Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a heat exchager wherein a liquid,
in particular a suspension, is heated or cooled. More particularly, it re-
lates to such heat exchanger wherein such suspension is caused to flow
through a container in which has been placed a rotatably carried, largely
hDrizontal heat exch~nger unit consisting of a pipe set.
Heat exchange between tWD fluids, one of the~ being heated or va-
pourised and the other being cooled or condensed, usually takes place in sur-
face heat exchangers in which both fluids are caused to flow past a heat
transfer wall, which serves tWD purposes, namely the transfer of a heat flow
as a consequence of te~perature differences between the fluids, and preven~-
ing nixing of the fluids. In order to obtain efficient heat transfer between
a fluid in a surface heat exchanger and its heat transfer wall, a relative
velocity between wall and fluid is required. This is nornally acoomplished
by allowing the fluid to flow through sufficiently narrow closed flow ducts
which are confined by the heat transfer wall at least in part. If the fluid
is a suspension with a relatively high content of solid particles, it will
be viscous, and thus a high input pressure has to be produced by means of a
pump in order to transport the suspension through the flow passages will be-
oome blocked by the solid material found in suspension. Likewise there is a
risk that this material m~y, within a short time, form a deposit or coating
on the heat transfer wall, which is detrImental to heat flow.
It is well kncwn that a relative velocity of the suspension with
respect to the heat transfer w~ll may also be produced with the aid of a
drive to set the heat transfer wall in m~tion within a stationary or slowly
flowing suspension. In such case, a pump is not absolutely necessary to
transport the suspension through the heat transfer apparatus.
Swedish Patent No. 384 569 discloses a heat exchanger
fe~turing a rotatLng hating loop. This loop rotates in a container substan-
tially totally filled with the heat-receiving fluid. If this fluid is
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viscous, and if there are several layers of tubes in radial direction in the
rotating tube set, the tube set will also tend to impart a rotation to the
contents of the container. In tllis manner the relative velocity of the con-
tents and the tube set with reference to each other, which is necessary for
heat transfer, will be low.
An object then of one aspect of the present invention is to provide
a heat exchanger which is fitted with a rotating tube set wherein the rotation
of the contents of the container is substantially prevented, so that a high
relative velocity is obtair.ed even between a viscous suspension and the heat
transfer wall.
An object of another aspect of this inventlon is to provide such a
heat exchanger in which the heat transfer wall is essy to clean of deposits.
The heat exchanger of a broad aspect of this invention is based on
the principle of providing a central tube which is concentrically disposed
in relation to the rotational axis of the heat exchanger unit between the end
pieces amoung the heat exchanger tubes, the diameter of the central tube belng
not less than 40% of the largest distance between any two heat exchanger tubes,
measured at right angles to the rotational axis, and of assuring that at least
the lower edge of the outflow from that container in which the heat exchanger
unit has been placed is located at a level lower than the topmost part of the
central tube, so that the latter can be kept above the free liquid level ln
the container.
Thus by a broad aspect of this invention a heat exchanger is prov~ded
for the heating or cooling of a liquid, in particular a suspension having a
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high content of solid particles, comprising: a container, having an inlet
for the liquid positioned at one end of the container and an
outlet for the liquid at the opposite end of the con~ainer, at least one
substantially horizontal heat exchange unit being rotatably mounted in
the container and comprising two end chambers communicating through a plur-
ality of pipes arranged in a generally annular configuration, the container
having, below a horizontal plane through the rotational axis of the heat
exchange unit, a circular cylindrical shape to closely confor~ to the heat
exchange unit; means for feeding a heat exchange fluid thorugh the end
chambers and the plurallty of pipes; a central tube extending concentrically
in relation to the rotational axis between the end chambers and being closed-
off from them and from the container, the central tube having a diameter not
less than 40% of the greatest distance between any two pipes of the heat
exchange unit measured at right angles to the rotational axis; and the outlet
from the container having a lower edge at a level lower than the uppermost
portion above the free surface level of t~e liquid in the container.
