Note: Descriptions are shown in the official language in which they were submitted.
8~,~
1 TEMPERATURE-CONT~OLLED TANK CONTAINER
Specification
A temperature-controlled tank container is known from
DE-A-2,917,35~, which has a tank mounted between two frame end
structures and composed of a cylindrical shell and two end
bottoms. The tank surface is surrounded on all sides by an in-
sulating jacket, on one end face of which two port-holes for
introducing and discharging a temperature control medium are
disposed one above the other. Division webs are provided be-
tween the tank surface and the insulating jacket for causing a
forced flow of the temperature control medlum along the tank
surface.
It is emphasized in the above document that the insulat-
ing jacket is disposed on the planar wall surfaces of a paral-
lelepiped-shaped container frame. Between these planar wall
surfaces and the cylindrical container, there exist large
triangular flow cross-sections so that a large portion of the
temperature control medium is permitted to flow without con-
tacting the container surface, all the more as through-holes
for the medium, that are formed in supporting walls disposed
transversally to the longitudinal tank axis, are provided at a
relatively large distance from the container surface.
Moreover, the space between the container surface and the
insulating jacket of the known tank container is partitioned
by division webs in such a way that the temperature control
medium flows substantially axially of the tank, so that a
laminar flow may occur over large distances. Depending on the
arrangement of the division webs, a flow path is formed which
amounts to no more two to four times the tank length. For
these reasons, the extent to which the temperature control
medium, that may serve either for cooling or heating the tank,
can be utilized is restricted. In addition, the disposition of
the insulating jacket on the planar surfaces of the container
frame requires considerable expense in terms of insulating and
covering material and is accompanied by a considerable in-
crease in the tare weight of the overall tank container.
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1 Finally, the known tank container requires a box-like con-
tainer framework; lacking this, the known design is un~uited.
DE-A-2,917,364 referred to above briefly mentiones an al-
ternative design in which helical division webs are provided
to partition the space between outer and inner shells to form
flow channels for a temperature control medium. The document
does not disclose, however, any details of the arrangement
required to achieve a forced flow of the temperature control
medium along a closed path from the inlet port-hole to the
outlet port-hole.
Temperature-controlled tanks are required particularly
for shipping food. Such tanks are usually made of special
steel and are formed with walls that are as thin as possible
for economical reasons. Conventional tank containers of this
16 type therefore require reinforcing rings welded to the outer
tank surface to obtain the required strength of the tank body.
It is an object of the invention to devise a temperature-
controlled tank container which does not require a complete
container framework, which - while having a simple structure
and minimum tare weight - permits uniform contact of the tank
surface by the temperature control medium flowing around it
with good utilization of the temperature difference, and which
has sufficient strength even at reduced thickness of the tank
shell material.
To meet this object, an even number of division webs are
substantially equi-angularly distributed round the tank cir-
cumference and form a continuous circulation channel from the
input port-hole to the outlet port-hole. At the same time~ the
division webs are formed as section bars to reinforce the tank
shell and thus replace the otherwise required reinforcing
rings.
The -temperature control medium is passed as a layer of
uniform thickness of only a few centimeters in practice along
a helical path about the cylinder circumference in intimate
contact with the tank surface, and that at least once in
either direction. The uniform and small spacing of the insu-
lating jacket from the tank shell co-operates with the helical
shape of the flow path to achieve a continuous rotation of the
2 ~
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1 temperature control medium, so that the entire flow volume is
utili~ed for extensive heat exchange on the tank surface.
Due to the fact that the tank is closely enveloped, a
comparatively small amount of insulating and covering material
is required for the insulating jacket, and the tare weight of
the tank container is minimized. The helically extending di-
vision webs are easily mounted, and they result in a more
stable support for the insulating jacket than the conventional
rings which extend circumferentially, because the former pro-
vide load transfer points at locations which change continual-
ly in the axial direction
In contrast to the prior-art tank container referred to
above, the invention does not require a closed box-like con-
tainer framework. Rather, the s~ructure of the present inven-
tion is suited for tank containers in which the frame is re-
duced to just two end structures which are joined to the
bottoms of a self-contained tank.
It is known from DE-U-1,851,590 for a double walled stor-
age tank to use helically disposed wires so as to keep por-
tions of an outer shell i.n spaced relationship from an inner
shell. Apart from the fact that the outer and inner shells of
; the known tank are only partially spaced from each other, the
wires used therein are neither intended nor suited to form
continuous and mutually spaced passageways for the flow of a
temperature control medium. In addition to this difference,
the division webs of the present invention, by virtue of being
formed as section bars, increase the compressive strength of
the cylindrical tank shell similar to conventional circular
reinforcing rings.
