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  3. Numerical simulation of hydrodynamic characteristics and heat transfer of an ultrasonic ejector device

Numerical simulation of hydrodynamic characteristics and heat transfer of an ultrasonic ejector device

Number of pages: 96 File Format: word File Code: 32585
Year: 2014 University Degree: Master's degree Category: Facilities - Mechanics
Tags/Keywords: ejector - Heat transfer - Hydrodynamic characteristics - Mach number - Numerical simulation - reverse flow - Shock phenomenon - suction ratio - Ultrasonic ejector device
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  • Summary of Numerical simulation of hydrodynamic characteristics and heat transfer of an ultrasonic ejector device

    Master's thesis in the field of mechanical engineering, energy conversion trend

    Abstract

     

     
    In this thesis, using CFD computational fluid dynamics technique, the effect of key parameters such as the effect of secondary inlet pressure on the device The ejector, the suction ratio, the return flows caused by the secondary inlet pressure and the effect of all these parameters on the hydrodynamic characteristics of the fluid including pressure, temperature and Mach number have been investigated. The fundamental equations of the flow field were solved by Fluent commercial software and assuming a symmetric two-dimensional compressible model and k-? turbulence model. In this research, the effect of secondary inlet pressures of 0.8, 1, 1.2, 1.4 and 1.5 bar on the fluid behavior was investigated and the results indicate that for low inlet pressures due to the occurrence of shock phenomenon, reverse flow occurs and with increasing pressure, the effect of this phenomenon is reduced and the flow regime is improved. The numerical results obtained with the existing experimental and analytical solution results have been initialized and there is an acceptable agreement between them. Shock phenomenon

    1-1 Introduction

    According to the amount of vacuum required, vacuuming is done by various types of vacuum pumps or ejectors. A vacuum pump is a device capable of sucking liquid vapors and creating a relative vacuum. These types of pumps have types such as displacement, momentum transfer pumps and wire pumps. Ejector is a device that can transfer gas, liquid or solid flow by creating a vacuum. The ejector is actually a type of vacuum pump and the only difference is that its work is based on the conversion of speed and pressure energy. The main parts of the ejector include the driving fluid nozzle, the driving fluid chamber, the suction part, and the diffuser. In an ejector, a high-pressure fluid (driving fluid) is used to create a vacuum. This fluid, which can be steam, air or water, enters the ejector through the nozzle, and while passing through the nozzle, its pressure energy is converted into velocity energy. This causes the speed of the fluid to increase, its pressure to drop and create a jet or suction at the exit of the nozzle. In this way, the fluid that is supposed to be sucked is drawn from the suction part to the ejector chamber and mixed with the driving fluid. After passing through the diffuser section, the mixture of the driving fluid and the suctioned fluid exits the ejector with high pressure due to the conversion of velocity energy into pressure energy.

    In this study, using the computational fluid dynamics technique, the effect of the secondary inlet pressure to the ejector device and the effect of changes in these parameters on the behavior of the fluid, including pressure and Mach number, are investigated. The fundamental equations of the flow field were solved by the standard code of Fluent software and with an axisymmetric two-dimensional compressible model and turbulence with the standard k-? model. In order to understand and investigate the effect of the aforementioned parameters on the fluid behavior, the results are extracted and analyzed for different secondary inlet pressures. The performance of the ejector structure and its uses, its advantages and disadvantages, the determination of the cross-sectional area ratio of the diffuser throat to the nozzle throat, and the determination of the size of the ejector and the amount of steam required as a driving fluid in single-stage and two-stage ejectors have been discussed. In the third chapter, a history of related works will be mentioned. In the fourth chapter, the governing equations and the numerical method used in this thesis will be discussed. In the fifth chapter, the results obtained from software analysis are discussed. Finally, the sixth chapter is dedicated to general conclusions and suggestions for future work.... rtl;">

    Chapter Two

    Introduction of the ejector and its applications

    2-1 Introduction

    According to the amount of vacuum required, vacuuming by various types of vacuum pumps or face ejectors takes A vacuum pump is a device capable of sucking liquid vapors and creating a relative vacuum. These types of pumps have types such as displacement, momentum transfer pumps and tele pumps.