By variants thereof, the inlet and the outlet are either at oppo-
site ends of the apparatus, or at opposite sides of the apparatus.
sy a variant thereof, the inlet to and the outlet from
the container are at opposite sides of the apparatus.
By another variant, the heat transfer fluid is conducted
in ana out through one and the same double jacketed hollow shaft
at one end of the container.
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By a further variation, the rotating unit has supporting plates
positioned at right angles to the rotatlonal axis and affixed thereto, the
supporting plates being adapted to support the heat transfer pipes and at
the same time guide the flow of the liquid or suspension present on the out-
side of the pipes substantially at right angles to the pipes, the supporting
bracing plates having an open portion adapted to allow flow in an axisl
direction.
By still another variation, the heat exchanger has a supporting
structure adapted to impart an inclination to the heat exchanger such that
its rotational axis i9 inclined at such an angle against the horizontal
plane that the fluid flowing through the container on the outside of the
heat exchange unit is adapted to reach substantially e~ually high up on the
ceDtral tube on the length thereof when the heat exchange unit is rotating.
In the accompanying drawings, - .
Fig. 1 illustrates the apparatus of one aspect of this invention
in the form of a schematic vertical section carried through the rotational
axis of the heat exchanger unit;
Figs. 2 and 3 show the same means, presented in a schematic verti-
cal section at right angles to the rotational axis alohg the lines indited
by II-II and III-III respectively in Fig. l;
Figs. 4 and 5 show the same section as Fig. 2, with the movement
of the suspension in the apparatus indicated in them; and
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Fig. 6 shows the apparatus of ~ig. 1, schematically viewed from
akove.
In these figures, 1 is the container through which the suspension
is caused to flow with inflow through the input 2 and wqthdrawal by the out-
put 3. me container may be open at the top or provided with cover 4. The
rotating heat exchanger unit is accomodated within the container, its shaft
S on the drive side being carried in the bearing 6 and sealed against the
container within the seal 7. On the opFosite side, the heat exchanger unit
has a aou~le jacXeted hollow s~l~ft 8, which is carried on the outside of the
container in the bearing 9 and which is sealed against the container within
~he seal 10. m e h~llcw .shaft terminates in a double stuffing kox 11, which
is connected to the input 12 and output 13 of the heat exchange.
This fluid may be, for
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instance, ccoling water, hot water or condensing steam.
me input 12 and output 13 c~icate by the hollow shaft 8 in
open connection each with one of the mutually separated divisions 14 and 15
in an end piece 16. On the drive side of the ap~aratus an e ~ivalent end
piece 17 is provided. mese end pieces are connected to an air-filled cen-
tral tube 18 disposea concentrically around the rotational axis. On the
outside of the central tube a plurality of pipe lines 19 are disposed be-
tween the end pieces 16 ~nd 17,which constitute opem ccnnections bet~en
the end pieces and the divisions 14, 15 and 20 separated in them by means of
partitions, and w~ich arrangement cQmpels any liquid introduced int~ the end
piece to flow through serics-connected pipe blmdles of pipe ]ines lg connec-
te~ in parallel. In the particular apparatus i5 s}x~wn in Fig. 2, one has
four such pipe bundles with 40 pipe lines each. Other numbers of pipe lines
and of pipe bundles may also be used. ~ provide bracing of the pipe ]ines
19 which constitute the heat transfer wall, and also to guide the flow course
within the apparatus, the apparatus includes hracing plat~s 21 affixed to
the central tube 18. m ese plates 21 have cut-outs so as to cause ~ch plate
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to brace or sup~rt part of the pi~)es 19 and at the same time to leave open
another part 22, through which th~ suspension may flow in an axial direction.
