In physics and engineering, mass flow rate is the mass of a substance which passes per unit of time. Its unit is kilogram per second in SI units, and slug per second or pound per second in US customary units. The common symbol is
m
˙
{\displaystyle {\dot {m}}}
(ṁ, pronounced "m-dot"), although sometimes μ (Greek lowercase mu) is used.
Sometimes, mass flow rate is termed mass flux or mass current, see for example Schaum's Outline of Fluid Mechanics. In this article, the (more intuitive) definition is used.
Mass flow rate is defined by the limit:
m
˙
=
lim
Δ
t
→
0
Δ
m
Δ
t
=
d
m
d
t
{\displaystyle {\dot {m}}=\lim \limits _{\Delta t\rightarrow 0}{\frac {\Delta m}{\Delta t}}={\frac {{\rm {d}}m}{{\rm {d}}t}}}
i.e. the flow of mass m through a surface per unit time t.
The overdot on the m is Newton's notation for a time derivative. Since mass is a scalar quantity, the mass flow rate (the time derivative of mass) is also a scalar quantity. The change in mass is the amount that flows after crossing the boundary for some time duration, not the initial amount of mass at the boundary minus the final amount at the boundary, since the change in mass flowing through the area would be zero for steady flow.
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At first, I inputted h(t), of which I solved for, into the mass flow rate formula.
So it looked something like this, m-dot(t) = -(density)*[sqrt(g*(H-(g*d^4*t^2/D^4)]*(pi/4)*d^2
But I don't think that's right? Any thoughts?
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Working out as follows
x= (20-6)/20 = 0.7
Fk = k / air specific heat ratio
Fk = 1.31/1.4
Fk = 0.94
xT = Fk * x
0.94 x 0.7 = 0.658
because xT < x = 0.658<0.7 flow through the valve is choked
Expansion factor Y
Y = 1 - x/( 3 x Fk x xT )
Y= 1- 0.7/( 3 x 0.94 x 0.658)
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[crackpot youtube video deleted by moderator @russ_watters ]
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< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >
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Homework Equations
PV=RT
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http://www.colormaxsystems.com/wp-content/uploads/2013/11/5-screws-300x222.jpg
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