AU710808B3

AU710808B3 - Improvements in tubular heat exchangers

Info

Publication number: AU710808B3
Application number: AU32336/99A
Authority: AU
Inventors: Alan Paul Baker
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-06-01
Filing date: 1999-05-31
Publication date: 1999-09-30
Anticipated expiration: 2005-05-31

Description

AUSTRALIA

Patents Act 1990 Alan Paul Baker

ORIGINAL

COMPLETE SPECIFICATION PETTY PATENT Invention Title: Improvements in tubular heat exchangers The following statement is a full description of this invention including the best method of performing it known to us:- Field of the Invention This invention relates to tubular heat exchangers also known as tube in tube or pipe in pipe, mono-tubular heat exchangers.

Background of the Invention With reference to Figure 1 of the accompanying drawings, traditional tube-in-tube, or pipe-in-pipe heat exchangers include an inner tube or pipe 1 and an outer tube or pipe 2 which forms a jacket around the inner tube.

Primary fluid flow which is normally a fluid or slurry which is to be heated or cooled passes along the inner tube. Secondary fluid flow passes along the annular space 3 between the outer tube or jacket and the outside of the inner tube in the opposite or the same direction to the direction of the primary flow.

Conventionally, these simple tube-in-tube tubular heat exchangers are grouped together to form a multiple assembly such as is illustrated in Figure 1. U-shaped tubes 4 are welded or union connected between the ends of the primary fluid pipes of two adjacent elongate heat exchanger tubes to define a primary fluid flow path. The jackets of each tube define T pieces 5 at each end of the jacket which are then interconnected by short lengths of pipe 6 so that the interconnected jackets define the secondary flow path.

The structure of such an assembly has the advantage that it can be quite compact, can be effectively insulated, if desired, and may even be mounted on a trolley or the like for portability. Typical uses of such monotubular heat exchangers include wine and must cooling, steam/water heating, heat recovery from industrial effluent, yoghurt pasteurisation, pet food and meat processing, pyrogen free water systems and fruit juice and pulp processing. However, the existing assembly and tube design has a number of disadvantages. Such heat exchangers are quite time consuming to assemble.

Experience is required to calculate the correct length and size of the heat exchanger tubing for the required application and after the heat exchanger has been assembled, and if desired, insulated, it is difficult to adjust the performance of the heat exchanger since the structure of the heat exchanger is fixed.

It is thus an object of the present invention to provide an improved tubular heat exchanger.

Summary of the Invention In a broad aspect, the present invention provides an end module which allows the introduction of two distinct flow paths to the tubes in a tubular heat exchanger whilst allowing a modular grouping of a plurality of the tubes to form two continuous flow paths in the tubular heat exchanger with any number of tubes in the assembly.

In particular, the invention provides an end fitting for use in a modular tubular heat exchanger including an inner tube defining a part of a primary flow path of the heat exchanger disposed inside an outer tube with a part of a secondary, generally annular, flow path of the heat exchanger being defined between the inner and outer tubes, said end fitting being adapted to receive an inner tube and the end of an outer tube of the heat exchanger and defining: a front wall having a first hole therein which is sized to fit around or butt weld to the exterior of a section of outer tube of the tubular heat exchanger; an exterior wall extending at least part way round the perimeter of the front wall, the exterior wall having an aperture therein; a secondary wall disposed behind the front wall in which defines a second hole which is sized to allow the inner tube only of the tubular heat exchanger to pass through; and walls extending between the secondary wall and the front wall of the closure and to also to the aperture in the exterior wall of the end fitting so as to define a closed passage which defines a flow path for fluid from the secondary flow path into the end fitting and thence to the aperture in the exterior wall, said secondary flow path being entirely distinct and separate from the primary flow path along the inner tube, the module being connectable to an adjacent similar module with the aperture of the module being in fluid communication with an aperture in an exterior wall of the adjacent module.

In a preferred feature of the invention the end fitting includes a front wall having a hole therein which is sized to fit around or butt weld to the exterior of a section of outer tube of the tubular heat exchanger; a secondary wall disposed behind the front face in which there is a hole which is sized to allow the inner tube only of the tubular heat exchanger to pass through; side walls extending between the secondary wall and the front of the closure and to also to an aperture in the exterior of the end fitting so as to define a flow path for fluid from the secondary or annular flow path into the end fitting and thus to the aperture in exterior of the end fitting said secondary flow path being entirely distinct and separate from the primary flow path along the inner tube.

