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Numerical investigation of the effect of nanoparticles in phase change materials in a three-dimensional square closed chamber

Number of pages: 152 File Format: word File Code: 32329
Year: 2009 University Degree: Master's degree Category: Facilities - Mechanics
Tags/Keywords: aspect ratio - Cavity - cavity - heat transfer - incompressible - Nano particles - phase change - Thermal energy
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  • Summary of Numerical investigation of the effect of nanoparticles in phase change materials in a three-dimensional square closed chamber

    Master's thesis

    Energy conversion trend

    Abstract:

    Increasing heat transfer and also increasing the efficiency of energy storage systems due to the limitation of natural resources and with the aim of reducing costs has always been one of the most basic concerns of engineers and researchers. This is especially important in fluids due to the small thermal conductivity coefficient. One of the most important ways to achieve this, which has received a lot of attention in recent years, is the addition of solid particles with high thermal conductivity in nano dimensions. Heat transfer along with phase change is extremely important in many applications, especially in thermal energy storage systems. In these energy storage units, the purpose is to use the latent heat of fusion during the phase change process. The purpose of this research is to investigate the effect of adding nanoparticles to the base incompressible fluid on heat transfer and phase change of the material. In this research, a base fluid of water and four types of solid nanoparticles of copper (Cu), aluminum (Al), TiO2 and aluminum oxide (Al2O3) have been used for six different volume ratios (0.2, 0.15, 0.1, 0.05, 0.025, ?=0). The smooth flow is considered within the limits of Buzinsk assumption and the results are presented for three Grashev numbers 105, 106 and 107. Using FLUENT software, the modeling of phase change in slow fluid flow has been done, and the addition of nano particles to the base fluid has been done by writing UDF. The results have shown that the presence of nanoparticles suspended in the fluid increases the heat transfer rate and reduces the time required for the complete freezing of the fluid. Also, the results have shown that the Nusselt number before the start of phase change increases with the increase in the volume ratio of nano particles. Also, the addition of copper particles in nano dimensions reduces the time required for complete freezing more than the addition of other nano particles to the base fluid. The comparison of the results obtained from the flow solution with previous research shows that these results are acceptable.

    Key words: Heat Transfer, Nanofluid, Incompressible, Cavity, Aspect Ratio

    Introduction

    1-1        Introduction

    Heat transfer along with phase change occurs in many physical phenomena in various industrial and non-industrial applications, and some of the natural phenomena in this field are: the process of melting snow, freezing lake water, and burning candles. Some of the industrial processes that are accompanied by phase change are: welding and casting.

    The process of heat transfer with phase change is known as Stefan's problem because of the work done by Stefan (Stefan) in 1889.

    Among the applications related to the phase change process, thermal energy storage units are very important because in most of the physical phenomena that are accompanied by phase change are, this process is done unintentionally. For example, in the casting industry, if the latent heat of the alloy is less, we will naturally need less energy, cost and time for production, but in energy storage units, the goal is to use the latent heat of melting during the phase change. The high capacity of thermal energy storage makes it possible to build small storage units and they can be produced in a compact way. This feature makes the use of energy storage units in commercial applications that are usually limited in size, as an example, energy storage systems with phase change can be used to provide thermal energy in residential areas.

    It can be pointed out that one kilogram of concrete can store about 1 kJ/kg k of energy, while one kilogram of Cacl2-6H2O can release or absorb 190 kJ of energy during phase change.

    Knowing the factors and parameters affecting the efficiency of the storage and the ability to determine the impact of these factors on the efficiency of the system makes it possible to optimize the operation of energy storage and discharge.

    Today, due to the scarcity and depletion of fossil energy sources and the issue of air pollution caused by the consumption of these materials for energy supply, the issue of using alternative energies has become more important. Currently, oil, gas and coal supply 80% of the world's energy consumption. Energy consumption in the last fifty years has been more than the energy consumption in the previous two centuries. The US Energy Information Administration has predicted that world energy consumption will increase by 57% by 2030. Due to the problems of fossil fuels (environmental pollution, limited and finite resources, non-renewability and the direct effect of politics on it), the world is turning to new energies including the sun, wind (for today's wind machines), bio-energy, geothermal, hydrogen, nuclear energy and so on. has shown a desire.

    One ??of the new energies is solar energy, the most important issue in solar energy is its absorption and storage. Absorption of solar energy by different collectors for different purposes such as: electricity generation, water heating, space heating, etc. takes place The abundance and cheapness of energy in some hours of the day and night is one of the important reasons for saving energy. Solar energy is found in abundance during the day, but one of the major drawbacks of this energy is the lack of access to it at night. In some countries, such as China, where electric energy is mostly used for heating homes, due to the fact that electric energy is cheap during the day and the tariff is about 1.5 times more expensive at night (due to peak consumption hours), energy storage is considered one of the important solutions. The storage of thermal energy is done in a tangible form (through the specific heat of materials such as water, earth, etc.) and hidden (through the phase change of materials such as paraffin, salt hydrates, etc.), which we will continue to examine the types of energy storage.

