The behaviour of room airflows under fully turbulent conditions is well known both in terms of experiments and numerical calculations by computational fluid dynamics (CFD). For room airflows where turbulence is not fully developed though, i.e. flows at low Reynolds numbers, the existing knowledge is limited. It has been the objective to investigate the behaviour of a plane isothermal wall jet in a full-scale ventilated room at low Reynolds numbers, i.e. when the flow is not fully turbulent. The results are significantly different from known theory for fully turbulent flows.
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.
A series of CFD and model experiments were carried out in order to find the most effective ventilation system in a separated refuse disposal facility. The ventilation system needed in the facility protects the working space from dust and odors generated by handling refuse. The desired ventilation system is to introduce the outdoor air from the one side of the working area and to exhausts the contaminated air through the opposite side of the refuse stock yard, so-called the unidirectional airflow ventilation.
This paper presents results belonging to a larger investigation on low velocity indoor air jets. The experiment is undertaken in a climate room where an isothermal air jet is issued from the centre of one lateral wall. Measurements are performed with a single fiber film probe, and with Particle Streak Velocimetry system. With Particle, Streak Velocimetry has been developed a three dimensional analysis of the instantaneous velocity field. With the use of fiber filmprobe, the fluid-dynamics of the jet flow is explored in terms of mean longitudinal velocity, and relative turbulence intensity.
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:
Studies of airflow between two adjacent spaces of building were carried out using CFD simulation. The results of CFD simulation were validated against test data set obtained from full-scale experimental tests. The agreement and discrepancy between the prediction and measurement results were discussed. Further numerical exercises were carried out to study under the conditions that were difficult to achieve by experiments and the results obtained were supplemented to the understanding of convective heat transfer between adjacent rooms.
Under the conditions that the air in each room is in the state of perfect mixing and ventilation is in steady state, a method to estimate steady state concentration distribution to match an arbitrary contaminant generation distribution is proposed, using concentration data obtained from short-time tracer gas experiment. Also, a method is proposed, which is used to estimate ventilation rate by adding other available equations.
The purpose of this study is to identify the ventilation effectiveness of a displacement ventilation system in a concert hall with 501 seats, where a large amount of outside air is required for ventilation. Displacement ventilation was considered appropriate to reduce the amount of outside air. Light bulbs were placed on all the seats to simulate the heat source from the audience. From the measured concentrations, the local mean age of air at the breathing point with the displacement ventilation system was found around one third of that of the fully mixed condition.
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