The energy engineer should be involved in the design considerations that develop the necessary effluent dispersion from the exhaust vent. The necessary effluent dispersion is assured when the exhaust vent produces a specified level of dilution at any building air intake from the "available dilution." This "available dilution" is the combination of three effects: [Ratcliff, 1999]
·internal system dilution,
·wind dilution, and
·stack dilution (resulting from stack height and vertical plume rise).
Of particular interest to the energy engineer is stack dilution, specifically, the exhaust exit velocity that produces the vertical plume rise. The height of the exhaust stack has a direct influence on the minimum exit velocity. Wind modeling can help to calculate full-scale dilution at "critical" wind speed and helps design the most energy-efficient stack. [Wilson, 1983] [Doughty, 1999]
Available dilution concept