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Application of for Predicting Indoor Airflow and Thermal Comfort

Application of for Predicting Indoor Airflow and Thermal Comfort. Preview. Introduction CFD Theory Thermal Comfort Airpak Case Study Future Works. Introduction. Indoor environment design and assessment Airflow pattern, velocity, temperature, and contaminant concentration.

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Application of for Predicting Indoor Airflow and Thermal Comfort

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  1. Application of for Predicting Indoor Airflow and Thermal Comfort

  2. Preview • Introduction • CFD Theory • Thermal Comfort • Airpak • Case Study • Future Works

  3. Introduction • Indoor environment design and assessment Airflow pattern, velocity, temperature, and contaminant concentration • Indoor energy analysis • Energy programs: uniform distribution of air temperature • Complication: forced ventilation and natural ventilation

  4. Computational Fluid Dynamics (CFD) Advantages: Low cost, high speed, complete information, ability to simulate realistic conditions and ideal conditions. Disadvantages: fast computer with a large memory Introduction • Experimental measurements and computational simulations

  5. Ventilation CFD Model The Navier-Stokes equations Mass continuity Momentum (u, v, w) Temperature Species

  6. High High Computing time Accuracy Indoor zero-equation model Model Standard Mixing-length model RNG Model Low Low Viscosity Models • Laminar flow (Re < 2500) • Turbulent flow (Re>= 2500)

  7. Flux Laws Conservation Principles Mathematical Models Numerical Method Finite Volume Formulations Computer Programs Grid or Mesh Generation Methods Finite Element Formulations Numerical Predictions Problem Parameters Post Processing Tools Interpretation CFD Elements Mathematical Description of the Problem of Interest

  8. ASHRAE Summer and Winter Comfort Zone: ASHRAEthermal sensation scale: • + 3 Hot • + 2 Warm • + 1 Slightly Warm • 0 Neutral • 1 Slightly Cold • 2 Cool • - 3 Cold Humidity ratio, g/kg Dew point temperature 0C winter summer Operative temperature (ASHRAE standard 55) Thermal Comfort

  9. PMV (Predicted Mean Vote) PPD (Predicted Percentage of Dissatisfied) (ASHRAE Fundamental, 2001) 80 50 PPD % 30 20 10 5 -1.5 -2.0 1.5 2.0 -0.8 -0.5 0.5 0.8 0 PMV

  10. FLUENT Is a virtual prototyping CFD software that lets you evaluate and understand your ventilation system performance. • Airflow patterns • Air turbulence • Contaminant transport • Temperature and humidity distribution • Thermal comfort • Room pressurization • Equipment effects • Process exhaust

  11. 1. Building Objects

  12. 2.Physical Modeling and Boundary Conditions Steady or Transient ? Laminar or Turbulent ? Solving variables? Physical models? Initial conditions? Boundary Conditions?

  13. Examine the mesh • Aspect ratio • Face alignment • Volume Refine the mesh Generate new mesh No Re-examine the mesh • Flow objects • Local mesh control • Object-specific meshing control OK Solve 3. Meshing Generate first mesh Mesh quality is important!!!

  14. Setup: • Maximum number of iterations • Convergence criteria • Discretization scheme • Under-relaxation factors Accuracy depends on: • Accuracy of physical models • Accuracy of boundary conditions • Accuracy of the modeling assumptions • Numerical scheme • Resolution of mesh 4. Solving the Problem

  15. Case study Edward Ben

  16. 12 L/s 53 L/s, 15.8 0C 28 L/s 23 L/s Case study (a) Computer 108 w Light 120 w People 73 w Ben Outlet vent Induction Unit 40 L/s, 21 0C 04/06/2003

  17. Temperature 04/06/2003,Cooling

  18. Temperature Validation Sensor 3 Sensor 1 Sensor 2 6% 5% 2% 4% Sensor 4 z Sensor x Ben 04/06/2003

  19. Y = 1.1 m z x PMV Ben 04/06/2003

  20. Airflow Ben 04/06/2003

  21. Airflow y z Ed Ben

  22. y x Airflow Ed

  23. Case study (b)

  24. Temperature Comparison Nozzle diffuser Slot diffuser

  25. Airflow Comparison Nozzle diffuser Slot diffuser

  26. Y = 1.1 m z x PMV Comparison Ben Ben Nozzle diffuser Slot diffuser

  27. Next! www.rehva.com www.haltoncompany.com Displacement ventilation Mixing ventilation www.york.com Occupied Zone Underfloor ventilation

  28. Recommendations for future works $ $$$$$$$ $ $$$$$$$ $ $$$$$$$ $ $$$$$$$ $ $$$$$$$ $ $$$$$$$ $ $$$$$$$ $ $$$$$$$ $ $$$$$$$ $$$$$$ $ $$$$$$$ $ $$$$$$$ $ $$$$$$$ $$$ $$$$$ Energy Simulation Program + = 1. Cost Analysis

  29. Recommendations for future works 2. Office Space Template

  30. Personal Inlet Diffuser Outlet Personal Inlet Diffuser

  31. Airflow • Temperature • Relative Humidity • Indoor Air Quality • Thermal Comfort Energy Simulation Program $ $ $ Cost Analysis A tool to assist Real Property Operations in improving the quality of indoor office environments and reducing energy waste.

  32. Thanks!

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