    Ejector or injector is a device that is able to transfer gas, liquid or solid flow such as powder, granules and sludge by creating a vacuum, which of course is based on the type of user that can create a vacuum alone, transfer materials, mix materials and so on. Yes, it is also called thermocompressor, eductor or hydraulic exhauster, but the basis of their operation is the same. The ejector is actually a type of vacuum pump and the only difference is that its work is based on the conversion of speed and pressure energy. The main parts of the ejector include the driving fluid nozzle, the driving fluid chamber, the suction part, and the diffuser, which is shown in Figure 2-1, an example of an ejector along with its components. style="direction: rtl;">In an ejector, a high-pressure fluid (driving fluid) is used to create a vacuum. This fluid, which can be steam, air or water, enters the ejector through the nozzle, and while passing through the nozzle, its pressure energy is converted into velocity energy. This causes the speed of the fluid to increase, its pressure to drop and create a jet or suction at the exit of the nozzle. In this way, the fluid that is supposed to be sucked is drawn from the suction part to the ejector chamber and mixed with the driving fluid. After passing through the diffuser section, the mixture of the driving fluid and the suctioned fluid is ejected from the ejector with high pressure due to the conversion of velocity energy into pressure.

    Ejectors, compared to vacuum pumps, have lower initial and maintenance costs and easier maintenance, and since ejectors do not have any moving parts, they do not need to be repaired if there is no corrosion. Installing the ejectors is very easy and controlling the operation is also simple. One of the characteristics of the ejector is the mixing of the driving fluid with the process fluid, which is important in the design of the process and needs to be taken into account. It should be noted that ejectors have the ability to transfer solid and two-phase materials, while vacuum pumps are unable to do this. Compared to ejectors, vacuum pumps have the following advantages:

    The conditions of the feed steam have no effect on the pump operation system.

    Starting can be done even in the absence of steam.

    The vacuum pump system has the capability of fully automatic operation.

    The operating speed of the pump The vacuum is very high.

    No mixing of the process fluid with steam or other impurities.

    In general, the uses of ejectors can be described in three general categories:

    Creation of vacuum

    Transfer of materials, which includes pumping, ventilation, etc.

    Creation of mixing between materials in order to increase fluid pressure or heat exchange between them.

     

    2-2 The basis of ejector operation

    The basis of ejector work is based on Euler's principle. According to Euler's principle, the amount of energy of a stable and non-viscous flow is constant and its value is equal to the sum of kinetic energy, potential energy and pressure energy.

  • Contents & References of Numerical simulation of hydrodynamic characteristics and heat transfer of an ultrasonic ejector device

    List:

    1-1 Introduction 2

    1-2 Thesis structure.    3 Chapter Two: Introduction and introduction of the ejector and its applications 2-1 Introduction. 5 2-2 The basis of the ejector function 7 2-3 Structure of the ejector 11 2-3-1 Determining the cross-sectional area ratio of the diffuser throat to the nozzle throat 13 2-4 types of ejectors..14

               2-4-1 types of ejectors in terms of driving fluid.

    2-4-2 types of ejectors in terms of use. 2-5-2 Determining the size of the ejector and the amount of steam required as a driving fluid in two-stage ejectors 30 2-6 Factors causing malfunction of the ejector Operation..38

               2-8-1 air infiltration into the system. 39

          2-9 information about the structure of the ejector and condensers.

    Chapter three: review of past works

    Introduction 3-1..47

         3-2 Works related to ejector design..47

         3-3 Analytical design...50

     

    Chapter four: Governing equations and solution method

        4-1 Equations 52

               4-1-1 turbulence modeling. 54

          4-2 flow simulation by computational fluid dynamics method. 56

         4-3 boundary conditions governing the problem. 58

        

    Chapter five: checking the results of numerical solution

         5-1 checking the independence of numerical results from meshing.  61

          5-2 Comparison of numerical results with experimental and validation of numerical results.    61

    5-3 Analysis of the flow inside the ejector.  63

    5-3-1 Investigating the effect of secondary inlet pressure on Mach changes.  67

      73

               4-3-3 Investigating the effect of secondary inlet pressure on temperature changes. 78

    Suggestions ..  83

    List of references ..  

    Source:

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    [8] J.R. Lines Graham Corp. Batavia, NY, “Undrestanding ejector systems necessary to troubleshoot vacuum distillation”, 1997. [9] http://www.stress.com/servicetier3.php?pid=284. [10] E. A. Avallone & Th. Baumeister "Marks' Standard Handbook for Mechanical Engineers", 10th Edition, 1996. [11] www.setprocess.com. [12] M. Mohitpour & H. Golshan & A. Murray "Pipeline Design & Construction: A Practical Approach", 2nd Edition, 2000.

    [13] http://www.wikipedia.org.

     

    [14] J. T. Munday, D. F. Bagster, A new ejector theory applied to steam jet refrigeration, Industrial Engineering Chemistry, Vol. 16, No. 4, 1977.

