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Strategically Targeted Research in Intelligent Built.

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Presentation on theme: "Strategically Targeted Research in Intelligent Built."— Presentation transcript:

1 Strategically Targeted Research in Intelligent Built Environmental Systems EPA Contracts # CR 83199201-0 & X-83269001-0 Computation of Transport in PME I. Flow and Pollutant Transport Computation of Transport in PME I. Flow and Pollutant Transport Task 2C Chris Sideroff and Thong Dang Syracuse University

2 SAC Review 07/31-08/01/07 - 2 Purpose  For high IAQ need to address: u Source control u Air-cleaning u New ventilation approaches (e.g. PV)  Ventilation systems involving localized gradients are difficult to design with traditional IAQ methods  Need to look beyond conventional techniques Fanger SU Lecture June 2006 Fanger: “99% of Clean Air is Wasted” “Better” Indoor Air Quality

3 SAC Review 07/31-08/01/07 - 3 Overview  Extend CFD verification and validation  Evaluate LES turbulence model  Impact of radiation  How to include effects of radiation  Applications u PV in aircraft cabin (NASA Space Grant funded) u Realistic details – breathing, body motion and posture (current work)  Transient breathing – affect on plume and re-inhalation  Head motion – affect on plume and re-inhalation  Posture – seated vs. standing

4 SAC Review 07/31-08/01/07 - 4 Current State-of-the-Art  In open literature, grid resolutions are typically on the order of a few hundred thousand (for 3D)  Traditional turbulence models u zero-equation (mixing length)  k-  family  Single-point, omni-directional measurements u velocity magnitude, no components u no turbulence information (length scale, intensity) u minimal (or no) error estimation  Rarely detailed measurements of contaminant (or tracer)  Steady-state u Some breathing work, usually steady inhalation/exhalation u Very little investigations of body motions  Very active area of research – regular ASHRAE symposiums

5 SAC Review 07/31-08/01/07 - 5 Benchmark Case  Inlet vent (front, bottom) = 0.2 m/s (33 CFM), 22°C (72°F),  = 0  Heat loss from body = 76 W (4.3 BTU/min) and insulated walls  Mass flux from body = 1 Displacement Ventilation , Mid-plane χ = 1: clean χ = 0: well-mixed χ < 0: worse than well-mixed Exposure Index →

6 SAC Review 07/31-08/01/07 - 6 Grid Convergence Study  Velocity sensitive to BL resolution - some regions show more difference  Gaseous concentration relatively insensitive  Grid converged with two finest grids (~5M cells) – BL resolution Forward of Torso Forward of Face

7 SAC Review 07/31-08/01/07 - 7 Large Eddy Simulation  RANS often not robust for low Reynolds and Raleighs numbers  LES computes large scales, models sub-grid scales  Plume exhibits unsteadiness with large structures TT + 5 sec. T + 10 sec.T + 15 sec.

8 SAC Review 07/31-08/01/07 - 8 Experimental Comparison  RANS models over-predict the magnitude and mis-predict shape  LES marginally better – missing physics?  Assumed convective heat transfer only (1/2 total) Above Head Forward of Face

9 SAC Review 07/31-08/01/07 - 9 Radiative Heat Transfer  Major human heat transfer mechanisms: convection and radiation  If heat-flux BC is used can not neglect radiation Surface temperature comparison Plume comparison

10 SAC Review 07/31-08/01/07 - 10 Radiative Heat Transfer  Radiation calculation of non-participating medium  Noticeable improvement over convection only results  RANS provide nearly same results as LES Above Head Forward of Face

11 SAC Review 07/31-08/01/07 - 11 Effects of Radiation  Radiation only involves surfaces → use surface temperature instead  Detail description of temperature difficult  Averaged surface temperature → minimal impact on PME flow Above Head Forward of Face

12 SAC Review 07/31-08/01/07 - 12 Applications  Personal ventilation in aircraft cabin (NASA Space Grant funded)  Realistic details u Breathing u Motion u Posture Seated Posture outlet top inlet bottom inlet PV in Aircraft

13 SAC Review 07/31-08/01/07 - 13 Breathing  In seated position, wide plume overwhelms exhaled air  Breathing appears to enhance mixing in breathing zone – plume tracer considerably different Forward of FaceBreathing – Exhale Trace

14 SAC Review 07/31-08/01/07 - 14 Head Motion  People typically are not completely stationary for long periods of time  Including head motion doesn’t increase mixing in breathing zone beyond breathing alone  Small amounts re-inhaled air Forward of Face Motion + Breathing – Exposure Index

15 SAC Review 07/31-08/01/07 - 15 Posture  Plume not as wide as seated in standing position  Plume tracer in breathing zone region generally different – standing position has some influence  Small amounts of re-inhaled air Forward of Face ref: Clark and Edholm– Man and His Thermal Environment

16 SAC Review 07/31-08/01/07 - 16 Summary  RANS models sufficient provided BL resolved  Radiation is key - should not be neglected  If PME flow (not thermal comfort) is of interest, averaged surfaces temperature sufficient  Breathing appears to have significant impact on our plume – enhances mixing in breathing zone  Head motion has some impact but not as much as breathing  Due to a narrower plume, standing position + breathing has some increased influence on plume

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