GB2037417A

GB2037417A - Heat exchanger with fins

Info

Publication number: GB2037417A
Application number: GB7931568A
Authority: GB
Original assignee: AMUNDIN STEN ING
Current assignee: AMUNDIN STEN ING
Priority date: 1978-09-12
Filing date: 1979-09-12
Publication date: 1980-07-09
Also published as: NO145854B; SE428159B; FR2436353A1; NO145854C; FR2436353B3; NO792944L; SE7809555L; NL7906605A; DE2936714A1; DK378079A

Abstract

A heat exchanger comprises finned elements (10) fitted onto a tube (20). The elements are formed with fan like blades formed with a transverse portion (11) and an inclined portion (12). Adjacent elements are secured to each other and the tube by a push fitting arrangement which may include rings (21). The push fitting may be by means of a tool (30). The heat exchanger may be used for heating by means of steam, oil, water or electric energy or may be used for cooling by means of water or oil. Finned elements may be fitted inside a tube as illustrated in Fig. 8 (not shown). <IMAGE>

Description

SPECIFICATION Heat exchanger means The invention relates to a rod- or pipe-shaped heat exchanger means (such as an electric heating rod or tube) which for better heat exchange with a surrounding or passing medium is provided with a plurality of separate disc-shaped, area-enlarging elements arranged transversally to the longitudinal axis of the means, each element being provided with a plurality of radially extending fins.

The invention relates also to a method of producing such heat exchanger means.

A heat exchanger means with area-enlarging elements comprising a plurality of radially extending fins is shown in German patent specification No. 1,950,246, wherein on a pipeshaped heat exchanger means, a strip with protruding fins radially and essentially at right angles to the longitudinal axis of the means helically arranged in a groove cut-in in the heat exchanger body. In U. S. Patent specification No.

3,752,228 a similar strip is shown with radially extending fins which all are bent to an inclined position relative to the longitudinal axis of the heat exchanger body. The strip is helically arranged by being welded to a pipe-shaped heat exchanger body.

In both cases the fins have been obtained by removal of portions of the respective strip between two adjacent fins. The arrangement has thus a smaller total thermal transmission area than what the strip would have without fins. In the said German patent specification also an alternative without fins is shown, but then apparently no medium can flow through the areaenlarging elements, but only past them. Moreover, cutting-in of a helical groove in the heat exchanger means itself, as well as welding thereon, are relatively expensive production operations. It has also been known (U. S. A. Patent Specification No.

695,674) to fasten separate disc-shaped, areaenlarging elements to a heat exchanger means by the process of first heating and then crimping as the element are cooling-off, which is also a rather expensive operation due to the heating step.

A heat exchanger means according to the present invention comprises a plurality of separate disc-shaped, area-enlarging elements extending transversally to the longitudinal axis of the heat exchanger body, each such element being provided with a plurality of radially extending fins, wherein at least some of the elements are provided with fins which have a first sector lying in a common plane transverse to the longitudinal axis and having one free edge, and a second sector which on its entire one side is attached to the first sector along a radially extending iine, has on the other side a free edge, and is inclined relative to this first sector at a predetermined angle, free spaces for the passage of a medium being thereby provided between each two adjacent fins, and the free spaces being limited by the free edge of the first sector in the one fin and the free edge of the second sector in the other fin.

In the heat exchanger means of the invention the advantages of fins extending at right angles and fins extending obliquely to the lenght axis are combined, the medium can flow through the areaenlarging elements, and these elements nevertheless preserve their maximal thermal transmission area, furthermore the area-enlarging elements can be affixed to heat exchanger body by an inexpensive manufacturing operation, viz. cold crimping. In particular the heat exchanger means according to the present invention has a greater effect and can be produced more easily at the same time than either of the known exchanger means of the prior art discussed above.

The invention will now be explained more in detail with the aid of the attached drawings, which refer to exemplary embodiments and in which: Fig. 1 shows an area-enlarging element according to the invention in front view, Fig. 2 shows the element of Fig. 1 in a crosssection along the plane 11-Il of Fig. 1, Fig. 3 shows the element of Fig. 1 in a crosssection along the plane Ill-Ill of Fig. 1, Fig. 4 shows a locking ring in front view, Fig. 5 shows a locking ring in a cross-section along the plane V-V of Fig. 4, Fig. 6 is a cross-section through a heat exchanger means according to the present invention in two different production stages, Fig. 7 shows, at a larger scale, the area within the circle.B of Fig. 6 in an alternative embodiment, Fig. 8 is a cross-section through a heat exchanger means according to the present invention with an area-enlarging element on the inner side, and Fig. 9 shows, at a larger, scale, a detail of an alternative to Fig. 8.

