Cut Size Diameter Research Articles

Multi-Objective optimisation of oil demisters geometry for Ultra-Low charge ammonia chillers

Driven by global climate objectives, the pursuit for eco-friendly refrigeration solutions has catalysed impressive advancements in the sector. Ammonia, a historically utilized refrigerant, is now widely adopted in light industrial applications, largely due to the growth of Ultra-Low Charge package chillers. Opportunities, however, persist for refining system components to further diminish refrigerant charge, fostering safer and more efficient solutions. This paper focuses on optimizing the oil separator geometry of an experimentally tested Ultra-Low Charge ammonia chiller. The principal aim and novelty is to lower the specific refrigerant charge while enhancing the separation efficiency and the pressure drop performance. Assessing the separation efficiency involves an analytical model grounded in the “orbit-equilibrium” concept, while the pressure drop is evaluated with consideration of liquid particles presence. Utilizing the validated model, a Multi-Objective Optimization process driven by the eaMuPlusLambda algorithm produces geometries able to reduce the cut-size diameter by 1.4 % up to 15.4 %, pressure drop by 66.7 % up to 89.1 %, and internal volume by 51.3 % up to 68.9 %, compared to the baseline setup. This accomplishment stems from meaningful parameter adjustments, encompassing a 12.1 – 30.0 % decrease in the main diameter, 35.8 % reduction in the main height, 25.4 – 41.2 % contraction in the outlet diameter, 10.9 – 47.1 % augmentation in the inlet diameter, and the vortex finder elimination. Consequently, this translates to a 5% to 14% decrease in the chiller’s specific charge. This study intends an initial step in optimizing oil separators for Ultra-Low Charge ammonia chillers, presenting prospects for specific charge reduction and inciting further exploration through experimental testing or Computational Fluid Dynamics.

The effects of inlet number and positions on the flow pattern and performance of a Stairmand cyclone

This study conducts numerical investigations to analyze the influence of inlet number and vertical positioning on flow patterns, collection efficiency, pressure drop, and efficiency of Stairmand cyclones. The maximum displacement of inlets is considered approximately equal to the cyclone diameter, and the inlets are arranged in a gradual manner. The Reynolds Stress Turbulence model (RSM) was employed to calculate flow properties in turbulent conditions. Out of the 44 cases examined, the four-inlet cyclone with L4=0.1 exhibited the smallest cut-size diameter, while the single-inlet cyclone with L1=0.9 displayed the lowest pressure drop. Notably, shifting one of the inlets of the two-inlet cyclone by 20% relative to the cyclone diameter resulted in higher pressure levels on the cyclone wall compared to other geometries explored in this study. Collection efficiency in cyclones is generally enhanced by an increase in tangential velocity, but it is also influenced by the position of the inlet(s).

Cut-Size Diameter Calculation of Salt Crystals From A Hydrocyclone

A hydrocyclone is physical separation equipment employed in solid-liquid processing. An important parameter in hydrocyclone design is the so-called cut-size diameter (D50), which determines the minimum size of the separated solids when the equipment performs at 50% separation efficiency. This paper discusses the calculation of the cut-size diameter (D50) of a hydrocyclone operating in a salt purification pilot plant in Manyar, East Java, Indonesia. The cut-size D50 is calculated based on the residence time approach and compared with the collection efficiency from the mass balance. D50 was found to be 69.73 microns. Moreover, by using Zanker’s nomograph, it was found that at the solid separation efficiency of 80.48%, the minimum diameter of salt crystal (Dmin) is 85 microns. Because the D50 of HC-1 is smaller than Zanker’s design, it can be concluded that the hydrocyclone will work efficiently in separating the expected products.

Computational Study of Operating Parameters on Performance of Compound Hydrocyclone

The dynamics of hydro cyclones is complex, because it is a multiphase flow problem that involves interaction between a discrete phase and multiple continuum phases. The performance of hydro cyclones is evaluated by using Computational Fluid Dynamics (CFD), and it is characterized by the pressure drop, split water ratio, and particle collection efficiency. In this paper, a computational model to improve and evaluate hydro cyclone performance is proposed. Computational turbulence models (renormalization group (RNG) k-ε, Reynolds’s stress model (RSM), and large-eddy simulation (LES)) are implemented, and the accuracy of each for predicting the hydro cyclone behavior is assessed. Four hydro cyclone configurations were analyzed using the RSM model. By analyzing the streamlines resulting from those simulations, it was found that the formation of some vortices and saddle points affect the separation efficiency. Furthermore, the effects of inlet width, cone length, and vortex finder diameter were found to be significant. The cut-size diameter was decreased compared to the Hsieh experimental hydro cyclone. An increase in the pressure drops leads to high values of cut-size and classification sharpness. If the pressure drop increases to twice its original value, the cut-size and the sharpness of classification are reduced to their initial values, respectively.

