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Published byMiranda Conley Modified over 8 years ago
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Reactor Models for Ventilation Modeling Solve differential equation Manipulate terms Ventilation rate Set up and solve generic problem
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Ventilation Top 3 reasons why ventilation is important 1.Profound impact on IAQ and exposure 2.Energy costs/OAQ impacts 3.Human comfort
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You Have Three Options 1.Source Control 2.Dilution 3.Air Cleaning Can evaluate these options with a reactor model
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Ventilation – Reactor Model ventilation deposition emission reaction
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Assumptions: 1) Well mixed 2) Constant air density 3) Constant outdoor concentration, emission rate 4) First–order loss and reaction processes
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Solution Strategies
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Equation Solutions
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Initial and Steady State Concentration 1.Initial concentration doesn’t influence the concentration after a long time period. 2. If there is no source of a pollutant (including outdoor air), then C ss will be zero.
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Examples Source Control How much better off would be with a building material that emitted half as much as an existing material? Ventilation How much does air exchange help reduce indoor concentrations? Air Cleaning Problem 1 from last year
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Dilution is the Solution to Pollution Concentration Ratio λ = 0.5 hr -1 λ = 1 hr -1 λ = 2 hr -1
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Relaxing Assumptions 1.Well-mixed Use a CFD model 2.Constant air density Track mass flows rather than volumetric flows 3.Constant variables (emission, etc.) Use a numerical solution 4.First–order loss and reaction processes Use a numerical solution
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Ideal Gas Law PV = nRT R= 8.314 pa m 3 /mol /K = 82.05 × 10 -6 atm m 3 /mol /K Dalton’s law of partial pressures
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Common Mole Fraction and Mass Concentration Units %, ppm, ppb, ppt Often called concentrations, not strictly correct μg/m 3, ng/m 3
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