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Multizone Modeling: Convergence Issues and Applications in Indoor Air Quality Analysis

Explore convergence challenges, "false time step" relaxation, and examples in CONTAM and COMIS. Learn boundary conditions, simplifications, and CFD software for multizone modeling. Enhance your skills in airflow simulations for building design and research.

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Multizone Modeling: Convergence Issues and Applications in Indoor Air Quality Analysis

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  1. Lecture Objectives • Discuss HW4 • Convergence issues • Learn about “false time step” relaxation • Multizone modeling • Review class material

  2. Multizone modeling

  3. Example

  4. Multizone modeling CONTAM and COMIS • http://www.bfrl.nist.gov/IAQanalysis/ • NO momentum equation • Just pressure, temperature, and continuity • Depends heavily on boundary condition and orifice coefficients that define flow between zones • Good for buoyancy driven flow

  5. Boundary condition for multizone modeling • Exterior pressure (wind) • Temperature distribution (requires some assumption or energy modeling)

  6. Wind pressurearound building Very complex and unsteady For multizone we are introducing many simplifications: ….

  7. Multizone vs. Moltizonla • “Multizonal” is like CFD (detailed grid with no orifice between i- between zones) but no momentum equation

  8. Commercial: Fluent (Airpak) www.fluent.com/ Star CD https://mdx.plm.automation.siemens.com/ Ansys CFX http://www.ansys.com/Products/Fluids/ANSYS-Fluent Phoenics www.cham.co.uk/ Flomerics (Flowvent) www.flomerics.com/ and many other Some free research: OpenFOAM https://www.openfoam.com/ NIST FDS and Smokeview www.fire.nist.gov/fds/download/ ASHRAE - zero equation (published only source code) Many more CFD software

  9. Summary of Course Objectives • Recognize the physics behind various numerical tools used for solving airflow problems. • Employ basic numerical methods for solving Navier-Stokes Equations. • Apply CFD 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.

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