EP1450114A1 - Heat exchanger with a optimised fluid flow heat absorbing channel, in particular for heating apparatus - Google Patents

Abstract

Heat exchanger comprises a base body (10) with a heat-releasing flow channel (19) for a heat-releasing medium and a heat-receiving flow channel (25) for a heat-receiving medium. The heat-receiving flow channel has different flow cross-sections along its spiral-like extension so that the flow speed of the heat-receiving medium fits the heat load of the corresponding region of a heat transfer wall (11). Preferred Features: Windings (25.1-25.8) are formed on the outer side of the heat transfer wall to form the heat-receiving channel. The cross-section of the windings is fitted locally to the heat load of the corresponding region of the heat transfer wall.

Description

The invention relates to a heat exchanger with a flow-optimized heat-absorbing flow channel, in particular for a heater, after the Preamble of claim 1.

State of the art

A heat exchanger of this type for a heater is known from FR 695 311: a cylindrical base body, which is made by casting, with a heat-transferring wall. The base body has one inside Hot gas flue for a hot gas serving as a heat-emitting medium. On the outside the heat-transferring wall has a helical base Water channel for a heating water serving as a heat-absorbing medium. The Water channel as a heat-absorbing flow channel is through one in the Shell surface of the outer wall formed into a helically shaped trench, according to the is surrounded on the outside with a separate covering surrounding the outer wall, so that the closed, helical water channel on the outer surface of the basic body results. The water channel is helical over its entire length Extension carried out with a constant cross-section, so that the Flow rate of the heating water at every point in the water channel in the Is essentially the same.

EP 287 142 B1 discloses a further heat exchanger manufactured by casting. where the cross section of the water channel is lower than that in the zone Heating gas temperature arranged inlet to the high heating gas temperature in the zone arranged outlet decreases.

With a heat exchanger in NL 100 13 74 A protrude to enlarge the heat transfer surface flow rib in the heat absorbing heating water into it.

The object of the present invention is to provide a heat exchanger in which an optimal heat transfer from the heat-emitting medium to the heat-absorbing medium is accomplished.

Advantages of the invention

The heat exchanger according to the invention with the characterizing features of Claim 1 has the advantage that the heat transfer from the heat emitting Medium is improved on the heat-absorbing medium. By adjusting the Flow rate of the heat-absorbing medium in the heat-absorbing Flow channel to the local heat load of the heat transfer wall of the Heat exchanger in the respective area or at the respective location of the heat-absorbing flow channel, the heat transfer from heat-emitting medium optimized for the heat-absorbing medium. In places high heat load becomes the flow rate of the heat absorbing Medium by reducing the cross section of the heat absorbing Flow channel increased. On the other hand, in places with low heat loads Flow cross section of the heat-absorbing flow channel extended to Flow rate of the heat-absorbing medium in these areas to make it smaller. They also serve the local heat load of the heat transferring wall of the base body adapted different Flow rates of the heat-absorbing medium to add up to generate a minimal pressure drop in the heat-absorbing medium. This allows minimized or optimized pressure drop of the heat-absorbing medium, that is necessary for the circulation of the heat-absorbing medium Circulation pump can be adjusted for optimal performance. In this respect, the The present invention also reduces the pressure drop within the heat exchanger to keep small.

Advantageous developments of the invention are the measures of Subclaims possible. The adjustment of the flow velocity to the Thermal load of the respective area of the heat exchanger over the cross section of the heat-absorbing flow channel can be varied by varying the depth and / or the width of the heat-absorbing flow channel can be realized, so that the cross section of the flow channel along its spiral extension corresponding to the heat load in the respective area or on the respective Place of the heat transfer wall of the heat exchanger is adjusted. by virtue of of the design concept of an open trench-shaped depression on the outer wall of the base body of the heat exchanger executed heat-absorbing Flow channel is the variation of depth and / or width of the flow channel along its helical extension by manufacturing in Sand casting or permanent mold casting is easy to implement. A change in the course of depth and / or width of the flow channel due to the elaborate production of lost In contrast, cores would be difficult. The present coreless production The flow channel allows a completely free and flexible design of the Guiding the heat-absorbing medium on the outer wall of the base body of the Heat exchanger.

