A PLATE HEAT EXCHANGER WITH A CONNECTION MEMBER

Abstract: The invention relates to a permanently joined plate heat exchanger with plates provided with port openings. The heat exchanger comprises at least one connection member in the form of a connection block (17, 18) for connection to an in- or outlet conduit. Said connection block is provided with at least two through-holes and is connected to an outer heat transfer plate in, or an end plate permanently joined with, the plate pack by means of a permanent joint. At least one of the through-holes in the block is internally threaded. The permanent joint is formed such that it extends around at least both of the through-holes (19, 20, 21, 22) for forming a connection between the connection block (17, 18) and the outer heat transfer plate or end plate that is resistant to torsional stress. Thereby, connecting devices provided with external threads can be screwed to the plate heat exchanger without rupturing the permanent joint.

Description: A PLATE HEAT EXCHANGER WITH A CONNECTION MEMBER The present invention concerns a plate heat exchanger comprising a plate package of permanently joined heat transfer plates, between which passages for at least two heat exchange fluids are formed. Each heat transfer plate is provided with port holes, which together with corresponding port holes in the other heat transfer plates form port channels through the plate package. The plate heat exchanger further comprises at least one connection member adapted for connection with a conduit through which one of said heat exchange fluids is intended to flow to or from the plate heat exchanger. The connection member, by means of a permanent joint, is connected with an outer heat transfer plate in the plate package or with an end plate permanently joined therewith. The connection member has a through hole and is herein provided with internal threads. The hole communicates with one of said port channels through the plate package. The heat transfer plates in a plate heat exchanger of this kind are usually permanently joined with each other through welding or brazing. In a plate heat exchanger where the heat transfer plates have been joined with each other through brazing the heat exchanger mostly is provided with two end plates, which are thicker than the heat transfer plates and are brazed together with the two respective outer heat transfer plates in the plate package. Usually, one of the end plates is provided with holes opposite to the port channels through the plate package, but also the other end plate can be provided with one or more holes opposite to the port channels. Onto at least one of the end plates connection members, usually in the form of pipe sockets, are fastened by brazing around the respective holes of these plates. Each one of the end plates does not have to be made in one piece but can be made of two or more parts. The passages for heat exchange fluids between the heat transfer plates are normally connected to the port channels in a way such that every second passage will be flowed through by one of the heat exchange fluids and, accordingly, is included in a first set of passages. The remaining passages form a second set of passages, which will be flowed through by the other heat exchange fluid. When the plate heat exchanger is in operation the first heat exchange fluid flows through a first pipe socket into a first port channel, further through the first set of passages to a second port channel and out through a second pipe socket. The second heat exchange fluid flows through a third pipe socket into a third port channel, further through the second set of passages to a fourth port channel and out through a fourth pipe socket. Plate heat exchangers of this kind are used in many areas. One such area is cooling of hydraulic oil. In hydraulic systems, a plate heat exchanger normally is coupled to the low pressure side. The conduits for hydraulic oil on the low pressure side of a hydraulic system have a comparatively large diameter for obtainment of pressure losses as small as possible. Furthermore, special connecting devices are used for connecting the conduits to various components included in the hydraulic system. These connecting devices are often provided with external threads. When a plate heat exchanger is to form part of a hydraulic system, it must be possible to screw such connecting devices with external threads into the connection members of the plate heat exchanger. Thus, the connection members of a plate heat exchanger must be provided with holes having internal threads. A problem experienced in connection with plate heat exchangers for cooling of hydraulic oil, which are provided with connection devices in the 3 form of internally threaded pipe sockets, is that the joints between the pipe sockets and the end plate have ruptured when connecting devices have been screwed into the pipe sockets. The problem has partly been due to the large conduit diameters being used, which have required use of correspondingly large connecting devices. This has, in turn, necessitated large diameter pipe sockets on the plate heat exchangers. A consequence of such large diameters is that the said joints are subjected to large torsional moments when connecting devices are screwed in to