     

    [15] B. J. Huang, J. M. Chang, C. P. Wang, V. A. Petrenko, A 1-D analysis of ejector performance, International Journal of Refrigeration, Vol. 22, No. 5, pp. 354-364, 1999. [16] E. D. Rogdakis, G. K. Alexis, Investigation of ejector design at optimumAlexis, Investigation of ejector design at optimum operating condition, Energy Conversion and Management, Vol. 41, pp. 1841-1849, 2000.

     

    [17] A. Dahmani, Z. Aidoun, N. Galanis, Optimum design of ejector refrigeration systems with environmentally benign fluids, International Journal of Thermal Sciences, Vol. 50, pp. 1562-1572, 2011. [18] D.W. Sun, Variable geometry ejectors and their applications in ejector refrigeration systems, Energy, Vol. 21, No. 10, pp. 11, 1996.

     

    [19] A. Selvaraju, A. Mani, Analysis of an ejector with environmentally friendly refrigerants, Applied Thermal Engineering, Vol. 24, No. 5-6, pp. 827-838, 2004. [20] D.W. Sun, I. W. Eames, Performance characteristics of HCFC-123 ejector refrigeration cycles, International Journal of Energy Research, Vol. 20, pp. 871-885, 1996.

     

    [21] A. Selvaraju, A. Mani, Analysis of a vapor ejector refrigeration system with environmentally friendly refrigerants, International Journal of Thermal Sciences, Vol. 43, No. 9, pp. 915-921, 2004.

     

    [22] A. Sorouradin, A. S. Mehr, S. M. S. Mahmoudi, Development of new model for predicting the performance of ejector refrigeration cycle, MME Journal, Vol. 12, No. 4, pp. 133-147, 2012.

     

    [23] S. B. Riffat, S. A. Omer, CFD modeling and experimental investigation of an ejector refrigeration system using methanol as the working fluid, International Journal of Energy Research, Vol. 25, pp. 14, 2001.

     

    [24] P. Desevaux, A. Mellal, Y. Alves de Sousa, Visualization of secondary flow choking phenomena in a supersonic air ejector, Journal of Visualization, Vol. 7, No. 3, pp. 249-256, 2004.

     

    [25] E. Rusly, L. Aye, W. W. S. Charters, A. Ooi, CFD analysis of ejector in a combined ejector cooling system, International Journal of Refrigeration, Vol. 28, pp. 10, 2005. [26] Y. Bartosiewicz, Z. Aidoun, Y. Mercadier, Numerical assessment of ejector operation for refrigeration applications based on CFD, Applied Thermal Engineering, Vol. 26, pp. 9, 2006.

     

    [27] A. Hemidi, F. Henry, S. Leclaire, J.M. Seynhaeve, Y. Bartosiewicz, CFD analysis of a supersonic air ejector. Part I: Experimental validation of single-phase and two-phase operation, Applied Thermal Engineering, Vol. 29, No. 8-9, pp. 1523-1531, 2009.

    [28] T. Sriveerakul, S. Aphornratana, K. Chunnanond, Performance prediction of steam ejector using computational fluid dynamics: Part 1. Validation of the CFD results, International Journal of Thermal Sciences, Vol. 46, pp. 11-18, 2007. [29] K. Pianthong, W. Seehanam, M. Behnia, T. Sriveerakul, S. Aphornratana, Investigation and improvement of ejector refrigeration system using computational fluid dynamics technique, Energy Conversion and Management, Vol. 48, pp. 2556-2564, 2007.

     

    [30] S. Balamurugan, V. G. Gaikar, A. W. Patwardhan, Effect of ejector configuration on hydrodynamic characteristics of gas–liquid ejectors, Chemical Engineering Science, Vol. 63, pp. 11, 2008. [31] T. Sriveerakul, S. Aphornratana, K. Chunnanond, Performance prediction of steam ejector using computational fluid dynamics: Part 2. Flow structure of a steam ejector influenced by operating pressures and geometries, International Journal of Thermal Sciences, Vol. 46, pp. 11-19, 2007. [32] E.S. R. Negeed, Enhancement of ejector performance for a desalination system, International Journal of Nuclear Desalination, Vol. 3, pp. 13, 2009.

     

    [33] X. Li, T. Wang, B. Day, Numerical analysis of the performance of a thermal ejector in a steam evaporator, Applied Thermal Engineering, Vol. 30, pp. 2708-2707, 2010. [34] V. Kumar, G. Singhal, P.M.V.

Numerical simulation of hydrodynamic characteristics and heat transfer of an ultrasonic ejector device
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