scholarly journals Numerical Investigation of the Effect of Air Leaking into the Working Fluid on the Performance of a Steam Ejector

2021 ◽  
Vol 11 (13) ◽  
pp. 6111
Author(s):  
He Li ◽  
Xiaodong Wang ◽  
Jiuxin Ning ◽  
Pengfei Zhang ◽  
Hailong Huang
Keyword(s):  
Flow Structure ◽  
Mass Fraction ◽  
Internal Flow ◽  
Working Fluid ◽  
Physical Parameters ◽  
Entrainment Ratio ◽  
Air Mass ◽  
Steam Ejector ◽  
Primary Fluid ◽  
Mass Fractions

This paper investigated the effect of air leaking into the working fluid on the performance of a steam ejector. A simulation of the mixing of air into the primary and secondary fluids was performed using CFD. The effects of air with a 0, 0.1, 0.3 and 0.5 mass fraction on the entrainment ratio and internal flow structure of the steam ejector were studied, and the coefficient distortion rates for the entrainment ratios under these air mass fractions were calculated. The results demonstrated that the air modified the physical parameters of the working fluid, which is the main reason for changes in the entrainment ratio and internal flow structure. The calculation of the coefficient distortion rate of the entrainment ratio illustrated that the air in the primary fluid has a more significant impact on the change in the entrainment ratio than that in the secondary fluid under the same air mass fraction. Therefore, the air mass fraction in the working fluid must be minimized to acquire a precise entrainment ratio. Furthermore, this paper provided a method of inspecting air leakage in the experimental steam ejector refrigeration system.

scholarly journals A Steam Ejector Refrigeration System Powered by Engine Combustion Waste Heat: Part 1. Characterization of the Internal Flow Structure

2019 ◽  
Vol 9 (20) ◽  
pp. 4275 ◽  
Author(s):  
Yu Han ◽  
Lixin Guo ◽  
Xiaodong Wang ◽  
Anthony Chun Yin Yuen ◽  
Cuiling Li ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Flow Structure ◽  
Waste Heat ◽  
Mixing Layer ◽  
Internal Flow ◽  
Fluid Temperature ◽  
Refrigeration System ◽  
Shock Train ◽  
Steam Ejector ◽  
Primary Fluid

With the escalating production of automobiles, energy efficiency and environmental friendliness have always been a major concern in the automotive industry. In order to effectively lower the energy consumption of a vehicle, it is essential to develop air-conditioning systems that can make good use of combustion waste heat. Ejector refrigeration systems have become increasingly popular for this purpose due to their energy efficiency and ability to recycle waste heat. In this article, the elements affecting the performance of a typical ejector refrigeration system have been explored using both experimental and numerical approaches. For the first time, the internal flow structure was characterized by means of comprehensive numerical simulations. In essence, three major sections of the steam ejector were investigated. Two energy processes and the shock-mixing layer were defined and analyzed. The results indicated that the length of the choking zone directly affects the entertainment ratio under different primary fluid temperature. The optimum enterainment ratio was achieved with 138 °C primary fluid temperature. The shock-mixing layer was greatly affected by secondary fluid temperature. With increasing of back pressure, the normal shock gradually shifted from the diffuser towards the throat, while the shock train length remains lunchanged.

Internal Flow Structure of a Pressure-Swirl Atomizer at Two Different Density Ratios

2000 ◽  
Author(s):  
Dexin Wang ◽  
Zhanhua Ma ◽  
San-Mou Jeng ◽  
Michael A. Benjamin
Keyword(s):  
Reynolds Number ◽  
Flow Structure ◽  
Large Scale ◽  
Ambient Medium ◽  
Density Ratio ◽  
Internal Flow ◽  
Sudden Expansion ◽  
Working Fluid ◽  
Swirl Atomizer ◽  
Density Ratios

The flow fields of large-scale simplex nozzles were investigated by 2-D back-scattered Laser Doppler Velocimetry (LDV). The internal flow structures of a simplex nozzle at two different density ratios of the working fluid and the ambient medium were obtained. The effects of the density ratio, Reynolds Number and orifice geometry on the flow structure were examined. The results revealed that the density ratio only affects the internal flow field in the region where the radius is smaller than the orifice radius. The density ratio and Reynolds Number have stronger influence on the internal flow structure of a sudden contraction and 45° expansion orifice configuration than on that of a 45° contraction and sudden expansion orifice configuration. When the density ratio is one, the effect of the contraction geometry from swirl chamber to orifice on the internal flow is very small compared to the effect of the expansion geometry.

