EP1217319B1 - Heat exchanger for heat transfer between a refrigerant and a water/glycol mixture - Google Patents

Abstract

The heat transfer assembly, and especially between a coolant and a water/glycol mixture, has at least one spiral packet (2) within the cylindrical mantle of the heat exchanger (1), to carry a high pressure coolant flow e.g. of carbon dioxide, tetrafluoroethane or propane. A heat/cold carrier flows through the cylindrical structure, to transfer heat/cold between the flow and the coolant in a counter flow or a common flow or intersecting flows. The assembly has connections for coolant feed (3) and outflow (4), for the inflow (5) of the heat/cold carrier and its outflow (6).

Description

The invention relates to a heat exchanger for heat transfer between a refrigerant and a water / glycol mixture.

Heat exchangers are apparatuses or components in which an indirect heat transfer takes place. In this case, heat is transferred from a fluid stream of higher temperature to another fluid stream of lower temperature. The two streams flow through the heat exchanger, without mixing, so are spatially separated from each other.

In a classic refrigeration system or heat pump, at least two heat exchangers are present. The evaporator and the condenser / gas cooler, but often also an internal heat exchanger. The refrigerant circuit is a material cycle in which heat is absorbed in the evaporator with evaporation of the refrigerant and in the condenser, heat is released from the refrigerant.

In the prior art, a variety of heat exchangers for a variety of applications are known.
Very special requirements are placed on heat exchangers, which work at high fluid pressures of the material flows.

Such heat exchangers are e.g. from documents DE 19808893, DE 19635454, US 3340588, DE 19623259 and EP 0529819.

For such an application, heat exchangers are used according to the preamble of the present invention.

In the recent past, carbon dioxide is increasingly being studied as a refrigerant and the production of such systems is being considered. at Carbon dioxide (R744) is referred to as a high-pressure refrigerant, since the critical temperature of the carbon dioxide in the range of the ambient temperature (31 ° C) and the associated pressure is significantly higher than that of today's conventional refrigerants (R134a, R290, R212).
The maximum occurring high pressure is in systems with carbon dioxide as a refrigerant in a range of 100 to 170 bar, depending on the application of the system.

Heat exchangers are already known for the use of the refrigerant carbon dioxide in the refrigeration plant - heat pump process, which operate with very small flow cross sections and capacities in the heat exchangers.

Increasingly, carbon dioxide is used as refrigerant for vehicle air conditioning in mobile refrigeration systems, heat pumps or combinations of these. In such a case, heat is transferred between a water / glycol mixture and carbon dioxide or another refrigerant. Thus, the requirements for a heat exchanger for this application increase in several respects. From the point of view of safety, susceptibility to damage and destructibility as well as from the point of view of minimum space requirements exist, which are not achieved by known in the art heat exchangers.

It is an object of the invention to form a heat exchanger, in particular for heat transfer between a refrigerant and a water / glycol mixture such that it works with a low volume at high heat transfer streams transmitted and at the same time the safety requirements are met for the use of a high-pressure refrigerant.

According to the invention the object is achieved with a heat exchanger according to claim 1.

According to the concept of the invention, the spiral package is structurally designed so that the safety requirements are met by maintaining low flow cross-sections in the refrigerant channels and small filling volume in the spiral package.

The spiral packages consist of flat tube with refrigerant channels, wherein the flat tube is wound along its length.

In a preferred embodiment, the position of winding axis of the spiral pack and cylinder axis of the heat exchanger is identical.

Furthermore, the flat tube is advantageously formed with ribs for spacing between adjacent windings and channeling for the heat / cold carrier in the wound state and for enlarging the surface.

The advantages of the heat exchanger according to the invention are that in a confined space a heat exchanger is provided, which has a large heat-transferring surface and also by its design meets the safety requirements for use in a circuit with refrigerant.

Fig. 1:

Längsschnitt eines Wärmeübertragers

Fig. 2a:

Querschnitt eines Wärmeübertragers mit einem zweiflutigen Kältemittelstrom im Spiralpaket

Fig. 2b:

Querschnitt eines Wärmeübertragers mit einem einflutigen Kältemittelstrom im Spiralpaket

Fig. 2c:

Querschnitt eines Wärmeübertragers mit einer Einfachspirale, der nicht Teil der Erfindung darstellt.

