Improvements in the Process and Apparatus for the Self-intensive Refrigeration of Gases by Expansion and Counter-current Interchange.
Year: 1898

page_text: Date of Application, 1st
4000
Complete Specification Left, 2nd Jan., 1899-Accepted, 4th Mar., 1899
Date of Application,
Complete Specification Left, 2nd Jan., 1899-Accepted, 4th Mar.,
1899
PROVISIONAL SPECIFICATION.
Improvements in the Process and Apparatus for the Self-intensive
Refrigeration of Gases by Expansion and Counter-current
Interchange.
I, WILLIAM HAMPSON, M.A., Oxford, L.S.A., London, of 20, Gower Place,
London, W.C., and of Nannerch, Mold, North Wales, do hereby declare the nature
of this invention to be as follows:-
This is an invention for improvements in the details of the process for the self
intensive refrigeration of gases by expansion and counter-current interchange
year
1895.
which is described in my Patent No. 10165 dated 23 May in the
Firstly, in the arrangement and construction of the interchanger, whereby the
compressed gas is brought as nearly as possible to the lowest temperature of the
expanded gas, and the expanded gas as nearly as possible to the temperature at
which the compressed gas reaches the apparatus, it is desirable to realise as far
as possible the following conditions:--
The external surface of the interchanger is to be kept as small as possible, so as
to diminish the amount of surface by which external heat can pass inwards.
The surface of pipes, through which the interchange of temperatures takes
place is to be kept as large as possible, relatively to the rate at which the gas
passes, in order to make the interchange as complete as possible.
The thickness of such pipes is to be kept as small as possible, to facilitate the
passage of heat.
The amount of construction material exposed to low temperature is to be as
small as possible, that the gas may not have much material to cool down.
The returning expanded gas is to pass over the pipes containing the compressed
gas in as thin layers as possible, that it may all be closely exposed to the tempera-
ture of the compressed gas at every point. To realise these conditions, the com-
pressed gas is allowed to expand nearly to atmospheric pressure, the excess pres-
sure being only as much as will make it pass at the required speed through the
passages and over the coils, that is to say a pressure equal to a few inches of
water. This avoids the mass of material involved in the use of strong outer
coils enclosing the inner coils, and allows the walls of the interchanger to be
The interchanger is filled very full of
lightly made and to contain little mass.
the coils of pipe for the compressed gas, so that vertically the layers of pipe rest
on one another, requiring no structural material to support them, and horizontally
are very nearly in contact, so that a little material of small weight can keep them
in position. A convenient arrangement is to let the valve spindle run down the
centre of the interchanger, and to let the layers of coil wind alternately. inwards
5 from the outer boundary to the valve spindle and outwards from the valve spindle
to the outer boundary. To make the layers of expanded air as thin as possible
the turns of the spirals are horizontally at the smallest distance apart which will
allow sufficient open cross section area to let the expanded gas pass at the required
speed without having near the expansion point too much excess pressure above

page_text: The above arrangement of coils makes the external surface of the interchanger
as small as possible.
With coils arranged as above, nothing is required to hold them in position
vertically, and horizontally they are kept at the proper distances by a little light
wire, or a few drops of solder.
Secondly, for the efficient working of such apparatus, it is important to have the
circulating gas free from vapours which are condensible at too high a temperature,
as in the case of air from moisture and carbonic acid. If these impurities are
removed on the high pressure circuit by preliminary refrigerants, such as ice and
salt surrounding the coils, the purification is incomplete, and it involves additional
trouble. If it be done before compression, the purifier is bulky, and moisture
in small quantities is subsequently picked up from the lubricating water in the
pump. It is more effective and convenient to purify the gas after compression,
by letting it pass, on its way to the interchanger, through a cylinder strong enough
to resist the necessary pressure, which contains a suitable purifying material,
such as caustic potash.
A
Thirdly. To secure a vacuum vessel in position without having it made to
exact sizes, without risk of breaking, and without leakage, to compensate for the
deterioration of the vacuum with time, and by giving additional insulation to
enhance its efficiency in any case, it is attached in the following manner.
number, such as four, of concentric glass cylinders, with an internal space of
greater diameter than the external diameter of the vacuum vessel, rest upon a
ring of suitable material, such as vulcanite, which is held up towards the bottom
of the interchanger by small rods. The aperture in this ring is closed by a screwed
cap of similar material on which rests the bottom of the vacuum vessel. The joint
between the cap and the ring, that between the ring and the bottom of the con-
centric glass cylinders, and that between the top of the cylinders and the bottom
of the interchanger, are made good with suitable material, such as rubber or
leather, and there need be no tight fitting of the vacuum vessel itself, convection
currents being prevented by surrounding its upper part with compressible material
such as ironing baize. The air spaces between the concentric glass cylinders pro-
vide insulation in addition to that given by the vacuum vessel.
