EP3426986B1

EP3426986B1 - Sectional heat exchanger for use in a heat cell

Info

Publication number: EP3426986B1
Application number: EP17707588.4A
Authority: EP
Inventors: Harshit Gupta; Raymond Westers; Omke Jan Teerling
Original assignee: Bekaert Combustion Technology BV
Current assignee: Bekaert Combustion Technology BV
Priority date: 2016-03-09
Filing date: 2017-03-03
Publication date: 2019-11-20
Anticipated expiration: 2037-03-03
Also published as: EP3426986A1; CL2018002525A1; EA201892014A1; EA034441B1; CN108779937A; US20190011149A1; WO2017153280A1

Description

Technical Field

The invention relates to the field of sectional heat exchangers for use in a heat cell. Such heat exchangers comprise several segments. When assembling the sectional heat exchanger, the number of segments is selected as a function of the required capacity of the sectional heat exchanger. More specifically, the sectional heat exchanger of the invention has a combustion chamber in which a burner can be installed - thereby forming a heat cell - for the generation of flue gas that will transfer its thermal energy to heat water. Such heat cells can be used in boilers.

Background Art

Sectional heat exchangers are built up of a number of sections or segments. Sectional heat exchangers, e.g. out of aluminium, exist that comprise a number of identical intermediate segments positioned next to each other; and two end segments. The number of intermediate segments that is used in the assembly of the heat exchanger depends on the required capacity of the heat exchanger. The heat exchanger has a number of channels - at least one channel in each intermediate segment - in parallel flow connection for water to be heated, and flue gas channels extending from the one or more than one combustion chambers in the heat exchanger.
A sectional heat exchanger, using cast intermediate segments, is provided in DE102005014616B3 , in which one single burner can be mounted in the one combustion chamber of the sectional heat exchanger.
GB2441183A discloses a sectional heat exchanger according to the preamble of claim 1 and shows a heat exchanger for use in a condensing boiler comprising a plurality of heat exchanger sections having at least one internal flow passage with an inlet and an outlet for the passage of a heat exchange medium and a plurality of elongate fins on at least one side of each section defining flue gas flow channels, a burner to produce hot flue gas, a means to guide the flue gas from the burner through the flow channels from a primary part to a secondary part of the heat exchanger, and a means to promote unidirectional flue gas flow before entering the primary part. Promotion means may be a U-shaped barrier that changes the flue gas from a radial to the unidirectional flow and also changes from a downward to an upward flow. The promotion means may comprise a plurality of elongated fins disposed between, and parallel to, vertical arms of the U-shape.