Another tank is known from US-A-3,335,904, wherein a fil-
ler material of relatively low structural strength and a heli-
cal reinforcing rib are disposed between an inner skin and an
outer skin of the tank shell. This known container, however,
is made of glass fibre reinforced plastics, the space between
; 35 the outer and inner skins of the tank shell is completely
filled, and the reinforcing rib does not serve to provide
channels for flowing a temperature control medium.
Similarly, US-A-4,548,335 discloses a liquid gas con-
, r;
tainer were the space between an outer vessel and an inner
vessel is filled with insulating material. A tube which is
helically disposed within the insulating material serves to
discharge liquid gas and is arranged immediately adjacent the
outer vessel to increase the heat transfer for conversion of
the liquid to the vapour phase. Again, the helical structure
does not serve to partition the space between the outer and
inner vessels to form flow channels for a temperature control
medium.
In accordance with one aspect of the invention there is
prcvided a temperature-controlled tank container comprising: a
tank having a jacket formed of a cylindrical shell and a pair
; of end bottoms, an insulating jacket surrounding the tank on
all sides, two openings for introducing and is charging a
15 temperature control medium being formed above one another in
one end face of the insulating jacket, and at least two
separating webs disposed between the tank jacket and the
insulating jacket and helically surrounding the shell of the
tank jacket for enforcing a flow of the temperature control
20 medium round the tank jacket, such that: the separating webs
are formed of section bars reinforcing the tank jacket in a
self-supporting manner, the tank is connected to end frames
via end rings fitted to the tank bottoms, at the said one end
face provided with the introducing and discharge openings, at
25 least some of said separating webs are joined tc the end ring,
with flow channels each formed between two separating webs
being connected to the openings via through-hol~s in the end
ring, and at the other end face, at least some of the
separating webs terminate at a distance from the end ring.
Preferred embodiments of the present invention will now
be described in detail with reference to the accompanying
drawings, in which
Fig. 1 is a schematic side view of the temperature-
controlled tank container,
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Fig. 2 is an end view of the kank container, wherein
the left half of Fig. 2 is an end view of the
tank container of Fig. 1 as viewed from the
left and the right half is an end view of as
viewed from the right,
Fig. 3A and 3B are schematic illustrations of the two end
faces of a different embodiment of the tank
container.
As shown in Figs. 1 and 2 the tank surface is composed of
a cylindrical shell 10 and bottoms 11, 12 attached at either
end thereof, said bottoms being respectively joined via end
rings 13 with diagonal braces 14 of frame end structures 15.
Such a purely endwise suspension of a cylindrical tank from
two end structures 15 is known from DE-C-3,212,696. In
Fig. 1, the end structures 15 are shown to be additionally
interconnected by lower longitudinal rails 16. The right-hand
tank bottom 12 as viewed in Fig. 1 is provided with a manhole
17 and a discharge fitting 18. Also, a filling connection 19
is illustrated near the left-hand (as viewed in Fig. 1) kank
bottom 11 in the vertex line of the cylindrical tank shell 10.
Two division webs 20, 21 extending along two helices
offset by 180 are placed about the cylindrical shell 10 of
the tank surface. It is assumed in Fig. 1 that each division
web 20, 21 surrounds the tank surface twice, all four corner
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points of said division webs being disposed - in the illustra-
tion of Fig. 1 - in a horizontal plane including the tank
axis. The two division webs 20, 21 may be rectangular-section
strips of, for instance, 8 mm x 30 mm which have their narrow
edge welded to the tank surface. They thus fulfil the function
of reinforcing ring normally provided on cylindrical tanks. In
order to avoid peak stresses at the end points of the division
webs 20, 21, the webs extend from pipe sections 22 each welded
to the tank surface with a closed circular seam.
The division webs 20, 21 keep an insulating jacket gener-
ally referenced 23 in spaced relationship from the tank sur-
; face. As indicated in the partially sectional view at the bot-
tom of Fig. l, the insulating jacket 23 is composed of an
inner skin 24, an outer skin 25 and an insulating material 26
sandwiched therebetween. In areas between the division webs
20, 21 the inner skin 24 of the insulating jacket 23 may be
; supported on the tank surface by additional spacer members in
the form of bead- or socket-like shaped portions 27.
Preferably, the insulating material 26 is formed large-
sized foamed polyurethane slabs which are pre-slotted on their
surfaces facing the inner skin 24 so that they can be given
the required cylindrical shape.
The insulating jacket 23 extends with the cylindrical
shape defined by the division webs 20, 21 along the entire
length of the tank container right to the end structures 15 to
terminate on flat or curved insulating plates 28 which are in-
serted in said end structures 15 and may have a design similar
to the insulating jacket 23. Thus the tank is insulated on all
sides.
As will be apparent from the left-hand part of the end
view of Fig. 2, the left-hand (as viewed in Fig. 1) bottom 11
of the tank is provided with the two openings 31, 32 for con-
nection to a supply system for the temperature control medium.
