Investigation of Airflow Distribution and Contamination Control with Different Schemes in an Operating Room
Abstract
:1. Introduction
2. System Description
3. Methodology
3.1. Field Measurement Tests
3.2. CFD Simulation and Improvement Strategy
- Case 1: at-rest condition with no personnel and equipment inside the operating room.
- Case 2: operational condition with personnel inside performing a surgery.
- Case 3: actual condition with personnel inside and equipment blocking the return air.
3.3. Airflow Modelling and Boundary Conditions
3.4. Grid Independence Test and Validation
4. Results and Discussion
4.1. Experimental Results
4.2. Airflow Pattern Distribution
4.3. Contamination Removal Analyses in Different Cases
4.4. Effect of Ventilation Rate on the Operating Room Concentration
4.5. Ventilation Efficiency
4.6. Bioaerosol Flow Path Model
4.7. Pressurization
5. Conclusions
- The experimental data were retrieved during unoccupied conditions (at-rest), and this condition reached the design specification following ASHRAE 170 standard and ISO 14644.
- The results of concentration contamination and bioaerosol flow path revealed that case 1 presents a good airflow distribution and less particle concentration when unoccupied with the average concentration value of 404 ppm, while case 2 generated a higher concentration while performing a surgery with an average concentration value of 420 ppm. Then, some medical equipment blocked the outlet air in case 3, resulting in the highest concentration with an average concentration value of 474 ppm.
- Increasing the ventilation rates could result in a lower concentration. Increasing ventilation rates does not always present a good concentration dilution, but the air distribution pattern could also affect it. Some medical equipment is recommended not to block the outlet air grilles for dilution purposes. The average concentration in case 3 with different ventilation rates: 15 ACH, 22 ACH, and 29 ACH were 495 ppm, 474 ppm, and 446 ppm, respectively.
- According to case 1, the ventilation efficiency in case 2 and case 3 dropped around 6% and 17.91%, respectively. Ventilation efficiency also decreased along with decreasing ACH, while with increasing ACH, the ventilation efficiency in the case 3 actual condition increased, approaching case 2 in an ideal condition.
- The blocked return air also affected the bioaerosol distribution that could not be directly removed or diluted through the outlet. It could obstruct the flow path resulting in the airflow distribution that could carry the particles reaching almost the ceiling corner, and even deposited in behind the surgical table.
- The reduction in ventilation could increase the concentration inside the room and would not be possible to implement when the operating room is performing surgery. The reduction also has a limitation that should be met with the design requirements such as temperature, relative humidity, pressurization, and particle counts. It could be implemented during the unoccupied state condition to achieve energy saving.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Conflicts of Interest
References
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Parameters | Apparatus Model | Operative Range | Accuracy |
---|---|---|---|
Velocity, Pressure | TSI PH-731 | 0.125–12.5 (m/s) Differential ± 3735 pa | 3% 2% |
Particles | Met One 3413 | 0.3, 0.5, 1, 3, 5, 10 µm | 5% |
Temperature, Humidity | TSI 9565P | −10~60 (°C), 0–100 (%RH) | 0.3 °C 3%RH |
Parameter | Type | Value |
---|---|---|
Supply Air | Velocity Inlet Discrete phase: escape | Velocity: 0.298 m/s Temperature: 20.2 °C Concentration: 400 ppm |
Return Air | Pressure Outlet Discrete phase: trap | Temperature: 25 °C Pressure: +10.6 Pa |
CO2 Concentration | Velocity Inlet | Velocity Inlet: 0.18 m/s Exhale: 38,000 ppm [29] |
Bioaerosol | DPM: Injection | Velocity: 1.5 m/s Flowrate: 0.17 kg/s Particle Size: 1–5 µm, median 2.5 µm |
Patient | Wall | Heatflux: 17.45 W/m2 [30] |
Surgeon | Wall | Heatflux: 33.55 W/m2 [30] |
General Lightings | Wall | Heatflux: 288 W/m2 [30] |
Operating Lightings | Wall | Heatflux: 320 W/m2 [30] |
Case Study | C (ppm) | Cs (ppm) | Ce (ppm) | Ventilation Efficiency (%) |
---|---|---|---|---|
Case 1 (22 ACH) | 404 | 400 | 403.7 | 92.50 |
Case 2 (22 ACH) | 420 | 400 | 417.3 | 86.50 |
Case 3 (22 ACH) | 474 | 400 | 455.2 | 74.59 |
Case 3 (15 ACH) | 495 | 400 | 465.5 | 68.95 |
Case 3 (29 ACH) | 446 | 400 | 438.1 | 82.83 |
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Wang, F.; Permana, I.; Rakshit, D.; Prasetyo, B.Y. Investigation of Airflow Distribution and Contamination Control with Different Schemes in an Operating Room. Atmosphere 2021, 12, 1639. https://doi.org/10.3390/atmos12121639
Wang F, Permana I, Rakshit D, Prasetyo BY. Investigation of Airflow Distribution and Contamination Control with Different Schemes in an Operating Room. Atmosphere. 2021; 12(12):1639. https://doi.org/10.3390/atmos12121639
Chicago/Turabian StyleWang, Fujen, Indra Permana, Dibakar Rakshit, and Bowo Yuli Prasetyo. 2021. "Investigation of Airflow Distribution and Contamination Control with Different Schemes in an Operating Room" Atmosphere 12, no. 12: 1639. https://doi.org/10.3390/atmos12121639