A SHELL AND TUBE HEAT EXCHANGER AND A PROCESS FOR THE MANUFACTURE OF PERFORATED MANIFOLD END PLATES FOR SUCH HEAT EXCHANGER

Abstract: In shell and tube heat exchangers it is appropriate to fit a large number of heat exchanger tubes (6), e.g. glass tubes, between endplates (2), whereby these plates have to display a large number of holes (4) which each has an intermediate seat recess (18) for a sealing ring to abut the outer wall of the respective tube ends. The manufacture of these numerous seat recesses may present difficulties, but according to the invention they are formed in a simple manner by making each end plate a sandwich of three plates (8, 10, 12) which are readymade with ordinary holes, the holes (14) in the intermediate and thickest plate (8) are slightly larger than the holes (16) in the outer plates. When the plates are connected with the holes coaxially, the seat recesses (18) will be formed automatically. The sealing rings may be easily fitted by inserting them into the holes (14) of the intermediate plate before the last outer plate (12) is fitted to the intermediate plate (8).

Description: A shell and tube heat exchanger and a process for the manufacture of perforated manifold end plates for such heat exchanger. The present invention concerns a heat exchanger of the kind indicated in the introductory part of claim 1. It is well known that it is possible to manufacture a very useful type of heat exchanger by fitting a number of parallel glass tubes between two opposite walls in a heat exchanger chamber, but it is a permanent problem how to fix the tube ends to the walls in or at corresponding holes therein. For a number of reasons it is preferred that the tube ends are held inside the holes, i.e. by letting the holes surround the tube ends rather than letting these abut axially to the edge areas of the holes. The tube ends must not be rigidly fixed but the known solutions to this problem are rather costly. It is obvious to use holes which have a larger diameter than the tubes and have the character of passages wherein may be formed circular grooves for recieving sealing rings having an inside diameter which is smaller than the outside diameter of the tubes. Thus the tube ends may be held sealingly yet locally moveably, not only axially e.g. caused by thermal changes, but equally as regards slight tilting movements which would cause rigidly fixed glass tubes to burst. However manufacture of such holes would be very expensive if it had to take place by machining because of the quite large number of holes involved. A reasonably useable manufacturing process is described in DK-C-146 286 in which the plate elements are manufactured by casting in e.g. a poly-urethane material using a mould with cores corresponding to the the holes mentioned in the cast plates, the cores being fitted with sealing rings before casting, the outside of which acting as supplementary cores so that the rings form their own grooves in the holes. When the mould is removed the sealing rings are pulled off the cores and hence remain in the grooves so that they do not have to be fitted afterwards. This process, however, has a couple of noticeable disadvantages, on one hand that the cast plates are not serviceable for use in high temperatures, such as a heat exchanger for hot exhaust gases, and on the other hand that the manufacture is tied to the use of fairly expensive moulds whereby this process is only useful for the manufacture of large series of identical plate elements. For many purposes it is desirable that the plate elements are made of metal or another ready-made plate material, and the present invention has the purpose of providing a process by which this becomes an attractive possibility whereby the manufacture in small series of plate elements having special sizes or hole distributions is enabled, without any need for additional machining of the holes either singly or. at all. By the process according to the invention the idea of the plate element being "a plate" is given up, in that the plate element is built as a laminate of three plates which are pre-drilled in the relevant places. With modern punching and cutting technology it is a fairly simple matter to provide plate blanks having any desired dimension and any desired hole pattern, and small series of plate elements with particular sizes or hole patterns may be manufactured more cheaply than by the use of casting moulds, and both small and large series may be manufactured from heat resistant ready- made plate materaial. The thing to avoid is the machining of every hole for creating a groove for the sealing ring mentioned, and just this is obtained by the laminated construction mentioned. In this the holes in the intermediate layer may have a slightly larger diameter than the holes in the outer cover plate layers which by themselves have a diameter which is slightly larger than the diameter of the heat exchanger tubes, so that the hole in the intermediate layer will have the character of a turned groove between the hole edges of the outer cover plates whereby the desired result will be obtained without any other machning than the manufacture of simple holes in the intermediate plate and the outer plates respectively. Furthermore one will have limitless choice of the plate material to be used, and according to need it. may be a plastics material, galvanized sheet steel or stainless steel. The plates may be joined by any suitable means, such as cementing, spot welding, resistance seam welding, or riveting. The sealing rings which are preferable ordinary 0- rings may be fitted in the holes after the joining of the plate elements, or they more simply be deposited in the the holes of the intermediate plate when adjacent to one of the outer plates but before the other is fitted. The invention obviously also covers heat exchangers manufactured by the process here specified. The invention will be explained in detail in the following with reference to the drawing as way of example, in which Fig. 1 is a schematic perspective drawing of endplates and tubes for a tube unit for a heat exchanger according to the invention, Fig. 2 is a perspective section to illustrate the construction of the endplates, and Fig. 3 is a section of an end plate after assembly In Fig. 1 is shown two perforated endplates 2 with holes 4, the two endplates being connected by glass tubes which have to be tightly connected to the holes. Subsequently the connected unit is fitted into an outer box with a supply at one end and a drain at the other, in order that a fluid medium may exchange heat with another fluid medium which is caused to flow through the tubes 6. Each of the plates 2 is constructed as a sandwich with an intermediate plate 8, figs. 2 and 3, and outer cover plates 10 and 12. The intermediate plate 8 which is the thickest of the plates is supplied with holes 14 which are somewhat larger than corresponding holes 16 in the outer plates 12. The plates are held closely together and are fixed to each other in any suitable fashion with the holes 14 and 16 coaxial. As it is shown in Fig. 3 the joining of the plates will create plate holes 4 which have a ringshaped expansion or recess 18. These recesses are suitable for receiving O-rings 20, while care is taken that the holes 14 are slightly larger than the outer diameter of the O- rings while the inner diameter of the O-rings is slightly smaller than the outer diameter of the glass tubes. Subsequently the ends of the tubes 6 may be inserted through the holes 4 for obtaining a tight connection, and the completed unit 2,6,2 may then be fitted into the outer box mentioned in order to create a heat exchanger. The holes 16 in the outer plates are slightly larger than the outer diameter of the tubes in order that the tubes may be tilted slightly without suffering damage. The plates 8, 10, and 12 may each consist of a suitable material, and they may be fairly thin and hence light. The holes may be formed with great precision in a numerically controlled machine tool which may also be used for plates having other desired hole configurations in large or small series. The O-rings may be fitted in such a manner that one outer plate is fitted to the intermediate plate 8, the 0 rings are inserted into the holes 14 from the other side of the intermediate plate, whereupon the last outer plate is fitted and fastened. It has been mentioned that the tubes 6 are made of glass, but they may obviously be made of other materials as well, e.g. aluminium. The invention further comprises the process for preparing the holes and for mounting the rings. It will be understood that holes may be prepared in several plates in one operation.

