GB2312276A

GB2312276A - Vortex flow inducer

Info

Publication number: GB2312276A
Application number: GB9607935A
Authority: GB
Inventors: Stephen James Morris
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-04-17
Filing date: 1996-04-17
Publication date: 1997-10-22
Anticipated expiration: 2016-04-17
Also published as: GB9607935D0; GB2312276B

Abstract

A vortex flow inducer comprises a body 1 which is either a cylindrical tube, a tapered tube or comprises a combination of a cylindrical tube portion and a tapered tube portion. A helical projection 2 on the body inner surface induces vortex flow in a fluid passing from an inlet 3 to an outlet 4. The projection may be single or multi start may divide or merge may be of varying cross-section and may split or cease and then continue. The projections 2 may not extend from the inlet to the outlet but may cease at a diameter which corresponds to the size of a cleaning component. The inducer is located in use at the inlet to a heat exchange tube.

Description

VORTEX FLOW INDUCER 7 A vortex flow inducer comprises of a member (1) which can be either cylindrical tube or a taper tube shaped or comprise of both a cylindrical and tapered section together. There is a helical projection on the inner surface of the member (2). This helical projection can lead from a peripheral flow inlet arrangement (3) to a central outlet arrangement (4) at which the fluid can exhaust through an outlet (4).

The helical projection may also be single or multi-start, may divide or merge, may be of varying cross-section along its length, may split or cease and then continue in a different orientation and/or geometry along the axial length of the member.

The helical projection may extend radially inwards and cease axially at a diameter d to reveal a bore hole extending along the entire length of the member. Alternatively, the helical projection may extend radially inwards fully so as to meet at the axial centre-line of the member. The included angle ff of the tapered faces on the tapered member and/or section may vary but is preferably in excess of 0 and no greater than 1800.

The invention relates to a vortex flow inducer.

X,} In conventional surface heat exchangers, where single phase turbulent forced convection occurs, heat transfer is generally limited by the tube-side heat transfer coefficient. This often contributes the largest thermal resistance. Any mechanism which increases this component of the heat transfer would therefore be expected to be of primary benefit towards the enhancement of the overall thermal efficiency performance of the heat exchanger.

The heat transfer coefficient can be increased by promoting more vigorous mixing and turbulent flow within the tube-side fluid particularly at the heat transfer boundary layer. A vortex flow motion represents a favourable form of turbulence as it is effective in enhancing convective heat transfer.

Mechanical methods of inducing a vortex flow motion in a fluid being conveyed axially along the tube-side of a heat exchanger have been known for years and generally comprise of either of the following : i) A helical coiled wire inserted internally in a plain tube so that its outer surface is positioned against the bore inner surface of the tube.

ii) A helically corrugated groove in the bore inner surface of the tube which is usually formed during manufacture.

Both of the above helical forms may be of vary varied construction, for example, the wire or grqove may run-out to nothing or may extend axially fully or partly.

The enhancement in heat transfer is primary attributed to the 'swirl' flow motion and secondary to the centrifugal convection effect, both of which are indued by the helical projection.

Fluid entering the tube is acted upon by the presence of the tube-side helical form which begins to induce a vortex 'swirl' flow motion upon the fluid. At a point downstream of the tube inlet the vortex motion becomes fully developed and is typically proportional to the helical form. Only at this downstream point is the tube experiencing an enhanced heat transfer coefficient.

The axial distance along the tube at which this point occurs and the inducement of the 'swirl' flow motion is dependent upon fluid characteristics, fluid entry dynamics, heat exchanger design and helical form geometry.

Generally, all previous proposed vortex inducers have taken the form of an internal tube-side helical groove which is an ptegral part of the heat exchanger tube. All previous vortex Ainducers can increase the drag characteristics of the tube-side fluid, particularly for turbulent flows, and also result in increased surface fouling both of which are detrimental to heat transfer performance. Generally, it may not be functionally possible to employ an in-service mechanical tube-side cleaning system (where tube walls are wiped clean by the action of a component having frictional contact) in conjunction with all previous vortex inducers.

According to the invention a vortex flow inducer comprises of a member which can be either a cylindrical tube or tapered tube shaped or comprise of both a cylindrical and tapered tube section together having a helical projection on the inner surface. The member is located inside the fluid inlet section of the heat exchanger. The inlet arrangement (3) faces towards the fluid inlet section whilst the outlet arrangement (4) locates adjacent to the tube inlet end and on the same axial plane.

Conveying fluid presented at the inlet position of a member is induced into a vortex 'swirl' motion by the presence of the helical projection and exhausts from the outlet in a fully developed helical vortex motion. Hence, the fluid flow delivered at the inlet to the heat exchanger tube is in a state of fully developed helical motion.

