WO2014127964A1

WO2014127964A1 - Heat exchanger

Info

Publication number: WO2014127964A1
Application number: PCT/EP2014/051718
Authority: WO
Inventors: Klaus Irmler
Original assignee: Behr Gmbh & Co. Kg
Priority date: 2013-02-20
Filing date: 2014-01-29
Publication date: 2014-08-28
Also published as: DE102013202790A1

Abstract

A heat exchanger (30, 8, 40) having a first flow channel through which a first fluid can flow and having a second flow channel through which a second fluid can flow, said first flow channel having a fluid inlet, a collecting region (7, 32, 42) on the inlet side, a plurality of sub-channels (5, 41) and a collecting region (45) on the outlet side. Means which reduce or prevent phase separation of the first fluid are provided in the collecting region (7, 32, 42) on the inlet side.

Description

Heat exchanger

description

Technical area

The invention relates to a heat exchanger having a first flow channel, through which a first fluid can be flowed and with a second flow channel, through which a second fluid can be flowed, wherein the first flow channel a Fiuideinlass, an inlet side collecting region, a plurality of sub-channels and an outlet side collecting region having.

State of the art

During the evaporation of a fluid within a heat exchanger, instabilities may occur, especially in the two-phase flow. The two-phase flow refers to areas in which both liquid and gaseous constituents of the fluid are present.

These instabilities lead to unequal distributions of the fluid within the heat exchanger. These unequal distributions of the fluid in turn lead to temperature differences within the heat exchanger, which on the one hand has an increased component load and can continue to cause the fluid partially exceeds the limit temperature and it comes to decomposition processes. Furthermore can lead to uneven temperature distributions within the heat transfer.

Various types of heat exchangers can be used to vaporize a fluid. In addition to tube bundle heat exchangers, it is possible, inter alia, to use old heat exchangers in pipe inspection systems.

A disadvantage of the heat exchanger according to the prior art is that either no suitable precautions are taken to reduce or avoid the phase separation of the fluid.

Presentation of the invention, object, solution, advantages

It is the object of the present invention to provide a heat exchanger having means that effectively reduce or prevent phase separation of the fluid, especially in the two-phase flow.

The object of the present invention is achieved by a heat exchanger with the features of claim 1. An embodiment of the invention relates to a heat exchanger having a first flow channel through which a first fluid is ström bar and with a second flow channel through which a second fluid is ström bar, wherein the first flow channel fluid inlet, an inlet side collecting region, a plurality of sub-channels and an outlet-side collecting region, wherein means are arranged in the inlet-side Sammetbereich, which reduce or prevent a phase separation of the first fluid.

In heat exchangers and in particular in evaporators or condensers, it may happen that the fluid flowing through the heat exchanger is present in a two-phase mixture. The mixture then consists of both a liquid phase and a gaseous phase. The two phases each have a different density and inertia, which can lead to a Phasensepa ratton of the two phases, ie to a demixing of the mixture.

A phase separation can lead to an uneven distribution of the fluid within the heat exchanger. This can adversely affect the efficiency of the heat exchanger and also lead to increased stress on the material of the heat exchanger. The increased stress results in particular from a non-uniform temperature distribution within the heat exchanger. By providing means for reducing or preventing the phase separation of the first fluid, these negative effects can be reduced or completely prevented. An arrangement of means for reducing or preventing the phase separation is therefore particularly advantageous. Furthermore, it may be particularly advantageous if the inlet-side collecting region has a substantially round cross-section.

A round inner diameter is particularly streamlined and counteracts the formation of traffic jams within the intake side collecting area.

A preferred embodiment is characterized in that the means for reducing or preventing the phase separation of the first fluid is formed by a helix. A helix disposed in the interior of the inlet-side collection region may impart a spin to the fluid flow that reduces or prevents phase separation of the first fluid. This leads to a better distribution of the two phases within the inlet-side collecting region and thus also to a more advantageous distribution of the fluid within the heat exchanger as a whole. At the same time, the helix represents a relatively low flow resistance for the fluid. This is particularly advantageous since the additional force caused by the helix Loss of pressure does not lead to a significant reduction in the efficiency of the heat exchanger.

It is also preferable if the helix extends over the entire length of the inlet-side collecting area.

The turn can either extend only over part of the inlet-side collecting area or advantageously over the entire length of the inlet-side collecting area. The length of the inlet-side collecting area indicates the extent in the main flow direction of the first fluid. An extension over the entire length is advantageous because in this way the phase separation of the first fluid is prevented in the entire intake-side collecting area.

