Note: Descriptions are shown in the official language in which they were submitted.
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The present invention concerns a tubular heat exchanger passed through
by a primary fluid used to reheat a secondary fluid such as pool water
or sea water.
Heat exchangers of this type are already known and, in this connection,
reference is made to e.g. FR-A-2 441 819, FR-A-2 482 717, DE-A-3 038 344
and US-A-4 739 634. The exchangers described in these documents are
formed by a cylindrical body provided with an inlet and an outlet for
the secondary fluid. Inside the body, a helical coil is provided which
is passed through by a priniary fluid intended to transfer its calories
to the secondary fluid circulating in the body.
Generally, in order to increase the efficiency of the heat transfer, the
secondary fluid is circulated as much in contact as possible with the
coil. To accomplish this, the latter is housed in the annular space
formed between the inside wall of the body and the outside wall of an
annular sleeve. Thus, the secondary fluid circulates helically between
two coil turns.
This, then, creates corrosion problems which, in the majority of
applications, are solved, as in the patents DE-A-3 038 344 and US-A-4
739 634, by using separators between the outside body and the sleeve.
Nevertheless, taking into account the particular use for which the
exchangers of the invention are intended, namely reheating pool water
and sea water, this measure is not adequate. In fact, pool water
contains an oxidizing agent, for example chlorine, and is therefore
corrosive.
It is, therefore, the object of the invention to provide a heat
exchanger designed especially for reheating a corrosive secondary fluid,
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such as pool water or sea water.
It was found that satisfactory results were obtained by making the
outside body from a plastic-based material and the coil tube of titanium
and by furnishing the coil with separators between the outside wall of
the sleeve and the inside wall of the body.
A heat exchanger according to the invention is shown in Fig. 1 in a
longitudinal section.
It comprises an external body 1 having a hollow cylindrical shape and
closed airtight on the upper end by a cover 2 and, on its lower end, by
a base 3. The base 3 is provided with means, such as holes 4 for the
passage of screws 5, which allow the exchanger to be fixed to the
ground.
At the lower end, in the cylindrical wall of the body 1, a pipe
connection 6 is provided which forms the inlet for the secondary fluid
by which the water to be reheated is introduced, for example, the water
coming from a pool. At the upper end, on the same generator as pipe
connection 6, a pipe connection 7 is provided which forms the outlet by
which the reheated water in the exchanger returns to the pool.
The inside diameter of the pipe connections 6 and 7 is dimensioned such
that the exchanger can be connected to a circuit in which the secondary
fluid can circulate, without loss of excessive voltage, with a
relatively significant output, that is between 5 and 20 m3/hour, by
means of a pump. These diameters are, for example, in the order of
40 mm.
The fact that the exchanger can be operated at relatively high rates
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prevents the forniation of deposits coming from the pool water and from
its filtration system.
Inside the body 1, a sleeve 8, formed by a cylindrical tube furnished
with an internal radial partition 9, is provided coaxially.
In the annular space between the inside wall of the body 1 and the
outside wall of the sleeve 8, a coil 10 formed by a helical tube is
mounted. At its upper end, the coil 10 ends in an elbow 11 extending,
tightly sealed, through the cover 2 and has an inlet 12 by which the
primary fluid is introduced. At the other end, the coil 10 forms an
elbow 13 extended by a rectangular part 14 which also passes, tightly
sealed, through the cover 2, running into an outlet 15 which is in the
vicinity of input 12 and by which the primary fluid leaves after having
transferred its calories. The rectangular part 14 also passes through
the inside partition 9 of the sleeve 8.
Sleeve 8 is fixed to the coil 10 by appropriate means (not shown).
At the lower erid of the body 1, a teniperature pick-up 16 is mounted
whose output signal can be used to control the circulation of the
primary and secondary fluids in the exchanger.
According to the invention, the body 1 and the sleeve 8 are made from a
plastic-based material, either reinforced or not, such as PVC or,
advantageously, polyester reinforced with glass fibers. The coil 10 is
made of titanium.
On t[ie one hand, separators 17a are provided between the inside wall of
the body 1 and the coil 10, said separators being in the form of a
vertical band smaller in width in relation to the diameter of the body 1
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and provided with housings for each of the turns of the coil 10 and, on
the other hand, separators l7b are provided between the outside wall of
the sleeve 8 and the coil 10, these separators being in the form of a
band which is also smaller in width in relation to the diameter of the
sleeve 8. The separators 17a and 17b keep the coil 10 at a distance of
about 2 mm, both from the body 1 and from the sleeve 8.
The function of the separators 17a and 17b is multiple. It facilitates
mounting of the coil 10 which appears, once the separators 17a are in
position, in the form of a single rigid part. It also avoids relative
movements between, on the one hand, body 1 and sleeve 8 and, on the
other hand, coil 10, such niovements being produced by vibrations of
pumps and accessories about the exchanger and which can lead to friction
which deteriorates the elements of the exchanger.
It is also used to solve the problems associated with corrosion in two
ways. On the one hand, separators 17a and 17b create areas situated
between sleeve 8 and coil 10 and between body 1 and coil 10 which are,
from the point of view of corrosion, dead. On the other hand, by
dividing the flowing spaces of the secondary fluid about coil 10, they
facilitate its flow and allow its circulation at higher rates.
In conclusion, it will be noted that the fact that the separators l7a
have housings for each turn of the coil 10 allows release of the coil
diarneter gaps of each turn, these gaps being compensated by the
differences in thickness which hold, when the exchanger is assembled,
the separators 17a between their outer side and their housing.
The water to be reheated flows helically upward in the body 1(arrows
A), on the one hand, between two consecutive turns of the coil 10 and,
on the other hand, between coil 10 and body 1 or sleeve 8. In
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contrast thereto, the primary fluid flows downward (arrows B) in coil
10, that is, countercurrently to the water of the secondary fluid.
The primary fluid is, for example, a refrigerating agent coming from a
heat pump (not shown), but could also be water vapor or hot water.
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