A generic-tee-plenum mixing system for application to single point aerosol sampling in stacks and ducts

Area of Science:

• Environmental Engineering
• Industrial Hygiene
• Fluid Dynamics

Background:

• The ANSI/HPS N13.1-1999 standard requires representative sampling from uniform velocity and contaminant profiles.
• Predicting mixing efficiency in arbitrary ducts is challenging without experimental data.
• Existing methods struggle to meet the stringent requirements for uniform sampling locations.

Purpose of the Study:

• To develop experimental data for mixing elements in S-shaped duct systems.
• To evaluate the performance of Generic-Tee-Plenum (GTP) systems for stack sampling.
• To assess GTP systems against ANSI/HPS N13.1-1999 mixing criteria.

Main Methods:

• Tested five mixing elements, including elbows, a static mixer, and three GTP systems (SH-GTP, SV-GTP, LH-GTP).
• Measured coefficients of variation (COVs) for velocity, tracer gas, and 10-µm aerosol particles.
• Evaluated GTP performance across different sizes and flow conditions (Reynolds number).

Main Results:

• GTP systems achieved COVs below 8% for velocity, gas, and aerosol profiles, meeting ANSI/HPS N13.1-1999 criteria (<20%).
• GTP performance was consistent regardless of size or velocity (Reynolds number).
• GTPs offered a low-pressure drop solution, suitable for new and retrofitted applications.

Conclusions:

• The developed GTP systems effectively meet the ANSI/HPS N13.1-1999 standard for representative sampling.
• GTPs provide a viable solution for achieving uniform flow profiles in S-shaped ducts.
• The GTP concept can be applied to new installations and retrofitted to existing systems.