~y arranging the cut-outs 22 of different bracing plates to be contiguous
with different pipes 19, all these pipes can be braced. In one alternate
emkodiment, however, the cut-outs 22 may be omitted.
m e container 1 is cylindrical in its lower part with merely a
narrow gap bet~een the outermost of pipes 19 and the container wall~ Upward-
ly from the plane of the rotational axis the walls of the container are pre-
ferably vertical, so that the rotating part may be lifted out of the contain-
0 er if required.m e structure supporting the apparatus has not been depicted In
Figs. 1-6. It is of a conventional kind and it is so constructed that the
axis of the heat exchanger unit is horizontal or has an inclination so that
the end of the apparatus where the input of the suspension is located l~as a
higher elevation th~n the outflow end.
m e apparatus operates in a continuous steady state in one of tw~
alternative ways. According to one variant, the heat exchanger unit rotates
within the container in a direction such that the pipe lines move upwardly
on that side where the input 2 of the suspension is located. This is illus-
trated by Fig. 4. Since the output 3 of the suspensicn is located at anelevation lower than the input 2, partly due to its placement in the con-
tainer 1 and partly owing to the potential inclination of the apparatus with
refexence to the horizontal plane, the suspension will only partially fill
the container 1 and there will be a free suspension surface in the appara-
tus. This free suspension level will, as a result of the rotation of the
heat exch3nger unit adjust itself at a higher level 23 on the suspension in-
put side fr~m ~he central tube 18 com~ared wi-th the level 24 on the opposite
side. This difference in level pr~duces a flow of suspension at right angles
to the pipes 19 and to their ~;rection of motion. The flow in axial direc-
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tion ix adjust~l by ~nc ms o~ the (-llt-outs 22 in the bracing plates 21, and
the susp~nsion is witl~rawn, for instance, by free overflow through the out-
put 3 at the other ~nd of the appara-tus.
By appropriate choice of the clistances hetween pipes 19 and of the
peripheral velocity of the heat exchanger unit, the pressure drop
encountered as the suspension flows at right angles to the pipes 19 may be
kalanced by the static differential pressure which arises from the differ-
ence ~ level between surfaces 23 and 24, in such m~nner that the surface 23
will not rise past t~le highest point 25 of the central tube 18. m e sus-
pension is thus substantially prevented frcm rotating along with the heattransfer pipes 19, and one achieves a relative velocity which is necessary
for efficient heat transfer, bet~en the heat transfer pipes 19 and the
suspension. In addition to this function, the central tube affords the re-
quisite rigidity to the rotating part of the apparatus.
The second mode of use or variant is illustrated by Fig. 5.
According to this variant, the heat exchanger unit rotates in such direction
within the container that the pipe lines 19 move downwardly on the side where
the input 2 of the suspension is located. By effect of the rotation, the
free surface of the suspension 23 on the susp~nsion output sicle from the
central tube 18 will be at an elevation higher than the free surface 24 on
the opposite side. In this case too, it is possibl~ ~y appropriate selec-
tion of peripheral velocity of the ~eat exchanyer, to make the surface 23
adjust itself to remain below the highest p)int 25 of the central tube, so
that the suspensi-on cannot rotate in the a~paratus with a velccity identical
to that Gf the heat exchanger unit. In this a~plication, too, the ~racing
plates ~1 substantially prevent free axial flGw of the suspensicn from in-
put to output. In an apparat~is with this particular direction of rotation
the outp~t r~ay be located Gn th~ same elevational level as the input.
It has b~en assum~d in the preceediny description of th~ operation
of aspe~ts of this invention ~lat the inpllt 2 arK1 output 3 of the sus~nsion
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~rc flurn~s wi~l a fre~ Æ ~ace. Ii~w~ver, ~he input and output ~y equally
be closæ pipelines, in which comlection modified places of connection and
which E~ mit the maintaininy of a free liquid level in th~ oontainer are
F,ossible without digression from within the scope of the invention.
The apF~lratus may also be used to warm and oool liquids oontaining
no solid F~articles. m~ heat trarsfer pipes are easy to clean on the side
which is in contact with the susp~nsion, even without any need to empty the
aF~paratus, since all heat transfer pip~s can be brought into a position ir.
which they are above the suspension surface.