The function of the vortex flow inducer is to deliver a fully developed helical motion upon the fluid at the inlet of a heat exchanger tube which ideally is sustainable along the total axial length of the tube. Hence, an enhanced heat transfer coefficient is achieved along the total length of the tube. The geometry of the vortex flow inducer member may vary depending upon fluid characteristics and flow dynamics, heat exchanger design and/or operation and the type of in-service mechanical tube-side cleaning process employed.

Vortex flow inducer members can be located individually at the tube inlet. Alternatively, several members can be coupled together in a configuration which corresponds with all or part of the total heat exchanger tube nets arrangement geometry as show on Fig.25/26, Fig.27/28, Fig.29/30 and Fig.31/32. The respective radial gaps (40),(41),(42) and (43) resulting from such coupling together of the members may be solidly enclosed so that several members can be manufactured into one component.

A vortex flow inducer according to the invention can establish fully developed helical flow moron upon the fluid at the inlet to a heat exchanger tube. The resultant centrifugal force acting on the fluid by the vortex flow motion will have the combined natural effect of transporting the lower temperature (high density) fluid particles radially outwards towards the tube periphery heat transfer boundary layer and higher temperature (lower density) particles radially inwards towards the tube centre axis. This process would ideally be sustainable throughout the length of the tube thus enhancing the heat transfer process and resulting in greater efficiency heat exchangers.

The helical flow motion induced in the fluid by the vortex flow inducer may also help to provide a high level of tube-side cleanliness by preventing foreign body accumulation. Hence, reducing heat transfer resistance and maintaining optimum heat exchanger efficiency.

The presence of the vortex flow inducer and the resultant helical flow produced at the tube inlet may reduce entry losses within the fluid, ie/. reduce vina-contractor effect and eddy formation, and hence may improve flow dynamic efficiency and may reac material degradation at the tube inlet.

The invention is diagrammatically illustrated by way of example in accompanying drawings in which :- J Figures 1 and 4 are respectively a sectional view through a first embodiment of a cylindrical vortex flow inducer according to the invention and a plan view of one component thereof Figures 2 and 5 are respectively a sectional view through a first embodiment of a vortex flow inducer comprising of both a cylindrical and tapered section according to the invention and a plan view of one component thereof Figures 3 and 6 are respectively a sectional view through a first embodiment of a tapered vortex flow inducer according to the invention and a plan view of one component thereof ; Figures 7 and 8 are views corresponding to Figures 4 and 1 respectively of a second embodiment of a cylindrical vortex flow inducer according to the invention Figures 9 and 10 are views corresponding to Figures 4 and 1 respectively of a third embodiment of a cylindrical vortex flow inducer according to the invention Figures 11 and 12 are views corresponding to Figures 4 and 1 respectively of a fourth embodiment of a cylindrical vortex flow inducer according to the invention ; 7 Figures 13 and 14 are views corresponding to Figures 5 and 2 respectively of a second embodiment of a cylindrical/tapered vortex flow inducer according to the invention Figures 15 and 16 are views corresponding to Figures 5 and 2 respectively of a third embodiment of a cylindrical/tapered vortex flow inducer according to the invention Figures 17 and 18 are views corresponding to Figures 5 and 2 respectively of a fourth embodiment of a cylindrical/tapered vortex flow inducer according to the invention Figures 19 and 20 are views corresponding to Figures 4 and 1 respectively of a first embodiment of a cylindrical vortex flow inducer in which the helical projection extends radially inwards fully according to the invention Figures 21 and 22 are views corresponding to Figures 5 and 2 respectively of a first embodiment of a cylindrical/tapered .vortex flow inducer in which the helical projection extends radially inwards fully according to the invention ; D Figures 23 and 24 are views corresponding to Figures 6 and 3 respectively of a first embodiment of a tapered vortex flow inducer in which the helical projection extends radially inwards fully according too the invention Figures 25 and 26 are respectively a part sectional view showing the location details of typical cylindrical/tapered vortex flow inducers in relationship to a square heat exchanger tube configuration and a plan view on the inlet tube plate and the components thereof according to the invention ; Figures 27 and 28 are respectively a part sectional view showing the location details of typical cylindrical/tapered vortex flow inducers in relationship to a diagonal heat exchanger tube configuration and a plan view on the tube plate and the components thereof according to the invention Figures 29 and 30 are respectively a part sectional view showing the location details of typical cylindrical vortex flow inducers in relationship to a square heat exchanger tube configuration and a plan view on the tube plate and the components thereof according to the invention; Figures 31 and 32 are respectively a part sectional view showing the location details of typical cylindrical vortex flow inducers in relationship to a diagonal heat exchanger tube configuration and a plan view on the tube plate and the components thereof Referring to the drawings and firstly to Figures 1, 2 and 3.

