WO2009062487A2

WO2009062487A2 - Heat exchanger

Info

Publication number: WO2009062487A2
Application number: PCT/DE2008/001870
Authority: WO
Inventors: Christian Wüllner; Ludwig Suhr; Jörg Brüggemann
Original assignee: GEA Luftkühler GmbH
Priority date: 2007-11-14
Filing date: 2008-11-13
Publication date: 2009-05-22
Also published as: WO2009062487A3; DE102007054703A1; DE102007054703B4

Abstract

A heat exchanger (1) has exchanger tubes (2, 3, 4) which are arranged adjacent to one another in a plurality of rows (R, R1, R2) which are situated one on top of the other, which exchanger tubes (2, 3, 4) are acted on at the inside with a product (P) to be cooled and are subjected to a flow of cooling air (KL) from below. At least the exchanger tubes (2) of the lowermost row (R) are provided with inner tubes (10) which can be acted on with a heating medium (HM).

Description

heat exchangers

The invention relates to a heat exchanger according to the features in the preamble of claim 1.

Such a heat exchanger is used, inter alia, in a chemical production process in which arise products that falter at temperatures between 0 ⁰ C and 50 ⁰ C. That is, they become viscous or solid. This is the case, for example, with tar, wax or ice. Nevertheless, such products must be cooled in the still liquid state of higher production temperature, for example in the range of 100 ⁰ C to 120 ⁰ C, to store them in this liquid state in storage tanks or intermediate tanks or can continue to transport.

If cooling air in the form of ambient air between about -20 ⁰ C and +35 ⁰ C is used in the heat exchanger used, it can cause problems in such an air-cooled heat exchanger, since the temperature of the ambient air is not constant. For example, if a heat exchanger for a temperature of summer ambient air in height of about +30 ⁰ C, for a cooling of the product from 120 ⁰ C to 50 ⁰ C and on the further condition that the product has a pour point of +40 ⁰ C, so there is a risk that in the in Flow direction of the cooling air lower rows of tubes of the heat exchanger because of the lowest cooling air temperature, the product reaches the pour point already at +20 ⁰ C ambient air and then due to its consistency can not be pumped through the exchanger tubes of the heat exchanger. As a result, heat is no longer transferred to the ambient air in these lower rows of tubes, so that the ambient air passing through the heat exchanger is no longer heated and therefore reaches the upper rows of tubes of the heat exchanger in a comparatively cold state, so that the product begins to stall there too , This ultimately has the consequence that the entire heat exchanger is filled with solid product. He can then no longer fulfill his task and must be heated with comparatively complex measures from the outside.

Similar to a heat exchanger used for cooling, the conditions in capacitors, in which ice can form in the lower rows of tubes, so that they can freeze completely and possibly even destroyed.

Nevertheless, in order to be able to cool products that are endangered relatively reliably, several methods have hitherto been used in practice. In one method, the switching of the product to be cooled takes place in the thermodynamically unfavorable direct current to the cooling air. This has the disadvantage that the heat exchanger must be larger than in a countercurrent circuit. In addition, this process only protects up to a certain temperature range. Below this temperature range, it still comes to stagnation of the product.

Another method is to switch on an intermediate cooling circuit. In this, with the help of an air-cooled plant for example water in the Cooled circuit to a temperature of above 45 ⁰ C and then used in another heat exchanger to cool the stock-endangered product.

Further engage with steam or heated fluid heating bundles are used, which are arranged on the air side prior to the actual heat exchanger and pre-heat controlled to about 25 ⁰ C to 30 ⁰ C, the cooling air over the entire year.

Finally, it is still known to use so-called circulating air coolers in which, with the help of blinds and air ducts exiting at the upper end of the heat exchanger heated cooling air is at least partially passed down again below the heat exchanger and the new ambient air is mixed, so that they themselves on for example 30 ⁰ C can level.

However, all the solutions described above, in particular because of technical disadvantages, because usually a considerable overhead on equipment and devices to be installed must be driven.

The invention is - based on the prior art - the object to provide an air-cooled heat exchanger, which reliably avoids the stagnation or freezing of the product to be cooled or condensed even at low temperatures of the cooling air.

The solution to this problem consists according to the invention in the features of claim 1.

