model

The paper reports on findings from a series of experiments where the supply flow rate wasvaried periodically in time. All experiments were conducted in a small scale model with water as operating fluid. The flow was visualised by adding particles to the water and the streaks were recorded with a digital camera. The main result is that there exist variations that generate a role up of the base flow by generation of vortices that are shed into the stagnant region.

The accumulation of heat, contaminant and water vapour into the upper part of rooms is utilized in stratification and zoning room air conditioning strategies. For the zoning strategy the plume penetration through the supply air jet is an essential parameter in modelling the temperature, concentration and humidity in the lower and upper zones of the room. This paper presents an analytical method for modelling the plume penetration for an air distribution method based on horizontal inclined jets of industrial grilles.

A Lagrangian-Eulerian model for the dispersion of solid particles in a three-dimensional, incompressible, laminar or turbulent flow is reported, tested and partly validated. Prediction of the continuous phase is done by solving an Eulerian model using a Control-Volume Finite Element Method (CVFEM). A Lagrangian model is also applied, using alternatively an analytical and a Runge-Kutta 4th order method to obtain the particle trajectories. The effect of fluid turbulence upon particle dispersion is taken into consideration through a simple stochastic approach.

The paper describes the design of a fire and a smoke source for scale-model experiments with smoke ventilation. It is only possible to work with scale-model experiments when the Reynolds number is reduced compared to full scale, and it is demonstrated that special attention to the fire source (heat and smoke source) may improve the possibility of obtaining Reynolds number independent solutions with a fully developed flow. The paper shows scale-model experiments for the Ofenegg tunnel case.

The selection and design of air conditioning systems in Hungary are based on a determined modelling state. In the last decade this was a safe enough basis for the management of systems. As a result of the changes in the macroclimate, however, there has been a major increase in summer temperatures. Taking into account this fact and the need to develop the earlier deterministic modelling techniques we chose to focus on risk-based modelling.

The capture efficiency of the total system must be guaranteed so that the spread of impurities throughout the kitchen is prevented. A capture efficiency model is derived and it is used to estimate the efficiency of a ventilated ceiling. This paper demonstrates that a simple equation that includes the average contaminant level in the occupied zone and the exhaust concentration could be a suitable platform for capture efficiency analysis in both measurements and simulations.

Previous work on an Underfloor Air Distribution (UFAD) system with a single heat source anda single cooling diffuser at floor level developed by Lin has been extended to study the effects of the vertical location of the heat source and of multiple cooling diffusers. This is an attempt to produce more realistic models of UFAD systems. Both experimental and theoretical modeling is described in this paper. In the experiments, a plume and fountains represent a heat source and cooling diffusers respectively.

Aerosol particles are one of the main causes to pollute indoor air. Reliable models for particletransport save time, money and help to reduce risk of health problems for occupants. In this work, we simulate particles transport in a two-zone enclosure with different particle characteristics. A statistically based analytical model is used for particles equilibrium whereas a Lagrangian model is employed to determine particle trajectories.

A detailed study using Computational Fluid Dynamics (CFD) was conducted on the influenceof the difference in the effective diameters of air supply outlets (wind velocity, assuming the airflow rate to be constant) when using personal air conditioning with isothermal air currents. A method to analyze the new age of air (SVE3*) and the residual lifetime of air (SVE6*) was proposed and studied focusing on the individual supply openings and exhasut openings in a room with multiple supply openings and exhasut openings when using personal air conditioning.

A three-dimensional drift-flux model combined with the deposition boundary conditions for wall surfaces in ventilated rooms are presented to study the particle dispersion in displacement ventilation rooms. Three ventilating air flow rates, 2 ACH, 5 ACH, 8 ACH and several particle sizes, 1, 2.5, 5, 7.5, 10 micron, are investigated. The results show that the particle dispersion characteristics are very different in displacement ventilated rooms with different air supply volume. In rooms with the same air supply volume, large-diameter particles diffuse more widely than small ones.