CA1185964A

CA1185964A - Spiral tube heat exchanger

Info

Publication number: CA1185964A
Application number: CA000404292A
Authority: CA
Inventors: Ingemar Persson
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-06-02
Filing date: 1982-06-02
Publication date: 1985-04-23

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.

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.

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.