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

2017 ◽  
Vol 2 (1) ◽  
pp. 19
Author(s):  
Novi Indah Riani ◽  
Syamsuri Syamsuri ◽  
Rungky Rianata Pratama
Keyword(s):  
Operating Conditions ◽  
Vapor Compression ◽  
Cooling Process ◽  
Entrainment Ratio ◽  
Steam Ejector ◽  
Mixing Chamber ◽  
Exit Nozzle ◽  
Flow Phenomena ◽  
Ejector Nozzle ◽  
Simulation Results

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.

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.

scholarly journals Parametric analysis of a combined ejector-vapor compression refrigeration cycle

2020 ◽  
Vol 15 (3) ◽  
pp. 398-408
Author(s):  
I Ouelhazi ◽  
Y Ezzaalouni ◽  
L Kairouani
Keyword(s):  
Current Model ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Refrigeration Cycle ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Entrainment Ratio ◽  
Constant Area ◽  
Vapor Compression Refrigeration Cycle ◽  
Vapor Compression Refrigeration

Abstract From the last few years, the use of efficient ejector in refrigeration systems has been paid a lot of attention. In this article a description of a refrigeration system that combines a basic vapor compression refrigeration cycle with an ejector cooling cycle is presented. A one-dimensional mathematical model is developed using the flow governing thermodynamic equations based on a constant area ejector flow model. The model includes effects of friction at the constant-area mixing chamber. The current model is based on the NIST-REFPROP database for refrigerant property calculations. The model has basically been used to determine the effect of the ejector geometry and operating conditions on the performance of the whole refrigeration system. The results show that the proposed model predicts ejector performance, entrainment ratio and the coefficient of performance of the system and their sensitivity to evaporating and generating temperature of the cascade refrigeration cycle. The simulated performance has been then compared with the available experimental data from the literature for validation.

Numerical Simulation of Performance of Steam Ejector Influenced by the Distance between Nozzle Outlet and Mixing Chamber Inlet

2011 ◽  
Vol 299-300 ◽  
pp. 970-973
Author(s):  
Xiao Chun Dai ◽  
Guo Jin Liao
Keyword(s):  
Numerical Simulation ◽  
Geometric Parameters ◽  
Experimental Results ◽  
Nozzle Outlet ◽  
Entrainment Ratio ◽  
Optimum Range ◽  
Steam Ejector ◽  
Mixing Chamber ◽  
Throat Diameter

The performance of a steam ejector was simulated using FLUENT. The performance of steam ejector was studied by changing the distance between primary nozzle outlet and mixing chamber inlet (DPM) while operating pressures and other geometric parameters were not varied. The entrainment ratios of the steam ejector with different values of DPM were calculated. The optimum range of DPM was given, which is changed from 1.8 to 2 times of the throat diameter of hybrid diffuser pipe. The errors of the CFD results to the experimental results of the entrainment ratio are not more than 15%.

scholarly journals A Numerical Study on the Supersonic Steam Ejector Use in Steam Turbine System

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Lin Cai ◽  
Miao He
Keyword(s):  
Steam Turbine ◽  
Numerical Study ◽  
Fluid Pressure ◽  
Ideal Gas ◽  
Entrainment Ratio ◽  
Real Gas ◽  
Steam Ejector ◽  
Mixing Chamber ◽  
Cfd Method ◽  
Ideal Gas Model

Supersonic steam ejector is widely used in steam energy systems such as refrigeration, wood drying equipment, papermaking machine, and steam turbine. In this paper the Computational Fluids Dynamics (CFD) method was employed to simulate a supersonic steam ejector, SST k-w turbulence model was adopted, and both real gas model and ideal gas model for fluid property were considered and compared. The mixing chamber angle, throat length, and nozzle exit position (NXP) primary pressure and temperature effects on entrainment ratio were investigated. The results show that performance of the ejector is underestimated using ideal gas model, and the entrainment ratio is 20%–40% lower than that when using real gas model. There is an optimum mixing chamber angel and NXP makes the entrainment ratio achieve its maximum; as throat length is decreased within a range, the entrainment ratio remains unchanged. Primary fluid pressure has a critical value, and the entrainment ratio reaches its peak at working critical pressure; when working steam superheat degree increases, the entrainment ratio is increased.

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.

scholarly journals INVESTIGATION OF EVAPORATION AND CONDENSATION PROCESS OF INDUCED FLOW USING STEAM EJECTOR

2021 ◽  
Vol 16 (2) ◽  
Author(s):  
Shahad Jamal
Keyword(s):  
Mathematical Model ◽  
Mass Flow ◽  
Nozzle Outlet ◽  
Entrainment Ratio ◽  
Flow Rates ◽  
Steam Ejector ◽  
Secondary Steam ◽  
Induced Flow ◽  
Ejector Nozzle ◽  
The Mathematical Model

