EP0048873B1 - Heat transfer device - Google Patents

Abstract

1. Heat transfer device for the transfer of heat between two flowing media which are separated from each other by heat transfer surfaces, in which the heat transfer surfaces are formed as at least two tubes (2) arranged in a tubular jacket (1) and through each of these tubes there extends at least one conduit tube (3) such that a clearance space (13) is formed between each conduit tube and the inner wall surface of the associated tube, and in which both the tubular jacket and also the conduit tubes are connected to each other by way of a distributing chamber (10) for a first medium on the one hand and a collector (15) for the first medium on the other hand, said distributing chamber and collector being separated respectively from a distributing chamber (5a) and collecting chamber (5) for a second medium connecting the tubes and the clearance spaces to each other, characterised in that the tubular jacket (1) and the tubes (2) which are arranged therein and which each surround a conduit tube (3) each have a rectangular cross-section and each conduit tube (3) has a circular cross-section, and, both in the clearance space (30) formed between the outer wall surfaces of the tubes (2) and also in the clearance space (14) formed between the outer wall surfaces of the tubes (2) and the inner wall surface of the tubular jacket (1), there are arranged flow-guiding devices (12) in the form of meander wires having a thickness corresponding to the effective width of the clearance spaces (14, 30).

Description

The invention relates to a heat exchanger for transferring heat between flowing media which are separated from one another by heat transfer surfaces, in which the heat transfer surfaces are designed as at least two tubes arranged in a jacket tube and at least one guide tube extends through each of these tubes in such a way that between a gap space is formed for each guide tube and the inner wall of the associated tube, and in which both the jacket tube and the guide tubes are connected to one another via a distribution space on the one hand and a collector for a first medium, each of which connects the tubes and the gap spaces to one another Distribution chamber or collector chamber for a second medium are separated.

Heat exchangers of this type are becoming increasingly important in the context of increasing energy shortages. This arises from the tendency of rising energy prices, on the basis of which it is increasingly proving to be worthwhile to use, for example, previously unused residual energy via an exchange process. In addition, efficient and inexpensive heat exchangers are required as part of the heat pump technology that is becoming increasingly important.

A large number of heat exchangers, such as coaxial heat exchangers, tube bundle heat exchangers, plate heat exchangers, lamellar tube bundle heat exchangers, are known. It has been found, however, that when using plate heat exchangers, for example, a favorable heat transfer can be achieved due to large heat transfer surfaces, this advantage is countered by major manufacturing disadvantages. Because of the large specific load, it is necessary to use corset constructions that are highly resistant to static loads. Because of this necessity, the cost of materials is high and the construction is necessarily heavy. In addition, there is a need for a large number of surface interlinking points, which on the one hand make production more difficult and on the other hand cost-intensive. Tube heat exchangers also have this disadvantage. In this case, the cost-intensive production is caused in particular by the high-quality material of the welded-in tube bundles and, furthermore, by complex distributor structures, such as spiders, throttles and regulators, which are necessary for optimal operation and which are expensive and produce high pressure losses.

In order to avoid these disadvantages, some have started to use long pipes with small cross sections. But the high pressure losses that arise in this way also prevent optimal operation of the entire system.

It has now become known from FR-PS 603 110 a heat exchanger of the type mentioned and thus corresponding to the preamble of claim 1. In this known heat exchanger only tubes with a circular cross-section are used, namely a jacket tube, tubes arranged therein and, in turn, guide tubes enclosed by them, each with a circular cross-section. This results in the very significant disadvantage for the heat exchanger function that very different passage cross sections are formed for the heat exchanger medium, so that again completely uneven and, above all, uncontrollable flow conditions prevail. This applies particularly to the edge area near the tubular casing with a circular cross-section. The same applies to a heat exchanger of a similar type according to DE-OS-21 43 276. Here too, only tubes with a round or circular cross section are used in the area of the heat exchanger function. For this known heat exchanger, the constructional disadvantages described in the introduction apply.

