WO2019011739A1

WO2019011739A1 - Element for a sectional heat exchanger

Info

Publication number: WO2019011739A1
Application number: PCT/EP2018/068037
Authority: WO
Inventors: Hasan TASHACORI; Gertjan Zwiggelaar; Mathieu VERHOOGT
Original assignee: Bekaert Combustion Technology B.V.
Priority date: 2017-07-13
Filing date: 2018-07-04
Publication date: 2019-01-17

Abstract

An element for a sectional heat exchanger comprises a combustion chamber for the generation of flue gas; a water channel; and two metal walls delimiting the water channel. At least one of the two metal walls is provided with pins extending perpendicularly from the metal wall for increasing the heat transfer from flue gas generated in the combustion chamber to water flowing in the water channel. The at least one of the metal walls comprises a first region in which the length of the pins is set by machining the pins such that the pins in the first region have a flat tip, such that all pins in the first region have the same length; and such that the flat tips are provided in a plane parallel with the metal wall on which the pins are provided. The at least one of the metal walls comprises a second region, provided in flue gas flow direction more upstream than the first region. Pins in the second region are provided in rows of pins of the same length; the rows are provided perpendicularly to the metal wall. In the second region pins in rows in flue gas flow direction further away from the combustion channel are longer than pins in rows in flue gas flow direction closer to the combustion channel. The at least one of the metal walls comprises a third region, provided in flue gas flow direction more upstream than the second region. Pins in the third region are provided in rows of pins of the same length; the rows are provided perpendicularly to the metal wall. In the third region pins in rows in flue gas flow direction further away from the combustion channel are longer than pins in rows in flue gas flow direction closer to the combustion channel. The at least one of the metal walls comprises a fourth region, provided in flue gas flow direction from the combustion chamber between the second region and the third region. In the fourth region the length of the pins is set by machining the pins such that the pins in the fourth region have a flat tip, such that all pins in the fourth region have the same length; and such that the flat tips are provided in a plane parallel with the metal wall on which the pins are provided.

Description

Element for a sectional heat exchanger

Description

Technical Field

[0001] The invention relates to elements for sectional heat exchangers and to heat exchangers made with such elements.

Background Art

[0002] WO2015/024712A1 discloses a sectional heat exchanger comprising cast elements

assembled side by side. A number of flue gas channels are provided in parallel, extending from a combustion chamber. The cast walls of the cast elements comprise a plurality of protrusions extending in the flue gas channels in order to increase heat exchange between flue gas flowing through the flue gas channels and the water to be heated in the sectional heat exchanger.

Disclosure of Invention

[0003] The first aspect of the invention is an element for a sectional heat exchanger. The

element comprises a combustion chamber for the generation of flue gas; a water channel; and two metal walls delimiting the water channel. At least one of the two metal walls - and preferably both metal walls - are provided with pins extending perpendicularly from the metal wall for increasing the heat transfer from flue gas generated in the combustion chamber to water flowing in the water channel. The at least one of the metal walls comprises a first region. In the first region the length of the pins is set by machining the pins, such that the pins in the first region have a flat tip and the same length; and such that the flat tips are provided in a plane parallel with the metal wall on which the pins are provided. The at least one of the metal walls comprises a second region. The second region is provided in flue gas flow direction more upstream than the first region. Pins in the second region are provided in rows of pins of the same length. The rows are provided perpendicularly to the metal wall. Within rows of pins in the second region, each pin has the same length. In the second region pins in rows in flue gas flow direction further away from the combustion channel are longer than pins in rows in flue gas flow direction closer to the combustion channel. The at least one of the metal walls comprises a third region. The third region is provided in flue gas flow direction more upstream than the second region. Pins in the third region are provided in rows of pins of the same length. The rows are provided perpendicularly to the metal wall. Within rows in the third region, each pin has the same length. In the third region pins in rows in flue gas flow direction further away from the combustion channel are longer than pins in rows in flue gas flow direction closer to the combustion channel. The at least one of the metal walls comprises a fourth region. The fourth region is provided in flue gas flow direction from the combustion chamber between the second region and the third region. In the fourth region the length of the pins is set by machining the pins such that the pins in the fourth region have a flat tip, such that all pins in the fourth region have the same length; and such that the flat tips are provided in a plane parallel with the metal wall on which the pins are provided. [0004] The cast element of the invention allows that a compact sectional heat exchanger can be built with high capacity and high efficiency. The machined pins in the first region of the metal wall allow that the gap between pins of opposing metal walls of a sectional heat exchanger can be made as small as possible. This is possible, as machining the tips provides much smaller tolerances on pin length than casted pins. As a consequence, the efficiency of heat transfer by the pins is maximized for the distance between opposed metal walls. A gap - preferably as small as possible - between opposing pins is required, to cope with thermal expansion of the pins when the sectional heat exchanger is in use. The smallest possible gap as possible by the invention, also increases the amount of latent heat (derived from condensation out of the flue gas) extracted from the flue gas and transferred to water flowing through the sectional heat exchanger, as longer pins are provided than possible without machining the pins, as pins with cast tips have a large tolerance in length. Furthermore, the pin arrangements in the second region, in the third region and in the fourth region synergistically add to the benefits in creating a heat exchanger with higher efficiency, without creating risk of overheating pins, which would lead to early failure of the heat exchanger.

