Room Air Distribution and Indoor Air Quality of Hybrid Air
Conditioning System based
on Natural and Mechanical Ventilation in an Office
Hyunjae
Chang1, Shinsuke Kato2, Tomoyuki Chikamoto3
1
Architectural Environmental
Engineering Lab., Hanyang University, Seoul, Korea
2 Institute
of Industrial Science, University of Tokyo, Tokyo, Japan
3
Environmental Eng. Group, Nikken Sekkei, Ltd., Tokyo, Japan
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Abstract
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 zone’s temperature at a
target temperature. Results show that the thermal environment at the task
zone is maintained comfortably with the aid of mechanical air conditioning
and indoor air quality is achieved by providing natural ventilation
through window opening. When the
temperature of the in-flowing
outdoor air rises and the vertical width of the
window opening that lets in the air decreases,
the inflow jet flows deeper into the room and therefore mixes easily with
the indoor air. When the in-flowing outdoor air
volume increases, the inflow jet exhibits a 3-dimensional aspect in a
room. A vertical temperature gradient
appears at the task zone with the increase of the temperature
and volume of the in-flowing outdoor air.
The distribution of the age of air is strongly influenced by the
flow fields. The average age of air at the task zone depends mainly on
the natural ventilation rate.
Key words: hybrid air conditioning,
natural ventilation, task/ambient air conditioning, CFD (computational
fluid dynamics), age of air.
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