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Schlieren Flow Visualization
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Schlieren flow visualization is a non-intrusive approach to effluent
flow observation. This technique is crucial to understanding the flow
of heat and effluents generated by commercial cooking equipment. The
videos below demonstrate the Schlieren flow visualization technique
applied to commercial kitchen ventilation.
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Description
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Schlieren technology utilizes a light source, an imaging lens and an
image plane to capture "bent" light paths due to light refraction.
Light refraction is due to a change in the refractive index of air at
different temperatures. The result is a well defined image illustrating
air at different temperatures.
In the case of kitchen ventilation, hot air
is of interest. The Schlieren flow visualization technique is used
to determine whether or not the heat, generated by the cooking
equipment, is being captured by the kitchen exhaust hood. From this,
a value for exhaust flow rate of the hood can be determined to fully
capture the heat generated by the cooking equipment.
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| Videos and Test Parameters |
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The product being displayed below is a wall canopy hood with various
flows and configurations of make-up air. The videos in the left column
demonstrate the heat produced from two gas charbroilers. The videos in
the right column are illustrations of heat generated from two electric
griddles.
The hood utilized in these videos is 8' in length, 24" tall and
54" wide. The left and right overhang of the hood is 6" and the front
overhang is 24".
All make-up air temperatures are 85°F. All tests were conducted to ASTM-1704 and below are the videos and
the results of the tests:
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| Exhaust Only with No Make-Up Air Full Capture and Containment |
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| Gas CharBroiler (700°F) |
Electric Griddle (400°F) |
- Exhaust rate = 2100 CFM (263 CFM/lnft)
- Supply rate = 0 CFM (0 CFM/lnft)
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- Exhaust rate = 1350 CFM (169 CFM/lnft)
- Supply rate = 0 CFM (0 CFM/lnft)
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[ Download Video ]
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[ Download Video ]
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| Gas CharBroiler with End Panels (700°F) |
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- Exhaust rate = 1950 CFM (244 CFM/lnft)
- Supply rate = 0 CFM (0 CFM/lnft)
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[ Download Video ]
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Closing Comments
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We hope this information facilitates the use of this new product into
your submittals and application engineering.
We are aware that flow rates determined by
the Schlieren flow visualization technique are laboratory produced
values and are not suitable for every application. This information
is presented to be used as a tool in the design and understanding
commercial kitchen ventilation systems.
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