Fig. 3a:

perspektivische Ansicht des Flachrohrs mit Quer- und Längsschnitt

Fig. 3b:

Querschnitt des Flachrohrs

Fig. 4a:

Längsschnitt des Flachrohrs mit Rippen auf der Oberseite

Fig. 4b:

Längsschnitt des Flachrohrs mit Rippen auf der Ober - und Unterseite

Fig. 4c:

Längsschnitt des Flachrohrs mit Rippen entweder auf der Ober - oder der Unterseite jeweils auf einem bestimmten Abschnitt

Fig. 5a:

Draufsicht auf ein Flachrohr mit Rippen quer zur Kältemittelströmungsrichtung

Fig. 5b:

Draufsicht auf ein Flachrohr mit Rippen schräg zur Kältemittelströmungsrichtung

Further details, features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Show it:

Fig. 1:

Longitudinal section of a heat exchanger

Fig. 2a:

Cross-section of a heat exchanger with a double-flow refrigerant flow in the spiral package

Fig. 2b:

Cross-section of a heat exchanger with a single-flow refrigerant flow in the spiral package

Fig. 2c:

Cross section of a heat exchanger with a single spiral, which does not form part of the invention.

Fig. 3a:

Perspective view of the flat tube with transverse and longitudinal section

3b:

Cross section of the flat tube

Fig. 4a:

Longitudinal section of the flat tube with ribs on the top

Fig. 4b:

Longitudinal section of the flat tube with ribs on the top and bottom

4c:

Longitudinal section of the flat tube with ribs either on the top or bottom on a specific section

Fig. 5a:

Top view of a flat tube with ribs transverse to the refrigerant flow direction

Fig. 5b:

Top view of a flat tube with ribs obliquely to the refrigerant flow direction

An advantageous embodiment of the heat exchanger according to the invention is shown in Fig. 1 in longitudinal section.
The cylindrical jacket of the heat exchanger 1 is designed as a circular cylinder in the form of a tube which is tapered at its ends to connecting piece 7. In the interior of the heat exchanger 1 is at least one, in the present case three spiral packets 2 are arranged, which are flowed around in order from the heat / brine. The heat exchanger 1 further has connection possibilities for the refrigerant supply 3 and the Refrigerant discharge 4, the heat / refrigerant supply 5 and the heat / refrigerant removal 6 on.

The spiral packets 2 are flowed through by a refrigerant and flows around it by a heat / refrigerant, wherein heat is transferred between the high-pressure refrigerant and the heat / refrigerant in the cross-flow or Kreuzgegen- or cross-direct current.

The spiral packages 2 are formed of a flat tube 9 having the width (B) of five to one hundred and twenty millimeters (5 to 120 mm) and the height (H) of one to ten millimeters (1 to 10 mm). The flat tube 9, which has at least one refrigerant channel 10, is flowed through by these refrigerant channels of refrigerant. The spiral packets 2 are formed from wound flat tube 9, which is wound along its length (L) in a double layer. The winding axis 13 of the spiral package 2 is shown in FIG. 1 advantageously in the same position as the cylinder axis 13 of the heat exchanger. 1

In a particularly advantageous embodiment, the flat tube 9 ribs 11 for spacing between adjacent windings within the spiral pack 2 and channel formation for the heat / cold carrier in the wound state and to increase the surface area.

The heat exchanger 1 also has a safety device 8 against overpressure, for example in the form of a rupture disk or a safety valve and is equipped at a suitable location with a venting device.

The inventive design of the spiral packets 2 is shown in Figures 2a and 2b in cross section. You can see double spirals, which can be produced in a particularly simple way, The heat exchanger 1 with spiral packages 2 of simple spirals, according to FIG. 2c, however, does not form part of the invention.

FIG. 2 a shows the cross section of a heat exchanger 1 with a double-flow refrigerant flow in the spiral pack 2. The double spiral is then flowed through in multiple flutes spirally from inside to outside by refrigerant and exits at the refrigerant discharge 4 from the spiral pack 2 and leaves the heat exchanger 1.

