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DEVELOPMENT OF TURBOEXPANDER BASED DEVELOPMENT OF TURBOEXPANDER BASED NITROGEN LIQUEFIER
ByBy
P f R jit K S hProf. Ranjit Kumar Sahoo
Prof. Sunil Kumar SarangiDIRECTOR, NIT ROURKELA
Department of Mechanical EngineeringNIT R k l NIT Rourkela
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CONTENTS
1 Liq efaction S stems1. Liquefaction Systems
2. Process Design
3 Major Components of Liquefier
4. Design of Heat Exchanger
5 Design of Turboexpander
3. Major Components of Liquefier
5. Design of Turboexpander
6. Design of JT Valve
7. Design of Phase Separator
8. Assembly of the Liquefier
9. References
7. Design of Phase Separator
9
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i f i S1. Liquefaction Systems
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Linde Cycle
In 1895, Carl Von Linde made this air liquefaction system
CompressorT=const
12
21 3Heat Exchanger
JouleThomson a
ture
, T
4g1
Thomson Valve
Tem
pera
3
fPhaseseparator Liquid
3
4 gf
Fig. 1 Fig. 2Entropy,s
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Claude System
In 1902, Georges Claude made an air liquefaction system with anexpansion engineexpansion engine.
H E h
T=const1
2
3Compressor
Heat Exchangers
421 3 5
ture
, T
3
9
JTValve
g
1 78
6
9
3
Tem
pera
t
5
47
Expander
g
fe LiquidPhase6 gf
e
8
Fig. 3 Fig. 4
qPhaseseparator
Entropy,s
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Kapitza System
In 1939 Claude cycle is modified by eliminating the third or lowIn 1939, Claude cycle is modified by eliminating the third or lowtemperature heat exchanger.
CompressorHeat Exchangers
421 3
JTValve
5
78
69
3
Expander
fe LiquidPh fe LiquidPhase
separator
Fig. 5
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Heylandt Systemy y
In 1949, Davies modified the Claude cycle by eliminating the first heatexchanger
CompressorHeat Exchangers
exchanger.
Compressor
421 3
789JTValve
5
78
6
9
3
Expander
fe LiquidPhaseseparatorseparator
Fig. 6
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P D i2. Process Design
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CASE -1 (Claude Cycle)
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CASE -2 (Modified Claude Cycle Eliminating Last Heat Exchanger)Last Heat Exchanger)
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CASE -3 (Modified Claude Cycle Eliminating First Heat Exchanger)First Heat Exchanger)
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CASE -1 Pressure 10 20 30 50 80 100 130 150
0 93 0 89 0 86 0 83 0 73 0 7 0 67 0 66 0.93 0.89 0.86 0.83 0.73 0.7 0.67 0.66Pinch1 3 3 3 3 3 3 3 3Pinch2 2 2 2 2 2 2 2 2Pinch3 1 1 1 1 1 1 1 1t 50% 50% 50% 50% 50% 50% 50% 50%m 1 1 1 1 1 1 1 1mf 0.05534 0.07933 0.09567 0.1155 0.142 0.1521 0.1644 0.171
CASE -2Pressure 10 20 30 50 80 100 130 150Pressure 10 20 30 50 80 100 130 150 0.93 0.89 0.85 0.82 0.71 0.68 0.65 0.62Pinch1 3 3 3 3 3 3 3 3Pinch2 1 1 1 1 1 1 1 1t 50% 50% 50% 50% 50% 50% 50% 50%
1 1 1 1 1 1 1 1m 1 1 1 1 1 1 1 1mf 0.05581 0.0797 0.09579 0.1161 0.1412 0.1517 0.1636 0.17
CASE -3Pressure 10 20 30 50 80 100 130 150 0.14 0.14 0.15 0.2 0.3 0.35 0.38 0.4Pinch1 3 3 3 3 3 3 3 3Pinch2 1 1 1 1 1 1 1 1t 50% 50% 50% 50% 50% 50% 50% 50%m 1 1 1 1 1 1 1 1m 1 1 1 1 1 1 1 1mf 0.003936 0.01319 0.0237 0.04673 0.07726 0.09425 0.1147 0.126
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Fig. 7 Variation of Yield with compression pressure
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Claude cycle (Case-1) (At 10 bar)
300 K 127.12 K103.93 Kx=0.2372
103.93 Kx=0.3230
105.34 K297 K
78.44 K90.45 K 102.93 K186 kW 14 kW 1.4kW
Kapitza cycle (Case-2) (At 10 bar)
300 K127.09 K 103.93 K
x=0.2355300 K
297 K 88 97
0 355
105.35 K 88.97
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Animated Process Flow Diagram