[0005] Observing the tips of pins, it can easily be distinguished whether the tips of the pins are "as cast" or the tips of the pins have been machined to provide a flat tip.

[0006] Preferably, the water channel is a meandering water channel; and intermediate walls are provided between the two metal walls to create the meandering water channel.

[0007] Preferably both metal walls have the same pin arrangement.

[0008] Preferably, the pins in the first region comprise an elongated segment and a tip. The entire tip is flat and the tips of all pins are provided in a plane parallel with the metal wall on which the pins are provided. Preferably, the pins in the first region have a cylindrical shape with circular cross section. It is to be understood that the cylindrical shape comprises a small cone angle as known in the field to allow mould release after casting.

[0009] Preferably, in the second region, pins in consecutive rows are provided in staggered positions. Preferably, the pins in the second region have a larger diameter than the pins in the first region.

[0010] Preferably, pins in consecutive rows of the second region are provided in staggered positions. It is meant that the position of the pins in a second row is advanced with respect to pins in a first row.

[001 1] Preferably, the pins in the second region have a cylindrical shape with circular cross section. It is to be understood that the cylindrical shape comprises a small cone angle as known in the field to allow mould release after casting.

[0012] Preferably, the length of each of the pins of the third region is smaller or equal to the length of the longest pin in the second region.

[0013] Preferably, pins in consecutive rows of the third region are provided in staggered

positions. [0014] Preferably, the pins in the third region have a cylindrical shape with circular cross section.

It is to be understood that the cylindrical shape comprises a small cone angle as known in the field to allow mould release after casting.

[0015] Preferably, the diameter of the pins in the second region is smaller than the diameter of pins in the third region. The provision of smaller diameter pins in the second region than in the third region synergistically - together with the differences in length of the pins in the rows of pins in the second region - provides a heat exchanger with even higher efficiency and without the risk of overheating pins.

[0016] In a preferred element, the number of rows of pins in the second region is larger than the number of rows of pins in the third region.

[0017] Preferably, the pins in the fourth region have the same diameter as the pins in the third region. Such embodiments synergistically provide higher efficiency of the sectional heat exchanger comprising such elements.

[0018] Preferably, the element is a mono-cast metal element. The pins are integrally cast with the metal walls. The pins of the first section - and if present of the fourth section - are set to length by machining. More preferably, the element is out of aluminum or out of an aluminum alloy.

[0019] The second aspect of the invention is a sectional heat exchanger comprising a plurality of elements as in any embodiment of the first aspect of the invention. The elements are assembled side by side such that the combination of the combustion chambers of the plurality of elements provides an elongated chamber for the installation of a premix gas burner for the generation of flue gas. The water channels of the plurality of elements are arranged in parallel flow. Between the elements, parallel flue gas channels are provided extending from the elongated chamber for heat transfer from the flue gas through the metal walls to water flowing through the water channels.