the pipe sockets. Earlier, in order to solve this problem, each pipe socket has been provided on its outside with two parallel surfaces, by means of which the pipe socket could be firmly held when a connecting device was screwed into the pipe socket. Despite this, the joint between the end plate and the pipe socket has often ruptured. The object of the present invention is to provide a solution to the problem now discussed, which is better than solutions suggested so far. According to the invention, this object can be achieved in that said connection member is in the form of a connection block and has at least one further through hole and that the connection block is connected with the said outer heat transfer plate or the said end plate such that the further through hole communicates with a second one of said port channels through the plate package, the said permanent joint extending at least around both of the through holes, thereby forming a connection between the connection block and the outer heat transfer plate or end plate, which is resistant to torsional stress. A connection block of this kind has a considerably larger surface in contact with the outer heat transfer plate or end plate than a pipe socket and, thus, the joint in question can be formed so that it covers a considerably larger area than before. 4 Thereby, the joint definitely can take up the torsional moment arising when a connecting device is screwed into the plate heat exchanger. A result of the large conduit diameters often is that at least one of the holes in the connection block must have a larger diameter than the port holes in the heat transfer plates. Thanks to the connection block according to the invention, it is possible to have holes with a larger diameter than was possible earlier, when the material thickness of two adjacent pipe sockets was a limiting factor for the hole diameter. In an embodiment of the invention, the said connection block is provided with internal threads in the said further through hole. Thus, this embodiment of the invention makes possible the screwing of two connecting devices into a common connection member. In a plate heat exchanger according to one embodiment of the invention each of the heat transfer plates has a width which is less than its length and a thickness which is within the interval 0.05-1.5 mm, said connection block having an extension across essentially the hole width of the heat transfer plates but only across part of the length of the heat transfer plates, in addition to which the connection block has a thickness considerably larger than that of a heat transfer plate. Thus, the connection block has to cover only a part of the outer heat transfer plate or end plate in the area for a pair of port channels. This means saving of material in comparison with an arrangement in which the connection block would cover all of the outer heat transfer plate or the end plate. Advantageously, the connection block may have two parallel sides intended to be used for holding of the connection block by means of a 5 tool, when a connecting device provided with external threads is to be screwed into a through hole in the connection block. The present invention will be described more closely by means of enclosed drawings, in which fig. 1 shows a previously known plate heat exchanger, fig. 2 shows a section along the line ll-ll of the plate heat exchanger in fιg.1 , fig. 3 shows a side view of a plate heat exchanger according to the invention and fig. 4 shows a front view of the plate heat exchanger in fig.3. Fig. 1 shows a previously known plate heat exchanger 1 comprising a stack of heat transfer plates 2 brazed together to a plate package. End plates 3,4, which are thicker than the heat transfer plates 2, are fastened by brazing onto the outer heat transfer plates of the plate package. One of the end plates 4 is provided with four holes around which the respective pipe sockets 5, 6, 7, and 8 are fastened by brazing. Fig. 2 shows a section along the line ll-ll of the plate heat exchanger in fig. 1. Each heat transfer plate 2 is provided with four port holes, of which port holes 9 and 10 are shown in fig. 2. The heat transfer plates 2 abut in pairs against each other around the port holes such that four port channels are formed through the plate heat exchanger 1. Fig. 2 shows two port channels 11 and 12, respectively. 6 The heat transfer plates 2 are further provided with a press pattern of depressions and elevations 13. In this way passages 14 for heat exchange fluids are formed between the heat transfer plates 2. As shown in fig. 2 each pipe socket 6, 7 has only a small surface 15 in contact with the end plate 4. At this surface 15 the pipe socket 6, 7 is connected with the end plate 4 by means of a brazing joint. If the pipe socket 6, 7 is provided with an internal thread and a connecting device having an external thread is to be screwed into the same, the said brazing joint must be able to take up a resulting torsional moment. In a plate heat exchanger 16 according to the present invention, shown in fig. 3, two connection blocks 16, 17 are brazed together with the end plate 4 provided with holes. Fig. 4 shows a plate heat exchanger 16 from the side of the end plate 4. Each of the connection blocks 17, 18 is