The invention has for its object to simplify and improve the structure in terms of design and manufacture in a heat exchanger according to the preamble of claim 1, but above all to significantly improve the heat exchange function of the heat exchanger, both by influencing the flow of the flow cross sections provided as well as the design of these flow cross sections with each other.

According to the invention, this object is achieved in a heat exchanger according to the preamble of claim 1 in that the jacket tube and the tubes arranged therein, each enclosing a guide tube, have rectangular cross-sections and each guide tube is round in cross-section, and both in the between the outer walls of the tubes surrounding the guide tubes formed gap space and in the gap between the outer walls of the tubes surrounding the guide tubes and the inner walls of the casing tube flow-guiding devices in the form of meander wires are arranged, the thickness of which corresponds to the inside width of the gap spaces.

This structure initially allows economical production. It is essential here that the individual connections, in particular welding points, are easily accessible and, on the other hand, that the individual parts can be joined together in the simplest way. Because of their dimensional stability, the pipes that are joined together meet high strength requirements. Continue to pretend partly noticeable that inexpensive semi-finished products can also be used within the structure.

Furthermore, significant advantages are achieved with regard to the heat exchange function: since the jacket tube and the tubes surrounding the guide tubes are provided with a rectangular, preferably square cross-section, it is possible to separate the gaps between the jacket tube and the tubes surrounding the guide tubes and between the tubes surrounding the guide tubes themselves to be provided with a completely constant cross-section. In this way, it is initially achieved in principle that the flow conditions in all of the gap spaces formed in this way are constant, which in turn means very good use of space within the body formed by these tubes and the jacket tube with its gap spaces. Due to this constant cross section, the pressure losses that are particularly significant in such a heat exchanger are limited to a minimum. The rectangular or square cross-sectional shapes of the pipes mentioned also lead, in conjunction with the meandering wires guided through the gap spaces, to complete and secure support of these pipes with one another, which is essential in the case of the considerable pressure differences that occur. At the same time, the meander wires arranged in the gap cross-sections which remain the same create a flow guide which leads to automatic turbulence, so that the laminar flows which are disadvantageous for heat transfer are reliably and completely avoided. Thus, the constructively and functionally achieved effects combine to an essential advantage with regard to the heat exchange function, namely with regard to a safe, uniform and particularly good heat transfer.

Another very important advantage results from the combination according to the invention of the guide tubes with a round cross-section with the tubes surrounding them with a rectangular, in particular square, cross-section. This leads to a significant advantage with regard to the flow characteristics for the further transmission medium. Zones with different flow cross-sections are formed in the space between the round guide tube and the rectangular or square tube surrounding it, so that in the zones with a small cross-section (outer wall of the guide tube opposite the respective side wall of the surrounding tube) it cools down faster and thus to a Compression of the medium there in the case of a gas and in the extreme case for condensation. Since the zones in the respective corner cross sections between the round guide tube and the surrounding rectangular or square tube have a much larger heat transfer path, even slight temperature differences lead to deliberate turbulence and fluidized bed formation, which also avoid laminar flow and in turn lead to better utilization of the exchange surface, because a better distribution of the medium flow is achieved. This is a very important advantage for the evaporation and condensation process within the pipes.

The described mutual support of the tubes surrounding the guide tubes and the jacket tube in each case creates a type of honeycomb structure which brings about a high overall strength even with small wall thicknesses of the individual tubes. The heat exchanger can therefore be used at a high pressure level without the need for high-strength materials for its formation.

Further advantageous developments of the invention are characterized in the subclaims. The invention is explained in the following description of an embodiment with reference to the drawing, which shows a longitudinal section through a heat exchanger according to the invention.

The basic components of the heat exchanger are a jacket tube 1, tubes 2 and guide tubes 3. The casing tube 1 has a rectangular, preferably a square cross section. The tubes 2, which have a rectangular, preferably square, cross section adapted to the cross section of the jacket tube 1, extend through this jacket tube 1 in the longitudinal direction, so that four tubes 2 are distributed over the cross section of the jacket tube 1.

