FIELD OF THE INVENTION

The present invention relates to a brazed plate heat exchanger comprising a number of heat exchanger plates stacked in a stack and being provided with a pressed pattern of ridges and grooves adapted to keep the heat exchanger plates in the stack on a distance from one another by crossing points between the ridges and grooves of neighboring plates under formation of interplate flow channels, said flow channels being in selective fluid communication with port openings such that fluids to exchange heat can flow from one port opening to another through the interplate flow channels under heat exchange with a fluid flowing through at least one neighboring interplate flow channel, the plate heat exchanger further comprising and end plate which is provided with at least one reinforcement groove provided between neighboring port openings.

PRIOR ART

In the art of brazed heat exchangers, there is an increasing urge to be able to connect fluid pipes to the heat exchanger without providing the end plate of the heat exchanger with connections. Instead, a device often referred to as a "hydro block" is pressed against the end plate, wherein gaskets are provided to seal between the hydro block and the end plate.

As mentioned above, the hydro block is pressed against the end plate. The pressure will deform the gaskets and also counteract the forces emanating from the pressure of the fluid to exchange heat. The forces emanating from the pressure are a function of pressure and port area - large port openings will give large forces and high pressures will also give large forces.

In order to press the hydro block against the end plate, there may be provided "ears" on the end plate, the ears being situated such that screws or the like may be used to press the hydro block towards the end plate.

It is also possible to attach a stud bolt to the end plate and fasten the hydro block to the end plate by using this bolt.

The stud bolt may be fastened to the end plate in several ways, e.g. by welding or brazing. However, it is advantageous if the stud bolt is fastened to the end plate after the heat exchanger itself has been brazed, since the stud bolt will extend from the general plane of the end plate, hence making packing of the heat exchangers less efficient than necessary.

One inherent drawback with fastening of a stud bolt to the end plate is that the end plate is not strong enough. Especially, the connection between the end plate and the neighboring heat exchanger plate has proven to be a weak point, since the forces acting on the end plate via the stud bolt tend to separate the end plate from its neighboring heat exchanger plate.

In the prior art, several attempts have been made to increase the strength of the end plate. One example of a design that increases the strength is found in EP 0 347 961. Here, the end plate is provided with an upwardly directed ridge extending between the port openings. This ridge will help transferring force over the width of the heat exchanger, but it will not transfer any force to the neighboring heat exchanger plates.

Another attempt of providing the area between the port opening with more strength is shown in SE 529 769. Here, the area between the port openings has been strengthened by providing elongate ridges extending outwards from the neighbouring end plates. The technical effect is equal to the effect of the ridge of EP 0 347 961.

It is the object of the present invention to provide a heat exchanger having an improved strength between the end plate and the neighboring heat exchanger plate, hence allowing for higher pressures between a hydro block and the end plate.

SUMMARY OF THE INVENTION

According to the invention, the above and other problems are solved, or at least mitigated, by at least one reinforcement groove, being a groove pressed in the end plate, wherein the at least one reinforcement groove is pressed towards the neighboring heat exchanger plate and wherein a reinforcement pattern adapted to receive the at least one reinforcement groove of the end plate is provided in the heat exchanger plate neighboring the end plate.

In order to secure that the reinforcement groove and the reinforcement pattern are brazed together, the reinforcement pattern of the heat exchanger plate may have a size such that the at least one reinforcement groove of the end plate will be brazed to the reinforcement pattern of the neighboring heat exchanger plate during a brazing operation wherein the stack of heat exchanger plates and the end plate is brazed to form the heat exchanger. In order to enable use of prior art heat exchanger plates, the at least one reinforcement groove of the end plate may be adapted to cooperate with the ridges and grooves of the neighboring heat exchanger plate.

In order to obtain a large force transferring area, the at least one reinforcement groove of the end plate may run parallel and synchronous with the ridges and grooves of the neighboring heat exchanger plate.

In order to provide for an interplate flow channel in the case of the

reinforcement groove and the reinforcement pattern running parallel and synchronous, the at least one reinforcement groove of the end plate may have a section resembling a truncated cone, such that a flow channel is formed between the ridges and grooves of the heat exchanger plate and the reinforcement pattern of the end plate.

