Entrained Flow Rate Research Articles

Analysis of HEM applicability for a subcritical flashing ejector at low motive pressure

Validated CO2 ejector models are essential for developing high-performance refrigeration and heat pump cycles. This study focuses on assessing the Homogeneous Equilibrium Model’s applicability to simulate a CO2 flashing ejector at a reduced pressure of 0.47. The model was implemented in FLUENT, integrating a user-defined real gas model. Simulation results with different boundary condition options were compared to experimental data. The analysis was carried out to evaluate the predictive capabilities of the model and assess the experimental data quality. The results indicate that the developed model accurately estimated the motive mass flow rate, with a maximum relative error of 5.7%, showing better performance than previously reported data. The entrained flow rate, assuming double choking operation, was significantly higher than the experimental measurement, and the CFD-predicted wall static pressure underestimated the experimental profile, suggesting single-choked ejector operation. In contrast, the outflow density was better predicted under the same assumption, with an average error of 8.6%. Nevertheless, the simulated temperature profiles showed good agreement with the experimental data, especially when using the experimental entrained mass flow rate as a boundary condition.

Comparative analysis of isopropyl alcohol dehydration using ionic liquids and deep eutectic solvent

The current article deals with the separation of the azeotropic mixture of isopropyl alcohol (IPA) and water using an ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) and Deep Eutectic Solvents (DESs), Choline Chloride/glycerol (Glyceline) and Choline Chloride/Ethylene Glycol (Ethaline). Conventional dimethyl sulfoxide (DMSO) solvents are used to compare the results for IPA dehydration. Process modelling and simulation were carried out in the Aspen Plus simulator (v.8.6). The NRTL model was used to calculate the thermodynamic properties as well as the vapour-liquid equilibria of the ternary systems. The process parameters such as entrainer flow rate, binary feed stage, entrainer feed stage, column stages, reflux ratio, reboiler and condenser duties were evaluated using sensitivity analysis and design spec tools of the simulator. The industrial process for both systems, containing a separation column and a recovery column, was simulated at a steady state. Both processes were optimised using the optimisation tool of the simulator and compared based on the energy requirement. Further, based on the simulation results, we proposed an alternate process design for solvent recovery using a flash drum. The results show that more than 99.9 mol% IPA purity can be achieved using both ILs as well as DESs. The overall energy requirement for the separation of IPA-water mixture using [EMIM][BF4] entrainer in a conventional process was found to be lower than DMSO. The proposed alternate process further reduces the energy requirement compared to the conventional process for both IL and DESs systems.

A new metric for the evaluation and selection of energy-intensified extractive distillation sequences

Extractive distillation is a widely-used but energy-intensive method for separating homogeneous azeotropic mixtures into pure components. Numerous design alternatives have been proposed for reducing energy consumption in such processes, including alternatives with side-streams, column stacking and thermally coupled sequences. However, there is very little guidance in the literature about which alternative is likely to work the best in a given situation.To address this deficiency, in this work, seventeen industrially-relevant chemical systems comprising two species that form a minimum boiling azeotrope and a heavy entrainer are selected for study. Two ordinary and six energy-saving flowsheet alternatives for extractive distillation processes were also selected. Each of the eight flowsheet alternatives was optimized for each of the 17 chemical systems. A novel metric RCB (the ratio of the entrainer flow rate to the heavy key flow rate) is proposed to facilitate interpretation of the results. General trends in the relative attractiveness of the three energy-saving strategies (side streams, thermal coupling, column stacking heat integration) were found as RCB changes. An understanding of these trends can help engineers to understand the conditions for which various energy-savings strategies are most likely to be effective.

Flame morphology of horizontal jets under sub-atmospheric pressures: Experiment, dimensional analysis and an integral model

This paper investigated the flame morphology including horizontal projection length and vertical height of horizontal turbulent jets under various sub-atmospheric pressures, for which both data and model are few. Experiments are conducted for various nozzle diameters in the range of 3 mm to 7 mm. Propane is used as the fuel in this study. The sub-atmospheric pressures, created by a reduced pressure chamber, are varied from 40 kPa to 100 kPa. A digital video camera is used to measure the flame morphologic characteristics. The experimental results show that the flame horizontal projection length increases with the increasing of heat release rate or the decreasing of chamber pressure. Meanwhile, the flame vertical height first increases then decreases with the increasing of heat release rate or the decreasing of chamber pressure, which shows a non-monotonic behavior. A characteristic length scale is proposed by dimensional analysis considering jet initial momentum, flame buoyancy and ambient air density to illustrate the controlling mechanisms in the flow development. And the characteristic air entrainment flow rate ρ∞Lm2g′Lm is used to normalize the stoichiometric mass flow rate at the flame tip, which determines the total length of the trajectory. Non-dimensional formulas are developed based on the derived length scale and characteristic air entrainment flow rate to describe the flame horizontal projection length and vertical height of horizontal jets under various sub-atmospheric pressures. Finally, an integral model considering air entrainment mechanism, top hat profiles and strong plume theory for the conservation of mass and momentum in horizontal and vertical directions is developed, which shows to describe the flame morphologic characteristics well.