In addition, it may be advantageous if the helix is formed substantially from a strip of material twisted about a central axis.

The production of a helix in this way is particularly simple and inexpensive.

It is also preferable if the two end regions of the helix lie in a common plane.

By arranging the two end regions in one plane, the helix can advantageously be positioned within a collection region. Furthermore, such a

Independence of the mounting orientation of the coil can be achieved, which simplifies the manufacturing process of the heat exchanger.

In a particularly favorable embodiment of the invention, provision is also made for the helix to be connected to the inner wall of the inlet-side collecting region in a fluid-tight manner. By means of a fluid-tight connection of the helix to the inner wall of the inlet-side collecting region, it is possible to prevent subsets of the fluid from flowing past the helix. A leakage current past the helix could lead to a phase separation in the bypassing subset of the fluid. In addition, stagnation sites can develop in which the flow of the fluid is inhibited. This inevitably leads to a reduction in the efficiency of the heat exchanger as the fluid flow is adversely affected. A fluid-tight connection of the helix to the inner wall is therefore particularly advantageous.

It is also advantageous if the helix has a predeterminable pitch.

The slope of the helix can be used to influence the flow propagation along the helix. Depending on the expected mass flow rate and the regularly occurring flow rate, the helix can thus be adapted to the respective heat exchanger.

In an alternative embodiment of the invention, provision may be made for a plurality of guide elements to be arranged in the region of the fluid inlet of the first fluid in the interior of the inlet-side collecting area and / or in the interior of a feed line, the guide elements being the center for reducing or preventing it form the phase separation of the first fluid.

The guide elements, which are arranged in the flow path of the first fluid, are particularly advantageous because they can put the fluid flowing past into a twist. A two-phase mixture imparted with a swirl has a small tendency to phase separation than a non-swirled two-phase

Mixture has.

The region which has the guide elements is also referred to as a so-called mixer. The mixer causes the passing two-phase mixture via its guide elements in a swirl, whereby the phase separation of the mixture is reduced or completely prevented. It is particularly advantageous that such a mixer easily can be connected to a regular heat exchanger by, for example, upstream of the fluid inlet. This can be realized for example by an integration in the Ftuidzuleitung.

In addition, it may be advantageous if the guide elements protrude radially from an inner wall of the inlet-side collecting area and / or from an inner wall of a feed line and are formed by at least partially circumferential circumferential projections which have a predeterminable pitch in the axial direction.

By flowing past the partially circumferential circumferential projections, the two-phase mixture can be set in a spin, which reduces or prevents a separation of the mixture. The slope of the projections is advantageously designed such that the flow resistance due to the projections as low as possible. Depending on the expected mass flow or on the expected flow rate, the slope and the number of projections can be varied. This is particularly advantageous because it allows a simple adaptation of the mixer to different heat exchangers can be achieved.

It may also be expedient if the guide elements at least partially overlap in a view along the main flow direction of the first fluid.

By partially covering the guide elements, it can be prevented that too large a proportion of the two-phase mixture flows past the guide elements. Furthermore, it can be particularly advantageous if the region which has the guide elements has a variable cross-section along the main flow direction of the first fluid.

By means of a variable cross-section, the flow of the mixture can be further influenced. In particular, the pressure drop of the mixture by a

Cross-sectional change can be influenced. The area which the guiding elements may expand or taper, for example, in the main flow direction of the mixture, whereby the flow velocity is also afflicted.

An alternative embodiment of the invention may provide that the guide elements are arranged on an inner wall of a hollow body, wherein the hollow body has a first opening and a second opening through which the first fluid is flowable, the hollow body in such a supply line and / or can be inserted into the inlet-side collecting region of a heat exchanger and can be connected to it in a fluid-tight manner, in that the first fluid can flow into the hollow body through the first opening and can be flowed out through the second opening.

The hollow body, which has the guide elements and can be integrated into the supply line or the inlet-side collection region, can also be equipped with a means for preventing heat transfer from occurring, which prevents a phase separation of the two-phase mixture. This is particularly advantageous because the flexibility in the production process is increased, since a variant specification must be made only at a late stage in the production process.

According to a particularly preferred development of the invention, it may be provided that the means for reducing or preventing a phase separation of the two phases of the first fluids is formed by a singular or plurality of orifices which are arranged within the inlet-side collecting region and the flow cross-section of the inlet-side collecting region reduce locally.

