ES2870501T3 - Tube bundle heat exchanger - Google Patents

Abstract

Tube bundle heat exchanger, comprising: a shell (9) defining a containment volume, said shell (9) having an inlet conduit (10) and an outlet conduit (11) from the appropriate containment volume to transport a first fluid in a liquid state to be cooled or heated, and at least one perforated tube plate (2) with through holes (3) suitable to allow the tubes (1), of a bundle of tubes, to pass through the themselves in a waterproof manner, a bundle of tubes (1), each tube of said bundle of tubes being inserted in a watertight manner through a respective hole of said through holes (3) of the perforated tubesheet (2), a chamber of supply (6) of a second fluid under pressure to be heated or cooled with a phase change, defining an inlet opening suitable to be placed in fluid communication with a supply conduit (4) of the second fluid, and a plurality of openings output, each being d These outlet openings suitable for being placed in fluid communication with a respective tube of the tubes (1) of the tube bundle, an aspiration chamber (7) of the second fluid, which defines a plurality of inlet openings, each one being said inlet openings suitable to be placed in fluid communication with a respective tube of said tubes (1) of the tube bundle, and a drainage opening suitable to be placed in fluid communication with a return conduit (8) of the second fluid, the tubes (1) of said bundle of tubes are inserted into the through holes (3) of said perforated tube sheet (2) and have first ends (12) and second ends (13) that are fixed to the tube sheet perforated (2) of the shell (9) of the heat exchanger; characterized in that each chamber of said supply chamber (6) and said suction chamber (7) is delimited by respective walls and all said respective walls are distinct and are separated from each other and from said casing (9), so that all the respective walls of the supply chamber (6) and of the suction chamber (7) are enveloped by air from the environment in which the heat exchanger is installed; each end of said first ends (12) of the tubes (1) of the tube bundle is fixed in fluid communication and in a non-removable manner to a respective opening of said outlet openings of the supply chamber (6) either by welding strong, or by welding, or by gluing, or by mechanical expansion or by mechanical connection; each end of said second ends (13) of the tubes (1) of the tube bundle is fixed in fluid communication and in a non-removable manner to a respective opening of said inlet opening of the suction chamber (7) either by means of brazing, or by welding, or by gluing, or by mechanical expansion or by mechanical connection.

Description

DESCRIPTION

Tube bundle heat exchanger

TECHNICAL SECTOR

The present invention relates to heat exchangers and more particularly to a tube bundle heat exchanger of the dry expansion type where a fluid that changes its state under pressure is contained in a supply chamber to be heated / cooled with change of state by means of another fluid in liquid state, contained in the casing, and where the supply chamber and the suction chamber of the heat exchanger are delimited by different walls and separated from each other and from the casing, and all are enclosed by air from the atmosphere of the surrounding environment outside the exchanger shell.

STATE OF THE PRIOR ART

Shell and tube bundle heat exchangers are well known and widely used for cooling / heating fluids. These exchangers comprise a shell that surrounds a bundle of tubes, in which a first fluid, for example, water, or a mixture of glycols or other suitable liquid (for example, oil), which flows in the space delimited between the inner surface of the shell and the outer surfaces of the pipes, it is heated / cooled by a second fluid that flows within the tube bundle, for example, a pressurized fluid that changes state (as Freon) when it crosses the tube bundle. Among heat exchangers, evaporators are called dry expansion evaporators when the heat exchange surface is externally enveloped by the first fluid, which transfers or absorbs heat, for example, water.

In order to inject the second fluid under pressure, which will change state, through the tube bundle, maximizing the efficiency of heat exchange, it is necessary to ensure that it is distributed equally among the plurality of tubes. For this reason, a structure of the type shown in figure 1 is commonly used. The tubes 1 of the tube bundle are fixed imperviously to a tube plate 2 of an evaporator shell 9, which is fixed by means of a flange. 15 to the tube plate 2 and defining a containment volume intended to contain the tube bundle 1 immersed in a first fluid in a liquid state to be cooled / heated. The tubesheet 2 has through holes 3 running through its thickness and has the tubes (of tube bundle 1 in the containment volume) inserted into respective through holes 3 and attached thereto.