Particle separation of a modified feed nozzle hydrocyclone under different operating parameters

During the operation of the hydrocyclone the cut size diameter is the most important data. This is connected to feed rate, which is closely related to the feed cross section. Preliminary research has revealed that square cross-section is more effective than circular cross-section. The research compared 2 types of feed cross sections at 5 different feed rates. One is a standard rectangular cross-section and the other is a square cross-section that narrows with a baffle plate. Preliminary calculations for cut size diameter have shown that better particle separation at all speeds can be achieved with the baffle plate solution. In both types, the increased velocity created decreased cut size diameter. During the simulation, the baffle plate did not cause any abnormalities in the internal pressure and velocity distributions. The simulation revealed that the particles did not behave as previously calculated.

CFD Modeling of Hydrocyclones—A Study of Efficiency of Hydrodynamic Reservoirs

The dynamics of hydrocyclones is complex, because it is a multiphase flow problem that involves interaction between a discrete phase and multiple continuum phases. The performance of hydrocyclones is evaluated by using Computational Fluid Dynamics (CFD), and it is characterized by the pressure drop, split water ratio, and particle collection efficiency. In this paper, a computational model to improve and evaluate hydrocyclone performance is proposed. Four known computational turbulence models (renormalization group (RNG) k- ε , Reynolds stress model (RSM), and large-eddy simulation (LES)) are implemented, and the accuracy of each for predicting the hydrocyclone behavior is assessed. Four hydrocyclone configurations were analyzed using the RSM model. By analyzing the streamlines resulting from those simulations, it was found that the formation of some vortices and saddle points affect the separation efficiency. Furthermore, the effects of inlet width, cone length, and vortex finder diameter were found to be significant. The cut-size diameter was decreased by 33% compared to the Hsieh experimental hydrocyclone. An increase in the pressure drop leads to high values of cut-size and classification sharpness. If the pressure drop increases to twice its original value, the cut-size and the sharpness of classification are reduced to less than 63% and 55% of their initial values, respectively.

Effect of changes in the feed duct on hydrocyclone performance

In recent years, hydrocyclones have been studied to improve their performance. This study aimed to evaluate the modification of the feed duct of a hydrocyclone from circular to square and rectangular using 3D CFD simulations under single-phase to assess the flow hydrodynamics. The simulations suggest that a non-circular feed duct provided small changes in Euler numbers (Eu), suggesting improvements in the classification efficiency. As indicated in the simulations, experimental tests performed with circular duct and square feed duct hydrocyclones, using a diluted aqueous quartzite suspension (1% v/v), provided increases of 7.6% and 12.5% in the underflow-to-throughput ratio and Euler number, respectively, and a 32% decrease in the cut size diameter for the square feed duct compared to standard hydrocyclone. Therefore, a simple change in the shape of the hydrocyclone feed duct improves the solids separation performance of equipment previously designed for high separation efficiency.

Improvement of collection efficiency in a cyclone separator using water nozzles: A numerical study

Wet cyclonic separators can be a viable solution for process intensification of gas-cleaning in industries. Owing to the difficulty of modeling interactions between droplets and particles as well as the high computational effort needed to simulate this process, this field has been rarely studied. In this study, a model for determining the collection efficiency of a cyclonic scrubber for gas-cleaning was applied by combining a mechanistic model for kinematic coagulation with Euler–Lagrange computational fluid dynamics (CFD) simulations to predict gas-particle and gas-droplet flows. The calculation results show that cyclonic scrubbers are highly efficient mainly for smaller particles, as the cut-size diameter reduced about 55% and the overall efficiency increased around 11% when compared to the conventional dry cyclone of same size operating under the same conditions. The results also confirm that the particle residence time has a lower influence on the gas-cleaning factor than the size of the particle interacting with a range of droplet diameter distribution.