Compressor
HX-
2b
HX-
2a
HX-
1 JTValve
Turboexpander
Phase separator
Fig. 8
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8 bar310 K
1.1 bar300 K 7 95 bar
7.9 bar100 2 K
7.9 bar100 2 K
HX-
2b
HX-
2a
HX-
1
4g
9
C
Mixer-2
JTValve
310 K300 K 7.95 bar 100.2 K
Make Up
12
8
3
p 7
4
100.2 K
1.15 bar1.15 bar1.1 bar 1.2 bar
1.3 bar
1.2 bar78.8 K
1.2 bar78.8 K
Mixer-1UpFluid
5
5g
TurboexpanderLiquid
1.2 bar78.8 K
6
5f
Phase separator
Fig. 9 Process Diagram of Nitrogen Liquefier
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Fig. 10 T-S Diagram of Nitrogen Liquefier
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Parameters and Variables
Parameters
Eff ti f h t h 1 1Effectiveness of heat exchanger 1,1
Pinch point for heat exchanger 2, p
Efficiency of turbo expander,Efficiency of turbo expander,
Mass flow ratio diverted through Turbo expander,
Initial Values
Yield, y
Enthalpy of cold fluid at outlet of HX1,h9
Unknown Variables:
hp,h3, h4, h5, h6, h6s, h7, h8, h9, x5, y p 3 4 5 6 6s 7 8 9 5 y
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i. Pinch point specification of Heat exchanger-2
Splitting the HX2 into two parts, First heat exchanger being the one where the hot
nitrogen gas is cooled up to the saturation temperature of 100.13 K & the second part
being the condensing part. The minimum temperature difference occurs at the point
where the condensation begins and is called as pinch point.
For the specified pinch value p, for HX2, we have
TT 4g3
pTT g4p =
We can get enthalpy hp, at that pinch
Pinch, p
pera
ture
g
4g
7
8
p
temperature and pressure
DistanceTe
m
7
Fig. 11
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ii. HX1 and HX2a
Assume'219 hh = ( )18219 1h'hh +=Q
From HX1 and HX2a Energy balance
1y)](1h)(1h)(1h)y)(1(1[h
h p4g29+
=1. y)])(1[(h8
=
)]hh)(y1()1(h[ p8g4 +2. )1(
)])(y()([h p8g43
=
3. 81219 h)1('hh +=
Fig. 12
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iii. Turbo-expander
From the figure,From Allprops, find s3, at h3 and p3.3 6s is the isentropic expansion3-6s is the isentropic expansion3-6 is the actual expansions6 > s6sg, the hot gas is not wet at the end of expansion
3s6 ss =The enthalpy at the end of expansion is found out as
h6 b t f 6 d 6 tur
e, T
h6s can be get from p6s and s6s.
Tem
pera
t
( ))hh(
hh
s63
63
=
)hh(hh s6336 =
Entropy,s
Fig. 13
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iv. Mixer-2
]h)y1(h[h g567
+=
Applying energy balance equation for the mixer, enthalpy at outlet of mixer is
6 1.3 bar 1.2 bar 7)y1(
h7 1.3 bar
1.2 bar78.8 K 5g
Enthalpy at outlet of hot fluid is found out by energy balance between hot and cold fluids as
v .Heat Exchanger 2 Fig. 14
hot and cold fluids as
)1()]hh)(y1()1(h[h 7834
=
)1(
Fig. 15
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vi. JT valve
45 hh =
Throttling is an isenthalpic expansion process. Equating the enthalpies before and after throttling
7.9 bar100.13 K4
45 hh =
)hh()hh(x f555
=
1.2 bar78.8 K
5
)hh( f5g5
vii. Yield
Th li id i ld bt i d k f i th h th th ttli l
Fig. 16
The liquid yield obtained per kg of gas passing through the throttling valve Is (1-x5), Here (1-) kg of gas passing through the throttling valve is
)x1)(1(y 5=
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Fig. 17 Snapshot of the process design Program
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3:Inlet to turboexpander and HX-2
3-6: Expansion in turbine
3-4: High pr. Stream in HX-2
1
92 4-5: Expansion in JT valve
7(5g+6) -8: Low pr. Stream in HX-2
P: Pinch point temp. (100.13-99.13)
4g
3
4 8
T-S Diagram5g
5 76
P
T S DiagramFig. 18
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Parametric Study
Yield increases with increase inmass fraction through theturboexpander.
