EP0910778A1

EP0910778A1 - Flat tube evaporator with vertical flat tubes for motor vehicles

Info

Publication number: EP0910778A1
Application number: EP98922800A
Authority: EP
Inventors: Roland Haussmann
Original assignee: Valeo Klimatechnik GmbH and Co KG
Current assignee: Valeo Klimatechnik GmbH and Co KG
Priority date: 1997-05-07
Filing date: 1998-05-05
Publication date: 1999-04-28
Anticipated expiration: 2018-05-05
Also published as: BR9804884A; CN1225713A; WO1998050741A1; DE19719263C2; DE19719263A1; EP0910778B1; US20010003310A1

Abstract

A flat tube evaporator for a motor vehicle air conditioning system has vertical flat tubes (2) and zigzag blades (8) arranged between the flat tubes (2). The heat exchange fluid can flow along the apex of the zigzag branches (38) of the blades (flow direction indicated by arrow 9). According to the invention, a water flow gutter (50) extending downwards on both sides of the flat tubes (2) is designed next to the rear end region (52) of the zigzag blades (8), seen in the flow direction (arrow 9) of the outer heat exchange fluid.

Description

Flat tube evaporator with vertical longitudinal direction of the flat tubes in motor vehicles

The invention relates to a flat tube evaporator, in particular made of aluminum or an aluminum alloy, for motor vehicle air conditioning systems with the features of the preamble of claim 1. Such a flat tube evaporator is known, for example, from US-A-4,350,025.

When operating a flat tube evaporator for automotive air conditioning systems, it is a general endeavor to prevent condensed water or other moisture from being blown under the inflow of the external heat exchange fluid, generally air, into areas of the automotive air conditioning system which are further back, where the occurrence or even the accumulation of moisture annoying to harmful.

In a known multi-flow flat tube evaporator, in which separately manufactured flat tubes are assigned to the individual floods, vertical gaps remain between these separately manufactured flat tubes, which can be used as vertical drainage channels for moisture if necessary. If necessary, water drained off in this way can be collected and discharged through a drip tray (EP-A2-0 709 643).

Problems of water drainage exist, however, if the flat tube is provided undivided. Such undivided use of flat tubes, however, offers less manufacturing effort than the assembly of separately manufactured flat tubes. The flat tube evaporator according to US Pat. No. 4,350,025 ensures, especially when using only one-piece flat tube arrangements, that moisture is removed, which is caused by the zigzag lamellae inside the ribbing. len may arise. This is because experience shows that moisture, such as, in particular, condensed water, is initially carried along by the outer heat exchange medium in the ribbing by the zigzag fin and only accumulates at the end of the flow path through the ribbing. In the flat tube evaporator according to US Pat. No. 4,350,025, therefore, following the end region of the zigzag fins lying at the back in the flow direction of the external heat exchange fluid, a water drainage channel running through from top to bottom is attached to an extension piece integrally produced with the flat tube the narrow end face of the flat tube, which is formed by a T-profile, the central web of which is connected to the narrow end face of the flat tube and which projects beyond the zigzag fins in the direction of flow of the external heat exchange fluid.

In this known flat tube evaporator, the T-shaped lugs on the end regions of the flat tubes lying at the rear in the flow direction of the external heat exchange fluid increase the material expenditure and the structural depth of the flat tube evaporator and require complex production technology. In addition, the approaches freely protruding from the zigzag lamellae cannot absorb and dissipate such moisture that sticks like drops within the area of the zigzag lamellae and thus cannot get from the external heat exchange fluid to the water drainage channels arranged behind the zigzag lamellae in its flow direction.

The invention is therefore based on the object of being able to achieve an effective water drainage function from the zigzag lamellae with simple production technology without additional expenditure on material and structural depth.

This object is achieved in a flat tube evaporator according to claim 1.

It is known per se in a flat tube evaporator, the plates of which run vertically like the flat tubes and nested zigzag fins between the plates are to form a vertical water drainage channel on the outside of the plates. The plates of flat tube evaporators, however, have relatively thick walls of their channels, in which the formation of a water drainage channel is possible much more easily than with flat tubes, in which the design of such a channel directly in the flat tube area within which the individual channels run, with an influence on the Channel cross-section is connected by the indentation, by means of which the condensate drainage channel is to be formed. Such an arrangement of a vertical condensate drainage channel in the flat outside of a flat tube therefore does not require considerations to date to what extent the entire thermodynamic operation of the flat tube evaporator can still be maintained with good efficiency. In this sense, the concrete solution of claim 2 is original.

