Heat Exchanger with a Tube Bundle and Shell with a Flow at the Shell Side with Improved Efficiency

Abstract

There is described a heat exchanger comprising a plurality of tubes arranged parallel with each other in order to form one or more tube bundles axially inserted into a shell. A first fluid, fed through one or more first inlet nozzles flows inside the tubes and a second fluid, fed through at least one second inlet nozzle, flows inside the shell in order to perform the heat exchange with the first fluid through the walls of the tubes. Inside the shell two or more baffles are formed and arranged perpendicularly with respect to the centre axis of the shell. Between each baffle and the inner walls of the shell there is defined a corresponding window constituted by the cross-section for the passage of the second fluid, with a crossing direction parallel with the centre axis of the shell and the tubes, delimited by the free edge of the respective baffle on the one side and by the inner profile of the shell, at the intersection of the shell with the plane of the baffle, on the other side. The cross-section for the passage of the second fluid placed between two adjacent baffles is constant and has a rectangular shape, that is to say, with all the inner angles congruent with each other. Each baffle has a rectangular shape. Each window has a rectangular shape and has no tubes therein.

Claims

1. Heat exchanger comprising a plurality of tubes arranged parallel to each other in order to form one or more tube bundles axially inserted into a body which has an elongated shape and a cylindrical geometry forming the shell of the heat exchanger, a first fluid, fed through one or more first inlet nozzles, placed at a first end of the shell and axially oriented, flowing inside the tubes and a second fluid, fed through at least one second inlet nozzle, flowing inside said shell in order to perform the heat exchange with the first fluid through the walls of the tubes, inside the shell two or more baffles being obtained, arranged perpendicularly with respect to the central axis of said shell, between each baffle and the inner walls of the shell a corresponding window being defined, consisting of the cross-section for the passage of the second fluid, with a crossing direction parallel to the central axis of the shell and to the tubes, delimited by the free edge of the respective baffle on the one side and by the inner profile of the shell, at the intersection of said shell with the plane of said baffle, on the other side, in the heat exchanger the cross-section for the passage of the second fluid placed between two adjacent baffles is constant and has a rectangular shape, i.e. all its inner angles are congruent to each other, each baffle has a rectangular shape, each window has a rectangular shape and has no tubes therein.

2. Heat exchanger according to claim 1, wherein the cross-section for the passage of the second fluid placed between two adjacent baffles has a square shape, i.e. all its inner angles and its four sides are congruent to each other.

3. Heat exchanger according to claim 1, wherein each baffle has a square shape.

4. Heat exchanger according to claim 1, wherein the shell has a rectangular-shaped cross-section at its longitudinal axis.

5. Heat exchanger according to claim 4, wherein the shell has a square-shaped cross-section at its longitudinal axis.

6. Heat exchanger according to claim 1, wherein the shell has a circular-shaped cross-section and is internally provided with longitudinal partitions, said longitudinal partitions forming the walls that surround the windows and the cross-sections for the passage of the second fluid inside the heat exchanger.

7. Heat exchanger according to claim 1, wherein it comprises straight tubes whose opposed open ends are connected with two respective tube plates, said tube plates separating the second fluid from the first fluid.

8. Heat exchanger according to claim 1, wherein it comprises tubes whose open ends are fixed at a same tube plate arranged at an end of the shell, whereas a non-perforated closing bottom is provided at the opposite end of said shell.

9. Heat exchanger according to claim 1, wherein the second inlet nozzle is placed on the side surface of the shell.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIGS. 1A and 1B are cross-sections which show the main components of a heat exchanger with a tube bundle and shell in the configuration with a single passage and in the configuration with multiple passages (double) for the fluid at the tube side, respectively,

[0039] FIGS. 2A, 2B and 2C show respective configurations of heat exchangers with a tube bundle and shell with baffles of the longitudinal type;

[0040] FIG. 3A shows a set of baffles with axial flow through a heat exchanger with a tube bundle and shell;

[0041] FIGS. 3B and 3C show some specific configurations of the axial flow baffles of FIG. 3A;

[0042] FIGS. 4A and 4B show two configurations of the baffles in a heat exchanger with a tube bundle and shell, with tubes in the window and without tubes in the window, respectively;

[0043] FIG. 4C shows a configuration of a baffle with a double segment in a heat exchanger with a tube bundle and shell;

[0044] FIG. 4D shows a configuration of a baffle with a triple segment in a heat exchanger with a tube bundle and shell;

