SPIRAL TUBE HEAT EXCHANGER

ECHANGEUR DE CHALEUR A TUBES BOUDINES

English Abstract

Abstract

A heat exchanger assembly is disclosed which comprises
two tubes for carrying respective fluids between which heat
is to be exchanged arranged in a stack. The tubes have
contiguous walls such that heat is transferred by conduc-
tion therethrough. The tubes are coiled alternatingly
and pressed against each other so that the internal pressure
of the fluids in the tubes causes the area of contact and
contact pressure to increase.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:


1. A spiral tube heat exchanger comprising spiral
tubes forming together at least primary and secondary flow
paths and coiled pairwise with tubes of each one of the said
flow paths in close relationship to one another in a winding,
the tubes associated with the primary and secondary flow
path, respectively, alternating with one another, such that
one turn in the winding is associated with the primary path
and an adjacent turn is associated with the secondary path
in any cross section perpendicular to the axis of the winding.

2. A spiral tube heat exchanger according to claim 1,
in which a tertiary flow path is formed by spiral ducts in-
cluding the spacing between the tubes in the winding and re-
stricted by the inside of a heat exchanger vessel enclosing
the winding.

3. A spiral tube heat exchanger according to claim 1,
in which the cross sections of the tubes of the one and the
other path are elliptical and the long axis of the elliptical.
cross section is parallel with the axis of the winding.

Description

5~

The invention relates -to a heat exchanger of the type
having two parallel tubes in contact with each other and in
which a firs~ medium flows throuc~h one tube and a second
medium flows through the other tubeO The tubes are normally
spirally arran~ed on a former and a third medium may be ar-
arranged to flow through a plurality of ducts formed between
first and second tube spirals constituting an assembly en-
closed in a suitable vessel.

The metallic contact between the tubes through which the
different media flow to eEfect a heat exchange is priorly
known in heat exchanging procedures. It is priorly known by
such heat exchangers to achieve an improved heat transfer
by a special design of the cross section of the spiral tubes
so that the contact area between two adjacent tubes is
increased. Another feature increasing the effect of this
metallic contac-t is the contact press~re between the tubes.

~n object of the present invention is to improve the
heat exchange properties of known heat exchangers of this
type. This is achieved by a co-winding of the two tubes in
such a way that the one tube is wound outside the other and
a metallic contact is established between all turns of the
tllbes Erom the innermost to the outermost turns.
~5
~ ccordin~ly, the present invention provides a heat ex-
changer assembly comprising spiral tubes forming together at
least primary and secondary flow paths and coiled pairwise
with a tube of each one of said flow paths in close relation-
ship to one another in a winding in which the tubes associatedwith the primary and, respectively, the secondary flow path
alternate with one another meaning that, in any cross section
perpendicular to the axis of the winding, one turn in the
winding is associated with the primary path and an adjacent
3~ turn is associated with the secondary path, and so on.

The invention will now be described in more detail by way
o~ example only, with reference to the accompanying drawings,
in which:

Fig. 1 is a cross sec-tion through an assembly of two tube
circuits in metallic contact;

~ig. 2 is a vertical sectïonal view through a heat ex-
changer having three circuits;
Fig. 3 is a winding schedule of this heat exchanger; and

Fig. 4 is a part section of Fig. 2.

The heat exchanger assembly shown in Fig. 1 comprises an
inlet 10 and an outlet-ll for a first medium and an inlet 12
an an outlet 13 for a second medium. The assembly comprises
a plurality of turns of parallel spiral wound tubes 14, 15
which enclose and conduct the media from the inlets to the
outlets thereof, respectively,. The tubes are wound on a coil
body or a former 16 or only form a stack of turns. The ends
o the tubes 14, 15 of the respective circuits starting from
the inlets 10 and 12 go into the winding together, the one
outside the other, i.e. -they alternate from the one layer to
the other so that every second layer is associated with one
circuit and the lntervening layers with the other circuit.
The tubes 14, 15 are pressed against each other turn b~7 turn
in the radial direction. The metallic contact causes :heat
conduction from the tube 14 to the tube 15. This type of
winding of the tubes used in the assembly restricts the ex-
pansion of the tubes in the loaded state and brings about an
increase in the area of contact between the ad~acent tubes in
the assembly. This increase in the contact area and the in-
creased pressure which the tubes exert vn each other improve
the heat transfer by the metallic contact between the tubes.

In a variant shown in Fi~. 2 the assembly is enclosed
in a vessel 17 containing a third medium which, e.g. may be
water. It has an end wall 18 at the bottom and another end
wall 19 at the top and is closed to keep the water under
pressure so that it can circulate to radiators or the like.
The assembly is located in the cen~er of the vessel and pro-
vided with in~et and outlet manifolds for the third medium.
The assembly comprises a stack of tubes coiled as hereinbefore
described wi~h reference to Fig. 1 and conducting the media
from the respective inlet to outlet manifolds. The third
medium flows from a pipe 20 and is heated by the tube 14 en-
closing the ~irst medium during passage through the assembly
outwardly in spiral shaped ducts 21 between the tubes to the
outlet through a pipe 22 extending through the wall of the
vessel 17. The tubes 14, 15 are pressed together in the
assembly in the axial direction as hereinbefore described.
This causes an increase in the area of contact between the
tubes and also improves the heat transfer which in a known
way is also effected by the third medi~.
As can be seen in Fig. 4 the tubes in the coil are de-
Eormed into an oval cross section. This brings about an
increase of the said contact area and an improvement of the
heat transfer between the tubes.
The embodiments now shown and described shall only be
cons,idered an example how to exercise the invention. Various
alternative embodiments are of course possible. The tube
14 may, for instance, form the layers of an odd number in a
horizontal section of the coil but even number in an adjacent
section, while the tube 15 then, of course has an even number
and odd number, respectively, in the same sections.




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