scholarly journals Effects of Shock Wave Phenomenon on Different Convergent Lengths in the Mixing Chamber of the Steam Ejector

2021 ◽  
Vol 03 (01) ◽  
pp. 93-100
Author(s):  
Stefan Mardikus ◽  
Keyword(s):  
Shock Wave ◽  
Wave Phenomenon ◽  
High Speed ◽  
Working Fluid ◽  
Operating Pressure ◽  
Wave Effect ◽  
Primary Flow ◽  
Entrainment Ratio ◽  
Steam Ejector ◽  
Mixing Chamber

The shock wave phenomenon is a phenomenon in a steam ejector that caused when the working fluid has high pressure, and suddenly it turns into low pressure and high speed. The shock wave effect will be investigated to the different convergent length in the mixing chamber to find the highest entrainment ratio as the performance of steam ejector. Operating pressure in the primary flow was in the range 0.68 MPa - 1.39 MPa, and the secondary flow was set 0.38 MPa to 0.65 MPa. The result of this study demonstrated that the highest entrainment ratio occurred in the convergent length of 69 mm.

Analysis of Flow Field in an Ejector With Steam as Working Fluid

2004 ◽  
Author(s):  
Haijun Li ◽  
Shengqiang Shen
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Fluid Pressure ◽  
Navier Stokes ◽  
Working Fluid ◽  
Complex Flow ◽  
Entrainment Ratio ◽  
Navier Stokes Equations ◽  
Saturated Water ◽  
Steam Ejector

Two-dimensional Navier-Stokes equations were solved to obtain local distributions of pressure, temperature and Mach number of the complex flow field in a steam ejector. From the computational results, we obtain that there is a critical discharging pressure for given motive pressure and suction pressure. The effects of motive fluid pressure, motive fluid overheat, suction fluid pressure and discharge fluid pressure on the entrainment ratio and critical discharging pressure were concluded in detail. Analysis was also done to comprehend the reason of shocks emerging, their positions, and their effects on ejector performance. Phase transition phenomenon occurred in the ejector when using steam as working fluid was obtained through calculating the percent of saturated water in the mixture. The effect of the ejector’s geometrical structure on its performance is further studied and high COP of the ejector is gained by optimizing its structure.

CFD Study on Supersonic Ejectors Used for Suction of Two Different Gases

2015 ◽  
Author(s):  
Mohsen Tavakol ◽  
Maziar Shafaee
Keyword(s):  
Numerical Simulation ◽  
Water Vapor ◽  
Mass Fraction ◽  
Pure Water ◽  
Variable Mass ◽  
Working Fluid ◽  
Gas Streams ◽  
Mass Fractions ◽  
Suction Flow ◽  
Different Gases

In ejector refrigeration cycles, ejector working fluids include various refrigerants with different properties. In some cases, ejector works with mixture of two different refrigerants; that each refrigerant have distinct properties. The purpose of this paper is to evaluate the performance of an ejector used for suction of a mixture of air and water vapor. In this regard, the ejector performance was numerically studied under the operating condition that a mixture of air and steam with variable mass fractions, were sucked into the ejector. With the help of numerical simulation, various conditions for two perfect gas streams of air and water vapor were investigated. Initially, the numerical simulation was carried out for the case that pure water vapor was considered as the working fluid of ejector. After validation of initial case with experimental data, numerical method was expanded for a specific case that, water vapor was considered as the working fluid of motive flow and a mixture of air and water vapor was considered for suction flow. Numerical simulations were done for different mass fraction of air and water vapor for suction flow mixture. Results indicated that, variations of the mass fraction of air in suction flow, leads to obvious changes in ejector performance. Also, it was observed that the increment of suction flow pressure, leads to increment of the ejector performance sensitivity to variations of suction flow mass fraction.

scholarly journals Thermodynamic investigations of Zeotropic mixture of R290, R23 and R14 on three-stage auto refrigerating cascade system

