WO2000068629A1

WO2000068629A1 - Heat exchanger

Info

Publication number: WO2000068629A1
Application number: PCT/NL2000/000288
Authority: WO
Inventors: Walter Bloksma
Original assignee: Bloksma BV
Current assignee: Kelvion Machine Cooling BV
Priority date: 1999-05-11
Filing date: 2000-05-03
Publication date: 2000-11-16
Anticipated expiration: 2001-11-11
Also published as: EP1180232A1; AU4625300A; US20020046829A1; DE60024078D1; DE60024078T2; DK1180232T3; EP1180232B1; NL1012029C2; ATE310222T1

Abstract

Heat exchanger (1) provided with a housing (2) having a core (3). The core (3) comprises a series of plate-shaped fins (10) placed at least almost parallel to each other, in which each fin (10) is provided with pipe openings (13), and a bundle of pipes (8) for passing a first heat exchange medium. Each of the pipes (8) extends through respective pipe openings (13) of respective fins (10). The housing (2) is provided with an inlet (5) and an outlet (7) for passing a second heat exchange medium through the housing (2). At least one of the fins (10) is further provided with mix openings (20). Preferably at least one of the fins (10) is further provided with local elevations (23). Preferably between the core (3) and the housing (2) a strip (14), preferably of springy material, has been arranged for reducing leakage between the core (3) and the housing (2).

Description

Heat exchanger

The present invention relates to a heat exchanger provided with a housing having a core, comprising a series of plate-shaped fins placed at least almost parallel to each other, in which each fin is provided with pipe openings, and a bundle of pipes for passing a first heat exchange medium, in which each of the pipes extends through respective pipe openings of respective fins, in which the housing is provided with an inlet and an outlet for passing a second heat exchange medium through the housing.

Such a heat exchanger is known from Dutch patent application 9500633. Although the known heat exchanger functions well, the efficiency of the heat exchanger may not be optimal depending on the second heat exchange medium. For instance when the heat exchanger is used as oil cooler, so in cases in which the second heat exchange medium is oil, the oil can supposedly "freeze to" the plate-shaped fins and the pipes, which have a lower temperature than the oil. This means that oil flowing between the fins and pipes does not optimally contact the fins and the pipes because a layer of oil is "frozen" on them. The degree of "freezing" strongly depends on the kind of second heat exchange medium, but causes a blockage for the second heat exchange medium, which leads to a high drop in pressure and a low heat exchange.

It is amongst others an objective of the present invention to provide a heat exchanger with which an improved efficiency of the heat exchange can be obtained. It is noted here that a heat exchanger is not only suitable to be used as oil cooler for for instance generators, motors and the like, but that the heat exchanger may for instance also be used for indeed heating the second heat exchange medium.

To that end a heat exchanger of the kind described above according to the present invention is characterized in that at least one of the fins is further provided with mix openings. Because the second heat exchange medium during use flows past the mix openings, said flow in comparison to the flow over the locations of the fins where no mix openings have been arranged, is disturbed such that the flow can reach the plate-shaped fins and the pipes, thus improving the efficiency of the heat exchanger. So although the arranging of mix openings reduces the effective surface of the fins, and therefore a lower efficiency would be expected, it appears that the efficiency is indeed improved.

When the mix openings are placed there where a rate of flow of the second heat exchange medium is high in comparison to the rate of flow on other locations, a further improvement of the efficiency is achieved. Preferably the pipe openings are situated in rows next to each other. In particular each of the mix openings are situated between respective adjacent pipe openings.

Although between two adjacent pipe openings one mix opening can be arranged, it is preferred in a heat exchanger, in which the centres of two adjacent pipe openings are connected to each other by an imaginary connecting line, that two mix openings are placed on either side at equal distance from the connecting line. As a result the efficiency of the heat exchanger is further improved.

The mix openings may have different shapes, but depending on the second heat exchange medium it is preferred that the mix openings are semicircular, circular or oval. Preferably around a mix opening the respective plate-shaped fin is provided with a torsion. As a result the disturbance of the flow of the second heat exchange medium is further increased, as a result of which the efficiency is even further improved. Although any given disturbance results in improvements, it is preferred that the torsion is such that a flow of second heat exchange medium is directed at a pipe and to a plate-shaped fin, respectively. As a result it is ensured that the "frozen" layer of second heat exchange medium on the pipe and the fins is accurately broken through.

A further disturbance of the flow, which benefits the efficiency, is provided because at least one of the fins is further provided with local elevations. Preferably at least one of the elevations is provided with a groove, which is able to give a certain direction to the disturbance. Said direction may be adjusted depending on the wanted effect and the second heat exchange medium.

An improved distribution of the second heat exchange medium, and thus an improved efficiency is achieved because several fins are provided with mix openings, and because the heat exchanger is further provided with one thread which extends through respective openings of respective fins.

Preferably the thread is located near the circumferential edge of the respective fins.

For reducing the leakage, for instance oil leakage, between the housing and the core a strip has been arranged between the core and the housing.

