Determination of the Air Change Rate for Natural Ventilation with Regard to Energy Efficiency and Building Physics

The air exchange in a room with different windows and window geometries is investigated. The aim is to get reliable data for the air change rate and the air exchange efficiency for natural ventilation. Before using a CFD program for the calculations experimental studies have been carried out. In order to meet different demands we distinguish between short time and continuous ventilation. The results are availabe as figures, graphs or approximate equations.

Thermal effects on the dispersion of a gaseous contaminant in a naturally-ventilated room

The influence of thermal effects on the dispersion of a gas in a naturally-ventilated room is investigated using CFD in conjunction with measurements. The gas dispersion inside the room, with and without thermal effects, is characterised by a statistical analysis of the CFD-predicted gas concentrations at a large number of points across the room with a view to quantifying the thermal effects. It is concluded that even small temperature differences can lead to significantly different cross flow behaviour and rates of gas concentration decay at the relatively low air change rate considered.

Applications of the Integrated Multi-zone Model and CFD Simulation in Buoyancy Ventilation

Predicting the performance of natural ventilation is difficult, especially for the large scale naturally ventilated buildings, because of the lack of accurate and efficient prediction tools. This paper presents a strategy, integrating a multi-zone model and computational fluid dynamics (CFD), to improve natural ventilation prediction and design. Large openings and atrium are broadly used in naturally ventilated buildings to promote buoyancy force and optimize air movement. How to properly deal with large openings and atrium is discussed and compared in this paper.

A CFD parameter study of discharge coefficients for single-sided ventilation through large rectangular openings

As part of an investigation into single-sided natural ventilation, a computational fluid dynamics study was performed to analyse the impact on the airflow rate of the dimensions and position of a large rectangular opening and of the temperature difference between inside and outside air. An empty room with a rectangu-lar opening in the external wall was assumed and the Bernoulli formula used to calculate discharge coefficients Cd. The vertical position of the opening was found to have the greatest impact on the discharge coefficient.

Experimental and CFD Analyses Examining Ozone Distribution in a Model Room with a Two-dimensional Flow Field

This paper reports the results of room model experiments and Computational Fluid Dynamics(CFD) analysis of ozone distribution in indoor air. The analyzed room model had one supply inlet and one exhaust outlet, with a cavity of dimensions 1.5m (x) 0.3m (y) 1.0m (z) in which a two-dimensional flow field was developed. In order to discuss the order of wall surface deposition for ozone, the concentration distributions of ozone in the model room were measured. CFD analysis corresponding to the experimental conditions and with a built-in ozone wall surface deposition model was carried out.

CFD Codes Efficiency Case Study: Ability to Perform Numerical Simulations in the Refrigerated Compartment of a Foodstuff Transportation Vehicle

The purpose of the present work is to describe the ability of the advanced computer packages(CFD codes) to perform numerical simulations of general refrigeration engineering problems. The case study concerns the modelling of three-dimensional turbulent airflow with thermal buoyant effects and air temperature distribution in the refrigerated compartment of a perishable foodstuff transportation vehicle.The numerical predictions obtained with three commercial codes (PHOENICS, FLUENT and CFX) and an academic one are evaluated and compared with experimental data.

CFD Simulation and Measurements in Near Zone of a High Induction Swirl Diffuser

This article describes CFD simulation results and measurements using a swirl diffuser. Thediffuser is able to provide relatively low velocities within the occupied zone while supplying high airflow rates. The flow pattern produced by the air diffuser was validated by measurements with a flow rate of 133 l/s and 4 C lower temperature than ambient air. Turbulence was modelled using the RNG k- e model with additional swirl modification.

Application of Simple CFD Models in Smoke Ventilation Design

The paper examines the possibilities of using simple CFD models in practical smoke ventilationdesign. The aim is to assess if it is possible with a reasonable accuracy to predict the behaviour of smoke transport in case of a fire. A CFD code mainly applicable for ordinary ventilation design is used for the examination. The CFD model is compared with benchmark tests and results from a special application fire simulation CFD code. Apart from benchmark tests two practical applications are examined in shape of modelling a fire in a theatre and a double faade, respectively.

About the validity of turbulence models for the computational fluid dynamics of a non-isothermal developing plane jet in aiding mixed convection regime

A comparative study between experiments and numerical simulations in the developingzone of a non-isothermal plane vertical jet is presented. Low velocity airflow, in aiding mixedconvection regime, discharging from a large rectangular nozzle in a quiescent medium at a highertemperature is considered (Re = 4220).The "Reynolds-Averaged" Navier-Stokes equations (RANS) are solved with two codes, the CFD code Fluent and the Aquilon code, including different turbulence models.

Zone Resistance in Embedded CFD Modeling

Seeking to realistically model details of room airflows, researchers have recently embeddeddetailed CFD or sub-zone (zonal) models within multi-zone idealizations of building systems. However a number of issues remain to be resolved to assure the success of this approach. Foremost is the question of zone resistance which is ignored in multi-zone models yet implicitly included in CFD and sub-zone models.This paper defines a fundamental means to measure zone resistance and presents the results of CFD studies to evaluate its relative significance for representative geometries.