Ejector Nozzle Research Articles

Effect of ejector operation on the oxygen transfer in a pilot jet loop reactor

Jet loop reactors (JLRs) are an alternative reactor type for the intensification of aerobic bioprocesses which are normally carried out in stirred tank reactors (STR). A JLR is capable to generate the same oxygen transfer rate (OTR) at a higher efficiency compared to a STR. If the ejector nozzle of a JLR is used for headspace pressurization, the oxygen mass transfer can be increased even further. However, intensified mass transfer usually requires increased power inputs while mass transfer efficiencies are decreased. In this respect, the energy efficiency of a JLR designed for intensification of an industrial bioprocess was evaluated. Compared to a STR, the JLR achieved a 70% higher mass transfer rate at identical power input. Based on the results obtained for mass transfer performance, an increase in aerobic biomass formation up to 100% can be expected for the JLR in comparison to the STR.

Visualization of two-phase flow in primary nozzle of a transcritical CO2 ejector

The two-phase flow in the primary converging-diverging nozzle of a transcritical CO2 ejector was investigated by a visualization measurement experiment using the direct photography method. The transition of the phase change position in the primary nozzle was discovered experimentally and analyzed theoretically based on the isentropic expansion process. The pressure distribution along the primary nozzle was measured by the pressure sensors simultaneously under different operating conditions. The expansion state of the primary flow and the nozzle outlet quality were studied by comparing the nozzle outlet pressure with the suction flow inlet pressure. The visualization images revealed that the phase change could start after or before the throat according to the operating conditions, which was consistent with the isentropic analysis results. In addition, the phase change position moved upwards when the primary flow inlet pressure and temperature decreased simultaneously. The pressure measurement results found that the nozzle outlet pressure was obviously higher than the suction flow inlet pressure in the experiment, which indicated that the primary flow was under-expanded in the primary nozzle. The nozzle outlet quality calculated with the nozzle outlet pressure was less than that calculated with the suction flow inlet pressure. The visualization experiment can be used to improve the CO2 ejector geometry and provide useful data for CO2 ejector model validation to better interpret the internal complex flow phenomena.

Optimal Design and Experimental Study of Ejector for Ladle Baking

Current regenerative ladle preheating devices for steel plants are supposed to be equipped with an induced draft fan to suction high‐temperature flue gas, which flows through the regenerator and heats it simultaneously. Replacing the traditional draft fan of ladle preheaters with high‐pressure air of steel plants and ejectors is of great significance in energy conservation and emission reduction. The influence of the ejector nozzle diameter, nozzle to throat clearance, diffuser chamber structure, and primary gas inlet pressure on the ejector performance is analyzed through a combination of establishing a three‐dimensional ejector model and simulation work with the numerical simulation software Fluent. The optimal ejector design parameters are proposed and validated using experimental data. The research showed that the ejector can achieve the best performance with the parameters of 0.42 MPa inlet pressure for high‐pressure primary gas, 0.027 m ejector nozzle diameter, 0.11 m nozzle to throat clearance, 8° divergence angle of the diffuser, and 0.19 m length of diffuser chamber. The entrained mass flow rate of the secondary gas is 1.14 kg s−1 for the optimal ejector. The experimental results are consistent with those of the numerical simulation and verified that the optimal design of ejector device met the practical requirements.

Investigation of the ejector nozzle in refrigeration system

This study presents a model for quantifying the performance of primary nozzles within the context of ejectors in the refrigeration systems. The effects of real and ideal gas properties are compared and two equations for the two-phase speed of sound are tested against experimental data for vapor nozzles working with R245fa, N2 and R141b and also a two-phase nozzles processing CO2. Results show that the predicited performance of ejector nozzles based on the ideal gas assumptions can be greatly different from that based on the real fluid properties. For the two-phase nozzle the value of the speed of sound is important as it was found to be because errors in this lead to large differences in the nozzle performance and even predictions of nozzle efficiency values greater than one. It is expected that this paper and the study described within will be useful for those wishing to model or design ejector nozzles and contributes to the further understanding of related investigations, especially on the two-phase nozzle.

