I need to accurately measure gas flow in a very large duct. What type of mass flow meter should I specify ?
Specify a multipoint, insertion flow element. Single-point, insertion flow meters are a sensible choice when flow rate measurements must be made in large size pipes or ducts. However, because gross flow velocity profile distortions are likely in very large ducts, a single-point flow meter cannot accurately measure these highly skewed flow conditions (see sketch). Selecting a technology that allows for the averaging of multiple measurements provides a reasonable solution to this problem. When making multipoint air or gas flow measurements in large ducts, thermal dispersion technology offers significant benefits that place it far ahead of the other technologies. Thermal technology offers direct mass flow measurement (without separate temperature, pressure, or density measurement), fouling immunity, low flow sensitivity, and wide rangeability.
