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Numerical analysis of thermal energy storage in heat exchangers with phase change materials

Number of pages: 112 File Format: word File Code: 32619
Year: 2014 University Degree: Master's degree Category: Facilities - Mechanics
Tags/Keywords: Energy storage - fluid - Heat exchangers - Numerical analysis - PCM - Phase change material - Thermal energy - Thermal energy storage
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  • Summary of Numerical analysis of thermal energy storage in heat exchangers with phase change materials

    Dissertation of Master's course in mechanical engineering, energy conversion trend

    Abstract

    The storage of thermal energy and phase change materials for use in the heating and cooling system of buildings has become an important issue in the last 20 years. When there is a mismatch between energy production and its consumption time, the issue of energy storage becomes important. In the present work, the fluid flowing in the three-pipe heat exchanger is affected by the heat source and this fluid causes the melting of the phase change material which is solid in the initial state. In this thesis, we analyze the numerical analysis of the effect of expanded surfaces on the paraffin melting process in order to reduce energy loss in an unsteady, two-dimensional, incompressible and freely moving fluid.  In order to increase the efficiency of the system, longitudinal fins are placed inside the heat exchanger. The effect of the number, height and thickness of fins as well as the change of fluid temperature and the type of exchanger on heat transfer and paraffin melting process has been investigated. The results showed that with the increase of each parameter, the number, height and thickness of the blade, the melting time of the phase change material decreases, and the effect of the number and height is more noticeable. Also, increasing the temperature of the inlet fluid increases the heat transfer from the fluid to the phase change material, which improves the energy storage in the system. In addition, by examining different types of exchanger, the studied system showed better results for copper.

    Key words: numerical analysis, heat exchanger, phase change material, thermal energy storage.

    What is phase change material (PCM)?

    (Phase Change) Material) PCM is called a phase change material. These materials are organic or inorganic compounds that have the ability to absorb and store large amounts of heat energy. Thermal energy storage in these materials occurs during the phase change process (change from solid to liquid or vice versa). When these materials change phase from solid to liquid or from liquid to solid, they absorb this heat from the environment or give it back to the environment. The phase change material has the ability to keep this latent heat energy inside itself without any change even after thousands of phase change cycles. When these materials are used in the building, they exchange large amounts of heat with the environment through successive cycles of melting and freezing during extreme changes in air temperature (for example, between night and day) and in this way provide a more balanced air temperature for the space inside the building. rtl;"> The first reports about the use of these materials in the building emerged from 1940. Then, the use of these materials in the building has been widely studied since the 1980s, and today their use in the construction industry has a special place. These materials can be used in the building and in separate components for heating and cooling applications, such as shutters, walls facing the sun, plasterboard, floor heating systems and ceiling boards. Also, after World War II, these materials were used as PCM to build the first storage in the solar house.

    1-3 How phase change materials work:

    Materials exist in nature in three phases: liquid, solid and gas. If a substance changes from one phase to another, it absorbs or releases some heat, which is called latent heat. For example, after a solid substance is heated and reaches its melting point, it absorbs a large amount of energy (which is called the latent heat of fusion) and changes its state from solid to liquid. Phase change materials have the property to change their state in a certain temperature range, in the sense that during the state change process, they maintain their temperature for the duration of the state change. In fact, the working method of these materials to store thermal energy is that during the process of heating the environment, they are heated parallel to the environment until they reach their melting temperature (phase change) [2]..

    After reaching this temperature, despite the fact that the temperature of the environment continues to increase, the temperature of these materials and of course the environment around it remains constant because it is changing phase and resists the increase in temperature. In fact, during this period of time, which usually lasts several hours, the phase change material absorbs a large amount of heat from the environment, but it does not use it to increase its temperature, but uses this absorbed heat to change its phase from solid to liquid, and during the phase change process, it keeps its temperature and that of its surrounding environment constant. This process of temperature changes and absorption of heat energy can be clearly seen in Figure 1-1 [3]. In the white square area, the phase change process is taking place and it is in this area

    that the heat energy absorbed by the material inside it is stored.