According to the invention, the drainage channel required in each case can be formed by pressing in without additional manufacturing, material and structural expenditure when cutting the flat tubes from a coil. If necessary, several drainage channels can be provided with indentations and condensate accumulated in the area of the zigzag lamellae, in the case of early accumulation of condensate in the package of zigzag lamellae even after a possibly relatively small section of the flow, and practically drained off in the statu nascendi.

The development according to claim 2 is particularly interesting when the ribbing by means of the zigzag lamellae has legs that are relatively closely adjacent to one another. It has been shown that, on the one hand, the shape according to claim 2 in the manufacture of the flat tube evaporator is still relatively simple and, on the other hand, the relatively narrow distance between the legs of the zigzag lamella in the vicinity of the water drainage channel leads to moisture automatically at this constriction accumulates, all gradually grows to a larger build-up and then, when it grows up to the condensate drainage channel, can run off again largely without residue. This further counteracts the entrainment of moisture in the flow direction by means of the inflowing external heat exchange fluid.

For the function of the invention it is therefore necessary that the drainage channels are provided in the area of the lamellae where the condensed water is produced. However, such drainage channels are disturbing at the connection ends of the flat tubes, where soldering is carried out, for example, to a tube sheet. Claim 3 provides here to refrain from the indentation which the water drainage channel can form in the soldering area. For this purpose, according to US-A-4,350,025, the T-profile web there had to be cut to length, which requires complicated post-processing, for example by sawing out or milling. In the context of the invention, the same effect can be achieved without problems by not indenting the indentation in the end regions of the flat tubes when they are cut to length from the coil.

The invention is explained in more detail below with the aid of schematic drawings using several exemplary embodiments. Show it:

Figure 1 is a perspective view of a flat tube evaporator, in which the longitudinal extent of the flat tubes 2 is vertical.

FIG. 2 shows a cross section in the flow direction of the outer heat exchange fluid through a section of the block arrangement of flat tubes and zigzag fins with a detailed illustration at the rear end of the illustration of FIG. 2 in the flow direction of the outer heat exchange fluid; such as

Fig. 3 in an enlarged scale a plan view of a zigzag lamella nested between two adjacent flat tubes, looking in the direction of flow of the external heat exchange fluid.

The flat tube heat shown in Fig. 1 metauscher is double-flow and designed as an evaporator of a refrigerant circuit.

This does not rule out the transfer of the features shown to flat tube heat exchangers with a different number of flows.

The flat tube evaporator has the following general structure:

A larger number of typically twenty to thirty flat tubes 2, which extend vertically, are arranged with constant mutual distances and aligned end faces 4. A zigzag lamella 8 is sandwiched between the flat sides 6 of the flat tubes. Likewise, a zigzag fin 8 is also arranged on the two outer surfaces 4 of the outer flat tubes. Each flat tube has inner stiffening webs 10 which divide chambers 12 acting as continuous channels in the flat tube. Depending on the overall depth, a number of chambers 12 of ten to thirty is typical.

The specified typical ranges of the number of flat tubes 2 and their chambers 12 are only intended to be preferred and not restrictive.

In a motor vehicle air conditioning system, the block arrangement of the flat tubes 2 and the zigzag fins 8 is flowed through by outside air in the direction of the arrow 9 shown in FIGS. 1 and 3 in the depth direction as the external heat exchange medium in the finished state.

The internal heat exchange medium in the evaporator is a refrigerant such as, in particular, fluorocarbon, which enters the heat exchanger via a feed line 14 and exits the heat exchanger via an outlet line 16. The supply line comes from the condenser in the refrigerant circuit. The output line 16 leads to the compressor of the refrigerant circuit.

From the feed line 14, the refrigerant is distributed on the inlet side to the individual flat tubes by a so-called distributor. On the output side it will Refrigerant collected is fed to the outlet line 16. If the distribution and the collection can also be assigned to separate boxes, both functions are combined in a common collector 18.

This collector 18 is then arranged on one end face 4 of the flat tubes 2, while on the other end face 4 of the flat tubes 2 there is only a flow reversal between the floods, here according to FIG. 1 in a common deflection header 22.