After a maximum mass fractionthrough the turboexpander, yieldstarts decreasing.g
The maximum mass fractiondecreases with increase in thepressure of compression
Fig. 19 Effect of Variation of mass fraction through
Turboexpander
pressure of compression.
Turboexpander
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Parametric Study
Yield increases with increase inthe effectiveness of the HX-1.
A i i ff ti i A minimum effectiveness ispresent after which the yieldbecomes zero.
Requirement of higheffectiveness increases withincrease in compression
Fig. 20 Effect of Variation of
pressure
Fig. 20 Effect of Variation of effectiveness 1 of HX-1
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Parametric Study
Yield decreases with increasein the pinch point of the HX-2.
The rate of decrease in yield isless with pinch point of HX-2p p
yield increases with increase incompression pressure
Fig. 21 Effect of Variation of pinch point of second heat exchangerpoint of second heat exchanger
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Parametric Study
Yield increases with increase inthe efficiency of theturboexpander.
yield increases with increase inycompression pressure.
Fig. 22 Effect of Variation of turbo expander efficiency turbo expander efficiency
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M j C t f Li fi 3. Major Components of Liquefier
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Major Components Of The Liquefier
i. Compressor
ii. Cold Boxii. Cold Box
iii. Heat Exchangers
iv. Turboexpanderiv. Turboexpander
v. JT Valve
vi Liquid nitrogen Separator along with vi. Liquid nitrogen Separator along with transfer line
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i. Compressor
Screw oil flooded,compressor : 340
3/h 11 bnm3/hr, 11 bar(Kaeser make)
This compressor isThis compressor isavailable in ourlaboratory with oil filter,pressure controller andppipe layout.
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ii Cold Boxii. Cold Box
It is a double walled 750di 1800mm dia x 1800 mm
height cylinder.
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4. Design Plate Fin Heat Exchanger
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Basic Components of a Plate Fin Heat Exchanger
Parts of plate fin heat exchanger
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Cross Flow and Counter Flow
Types of flow in a Heat exchanger
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FIN TYPES
Fig. 25 Different types of fin
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Advantages of Offset Strip Fins Plate Fin Heat Exchanger
Large heat transfer area per unit volume
Flow area goodness factor: Ratio of the Colburn factor tofriction factor for the given surface is higher for the OSF asfriction factor for the given surface is higher for the OSF ascompared to other fins.
High effectiveness: very close temperature approachesHigh effectiveness: very close temperature approachesbetween streams.
Significant reductions in size, weight.
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Thermal input data for HX-1
Thermal data of process stream Nitrogen
Hot FluidInlet temperature 310 K
Outlet temperature 120 45 K
Cold Fluid
Inlet temperature 100.74 K
Outlet temperature 305 8 KOutlet temperature 120.45 K
Mass flow rate 82.22 g/sec
Pressure at inlet 8 bar
Allowable pressure drop 0 05 bar
Outlet temperature 305.8 K
Mass flow rate 78.68 g/sec
Pressure at inlet 1.15 bar
Allowable pressure drop 0.05 barAllowable pressure drop 0.05 bar Allowable pressure drop 0.05 bar
All properties like density , enthalpy, specific heat, viscosity, prandtlnumber are determined at mean temperature and pressure.number are determined at mean temperature and pressure.
Effectiveness , UA , heat load are also calculated from the above inletand exit conditions.
