IJV2

During the last two decades the significance of indoor environmental quality in buildings has been appreciated, not only in relation to thermal comfort, but also to indoor air quality. Ventilation is an important tool for securing both a good indoor climate and air quality. However, in buildings without mechanical ventilation and air conditioning systems (which comprise the majority in most European countries) natural ventilation presents the only means to satisfy indoor air quality needs.

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.

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.

The wind and buoyancy pressure driving forces for natural ventilation of buildings are very low, typically less than 10 Pa. Depending upon the prevailing climatic and thermal conditions, or even the location of a building on a site in relation to other surrounding buildings and landscape, the predominant pressure force incident on a purpose-provided natural ventilation opening can either be closer to the lower range of pressure differentials (< 2 Pa) or vary over a wider range of higher pressures (2 - 10 Pa).

Natural ventilation is a sustainable, energy-efficient and clean technology that is well accepted by occupants. It can be used to provide fresh air for occupants as necessary, to maintain acceptable air quality levels and to cool buildings in cases where climatic conditions allow. The successful application of natural ventilation techniques and the effectiveness of natural ventilation are determined by the prevailing outdoor conditions and microclimate as well as by building design and building use.

An overview is given of the current position regarding the use of wind tunnel modelling and envelope flow theory for determining natural ventilation through large openings. The overview is, to a large extent, a personal one and is illustrated primarily by recent research carried out in Nottingham, some of which has yet to be published in full.

CFD (Computational Fluid Dynamics) modelling of particle transport has been applied for the control of airborne particles in the operating zone above the surgery table in an operating room. Based on the numerical results, it has been found that the particle source location, air (supply) inlet design, operating table location, and lamp design are among the critical parameters responsible for the particle distribution within the operating room.

This study simulated the performance of various mechanical supply and exhaust ventilation systems, incorporating heat recovery, in a typical Finnish residential apartment building. Dynamic thermal simulations were undertaken, representing a period of a year. These simulations incorporated the building details combined with information about the HVAC-systems, internal thermal loads and outdoor climate.

The characteristics of a hybrid air-conditioning system, utilising natural and mechanical 'task' ventilation, are investigated in an office setting. The characteristics of the indoor environment are examined by means of CFD (Computational Fluid Dynamics) simulations under various conditions of incoming outdoor air. The control of the task air conditioning system (VAV system) is included in the calculation through changing the supply air volume to keep the task zones temperature at a target temperature.

Creating a computer model that is able to simulate different ventilation scenarios within a structure is essential for improving the understanding of passive designs that are both sustainable and environmentally acceptable. The purpose of this investigation was to build a prototype model that could be heated from both the outside and inside to duplicate an occupied structure during the morning hours. Two Computational Fluid Dynamic (CFD) models were created for this study to firstly compare and then validate results obtained from experimental data.