ES2707951T3 - Shell and tube heat exchanger, final cover and method of manufacturing them - Google Patents

Abstract

A shell and tube heat exchanger comprising: a housing (5) containing a stack of tubes (13), an inlet of the housing (11) and an outlet of the housing (12) whereby the fluid to be cooled it can flow through the tubes (14) in the tube stack (13); and at least one dome-shaped end cover (100) attached to one end of the housing (5), the final cover comprising: a plastic or plastic composite body; at least one port (115) in the final cover in fluid communication with the tubes (14) of the tube stack by means of which a refrigerant fluid can be flowed into the tubes, the shell and tube heat exchanger being characterized by a Metal plate element (110) completely coated by the plastic body to provide structural rigidity to the plastic body.

Description

DESCRIPTION

Heat exchanger casing and tubes, final cover and method of manufacturing thereof.

The present invention relates to a shell and tube heat exchanger according to the preamble of claim 1 and to a method of manufacturing said heat exchangers. Such exchangers are known from the patent document US 3,804,161. Preferred embodiments have particular application to shell and tube heat exchangers and heat exchangers used in a marine or other corrosive environment.

The shell and tube heat exchanger is well known per se in the state of the prior art and, in fact, many types of these heat exchangers are commercially available. A brief description of the operation of a casing and tube heat exchanger is now given with reference to the example shown in Figure 1; showing Figure 2A, a longitudinal section of the heat exchanger of Figure 1; and showing Figure 2B, an exploded drawing of the heat exchanger of Figure 1. The heat exchanger 1 comprises an outer housing in the form of a generally cylindrical housing 5 with fixed end covers on each end of the housing 5. The housing 5 has one the entrance 11 at one end and one exit 12 at the other end. These are commonly known as ports or side nozzles of the housing. A tubular stack 13 is disposed in the housing 5. It comprises a plurality of tubes 14 extending longitudinally from one end of the housing 5 to the other. The tubes 14 are held in place by a tubular plate 15 at each end, through which the tubes extend 14 and are fixed. This serves to hold the tubes 14 in place, as well as to provide a sealing coupling with the inner surface of the casing 5. Therefore, the tubes 14 provide a series of channels through the casing 5 which are hermetically maintained separated from the conduit through the housing provided by the side ports of the housing, the inlet 11 and the outlet 12. One or more baffles 16 may be included in the stack of pipes 13 to guide the fluid flow from the housing side back and forth through the tubes 14, increasing the speed and efficiency of heat transfer. The deflectors 16 also serve to hold the tubes 14 and prevent vibrations.

The end covers 10 comprise generally circular plates having bolt holes spaced around the periphery. The end covers 10 are screwed to the flanges at each end of the housing 5 by the bolts 19 which are screwed into the threaded holes 20 at the ends of the flanges. A round O-ring seal 22 is disposed between the end cover 10 and the flanges 21 at the ends of the cover 5 to help seal the final cover to the cover 5. The end covers have internally threaded ports 24 which provide a input and an output of 25, 26 in the fluid communication with the tubes in the stack of tubes 13. These ports are generally known as side ports of the tubes.

A stack of tubes 13 may be floating to minimize thermal stresses or have a bellows construction. In operation, the fluid to be cooled is pumped through the housing 5 through ports 11 and 12. A cooling fluid is pumped through the tubes 14 through the side ports of the tubes 25, 26. The tubes 14 provide the heat transfer surface between a fluid flowing through the tubes 14 and the other fluid flowing through the outside of the tubes 14. Therefore, the heat can be exchanged between the two fluids. The final cover may also have an additional threaded hole 28 through which a drain plug 29 is screwed. By unscrewing the drain plug 29 of the end cover 10, the fluid can be drained from the side channel of the tube passing through the heat exchanger. heat 1.

Many variations of this basic example of a shell and tube heat exchanger 1 are known. For example, the fluid on the side of the tube can make more than one lateral passage through the tube. In this case, one or both end covers 10 can provide a step divider to maintain the fluid in different separate steps. The shell and tube heat exchangers 1 are often used in a corrosive environment. For example, shell and tube heat exchangers 1 can be used with marine engines to cool various fluids associated with the engine. Figure 3 shows a typical arrangement showing the position of several heat exchangers 1 used to cool a marine engine 500. Seawater is pumped through the side ports 25, 26 of the tube, as indicated by arrows 501. The fluid to be cooled from the exhaust manifold and engine oil coolers 500 is pumped in a closed circuit through the side ports of the housing 11, 12 in the respective heat exchangers 1, as indicated the arrows 502, to be cooled by the seawater flowing through the tubes 14 in the heat exchangers 1.

