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.
The first part of the paper will show some aspects of experimental research on air distribution in ventilated rooms. The study has been carried out to get an understanding of the air movement and the ventilation effectiveness by means of tracer gas measurements. It has been investigated the velocity and the distribution of the concentration in a two-dimensional isothermal flow issue of a linear supply opening. The second part of the paper will describe a proposed zonal model in 9 zones.
The effect of recirculation on the age of air is described. A new effectiveness measure called the relative air-change effectiveness is defined in such a way that the air distribution pattern in a room may be quantitatively characterized even when the age of the supply air is non-zero. This admits the evaluation of air distribution patterns in single-zone systems that recirculate air, and also multizone systems with or without recirculation.
This study is done by order of a Finnish air cooler manufacturer and it is founded to a master's thesis of the same subject matter. The company produces e.g. unit air coolers with electric fans and so the aim of the study was to reduce draught problems caused by cold air jets.
Adequate ventilation with the "right amount of air, to the right place and at the right time" are important factors for achieving a good indoor climate. Thus it is of prime importance that the ventilation system is working properly. Using traditional methods, it is a very time consuming, and some times even impossible, task to balance ventilation systems to achieve correct air distribution. In most countries the growing concern about Indoor Air Quality has resulted in Building Codes demanding increased ventilation rates.
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