provided with two through holes 19, 20 and 21 , 22, respectively, opposite to the respective port channels through the plate package. In the through holes 19, 20, 21 , 22 the connection blocks are provided with internal threads, so that connecting devices with external threads can be screwed into the holes. The connection blocks 17, 18 have surfaces 23, 24, shown in fig. 3, in contact with the end plate 4, which are considerably larger than the surfaces 15 in a plate heat exchanger according to fig.1 and 2. Brazing joints covering the respective surfaces 23, 24 mean that the connection blocks 17, 18 can be subjected to the required torsional moment, when connecting devices are tightened, without the brazing joints being ruptured. Each connection block 17, 18 has two parallel sides 25, 26 spaced from each other, such that they can constitute grip surfaces for a tool by 7 means of which the connection blocks 17, 18 can be firmly held, when connecting devices are screwed into the holes 19, 20, 21 , 22. The invention is not limited to the embodiment shown in fig. 3 and 4. For instance, the plate heat exchanger can be without the end plate 4. In this case the connection blocks are brazed onto an outer heat transfer plate in the plate package. The connection blocks are formed such that they abut against the outer heat transfer plate around its port holes and, possibly, against some of the elevations 13 of the outer heat transfer plate. The connection blocks and the outer heat transfer plate are brazed together in the areas where they abut against each other. It is important that no leakage occurs through the brazing joints between the connection blocks and the outer heat transfer plate. The brazing of each connection block to the outer heat transfer plate around its ports results in a brazing joint, which extends over a relatively large area and which, accordingly, can take up the necessary torsional moment. Naturally, the connection blocks may alternatively be arranged one on each of the end plates. Furthermore, in certain cases the heat transfer plates in a plate package are arranged such that at least one of the heat exchange fluids flows in several so called passes through the plate heat exchanger. Then, a need of more than two connection blocks in the plate heat exchanger may arise, e.g. two connection blocks on one of the end plates and one connection block on the other end plate. In such a case some of the connection blocks may be provided with only one through hole.

Claims: 8 Claims 1. A plate heat exchanger (16) comprising - a plate package of permanently joined heat transfer plates (2), between which passages (14) for at least two heat exchanger fluids are formed, each of the heat transfer plates (2) being provided with port holes (9, 10), which together with corresponding port holes (9, 10) in the other heat transfer plates (2) form port channels (11 , 12) through the plate package, and - at least one connection member adapted for connection with a conduit through which one of said heat exchange fluids is intended to flow to or from the plate heat exchanger (16), which connection member by means of a permanent joint is connected with an outer heat transfer plate in the plate package or with an end plate (4) permanently joined therewith, and has a through hole, in which the connection member is provided with internal threads, the through hole communicating with a first of said port channels (11 , 12) through the plate package, c h a r a c t e r i z e d in that said connection member is in the form of a connection block (17) and has at least one further through hole (20) and that the connection block (17) is connected with said outer heat transfer plate or said end plate (4) such that the further through hole (20) communicates with a second one of said port channels (11 , 12) through the plate package, said permanent joint extending at least around both of the through holes (19, 20), thereby forming a connection between the connection block (17) and the outer heat transfer plate or end plate (4), which is resistant to torsional stress. 2. A plate heat exchanger according to claim 1 , wherein said connection block (17) is provided with internal threads in said further through hole (20). 3. A plate heat exchanger according to anyone of the preceding claims, wherein each of said heat transfer plates (2) has a width which is less than its length and a thickness which is within the interval 0.05-1 ,5 mm, said connection block (17) having an extension across essentially the whole width of the heat transfer plates (2) but only across a part of the length of the heat transfer plates (2) and having a thickness considerably larger than that of a heat transfer plate (2). 4. A plate heat exchanger according to anyone of the preceding claims, wherein the connection block (17) has two parallel sides (25, 26) intended to be used for holding the connection block (17) by means of a tool, when a connecting device provided with external threads is to be screwed into a through hole (19, 20) in the connection block (17).

Inventors: LAUREN NAESLUND BO PATRICK, LAUREN NAESLUND, BO, PATRICK
Applicants: ALFA LAVAL AB, LAUREN NAESLUND BO PATRICK, LAUREN NAESLUND, BO, PATRICK
Application year: 1999
Main classification: F28D9
IPC codes: F28D9