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Rate in Fluid Systems. 3.2. Volume Flow Rate. Change in volume per unit time Volume flow rate = change in volume/time interval volume is in m 3 , cm 3 , ft 3 , in 3 , liters or gallons volume flow rate is in m 3 /s, ft 3 /min, liters/h. Mass Flow Rate. Mass of fluid moved per unit time
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Volume Flow Rate • Change in volume per unit time • Volume flow rate = change in volume/time interval • volume is in m3, cm3, ft3, in3, liters or gallons • volume flow rate is in m3/s, ft3/min, liters/h
Mass Flow Rate • Mass of fluid moved per unit time • Mass flow rate = change in mass/time interval • Mass flow rates are in slugs/s and kg/s
Measuring Fluid Rates • Easiest method is to collect fluid and measure the amount of fluid collected over a time interval • Average flow rate—volume or mass of fluid collected divided by the time interval • Flowmeters measure indirectly and do not significantly interrupt the flow. (They measure pressure or velocity.)
Measuring Fluid Rates • Volume flow rate = cross-sectional area x fluid speed • Mass flow rate = fluid density x cross-sectional area x fluid speed
Processes that Use Rates of Fluids • Bottling machine • City water supply system • Air compressor to tool
Conversion factors to know: • 1 gal = 231 in3 • 1 gal = 0.1337 ft3 • 1 gal = 3.785 x 10-3 m3