Zoning Strategy

8.6.5.1Description

The idea of the zoning air conditioning strategy is to have control over the certain area or volume of the room, while the rest of the room is left with less

(ii) Low-impulse supply from floor level

(r) Low-impulse supply above aisles—2

(/>) Low-impulse supply above aisles —1

> V	If A

(c) Negative buoyancy

(d) Sparc floor supply

(/’) Floor heating

Attention. In most cases the accumulation of heat, concentration, or humidity outside the controlled zone is desired and utilized. The room airflows are con­trolled both by the supply air jets and the buoyancy sources. The ventilation effectiveness (temperature, contaminant removal, humidity) using the /oning air conditioning strategy is expected to settle between the values n! mixing and stratification strategies. However, the effectiveness is strongly dependent on the methods used and the operating conditions. Concentration and tempera­ture are more homogeneously distributed in the controlled zone than with the stratification strategy.

Zoning can be either vertical or horizontal. Typically vertical zoning is ap­plied in high rooms, when the supply air is distributed close to the occupied zone near floor level and the exhaust air openings are located close to the ceil­ing. Horizontal zoning can be applied, for example, using air or portable/par­tial (plastic, etc.) curtains in order to divide room space into different blocks. Within these blocks it is possible to further apply different strategies in the vertical direction semi-in depen dently.11

8.6.5.2Advantages and Disadvantages

The zoning method offers better contaminant removal and thermal effec­tiveness than with mixing, limited control of the flow patterns in the ventilated zone, and the ability to avoid stagnant areas with high local concentrations in the ventilated zone. However, partial mixing of contaminants in the ventilated zone decreases its effectiveness.

8.6.5.3Design Criteria

Each method has its own design criteria, but common to most ol the methods is that air supply is located close to or inside the controlled zone and the exhaust openings are located inside the uncontrolled zone. The location and power of the buoyancy sources in relation to the supply air jets have a re­markable influence on the accumulations of heat, contaminants, and humidity within the room.

8.6.5.4Application

A large variety of methods can be used for zoning, such as inclined jets, horizontal cooled jets, vertical jets, floor jets, nozzle ducts, and vortex. Exam­ples of different methods are illustrated in Fig. 8.13.

Posted in INDUSTRIAL VENTILATION DESIGN GUIDEBOOK