Using a cloud-based CFD software is a cost-efficient and accessible way for HVAC, Civil and Fire Safety Engineers to maintain good air quality in underground or multilevel parking garages, metro stations, tunnels or other enclosed spaces. This presentation was used in a free webinar hosted by SimScale’s CEO David Heiny. The participants learned how CFD simulations can help engineers virtually test and optimize basement ventilation for smoke management and clearance or the removal of carbon monoxide and other pollutants (passive scalar transport). A cloud-based CFD platform like SimScale can help you easily validate exhaust fan and jet fan placement, or ventilation system design configurations for smoke control. Learn more about improving indoor air quality with the aid of simulation and watch the webinar recording below: - Webinar recording: https://www.simscale.com/webinars-workshops/garage-ventilation-validation-cfd/ - Blog article: https://www.simscale.com/blog/2018/02/garage-ventilation-system-jet-fan/ - Simulation project template: https://www.simscale.com/projects/vaibhav_s/pollutant_extraction_from_parking_garage_-_editorial_demo/

1. How to predict ventilation system effectiveness with
SimScale
March 2018
CFD for Ventilation System Design

2. Why Should I Care about CFD in Ventilation System Design?
Important Ventilation Scenarios:
1. CO Concentration under normal operating conditions
2. Smoke clearance in case of a fire scenario
→ CFD allows to check regulatory compliance just based on CAD

3. CO Level – Regulatory Requirements
Time (hrs) PPM
ASHRAE
ICBO
NIOSH/OSHA
ACGIH
Canada
Netherlands
U.K.
8 / 1 9 / 35
8 / 1 50 / 200
8 / Max 35 / 200
8 25
8 / 1 11 / 25
0.5 200
8 50
Table: Exemplary overview* of international standards for enclosed
parking garage ventilation requirements
Typical Design Constraints:
1. 30 PPM LTEL (Long Term Exposure Limit)
2. 200 PPM STEL (Short Term Exposure Limit)
*Source: Krarti, Ayari - “Ventilation for Enclosed Parking Garages”, ASHRAE JOURNAL
2001

4. Design Scenario
Watch the full webinar recording for free

5. CO Level Under Normal Operating Conditions
Fresh Air Supply3x 18,000
CMH
Fresh Air Supply18,000
CMH
Ramp
Open to environment
Exhaust Openings3x 28,800
CMH
CO Production80 moving cars, each 8.2 mg/s
CO
40% of total car capacity (worst case)

6. CO Level Under Normal Operating Conditions
Ramp
Open to environment
Fresh Air Supply
3x 18,000 CMH
Fresh Air Supply
18,000 CMH
Exhaust Openings
3x 28,800 CMH
CO Production
80 moving cars, each 8.2 mg/s CO
Design Challenges:
Ventilation Performance Specifics?
CO on acceptable levels?
Should we add jet fans ?
If yes, where to best place them?

7. Why SimScale?
Create a free account (no credit card required)

8. SimScale – World’s First Cloud-Based Simulation Platform
Zero hardware and software footprint.
Unlimited computing power via a web
browser.
Accessible
Flexible pricing model with low entry prices
and on-demand computing power.
Cost-efficient
Easy to use via collaboration functionality, real
time support and a large community.
For everyone

9. 2) Simulation
All steps necessary to define and run a
simulation are done within SimScale
1) CAD Import
Designs are uploaded from the desktop
or imported from other cloud services
3) Design Decision
The simulation results help to make
better design decisions faster and earlier
End-To-End CFD – Simply via a Web Browser

10. Fluid Dynamics Analysis (CFD) Capabilities
● Internal & External Flow
● Mass & Heat Transport
● Single- & Multiphase
● Laminar & Turbulent
● Steady-state & Transient
● In- & Compressible
● Rotating Machinery
● Porous Media
● ...
Ship Hull Resistance Prediction via Multiphase Flow SimulationExternal Aerodynamic Analysis of a Race Car
Turbulent and Compressible Flow simulation of a turbocharger HVAC System Analysis of a Restaurant Building Layout