Thereafter, at least the exchanger tubes are provided in the first of the cooling air flowed lower row of tubes of a heat exchanger (liquid cooler or condenser) with feedable from a heating medium inner tubes. The heating medium is preferably steam or hot or hot water. In some operating situations, it may also be conceivable that the product itself is used as a heating medium. In the annular gaps between the inner tubes and the exchanger tubes flows the product prone to stagnation or freezing. At normal ambient temperatures, for example above 20 ^° C., the product is cooled without risk of stagnation. No heating medium is needed. Sinks however the temperature of the cooling air below 20 ⁰ C, so depending on the local temperatures, at least the inner tubes in the bottom row of tubes are charged with the heating medium. Possibly. It is also necessary to apply a heating medium to the inner tubes of at least one further row of tubes. Thus, for example, a heating medium in the form of water at a temperature of 40 ⁰ C are passed into the inner tubes. Thus, the necessary heat is supplied to the product to be cooled, thus preventing the sticking in the heat exchanger. If the cooling air temperature continues to drop, it is possible to regulate even warmer heating medium to prevent product stagnation.

A particular advantage of the invention is the very compact design of a heat exchanger over such heat exchangers, which are provided with plate packs and recirculation devices. Although the integration of inner tubes for guiding the heating medium means a production-related additional effort. However, the cross-section of the inner tubes relative to the cross-sectional area of the product-carrying exchanger tubes can be kept so low that in view of the space gain of the slightly higher pressure loss can be ignored within the heat exchanger. In addition, in the design of the heat exchanger according to the invention to take into account that the tube lengths are often more than 10 meters. It is therefore usually very large investments. Such systems must perform their services even at maximum air temperature, that is, even in summer operation reliably cool. Consequently, in summer operation, a countercurrent of cooling air and product without additional heating sought, while in winter operation, the heating medium should flow in opposite directions to the product.

The admission of the inner tubes with a heating medium can be combined with further measures to ensure the most economical operating state of the heat exchanger as a function of the respective temperatures of the ambient air. Thus, it is possible according to the features of claim 2, that the exchanger tubes in the flow direction of Cooling air from tube row to tube row are provided with an increasing number of ribs. This measure takes into account the fact that the cooling air in an air-cooled heat exchanger from tube row to row of tubes heats from bottom to top, so that the cooling in the lower rows of tubes is the most intense and thus the risk of stagnation is greatest there. To reduce this risk, it is advisable to change the rib pitch from tube row to tube row. In extreme cases, the lowermost row of tubes may even consist only of smooth tubes, in order then to allow the rib pitch from row of tubes to row of tubes to become smaller with increasing temperature of the cooling air.

Preferably, according to claim 3, the product inlet in the region of the uppermost row of tubes and the product outlet are provided in the region of the lowermost row of tubes. That is, the product flows in crossflow in countercurrent to the cooling air through the heat exchanger.

In this context, it may be advantageous according to claim 4, that the inner tubes are fed in the same direction to the acted upon by the product exchanger tubes with the heating medium. This switching mode is appropriate when the temperature of the ambient air is still in a higher range. The heating medium would namely cool down in the flow direction, as well as the product. That is, the area of the heat exchanger near the product outlet is at risk because it is the coldest and therefore most likely to be stagnant.

With decreasing temperatures of the ambient air, therefore, a circuit according to the features of claim 5 is more advantageous. Thereafter, the inner tubes are fed in opposite directions to the treated with the product exchanger tubes with the heating medium. That is, the area of the heat exchanger in the vicinity of the product outlet would sooner be in contact with the still moderately high temperature heating medium, so that stagnation can be effectively avoided. The variant according to the invention is even more advantageous according to claim 6. In this case, the product is diverted on several occasions from tube row to tube row S-shaped on its way from the upper product inlet to the lower product outlet, wherein the inner tubes are respectively charged in opposite directions with the heating medium.

If the temperatures of the cooling air drop, it is more advantageous to use the features of claim 7, according to which the product is diverted in an S-shape several times from pipe row to pipe row on its way from the upper product inlet to the lower product outlet, but the inner pipes are in each case charged in the same direction with the heating medium are.

The opposite direction or the same direction switching the product flow to the heating medium and vice versa can be done with the help of 3-way valves or conventional shut-off valves.

In the variant according to the features of claim 8, the product itself is used as the heating medium. For this purpose, the product is first passed through inner tubes and heats up here in the exchanger tubes in the opposite direction flowing back through an air flow cooled product.

