Conservation of matter
Conservation of matter or the continuity equation is merely a mathematical statement that, during a flow process, matter is neither created nor destroyed.
Thus the mass flow in a fluid element (assuming no leakage to outside) remains constant i. e.,
= p2A2v2 Equ3.1
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Where: |
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Pi |
= air or gas density at position 1 (kg/m3) |
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P2 |
= air or gas density at position 2 (kg/m3) |
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Ai |
= cross-sectional area at position 1 (m2) |
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A2 |
= cross-sectional area at position 2 (m2) |
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Vi |
= air or gas velocity at position 1 (m/s) |
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V2 |
= air or gas velocity at position 2 (m/s) |
I n the particular case of flows where the pressures are less than about 2.0 kPa, air and many other gases may be treated as if they were incompressible. Thus pi = p2 i. e., the density of the air/gas remains constant and
A, v, = A2v2 Equ 3.2
Posted in Fans Ventilation A Practical Guide