Preferably the strip is made of springy material. Because of the strip the leakage length of the second heat exchange medium is increased. Moreover the strip may be of such a shape that the path the second heat exchange medium has to traverse is complicated, so that the leakage resistance is increased. Said strip also gives plate-shaped fins without mix openings a good leakage reduction. This is contrary to Dutch patent ap- plication 9500633, in which between the housing and the core a sleeve is arranged.

Some embodiments of a heat exchanger and fin according to the present invention will by way of example be described on the basis of the drawing.

Figure 1 schematically shows a longitudinal cross-section of a heat exchanger according to the invention,

Figure 2 schematically shows a top view of a part of a fin according to the present invention, to be used in a heat exchanger according to the present invention,

Figure 3 and 4 schematically show the torsion of a fin around respective mix openings,

Figures 5A and 5B schematically show alternative embodiments of a local elevation in a fin in cross-section, and

Figure 6 and 7 show a cross-section and a view, respectively, of a strip for reducing leakage between housing and core.

The heat exchanger 1 as shown in the drawing comprises a substantially cylindrical housing 2 having a core 3 accommodated in there. At the top side near a first end 4, the housing 2 has an inlet 5 and at the opposite side 6 an outlet 7. The inlet 5 and the outlet 7 can be connected to a supply and return lead for a second heat exchange medium, for instance oil to be cooled. During use, apart from the inlet 5 and outlet 7, the housing 2 with the core 3 accommodated in there is entirely enclosed, and the oil can be led through the housing under high pressure. The inlet and the outlet may for that matter also be differently positioned and several inlets and/or outlets may be arranged.

The core 3 comprises a bundle of pipes 8 extending almost parallel to each other and in longitudinal direction of the housing 2. On both ends of the core 3 an end plate 9 has been arranged which can fittingly be accommodated in or against the housing 2. The pipes 8 extend through the end plates, as a result of which the ends of the pipes are open and may be connected to a supply and discharge, respectively, of a first heat exchange medium, for instance water or another cooling fluid. Between the end plates 9 a large number of fins 1 0 have been arranged which extend almost parallel to the end plates and to each other, through which fins the pipes extend. The fins 1 0 therefore extend almost at right angles to the longitudinal direction of the pipes 8 and are placed at a little distance from each other. The fins 10 and the pipes 8 contact each other closely, for instance because the pipes 8 are somewhat flared within the fins 1 0, as a result of which good heat conductance between the fins 1 0 and the pipes 8 is guaranteed. The fins 1 0 and the pipes 8 may of course for that matter also be connected one to the other in a conducting manner in other ways.

The fins 1 0 are all almost identical and are made of relatively thin plate.

Each fin 10 has an almost circular cross-section with flattened top side 1 1 and a bottom side 1 2. Over the surface a number of holes 1 3 corresponding to the number of pipes has been arranged in a regular distribution, through which holes the pipes 8 can be arranged. For simple assembly the holes 1 3 are a little larger that the cross-section of the pipes 8 in the outlet shape.

Around the core and between the end plates 9 a strip 14 (see figures 6 and 7) has been arranged. The strip 14 increases the leakage resistance for oil, so that a considerable reduction of oil leakage arises. In particular the strip 14 is made of springy material so that a good fitting is realised. A good fitting in a certain housing may also be obtained by correct dimensioning of the strip. The reduction of leakage is also obtained with plate- shaped fins without mix openings. As a result of correct design of the strip, for instance as shown in figure 6, leakage resistance may further be increased.

Figure 2 schematically shows a top view of a part of a fin 1 0 according to the present invention, to be used in a heat exchanger according to the present invention. The fin 10 is further provided with mix openings 20. Because the second heat exchange medium, for instance oil, during use flows past the mix openings 20, said flow in comparison with the flow over places of the fin 10 where no mix openings 20 have been arranged, will be disturbed such that the flow can reach the pipes 8 or the adjacent fins, thus improving the efficiency of the heat exchanger.

Although the mix openings 20 can be arranged on various places on the fin 1 0, it is preferred that the mix openings 20 are placed there where a rate of flow of the second heat exchange medium is high in comparison to the rate of flow on other locations. The highest rate of flow appears to be present between two adjacent pipes, so that preferably each of the mix openings 20 is situated between respective adjacent pipe openings 1 3, as shown in figure 2.

In the example shown centres 30, 31 of two adjacent pipe openings 1 3 may be connected by an imaginary connecting line 32. Two mix openings

20, and 20₂ are placed on either side at equal distance from the connecting line 32, so that a considerable improvement of the efficiency of the heat exchanger is obtained.

Although in the shown exemplary embodiment the mix openings are substantially circular, other shapes may be suitable depending on the kind of second heat exchange medium. Semi-circular and oval mix openings should particularly be kept in mind here.

Preferably around a mix opening 20₃ and 20₄ the respective plate-shaped fin 10 is provided with a torsion. Because of such a torsion the flow of the second heat exchange medium is further disturbed as a result of which the efficiency of the heat exchange is further improved. Although any given disturbance will result in improvements, excellent results can be obtained when the torsion is such that a flow of second heat exchange medium is directed to a pipe 8 or an adjacent plate-shaped fin. An attempt to show said torsion in a drawing, is made in figures 3 and 4. In figure 3 a channel through the area between the pipe openings 1 3 is indicated, through which channel the flow takes place. The triangular area 22 (figure 2) indicates a local bulge as a result from the torsion which causes further efficiency- improving disturbance of the flow. In figures 3 and 4 the torsion of the fin

1 0 is schematically shown by the waviness. By directing the flow to the pipe 8 or an adjacent fin, it is ensured that the "frozen" layer of second heat exchange medium is accurately broken through.

