The Modeling of Spills and Fumehood Containment in
Laboratory Environments Using Large Eddy Simulations(LES)
Duncan Phillips, Ph.D., PE, Vincent
Tang, M.A.Sc., and Ray Sinclair,
M. Sc.(Eng), PE, Rowan Williams Davies & Irwin Inc.
The use of Computational Fluid Dynamic (CFD) modeling techniques
has become more common for the design of specialized laboratories.
CFD is a computer modeling technique in which the standard equations
describing fluid flow (conservation of mass, momentum, energy, contaminants,
etc.) are solved at many locations within a space using a computer.
In addition, a mathematical representation of the effects of turbulence
within the flow are typically included within the simulation. The
manner in which the turbulence is modeled represents a challenge
for many environments. There are a number of methods to represent
turbulence in CFD simulations LES being one of these. This paper
briefly reviews CFD modeling techniques and discusses the advantages
of Large Eddy Simulation.
The containment of contaminants within a fumehood, and the rate
at which a spilled contaminant is dispersed about a room depend
greatly on the HVAC system within a room. While CFD modeling of
flows within laboratory environments is becoming more common, the
use of LES modeling techniques permits one to assess the flows and
challenges to safety with more fidelity.
This presentation will demonstrate using a number of examples how
LES simulations have been used to assist in the design of laboratories.
The examples highlight how LES modeling permits the design team
to assess HVAC designs, assess the impact of energy saving initiatives
and evaluate the risks to occupants associated with chemical spills
and poor fumehood containment.
Findings:
The authors have applied both LES and traditional Reynolds Average
Navier Stokes (RANS) CFD modeling methods to laboratory environments.
For some design questions, LES has demonstrated significant advantages
over the RANS CFD modeling. Findings that will be shared with the
participants include:
- Some observations about the importance of balancing the supply
and exhaust within a laboratory;
- How a higher air change rate (ACH) does not necessarily correlate
to a safer laboratory and why; and,
- How fumehood containment can be challenged by the HVAC system
setup.
Labs21 Connection:
CFD modeling is an effective way to assess HVAC designs in advance
of constructing the laboratory. LES modeling provides additional
advantages in that it provides more fidelity in the simulation results.
The contents of this presentation highlight how this form of modeling
can:
- Minimize overall environmental impacts - the impact of design
changes which minimize energy use can be assessed in advance of
construction.
- Protect occupant safety - both fumehood containment and a spill
scenario are direct challenges to an occupant's safety. This presentation
discusses both.
- Establish goals, track performance, and share results for continuous
improvement - the comfort of an occupant within a space is important
to their productivity. CFD simulations have been used to assess
thermal comfort within laboratories and other occupied spaces
with the objective to enhance occupant comfort.
Biographies:
Duncan A. Phillips, Ph.D., PE
Duncan Phillips has a Ph.D. in Mechanical Engineering from the University
of Waterloo in Ontario. During his graduate work he investigated
the measurement and quantification of room air and contaminant mixing
within occupied spaces. This work involved both the development
of instrumentation for, and measurements of, contaminant transport.
Duncan is a registered Professional Engineer in the Province of
Ontario.
Duncan joined Rowan Williams Davies & Irwin Consulting Engineers
in 2000. He is a Senior Specialist for CFD and Ventilation. He is
an Associate of the firm. His role at RWDI as the Senior member
of the CFD and ventilation team is to technically oversee the execution
of client based projects. In addition he is responsible as coordinating
the technical advancement of RWDI's ventilation and modeling services.
Vincent Tang, M.A.Sc.
Vincent joined RWDI in 2001 after completing his M.A.Sc. in Mechanical
Engineering at the University of Toronto. He is responsible for
executing client based projects including flows within laboratories,
atria, and pollution control equipment. As a member of RWDI's R&D
department, he is actively involved in the development of RWDI's
ventilation and CFD capabilities.
Ray Sinclair, Ph.D.
As a Principal of RWDI, Dr. Sinclair provides technical direction
and leadership on a wide range of projects involving building &
tunnel ventilation, fire safety, air pollution, sustainable design,
wind engineering and industrial processes. He joined RWDI in 1991
after completing a Ph.D. in Mechanical Engineering. He is a leader
of the Computational Fluid Dynamics (CFD) modeling group and the
Marketing Division Leader for RWDI's Environmental Modeling Division.
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