Model Experiments in Connection with Local Ventilation in the Industrial Environment

Experiments on the scale of 1 to 1 are often used to study the local ventilation around an operator’s workplace. Tracer gas is used to simulate the contami­nant transport, and a high concentration level of the model tracer gas makes it possible to work with a convenient level of concentration for the measure­ments. Figure 12.31 shows an enclosure with an emission source S and a labo­ratory setup with a model source Sr The dimensionless concentration C/cR is

‘Rt

__ / C

1

/

/

/

I

Vs

I

H

CR

“7oi

FIGURE 12.31 Enclosure with a containment source S and a laboratory model with a model source S,

Identical with C/cKt in the laboratory model if the Archimedes numbers are identical in the full scale and in the model, and if the Reynolds numbers in

Both cases are identical or above the critical value for the concentration

Distribution.

The concentration at a given position close to an emission source can be calculated from

C = ct^, (12.64)

CRt

Where Ct, cRt and CR are tracer gas concentration at the corresponding position in the laboratory model, tracer gas concentration in the reference point in the laboratory model (return opening), and contaminant concentration in the ref erence point, respectively.

The emission source can be found from

S = sЈlSL (12.65)

Where Q0 is the volume flow around the local ventilation and Q0t is the volume flow around the model.

Posted in INDUSTRIAL VENTILATION DESIGN GUIDEBOOK