The work in this paper contributes to the work in the IEA - Annex 20 "Air Flow Patterns within Buildings" and presents a series of full-scale measurements of the concentration distribution in a room with isothermal mixing ventilation. Vertical profiles of the concentration in the middle of the room have been measured under different conditions. With the contamination source in the middle of the room the vertical profiles were changed radically with an increase of the air change rate from n= 1.5h^-1 to n=6h^-1 due to a change in the flow structure in the room.
In the field of ventilation engineering the understanding of jet types of flow is well established. However, the behaviour of buoyant flows with high initial Archimedes numbers has been much less explored. The aim of this short note is to highlight some of the differences between ordinary jet flow and the discharge from low velocity air terminals. Results are presented both from tests carried out in a full scale mock up and from model tests with water as operating fluid.
Ventilation systems perform a number of tasks. They must remove contamination/pollution, they act as heat/cold transporters and they must create a satisfactory room climate without causing draughts. States that users must be aware of the limitations of ventilation systems and that ventilation systems are not able to carry out all tasks completely satisfactorily. Compares the efficiencies of displacement and mixing systems and gives guide values for temperature differences between room air and supply air for office and industrial applications.
Login