To distribute the second fluid between the tubes 1, the holes 3 in the tubesheet 2 are made so that they flow into a supply chamber into which the tubes of the tube bundle are directed: the second fluid, transported through a delivery duct 4 passes into the supply chamber, and from there it is equally distributed among all the tubes 1 passing through the holes 3.

Typically, the supply chamber is formed by a head wall 5 shaped to define at least one concave profile 6 on the tube plate 2 facing surface of the housing, as shown in Figure 2. The head wall 5 is screwed against the tube sheet 2 of the housing, so that the concave profile 6 of the head wall 5 forms with the tube sheet 2 a cavity that is filled with the second fluid from the conduit 4, to distribute the second fluid, which will change its state, between the various tubes of bundle 1 that flow into it. On the same head wall 5 other concave profiles 7 are defined that form, with the tube sheet 2, the suction chambers in which the second fluid is collected, which is sucked in from the return ducts 8.

Although this embodiment is commonly considered satisfactory, applicants have set themselves the objective of reducing the production costs of evaporators while maintaining their performance unchanged.

Among the expenses that most affect the final cost of this type of heat exchangers is the expense to certify the product in accordance with the Pressure Equipment Directive 2014/68 / EU, currently in force in Italy. This directive, commonly referred to as PED, by the English name Pressure Equipment Directive, provides various certification procedures according to a hazard category of general equipment under pressure.

Applicants have observed that the supply chamber and the suction chamber, made within the tubesheet, make it necessary to require the most onerous certification procedure, which has a significant impact on the final costs of the apparatus. Therefore, the problem of how to make the supply chamber and the suction chamber was addressed, without incurring the costly legal obligations foreseen by the regulations currently in force and without penalizing the efficiency of the heat exchange of the entire evaporator.

Patent document FR1335130 of the prior art, on the basis of which the preamble of claim 1 is formulated, shows a heat exchanger in which the supply chamber and the suction chamber are not delimited by separate and distinct walls, but that coexist inside the same dome-shaped tube sheet, equipped with internal separation partitions. In addition, as in the heat exchanger of In the prior art of figure 1 discussed above, also the heat exchanger described in patent document FR1335130 has the tube plate (indicated by reference number 7) separated by a tube plate (indicated by reference number 4 ), so it is also subject to the most onerous certification procedure.

Patent document US2006 / 266504 shows (see Figures 2 and 4) the tubesheet (indicated with reference 201) illustrated in attached Figure 1, screwed to a tubesheet (indicated with reference 115) to define two supply chambers and two suction chambers.

Patent document US2005 / 061025 describes (see figure 1) a head wall (indicated with reference 36) in the form of a dome fixed by means of a flange (indicated with reference 12) to a tube plate 28, defining in its inside a supply chamber and a suction chamber, as in the known exchanger of figure 1 described above.

Patent document US3,800,867 discloses an evaporator having a dome-shaped head wall attached to a tube plate and defining inside, together with the tube plate, a supply chamber and a discharge chamber. aspiration.

CHARACTERISTICS OF THE INVENTION

Applicants have found that so-called dry expansion evaporators are subject to costly certifications, since the supply / suction chamber, in which the second fluid is collected, which is distributed among the various tubes of the tube bundle in which it is undergoes a change of state, to then be transported to the suction chamber that supplies the fluid now transformed into gas to an external device, it is delimited by at least one wall in direct contact with the first fluid in liquid state contained within the evaporator housing. Furthermore, the supply chamber is defined by screwing the end wall against the shell tube plate, for which the separable joint of these two parts must be certified as perfectly waterproof and perfectly secure.

To obviate these drawbacks, the applicants have made a tube bundle heat exchanger of the dry expansion type in which there is no head wall, but there is a supply chamber and a suction chamber to which a conduit is connected. respective supply / return. The supply / suction chamber is substantially a single piece, without screwed parts, and is installed outside the heat exchanger housing and is not delimited by any wall in direct contact with the first fluid in liquid state to be cooled / heated, but it is enveloped by the air of the atmosphere of the environment in which the exchanger is located. The supply / suction chamber is attached to the tubes of the tube bundle, which have singularly accessible terminations attached to the tube plate of the housing and which are in fluid communication with corresponding openings in the supply chamber.