Fourthly. When the interchanger is used to liquefy the more permanent gases
without the concurrent use of a compressor, the gas having been previously com-
pressed into a cylinder, preliminary refrigeration by carbonic acid is employed.
The cold vapour of carbonic acid is introduced as directly as possible to that part
of the coils where the lowest temperature is to be obtained; from there it passes
over the coils, reducing them as nearly as possible to the temperature of solid
carbonic acid. The supply of carbonic acid vapour is then cut off. before the
compressed gas is allowed to expand from the coils, which coils, being already
cooled to this low temperature, cool the gas as it passes along them, and so cause
it to reach the expansion point at the lowest temperature obtainable from carbonic
acid gas, and from the first commencement of its expansion to expand from that
temperature.
Fifthly. To pass into the apparatus carbonic acid vapour approximately at the
temperature of solid carbonic acid without risk of blocking at the valve or its
approaches or further along its passages by deposit of solid carbonic acid, and to
make all the cold which is stored in the solid carbonic acid from the expanding
liquid available for cooling the coils with cold vapour, a compound valve is used
in which the nozzle where the liquid is released, and from which it escapes as
a stream of solid and vapour, is surrounded by vapour at a higher temperature,
the warmth of which tends to prevent the nozzle and its approaches from blocking
under excessive cold and to vaporise the snow like solid in the stream issuing from
the nozzle. The valves are so regulated that the stream of warmer vapour is
almost, but not quite sufficient to prevent any solid appearing during the opera-
tion. The stream of warmer vapour is supplied either by a pipe from the upper
end of a cylinder containing liquid carbonic acid, or by letting the stream of solid

page_text: and cold vapour induce, by ejector action, a stream of warmer vapour from the
escape by which the vapour which has already passed over the coils and been
warmed by them leaves the apparatus.
Improvements in the Process and Apparatus for the Self-intensive
Refrigeration of Gases by Expansion and Counter-current
Interchange.
I, WILLIAM HAMPSON, M.A., Oxford, L.S.A., London, formerly of 20, Gower
Place, London, W.C., now of 34, Alfred Place, W.C., and of Nannerch, Mold, North
Wales, do hereby declare the nature of this invention and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement:-
This is an invention for improvements in the details of the process for the self
intensive refrigeration of gases by expansion and counter-current interchange
which is described in my Patent No. 10165 dated 23rd May in the year 1895.
In that process I cause a current of compressed gas after passing through a long
pipe or pipes, and expanding to a lower pressure whereby it is cooled, to return
in its expanded state over the pipes through which it had passed in the compressed
state, from the point of expansion to the point of admission, in such a way as
to continually intensify the cooling produced by expansion. This process is
diagrammatically illustrated in Figure 1 on Sheet 1 of the drawings furnished
with this specification. In that Figure 1 is the pipe by which the compressed
gas enters the interchanger 2, 3, and along the continuation of which in the inter-
by the valve actuated by the hand wheel 5. The gas, cooled by expansion, passes
changer coils it passes to the expansion point 4, where its expansion is controlled
upwards through the interchanger over the coils down which the compressed gas
is passing, and thereby cools it before its expansion, so that when further cooled
by expansion it reaches a lower temperature than before, and by communicating
this lower temperature to the compressed gas in the interchanger coils, intensifies
the cooling produced by expansion till some of the gas collects as liquid in the
receiving chamber 6. The expanded gas after passing over the interchanger-coils,
escapes by the pipe 7.
The present invention relates to improvements in the details of the apparatus
for carrying out the process described above.
Firstly, in the arrangement and construction of the interchanger, whereby
the compressed gas is brought as nearly as possible to the lowest temperature of
the expanded gas, and the expanded gas as nearly as possible to the temperature
at which the compressed gas reaches the apparatus, it is desirable to realise as
far as possible the following conditions:-
The external surface of the interchanger is to be kept as small as possible, so
as to diminish the amount of surface by which external heat can pass inwards.
The surface of pipes, through which the interchange of temperatures takes
5 place is to be kept as large as possible, relatively to the rate at which the gas
passes, in order to make the interchange as complete as possible.
The thickness of such pipes is to be kept as small as possible, to facilitate the
passage of heat
The amount of construction material exposed to low temperature is to be as
O small as possible, that the gas may not have much material to cool down.

