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.

CFD Simulation of the Supersonic Steam Ejector

2010 ◽  
Author(s):  
Zhiming Li ◽  
Jinli Wang ◽  
Hongtao Zheng ◽  
Cailin ◽  
Yajun Li
Keyword(s):  
Mass Flow Rate ◽  
Flow Rate ◽  
Critical Pressure ◽  
Ideal Gas ◽  
Back Pressure ◽  
State Equations ◽  
Entrainment Ratio ◽  
Real Gas ◽  
Steam Ejector ◽  
Ideal Gas Model

The supersonic steam ejector is widely used in many industries which are steam powered such as oil, thermoelectric, refrigeration and so on. Many scholars analyzed the steam ejector by using ideal gas model and they ignored phase change, this may bring some errors for the flowing field of the ejector. In this study, the supersonic steam ejector was simulated using CFD (Computational Fluid Dynamics). Flowing field of the ejector was analyzed by using different state equations. The results shows that performance of the ejector was underestimated under the ideal gas model, and the entrainment ratio is 20%–40% lower than using real gas model. When phase changing was considered under real gas state equations, influences of working fluid pressure and back pressure were investigated. The results illustrates that working critical pressure and back flow critical pressure exist in the flow, and the entrainment ratio reaches its peak at working critical pressure. The performance of the ejector was almost the same when the outlet pressure was lower than critical back pressure. Effects of ejector geometries were also investigated in this paper. It shows that there are optimums of the relative position of the steam nozzle and the taper of the mixing section, length of mixing chamber and diameter of throat according to mass flow rate of second fluid. There are also critical length of diffuser and throat. Mass flow rate stayed the same when the length of diffuser or throat grows. This paper will provide a theoretical basis for ejector’s energy-saving and geometry optimization.

Computational fluid dynamics simulation of the supersonic steam ejector. Part 1: Comparative study of different equations of state

2011 ◽  
Vol 226 (3) ◽  
pp. 709-714 ◽  
Author(s):  
H T Zheng ◽  
L Cai ◽  
Y J Li ◽  
Z M Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Equations Of State ◽  
Ideal Gas ◽  
Dynamics Simulation ◽  
Real Gas ◽  
Steam Ejector ◽  
Ideal Gas Model ◽  
The Ideal

The aim of this study is to investigate the use of computational fluid dynamics in predicting the performance and geometry of the optimal design of a steam ejector used in a steam turbine. Many scholars have analysed the steam ejector using the ideal gas model, which lacks accuracy in terms of calculating the flow field of the ejector. This study is reported in a series of two papers. The first part covers the validation of CFX 11.0 results using different equations of state (EOS) on the converging–diverging nozzle flow field carried out with the experimental value. The IAPWS IF97 real gas model works well with the experimental value. The flow field of the ejector was analysed using different EOS after grid-dependent learning. The results show that the performance of the ejector was underestimated under the ideal gas model; the entrainment ratio was 20–40 per cent lower than when using the real gas model. The effect of the optimal geometrical design and operating conditions will be discussed in Part 2.

scholarly journals Mathematical Model of Small-Volume Air Vessel Based on Real Gas Equation

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 530 ◽  
Author(s):  
Weixiang Ni ◽  
Jian Zhang ◽  
Lin Shi ◽  
Tengyue Wang ◽  
Xiaoying Zhang ◽  
...  
Keyword(s):  
Water Depth ◽  
Small Volume ◽  
Pressure Oscillation ◽  
State Equation ◽  
Ideal Gas ◽  
Pipeline System ◽  
Real Gas ◽  
Polytropic Equation ◽  
Real Gas Equations ◽  
Ideal Gas Model

The gas characteristics of an air vessel is one of the key parameters that determines the protective effect on water hammer pressure. Because of the limitation of the ideal gas state equation applied for a small-volume vessel, the Van der Waals (VDW) equation and Redlich–Kwong (R–K) equation are proposed to numerically simulate the pressure oscillation. The R–K polytropic equation is derived under the assumption that the volume occupied by the air molecules themselves could be ignored. The effects of cohesion pressure under real gas equations are analyzed by using the method of characteristics under different vessel diameters. The results show that cohesion pressure has a significant effect on the small volume vessel. During the first phase of the transient period, the minimum pressure and water depth calculated by a real gas model are obviously lower than that calculated by an ideal gas model. Because VDW cohesion pressure has a stronger influence on the air vessel pressure compared to R–K air cohesion pressure, the amplitude of head oscillation in the vessel calculated by the R–K equation becomes larger. The numerical results of real gas equations can provide a higher safe-depth margin of the water depth required in the small-volume vessel, resulting in the safe operation of the practical pumping pipeline system.

