Reactor Models for Ventilation Modeling Solve differential equation Manipulate terms Ventilation rate Set up and solve generic problem

Ventilation Top 3 reasons why ventilation is important 1.Profound impact on IAQ and exposure 2.Energy costs/OAQ impacts 3.Human comfort

You Have Three Options 1.Source Control 2.Dilution 3.Air Cleaning Can evaluate these options with a reactor model

Ventilation – Reactor Model ventilation deposition emission reaction

Assumptions: 1) Well mixed 2) Constant air density 3) Constant outdoor concentration, emission rate 4) First–order loss and reaction processes

Solution Strategies

Equation Solutions

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.

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

Dilution is the Solution to Pollution Concentration Ratio λ = 0.5 hr -1 λ = 1 hr -1 λ = 2 hr -1

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

Ideal Gas Law PV = nRT R= pa m 3 /mol /K = × atm m 3 /mol /K Dalton’s law of partial pressures

Common Mole Fraction and Mass Concentration Units %, ppm, ppb, ppt Often called concentrations, not strictly correct μg/m 3, ng/m 3