This document discusses gas liquefaction systems. It describes the basic components used in liquefaction cycles like compressors, heat exchangers, and expanders. It then explains several common liquefaction cycles in more detail, including the Linde-Hampson system, precooled Linde-Hampson system, Claude system, Kapitza system, and Collins system. Each system uses different arrangements of these components and thermodynamic processes to efficiently produce low temperatures needed for gas liquefaction. The document also discusses parameters used to evaluate and compare the performance of different liquefaction systems.

1. GAS LIQUEFACTION
SYSTEMS

2.  Basics of Refrigeration/Liquefaction
 Production of low temperatures
 Ideal thermodynamic cycle
 Various liquefaction cycles

3. Symbols used in Liquefaction Cycle Schematics
 Compressor
 A compressor increases the pressure of the gas. It interacts with
the surroundings in the following ways.
 QR – Heat of compression.
 WC – Work required for compression.

4.  Connecting Flow Lines
 The flow of liquid is assumed to be frictionless and there is no
pressure drop during this flow.
 The direction of the arrow indicates the flow direction.
 Liquid Container
 It is assumed that the container is perfectly insulated from the
surroundings.

5.  Expander
 The expansion is isentropic and during expansion it produces work
We.
 Heat Exchanger
 It can either be a two-fluid type or triple-fluid type depending upon the
number of inlets and outlets attached to the HX.

6. Methods of production of Low Temperature
 Large systems may be formed by combination of above two
methods
 To increase the capacity of the system or
 To reach very low temperatures.

7.  Arrangements like pre cooling, Joule – Thompson expansion,
expansion devices like reciprocating or turbo expanders may be
used in these systems

8. Refrigerator
 A refrigerator operates in a closed thermodynamic cycle.
 The rate of mass flow is same at any point inside the system.
 The heat is exchanged between the cold end and the object to be
cooled.
 This cold end heat exchanger can also be used to liquefy gases.

9. Liquefier
 A Liquefier often produces cold liquid, that is drawn off from the
system.
 For example, a nitrogen liquefier produces LN2.
 Since the mass is drawn out from Liquefied gas the system, it
operates in an open thermodynamic cycle.
 The mass deficit occurring due to loss of the working fluid is
replenished by a makeup Gas connection.

10. Refrigerator & Liquefier
 Systems can also be used to liquefy gas (liquefier) as well as to
cool the object (refrigerator).
 A cold heat exchanger is used to transfer cold from the liquid
container to the object to be Object cooled.

12. Joule Thompson Expansion
 From 1st Law of Thermodynamics
 The changes in Heat (Q ) and Work (W ) are net zero for this
expansion device.
 The changes in the velocities and datum levels are very small and
can be neglected.

13.  Mass flows are equal at inlet and outlet sections.
 Hence, a Joule – Thompson expansion is an isenthalpic
expansion.

14. Joule – Thompson Effect
 T – p plot for any gas at constant enthalpies are as shown.
 The constant enthalpy line shows a maxima at a
particular temperature.
 The line joining maximas divides the space into
Region-1 and Region-2.

15.  Consider gas at state A in the region-1 with pressure and
temperature .
 It is expanded from state A to state B at a constant enthalpy.
 This results in increase in temperature of the gas.

16.  Consider the gas sample at state C in region-2 with pressure and
temperature as shown.
 The gas is expanded from state C to state D at constant enthalpy.
 This decrease in pressure results in drop in temperature.

17.  The ratio is negative for A ---->B where as, it is positive for C --->D.
 This ratio is called as Joule –Thompson coefficient and
this effect is called as Joule – Thompson Effect (J – T).

18.  Mathematically,

19.  This dividing line is called as Inversion Curve.
 The temperature on the inversion curve at p = 0 is called as
Maximum Inversion Temperature, T inv.
 The initial state of the gas should be inside the region-2 or below
T inv to have a cooling effect.
 For an ideal gas
 It means that the ideal gas does not show any change in temperature
when it undergoes J – T expansion.

20. GAS LIQUEFACTION
SYSTEMS

21. Gas Liquefaction Systems
 Thermodynamically Ideal System
 Linde Hampson System
 Precooled Linde Hampson System
 Linde Dual Pressure System
 Claude System
 Kapitza System
 Heylandt System
 Collins System

22. Thermodynamic Ideal System
 The salient features of this system
 All the gas that is compressed, gets liquefied.
 All the processes are ideal in nature and there are no
irreversible pressure drops.
 Process of compression and expansion are isothermal and
isentropic respectively.