  • Contents & References of Numerical analysis of thermal energy storage in heat exchangers with phase change materials

    List:

    The first chapter: Introduction 1

    1-1 What is phase change material (PCM)? 2

    1-2 History of using phase change materials 2

    1-3 How phase change materials work 2

    1-4 Characteristics of phase change materials 4

    1-5 Different types of phase change materials 5

    1-6 Phase change process 7

    1-7 Applications of phase change materials 9

    1-7-1. Reducing temperature fluctuations inside the building 11

    1-7-2. Use of phase change material in solar systems 11

    1-7-3. Phase change materials and their application in textiles. 12

    1-7-3-1 Astronautics. 13

    1-7-3-2 sports clothes. 13

    1-7-3-3 sleeping accessories. 13

    1-7-3-4 Medical applications. 14

    1-8 Energy storage methods 14

    1-8-1. Mechanical energy storage 14

    1-8-2. Electric energy storage 14

    1-8-3. Thermal energy storage 14

    1-8-4. Thermochemical energy storage 15

    1-9 Phase change materials and energy storage 15

    1-9-1. Recovery of thermal waste in condensation refrigeration systems 18

    1-9-2. Thermal waste recycling in buildings and greenhouses 19

    10-1.. Methods to increase heat transfer 20

    1-10-1.. Microchannels 21

    1-10-2.. Additives to liquids 21

    1-10-3.. Use of nano fluid 22

    1-10-4.. Use of expansion surfaces Finding 23

    1-10-5 use of mixing vanes 24

    1-10-6.. increasing eddy heat transfer 25

    1-10-7.. injection 25

    1-10-8 suction 25

    1-10-9.. creating interruptions and breaks in the flow 26

    1-10-10 fluctuation of surface and fluid 26

    The second chapter:  Review of past works 27

    2-1. Reviewing the background of the work done 28

    Chapter 3 modeling and analysis of results 43

    3-1. Introduction. 44

    3-2. Problem simulation. 44

    3-2-1. An introduction to computational fluid dynamics. 44

    3-2-2. Introduction to Fluent. 46

    3-2-3. Geometry of the problem. 49

    3-2-4 networking. 51

    3-2-5. Grid-independent solution and time interval sensitivity. 57

    3-3. Governing equations in this research. 61

    3-3-1. Boundary and initial conditions. 62

    3-4. Validation. 63

    3-5. Check the results. 66

    3-5-1. Checking the effect of the number of blades 66

    3-5-2 Checking the effect of the height of the blades 70

    3-5-3. Investigating the effect of blade thickness 74

    3-5-4 Investigating the effect of separating the phase change material by blades 78

    3-5-5. Investigating the effect of changing the gender of the converter. 82

    3-5-6. Examining the effect of fluid temperature changes 86

    Chapter four: Conclusion and suggestions 91

    4-1. conclusion 92

    4-2. Suggestions for further work 93 References 95 Source: [1] Kinga Pielichowska, Krzysztof Pielichowski, Phase change materials for thermal energy storage, Progress in Materials Science 65 (2014) 67-123. [2] Lane G. A., Solar Heat Storage: Latent Heat Materials, Boca Raton, Florida: CRC Press Vol. I. 1983.

    [3] Lane, G. A., Phase Change Thermal Storage Materials, the Handbook of Applied Thermal Design, ed. McGraw-Hill, New York 1987.

    [4] Marco, I., 2005. Seminar on phase change materials and innovation products. Brianza Plastica. Beijing, China, October 20, Tsinghua University.

    [5] Sharma SD Thermal energy storage systems using phase change material for temperature application. Ph.D. thesis 1999.

    [6] Zalba B, Testing of a PCM energy storage system for space heating. International Journal Refrig 2004;27:839-49.

    [7] Belen Zalba, Jose Ma Mar?n, Luisa F. Cabeza, Harald Mehling, Review on thermal energy storage with phase change: materials, heat transfer analysis and applications, Applied Thermal Engineering 23 (2003) 251-283.

    [8] Belen Zalba, Belen Sanchez-valverde, Jose Marin, An experimental study of thermal energy storage with phase change materials by design of experiments, Journal of Applied Statistics; 32(4):321-332.

    [9] Zhang, Y., Lin, K., Zhang, Q., Di, H. 2006. Ideal Thermophysical Properties for Free-Cooling (or Heating)Ideal Thermophysical Properties for Free-Cooling (or Heating) Buildings with Constant Thermal Physical Property Material. Energy and Buildings, 38, 1164–70.