2016 ◽  
Vol 20 (6) ◽  
pp. 2073-2086
Author(s):  
Mayilsamy Sivakumar ◽  
Periasamy Somasudaram
Keyword(s):  
Mass Fraction ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Cascade System ◽  
Environment Friendly ◽  
Mass Fractions ◽  
Zeotropic Mixture ◽  
Efficiency Defect ◽  
Low Temperature Refrigeration ◽  
System Operating

The zeotropic mixture of environment friendly refrigerants (hydrocarbons and hydrofluorocarbons) being the only alternatives for working fluid in low temperature refrigeration system. Hence, three-stage auto refrigerating cascade system was studied for the existence using four combinations of three-component zeotropic mixture of six different refrigerants. The exergy analysis confirmed the existence of three-stage auto refrigerating cascade system. The performances of the system like coefficient of performance, exergy lost, exergic efficiency, efficiency defect, and the evaporating temperature achieved were investigated for different mass fractions in order to verify the effect of mass fraction on them. In accordance with the environmental issues and the process of sustainable development, the three-component zeotropic mixture of R290/R23/R14 with the mass fraction of 0.218:0.346:0.436 was performing better and hence can be suggested as an alternative refrigerant for three-stage auto refrigerating cascade system operating at very low evaporating temperature in the range of ?97?C (176 K), at coefficient of performance of 0.253 and comparatively increased exergic efficiency up to 16.3% (58.5%).

scholarly journals New Knowledge on the Performance of Supercritical Brayton Cycle with CO2-Based Mixtures

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1741 ◽  
Author(s):  
Aofang Yu ◽  
Wen Su ◽  
Li Zhao ◽  
Xinxing Lin ◽  
Naijun Zhou
Keyword(s):  
Mass Fraction ◽  
High Efficiency ◽  
Cycle Performance ◽  
Working Fluid ◽  
Temperature Cycle ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Critical Temperatures ◽  
Mass Fractions ◽  
Compressor Inlet

As one of the promising technologies to meet the increasing demand for electricity, supercritical CO2 (S-CO2) Brayton cycle has the characteristics of high efficiency, economic structure, and compact turbomachinery. These characteristics are closely related to the thermodynamic properties of working fluid. When CO2 is mixed with other gas, cycle parameters are determined by the constituent and the mass fraction of CO2. Therefore, in this contribution, a thermodynamic model is developed and validated for the recompression cycle. Seven types of CO2-based mixtures, namely CO2-Xe, CO2-Kr, CO2-O2, CO2-Ar, CO2-N2, CO2-Ne, and CO2-He, are employed. At different CO2 mass fractions, cycle parameters are determined under a fixed compressor inlet temperature, based on the maximization of cycle efficiency. Cycle performance and recuperators’ parameters are comprehensively compared for different CO2-based mixtures. Furthermore, in order to investigate the effect of compressor inlet temperature, cycle parameters of CO2-N2 are obtained under four different temperatures. From the obtained results, it can be concluded that, as the mass fraction of CO2 increases, different mixtures show different variations of cycle performance and recuperators’ parameters. In generally, the performance order of mixtures coincides with the descending or ascending order of corresponding critical temperatures. Performance curves of these considered mixtures locate between the curves of CO2-Xe and CO2-He. Meanwhile, the curves of CO2-O2 and CO2-N2 are always closed to each other at high CO2 mass fractions. In addition, with the increase of compressor inlet temperature, cycle performance decreases, and more heat transfer occurs in the recuperators.

Numerical Investigation of the Effects of Primary Nozzle Diverging Portion on Performance of the Supersonic Ejector of an Ejector Refrigeration Cycle

2019 ◽  
Vol 27 (03) ◽  
pp. 1950030
Author(s):  
Shaban Alyari Shourehdeli ◽  
Kamran Mobini ◽  
Ali Asakereh
Keyword(s):  
Method Of Characteristics ◽  
Consumption Rate ◽  
Internal Flow ◽  
Parallel Flow ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Refrigeration System ◽  
Entrainment Ratio ◽  
Supersonic Ejector ◽  
Energy Consumption Rate

A supersonic ejector with desirable performance characteristics reduces the energy consumption rate of an ejector refrigeration system and increases its coefficient of performance (COP). In this paper, the effects of using different primary nozzles on the performance of a supersonic ejector of an ejector refrigeration system have been numerically studied, while the working fluid is steam. To this end, conical, Rao and parallel-flow primary nozzles with identical converging portions and equal exit area to throat area ratios have been tested. The diverging portion curves for the parallel-flow and Rao nozzles were derived using the method of characteristics. Using the Rao nozzle, the critical entrainment ratio and the critical back pressure were increased compared to the conical nozzle by 6.3% and 2.08%, respectively. It was also found that the physics of the internal flow of the ejector was changed by changing the diverging curve of the primary nozzle.

