Fluid flow
Derived units:
Force n kg m/s
Energy or work joule kg m / s nm
Power watt kg m/s j/s
Pressure Pascal kg m/s n/m
Viscosity kg m/s ns/sm
Conversion of units
Example 1
Convert t poise to British engineering units and si units
Sol
1 poise = 1 9/cm s = 19 /1cm * 1s
= 19 * ib
Ex 2
Convert 1 kw to h.p
Sol
1kw = 1000 w = 1000 j/s
1 h.p = o.746 kw
Pressure
1 ibf / in 6.895 kn/ m
1 atm 101.3 kn/ m
1 bar 100 kn /m
1 ft water 2.99kn /m
1 in water 249 n/m
1 in hg 3.39 kn /m
1 mm hg 133 n/m
Pressure
P= f/a =mg/a Newton s law
Where m= the mass of piston , pan , and weight
g = local acceleration of gravity
a = cross – sectional area of piston
the mass m= ahƒ
a= the cross – sectional area
h= height
p = density
p=f/A = mg/A = Ah g/ A = h g
late = 101325 pa = 101.325 kpa = 0.10132 mpa
lbar = 10000 pa ……………..
ex
dead – weight gauge with a 1- cm diameter piston is used to measure pressure very accurately .in a particular instant a mass of 6.14 kg (include piston pan) . if the local acceleration of gravity 9.82 m/s .what the gauge pressure being measured .if the barometric pressures 748 to what the absolute pressure
f = mg = 6.14 * 9.82 = 60.295 n
gauge pressure = f / a = 60.295 / = 76.77 n/ cm
the absolute pressure = p = 76.77 + 748 (0.01332)
= 86.74 n/cm
Ex at 27 c a manometer filled with mercury reads 60.5 cm . the local acceleration of gravity is 9.784 m/s . what pressure dose this height of mercury correspond
P = hg at 27 c the density of mercury is 13.53 g/cm then
p = g 0.5 cm k 13.53 g/cm * 9.784 m/sec
= 8009 / ms cm
P = 8.009 kg m/s cm = 8.009 n / cm
P = 80.09 kpa = 0.8009 bar
For incompressible fluid
U1 A1 = u2 a2
Momentum changes in a fluid
Pda force up stream pressure fluid in a stream tube
P +dp /dl
The net force along tube to the pressure gradient is
pdA - [ p + dp / dl dl ] [ dA +
the force acting is the weight of the fluid
the component of this force a long the stream tube is
neglected second order terms and noting that sin? = dz/ dl
total force on fluid =
the rate change of momentum of the fluid along the stream tube
Energy of a fluid in motion
Internal energy
When a fluid flows from location to another , energy will converted from one for m to another , this energy is known as internal energy
dv =
dv internal energy
sw net work
sq heat added
potential energy
the potential energy of the fluid , due to its position in the earth s gravitational field .
the potential energy is gz
where
g acceleration
z position
kinetic energy
if the fluid is moving with a velocity u ,the kinetic energy is 1/2 u
pressure energy
this represents the work which must be done in order to introduce the fluid , without change in volume
therefore pv
where
p the pressure
? the volume per unit mass of fluid
? The total energy of unit mass of fluid is , therefore
U + p? +pz + 1/2 u ?
If the fluid flows from section 1 to section 2 and is the net heat absorbed from the surroundings and ws is the net work done by the fluid on the surrounding
? u2
?
Where w = ws + ?(p?)
H = U + p?
Where H the enthalpy
جريان موائع بوليمر المرحلة الثالثة
Fluid flow
Derived units:
Force n kg m/s
Energy or work joule kg m / s nm
Power watt kg m/s j/s
Pressure Pascal kg m/s n/m
Viscosity kg m/s ns/sm
Conversion of units
Example 1
Convert t poise to British engineering units and si units
Sol
1 poise = 1 9/cm s = 19 /1cm * 1s
= 19 * ib
Ex 2
Convert 1 kw to h.p
Sol
1kw = 1000 w = 1000 j/s
1 h.p = o.746 kw
Pressure
1 ibf / in 6.895 kn/ m
1 atm 101.3 kn/ m
1 bar 100 kn /m
1 ft water 2.99kn /m
1 in water 249 n/m
1 in hg 3.39 kn /m
1 mm hg 133 n/m
Pressure
P= f/a =mg/a Newton s law
Where m= the mass of piston , pan , and weight
g = local acceleration of gravity
a = cross – sectional area of piston
the mass m= ahƒ
a= the cross – sectional area
h= height
p = density
p=f/A = mg/A = Ah g/ A = h g
late = 101325 pa = 101.325 kpa = 0.10132 mpa
lbar = 10000 pa ……………..
ex
dead – weight gauge with a 1- cm diameter piston is used to measure pressure very accurately .in a particular instant a mass of 6.14 kg (include piston pan) . if the local acceleration of gravity 9.82 m/s .what the gauge pressure being measured .if the barometric pressures 748 to what the absolute pressure
f = mg = 6.14 * 9.82 = 60.295 n
gauge pressure = f / a = 60.295 / = 76.77 n/ cm
the absolute pressure = p = 76.77 + 748 (0.01332)
= 86.74 n/cm
Ex at 27 c a manometer filled with mercury reads 60.5 cm . the local acceleration of gravity is 9.784 m/s . what pressure dose this height of mercury correspond
P = hg at 27 c the density of mercury is 13.53 g/cm then
p = g 0.5 cm k 13.53 g/cm * 9.784 m/sec
= 8009 / ms cm
P = 8.009 kg m/s cm = 8.009 n / cm
P = 80.09 kpa = 0.8009 bar
For incompressible fluid
U1 A1 = u2 a2
Momentum changes in a fluid
Pda force up stream pressure fluid in a stream tube
P +dp /dl
The net force along tube to the pressure gradient is
pdA - [ p + dp / dl dl ] [ dA +
the force acting is the weight of the fluid
the component of this force a long the stream tube is
neglected second order terms and noting that sin? = dz/ dl
total force on fluid =
the rate change of momentum of the fluid along the stream tube
Energy of a fluid in motion
Internal energy
When a fluid flows from location to another , energy will converted from one for m to another , this energy is known as internal energy
dv =
dv internal energy
sw net work
sq heat added
potential energy
the potential energy of the fluid , due to its position in the earth s gravitational field .
the potential energy is gz
where
g acceleration
z position
kinetic energy
if the fluid is moving with a velocity u ,the kinetic energy is 1/2 u
pressure energy
this represents the work which must be done in order to introduce the fluid , without change in volume
therefore pv
where
p the pressure
? the volume per unit mass of fluid
? The total energy of unit mass of fluid is , therefore
U + p? +pz + 1/2 u ?
If the fluid flows from section 1 to section 2 and is the net heat absorbed from the surroundings and ws is the net work done by the fluid on the surrounding
? u2
?
Where w = ws + ?(p?)
H = U + p?
Where H the enthalpy