snjb s kbj college of engineering, chandwad · in an experiment, a sample of wet steam is passed...
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SNJB’s KBJ College of Engineering, Chandwad
Department
of Mechanical Engineering
TYPES OF CALORIMETER TO
MEASURE DRYNESS
FRACTION OF STEAM.
Presented by;
Prof. Rajendra.C.Patil
Prof. Sumeet.D.Sanyashiv
TYPES OF CALORIMETER(MEASUREMENT OF
DRYNESS FRACTION )
❖ There are four methods of determining the
dryness fraction of steam experimentally. They
are as follows:
(A) Bucket or barrel calorimeter
(B) Separating calorimeter
(C) Throttling calorimeter
(D)Combined separating and throttling
calorimeter.
BUCKET OR BARREL CALORIMETER
It consists of a copper vessel whichcontains known quantity of coldwater.
The copper vessel is insulated fromthe surrounding so as to preventany heat transfer from or to thesystem.
The top of the vessel is also coveredby some detachable insulatingmedium.
A thermometer is inserted in the waterto record the temperature of it.
As steam condenses, the mass and temperature of water increases.
BUCKET OR BARREL CALORIMETER
Value of x is incorrect since heat losses due to convection and radiation are not taken into account.
( )( )
( )( )
fg
2satPw12PwwPcc
12PwwPcc
fg2satPw
vapourwater
h
)TT(CTTCmCm
TTCmCmQ
xh)TT(CQ
qqQ
−−−+=
=
−+=
+−=
+=
s
s
s
s
m
mx
by watergain steamby lost
rcalorimetein by water gain
msteamby lost
msteamby lost
kg condensed steam of massm
kgr calorimetein water of massm
kgr calorimete barrel of mass m
Where
s
w
c
=
=
=
BUCKET OR BARREL CALORIMETER
kg/kJh
CT
CT
C
fg
sat
2
Pgiven at steam ofheat latent
Pgiven at steam of re temperatusaturation
waterof re temperatufinal
waterof re temperatuinitial T
kJ/kgK water ofheat sp.C
kJ/kgKr calorimete barrel ofheat sp.C
Where
0
0
0
1
Pw
Pc
=
=
=
=
=
=
Bucket calorimeter
The steam at pressure of 5.5 bar is passed into tank filled with 80kg of
water at 250C. The tank is made of copper, is 10 kg in mass and has a
specific heat of 0.406kJ/kg K. After steam has condensed and mixed with
water, its temperature reaches 400C and the mass of mixture becomes
82.5kg. Determine the dryness fraction of steam.
( )( )
( )( )749.0
m
)(mx
by watergain steamby lost
rcalorimetein by water gain
)(msteamby lost
msteamby lost
s
2s12
12
2s
s
=
−−−+=
=
−+=
+−=
+=
fg
satPwPwwPcc
PwwPcc
fgsatPw
vapourwater
h
TTCTTCmCm
TTCmCmQ
xhTTCQ
qqQ
It separates water particles from wet steam
mechanically by centrifugal action.
It consists of two concentric chambers, the
inner chamber and the outer chamber,
which communicates with each other
through an opening at the top.
As the steam discharges through the metal
basket, which has a large number of holes,
the water particles due to their heavier
momentum get separated from the steam
and collect in the chamber.
The comparatively dry steam in the inner
chamber moves up and then down through
the annular space between the two
chambers and enters the outer chamber
where it is condensed and measured.
SEPARATING CALORIMETER
kg suspensionin particles water of massm
kg steam saturated anddry of mass m
Where
w
g
=
=
gw
g
mm
mx
+=
SEPARATING CALORIMETER
Value of x is not accurate, but it is
just close approximation.
In an experiment, a sample of wet steam is passed through a separating
calorimeter. At some instant, the mass of water collected in the separator
was 0.2kg, while the amount of steam condensed was found to be 2.5kg.
Determine the dryness fraction of steam entering the calorimeter.
925.05.22.0
5.2=
+=
+=
gw
g
mm
mx
It consists of a narrow throat (Orifice).
Pressure and temperature are
measured by pressure gauge and
thermometer.
The steam after throttling process
passes through the heat
exchanger and condensate is
collected.
A sample of wet steam (P1) is
throttled through a partially opened
or restricted valve to P2 and T2 in
such a way that the steam reaches
the superheated region. (During
process enthalpy of steam remains
constant)
THROTTLING CALORIMETER
Since h = constant, draw a horizontal line up to 2(locate 2 by P2 and
T2)
Locate 1 by P1
Find x1.
THROTTLING CALORIMETER
1fg
1f2
h
hh
1
21fg11f
21
x
hhxh
hh
−=
=+
= Using
]T;TT)[TT(Chh
h
kg/kJh
h
sat2supsatsupsupP2g2
2
1fg
1f
2
22
1
1
Pat
kJ/kg T and P steam dsuperheate ofentalphy
Pgiven at steam ofheat latent
kJ/kg,P steam ofheat sensible
Where
=−+=
=
=
=
To obtain good approximation from a throttling calorimeter, the steam after
throttling should be superheated at least by 5 degree centigrade.
If steam is very wet, the resultant dryness fraction x obtained is inaccurate.
In a throttling calorimeter, the steam is admitted at 10 bar, it is throttled to
atmospheric pressure and 1100C. Determine the dryness fraction of steam.
Assume the specific heat of superheated steam as 2.2 kJ/kg K
( )
96.0
6.2013
6.7621001102.22676
Using
1
1
2111
21
1
12
=
−−+==
=+
=
−
x
x
hhxh
hh
fg
f
h
hh
fgf
COMBINED SEPARATING
ANDTHROTTLING
CALORIMETER
Function of Experimentation :-Find the Dryness fraction (x) of Steam.
For very wet steam, this calorimeter is used.
Firstly, steam passes through separating calorimeter and some part of
moisture is removed due to sudden change in direction.
The resulting semi-wet steam is then throttled into a throttling
calorimeter.
The steam coming out throttling calorimeter is superheated at P2 and
T2. This is condensed in condenser and its mass is measured.
Throttling calorimeter is well insulated.
steam offraction drynesss final x
rcalorimete trottlingfrom steam offraction dryness x
rcalorimete separating from steam offraction dryness x
kg ttlingafter thro condensed steam of mass m
kgseparator in collected (moisture) particles water of massm
Let
2
1
g
w
=
=
=
=
=
COMBINED SEPARATING & THROTTLING CALORIMETER
COMBINED SEPARATING & THROTTLING CALORIMETER
21
1fg
1f22
gw
g
1
xxx
h
hhx
mm
mx
=
−=
+=
A combine separating and throttling calorimeter was used to determine the
dryness fraction of steam flowing through a steam main at a pressure of
9bar. The pressure and temperature of steam after throttling were 1.25bar
and 1150C respectively. The mass of steam condensed after throttling was
2.2kg and the mass of water collected in the separator was 0.20kg. Find
the dryness fraction of steam in the main.
kgkJ
TAsT
CT
CTsatbarP
kgkJh
kgkJh
wetbarP
sat
given
fg
f
/2704h
)@PT-(TChhh
dSuperheate is Steam
115
106;25.1
ThrottlingAfter
/5.2029
/6.742
)(9
2
2satsuppsg2sup2
given
0
0
2
1
1
1
=
+==
=
==
=
=
=
8854.0966.09166.0
is steam wet of sample offraction dryness Final Hence
966.0
rCalorimete Throttling
9166.02.220.0
2.2
mm
mx
rCalorimete Separating
21
2
21
sw
s1
===
=
=
=+
=+
=
xxx
x
hh