Claims: P A T E N T C L A I M S: 1. A shell and tube heat exchanger with a tube unit consisting of a pair of end plates (2) and a number of tubes (6) connecting them, said tubes being inserted through holes (4) in the plates, said holes having seat recesses (18) for receiving sealing rings (20) for frictionally holding the tube ends and leak-tight connection between their outsides and the holes, c h a r a c t e r i s t i c i n , that the end plates are each made of three plates which are sandwiched and mutually joined, said plates having essentially coaxial holes (14, 16), the holes (14) in the intermediate plate (8) are larger than the holes (16) in the outer plates (10, 12) to such a degree that these holes (14) in the joined condition of the plates appear as said seat recesses. 2. A process for the manufacture of end plates for a tube unit for a shell and tube heat exchanger according to claim 1 , c h a r a c t e r i s t i c i n , that holes are prepared in the respective plates by punching, drilling or milling, that the plates are joined to form a plate element, in the seat recesses of which are fitted sealing rings, possibly by inserting into the larger holes in the intermediate plate before fitting and joining the last outer plate.

Inventors: LUND HENRIK, LUND, HENRIK
Applicants: LUND HENRIK, LUND, HENRIK
Application year: 1991
Main classification: B21D39
IPC codes: B21D39, B23P15, F28D7, F28F9, F28F21