Liquid Ejector Research Articles

Energy and exergy analysis of a novel ejector powered CO2 liquefaction system (EPLS) and comparative evaluation with four other systems

CO2 emissions from industrial activities has been imposed several environmental problems to the human life. Mitigation actions like designing and implementing the CO2 capture systems is a beneficial way to reduce the amount of carbon dioxide in the atmosphere. In the last part of capturing process, the CO2 needs to be pressurized to be transported, stored, or used elsewhere. In the present study, five different systems for the carbon dioxide post-capture are designed and compared with each other which include a multi-stage compression, basic and modified Claude, the ejector boosted absorption systems, and the new introduced ejector powered liquefaction system (EPLS). The effect of several decision parameters on the performance of each system is evaluated and the detailed energetic and exergetic analysis of the components in each system is carried out. The results show that the new introduced EPLS system has better performance (in terms of COP and second law efficiency) than other four systems and the multi-stage compression system has the nearest values to the EPLS. The dependency of the EPLS performance to the main decision parameters including the pressure ratio and the intercooling temperature is considerably lower than other evaluated systems. In this regard, the multi-stage compression system indicates the largest dependence to the pressure ratio and intercooling temperature of compressors. The evaluations on the components of each system reveals that by the modifications in the Claude layout, the modified Claude system requires less cooling demand than other systems (585.5 kW at the basic conditions) and on the other hand, the DEBARS system has the lowest power consumption between the other systems (280.6 kW at the basic conditions). Evaluations on the exergetic efficiencies of components show that the intercoolers beside the compressors in the main subsystems and the liquid ejector in DEBARS, have the highest exergy destruction ratio in each system.

Proposal of a double ejector-two flash tank absorption refrigeration cycle: Energy, exergy and thermoeconomic evaluation

This research presents the proposal of a double ejector-two flash tank absorption refrigeration cycle, in which vapor and liquid ejectors are implemented simultaneously before the condensers and absorbers components. For the vapor ejector simulation, the shock circle approach is used. The internal environment of the vapor ejector, including the chocking phenomenon and the irreversible shock process, is also thoroughly examined. It is proposed that ejectors and flash tanks can improve the system performance. It is possible to improve the ejector entrainment ratio by incorporating a flash tank between the evaporator and condenser, which would also increase the evaporator cooling effect. Moreover, a second flash tank is installed between the generator and the absorber, which allows the generator to operate at a lower temperature and thus reduces the generator heat load. Consequently, the system's COP (coefficient of performance) increases. Furthermore, the unit cost of the final product in a wide range of operational conditions is calculated. The findings revealed up to 56.8% increase in the COP. The improvement of the maximum exergetic efficiency in the new cycle compared to the basic cycle also reaches 22.5%. Moreover, the thermoeconomic investigation show up to 34.6%. reduction in product cost.

Research on performance optimization of gas–liquid ejector in multiphase mixed transportation device

ABSTRACT In the process of oil and gas extraction, a system that uses a pump and reversing mechanism to achieve high-efficiency export of gas–liquid mixture is devised. A gas–liquid ejector is fitted in the front of the device to boost pressure inside the tank in order to store more gas in the tank under a given volume. To meet the working conditions of gas–liquid high-efficiency transport device and obtain a larger outlet pressure and better ejection performance, this paper investigates the effect of outlet pressure, ratio of throat inlet area to nozzle outlet area and nozzle contraction angle on the ejection performance of gas–liquid ejector, and simulations using the computational fluid dynamics approach. At the same time, an experiment platform is built for testing. The research findings show that the ejection gas flow rate and ejection ratio of gas–liquid ejector decrease with the increase of the outlet pressure; as the ratio of throat inlet area to nozzle outlet area increases, the ejection gas flow rate and the ejection ratio of gas–liquid ejector increase first and then decrease. Different nozzle diameters correspond to different optimal area ratios; under the specified working parameters, with the increase of the nozzle contraction angle, the ejection gas flow rate and injection ratio of the gas–liquid ejector increase first and then decrease, and there is an optimal nozzle contraction angle.

