English

Computational fluid dynamics may be used to predict the details of airflow in rooms served by displacement ventilation systems, provided a suitable turbulence model can be found. Since buoyant plumes are central to the displacement ventilation strategy, four turbulence models - three eddy-viscosity models (the 'standard' k-s model, a modified k-s model, and an RNG k-s model) and the Reynolds stress model - were applied to simulate airflow in a turbulent buoyant plume.

This paper deals with the description and determination of the purging flow rate, U_P for ventilation systems or equivalent flow systems. The regional purging flow rate and its use are discussed and proposed. By using the mass conservation principle, U_P is embodied in various accessible mathematical expressions in terms of the transfer probability. Some U_P-related parameters are described. A Markov chain model is proposed for determining the transfer probability and exploring several useful ventilation indices.

The largest-ever exercise to validate dynamic thermal simulation programs (DSPs) of buildings has recently been completed. It involved 25 program/user combinations from Europe, the USA and Australia, and included both commercial and public domain programs. Predictions were produced for three single-zone test rooms in the UK. These had either a single-glazed or double-glazed south-facing window, or no window at all. In one 10-day period the rooms were intermittently heated and in another 10-day period they were unheated.