Disclosure of Invention

The primary object of the invention is to provide sectional heat exchangers that are less prone to boiling when used in heat cells for boilers.
The invention is a sectional heat exchanger for a condensing heat cell according to claim 1. The sectional heat exchanger comprises two end segments and one or more than one intermediate segment(s) provided between the two end segments. The one or the more than one intermediate segment(s) and the two end segments are assembled in the heat exchanger. A combustion chamber is provided in the sectional heat exchanger, preferably perpendicular to the one or to the more than one intermediate segment(s). Each of the one or the more than one intermediate segment(s) comprises at least one water flow channel for water to be heated. In between each two consecutive segments - between two intermediate segments if more than one intermediate segment is provided as well as between intermediate segments and end segments - at least one flue gas flow channel is provided, extending from the combustion chamber. As a consequence, flue gas can flow from the combustion chamber into the flue gas flow channels of the sectional heat exchanger. The one or the more than one intermediate segment(s) each comprise a horizontal row of ribs extending into the flue gas flow channel in order to increase heat exchange from the flue gas to the water to be heated. Ribs at the two outer sides of the horizontal row of ribs have a larger height than ribs in the middle of the row of ribs. With height of the rib is meant the dimension of the rib in the vertical direction of the sectional heat exchanger. The more than one intermediate segment(s) each comprise a plurality of rows of pins extending in the flue gas channel to increase heat transfer. Preferably, each row of pins is provided in serial flue gas flow direction. Preferably the pins have a circular cross section.
Preferably, the rib has a substantially rectangular cross section, with its largest side aligned in the vertical direction of the heat exchanger. More preferably, the substantially rectangular cross section is a rectangular cross section having rounded edges.
The sectional heat exchanger of the invention has the surprising benefit that boiling of water in the water flow channels is prevented. This benefit is believed to be achieved thanks to the modified heat exchange at the horizontal row of ribs because of the differences of height of the ribs. The lower height of the ribs in the middle of the row of ribs will obviously involve a reduced heat transfer, negative for efficiency of the heat exchanger.
Preferably, the intermediate segment is provided such that parallel flows of flue gas flow along all of the ribs of the horizontal row of ribs. Meant is that no gas flow flows first along one rib of the horizontal row of ribs and then in serial flow arrangement along another rib of the horizontal row of ribs.
Preferably, the height over width ratio of each of the ribs of the horizontal row of ribs is more than 2.
In a preferred embodiment, the one or the more than one intermediate segment(s) each comprise only one row of ribs extending into the flue gas flow channel in order to increase heat exchange from the flue gas to the water to be heater.
Preferably, the sectional heat exchanger is a condensing heat exchanger.
In a preferred heat exchanger, ribs in the middle of the row of ribs have less than 70% - more preferably less than 55% - of the height of the ribs at the two outer sides of the horizontal row of ribs.
Preferably, the two end segments each comprise a horizontal row of ribs extending into the flue gas flow channel in order to increase heat exchange from the flue gas to the water to be heated. Ribs at the two outer sides of the horizontal row of ribs have a larger height than ribs in the middle of the row of ribs. With height of the rib is meant the dimension of the rib in the vertical direction of the sectional heat exchanger. In a more preferred embodiment, the two end segments each comprise only one row of ribs extending into the flue gas flow channel in order to increase heat exchange from the flue gas to the water to be heated.
Preferably the one or the more than one intermediate segment(s) and/or the two end segments are aluminium or aluminium alloy segments, preferably separate segments.
Preferably the one or the more than one intermediate segment(s) and/ or the two end segments are cast segments, preferably separate cast segments.
In a preferred embodiment, the sectional heat exchanger comprises at least two intermediate segments; and the at least two intermediate segments are provided parallel to each other in the sectional heat exchanger.
In a preferred heat exchanger, at least some ribs in the middle of the row of ribs only partially overlap in height direction the height of the first section of the water flow channel located below the combustion chamber. With the first section of the water flow channel located below the combustion chamber is meant the elongated full width section of the water flow channel immediately below the combustion channel. Such embodiment has shown to synergistically contribute to reduced risk of boiling of water in the water flow channel.
In a preferred embodiment, the distance between ends in the flue gas channel of ribs of the row of ribs and ends of ribs positioned on the opposing segment is constant for all ribs in the row of ribs.