11. Demo Time!

12. Design 1: Airflow Velocity

13. Design 1: CO Concentration

14. Design 1: Air Velocity & CO Concentration
Air Velocity Carbon Monoxide Concentration:
163.9 PPM

15. Improving the Design

16. Where to place Jet Fans?

17. Placing Jet Fans for CO Removal
6x Jet Fans
Generating 10m/s air velocity

18. Design 2: Airflow Velocity

19. Design 2: CO Concentration Level

20. Design 2: Air Velocity & CO Concentration

21. Results Comparison: Velocity Contours at Jet Fans Height
Design 1 (no Jet Fans) Design 2 (with Jet Fans)

22. Design Comparison: CO Concentration
Design 1 (no Jet Fans):
163.9 PPM
Design 2 (with Jet Fans):
73.67 PPM

23. Scenario: CO Concentration in PPM at 1.8m Height
Design 1 (no Jet Fans):
163.9 PPM
Design 2 (with Jet Fans):
73.67 PPM

24. Design Comparison: Regions with CO > 60 PPM
Design 1 (no Jet Fans):
163.9 PPM
Design 2 (with Jet Fans):
73.67 PPM

25. Maximum CO Concentration
-55.1 %

26. Wrap-up
Read this blog article to learn more

27. Investment
● ~5h manual time
● ~8h computing time
● ~760 core hours
Return
● Reduction in CO
Concentration
● Optimized Jet Fan
Placements
● Detailed Performance
Insights & Confidence
Simulation ROI in a Nutshell

28. How do I get started?
1
2
Two Steps:
1. www.simscale.com
2. Individual Demo
- or -
Try for free

29. Thank you!
David Heiny
CEO
dheiny@simscale.com

30. Mechanical Ventilation Design – Recommendations
● Adequate number of air changes per hour
○ Depends on acceptable CO levels
○ Number of cars in operation during peak conditions
○ Length of travel and operation time of vehicle
○ CO emission rate of a typical vehicle under various conditions
● Jet Fans or Induction Fans
○ Take up less space (complex duct work is not needed anymore)
○ Less noise generation
○ Cost less than a comparable ducted system
○ Energy savings – lower power consumption
○ Flexible positioning

31. Carbon Monoxide - Gas Facts
● Carbon Monoxide (CO) is fractionally lighter than air.
● CO will linger at one level or gradually rise toward the ceiling or roof space of a car park.
● The exposure limits for CO are:
30 PPM as a time weighted average (TWA) over an 8-hour working period known as the Long Term
Exposure Limit (LTEL).
● 200 PPM as a TWA over a 15 minute period, known as the Short Term Exposure Limit (STEL).
● Its physiological effects are tiredness, headaches, nausea and ultimately death. Its effects are,
however, reversible if detected at an early stage.

32. Why Ventilate ?
Why ventilate a Car Parking Garage?
POLLUTION, SMOKE,
FIRE HAZARDS, FIRE SAFETY !!!
Maintaining air quality while satisfying safety
requirements is a key challenge for car park
ventilation

33. Scenario Details – Boundary Conditions
Fresh Air Inlets [ 4 X 18000 CMH = 72000 CMH]
Exhausts Opening [ 3 X 28800 CMH = 86400 CMH]
Open Boundary - Ramp
Jet Fans - 6

34. Scenario: CO Extraction
Design Challenge:
● CO under accepted levels?
● Jet Fans ?
● Mechanical Ventilation ?

35. Volume of Underground Parking Garage (m^3) 23642
Total Number of Vehicles Parked 200
% of Moving Cars (Entering/Exiting the Garage In Peak
Hours - worst case scenario)
40
Total Number of moving cars 80
CO emission rate per vehicle (mg/s) 8.1944
Total Volumetric CO source (Kg/m^3-s) 2.77E-08
Scenario Details - CO Source Term Calculation