WO2019008006A1

WO2019008006A1 - Cast segment for a sectional heat exchanger

Info

Publication number: WO2019008006A1
Application number: PCT/EP2018/068026
Authority: WO
Inventors: Hasan TASHACORI; Gertjan Zwiggelaar
Original assignee: Bekaert Combustion Technology BV
Current assignee: Bekaert Combustion Technology BV
Priority date: 2017-07-07
Filing date: 2018-07-04
Publication date: 2019-01-10
Anticipated expiration: 2020-01-07
Also published as: CN110832257B; CN110832257A

Abstract

A cast segment for a sectional heat exchanger of a condensing heat cell comprises two cast walls, a combustion chamber for the generation of flue gas, and a water flow channel delimited by the two cast walls. The water flow channel is provided for the flow of water to be heated by flue gas via heat transfer through at least one of the two cast walls. The water flow channel comprises along its length a first section, a second section and a third section. In the first section intermediate walls are provided between the two cast walls such that a meandering flow channel is provided in the first section. The third section surrounds the combustion chamber over at least 330°. The second section connects the first section with the third section. The second section is parallel with and running along at least part of the third section. The average distance between the two cast walls in the second section is larger than the average distance between the two cast walls in the third section. The average distance between the two cast walls in the second section is larger than the average distance between the two cast walls in the first section.

Description

Cast segment for a sectional heat exchanger

Description

Technical Field

[0001] The invention relates to cast segments for a sectional heat exchanger, to sectional heat exchangers comprising such cast segments, and to heat cells.

Background Art

[0002] Sectional heat exchangers constructed by assembling cast segments side by side are known. WO2016/055395A1 shows an example of such sectional heat exchanger.

[0003] WO2015/024712A1 discloses a sectional heat exchanger for a heat cell. The sectional heat exchanger has two end segments and one or more intermediate segments provided between the two end segments which are assembled in the heat exchanger. A combustion chamber is provided in the sectional heat exchanger, perpendicular to the intermediate segments. Each of the intermediate segments have at least one flow channel for a fluid to be heated. In between each two consecutive segments at least one flow channel for flue gas is present. The total width of the sectional heat exchanger decreases over at least part of the length in the direction away from the combustion chamber. The depth of the flow channels for flue gas decreases in the direction away from the combustion chamber. The distance between the two walls delimiting the intermediate segment increases in the direction away from the combustion chamber.

Disclosure of Invention

[0004] A first aspect of the invention is a cast segment for a sectional heat exchanger of a

condensing heat cell. The cast segment comprises two cast walls, a combustion chamber for the generation of flue gas, and a water flow channel delimited by the two cast walls. Preferably, the two cast walls are parallel to each other. The water flow channel is provided for the flow of water to be heated by flue gas via heat transfer through at least one of the two cast walls; and preferably through each of the two cast walls. The water flow channel comprises along its length a first section, a second section and a third section. In the first section intermediate walls are provided between the two cast walls such that a meandering flow channel is provided in the first section. The third section surrounds the combustion chamber over at least 330°, preferably over at least 340° more preferably over at least 350°. The second section connects the first section with the third section. The second section is parallel with and running along at least part of the third section. The average distance between the two cast walls in the second section is larger than the average distance between the two cast walls in the third section. The average distance between the two cast walls in the second section is larger than the average distance between the two cast walls in the first section.

[0005] The cast segment of the invention has the benefit - thanks to the larger width of the

second section of the water flow channel - that better cooling of the combustion chamber is obtained when using the cast segment in a sectional heat exchanger. Surprisingly, lower NOX levels can be obtained with such a sectional heat exchanger. [0006] When pins - protruding at the outside of the cast walls - are provided on the second section, because of the larger width of the second section of the water flow channel, the pins are shorter and consequently, the temperature of the pins stays below the maximum allowable pin temperature.

[0007] A further positive effect is that less expensive sealing material can be used between

neighbour cast segments in the sectional heat exchanger, as the temperature of the surfaces to be connected in a sealed way is reduced.