[0020] In a preferred sectional heat exchanger, the distance between opposing metal walls of neighbor elements is less than 80 mm and preferably more than 70 mm, e.g. 72 mm.

[0021] Preferably, in cold condition of the sectional heat exchanger, the gap between opposing pins of the first regions of opposing metal walls of neighbor elements is less than 2 mm, more preferably less than 1.7 mm, and even more preferably less than 1.5 mm. The small gap - smaller than can be achieved without machining the tips of the pins, because of the tolerances in casting - further increases the efficiency of the sectional heat exchanger, as less short cut is provided between pins for the flue gas to flow. Such short cut would reduce the transfer of heat from the flue gas to the water flowing through the sectional heat exchanger.

Brief Description of Figures in the Drawings

[0022] Figure 1 shows an element according to the invention.

Figure 2 shows a cross section of the element of figure 1.

Figure 3 shows a section along plane Ill-Ill of figure 1. Mode(s) for Carrying Out the Invention

[0023] Figure 1 shows an element 100 according to the invention. Figure 2 shows a cross

section 200 of the element of figure 1 in between the two metal walls 105 of the element. Figure 3 shows a section 300 along plane Ill-Ill of figure 1.

[0024] Figures 1 , 2 and 3 show an inventive element for a sectional heat exchanger. The

element comprises two metal walls 105 delimiting the water channel. Both metal walls are provided with pins extending perpendicularly from the metal wall for increasing the heat transfer from flue gas generated in the combustion chamber to water flowing in the water channel. Both metal walls of the elements have the same pin arrangement. The element comprises a combustion chamber 102 for the generation of flue gas and a meandering water channel 104. Intermediate walls 1 12 are provided between the two metal walls 105 to create the meandering water channel. The water channel comprises baffles 126 to direct the water flow; and reinforcing pins 130, 132 extending between the two cast walls.

[0025] The metal walls comprise a first region 142, a second region 144, a third region 146 and a fourth region 148. The second region is provided in flue gas flow direction more upstream than the first region. The third region is provided in flue gas flow direction more upstream than the second region. The fourth region is provided in flue gas flow direction from the combustion chamber between the second region and the third region.

[0026] In the first region the length of the pins 152 is set by machining the pins, such that the pins in the first region have a flat tip and all the same length; and such that the flat tips are provided in a plane parallel with the metal wall on which the pins are provided. The pins in the first region comprise an elongated segment and a tip. The entire tip is flat and provided in the plane parallel with the metal wall on which the pins are provided. The pins in the first region have a cylindrical shape with circular cross section. The cylindrical shape comprises a small cone angle as known in the field to allow mould release after casting.

[0027] Pins 154 in the second region are provided in rows of pins of the same length. The rows are provided perpendicularly to the metal wall. Within rows of pins in the second region, each pin has the same length. In the second region pins in rows in flue gas flow direction further away from the combustion channel are longer than pins in rows in flue gas flow direction closer to the combustion channel. In the second region, pins in consecutive rows are provided in staggered positions. The pins 154 in the second region have a larger diameter than the pins 152 in the first region. The pins in the second region have a cylindrical shape with circular cross section. The cylindrical shape comprises a small cone angle as known in the field to allow mould release after casting.

[0028] Pins 156 in the third region are provided in rows of pins of the same length. The rows are provided perpendicularly to the metal wall. In the third region pins in rows in flue gas flow direction further away from the combustion channel are longer than pins in rows in flue gas flow direction closer to the combustion channel. The length of each of the pins of the third region is smaller or equal to the length of the longest pin in the second region. Pins in consecutive rows of the third region are provided in staggered positions. The pins in the third region have a cylindrical shape with circular cross section; the cylindrical shape comprises a small cone angle as known in the field to allow mould release after casting.

[0029] The diameter of the pins in the second region is smaller than the diameter of pins in the third region. The number of rows of pins in the second region is larger than the number of rows of pins in the third region.