The research aims to understand the design parameters of steam ejector nozzle on the performance of flash evaporation induced by the effect of a steam jet passing through it. The research concentrates on studying the effect of ejector nozzle outlet diameter on induced flow from preheated water in a specified evaporator using a subsonic ejector. The thermal energy extracted from the condensed steam mixture in the condenser is used to heat the water in the evaporator. The experimental tests investigate the effect of nozzle geometry on the induced evaporation process by changing nozzle outlet diameter while keeping the pressure of evaporator, condenser and primary steam constant. The experimental results proved that both primary and secondary steam mass flow rates increase versus nozzle outlet diameter, while the entrainment ratio of secondary to primary steam flow rates decreases due to the restricted increase of the secondary steam mass flow rate. The mathematical model prepared to simulate the behaviour of the subsonic ejector is validated using the comparison between experimental and theoretical results. The mathematical model showed that maximum entrainment of 0.57 is obtained at a primary steam pressure of 2 bars when the nozzle outlet diameter is fixed at 1.5 mm, while minimum entrainment ratio of 0.17 is estimated at 1.5 bar pressure related to primary steam when the nozzle outlet diameter is fixed at 2.5mm. The authors recommend defining nozzle geometrical parameters according to the operating conditions of the experimental test rig to enhance ejector efficiency.

scholarly journals A Numerical Analysis of the Influence of Nozzle Geometric Structure on Spontaneous Steam Condensation and Irreversibility in the Steam Ejector Nozzle

2021 ◽  
Vol 11 (24) ◽  
pp. 11954
Author(s):  
He Li ◽  
Xiaodong Wang ◽  
Hailong Huang ◽  
Jiuxin Ning ◽  
Jiyuan Tu
Keyword(s):  
Entropy Generation ◽  
Wet Steam ◽  
Steam Condensation ◽  
Throat Radius ◽  
Spontaneous Condensation ◽  
Steam Ejector ◽  
Expansion Angle ◽  
Ejector Nozzle ◽  
Throat Diameter ◽  
Simulation Results

The spontaneous condensation of wet steam often occurs in the steam ejector nozzle, this deteriorates the performance of the steam ejector. In this paper, we take changing the geometric parameters of the nozzle as the focus of our research and construct an internal connection between steam’s condensation behavior and the nozzle’s throat radius, the nozzle’s divergent section expansion angle, and the nozzle’s divergent section length. Our numerical simulation results indicate that an increase in the throat diameter and reduction of the divergent section’s expansion angle can inhibit steam condensation behavior, to a certain extent. In particular, the steam condensation behavior will disappear at a 0° expansion angle, but it is not affected by the change in the divergent section’s length. In addition, the irreversibility that is seen under different changes to the nozzle’s structure parameters was investigated and the results show that the entropy generation that is caused by a phase change accounts for a much higher proportion of the total entropy generation than heat transport and viscous dissipation do. This indicates that steam’s condensation behavior makes a large amount of irreversible energy, resulting in energy waste and reducing the performance of the nozzle. Therefore, this study can provide a theoretical reference for suppressing the spontaneous condensation behavior of steam by changing the nozzle’s geometry.

Experimental Studies on the Effect of Suction Chamber Angle on the Entrainment of Passive Fluid in a Steam Ejector

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
A. S. Ramesh ◽  
S. Joseph Sekhar
Keyword(s):  
Experimental Studies ◽  
Operating Conditions ◽  
Entrainment Ratio ◽  
Strong Function ◽  
Flow Equations ◽  
Steam Ejector ◽  
Minor Influence ◽  
A Minor ◽  
The Impact ◽  
Chamber Angle

In this experimental study, the impact of suction chamber angle (SCA) on the entrainment ratio of a steam ejector refrigeration system (ERS) of 700 W was investigated. The basic dimensions of the ejector were derived from the compressible fluid flow equations using matlab. The system was tested with six different SCAs with various operating conditions, and its performance was analyzed. It is inferred that the entrainment of passive fluid from the evaporator is the strong function of the SCA. For all the active steam pressures, the entrainment of the passive fluid increases up to 12 deg of SCA, and above that the performance decreases significantly. Optimum angle of suction chamber increases the entrainment ratio for at least 49.96%. It is also found that the SCA has a minor influence on the back pressure.

Performance Analysis of Refrigerants R1234yf, R1234ze and R134a in Ejector-Based Refrigeration Cycle

2018 ◽  
Vol 26 (03) ◽  
pp. 1850026 ◽  
Author(s):  
Ajay Kumar Yadav ◽  
Neeraj
Keyword(s):  
Heat Pump ◽  
Power Plants ◽  
Operating Conditions ◽  
Refrigeration Cycle ◽  
Vapor Compression ◽  
Entrainment Ratio ◽  
Evaporator Temperature ◽  
Wide Range ◽  
Vapor Compression Refrigeration Cycle ◽  
Vapor Compression Refrigeration

Performance enhancement of refrigeration and heat pump systems by cycle modification is an emerging research topic now-a-days to reduce the electricity consumption leading to mitigate the problems related to the environmental pollution by utility power plants. Due to no moving parts, low cost, simple structure and low maintenance requirements, the use of two-phase ejector has become a promising cycle modification recently. Use of ejector as an expansion device by replacing the throttle valve in the vapor compression refrigeration cycle seems to be one of the efficient ways to reduce the throttling losses or the expansion irreversibility in the refrigeration/heat pump cycle. Ejector also reduces the compressor work by raising the suction pressure to a level higher than that in the evaporator leading to the improvement of COP. The present work aims to evaluate the performance of an ejector based vapor compression refrigeration cycle under a wide range of operating conditions. Two newly proposed refrigerants i.e., R1234yf and R1234ze, and commonly used refrigerant R134a are considered for simulation and a comparative study has been carried out. A numerical model is developed and a parametric study of important parameters such as entrainment ratio, high side pressure (condenser pressure) and evaporator temperature are analyzed for the improvement of COP of the system. Results show that the COP of the R1234ze is highest compared to R1234yf and R134a for the given evaporating and condensing temperature.

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.

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