Performance evaluation and parametric studies on variable nozzle ejector using R134A

Computational fluid dynamics of variable nozzle ejector has been studied to determine the optimum nozzle exit position for reliable ejector cooling cycle operations. The flow rates of primary and secondary stream were varied to obtain the optimum entrainment ratio under different ranges of operating conditions.The refrigerant R134a was chosen based on the merit of its environmental and performance characteristics, the refrigerant was chosen because currently is used widely in air conditioning system. It was found that the computational fluid dynamics showed that the optimum positioning of nozzle exit position, which was based on the parameters such as pressure inlet variation the temperature inlet. The results obtained after the optimization of the results showed that the optimum nozzle exit position was found at 3 mm from the mixing chamber inlet when the operating conditions pressure inlet, secondary pressure inlet, primary temperature inlet and outlet pressure were at (18bar,6bar,373K,and5.6bar) respectively. Similarly, the range of entrainment ratio was varied between 0.24−1.283 at a constant area ratio, and at varied operating conditions.

Analytical and experimental investigation of satellite thruster vacuum performance employing supersonic ejectors

The present study is carried out to investigate the performance of a cold gas thruster operating under the vacuum with a high expansion ratio. A pressure recovery system employing diffuser and multistage ejectors is employed to evacuate a vacuum cell whose pressure is an indicating parameter of an operating altitude (i.e. nozzle exit condition). The cold gas thruster has an expansion area ratio of 60. For ejector design, the parameters like the length to diameter ratio (L/De) and ejector nozzle stagnation pressure (Ptot) seem to have significant importance, and their effects on vacuum cell pressure are studied by using both analytical and experimental techniques. Role of second throat type diffuser in the overall pressure recovery is also investigated. The required exit pressure is achieved by a two-stage ejector system having constant area mixing chambers. The ejectors’ stagnation pressures are considered from 12 to 20 bars, while (L/De) is considered from 4.5 to 15 and 2.5 to 16.5 for Ejector-1 and Ejector-2, respectively. Minimum vacuum cell pressure is achieved with the (L/De) of 7 and 9 and stagnation pressure (Ptot) of 18 and 20 bars for Ejector-1 and Ejector-2, respectively. The thrust coefficient (CF) and the specific impulse (Isp) were found in good agreement with the theoretical results.

System model derivation of the CO2 two-phase ejector based on the CFD-based reduced-order model

The developed reduced-order model (ROM) of the R744 two-phase ejector was presented in this paper. The proper orthogonal decomposition (POD) model was employed together with the radial basis function (RBF) to evaluate the ejector performance at the motive nozzle operating regime from 70 bar to 100 bar. The proposed model was built based on the full CFD model of the R744 two-phase ejector with homogeneous equilibrium flow assumption. The validation procedure was performed to evaluate the ejector nozzles mass flow rate discrepancies of ROM compared to the CFD results and experimental data. In addition, the accuracy analysis of the ROM flow field results compared to the CFD results was performed. The validation process based on the CFD results and experimental data indicated the high accuracy of ROM for both nozzles mass flow rate within ±10% for most of the investigated operating points. Hence, the high accuracy of the computed mass flow rates allows ROM implementation into the dynamic simulations of the refrigeration system to evaluate the ejector performance at given operating points with negligible time effort.

Analysis of Low-Grade Waste Heat Driven Systems for Cooling and Power for Tropical Climate