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 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.

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.

Thermodynamic Property Models for Moist Air and Combustion Gases

2002 ◽  
Vol 125 (1) ◽  
pp. 374-384 ◽  
Author(s):  
D. Bu¨cker ◽  
R. Span ◽  
W. Wagner
Keyword(s):  
Ideal Gas ◽  
Moist Air ◽  
Combustion Gas ◽  
Real Gas ◽  
New Model ◽  
Combustion Gases ◽  
Dissociation Model ◽  
The Individual ◽  
Ideal Gas Model ◽  
The Ideal

A new model for the prediction of caloric properties of moist air and combustion gases has been developed. The model very accurately predicts ideal gas caloric properties of undissociated gas mixtures at temperatures from 200 K to 3300 K. In addition, a simple model has been developed to account for caloric effects of dissociation at temperatures up to 2000 K. As a part of the project, scientific equations for the ideal gas isobaric heat capacity of the individual combustion gas components have been established. Based on this reference, an assessment and comparison of the new model with the most common technical models have been carried out. Results of the simplified dissociation model are compared to the results of complex chemical equilibrium programs. To mark out the limits of the ideal gas hypothesis, some sample calculations are given, which compare results of the new ideal gas model to results from sophisticated real gas models.

AN APPLICATION OF NONEXTENSIVE PARAMETER: THE NONEXTENSIVE GAS AND REAL GAS

2007 ◽  
Vol 21 (06) ◽  
pp. 947-953 ◽  
Author(s):  
YAHUI ZHENG ◽  
JIULIN DU
Keyword(s):  
Heat Capacity ◽  
Second Virial Coefficient ◽  
Ideal Gas ◽  
Quasi Equilibrium ◽  
Equilibrium System ◽  
Real Gas ◽  
Nonextensive Statistics ◽  
Thomson Coefficient ◽  
Ideal Gas Model ◽  
The Ideal

By application of the nonextensive statistics to the ideal gas model, we establish a nonextensive gas model. If we regard the nonextensive gas as a real gas, we can use the nonextensive parameter q ∈ ℝ in Tsallis statistics to describe Joule coefficient, Joule–Thomson coefficient, second virial coefficient and etc. We also derive an expression, with a multiplier T1-q, of the heat capacity of the nonextensive gas. We can prove that in the quasi-equilibrium system there is 1 - q > 0, 2 so the heat capacity still vanishes if temperature tends to zero, just as that in Boltzmann-Gibbs statistics.

CFD-Simulation of Centrifugal Fan Performance Characteristics Using Ideal and Real Gas Models for Air and Organic Fluids

2019 ◽  
Author(s):  
Manuel Fritsche ◽  
Philipp Epple ◽  
Karsten Hasselmann ◽  
Felix Reinker ◽  
Robert Wagner ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Ideal Gas ◽  
High Tech ◽  
Test Case ◽  
Centrifugal Fan ◽  
Real Gas ◽  
The Real ◽  
Organic Fluids ◽  
Ideal Gas Model ◽  
The Ideal

Abstract Efficient processes with organic fluids are becoming increasingly important. The high tech fluid Novec™ is such an organic fluid and is used, for example, as a coolant for highperformance electronics, low-temperature heat transfer applications, cooling of automotive batteries, just to mention a few. Thus, efficient designed fans for the transport of organic fluids are becoming more and more important in the process engineering. CFD-simulations are nowadays integral part of the design and optimization process of fans. For air at the most usual application conditions, i.e. no extreme temperatures or pressures, the ideal gas model is in good agreement with the real gas approach. In the present study, this real gas approach for organic fluids have been investigated with CFD methods and, the deviation from the ideal gas model has been analyzed. For this purpose, a simulation model of a centrifugal fan with volute has been designed as a test case. First, the ideal gas model approach has been compared with the real gas approach model of Peng-Robinson for air using the commercial solver ANSYS CFX. Thereafter, the same comparison has been performed using the organic fluid Novec™. After a detailed grid study, the entire fan characteristics, i.e. the design point and the off-design points, have been simulated and evaluated for each fluid (air and Novec™) and gas model (ideal gas and Peng-Robinson real gas). The steady state simulations of the centrifugal fan have been performed using the Frozen Rotor model. The simulation results have been compared, discussed and presented in detail.

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