The introduction of orifices into the inlet-side collecting region results in that the flow cross-section of the inlet-side collecting region is locally reduced by the diaphragms. This results in that the phase separation of the mixture is reduced or completely prevented. Advantageously, a plurality of apertures can be provided which reduce or prevent phase separation over the entire length of the inlet-side collecting area. It is also advantageous if the diaphragms are formed by partitions which each have at least one opening.

Furthermore, it is preferable if the singular or plurality of diaphragms are fluid-tightly connected to an inner wall of the inlet-side collecting region.

By a fluid-tight connection of the diaphragm with an inner wall, it can be prevented that a leakage flow flows laterally past the diaphragm.

Advantageous developments of the present invention are described in the subclaims and the following description of the figures.

Brief description of the drawings

In the following the invention will be explained in detail by means of embodiments with reference to the drawings. In the drawings show:

1 in the left part of the side view of a helix, as it can be introduced into an inlet-side collecting region of a heat exchanger and in the right part of a plan view of the end portion of the helix,

2 is a view of an inlet side manifold of a heat exchanger with a coil inserted into the manifold, wherein the outer wall of the manifold is not shown,

3 shows a side view of a so-called mixer, which can be arranged in the region of the fluid inlet at a collecting area and a plan view of the mixer with the viewing direction in the main flow direction of a fluid flowing through the mixer, Fig. 4 is a side view and a plan view of a mixer, an alternative embodiment to the. represents mixer shown in Figure 3,

Fig. 5 is a view of a manifold of a heat exchanger, wherein a region is provided, in which the mixer can be used, and

6 shows a view of a heat exchanger, wherein a plurality of diaphragms are arranged in the collecting tube, which has the fluid inlet.

Preferred embodiment of the invention

FIG. 1 shows a side view of a helix 1 in the left part. This coil 1 is generated in the simplest case of a material twisted in itself stiff. For this purpose, in principle, all materials can be provided which have a sufficiently high temperature resistance and a sufficiently high resistance to any corrosive effects of the fluid and can be connected to the heat exchanger in a simple manner. In particular, metal materials are suitable for producing a coil 1. The helix 1 in this case has a pitch, which can be varied by engaging in the production process and thus the helix 1 can be specified.

A coil 1 may preferably be inserted into the interior of a collecting area of a heat exchanger, so as to impose a Drailbewegung the fluid flow flowing through the collecting area. Preferably, for this purpose, the outer contour 2 of the helix 1 is designed such that it can be fluid-tightly connected to the inner wall of the respective collecting area. In this way, an unwanted passing of the fluid past the helix 1 can be avoided. In an alternative embodiment, it is also conceivable that the helix is not fluid-tightly connected to the inner wall of the collecting area. For this purpose, the helix can for example be made narrower than the inner region of the collecting area. In this way, the passage of the fluid from the collecting area into the partial passages of the heat exchanger can be simplified.

The right part of Figure 1 shows a plan view in the direction of the main flow direction of the fluid, which can flow around the coil 1. In it can be seen that the coil 1 is made of a thin strip of material. In alternative embodiments, the helix 1 can in each case be matched in terms of its length in terms of the number of twists and also their pitch to the corresponding heat exchanger or the corresponding collecting area. The helix 1 can preferably be connected by gluing, soldering or welding to the interior of a collecting area.

The main task of helix 1 is to impose a twist on the fluid flow within the collection area. By this twist, an unwanted phase separation of a fluid mixture, in particular a two-phase Fiuidgemisches to be avoided. As a rule, a two-phase fluid mixture consists of a gaseous phase and a liquid phase.

Due to the different inertia of the two phases, there is a tendency to separate the two phases within the flow path. Since this leads to a temperature inequality and fluid distribution within the heat exchanger, this should be avoided. By enforcing a twist phase separation can be effectively reduced or completely avoided.

FIG. 2 shows a view of a heat exchanger 8 with a collecting area 7, in which a coil 1, as shown in FIG. is introduced. The heat exchanger 8 is not completely shown in FIG. In particular, it can be seen in FIG. 2 that the helix 1 runs along the entire length of the collecting region 7. The outer wall of the collecting area 7 is not shown in FIG. 2 for the sake of clarity.

The collecting region 7 is acted upon by a fluid via a fluid supply line 6. The collecting area 7 serves to distribute the fluid over the height of the heat exchanger, which is not shown in FIG. 2, and continues from the interior of the collecting area 7 into the plurality of flat tubes 5, which are indicated in FIG. The more strongly the phase separation of the two-phase mixture within the collecting region 7 can be reduced, the more uniformly the fluid is distributed in its two phases over the entire height of the heat exchanger, which in turn contributes to a better Temperaturverteüung and thus a higher efficiency and lower material load of the heat exchanger.

