HYDRO BLOCK

FIELD OF THE INVENTION

The present invention relates to a heat exchanger comprising a number of heat exchanger plates provided with a pressed pattern arranged such that flow channels for media to exchange heat will be formed between the number of heat exchanger plates when the plates are stacked onto one another to a heat exchanger plate stack, wherein port openings are provided for selective communication with the flow channels, the selective communication being achieved by placing areas surrounding said port openings at different heights, such that such areas of neighbouring plates contact one another when no communication is desired and do not contact one another when communication is desired.

PRIOR ART

In the art of brazed plate heat exchangers, there has been a long felt need for increasing the strength of the port area, especially the area between the port openings. Brazed plate heat exchangers are inherently weak in the port area, due to pressure in the port acting on the port areas and relatively few contact points between the neighbouring plates.

Another issue with plate heat exchangers is the connection to internal piping for the fluids to exchange heat. In some cases, connections are brazed on a start plate of the heat exchanger, wherein the connections are provided with fastening means for the external piping. One drawback with such connections is that the connection either must be soldered to the heat exchanger after the heat exchanger has been brazed;

alternatively, the connections can be brazed in connection to the heat exchanger being brazed, but this comes with the prize that the brazing process will get less efficient due to reduced packing in the brazing furnace.

One common way of connecting a heat exchanger to external piping is so- called hydro-blocks. Hydro-blocks comprise a main body adapted to be pressed against a start plate, i.e. an upper plate of the heat exchanger being provided with port openings for the fluids to exchange heat, of the heat exchanger. The hydro-block is provided with openings corresponding to the port openings of the heat exchanger and sealings arranged to seal between the hydro-block and the start plate. In order to create the force urging the hydro-block against the start plate, some various options are known in the prior art - the most common being a bolt having an internal thread adapted to mate with a screw that can be used to create the force. This solution has the benefit that the heat exchanger is very easy to mount to the hydro-block. It gives, however, no additional strength to the heat exchanger.

One way of fastening a heat exchanger to a support member or mounting plate is shown in US 5 992 510. In this document, a heat exchanger having a through hole for housing a screw, bolt or other attachment means is shown. The through hole is sealed from communication with interplate flow channels and placed just by a short side between two neighboring port openings. This placement of the through opening will make fastening of a hydro-block cumbersome, or even impossible. Moreover, very little pressure capability increase, if any, will be gained. Furthermore, the distribution of fluid to exchange heat will be negatively influenced, since the through opening will hinder fluid entering a port opening from being distributed in a sideway direction.

SUMMARY OF THE INVENTION

The above and other problems are solved, or at least mitigated, by an opening extending through the entire heat exchanger stack, the opening being arranged in line with an axis extending centrally between two neighbouring port openings and being closed from communication with the flow channels.

In one embodiment, the opening is closed from communication with the flow channels by surfaces neighbouring the opening on each heat exchanger plate being provided at different heights, such that such areas of neighboring plates always contact one another. This embodiment is beneficial in that the opening may be made in any size, even a very small size.

In another embodiment, the opening is closed from communication with the flow channels by the opening on each heat exchanger plate being provided with a skirt circumscribing the opening, said skirt extending frustoconically from the plane of the heat exchanger plate, wherein the skirt circumscribing the port of each port opening has a shape such that an outer surface thereof snugly fits inside a skirt of a neighbouring plate when the heat exchanger plates are stacked in the stack forming the heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described with reference to the appended drawings, wherein: Fig. 1 is a perspective view showing a heat exchanger according to one embodiment, being provided with hydroblocks for the connection of the heat exchanger to external piping;

Fig. 2a is a plan view of a heat exchanger according to a first embodiment;

Fig. 2b is a section view of a heat exchanger according to the first embodiment, taken along the line A-A of Fig. 2a;

Fig 3 a is an exploded perspective view of a heat exchanger according to the first embodiment;

Fig. 3b is a close-up view of the area A of Fig. 3a;

Fig. 4a is a plan view of a heat exchanger according to a second embodiment;

Fig. 4b is a section view of a heat exchanger according to the second embodiment, taken along the line A-A of Fig. 4a;

Fig. 5 is a perspective view of a heat exchanger plate comprised in the heat exchanger according to the second embodiment; and

Fig. 6 is an exploded perspective view of a heat exchanger according to the second embodiment.

DESCRIPTION OF EMBODIMENTS

This invention concerns brazed heat exchangers, i.e. heat exchangers where heat exchanger plates are bonded to one another by a thermal process wherein a brazing alloy is placed at or in the vicinity of contact points between neighboring plates and the temperature of the heat exchanger plates is increased sufficiently to cause the brazing alloy to melt. After the brazing alloy has melted, the temperature of the heat exchanger plates is lowered, whereupon the brazing alloy solidifies and hence binds the plates together at the contact points.

In Fig. 1 , a heat exchanger HE is shown. The heat exchanger HE is fastened to two "hydro-blocks" HB, having the function to enable a connection between the heat exchanger HE and external piping (not shown) containing fluids to exchange heat, e.g. refrigerant and/or brine solution. Except from exhibiting means for the connection of said external piping, the hydro-block HB also has the function of providing a sealing between the heat exchanger and itself. Usually, this sealing is achieved by e.g. an O-ring provided in a groove of the hydro-block; when the hydro-block is pressed against the heat exchanger, the O-ring will create a reliable seal between the heat exchanger and the hydro-block. The hydro-blocks HB are provided with fastening holes F. Such fastening holes F extend through the hydro-block HB, on a position basically in line with openings O provided for connection to external piping and for communication with equally sized and placed port openings of the heat exchanger HE. The in-line positioning is crucial in order to get an even pressure applied to the O-rings. Whether the opening is placed centrally between the openings O is not crucial - in some cases, it might actually be beneficial with an eccentric positioning of the opening O, especially if fluids to exchange heat having different operating pressure are heat exchanged in the heat exchanger. In such cases, it is advantageous to provide the opening O at a position closer to the opening for the fluid having the higher pressure. The opening O shall, however, be positioned in-line with the port openings.