Further synergistic effects are obtained by a sectional heat exchanger in which the distance between ends in the flue gas channel of ribs of the row of ribs and ends of ribs positioned on the opposing segment is less than 4 mm, and preferably less than 3 mm. Preferably the distance between ends in the flue gas channel of each of the ribs of the row of ribs and ends of ribs positioned on the opposing segment is less than 4 mm, and preferably less than 3 mm. More preferably, the distance between ends in the flue gas channel of ribs of the row of ribs and ends of ribs positioned on the opposing segment is constant for all ribs in the row of ribs.
In a preferred heat exchanger, the row of ribs comprises - and preferably consists out of - ribs of a first height and ribs of a second height. The first height is larger than the second height. Ribs at the outer sides of the horizontal row of ribs are ribs of the first height. Ribs in the middle of the row of ribs are ribs of the second height. More preferably, all other ribs than the ribs of the first height are ribs of the second height. Even more preferably, less than 60% of the ribs of the row of ribs are ribs of the first height. Even more preferable, less than 40% of the ribs of the row of ribs are ribs of the first height. In a preferred embodiment, the ribs of a second height have less than 70% - more preferably less than 55% - of the height of the ribs of a first height.
Preferably, the intermediate segment(s) comprise a first horizontal row of pins below the row of ribs, wherein the pins of the first horizontal row of pins extend into the flue gas flow channel. With first horizontal row of pins is meant the horizontal row of pins immediately below the row of ribs. This row of pins comprises at its two outer sides pins extending into the flue gas flow channel so that a distance of less than 4 mm - and preferably less than 3 mm - is created with pins extending from the opposed segment into the flue gas shaft. This row of pins comprises in its middle pins extending into the flue gas shaft so that a distance of more than 10 mm - and more preferably of more than 20 mm - is created with pins extending from the opposed segment into the flue gas shaft. Such embodiments contribute synergistically to the prevention of boiling of water in the water flow channel. In a more preferred embodiment, below the first horizontal row of pins, further horizontal rows of pins extending into the flue gas channel are provided. Preferably within such horizontal row of pins, the distance between the pin and the pin extending into the flue gas flow channel from the opposed segment is constant over the width of the horizontal row of pins.
Preferably, the intermediate segment(s) comprise a plurality of horizontal row of pins below the row of ribs, wherein the pins of the horizontal rows of pins extend into the flue gas flow channel. Each of these rows of pins comprises at its two outer sides pins extending into the flue gas flow channel so that a distance of less than 4 mm - and preferably less than 3 mm - is created with pins extending from the opposed segment into the flue gas shaft. These rows of pins comprise in their middle pins extending into the flue gas shaft so that a distance of more than 10 mm - and more preferably of more than 20 mm - is created with pins extending from the opposed segment into the flue gas shaft. Such embodiments contribute synergistically to the prevention of boiling of water in the water flow channel.
In a more preferred embodiment, additional horizontal rows of pins extending into the flue gas channel are provided - preferably below the plurality of rows of pins that extend over different length in the flue gas channel. Within such additional horizontal row of pins, the distance between the pin and the pin extending into the flue gas flow channel from the opposed segment is constant over the width of the horizontal row of pins.
Preferably, the combustion chamber has perpendicular to its length axis a cylindrical shape with a circular cross section.
Preferably, the water flow channel in the intermediate segment runs over at least 80% - and more preferably over at least 90% - of the circumference of the combustion chamber around the combustion chamber.
Preferably, the sectional heat exchanger comprises at least two intermediate segments. The at least two intermediate segments are provided parallel to each other in the sectional heat exchanger.
Preferably, in the intermediate segment, the water flow channel follows a meandering flow path.
A preferred sectional heat exchanger comprises more than one intermediate segment. Water flow channels of the more than one intermediate segment, and preferably also of the two end segments, are connected in parallel flow connection.
Preferably, the water flow channels in the one or in the more than one intermediate segment(s) are provided for counter flow of the water with respect to the flow direction of the flue gas channels.
An embodiment of the invention is a heat cell. The heat cell comprises a sectional heat exchanger according to the invention; and a, preferably one, more preferably only one, burner, preferably a premix gas burner, and preferably a cylindrical burner, provided in the combustion chamber for the production of flue gas to flow in parallel flow connection through the flue gas flow channels between the segments of the heat exchanger. The burner is preferably mounted so that it extends in the combustion chamber perpendicularly to the one or to the more than one intermediate segment(s).
Preferably, the heat cell has a condensation sump at the bottom of the heat cell.