In order to fully exploit the benefits of the heat exchanger according to the invention, it may comprise an attachment member fastened to the end plate.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Fig. 1 is an exploded perspective view showing e.g. heat exchanger plates and end plates comprised in a heat exchanger according to one embodiment of the present invention;

Fig. 2 is a perspective view showing the heat exchanger according to Fig. 1 in an assembled state;

Figs 3 a and 3b are a section view and a plan view, respectively, of a heat exchanger plate comprised in a heat exchanger according to one embodiment of the invention, the section view of Fig. 3a being taken along the line L-L of Fig. 3b;

Fig. 4a and 4b are a section view and a plan view, respectively, of an end plate comprised in a heat exchanger according to one embodiment of the invention, the section view of Fig. 4a being taken along the line L2-L2 of Fig. 4b;

Fig. 5 is an exploded perspective view of an exemplary embodiment of the invention and

Figs. 6a and 6b are a plan view and a section view, respectively, of still another embodiment of the present invention. DESCRIPTION OF EMBODIMENTS

With reference to Fig. 1, a heat exchanger 100 according to the present invention comprises an end plate 110, a number of heat exchanger plates 120, 130, 140, 150 (the number of heat exchanger plates may vary within wide limits, depending on the required heat exchange performance). A start plate 160 is located on an opposite side of the heat exchanger 100 as compared to the end plate 110.

All the plates are provided with a pressed pattern of ridges R and grooves G adapted to keep the plates on a distance from one another due to crossings of the ridges R and grooves G of neighboring plates under formation of interplate flow channels. Moreover, all plates except for the start plate 160 are provided with port openings A, B, C and D for allowing selective communication with the interplate flow channels. The selective communication is achieved by providing areas surrounding the port openings on different levels; if the levels of the areas surrounding the port openings on two neighboring plates are such that the areas contact one another, there will be no communication to the interplate flow channel defined by that specific pair of plates; vice versa, if the areas surrounding the port openings of neighboring plate do not contact one another, there will be a communication between the port opening and the interplate flow channel defined by these two plates.

Moreover, the end plate 110 of the heat exchanger 100 is provided with reinforcing grooves 111, which are arranged between the port openings A, B and C, D, respectively. The reinforcing grooves 111 are depressions in the end plate 110 and the depth of the reinforcing grooves may be from about 30% of the depth of the grooves G to about 70% of the depth of the grooves G. Tests have shown that an advantageous embodiment includes reinforcement groves having a depth of about 50% of the depth of the grooves G.

At least the neighboring heat exchanger plate 120 is provided with a reinforcement pattern 121, the shape of which corresponding to the shape of the reinforcing groove 111 of the end plate 110. However in the neighboring heat exchanger plate 120, the reinforcing pattern 121 is provided in the pressed pattern of ridges R and grooves G, such that the height of the ridges R is limited where the reinforcement groove 111 cooperates with the reinforcement pattern 121. The cooperation between the reinforcement groove 111 and the reinforcement pattern 121 will be described later with reference to Figs. 3 and 4. The start plate 160 is provided with a pressed pattern of ridges R and grooves G according to the pattern of the heat exchanger plates 120-150, but it is not provided with any port openings.

Also, two attachment members 200, 210 are shown. These attachment members are preferably fastened to the end plate 110 after the plate heat exchanger per se has been manufactured. This will be described later on.

In Fig. 2, the heat exchanger 100 is shown in an assembled state. Preferably, the heat exchanger 100 is manufactured by stacking the start plate 160, the heat exchanger plates 150-120 and the end plate 110 to a stack, wherein a brazing material is placed at least in the contact points between ridges R and grooves G of neighboring plates. The brazing material may be any suitable material, but preferably, the brazing material is a metal or an alloy having a lower melting point than the metal from which the heat exchanger plates is manufactured, which is usually stainless steel. After the stacking of the plates and the brazing material, the stack is placed in a furnace and brazed to form a heat exchanger. The brazing may occur in either continuous tunnel furnace or in a furnace for batchwise brazing.

