Patent Description:
Such a heat exchanger is known from European patent <CIT> in the name of the same applicant. It is an object to improve the heat exchanger described in <CIT>.

A heat exchanger is also known from <CIT>. This document discloses in a condensation boiler of the type comprising a plurality of pipes defining a water flow path between a return section from a heating plant to a delivery section to the heating plant, at least two covers mounted at an end of the plurality of pipes and provided internally with dividing walls that realize connecting chambers between the pipes and define the conformation of the water flow path. The connecting chambers also serve the function of front wall of a wet combustion chamber.

In an embodiment of the heat exchanger according to the invention said receiving space is arranged between at least a part of the pipes of the first pattern located near the open end of the U-shape body in such a manner that in use at least a part of the pipes of the first pattern surround a flame provided by said burner.

An advantage of this embodiment is that the casing is protected from the heat of the flame by said pipes of the first pattern that surround said flame. In the heat exchanger described in <CIT> the flame was present in an area not bounded by pipes. Practically the heat exchanger therefore had a sealing arranged to protect the casing from the heat, which sealing is quite expensive. An advantage of this embodiment is therefore that no or less sealing is required, thereby reducing the costs of the heat exchanger.

In the heat exchanger according to the invention a distance between all pairs of adjacent pipes of each leg of the first pattern is maximally <NUM>.

It is noted that said distance is defined as the distance between the adjacent outer surfaces of each pair of adjacent pipes. An advantage of such small distances between adjacent pipes of the legs of the first pattern is that the mass flow of flue gas that will flow through the spaces between adjacent pipes to an area between the pipes of the legs of the first pattern and the casing is restricted, such that the flue gas that will enter this area will be cooled down by the liquid in the pipes to such an extent that the flue gas will have a relatively low temperature that is more or less similar to or slightly higher than the temperature of the walls of these pipes. As a result the casing will only be exposed to this relatively low temperature, such that no or less sealing of the casing is required, thereby reducing the costs of the heat exchanger.

It is noted that in the heat exchanger described in <CIT>a distance between at least some pairs of adjacent pipes was larger than the above described maximum distances, such that more flue gas could enter the area, which flue gas entering the area therefore could have a higher temperature, and such that the U-shaped body required a substantially U-shape sealing covering said U-shape body to protect it from the heat. Such a relatively large sealing is quite expensive.

In another embodiment of the heat exchanger according to the invention said heat exchanger comprises a sealing arranged between the outer surface of the pipes arranged at a first end of each leg of the first pattern near the open end of the U-shape body and the substantially U-shaped body.

An advantage of this sealing that hot flue gas is prevented from flowing in the area between the pipes of the first pattern and the casing via a space present between the pipes arranged at the first ends of each leg of the first pattern and the U-shaped body, because this space is sealed off by said sealing. This way a relatively small amount of sealing is required for protecting the casing from being exposed to hot temperatures, at relatively low costs.

In another embodiment of the heat exchanger according to the invention the distance between the legs of the U-shape body and the pipes of the first pattern is maximally <NUM>, preferably maximally <NUM>.

It is noted that said distance is defined as the distance between the outer surfaces of the pipes of the first pattern that are facing the U-shape body and the legs of the U-shape body. An advantage of such a relatively small distance is that the volume of the area between the pipes and the U-shape body is relatively small, thereby also contributing to the restriction of the mass flow of flue gas into this area and thereby contributing to the reduction in temperature to which the casing is exposed.

The second part of the pipes may be arranged such that a formula: <MAT> is substantially fulfilled, wherein:.

Relatively hot flue gas has a relatively large volume and vice versa. As such, as seen in a flow direction of the flue gas, the flue gas coming from the burner has a relatively large flow rate as the flue gas is relatively hot, thereby requiring a relatively large surface area between adjacent pipes arranged near the burner space in order to have the velocity of the flue gas being maximally said value C. The pipes arranged near the outlet opening however require a smaller surface area there between in order to have the velocity of the flue gas being maximally said value C, as the flue gas is already cooled down to some extent by the heat exchanger and the flow rate is relatively small. An advantage of a substantially constant velocity of the flue gas throughout the heat exchanger is that such a substantially constant velocity reduces the pressure drop. It is therefore an advantage of this embodiment to arrange said second part of the pipes such that this formula is fulfilled.