Another measure to increase the heat transfer is possible that in places of high thermal stress, such as in areas that are on the side of the heat-emitting medium are ribbed, additional ribs in the protrude into the heat-absorbing flow channel and from the heat-absorbing Medium flows around, causing the heat transfer surface to heat-absorbing medium is further increased. In addition, longitudinal ribs in be introduced into the flow channel, these being so high in the flow channel protrude that the flow channel into individual, parallel connected individual channels is divided. Different channels are formed in the individual channels Flow rates of the heat-absorbing medium. This will make the heat transfer surface increased to a maximum value. Another Possibility to improve the heat transfer consists in the formation of Flow chicanes in the flow channel, which lead to turbulence and to the mixing of the Boundary layer on the wall and thus lead to increased heat transfer. The Flow baffles can be designed so that they also heat dissipate and thereby further enlarge the heat transfer surface. A Particularly expedient execution of the flow baffles is that these serve at the same time as heat-transferring fins and at an angle of approx. 45 ° are inclined in the flow channel. This creates a mix different flow threads, whereby the forming in the flow channel Temperature stratification is more mixed and that on the wall heat-emitting medium flowing hot layers with from this wall spaced colder layers mix more easily. This will make the Heat transfer increased and boiling of the heat-absorbing medium avoided.

drawing

Embodiments of the invention are shown in the drawing and in the following Description explained in more detail.

Figur 1

eine Schnittdarstellung durch einen erfindungsgemäßen Wärmetauscher gemäß einem ersten Ausführungsbeispiel,

Figur 2

eine Schnittdarstellung nach der Linie II - II in Figur 1 gemäß einem zweiten Ausführungsbeispiel und

Figur 3

eine Seitenansicht eines Grundkörpers eines erfindungsgemäßen Wärmetauschers gemäß einem dritten Ausführungsbeispiel.

Show it:

Figure 1

2 shows a sectional illustration through a heat exchanger according to the invention in accordance with a first exemplary embodiment,

Figure 2

a sectional view along the line II - II in Figure 1 according to a second embodiment and

Figure 3

a side view of a base body of a heat exchanger according to the invention according to a third embodiment.

embodiments

The heat exchanger shown in Figure 1 for a heater, especially a Condensing boiler, has a base body 10 with a heat-transferring wall 11 and with a burner end section 13 and an exhaust end section 14 on. In the end section 13 on the burner side there is an opening 17 into which there is no opening shown burner is used. The space attached to the burner a combustion chamber 15 formed within the base body 10 a heating gas flue 19 closes within the base body 10 as a heat source Flow channel through which the heating gas generated by the burner as a heat emitting Medium flows. The heat-transferring wall 11 has inside the heating gas flue 19 on the inside various longitudinal ribs 21 and transverse ribs 22 to enlarge the Heat exchanger surface. An exhaust opening 18 is located in the exhaust-side end section 14 available, via which the heating gas generated by the burner is discharged as exhaust gas. In the According to FIG. 2, a filler 50 can be inserted in the center of the heating gas flue 19. The Filler 50 causes the heating gas to the transverse ribs 22 and the wall 1 is directed.

The base body 10 is, for example, an aluminum sand casting component that is based on Because of its corrosion resistance and heat absorption capacity and Thermal conductivity is particularly suitable as a material for heaters that are condensing Operation. The base body 10 has a circular cross section executed and runs in the direction of flow of the heating gas with decreasing Diameter slightly conical. However, it is also possible to base body 10 cylindrical or with an oval cross-section.

On the outside of the heat-transferring wall 11 there is a spiral trench-shaped depression 23 with a circumferential wall 24, the turns as Windings 25.1 to 25.8 are designated. The recess 23 is on the base body 10 initially open to the outside. To close the recess open to the outside 23, the base body 10 is surrounded by an envelope 20, which for example consists of Steel is executed. The envelope 20 is a separate component that with the Base body 10 connected in a suitable manner, as will be described below becomes. After assembly of the base body 10 with the casing 20, a helically extending, heat-absorbing flow channel 25 for a heat absorbing medium. In the present embodiment this is heat-absorbing medium the heating water for a heating circuit, not shown, so that the heat-absorbing flow channel 25 on the outer surface of the base body 10 hereinafter referred to as the water channel for the heating water.

Is located on the burner end section 13 and on the exhaust end section 14 in the base body 10 each have a circumferential groove 26, in each of which there is a sealing ring 30 located. For the manufacture of the heat exchanger, the envelope 20 is of the Exhaust side pushed onto the base body 10 until the sheath 20 on the outer Shell surface of the base body 10 rests. To achieve a sealing effect between cover 20 and base body 10 is in the area of the grooves 26 in the Envelope 20, for example, a circumferential, plastic deformation 33 in Formed a bead. The circumferential deformation 33 is expedient generated by rolling, the depth of the deformation must be designed such that the deformation 33 exerts a pressing force on the respective sealing ring 30. To the Connection of a heating water supply has the casing 20 on the burner side End section 13 on a connection piece, not shown. Not one either illustrated further connection piece for the heating water return is for example on the end face of the exhaust-side end section 14 on the base body 10.