The invention also provides a modular tubular heat exchanger assembly for tubular heat exchangers including a plurality of end fittings and a plurality of tubular heat exchanger sections each comprising an inner tube and an outer tube defining a substantially annular flow path therebetween, wherein an aperture in the exterior of one end fitting is connected to an aperture of an adjacent end fitting, to join the secondary flow paths of adjacent heat exchanger sections and wherein the inner pipes of adjacent tubular heat exchanger section are connected by curved pipes or the like, externally of the fitting.

In a particular embodiment the invention provides an end module adapted to sealingly receive the ends of both an inner tube and outer jacket, the end piece defining a flow path for fluid in the annular jacket separate from the flow path from the fluid in the inner primary tube which flow path flows from the outer jacket to the exterior of the end closure.

The end module may be a stainless steel or other alloy casting.

In the finished assembly, the primary fluid path of the inner tubes can be connected by C or U shaped pipes located at the end of each closure.

In one particular embodiment, the enclosure is a stainless steel casting, which defines a generally square front face and a circular hole therein which is sized to fit around or butt weld to the exterior of a section of tubular heat exchanger. Behind the front face, a secondary wall is defined in which there is a hole which is sized to allow the inner tube only of the tubular heat exchanger to pass through. Walls extend between the secondary wall and the front of the closure and to one of the four sides of the end closure so as to define a flow path for the secondary fluid into the end closure and to a aperture in the wall of the end closure being a flow path distinct from that of the flow in the primary tube.

The invention allows for the insertion of both primary or inner tube and an outer jacketing tube to a casting or module embodying the present invention and in which the inner tube and the jacket can be either welded or sealed with O-ring type seals to the casting, thus producing distinct and separate flow paths for the primary fluid and secondary fluid. A tubular heat exchanger section with castings at both ends can be bolted to an adjacent annular tube with similar castings at both ends, with the apertures superposed such that the secondary fluid flow is along one jacket into a casting through the aperture of the first casting into the second casting from the casting along the annulus of the second tubular heat exchanger section and so on.

The invention allows a modular grouping of a plurality of tubes to form a heat exchanger with any number of tubes. If a heat exchango duty is varied or increased in service conditions from the original design selection, it then becomes a simple matter to add on additional modules as required so that the required length of tube is provided to perform a specific heat exchange duty.

Brief Description of the Drawings A specific embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a schematic view of a prior art tubular heat exchanger; Figure 2 is a an exploded view of a tubular heat exchanger assembly embodying the present invention; and Figure 3 is a schematic section through clip on insulation and cladding for the assembly of Figure 2.

Detailed Description of a Preferred Embodiment Figure 2 of the drawings shows a mono tubular heat exchanger including end fittings or modular end closures generally indicated at 10. A series of inner tubes 12 and outer tubes 14 are inserted in end fittings 16.

The end fittings are stainless steel or alloy castings. Each fitting 16 includes a front face 18 which is generally square and defines a central circular aperture 20 which is marginally larger in diameter than the diameter of the outer tube 14. Four side walls extend away from the front face 18. One of those sides 22 defines a elongate aperture or entry discharge port 24 and two bolt holes 26 one either side of the aperture 24. The other three sides 28 each define a single centrally located bolthole Behind the front face 18, there is an end wall 34 which defines an aperture 36 which is narrower than the diameter of the outer tube 2 and marginally larger than the diameter of the inner tube 12. Thus the inner tube 12 will pass through the aperture 9 but not the outer tube 14. The wall 34 extends from the centre of the casting to side 24 of the end fitting and includes a depending wall 38 which extends to the rear of the front face 18 so as to provide a secondary fluid flow path from the annular gap between tubes 12 and 14 and the aperture 24 in the side of the end fitting. The size of the aperture 24 ensures that there is no possibility of the fluid being retained in the annuli should the secondary fluid flow path need to be emptied.