It is noted that in particular at low loads C may be less than said maximum value of <NUM>/s.

The connecting means may be arranged to provide a liquid through flow connection between groups of at least two determined pipes at each longitudinal end zone of said U-shape body in such a manner that a second formula: <MAT> is substantially fulfilled, wherein:.

An advantage of this embodiment is that the heat exchanger is designed such that the distribution of the liquid flow over determined groups of pipes is chosen such that the quantity of heat Q discharged from the flue gas and transferred to the liquid flowing in each pipe is substantially constant anywhere in the heat exchanger. As a result thereof, the pipes are exposed to less thermal stresses as the pipes are exposed to more or less similar heat transfer. Furthermore, the liquid flow through the pipes is optimized with respect to pressure drop and blockage of the pipes due to lime scale deposition is prevented by preventing the pipes from becoming too hot. This is especially advantageous in heat exchangers where a relatively large number of pipes with a relatively small throughflow area is used.

In another embodiment of the heat exchanger according to the invention at least one of the connecting means comprises a liquid distributor for substantially equally distributing liquid over pipes being connected to said connecting means.

Without such a liquid distributor it is possible that the liquid is not equally distributed over the pipes connected to the connecting means. This way, some pipes with less liquid flowing there through can become too hot and thereby exposed to high thermal stresses. An advantage of the liquid distributor is therefore that the liquid is substantially equally distributed over pipes that are connected to said connecting means, thereby reducing the thermal stresses of the pipes.

In another embodiment of the heat exchanger according to the invention the second part of the pipes comprise at least three groups of pipes, wherein a first group located near the base of the U-shape body has a first, smallest diameter, wherein a second group located near the first group at a side of the first group opposite to the base of the U-shape has a second diameter, and wherein a third group located near the open end of the U-shape body has a third, largest diameter, which third group is located at a predetermined distance from the second group.

An advantage of this arrangement of the pipes is that the third group is arranged nearest to the burner space. The flue gas coming from the burner is cooled down relatively fast by this third group of pipes arranged near the burner with relatively large diameter and thereby relatively large liquid flow, such that the production of NOx is efficiently reduced. Between the third and second group said predetermined distance is present, such that over this distance the flue gas is substantially not cooled down and a relatively large time period is provided for the conversion of CO into CO<NUM>, such that the emission of CO is reduced and preferably prevented.

It is noted that said distance is preferably between <NUM> and <NUM>, more preferably between <NUM> and <NUM>. Said distance is defined between the outer surfaces of the row of pipes of the third group and the row of pipes of the second group arranged nearest to the third group and especially between the facing outer surfaces thereof.

In another embodiment of the heat exchanger according to the invention a part of the pipes of the first group is arranged at least partly between a part of the pipes of the second group.

An advantage of such an arrangement is that the flow of flue gas along substantially the whole outer surface of the pipes arranged upstream of said part of pipes of the second group as seen in the direction of the flow of flue gases is enhanced.

The invention also relates to an assembly of a heat exchanger according to any of the claims <NUM> - <NUM> and a burner, wherein the burner is arranged in said receiving space.

Such an assembly provides the advantages of the heat exchanger described above.

In an embodiment of the assembly according to the invention the assembly comprises the heat exchanger according to at least claim <NUM>, wherein the burner is arranged in said receiving space in such a manner that in use at least a part of the pipes of the first pattern surround a flame provided by said burner.

As described above such an assembly provides the advantage that said part of the pipes of the first pattern protect the casing from heat of the flame of the burner.

In another embodiment of the assembly according to the invention said burner comprises a damper.

Such a (Panel Helmholtz resonance) damper efficiently dampens any noise of the heat exchanger.

Practically said burner comprises a burner plate that is connected to or is integrally formed with said damper.

An advantage of this embodiment is that the functions of the burner plate and the damper are combined in one integrally formed or connected element.

In another embodiment of the assembly said burner comprises a gas/air-mixture distribution plate that is connected to or integrally formed with said damper and/or burner plate.

