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Using isothermal full-scale experiments and 3-dimensional CFD simulations it is investigated how normal office furniture influences the air movements in a mixing ventilated room.Two different types of inlets are used in the experiments and a set-up with normal office furniture is made. The set-up is simulated with one of the inlets where a volume resistance represents the furniture.

The laminar flow for a backwards facing step is studied. This work was initially part of the work presented in. In that work low-Reynolds number effects was studied, and the plan was also to include laminar flow. However, it turned out that when the numerical predictions of the laminar flow (Re= 118) was compared to the experiments of Restivo , we found a large discrepancy. We believe that there is something wrong in that experimental investigation. To support that conclusion, we present in this report prediction of other backward facing flow configurations, where we show that our predictions agree well with experimental data.

This paper discusses the use of different turbulence models and their advantages in given situations. As an example, it is shown that a simple zero-equation model can be used for the prediction of special situations as flow with a low level of turbulence. A zero-equation model with compensation for room dimensions and velocity level also is discussed.

The ventilation design concept, model experiment results, two-dimensional computational fluid dynamics simulation, and on-site measurements are presented for the Danish Pavilion project at the 1992 World Exhibition in Seville.The paper gives a short project history for the building and the ventilation system.

This paper will show the experiments with local ventilation of a filling machine from the paint industry, local ventilation of a film developing machine, experiments with a vortex exhaust opening and local heating of a checkout assistant's working place.

Emission of volatile organic compounds (VOCs) from materials is traditionally determined from tests carried out in small-scale test chambers. However, a difference in scale may lead to a difference in the measured emission rate in a small-scale test chamber and the actual emission rate in a full-scale ventilated room when the emission is fully or partly evaporation controlled. The objective of the present research work has been to investigate the change of emission rates from small-scale experiments to full-scale ventilated rooms and to investigate the influence of the local air velocity field near the source.

The aim of this research is to see if the displacement ventilation principle can protect a person from exposure to passive tobacco smoking. This is done by full-scale experiments with two breathing thermal manikins, smoke visualisations, and tracer gas measurements. In some situations, exhaled smoke will stratify in a certain height due to the vertical temperature gradient. This horizontal layer of exhaled tobacco smoke may lead to exposure. In other situations, the smoke is mixed into the upper zone, and the passive smoker is protected to some extent by the displacement principle and the convective boundary layer flow around the body.

A displacement ventilation system works better the more uni-directional the air flow through the ventilated room is: from floor to ceiling. Thus, from an air quality point of view, there should be as little vertical mixing of the room air as possible. It is therefore comprehensible that physical activity in the room -like peoples movements -in previous studies has been shown to influence the effectiveness of the ventilation. In this study we have compared results from previous tests, where a cylindrical person simulator was used, to results obtained when using a person simulator of more human-like shape.

Full-scale experiments were made in a displacement ventilated room with two breathing thermal manikins to study the effect of movements and breathing on the vertical contaminant distribution, and on the personal exposure of occupants. Concentrations were measured with tracer gas equipment in the room and in the inhalation of both manikins. Tracer gas was added in the heat plume above a sitting manikin, or in the exhalation through either the nose or the mouth. The other manikin moved back and forth at different speeds on a low trolley. The mentioned experimental conditions have a significant influence on contaminant distributions and personal exposures.

We have done Large Eddy Simulations (LES) of the flow in a three-dimensional ventilated room. A finite volume method is used with a collocated grid arrangement. The momentum equations are solved with an explicit method using central differencing for all terms. The pressure is obtained from a Poisson equation, which is solved with a conjugate gradient method. For the discretization in time we use the Adam-Bashfourth scheme, which is second-order accurate.

Air distribution in ventilated rooms is a flow process that can be divided into different elements such as supply air jets, exhaust flows, thermal plumes, boundary layer flows, infiltration and gravity currents. These flow elements are isolated volumes where the air movement is controlled by a restricted number of parameters, and the air movement is fairly independent of the general flow in the enclosure. In many practical situations, the most convenient· method is to design the air distribution system using flow element theory.

The vertical temperature gradient is normally given as a linear temperature distribution between a minimum temperature close to the floor and a maximum temperature close to the ceiling. The minimum temperature can either be a constant fraction of a load dependent difference or it can be connected to the volume flow to the room. This paper describes a new model which takes the different types of heat sources in the occupied zone as well as the characteristic Archimedes number of the flow into account.

Two-dimensional, isothermal full-scale experiments and CFD (Computational Fluid Dynamics) simulations are used to investigate the influence of obstacles in the occupied zone. The shape of the vertical velocity profiles, the maximum velocities in the occupied zone, the velocity decay through the room, and the momentum flow are investigated.

Test conditions such as temperature, relative humidity, and air velocities are chosen within the range that are found in ventilated rooms. H:owever, the difference in scale can lead to some problems and misconception of the size of the actual emission rate for a building material. This paper highlights some of these problems and introduce an approach on how to overcome them and produce useful results. The paper concentrates on describing situations where the air velocity field near the source influence the emission rate.