Later, reference to Fig. 1 will be done again.

In Figs. 2a and 2b, an exemplary heat exchanger 100 according to a first embodiment is shown. In Fig. 2b, a section view along the line A-A in fig 2a shows:

Four heat exchanger plates 1 10, each of which being provided with a pressed pattern of ridges R and grooves G adapted to keep the plates on a distance from one another under formation of interplate flow channels 130, when the heat exchanger plates are stacked in a stack to form the heat exchanger 100. Moreover, each of the plates is provided with port openings 120, wherein each port opening of each heat exchanger plate is circumscribed by a plate area being provided either level with the ridges R or level with the grooves G. Hence, in a way well known by persons skilled in the art, selective communication between the port opening 120 and the interplate flow channels 130 can be achieved - if the areas surrounding the port openings of neighbouring plates contact one another, there will be no communication between the port opening and the interplate flow channel limited by such neighbouring plates, whereas if there is no contact between the areas surrounding the port openings, there will be a communication between the port opening and the interplate flow channel limited by such neighbouring plates.

According to one embodiment, a through-opening 140 extending through the entire plate pack is arranged between the port openings 120. This through-opening is arranged by providing the heat exchanger plates with a hole 150. Areas surrounding the hole 150 are provided at different heights (corresponding to the height of the ridges R and grooves G) and arranged such that any of the surfaces surrounding a hole always will contact a corresponding area of a neighbouring plate, hence creating a through- opening being completely sealed off from communication with the interplate flow channels. More details concerning the arrangement of the areas surrounding the holes of each heat exchanger plate will be given in connection to Fig. 3b.

In Fig. 3 a, an exploded view of a heat exchanger 100 according to one embodiment is shown, As mentioned above, the heat exchanger 100 comprises four heat exchanger plates (although the actual number of heat exchanger plates in a real-world heat exchanger often is significantly higher). With reference to the description of Figs. 2a and 2b, the pressed pattern comprising ridges R and grooves G are provided in a herringbone pattern; every other plate is rotated 180 degrees in its plane, meaning that an "arrow" of the herringbone pattern will point consecutively upwards and downwards. Due to the combination of rotating every other plate 180 degrees and the herringbone pattern, the ridges R and grooves G of neighboring plates will have directions crossing the direction of one another plate - hence, the plates will be kept on a distance from one another by the contact points formed between the crossing neighboring ridges and grooves.

Moreover, skirts 160 extend along the circumference of the heat exchanger plates. The skirts 160 extend in an angle being substantially perpendicular to the plane of the heat exchanger plate and are arranged to contact one another such that a seal is formed along the edges of the interplate flow channels.

As can be seen in Fig. 3b, and as mentioned earlier, each hole 150 is surrounded by two circular areas 170 and 180, provided on different heights. By this provision on different heights, either the circular areas 180 or the circular areas 170 of neighboring plates will contact one another when the plates are placed in a stack to form the heat exchanger 100. Hence, the holes 150 will be sealed off from communication with the interplate flow channels.

It should be noted that the holes 150 are placed in line with the port openings

120. By this positioning of the holes 150, several advantages are achieved: First, forces emanating from the pressure of the fluids to exchange heat in the heat exchanger will not "tilt" the hydro-block HB when it is fastened to the heat exchanger, and secondly, the central positioning will allow for flow channels being formed between a short-side of the heat exchanger and the port openings 120 and holes 150, including its neighbouring areas 170, 180. This will allow for a good flow distribution over the heat exchanger area, since fluids to exchange heat will be able to flow directly from one port opening towards and around its neighbouring port opening (which is sealed from communication with the flow channel communicating with the neighbouring port opening). Also shown in Fig. 3a are a start plate 190 and an end plate 195. The start- and end plates are similar in design to the heat exchanger plates 120, but may be made from a thicker gauge sheet metal. Also, areas surrounding port openings of the start plate are provided at the same height, whereas there are no port openings at all at the end plate.

In order to mount the hydro-block to the heat exchanger, two screws 300 protrude through the holes 150 of each of the heat exchanger plates. The screws are provided with an external thread that mates with an internal thread of the hydro-block HB, and by tightening the screw 300, the hydro-block will be pressed towards the start plate 190. By the provision of sealing means 310 housed in grooves circumscribing the openings 120, the connection between the start plate and hydro-block will be sealed.

In Figs 4a-6, a second embodiment is shown. This embodiment is identical to the first embodiment, except for the holes 150 of the first embodiment being substituted by frustoconically extending skirts 250 having a central opening 255. The

frustoconically extending skirts 250 are sized and arranged such that an external surface of one frustoconically extending skirt will fit snugly against an inner surface of a frustoconically extending skirt of a neighbouring plate when the heat exchanger plates are stacked into a stack to form the heat exchanger. The central openings 255 will form a through opening extending through the entire heat exchanger.

Common for both embodiments is that the strength of the heat exchanger will increase significantly. As well known by persons skilled in the art of brazed heat exchangers, they tend to burst in the vicinity of the port openings - this is due to a combination of a low contact point density between ridges and grooves of neighboring plates and the force emanating from the pressure of the fluids to exchange heat acting on the port area. By the provision of the through openings 150; 250 and the screws or bolts extending through the heat exchanger and being connected to the hydro-block and an opposite side of the heat exchanger, a large portion of the force generated by the pressurized fluid acting on the hydro-block will be transferred through the screws or bolts rather than the sparsely distributed contact points.