[0045] FIG. 4E shows a configuration of a baffle with a disk and perforated disk in a heat exchanger with a tube bundle and shell;

[0046] FIG. 5A shows a heat exchanger with a tube bundle and shell in a configuration with three circuits for the fluid at the shell side;

[0047] FIG. 5B shows a heat exchanger with a tube bundle and shell in a configuration with four circuits for the fluid at the shell side;

[0048] FIG. 6 shows a heat exchanger with a tube bundle and shell in another configuration with three circuits for the fluid at the shell side, without tubes in the window;

[0049] FIG. 7 shows a heat exchanger with a tube bundle and shell in another configuration with four circuits for the fluid at the shell side, without tubes in the window;

[0050] FIG. 8 shows a heat exchanger with a tube bundle and shell in another configuration with three circuits for the fluid at the shell side, with tubes in the window;

[0051] FIG. 9A is a perspective view of a first type of heat exchanger with a tube bundle and shell according to the prior art;

[0052] FIG. 9B shows a qualitative profile of the component in cross-flow of the speed vector of the fluid at the shell side, obtained in the region of the cross-section A and the cross-section B of FIG. 9A, respectively;

[0053] FIG. 10A is a perspective view of another type of heat exchanger with a tube bundle and shell according to the prior art;

[0054] FIG. 10B shows a qualitative profile of the component in cross-flow of the speed vector of the fluid at the shell side, obtained in the region of the cross-section A and the cross-section B of FIG. 10A, respectively;

[0055] FIG. 11A is a perspective view of a heat exchanger with a tube bundle and shell according to the present invention;

[0056] FIG. 11B shows a qualitative profile of the component in cross-flow of the speed vector of the fluid at the shell side, obtained in the region of the cross-section A and the cross-section B of FIG. 11A, respectively;

[0057] FIG. 12 is a cross-section of a first embodiment of the heat exchanger with a tube bundle and shell according to the present invention, with a shell having a square cross-section;

[0058] FIG. 13 is a cross-section of a second embodiment of the heat exchanger with a tube bundle and shell according to the present invention, with a shell having a rectangular cross-section;

[0059] FIG. 14 is a cross-section of a third embodiment of the heat exchanger with a tube bundle and shell according to the present invention, with a shell having a circular cross-section and a square baffle; and

[0060] FIG. 15 is a cross-section of a fourth embodiment of the heat exchanger with a tube bundle and shell according to the present invention, with a shell having a circular cross-section and a rectangular baffle.

DETAILED DESCRIPTION OF THE INVENTION

[0061] It should be noted that, in the appended Figures and in the following description, identical reference numerals indicate mutually identical or equivalent elements.

[0062] With particular reference to FIGS. 11A to 15, there are shown some preferred embodiments of the heat exchanger with a tube bundle and shell according to the present invention, which heat exchanger is generally designated 10. The heat exchanger 10 comprises in a manner known per se a plurality of tubes 12 which are arranged parallel with each other in order to form one or more tube bundles. The tubes 12 are inserted axially into a member 14 which is of elongate form and which has a cylindrical geometry and which constitutes the shell of the heat exchanger 10. In the present specification, the term member having a cylindrical geometry is intended to be understood to be the locus of the generating lines parallel with a predefined direction and passing through the single points of a predetermined directrix curve and which is delimited by two opposing bases which are substantially parallel with the directrix. The directrix, which is always a closed line, may be, for example, a square (FIG. 12), a rectangle (FIG. 13), a circle (FIGS. 14 and 15), or may generally be in the form of any polygon.

[0063] A first fluid, fed through one or more first inlet nozzles 16, placed at a first end of the shell 14 and axially orientated, is capable of flowing inside the tubes 12 of the tube bundle and is discharged via a first discharge nozzle 26, positioned in the region of the opposite end of the shell 14 and also axially orientated. A second fluid, fed through at least one second inlet nozzle 28, typically positioned on the side surface of the shell 14, instead flows inside the shell 14 itself and flows over the outer walls of the tubes 12. The second fluid is discharged via a second discharge nozzle 32, also positioned on the side surface of the shell 14. Therefore, the heat exchange between the first fluid and the second fluid is brought about via the walls of the tubes 12.

[0064] In the configuration which has a single passage for the fluid at the tube side and which is shown in FIG. 1A, the opposite ends of the tubes 12 of the tube bundle are connected to two tube plates 34 which are positioned in the region of the first inlet nozzle 16 at one side and the first outlet nozzle 26 at the other side. The tube plates 34 allow separation of the second fluid at the shell side, that is to say, the fluid which flows inside the shell 14, from the first fluid at the tube side, that is to say, the fluid which flows inside the tubes 12 of the tube bundle.

