Patent Description:
More specifically, the present invention relates to a brazed plate heat exchanger comprising an end plate and a stack of heat exchanger plates provided with a pattern comprising ridges and grooves adapted to form contact points between neighbouring heat exchanger plates such that the heat exchanger plates form interplate flow channels for media to exchange heat over the heat exchanger plates. The heat exchanger plates are further being provided with port openings for selective fluid communication with the flow channels, wherein the port openings are surrounded by port opening areas for sealing against a corresponding port opening area of an adjacent heat exchanger plate. Neighbouring heat exchanger plates are connected by brazing joints at said contact points. The end plate is provided with port openings and flat areas around the port openings in a common plane. A plurality of ridges of the heat exchanger plates, in an area overlapping a flat area of the end plate, are formed with an indentation, wherein said indentations of a heat exchanger plate adjacent the end plate connect a flow channel, formed between the end plate and the adjacent heat exchanger plate, with a neighbouring flow channel to allow distribution of media between them.

When exchanging heat between different media in any type of heat exchanger, it is generally favourable to avoid stagnant media, i.e. media that does not follow the general flow path but rather stands still. Stagnant media is cumbersome for many reasons: bacterial or microbial growth may occur in the stagnant zones and media may freeze, hence breaking the heat exchanger. Moreover, the general efficiency of the heat exchanger may be impeded. For brazed plate heat exchangers comprising a pressed pattern of ridges and grooves keeping heat exchanger plates on a distance from one another, a historically critical area for the formation of stagnant media is between an end plate having a flat area in the vicinity of the port openings and a neighbouring heat exchanger plate, wherein the end plate forms dead-end flow channels between the end plate and the neighbouring heat exchanger plate where the media easily becomes stagnant.

<CIT> solves the problem with stagnant media in the space between flat areas of an end plate and the neighbouring heat exchanger plate by providing distribution channels between flow channels, which otherwise would be dead-end flow channels, and neighbouring flow channels. The distribution channels allow for a flow that otherwise would be "stuck" in dead-end flow channels. The distribution channels of <CIT> are arranged immediately adjacent a port opening area, i.e. at the very end of the ridges. Although the solution disclosed in this patent is efficient for avoiding stagnant media, it has some drawbacks when it comes to strength.

Hence, one problem with prior art heat exchangers is that they are weak and cannot withstand high pressure.

It is the object of the present invention to provide a brazed plate heat exchanger with reduced risk of stagnant media while increasing the number of contact points between the ridges and grooves of neighbouring plates around port opening areas and hence increase the strength of the heat exchanger.

The present invention is related to a brazed plate heat exchanger as defined in claim <NUM>.

By the provision of the indentations, trans-ridge flow channels are formed for distributing media and prevent stagnant media in flow channels that otherwise would be dead-end flow channels in the space between the end plate and the adjacent heat exchanger plate, such as the first or last heat exchanger plate in the stack. In addition it has surprisingly been found that by arranging said indentations with a small distance from the very end of the flow channel, i.e. on the ridge at a distance from the nearest port opening area, space is provided for a contact point and thus a brazing joint, while stagnant media in the flow channel still is prevented. Hence, it has been found that a favourable flow of media is achieved also when a brazing joint is arranged between the indentation and the port opening area. The brazing joints between the port opening area and at least some of the indentations result in a stronger heat exchanger. Also, contact points closer to the port opening areas is achieved, which results in smaller pressure areas around the ports. Additional contact points are achieved. Also, contact points closer to the port openings are achieved. For example, a distance between the port opening and a first row of contact points can be shorter than in the prior art and an area around the port opening exposed to media pressure is smaller. Also, a higher contact point density in the immediate vicinity of the port opening can be achieved. Together this results in a strong heat exchanger while stagnant media in the dead-end flow channels is prevented.

The end plate can be a conventional end plate with flat areas around the port openings, such as in the end sections of a rectangular end plate. The port openings and the flat areas of the end plate are arranged in a common plane. The end plate can be a front end plate or a back end plate. The flat areas of the end plate can be adapted to be connected to a hydroblock or similar conventional fittings. The end plate can be provided with a pattern of ridges and grooves in a central portion thereof.

