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Air Grilles Designed to Prevent Backflows in Natural Ventilation Stacks – Experimental Investigation

Piotr Koper
Piotr Koper
 e 
Dominik Szpank
Dominik Szpank
   | 20 lug 2023
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Pubblicato online: 20 lug 2023
Pagine: 161 - 169
Ricevuto: 03 feb 2023
Accettato: 12 mag 2023
DOI: https://doi.org/10.2478/acee-2023-0025
Parole chiave
© 2023 Piotr Koper et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Figure 1.

Examples of shapes of air channels where pressure loss strongly depends on flow direction a) Tesla valve [13, 14], b) diffuser, pressure loss coefficient × from [15]
Examples of shapes of air channels where pressure loss strongly depends on flow direction a) Tesla valve [13, 14], b) diffuser, pressure loss coefficient × from [15]

Figure 2.

Cross-section of the test setup: 1 – chamber representing a fragment of the room, 2 – chamber representing ventilation stack, 3 – thermoanemometers, 4 – fan (can be placed at another outlet), 5 – channel for tested air grill, 6 – pressure difference measurement ports, connected to micromanometer
Cross-section of the test setup: 1 – chamber representing a fragment of the room, 2 – chamber representing ventilation stack, 3 – thermoanemometers, 4 – fan (can be placed at another outlet), 5 – channel for tested air grill, 6 – pressure difference measurement ports, connected to micromanometer

Figure 3.

Photos of the test setup: a) overall view, b) air grill installed for testing, c) air speed measurement, d) pressure difference measurement
Photos of the test setup: a) overall view, b) air grill installed for testing, c) air speed measurement, d) pressure difference measurement

Figure 4.

Ordinary air grill tested for comparison
Ordinary air grill tested for comparison

Figure 5.

Air grill with moving flaps
Air grill with moving flaps

Figure 6.

Air grill shaped to prevent backflow
Air grill shaped to prevent backflow

Figure 7.

CFD simulation of the air inlet a) geometry with boundary conditions: blue – opening, green – outlet with defined mass flow, red cross – location of the thermoanemometer sensor, b) example of results of the simulation – velocity profile in cross-section for mass flow 35 kg/h
CFD simulation of the air inlet a) geometry with boundary conditions: blue – opening, green – outlet with defined mass flow, red cross – location of the thermoanemometer sensor, b) example of results of the simulation – velocity profile in cross-section for mass flow 35 kg/h

Figure 8.

Results of the pressure drop measurements for all three air grilles
Results of the pressure drop measurements for all three air grilles

Figure 9.

Mass flow for all the air grilles with a pressure difference of 15 Pa
Mass flow for all the air grilles with a pressure difference of 15 Pa

Figure 10.

Hydraulic losses at both ends of the diffuser-shaped air grill
Hydraulic losses at both ends of the diffuser-shaped air grill

Hydraulic loss coefficient (x) for the tested air grills

Diffuser Forward flow Reverse flow
9 9
19 616
270 260

Characteristics of measuring devices used in the experiments

Device Type Measurement range accuracy
Thermoanemometer AirDistSys 5000 0.05 to 5 m/s ±0.02 m/s ±1% of readings
Difference micromanometer CMR-10 0 to 1500 Pa ±0.1Pa
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