    [10] Zhang, Y., Zhou, G., Lin, K., Zhang, Q., Di, H., 2007. Application of latent heat thermal energy storage in buildings: State-of-the-art and outlook. Building and Environment, 42, 2197–2209.

    [11] Zhou, G., Zhang, Y., Lin, K., Xiao, W. 2008. Thermal Analysis of a Direct-Gain Room with Shape-Stabilized PCM Plates. Renewable Energy, 33, 1228–1236.

    [12] Zhang Y., Chen Z., Wang Q., Wu Q., Melting in an enclosure with discrete heating at a constant rate, Experimental Thermal Fluid Science 6 1993 196–201.

    [13] Lehmann P., Moreau R., Camel D., Bolcato R., Modification of interdendritic convection in directional solidification by a uniform magnetic field, Acta Materialia, 46 1998 4067-79.[14] Abhat, A., 1983. Low temperature latent heat thermal energy storage: heat storage materials. Solar Energy, 30, 313–332.

    [15] Ng K. W., Gong Z. X., Mujumdar A. S., Heat transfer in free convection-dominated melting of a phase change material in a horizontal annulus, Int Communicatin Heat Mass Transfer 25 1998 631–40.

    [16] Jellouli Y., Chouikh R., Guizani A., Belghith A., Numerical study of the moving boundary problem during melting process in a rectangular cavity heated from below, Am J Appl Sci,4, 2007, 251-6.

    [17] Huseyin Benli, Ayd?n Durmus, "Performance analysis of a latent heat storage system with phase change material for newly designed solar collectors in greenhouse heating", Solar Energy, 2009.

    [18] Kenisarin M., Mahkamov M., Solar energy storage using phase change materials, Renewable and Sustainable Energy Reviews 11 2007 1913-65.

    [19] Elham Fallahi, Mohammad Hakit Kish, Mohammad Barmer, Application of phase change materials (PCM) in textile, 6th National Conference on Textile Engineering of Iran, 18 to 19 May 1386, Isfahan University of Technology - Faculty of Engineering Textiles. [20] Milad Maleki Pirbazari, Seyed Mojtabi Sadramili, Hamed Sharifi, Mohammad Vaez, Safa Farajzadeh, investigation of phase change materials as a thermal energy storage system for building heating and cooling, the first annual clean energy conference of the International Center for Advanced Science and Technology and Environmental Sciences, March 4 and 5, 1389, Kerman [21] Tewari S. N., Shah R., Song, H., Effect of magnetic field on the microstructure and macrosegregation in directionally solidified Pb-Sn alloys, Metallurgical and Materials Transactions A 25 (7) 1994 1535-44.

    [22] Alan Gholam Vaisi, The role of phase change materials (PCM) in energy recovery, the first specialized conference and exhibition on environment, energy and clean industry, Tehran 1387

    [23] Farid, M.M, Khudhair, A.M, Razack, S.A.K, Al-Halliaj, S.A, (2004), "A review on phase change energy storage materials and applications", Energy Convers. Manage, Vol. 45, pp. 1593-1615;

    [24] Agyenim.F, Neil Hewitt, Philip Eames, Mervyn Smyth,(2010), “A review of materials, heat transfer and phase change problem formulation for latent heat thermal energy storage systems (LHTESS)”, Renewable and Sustainable Energy Reviews, 14, 615-628.

    [25] Antony Aroul Raj.V, Velraj. R. (2011), "Heat transfer and pressure drop studies on a PCM - heat exchanger module for free cooling applications", International Journal of Thermal Science, 1-10.

    [26] H. Huseyin Ozturk, "Experimental evaluation of energy and exergy efficiency of a seasonal latent heat storage system for greenhouse heating", Energy Conversion and Management, Vol. 46, pp. 1523–1542, 2005. [27] V.P. Sethi, K. Sumathy, Chiwon Lee, D.S. Pal, Thermal modeling aspects of solar greenhouse microclimate control: A review on heating technologies, Solar Energy 96 (2013) 56–82.

    [28] J. Lee, I. Mudawar, "Assessment of the effectiveness of nanofluids for single-phase and two-phase heat transfer in micro-channels", International Journal of Heat and Mass Transfer, Vol. 50, pp. 452–463, 2007. [29] J. C.

Numerical analysis of thermal energy storage in heat exchangers with phase change materials
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