A contact point is arranged on the ridge on both sides of the indentations or a plurality of the indentations connecting a flow channel, which otherwise would form a dead-end flow channel together with the end plate, with a neighbouring flow channel. Hence, a very strong heat exchanger is achieved while preventing stagnant media. Hence, the heat exchanger plates can be connected to each other by a plurality of rows of brazing joints, wherein the indentations or a plurality of indentations can be arranged between the first and second rows of brazing joints counted from the port opening area closest to the indentation.

In the following, the invention will be described with reference to appended drawings, wherein:.

With reference to <FIG>, a heat exchanger <NUM> according to one embodiment of the present invention is illustrated schematically. The heat exchanger <NUM> comprises an end plate <NUM> and a plurality of heat exchanger plates <NUM> stacked in a stack to form the heat exchanger <NUM>. In the embodiment of <FIG>, the heat exchanger plates <NUM> are identical.

The heat exchanger plates <NUM> are made from sheet metal and are provided with a pattern of ridges R and grooves G such that interplate flow channels for fluids to exchange heat are formed between the plates when the plates are stacked in a stack to form the heat exchanger <NUM> by providing contact points between at least some crossing ridges and grooves of neighbouring plates <NUM> under formation of the interplate flow channels for fluids to exchange heat. The pattern according to the embodiment of <FIG> is a herringbone pattern. However, the pattern may also be in the form of obliquely extending straight lines as described below. The pattern of ridges R and grooves G is a corrugated pattern having a corrugation depth. The pattern is a pressed pattern. The pattern is adapted to keep the plates <NUM> on a distance from one another, except from the contact points, to form spaces between adjacent heat exchanger plates and the flow channels.

In the illustrated embodiment, each of the heat exchanger plates <NUM> is surrounded by a skirt S, which extends generally perpendicular to a plane of the heat exchanger plate <NUM> and is adapted to contact skirts of neighbouring plates <NUM> in order to provide a seal along the circumference of the heat exchanger <NUM>.

The heat exchanger plates <NUM> are arranged with port openings <NUM>-<NUM> for letting fluids to exchange heat into and out of the interplate flow channels. In the illustrated embodiment, the end plate <NUM> and the heat exchanger plates <NUM> are arranged with four port openings <NUM>-<NUM>. In <FIG> some port openings are missing, which is understood by a skilled person and does not affect the disclosure of the present invention. Port opening areas <NUM> surrounding the port openings O1 to O4 are provided at different heights, i.e. different levels, such that selective communication between the port openings and the interplate flow channels is achieved. For example, the port opening areas <NUM> are flat. The port opening areas <NUM> are arranged for sealing against a corresponding port opening area <NUM> of an adjacent heat exchanger plate <NUM>. For example, the port openings <NUM>-<NUM> and the port opening areas <NUM> are arranged in a conventional manner.

In the heat exchanger <NUM> of <FIG>, the port opening areas <NUM> are arranged such that first and second port openings O1 and O2 are in fluid communication with one another through interplate flow channels, whereas the third and fourth large port openings O3 and O4 are in fluid communication with one another by neighboring interplate flow channels. In the illustrated embodiment, the heat exchanger plates <NUM> are rectangular with rounded corners, wherein the port openings <NUM>-<NUM> are arranged near the corners. Alternatively, the heat exchanger plates <NUM> are square, e.g. with rounded corners. Alternatively, the heat exchanger plates <NUM> are circular, oval or arranged with other suitable shape, wherein the large port openings <NUM>-<NUM> are distributed in a suitable manner. In the illustrated embodiment, each of the heat exchanger plates <NUM> is formed with four port openings <NUM>-<NUM>. Alternatively, the heat exchanger plates <NUM> are formed with another number of ports, such as six, eight or ten. In the embodiment of <FIG>, the heat exchanger plates <NUM> are identical and every other plate <NUM> is turned <NUM> degrees in its plane in relation to adjacent heat exchanger plates <NUM>.