The water channel 25 points along its helical course at certain points a different cross-section, so that the flowing in the water channel 25 Heating water locally at different locations Has flow rate. The flow cross section of the Water channel 25 and thus the flow rate of the heating water in Water channel 25 selected such that in the areas or at the points of heat-transmitting wall 11, on which there is a high thermal load, a high flow rate of heating water, and in the areas or in the places the heat-transmitting wall 11, on which there is less thermal stress, the heating water flows at a lower speed. Areas with a high heat load has the heat transfer wall 11 where that Heating gas in the heating gas duct 19 has a high heat input into the heat-transferring wall 11 generated. The thermal load is that in the heat-transferring wall 11 amount of heat available per area and per time, the amount of heat from the heat flow emitted by the heating gas is determined. The greatest heat load lies in the heat exchanger of the present embodiment in which the Combustion chamber 15 subsequent section. In the direction of flow of the heating gas the thermal load then decreases towards the exhaust-side end section 14. In the area the combustion chamber 15 itself is in the heat exchanger of the present Embodiment encounter a lower heat load than that in which the Combustion chamber 15 adjoining section.

To realize the local heat loads on the heat transfer wall 11 adjusted flow rates of the heating water are the widths X 1 to X8 and / or the depths Y1 to Y5 of the trench-shaped depressions 23 accordingly varied. Thus, in the present exemplary embodiment, the turns 25.1 and 25.2 of the Water channel 25 executed with a depth Y1. The width X2 of the turn 25.2 is however, larger than the width X 1 of the turn 25.1, which results in the turn 25.2 a larger flow cross section and thus a smaller one Setting the flow rate of the heating water. In the section that addresses the Combustion chamber 15 connects and which has a higher heat load, the Turns 25.3 and 25.4 a smaller depth Y2, the width X4 being less than the width X3. This creates a larger one in turn 25.4 Flow rate of the heating water. The turn 25.5 has a special one Execution on, wherein the cross section of the turn in the flow direction of Heating gas continuously expanded. This creates a turn 25.5 local reduction of the flow velocity within the water channel 25. The Turn 25.5 is at the transition from an area with a high thermal load to an area of lower heat load, which is in the local Areas with a smaller cross section with depth Y3 have a higher one Flow rate sets than in the larger cross-sectional area with the Depth Y4, where Y3 <Y4. Following the turn 25.5, the turns point 25.6, 25.7 and 25.8, which in the present exemplary embodiment have the same depth Y5 have a larger width X6 to X8 and thus a larger cross section. The lower flow velocity occurring in turns 25.6 to 25.8 of the heating water is sufficient to withstand the lower heat load present there dissipate.

A further optimization of the heat transfer is achieved if according to the Embodiment in Figure 2, the wall 11 at the points where a high or highest heat load or heat flow density is present, has a thickening 27. The thickening 27 is indicated in Figure 2 by a dashed line. The highest Heat flow density exists where the transverse ribs 22 with the largest surface protrude into the heating gas flue and the heat flow of the heating gas into the wall accordingly 11 couple. Through the thickening 27 of the wall 11 in the direction of the flow channel 25, the depth Y of the trench-shaped depression 23 is reduced, as a result of which Set the flow cross section of the heat-absorbing flow channel 25 reduced. This increases the flow rate of the heating water in it Sections or at these points, which results in better heat transfer to these Places occurs. In addition, through the thicker wall 11 at these points the from Transverse fins 22 heat flow coming more evenly to the water channel 25 facing side of the wall 11 distributed. This reduces hot spots. A further possibility for optimizing the heat transfer exists according to FIG. 2 in that in the trench-shaped recess 23 opposite the transverse ribs 23 knobs 43 are formed which protrude into the water channel 25. This will make the Transverse ribs 22 outgoing greatest heat flow better introduced into the water channel 25.

Another embodiment is shown in Figure 3. In the case of FIG. 3 illustrated base body 10 of a heat exchanger are the depths Y of the individual Windings 25.1 to 25.7 are essentially the same size. The widths X1 to X7 of the trench-shaped depressions 23 are, as in the exemplary embodiment according to FIG the corresponding local heat loads in the base body 10 are adapted. Here is the width X2 of the turn 25.2 is greater than the width X3 of the turn 25.3 and the Width X3 of the turn 25.3 is greater than the width X4 of the turn 25.1. From the turn 25.5 the widths X5, X6 and X7 increase again, where X5 <X6 <X7. Thereby Different cross sections of the water channel 25 are realized, so that within these turns have different flow rates for the heating water occur.

