Mass flow

Physical size
Surname	Mass flow
Formula symbol	${\displaystyle q_{m}}$
Size and unit system unit dimension SI kg · s -1 M · T −1
See also: flow (physics) , volume flow

A mass flow , also known as mass throughput , is the mass of a medium that moves through a cross-section over a period of time .

The mass flow is given in kilograms per second, also per minute or hour with slow flow.

The mass flow

${\displaystyle q_{m}={\dot {m}}={\frac {\mathrm {d} m}{\mathrm {d} t}}}$

is calculable in fluid mechanics through

${\displaystyle {\dot {m}}=\varrho \cdot {\dot {V}}=\varrho \cdot c\cdot A={\frac {\gamma }{g}}\cdot {\dot {V}}}$

With

${\displaystyle \varrho }$: Density of the medium in kg / m³,

${\displaystyle c}$: mean flow velocity in m / s,

${\displaystyle A}$: Cross-sectional area in m²,

${\displaystyle {\dot {V}}}$: Volume flow in m³ / s,

${\displaystyle \gamma }$: specific weight in N / m³ = kg / (m²s²) and

${\displaystyle g}$: Acceleration of gravity in m / s².

With regard to density, it should be noted that in the case of gases ( i.e. compressible media) the calculation must be expanded to include the possible changes in volume. The mean flow velocity is determined via integration , see also volume flow . To measure the flow there are different measurement methods.

Examples of mass flows: wind , exhaust gas mass flow , river , ocean current , landslide , landslide , grain flow , debris flow , pyroclastic density flow

literature

• Alfred Böge (Hrsg.): The technician's manual, basics and applications of mechanical engineering . 15th edition. Vieweg, Braunschweig and Wiesbaden 1999, ISBN 3-528-34053-3 .

Individual evidence

1. ^ ^{A b} Alfred Böge Das Techniker Handbuch , p. 320.
2. ^ Alfred Böge Das Techniker Handbuch , p. 337.
3. ^ Alfred Böge Das Techniker Handbuch , p. 330.
4. ↑ Holger Foysi: Measurement of volume and mass flow. (PDF; 1.8 MB) University of Siegen , April 2, 2015, accessed on November 25, 2018 .