Modeling of a CO2-Based Integrated Refrigeration System for Supermarkets

An integrated energy system that consists of a centralized refrigeration unit can deliver the entire HVAC&R (heating, ventilation, air conditioning, and refrigeration) demand for a supermarket. CO2 (R744) is a natural refrigerant that is becoming increasingly popular for these centralized units due to significant energy and cost savings, while also being sustainable, safe, and non-toxic. This study focuses on the fully integrated CO2 refrigeration system configuration for a supermarket in Porto de Mos, Portugal, which was equipped and fully monitored through the EU-funded project MultiPACK. A dynamic system model was developed in Modelica and validated against measurement data from the site recorded for one week. The model is used to provide additional ejector performance data supporting the obtained measurement data and to evaluate the system configuration at equivalent boundary conditions. The simulation results show that the installation of a vapor ejector (high-pressure lift) is sufficient to improve the efficiency of the unit compared to an ejector-less (high-pressure valve) system. However, more notable enhancements are achieved by including additional flooded evaporation with liquid ejectors and smart regulation of the receiver pressure, adding up to a global efficiency increase of 15% if compared to the high-pressure valve system during the validation week.

Optimization of liquid jet ejector geometry and its impact on flow fields

Liquid jet liquid (LJL) ejectors have wide industrial application and the improvement in their efficiency is sought to increase the viability of their use. This study performs the optimization of the entire geometry of an LJL ejector with multiple parameters to maximize energy efficiency. The approach with multiple parameters allows to identify key geometrical features and interdependent parameters, like nozzle position and mixing chamber length, with respect to performance. Computational fluid dynamics (CFD) and optimization simulations were performed to optimize the parameters of Bézier curves that characterize the device's geometry. The optimization results showed that the ejector efficiency curve is sensitive to the nozzle and the suction chamber geometries. Simulations that consider the nozzle diameter and the nozzle position along ejector axis (NXP) as parameters of the optimization process resulted in higher efficiency values than those that kept these parameters fixed. The optimization of the diffuser curve, including the diameter of the diffuser and the length of the mixing chamber, also contributed to increase the efficiency of the device. It was observed that the increase in the length of the mixing chamber and the spacing of the nozzle imply similar effects in the efficiency and in the pressure, velocity and energy dissipation rate profiles confirming some correlation of these parameters on the performance. One may observe the effect of geometry modification through optimization on the flow profiles in key sections of the ejector: the flow profiles in the optimized geometry tend to be more homogenous, hence less dissipative, and it is also confirmed by local energy dissipation rate.

Numerical Simulation of Double Surface Liquid Ejector with Flow Swirl for Centrifugal Pump

Many systems with liquid ejectors and centrifugal pump are known. Often, jet pumps are used to provide a self-priming mode, as well as an acceptable pressure level for cavitation-free operation. The main disadvantage of such systems is the relatively low efficiency associated with the peculiarities of energy transfer in ejector. To increase efficiency double surface jet pump with driving and suction flow swirl (with circumferential component of velocity) is proposed. The active flow swirling is ensured by using of multi-nozzle tangential nozzle inlet and passive flow part by a special blade system. Combination of these factors makes it possible to improve the efficiency of energy conversion process. In comparison with the known design increases pump efficiency by 10 % – 15 %. Flow swirl also permits to reduce horizontal overall size by increasing the diffuser angle and reducing the mixing chamber length. These positive effects can be achieved by using methods and recommendations given in this paper. The paper also includes ANSYS CFX numerical simulation study results of double surface jet pump and analysis of the impact of nozzle position, length of the mixing chamber and other geometry parameters on pump performance. The results allow optimize the constructive solutions.

Design and performance evaluation of a double ejector boosted multi-pressure level absorption cycle for refrigeration

In this work, a multi-pressure double ejector boosted absorption refrigeration system (DEBARS) is designed and analyzed; two vapor and liquid ejectors are implemented simultaneously before the condenser and absorber components and both of the solution and refrigerant heat exchangers are included in the cycle. Vapor and liquid ejectors are simulated and analyzed in details and the shock circle method is used for the vapor ejector simulation. The characteristics inside the vapor ejector involving the chocking phenomenon and the irreversible shock process are also considered comprehensively. The proposed system is compared with the basic and three-pressure level absorption refrigeration cycles. The results show that the multi-pressure level cycle has the superior performance to both of the previous cycles; The maximum Coefficient of performance (COP) and second law efficiency (ηII) in the new cycle is improved up to 108.35/33.11 and 31.61/46.62 percent in comparison with the basic and three-pressure level cycles, respectively. The generator activation temperature of the DEBARS is in the range of basic cycle and 36–55 °C lower than the three-pressure level cycle; Also, the evaporator start-up temperature in the DEBARS is considerably lower than both of the basic and three-pressure level cycles.

ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ И ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ ЖИДКОСТЬ-ЖИДКОСТНОГО ЭЖЕКТОРА С КРИВОЛИНЕЙНЫМ НАЧАЛЬНЫМ УЧАСТКОМ КАМЕРЫ СМЕШЕНИЯ И С ПРЯМОЛИЕЙНОЙ КАМЕРОЙ СМЕШЕНИЯ

The article presents the results of numerical simulations and experimental studies of a liquid-liquid ejector with a curved initial portion of the mixing chamber. The experiment was conducted on liquid-liquid ejectors, models of which are made on a 3D printer, by the method of layer-by-layer deposition. The influence of possible manufacturing errors of the ejector on its characteristics is estimated. The issues of the use of liquid ejectors designed to work in the field of various predetermined ejection coefficients are considered. The theoretical ejection coefficient and the reasons for reducing the ejection coefficient in real ejectors are determined. The obtained dependences make it possible to determine the optimal design parameters of a liquid ejector and thereby increase its ejection coefficient. The relative pressure drop is shown at a low coefficient and at a high ejection coefficient. The calculated and experimental results of determining the ejection coefficient for liquid ejectors, which are widely used in various fields of technology, are presented. The results of numerical simulation of internal processes in the ANSYS-Fluent hydro-gasdynamic application package flowing in a single-phase liquidliquid ejector based on the study of a small-sized model are presented. As a result of the simulation, a good agreement was obtained between the calculation results of the model corresponding to the real prototype and the experimental data and comparison with the results of other authors. Several conclusions can be drawn from the results of the study. For example, a region of values of the ejection coefficient was found in which the relative pressure drop created by the ejector increases with an increase in the ejection coefficient.

Performance operation of liquid ejectors for a R744 integrated multi-ejector supermarket system using a hybrid ROM

Performance maps were generated for designed liquid ejectors installed in a multi-ejector module in an R744 integrated supermarket system using a hybrid of the reduced-order model (ROM). Hybrid ROMs of the investigated liquid ejectors were developed based on experimental data and CFD results. The CFD model achieved satisfactory accuracy at motive nozzle pressures above 59 bar, and the hybrid ROM improved the mass flow rate prediction. Maps were generated for the motive nozzle mass flow rate and the mass entrainment ratio at different ambient conditions related to cold, moderate, and hot climate zones. The set of the pressure lift for ejector efficiency maximisation at different ambient conditions is presented for refrigeration and air-conditioning applications. The developed liquid ejectors hybrid ROMs can be used to optimise work of the R744 integrated supermarket system equipped with the vapour and liquid ejectors.

Estimation of gas induction in jet loop reactors: Influence of nozzle designs

Jet loop reactors are used widely for conducting gas liquid reactions because of the high mass transfer achieved in the gas–liquid ejector. Studies have shown that the mass transfer has a very strong correlation to the amount of gas induced in the ejector, and hence it is important to understand gas induction to enhance the performance of any gas–liquid nozzle. In this work, we used a single phase CFD model of the ejector with one adjustable parameter for estimating gas induction rates. After establishing that the model adequately describes the experimental data, the model was used for a quick evaluation of ejector geometries. Influence of key geometric parameters of gas–liquid ejectors like nozzle diameter, mixing tube length, distance between the nozzle outlet and mixing tube, suction chamber geometry and diffuser angle was investigated. It was found that dependence of gas induction on geometric parameters like distance between nozzle—mixing tube, suction chamber geometry, diffuser angle was either weak or had a clear maxima at or beyond a certain value of the geometric parameter. Other parameters like mixing tube length and nozzle diameter have a more complex impact on gas induction. The presented approach and results will be useful for quantifying influence of nozzle designs on gas induction rate in jet loop reactors.

Numerical investigation of an R744 liquid ejector for supermarket refrigeration systems

This paper presents a numerical investigation of an R744 liquid ejector applied to a supermarket refrigeration system. The use of the liquid ejector enables the operation of the evaporator in a flooded mode and recirculates the R744 liquid phase, which improves the energy efficiency of the refrigeration system. The investigation was performed using two ejectors of different sizes installed in a multi-ejector block. The numerical model was formulated based on the homogenous equilibrium model and validated with the experimental results. The influence of the pre-mixer, mixer and diffuser dimensions on the ejector performance measured using the mass entrainment ratio is presented. The results show that the best liquid ejector performance was obtained for the short lengths of the pre-mixer and mixer compared to the broadly investigated two-phase ejectors connected to the evaporator port. In addition, wide diffuser angles improved the mass entrainment ratio of both liquid ejectors, which may lead to a reduction in the diffuser length.