The guide tubes 3 with a round cross section extend through the tubes 2 parallel to these. These have an insignificantly smaller cross-section than the tubes 2. The guide tubes 3 are provided with outer surfaces, between which and the inner surfaces of the tubes 2 opposite them a relatively small gap space 13 is provided, which has a small flow cross-section.

The casing tube 1 is closed at both ends with covers 8, 8a. These covers 8, 8a delimit anterooms 7, 7a on their inner sides facing the tubes 2, into which the guide tubes 3 open. In the area of the mouths of the guide tubes 3, these are connected to one another via tube plates 6, 6a. These tube sheets 6, 6a delimit the vestibules 7, 7a in the casing tube 1 on the side opposite the covers 8, 8a.

The vestibules 7, 7a are connected via inlet openings 20, 21 to an inlet nozzle 11 and an outlet nozzle 11a. Depending on the circuit provided in each case, a medium enters or exits the heat exchanger in these inlet connections 11, 11a. The medium entering through the inlet nozzle 11 flows through the inlet opening 20 into the antechamber 7, flows through the interior of the guide tubes 3, collects in the antechamber 7a and exits via the inlet opening 21 through the outlet nozzle 11a.

The tube sheets 6, 6a limit on their from

A distributor chamber 5a or a collector chamber 5 facing away from the anterooms 7, 7a. This distributor chamber 5a or collector chamber 5 is delimited on its side facing away from the tube sheets 6, 6a by orifices 22, 23, which are formed by flanging the distributor chamber 5a or Collector chamber 5 facing ends 24, 25 of the tubes 2 are formed. These ends 24, 25 are connected to one another via welds 4. Depending on the quality of the medium acting on the tubes 2, all other connection options of the ends 24, 25 can also be used, for example adhesive connections. In addition, the ends 24, 25 are also connected on their sides facing the jacket tube 1 to the latter via weld seams 4. Other connection options can also be used here.

The distributor chamber 5a and the collector chamber 5 are each connected via openings 26, 27 to an outlet nozzle 9 and an inlet nozzle 9a. A second medium acting on the guide tubes 3 on their outer sides passes through these openings 26, 27. This medium flows through gap spaces 13 so that it achieves a relatively high passage speed in view of the small passage cross section of these gap spaces 13.

The inlet nozzle 11 and the outlet nozzle 11 are each connected via a distributor space 10 or collector 15 to the inlet openings 20 or 21 and also to a further inlet opening 28 or 29 which are arranged in the casing tube 1. Through these inlet openings 28, 29, the medium flowing through the inlet nozzle 11 or flowing out of the outlet nozzle 11a can enter or exit an interior space 30 formed by the casing tube 1. This interior 30 is traversed by the tubes 2, so that only gap spaces 14 remain of it, through which the medium flowing through the nozzles 11, 11a passes. This medium enters through the inlet opening 28, flows through the gap spaces 14 and merges via the outlet opening 29 with the medium emerging from the vestibules 7, 7a in the region of the distributor space 10 or collector 15.

The gap spaces 14 are traversed by flow-guiding devices in the form of meandering wires 12, the diameter of which corresponds approximately to the clear width of the gap spaces 14. In this way it is achieved that the tubes 2 are mutually supported. In addition, the meandering wires 12 are used to support the tubes 2 with respect to the jacket tube 1. The meander wires are laid in the manner that is most favorable for the respective heat transfer purpose. For example, it is conceivable to wind the meandering wires spirally around the tubes 2, so that a crosswise or opposite to the medium passing through the guide tubes 3. Cross flow of the second medium passing through the casing tube 1 is achieved. In addition to this laying of the meander wires, any other type of fastening can also be considered, so that any type of mutual flow conditions can be realized in the heat exchanger.