In the 21st conference of the parties (COP21) of United Nations, both renewable energy and energy efficiency were recognized as essential means for low-carbon future. It is estimated that around 20-50 % of energy input to industries is lost as waste heat. Low-grade heat is abundantly available from renewable sources like solar, biomass and geothermal. There is a need to develop technologies which can utilize very low-grade heat (<100 °C). This paper reports the design and optimization of heat driven systems for utilizing very low-grade waste heat in tropical conditions. The Ejector Refrigeration System (ERS) has been selected, designed and simulated to producing cooling from low-grade heat. Organic Rankine Cycle (ORC) has been designed and simulated for producing power and a novel hybrid configuration is proposed to produce power and cooling simultaneously. The ERS and ORC optimization involves the selection of most suitable working fluids, working conditions, sizing of components, and optimizing configurations. For system level modeling with real properties of working fluids, EES (engineering equation solver) and EBSILON (a commercial thermal system design tool) are being used in this work. For design optimization of ejector, EES and ANSYS-FLUENT (a commercial CFD solver) are being used. With EES model, the ORC system has been found to operate at 5.2 % overall efficiency. The results from EES model have been verified by the EBSILON model. The EES model for ERS gives the COP of 0.48. The EES model developed for ejector nozzles can be used to design any supersonic nozzle for the desired inlet and outlet pressers and exit velocity. A novel hybrid cycle configuration has been proposed. This novel configuration uses ejector simultaneously for two purposes; to reduce the work-producing-expander outlet pressure and to compress vapor for cooling cycle. The preliminary modeling results show that the output of this configuration is 27 % higher than simple ORC.

Simulasi Numerik Aliran Melewati Nozzle Pada Ejector Converging – Diverging Dengan Variasi Diameter Exit Nozzle

In the process of cooling or refrigeration, are required components where capable to flow the fluid to create a cycle of the cooling process. Among some of the vapor compression systems, the usage of ejector is the simplest system. Ejector has three main parts: primary nozzle, mixing chamber and diffuser. Various experiments of steam ejectors developed to increase the value of the COP. Entrainment ratio directly affects to the COP value generated by the system, where the geometric shapes and operating conditions in the steam ejector will affect to the value entrainment ratio. This research was carried out numerical simulations using CFD commercial software with k-epsilon to predict flow phenomena which passes through the ejector nozzle in the ejector converging-diverging which varying exit diameters 3.5 mm; 4mm; 5 mm; and 5.5 mm. Respectively the simulation results showed exit nozzle steam ejector that the smallest diameter of 3.5 mm give the optimum performance because it provide the highest speed of fluidity. While the state of vacuum in mixing chamber increase, it cause the secondary mass flow higher as well as the value of the entrainment ratio.

Influences of area ratio and surface roughness on homogeneous condensation in ejector primary nozzle

Homogeneous condensation inside the ejector has been ignored by numerous researchers. In this paper, the wet steam model was utilized to study the influences of nozzle area ratio and surface roughness on homogeneous condensation in a primary nozzle. A substantial amount of latent heat is released during the homogeneous condensation process to increase static pressure and reduce Mach number. The increase of nozzle area ratio reduces condensation intensity and lowers nozzle pressure but increases liquid mass fraction. Furthermore, with the growth of surface roughness, the slightly increased dryness fraction is almost ineffective for alleviating erosion caused by tiny droplets; the slight decrease in mass flow rate will reduce ejector performance to some extent, while the sharp increase of entropy generation results in more energy wastes. Therefore, nozzle area ratio and surface roughness should be carefully designed to alleviate potential condensation and enhance ejector performance at the same time.

Experimental investigation on mixed jet and mass transfer characteristics of horizontal aeration process

Experiments were performed to investigate the mixed jet and mass transfer characteristics of a horizontal aeration process with the primary nozzle distance ratio of an annular nozzle ejector and the control valve opening. A direct visualization technique with a high speed camera was used to capture the images of the horizontal mixed jet, and a binarization technique was used to analyze the images. The clean water unsteady state technique was used for the oxygen mass transfer measurement. The measured data were used to calculate the air volume fraction, specific input power, volumetric mass transfer coefficient and mass transfer efficiency. Experimental results showed that the horizontally discharged mixed jet behaved like a buoyancy jet, a quasi-horizontal bubble jet, or a horizontal momentum jet due to the horizontal momentum of primary flow and the buoyancy force of the suction air bubble. It was found that the input power and air volume fraction decreased with the primary nozzle distance ratio, while the volumetric mass transfer coefficient and mass transfer efficiency increased and then decreased. It was also found that the average volumetric mass transfer coefficients with the primary nozzle distance ratio and Reynolds number for the full valve opening were higher than those for the 1/5 valve opening, while the average mass transfer efficiencies for the full valve opening were lower than those for the 1/5 valve opening. Based on the experimental results, an empirical correlation to predict the effects of Reynolds number, air volume fraction and specific input power on the volumetric mass transfer coefficient was proposed.