According to Figs. 1 to 3, a disc-shaped, areaenlarging element 10 is provided with a plurality (eight in this example) of first radially delimited sectors 11 radiating from a central hub portion 13 and defining a system of fins extending transversally, preferably at right angles to the length axis A-A (Fig. 6) of the heat exchanger means. In the hub portion 13 is an aperture 14 provided which enables the element to be slippedon a heat exchanger means 20 (Fig. 6).

The aperture 14 is surrounded by a mounting collar 1 5 which is firmly affixed to the element or disc 10. The sectors 11 lie in the plane of the drawing Fig. 1 (plane E-E in Figs. 2 and 8) and to one of their limiting radii, viz. radius 1 6a, bent-out second sectors 12 are attached so that free spaces 1 7 are obtained between each two first sectors 11. The second sectors 12 have conveniently been obtained in such a way that through-perforations have been punched along the other limiting radii 1 6b of the first sectors and bend-indication lines have been punched along the said first limiting radii 1 6a, whereafter the second - sectors 12 have been bent-out in the desired angle cr. This angle a between the first and second sectors may have arbitrary values between a value "somewhat greater than zero" an a value "somewhat smaller than 1800". The lower limit depends on how great a free space 1 7 is minimally desired to obtain. The upper limit is motivated by the recognition that the second sectors 12 are not totally ineffective even at values over 900 of the angle a. The second sectors 12 define a system of fins which with the angle a are oblique to the plane of the first sectors 1 transversal to the longitudinal axis A-A.

As an alternative, and preferably, punching of the through-perforations and the bending-out of the second sectors may be carried out in one operation, i.e. not split up into the three steps: punching-out, punching-in of the bend-indication lines and bending.

The total effective area for the heat exchange has thus in no way been reduced, but nevertheless a flowing medium may pass through the free spaces 17, where a turbuiance arises in the medium as well in front of, as behind the bent second sectors 12, in consequence of which not on!y greater speed is achieved in the medium passing the area-enlarging element, but also the faces of this element automatically are flushed clean. The heat exchanger means needs therefore not be dismounted for cleaning.This circumstance, together with the possiblility for the medium to flow through the element inside its outer periphery, is particularly important on the one hand when it is desired to arrange an outer cover 24 (Fig. 6) around the heat exchanger means, and on the other hand when the areaenlarging elements are disposed inside a pipeshaped heat exchanger body as will be explained more in detail in connection with Fig. 8.

For fastening the individual elements on the outside of a heat exchanger means, conveniently separate locking rings, crimp rings 21 according to Figs. 4 aid 5 in the instance, are used. Their internal diameter 4imin corresponds to the outer diameter D (Fig. 6) of the heat exchanger means plus the double wall thickness t (Fig. 2) of a mounting collar, minus a certain reduction, e.g.

0.1 mm with D in the order of magnitude of approximately 15 mm (i.e. a reduction of approximately 0.5 to 0.8% of D). This enables crimping with a tolerance h 11.

For easier pressing-on on the mounting collar, the locking or crimp ring 21 is on the edge which is its front edge when the ring is slipped-on, provided with an internal bevel 21-b. The bevel extends from the said diameter 5imln to a diameter NbmaX which corresponds to the outer diameter D of the heat exchanger means plus the double wall thickness t, plus a certain addition, e.g. 0.5 mm when D is in the order of magnitude of 1 5 mm (i.e.

an addition of approximately 2 to 5% of D).

When mounting e.g. on a rod-shaped heat exchanger body 20 according of Fig. 6, a disc shaped, area-enlarging element 10, and a crimp ring 21 are alternatively slipped-on the heat exchanger means. When the heat exchanger means is full, the pack is pressed together in the sense of the arrow P, e.g. with the aid of a compressed-air tool 30. As an alternative, and preferably, the compression is carried out each time one disc element and one crimp ring has been slipped-on, whereafter the next pair is slipped-on and compressed, etc. Hereat glide the locking rings with their bevels 21 b on the mounting collars 1 5 and press them against the heating rod 20, so that good thermal contact is achieved.