An advantage of this embodiment is that the functions of the burner plate and/or the damper and/or the gas/air-mixture distribution plate are combined in one integrally formed or connected element.

In particular, said (Panel Helmholtz resonance) damper may be provided with through holes for distributing the gas/air-mixture, such that said damper functions also as said gas/air-mixture distribution plate.

Practically said assembly comprises a sealing that is provided between the casing and the gas/air-mixture distribution plate.

Said gas/air-mixture distribution plate is arranged upstream of the burner plate and distributes the gas/air-mixture prior to passing though the burner plate. As the gas/air-mixture distribution plate and the burner plate are connected or integrally formed in one element, the gas/air-mixture exiting the gas/air-mixture distribution plate cannot by-pass the burner plate. Said sealing prevents the gas/air-mixture from entering the burner room alongside said element comprising the gas/air-mixture distribution plate and the burner plate. The gas/air-mixture flowing through the gas/air chamber will cool down the gas/air chamber and the gas/air-mixture distribution plate/damper. The life time of the burner is hereby enhanced.

The invention is further elucidated with reference to figures shown in a drawing, in which:.

<FIG> and <FIG> show a heat exchanger <NUM>. Said heat exchanger <NUM> comprises a casing with a substantially U-shaped body <NUM> as seen in cross-section and extending in a longitudinal direction L. The base <NUM> of the body <NUM> arranged at the lower end of the body <NUM> comprises a gas outlet opening (not shown). At the end opposite to the base <NUM>, i.e. the upper end, the body <NUM> is open and comprises a receiving space <NUM> for receiving a burner (not shown). The flue gases from the burner flow downwards through the casing <NUM> and are discharged via said gas outlet opening. At each longitudinal end zone <NUM> of the body <NUM> the body <NUM> comprises an end plate <NUM>. A plurality of pipes <NUM> is arranged within said casing and is connected to said end plates <NUM>, in particular to holes in said end plates <NUM>. In use of the heat exchanger <NUM> a liquid, practically water, flows though the pipes <NUM> for taking up heat from the flue gases, thereby heating the water and cooling the flue gases. Panels <NUM> are provided to cover the end plates <NUM>. Each panel <NUM> comprises a plurality of hollow spaces <NUM>, each hollow space <NUM> connecting at least two pipes <NUM> at each longitudinal end zone <NUM> of the body <NUM>, such that liquid flowing through a first pipe <NUM> of the at least two pipes <NUM> is directed to the other pipe <NUM> of the at least two pipes <NUM>. Liquid flowing through the pipes <NUM> thereby flows from the one longitudinal end zone <NUM> to the other longitudinal end zone <NUM> via the plurality of pipes <NUM> and hollow spaces <NUM>. A water inlet <NUM> and a water outlet <NUM> are provided in one panel <NUM> at one longitudinal end zone <NUM>, for feeding relatively cold water to the pipes <NUM> via the water inlet <NUM> and for discharging relatively hot water from the pipes <NUM> via the water outlet <NUM>. Said hot water may be used for central heating or tap water.

As is clearly shown in <FIG>, a first part of the pipes <NUM> is arranged in a first pattern <NUM> defining two legs of a substantially U-shape as seen in cross-section, said first pattern being arranged substantially parallel to legs of said U-shape body <NUM>. The receiving space <NUM> for the burner is arranged between at least a part of the pipes <NUM> of the first pattern <NUM> located near the open end of the body <NUM> in such a manner that in use at least a part of the pipes <NUM> of the first pattern <NUM> surround a flame provided by said burner. This way, said part of the pipes <NUM> of the first pattern <NUM> protect the casing from the heat of the flame. A distance between all pairs of adjacent pipes <NUM> of each leg of the first pattern <NUM> is maximally <NUM>, thereby restricting the mass flow of flue gas that will flow through the spaces between adjacent pipes <NUM> to an area between the pipes of the legs of the first pattern <NUM> and the casing, such that the flue gas that will enter this area will be cooled down by the liquid in the pipes <NUM> to such an extent that the flue gas will have a relatively low temperature that is more or less similar to or slightly higher than the temperature of the walls of these pipes <NUM>. The distance between the legs of the U-shape body <NUM> and the pipes <NUM> of the first pattern <NUM> is preferably maximally <NUM>, more preferably maximally <NUM>, thereby also contributing to the restriction of the mass flow of flue gas into this area and thereby contributing to the reduction in temperature to which the casing is exposed. A sealing <NUM> is arranged between the outer surface of the pipes <NUM> arranged at a first end of each leg of the first pattern <NUM> near the open end of the body <NUM> and the body <NUM>, thereby sealing off the space there between and thereby preventing the flue gases from flowing in the area between the pipes <NUM> of the first pattern <NUM> and the casing via said space.