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INPUT :
1 Fin frequency f1. Fin frequency, f
2. Fin thickness, t
3. Fin length, lf
4. Fin height, hg
5. Plate thickness, p
Basic dimensions of fin used in the heat exchangerBasic dimensions of fin used in the heat exchanger
HX-1 Fin Specification Hot and Cold Side
Fin frequency 714 fins/mFin metal thickness 0.2 mmFin length 1.5 mmFin height 6.3 mmSeparating plate thickness 0 8 mmSeparating plate thickness 0.8 mm
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l
CALCULATION :
Fi P t
1. Fin spacing,
2. Plate spacing, b=h+t
ffts )( = 1
Fin Parameters
S- fin spacingH- fin heightT- fin thicknessl- strip length
2. Plate spacing, b h t
3. Free flow area per fin,
4 F t l fi
htsaff )( =
))(( thtGeometry of a typical offset strip fin surface
l strip length4. Frontal area per fin,
5. Heat transfer area,
))(( thtsafr ++=
slhthlas 222 ++=
6. Fin area,
7. Equivalent diameter,
hthlaf 22 +=
slhthlhltsDe ++
=
=
)(area transferheattotal
lengthareaflow free total 24
8. Ratio of fin area with total surface area,
9. Frontal area ratio,s
f
aa
=
ff
aa
=fra
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10.Dimensionless parameters for the finhsh
=
sl
=
t
Assume width of heat exchanger, W and No. of layers in hot and cold side, nh and nc.
st
=
11.Total area between plates,
12.Total free flow area,
WnbAfr =
fff AA = 12.Total free flow area, frff AA =
13.Core mass velocity,ffAmG =
GD14.Reynolds number,
15.Critical Reynolds number
eGD=Re
217043312170581568 ... )()()(.*Re = jj19601006023648 ... )()()(.*Re = f
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Maiti Correlations for offset serrated fins
For Re>Re*,005018402880420180 )()()((R ) j
0230185022102860320 .... )()()((Re). = f
F R R *
005018402880420180 .... )()()((Re).= j
06302702750510360 .... )()()((Re). = j
104018101960700
For Re
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Manglik and Bergles Correlations for OSF fins
0678.01499.01541.05403.0Re6522.0 = j
[ ] 1.0055.1546.0504.0340.15 Re10269.51 + 2659.03053.01856.07422.0Re6243.9 =f
[ ] 1.0236.0767.3920.0429.48 Re10669.71
+
f
Where
hs
=
lt
=l
st
=
shlD 2( ) tsslhthlDe +++= 2
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Joshi and Webb Correlations for OSF fins
For Re
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17.Convective heat transfer coefficient, 6670.(Pr))( cjGh =
18.Fin parameter,
19.Fin effectiveness,
)*()*(tKhM
f
c2=
tanh( )f
Ml =19.Fin effectiveness,
20.Surface effectiveness,
21 O ll h t t f ffi i t
( )f Ml =
)()( fo
fo A
A = 11
h )/A(ApA1121.Overall heat transfer coefficient,
22.The ratio of total heat transfer surface area
coc
ohoc
WW
o
hoho h)/A(A
AKpA
hU++=
11
* tNf1to the separating surface area (wall area) ,
23.Heat transfer area may now be calculated as )/(
*/of
wo AAtNfAA
=1
1
UoUoAoAo =
24.The required length of the heat exchanger is calculated from the equivalent diameter definition, as
AffAoDeL
**
4=
2
25.The pressure dropbDe
fLGp2
2=
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Effect of longitudinal heat conduction
1. Frontal area of fin, HWAfrt *=
2. Free flow area for hot fluid Affh
3. Free flow area for cold fluid, Affc
4. Wall conduction area,
5 Conductivity of fin K
frcfrhfrtw AAAA =
5. Conductivity of fin, Kw
6. N.T.U required
==
11
11 .ln
)(.. R
R
CC
UTN
7. Assuming a Factor of safety = F.S
8. N.T.U (considering longitudinal heat conduction), SFUTNUTN lc .)..()..( =
9. UA considering longitudinal conduction min*)..()( CUTNUA lclc =
-
10.Area considering longitudinal conduction,UUAA lc)(=
AD 11.Length of the heat exchanger (considering longitudinal heat conduction)
12.Wall conduction parameter,ff
oe
AADL
=4
minLCAwKw=
13.Dimensionless parameters,
14.-
CrUTNy *..*=
))(()(yCr
Cr+
=
111
15.-
))(( yCr +11
+
++=
yyyy
)()()/(( /
11
11 21
16.-
17
)()(
+
=11
UTNCr r1 ..*)(17. -
18. Ineffectiveness
CrNTUr r
+=
11)(
CrrCr
=)exp(
)()(1
11
19.Effectiveness
)( 1
)]([ = 11
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Dimensions of the HX-1
D k M lik J hi & Deepak Manglik Joshi & Webb
Core length 2002 1888 2277
Core width 180 180 180
Core Height 165 165 165Core Height 165 165 165
Number of layers in hot side 10 10 10
Number of layers in cold side 9 9 9
