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

Where:

Pi

= air or gas density at position 1 (kg/m3)

P2

= air or gas density at position 2 (kg/m3)

Ai

= cross-sectional area at position 1 (m2)

A2

= cross-sectional area at position 2 (m2)

Vi

= air or gas velocity at position 1 (m/s)

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


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