FIG. 2 b shows the cross section of a heat exchanger 1 with a single-flow refrigerant flow in the spiral package 2. In this case, the double spiral is first flowed through by the refrigerant supply 3 from the outside to the inside of the refrigerant and after reaching the winding and cylinder axis 13, the refrigerant flows from the inside to the outside to the refrigerant discharge 4, through which the spiral pack 2 and after the heat exchanger 1 is left.

Fig. 2c shows an embodiment of a spiral package 2 as a single spiral with single-flow refrigerant flow from the inside to the outside or from outside to inside, which is not part of the invention.

The spiral packages are formed according to the flat tube 9. Fig. 3a shows a perspective view of the flat tube with a transverse and longitudinal section. Arrows indicate the flow of the refrigerant through the refrigerant channels 10 and the flow of the water / glycol mixture between the ribs 11.

In this case, the refrigerant channels 10 are shown in cross section also in FIG. 3b in their sectional view as a circle. Equally possible, but less advantageous because of the pressure resistance, the formation of the refrigerant channels 10 in an oval or polygonal cross-sectional geometry.

Also, the ribs 11 of the flat tube 9 are shown in Fig. 3a and the penetration of the flat tube 9 of refrigerant channels 10 along the length L of the flat tube is to be seen by the longitudinal section in the refrigerant flow direction.

The flat tubes 9 are advantageously formed with a large width B and height H ratio.

Not shown but is advantageous if the flat tube 9 is flattened at the ends of its width B, which is aerodynamically advantageous in the flow and outflow of heat / brine and from the spiral package 2 and large-volume accumulation areas along the height H of the flat tube are thereby avoided.

The formation of the flat tube 9 with ribs 11 on the upper side is shown in FIG. 4a. The ribs 11 are shown as rectangular elevations on the flat tube 9. This form is favorable in terms of manufacturing and easily results in the winding of the flat tube 9 along its length L channel formation for the flow of heat / refrigerant, however, wide rib shapes are also advantageously used , Both round, oval or triangular shapes are possible embodiments for ribs 11 of the flat tube 9.

The flat tube 9 according to FIG. 4 a is preferably to be used in simple spiral windings of the flat tube 9, wherein in each case one upper side comes into contact with the underside of the flat tube 9 and the spaces forming between the ribs 11 form the channels for the heat / cold carrier.

For the double helical windings according to the invention, the formation of the flat tube 9 according to FIG. 4b is advantageous because in the production of the spiral package 2, the flat tube 9 is bent in the region of the winding axis 13 by 180 ° and thus the top and bottom of the flat tube 9 to each other lie. In order to realize the channel formation for the heat / refrigerant flow, the flat tube 9 is provided with ribs 11 both on the upper and lower side.

FIG. 4c shows an embodiment in which the flat tube 9 was provided with ribs 11 along a region A with ribs 11 on the upper side and along a region B on the underside.
This design is advantageous for the production of a double spiral, provided that the winding axis 13 is placed in the region of the transition of the change of the ribs 11 from the top to the bottom.

The ribs themselves have a height of 0.01 to 10 mm. The range from 4 to 10 mm is used for large flow cross sections. A preferred embodiment of the ribs 11 for smaller flow cross sections, such as for heat exchangers for use in refrigeration systems or heat pumps in motor vehicles consists at a height of 0.1 to 2 mm. For special applications with thin thin tube 9 and correspondingly many windings ribs 11 are used from 0.01 to 0.1 mm.

According to a preferred application of the invention, the ribs 11 according to FIG. 5a extend at an angle of 90 ° to the refrigerant channels 10, whereby the heat transfer between the heat / cold carrier and the high-pressure refrigerant takes place in crossflow. In this case, the flat tube 9 is shown in plan view. The heat / refrigerant flows through the channels formed between the ribs 11 and the refrigerant 3 flows in the flat tube 9 through the refrigerant channels 10. If, according to FIG. 1, the refrigerant supply 3 is displaced after the refrigerant discharge 4 in the flow direction of the heat / cold carrier, then there is a coupled cross counterflow. Other circuit variants, such as the cross-direct current or mixed forms can also be realized with the heat exchanger 1 according to the invention.

