baffle spacing and baffle cut on thermal-hydraulic characteristics of the fluid flow

This article presents the results of investigations of the influence of baffle spacing and baffle cut on the size of dead zone formed near the cross baffles using numerical simulation methods. It is showed the structure of an additional baffle plate which can be used to reduce the dead zone and smoother flow distribution over the cross section.

THE USE OF ADDITIONAL BAFFLES TO IMPROVE EFFICIENCY OF SHELL-AND-TUBE HEAT EXCHANGER

This article is devoted to the study of fluid flow in the shellside of shell-and-tube heat exchanger. Heat transfer in shell-and-tube heat exchangers is a complex process depending on many factors: the fluid properties, the geometric parameters of the flow region, the quality of the heat transfer surface caused by physical properties, surface roughness and fouling rate Selection of the optimum ratio of geometrical parameters in order to achieve maximum energy efficiency of the heat exchanger must be based on the study of thermal and hydraulic characteristics of the flow. The most effective method for studying hydrodynamic and heat transfer processes is now the method of computational fluid dynamics implemented in finite element analysis systems. Advantages of CFD is the high speed of calculation, the accuracy and completeness of the result data, which gives an understanding of distribution and flow rates in the apparatus, pressure drop of the interior space as a whole and its individual regions. The article describes a finite element model of the heat exchanger. Model consists of three domains (tubeside, metal pipe, shell-side) and the domain interfaces. The simulation results give a complete picture of the distribution of of thermal and hydraulic parameters. Of particular interest is the flow in the shell-side, that has a more complex configuration. Simulation allowed us to estimate the distribution of the fluid flow, to determine the qualitative and quantitative characteristics of the influence of gaps and baffle spacing. The efficiency of heat transfer in STHE can be increased by restricting dead zones formed near the cross baffles. For this purpose, еру use of the additional baffles, promoting more uniform flow distribution is offered. The results of investigations of the additional baffles influence on efficiency of heat transfer in shellside were carried out in this article.

Numerical simulation of air purging conditions during steel sheet temper rolling process

The application of the lubricant in the temper rolling process of tinplate manufacturing improves the mechanical properties and surface quality of the steel sheet. The removal of the residual lubricant deserves and has rarely been studied via numerical simulation. A simplified model of a single stand temper mill was established and was discretized into cells of block-structured grids. The criterion whether the lubricant could be removed was decided via multiphase simulation of a smaller model. Three parameters, the gap between the deflector and the rolls, the length of an additional baffle and the velocity of the purging air, were considered and scores of different working conditions were performed. The shapes of the steel sheet between the temper rolls and the bridle roll were also studied to screen out the conditions that the sheet could move steadily.

파이롯 규모 SI 공정 시험 설비에서의 헬륨 가열 장치 설계

In this study, researchers performed preliminary design and numerical analysis for a pilot-scale helium heating system in- tended to support full-scale construction for a sulfur-iodine (SI) cycle. The helium heat exchanger used a liquefied petroleum gas (LPG) combustor. Exhaust gas velocity at the heat exchanger outlet was approximately 40 m/s based on computational thermal and flow analysis. The maximum gas temperature was reached with six baffles in the design; lower gas temperatures were observed with four baffles. The amount of heat transfer was also higher with six baffles. Installation of additional baffles may reduce fuel costs because of the reduced LPG exhausted to the heat exchanger. However, additional baffles may also increase the pressure dif- ference between the exchanger's inlet and outlet. Therefore, it is important to find the optimum number of baffles. Structural analy- sis, followed by thermal and flow analysis, indicated a 3.86 mm thermal expansion at the middle of the shell and tube type heat exchanger when both ends were supported. Structural analysis conditions included a helium flow rate of 3.729 mol/s and a helium outlet temperature of 910°C. An exhaust gas temperature of 1300°C and an exhaust gas rate of 52 g/s were confirmed to achieve the helium outlet temperature of 910°C with an exchanger inlet temperature of 135°C in an LPG-fueled helium heating system.

ELECTROSTATIC ION THRUSTERS - TOWARDS PREDICTIVE MODELING

For satellite missions, thrusters have to be qualified in large vacuum vessels to simulate space environment. One caveat of these experiments is the possible modification of the beam properties due to the interaction of the energetic ions with the vessel walls. Impinging ions can produce sputtered impurities or secondary electrons from the wall. These can stream back into the acceleration channel of the thruster and produce co-deposited layers. Over the long operation time of thousands of hours, such layers can modify the optimized geometry and induce changes of the ion beam properties, e.g. broadening of the angular distribution and thrust reduction. To study such effects, a Monte Carlo code for the simulation of the interaction of ion thruster beams with vessel walls was developed. Strategies to overcome sputter limitations by additional baffles are studied with the help of this Monte-Carlo erosion code.<br /><br />

Analysis for heat transfer enhancement of helical and electrical heating tube heat exchangers in vacuum freeze-drying plant

This paper investigates the heat transfer rate of the combined cooling-and-heating heat exchanger by using computational fluid dynamics (CFD) method. Several factors, such as additional baffles and heat transfer areas, are also discussed in order to improve the efficiency of heat exchanger in the vacuum freeze-drying system. The simulated result indicated that, for addition electrical heating tube, the heat transfer rate of the heat exchanger increased with the increasing length of the electrical heating tube. The increasing rates of secondary and primary drying stages were 2.774 and 2.986W/mm, respectively. For additional vertical baffle, the variation of the heat transfer rate with respect to vertical baffle length was in the U-shape format. The minimum heat transfer rates of secondary drying, primary drying and freezing stages were 716.79W and −195.17W and −670.71W, respectively. For additional W-shape vertical baffles, the heat transfer rate of this heat exchanger was maximum among these four designs. For the three stages of heat exchangers with these four designs, the shell side Nusselt number had the inverse linear relationship with the Reynolds number.