As will be appreciated, the use of seawater as a cooling fluid means that the pipe side conduit through the heat exchanger 1 must be resistant to corrosion. The end covers 10 are removable to allow the stack 13 to be removed and replaced if it is damaged or corroded. Currently, it is known that the final brass covers 10 are to be made to resist corrosion. Figures 4A and 4B show an example of a final cover made of brass as known in the prior art. The naval brass, comprising 40% zinc and 1% tin, is particularly preferred because of the resistance it exhibits against corrosion of seawater. However, the use of brass as a material is relatively expensive, so a less expensive alternative would be beneficial.

Cast iron end caps are sometimes used with fresh water, that is, not for use with contaminated water or sea water, due to corrosion problems. In less demanding applications, it is known to use plastic caps, for example, nylon with fiberglass. However, in many applications, the pressure exerted on the shell side fluid when it is pumped through the heat exchanger means that a plastic cover is not suitable, as it can deform or break under the pressures exerted on it. . In addition, the inlets made of plastic may not be strong enough to withstand the coupling to external pipes that channel the fluid to the side of the heat exchanger tube.

What is needed is a final cover that provides sufficient strength and rigidity for demanding applications, while retaining corrosion resistance, for example, from seawater, while being less expensive than using conventional materials, such as naval brass. In particular, naval brass connections are preferable for seawater inlets and drainage plugs. The material used must be sufficiently rigid over the area of the bolt hole. The final cover must not deviate around the round O-ring seal, compared to pressures of 30 bar or more.

According to a first aspect of the present invention, there is provided a shell and tube heat exchanger according to claim 1.

The use of plastics keeps the costs of the final cover low, besides being resistant to corrosion for applications where corrosive fluids pass through the heat exchanger, for example, seawater. The metal plate element provides structural rigidity to the plastic body and means that the final cover can withstand higher pressures than plastics alone could cope with. The metal does not need to be resistant to corrosion, since it can be completely covered by plastic, or at least mainly coated by plastic, so that at least the parts of the metal plate that would come into contact with corrosive fluids are protected. This creates a final cover at a lower cost, which can cope with higher pressures and is resistant to corrosion, as compared to the final covers of the prior art for casing and tube heat exchangers.

Preferably, the metal plate has a thickness between 0.5 mm and 3 mm.

Preferably, the metal plate extends over most of the radial extent of the final cover.

Preferably, the metal plate is formed from pressed steel, optionally having a zinc coating.

Preferably, the metal plate element is generally dome-shaped having a flange at its periphery, which corresponds in position with the contact face between the end cover and the housing.

In one embodiment, the end cover has a sealing face for contact against the housing, which has two or more bolt holes for screwing the end cover to the housing, wherein the contact face is arched between the holes of the housing. the bolts, so that it is elastically aligned against the cover when the final cover is bolted to the cover. The elasticity of the final cover means that the arched part "moves" against the cover, creating a better seal in the regions that are farthest from the bolt holes and that, therefore, are not fastened directly by the connections bolted. The degree of bowing preferably increases smoothly up to a maximum height approximately in the center between the bolt holes. Preferably, the arcuate portions are arranged so that a generally similar sealing pressure is maintained around the periphery of the final cover. This means that the final cover is advantageously capable of withstanding higher pressures for a given clamping force.

In one embodiment, the final cover comprises at least one metal insert adapted to receive a pin screw and which is covered by the plastic body. This provides the means to make safer and more reliable connections to the final cover for any reason, as compared to the direct connection to the plastic material.

In one embodiment, at least one metal insert is a port element, which provides an inlet to the side of the heat exchanger tube.

In one embodiment, the port element is internally threaded for connection.

In one form of embodiment, at least one insert provides a threaded connection for receiving a drain plug.

Preferably, at least one metal insert comprises a metal sleeve that provides a through hole in the bearing portion of the end cover, wherein a threaded fastener holds the end cover to the heat exchanger housing through the metal sleeve. This helps to achieve a higher strength grip without risk of damaging the plastic material around the outer periphery of the final cover and the contact face.

In one embodiment, at least one metal sleeve is mechanically locked with the metal plate element. This helps to stabilize the metal sleeve during fabrication and also helps to direct the forces of the bolted connection of the bolts to the metal plate, thus relieving stresses in the plastic material.