[0030] In the fourth region the length of the pins 158 is set by machining the pins such that the pins in the fourth region have a flat tip, such that all pins in the fourth region have the same length; and such that the flat tips are provided in a plane parallel with the metal wall on which the pins are provided. The pins in the fourth region have the same diameter as the pins in the third region.

[0031] The exemplary element is a mono-cast metal element out of an aluminum alloy. The pins are integrally cast with the metal walls. The pins of the first section and of the fourth section are set to length by machining. Observing the tips of pins, it can easily be distinguished whether the tips of the pins are "as cast" or the tips of the pins have been machined to provide the pin with a flat tip.

[0032] A plurality of the exemplary elements can be assembled side by side in a section heat exchanger. The combination of the combustion chambers of the elements creates a chamber for the installation of a premix burner. In such sectional heat exchanger using the exemplary elements, the distance between opposing metal walls of neighbour elements is 72 mm, and - when the heat exchanger is in cold status - the gap between the machined pins of the opposing metal walls is 1.5 mm.

Claims

1. Element for a sectional heat exchanger, comprising

- a combustion chamber for the generation of flue gas;

- a water channel; and

- two metal walls delimiting the water channel;

wherein at least one of the two metal walls - and preferably both metal walls - are provided with pins extending perpendicularly from the metal wall for increasing the heat transfer from flue gas generated in the combustion chamber to water flowing in the water channel;

wherein the at least one of the metal walls comprises a first region,

wherein in the first region the length of the pins is set by machining the pins such that the pins in the first region have a flat tip, such that all pins in the first region have the same length; and such that the flat tips are provided in a plane parallel with the metal wall on which the pins are provided;

wherein the at least one of the metal walls comprises a second region;

wherein the second region is provided in flue gas flow direction more upstream than the first region;

wherein pins in the second region are provided in rows of pins of the same length, wherein the rows are provided perpendicularly to the metal wall;

wherein in the second region pins in rows in flue gas flow direction further away from the combustion channel are longer than pins in rows in flue gas flow direction closer to the combustion channel;

wherein the at least one of the metal walls comprises a third region;

wherein the third region is provided in flue gas flow direction more upstream than the second region;

wherein pins in the third region are provided in rows of pins of the same length, wherein the rows are provided perpendicularly to the metal wall;

wherein in the third region pins in rows in flue gas flow direction further away from the combustion channel are longer than pins in rows in flue gas flow direction closer to the combustion channel;

wherein the at least one of the metal walls comprises a fourth region;

wherein the fourth region is provided in flue gas flow direction from the combustion chamber between the second region and the third region;

wherein in the fourth region the length of the pins is set by machining the pins such that the pins in the fourth region have a flat tip, such that all pins in the fourth region have the same length; and such that the flat tips are provided in a plane parallel with the metal wall on which the pins are provided.

2. Element as in claim 1 ; wherein the diameter of the pins in the second region is smaller than the diameter of pins in the third region.

3. Element as in any of the claims 1 - 2; wherein the number of rows of pins in the second region is larger than the number of rows of pins in the third region.

4. Element as in any of the preceding claims, wherein the pins in the fourth region have the same diameter as the pins in the third region.

5. Element as in any of the preceding claims, wherein the element is a mono-cast metal element, wherein the pins are integrally cast with the metal walls; and wherein the pins of the first section - and if present of the fourth section - are set to length by machining.

6. Sectional heat exchanger; comprising a plurality of elements as in any of the preceding claims; wherein the elements are assembled side by side such that the combination of the combustion chambers provides an elongated chamber for the installation of a premix gas burner for the generation of flue gas;

wherein the water channels of the plurality of elements are arranged in parallel flow; and wherein between the elements, parallel flue gas channels are provided extending from the elongated chamber for heat transfer from the flue gas through the metal walls to water flowing through the water channels.

7. Sectional heat exchanger as in claim 6, wherein the distance between opposing metal walls of neighbour elements is less than 80 mm and preferably more than 70 mm.

8. Sectional heat exchanger as in any of the claims 6 or 7, wherein - in cold condition - the gap between opposing pins of the first regions of opposing metal walls of neighbour elements is less than 2 mm.