Pressure Drop, Air Entrainment, and Moments of the Axial Velocity in the Laminar-Turbulent Transition Jet Flow in Domestic Gas Injectors

Abstract This work aims at characterizing the flow in the outlet of three gas injectors used in atmospheric burners and developing correlations for the discharge coefficient, air entrainment, momentum, and energy flow rates. These devices have millimeter-sized orifices, a cup-like region at the injector outlet, and the flow occurs in the transition from the laminar to the fully turbulent regimes. The pressure drop was measured and correlated as a function of the orifice Reynolds number for the three injectors. The correlations are able to predict the discharge coefficient within ±5% deviation from the measurements in the range 90≤Re≤4400. The axial velocity and turbulent intensity were measured at the outlet of the injectors using a hot-wire anemometer at the orifice Reynolds number of 3060, which is typical of the applications. The measurements were compared to computational fluid dynamics (CFD) solutions using the γ−Reθ Reynolds-averaged Navier–Stokes transition model in the star-ccm+ commercial package. The results indicate the strong influence of the shape of the outlet cup-like region of the injectors on the development of an internal mixing layer and the external mixing layer in the free jet. The momentum and energy flow rates for the injector model with the largest cup are reduced to 50% and 21%, respectively, of the simplest gas injector. However, the gas jet in this injector carries 28% of the stoichiometric air before leaving the cup. These aspects must be taken into account in the preliminary design of atmospheric burners.

Modeling of Gas Entrainment Flow Rate by Bathtub Vortex

In the design study on sodium-cooled fast reactors, .it is important to investigate the gas entrainment (GE) phenomena in detail. In fact, a lot of analytical, experimental and numerical studies have been conducted to clarify the onset condition of GE and some GE onset models have been proposed. However, few studies on the modeling of entrained gas flow rate has been conducted due to the difficulty on modeling the gas bubble entrainment at a free surface, which is accompanied by complicated free surface deformation. In this paper, the authors propose a mechanistic model to predict the entrained gas flow rate by a free surface vortex. The model contains the theoretical equation of transient gas core elongation and the empirical equation of critical gas core length for gas bubble detachment. The mechanistic model is applied to predict the entrained gas flow rate in a simple GE experiment. As a result, the predicted results show qualitatively good agreement with the experimental results of the entrained gas flow rate. Therefore, it is confirmed that the proposed mechanistic model can predict the entrained gas flow rate by a free surface vortex.

Development of an adaptive bypass element for passive entrainment flow control in dry powder inhalers

The release of drug from dry powder inhalers is strongly dependent on the patient's inhalation profile. To maximise the effect of the treatment, it is necessary to optimise dry powder inhalers to achieve drug delivery that (A) is independent of the inhalation manoeuvre and (B) is targeted to the correct site in the lung. The purpose of this study is to develop a dry powder inhaler with an adaptive bypass element that achieves desired drug delivery behaviour. Computational and experimental methods are used. First, the effect of a generic variable bypass element on entrainment behaviour is modelled. This is done by modelling a dry powder inhaler as a network of flow. Second, the behaviour of a potential variable bypass element, a flap valve, is studied both computationally and experimentally. Third, the flow resistances are optimised to achieve consistent and desired entrainment behaviour for patients with very different inhalation manoeuvres. A simulated dry powder inhaler device design was found that achieves an approximately constant entrainment flow rate of 12 L/min when total flow rates larger than 20 L/min are applied. The developed dry powder inhaler is predicted to accurately deliver drug for patients with highly different inhalation manoeuvres.

On the total entrained flow rate of artificial downwelling

Artificial downwelling potentially counteracts severe eutrophication and hypoxia in coastal regions. The entrainment that commonly occurs in the downwelling-induced plume can develop around a compensatory downward flow at a scale of kilometers, which favors below-pycnocline ventilation and thus mitigates hypoxia in bottom water. However, little discussion has been made on the entrainment of artificial downwelling. The paper focus on the total entrained (TE) flow rate that represents the magnitude of entrainment transport. Injection of a negatively buoyant jet from a round pipe into a stagnant and homogeneous ambient medium is numerically studied using a verified standard k- ε turbulence model, in which different initial pipe flow speeds, density differences and pipe radii are involved. Previous theories and experiments confirm the numerical model. An empirical formula is fitted to the simulation data to calculate the TE flow rate, which permit quantitative analysis of the capacity of ventilation for artificial downwelling. The efficiency index of ventilation (EIV) is also defined and applied to study a typical downwelling device, i.e., a tidal pump, to suggest optimal engineering parameters.