    The use of nanoparticles (with a diameter of less than 50 nm) and the effect of nanoparticles in phase change materials (NEPCM[1]) is a new window for the development of modern technology in the composition Materials, bio-technology, design of microfluidic tools, etc. are open to researchers.

    Common fluids used for heat transfer and energy storage have a low thermal conductivity coefficient, while metals have thermal conductivity higher than three times of such fluids. Therefore, the use of solid metal particles in nano dimensions and their combination with such fluids to increase the thermal conductivity coefficient and as a result increase the thermal efficiency seems very desirable. In the rest of this chapter, the ways of increasing the efficiency of the system will be discussed.

    1-2 nano

    The prefix nano is originally a Greek word, equivalent to Latin. This word is Dwarf, which means dwarf and short. In the science of scales, this prefix means one billionth, so one nanometer is 9-10 m. This scale can be better understood by citing concrete examples. An average human hair has a diameter of about 50,000 nanometers. A bacterial cell has a diameter equivalent to several hundred nanometers. The smallest objects visible to the unaided eye are about 10,000 nanometers in size, and only about 10 hydrogen atoms in a line make one nanometer.

  • Contents & References of Numerical investigation of the effect of nanoparticles in phase change materials in a three-dimensional square closed chamber

    List:

    The first chapter. 1

    Introduction. 1

    1-1 Introduction. 1

    1-3 nanotechnology. 4

    1-3-1 Why "nano" technology? 5

    1-4 History of nanotechnology. 5

    1-5 application of nanofluids. 6

    1-6 energy storage methods. 7

    1-6-1 Mechanical energy storage. 7

    1-6-2 Electric storage. 7

    1-6-3-1 sensible heat storage. 8

    1-6-3-2 latent heat storage. 8

    1-6-3-3 thermochemical energy storage. 8

    1-7 features of cache system. 10

    1-8 characteristics of phase change materials. 10

    1-10-1-1 paraffins 12

    1-10-1-2 non-paraffins 13

    1-10-2 inorganic phase change materials. 14

    1-10-2-1 salt hydrates. 14

    1-10-2-2 metals. 15

    1-10-3 Eutectics 15

    1-11 Encapsulation of phase change materials. 15

    1-12 thermal energy storage systems. 17

    1-12-1 Solar water heating systems. 17

    1-13 Applications of phase change materials in building. 17

    1-14 Application of phase change materials in other fields 18

    1-15 Techniques to increase the efficiency of the energy storage system. 19

    1-15-1 Use of extended levels. 19

    1-15-2 Using a network of PCMs in the system. 20

    1-15-3 Increasing PCM thermal conductivity. 21

    1-15-4 PCM microencapsulation. 23

    The second chapter. 25

    Background of the subject and definition of the problem. 25

    2-1- Introduction. 25

    2-2- Nanofluid flow modeling methods. 25

    2-3- Existential logic of nanofluids. 28

    2-4- parameters of heat transfer in nanofluids. 31

    2-4-1- Accumulation of particles. 31

    2-4-2- volume ratio of nano particles. 32

    2-4-3- Brownian motion. 33

    2-4-4- thermophoresis. 33

    2-4-5- size of nanoparticles. 34

    2-4-6- Shape of nanoparticles. 34

    2-4-7- The thickness of the fluid layer between nano particles. 35

    2-4-8- Temperature 36

    2-5- Types of nanoparticles. 36

    2-5-1- ceramic nanofluids. 36

    2-5-2- metallic nanofluids. 37

    2-5-3- nanofluids, containing carbon and polymer nanotubes. 38

    6-2- Theories on nanofluids. 39

    2-6-1- The theoretical relationships presented in the field of effective thermal conductivity coefficient of nanofluids. 39

    2-6-2- Experimental work done in the field of effective thermal conductivity coefficient of nanofluid. 43

    2-6-3- Experimental work done in the field of effective viscosity of nanofluid. 44

    2-7- Experimental work done in the field of heat transfer in nanofluids. 44

    2-8- Numerical work done in the field of heat transfer in nanofluid inside a square cavity 45

    2-9- Work done in the field of phase change of matter. 45

    2-10- Problem definition. 48

    The third chapter. 49

    Governing equations and solution methods. 49

    3-1 assumption of continuity. 49

    3-2- Equations governing the laminar regime of a pure fluid. 50

    3-3- Buzinsk model. 51

    3-4- Nanofluid properties. 51

    3-5 - Equations governing the present research. 52

    3-6- Boundary and initial conditions. 53

    3-7- Phase change investigation method in this research. 54

    3-7-1 Phase change with discrete boundary 54

    3-7-2 Phase change of alloys 54

    3-7-3 Continuous phase change. 54

    3-8- Equations governing the enthalpy method. 56

    3-8-1 Equation governing heat transfer based on enthalpy method. 56

    3-8-2 Final equations governing heat transfer based on generalized enthalpy method. 58