Influence of Structural Parameters of Two-throat Nozzle Ejector on Performance of Two-phase Flow Ejector Refrigeration System

The expansion work can be recovered and the inlet pressure of the compressor can be increased by using the two-phase flow ejector, so as to reduce compressor power consumption and improve the system performance. In this paper, the experimental study on the performance of R134a two-phase flow ejector with two-throat nozzle refrigeration system is carried out. The influence of the structure parameters of the ejector on the performance of the ejector and the refrigeration system was discussed. The experimental results indicate that the smaller nozzle distance is beneficial to improve the performance of ejector. Under the condition of the condensing temperature of 40°C and the evaporation temperature of -10°C, the performance of the ejector and the ejector system is the best as the divergence angle of the first nozzle is 8°. The refrigeration capacity of the system can be adjusted by changing the position of the injection needle. As the effective area ratio of the nozzle throat is 90%, the performance of the system and the ejector can reach the maximum value.

Numerical study on optimization of ejector primary nozzle geometries

In an ejector refrigeration system (ERS), ejector acts as a compressor but without using any moving parts. To some extent, ejector performances are subjected to primary nozzle's geometries with the action of shock waves. In this paper, CFD simulation was conducted to improve the ejector performance by varying the following ejector primary nozzle's geometries and surface roughness: two angles of convergent and divergent portion, three lengths and surface roughness of throat, convergent and divergent portion. The CFD model was validated with the test results of an ERS experimental rig with working fluid of R134a. The optimum geometric parameters and surface roughness of the primary nozzle were obtained with the CFD analysis. The simulation results revealed that the throat and divergent portion of the primary nozzle should be paid more attention when designing ejector since the entrainment ratio of the ejector is rather sensitive to the length and surface roughness of these two portions.

Измерение скорости бронзовых частиц в потоке из эжекторного сопла для холодного газодинамического напыления

Измерение скорости бронзовых частиц в потоке из эжекторного сопла для холодного газодинамического напыления

Numerical study on collision characteristics for non-spherical particles in venturi powder ejector

The venturi ejector forms vacuum causing by venturi effect which makes particles enter into ejector. The conveying process of two kinds of non-spherical particles in the venturi powder ejector was respectively simulated with using CFD-DEM coupling approach, and the collision characteristics among particles were analyzed. The influence of the particle impact on the wall stress was analyzed, and the changed reason of the wall stress from collision behaviors among particles was deeply discussed with using DEM-FEM coupling approach. The present analyses show that hot spots of particle-wall collision occur around the ejector nozzle, both the particle-particle and particle-wall collision frequencies for the cylinder-shaped particles are larger than those for the tablet-shaped particles, and the force strength by collisions for the cylinder-shaped particles is larger than that for the tablet-shaped particles.

Experimental investigation on motive nozzle throat diameter for an ejector expansion refrigeration system

In this study, ejector was used to reduce throttling losses in a vapour compression refrigeration system. Effects on system performance of throat diameter and position of motive nozzle of ejector were investigated experimentally. An ejector was designed based on the established mathematical model and manufactured. The experiments were carried out by using different primary nozzle throat diameters. The experiments were further conducted by changing condenser water inlet temperature, which is one of the external parameters. The experimental results of the ejector system and those of the classic system were compared under same external operating conditions and for the same cooling capacity. In order to obtain same external operating conditions in both systems, the inlet conditions of the brine supplied to the evaporator and inlet water conditions (flow rate and temperature) to the condenser were kept constant. Maximum performance was obtained when the primary nozzle throat diameter was 2.3mm within the areas considered in this study. When compared, it was experimentally determined that the ejector system that uses the optimum motive nozzle throat diameter exhibits higher COP than the classic system by 5–13%. Furthermore, it was found that the variation of coefficient of performance based on position of motive nozzle in two-phase ejector expander refrigeration cycle is lower than 1%.