Experimental Study of Air Entrainment Rates due to Inclined Liquid Jets

AbstractThe air entrainment rate due to inclined liquid jet plunging into a pool was investigated experimentally. Three types of fluids with varying physical properties in terms of viscosity and surface tension were utilized. For the impinging jet test section, nozzles with different inner diameters were selected. The inclination angles and liquid jet velocities at the nozzle outlet were varied and the entrained air rate was measured by the soap meniscus method. Taking the falling velocity of the liquid jet as a characteristic velocity, it was found that the air entrainment rate under the present experimental condition largely depended on the Weber number. From the obtained database, a new empirical model dependent on the Weber number and Laplace length scale is proposed which is capable of predicting the air entrainment flow rate at a mean absolute relative deviation of 21.7 %.

Improved design and optimization for separating tetrahydrofuran–water azeotrope through extractive distillation with and without heat integration by varying pressure

From the view of thermodynamic insight, a new concept (ROE: FE,Pope/FE,Pref), the ratio of the entrainer flow rate (FE) needed for reaching given relative volatility at operating pressure (Pope) to reference pressure (Pref), is firstly proposed to quantitatively determine the search space of operating pressure of the extractive column in a homogeneous extractive distillation (ED) process for the separation of binary minimum azeotrope with heavy entrainer. This novel concept is illustrated by the extractive distillation of tetrahydrofuran–water minimum boiling point mixture with an entrainer dimethyl sulfoxide. Six process designs under different pressures are obtained by a two-step optimization procedure and compared from the economic view based on total annual cost (TAC). Furthermore, three double-effect heat integration (DEHI) processes, are employed under atmospheric and a reduced pressure for the first time to further improve the energy efficiency and investigate the effect of pressures on the studied ED process. The final results of case study demonstrate the optimal heat integration approach with a suitable low pressure is the most economic one among the three DEHI processes. The TAC of the best proposed design exhibits a 20.3% reduction than that at atmosphere pressure. The proposed pressure selection rule and optimization process are helpful for reducing the TAC of the ED process.

Experimental investigation of air entrainment by vertical plunging liquid jet

This paper presents experimental results and predictive model on the air entrainment flow rate due to the vertical plunging liquid jet. Three types of fluids with different physical properties were utilized as a working fluid for the experiment. Air entrainment flow rate was measured using soap meniscus method and various geometrical parameters including nozzle diameter (13–16 mm), fall height (105–210 mm), pool depth (30–180 mm), and angle of the bottom pool surface (0–75°) were changed to investigate the effects on air entrainment rate. Plunging tube was installed around the falling jet and impinging point. For the current experimental conditions, it was found that the air entrainment rate depends on the product of Weber number and Laplace length scale, and new predictive model on air entrainment ratio, defined as the entrained air flow rate divided by impinging jet flow rate, is proposed. The proposed model is capable of predicting air entrainment ratio at a mean absolute relative deviation of 15.9% at the given experimental conditions.

Optimization of pre-concentration, entrainer recycle and pressure selection for the extractive distillation of acetonitrile-water with ethylene glycol

We optimize the extractive distillation process for separating the acetonitrile – water azeotropic mixture with ethylene glycol by using a multi-objective genetic algorithm for minimizing under purity constraints the total cost, the energy consumption and the separation efficiency. For the first time we have shown the interest of five aspects by considering them simultaneously (1) the pre-concentration column has been included and (2) there is no need to set a distillate composition constraint (like being at the azeotropic composition) in the pre-concentration column. (3) The operating pressure should be lower than 1 atm because it enhances the relative volatility for 1.0-1a class system. (4) A closed loop optimization must be run, to handle the effect of impurity in the entrainer recycle since too much impurity limits the main product recovery and purity from the extractive column. (5) All three columns process must be optimized together rather than sequentially and with multiple objectives. The studied system belongs to class 1.0-1a and the impurity of the recycled entrainer has strong effect on the purity of acetonitrile product. Overall, 17 variables are optimized; column trays, all feed locations, refluxes, entrainer flow rate and all distillate products; under purity constraints for the acetonitrile and water product and for the entrainer recycle impurity. Among nearly 400 designs satisfying the purity specifications, the design case 3 shows an energy consumption and TAC reduced by more than 20% than a literature reference case, thanks to smaller entrainer flow rate, a reduction of 32 trays and lower operating pressures. The best design is a trade-off between first a feasibility governed by thermodynamics through composition profiles and relative volatility maps and second process cost and energy demands.

