A HEAT EXCHANGER

Abstract: A heat exchanger comprising heat delivery surfaces (1a) and flow channels (6, 7, 10, 11) with inlets and outlets (8, 9, 12, 13) for the primary and secondary flows. The heat delivery surfaces are formed into at least one heat transfer unit (1) consisting of corrugated plate components (1a) joined together tightly, in which there are connecting orifices (4, 5) for the primary flow, which orifices form two flow channels (6, 7) in the longitudinal direction of the heat exchanger for the primary flow; every second space between plates of the unit (1) comprising transverse flow channels (10) for the primary flow, and on the other hand, open spaces between plates next to said spaces between plates forming transverse flow channels (11) for the secondary flow; the heat transfer unit (1) being further surrounded by a casing (2) with an inlet (12) and an outlet (13) for the secondary flow, the casing being shut at its both ends by end plats (3), at least one of which has an inlet (8) and an outlet (9) for the primary flow.

Description: A heat exchanger The invention relates to a heat exchanger, com¬ prising - several plate components joined together tightly and provided with orifices for flow, which components form at least one heat transfer unit, - spaces between the plate components for the primary and secondary flows of the heat exchanger, - inlets and outlets for the primary and sec¬ ondary flows, - end plates at the ends of the heat exchanger, through which end plates at least a part of said in¬ lets are arranged. By means of a heat exchanger energy is trans¬ ferred from one medium to another. The most common heat exchanger is a so-called recuperator, in which heat is transferred through heat delivery surfaces from one medium to another (liquid/liquid, liquid/ gas, gas/gas). The inention relates to a heat ex¬ changer of just this type. The conditions (pressure, temperature etc. ) on the primary and secondary side of this heat exchanger can be independent of each other, supposing that the heat delivery surfaces en- -dure the conditions in question. Recuperators are divided into two generally known main types, i.e. tube heat exchangers and plate heat exchangers. As heat delivery surfaces of a tube heat ex- changer tubes are used, in which one medium is inside the tubes and another medium flows outside the tubes, inside a casing surrounding the tubes. Advantages of the tube heat exchanger are a simple structure, a good resistance to pressure and temperature and a possibility of using standard parts at the manufac- ture. On the other hand, drawbacks are bad heat transfer properties of the tube, whereby lots of tubes are needed for providing a sufficient heat power, which makes the device expensive and big. Moreover, standard tubes are thick-walled, which makes the device heavy. As heat delivery surfaces of a plate heat ex¬ changer no tubes, but thin-walled (0,4 to 1,0 mm) corrugated plates are used, which usually are right- angled. The plates are joined tightly together by means of rubber gaskets and the upper and lower ends thereof are provided with connecting orifices for both the primary and the secondary flow. The primary and secondary flows can flow between the plates con- trolled by the rubber gaskets without getting mixed with each other. The plates are pressed between two end plates by means of separate tightening means. The thickness of the end plates is generally 20 to 40 mm. Firstly, an advantage of a plate heat exchanger is usually at least double heat transfer properties compared with a tube exchanger. Good heat transfer properties have been provided in such a way that there is considerably more heat delivery surface in a narrow space than on a tube with the same cross-sec- tion. Further, a corrugation or a folding of a plate provides a turbulent flow, whereby the heat transfer is more effective compared to the even flow of the tube exchanger. Additionally, the plate heat exchang¬ er is light and small compared to the tube exchanger. On the other hand, the plate heat exchanger has also the following bad properties. Because there are at least four connecting orifices in total at the up¬ per and lower end of the plates, plenty of good and expensive heat delivery surface is lost. The area occupied by the connecting orifices is 20 to 30 % on an average of the area of the whole plate. Because of rubber gaskets, the working life of the plate heat exchanger is short, since rubber ages rapidly under the influence of open air and looses its resilience at the same time, whereby the heat exchanger looses its pressure resistance, i.d. it begins to leak. Ad¬ ditionally, the straight end plates are very thick, which makes the device heavy, especially if the work¬ ing pressure is high or the size of the plate is big. The object of the present invention is to pro¬ vide a totally new heat exchanger, which does not have the bad properties of the tube heat exchanger or the plate heat exchanger. This object is achieved by means of a heat exchanger according to the invention, which is characterized in that - each plate component is corrugated and each