page_text: The returning expanded gas is to pass over the pipes containing the compressed
gas in as thin layers as possible, that it may all be closely exposed to the tempera-
ture of the compressed gas at every point.
To realise these conditions, the compressed gas is allowed to expand nearly to
atmospheric pressure, the excess pressure being only as much as will make it pass
at the required speed through the passages and over the coils, that is to say a
pressure equal to a few inches of water, or a few inches of mercury, according to
the rate of working and the position in the coil where the pressure is measured.
When the compressed gas is allowed to expand to some lower pressure which is
substantially higher than atmospheric as for example in working on a large scale
where thermo dynamic efficiency is of greater importance this expansion pressure
must also have in the expansion chamber as much excess pressure beyond the
exit pressure as will suffice to drive it over the coils of the interchanger.
The method of close coiling and relative reduction of the size of interchanger
enables me to obtain much greater efficiency than by the use of outer coils with
their greater total mass enclosing the inner coils, and allows the walls of the inter-
changer to contain comparatively little mass, and where the lower pressure, is
nearly atmospheric to be very lightly made and in either case to contain com-
paratively little heat to be removed and to expose comparatively little surface for
the ingress of external heat.
The interchanger is filled very full of the coils of interchanging pipe for the
passage downwards of the compressed gas, so that vertically the layers of pipe
rest on one another, requiring no structural material to support them, and hori-
zontally they are very nearly in contact, so that a little material of small weight
can keep them in position. A convenient arrangement is to let the valve spindle
run down the centre of the interchanger, and to let the layers of coil wind alter-
nately inwards from the outer boundary to the valve spindle and outwards from
the valve spindle to the outer boundary. To make the layers of expanded air as
thin as possible the turns of the spirals are horizontally at the smallest distanco
apart which will allow sufficient open cross sectional area to let the expanded gas
pass at the required speed without having near the expansion point too much excess
pressure above atmospheric or other higher expansion pressure.
Figures 2, 3 and 4 show this arrangement, Figure 2 being a part longitudinal
section of the interchanger and Figures 3 and 4 transverse sections on the lines 3-3
and 44 Figure 2. In this case two pipes ab coiled side by side are shown but
a single pipe or three or more may be used.
The length of the interchanger in the example in the drawing is 12 inches,
and its internal diameter 23, the diameter of the outer spindle is an inch and
the external diameter of the tubes about of an inch the spaces between them
being of an inch. If the spaces were much smaller it would in many cases
injuriously affect the flow of the gas whilst on the other hand they should never
exceed 10 of an inch and this is usually too large. Moreover each spiral is
shown at its inner and outer horizontal limits to be in actual contact with the
casing and core of the interchanger so that no more air can pass the outer and
inner limits than between the adjacent turns of the spiral.
The above arrangement of coils makes the external surface of the interchanger
as small as possible in a cylindrical form which in view of all circumstances I con-
sider to be the best although theoretically it should be spherical.
With coils arranged as above, nothing is required to hold them in position
vertically, and horizontally they are kept at the proper distances by a little light
wire or a few drops of solder.
Secondly, for the efficient working of such apparatus, it is important to have the
circulating gas free from vapours which are condensible at too high a temperature,
as in the case of air, from moisture and carbonic acid. If these impurities are
removed on the high pressure circuit by preliminary refrigerants, such as ice and
salt surrounding the coils, the purification is incomplete, and it involves additional
trouble. If it be done before compression only, the purifier, unless it be very bulky,

page_text: pump.
It
es not completely remove all traces of carbonic acid, and mo
antities is subsequently picked up from the lubricating water in the
more effective and convenient to purify the gas after compression, by letting
pass, on its way to the interchanger, through a cylinder strong enough to resist
e necessary pressure, which contains a suitable purifying material, such as caustic
otash or caustic soda, or other material suitable for the absorption of carbonic
cid and moisture. The charge of absorbent material in this high pressure purifier
an be made to last longer by combining with it an ordinary purifier on the low
ressure circuit.
Thirdly. To secure a vacuum vessel when a receiver of that kind is required,
n position without having it made to an exact size, without risk of breaking, and
ithout leakage; to compensate for the deterioration of the vacuum with time,
nd by giving additional insulation to enhance its efficiency in any case; it is
A number, such as three or four, of concentric
ttached in the following manner.
lass cylinders with an internal space of greater diameter than the external diameter
of the vacuum vessel, rest upon a ring of suitable material, such as vulcanite,
which is held up towards the bottom of the interchanger by small rods, or a frame
or clip, or other suitable arrangement. The aperture in this ring is closed by
screwed cap of similar or other suitable material on which rests, with suitable
insulation interposed, the bottom of the vacuum vessel. The joint between the
cap and the ring, that between the ring and the bottom of the concentric glass
cylinders, and that between the top of the cylinders and the bottom of the inter-
changer, are made good with suitable material such as rubber or leather and there
need be no tight fitting of the vacuum vessel itself, convection currents being
prevented by surrounding its upper part with compressible material such as iron-
ing baize. The air spaces between the concentric glass cylinders provide insula-
tion in addition to that given by the vacuum vessel.