Such supply systems are common especially in container ships
where the temperature control medium is especially cooling air
which is available in large flow volumes at small pressure
differences. Similar supply systems are also provided in con-
tainer yards in ports.
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In such a cooling system the openings 31, 32 of the tank
container are also called "port-holes", the lower opening 31
forming an inlet port-hole and the upper opening 32 forming an
outlet port-hole. The flow of cooling medium is caused by an
overpressure existing at the inlet port-hole 31 and a corres-
ponding negative pressure existing at the outlet port-hole 32.
As will be further apparent from Figs. 1 and 2, the space
enclosed between the left-hand tank bottom 11, the insulating
jacket 23 and the end structure 15, which terminates in an in-
sulating plate 28, is divided both inside and outside of theend ring 13 by means of a division plate 33 extending in the
horizontal centre plane. The division plate 33 starts from the
two pipe sections 22 where the division webs 20, 21 terminate
on the two opposite sides of the tank surface. The end ring 13
is provided with through-holes 34 both above and beneath the
division plate 33. Corresponding through-holes may alterna-
tively or additionally be provided in the flanges of the dia-
gonal braces 14, which flanges extend in the longitudinal di-
rection of the tank. A further possible modification resides
in passing the cooling medium about the diagonal braces 14
provided a sufficient distance is maintained between said bra-
ces and the insulating plate 28 as well as betweem the braces
and the insulating jacket 23.
In this way a flow passageway for the temperature control
medium is defined which extends from the lower inlet port-hole
31 through the lower through-holes 34 in the end ring 13, one
of the two helical flow passageways defined between the two
division webs 20, 21 to the area of the right-hand tank bottom
12 (as viewed in Fig. 1), thence back through the other of the
two helical flow passageways and through the upper through-
holes 34 in the end ring 13 to the outlet port-hole 32. Since
the flow passageways between the two division webs 20, 21 have
a relatively small uniform height, the temperature control me-
dium flows around the entire tank surface in intimate contact
contact therewith. The helical design of the flow passageways
simultaneously causes continuous rotation of the temperature
control medium whereby the generation of a laminar flow, which
would be detrimental to heat transfer, is prevented.
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As will be apparent from Fig. 1 and 2, the end ring 13
which joins the right-hand tank bottom 12 to the ~nd structure
15, is continuous and is interrupted only in the vicinity of
the discharge fitting 18. The diagonal braces 14, which con-
nect this end ring 13 to the end structure 15, also are formedwith small through-holes. On the other hand, the two division
webs 20, 21 end at a distance from the end ring 13 so that
there is room for the passage of the temperature control me-
dium. In this embodiment the temperature control medium does
not flow across the portion of the tank bottom 12 disposed
inwardly of the end ring 13. Normally, -temperature control of
the inner portions of the tank bottoms 11, 12 need not be pro-
vided in view of the extensive flow of medium especially
around the entire cylindrical shell 10. If, however, tempera-
ture control for this portion is required, the division webs
20, 21 will be extended to the right-hand end ring 13, and the
latter of the corresponding diagonal braces 14 will be provi-
ded with through-holes 34 similar to those indicated in the
left-hand part of Fig. 1.
Whereas the embodiment illustrated in Fig. 1 is provided
with only two helical division webs 20, 21 offset by 180, it
is basically possible to provide four or a larger even number
of division webs which result in a correspondingly increased
number of helical flow passageways so that the entire flow
path for the temperature control medium along the tank surface
is extended.
Fig. 3A schematically shows the end face of a tank con-
tainer provided with the inlet and outlet port-holes 31, 32,
said tank container being provided with four helically dis-
posed division webs 35, 36, 37, 38. Fig. 3B shows the oppositeend face of the same tank container. Along the end face illus-
trated in Fig. 3A the division webs 35 to 38 extend right to
the end ring 13. Also, each of the two port-holes 31, 32 opens
into a communicatlng passageway 40 defined by two limiting
webs 39 extending at an acute angle, said communicating pas-
sageway 40 being in connection communicated via through-holes
in the end ring 13 with the respective flow passageway de-
fined between a pair of division webs 35, 36 and 37, 38, re-
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spectively. Outside the communicating passageways 40 the end
ring 13 is provided with further through-holes which communi-
cate the flow passageway defined between the division webs 36,
37 across the hemispherical portion of the bottom to the oppo-
site flow passageway defined between the division webs 35, 38.
At the other end face shown in Fig. 3B, the division webs 35,
i 37 extend right to the end ring 13 provided therein, while the
other two division webs 36, 38 terminate in spaced relation-
ship therefrom. With this embodiment the temperature control
medium flows from the intlet port-hole 31 along the path indi-
cated by the arrows A, B, C, D and E towards the outlet port-
hole 32, said path winding four times helically around the
tank.