Experimental evaluation of an ejector as liquid re-circulator in a falling-film water chiller

To experimentally evaluate the performance of an ejector working as a liquid re-circulator in a horizontal-tube falling-film evaporator with R134a, experimental tests are performed using a horizontal-tube falling-film water chiller prototype. Experimental observations on intertube liquid flow pattern of tube bundle validate the feasibility of the liquid re-circulation system using a liquid–liquid ejector. The analysis results show that the influence of the motive flow rate on the entrainment ratio of the ejector is small, and the average entrainment ratio of the ejector is about 2.03. With the increase of the valve opening of the regulating valve, the evaporating capacity of the falling-film water chiller rises 4.8%, from 940.2 kW with the re-circulation ratio of one, to 985.5 kW with the re-circulation ratio of 1.135. The COP of the falling-film water chiller reaches a maximum and then drops down with the increase of the re-circulation ratio, and the optimal re-circulation ratio is 1.135.

Numerical and experimental study on parameters distribution inside a two-phase ejector

The two-phase flow process in an ejector was numerically and experimentally studied using R141b as a working fluid. A modified one-dimensional gas–liquid ejector model was proposed to remedy the defect in the traditional one. Gas–liquid boundary layer regions were discussed and used to close the model. Mac Cormack method is used to discrete controlling equations of gas–liquid two-phase flow in the ejector. The radial distribution of velocity and temperature, the variation of void fraction, the axial velocity variation and the influence of primary steam pressure on the mixing process were predicted with the numerical model. An experimental rig was set up to validate the model by comparing the experimental pressure distribution in the ejector with the calculating one.

Operation of a centrifugal pump and a liquid ejector with an isobaric mixing chamber

The influence of simultaneous operation of a centrifugal pump and an isobaric ejector on the pump’s cavitational stability is investigated.

Configuration dependence and optimization of the entrainment performance for gas–gas and gas–liquid ejectors

This paper describes a numerical study of entrainment behavior and its configuration dependence for gas–gas and gas–liquid ejectors. A computational fluid dynamics (CFD) model is developed and experimental validation is undertaken over a wide range of operation conditions for ejector with different configurations. The predicted values by CFD simulation prove to be in good agreement with the experimental data. The investigation results indicate that pseudo-shock length has a dominant effect on entrainment performance and geometry optimization. Significant difference is noted in pseudo-shock length for gas–gas and gas–liquid ejectors, and this is mainly because the viscosity similarity markedly differs within the range of 0.01–1.0, depending on the primary and secondary fluids of usage. Therefore the optimum mixing tube length to diameter ratio is about 1–2 for general gas–liquid ejectors while 5–7 for gas–gas ejectors. As an exception to the general gas–liquid ejectors, the optimum L/D ratio in He–LH2 ejector is about 4, lying between that of the gas–gas ejector and gas–liquid ejector but still consistent with the pseudo-shock length. If the maximum allowable length of ejector mixing tube is less than the optimum value, placing the primary nozzle exit upstream of the mixing tube can greatly improve the entrainment performance.

Investigation on the Mechanism of Energy Saving and Efficiency Enhancement for Fluid Ejector

Experiments were implemented on a prototype commercial liquid ejector to measure its hydraulic efficiency and the change of which along with a certain range of water flow rate variation was also recorded. Based on theoretical analysis and numerical simulation methods, we improved the ejector’s structure by modifying the suction part of it. Four ameliorated ejector structures, with increased pumping power and reduced flow resistance compared to the prototype, are proposed. Under the same working flow rate condition, flow field computations were conducted on the prototype and the four improved structures. The computational results show that the pumping power increases by 75.97%, the drag coefficient reduces 0.0908, the maximum turbulent energy dissipation rate decreases by 38.88% and the absolute value of the efficiency increases by 13.66%. The work validates the correctness of the theoretical analysis about the mechanism of energy-saving and efficiency enhancement for fluid ejector, and provides a more effective method to improve the performance of liquid ejector.

