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Analytical solutions for buoyancy-driven natural ventilation in buildings with three openings.

This paper derives some new analytical solutions for buoyancy-driven natural ventilation in buildings with three openings. The new solutions are used to analyse the effect of the middle opening height and area on the natural ventilation performance. The criteria for flow direction switching for the middle opening is established. It is also proved that the neutral plane level in the three-opening buildings depends only on geometrical parameters. Natural ventilation of buildings with two openings affecting by supply- or exhaust-only mechanical systems are also investigated analytically.

CFD analysis of airflow and temperature fields in a dome with openings.

The paper simulates the airflow and temperature fields in a dome Shanghai International Gymnastics Center (SIGC) at one summer day with the computational fluid dynamics (CFD) software PHOENIS. The comparisons of indoor vertical temperature distributions show that the predicted results are in good agreement with the on-site measured ones. And some analyses on the thermal characteristics in the actual dome are carried out.

Development of a control algorithm to optimize airflow rates through variable size windows.

The potential of natural ventilation control techniques when applied to full scale buildings is investigated with the use of both experimental and theoretical tools. An outdoor test cell was used to conduct experiments and two window types (bottom hung and sliding) were tested in different configurations under various meteorological conditions. Describes how theoretical methods for calculating airflow rates through the windows were developed, based on the experimental results and specific modelling activities. On comparison, good agreement was observed.

Passive downdraught evaporative cooling. II Airflow modelling.

Describes a three-year EU funded research project into the application of passive downdraught evaporative cooling (PDEC) to non-domestic buildings. This paper specifically discusses the use of computational fluid dynamics (CFD) to model PDEC. Using a hypothetical office building in Seville, Spain, it describes modelling techniques used and applications in an investigation of the building's performance.

Local Dynamic Similarity Model of Cross-Ventilation Part 1 - Theoretical Framework

A new model has been proposed for evaluating the discharge coefficient and flow angle at an inflow opening for cross-ventilation. This model is based on the fact that the cross-ventilation flow structure in the vicinity of an inflow opening creates dynamic similarity under the condition that the ratio of the cross-ventilation driving pressure to the dynamic pressure of cross flow at the opening is consistent. It was confirmed, from a wind tunnel experiment, that the proposed model can be applied regardless of wind direction and opening position.

3-D modelling of solar chimney based ventilation system for building.

A computer model for predicting natural ventilation in buildings by solar chimney alone is presented. The simulations are based on the solution of the 3-D steady laminar conservation equations of mass, momentum and thermal energy with an appropriate set of boundary conditions. The equations are discretized using a finite difference formulation and solved by the Marker and Cell (MAC) scheme. Indoor airflow fields and temperature distributions are discussed with respect to human comfort at the living level, 1 m above floor.

Insulating an attic access.

                 

Local Dynamic Similarity Model of Cross-VentilationPart 2 - Application of Local Dynamic Similarity Model

The proposed local dynamic similarity model of cross-ventilation predicted ventilation flow rates more accurately than the conventional orifice flow model assuming constant discharge coefficients when discharge coefficients actually decreased with change of wind direction. This model was used to develop a new method for evaluating the ventilation performance of window openings. The obstructive effect of model size on flow fields in a wind tunnel was avoided by installing the opening parallel to the wind tunnel floor.

How do winds affect buoyancy-driven ventilation in buildings?

This paper examines theoretically the effects of wind on buoyancy-driven ventilation via some new analytical solutions recently developed by the authors. Three air change rate parameters are introduced to characterise respectively the effects of thermal buoyancy, the envelope heat loss and the wind force. The wind can either assist or oppose the airflow. For the first time, it has been found that for opposing winds, there are two stable ventilation flow rates for a given set of wind and thermal parameter, i.e. the natural ventilation flow exhibits hysteresis.

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