The end plate <NUM> according to <FIG> is formed with flat areas <NUM> with the port openings O1-O4. The port openings <NUM>-<NUM> of the end plate <NUM> are aligned with the port openings of the heat exchanger plates <NUM> in a conventional manner. For example, the end plate <NUM> comprises a first end section with a first flat area and neighbouring port openings O1 and O3 and a second end section with a second flat area and neighbouring port openings O2 and O4. For example, the end plate <NUM> is a conventional end plate. In the illustrated embodiment, the end plate <NUM> comprises a central portion having a pattern of ridges (R) and grooves (G) similar to the heat exchanger plates <NUM>. The end sections do not have the pattern of ridges and grooves. Instead the end sections are formed with the flat areas <NUM>, at least around the port openings O1-O4. The port openings <NUM>-<NUM> and the flat areas <NUM> are arranged in a common plane. Hence, the flat areas <NUM> of the end plate <NUM> form flow channels together with the grooves (G) of the adjacent heat exchanger plate <NUM>, such as a first heat exchanger plate in the stack of heat exchanger plates. The flat areas <NUM> form flow channels together with the neighbouring heat exchanger plate <NUM> in the vicinity of port opening areas <NUM> of the neighbouring heat exchanger plate <NUM>.

When the heat exchanger plate <NUM> and the end plate <NUM> are mounted in order to form a part of a plate heat exchanger <NUM>, two of the port opening areas <NUM> will come in contact with the flat areas <NUM> of the end plate <NUM>. Also, ridges R of the heat exchanger plate <NUM> will also come in contact with the flat areas <NUM> of the end plate <NUM>. Hence, flow channels are formed between the flat area <NUM> in the end section of the end plate <NUM> and the adjacent heat exchanger plate <NUM>. Flow channels are formed in an area between neighbouring port openings of the heat exchanger plate <NUM>. For example, flow channels are formed between the flat areas <NUM> and the neighbouring heat exchanger plate <NUM> by the grooves G connected to the first port opening O1, wherein some grooves (G) ends when said grooves G reach the port openings area <NUM> around the neighbouring third port opening O3.

With reference also to <FIG>, the heat exchanger plate <NUM> is provided with indentations <NUM>. The indentations <NUM> are arranged to provide for trans-ridge flow channels. The indentations <NUM> are arranged in ridges R of the heat exchanger plate <NUM>, wherein at least some ridges are formed with at least one indentation <NUM>. At least some of the indentations <NUM> are arranged in the vicinity of the port openings O3, O4 to connect a groove G, which together with the flat area <NUM> forms a flow channel, with a neighbouring groove G to prevent stagnant media in said flow channel between the heat exchanger plate <NUM> and the flat area <NUM> of the end plate <NUM>. By the provision of the indentations <NUM> dead-end flow channels delimited by ridges R and the flat end sections <NUM> of the end plate <NUM> are avoided. The indentations <NUM> are arranged with a depth corresponding to at least <NUM>% of the corrugation depth of the heat exchanger plates <NUM>. For example, the depth of the indentations <NUM> are less than <NUM>% of the corrugation depth. For example, the depth of the indentations <NUM> is <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>% or <NUM>% of the corrugation depth.

With reference to <FIG> contact points <NUM> between the heat exchanger plate <NUM> and a further heat exchanger plate are illustrated schematically. Generally, a brazing joint is arranged in the contact points <NUM>, wherein the contact points <NUM> correspond to brazing joints. For example, each contact point <NUM> between adjacent heat exchanger plates <NUM> corresponds to a brazing joint. In <FIG> the contact points <NUM> are illustrated on the back side of the heat exchanger plate <NUM> and the contact points <NUM> with a neigbouring heat exchanger plate on the front side is understood by a skilled person to be in the corresponding positions on the ridges R as illustrated schematically for a few positions by means of squares in the vicinity of the third port opening O3 in <FIG>. As can be seen in <FIG> at least some of the indentations <NUM> are arranged with a distance to the port opening area <NUM> of the third port opening O3 and the fourth port opening O4 leaving space for a brazing joint between the indentation <NUM> and the port opening O3, O4. Hence, a brazing joint for connecting a heat exchanger plate with a neighbouring heat exchanger plate is arranged between the port opening area <NUM> and at least one of the indentations <NUM>. A plurality of ridges R of the heat exchanger plates <NUM> is formed with an indentation <NUM> in an area overlapping a flat area <NUM> of the end plate <NUM>. The indentations <NUM> of a heat exchanger plate <NUM> adjacent the end plate <NUM> connect a flow channel, formed between the flat area <NUM> of the end plate <NUM> and the adjacent heat exchanger plate <NUM>, with a neighbouring flow channel to allow distribution of media between them and prevent stagnant media therein. At the same time, in the area overlapping the flat area <NUM> of the end plate <NUM>, brazing joints for connecting neighbouring heat exchanger plates <NUM> are arranged between the port opening area <NUM> and at least one of the indentations <NUM> or a plurality of the indentations <NUM> or all of them.