A method of carrying out this arrangement is shewn in Figure 5; Sheet 3, where
a cast frame which
1 is the vacuum-vessel, 2 the supporting cap, 3 the ring,
holds the preceding parts up towards the interchanger, and 5, 6, 7, are rubber
joints. A joint may also be made above the glass cylinders, as at 8, so that in
case of accident to them, they can be dispensed with.
Fourthly, When the interchanger is used to liquefy the more permanent gases
without the concurrent use of a compressor, the gas having been previously com-
pressed into a cylinder, preliminary refrigeration by carbonic acid is employed.
The cold vapour of carbonic acid is introduced as directly as possible to that part
of the coils where the lowest temperature is to be obtained; from there it passes
over the rest of the coils, reducing them as nearly as possible to the temperature of
solid carbonic acid. The supply of carbonic acid vapour is then cut off before the
compressed gas is allowed to expand from the coils, which coils, being already
cooled to this low temperature, cool the gas as it passes along them, and so cause
it to reach the expansion point at the lowest temperature obtainable from carbonic
acid gas, and from the first commencement of its expansion to expand from that
temperature.
Fifthly. To pass into the apparatus carbonic acid vapour approximately at the
temperature of solid carbonic acid without risk of blocking at the valve or its
approaches or further along its passages by deposit of solid carbonic acid, and to
make all the cold which is stored in the solid carbonic acid from the expanding
liquid available for cooling the coils with cold vapour, a compound valve is used
in which the nozzle where the liquid is released, and from which it escapes as
a stream of solid and vapour, is surrounded by vapour at a higher temperature,
the warmth of which tends to prevent the nozzle and its approaches from blocking
is
under excessive cold and to vaporise the snow-like solid in the stream issuing from
the nozzle. The valves are so regulated that the stream of warmer vapour
5 almost, but not quite sufficient to prevent any solid appearing during the opera-
tion. The stream of warmer vapour is supplied either by a pipe from the upper
end of a cylinder containing liquid carbonic acid, or by letting the stream of solid

page_text: and cold vapour induce, by ejector action, a stream of warmer vapour from the
escape by which the vapour which has already passed over the coils and been
warmed by them leaves the apparatus. Or it is obvious that the warmer gas may
be supplied from a cylinder of compressed air, and this may conveniently be a
cylinder which having been previously emptied as far as is useful for liquefaction,
still contains enough air for use in the compound carbonic acid valve. Such a
compound valve is shewn in Figure 6, where 1 is the expansion point for the liquid
carbonic acid, 2 is the inlet of the warmer gas or vapour, and 3 is a separating
chamber with transparent glass sides, giving a view of the operation, and allowing
the cold vapour to filter itself free of the solid through the wire gauze and cloth
ring 4, and thence to pass onward along grooves 5, in the ring of the casing,
through the pipe 7, and down the hollow spindle 8, of the interchanger, or by some
other course, to the coils in the neighbourhood of the expansion point.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. An interchanger consisting of a tube or tubes coiled into spirals the con-
volutions of which are separated by very narrow spaces and with the coils lying onę
upon the other.
2. An interchanger in which the spaces between the tubes do not exceed a
tenth of an inch in width.
3. Interchangers substantially as described and illustrated in the drawings.
4. In self-intensive refrigerators purifying the gas after it has been compressed
by means of caustic potash or the like.
5. The method of supporting the vacuum vessel substantially as described and
illustrated in the drawings.
6. Passing cold carbonic acid vapour or the like onto the coils in the neighbour-
hood of the expansion point and from thence over the other parts of them before
beginning the expansion of the compressed gas from them.
7. The use of a compound valve for carbonic acid liquid and gas, whereby
blocking of passages and waste of the preliminary refrigerant, are prevented by
letting warmer gas or vapour pass over the parts liable to blocking, and mix with
the steam of solid and vapour, the solid being prevented by filtering material from
passing forward beyond a separating chamber.
8. The compound valve substantially as described and illustrated in the draw-
ings.
Dated this 20th day of December 1808