In addition to the arrangement of four pipes 2 in the casing pipe 1, any other arrangement of pipes 2 in the casing pipe 1 can also be carried out. It is essential that the respective gap spaces 13 and 14 are provided with such a narrow passage cross-section that the media passing through them are suitable for the respective gap spaces 13 and 14 by appropriate selection of cross sections of both the casing tube 1 and the tube 2 and the guide tubes 3 get an optimal heat transfer necessary passage speed. For example, it is conceivable to also arrange tubes 2 to be dimensioned in a jacket tube 1 with a square cross section in a number that corresponds to the square number of the basic numbers. However, it is also possible to give the jacket tube 1 a rectangular cross section with a corresponding number of tubes 2. In any case, the dimensioning of both the casing tube 1 and the tube 2 and the guide tubes 3 will have to be based on the dimensions to which the corresponding tubes can be obtained cheaply, for example as semi-finished products.

The heat exchanger works as follows: a medium, for example cooling water, enters both the antechamber 7 and the interior 30 through the inlet connection 11 and the distributor space 10. It is distributed over the interior of the guide tubes 3 and is simultaneously guided past the outer walls of the tubes 2 through the braided wires 12. This medium portion pouring out through the interior 30 of the heat exchanger enters the collector 15 through the outlet opening 29 and is passed on by the latter in the direction of the outlet opening 11a. The medium portion passing through the guide tubes 3 collects in the vestibule 7a, enters the distribution space 15 through the opening 21 and is also discharged through the outlet opening 11a.

In contrast, the other medium, for example hot gas, is introduced into the distribution chamber 5a through the inlet opening 9a. The medium is distributed over the gap spaces 13 and rises in the longitudinal direction of the tubes 2 in the direction of the collector chamber 5. It then exits through the openings 26 in the direction of the outlet nozzle 9.

Instead of the distribution of liquid or gaseous media described here, other media constellations can also be passed through the heat exchanger. In addition, it is also conceivable to adhere to other flow directions. So it is z. B. conceivable to switch the inlet or outlet nozzle 11, 11a and the outlet or inlet nozzle 9, 9a so that the media act either in countercurrent or in cocurrent. As far as gas is used, it is safe Lich expedient to initiate this through the inlet port 9a in the gap spaces 13. On the basis of the construction just described, it can be seen that the complex and heavy corset constructions necessary for plate heat exchangers are superfluous in the subject matter of the invention. The fastening of tube bundles in perforated plates, for example by rolling in or soldering in or welding in, is not necessary.

The heat exchanger according to the invention can be used both as an evaporator and as a condenser. If it is used as an evaporator, it has an optimal gas distribution as a partial pipe apparatus and works due to its design features such as. B. in the prechambers 7, 7a even in flooded operation of the distributor with evenly distributed pressure losses. If, on the other hand, it is used as a condenser, all surfaces involved in the heat transfer are evenly acted upon and utilized by means of uniform evaporation and condensate drainage on the hot gas side. The application of these heat transfer surfaces is arithmetically uniform due to the constructive arrangement of the parallel fluid paths.

The design of the heat exchanger works like a multi-plate heat exchanger, since the heat always passes from one gas path to two parallel liquid paths. Additional distribution apparatuses and / or collectors are unnecessary due to the structural geometry and the vestibules 7, 7a.

By simply joining the pipes 2 and welding them, impairments in strength are eliminated. The compact design of the heat transfer surfaces enables installation in machines in the smallest of spaces.

Since a pure welded construction can be realized, there is no fear of corrosion damage from the oil-contaminated gas side. However, these have to be accepted for silver solders with a high phosphorus content. In addition, any manufacturing leaks that may occur can be remedied inexpensively by simple re-welding.

Pressure losses are very small compared to conventional designs, since very short path lengths are operated in parallel. The heat exchanger can also be used in a large number of applications, since it can be used as a countercurrent, cocurrent, crossflow or crossflow exchanger.

In addition to the structure described and its function, it is also possible to separate the gap spaces 14 and 30 from the anterooms 7, 7a and to assign them separate connection nipples separate from the inlet connections 11, 11a for the anterooms 7, 7a. As a result, the heat exchanger can be used as a tertiary exchanger with three separate heat transfer media.