of them has only two orifices for flow functioning as connecting orifices for the primary flow and forming in the unit only two flow channels in the longitudi- nal direction of the unit for the primary flow, the inlet and outlet of which channels are arranged through the end plates, - every second space between the plate com¬ ponents of the unit is shut, whereby these spaces form transverse flow channels for the primary flow, - that spaces next to the abovementioned spaces are open outside the connecting parts partially form¬ ing the longitudinal channels for the primary flow, and - the unit is surrounded by a casing having an inlet and an outlet for the secondary flow, whereby said open spaces and the space between the unit and the casing form a flow space for the secondary flow. The solution of the invention is based on the idea of replacing the tube systems of a tube exchang- er by a simplified plate heat exchanger designed in a new manner, which makes it possible to combine the good thermic properties of the plate heat exchanger and the simplicity of the tube exchanger. The con- necting orifices of the plate components of the heat transfer unit are reduced by half, because only two of them are needed in each component; thus, the area of the heat delivery surface increases also when com¬ pared to the plate heat exchanger. It is also pos- sible to make the end plates thinner, for the end plates of the tube exchanger can be used. In order to intensify the heat transfer fur¬ ther, it is possible that in the space between the casing and the heat transfer unit are arranged flow control plates substantially in the longitudinal direction of the heat exchanger to control the secondary flow. The plate components are most preferably joined together by welding, whereby the weld joints form a necessary sealing and define together with the plate components the flow channels for the primary flow. In this way, the heat exchanger can be made into a reli¬ able structure with a very long working life with re¬ spect to the resistance to pressure and temperature. In the following, the invention is described more closely by means of some preferable embodiments with reference to the enclosed drawings, in which Figure 1 shows schematically a longitudinal cross-section of a heat exchanger according to the invention, Figure 2 the device of Figure 1 cut and seen from the end direction, Figures 3a-3d show manners of joining plate components of the heat exchanger according to the Figures 1 and 2, and Figure 4 shows another embodiment of xhe plate heat exchanger of the invention. The heat exchanger shown in the Figures 1 to 3 comprises a heat transfer unit 1 formed of plate com- ponents la joined together tightly, a casing 2 sur¬ rounding this and end plates 3 shutting the ends of the casing 2. The plate components la most preferably made of rolled thin plate with a thickness of 0,3 to 0,7 mm serve as heat delivery surfaces of the heat exchanger and they are corrugated or folded in shape. Each plate component la has two connecting orifices 4 and 5 for the primary flow. The connecting orifices 4 and 5 form two flow channels 6 and 7 in the longitudinal direction of the heat exchanger and the heat transfer unit 1, respectively, for the primary flow. Then the first channel 6 serves as an inlet channel and the second channel 7 as an outlet channel. For the prima¬ ry flow are arranged an inlet 8 and an outlet 9 in one of the end plates 3. In every second space be¬ tween the plates of the heat transfer unit 1 are formed flow channels 10 for the primary flow, which channels are transverse with respect to the heat ex¬ changer and in connection with the longitudinal flow channels 6 and 7 only. On the other hand, open spaces between plates next to the abovementioned spaces be¬ tween plates form transverse flow channels 11 for the secondary flow, for which are arranged an inlet 12 and an outlet 13 in the casing 2. The cross-section of the casing 2 (Figure 2) corresponds to the shape of the plate components la, i.e. the shape of the casing is for instance cylin¬ drical. Between the casing 2 and the heat transfer unit there is an annular space 14, in which are pre- ferably arranged flow control plates 15 mainly in the longitudinal direction of the heat exchanger for the control of the secondary flow. Consequently, the sec¬ ondary flow is controlled by means of the flow con¬ trol plates 15 for instance transversely through the heat transfer unit 1. The plate components la are most preferably joined together by welding (see Figures 3a and 3b). At the spaces between plates to be left open, i.e. at the flow channels 11 of the secondary flow, the join- ing has been carried out around the connecting ori¬ fices 4 and 5. These weld joints are indicated by reference numerals 16 and 17. On the other hand, those plate components la between which the trans¬ verse flow channels 10 for the primary flow are lo- cated have been welded together with a weld joint 18 situated close to the edges of the plate components la. The weld joints 16 to 18 have then been made such that they also constitute a necessary sealing. At