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

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

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

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

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

9 PMV (Predicted Mean Vote) PPD (Predicted Percentage of Dissatisfied) PMV -0.50.5 10 20 PPD % -0.8 0 0.8 5 -1.5 -2.01.52.0 30 50 80 ( ASHRAE Fundamental, 2001)

10 1.Airflow patterns 2.Air turbulence 3.Contaminant transport 4.Temperature and humidity distribution 5.Thermal comfort 6.Room pressurization 7.Equipment effects 8.Process exhaust Is a virtual prototyping CFD software that lets you evaluate and understand your ventilation system performance. FLUENT

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 3. Meshing Mesh quality is important!!! Generate first mesh Examine the mesh Re-examine the mesh 1.Flow objects 2.Local mesh control 3.Object-specific meshing control Refine the mesh Generate new mesh Solve OK No 1.Aspect ratio 2.Face alignment 3.Volume

14 4. Solving the Problem 1.Maximum number of iterations 2.Convergence criteria 3.Discretization scheme 4.Under-relaxation factors Setup: 1.Accuracy of physical models 2.Accuracy of boundary conditions 3.Accuracy of the modeling assumptions 4.Numerical scheme 5.Resolution of mesh Accuracy depends on:

15 Case study Ben Edward

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

17 Temperature 04/06/2003,Cooling

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

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

20 Airflow Ben 04/06/2003

21 z y Airflow BenEd

22 x y Airflow Ed

23 Case study (b)

24 Slot diffuser Nozzle diffuser Temperature Comparison

25 Slot diffuser Nozzle diffuser Airflow Comparison

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

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

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

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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