It is essential for the exemplary embodiment in FIG. 3 that at locations with a large Heat load in the water channel 25 additional ribs 41 and / or on the water side Flow baffles 42 and / or knobs 43 are present. The flow chicanes 42 are inclined in the flow direction of the heating water at an angle of for example 45 ° attached. Through the ribs 41, the heat transfer Surface within the water channel 25 increases and thus the heat transfer improved. The flow baffles 42 lead to turbulence and through mixing the boundary layers on the inner wall of the water channel 25 to an increased Heat transfer from the base body 10 to that flowing in the water channel 25 Heating water. The flow baffles 42 can be designed so that they also dissipate heat and thereby the heat transfer surface enlarge. By arranging the flow baffles at an angle of approx. 45 ° there is a mixture of different flow threads, which results in the Water layer 25 forming temperature stratification disturbed and that on the wall 11 flowing hot layer is mixed with the spaced colder layers. This also increases the heat transfer and the boiling of the heating water avoided.

Finally, at least one turn 25.7 is formed with longitudinal ribs 44 possible, which can be arranged in height in the water channel 25 in such a way that the flow channel or the winding at the corresponding point in individual parallel divides switched individual channels 45 so that within one turn in the water channel 25 different flow velocities arise. This will make the heat transfer surface increased to a maximum possible value. The Formation of water-side ribs 41 and / or flow baffles 42 and / or Knobs 43 and / or longitudinal ribs 44 is also in the embodiments according to the Figure 1 and 2 possible.

The heat exchangers described are not only for use in heaters possible, but it is also conceivable to design the flow channels 19 and 25 for to use a heat exchanger for cooling.

LIST OF REFERENCE NUMBERS

10

body

11

heat transfer wall

13

burner end section

14

exhaust-side end section

15

combustion chamber

17

opening

18

exhaust port

19

heat-emitting flow channel / heating gas flue

20

wrapping

21

longitudinal ribs

22

transverse ribs

23

trench-shaped depression

24

wall

25

heat-absorbing flow channel / water channel

25.1 to 25.8

turns

26

groove

27

thickening

30

seal

33

deformation

41

ribs

42

flow baffles

43

burl

44

longitudinal ribs

45

individual channels

50

packing

Claims (11)

Heat exchanger with a base body, in which a heat-emitting flow channel for a heat-emitting medium and a heat-absorbing flow channel for a heat-absorbing medium are formed, heat transfer from the heat-emitting medium to the heat-absorbing medium taking place via a heat-transferring wall, and the heat-absorbing flow channel being helical along of the heat-transferring wall, characterized in that the heat-absorbing flow channel (25) has locally different flow cross-sections along its helical extension in such a way that the flow velocity of the heat-absorbing medium flowing within the heat-absorbing flow channel (25) to the thermal load of the corresponding area of the heat-transferring wall ( 11) is customizable. Heat exchanger according to claim 1, characterized in that on the outside of the heat-transmitting wall (11) windings (25.1 to 25.8) are formed which form the heat-absorbing flow channel (25), and in that the cross-section of the windings (25.1 to 25.8) locally to the Heat load of the corresponding area of the heat-transferring wall (11) can be adjusted. Heat exchanger according to claim 2, characterized in that the cross section of the windings (25.1 to 25.8) can be adjusted over a corresponding width (X) and / or depth (Y) in the corresponding region of the heat-transmitting wall (11). Heat exchanger according to claim 1, characterized in that the heat-transmitting wall (11) has a thickening (27) in areas with a high thermal load. Heat exchanger according to claim 4, characterized in that the thickening (27) of the flow cross section of the heat-absorbing flow channel (25) can be reduced. Heat exchanger according to claim 1, characterized in that the heat-absorbing medium within the heat-absorbing flow channel (25) has a higher flow rate in the areas of the heat-transferring wall (11) with a high heat load than in the areas with a lower heat load. Heat exchanger according to Claim 1, characterized in that ribs (41) and / or knobs (43) narrowing the cross section are arranged in the heat-absorbing flow channel (25) in order to enlarge the heat-transferring surface. Heat exchanger according to claim 1, characterized in that flow baffles (42) are formed in the heat-absorbing flow channel (25) for mixing the heat-absorbing medium flowing in the flow channel (25). Heat exchanger according to claim 8, characterized in that the flow baffles (42) are arranged at an angle of approximately 45 ° to the flow direction of the heat-absorbing medium. Heat exchanger according to claim 1, characterized in that longitudinal ribs (44) are formed in the heat-absorbing flow channel (25), which divide the winding (25.1 to 25.8) into individual parallel individual channels (45) such that within the respective winding (25.1 to 25.8) set different flow velocities. Heat exchanger according to one of the preceding claims, characterized in that an outwardly trench-shaped, helical depression (23) is formed on the base body (10) and that the base body (10) is enclosed by a separate sheath (20), so that the depression (23) forms the heat-absorbing flow channel (25).

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