[0065] In the configuration which has a double passage for the fluid at the tube side and which is shown in FIG. 1B, however, it is possible to use tubes 12 which are U-shaped or with a different suitable geometry, wherein the open ends of each tube 12 are fixed to the same tube plate 34 which is arranged in the region of an end of the shell 14, while in the region of the opposite end of this shell 14 there is provided a closure base 42 which is not perforated.

[0066] Apart from the configuration of the heat exchanger 10, there are formed inside the shell 14 two or more baffles 30 which are arranged perpendicularly with respect to the centre axis of the shell 14 itself. There is defined between each baffle 30 and the inner walls of the shell 14 a corresponding window 36 which is constituted by the cross-section for the passage of the second fluid, with a crossing direction parallel with the centre axis of the shell 14 and the tubes 12, delimited by the free edge 38 of the respective baffle 30 on the one side and by the inner profile of the shell 14, at the intersection of this shell 14 with the plane of the baffle 30 itself, on the other side.

[0067] According to the invention, the cross-section for the passage of the second fluid which is positioned between two adjacent baffles 30 is constant and has a rectangular shape, that is to say, with all the inner angles congruent with each other. In particular, the cross-section for the passage of the second fluid which is positioned between two adjacent baffles 30 may have a square shape, that is to say, both with all the inner angles and with the four sides congruent with each other. In addition, each baffle 30 also has a rectangular shape or more particularly a square shape. Finally, each window 36 also has a rectangular shape and does not have any tubes 12 therein.

[0068] The above-mentioned configurations may be constructed by using a shell 14 with a cross-section, at its own longitudinal axis, of square shape (FIG. 12) or of rectangular shape (FIG. 13), or by using suitable longitudinal partitions 40 which are positioned inside a shell 14 with a cross-section having a circular shape (FIGS. 14 and 15). In this last case, the longitudinal partitions 40 form the walls that surround the windows 36 and generally the cross-sections for the passage of the second fluid inside the heat exchanger 10.

[0069] It has thereby been seen that the heat exchanger with a tube bundle and shell according to the present invention achieves the objectives set out above. Using the configuration to which the invention relates, the flow of fluid at the shell side will be confined to the heat exchanger with the tube bundle via cross-sections of passage having a constant area for each crossing between two adjacent baffles, thereby benefitting from a greater uniformity including along the axis which is orthogonal to the direction of flow during the crossing in cross-flow, as a result of the use of windows with a geometry with double symmetry, which are rectangular or square, without tubes extending therein.

[0070] With respect to the heat exchangers of the known type, with a cylindrical shell having a circular directrix curve with plate baffles with a single segment and with or without tubes in the window, the heat exchanger with a tube bundle and shell according to the present invention allows the following advantages to be achieved:

[0071] greater heat exchange efficiency and consequently a reduction in the exchange surface necessary;

[0072] homogeneous/uniform operation of all the tubes, with resultant greater stability during control in applications with a refrigerating cycle;

[0073] greater heat exchange efficiency in applications with a multi-circuit (more than two circuits) at the tube side both at full charge (that is to say, with all the circuits active) and at partial charge (for example, with a single active circuit).

[0074] Those advantages are achieved as a result of:

[0075] constant geometry of the cross-sections of passage of the tube bundle in cross-flow of the fluid between two adjacent baffles (see FIG. 11A);

[0076] geometry with double symmetry (rectangular or square) of the window of the baffle, without tubes extending therein, which allows greater uniformity of heat exchange (better redistribution of the fluid after crossing through the window) including along the axis which is orthogonal to the direction of flow during the crossing in cross-flow (see FIG. 11B);

[0077] identical geometry and identical conditions of heat exchange for each circuit, with consequent homogeneous/uniform operation of all the tubes of the active circuits;

[0078] geometry of each circuit which allows the use of connections for the refrigerating fluid having optimized dimensions in order to reduce the pressure drops.

The heat exchanger with a tube bundle and shell configured in this manner is capable in any case of a number of modifications and variants, all included within the same innovative concept; furthermore, all the details can be replaced with technically equivalent elements. In practice, the materials used as well as the forms and the dimensions may be freely selected in accordance with the technical requirements.

[0079] The scope of teaching of the invention is therefore defined by the appended claims.