A displacement ventilation system exploits the use of energy efficiently because it is possible to remove exhaust air from a room with a temperature that is several degrees above the temperature in the occupied zone. This process will allow a higher air inlet temperature at the same load in comparison with mixing ventilation. It is necessary to have a design method for the temperature distribution used for instance in connection with the tlow element method and the energy calculations. The temperature distribution is also important in connection with thermal comfort in a room. It is necessary to consider the temperature gradient in the occupied zone, as well as the asymmetric radiation from the ceiling, in connection with the design of a displacement ventilation system and the evaluation of thermal comfort. This paper will introduce five temperature distribution models with different levels of complexity.

The objective of this study has been to determine the personal exposure to a contaminant source in a uniform velocity field. This was done by full-scale measurements and computer simulations. The results showed a significant dependence on the velocity field both regarding the direction and the magnitude. The results also showed that the disturbance created by a person in a flow field may be a very important factor to consider, when the person is turning the back to the flow field. It was found that the wake created behind a person was able to entrain contaminants from a distance exceeding the usual operation range. Guidelines for personal exposure reduction in a uniform velocity field are discussed.

This experimental work deals with the basic problem of merging thermal plumes from heat sources situated in the vicinity of each other. No studies have been made yet of how close two heat sources must be to each other, before they can be considered as a single source with a cumulative heat effect, and how far apart they must be to be considered separate. Also, it is not known how the flow field behaves in the intermediate fase, where the plumes are neither completely joined nor completely separate. A possible, very simple, solution of the velocity distribution between two plumes is to assume addition of the velocities from each plume.The main objective of his research is to compare this assumed distribution with measurements made in a full scale experiment with typical room air temperatures and with heat sources similar to human beings.

The fluid dynamics research is strongly influenced by the increasing computer power which has been available for the last decades. This development is obvious from the curve in figure 1 which shows the computation cost as a function of years. It is obvious that the cost for a given job will decrease by a factor 10 every eight years.

An optimal design of the ventilation system needs a proper prediction of the velocity, temperature and contaminant distribution in the room. Traditionally this is done either by the use of simplified models or by a somewhat more comprehensive CFD-simulation. Common to both methods is usually the lack of consideration for the persons present in the room. This paper deals with some of the effects of persons present in a displacement ventilated room, especially the effect on the contaminant distribution.

This paper deals with personal exposure in rooms with concentration gradients and persons present. Results from case studies including a breathing thermal manikin in a displacement ventilated room and in a wind channel are presented.

Numerical modelling of direct capture efficiency of a local exhaust is used to compare the tracer gas technique of a proposed CEN standard against a more consistent approach based on an imaginary control box. It is concluded that the tracer gas technique is useful for field applications.

The research on air distribution in rooms is often done as full-size investigations, scale-model investigations or by Computational Fluid Dynamics (CFD). New activities have taken place within all three areas and this paper draws comparisons between the different methods. The outcome of the lEA sponsored research "Air Flow Pattern within Buildings" is used for comparisons in some parts of the paper because various types of experiments and many countries are involved.

This paper describes experiments with wall-mounted air terminal devices. The stratified flow in the room is analyzed, and the influence of stratification and the influence of room dimensions on the velocity level and on the length scale are proved. The velocity level in the occupied zone can be described by a single equation based partly on stratified flow theory and partly on measurements.

Capture efficiency of a local exhaust system, e.g. a kitchen hood, should include only contaminants being direct captured. In this study basic concepts of local exhaust capture efficiency are given, based on the idea of a control box. A validated numerical model is used for estimation of the capture efficiency. An experimental technique is introduced for field studies taking into account knowledge of flow patterns of air and contaminants obtained from smoke testing and contaminant concentrations. Holding together numerical and experimental data a fair agreement is observed.

Model experiments are one of the methods used for the determination of airflow in large spaces. This paper will discuss the formation of the governing dimensionless numbers. It is shown that experiments with a reduced scale often will necessitate a fully developed turbulence level of the flow. Details of the flow from supply openings are very important for the determination of room air distribution. It is in some cases possible to make a simplified supply opening for the model experiment.

This paper discusses various possibilities for describing supply openings in numerical models of room air distribution.

The paper shows a description of the flow from a low level diffuser which is suitable for a design procedure in displacement ventilation.

Measurements are performed in a full-scale test room with displacement ventilation with focus on the velocity and temperature field in the region close to the inlet device.Investigations based on these detailed measurements have been made in order to see if it is possible to describe the velocity decay and the shape of velocity and temperature profiles in front of the inlet device by traditional jet theory, by stratified flow theory or by a combination of the two theories.