Computational fluid dynamics simulation of the supersonic steam ejector. Part 2. Optimal design of geometry and the effect of operating conditions on the ejector

2011 ◽  
Vol 226 (3) ◽  
pp. 715-723 ◽  
Author(s):  
L Cai ◽  
H T Zheng ◽  
Y J Li ◽  
Z M Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Optimal Design ◽  
Critical Pressure ◽  
Operating Conditions ◽  
Dynamics Simulation ◽  
Working Fluid ◽  
Entrainment Ratio ◽  
Steam Ejector ◽  
Mixing Chamber

The aim of this study is to investigate the use of computational fluid dynamics in predicting the performance and optimal design of the geometry of a steam ejector used in a steam turbine. In the current part, the real gas model was considered using IAPWS IF97 model, and the influences of working fluid pressure and backpressure were investigated. The results illustrate that working critical pressure and backflow critical pressure exist in the flow. Moreover, the entrainment ratio reaches its peak at the working critical pressure. The performance of the ejector was nearly the same when the outlet pressure was lower than the critical backpressure. Effects of ejector geometries were also investigated. The distance between the primary nozzle and the mixing chamber was at optimum, the length of the mixing chamber and the diameter of the throat had an optimal value according to the entrainment ratio. When the length of the diffuser or throat was decreased within a range, the entrainment ratio did not change significantly.

A technique for uranium and plutonium determination using coulometric potentiostatic facility UPK-19 for analysis of mixed-oxide fuel

2020 ◽  
Vol 86 (12) ◽  
pp. 15-22
Author(s):  
N. A. Bulayev ◽  
E. V. Chukhlantseva ◽  
O. V. Starovoytova ◽  
A. A. Tarasenko
Keyword(s):  
Acid Solution ◽  
Mass Fraction ◽  
Background Electrolyte ◽  
Stable State ◽  
Sulfamic Acid ◽  
Oxide Fuel ◽  
Oxidation Current ◽  
Mox Fuel ◽  
Mass Fractions ◽  
Uranium Plutonium

The content of uranium and plutonium is the main characteristic of mixed uranium-plutonium oxide fuel, which is strictly controlled and has a very narrow range of the permissible values. We focused on developing a technique for measuring mass fractions of uranium and plutonium by controlled potential coulometry using a coulometric unit UPK-19 in set with a R-40Kh potentiostat-galvanostat. Under conditions of sealed enclosures, a special design of the support stand which minimized the effect of fluctuations in ambient conditions on the signal stability was developed. Optimal conditions for coulometric determination of plutonium and uranium mass fractions were specified. The sulfuric acid solution with a molar concentration of 0.5 mol/dm3 was used as a medium. Lead ions were introduced into the background electrolyte to decrease the minimum voltage of hydrogen reduction to –190 mV. The addition of aluminum nitride reduced the effect of fluoride ions participating as a catalyst in dissolving MOX fuel samples, and the interfering effect of nitrite ions was eliminated by introducing a sulfamic acid solution into the cell. The total content of uranium and plutonium was determined by evaluation of the amount of electricity consumed at the stage of uranium and plutonium co-oxidation. Plutonium content was measured at the potentials, at which uranium remains in the stable state, which makes it possible to subtract the contribution of plutonium oxidation current from the total oxidation current. The error characteristics of the developed measurement technique were evaluated using the standard sample method and the real MOX fuel pellets. The error limits match the requirements set out in the specifications for MOX fuel. The technique for measuring mass fractions of uranium and plutonium in uranium-plutonium oxide nuclear fuel was certified. The relative measurement error of the mass fraction of plutonium and uranium was ±0.0070 and ±0.0095, respectively. The relative error of the ratio of the plutonium mass fraction to the sum of mass fractions of uranium and plutonium was ±0.0085.

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