The crimp rings 21 are preferably shaped so, that their breadth 21 a (Fig. 5) corresponds to the distance C (Fig. 6) which it is desired to have in the finished heat exchanger between the individual discs. The breadth of the mounting collars is then made conveniently somewhat smaller than 21 a. As an alternative, said mutual distance C may be defined by the mounting collar or by special spacer means.

The locking rings 21 are preferably made of the same material, or at least of a material with identical or similar thermal expansion coefficient, as the heat exchanger means 20. Loosening due to thermal expansion is thereby prevented. The finished heat exchanger means may be provided with an outer cover 24 (Fig. 6) covering the discshaped area-enlarging elements.

In Fig. 7 an alternative embodiment is shown in which the separate locking rings have been substituted by inward circumferential grooves 1 9 in the area-enlarging element 10 itself. The mounting collar 1 8 has two portions, of which the portion 1 8a acts as the mounting collar proper, and the portion 1 8b fills the function of the locking ring. It will be noted that portion 1 8b, is stiffened by the adjoining hub portion 13, and moreover, its wall thickness may possibly be made greater than that of the portion 1 8a. The edge 1 8c may be provided with the same bevel as already mentioned, and a bevel in reverse sense may also be arranged at the edge 1 8d. The total length of the mounting collar 1 8 defines the distance C (Fig.

6). The process of mounting is principally the same as described in connection with Fig. 6, with the exception that no alternating slipping-on of discs and separate locking rings takes place. The compressior; is conveniently carried in pairs.

According to Fig. 8, an area-enlarging element 10' with first radial sectors 11 and second radial sectors 12 is disposed inside a pipe-shaped heat echanger body 25 (for clarity the adjacent identical elements are not shown in the drawing).

The central hub portion 13' of the element 10' is in the exemplary embodiment shown unperforated, but if desired, a through-opening for the through-flow of the medium may be provided there. The mounting collar 17' is arranged at the outer periphery of the element and is firmly connected to the first sectors 11. Instead of a locking ring being a crimp ring, a locking ring being an expansion ring 21' with an outer bevel 21' is however now used. For easy introduction, of the element 10' into the body 25 the outer diameter of the mounting collar 17' is like the arrangement according to Figs. 1 to 6, somewhat smaller than the inner diameter of the heat exchanger pipe 10', and the outer diameter of the expansion ring 21' is somewhat greater than the inner diameter of the mounting collar 1 7' to achieve an "outwardly directed crimping effect".

Even in this case, the separate expansion ring 21' may be substituted by outward circumferential grooves 1 9', now at the outer periphery of the element 10'. The disposition will be readily understood from Fig. 9 (where hyphened references denote similar parts as in Fig. 7).

The compression is also with the embodiments according to Figs. 8 and 9 conveniently carried out in pairs.

A heat exchanger according to the present invention is conveniently produced in the following manner: Plane disc blanks of convenient material (e.g. metal sheet) are prepared in desired amount and are provided with a mounting collar at that periphery - the outer one or the inner one which in any given case will bear on the body of the heat exchanger. In the second named case, i.e.

the inner periphery bearing on the body, also a central opening is provided in the blank, the edge of which opening defines said inner periphery.

Thereupon a system of radial, elongated perforations is provided in the blank in an amount which corresponds to the desired number of pairs of first and second sectors. Simultaneously, or thereafter, a portion of each area enclosed between two adjacent perforations, namely that portion which will define the second sector, is bent-out in a desired angle. Conveniently, a system of radial bend-indication lines is before that pressed into the blank, so that between each two adjacent perforations one bend-indication line lies at a desired location (which in no way must be in mid-distance between two adjacent perforations; the first and second sectors in general may have or may not have identical areas).

The discs are then slipped-on a rod- or pipeshaped heat exchanger body (in the case of areaenlarging elements on the outside of the heat exchanger) or they are introduced into a pipeshaped heat exchanger body (in the case of areaenlarging elements on the inner side). The central opening in the first named case, and the outer periphery in the second named case, are produced with a convenient allowance so that the slippingon or the introduction can be carried out with ease. In the alternative according to Fig. 6 one disc and one separate crimp or expansion ring are alternately slipped-on or introduced.

When one disc and one ring, or alternatively all discs and all rings, have been slipped-on, the pack is compressed so that the free ends of the mounting collars are pressed into the crimp or expansion rings or in the corresponding grooves in adjacent discs. The first and the last elements may moreover be secured in conventional manner to the heat exchanger body, even if this does not appear to be necessary.