Investigation of entrainment behavior and characteristics of gas–liquid ejectors based on CFD simulation

The aim of this paper is to investigate the entrainment behavior and performance of gas–liquid ejectors. computational fluid dynamics (CFD) model and the corresponding algorithm are developed and validation experiment has been carried out over a wide range of operation conditions for ejector with different configurations. Good agreement has been achieved between the predicted values from CFD simulation and the actual data by experimental measurement. The flow patterns that occur within the primary nozzle region are analyzed on the basis of one-dimensional isentropic compressible flow theory. The fluid pairs, consisting of the motive and the entrained fluids, are considered during the investigation with N2–H2O and He–LO2 selected as the representative fluids. The investigation results indicate that for fixed primary flow and secondary flow pressures (PP and PS, respectively), the entrained mass flow rate mS decreases linearly with the increasing pressure difference ΔP, while for fixed ΔP and secondary flow pressure PS, the entrainment rate mS monotonically increases with an increase in primary flow pressure PP until a constant value is reached. Moreover, the mixing tube length has proven to be an important design parameter and can exert a remarkable influence on ejector performance. The optimum mixing tube length of gas–liquid ejector is about 1–2 times the mixing tube diameter, and deviation from the optimum value can dramatically degrade its entrainment performance. In other words, an obvious peak value of entrainment ratio appears at the optimum L/D. However, the optimum value of L/D for single-phase ejector happens in the range of 5–7, which differs significantly from that of gas–liquid ejector. Moreover, an inapparent effect has been observed when the mixing tube of single-phase ejector is longer than the optimum value. A detailed description of this phenomenon is presented in this paper. The conclusions of the research can be served as a guideline for ejector design.

Effect of ejector configuration on hydrodynamic characteristics of gas–liquid ejectors

Ejectors are gas–liquid contactors that are reported to provide higher mass transfer rates than conventional contactors. Detailed experiments were performed and computational fluid dynamics (CFD) modeling studies were undertaken to understand the hydrodynamic characteristics of the ejector geometry. The CFD model provides a basis for quantifying the effects of operating conditions on the ejector performance. CFD studies shows that there is an optimum ratio of nozzle area to throat area (area ratio), at which the liquid entrainment rate is the highest. This can lead to substantial economic benefit in the industrial practice. The liquid entrainment rate correlates with pressure difference between the water surface in the suction chamber and the throat exit for a wide variety of ejector geometries and operating conditions.

Hydrodynamics and mass transfer characteristics of gas–liquid ejectors

In the present work, experimental investigations have been carried out on ejectors employing air as a motive fluid and water as the entrained fluid. A semi-empirical model has been developed to predict the liquid entrainment rate taking into account: (i) the compressible nature of air, (ii) pressure drop for two-phase flow and (iii) losses due to changes in cross sectional area. The effects of gas velocity, liquid level in the suction chamber, nozzle diameter and throat diameter on the liquid entrainment, entrainment ratio (L/G), pressure drop, gas hold-up, mass transfer coefficient and interfacial area have been investigated. The liquid entrainment rate increases with the increased liquid level in the suction chamber and with the increase in gas velocity. The ratio of throat cross sectional area to the nozzle cross sectional area (area ratio) was found to be a critical parameter. These results have been explained on the basis of pressure profiles of ejector (along the centre line of the ejector). The liquid entrainment rate predicted from the semi-empirical model is in good agreement with the experimental values. The mass transfer coefficient and interfacial area increase with increase in gas velocity. Correlations have been proposed to estimate the fractional gas hold-up, mass transfer coefficient and interfacial area in the ejectors.

Hydrodynamic Characteristics of Gas–Liquid Ejectors

In the present work, experimental investigations have been carried out on ejectors employing gas (air) as a motive fluid and liquid (water) as the entrained fluid. A semi-empirical model has been developed to predict the liquid entrainment rate taking into account, (1) the compressible nature of air, (2) pressure drop for two phase flow and (3) losses due to changes in cross sectional area. The effects of gas velocity, liquid level in the suction chamber, nozzle diameter, throat height and throat diameter on the liquid entrainment, entrainment ratio and pressure drop have been investigated. It has been observed that the liquid entrainment rate increases with an increase in the liquid level in the suction chamber. It was also found to increase with an increase in the gas velocity. The ratio of throat cross-sectional area to the nozzle cross-sectional area (area ratio) was found to be a critical parameter. The results have been explained on the basis of pressure profiles. The values of liquid entrainment rate predicted from the semi-empirical model were found to be in good agreement with the experimental measurements.