According to the features of claim 9, it is also possible depending on the season and the then prevailing temperatures of the ambient air, that the product inlet in the region of the lowermost row of tubes and the product outlet are provided in the region of the uppermost row of tubes.

According to claim 10, it is expedient that the position of the inner tubes in the exchanger tubes is ensured by the fact that the inner tubes are supported by spacers in the exchanger tubes.

In this context, it is then advantageous according to claim 11, that the inner tubes are arranged concentrically in the outer tubes. As a result, the same length spacers can be used. The invention is explained in more detail with reference to embodiments illustrated in the drawings. Show it:

Figure 1 in the diagram a vertical longitudinal section through an air-cooled heat exchanger;

Figure 2 also in the diagram a vertical longitudinal section through an air-cooled heat exchanger according to a further embodiment;

Figure 3 in the diagram a circuit for a heating medium of

Heat exchanger of Figure 2;

Figure 4 is a schematic of a variant of a circuit for the heat exchanger of Figure 2;

5 shows a cross section through the representation of Figure 1 along the

Line V - V seen in the direction of arrows Va and

Figure 6 in the diagram a vertical longitudinal section through an air-cooled heat exchanger according to a third embodiment.

1, a heat exchanger is designated in FIG. 1, which has juxtaposed exchanger tubes 2, 3, 4 in several superimposed rows of tubes R, R1, R2, which are acted upon internally by a product P to be cooled and are flowed from below by means of cooling air KL.

The lying in the bottom row R exchanger tubes 2 are designed as smooth tubes without ribs. In the two rows above R1 and R2 are exchanger tubes 3, 4 with ribs 5, wherein the ribs 5 of the exchanger tubes 3 in the row R1 have a greater distance from each other than the ribs 5 of the exchanger tubes 4 in the row R2.

The exchanger tubes 2, 3, 4 are connected at one end to a distribution chamber 6, which is provided with an upper inlet 7 for the product P. At the other end of the exchanger tubes 2, 3, 4 is a collection chamber 8, which is provided at the lower end with an outlet 9 for the product P.

In the exchanger tubes 2, 3, 4 are - as the figure 5 reveals - concentrically arranged inner tubes 10 retracted. The inner tubes 10 are supported by spacers 11 opposite the exchanger tubes 2, 3, 4 and terminate on the one side in a distribution chamber 12 for a heating medium HM and on the other hand into a collection chamber 13 for the heating medium HM. Correspondingly, an inlet 14 for the heating medium HM and at the collecting chamber 13 an outlet 15 for the heating medium HM are provided on the distribution chamber 12.

As can be seen from FIG. 1 with reference to the arrows drawn in solid lines, the product P first flows via the product inlet 7 into the distribution chamber 6, from here via the annular spaces 16 between the inner tubes 10 and the exchanger tubes 2, 3, 4 to the collection chamber 8 and from this via the product outlet 9 for further use.

The heating medium HM passes from the inlet 14 into the distribution chamber 12 and from there according to the arrows shown in broken lines through the inner tubes 10 into the collection chamber 13 and from the collection chamber 13 via the outlet 15 to a heat source, not shown.

The heating medium HM thus flows in the same direction to the product P through the inner tubes 10. Both the product P and the heating medium HM flow in cross-flow to the cooling air KL.

In the embodiment of Figure 1 but it is also conceivable that the inlet 14 and the outlet 15 are exchanged for the heating medium HM, so that then the heating medium HM flows in opposite directions to the product P through the inner tubes 10. Furthermore, it is conceivable that the product P flows from bottom to top through the heat exchanger 1.

2 shows a heat exchanger 1a, which is in principle constructed as the heat exchanger 1 of Figure 1. It has in three rows R, R1, R2 arranged side by side exchanger tubes 2, 3, 4, each traversed by inner tubes 10 according to FIG are. The exchanger tubes 2 in the bottom row R have no ribs, while the exchanger tubes 3, 4 of the rows R1 and R2 are provided with ribs 5. The ribs 5 of the exchanger tubes 3 in the row R1 have a greater relative distance than the ribs 5 of the exchanger tubes 4 in the top row R2.

In the embodiment of Figure 2, the product P flows according to the arrows shown in solid lines, first via the product inlet 7 and a distribution chamber into the annular spaces 16 of the exchanger tubes 4 in the uppermost row R2.