the same time, the weld joints 16 to 18 also define to- gether with the plate components la the flow channels 6, 7 and 10 for the primary flow. The weld joints 16 to 18 can also be replaced by rubber gaskets, whereby it is most preferable to use double gaskets 19 to 21 according to Figures 3c and 3d, which gaskets guarantee that the primary and secondary flows in no situation can get mixed with each other. If leakage flow occurs, it runs between the double gaskets 19 to 21 through orifices 22 and 23 of the plate components la into the next space between plates and further through an orifice (not shown) in the end plate out of the heat exchanger. Figure 4 shows one embodiment of the heat ex¬ changer of the invention, in which two heat transfer units 1' and 1" joined together are arranged inside a common casing 2' and independent flows separated from each other run inside each of these units. The heat¬ ing running inside the casing 2' and through the heat transfer units 1' and 1" can, for instance, heat the above two flows running in the heat transfer units. The flow running inside the casing 2' can be con¬ trolled by means of spacing plates 15'. The invention has been described above in the light of some preferable exemplifying structures on¬ ly. As to the details, however, the heat exchanger of the invention can vary within the scope of the en¬ closed claims. As far as e.g. materials are concern¬ ed, it can be stated that the plate components and the casing can both be made of the same material or of different materials. The casing, for instance, can be made of plastic and the plate components of metal, or both the casing and the plate components of plas¬ tic, for example. The total weight can be substanti¬ ally regulated by means of these' solutions. Further, the heat transfer unit and the casing can be e.g. rectangular in shape and the connection points can be located at the casing arbitrarily, if it is justified considering the flow/heating techni¬ ques. It is, moreover, possible to carry out a unit with no flow control unit at all. Such a use is for instance a coil for moving water in an oil vessel, in which the secondary flow functions at free circula¬ tion.

Claims: Claims : 1. A heat exchanger, comprising - several plate components (la) joined together tightly and provided with orifices (4, 5) for flow, which components form at least one heat transfer unit (1; 1'; 1"), - spaces (10, 11) between the plate components (la) for the primary and secondary flows of the heat exchanger, - inlets and outlets (8, 9, 12, 13) for the primary and secondary flows, - end plates (3) at the ends of the heat ex¬ changer, through which end plates at least a part of said inlets ( 8 , 9 , 12, 13 ) are arranged, c h a r a c t e r i z e d in that - each plate component (la) is corrugated and each of them has only two orifices (4, 5) for flow functioning as connecting orifices for the primary flow and forming in the unit (1; 1'; 1") only two flow channels (6, 7) in the longitudinal direction of the unit for the primary flow, the inlet and outlet of which channels are arranged through the end plates (3), - every second space (10) between the plate components (la) of the unit (1; 1'; 1") is shut, whereby these spaces (10) form transverse flow chan¬ nels (10) for the primary flew, - that spaces (11) next to the abovementioned spaces (10) are open outside the connecting parts (16 to 18, 19 to 21) partially forming the longitudinal channels for the primary flow, and - the unit (1; 1'; 1") is surrounded by a cas¬ ing (2; 2' ) having an inlet (12) and an outlet (13) for the secondary flow, whereby said open spaces (11) and the space between the unit and the casing form a flow space for the secondary flow. 2. A heat exchanger according to claim 1, c h a r a c t e r i z e d in that in an substantial- _f# 5 ly annular space (14) between the casing (2) and the heat transfer unit (1) are arranged flow control plates (15) substantially in the longitudinal direc¬ tion of the heat exchanger for the control of the secondary flow. 10 3. A heat exchanger according to claim 1 or 2, c h a r a c t e r i z e d in that the plate compo¬ nents (la) are joined together by welding, whereby the weld joints (16 to 18) form a necessary sealing and define together with the plate components (la) 15 the flow channels (6, 7, 10) for the primary flow. 4. A heat exchanger according to claim 1 or 2, c h a r a c t e r i z e d in that the plate compo¬ nents (la) are joined together by means of rubber gaskets (19 to 21), which together with the plate 20 components (la) define the flow channels (6, 7, 10) for the primary flow. 5. A heat exchanger according to claim 4, c h a r a c t e r i z e d in that the rubber gaskets (19 to 21) are double seals, whereby the plate compo- 25 nents (la) between the seal halves are provided with orifices (22, 23) leading out of the heat exchanger and forming a channel, so as to lead a possible leak¬ age flow out of the heat exchanger. 30

Inventors: KONTU MAURI, KONTU, MAURI
Applicants: KONTU MAURI, KONTU, MAURI
Application year: 1990
Main classification: F28D1
IPC codes: F28D9, F28F3