air flow pattern

The Particle Streak Tracking System (PST) is a fast method to measure two- and three-dimensional velocity fields in room air flows with measuring areas up to 5 m2. The two-dimensional method works with a single pulsed white light sheet and one digital camera. For three-dimensional velocity measurements in planes a laser light sheet system using three separate laser sheets with two different wavelengths and two CCD-cameras is employed. To visualise the flow helium filled bubbles are used. A description of the set-up will be given and the data evaluation process will be explained.

In this study the spatio-dynamic temperature response in a ventilated room to variations of the supply air temperature was modelled for a wide range of ventilation rates. The model structure was first formulated by applying standard heat transfer theory to zones of better mixing. Spatio-temporal temperature data were then exploited in statistical terms to estimate the physically meaningful model parameters. The dynamic model yielded an excellent fit to the experimental data and was found to characterise the spatially heterogeneous nature of the air flow pattern quite well.

A new method for providing ventilation in large enclosures, which utilizes the principle of 'selective withdrawal' of contaminants while ensuring energy-efficiency and allowing a better use of space, is presented in this study. The concept is based on dividing the enclosed space ventilation-wise into separate zones using a combination of horizontal partitions by stratification and vertical partitions by temporary walls. This gives a high degree of flexibility in the use of available space.

This study focuses on the way to apply CEN test methods to a full range of air diffusers and is dedicated to the improvement of these methods proposed by the CEN TC l 56/WG4 of which both authors are members. Air terminals of different sizes have been tested on aerodynamic and acoustic aspects both in a Spanish and a French laboratory. The tests were made according to pr EN 12238 ''Air Terminal devices - Aerodynamic testing and rating for mixed flow applications" and to EN 25135 (ISO 5135).

Air flow patterns and temperature distribution within courtyard have been studied. Wind and thermally driven flow have been thoroughly analysed as a function of the depth to width ratio (Aspect ratio) as main parameter. CFD results show a quite similar behaviour regarding to velocity profiles for all the cases, though temperature profiles are highly affected by dimensions of the courtyard. The whole study can be extrapolated to urban canyons, where air flow patterns are quite similar as a result of having the same geometry.

This paper compares two well-known modelling approaches for natural ventilation in a multi-zone building with thermal stratification and large openings. The zonal approach in this paper assumes a fully mixed condition in each zone, and considers the bi-directional flows through all large openings. The zonal model is integrated into a thermal analysis code to provide simultaneous prediction of both ventilation flow rates and air temperatures in each zone. The CFD approach uses a finite-volume method for turbulent flows.

In a hot climate, a large amount of solar heat irradiates on a roof and it is transmitted to an occupied space beneath it through an attic. To interrupt this heat to attain a comfortable condition in the occupied space, ventilation of the attic is an important and effective measure. There are two ways of the ventilation, one is natural and the other is forces ventilation. The former measure should be considered prior to the latter from such reasons as simplicity in practice and power saving.

The air flow in a doorway is governed by density difference caused by temperature difference and pressure difference caused by mechanical ventilation. Tests have been carried out in a unique indoor test house where the room to room to temperature difference could be controlled very accurately with a new control system. In addition to these tests some tests were carried out in a scale model with water as the operating fluid. Two main criteria of unidirectional flow in a doorway have been explored:

In modem livestock buildings the design of the ventilation systems is important in order to obtain good air distribution. The use of Computational Fluid Dynamics for predicting the air flow and air quality makes it possible to include the effect of room geometry, equipment and occupants in the design of ventilation systems. However, it is not appropriate to include the detailed geometry of a large group of lying or standing animals affecting the air flow in the building. It is necessary to have relatively simple models of the animals, which are easier to implement in the computer models.

A problem in a livestock building ventilated in the system with wall inlet at two sides is wind effects to the indoor air flow patterns. The in-proper inlet jet penetration profiles may cause draught at occupied zone and unnecessary stress of animals. The wind effects on such a system can be reduced by applying windbreak to the inlets from design point of view. However, a remain issue is if the effect could be reduced by regulating inlet opening and how to perform the control operation.