In a further embodiment of the invention, the ribs 11 extend at an angle α according to FIG. 5b of greater than 0 ° and less than 90 ° or greater than 90 ° and less than 180 ° to the refrigerant channels 10, whereby the heat transfer between the heat - / Brine and the high pressure refrigerant is carried out directly in cross-counter or DC. In this embodiment, a particularly good heat transfer is achieved, wherein the angle α is to be selected for a particularly efficient heat transfer between 30 ° and 50 °.

The arrangement of several spiral packets 2 in the heat exchanger 1, depending on the application, carried out such that the high-pressure refrigerant flows through the spiral packets 2 in a series circuit or in parallel.

As refrigerant in the context of the preamble of the invention, carbon dioxide (R744), tetrafluoroethane (R134a) and propane (R290) are to be regarded in particular.

LIST OF REFERENCE SIGNS

1

Heat exchanger

2

spiral package

3

Refrigerant supply

4

Refrigerant discharge

5

Heat / brine feed

6

Heat / refrigerant removal

7

spigot

8th

safety device

9

flat tube

10

Refrigerant passage

11

rib

12

venting device

13

Winding axis / cylinder axis

B

Flat tube width

H

Flat tube height

L

Flat tube length

Claims (11)

1. Heat exchanger for heat transfer between a refrigerant and a heat transfer medium/secondary refrigerant, comprising a cylindrical jacket containing at least one spiral package (2) of wound flat tubing (9) with channels (10) for refrigerant to flow therethrough and winding spacers provided thereon for formation of channels for the heat transfer medium/secondary refrigerant to flow therethrough, wherein connections for the refrigerant supply (3) and removal (4) and for the heat transfer medium/secondary refrigerant supply (5) and removal (6) are provided,
   characterised in
   that a spiral package (2) has the form of a double spiral around a winding axis (13),

   - wherein the flat tubing (9) is wound from the region surrounding the winding axis (13) along its length L in a double layer, and

   - wherein an S-shaped run-out of the flat tubing (9) bent through an angle of 180° is provided around the winding axis (13), wherein the upper side and the lower side of the flat tubing (9) are superposed at the S-shaped run-out.
2. The heat exchanger according to claim 1,
   characterised in that fins (11) are provided on the flat tubing (9) as winding spacers of the wound flat tubing (9) and to form channels for the heat transfer medium/secondary refrigerant to flow therethrough, said fins being attached at the top and/or the bottom side of the flat tubing (9).
3. The heat exchanger according to claim 1,
   characterised in that associated with the cylindrical jacket are radially directed spacers which are joined to the cylindrical spiral end winding.
4. The heat exchanger according to claim 1 to 3,
   characterised in that the double spiral (2) is constructed for a single-flow refrigerant stream wherein the refrigerant connections (3, 4) of the double spiral (2) are provided in the central region around the winding axis (13) and in the area of the cylindrical jacket.
5. The heat exchanger according to claim 1 to 3,
   characterised in that the double spiral (2) is constructed for a double-flow refrigerant stream wherein the refrigerant connections (3, 4) of the flat tubing (9) are provided in the area of the cylindrical jacket.
6. The heat exchanger according to claim 1 to 5,
   characterised in that the flat tubing (9) of the double spiral (2) is provided with fins (11) directed from the winding axis (13) on its first region (A) of one spiral on the upper side and is provided with oppositely directed fins (11) in the region (B) of the other spiral on the underside.
7. The heat exchanger according to any one of claims 2 or 6, characterised in that the fins (11) run at an angle α greater than 0° and smaller than 90° to the refrigerant channels (10) whereby heat transfer between the fin-supported heat transfer medium/secondary refrigerant channels and the refrigerant channels (10) takes place within the flat tubing (9) in the cross counter-current or cross concurrent stream.
8. The heat exchanger according to any one of claims 1 to 7, characterised in that a plurality of spiral packages (2) are arranged in a row or parallel inside the cylindrical jacket.
9. The heat exchanger according to any one of claims 1 to 8, characterised in that at least one safety device (8) and/or ventilation device (12) is provided.
10. The heat exchanger according to any one of claims 1 to 9, characterised in that the heat transfer medium/secondary refrigerant is a water/glycol mixture.
11. The heat exchanger according to any one of claims 1 to 10, characterised in that the refrigerants carbon dioxide R744, tetrafluoroethane R134a or propane R290 are provided as high-pressure refrigerant.

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