Patent Publication Number: US-9841240-B2

Title: Heat exchanger

Description:
RELATED APPLICATIONS 
     This application is a national phase entrance of and claims benefit to PCT Application for a heat exchanger, PCT/CN2013/000306, filed on Mar. 18, 2013, which claims benefit to Chinese Patent Application 201210072963.3, filed on Mar. 19, 2012. The specifications of both applications are incorporated herein by this reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a heat exchanger, in particular to a heat exchanger with non-detachable casing and core, which is applicable to high-temperature high-pressure hydrogenation devices, hydrocracking and hydrofining devices, and chemical refining equipments for reforming and aromatic hydrocarbons. 
     DESCRIPTION OF THE PRIOR ART 
     As common heat exchange equipment, as shown in  FIG. 4 , a heat exchanger includes a core  6 ′ and a casing, which may be in detachable connection with each other or designed into a non-detachable structure as required. Each end of the casing of a non-detachable heat exchanger generally includes a cylinder  1 ′ and two convex heads  2 ′ (spherical heads or elliptical heads) located at the two ends of the cylinder  1 ′; a larger port of each of the convex heads  2 ′ is designed to have a same diameter as that of an opening of the cylinder  1 ′, as shown in  FIG. 4 , while a tube sheet  5 ′ is provided on a smaller port of each convex head  2 ′ to support one end of the core  6 ′; and a channel  7 ′ is welded on the outer side of the tube sheet  5 ′ to serve as a tube side passage  8 ′. A heat exchanger with such a structure, although may achieve the heat exchange function, has the following disadvantages. First, the smaller port of each convex head  2 ′ is needed to provide with a tube sheet  5 ′, so that the convex head  2 ′ may not have a too small caliber. That is, the caliber of the smaller port of the convex head  2 ′ is relatively approximate to that of the larger port. As a result, the axial dimension L of the convex head  2 ′ can not be too large. In this case, the heat transfer medium passage  3 ′ can be formed only on the cylinder  1 ′. Consequently, when the heat transfer medium enters the casing, on one hand, a dead area is likely to form at the convex head  2 ′, and on the other hand, bias flow of the heat transfer medium, non-uniform flow resistance and inconsistent flow velocity are likely to occur in an effective heat exchange area of the casing, directly resulting in non-uniform heat exchange, decreased efficiency of the heat exchanger and increased pressure drop. Therefore, in order to meet the requirements of subsequent processes on the material flow temperature, generally, an auxiliary device such as a heating furnace is additionally provided on the down stream of the heat exchanger, so as to further raise the temperature of the material flow. Apparently, the use of such a heat exchanger will inevitably causes the whole system huge, and also increases the initial investment cost and the running cost in the future. Second, due to the limited space at the ends of the heat exchanger, auxiliary devices such as flow guide plates and check rings can not be additionally provided in this space, that is to say, the flow form of the casing side medium can not be changed, so that the heat exchange efficiency of the heat exchanger can not be improved effectively. Third, particularly, with a heat exchanger with such end structure, the welding between the cylinder  1 ′ and the convex heads  2 ′ can be performed on only one side because there is no space large enough to accommodate construction personnel at the ports of the casing, influencing the selection of material for the heat exchanger. For example, in the case that the casing is made of clad steel plate material and a surfacing structure, or, in the case that the material of the casing is selected from some kinds of chrome-molybdenum steel which are infeasible for one-side welding, it is difficult to manufacture a heat exchanger due to this conventional structure, thereby seriously influencing the design development and extensive application of the heat exchanger. Fourth, at the end of welding, the testers are still unable to access the ends of the casing to carry out inspection and nondestructive testing. At the end of welding, heat treatment, if required by the welding part, can be carried out by external heating only. Furthermore, it is quite difficult to take protective measures against sensitization of the stainless steel core during the heat treatment. As such, during the future maintenance of the equipment, the maintenance personnel are still unable to access the casing to do maintenance, so maintenance in the future is also quite inconvenient. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a heat exchanger with the advantages of convenient construction and maintenance, improved flow condition of the heat transfer medium, and extended range of material selection of the heat exchanger. 
     For achieving the above stated object, a heat exchange comprises: a casing having a cylinder with two ends; two connectors, each connector having a large opening and a small opening, each connector being attached to one end of the cylinder through the small opening; two convex heads, each convex head having an opening end and a tube sheet opposing to the opening end, each convex head being connected through the opening end to the large opening of a connector, each convex head having an internal space which can hold at least an adult; a core with two ends disposed inside the casing, each end of the core supported by the tube sheet on each convex head; and two heat transfer medium passages, one heat transfer medium passage being formed on one convex head; wherein, each connector comprises an annular body with an internal circular edge and an external circular edge which are extended reversely along axial direction of the annular body to form a first circular extension with a first thickness and to form a second circular extension with a second thickness, the large opening is formed in the first circular extension, the small opening is formed in the second circular extension, each annular body has a thickness greater than the first thickness and the second thickness; rectangular corner is respectively formed on the internal circular edge and the external circular edge of each annular body. 
     Preferably, the large opening of each connector has an external surface for matching a peripheral surface of each convex head, thus enabling the heat transfer medium to flow more smoothly. 
     Preferably, the casing can be made of clad steel plate and some kinds of chrome-molybdenum steel which are feasible for two-side welding from both inside and outside of the casing. 