    3-9 Review of numerical methods. 61

    3-9-1 Discrete solution method. 62

    3-9-2 continuous solution method. 64

    3-9-3 linearization: implicit method and explicit method. 65

    3-9-4 Choosing the solver 67

    3-10 Linearization. 69

    3-10-1 first-order upstream method. 70

    3-10-2 The upstream method of power-follower 70

    3-10-3 The upstream method of the second order. 72

    3-10-4 QUICK method. 73

    3-11 The linearized form of the discretized equation. 74

    3-12 under liberation. 75

    3-13 Discrete solver. 75

    3-13-1 Discretization of momentum equation. 75

    3-13-1-1 pressure interpolation method 76

    3-13-2 discretization of continuity equation. 77

    4-13-3 pressure-velocity link. 78

    3-13-3-1 SIMPLE. 79

    3-13-3-2 SIMPLEC. 80

    3-13-3-3 PISO.80

    3-14 Choice of discretization method. 81

    3-14-1 first order and second order. 81

    3-14-2 Tuan-Piro and QUICK methods. 82

    3-14-3 Selection of pressure interpolation method 82

    3-15 Selection of pressure-velocity link method. 83

    3-15-1 SIMPLE and SIMPLEC. 83

    3-15-2 PISO. 84

    3-17 time-dependent modeling. 84

    3-17-1 Time-dependent discretization. 85

    3-17-2 Implicit time integration. 85

    3-17-3 Explicit time integration. 86

    3-17-4 Selection of time interval size. 87

    3-18 Selection of solution methods. 87

    3-19 Networking and time step. 89

    3-19-1 Test of non-dependence of results on the number of grid points and time step. 89

    3-20- Problem solving steps. 91

    The fourth chapter. 92

    Examination of numerical results. 92

    4-1 problem validation. 93

    4-2 The effect of adding nanoparticles. 98

    4-3 Investigating the effect of adding nano particles in the models mentioned in the validation section 114

    Chapter Five. 124

    5-1 Conclusion. 124

    5-2 suggested activities to continue the work. 126 References 127 Source: [1] Maxwell, J.C., A Treatise on Electricity and Magnetism, second ed., Oxford University Press, Cambridge, 1 (1904) 435-441. [2] Hamilton, R.L., and Crosser, O.K. , Thermal Conductivity of Heterogeneous Two Component Systems, Industrial and Engineering Chemistry Fundamentals, 1 (1962) 187-191.

    [3] Wasp, E.J., Kenny, J.P., and Gandhi, R.L., Solid – Liquid Flow Slurry Pipeline Transportation, Series on Bulk Materials Handling, Trans. Tech. Publications, 1:4, Clausthal, Germany, 1977.

    [4] Masuda, H., Ebata, A., Teramae, K., Hishinuma, N., Alteration of thermal conductivity and viscosity of liquid by dispersing ultra-fine particles, Netsu Bussei 7 (1993) 227-233.

    [5] Choi U.S., Enhancing thermal conductivity of fluids with nanoparticles, in Developments and application of non-newtonian flows, ASME, (1995) 99-105.

    [6] Das, S.K., Putra, P., and Roetzel, w., Temperature Dependence of Thermal Conductivity Enhancement for Nanofluids, Transactions of ASME, Journal of Heat Transfer, 121 (2003) 567-574.

    [7] Prakash, M., Giannelis, E. P., Mechanism of Heat Transport in Nanofluids, Journal of Computer-Aided Material Design 14 (2007) 109-117.

    [8] Karthikeyan, N. R., Philip, J., Raj, B., Effect of Clustering on the Thermal Conductivity of Nanofluids, Materials Chemistry and Physics 109 (2008) (50-55).

     

    [9] Wang, X., Xu, X., Choi, S. U. S., Thermal Conductivity of Nanoparticle-Fluid Mixture, Journal of Thermophysics and Heat Transfer 13 (1999) 474-480.

    [10] Jang, S. P., Choi, S. U. S., Effects of Various Parameters on Nanofluid Thermal Conductivity, ASME Journal of Heat Transfer 129 (2007) 617-623.

    [11] Jang, S. P., Choi, S. U. S., Role of Brownian Motion in the Enhanced Thermal Conductivity of Nanofluids, Applied Physics Letters. 84 (2004) 4316-4318.

    [12] Chon, C. H., Kihm, K. D., Lee, S. P., Choi, S. U. S., Empirical Correlation Finding the role of Temperature and Particle Size for Nanofluid (Al2O3) Thermal Conductivity Enhancement, Applied Physics Letters 87 (2005) 153107.

    [13] Prasher, R., Bhattacharya, P., Phelan, P. E., Brownian-Motion-Based Convective-Conductive Model or the Effective Thermal Conductivity of Nanofluids, ASME Journal of Heat Transfer 128 (2006) 588-595.

    [14] Yu, W., France, D. M., Routbort, J. L., Choi, S. U. S., Review and Comparison of Nanofluid Thermal Conductivity and Heat Transfer Enhancements, Heat Transfer Engineering 29 (2008) 432-460.

    [15] Yu, C. J., Richter, A. G., Datta, A., Durbin, M. K., Dutta, P., Observation of Molecular Layering in Thin Liquid Films Using X-Ray Reflectivity, Physical Review Letters 82 (1999) 2326-2329.

    [16] Ren, Y., Xie, H., Cai, A.

Numerical investigation of the effect of nanoparticles in phase change materials in a three-dimensional square closed chamber
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