By introducing a helix into the interior of a collecting area 7, the pressure drop within the collecting area 7 is increased. This increase in pressure drop must be considered when designing the heat exchanger.

FIG. 3 shows in the left-hand part a perspective approach of a so-called mixer 10. The mixer 10 is formed from a cylindrical outer wall 1 which has a plurality of guide elements 12 inside. The cylindrical outer wall 11 of the mixer 10 has a peripheral flange area at its foot region 13 on. The mixer 10 is designed so that it can be used in a fluid supply line to the collection area or in the collection area itself. The Leiteiemente 12 are at least partially circumferentially circumferentially disposed on the interior of the wall 1 1 of the mixer 10. The guide elements 12 likewise have a pitch, similar to the helix already described. By way of these guide elements 12 with their characteristic, predeterminable pitch, the fluid flow which flows through the mixer 10 is forced by the helix 1 in a swirling motion. The right half of Figure 3 shows a plan view in the direction of flow of the fluid, which can flow through the mixer 10. It can be seen that the individual guide elements 12 at least partially overlap, so that an unwanted leakage flow past the guide elements 12 can not occur or only to a slight extent,

Along the central axis of the mixer 10, an opening 14 is provided, through which a part of the fluid mixture can flow independently of the portion which flows over the guide elements 12. This serves in particular to reduce the pressure drop generated by the mixer 10.

The peripheral flange portion 13 of the mixer 10 serves in particular as a stop when inserted into a fluid supply line or into the collecting area itself. The mixer can be glued, welded or soldered for better connection with a supply line or the collecting area.

The shaping and the respective gradient of the guide elements 12 can influence how much the mixer 10 influences the flow of fluid flowing through the mixer 10. 4 shows an alternative embodiment of a mixer 20. The mixer 20 also consists of a cylindrical wall 21, on which a plurality of guide elements 22 is arranged in the interior. The guide elements 22 of the mixer 20 have in relation to the guide elements 12 of the mixer 10 to a much lower pitch. The cylindrical wall 21 has a varying cross-section. Starting from the lower side of the mixer 20, the first section of the wall 21 is purely cylindrical with a constant opening cross-section.

From about the height of the guide elements 22, the wall 21 has a tapered tapered design, this tapered design is particularly advantageous so that the mixer 20 in a collecting area, which by a Collection tube can be formed, or can be used in a fluid supply line. The mixer 20 slips so far with the tapered part in the manifold or the Fiutdleitung until the inner diameter of the manifold or the fluid supply line rests against the outside of the wall 21. As well as the mixer 10 of Figure 3, the mixer 20 can be connected via common connection methods with the manifold and the fluid supply line. in the right part of Figure 4 is a plan view of the mixer 20 is shown with the view in the direction of the main flow direction. It can be seen from the right-hand part of FIG. 4 that the individual guide elements 22 do not overlap one another, as shown in FIG. In this way, it is also possible for a part of the two-phase mixture to flow through between the guide elements 22, without being deflected by the guide elements 22. In the center of the mixer 20, an opening 23 is also provided, through which a further portion of the two-phase mixture can flow through undisturbed. The opening 23 also serves to reduce the total pressure drop occurring through the mixer 20.

The use of a mixer, as exemplified in FIGS. 3 and 4, is particularly recommended when high fluid flow rates and large mass flows are to be expected in the interior of the heat exchanger. It is particularly advantageous with the use of the mixers 10, 20 that the mixers 10, 20 can also be subsequently integrated into heat exchangers by being integrated into the region of the fluid inlet of the collecting region or the collecting tube or into a part of the fluid supply line.

FIG. 5 shows a side view of a collecting region of a heat exchanger 30, wherein the collecting region is formed by a collecting tube 32. The rest of the heat exchanger 30 is indicated by the plurality of flat tubes 34. The collecting tube 32 has a fluid supply line 33, via which the fluid can flow into the collection tube 32. The area 31 shows a region in which, for example, one of the mixers 10, 20 of FIGS. 3 and 4 is used can. It can be seen that the mixer is directly upstream of the manifold 32, so that the fluid flow directly after the; Flow through the mixer still mt the swirl, which was generated by the mixer, flows into the manifold 32.

