Strategically Targeted Research in Intelligent Built Environmental Systems EPA Contracts # CR & X 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

SAC Review 07/31-08/01/ 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

SAC Review 07/31-08/01/ 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

SAC Review 07/31-08/01/ 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

SAC Review 07/31-08/01/ 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 →

SAC Review 07/31-08/01/ 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

SAC Review 07/31-08/01/ 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.

SAC Review 07/31-08/01/ 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

SAC Review 07/31-08/01/ 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

SAC Review 07/31-08/01/ 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

SAC Review 07/31-08/01/ 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

SAC Review 07/31-08/01/ 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

SAC Review 07/31-08/01/ 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

SAC Review 07/31-08/01/ 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

SAC Review 07/31-08/01/ 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

SAC Review 07/31-08/01/ 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