The Average Coverage of Sprayed Objects Depending on the Coefficient of Spray Surface for the Selected Nozzles

Abstract The primary objective of the experiment was to determine the average coverage of the sprayed liquid on the plant surface according to the adopted coefficient of the spray surface of plants (Wpo). Examinations were performed under laboratory conditions, using a sprayer, which was moving with a constant operating speed, at various operating pressures. During the study four types of nozzles were used: standard and ejector. They sprayed objects, which were artificial plants, equipped with probes in the form of water-sensitive papers. Probes were placed on the horizontal and vertical surfaces of the plants. The degree of coverage was determined by computer image analysis. The analysis of obtained results showed that the coefficient of the surface spray has a significant impact on the size of the average surface coverage of sprayed objects. It was found that in case where the Wpo &lt;1, standard nozzles are better for spraying, and when Wpo &gt; 1, ejector nozzles and standard double may be used more successfully.

Effects of superheated steam on non-equilibrium condensation in ejector primary nozzle

In order to reduce the non-equilibrium condensation occurring in ejector primary nozzle, wet steam model was adopted to investigate the relationship between steam superheated level and non-equilibrium condensation within ejector primary nozzle. Simulation data of axial static pressure along primary nozzles were validated with experimental data reported in literature. The non-equilibrium condensation process from homogeneous nucleation to droplet growth stage and the resulting products were carefully studied. Moreover, six inlet superheated levels from 5 K to 30 K with the increment of 5 K were compared, and simulation results showed that the increase of superheated level from 5 K to 30 K causes 40.22% delay in the location and 43.92% reduction in the intensity of the condensation shock. Furthermore, there is about 24.30% liquid mass fraction decrease when the superheated level raises to 30 K and total entropy generation increases slowly with the increase of superheated level.

Dynamic simulation of an improved transcritical CO2 ejector expansion refrigeration cycle

This paper presents a dynamic model of a transcritical CO2 ejector expansion refrigeration cycle with two-stage evaporation (EERC-TE), which is deemed to further improve the performance of a basic transcritical CO2 ejector expansion refrigeration cycle (EERC). The adjustments of compressor speed, the expansion valve opening, the throat area of ejector nozzle and the chilled water flow rate of evaporators are conducted as the disturbances to investigate the system transient responses. The presented results show the predictions have a good agreement with the experimental data. The change of compressor speed causes larger response of system parameters than that of the other disturbances. The expansion valve opening can result in obvious variation of the evaporator pressure and the pressure lift ratio of ejector, while the throat area of ejector nozzle leads to outstanding change of the gas cooler pressure and the ejector entrainment ratio. Moreover, these responses are compared with that of EERC and they show the similar change trends. Based on the transient results, the combination adjustment methods are proposed to improve the system performance, and the enhancement of COP of EERC-TE is more distinct and it is 2.58 times than that of EERC under the conditions of this study. In the basis of the transient simulations, flexible and diverse adjustment methods can be applied to improve the system performance and guide the system control.

CO&lt;sub&gt;2&lt;/sub&gt;冷凍サイクル用エジェクターの駆動ノズル部流れの速度計測

For the optimum design of two-phase flow nozzle of CO2 two-phase flow ejector, it is important to investigate fluid mechanics of high-speed gas-liquid two-phase flow. The purpose of this study is to investigate CO2 two-phase nozzle flow in view of both experimental and analytical aspects. In the experiment, CO2 in supercritical pressure condition was blown down into atmosphere through a divergent-convergent nozzle, where the mainstream profile of temperature was measured. Furthermore, velocity measurements of nozzle flow were conducted using by PIV system. Experimental data of both temperature and velocity show that the nozzle flow is considered to be supersonic flow. The experimental values of velocity are found to locate between the gas velocity and the liquid velocity of the 1-dimensional analysis by Kinoue et al.