In the borderline case of a single-flow heat exchanger, the deflection header 22 would be replaced by an output header, not shown.

The multiple flow means at least one reversal of the flow in the area of the individual channels formed by the chambers 12 in each flat tube 2. In the dual flow - the two floods in FIG. 1 are separated from each other by a stiffening web 10a in each flat tube 2 - the deflection collector 22 does not need further sub-chamber subdivision, only the one-time deflection function must be guaranteed. In the case of more than two-flow deflection, at least one partition is required in the deflection collector 22, so that, in the case of a four-flow arrangement, a double simple deflection takes place in the respective deflection collector 22. If the number of floods is even higher, the number of partitions may have to be increased.

The collector 18 is composed of a tube sheet 26 and a cover 28 without restriction of the generality, wherein further parts can optionally be provided for the construction of the collector 18.

The free ends of the flat tubes 2 facing away from the deflection header 22 engage tightly in communication with the interior of the header 18 in the tube sheet 26, which is accordingly provided with engagement slots and, if appropriate, inner and / or outer engagement nozzles.

Since the input function and the output function of the refrigerant are combined in the collector 18, the Collector 18 at least a two-chamber design, which separates an input side from the output side. For this purpose, the chamber subdivision has at least one flat web in the form of a longitudinal web 32 which separates the input area in the collector 18 which communicates with the feed line 14 from an outlet chamber 34 which runs continuously along the collector 18 and which communicates with the output line 16.

In the evaporator, it is also necessary for the inlet-side refrigerant to be fed as uniformly as possible to all flat tubes 2. In the limit case, the supplied refrigerant can be fed separately to each individual flat tube 2 via a so-called distributor. Usually, however, the supply to adjacent groups of flat tubes 2 takes place, in which at least some groups have a higher number of flat tubes than one, and the number of flat tubes 2 per group can also change. Each group of flat tubes 2 is assigned its own entry chamber, which communicates directly with the relevant group of flat tubes 2. The separate entry chambers are separated from one another in the chamber subdivision by transverse webs designed as flat webs.

In the double-flow evaporator, the transverse webs go off at right angles only from one side of the longitudinal web 32.

In the case of a four-flow evaporator, in addition to the longitudinal web 32 which adjoins the outlet chamber 34, a further longitudinal web parallel to this is provided. This is crossed at right angles by the transverse webs dividing the individual entry chambers of the groups of flat tubes up to the longitudinal web 32. In the extension of the transverse webs between the two longitudinal webs, an inner deflection chamber adjoining the respective respective outer entrance chamber for diverting the second flood into the third flood within the collector 18 is divided between these longitudinal webs.

With higher numbers of floods, which are guided by the collector 18 with a deflection function, speaking the number of longitudinal webs and the number of inner deflection chambers, which are then also nested in the transverse direction of the collector lying inside each other between the own inlet chambers of the groups of flat tubes 2 and the outlet chamber 34.

The feed line 14 communicates with the individual entry chambers via a feed line 44 running in the collector 18, which can be designed differently, e.g. summarized in a tube.

In the finished heat exchanger, the block of flat tubes 2 and zigzag fins 8 is laterally closed off by a side plate 36 which bears against the outer zigzag plate, so that the side plates 36 form an outer frame for the outside air flowing into the heat exchanger block.

The flat tubes 2, the zigzag fins 8, the tube plate 26 and the cover 28 of the collector together with the optionally provided chamber division as well as the side plates 36 of the heat exchanger consist expediently, like the feed line 14 and the outlet line 16, of aluminum and / or an aluminum alloy including the portions of the pipe connections adjacent to the heat exchanger to the finished evaporator brazed.

Without this being shown, in practice in refrigerant evaporators for motor vehicle air conditioning systems according to FIG. 1, the supply line 14 and the output line 16, which can pass into the collector 18 via corresponding connecting pieces, are connected to two corresponding connecting pieces of a thermostatically controlled block valve. On the opposite side, which is not visible, this has two further supply-side and outlet-side connecting pieces.

The tube sheet 26 and the cover 28 are formed from sheet metal pre-coated with solder. The free edge of the cover engages in the tube sheet 26 with at least one-sided overlap. 3, it can be seen that the sectional view in question is guided through a channel 12 by two flat tubes 2 running vertically parallel to one another. However, the following explanations also apply if a cut were considered which each runs through a stiffening web 10 of the same flat tube 2.

