Flow Network Model based on Power Balance as Applied to Cross-Ventilation

Abstract

This paper reviews the flow network model based on power balance as applied to wind-induced cross ventilation in a residential building. The characteristics of wind-induced cross-ventilation with open windows in buildings are different from those of air infiltration through cracks in walls. The features of the velocity and pressure distributions are apparently different. In cross-ventilation, it seems that a kind of stream tube is formed through the building. A large part of the dynamic pressure generated at the opening is preserved within the room, and a major part of the preserved energy is directly convected outside the room. The preservation of energy is reflected as a decrease in the value of the total pressure loss coefficient, ζ. The static pressure loss does not express the total pressure loss through an opening. The flows in the building usually converge and diverge and thereby lose energy. The lost energy should also be accurately evaluated as in the total pressure loss coefficient, ζ, in a consistent manner in the energy-losing process. In this paper, a flow network model, based on the power balance model, which considers preservation of dynamic pressure and energy loss evaluation, is introduced. The power balance model well describes the energy-loss process of diverging and converging flows. There seems to be a large possibility that the model introduced works well in predicting the air flow rate of wind-induced cross-ventilation in a residential bulding compared with the usual models based on the extended Bernoulli‘s equation within a stream tube (a one-dimensional energy equation).