In one embodiment, at least one metal sleeve has a circumferential groove around at least a portion of its outer surface, and wherein the metal plate has at least one cut-out portion at its periphery arranged to be mechanically engaged with the circumferential groove. . This is a preferred way of engaging the sleeves with the plate.

In one embodiment, the plastic is molded onto the metal plate element and / or at least one metal insert.

In one embodiment, the insert is made of brass.

According to a second aspect of the present invention, there is provided a method for manufacturing a casing and tube heat exchanger as described above, the method comprising: placing the element of the metal plate in an injection molding tool and molding the plastic on the element of the metal plate.

Preferably, the heat exchanger comprises at least one metal insert adapted to receive a pin screw and is partially covered by the plastic body, the method comprising placing the at least one metal insert in a pin to accurately place the insert in the tool of injection molding before molding the plastic on the insert and the element of the metal plate.

In one embodiment, the metal inserts comprise several metal sleeves providing through holes in the bearing portion of the end cover, for securing the end cover to the heat exchanger housing by means of threaded pin screws through the metal sleeves, the method comprising the mechanical engagement of the metal sleeves with the metal plate element before molding the plastics.

According to a third aspect of the present invention, a final cover for a casing and tube heat exchanger is provided, the final cover comprising:

a plastic body;

an element of metal plate covered by the plastic body to provide structural rigidity to the plastic body.

In embodiments, the final cover comprises the additional features of any form of embodiment described above.

The embodiments may have particular advantages when used in heat exchange methods when the side of the tube passing through the heat exchanger is corrosive, such as sea water, when used as a cooling fluid in a heat exchanger arranged to cool a marine engine or the like.

It will be appreciated that any feature expressed herein as provided "in an example" or as "preferable" may be provided in combination with one or more similar features in conjunction with one or more aspects of the present invention.

The embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a shell and tube heat exchanger of the prior art;

Figure 2A shows a longitudinal cross section of a heat exchanger of Figure 1; Figure 2B shows an exploded drawing of the heat exchanger of Figure 1;

Figure 3 shows the heat exchangers used to cool a marine engine;

Figures 4A and 4B show respectively a cross-sectional view and a plan view of a final cover of the prior art for a heat exchanger;

Figures 5A and 5B respectively show front and rear end views of an example of a final cover according to an embodiment of the present invention;

Figures 6A and 6B respectively show a longitudinal cross sectional view and an end plan view of the port inserts of the final cover of Figures 5A and 5B;

Figures 7A and 7B show, respectively, a longitudinal section and an end plan view of the insert for the drain plug in the final cover of Figures 5A and 5B;

Figures 8A and 8B respectively show a longitudinal cross-sectional view and a plan view of an insert for a drain plug of Figures 5A and 5B;

Figure 9A shows a plan view of the final cover of Figures 5A and 5B;

Figure 9B shows the final cover from the rear;

Figures 9C and 9D show cross-sectional views of the final cover.

Figure 10 shows a perspective view of a steel pressing for the final cover of Figures 5A and 5B.

Figures 5A and 5B show an example of a final cover 100 according to an embodiment of the present invention. Figure 5A shows a perspective view from the front, and Figure 5B shows a perspective view from the rear. The final cover 100 can be used, for example, with the shell and tube heat exchanger 1 in Figures 1 to 3. As many skilled in the art will appreciate, many types of shell and tube heat exchangers are known, and the final cover 100 of the present invention can be modified to work with different designs of heat exchangers using well-known principles.

The end cover 100 is a generally dome-shaped element for clamping and covering one end of the housing 5 of the heat exchanger and having a side hole of tube 101 which can be used as an inlet or outlet as desired and depending on which end of the housing 5 is attached. With reference to Figure 5B showing the end cover 100 from the back (ie, from the side of the cover), the end cover 100 has a central dome part 106 surrounded by a sealing face 107 around the periphery of the dome part 105 that abuts against it and creates a seal with the end of the housing of the heat exchanger 10. The end cover 100 has three bolt holes 102 through the sealing face 107 to screw the final cover 100 to the housing 5 of the heat exchanger 1. The end cover 100 also has an optional hole for a drain plug 103.

Referring still to Figure 5B, the rear part of the end cover 100 has an inner lip 108 for receiving the stack of tubes from the heat exchanger 1. The rear part of the end cover 100 also has a center rib 109 adjacent to the port. 101 which extends from the surface of the central part of dome 106 towards the housing 5 and which helps to channel the fluids passing through the heat exchanger 1.

