English

Previous research has shown that air movement has a significant influence on humans’ thermal comfort. For persons feeling cool, air movement tends to be perceived as draught, whilst when feeling warm air movements may provide a desired cooling effect. In the transition zone it therefore seems difficult to use constant air velocity as a tool for cooling without creating draught problems.

Passive cooling techniques such as night time cross ventilation can potentially provide substantial cooling energy savings in warm climates. The efficiency of night cooling ventilation is determined by three main factors: the external airflow rate in the room, the flow pattern and the thermal mass distribution. The aim of this paper is to analyse the effect of the enclosure shape and the situation of inlet/outlet openings on the total cooling energy stored in the structure.

The possible benefits of automatic ventilation control of trickle ventilators in dwellings are investigated. Such ventilators could offer an improvement in performance over fixed ventilators, due to their ability to adjust to environmental conditions without occupant interaction, thus improving energy efficiency and providing adequate indoor air quality.

Among the tools which serve to predict heat and mass transfer in a mechanically ventilated room, CFD is increasingly used. However, this type of tool needs a correct description of the boundary conditions, especially concerning the air inlet. The ventilation inlet is often geometrically complex and many models exist in order to simplify their equivalent boundary conditions included in CFD codes. Nevertheless, none of these simplified models can predict the correct behaviour of flows issuing, for example, from a T-pipe, a bend or a more complex ventilation system.

The effectiveness of various methods for saving energy and improving the indoor environment in buildings depends upon the building conditions under which those methods are applied. To find better design solutions in such situations, designers or building owners need to make reference to quantitative information so that they can choose appropriate methods, which fit to the design conditions. These include data such as climate, surrounding environment, construction, occupants lifestyle and economic constraints.

Localized ventilation systems typically create highly asymmetric or non-isothermal environments around occupants with significant vertical temperature gradient and highly non-uniform airflow regimes that could be directed toward a segment of the body. These effects may have pronounced impact on occupants thermal comfort. The airflow field and temperature distribution near the occupant can be determined either by performing full-scale measurements or by simulation methods. Usually, human subjects or manikins are used in field studies involving measurement techniques.

Ventilation characteristics of the Columbus module are numerically predicted on the basis of the Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) approaches. The steady-state RANS computations were performed using the high-Reynolds-number k-e turbulence model, and the Smagorinsky-Lilly subgrid-scale model was used for LES. The computed results were compared with experimental data available for spatial distributions of the time-averaged absolute velocity magnitude.

Cross-ventilation is a mechanism using the pressure difference between the outdoor environment and indoor space to provide an energy-saving method for ventilation design. Since the ventilating flow in the vicinity of the opening is highly turbulent and unsteady, the ideal numerical method to resolve the structure of the ventilating flow is by using a time-dependent approach such as large eddy simulation (LES). However, LES requires large computing resources and there are also some uncertainties associated with the discretisation of time scales and length scales of turbulence.

Knowledge of ventilation rates in dairy buildings is essential for determining indoor air quality and for estimating green house gases and particle emissions. Two new methods for estimating ventilation rates are introduced for situations where air velocities at ventilation inlets and outlets are tedious or impossible to measure. The first method is applicable to buildings whose ventilation can be stopped or closed totally.

Five fire scenarios have been simulated with the CFD model Fire Dynamics Simulator (FDS) to analyse the performance-based fire safety design of a 2935 m-long railway tunnel. The influence of tunnel longitudinal ventilation fan activation time, fire size and the type of burning materials on tunnel tenability was investigated based on variations of two primary scenarios: Scenario #1 assumed a 15 MW fire at the front end of a train, and Scenario #2 assumed a 15 MW fire at the rear of a train.