According to one aspect, the supply / aspiration chamber is in the form of a funnel having a fitting from the tapered end of the funnel to the delivery / return conduit and a plurality of outlet ports from the enlarged end of the funnel, each port being connected to a respective tube of the tube bundle.

According to one aspect, the supply / suction chamber has an inlet opening to which a supply conduit for a second pressurized fluid can be connected, which will change state, and a plurality of tubular outlets in fluid communication with respective tubes of the tube bundle, in which the tubular outlets are attached directly to the respective tube ends by brazing, welding, gluing, mechanical expansion, or mechanical connection.

According to one aspect, a heat exchanger according to the present invention comprises several supply / suction chambers, each having a tubular inlet, to connect to a supply / suction conduit for a second pressurized fluid, which will change state, and a plurality of tubular outlets directly attached to respective pipe terminations by brazing, welding, gluing, mechanical expansion or mechanical connection.

An evaporator is made by filling with water the containment volume defined by the shell, in which the bundle of tubes is contained.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates how a supply / suction chamber is formed in known-type evaporators with a head wall screwed to a tube plate of the shell.

Figure 2 shows the surface of the head wall with the recesses that form, with the outer surface of the casing tube plate, at least a supply chamber and a suction chamber.

Figure 3 is a profile view of an evaporator according to this invention in which the supply / suction chamber is completely enveloped by air, exposed to the atmosphere of the environment in which it is installed the evaporator.

Figure 4 is a perspective view of the evaporator of Figure 3.

Figures 5a to 5c are profile views of different embodiments of supply chambers or suction chambers usable in the heat exchangers of the present invention.

Figures 6a to 6c are perspective and transparent views of the supply chambers or suction chambers of Figures 5a to 5c.

Figure 7 shows another evaporator according to this invention.

Figure 8 is an exploded view of a detail of the exchanger of Figure 7, with removable, plug-in and threaded tubular outlets for coupling with a supply chamber or a suction chamber.

Figure 9 shows a pluggable removable tubular outlet and a threaded removable tubular outlet, for coupling a respective tube of the tube bundle with a supply chamber or a suction chamber.

DETAILED DESCRIPTION

A dry expansion tube bundle type evaporator according to the present invention is illustrated in Figures 3 and 4. Like common evaporators, it has an outer shell 9 that defines a containment volume filled with a first fluid in a liquid state to be cooled / heated, in which a bundle of tubes 1 is immersed, within which a second fluid under pressure circulates ( e.g. Freon or other similar fluids) to be heated / cooled with change of state. The first fluid in liquid state enters through the inlet conduit which, for example, may be conduit 10 (or conduit 11) placed above (below) the evaporator in the example of the figures, and is discharged through the conduit outlet which, for example, can be the conduit 11 (or the conduit 10) located below (above) the evaporator in the example of the figures.

Preferably, the tubes 1 of the tube bundle are U-shaped, so that the inlet ends 12 of the second fluid in the tube bundle 1 and the outlet ends 13 of the second fluid in the tube bundle all pass through the same tube sheet 2 of casing 9, as shown in the figures. However, what will be said also applies when the tubes are substantially straight and cross the casing 9 longitudinally, entering from the tubesheet 2 and exiting a wall longitudinally opposite the tubesheet.

Conveniently, within the containment volume defined by the evaporator shell 9, separating partitions (not shown) will be installed defining a zigzag path of the first fluid in liquid state to be cooled / heated, so that it passes through the duct. inlet 10 to outlet conduit 11, repeatedly passing between the tubes in a countercurrent direction with respect to the pressurized gas circulating in the pipes, to maximize the efficiency of heat exchange. However, the down-current configuration can be accomplished by reversing the flow of one of the two fluids.

The evaporator can be supported by feet 14, fixed to the tube plate 2, which keep it raised off the ground, as shown in figures 3 and 4, or it can have rings fixed to the casing 9, as shown in the figures 7 and 8, to be supported by hooks.