Characterization of water-air dispersed two phase flow

The analysis of two phase flow has a great relevance in many industrial sectors such as nuclear and process industry. The study and the measurement of the related phenomena are particularly difficult due to the variety of the parameters that affect the flow (void fraction, flow regime, orientation, etc.). Measurement instrumentation for two phase flow is nowadays very limited even if it would be highly useful in the industrial field. Before approaching the research and development toward the realization of innovative instrumentation for two-phase flow measurement, it is fundamental a precise description of the particular flow regime of interest. Dispersed water droplets in air/gas is a possible flow regime at high gas void fractions; therefore it is important to characterize this particular flow pattern in a detailed way. To reproduce this condition in a laboratory environment it is possible to use nozzles with very small outlet diameters and high pressure water supply. In this paper the characterization of dispersed flow is performed as function of the nozzle characteristic and water inlet pressure. The tests are performed using an experimental setup realized at the Energy Department at Politecnico di Torino. The water jet is observed in a PMMA (PolyMethylMethacrylate) pipe 1.8 meters long with an inner diameter of 78 mm. High pressure water is obtained using a plunger pump and pump inlet water pressure is adjustable in the range 1-4 bar. Water pressure upstream the nozzle and air entrainment flow rate are measured and used as primary parameters of the study. A sensitivity analysis on these two parameters is performed with the purpose to find the conditions that are optimal to reproduce a dispersed flow.

A bidirectional valveless piezoelectric micropump with three chambers applying synthetic jet

A new type of valveless piezoelectric micropump is presented. Synthetic jet and Coanda effect are utilized to achieve larger and bidirectional flow rate. The numerical simulation applying the velocity and pressure boundary conditions as well as the SST turbulence model were utilized to research the performance and internal flow state of the micropump. The simulation method was tested by the previous experimental data and the results matched well. The results suggest that the flow rate of the micropump is related to the Reynolds number and frequency. The entrainment flow rate of synthetic jet accounts for over 80% of the total outflow rate. The outflow rate is much larger than the volume change of the micropump chambers. There is an optimal frequency to obtain the maximum flow rate regarding the volume change of the chambers as a constant. The fluctuation of the flow rate decreases with the increase of frequency. When the frequency is higher than 25 Hz, the outflow can be continuous. Working at the Reynolds number of 1000 and optimal frequency of 50 Hz, the flow rate is 6.8 ml/min.

Low pressure design for reducing energy cost of extractive distillation for separating diisopropyl ether and isopropyl alcohol

We show how reducing pressure can improve the design of a 1.0-1a mixture homogeneous extractive distillation process and we use extractive efficiency indicators to compare the optimality of different designs. The case study concerns the separation of the diisopropyl ether (DIPE)–isopropyl alcohol (IPA) minimum boiling azeotrope with heavy entrainer 2-methoxyethanol. We first explain that the unexpected energy cost OF decrease following an increase of the distillate outputs is due to the interrelation of the two distillate flow rates and purities and the entrainer recycling through mass balance when considering both the extractive distillation column and the entrainer regeneration column. Then, we find that for the studied case a lower pressure reduces the usage of entrainer and increases the relative volatility of DIPE–IPA for the same entrainer content in the extractive column. A 0.4atm operating pressure is selected to enable the use of cheap cooling water in the condenser. We run an optimization of the entrainer flow rate, both columns reflux ratios, distillates and feed locations by minimizing the total energy consumption per product unit. Double digit savings in energy consumption are achieved while TAC is reduced significantly. An extractive efficiency indicator that describes the ability of the extractive section to discriminate the desired product between the top and the bottom of the extractive section of the extractive section is calculated for comparing and explaining the benefit of lowering pressure on the basis of thermodynamic insight.

