Wind Tunnel Investigations of Natural Ventilation

Requirements for similarity of natural ventilation in wind tunnel models and experimental methods for evaluating its effectiveness are reviewed and tested in a 1:25 wind tunnel model of the Florida Solar Energy Center Passive Cooling Laboratory (PCL). The experiments indicate that, in addition to the requirements for simulation of external flows around the building, an internal Reynolds number based on the maximum velocity and minimum dimension of each room should be larger than $2\times {10}^4\text{.}$ Internal to external velocity ratios are shown to give a detailed unbiased picture of the local internal climate. Dimensionless pressure difference coefficients, based on pressure measurements on the external envelope of the building model, and dimensionless dilution rates, based on tracer concentration decay measurements, can be used to evaluate the relative integral effectiveness of natural ventilation in different configurations. The advantages and limitations of each method, as demonstrated in the study of the PCL model, are reviewed.