A second part of said pipes <NUM> are arranged within a space <NUM> at least partly bounded by said first pattern <NUM>. The second part of the pipes are arranged such that a formula: <MAT> is substantially fulfilled, wherein:.

Relatively hot flue gas has a relatively large volume and vice versa. As such, as seen in a flow direction of the flue gas, the flue gas coming from the burner arranged in the receiving space <NUM> has a relatively large flow rate as the flue gas is relatively hot, thereby requiring a relatively large surface area between adjacent pipes <NUM> arranged near the burner space in order to have the velocity of the flue gas being maximally said value C. The pipes <NUM> arranged near the outlet opening in the base <NUM> of the body <NUM> therefor require a smaller surface area there between in order to have the velocity of the flue gas being maximally said value C, as the flue gas is already cooled down to some extent by the heat exchanger and the flow rate is relatively small. This is shown in <FIG>, showing that the closer the pipes <NUM> are arranged to the burner arranged in the receiving space <NUM>, the larger the surface area between the pipes <NUM>.

As is further shown in <FIG>, the second part of the pipes comprises three groups of pipes <NUM>, wherein a first group <NUM> located near the base <NUM> of the body <NUM> has a first, smallest diameter, wherein a second group <NUM> located near the first group <NUM> at a side of the first group <NUM> opposite to the base <NUM> of body <NUM> has a second, intermediate diameter, and wherein a third group <NUM> located near the open end of the body <NUM> has a third, largest diameter. As said third group <NUM> of pipes <NUM> has the largest diameter of the three groups, the flow rate of liquid flowing there through is also the largest of the three groups, thereby cooling down the flue gas coming from the burner relatively fast and efficiently reducing production of NOx. Between the third group <NUM> and the second group <NUM> a certain distance of preferably between <NUM> and <NUM>, more preferably between <NUM> and <NUM>, is present, such that over this distance the flue gas is substantially not cooled down and a relatively large time period is provided for the conversion of CO into CO<NUM>, such that the emission of CO is reduced and preferably prevented. The pipes <NUM> of the second group <NUM> have an intermediate diameter adapted to the amount of heat to be absorbed from the already partly cooled down flue gases, and the pipes <NUM> of the first group <NUM> have the smallest diameter adapted to absorb heat from the more cooled down flue gases. A part of the pipes <NUM> of the first group <NUM>, in particular three pipes <NUM> thereof, is arranged at least partly between a part of the pipes <NUM> of the second group <NUM>, wherein said part of the pipes <NUM> of the first group <NUM> and said part of the pipes <NUM> of the second group <NUM> are arranged alternately in a direction substantially orthogonal to the direction of the flow of the flue gases. As a result thereof, the flow of flue gas is directed along substantially the whole outer surface, in particular also along the lower surface, of the pipes <NUM> arranged directly upstream of said part of pipes <NUM> of the second group <NUM> as seen in the direction of the flow of flue gases.

<FIG> schematically shows the distribution of the liquid flow through the pipes <NUM> of the heat exchanger. This shows that the pipes <NUM> are divided over in total twenty-two groups. Appointment of the pipes <NUM> to each group is established with said hollow spaces <NUM> that connect any desired number of selected pipes <NUM> to a specific group. Liquid enters the first group I via the liquid inlet <NUM> that is in medium through flow connection with group I and exits the last group XX via liquid outlet <NUM> that is in medium through flow connection with group XX. The liquid flows alternatingly between the two end zones <NUM> via the groups in sequential order, thus via group I to group II, from group II to group III, etc. The number of pipes <NUM> belonging to each group and the selection of pipes <NUM> belonging to each group may be chosen as desired. Preferably, the selection and number of pipes <NUM> belonging to each group are chosen to fulfil a second formula: <MAT> is substantially fulfilled, wherein:.