The effect of particle humidity on separation efficiency for an axial cyclone separator

The objective of this study is to investigate the effects of particle humidity on the inlet particle size distribution, overall efficiency, grade efficiency and cut size diameter for an axial cyclone separator with inner diameter of 150 mm. The collection and grade efficiencies of the cyclone separator were measured by on-line method for inlet velocities, particle concentration and particle humidity in the ranges of 12–18 m/s, 30–500 mg/m3 and 8–30‰, respectively. By employing a set of fixed parameters for inlet velocity and particle concentration, the effect of particle humidity on separation efficiency was investigated. The experimental results show that the volume ratio of larger particle increases with the increasing of particle humidity due to particle agglomeration. When the inlet velocity and particle humidity remain constant, the collection and grade efficiencies improve greatly as the increasing of the particle concentration because of the particle aggregation. However, it was noticed that the grade efficiencies did not always increased with the increasing of particle humidity under the same conditions of inlet velocity and particle concentration. The trends of grade efficiency curves for different particle humidity change at the particle diameter of approximately 10 μm. The grade efficiency improves with the increasing of particle humidity when the particle diameter is larger than 10 μm, while a contrary tendency is observed when the particle diameter is smaller than 10 μm.

Optimizing swirl in compact uniflow cyclones

This paper presents an experimental examination of the velocity field distribution in the separation chamber of a uniflow cyclone with closed particle outlet to evaluate the swirl characteristics in the vortex finder region based on stereoscopic particle image velocimetry. A cold flow model with a closed particle outlet was used to assess different angles of attack and core size ratios at typical Reynolds numbers for the separation of low loaded gas‐solid flows. The focus of the study was on the relationship between swirl strength as well as performance data. At higher angles, the parabolic swirl strength distribution changed to a region with constant high acceleration of the particles in the separation zone. Integral and differential swirl numbers were correlated with the ratio of tangential to radial velocity and to the calculated cut size diameter. At low angles of attack, implying a strong redirection of flow perpendicular toward the main flow direction and small core size ratios, defined by the radial distance between hub and tip, the local differential swirl number can be more than twice as large as in the base configuration. Yet, the integral swirl number hardly changed. The velocity fields showed mean tangential to radial velocity ratios ranging from 0.73 to 6.85 at swirl vane angles of 15 °–60 °; core size ratios between 0.125 and 0.625 at vortex finder diameter were measured and calculated cut size diameters between 10 and 90 μm were derived. This data provides the foundation for further validation studies and the development of new design criteria. © 2018 American Institute of Chemical Engineers AIChE J, 65: 766–776, 2019

Study of the Influence of the Underflow Diameter on the Separation Process of an Optimized Hydrocyclone for Concentration Purposes

Hydrocyclones are equipment typically used in solid-liquid separation. Such equipment can be used with the purpose of classifying particles or concentrating suspensions. In this context, a new filtering hydrocyclone was conceived through Surface Response and Differential Evolution Algorithm techniques in order to optimize the Euler’s number. Based on this optimized geometry, the aim of the present paper was to verify the influence of the underflow diameter on the overall separation process at 147 kPa on the same optimized hydrocyclone geometry, but without the filtration effect, by performing laboratory experiments and CFD simulations using the commercial software Fluent®. The results showed that the use of the smallest underflow diameter increased up to 44% (v/v) the concentration of the underflow stream, compared to the suspension initially fed, with an Euler’s number of 862. Despite a small decrease (14%) in the total efficiency and an increase from 12.01 to 16.05 of the reduced cut size diameter, compared to the underflow diameter originally used in the optimization procedure, the benefits of recovering liquid by reducing the underflow diameter outweigh these disadvantages.

Development and characterization of an ice-selecting pumped counterflow virtual impactor (IS-PCVI) to study ice crystal residuals

Abstract. Separation of particles that play a role in cloud activation and ice nucleation from interstitial aerosols has become necessary to further understand aerosol-cloud interactions. The pumped counterflow virtual impactor (PCVI), which uses a vacuum pump to accelerate the particles and increase their momentum, provides an accessible option for dynamic and inertial separation of cloud elements. However, the use of a traditional PCVI to extract large cloud hydrometeors is difficult mainly due to its small cut-size diameters (< 5 µm). Here, for the first time we describe a development of an ice-selecting PCVI (IS-PCVI) to separate ice in controlled mixed-phase cloud system based on the particle inertia with the cut-off diameter ≥ 10 µm. We also present its laboratory application demonstrating the use of the impactor under a wide range of temperature and humidity conditions. The computational fluid dynamics simulations were initially carried out to guide the design of the IS-PCVI. After fabrication, a series of validation laboratory experiments were performed coupled with the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) expansion cloud simulation chamber. In the AIDA chamber, test aerosol particles were exposed to the ice supersaturation conditions (i.e., RHice > 100 %), where a mixture of droplets and ice crystals was formed during the expansion experiment. In parallel, the flow conditions of the IS-PCVI were actively controlled, such that it separated ice crystals from a mixture of ice crystals and cloud droplets, which were of diameter ≥ 10 µm. These large ice crystals were passed through the heated evaporation section to remove the water content. Afterwards, the residuals were characterized with a suite of online and offline instruments downstream of the IS-PCVI. These results were used to assess the optimized operating parameters of the device in terms of (1) the critical cut-size diameter, (2) the transmission efficiency and (3) the counterflow-to-input flow ratio. Particle losses were characterized by comparing the residual number concentration to the rejected interstitial particle number concentration. Overall results suggest that the IS-PCVI enables inertial separation of particles with a volume-equivalent particle size in the range of ~ 10–30 µm in diameter with small inadvertent intrusion (~ 5 %) of unwanted particles.

