On natural ventilation of a building with two openings.

Analytical solutions are derived for calculating natural ventilation flow rates in a single-zone building with two openings when no thermal mass is present. In these solutions, the independent variables are the heat source strength and wind speed, rather than given indoor air temperatures. Three air change rate parameters a, B and y are introduced to characterise respectively the thermal buoyancy force, the conduction heat loss effect, and the wind force. The wind can either assist the buoyancy force or oppose it. For assisting wind the flow is always upwards and the solutions are straightforward. For opposing wind, the flow can be either upwards or downwards depending on the relative strengths of the two forces. In this case the solution for the flow rate as function of the heat source strength presents some complex and unusual features.