Bernoulis equation:
It denotes the interconversion of energies
Forces that at includes
Rate of work done by pressure from surroundings
Rate of energy obtained from internal energy reversible conversion
Rate of energy obtained due to reversible conversion of energy
Rate of work done by mechanical forces
Consider a pipe with an inlet and out let
With pressure p1, area a1, velocity of fluid be v1 at inlet
P2, a2,v2 be at the outlet
P1,a1,v1 -------------------- p2,a2,v2,
--------------------
Total energy = kinetic energy+ potential enrgy
TE1 = KE1+PE1
TE1 = ½ mv1*v1 +mgz1
,m (v1*v1/2 +gz1)
TE2 = ½ mv2*v2 +mgz2
,m(v2*v2/2 +gz2)
W = ,m(v1*v1/2 +gz1)-,m(v2*v2/2 +gz2)
,m [(v2*v2/2- v12/2)+g(z2-z1)]
W = W2-W2
(P2*m/ſ)+(P1*m/ ſ)
,m(p2-p1)/ ſ
m(p2-p1)/ ſ = m [(v2*v2/2- v1*v1/2)+g(z2-z1)]
(p2-p1)/ ſ = [(v2*v2/2- v12/2)+g(z2-z1)]
(p2-p1)/ ſ - [(v2*v2/2- v12/2)+g(z2-z1)] = constant
Correction factors
1) kinetic correction factor = ά
To eliminate the problem of integration it must be introduced
(p2-p1)/ ſ - [ά (v2*v2/2- v1*v1/2)+g(z2-z1)] = constant
2)Pump work correction factor
ή= wp – Hfs / wp
wp – Hfs = ήwp
ήwp +(p2-p1)/ ſ - [ά (v2*v2/2- v1*v1/2)+g(z2-z1)] = constant
3)Friction correction factor:
ήwp +(p2-p1)/ ſ - [ά (v2*v2/2- v1*v1/2)+g(z2-z1)]+ hf = constant
limitations of bernoulis equation
1) applicable only for ideal fluids
2) Total heat cannot be transferd from one point to another completely
keywords: bernoulis equation , limitations of bernoulis equation, correction factors in bernoulis equation
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