Residual moisture content and separation efficiency optimization in pilot-scale vibrating screen

Vibrating screening is still one of the main operations considering solid–solid and solid–liquid separation processes. Although it is an equipment of simple design and execution, the full description of a screening unit operation may be difficult to predict, considering that several operational variables can influence it. Therefore, the main objective of this work was to evaluate the best possible combination between the process variables screen aperture size, the volumetric concentration of solids in the feed, and the g-force (measurement of the vibration). This configuration predetermined values for moisture content of the retained material over the screen and separation efficiency regarding particle size. For this, a suspension of phosphate rock concentrate (with a particle density of 3.25g/cm3 and average particle size of 95μm) was diluted in water to perform the experiments in a pilot-scale vibrating screen. The results were analyzed statistically and correlations for each response were fit. The highest values of separation efficiency were found with the lowest values of cut-size diameter, which is desirable in terms of separation. A multi-objective optimization in the experimental range was developed, finding the optimal point for the moisture content of 17.29% and the separation efficiency of 86.88%. The effects of screen aperture size and g-force had important roles in this study.

An empirical investigation into the influence of pressure drop on particle behaviour in small scale reverse-flow cyclones

The operation of small scale reverse-flow cyclones under high flow rates and light solid loadings is poorly understood. This empirical study extends previous investigations into the relationship between particle behaviour and cyclone operating conditions. Previous work concluded that particle agglomeration and attrition occurring in a small scale Stairmand cyclone were heavily dependent on inlet velocity. We report on the performance of two cyclones with similar geometries, but with a 66.2% difference in their vortex finder diameters. Despite inlet velocities that differ by less than 5.7%, the relative pressure drops vary between 96.5 and 105.7% from each other, which contributes to a significant difference in the separation efficiency curves of the two cyclones. The smaller vortex finder diameter produces superior separation efficiency and increased particle attrition. This implies that pressure drop across the cyclone and not inlet velocity is the critical parameter when considering particle behaviour in cyclones of different designs. The study also demonstrates the non-linear relationship between particle cut-size diameter and pressure drop, implying that the cut-size diameter may approach an optimum size. Further to these investigations the study reports near identical separation efficiency curves produced by two geometrically dissimilar cyclones. Although the inlet and vortex finder velocities of the two cyclones differ by 41.0% and 65.3% respectively, there is only a 2.1% difference in pressure drop. This observation prompts the suggestion that the influence of pressure drop on separation efficiency is greater than considerations of cyclone geometry and scale.

EFFECT OF CYCLONE INLET VELOCITY AND VORTEX FINDER HEIGHT ON COARSE WHEAT BRAN DUST SEPARATION

Experimental study was performed for evaluating a vast number of equations derived from reviews to determine the performance of cyclone for overall collection efficiency, cut size diameter and pressure drop of cyclone. These equations were used based on the geometrical design of cyclones for operation at the ambient temperatures under different vortex finder heights (0.0, 0.05, 0.10, 0.15 and 0.20 m) and inlet velocities (9.3, 11.5, 18.5, 25.4 and 28.3 m/s). The cut size diameter of coarse wheat bran as inlet dust was estimated using direct empirical method and by Stock's number based on Euler's number. Both methods were also used to predict the overall collection efficiency. Experimental data were compared with the predictions of Lapple's theory and Iozia & Leith's logistic method. The results showed that only the pressures drop based on Cocker model in the range of 9.3 to 18.5 m/s inlet velocity proved accurate predictions. The operation at inlet velocity of 18.5 m/s was the best operational condition due to high collection efficiency of 96.4, 98.9, 98.5, 98.3 and 98.7%; and low pressure drop of 1173, 1324, 1249, 1137 and 1419 Pa at vortex finder height of 0.0, 0.05, 0.10, 0.15 and 0.20 m respectively, across the cyclone.