A characteristic of the evaporator of this invention is the fact that it does not have a head wall 5, of the type shown in figure 1, which is instead present in known evaporators. As can be seen in Figures 3, 4, 7 and 8, the tubesheet 2 is flanged and screwed to a flange 15 of the casing 9, but does not define any supply chamber. Unlike known evaporators of the type shown in Figure 1, the tube bundle tubes located within the shell have individually accessible ends 12 and 13 attached to the tube sheet 2. The individually accessible outer ends 12 and 13 do not cause the second fluid leaks through the tubesheet 2 perforated by the shell 9, as they are made to adhere to the holes in the tubesheet 2, for example, by gluing, brazing or welding.

According to one aspect, illustrated in Figures 3 and 4, the ends 12 and 13 cross the tube sheet 2 of the casing 9 and protrude therefrom.

Like the supply chambers of known evaporators, the evaporator of the present invention has one or more supply chambers 6 connected to a supply conduit 4, through which the second pressurized fluid is transported, which will change state as it passes through the tube bundle. The tubes of the tube bundle flow into the supply chamber 6 and are individually attached thereto through the corresponding waterproof connections.

Unlike known evaporators, the supply chamber 6, as well as the suction chamber 7, is defined by distinct and separate surfaces of the casing 9, completely enveloped, submerged in the air of the atmosphere of the environment in which it is located. the evaporator. According to one aspect, the walls of the supply chamber 6 and of the suction chamber 7 are also at a distance from the housing 9 of the evaporator so as not to be physically in contact with it. In practice, the supply chamber 6 and the suction chamber 7 are delimited by different and discrete bodies, they do not have any wall that is externally in contact with the first fluid in the liquid state contained in the housing and each of them it appears as a single body with physically distinct walls that are separated by the evaporator shell 9. In addition, the beam tubes of tubes, which protrude from the tube sheet 2 of the casing 9, are fixed in a waterproof way to corresponding connections of the supply chamber 6, whereby the supply chamber 6 is an integral part of the circuit through which the second pressurized fluid to be heated / cooled circulates with change of state and does not share any wall with the circuit of the first fluid in liquid state to be cooled / heated contained in the casing.

As shown in Figures 3 and 4, also the suction chamber 7 will be realized as the supply chamber 6, with a plurality of inlet openings for the second fluid, coming from the tubes of the tube bundle heat exchanger, and an outlet opening placed in fluid communication with a return conduit 8 of the second fluid. The two suction chambers 7 shown in Figures 3 and 4 have separate walls separated from the casing 9 and at a distance from it, so that all surfaces of the suction chamber 7 are enveloped by the ambient air in which the evaporator is installed and does not have any wall in contact with the first fluid in liquid state.

According to one aspect, the suction chamber 7 (or the suction chambers, if there are at least two of them as shown in the figures) is made as the supply chamber 6, to avoid having to certify the evaporator according to the directive PED, minimizing certification costs to the maximum.

According to the embodiment shown in the figures, the supply chamber 6 has a plurality of tubular outlets 16 that draw out the internal volume of the supply chamber 6. Each of these tubular outlets 16 is firmly and directly attached to a respective end 12 which it exits housing 9 to place supply chamber 6 in sealed fluid communication with each tube of the tube bundle. These tubular outlets 16 are imperviously attached to the ends 12 of the tubes, for example, by brazing, welding, gluing, rolling, or mechanical connection.

In practice, with this embodiment it is even possible to distribute the second fluid through each tube of the tube bundle before it passes through the tubesheet 2.

According to an embodiment not shown in the figures, the ends 12 and 13 of the tubes coming out of the tube plate 2 of the casing 9 are welded directly to the walls of the supply chamber 6 or of the suction chamber 7. Without However, this embodiment is less preferred, since it is relatively difficult to weld all the tubes, which can be very numerous, to the same wall of the supply chamber 6 or the suction chamber 7.