Fig. 2 also shows the cooperation between the areas surrounding the port openings. In port opening A of the end plate 110, it can be seen how the areas surrounding the corresponding port opening of the neighboring heat exchanger plate 120 is in contact with the end plate 110, hence sealing the port opening A from fluid communication with the flow channel formed by the cooperation between the end plate 110 and the heat exchanger plate 120. Oppositely, in the port opening B of the end plate 110, it can be seen how the area surrounding the corresponding port opening of the neighboring heat exchanger plate is not in contact with the corresponding area of the end plate 110. Hence, there is a fluid communication between the port opening B and the flow channel formed by the cooperation between the end plate 110 and the neighboring plate. This pattern repeats itself, such that there is a communication between the port opening A and the interplate flow channels between heat exchanger plates 120 and 130 and between the heat exchanger 140 and 150, whereas there is communication between the port opening B and the plate interspaces between the end plate 110 and the heat exchanger plate 120, between the heat exchanger plates 130 and 140 and between the heat exchanger plates and between the heat exchanger plate 150 and the start plate 160. Likewise, there is selective communication between the plate interspaces and the port openings C and D. The port openings A and C communicate with one another and the port openings B and D communicate with one another.

The reinforcement portions 111, 11 lb are located between the port openings A and B and between the port openings C and D. Between the reinforcement portions 111,

I I lb, the attachment members 200, 210 are fastened. In the shown embodiment, the attachment members comprise an elongate central portion 201, in which a threaded opening 202 is provided. A base portion 203 has a larger diameter than the central portion 201 and is designed to be secured to the end plate 110. The securing of the base portion 203 to the end plate 110 can be achieved by e.g. soldering, spot welding, glueing, regular welding or any other suitable method. The securing of the attachment member 200, 210 can also be achieved during the brazing of the heat exchanger, but at least in the case of batchwise brazing, the packing of the heat exchangers in the furnace is disturbed if attachment members project out from the heat exchanger.

In the embodiment shown in the figures, there are two reinforcement grooves

I I I and 11 lb, and the attachment members 200, 210 are placed between these reinforcement grooves 111, 1 lb. In other embodiments, there might be just one reinforcement groove, and the attachment member might be arranged within this groove.

As mentioned above, the reinforcement grooves 111 and 111b cooperate with the neighboring plates; In Fig. 3 A, the heat exchanger plate 120 is shown in a plan view. The reinforcement patterns 121 are as can be seen located between the port openings A and B and C and D, respectively. A section line L-L is shown crossing the port openings A and B and the reinforcement pattern 121.

In Fig. 3B, a section taken along the line L-L of Fig. 3 A is shown. Starting from the left in Fig. 3B, a skirt S is shown. This skirt S extends all the way around the circumference of the plate, and is adapted to contact equal skirts S of neighboring plates to form a seal around the periphery of the interplate flow channels formed by the neighboring plates. Continuing from the left, two portions of two ridge R are shown and thereafter, the area surrounding the port opening A is shown. Please note that the area surrounding the port opening A is located on a low level, identical to the level of the grooves G; as disclosed above, this means that there will be a communication between the port opening A and the interplate flow channel between the end plate 110 and the heat exchanger plate 120. Continuing from left to right, the section continues along a ridge R until the longitudinally central portion of the plate 120. Along the longitudinal centre of the plate, the reinforcement pattern 121 is located. As can be seen, the reinforcement pattern 121 is located on a height corresponding to a height between the height of the rides R and the height of the grooves G (which corresponds to the height of the area

surrounding the port opening A). This makes it possible to accommodate the reinforcement groove 111 of the end plate 110, in a way to be described later.

Then, still continuing from the left, the line L-L continues along a ridge R and the area surrounding the port opening B. Please note that the area surrounding the port opening B is provided at the same level as the ridges R; consequently, the area surrounding the port opening B will contact the end plate 110, and there will hence be no communication between the port opening B and the interplate flow channel formed by the heat exchanger plate 120 and the end plate 110.

In Fig. 4A, the end plate 110 is shown. As seen, the two reinforcement grooves 111, 111b are located between the ports A and B. A section line L2-L2 extends through the port openings A and B and through the reinforcement groove 111 (the section of the line L2-L2 would look the same if the line would extend through the reinforcement groove 111b).

In Fig. 4B, the section along the line L2-L2 is shown. Starting from the left, there is shown a skirt S (equal to the skirt S of the heat exchanger plate 120, hence the identical reference sign), the port opening A and its surrounding areas, the

reinforcement groove 111 and the port opening B and its surrounding areas. Please note that all the shown components are located at the same height, except for the

reinforcement groove 111, which is provided at a height being significantly lower than the other portions.