Since 1985 the University of Aalborg and Nordfab A/S have been working on an exhaust principle which is quite different from traditional exhaust systems. The REEXS principle (Reinforced Exhaust System), which originally was designed for the agricultural sector, is particularly well-suited for industrial ventilation purposes. With the REEXS principle it is possible to create a flow pattern in front of the exhaust opening which will have a considerable influence on the general flow in a given room.

There is a great variation of production machinery and pollution sources in the paint industry. This paper shows the examination of a process where wood preservation is filled into cans in a process which releases organic solvents to the surrounding air.

The paper describes work on simplified design methods made in connection with the International Energy Agency programme" Air Flow Pattern within Buildings" , Annex 20, subtask 1. It is shown that simplified models are able to indicate design values as the maximum velocity in the occupied zone and penetration depth of a non-isothermal jet in a room.

Modem inlet devices applied in the field of ventilation of rooms are getting more complex in terms of geometry in order to fulfil the occupants' demand for thermal comfort in the room and in order to decrease the energy consumption. This expresses the need for a more precise calculation of the flow field. In order to apply CFD for this purpose it is essential to be able to model the inlet conditions precisely and effectively, in a way which is comprehensible to the manufacturer of inlet devices and in a way which can be coped with by the computer. In this paper a universal method is presented and tested. The method is based upon threedimensional - and radial wall jet theory and upon diffuser specific experimental data.

The present paper, which is within the work of the lEA - annex 20, presents a series of full-scale velocity measurements in a room with isothermal mixing ventilation. Themeasurements are in the Reynolds number range 1000 - 7000 based on inlet dimensions. This means that a transition from laminar to turbulent flow is occurring.

The design of a displacement ventilation system involves determination of the flow rate in the thermal plumes. The flow rate in the plumes and the vertical temperature gradient influence each other, and they are influenced by many factors. This paper shows some descriptions of these effects.

In the summer 1988 13 countries under the International Energy Agency established a cooperative work - Annex 20. This Annex is divided into two subgroups where Denmark contributes in subtask 1. This contribution is giving a historical background for the establishment and the contents of Annex 20. The purpose of Annex 20 is to carry out simulations and full-scale experiments and to compare these investigations. This is done to support a more common use of advanced numerical calculations in engineering flow calculations within the field of ventilation. In the project it is possible for the countries to make investigations which are of particular interest for them in order to increase the understanding of the complicated flow patterns in ventilated buildings.

The ventilation of a test room (LxWxH = 5.4x3.6x2.4 m) with a wall mounted heat source is investigated for two different air terminal devices.

The room ventilation is investigated for three different air terminal devices under isothermal conditions.Velocity distribution in the occupied zone is measured for each air terminal device at different air exchange rates. The maximum air exchange rate is determined on the base of both the throw of the jets and the comfort requirements applied to measured air velocities in the occupied zone.Normalized concentration distribution in the test room is determined along a vertical line through the middle of the room as a function of the air exchange rate and the density of the tracer gas.The relative ventilation efficiency, , based on the room average concentration is also determined as a function of the air exchange rate and the density of the tracer gas.The influence from the position of the return opening on the relative ventilation efficiency is found for one air terminal device.

Ventilation systems with vertical displacement flow have been used in industrial areas with high thermal loads for many years. Quite resently the vertical displacement flowsystems have grown popular as comfort ventilation in rooms with thermal loads e.g. offices.

The paper describes the development in airflow simulations in rooms . The research is, as other areas of flow research, influenced by the decreasing cost of computationwhich seems to indicate an increased use of airflow simulation in the coming years.

The air supply openings in ventilated rooms are often placed close to the ceiling. A recirculating flow is generated in the room, and the region between the ceiling and the occupied zone serves as an entrainment and velocity decay area for the wall jets. Ceiling-mounted obstacles may disturb this flow and, in particular, certain dimensions and positions of the obstacles cause a downward deflection of the jets into the occupied zone resulting in reduced thermal comfort for the inhabitants.

The paper describes measuring results of the air movement from three different types of diffusers for displacement ventilation. Two of the diffusers are lowlevelwall mounted diffusers, one with a low and one with a high initial entrainment. The third diffuser is of the floor mounted type.

Ventilation systems with vertical displacement flow have been used in industrial areas with extensive heat loads for many years. Hot and contaminant air is carried directly from the occupied zone towards the ceiling by hot processes and other activities which create a natural convection flow.

Ceiling-mounted slot diffusers in ventilated rooms will often generate a flow of the wall jet type. The jet follows the ceiling, entrains air from the occupied zone and generates a recirculating flow in the whole room.This paper will deal with the flow in the ceiling region. The wall jet flow is especially influenced by diffuser design and surrounding details such as distance to the ceiling and the ceiling structure. The flow is less influenced by other parameters in the room such as length, width, height and furnishings.

The purpose of an air distribution system in a ventilated room is to supply fresh air, remove heat load or supply heating, and create a pleasant and uniform climate in the occupied zone. A pleasant climate is in this context defined as a fairly low air velocity, small velocity and temperature gradients through the room and a low concentration of polluting substances, if any.