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Aerosol Instrumentation - Stack Inlet

Stack Inlet

The inlet system is designed to obtain a representative sample of the atmospheric aerosol at the field site.

The sample is brought into the aerosol system from a height of 10 m above ground level in order to avoid surface effects and contamination.

A rainhat and screen are used to keep precipitation and birds from entering the stack. Further into the stack, a finer screen is used to keep insects out of the sample line.

The main body of the stack consists of 20 cm (8 in) pvc pipe. Centered within the main body of the stack, about 6 m from the top, is a 5 cm (2 in) stainless steel heated inlet tube. The flow through the main stack is 1000 lpm. The sample flow in the inlet tube is 150 lpm and is pulled by a carbon vane pump. The excess flow of 850 lpm is pulled by a blower. In this photo, the excess flow is pulled horizontally out of the stack through the 10 cm (4 in) side pipe. The 150 lpm sample flow continues straight down through the roof to the flow splitter and aerosol instruments.

The 150 lpm sample flow is split at the "splitter" into five 30 lpm flows. Four of these are analyzer flows (e.g., through the aerosol system or through the filter system) and one is a bypass flow line which keeps flow smooth through the splitter to the analyzer lines. The sample temperature and RH are measured on the bypass line.