DYNAMICS OF THE VENTILATION AIR FLOW IN BUILDINGS OF VARIOUS THERMAL CAPACITIES OF PARTITIONS

摘要

The results of computer simulation of unsteady exchange of heat and ventilation flow rates in buildings with natural ventilation have been presented in this paper. To investigate the above phenomena a computer program has been created. The algorithm of computations has been based on the finite differences method, where feedback between the thermal model and the airflow model is applied. The research on heat and air exchange process has been conducted in four single-zone buildings with typical external partitions material structure of different thermal capacities. The calculations have been made for buildings fitted with an internal heat accumulating mass, and without it. The results of the simulations are as follows: time history for the indoor temperature, ventilation flow rates, overall heat accumulation in the object, heat losses and gains through walls, ceiling, and windows, time history for temperature in particular wall layers, and heat losses to the ground. Both modes of airflow throughout the buildings have been simulated. The first one regards an assisting wind, the second an opposite one. Due to limited space, the results of computation concerning the summer season represented by highly typical month of July have been presented. The heat and air exchange process in any naturally ventilated building is influenced by a large number of governing factors, including weather parameters as well as internal sources of heat, among others. The calculations are carried out with reference to the mean values of: ambient temperature, direct and diffuse solar radiation, and wind velocity. As regards the solar radiation, the commonly applied absorption model on external partitions, as well as the multiple reflection and absorption model for transparent partitions penetrating radiation, have been assumed. Next, the wind velocity normal components acting on the north oriented wall where ventilation opening is located, have been collected from azimuth ranging from 270° - 360°, and from 0° - 90°. In case of the south wall, velocities from the azimuth ranging from 90° - 270° have been collected. The mean monthly values of the above-mentioned weather parameters have been used for numerical simulation. Temperature and wind velocity are expressed by harmonic functions.