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2D Drawing views & Photograph of HX-1
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Thermal input data for HX-2
Cold fluidHot fluid Cold fluid
Inlet temperature 91.38 K
Outlet temperature 100.81K
Mass flow rate 78 68 g/sec
Inlet temperature 120.45 KOutlet temperature 100.2 K,
x= 0.064M fl / Mass flow rate 78.68 g/sec
Pressure at inlet 1.2 bar
Allowable pressure drop 0.05 bar
Mass flow rate 4.9 g/sec
Pressure at inlet 7.95 barAllowable pressure drop 0.05 bar
HX-2 fin specificationFin Density 714 & 500 Fins/mPlate spacing 6.5 mmPlate spacing 6.5 mmFin length 10 mm
Separating platethickness
0.8 mmthicknessFin metal thickness 0.2 mm
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2D Drawing views & Photograph of HX-2
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5. Design Turboexpander
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1. A turboexpander, is a centrifugal or axial flow turbine through
which a high pressure gas is expanded to produce work that is
often used to drive a brake compressor.
2 T d i h b d fi d f2. To design the turboexpander a fixed state of process stream
parameters or design point is required. So the design point is
fixed as per the process design done previouslyfixed as per the process design, done previously.
Working Fluid Nitrogen
The design points are as follows
Turbine inlet temperature, Tin 124 K
Turbine inlet pressure, Pin 7.97 bar
Discharge pressure, Pex 1.2 bar
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Mass flow rate, m 76.46 g/s
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Major Parts Of Turboexpander
Turbine Wheel
Brake Compressor
Shaft
Aerostatic Thrust BearingAerostatic Thrust Bearing
Tilting Pad Bearing
Nozzle
Diffuser
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Brake compressorBrake compressor
Shaft
Turbine Wheel
Shaft with brake compressor and Turbine wheel
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Turboexpander Assembly
Brake compressor
Turbine wheel
DiffuserBrake nozzleshaft
Nozzle
Tilting Pad Bearing
Aerostatic thrust Bearingg
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Turboexpander Assembly Animation
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Design Of Turbine Wheel
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ns ds diagram show the maximum obtainable efficiency and theoptimum design geometry as function of diameter and speed of thep g g y pturbine.
d s
ns
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ns ds diagram for radial inflow turbiness
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Specific speed and specific diameter of the turbine wheel are calculated by 3Qby
4/33
3
)( sins h
Q
=
4/132 )( hDd sin
(1)
(2)3
32 )(Q
d sins =
WhereexQkQ *13 =
(2)
(3)exQQ 13
)()( 023 exsinsin hhkh = (4)
To achieve the maximum possible efficiency, within the subsoniczone, the value of specific speed and specific diameter selectedfrom the n d diagram of Baljefrom the ns ds diagram of Balje.
ns= 0.5471and ds = 3.4728
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Ratio of eye tip diameter to turbine inlet diameter,tipD (5)2
0.6tipDD
= =
Ratio of eye hub to eye tip diameter ,
(5)
0.425hubtip
DD
= =
Power produced
(6)
0( ) 2.8523in exP m h h= =
Power produced,
(7)kW
Number of blades=10
Thickness of blades= 0.6 mm
Blade height at inlet,.
2 ( )t rmb
D Z t C= (8)
2 2 2( )t r t r mD Z t C ( )
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Dimensions of the Turbine wheel
O t di t f th t bi 29 6Outer diameter of the turbine : 29.6 mm
Speed of the turbine : 1,38,778 rpm
Eye tip diameter : 17.8 mm
Eye hub diameter : 8.9 mm
Number of blades : 10
Thickness of blades : 0.6 mm
Height of blade at turbine inlet : 0.7 mm
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Velocity Triangle
Inlet to Turbine (m/s) Exit to Turbine (m/s)
C2 187.38 C3 110.31
W2 94 48 W3 152 97W2 94.48 W3 152.97
U2 215.11 U3 96.8
2 60.38o 3 45.92o
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2 26o 3 95o
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Determination Of Blade Profile
The blade profile determined by Haselgrubbers method assumingThe blade profile determined by Haselgrubber s method assuming
pressure balanced flow path.
