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Modeling of Air and Pollutant Flows in Buildings

This course covers the fundamentals of fluid dynamics and introduces computational fluid dynamics (CFD) for analyzing and simulating airflow and pollutant distribution in buildings. Topics include turbulence models, numerical methods, CFD software, IAQ parameters, thermal comfort parameters, and more. Prerequisites include knowledge of fluid dynamics.

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Modeling of Air and Pollutant Flows in Buildings

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  1. The University of Texas at Austin Fall 2019 CAEE Department Course: Modeling of Air and Pollutant Flows in Buildings Instructor: Dr. Atila Novoselac Office: ECJ, 5.430 Phone: (512) 475-8175 e-mail: atila@mail.utexas.edu http://www.ce.utexas.edu/prof/Novoselac Office Hours: Tuesday and Thursday 11:00 a.m.–12:00 p.m.

  2. Today’s Lecture Objectives: • Discuss the Syllabus • Describe scope of the course • Introduce the course themes • Answer your question • Fluid dynamics review

  3. Introduce Yourself • Name • Background - academic program and status • Professional interests

  4. Motivation for Modeling of Indoor Air Distribution using CFD: • Major exposure to contaminant is in indoor environment • Ventilation system provides contaminant dilution Controlled airflow (ventilation) can considerably improve the IAQ and reduce the ventilation air requirement • Air-flow transports pollutants – gaseous and particulate • Contaminant concentration in the space is more or less non-uniform – It affects: emission, filtration, reactions, exposure

  5. Why to Care About Indoor Airflow Distribution ? Pollutant concentration is very often non-uniform - Exposure depends on dispersion • We can control exposure by controlling the flow field Perfect mixing

  6. Examples of Exposure Control by Ventilation Systems 1) Control Exhaust 2) Control Supply Supply diffusers

  7. Example of Buoyancy Driven Flow:Airflow in a Stairwell Heater (radiator)

  8. Example of Force Convection Contaminant Concentration in a Kitchen

  9. Example Particle Dispersion

  10. What CFD Does • Real flow • Modeling

  11. Fluid Dynamics Continuity: Momentum:

  12. Numerical Methods

  13. Simulation Software (CFD) Simulation Software Input Output If Garbage IN Then Garbage OUT

  14. Course Objectives • Recognize the physics behind various numerical tools used for solving airflow problems. • Employ basic numerical methods for solving Navier-Stokes Equations. • ApplyCFD for airflow simulations in buildings and use these tools in design and research. • Evaluate the thermal comfort and indoor air quality (IAQ) with different ventilation systems. • Assess human exposure to different pollutant types. • Critically analyze and evaluate CFD results.

  15. Topics: 1. Course Introduction and Background 1 wk 2. Fundamentals of fluid dynamics 2 wks 3. Turbulence models 1.5 wks 4. Numerical methods and parameters 2 wks 5. CFD modeling parameters 1.5 wks 6. Introduction to CFD software 1 wk 7. Application of CFD for building airflows 1 wk 8. Simulation of IAQ parameters 1 wk 9. Simulation of thermal comfort parameters 1 wk 10. Modeling of aerosols 1 wk 11. Air and pollutant flows in the vicinity of occupants 1 wk 12. Accuracy and validation of building airflow simulations 1 wk 30% 30% 40%

  16. Prerequisites - Fluid Dynamics Knowledge of the following is useful but not necessary: • Numerical analysis • Programming

  17. Textbook • An Introduction to Computational Fluid Dynamics, Versteeg, H.K. and Malalasekera, W. References: 2) Computational Fluid Dynamics –The Basics With Applications Anderson 3) Turbulence Modeling for CFD Wilcox

  18. Handouts • Copies of appropriate book sections An Introduction to Computational Fluid Dynamics I will mark important sections • Disadvantage - different nomenclature • I will point-out terms nomenclature and terminology differences • Journal papers and CFD software manual • Related to application of airflow simulation programs

  19. Energy simulation software Fluent Airpark

  20. Star CD Software – Supply airflow patern

  21. There is a large availability of CFD software ! • Star CD , Fluent (ANSYS and Airpak) We have it and you will use it - Phoenics • CFX • Flow Vent

  22. TENTATIVE COURSE SCHEDULE In the syllabus and on the website http://www.ce.utexas.edu/prof/Novoselac/classes/ARE372/Notes.html

  23. Grading Test 30% Homework Assignments 25% Midterm Project 10% Final Project & Presentation 30% Classroom Participation 5% 100%

  24. Participation 5% • Based on my assessment of your participation in the class • How to get participation points • Come to class • Submit all assignments/projects on time • Participate in class discussions • Come to see me in my office

  25. Homework 25% Targeted number: 3 • HW1 Problems related to fluid dynamic • HW2 Problem related to turbulence modeling • HW3 Problem related numeric

  26. Midterm Project 10% • Individual project • Use of CFD program for air and pollutant flow analysis • Primary goal is to get familiar with the CFD software

  27. Midterm Exam 30% • In-class exam (90 minutes) • After 2/3 of the course (sometime in October ) • we will arrange the exact time • Problems based on topics cover in the first two parts of the course

  28. Final Project 30% • Use of CFD for detail airflow, thermal and IAQ analyses • Different projects topics • Real engineering an/or research problems • Final presentation (~15 minutes)

  29. Previous Course projects-Human Exposure to Indoor Pollutants - dispersion of pollutant with DV

  30. Previous Course projects- Surface Boundary Layer

  31. Previous Course Projects- Hydro-Jet Screen

  32. Previous Course projects- Natural Ventilation

  33. Modeling of Smoke in Stairwell

  34. More CFD Final Project: • Design of ventilation system • Smoke management • Natural ventilation • Human exposure to various pollutants • Your suggestion

  35. Grading > 93 A 90-93 A- 86-90 B+ 83-86 B 80-83 B- < 80 C-, C, C+

  36. Course Website All course information: http://www.ce.utexas.edu/prof/Novoselac/Classes/ARE372/ • Except your grades and HW solutions Grades and progress on the Canvas • On the course website • Look at Assignments sections • Review class material ahead of time use posted class notes

  37. My Issues • Please try to use office hours for questions problems and other reasons for visit Tuesday and Thursday morning reserved - Class preparation • Please don’t use e-mail to ask me questions which require long explanations • Come to see me or call me • Suggestions are welcome • The more specific the better

  38. Fluid Dynamics Review

  39. Conservation equations

  40. Important operations Total derivative for fluid particle which is moving: V z any scalar y x Vector and scalar operators: scalar vector

  41. Shear and Normal stress τyx

  42. Continuity equation -conservation of mass Mass flow in and out of fluid element Infinitely small volume Volume V = δxδyδz Volume sides: Ax = δyδz Ay = δxδz Az = δxδy Change of density in volume = = Σ(Mass in) - Σ(Mass out) ………………. ……………….

  43. Momentum equation –Newton’s second law dimensions of fluid particle Stress components in x direction forces per unit of volume in direction x ……………….. ……………… ……………. total derivative

  44. Momentum equation Sum of all forces in x direction Internal source x direction y direction z direction

  45. Newtonian fluids Viscous stress are proportional to the rate of deformation (e) Elongation: Shearing deformation: For incompressible flow Viscous stress: 0 viscosity

  46. Momentum equations for Newtonian fluids After substitution: x direction: y direction: z direction:

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