Abstract

<p>Recently, thermal energy storage (TES) includes technologies for collecting and storing energy for later use in domestic and industry by using Phase Change Materials (PCMs) which is a main topic for many researchers. In this experimental and numerical study, melting process and thermal behavior due to a U-shaped heat source embedded in the PCM is investigated which has been simulated in COMSOL-3D Multiphysics. The three-dimensional governing equation is solved for the fluid flow and heat transfer behavior. Two different cases are analyzed in this study. In the first case, the experimental results of a rectangular cavity filled with PCM, and a Ushaped heating source embedded in it is validated with a numerical model. PCM is used that has melting point temperature 32 °C, and flow of water at temperature 39 °C for six hours period through the U-shaped tube to intensify the PCM`s temperature. PCM melts and absorbs latent heat as energy which is analyzed horizontally and vertically. PCMs temperature increased uniformly with increasing of time inside the cavity. The melting rate was high around the heating source than the far distances of heating source. After six hours, 100% PCM was melted around the U-shaped tube, however, far from the U-shaped tube was not significantly melted in both experimental study and numerical model. The numerical results are in good agreement with the experimental data with a small number of relative error in all cases. In the second case, PCM and Bentonite are used in four different models in the same rectangular cavity, then hot-water and, cold-water flowing through the U-shaped tube, and the numerical results were validated for all models. It was observed that, when Bentonite is used, the heat transfer rate was higher compare to the case when PCM is used for anywhere in the cavity. The reason is that, Bentonite has higher thermal conductivity and temperature gradient than the PCM. So, Bentonite was more sensitive for heat transfer whenever used in heating or cooling. It is clear from this study that PCM and Bentonite can be a good media for storing thermal energy for later use such as room heating, space heating, industrial and commercial uses. PCM has a great possibility to it, because of its low initial and maintenance cost, and its availability.</p>

Highlights

  • Introduction of Phase Change Material (PCM) and BentoniteThermal energy storage (TES) in general, and phase change materials have been a main topic in research and industry for the last 20 years

  • 1.3 Summary Based on the brief literature review: (a) the purpose of this study is to investigate an innovative way to store thermal energy for later uses. (b) PCM has a huge capacity for thermal energy storage which can uses later in industrial and domestic sectors. (c) the use of U-shaped heat source is a good alternative for heat transfer

  • 2.9 Summary From this chapter, the following summaries are drawn: (a) The governing equations have been solved by using COMSOL Multiphysics that used finite element technique for simulating the model and describes the fluid flow, and heat transfer inside the rectangular cavity. (b) A rectangular normal element is used same as the size and shape of experimental work to perform the numerical model. (c) No slip boundary condition was used in the rectangular cavity. (d) Open boundary condition was used in inlet, and outlet of U-shaped copper tube. (e) Preliminary results of heating and cooling indicate that the code is working as expected

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Summary

F d Stem Qh F0 t 3D T A P Nu I 2D QS FEM Ra Da EG Ha Re

Velocity (m/s) Body force (N/m3) Diameter (m) Stefan number Hot wall Fourier number time (s) Three dimensional Temperature (oC) Area (m2) Pressure (Pa) Nusselt number Identical vector Two dimensional Energy supply(w/m2) Finite element method Rayleigh number Darcy number Ethylene glycol Hartmann number Reynolds number xii qd nd qu ds ks cp phase 1 cp phase 2 kphase 1 kphase 2 ρ θ αm μ Ƞ ρphase 1 ρphase 2. Heat flow rate of thin layer (l/min) Normal direction of thin layer Initial heat flow rate of thin layer (l/min) Layer thickness (m) Layer thermal conductivity (w/m.K) Specific heat of solid PCM (J/kg.K) Specific heat of liquid PCM (J/kg.K) Thermal conductivity of solid PCM (w/m.K) Thermal conductivity of liquid PCM (w/m.K). Density (kg/m3) Phase change indicator Flow field Dynamic viscosity (Pa.s) Efficiency

Introduction of PCM and Bentonite
Introduction of Nanofluid
Thesis objectives The objectives of this study are: (a)
Thesis organization This study consists of four chapters: (a)
Introduction
Experimental Model Description Water Exit Water In
Boundary Conditions
Experimental Apparatus and Procedures Dr Ayman Mahmoud
Uncertainty Analysis
Numerical Model Descriptions
Governing Equations and Boundary Conditions
Mesh Sensitivity Analysis and Convergence Criteria
Temperature Contours of the Cavity
Thermal Energy Storage Media (Paraffin Wax)
Thermal Energy Storage Media (Bentonite)
Numerical Model with PCM and Bentonite
Model B
Model C
Summary From this chapter, the following summaries are drawn: (a)
Experimental Work and Numerical Model Validation
Surface temperature distributions at y = 0 m of the cavity along x-axis
Surface temperature distributions of the cavity along y-axis
Surface temperature distributions at x = 0 m of the cavity along y-axis
Numerical Model Validation between PCM and Bentonite
Surface temperature distributions of the cavity along x-axis
Heat Transfer Rate Analysis
Conclusion
Contributions
Findings
Future works
Full Text
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