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. 2022 Dec 1:61:105309.
doi: 10.1016/j.jobe.2022.105309. Epub 2022 Sep 28.

Local ventilation effectiveness dependence on the airflow pattern and temperature in the case of isothermal balanced ventilation

Tünde Kalmár  1 , Ferenc Szodrai  1 , Ferenc Kalmár  1
Affiliations

Local ventilation effectiveness dependence on the airflow pattern and temperature in the case of isothermal balanced ventilation

Tünde Kalmár et al. J Build Eng. .

Abstract

Appropriate ventilation may help in the mitigation of airborne transmission of viruses in buildings. Before the COVID-19 pandemic, the ventilation rate was determined depending on the number of occupants, net floor area, and building pollution category. Increasing the ventilation rate, the risk of cross infections may be reduced substantially. Ventilation effectiveness provides information about the airflow capacity to remove the pollutants from the breathing zone of occupants. In the present study, the interrelation between ventilation effectiveness and the air temperature was analysed in the case of different isothermal balanced ventilation strategies. Mixing, displacement, and personalized ventilation were investigated in a test room, measuring the CO2 concentration, and having the air exhaust positions above the floor and under the ceiling. The air temperatures were set between 21 °C and 26 °C. To illustrate the airflow patterns numerical simulations have been carried out. It was shown that there are significant differences between ventilation effectiveness depending on the air temperature and ventilation strategy. In most cases, the ventilation effectiveness was higher when the air exhaust was positioned under the ceiling. For investigated air temperatures, differences of even 20%-40% have been determined between ventilation effectiveness values in the case of a certain ventilation strategy.

Keywords: Airborne transmission; CO2 concentration; COVID-19; Ventilation effectiveness; Ventilation strategy.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Test room.
Fig. 2
Fig. 2
Air terminal devices used for diffuse (a) and displacement (b) ventilation.
Fig. 3
Fig. 3
Exhaust elements: AF (a) and UC (b).
Fig. 4
Fig. 4
PV desk.
Fig. 5
Fig. 5
ATD's location in the test room (1: MV ATD; 2: DV ATD; 3: PV-FS ATD; 4: PV-LS ATD; 5: UC exhaust ATD; 6: AF exhaust ATD).
Fig. 6
Fig. 6
Applied meshes: coarse (a), medium (b); fine (c).
Fig. 7
Fig. 7
Velocity measurement points alignments (a); velocity comparison (b) (red: person is not in the room; black: person is in the room). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
Fig. 8
Fig. 8
Velocity distribution at 25 °C in Case I (a); Case V (b); Case II (c); Case VI (d), Case III (e); Case VII (f); Case IV (g); Case VIII (h).
Fig. 9
Fig. 9
Ventilation effectiveness depending on the air temperatures.
Fig. A1
Fig. A1
Location of the measuring point
Fig. A2
Fig. A2
Velocity distribution at 21 °C in Case I (a); Case V (b); Case II (c); Case VI (d), Case III (e); Case VII (f); Case IV (g); Case VIII (h)
Fig. A3
Fig. A3
Registered supply air temperature
Fig. A4
Fig. A4
Registered indoor air temperature
Fig. A5
Fig. A5
Registered exhaust air temperature
Fig. A6
Fig. A6
Registered CO2 concentration in the supplied air
Fig. A7
Fig. A7
Registered CO2 concentration in the indoor air
Fig. A8
Fig. A8
Registered CO2 concentration in the exhaust air
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