23.  The initial condition 1 of the gas determines the position of point f.

24.  It is an open thermodynamic system because the working fluid
flows across the system.
 Consider a control volume for this system as shown in the figure.
 1st Law of Thermodynamics is applied to analyze the system.
 The changes in the velocities and datum levels are assumed to be
negligible.
 Using 1st Law , we get

25.  The work We produced by the expander is negligible as compared to other
terms
 Rearranging the terms, we have
 The compression process is assumed to be isothermal.
 Hence, from the Second Law of Thermodynamics, we can write
 Also, the expansion process is an isentropic process.
Therefore s2=sf.
 By substitution,

26.  This work of compression is done on the system. Hence, the value is expressed as a
negative quantity.
 Work required per unit mass of the gas compressed is given by
 Since in an ideal system, mass of gas compressed is same as mass of gas liquefied,
m1=mf.
 Work required per unit mass of the gas liquefied is given by
 Work required per unit mass of the gas is dependent on the initial
condition of the gas.

31. GAS LIQUEFACTION PARAMETERS
 In the refrigeration systems, the Carnot COP is often used as a benchmark
to compare the Performances.
 On the similar lines, there is a need to compare different liquefaction
systems.
 In liquefaction systems, an ideal cycle is used as a benchmark to compare
the performances.
 Different ratios and functions are defined to give a qualitative and
quantitative information of different liquefaction systems.

32. Performance parameters

33. FUNDAMENTALS
SIGN CONVENTION
 The work done by the system is taken as positive.
 The heat transferred to the system is taken as positive.
PRESSURE MEASUREMENT
 Bar or Pascal is the S.I. unit. The conversion table is as follows.
Pressure
 1 Pa = 1 N/m²
 1 bar = 10^5 Pa
 1 atm = 1.01325 bar

34. LINDE-HAMPSON SYSTEM
 The salient features of this system are as follows.
 Linde – Hampson cycle consists of compressor,
heat exchanger and a J – T expansion device.
 Only a part of the gas that is compressed, gets liquefied.
 Being an open cycle, the mass deficit occurring is
replenished by a Makeup Gas connection.

35. LINDE-HAMPSON SYSTEM
• All the processes are assumed to be ideal in nature and there are
no irreversible pressure drops in the system.
• Compression process is isothermal while the J-T expansion is
isenthalpic.
• The system incorporates a two fluid exchanger which
is assumed to be 100 % effective.

36. LINDE-HAMPSON SYSTEM

37. LINDE-HAMPSON SYSTEM

38. LINDE-HAMPSON SYSTEM

41. LINDE-HAMPSON SYSTEM

42. LINDE-HAMPSON SYSTEM

43. LINDE-HAMPSON SYSTEM

44. LINDE-HAMPSON SYSTEM

45. LINDE-HAMPSON SYSTEM

46. LINDE-HAMPSON SYSTEM

48.  As the compression temperature decreases, the yield y increases for a Linde –
Hampson system.
 The method of cooling the gas after the compression or before the entrance to the
heat exchanger is called as precooling.
 The Linde – Hampson cycle with a precooling arrangement is called as Precooled
Linde – Hampson cycle.

58. CLAUDE SYSTEM

60.  In order to achieve a better performance and to approach ideality, the expansion process should
be a reversible process.
 A J – T expansion is an irreversible isenthalpic expansion and expansion using an expansion
engine is an reversible isentropic process.
 For any gas, an isentropic expansion results in lower temperature irrespective of its inversion
temperature (TINV).

66. KAPITZA SYSTEM

71. HEYLANDT SYSTEM

74. COLLINS SYSTEM

79. SIMON HELIUM LIQUEFACTION
 Process(1-2)
 Helium gas is introduced into heavy walled
container at pressure of 100 atm to 150 atm.
 Process (2-3)
 L-N2 is introduced into the enclosing bath.
 The process cools the container to L-N2
temperature (77 K)
 During this process the vacuum space is filled
with helium at atmospheric pressure to act as heat
transfer medium.

80.  At the completion of this process the space b/w the
two vessels is evacuated thereby thermally isolating
the inner vessel.
 The Helium inlet valve remains open during this
process and helium gas flows into the heavy
container to maintain a constant pressure.
 Process (3-4)
 Liquid hydrogen is introduced in the upper part of
the inner container.
 Inner container and contents are cooled to LH2
temperature (20.4 K)
 Process (4-5)
 Pressure above L H2 is reduced to 1.7 mm of Hg
,Liquid boils as the pressure is lowered until
hydrogen solidifies. ( 10 K)

81.  Process (5-6)
 Pressure of the gaseous Helium is reduced to
atmospheric pressure by allowing the helium to be
released to a gas holder external to the system.
 During this process Helium that finally remains in
the container does work against the helium gas that is
discharged.
 This discharged gas removes energy from the system
, there by lowering the temperature of the remaining
helium.
 At the end of this process the container is usually with
75 to 100 % of LHe

83. HEAT EXCHANGERS, COMPRESSORS & EXPANDERS

84. HEAT EXCHANGERS

92. COMPRESSORS

95. EXPANDERS