In the embodiment of <FIG> the indentations <NUM> of the heat exchanger plate <NUM> are not all placed in the immediate vicinity of the port openings O3, O4. For example, every other indentation <NUM> is placed on a significant distance from the port openings O3, O4. For example, at least one indentation <NUM> or a plurality of indentations <NUM> is/are arranged at a distance from the nearest port opening area <NUM> corresponding to a brazing joint, wherein the indentation <NUM> is arranged immediately adjacent the brazing joint between the indentation <NUM> and the port opening area <NUM>. For example, more indentations <NUM> are arranged in the vicinity of the port opening area <NUM> surrounding the fourth port O4 than in the vicinity of the port opening area <NUM> surrounding the third port opening O3.

With reference to <FIG> a second embodiment of a heat exchanger <NUM> is illustrated, wherein the end plate <NUM> is similar to the one described above with reference to <FIG>. Also, in <FIG> some port openings are left out, which is understood by a skilled person. In the embodiment of <FIG> the heat exchanger plates <NUM> are identical and provided with a herringbone pattern of ridges R and grooves G, wherein every other heat exchanger plate <NUM> is rotated <NUM> degrees in its plane.

With reference also to <FIG>, the heat exchanger plate <NUM> is provided with a plurality of the indentations <NUM> forming a trans-ridge channels and connecting neighbouring grooves G. In the illustrated embodiment, the indentations <NUM> are arranged in ridges R of the heat exchanger plate <NUM> in the vicinity of and at a distance to the port openings O3, O4 to connect neigbouring grooves G and prevent stagnant media in the flow channels formed between the flat areas <NUM> and the adjacent heat exchanger plate <NUM>. In the embodiment of <FIG> all ridges R in the area between the first port opening <NUM> and the third port opening O3 are provided with an indentation <NUM> leaving space for a contact point <NUM>, and thus a brazing joint, between the port opening area <NUM> of the third and fourth port openings O3, O4 and each indentation <NUM> as illustrated schematically in <FIG>. Also in <FIG> the contact points <NUM> are illustrated schematically between the heat exchanger plate <NUM> and a further heat exchanger plate behind the illustrated one, wherein the contact points <NUM> on the front side towards another heat exchanger plate <NUM> is understood by a skilled person to be in the corresponding positions on the ridges R as illustrated schematically for a few positions by means of squares in the vicinity of the third port opening O3 in <FIG>. As can be seen in <FIG> the indentations <NUM> are arranged with a distance to the port opening area <NUM> of the third port opening O3 and the fourth port opening O4 leaving space for a brazing joint between the indentation <NUM> and the port opening O3, O4. Hence, a brazing joint is arranged between the port opening area <NUM> and the indentations <NUM>.

In the embodiment of <FIG> all but one of the indentations <NUM> in each end of the plate are provided between contact points <NUM>. Hence, most of the indentations <NUM> are arranged between contact points <NUM>. For example, at least four or at least five indentations <NUM> are arranged in the vicinity of the third port opening O3, whereas more, such as at least six or seven, indentations <NUM> are arranged in the vicinity of the fourth port opening O4. In the embodiment of <FIG> the indentations <NUM> in the vicinity of the third port opening O3 are arranged in a straight line in a longitudinal direction of the heat exchanger plate <NUM>, such as in parallel to a longitudinal centre line of the plate. For example, the indentations <NUM> form a continuous trans-ridge flow channel between the first and last of the indentations <NUM> in a row of indentations <NUM>. For example, the indentations <NUM> in the vicinity of the fourth port opening O4 are arranged in a corresponding manner, optionally with additional indentations <NUM> deviating from said straight line. For example, the heat exchanger plates <NUM> are connected to each other by a plurality of rows of contact points <NUM>, wherein a plurality of indentations <NUM> is arranged between the first and second rows of contact points <NUM> counted from the nearest port opening area <NUM>. Hence, indentations <NUM> are arranged outside the first row of contact points <NUM>. For example, a row of indentations <NUM> forming a continuous trans-ridge flow channel is arranged outside a first row of contact points <NUM>.