Claims (14)

1. Heat transfer device for the transfer of heat between two flowing media which are separated from each other by heat transfer surfaces, in which the heat transfer surfaces are formed as at least two tubes (2) arranged in a tubular jacket (1) and through each of these tubes there extends at least one conduit tube (3) such that a clearance space (13) is formed between each conduit tube and the inner wall surface of the associated tube, and in which both the tubular jacket and also the conduit tubes are connected to each other by way of a distributing chamber (10) for a first medium on the one hand and a collector (15) for the first medium on the other hand, said distributing chamber and collector being separated respectively from a distributing chamber (5a) and collecting chamber (5) for a second medium connecting the tubes and the clearance spaces to each other, characterised in that the tubular jacket (1) and the tubes (2) which are arranged therein and which each surround a conduit tube (3) each have a rectangular cross-section and each conduit tube (3) has a circular cross-section, and, both in the clearance space (30) formed between the outer wall surfaces of the tubes (2) and also in the clearance space (14) formed between the outer wall surfaces of the tubes (2) and the inner wall surface of the tubular jacket (1), there are arranged flow-guiding devices (12) in the form of meander wires having a thickness corresponding to the effective width of the clearance spaces (14, 30).

2. Heat transfer device according to claim 1, characterised in that the tubular jacket (1) and the tubes (2) arranged therein and each surrounding a conduit tube have a square cross-section.

3. Heat transfer device according to claim 1 or 2, characterised in that the meander wires (12) are offset relative to one another by 90° in order to create a spiral flow effect.

4. Heat transfer device according to one of claims 1 to 3, characterised in that the distributing chamber (5a) and the collecting chamber (5) are arranged within the tubular jacket (1) and are defined on the side opposite the tube ends (4, 24, 25) by tube base members (6, 6a) closing off the tubular jacket cross-section.

5. Heat transfer device according to claim 4, characterised in that the distributing chamber (5a) and the collecting chamber (5) are separated by the tube base members (6, 6a) from prechambers (7, 7a), which are connected to a distributing chamber (10) and to a collector (15) for the other medium and into which the conduit tubes (3) issue.

6. Heat transfer device according to claim 5, characterised in that the distributing chamber (10) and the collector (15) are each connected to the clearance spaces (14, 30) between the tubes (2) and the tubular jacket (1).

7. Heat transfer device according to claim 5 or 6, characterised in that each prechamber (7, 7a) is formed within the tubular jacket (1) immediately next to the distributing or collecting chamber (5, 5a) and is separated from this chamber only by the tube base member (6, 6a).

8. Heat transfer device according to claim 5, 6 or 7, characterised in that the prechambers (7, 7a) are connected to each other by way of the conduit tubes (3) and the clearance spaces (14, 30) between the tubes (2) and the tubular jacket (1).

9. Heat transfer device according to one of claims 1 to 8, characterised in that the distributing chamber (5a) and the collecting chamber (5) are connected to each other by way of the clearance spaces (13) with small throughput cross-section between the tubes (2) and the conduit tubes (3).

10. Heat transfer device according to one of claims 1 to 9, characterised in that the tubular jacket (1), the tubes (2) and the conduit tubes (3) extend in the vertical direction between the distributing chamber (5a) and the collecting chamber (5).

11. Heat transfer device according to one of claims 1 to 10, characterised in that liquid flows in the conduit tubes (3) and in the clearance spaces (14, 30) between tubular jacket (1) and tubes (2) and gas flows in the clearance spaces (13) extending between the conduit tubes (3) and the tubes (2).

12. Heat transfer device according to claim 11, characterised in that there is provision for heat transfer from the liquid to the gas.

13. Heat transfer device according to claim 11, characterised in that there is provision for heat transfer from the gas to the liquid.

14. Heat transfer device according to one of claims 1 to 13, characterised in that it is constructed as a condenser.

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