The special arrangement of a zigzag fin 4 is shown at right angles to the direction of flow of the external heat exchange fluid 9, with a view in the direction of the direction of flow. The individual legs 38 of the zigzag lamella extend in the flow direction of the arrow 9 of the external heat exchange fluid and are connected to one another by rounded apices 40 in the continuation direction of the zigzag lamella, that is to say in the vertical direction. The apices 40 are each fastened to the adjacent flat side of the adjacent flat tube 2 by brazing points 42. The arrangement and design of the legs 38 and the apex 40 is such that the free flow cross section for the external heat exchange fluid according to the arrow 9 is greater within the curvature of the apex 40 than in the area of the free distance 44 from two adjacent to the same flat tube 2 Vertex 40. Thus, the space 46 between adjacent legs 38 of the zigzag lamella 8 in the area of the free distance 44 is narrower than in the vicinity of the apex 40. This leads to the fact that it is under the influence in the area of the narrow point defined by the free distance 44 from surface tensions to capillary deposition 48 from moisture entrained by the external heat exchange fluid.

These deposits 48 of liquid collect at the rear ends in the flow direction of the external heat exchange fluid according to the arrow 9 of the width extension of the zigzag lamella 8 or of its legs 38. Within the scope of the invention, care is taken to ensure that when the zigzag lamellae are arranged and formed as shown in FIG 3, or else with an arrangement and design comparable with regard to the creation of liquid deposits 48, it is ensured that the deposits 48 do not remain in the zigzag lamella 8 and narrow their clear cross-section, but are selectively removed at least from time to time.

For this purpose, it is useful to arrange a device that removes the accumulated liquid in the vicinity of the liquid deposits 48, specifically at the rear area in the direction of flow of the external heat exchange fluid according to arrow 9.

For this purpose, in all three illustrated exemplary embodiments, in the vicinity of the rear end of the zigzag fin 8 in the direction of flow of the external heat exchange fluid according to the arrow 9 or of its legs 38, a water drainage channel 50 running vertically from top to bottom is formed on each of the two adjacent flat tubes 2.

In all of the exemplary embodiments, it is assumed that the zigzag lamella 8 projects in the direction of the arrow 9 in each case over the adjacent flat tubes 2 with a protrusion 52, a feature which is generally useful for realizing the invention.

2, the respective vertical water drainage channel 50 is formed by a vertical indentation 60 on the flat side of the adjacent flat tube 2 facing the adjacent zigzag lamella, the indentation advantageously being carried out on the wall surface of a channel 12. Although the indentation 60 in question can also take place on the channel 12 of the respective flat tube 2, which is at the rear in the direction of flow of the external heat exchange fluid according to arrow 9, FIG. 2 shows that the water drainage channel can also be seen in a previous channel, here the penultimate channel seen in the aforementioned Flow direction can be formed. It is expedient that this indentation in each case has a free distance 44 between adjacent legs 38 of the zigzag lamella.

As can also be seen from FIG. 1, the connection ends 62 of the flat tubes 2 are kept free from the formation of the respective indentation 60.

Claims

1. Flat tube evaporator, in particular made of aluminum or an aluminum alloy, for motor vehicle air conditioning systems with flat tubes (2), the longitudinal direction of which is vertical, and zigzag fins (8) arranged between the flat tubes (2) and the legs running along the apex (40) of their zigzag shape (38) from the external heat exchange fluid, in particular air, can flow against (arrow 9), the connection to the end region (52) of the zigzag fins (8) on the flat tubes (2) on the flat tubes (2), which are at the back in the flow direction (arrow 9) of the external heat exchange fluid A water drainage channel (50) running through from top to bottom is formed, characterized in that the water drainage channel (50) is formed on the outer surface as an indentation (60) of the flat side of the flat tube (2) and on the outer side in the direction of flow (arrow 9) Heat exchange fluid is located at the rear end region (52) of the zigzag fins (8).

2. Flat tube evaporator according to claim 1, characterized in that the space (46) between adjacent legs (38) of the zigzag fin (8) in the vicinity of Water drainage channel (50) is narrower (at 44) than in the vicinity of the apex (40).

3. Flat tube evaporator according to claim 1 or claim 2, characterized in that the connection ends of the flat tubes (2) are kept free from the formation of the respective indentation (60).