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Computational Fluid Dynamics Analysis of Air Flow and Temperature Distribution in Buildings

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Computational Fluid Dynamics Analysis of Air Flow and Temperature Distribution in Buildings Computational Fluid Dynamics Analysis of Air Flow and Temperature Distribution in Buildings Undergraduate Honors Thesis Presented in Partial Fulfillment of the Requirements for Graduation with Distinction in Mechanical Engineering By Bradley S. Hurak Defense Committee: Professor Sandip Mazumder Professor Yann Guezennec Abstract Energy consumption for the heating and cooling of residential buildings accounts for nearly half of total use. Because the physical configuration of heating and cooling inlets and outlets is often determined from historical practice or convenience rather than optimal performance, it stands to reason that there is an opportunity to gain effectiveness of these systems by applying engineering principles to their design. In this study, a computational fluid dynamic analysis was performed to investigate the effect of the physical configuration of inlet and outlet vents on the temperature and flow patterns inside a room modeled for simplicity as a two dimensional enclosure. It was determined that for use in both heating and cooling of a room, a low or floor located inlet vent coupled with an outlet that is positioned on the upper half of a wall yields the most desirable results in reaching, or nearly reaching, comfort conditions in the shortest amount of time. However, if either heating or cooling is expected to be the primary energy consumption, it may be advantageous to deviate from this configuration. ii Acknowledgements I would like to thank everyone who has supported me throughout the course of this project. I am appreciative for the help and patience of my advisor, Professor Sandip Mazumder. I have valued and learned from the constructive criticism that Professor Yann Guezennec has offered throughout the classroom sessions for this project. ESI Group is also acknowledged for providing lisences to their commercial software, CFD-ACE+. Finally, I am very grateful for the encouragement, support, and love that my parents have always given me. iii Table of Contents Abstract ......................................................................................................................................................... ii Acknowledgements ...................................................................................................................................... iii List of Figures ................................................................................................................................................ v List of Tables ................................................................................................................................................ vi 1 Introduction .......................................................................................................................................... 1 1.1 Literature Survey ........................................................................................................................... 1 1.2 Objectives of Current Research .................................................................................................... 2 2 Methods ................................................................................................................................................ 3 2.1 Two-dimensional Model Description ............................................................................................ 3 2.2 Three-dimensional Model Description ......................................................................................... 4 2.3 Parametric Study ........................................................................................................................... 5 2.4 Model Conditions .......................................................................................................................... 6 2.4.1 Hot Conditions ...................................................................................................................... 6 2.4.2 Cold Conditions ..................................................................................................................... 7 3 CFD Model ............................................................................................................................................. 8 3.1 Flow Module ................................................................................................................................. 8 3.1.1 Mass Conservation Equation ................................................................................................ 8 3.1.2 Momentum Conservation Equations .................................................................................... 8 3.1.3 Navier-Stokes Equations ....................................................................................................... 9 3.1.4 Other Flow Properties ......................................................................................................... 10 3.2 Heat Transfer Module ................................................................................................................. 11 3.2.1 Thermal Boundaries ............................................................................................................ 11 3.3 Turbulence Module ..................................................................................................................... 15 3.4 Three-dimensional Model Properties ......................................................................................... 16 4 Results ................................................................................................................................................. 17 4.1 Flow Data .................................................................................................................................... 17 4.2 Temperature Data ....................................................................................................................... 18 5 Conclusions ......................................................................................................................................... 29 6 Recommendations .............................................................................................................................. 33 Appendix A .................................................................................................................................................. 34 Bibliography ................................................................................................................................................ 45 iv List of Figures Figure 1: Two-dimensional model with inlets, outlets, and temperature probe. ........................................ 4 Figure 2: Three-dimensional model with inlets and outlets. ........................................................................ 5 Figure 3: Thermal resistance model of ceiling. ........................................................................................... 13 Figure 4: Thermal resistance model of side walls. ...................................................................................... 14 Figure 5: Thermal resistance model of floor. .............................................................................................. 14 Figure 6: Configuration 3-4, Cooling. .......................................................................................................... 18 Figure 7: Monitor point temperature data, Inlet 2, Outlet 1. ..................................................................... 19 Figure 8: Monitor point temperature data, Inlet 2, Outlet 2. ..................................................................... 20 Figure 9: Monitor point temperature data, Inlet 2, Outlet 3. ..................................................................... 20 Figure 10: Monitor point temperature data, Inlet 2, Outlet 4. ................................................................... 21 Figure 11: Monitor point temperature data, Inlet 2, Outlet 5. ................................................................... 21 Figure 12: Monitor point temperature data, Inlet 1, Outlet 2. ................................................................... 23 Figure 13: Monitor point temperature data, Inlet 2, Outlet 2. ................................................................... 23 Figure 14: Monitor point temperature data, Inlet 3, Outlet 2. ................................................................... 24 Figure 15: Monitor point temperature data, Inlet 4, Outlet 2. ................................................................... 24 Figure 16: Monitor point temperature data, Inlet 5, Outlet 2. ................................................................... 25 Figure 17: Transient temperature at monitor point for all configurations. ................................................ 29 Figure 18: Configuration 2-5, cooling at 2.5 minutes into transient........................................................... 30 Figure 19: Configuration 2-4, cooling at 2.5 minutes into transient........................................................... 31 v List of Tables Table 1: List of test numbers according to inlet and outlet position. ........................................................... 6 Table 2: Flow Model Constants. .................................................................................................................. 10 Table 3: Material type, thermal properties and thickness of ceiling thermal model layers. ...................... 13 Table 4: Material type, thermal properties and thickness
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