If desired, an outer cover is slipped-on on a heat exchanger means having area-enlarging elements on the outer side.

Heat exchanging means according to the present invention may be used either for heating a medium (steam, hot oil, hot water or electric energy may be used as heat delivering or heat generating medium) or for cooling, with e.g. cold water or cold heat transmitting oil as heat absorbing medium. Heat exchanger means according to the present invention can easily be coupled in series or in parallel by appropriate connection to a manifold.

The invention is not limited to heat exchanger means with circular cross-section, and neither has the outer contour line of area-enlarging elements arranged on the outside of the heat exchanger body to correspond to the inner periphery, i.e. to the contour line of the said body. It will be also readily understood that the mounting collar may extend, in cross-section, on both sides of plane of the first sectors.

Claims

1. A rod- or pipe-shaped heat exchanger means with a plurality of separate disc-shaped, areaenlarging elements extending transversally to the longitudinal axis of the heat exchanger body, each such element being provided with a plurality of radially extending fins, wherein at least some of the elements are provided with fins which have a first sector lying in a common place transverse to the longitudinal axis and having one free edge, and a second sector which on its entire one side is attached to the first sector along a radially extending line, has on the other side a free edge, and is inclined relative to this first sector at a predetermined angle, free spaces for the passage of a medium being thereby provided between each two adjacent fins, and the free spaces being limited by the free edge of the first sector in the one fin and the free edge of the second sector in the other fin.

2. The heat exchanger means of Claim 1, wherein each disc-shaped, area-enlarging element is along its periphery bearing on the heat exchanger body provided with a mounting collar having an outer diameter and an inner diameter, and a locking ring which is separate from the respective element and has an outer diameter and an inner diameter is provided for fastening the element to the heat exchanger body, the contacting diameters of the mounting and locking rings being dimensioned so that when the locking ring is urged onto or into the mounting collar, this mounting collar is pressed against the body of the heat exchanger.

3. The heat exchanger means of Claim 2, wherein the locking ring is a separate independent piece.

4. The heat exchanger of Claim 2, wherein the locking ring is defined by a circumferential groove in an adjacent disc-shaped, area-enlarging element.

5. The heat exchanger means of Claim 3, wherein the locking ring is made of a material with at least approximately identical heat expansion coefficient as the material from which the cooperating mounting collar is made.

6. The heat exchanger of any of the preceding claims wherein the individual disc-shaped, areaenlarging elements bear closely one on the other by means of their respective mounting collars.

7. A method for producing rod- or pipe-shaped heat exchanger means provided with a plurality of separate disc-shaped, area-enlarging elements arranged transversely to the length axis of the means and having radially extending fins, according to any one of the preceding claims, wherein a) a plane disc blank is, at the periphery thereof which is intended to bear on the body of the heat exchanger, provided with a mounting collar which with a certain allowance follows the contour lines of the said body b) the disc blank is provided with a plurality of radially extending through-perforations, c) a portion of each area situated between two said adjacent perforations is bent-out in a desired angle so that between each two adjacent perforations on the one hand a first sector in the plane of the disc, and on the other hand a second sector, attached to the first one and bent-out of the plane of the disc blank is obtained.

d) the discs are, urged onto or into a rod- or pipe-shaped heat exchanger body, in such a manner that the free ends of the mounting collars are directed towards a co-operating locking ring, and e) the pack of discs and locking rings thus obtained'is compressed till the mounting collars have penetrated into or have been pressed onto the locking rings and thereby have been by cold crimping deformed to bear closely on the body of the heat exchanger, wherein steps a) to c) may be performed in that order or in the sequence b), c), a) or b), a), c).

8. The method of Claim 7, wherein separate locking rings are provided for each disc-shaped, area-enlarging element and in step d) are slippedon or introduced into the body of the heat exchanger alternately with the elements.

9. The method according to Claims 7 or 8 wherein the mounting rings and/or the locking rings are produced with a breadth which corresponds to the mutual distance between the elements in finished state of the heat exchanger means and'that in step e) the pack is compressed till all parts bear one on the other.

10. The method according to any one or several ones of the Claims 7 to 9, wherein the mounting rings and/or locking rings are provided with a bevel on the edge which in step e) first contacts the other part.

11. A heat exchanger means substantially as described with reference to the accompanying drawings.

12. A method for producing a heat exchanger means substantially as described with reference to the accompanying drawings.