Flow meters measure volumetric flow rates (i.e., SCF/minute, cubic meters/minute, liters/minute, etc.) or mass flow rates (i.e., pounds /hour, kg/minute, tons/day, etc.).
I don't understand why any "Heat Exchanger testing procedure" would be concerned with ppm (which is unit of concentration). What "Heat Echanger test procedure"? Testing for what?
Please furnish more details.
Milton Beychok
(Visit me at www.air-dispersion.com)
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