Brief Description of Figures in the Drawings

Figure 1 shows a heat cell according to an embodiment of the invention, comprising a sectional heat exchanger according to the invention.
Figure 2 shows a view on an intermediate segment of a sectional heat exchanger according to the invention.
Figure 3 shows a cross section along plane III-III of an intermediate segment of the heat exchanger of figure 1.

Mode(s) for Carrying Out the Invention

Figure 1 shows a heat cell according to an embodiment of the invention, comprising a condensing sectional heat exchanger according to the invention. The figure shows a section 100 perpendicularly to the segments of the sectional heat exchanger. Figure 2 shows a view on an intermediate segment of a sectional heat exchanger according to the invention. Figure 3 shows a cross section along plane III-III of an intermediate segment of the heat exchanger of figure 1.
The exemplary sectional heat exchanger of figures 1, 2 and 3 comprises two end segments 102, 104 and two intermediate segments 106 provided between the two end segments 102, 104. The two intermediate segments and the two end segments are cast aluminum parts and are assembled in the heat exchanger. A cylindrical combustion chamber 108, 208, 308 with a circular cross section is provided in the sectional heat exchanger, in the example perpendicular to the intermediate segments and perpendicular to the end segments. A cylindrical gas premix burner 110 is provided in the combustion chamber, perpendicular to the intermediate segments and perpendicular to the end segments.
Each of the intermediate segments 106 and each of the end segments 102, 104 comprise a water flow channel 112, 312 for water to be heated. Water flow channels of the intermediate segments, and preferably also of the two end segments, are connected in parallel flow connection. The water flow channels in the intermediate segments and in the end segments follow a meandering flow path through the segment. The water flow channels in the intermediate segments as well as the water flow channels in the end segments run over more than 90% of the circumference of the combustion chamber around the combustion chamber. The water channels are provided for counter flow compared to the flue gas flow direction in the flue gas flow channels.
In between each two consecutive segments at least one flue gas flow channel 114 is provided, extending from the combustion chamber 108, 208, 308. The intermediate segments 106 - as well as both end segments 102, 104 - each comprise a horizontal row of ribs 116, 216 extending into the flue gas flow channel in order to increase heat exchange from the flue gas to the water to be heated. Ribs 218 at the two outer sides of the horizontal row of ribs have a larger height than ribs 220 in the middle of the row of ribs. In the example, the intermediate segments 106 and the two end segments 102, 104 each comprise only one row of ribs 116, 216 extending into the flue gas flow channel in order to increase heat exchange from the flue gas to the water to be heated. In the example, the ribs have a substantially rectangular cross section, with their largest side aligned in the vertical direction of the heat exchanger. In the exemplary heat exchanger shown in figures 1 - 3, the ribs 220 at the middle of the row of ribs of the intermediate segments as well as the ribs at the middle of the row of ribs of the end segments have 66% of the height of the ribs 218 at the two outer sides of the horizontal row of ribs. In another exemplary heat exchanger, the ribs 220 at the middle of the row of ribs of the intermediate segments as well as the ribs at the middle of the row of ribs of the end segments have 50% of the height of the ribs 218 at the two outer sides of the horizontal row of ribs.
In an exemplary heat exchanger, ribs in the middle of the row of ribs only partially overlap in height direction the first section of the water flow channel located below the combustion chamber.
In the example shown in figures 1 - 3, the distance between ends in the flue gas channel of each of the ribs of the row of ribs and ends of ribs positioned on the opposing segment is 2 mm.
The intermediate segments as well as the end segments comprise a first horizontal row of pins 132, 232 below the row of ribs. These pins extend into the flue gas flow channel. This row of pins 132, 232 comprises at its two outer sides pins extending into the flue gas flow channel so that a distance of less than 4 mm - and preferably less than 3 mm - is created with pins extending into the flue gas shaft from the opposed segment. This row of pins comprises in its middle pins extending into the flue gas shaft so that a distance of 28 mm is created with pins extending from the opposed segment into the flue gas shaft.
Below the first horizontal row of pins, further horizontal rows of pins 140, 240 extending into the flue gas channel are provided. In the exemplary heat exchanger, the distance between the pin and the pin extending into the flue gas flow channel from the opposed segment is constant over the width of the horizontal row of pins. In a further exemplary heat exchanger, each of the segment(s) comprises a plurality of horizontal row of pins below the row of ribs, wherein the pins of the horizontal rows of pins extend into the flue gas flow channel. Each of these rows of pins comprises at its two outer sides pins extending into the flue gas flow channel so that a distance of less than 4 mm - and preferably less than 3 mm - is created with pins extending from the opposed segment into the flue gas shaft. These rows of pins comprise in their middle pins extending into the flue gas shaft so that a distance of more than 20 mm is created with pins extending from the opposed segment into the flue gas shaft.