According to one aspect, illustrated in Figures 7 and 8, the ends 12 and 13 (not shown) are fixed to the tubesheet 2 and do not protrude therefrom. Basically, the ends 12 and 13 are within the thickness of the tubesheet 2 and do not protrude from the holes 3 towards the outside of the casing 9. The connection with the supply chamber 6 and the suction chamber 7 is effected by means of of the tubular outlets 16. These tubular outlets 16 may be integral with the supply chamber 6 or the suction chamber 7, respectively, or, as shown in Figures 8 and 9, they may be produced as separate tubular elements. According to one aspect, the tubular outlets 16 have:

- an apical portion 17a, configured to engage in a respective tube of the tube bundle 1;

- a projection 17b defining at least one abutment surface against the tubesheet 2;

- a distal portion 17c, configured to engage in the delivery chamber 6 or in the aspiration chamber 7. The apical portion 17a can be fixed to the respective tube of the tube bundle 1, expanded in the hole 3 of the tube sheet 2, by gluing, or by mechanical expansion or mechanical connection. Conveniently, the apical portion 17a will have a truncated conical shape to guide the insertion of the tubular outlet 16 by keeping it centered with respect to the hole 3 until the projection 17b is not against the tubesheet 2.

Similarly, distal portion 17c may also be frusto-conical, to guide insertion into aspiration chamber 7 (or delivery chamber 6) as shown in Figure 8, until projection 17b does not come into contact. Alternatively, the distal portion 17c may be threaded, as best shown in Figure 9, to be secured to the delivery chamber 6 (or aspiration chamber 7) by screwing, prior to engaging the apical portion 17a in the respective bundle tube. of tubes 1. The last solution seems preferred to firmly connect the supply chamber 6 in fluid communication with the tubes of the tube bundle 1, while the first solution seems preferred to connect the supply chamber 6 in fluid communication with the tubes of the tube. tube bundle 1 because the presence of a thread would reduce the span of the tubular outlet 16.

Conveniently, as shown in the figures, there may be a number of supply chambers 6, each with its own tubular inlet, to connect to a supply conduit 4 of the second pressurized fluid. In this way, the number of branches starting from each supply chamber 6 is limited, which can therefore be realized as a standard component with a predetermined number of tubular outlets 16.

All that has been said about the supply chamber can be repeated, mutatis mutandis, for the suction chambers 7, which collect the second fluid exiting the tube bundle before returning it to a compressor at through the return pipe 8.

The shape of the supply chamber 6, as well as the suction chamber 7, can be any, as shown schematically in the profile views of Figures 5a to 5c and in the corresponding semi-transparent perspective views of Figures 6a to 6c, illustrating supply chambers 6 or suction chambers 7 in the shape of a parallelepiped (Figures 5a and 6a), in the form of a hollow cylinder (Figures 5c and 6c), or in the shape of a funnel (Figures 5b and 6b), all provided tubular outlets 16. In the case illustrated in Figures 5b and 6b, the supply chamber 6 (suction chamber 7) will have a conical end for connection with the supply duct 4 (suction duct 8) of the second fluid and a plurality of outlet ports from the enlarged end of the funnel, each outlet port being connectable to a respective tube of the tube bundle through a respective tubular outlet 16.

With a supply chamber 6 and a suction chamber 7 delimited by completely separate walls of the evaporator shell 9 and externally attached to the tubes of the tube bundle, the efficiency of the heat exchange is not penalized. In addition, it is possible to commercialize evaporators at lower costs because it is easier to make them and avoid those construction characteristics that impose higher certification costs.

Claims (11)