This technique gives three dimensional contours of the blades andThis technique gives three dimensional contours of the blades and
simultaneously determine the velocity, pressure and temperature
fil i th t bi h lprofile in the turbine wheel.
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Design of Brake compressor
Input parameters:
Process gas : Air/Nitrogen
Power to be dissipated : 2.85 kWPower to be dissipated : 2.85 kW
Angular speed : 14534.67 rad/s (1, 38,777 rpm)
Inlet total pressure : 4.1 barp
Inlet total temperature : 300 K
Expected efficiency : 60%
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Specific speed and Specific diameter are given by
,
4/31
ss h
Q
=
p p p g y
(9)
1
4/12
QhDd ss
= (10)
951= 92=d
to achieve the subsonic operation within the constraints of available power and rotational speed,
and (11)95.1=s 9.2=sdand28524/)( 22
211
22 === DQUmP sfbsf W
(11)
(12)
i t f t 1 02 power input factor 1.02 = =Slip factor 0.9sf = =
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Dimensions of Brake Compressor
Di t t i l t 15Diameter at inlet : 15 mm
Diameter at outlet : 33.7 mm
Blade height at inlet : 3 mm
Number of blades : 12
Thickness of blades : 0.75 mm
Power to be dissipated : 2.85 KWPower to be dissipated : 2.85 KW
Angular speed : 14534 rad/sec
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Dimensions of Nozzle
Wt = Throat widthtDt = Throat diameter
Dn = Nozzle diameter
D2 = Turbine inlet diameter
Cn = Chord length
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Width at throat 84.1== trtmw mm (13)Width at throat, 84.1
tttnt CbZw
Throat angle, 01 06.29tan =
= mtt C
C
( 3)
(14)g ,
t
t C
Blade pitch length, 79.3== ntn ZDp mm (15)
Inner diameter of nozzle ring,829222 =+= CosDwwDD mm (16)8.292 =+= tttttin CosDwwDD
Chord length of the nozzle is given by
2 S
mm (16)
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4.4sin
2cot1
22
=
++
=
sz
nuSuCh
mm (17)
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Design of Diffuser
1 Kinetic energy at the rotor outlet should be recovered using a1. Kinetic energy at the rotor outlet should be recovered using a
diffuser.
2. The best suited diffusing angle which minimizes the loss ing g
pressure recovery is 5o-6o
20.0148 0 00087exQ
A (18)20.00087 m17
exex
ex
QA
C= = =
The exit diameter is found out to be 33.3 mm
(18)
Assuming radial clearance 0.1 mm
The inlet diameter is 29.8mm
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The length of the diffuser is 87.4 mm
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Design Of Shaft
We have chosen the diameter of the shaft and checked for maximum
stress and critical speed .
Di t f th h ft 16Diameter of the shaft = 16 mm
The length of the shaft and dimension of the collar depends upon the
dimensions of the bearings.
Length of the shaft = 108 1 mmLength of the shaft 108.1 mm
Diameter of the collar = 44 mm
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P i h l d t th ti f th ll
Check for maximum stress:
Peripheral speed at the tip of the collar(14534.67 0.036)
2 116.272surf
V d = = =1
(19)m/s
Stress at the root of the collar, MPaVsurf 23022531 2
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Gas Lubricated Bearings
Advantages of gas bearings1. Clean operation
2. Lower viscosity provides low friction,resulting in lower heat
generation.
3. Gases are chemically stable over a much wider range of
t t
Disadvantages of gas bearingstemperatures
1. Lower load carrying capacity.
2. Suffer from problem of instability.
3 Demand high mechanical precision
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3. Demand high mechanical precision.
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Gas Lubricated Bearings
Two types of bearings used for the turboexpandert
A. Thrust Bearingsi Aerostatic Thrust Bearing
rotor
i. Aerostatic Thrust Bearing
ii. Aerodynamic thrust bearing
iii. Thrust Foil Bearing
i. Rubber stabilized Aerostatic Journal Bearing
B. Journal Bearingsust o ea g
ii. Pivot less Tilting Pad Journal Bearing
iii. Aerodynamic Journal bearing
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iv. Journal Air Foil Bearing
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Aerostatic Thrust Bearings
A double or combined thrustbearing consists of a pair of thrustplates, with the shaft collar inbetween, forming the bearingsurfaces.
