Classification for Room Air Conditioning Strategies

As the focus of the proposed classification differs from the present practice, it is necessary to explain the terminology used. The aim of room air condition­ing is to maintain desired conditions, target levels, in the room during differ­ent operating conditions in the most economical way (energy, cost efficiency). Depending on the design criteria, the designer may choose different strategies in order to achieve specified targets. The room air conditioning design and evaluation process is illustrated in Fig. 8.9.

Target of the indoor air conditions

+22 °C. 45% RH 10 ppm 1.4 MUSS, 20,000 US$/a

I

Room air conditioning strategy

/ °C

/

°c

Jj

Air conditioning system & control

A

A

•r

1

Room

Indoor/outdoor

Loads

Disturbances

Air conditioning system performance valuation

подпись: room
indoor/outdoor
loads
disturbances
air conditioning system performance valuation

TABLE 8.7 Examples of Room Air Distributions, Exhausts, and Heating and Cooling Methods

Air distribution methods

Exhaust

Methods

Heating

Methods

Cooling methods

Vertical supply

Local

Convective Air heating Fan coils

Supply air cooling

Concentrated air jets

General

Radiative

Infrared

Convective Active, e. g., fan coils Passive, e. g., ceiling baffles

Low-impulse air supply

Mixed

M ixed

Radiative

Inclined jets

Local/general

The room air conditioning strategy is a fundamental scheme that describes the targeted temperature, humidity, and contaminant distributions as well as airflow patterns within the air-conditioned room. The room air conditioning system consists of different methods and their controls that together create the system performance. The system performance is evaluated by comparing the reached conditions to the chosen strategy. Both the methods (room air distribu­tion, exhaust, room heating and cooling, etc.) and processes and disturbances inside the room influence the resulting conditions. Different room air distribu­tions, exhausts, and heating and cooling methods are listed in Table 8.7. As an example of the terminology we can use a system consisting of low-impulse air devices supplying directly into the occupied zone (often called displacement ventilation) and cooled ceiling methods. At the Roomvent ’98 conference three separate papers were presented, which proved that the system behaves almost as a complete mixing strategy instead of replacement.6-8

I’he following presentation discusses the room air distribution method as a principal parameter to apply to a certain room air conditioning strategy and heating and cooling as assisting methods. However, it must be noted that in some cases a strategy can be fulfilled without any mechanical air distribution installations using buoyancy forces. The classification of ideal room air condi­tioning strategies is summarized in Table 8.8 and explained more in detail in the text. Though the main emphasis of this presentation is on general room air conditioning, the same ideas behind different strategies can be used for local ventilation. Additionally, as ideal, the classification is not affected by whether the flow direction is horizontal or vertical (upward or downward).

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