The ends of the inner tubes 12 are connected with curved C-shaped tubes 40 together with traditional unions of flanges. Tubes 12 and 14 and the casting 16 can either be welded together or sealed with O-ring seals in order to provide distinct separate and integral fluid paths for the (primary) product flow D and the (secondary) service fluid flow E.

The fact that the end fitting is square in cross section enables each end closure to be bolted together with bolts and nuts through the exposed boltholes 26 and 30 on any of the four walls so that the apertures 24 which can either act entry or discharge ports align for securing and sealing with a gasket 42 to form an assembled tubular heat exchanger of whatever size is desired without constraint. A fitting 44 is provided to attach to the entry port and exit port of the assembled heat exchanger for connecting a tubular supply pipe thereto. Fitting 44 can be removed when further modules are added and refitted to the last added module.

Optional clip on insulation 60 and cladding 62 (illustrated schematically in Figure 3) which will typically be formed from two identical halves which combined have a square outside section the same size as the end module and define a central tubular aperture of the same diameter as the outer tube 16 may be attached between two end faces 18 of opposed end modules.

The casting can be made in a variety of sizes to accommodate tubes typically ranging from 25mm to 200mm diameter.

One particular advantage of the modular construction of the present invention, is that in contrast with existing heat exchangers, if the duty of this type of heat exchanger is increased or decreased from the original selection, a resupply is often needed whereas with this invention it is a simple matter to vary the performance of the exchanger by adding further sections of pipe and end modules. They can simply be bolted on retrospectively. This would have been difficult with existing heat exchangers of the type illustrated in Figure 1.

The end castings provide total integrity for both fluid flow path D and E and do not allow the fluids to intermingle.

In the above described embodiment, all of the components are made from stainless steel or steel alloys. However, the particular material used in the modular heat exchanger is not critical providing it has the requisite performance characteristics. Other metals or materials having the requisite mechanical and other properties could be used.

m 7 Although the above described embodiment shows generally cylindrical tubes the terms tubular and tube as used herein are not restricted to tubes having a particular cross section or even to tube having a constant crosssection.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. An end fitting for use in a modular tubular heat exchanger including an inner tube defining a part of a primary flow path of the heat exchanger disposed inside an outer tube with a part of a secondary, generally annular, flow path of the heat exchanger being defined between the inner and outer tubes, said end fitting being adapted to receive an inner tube and the end of an outer tube of the heat exchanger and defining: a front wall having a first hole therein which is sized to fit around or butt weld to the exterior of a section of outer tube of the tubular heat exchanger; an exterior wall extending at least part way round the perimeter of the front wall, the exterior wall having an aperture therein; a secondary wall disposed behind the front wall in which defines a second hole which is sized to allow the inner tube only of the tubular heat exchanger to pass through; and walls extending between the secondary wall and the front wall of the closure and to also to the aperture in the exterior wall of the end fitting so as to define a closed passage which defines a flow path for fluid from the secondary flow path into the end fitting and thence to the aperture in the exterior wall, said secondary flow path being entirely distinct and separate from the primary flow path along the inner tube, the module being connectable to an adjacent similar module with the aperture of the module being in fluid communication with an aperture in an exterior wall of the adjacent module.

2. An end fitting as claimed in claim 1 characterised in that the front face of the end fitting is generally square and in that the exterior wall extends around the perimeter of the square front face and includes means for bolting or otherwise fixing the end module to the adjacent end module. F-i -x

3. A modular tubular heat exchanger assembly for tubular heat exchangers including a plurality of end fittings as claimed in claim 1 or claim 2, and a plurality of tubular heat exchanger sections each comprising an inner tube and an outer tube defining a substantially annular flow path therebetween, wherein an aperture in the exterior of one end fitting is connected to an aperture of an adjacent end fitting, to join the secondary flow paths of adjacent heat exchanger sections and wherein the inner pipes of adjacent tubular heat exchanger section are connected by curved pipes or the like, externally of the fitting, the arrangement being such as to allow any number or grouping of heat exchanger sections grouped so as to perform a specific heat exchanger duty. Dated this ninth day of August 1999 Alan Paul Baker Patent Attorneys for the Applicant: F B RICE CO