When put in a stack with the heat exchanger plates, the reinforcement groove 111 of the end plate 110 will be housed in the reinforcement pattern 121 of the heat exchanger plate 120. Preferably, the housing of the reinforcement groove 111 in the reinforcement pattern 121 is such that all neighboring surfaces are in immediate or almost immediate contact with one another. If the neighboring surfaces are located close to, or in direct contact with, one another, they will be connected during the brazing of the heat exchanger.

Due to the connection of the reinforcement grooves 111 and reinforcement patterns 121, especially along edges E and F, the connection of the end plate 110 to the neighboring heat exchanger plate 120 will be considerably stronger in terms of burst pressure and, above all, in terms of enabling load transfer from the attachment member (which, as mentioned, is fastened to the end plate 110) and the neighboring heat exchanger plate 120, which in turn transfers the load to the neighboring heat exchanger plate 130, and so on. Hence, the attachment member 200, 210 may be fastened to the end plate 110 without the risk that the end plate 110 will separate from the heat exchanger plate 120.

It should be noted that the height on which the reinforcement pattern 121 is provided is about inbetween the height of the groves G and the Ridges R. This allows a fluid flow also where the reinforcement portions are provided, which is important in the vicinity of the port openings.

The embodiment shown in Figs. 1-4 discloses one embodiment of the invention. In figs. 5-6, other exemplary embodiments are shown.

In Fig. 5, an embodiment wherein a reinforcement groove 112 is provided on the end plate 110 is shown. The reinforcement groove 112 cooperates with a

corresponding reinforcement pattern 122 of the neighboring heat exchanger plate 120. The reinforcement groove 112 and reinforcement pattern 122 of this embodiment differs from the reinforcement grooves and patterns of the previously described embodiment in that it is a single groove and pattern, extending over a larger length than the diameter of the port openings. This gives more reinforcement than the previously described embodiments, but it also makes it more difficult to fasten an attachment member to the end plate 110.

However, in the embodiment of Fig. 5, there is no attachment member according to the previous embodiment - instead, the port openings are provided with separate connections C1-C4. It should be noted that is possible to combine the embodiments with one another; it is hence possible to use an attachment member 200, 210 according to the previously disclosed embodiment also for a heat exchanger according to this embodiment. The connections C1-C4 may be internally threaded in order to allow for a threading engagement to connection pipes for fluids to exchange heat, but they may also be provided with a smooth internal surface in order to allow for the connection pipes to be brazed or soldered to the connection; this arrangement makes it unnecessary to use an attachment member according to the previous embodiment, but as mentioned, one can use both.

In still another embodiment, the reinforcement, or at least a portion thereof, may be wide enough to house a fastening area for an attachment member. This embodiment is advantageous in that the attachment member can be fastened in the same way as in the previous embodiment, while the strength is the same as in the embodiment of Fig. 5. A slight disadvantage of this embodiment is that the flow out from the port opening may be impaired.

Still another embodiment of the present invention is shown in Figs. 6a and 6b. In this embodiment, there is no reinforcement pattern provided in the heat exchanger plate; instead, the end plate 110 is provided with reinforcement grooves 113 having a shape corresponding to the shape of the ridges R and grooves G of the heat exchanger plate 120, with the difference that the reinforcement grooves 113 are more shallow than the ridges R and grooves G of the heat exchanger plate, such that there will be narrow flow channels between the reinforcement grooves 113 of the end plate 110 and the pattern of ridges R and grooves G of the heat exchanger plate although the

reinforcement pattern of the end plate 110 and the ridges R and grooves G of the heat exchanger plate run parallel and synchronous with one another. This is shown in Fig. 6b. As shown there, the reinforcement grooves 113 have a section resembling a truncated cone TC, and the flow channel is formed in the area where the tip of the cone would have been should it not had been truncated.

It is also possible to provide the reinforcement grooves 113 according to the embodiment of Fig.6A and 6B with a portion allowing for fastening of the attachment member 200, i.e. a flat surface centrally placed between the port openings.

In all of the embodiments shown above, the reinforcement grooves, the reinforcement patterns and the fastening members are shown as being provided centrally between the port openings. In other embodiments, which also form part of the invention, it is possible to provide either or all of the components eccentrically between the port openings.