[0008] Preferably, the water flow channel is provided for water flow in counter direction to the flow of flue gas.

[0009] In a preferred embodiment, the average distance between the two cast walls in the first section is equal to the average distance between the two cast walls in the third section.

[0010] Preferably, the largest distance between the two cast walls in the second section is at least double the largest distance between the two cast walls in the third section.

[001 1] Preferably, in the cross section of at least part of the second section, the width of the second section gradually increases up to the maximum width of the second section of the water flow channel.

[0012] In a preferred cast segment, the second section is delimited by the two cast walls and by a cast side wall. The cast side wall is provided to form part of the side wall of the sectional heat exchanger comprising the cast section. The outer side of the cast side wall is provided with a plurality of ribs. More preferably the ribs are integrally cast ribs. More preferably, the ribs are provided perpendicularly to the two cast walls. The ribs are provided to reinforce the second section of the water flow channel. In a more preferred embodiment, the two cast walls each comprise extensions extending outside the second section; and the ribs connect both extensions of the cast walls.

[0013] Preferably, at least one - and preferably both cast walls - comprise at the second section protrusions extending to the outside of the cast segment for increasing heat transfer to the water flowing through the second section. The protrusions can e.g. be pins fins or ribs; or a combination of pins, fins and/or ribs. Cast segments according to the invention can be provided as intermediate segments in a sectional heat exchanger. For such intermediate segment, both cast walls are preferably provided with protrusions extending outside the cast walls, to increase heat transfer of hot gas to the water flowing through the water channel. The front and end segments preferably only have protrusions on one of the two cast walls, more particularly on the cast wall that will come into contact with hot gas when the sectional heat exchanger is in use.

[0014] Preferably, at least one - and preferably both cast walls - comprise at the first section and at the third section protrusions extending from the cast walls to the outside in order to increase heat transfer from the flue gas to the water flowing through the water flow channel. The protrusions can e.g. be pins, fins or ribs; or a combination of pins, fins and/or ribs. Cast segments according to the invention can be provided as intermediate segments in a sectional heat exchanger. For such intermediate segment, both cast walls are preferably provided with protrusions extending outside the cast walls, to increase heat transfer of hot gas to the water flowing through the water channel. The front and end segments preferably only have protrusions on one of the two cast walls, more particularly on the cast wall that will come into contact with hot gas when the sectional heat exchanger is in use.

[0015] In cast segments wherein at least one - and preferably both - cast walls comprises

protrusions at the first section, at the second section and at the third section, preferably the density of protrusions on the cast wall of the second section is higher than the density of protrusions on the cast wall of the third section. Such cast segments provide further improved performance of the section heat exchanger in which the cast segments are assembled, thanks to the improved heat transfer from hot gas to water in the second section of the water flow channel. In such embodiments, preferably, the surface area of the cross section of the protrusions on the cast wall of the second section is smaller than the cross section of any of the protrusions on the cast wall of the third section

[0016] Preferably, the second section of the water flow channel does not comprise internal reinforcing pins nor internal reinforcing ribs.

[0017] Preferably, the first section and/or the third section comprise a plurality of reinforcing pins or ribs connecting the two cast walls.

[0018] Preferably, the cast segment is a mono-cast, also called a monobloc. It is meant that the cast segment is integrally cast in one casting operation.

[0019] Preferably, the cast segment is cast out of aluminum or an aluminum alloy.

[0020] A second aspect of the invention is a sectional heat exchanger. The sectional heat

exchanger comprises a plurality of cast segments as in any embodiment of the first aspect of the invention. The combination of the combustion chambers of each of the cast segments provides a chamber for the installation of a burner for the generation of flue gas. In the sectional heat exchanger, the cast segments are provided with the cast walls of the plurality of cast segments parallel to each other.

[0021] Preferably, the closest distance between the cast walls delimiting second sections of neighboring cast segments is less than 30 mm, preferably less than 25 mm.