     Compared with the prior art, in the present invention, owing to additionally providing the convex heads, the opening end of each convex head is enlarged as required, so that the axial dimension of each convex head can be increased under the same condition. In this way, the space at the ends of the casing of the heat exchanger may be enlarged, thereby providing a space large enough to accommodate the construction personnel and test personnel to carry out welding and testing operations therein. Therefore, such improvement creates conditions for two-side welding, so that the casing can be made of clad steel plate material or adopts build-up technology, and the material of the casing may be selected from some kinds of chrome-molybdenum steel which are infeasible for one-side welding. That is to say, the selection range of the material of the casing of the heat exchanger becomes wider and the design and manufacture of the equipment becomes more reliable, thereby largely extending the application fields of the heat exchanger. Meanwhile, due to larger space and axial distance of the improved ends of the convex heads, the heat transfer medium passages may be formed on the convex heads. In this way, on one hand, a buffer area is provided for the flow of the heat transfer medium, so that the heat transfer medium passages flows more smoothly, multiphase medium distribution is achieved along the cross-section of the casing, the pressure field and the velocity field become more uniform, the heat exchange efficiency of the heat exchanger is improved significantly, and the pressure drop of the heat transfer medium passages is reduced; on the other hand, baffles and check rings may be mounted inside the convex heads as required to reduce the impact force of the heat transfer medium passages to the core at inlet; meanwhile, auxiliary devices such as flow guide plates and distribution rings may be arranged to further ensure the sufficient heat exchange of the heat exchange area inside the casing. With the use of the heat exchanger provided by the present invention, the temperature of the material flow when discharged from the outlet may be approximate to the required temperature, thereby omitting the subsequent heating devices such as a heating furnace and reducing the running cost. Therefore, this heat exchanger is worthy of popularization and application in the current high-temperature high-pressure hydrogenation devices, hydrocracking and hydrofining devices, and reforming and chemical refining equipment (for example, with aromatic). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a heat exchanger according to the first embodiment of the present invention. 
         FIG. 2  is a partial sectional view of  FIG. 1  (removing a central cylinder). 
         FIG. 3  is a sectional view of a connector of  FIG. 2 . 
         FIG. 4  is a sectional view of the heat exchanger in the prior art. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     To enable a further understanding of the innovative and technological content of the invention herein refer to the detailed description of the invention and the accompanying drawings below: 
     Embodiment 1 
     As shown in  FIGS. 1-3 , a heat exchanger comprises a casing, a core  6  with two ends disposed inside the casing, each end of the core  6  supported by a tube sheet  5  on each convex head  2 , each convex head  2  having an internal space which can hold at least an adult, a central cylinder  9  disposed in the center of the core  6 , and two heat transfer medium passages  3  formed on the casing; the casing has a cylinder  1  and two convex heads  2 , and the tube sheet  5 , the core  6  and the central cylinder  9  are all of conventional configurations; the main improvement is to provide two connectors  4 , each connector  4  having two openings with different diameters. 
     In this embodiment, each connector  4  comprises an annular body  41  with an internal circular edge  4   c  and an external circular edge  4   d  which are extended reversely along axial direction  4   e  of the annular body  41  to form a first circular extension  43  with a first thickness d 1  and to form a second circular extension  42  with a second thickness d 2 ; each connector  4  has a large opening  4   b  and a small opening  4   a , the large opening  4   b  is formed in the first circular extension  43 , the small opening  4   a  is formed in the second circular extension  42 ; each convex head  2  has an opening end, and each convex head  2  is connected through the opening end to the large opening  4   b  of a connector  4 , each connector  4  is attached to one end of the cylinder  1  through the small opening  4   a ; rectangular corner  44  is respectively formed on the internal circular edge  4   c  and the external circular edge  4   d  of each annular body  41 , each annular body  41  has a thickness d greater than the first thickness d 1  and the second thickness d 2 . Such configuration is applicable to the working condition of high pressure. 
     Here, the convex heads  2  are designed into semi-spherical, the heat transfer medium passages  3  are respectively formed on one convex head  2 , and the large opening  4   b  of each connector  4  has an external surface for matching a peripheral surface of each convex head  2 , thus enabling the heat transfer medium to flow more smoothly. 
     During assembling, the small opening  4   a  of each connector  4  and the cylinder  1 , as well as the large opening  4   b  of each connector  4  and each convex head  2 , are fixedly butted in turn by means of two-side welding, then each tube sheets  5  is butted and welded to the end, opposing to the opening end, of each convex head  2 , and finally each channel  7  is welded on the outer side of each tube sheet  5  to serve as a tube side passage  8 . 
     In this embodiment, the space at the ends of the casing may be enlarged by using the connectors  4 , thereby making feasible for two-side welding and future maintenance and wider selection range of material of the casing of the heat exchanger. Meanwhile, the large space at the ends of the casing may be used as a buffer area of the heat transfer medium during the heat exchange of the heat exchanger, thereby optimizing the flow state of the heat transfer medium to improve the heat exchange efficiency. Furthermore, in such a structure, auxiliary devices such as flow guide plates and check rings may be additionally provided as required, to further improve the heat exchange efficiency. Moreover, as there is a large enough space at the ends of the casing, when the welding part requires heat treatment, heating modules may be placed on the inner and outer walls of the ends of casing for bilaterally heating, and insulating measures may be taken for the ends of the core  6  to avoid the sensitization of the stainless steel heat exchange tubes.