With reference to <FIG> and <FIG>, the heat exchanger plate <NUM> is provided with a plurality of the indentations <NUM> forming trans-ridge channels in another pattern, wherein a plurality of indentations <NUM> are distributed between the first port opening O1 and the third port opening O3 between the contact points <NUM>. In the embodiment of <FIG> and <FIG> a larger number of indentations <NUM> are distributed in a similar pattern over a bigger area between the second port opening O2 and the fourth port opening O4. For example, the pattern of indentations <NUM> is a regular pattern.

With reference to <FIG> another embodiment of the invention is illustrated, wherein <FIG> illustrates a first type of heat exchanger plate 12a and <FIG> illustrates a second type of heat exchanger plate 12b. The first and second types of heat exchanger plates 12a, 12b are stacked alternatingly and are provided with the end plate <NUM> to form a heat exchanger <NUM>. The first and second types of heat exchanger plates 12a, 12b are provided with a pattern with ridges R and grooves G in the form of obliquely extending straight lines. Hence, the heat exchanger <NUM> in the embodiment of <FIG> comprises two different types of heat exchanger plates 12a, 12b having a pattern of ridges R and grooves G forming interplate flow channels, wherein flow channels are formed between the flat areas <NUM> of the end plate <NUM> and the adjacent heat exchanger plate 12a in the areas between the port openings <NUM>-<NUM>, wherein the adjacent heat exchanger plate 12a being of the first type. At least the first type of heat exchanger plates 12a is provided with indentations <NUM> forming trans-ridge flow channels to prevent dead-end flow channels between the flat areas <NUM> of the end plate and the neighbouring heat exchanger plate 12a. In the embodiment of <FIG> indentations <NUM> are also distributed over a large portion of the first type of heat exchanger plates 12a, including a central heat exchanging area.

Claim 1:
A brazed plate heat exchanger (<NUM>) comprising an end plate (<NUM>) and a stack of heat exchanger plates (<NUM>, 12a, 12b) provided with a pattern comprising ridges (R) and grooves (G) adapted to form contact points (<NUM>) between neighbouring heat exchanger plates such that the heat exchanger plates form interplate flow channels for media to exchange heat over the heat exchanger plates, the heat exchanger plates further being provided with port openings (<NUM>-<NUM>) for selective fluid communication with the flow channels, wherein the port openings are surrounded by port opening areas (<NUM>) for sealing against a corresponding port opening area of a neighbouring heat exchanger plate, wherein neighbouring heat exchanger plates are connected by brazing joints at said contact points (<NUM>), wherein the end plate (<NUM>) is provided with port openings (O1-O4) and flat areas (<NUM>) around the port openings in a common plane, wherein a plurality of ridges (R) of the heat exchanger plates, in an area overlapping any of said flat areas (<NUM>) of the end plate (<NUM>), are formed with an indentation (<NUM>), wherein said indentations (<NUM>) of a heat exchanger plate (<NUM>, 12a) adjacent the end plate (<NUM>) connect a flow channel, formed between the end plate and the adjacent heat exchanger plate (<NUM>, 12a), with a neighbouring flow channel to allow distribution of media between them, characterised in that a contact point (<NUM>) is arranged on the ridge (R) on both sides of at least one of said indentations (<NUM>) connecting a flow channel, formed between the end plate (<NUM>) and the adjacent heat exchanger plate (<NUM>, 12a), with a neighbouring flow channel to allow distribution of media between them, and that a brazing joint for connecting neighbouring heat exchanger plates is arranged between the port opening area (<NUM>) and at least one of said indentations (<NUM>).