Claims

A sectional heat exchanger for a condensing heat cell,
- wherein the sectional heat exchanger comprises two end segments (102, 104) and one or more than one intermediate segment(s) (106) provided between the two end segments;

- wherein the one or the more than one intermediate segment(s) and the two end segments are assembled in the heat exchanger, wherein a combustion chamber (108, 208, 308) is provided in the sectional heat exchanger,

- wherein each of the one or the more than one intermediate segment(s) comprises at least one water flow channel (112, 312) for water to be heated,

- wherein in between each two consecutive segments at least one flue gas flow channel (114) is provided, and wherein the flue gas flow channel extends from the combustion chamber,

- wherein the one or the more than one intermediate segment(s) each comprise a horizontal row of ribs (116, 216) extending into the flue gas flow channel in order to increase heat exchange from the flue gas to the water to be heated;
wherein ribs (218) at the two outer sides of the horizontal row of ribs have a larger height than ribs (220) in the middle of the row of ribs; wherein with height of the rib is meant the dimension of the rib in the vertical direction of the sectional heat exchanger;
characterized in that the one or the more than one intermediate segment(s) each comprise a plurality of rows of pins extending in the flue gas channel to increase heat transfer.
A sectional heat exchanger as in claim 1, wherein at least some ribs (220) in the middle of the row of ribs only partially overlap in height direction the height of a first section of the water flow channel located below the combustion chamber.
A sectional heat exchanger as in any of the preceding clams, wherein the distance between ends in the flue gas channel of ribs of the row of ribs and ends of ribs positioned on the opposing segment is less than 4 mm, and preferably less than 3 mm.
A sectional heat exchanger as in any of the preceding claims,
wherein the row of ribs comprises ribs of a first height and ribs of a second height, wherein the first height is larger than the second height;
and wherein ribs at the outer sides of the horizontal row of ribs are ribs of the first height; and wherein ribs in the middle of the row of ribs are ribs of the second height.
A sectional heat exchanger as in any of the preceding claims,
wherein the intermediate segment(s) (106) comprise a first horizontal row of pins (132, 232) below the row of ribs, wherein the pins extend into the flue gas flow channel,
wherein this row of pins comprises at its two outer sides pins extending into the flue gas flow channel so that a distance of less than 4 mm - and preferably less than 3 mm - is created with pins extending from the opposed segment into the flue gas shaft;
wherein this row of pins comprises in its middle pins extending into the flue gas shaft so that a distance of more than 10 mm is created with pins extending into the flue gas shaft from the opposed segment.
A sectional heat exchanger as in claim 5,
wherein the intermediate segment(s) comprise a plurality of horizontal rows (140, 240) of pins below the row of ribs, wherein the pins extend into the flue gas flow channel,
wherein each row of pins comprises at its two outer sides pins extending into the flue gas flow channel so that a distance of less than 4 mm - and preferably less than 3 mm - is created with pins extending from the opposed segment into the flue gas shaft;
wherein each row of pins comprises in its middle pins extending into the flue gas shaft so that a distance of more than 10 mm is created with pins extending into the flue gas shaft from the opposed segment.
A sectional heat exchanger as in any of the preceding claims, wherein the combustion chamber (108, 208, 308) has perpendicular to its length axis a cylindrical shape with a circular cross section.
A sectional heat exchanger as in any of the preceding claims, wherein the water flow channel (112, 312) in the intermediate segment runs over at least 80% of the circumference of the combustion chamber around the combustion chamber (108, 208, 308).
The sectional heat exchanger as in any of the preceding claims, wherein the sectional heat exchanger comprises at least two intermediate segments (106) and wherein the at least two intermediate segments are provided parallel to each other in the sectional heat exchanger.
The sectional heat exchanger as in any of the preceding claims, wherein in the intermediate segment(s) (106), the water flow channel (112, 312) follows a meandering flow path.
The sectional heat exchanger as in any of the preceding claims, wherein the sectional heat exchanger comprises more than one intermediate segment (106) and wherein water flow channels (112, 312) of the more than one intermediate segment, and preferably also of the two end segments, are connected in parallel flow connection.
The sectional heat exchanger as in any of the preceding claims, wherein the water flow channels (112, 312) in the one or in the more than one intermediate segment(s) (106) are provided for counter flow of the water with respect to the flow direction of the flue gas channels (114).
A heat cell, comprising
- a sectional heat exchanger as in any of the preceding claims; and

- a burner (110),
wherein the burner (110) is provided in the combustion chamber (108, 208, 308) for the production of flue gas to flow in parallel through the flue gas channels (114) between the segments of the sectional heat exchanger.
A heat cell as in claim 13, wherein the burner (110) extends perpendicularly to the one or to the more than one intermediate segment(s) (106).