1. Tube bundle heat exchanger, comprising: a casing (9) defining a containment volume, said casing (9) having an inlet conduit (10) and an outlet conduit (11) from the containment volume suitable for transporting a first fluid in a liquid state to be cooled or heated, and at least one perforated tube sheet (2) with through holes (3) suitable to allow the tubes (1), of a bundle of tubes, to pass through them in a waterproof manner, a bundle of tubes (1 ), each tube of said bundle of tubes being inserted imperviously through a respective hole of said through holes (3) of the perforated tube sheet (2), a supply chamber (6) of a second fluid under pressure to be heated or cooled with a phase change, defining an inlet opening suitable to be placed in fluid communication with a supply conduit (4) of the second fluid, and a plurality of outlet openings, each of said outlet openings being suitable to be placed in fluid communication with a respective tube of the tubes (1) of the tube bundle, an aspiration chamber (7) of the second fluid, defining a plurality of inlet openings, each of said inlet openings being suitable to be placed in fluid communication with a respective tube of said tubes (1) of the tube bundle, and a drainage opening suitable to be placed in fluid communication with a conduit return (8) of the second fluid, The tubes (1) of said tube bundle are inserted into the through holes (3) of said perforated tube plate (2) and have first ends (12) and second ends (13) that are fixed to the plate of perforated tubes (2) of the shell (9) of the heat exchanger; characterized by what each chamber of said supply chamber (6) and said suction chamber (7) is delimited by respective walls and all said respective walls are distinct and are separated from each other and from said casing (9), so that all walls respective of the supply chamber (6) and of the suction chamber (7) are enveloped by air from the environment in which the heat exchanger is installed; each end of said first ends (12) of the tubes (1) of the tube bundle is fixed in fluid communication and in a non-removable manner to a respective opening of said outlet openings of the supply chamber (6) either by welding strong, or by welding, or by gluing, or by mechanical expansion or by mechanical connection; each end of said second ends (13) of the tubes (1) of the tube bundle is fixed in fluid communication and in a non-removable manner to a respective opening of said inlet opening of the suction chamber (7) either by means of brazing, or by welding, or by gluing, or by mechanical expansion or by mechanical connection. 2. Heat exchanger, according to the preceding claims, comprising a plurality of tubular outlets (16) fixed to the respective openings of said outlet openings of the supply chamber (6), each end of said first ends (12) being of the tubes (1) of the tube bundle fixed directly in a non-removable manner to a respective tubular outlet of said tubular outlets (16) either by brazing, by welding, by gluing, by mechanical expansion or by mechanical connection. Heat exchanger according to one of the preceding claims, comprising at least two identical supply chambers (6), in which each supply chamber (6) is delimited by walls separated by said casing (9) and at a distance thereof, and has a plurality of outflow openings, each fixed and in fluid communication with a respective tube of a subset of the tubes (1) of the tube bundle. Heat exchanger according to one of the preceding claims, wherein the casing (9) comprises a flange (15), wherein said flange (15) is screwed onto a perforated outer surface of the perforated tube sheet ( 2). Heat exchanger according to one of the preceding claims, in which said tubes (1) of the tube bundle are U-bent within the containment volume, enter and exit the containment volume through the same tube sheet perforated and have said first ends (12) and second ends (13) projecting out of the shell (9) of the heat exchanger. Heat exchanger according to claim 5, comprising a separation partition installed inside the casing (9) to define a cooling liquid circulation path, from the inlet conduit (10) to the outlet conduit ( 11), directed countercurrent or with the same direction of current (downcurrent) with respect to a path of circulation of the second pressurized fluid to be heated or cooled with phase transition in the tube bundle (1) from the first ends (12 ) to the second extremes (13). Heat exchanger according to any of claims 1 to 4, wherein said tubes (1) of the tube bundle are straight within the containment volume, enter the tube plate and exit from a perforated wall opposite the tube plate and have said first ends (12) and said second ends (13) projecting out of the shell (9) of the heat exchanger. Heat exchanger according to one of the preceding claims, wherein said perforated tube plate (2) of the shell (9) is integral with the tubes (1) of the tube bundle, and is removably attached to the casing (9) so that it flows to extract the tube bundle (1) from the casing (9). Heat exchanger according to one of the preceding claims, wherein all of said respective walls of said supply chamber (6) and of said suction chamber (7) are at a distance from said housing (9). Heat exchanger according to the preceding claim, in which the tubes (1) of said tube bundle pass through the through holes (3) of said perforated tube plate (2) and have the first ends (12) and the second ends (13) protruding from the perforated tube plate (2) out of the shell (9) of the heat exchanger. 11. Evaporator, comprising a heat exchanger according to one of the preceding claims, wherein said containment volume is filled with a first liquid to be cooled or heated.