PowerPoint PresentationThermal comfortSlide 3Slide 4Prediction of thermal comfortIAQ parametersSlide 7Single value IAQ indicators Ev and εAir-change efficiency (Ev)Air exchange efficiency for characteristic room ventilation flow typesContaminant removal effectiveness (e)Differences and similarities of Ev and eParticulate matters (PM)Particles Properties and sourcesSlide 15Two basic approaches for modeling of particle dynamicsLagrangian Model particle trackingSlide 18Algorithm for CFD and particle trackingFinish •Thermal Comfort and •Air Quality analyses in CFDStart particle modeling Lecture ObjectivesThermal comfortTemperature and relative humidityThermal comfortVelocityCan create draftDraft is related to air temperature, air velocity, and turbulence intensity.Thermal comfortMean radianttemperaturepotential problems AsymmetryWarm ceiling (----)Cool wall (---)Cool ceiling (--)Warm wall (-)Prediction of thermal comfortPredicted Mean Vote (PMV)+ 3 hot+ 2 warm+ 1 slightly warmPMV = 0 neutral-1 slightly cool-2 cool-3 coldPMV = [0.303 exp ( -0.036 M ) + 0.028 ] LL - Thermal load on the bodyL = Internal heat production – heat loss to the actual environmentL = M - W - [( Csk + Rsk + Esk ) + ( Cres + Eres )]Predicted Percentage Dissatisfied (PPD)PPD = 100 - 95 exp [ - (0.03353 PMV4 + 0.2179 PMV2)]Empirical correlations Ole FangerIAQ parametersNumber of ACH quantitative indicator ACH - for total air - for fresh airVentilation effectiveness qualitative indicator takes into account air distribution in the spaceExposure qualitative indicator takes into account air distribution and source position and intensityIAQ parameters-Age-of-air air-change effectiveness (EV)-Specific Contaminant Concentration contaminant removal effectiveness Single value IAQ indicators Ev and ε1. Contaminant removal effectiveness () concentration at exhaust average contaminant concentration Contamination level2. Air-change efficiency (v) shortest time for replacing the air average of local values of age of air Air freshnessCCεeτ2τEv n [sec] ACS/1τnAir-change efficiency (v)•Depends only on airflow pattern in a room•We need to calculate age of air ()Average time of exchange •What is the age of air at the exhaust?Type of flow–Perfect mixing–Piston (unidirectional) flow –Flow with stagnation and short-circuiting flow222222z)(y)(x)()(τtttzyxzVyVxτV [sec] ACH/1 τ,τ2τnexeAir exchange efficiency for characteristic room ventilation flow typesFlow patternAir-changeefficiencyComparison with average time of exchange Unidirectional flow 1 - 2n < exc < 2nPerfect mixing 1exc = nShort Circuiting 0 - 1exc > n τ2τexeContaminant removal effectiveness ()•Depends on:-position of a contaminant source-Airflow in the room•Questions1) Is the concentration of pollutant in the room with stratified flow larger or smaller that the concentration with perfect mixing?2) How to find the concentration at exhaust of the room?Differences and similarities of Ev and  Depending on the source position: - similar or - completely different air quality v = 0.41  = 0.19  = 2.20Particulate matters (PM)•Properties–Size, density, liquid, solid, combination, … •Sources –Airborne, infiltration, resuspension, ventilation,… •Sinks-Deposition, filtration, ventilation (dilution),…•Distribution- Uniform and nonuniform •Human exposureParticles Properties and sourcesASHRAE Transaction 2004ASHRAE Transaction 2004PropertiesTwo basic approaches for modeling of particle dynamics •Lagrangian Model–particle tracking–For each particle ma=F•Eulerian Model –Multiphase flow (fluid and particles)–Set of two systems of equationsLagrangian Modelparticle trackingA trajectory of the particle in the vicinity of the sphericalcollector is governed by the Newton’s equationm∙a=F(Vvolume) particle ∙dvx/dt=Fx(Vvolume) particle ∙dvy/dt=Fy(Vvolume) particle ∙dvz/dt=FzSystem of equation for each particle Solution is velocity and direction of each particle Forces that affect the particleLagrangian Modelparticle trackingBasic equations- momentum equation based on Newton's second law eFFtiVPPddrag36- dp is the particle's diameter, - p is the particle density, - up and u are the particle and fluid instantaneous velocities in the i direction,- Fe represents the external forces (for example gravity force). This equation is solved at each time step for every particle. The particle position xi of each particle are obtained using the following equation: iiVdtdxpuufFdragDrag force due to the friction between particle and air For finite time step tdt Algorithm for CFD and particle trackingAirflow (u,v,w)Steady state airflowUnsteady state airflowParticle distribution for time step Particle distribution for time step +Particle distribution for time step +2Steady stateInjection of particles…..Airflow (u,v,w) for time step Particle distribution for time step Particle distribution for time step +Injection of particles…..Airflow (u,v,w) for time step +Case 1 when airflow is not affected by particle flowCase 2 particle dynamics affects the airflowOne way coupling Two way