[0022] A third aspect of the invention is a heat cell. The heat cell comprises a sectional heat exchanger as in any embodiment of the second aspect of the invention. A burner is provided in the chamber for installation of a burner. Preferably, the burner is a surface stabilized fully premixed gas burner.

Brief Description of Figures in the Drawings

[0023] Figures 1 and 2 show an exemplary cast segment according to the invention.

Figure 3 shows a cross section along plane Ill-Ill of figure 1.

Mode(s) for Carrying Out the Invention

[0024] Figures 1 and 2 show a cast segment according to the invention. Figure 1 shows a front view 100 of the cast segment. The view on the other side of the cast segment is similar when the cast segment is a cast segment for an intermediate section of a sectional heat exchanger. When the cast segment is for a front or end section of a sectional heat exchanger, the other side is different, as at the other side, in the heat exchanger no flue gas will flow along the segment; and thus normally no protrusions for increasing heat transfer will be provided at that side. Figure 2 shows a cross section 200 through the cast segment. Figure 3 shows a cross section 300 along plane Ill-Ill of figure 1.

[0025] The exemplary cast segment is cast in one single casting operation out of an appropriate aluminum alloy; and is thus a monobloc or monocast.

[0026] The cast segment comprises a combustion chamber 102, 202 for the generation of hot gas; a water flow channel 204 for the flow of water to be heated; and two parallel cast metal walls 105, 305 delimiting the water channel, for transferring heat between the hot gas and water flowing through the water flow channel. When a number of cast segments are assembled parallel to each other, the combination of the combustion chambers provides a chamber for the installation of a premix gas burner for the production of hot flue gas that will transfer its heat through the two metal walls to the water flowing through the water channel.

[0027] When the segment is an intermediate segment for a sectional heat exchanger, the two metal walls 105 comprise at their outside protrusions 107, 108 extending perpendicularly from the metal wall to increase heat transfer from the hot gas to water flowing in the water channel. When the segment is an end or a front segment, preferably only one side (the side facing a channel through which hot gas flows) comprises such protrusions. The protrusions can be pins 107 and/or fins 108.

[0028] The water flow channel 204 comprises along its length a first section 230, a second

section 232, 332 and a third section 234, 334. In the first section intermediate walls 212 are provided between the two cast walls such that a meandering flow channel is provided in the first section. The third section surrounds the combustion chamber. The second section connects the first section with the third section. The second section is parallel with and running along at least part of the third section. As can be noticed from figure 3, the average distance between the two cast walls in the second section 232, 332 is larger than the average distance between the two cast walls in the third section 234, 334.

[0029] In the example, the largest width of the second section - which is the largest distance between the two cast walls in the second section of the water channel - is 85 mm. In the example, the largest width of the third section - which is the largest distance between the two cast walls in the third section of the water channel - is 35 mm. In the example, the largest width of the first section - which is the largest distance between the two cast walls in the first section of the water channel - is 35 mm. In the cross section of the second section, the width of the second section gradually increases up to the maximum width of the second section of the water flow channel; the width being determined by the distance between the two cast walls. [0030] In the exemplary cast segment, the average distance between the two cast walls in the second section is larger than the average distance between the two cast walls in the first section. This follows from the fact that the average distance between the two cast walls in the first section is equal to the average distance between the two cast walls in the third section.

[0031] The second section is delimited by the two cast walls 105, 305 and by a cast side wall 340. The cast side wall is provided to form part of the side wall of the sectional heat exchanger comprising the cast segment. The two cast walls each comprise extensions 142, 342 extending outside the second section. The outer side of the cast side wall is provided with a plurality of ribs 244. The ribs connect both extensions of the cast walls.

[0032] In the exemplary cast segment, both cast walls comprise at the second section a plurality of pins 150, 350 extending to the outside of the cast segment for increasing heat transfer to the water flowing through the second section. Both cast walls comprise at the first section and at the third section protrusions extending from the cast walls to the outside in order to increase heat transfer from the flue gas to the water flowing through the water flow channel. The density of protrusions on the cast wall of the second section is higher than the density of protrusions 107, 307 on the cast wall of the third section.