Using this formula the liquid flow is distributed such that the quantity of heat Q discharged from the flue gas and transferred to the liquid flowing in each pipe is substantially constant anywhere in the heat exchanger.

<FIG> show the effect of liquid distributors according to the invention. Said liquid distributors may be provided in any desired hollow space <NUM> for distributing the liquid over the pipes <NUM> connecting to that hollow space <NUM>. <FIG> shows a plurality of three pipes <NUM> of a group that are connected via a hollow space <NUM> to three pipes <NUM> of a subsequent group. The liquid tends to follow the largest curvature and thereby to enter the most outer pipe <NUM> of the three pipes of the subsequent group. The middle pipe therefor receives less liquid and will therefor become relative hot and exposed to high thermal stresses. With use of the liquid distributors shown in <FIG> each pipe <NUM> of a group is connected to a pipe <NUM> of the subsequent group. The liquid is thereby evenly distributed over the pipes <NUM> belonging to a specific group, independent of the location of the pipe <NUM>.

<FIG> is a perspective view of a burner according to the invention. Said burner comprises a casing <NUM>. In said casing <NUM> an element is provided comprising a ceramic burner plate <NUM> and a damper <NUM> that also functions as an aluminium gas/air mixture distribution plate and that is arranged upstream from the burner plate <NUM>. An anorganic insulation material <NUM> is provided between the burner plate <NUM> and the damper/distribution plate <NUM>. A sealing <NUM> is provided between the casing <NUM> and the damper/distribution plate <NUM>, such that the gas/air-mixture is prevented from entering the burner room alongside said element comprising the damper/distribution plate 21and the burner plate <NUM>. As the damper/distribution plate <NUM> and the burner plate <NUM> are combined in one element, the gas/air-mixture exiting the damper/distribution plate <NUM> cannot by-pass the burner plate <NUM>. The gas/air-mixture flowing through the gas/air chamber will cool down the gas/air chamber and the gas/air-mixture distribution plate/damper <NUM>. The life time of the burner is hereby enhanced.

<FIG> shows an assembly of the heat exchanger of <FIG>, <FIG> and the burner of <FIG>. The U-shape body <NUM> and the panels <NUM> of the heat exchanger are shown, as well as the casing <NUM> of the burner. The burner is arranged such in the receiving space of the body <NUM>, that the flames coming from the burner plate are surrounded by the upper pipes <NUM> of the legs of the first pattern <NUM> of pipes <NUM>.

Claim 1:
Heat exchanger (<NUM>), comprising:
- a casing (<NUM>), comprising:
- a substantially U-shaped body (<NUM>) as seen in cross-section and extending in a longitudinal direction, wherein a base (<NUM>) of the U-shape body (<NUM>) comprises a gas outlet opening and wherein an open end, opposite to the base (<NUM>), of the U-shape body (<NUM>) comprises a receiving space (<NUM>) for receiving a burner, and
- two end plates (<NUM>) arranged at the two longitudinal end zones (<NUM>) of said U-shape body (<NUM>);
- a plurality of pipes (<NUM>) arranged within said casing (<NUM>) and connected to said end plates (<NUM>), through which pipes (<NUM>) in use a liquid can flow;
- a plurality of connecting means for providing a liquid through flow connection between at least two pipes (<NUM>) at each longitudinal end zone (<NUM>) of said U-shape body (<NUM>), such that liquid flowing through a first pipe (<NUM>) of the at least two pipes (<NUM>) is directed to the other pipe (<NUM>) of the at least two pipes (<NUM>),
wherein a first part of the pipes (<NUM>) is arranged in a first pattern (<NUM>) defining two legs of a substantially U-shape as seen in cross-section, said first pattern (<NUM>) being arranged substantially parallel to legs of said U-shape body (<NUM>), and
wherein a second part of said pipes (<NUM>) are arranged within a space (<NUM>) at least partly bounded by said first pattern (<NUM>),
characterized in that a distance between all pairs of adjacent pipes (<NUM>) of each leg of the first pattern (<NUM>) is maximally <NUM>.