Flow pattern within hydrocyclone

The paper deals with the measurement methods of tangential, radial, axial velocities evolving in hydrocyclone and the characteristics of the velocity distributionsdefined in the course of the experiments. The definition of the cut-size diameter based on the so-called equilibrium model requires a review according to the authors. In the sense of the model there are only twoo forces acting on a unique particle settling: the centrifugal force and the one, opposite of the motion, resistance strength, and it does not take into consideration, that liquid flows in hydrocyclon. In the hydrocyclone the medium flowing inwards from the tapered cloak wall has a transport velocity and so an effect on the settling onto a particle may not be apart from attention to let. In the hydrocyclone the phenomenon of an air core taking shape in his axis line was explained by means of the basis equations of the hydrostatics till now. The authors demonstrated that the development of the air core is justifiable also with the necessities of the rotating bowls on an actual example.

Model based prediction of required cut size diameter for fractionation of fly ash from a grate-fired wood chip incineration plant

Utilization of biomass ash as a soil improvement material is limited by the admissible input of heavy metals. It is well known that heavy metal concentrations are increased in fine ash fractions. In this study, two models are investigated to describe the distribution of various heavy metals in different size fractions of fly ash from a grate-fired biomass incineration plant incinerating wood chips. The second model assuming a dependence of the heavy metal concentration from the reciprocal particle diameter to the power of the variable N correlated well with measured concentrations. This model was then used in the calculation of the required cut size of a classifier for the production of a coarse fraction with heavy metal concentrations below limits from a fly ash sample exceeding the Austrian limits for a soil improvement material. The predicted concentrations of the critical heavy metals Cd and Pb and the total mass of the coarse fraction produced corresponded well with measured values, and although the concentration of Zn was considerably underestimated in the model, the produced coarse fraction was within the limits for utilization.

Improved theoretical modeling of a cyclone separator as a diesel soot particulate emission arrester

Particulate matter is considered to be the most harmful pollutant emitted into air from diesel engine exhaust, and its reduction is one of the most challenging problems in modern society. Several after-treatment retrofit programs have been proposed to control such emission, but to date, they suffer from high engineering complexity, high cost, thermal cracking, and increased back pressure, which in turn deteriorates diesel engine combustion performance. This paper proposes a solution for controlling diesel soot particulate emissions by an improved theoretical model for calculating the overall collection efficiency of a cyclone. The model considers the combined effect of collection efficiencies of both outer and inner vortices by introducing a particle distribution function to account for the non-uniform distribution of soot particles across the turbulent vortex section and by including the Cunningham correction factor for molecular slip of the particles. The cut size diameter model has also been modified and proposed by introducing the Cunningham correction factor for molecular slip of the separated soot particles under investigation. The results show good agreements with the existing theoretical and experimental studies of cyclones and diesel particulate filter flow characteristics of other applications.

Comparison of separation performance between single and two inlets hydrocyclones

Experimental studies have been carried out about the particle separation performance of single and two inlets hydrocyclones. Two types of hydrocyclones having the same total inlet holes area were examined. Hydrocyclone A (with single inlet hole) and hydrocyclone B (with two inlet holes) were used. An aqueous slurry of silica particles (0.5 wt% with a median diameter of about 2.1 μm) was tested using a 20 mm-diameter hydrocyclone with a 15% underflow ratio. It was found that the optimum flow rate which gives the highest separation performance of the hydrocyclone B is the same flow rate for each inlet. Usage of the hydrocyclone B indicated smaller cut size and higher particle collection efficiency compared to that of the hydrocyclone A, under the same flow rate or same pressure drop conditions. The time of flight model was used to predict the 50% cut size diameter for single inlet hydrocyclone, and the model was modified to the two inlets hydrocyclone. It was found that the calculated results agree well with the experimental results for the hydrocyclone A, and for the hydrocyclone B under the low total flow rates conditions.

Filtration on Hydrocyclone of Optimized Geometric Relationships

The filtering hydrocyclone is a solid-liquid separation device patented by the Chemical Engineering School of the Federal University of Uberlândia, which consists of a hydrocyclone whose conical section was replaced by a conical filtering wall. During the operation of these separators, besides underflow and overflow streams, the existence of a filtrate stream generated by the filtering process is found in the permeable conical region of the hydrocyclones. Vieira et al. (2006) got a filtering hydrocyclone that simultaneously presented low Euler Number and cut size diameter because its geometric relationships has been optimized. The objective of this work was to analyze the behavior of this optimized filtering hydrocyclone through computational fluid dynamics and experimental studies. In the same operational conditions of the conventional hydrocyclone, the performance of this optimized filtering hydrocyclone was significantly influenced by the filtration. The filtration caused decreases in the Euler number and increment in the total efficiency.