Furthermore the fin 10 may be provided with local elevations 23, 23' (see figure 2, and figures 5A and 5B). Preferably the elevation 23, 23' is provided with a groove 24, 24' which can give a certain direction to the disturbance. Said direction can be adjusted depending on the wanted effect and the second heat exchange medium. In the example shown the direc- tion is approximately 45 ° with respect to the general flow direction, indicated by arrow S.

An improved distribution of the second heat exchange medium, and as a result an improved efficiency apparently can be obtained when several fins 10 are provided with mix openings 20 (figure 1 ), and that the heat exchanger is further provided with at least one thread 25, extending through respective mix openings 20 of respective fins 1 0. The largest effect is achieved when the thread 25 is situated near the circumferential edge of the respective fins 10, in other words when the thread is situated as close to the housing as possible.

In the heat exchanger known from NL-A-9500633 the distance between the fins is several mm. Reducing said distance is not possible there, because as a result larger laminar flow between the fins is generated, which would lower the efficiency, because of the fact that said laminar flow would even be less capable to contact the pipes in a heat exchanging manner. According to the invention it is possible, however, to reduce this distance in a range of 0.5 mm to 2.0 mm, for instance 0.6 mm, 0.8 mm or 1 .1 mm, which in practice is easy to realize. As a result the number of fins per cm is considerably increased which enlarges the heat exchanging capacity considerably.

From tests it appeared that a heat exchanger according to the present invention was capable to efficiently cool down oil of a temperature of 90° with cooling water of 20°C.

Claims

1 . Heat exchanger provided with a housing having a core, comprising a series of plate-shaped fins placed at least almost parallel to each other, in which each fin is provided with pipe openings, and a bundle of pipes for passing a first heat exchange medium, in which each of the pipes extends through respective pipe openings of respective fins, in which the housing is provided with an inlet and an outlet for passing a second heat exchange medium through the housing, characterized in that at least one of the fins is further provided with mix openings.

2. Heat exchanger according to claim 1 , characterized in that the mix openings are placed there where a rate of flow of the second heat exchange medium is high in comparison to the rate of flow on other locations.

3. Heat exchanger according to claim 1 or 2, characterized in that the pipe openings are situated in rows next to each other.

4. Heat exchanger according to claim 3, characterized in that each of the mix openings are situated between respective adjacent pipe openings.

5. Heat exchanger according to any one of the preceding claims, in which the centres of two adjacent pipe openings are connected to each other by an imaginary connecting line, characterized in that two mix openings are placed on either side at equal distance from the connecting line.

6. Heat exchanger according to any one of the preceding claims, characterized in that the mix openings are semi-circular.

7. Heat exchanger according to any of the claims 1 -5, characterized in that the mix openings are circular.

8. Heat exchanger according to any of the claims 1 -5, characterized in that the mix openings are oval.

9. Heat exchanger according to any one of the preceding claims, characterized in that around a mix opening the respective plate-shaped fin is provided with a torsion.

1 0. Heat exchanger according to claim 9, characterized in that the torsion is such that a flow of second heat exchange medium is directed at a pipe and to a plate-shaped fin, respectively.

1 1 . Heat exchanger according to any one of the preceding claims, characterized in that at least one of the fins is further provided with local elevations.

1 2. Heat exchanger according to claim 1 1 , characterized in that at least one of the elevations is provided with a groove.

1 3. Heat exchanger according to any one of the preceding claims, characterized in that several fins are provided with mix openings, and in that the heat exchanger is further provided with at least one thread which extends through respective openings of respective fins.

14. Heat exchanger according to claim 1 3, in which each respective fin has a circumferential edge, in which the thread is located near the circum- ferential edge.

1 5. Heat exchanger according to any one of the preceding claims, characterized in that the distance between two adjacent fins is within a range of 0.5 and 2.0 mm.

1 6. Heat exchanger according to any one of the preceding claims, characterized in that between the core and the housing a strip has been arranged for reducing leakage between the core and the housing.

1 7. Heat exchanger according to claim 1 6, characterized in that the strip is of a springy material.

1 8. Plate-shaped fin to be used in a heat exchanger according to any one of the preceding claims.

1 9. Heat exchanger provided with a housing having a core, comprising a series of plate-shaped fins placed at least almost parallel to each other, in which each fin is provided with pipe openings, and a bundle of pipes for passing a first heat exchange medium, in which each of the pipes extends through respective pipe openings of respective fins, in which the housing is provided with an inlet and an outlet for passing a second heat exchange medium through the housing, characterized in that between the core and the housing a strip has been arranged for reducing leakage between the core and the housing.

20. Heat exchanger according to claim 1 9, characterized in that the strip is of a springy material.