As already mentioned in the description of FIG. 4, this is particularly advisable when high flow velocities and large mass flows are to be expected. Otherwise, the swirl effect of the mixer would not be sufficient to effectively ensure a phase separation of the two-phase mixture over the entire length of the manifold 32. 6 shows a heat exchanger 40, which consists of a plurality of flat tubes 41 and a manifold 42 and a further manifold 45. In the manifold 42, which is associated with the side of the heat exchanger 40, in which the fluid flows through the fluid supply line 43, three orifices 44 are provided, which reduce the inner cross section of the manifold 42, respectively.

About the aperture 44, the phase separation of a two-phase Fiuidgemisches is prevented. Through the orifices 44 in the interior of the collecting pipe 42, the pressure drop within the heat exchanger 40 is significantly increased. The baffles 44 may be variably positioned at different locations within the collection tube 42. The exact positioning of the orifices 44 is to be selected depending on the expected flow velocities and the mass flow within the heat exchanger 40.

Compared to the helix 1 of Figures 1 and 2 or the mixers 10, 20 of Figure 3 and 4, the panels 44 are not subsequently integrated within the manifold. The heat exchanger must therefore already be designed in advance in such a way that different diaphragms are provided in the inlet-side manifold 42.

All embodiments shown in Figures 1 to 6 represent only individual embodiments and serve to illustrate the inventive concept. For their part, they have no restrictive character.

Claims

claims

1 . Heat exchanger (30, 8, 40) with a first flow channel, through which a first fluid is flowable and with a second flow channel, through which a second fluid is flowable, wherein the first flow channel, a fluid inlet, an inlet side collecting region (7, 32, 42 ), a plurality of Teitkanälen (5, 41) and an outlet-side collecting region (45), characterized in that in the inlet-side collecting region (7, 32, 42) means are arranged, which reduce or prevent a phase separation of the first fluid.

2. Heat exchanger (8) according to one of the preceding claims, characterized in that the means for reducing or preventing the

Phase separation of the first fluid by a helix (1) is formed.

3. Heat exchanger (8) according to claim 2, characterized in that the helix (1) is formed substantially from a twisted about a central axis strip of material.

4. Heat exchanger (8) according to any one of claims 2 to 3, characterized in that extending the helix (1) over the entire length of the inlet-side collecting area (7).

5. Heat exchanger (8) according to one of the preceding claims 2 to 4, characterized in that the helix (1) has a predeterminable slope.

6. Heat exchanger (30) according to claim 1, characterized in that a plurality of guide elements (12, 22) are arranged in the region of the fluid inlet of the first fluid in the interior of the inlet-side collecting area (32) and / or in the interior of a feed line (33) which the first fluid in a Dralf offset, wherein the Lettelemente (12, 22) form the means for reducing or preventing the phase separation of the first fluid.

7. Heat exchanger (30) according to claim 6, characterized in that the

Guide elements {12, 22) protrude radially from an inner wall of the inlet-side collecting area (32) and / or from an inner wall of a feed line (33) and are formed by at least partially circumferential projections which have a predeterminable pitch in the axial direction.

8. Heat exchanger (30) according to any one of the preceding claims 6 or 7, characterized in that the guide elements (12) overlap at least partially in a view along the main flow direction of the first fluid.

9. Heat exchanger (30) according to any one of the preceding claims 6 to 8, characterized in that the region which comprises the guide elements (22) has a variable along the main flow direction of the first fluid cross section.

10. Heat exchanger (30) according to any one of the preceding claims 6 to 9, characterized in that the guide elements (12, 22) on an inner wall (1 1, 21) of a hollow body (10, 20) are arranged, wherein the hollow body (10 , 20) has a first opening and a second opening, through which the first fluid can be flowed, wherein the hollow body (10, 20) can be inserted into a feed line (33) and / or the inlet-side collecting area (32) of the heat exchanger (30) and with these fluid-tight connectable, that the first fluid through the first opening in the hollow body (10, 20) is einström bar and can be flowed through the second opening.

1 1. Heat exchanger (40) according to claim 1, characterized in that the means for preventing a phase separation of the first fluid by a

A plurality or plurality of apertures (44) are formed, which are within the On the inlet side collecting area (42) are arranged and reduce the flow cross section of the inlet side collecting area (42) locally.

12. Heat exchanger (40) according to claim 1 1, characterized in that the apertures (44) are formed by partitions, each having at least one opening.

13. Heat exchanger (40) according to claim 1 1 or 12, characterized in that the singular or plurality of the orifices (44) are fluid-tightly connected to an inner wall of the inlet-side collecting region (42).