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Cfd Simulation of Stratified Thermal Energy Storage Tank Ecovat

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Cfd Simulation of Stratified Thermal Energy Storage Tank Ecovat Ecovat® Seasonal Thermal Energy Storage CFD SIMULATION OF STRATIFIED THERMAL ENERGY STORAGE TANK ECOVAT PREPARED BY: HAMED KHATAM BOLOURI SANGJOEEI SUPERVISION BY: ECOVAT TEAM Winter 2021 Abstract Ecovat as a stratified thermal storage tank brings the possibility of making optimal use of renewable energy demands flexibility for heating and cooling. Regarding utilization of Thermal stratification in the storage tank, some unbalancing for thermal stratification would emerge during charging and discharging. In this project, a Computational Fluid Dynamics investigation on Ecovat is performed to determine the effects of inlet hot water, thermocline thickness, temperature difference between inlet water and existing water in tank, and position of diffusers on the mixing and thermocline formation, which influenced the performance of Ecovat systems and thermal stratification. Furthermore, the CFD model would be Proposed for the the whole Ecovat system (Diffusers and Tank) for the first time and this model can be utilized to simulate the Ecovat with custom dimensions based on the client’s requirements. CFD Simulation will demonstrate how the Ecovat system will work in real operational cases. ii | P a g e Table of Contents Abstract ............................................................................................................................... ii Table of Contents ............................................................................................................... iii List of Figures ..................................................................................................................... v List of Tables ..................................................................................................................... vi Acronyms & Symbols ....................................................................................................... vii Acknowledgment ............................................................................................................. viii 1 Introduction ................................................................................................................. 9 2 Problem Statement .................................................................................................... 11 3 Motivation and goals................................................................................................. 13 4 Literature Review...................................................................................................... 14 5 Methodology and Approaches .................................................................................. 18 5.1 Pre-processing .................................................................................................... 19 5.1.1 Geometry..................................................................................................... 19 5.1.2 Mesh ............................................................................................................ 19 5.1.3 Physics (boundary condition and initial value) ........................................... 19 5.2 Solving ............................................................................................................... 20 5.2.1 Monitoring .................................................................................................. 20 5.3 Postprocessing .................................................................................................... 20 5.3.1 Result .......................................................................................................... 20 6 Software .................................................................................................................... 21 6.1 OpenFOAM ........................................................................................................ 21 6.2 blockMesh .......................................................................................................... 21 6.3 Paraview ............................................................................................................. 21 6.4 SnappyHexMesh ................................................................................................ 22 6.5 Python................................................................................................................. 22 7 2D simulation ............................................................................................................ 23 7.1 Description of the model .................................................................................... 23 7.2 Description of construction and solution steps .................................................. 23 7.3 Geometry ............................................................................................................ 24 7.4 Mesh Construction ............................................................................................. 25 7.5 Solver ................................................................................................................. 27 iii | P a g e 7.6 Boundary Conditions.......................................................................................... 29 7.7 Post-processing the results ................................................................................. 31 7.8 Case 1 Thermal Stratification ............................................................................. 31 7.9 Case 2 ................................................................................................................. 34 8 3D simulation ............................................................................................................ 36 8.1 Description of the model .................................................................................... 36 8.2 Description of construction and solution steps .................................................. 36 8.3 Geometry and Mesh generation ......................................................................... 36 8.4 Boundary Conditions.......................................................................................... 40 8.5 Postprocessing .................................................................................................... 41 8.6 Case 1 ................................................................................................................. 42 8.6.1 Case 1 Result............................................................................................... 43 8.7 Case 2 ................................................................................................................. 44 8.7.1 Case 2 Result.............................................................................................. 45 8.8 Case 3 ................................................................................................................. 46 8.8.1 Case 3 Result.............................................................................................. 47 8.9 Case 4 ................................................................................................................. 48 8.9.1 Case 4 Result.............................................................................................. 49 9 Conclusion ................................................................................................................ 50 10 References ................................................................................................................. 52 iv | P a g e List of Figures Figure 1 Thermal energy storage tank with district heating, Ecovat .................................. 9 Figure 2 Charging and Discharging process in TES (Azharul Karim, 2018) ................... 11 Figure 3 CFD Simulation, thermocline analysis (Azharul Karim, 2018) ......................... 14 Figure 4 water temperature contours from 6 minutes to 30 minutes (Olfa Abdelhak & Bournot, 2015) .................................................................................................................. 15 Figure 5 Different steps of CFD analysis ......................................................................... 18 Figure 6 2D diffuser modeling in Blender ........................................................................ 22 Figure 7 Ecovat Simplified 2D model .............................................................................. 24 Figure 8 generated mesh for the diffuser ......................................................................... 25 Figure 9 Generated mesh for the whole 2D model ........................................................... 26 Figure 10 Node discretization and numerical method ...................................................... 27 Figure 11 wall boundary condition ................................................................................... 29 Figure 12 Inlet and Outlet boundary condition ................................................................. 29 Figure 13 Empty boundaries ............................................................................................. 30 Figure 14 2D simulation of Thermal stratification in Ecovat ( Time: “seconds”)............ 33 Figure 15 2D simulation of the charging process in Ecovat ............................................. 35 Figure 16 diffuser geometry generated by using python code .......................................... 37 Figure 17 complete Ecovat geometry generated by using python code ........................... 37 Figure 18 Mesh Generated for 3D geometry ...................................................................
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