The final cover 100 comprises a thin metal element 110 molded onto a plastic or plastic composite element 105. Preferably, the nylon with glass fiber is used for molding the plastic to form the plastic body 105. The 50% GFN or any other suitable molded plastic and plastic composite material. The metal thin element 110 is shown in Figure 10. The metal thin element 100 has a dome-shaped central part and a flat peripheral rim, which corresponds to the dome shape 106 and the sealing face 107 of the final cover 100. The metal thin element 110 is preferably a mild steel pressing, which, optionally, is zinc plated to provide a improved chemical resistance. The inserts 115, 120, 125 are molded into the plastic to reinforce the various holes 101, 102, 103 in the final cover 100.

The hole 101 on the side of the tube has an internally threaded insert 115 that is molded into the plastic body of the end cover 100. The insert 115 is shown in Figures 6A and 6B. As can be seen, the insert 115 comprises a generally tubular body 116 with internal thread 117 to provide the female connection to the inlet port 101. The tubular body 116 has a flanged end 118 and axial ribs 119 to help secure the insertion 115 in Position in the plastic molded body. The insert 115 is preferably made of brass or some other material strongly resistant to corrosion.

Similarly, the drain plug 103 has an insert 120 which comprises a generally tubular body 121 having a threaded inner surface 122. The body 121 also has a flange 123 at one end and optionally ribs or other external features to help prevent that the insert 120 be moved in the molded plastic. The inserts are shown in Figures 8A and 8B. The insert 120 is preferably made of brass or some other material strongly resistant to corrosion.

Reinforcement inserts 125 are also provided for bolt holes 102. Inserts 125 are shown in Figures 7A and 7B in plan view and in cross section. The insert 125 comprises a generally tubular body 126 that extends through the hole 102 of the bolt. The insert 125 also has one or more circumferential grooves in the body 126 that can help maintain the insert 125 in its position in the plastic molded body. The inserts 125 are preferably made of metal.

Referring again to Figure 10, the dome-shaped metal insert 110 preferably has a thickness of between 0.5 mm and 3 mm, 1.5 mm thick in this example, with a lower rim 111 of radius 5. mm corresponding to the sealing face of the end cover 100 to provide extra support. The flange 111 preferably has cut-out portions 112 to support the insertions 125 of the bolt hole. The notches 112 form generally semicircular inserts in the thin metal element 110 which engage the grooves 127 in the inserts 125. This allows forces from the bolted connection to be transmitted through the bolt hole inserts 125 to the shaped steel element. of dome 110, thus distributing the efforts throughout the entire final cover 100.

The dome-shaped element 110 also has additional cuts 113 corresponding to the location of the tube-side port inserts 115 and the drain plug inserts 120, so that these inserts can protrude through the element 110.

Figures 9A and 9B show plan views of the final cover from the front and rear respectively, and Figures 9C and 9D show cross sections taken along the lines A-A and B-B. These show the positioning of the different inserts inside the plastic body.

With reference to Figure 9B, the sealing face 107 is preferably uniformly flat, but slopes slightly outwards in the areas 107a between the holes of the bolts 102 in the direction towards the housing 5. In this way, when the cover 100 it is attached to the housing 5 of the heat exchanger 1 by the bolts, the arcuate portions 107a are elastically aligned against the cover of the heat exchanger 1. This helps to create a good seal around the periphery of the end cover 100 and, particularly , in the areas of the sealing face 107 that are further away from the clamping force of the bolts.

To manufacture the final cover 100, the dome-shaped metal element 110 and the five inserts 115,120,125 for the bolt holes, the insertion of the drain plug and the side port of the tube can be assembled inside an injection molding tool and then the six parts completely covered by a plastic molding, preferably 50% nylon with fiberglass, to obtain the final cover 100. Precision pins are used in the injection molding tool to hold the insertions of the hole of the mold. bolt, to improve the precision of the bolt hole circle. Additional pins can be used for the inlet insertion of the tube side port 115 and the insertion of the drain plug 120. As described above, the dome-shaped element 110 preferably engages with the circumferential grooves 127 in the inserts of bolt hole 125, and, therefore, it remains in its position inside the injection molding tool.

