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]
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
Figure 3.
Photos of the test setup: a) overall view, b) air grill installed for testing, c) air speed measurement, d) pressure difference measurement
Table 1.
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 |
Figure 4.
Ordinary air grill tested for comparison
Figure 5.
Air grill with moving flaps
Figure 6.
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
Figure 8.
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
Figure 10.
Hydraulic losses at both ends of the diffuser-shaped air grill