Neutral Load on
Upper Thrust Plate
Thrust Collar
Lower Thrust PlateShaft
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W
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Aerodynamic Thrust Bearings
It has shallow angled groovescut in one of the bearingcut in one of the bearingsurfaces.
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Thrust Foil Bearings
T F il
Bump FoilBump foil Gas bearings consist of three parts: Top Foilparts:
a. top foil b. bump foil structure c. the bearing housing
Advantages:1 Self-acting
Bearing Housing
1. Self-acting.
2. Rotor dynamically stable.
3. Accommodate thermal growth.
4. Accommodate Misalignment.
5. High ability to damp.
66. Better wear resistant.
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Rubber Stabilized Aerostatic Journal Bearings
Rubber Stabilised Aerostatic Journal Bearings consists of a plain aerostaticbearing mounted on a pair of rubber O-rings. The O-rings convert the rigidaerostatic bearing to a flexible one, so that enough damping is provided topass over the limiting speed of half speed whirl.
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pass over the limiting speed of half speed whirl.
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Pivot less Tilting Pad Journal Bearings
It consists of three pads floatingaround the journal, within the padaround the journal, within the padhousing, surrounded by gas filmson all sides.
Pad made of high density metal impregnated graphitePad made of high density metal impregnated graphite
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Aerodynamic Journal Bearings
In a herringbone grooved journalHerringbone grooved bearingbearing, the grooves are cut in the
form of two opposing helices
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Journal Air Foil Bearings
Top Foil As the shaft rotates a Top Foil
Bump Foil
aerodynamic pressure isgenerated between therotating shaft and the p
Gas Filmsmooth top foil due towedging.
A d i Bearing Block Aerodynamic pressuredetermines the loadcarrying capacity of shaftand it deforms the top foiland it deforms the top foiland bump foil to preventcontact between rotor andbearing, which results zerobearing, which results zerowear of the bearings.
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Modification in Turboexpander
Present Model Modified Model
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Supporting structures
The major supporting structure of the turboexpander areThe major supporting structure of the turboexpander are
A. Cold end casing
B. Bearing housingg g
C. Warm end housing
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Supporting structures
A C ld d i1. The cold end housing is the lower
t t hi h i bl t h ld th
A. Cold end casing
most part which is capable to hold the
Teflon insulation rings so that the heat
could not enter into itcould not enter into it.
2. It contains nozzle diffuser centrally.
3 It takes the process gas inside and3. It takes the process gas inside and
cooled gas comes out centrally from
the diffuser.
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Supporting structures
B. Bearing block
The bearing housing is the central
component providing support to the
t j l b i d th ttwo journal bearings and the two
thrust bearings.
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Supporting structures
C Warm end housing1. The warm end housing has a nozzle to
the brake compressor which is fitted
C. Warm end housing
p
above brake compressor by shrink fit
operation.
2. There is an inlet and exit tube through
which air is sucked in and compressed
air goes outair goes out.
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Fabricated of Turboexpander Parts
Turbine wheel Brake compressor
Shaft
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Shaft
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Tilting pad journal bearing Aerostatic thrust bearing Nozzle Diffuser
N lLock Nut (Compressor Side) Lock Nut (Turbine Side)
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Nozzle coverLock Nut (Compressor Side) Lock Nut (Turbine Side)
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Spacer Exhaust gas plate
B i bl k C
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Compressor end Bearing block Cold end housing
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Photograph of Turboexpander test setup
H.P. Pressure Vessel
Bearing supply gas
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Turbine inlet gas Turbine exit gas
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v. JT ValveJ a e
A Swagelok make fine needle valve is converted to act as a expansionJT valve.
It is connected with a long pipe so that it will be easier to operate theIt is connected with a long pipe, so that it will be easier to operate thevalve from the top of the cold box flange, while it will be quite belowinside the cold box.
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vi. Phase Separator
A 25 liter capacity phase separator has been designed andfabricated.
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3D model of Liquefier3D model of Liquefier
Liq. Nitrogen exit
Exit to the CompressorInlet to the HX1
Turboexpander
Inlet to the HX1
HX2
HX1
Cold Box
Phase separator
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