Computer modelling of night-time natural ventilation
2010-12-06T10:32:02Z (GMT) by
Wind-induced ventilation has the potential to reduce cooling energy use in buildings. One method this can be achieved is by the use of night-time ventilation to cool down the structure of a building, resulting in lower air and radiant temperatures during the day. To design effective naturally ventilated buildings, evaluation tools are needed that are able to assess the performance of a building. The primary goal of this work was to develop such a tool, that is suitable for use in annual building energy simulation. The model presented, is intermediate in complexity between a CFD numerical model and current single air node models, having seven nodes. The thesis describes how numerical and experimental data have been used to develop the structure and define the parameters of the simplified nodal model. Numerical calculations of the flow and temperature fields have been made with a coupled flow and radiant exchange CFD code. Numerically derived velocity dependent convective heat transfer coefficients are compared with experimental measurements made in room ventilated by cross-flow means, and with empirical correlations cited by other studies. Bulk convection between the air nodes of the simplified nodal model has been derived from a numerical study of contaminant dispersal. The performance of the model is demonstrated by making comparisons with the predictions of a single air node model.