From here, the product P passes into a deflection chamber 18, is deflected in this by 180 ⁰ C and then flows through the annular spaces 16 of the exchanger tubes 3 in the row R1 to another deflection chamber 19 at the other end of the exchanger tubes 3. In the deflection 19 the product P is again deflected by 180 ⁰ C, flows in the annular spaces 16 of the exchanger tubes 2 of the bottom row R to a collection chamber 20 and from there via the outlet 9 for further use.

The distribution chamber 17 is separated from the underlying deflection chamber 19 by means of a wall 21. Likewise, the deflection chamber 18 between the exchanger tubes 4, 3 of the uppermost row R2 and the underlying row R1 of the collection chamber 20 by means of a wall 22 is separated. The product P experiences in this way a multiple S-shaped deflection on its way from the product inlet 7 to the product outlet 9.

In addition to the collection chamber 20 for the product P, a distribution chamber 23 is provided with an inlet 24 for a heating medium HM. From here flows the Hθizmedium HM according to the arrows drawn in broken lines through the inner tubes 10 in the exchanger tubes 2 of the bottom row R to a provided at the other end deflection 25. From the deflection chamber 25 flows through the heating medium HM through the inner tubes 10 of the exchanger tubes 3 of the series R1 a further deflection chamber 26, which is provided above the distribution chamber 23 and separated from the distribution chamber 23 also by means of the wall 22. From this deflection chamber 26, the heating medium HM enters the inner tubes 10 of the exchanger tubes 4 of the uppermost row R2 and from here into a collecting chamber 27, which is separated from the deflection chamber 25 by means of the wall 21. Via an outlet 28, the heating medium HM reaches a heat source, not shown.

It can therefore be seen from FIG. 1 that the heating medium HM flows in opposite directions to the product P in all three rows of tubes R, R1 and R2.

However, it is also conceivable in the embodiment of FIG. 2 that the inlet 24 and the outlet 28 of the heating medium HM are exchanged. In this case, the heating medium HM flows from top to bottom through the heat exchanger 1a and thus in the same direction to the product P.

In this context, FIGS. 3 and 4 show in the diagram a circuit for the different flow directions of the product to be cooled or of the heating medium HM. By way of example only, the possible flow paths of the heating medium HM will be explained with reference to Figures 3 and 4. These explanations can be particularly refer to the product flow, the flow direction can be changed in the same way.

If the heating medium HM flow from top to bottom through the heat exchanger 1a, the heating medium HM passes through a 3-way valve 29 and a 1st strand 30 in the Wärmetauscherweg WTW the rows of tubes R2, R1, R and is a second strand 31 and a 3-WegeΛ / entil 32 fed to a heat source. If the two 3-way valves 29, 32 switched so flows the heating medium HM according to the arrows in broken lines over the 3-way valve 29 and a third strand 33 in the heat exchanger WTW and passes from here via a 4th strand 34 to the second 3-way valve 32 and over this to the heat source.

The embodiment of a circuit for the heating medium HM according to Figure 4 corresponds in principle to that of Figure 3, it is only instead of the two 3-way Venti! E 29, 32 now four shut-off valves 35 - 38 are provided, depending on the circuit ensure that the heating medium HM via the 1st strand 30 and the heat exchanger WTW in the second strand 31 and from here to the heating source or via the 3rd strand 33 and the heat exchanger WTW in the 4th strand 34 and from here to the heating source ,

FIG. 6 illustrates an embodiment of a heat exchanger 1b, which has exchanger tubes 2, 3 in two rows R and R1, which are supplied with cooling air KL from below. The exchanger tubes 2 in the lower row R are unaffected, while the exchanger tubes 3 of the overlying row R1 have ribs 5.

In this embodiment, as the heating medium HM, the hot product P itself is used. For this purpose, provided in the lower row R inner tubes 10 are charged via a product inlet 38 with the heating medium HM. From here, the heating medium HM flows in opposite directions to the product P flowing in the exchanger tubes 2 to a deflection chamber 35 and from this deflection chamber 35 in inner tubes 10, which are arranged in the upper row R1 in the exchanger tubes 3. From these inner tubes 10, the heating medium HM enters a deflection chamber 36, where it is transferred into the exchanger tubes 3 of the upper row R1. From the exchanger tubes 3, the cooled heating medium HM passes into a deflection chamber 37 and from here through the exchanger tubes 2 of the lower row R into a collecting chamber. Via a product outlet 39 assigned to the collecting chamber, the product P is supplied for further use. REFERENCE CHARACTERS:

1 - heat exchanger

1a- heat exchanger 1b heat exchanger

2 - Exchanger tubes in R

3 - Exchanger tubes in R1

4 - Exchanger tubes in R2

5 - ribs at 3, 4

6 - distribution chamber f. P

7 - inlet f. P

8 - collection chamber f. P

9 - outlet f. P 10- inner tubes

11 - Spacers

12- distribution chamber f. HM

13- collection chamber f. HM

14- inlet f. HM

15- outlet f. HM

16- annular spaces zw.2 -4 u.10

17- distribution chamber f. P

18- deflection chamber f. P

19- deflection chamber f. P

20 - collection chamber f. P

21 - partition zw.17 u.19

22 - Partition zw18 u.20

23 - distribution chamber f. HM

24 - inlet f. HM

25- deflection chamber f. HM 26 - deflection chamber f. HM 27- collection chamber f. HM 28 - outlet f. HM 29- 3-way valve 30 - 1st strand

31 - 2nd branch 32- 3-way valve

33 - 3rd strand

34 - 4th strand

35 - Deflection chamber 36- Deflection chamber 37 - Deflection chamber 38- Product outlet 39 - Product inlet

HM - heating medium KL- cooling air P- product R- pipe series R1 - pipe series R2- pipe series WTW - heat exchanger path

Claims

claims

1. Heat exchanger, in a plurality of superimposed rows (R, R1, R2) juxtaposed exchanger tubes (2, 3, 4) which acted on the inside with a product to be cooled (P) and from below by means of cooling air (KL) are flowed in that at least the exchanger tubes (2) are provided with inner tubes (10) which can be fed by a heating medium (HM) in the lower row of tubes (R) initially flown by the cooling air (KL).

2. Heat exchanger according to claim 1, dad u rch geken nzeich net that the exchanger tubes (2, 3, 4) in the flow direction of the cooling air (KL) of tube row (R, R1) to tube row (R1, R2) with a larger number are provided on ribs (5).

3. A heat exchanger according to claim 1 or 2, characterized in that an inlet (7) for the product (P) in the region of the uppermost row of tubes (R2) and an outlet (9) for the product (P) in the range the lowest row of tubes (R) are provided.

4. Heat exchanger according to one of claims 1 to 3, dad u rch geken net nets that the inner tubes (10) in the same direction to the product (P) acted upon exchanger tubes (2, 3, 4) with the heating medium (HM) are charged ,

5. Heat exchanger according to one of claims 1 to 3, d ad u rch- geken designated that the inner tubes (10) in opposite directions to the product (P) acted upon exchanger tubes (2, 3, 4) with the heating medium (HM) charged are.

6. Heat exchanger according to one of claims 1 to 5, dadu rch geken nzeichnet that the product (P) on its way from an upper product inlet (7) to a lower product outlet (9) several times from tube row (R2, R1) to tube row (R1, R) is deflected S-shaped, wherein the inner tubes (10) are respectively charged in opposite directions with the heating medium (HM).

7. Heat exchanger according to one of claims 1 to 5, characterized in that the product (P), on its way from an upper product inlet (7) to a lower product outlet (9), is repeated several times from the row of tubes (R2, R1). to tube row (R1, R) is deflected S-shaped, wherein the inner tubes (10) are respectively charged in the same direction with the heating medium (HM).

8. Heat exchanger according to one of claims 1 to 5, dadu rch- characterized in that the product (P) on its way from a product inlet (39) to a product outlet (38) several times from tube row (R, R1) to tube row (R1, R), wherein the product inlet (39) to inner tubes (10) of the lower tube row (R) is connected, the product of the inner tubes (10) of the upper tube row (10) outlet and the exchanger tubes (2, 3) in the opposite direction to the flow direction in the inner tubes (10) flows to a product outlet (38).

9. A heat exchanger according to claim 1 or 2, characterized in that a product inlet in the region of the lowermost row of tubes (R) and a product outlet (9) in the region of the uppermost row of tubes (R2) are provided.

10. Heat exchanger according to one of claims 1 to 9, dadu rch- characterized in that the inner tubes (10) via spacers (11) in the exchanger tubes (2, 3, 4) are supported.

11. Heat exchanger according to one of claims 1 to 10, dadu rch geken nzeich net that the inner tubes (10) in the exchanger tubes (2, 3, 4) are arranged concentrically.