[0033] In the exemplary cast segment, the second section of the water flow channel does not comprise internal reinforcing pins nor internal reinforcing ribs. The first section comprises a plurality of reinforcing pins 252 connecting the two cast wall. Also the third section comprises a plurality of reinforcing pins 254, 354 connecting the two cast walls.

[0034] When the exemplary cast segments are assembled in a sectional heat exchanger, the closest distance between the cast walls delimiting second sections of neighboring cast segments is 21 mm.

Claims

1. Cast segment for a sectional heat exchanger of a condensing heat cell,

wherein the cast segment comprises

- two cast walls,

- a combustion chamber for the generation of flue gas, and

- a water flow channel delimited by the two cast walls, for the flow of water to be heated by flue gas via heat transfer through at least one of the two cast walls - and preferably through each of the two cast walls -;

wherein the water flow channel comprises along its length a first section, a second section and a third section;

wherein in the first section intermediate walls are provided between the two cast walls such that a meandering flow channel is provided in the first section;

wherein the third section surrounds the combustion chamber over at least 330°;

wherein the second section connects the first section with the third section;

wherein the second section is parallel with and running along at least part of the third section; characterized in that the average distance between the two cast walls in the second section is larger than the average distance between the two cast walls in the third section; and wherein the average distance between the two cast walls in the second section is larger than the average distance between the two cast walls in the first section.

2. Cast segment as in any of the preceding claims, wherein the largest distance between the two cast walls in the second section is at least double the largest distance between the two cast walls in the third section.

3. Cast segment an in any of the preceding claims,

wherein in the cross section of at least part of the second section, the width of the second section gradually increases up to the maximum width of the second section of the water flow channel.

4. Cast segment as in any of the preceding claims,

wherein the second section is delimited by the two cast walls and by a cast side wall;

wherein the cast side wall is provided to form part of the side wall of the sectional heat exchanger comprising the cast segment;

wherein the outer side of the cast side wall is provided with a plurality of ribs.

5. Cast segment as in claim 4,

wherein the two cast walls each comprise extensions extending outside the second section; and wherein the ribs connect both extensions of the cast walls.

6. Cast segment as in any of the preceding claims, wherein at least one - and preferably both cast walls - comprise at the second section protrusions extending to the outside of the cast segment for increasing heat transfer to the water flowing through the second section.

7. Cast segment as in any of the preceding claims, wherein at least one - and preferably both cast walls - comprise at the first section and at the third section protrusions extending from the cast walls to the outside in order to increase heat transfer from the flue gas to the water flowing through the water flow channel.

8. Cast segment as in claims 6 and 7; wherein the density of protrusions on the cast wall of the second section is higher than the density of protrusions on the cast wall of the third section.

9. Cast segment as in any of the preceding claims, wherein the second section of the water flow channel does not comprise internal reinforcing pins nor internal reinforcing ribs.

10. Cast segment as in any of the preceding claims, wherein the first section and/or the third

section comprise a plurality of reinforcing pins or ribs connecting the two cast walls.

1 1. Cast segment as in any of the preceding claims, wherein the cast segment is a mono-cast.

12. Sectional heat exchanger;

wherein the sectional heat exchanger comprises a plurality of cast segments as in any of the preceding claims;

wherein the combination of the combustion chambers of each of the cast segments provides a chamber for the installation of a burner for the generation of flue gas;

wherein in the sectional heat exchanger, the cast segments are provided with the cast walls of the plurality of cast segments parallel to each other.

13. Sectional heat exchanger as in claim 12,

wherein the closest distance between the cast walls delimiting second sections of neighboring cast segments is less than 30 mm, preferably less than 25 mm.

14. Heat cell, comprising a sectional heat exchanger as in any of the preceding claims 12 - 13; wherein a burner is provided in the chamber for installation of a burner.