CFD Optimization of Gas-Side Flow Channel Configuration Inside a High Temperature Bayonet Tube Heat Exchanger With Inner and Outer fins

In this paper, the gas-side fluid flow distribution inside a bayonet tube heat exchanger with inner and outer fins is numerically studied. The heat exchanger is designed based on the traditional bayonet tube heat exchanger, where compact continuous plain fins and wavelike fins are mounted on the outside and inside surfaces of outer tubes, respectively, to enhance the heat transfer performance. However, gross flow maldistribution and large vortices are observed in the gas-side flow channel of baseline design. In order to improve the flow uniformity, three modified designs are proposed. Three vertical plates and two inclined plates are mounted on the inlet manifold for Model B. For the Model C, another six bending plates are mounted on the middle manifolds and three pairs of them are connected together. The Model D has a similar structure as Model C except for the two additional baffles. The results indicate that the flow distributions of Models C and D are much more uniform under different inlet Reynolds number, especially in the high inlet Reynolds number. Although the flow distribution of Model D is the best, its pressure drop is 2.6 times higher than that of Model C. Therefore, the design of Model C is the most optimized structure. Compared with the original design, the nonuniformity of Model C can be reduced by 42% while the pressure drop is almost the same under the baseline condition.

Study of a Closed Divertor Configuration for the Three-Dimensionally Complicated Magnetic Structure in the LHD Plasma Periphery

The distribution of strike points in a closed divertor configuration with additional baffle plates installed in the toroidal ends of closed divertor components near lower/upper ports is calculated by tracing magnetic field lines from the last closed flux surface in various magnetic configurations (radial position of the magnetic axis, Rax = 3.50 ∼ 3.90 m). The calculation shows that the ratio of the number of strike points on additional plates is maximum for Rax = 3.60 m, showing that the plates are effective in this magnetic configuration. Neutral particle transport is investigated using a fully three-dimensional code EIRENE with one-dimensional plasma fluid analysis of divertor legs, where the plasma parameter profiles on the legs are obtained by an iterative calculation including interaction processes between the plasma and neutral particles. The plates raise the pressure of molecular hydrogen locally near the baffle plates to more than 0.2 Pa, which is enough for efficient particle control using vacuum pumping systems installed near the plates. The simulation proposes one possible candidate of optimized closed divertor configuration for the three-dimensionally complicated magnetic structure in the LHD plasma periphery.

A Computational Fluid Dynamics Based Integrated Disinfection Design Approach for Improvement of Full-scale Ozone Contactor Performance

A three-dimensional multiphase computational fluid dynamics (CFD) model has been developed, to address all the major components of ozone disinfection processes at the Charles DesBaillets Water Treatment Plant in Montréal, Canada. Good agreement was observed between the numerical results and full-scale tracer data. The CFD predicted flow fields showed that recirculation zones and short circuiting existed in the DesBaillets contactors. Installation of four additional baffles in the second chamber would significantly improve contactor mixing performance. The modeling results also indicated that ozone residuals at the cross section of the outlet of each chamber were very sensitive to the locations of monitoring points.

Gas–liquid and liquid–solid mass transfers in two types of stationary catalytic basket laboratory reactor

Measurements of gas–liquid and liquid–solid mass transfer coefficients were performed in two types of three-phase laboratory reactor equipped with stationary catalytic basket and multiple impeller. Those reactors are called Robinson–Mahoney reactors. Local liquid–solid mass transfer coefficients were measured using naphtol particle dissolution in n-heptane at several agitation speeds. Experiments had shown that local coefficients depended on the particle locations in the basket and agitation speeds. The local coefficient values and profiles were quite similar for both studied reactors even though the reactor designs were different. Similar values of RM basket thicknesses might account for this phenomenon because the liquid–solid mass transfers could be correlated with the ones in packed beds with forced liquid circulation. Gas–liquid mass transfer coefficients were measured using standard dynamic absorption methods in air–water or hydrogen–gas oil system. As in stirred tanks, the gas–liquid mass transfers were linked to the impeller designs and characteristics (gas-inducing or classical impeller) and to the operating conditions such as agitation speeds and fluid properties. However, correlations applicable to stirred tank reactors can be used with Robinson–Mahoney reactors, the baskets behaving like additional baffles or reduction of tank diameters.

FORCE COMPARISON OF AIR CURRENTS PRODUCED BY A STANDARD AND MODIFIED INFUSION CANNULA

To develop and characterize an infusion cannula that reduces the intraocular jet forces created during fluid-air exchange. A new infusion cannula was manufactured by adding a baffle 1.0 mm perpendicular to the distal opening of a 20-gauge infusion. The forces generated by the modified and standard cannulas were measured at a constant air infusion pressure of 50 mmHg by using a force sensor coupled to a schematic eye with eight radial positions from 0 degrees to 180 degrees along the circumference. Five different orientations relative to the baffle support of the modified cannula were evaluated at each position to assess the turbulent flow. The standard cannula produced a maximum force of 0.14 mmHg at 180 degrees from the sensor. The modified cannula generated a maximum pressure of 0.017 mmHg at 67.5 degrees from the sensor. Overall, the force from the modified cannula was an order of magnitude less than the standard infusion cannula (P < 0.01). The modifications of the new infusion cannula are passive with respect to its surgical performance. However, the additional baffle transforms laminar air currents into turbulent ones and allows dispersion of the jet forces, which should reduce barotrauma and desiccation of the retina during fluid-air exchange.