Transfer of Liquefied Natural Gas On Long Insulated Lines PDF
Transfer of Liquefied Natural Gas On Long Insulated Lines PDF
Transfer of Liquefied Natural Gas On Long Insulated Lines PDF
A. C H E R V I N S K Y and Y. M A N H E I M E R - T I M N A T
INCREASED ACTIVITY in the field of liquefied transfer of LNG in long vacuum insulated pipes, in order
natural gas (LNG) has given rise to feasibility studies on to explore the feasibility of the construction of LNG
transmission of natural gas in liquid rather than gaseous pipelines in Israel. The study is divided into the following
form. parts:
The major advantage of a LNG pipeline is the great
(a) Cool down period, in which liquefied gas is pumped
reduction in volume which enables the capacity of the
into the pipeline which is initially at some ambient
LNG pipeline to be three times that of the corresponding
gas phase line. 1 This fact together with the much lower temperature (for example, 27 C).
(b) Steady state operating period, in which the line is
friction of LNG per unit of throughput leads to the
operated at the design conditions and LNG is trans-
second advantage of LNG transmission; horsepower
ferred.
requirements for liquid lines are only one tenth of the
(c) Warm up period, which occurs when pumping of
corresponding gas phase lines.
the liquid stops and the stationary liquid in the pipe is
Studies of the technical aspects of LNG pipelines have
warmed up due to external heat leakages.
been carried out and have shown that these lines appear
to be feasible. 2,3 Most studies recommend the use of a 9~ The last section of the paper considers numerically a
nickel steel pipe covered with special insulating materials. particular pipeline showing the effect of different para-
It is however believed that better insulation and reduction meters.
of heat leakages in long pipes may be achieved by
vacuum insulation. Analysis
The advantages of LNG pipelines are offset to some (a) Cool down time and LNG requirements during cool
extent by the added cost of initially liquefying the gas and down period
maintaining it in the liquid phase. This requires a The initial operating period of any LNG pipeline is the
considerable expenditure for insulation and for com- cool down period in which liquefied gas is being pumped
pression and refrigeration stations along the pipeline. If, into the pipeline which is at some ambient temperature.
however, a vacuum insulated line is designed, the need Heat transfer from the pipe to the flowing liquid takes
for refrigeration stations may be eliminated by allowing place, resulting in the complete evaporation of the
controlled evaporation of LNG along the line. liquid. A decrease of the pipe temperature with time
Studies of the transfer of cryogenic liquids over short follows, giving rise to transient heat and mass transfer
and long distances have been reported? ,5,6 Most of them in the pipe. When the temperature of the pipe becomes
deal with the steady state and cool down periods of the equal to the saturation temperature of LNG, a steady
transmission of liquid hydrogen or nitrogen in pipes state is reached, in which the fluid flowing in the pipe is in
without considering the effect of primary evaporation of the liquid phase. Important parameters which must be
the liquid. determined are: the cool down time, meaning the time
The purpose of the present work is to analyse the elapsing before a steady state is reached, the rate of
liquid flow, and LNG requirements for cooling the system
The authors are with the Department of Aeronautical Engineer- down to the saturation temperature.
ing, Technion, Israel Institute of Technology, Haifa, Israel.
A.C. is at present with the Department of Aerospace and
Some theoretical and experimental work regarding the
Mechanical Sciences, Princeton University, Princeton, New transient operation of cryogenic liquid lines has been
Jersey. Received 6 November 1968. reported. Burke et al 4 measured temperatures, pressures
hz {pcf~ ~ 0"023
Outer insutoting '= LNO carrying
tube I tube c~oG × \--k--J: - (DG/kt:) °'z , . . (20)
O=5in.-- / 16
[111
~ 20
V)
/ /I (3
~72
P~=I arm
m = 3x106 [itres/day
/
" 15
pipe Length=lOSm
~, 70
t..
Q.
u
En
D= 20 in. L. D=5in.
~.
E
8 .C 6 ;\Q,~
D=10in. ~
I
2 I
I
10z 103 10'* 10 5 10s i i 1
Length of transfer [ine~ ff~ 0 1 2 3 /, 5 6 7 8 9 10 11 12 13
Q~ 42m5 g
hzTs x vol.
-
htTszr(D~
o
--D
~)L ~ -
0.002 L
=
5 1oo
0
100 200 300 400 'ks o"- '
~8009001( forx=105r~T Previous experimental and theoretical studies have shown
that the transfer of liquefied natural gas in long insulated
-04 pipelines is feasible. An analytical study of heat and mass
O
-0.8 x\ transfer during the cool down, steady state, and warm up
periods has been presented and discussed.
~ ~-1'2
The analysis enables one to calculate such parameters
~- -1" 6 as the cool down time of the pipeline, the amount of L N G
0 20 40 60 80 100 120 140 160 180 200 required for cooling, the pump discharge pressure, the
Figure 4. Temperature decay during cool down number of pumping stations along the line, and the time