Macroscopic formulation and solution of ventilation design problems.

This paper will present a general approach that may be used to solve natural ventilation designproblems typically addressed at the preliminary design stage - How wide should windows beopened in a given building for wind-driven cross ventilation on a moderate summer day? Howshould a ventilating monitor be configured to mitigate internal and solar gains on the samesummer day? Established macroscopic equations governing airflow and heat transfer inmultizone building systems will be reformulated to place airflow component characteristics -e.g., size of window opening, speed of a ventilating fan, or height of a monitor window - as keydesign parameters to be adjusted, selected, or in the special case of optimization, to beoptimized. The resulting equations will establish constraints that must be placed on thesedesign variables to guarantee the satisfaction of mass, momentum, and energy conservation. Tothese constraints, constraints relating to thermal comfort will be formulated in terms of thedesign parameters. It will be shown that together the conservation and comfort constraints serveto unambiguously define combinations of design parameters that are technically feasible - fromthese an optimal combination may be sought. The general approach will be applied to simplecases of cross ventilation and stack ventilation to demonstrate the utility of the approach.