The Emptying-box problem with a baffle of different porosity percentages

This research studies the Emptying-box problem with a porous baffle just behind the entrance opening. A theoretical model is extended to include the effect of a porous baffle, and the theoretical model taking account of porosity establishes the connections between two typical unidirectional displacement flow types. The salt-bath technique is employed to conduct the experiments using an acrylic reduced-scale model. Dye attenuation technique is used to analyze the light intensity data derived from the recorded images of experiments. According to the baffle porosity percentage (ϕ), the experiments are categorized into two series, EM(79%) and EM(60%). Each series respectively includes three different opening area ratios, which are 1, 0.5 and 0.33. Experimental results show that emptying processes for the cases with a baffle of the larger porosity percentage consist of emptying the dense layer and emptying the mixed layer, but there is only one process of emptying the dense layer for the cases with a baffle of the smaller porosity percentage. Experimental results are in reasonable agreement with the extended theoretical model developed in this research. Two extreme cases, those with and without an impenetrable baffle, are included in this paper to represent two typical flow types of the horizontal inflow denoted as EM(H), as that with ϕ=0%, and the vertical inflow denoted as EM(V), as that with ϕ=100%, i.e. the unidirectional classical displacement flow and the displacement flow with interfacial mixing. As the porosity percentage increases, the emptying time for the dense layer decreases, but the emptying time for the whole box tends to increase. The emptying time for the dense layer decreases, when the total effective opening area or the reduced gravity increases for the cases having the same porosity percentage. The initial interfacial height of the mixed layer increases, as the baffle porosity percentage increases for the cases having the fixed total effective opening area, or the total effective opening area increases for the cases with the same baffle porosity percentage. The initial buoyancy of the mixed layer is dependent on the penetrative entrainment flow rate from the dense layer to the mixed layer and the emptying time for the dense layer. As the total effective opening area or the porosity percentage increases, experimental results show that the initial buoyancy of the mixed layer tends to increase, and the penetrative entrainment flow rate increases as well, but the emptying time for the dense layer decreases.

A novel method for the search and identification of feasible splits of extractive distillations in ternary mixtures

This article describes a novel general method for the search and identification of possible splits of extractive distillations in any ternary azeotropic mixture – the method of infinitely sharp splits. This method finds all feasible product compositions that can be obtained in an extractive column at infinite height and finite reflux. Limiting parameters of mode for the entrainer flow rate and the reflux ratio are determined fast and robustly from the local K-values (vapor–liquid distribution coefficients) of all three components along the sides of the concentration triangle. For the given product specifications the method additionally determines the required number of trays in all the column sections. Hence, both operating and investment costs can quickly be analyzed without cumbersome simulations. The method can be extended to multi-component mixtures.

Improved Design and Efficiency of the Extractive Distillation Process for Acetone–Methanol with Water

We show how thermodynamic insight can be used to improve the design of a homogeneous extractive distillation process, and we define an extractive efficiency indicator to compare the optimality of different designs. The case study is related to the separation of the acetone–methanol minimum boiling azeotrope with water. The process flow sheet includes both the extractive distillation column and the entrainer regeneration column. Insight from analysis of the ternary residue curve map and isovolatility curves shows that a lower pressure reduces the minimal amount of entrainer needed and increases the relative volatility of acetone–methanol in the extractive column. A 0.6 atm pressure is selected to enable the use of cheap cooling water in the condenser. We optimize the entrainer flow rate, adjusting both column reflux ratios and feed locations, by minimizing the total energy consumption per product unit. The total annualized cost (TAC) is calculated for all processes. Double-digit savings in energy consumpti...

코안다 노즐에서 중심 축소관 유무에 따른 유입량 특성

코안다 노즐에서 중심 축소관 유무에 따른 유입량 특성

LES investigation on cavity shedding of a Clark-Y hydrofoil under different attack angle with an integration method

Numerical simulations of unsteady cavitating turbulent flow around a Clark-Y hydrofoil were performed using the Large Eddy Simulation method under different attack angles. The shedding of the cavity cloud was captured and the numerical results of the total vapour volume accords well with the experimental results. In this paper the concept of entrainment ability (generally adopted in water jet) was firstly introduced to describe the process of the cavity shedding. Based on the integral time averaged Navier-Stokes equations, the integration of p+ρ1v2 was adopted to describe the entrainment ability. A horizontal line from upstream to the leading edge was defined to monitor the flow rate and entrainment ability being transferred to the suction side. It is found that the entrainment ability directly determines the level of the re-entrant jet, which sees a sudden rise at the breakdown of the cavity cloud with the re-entrant jet reaching to the leading edge. Moreover, compared with no-cavitating flow, the entrainment ability was greatly hindered by the intensive cavity cloud over the foil. The pressure fluctuation at the trailing edge can be transferred upstream through the pressure side and influences the entrainment ability and flow rate across Line B(QB, Line B is defined as a horizontal line from upstream to the leading edge). In addition, as the attack angle increases, the time averaged QB greatly increases, while the time averaged entrainment ability experiences a marginal rise. Thus, the variation of attack angle only impacts the entrainment ability from Line A (mA), since mA varies linearly with QB.