In this way, a final cover 100 is provided which is relatively simple and economical to manufacture, while retaining the advantages of using a final deck completely of naval brass. In particular, they are provided brass connections and, preferably, naval brass connections for the insertion of the port 115 and the insertion of the drain plug 120. This is beneficial to prevent corrosion when seawater is pumped through the heat exchanger tubes 1 through these ports, and provides a threaded connection strongly resistant to corrosion to the male connection of the heat exchanger 1. At the same time, the use of relatively expensive brass is minimized. The plastic used for the main body of the final cover is reinforced by pressed steel 110. The pressed steel 110 provides the rigidity to the final cover 100 that the plastic alone can not provide. Therefore, the end cover 100 can be used in high pressure applications (eg, in preferred embodiments of up to 20 bar operating pressure and is tested up to 30 bar) without deviating around the sealing face of the round ring O-shaped casing. The arrangement of the bolt hole inserts 125, preferably entangled with the pressed steel 110, provides rigidity around the bolt hole clamping and distributes the tension through the end cover 100. Accordingly, the preferred embodiment provides a low cost and easy to manufacture end cover 100 of the present invention, which can be used with high pressure and high corrosion applications such as heat exchangers for marine engines and the like.

The embodiments of the present invention have been described with particular reference to the illustrated example. However, it will be appreciated that variations and modifications may be made with respect to the examples described within the scope of the present invention.

Claims (15)

1. A shell and tube heat exchanger comprising: a casing (5) containing a stack of tubes (13), an inlet of the casing (11) and an outlet of the casing (12) by means of which the fluid to be cooled can flow through the tubes (14) in the tube stack (13); and at least one dome-shaped end cover (100) attached to one end of the housing (5), the final cover comprising: a body made of plastic or plastic compound; at least one port (115) in the final cover in fluid communication with the tubes (14) of the stack of tubes through which a cooling fluid can be flowed into the tubes, the shell and tube heat exchanger being characterized by a metal plate element (110) completely covered by the plastic body to provide structural rigidity to the plastic body. 2. A heat exchanger according to claim 1, wherein the metal plate (110) extends over most of the radial extent of the final cover. 3. A heat exchanger according to claim 1 or claim 2, wherein the metal plate (110) is formed of pressed steel, which optionally has a zinc coating. 4. A heat exchanger according to any of claims 1 to 3, wherein the metal plate element generally has a dome shape having a flange (111) on its periphery which corresponds in position with the face of sealed between the final cover and the housing. A heat exchanger according to any of claims 1 to 4, wherein the end cover (100) has a sealing face for contact against the housing, having two or more bolt holes for screwing the end cover to the housing, wherein the contact face is inclined between the holes of the bolts so that it is elastically aligned against the cover when the end cover is screwed to the cover. 6. A heat exchanger according to any preceding claim, comprising at least one metal insert (120) adapted to receive a pin screw and which is covered by the plastic body. 7. A heat exchanger according to claim 6, wherein the at least one metal insert is a port element that provides an inlet to the tube side of the heat exchanger. 8. A heat exchanger according to any of claims 6 to 7, wherein at least one metal insert comprises a metal sleeve (125) providing a through hole in the bearing portion of the end cover, in which a screw Threaded pin holds the final cover to the heat exchanger housing through the metal sleeve. 9. A heat exchanger according to claim 8, wherein at least one metal sleeve is mechanically engaged with the metal plate member. A heat exchanger according to claim 9, wherein at least one metal sleeve has a circumferential groove (127) around at least a portion of its outer surface, and wherein the metal plate has at least a cut-away part. (112) at its periphery arranged to engage mechanically with the circumferential groove. 11. A heat exchanger according to any preceding claim, wherein the plastics are molded by coating the metal plate element and / or at least one metal insert. 12. A heat exchanger according to any preceding claim, wherein the insert is made of brass. A method for manufacturing a shell and tube heat exchanger according to any preceding claim, the method comprising: placing the metal plate member in an injection molding tool and molding plastics on the metal plate member. 14. A method according to claim 13, wherein the heat exchanger comprises the less a metal insert adapted to receive a pin screw and which is partially covered by the plastic body, the method comprising placing the at least one metal insert in a pin to accurately place the insert in the injection molding tool before molding the plastic on the insert and the metal plate element. 15. A method according to claim 14, wherein the metal inserts comprise a plurality of metal sleeves providing through holes in the bearing portion of the final cover for securing the final cover to the heat exchanger housing by means of threaded pins. through the metal sleeves, the method comprising mechanically engaging the metal sleeves with the metal plate member before molding the plastics.