A vortex flow inducer comprises of a single member (1) which can be either cylindrical tube or conical tube shaped. Fluid enters the vortex flow inducer via the inlet position (3) and is exhausted through the central outlet position (4). Fluid flows through the vortex flow inducer about a central axis (5). A helical projection (2) is present on the inner surface of the vortex flow inducer and may extend from the inlet position to the central outlet position.

The vortex flow inducer is of a tube-like form having an outer diameter a and an inner diameter positioned centrally about a centre-line (5). The inner diameter 8 corresponds to the inner diameter of the heat exchanger tube. The vortex inducer member (1) has an inlet (3) and outlet (4) sections and an internal helical projection (2). The internal diameter d at which the helical projection may cease corresponds with the size of any appropriate cleaning process component which may be employed.

The cylindrical shaped vortex flow inducer has a constant form intending axially throughout its length. The cylindrical/tapered taped vortex inducer comprises of an outer tapered tube portion (6) having an included angle d and an inner bore tube portion (7), with the junction (8) of both having radii. The relative proportions of both the conical portion (6) and bore portion (7) may vary. The included angle ff of the conical portion (6) may vary but is preferably in excess of 0 and no greater than 1800.

The shape of the vortex flow inducer and the geometry of the helical projection can be varied to suit the particular heat exchanger design for which it is intended, the type of in-service cleaning mechanism employed and the heat transfer fluid characteristics.

The embodiment of Figures 7 and 8 show a cylindrical shaped vortex flow inducer very similar to that of Figures 4 and 1 respectively but with a different helical projection. Figures 7 and 8 detail a two-start projection (9) and (10) each developed through 1800.

The embodiment of Figures 9 and 10 show a cylindrical shaped vortex flow inducer very similar to that of Figures 4 and 1 respectively but with a different helical projection. Figures 7 and 8 detail a four-start projection (11), (12), (13) and (14) each developed through 1800. The embodiment of Figures 11 and 12 show a cylindrical shaped vortex flow inducer very similar to that of Figures 3 and 1 respectively and having the same helical four-start projection (15), (16), (17) and (18) as detailed in Figures 9 and 10 but shown in a different orientation.

The embodiment of Figures 13 and 14 show a cylindrical /tapered vortex flow inducer very similar to that of Figures 5 and 2 respectively but with a different helical projection.

Figures 11 and 12 detail a two-start projection (19) and (20) each developed through 1800 and terminating at the junction of the conical and inner bore tube portions 21) thus resulting in a plain inner bore tube portion.

The embodiment of Figures 15 and 16 show a cylindrical /tapered vortex flow inducer very similar to that of Figures 5 and 2 respectively but with a different helical projection.

Figures 15 and 16 detail a four-start projection (22), (23), (24) and (25) each developed through 900 and terminating part way along the tapered tube portion. The embodiment of Figures 17 and 18 show a tapered inducer similar to that of Figures 4 and 2 respectively and having the same four-start projection (26), (27), (28) and (29) as detailed in Figures 15 and 16 but shown in different orientation.

The embodiment of Figures 19 and 20 show a cylindrical vortex flow inducer very similar to that of Figures 4 and 1 gspectively but having helical projections (30) and (31) which ,tends fully inwards.

The embodiment of Figures 21 and 22 show a cylindrical /tapered vortex flow inducer very similar to that of Figures 5 and 2 respectively but having helical projections (32) and (33) which extend fully inwards.

The embodiment of Figures 23 and 24 show a tapered vortex flow inducer very similar to that of Figures 3 and 6 respectively but having helical projections (34) and (35) which extend fully inwards.

Figure 25 and 26 are sectional assembly view showing location details of typical vortex flow inducers with respect to the heat exchanger tube (36) and tube-plate (37). The vortex flow inducer is located perpendicular to and up against the tube-plate so that its centre-line (38) corresponds to the tube centre-line (39).

Figures 25 and 26 are respectively a sectional view through an embodiment of an arrangement of cylindrical/tapered vortex flow inducers according to the invention showing coupling details when located on a square pitched heat exchanger tube-plate and a plan view of the components thereof. The radial gaps (40) may be solidly enclosed Figures 27 and 28 show a cylindrical vortex inducer very similar to that of Figures 25 and 26 respectively.

The radial gaps (41) may be solidly enclosed. Similar 7 arrangements of vortex flow inducer coupling details located on a square and diagonal pitched heat exchanger tube-plate are shown on Figures 29/30 and Figures 31/32. The radial gaps (42) and (43) may be solidly enclosed.

A vortex flow inducer according to the invention can provide an enhanced tube-side heat transfer coeffqcient within heat exchangers whether they are used on plain tubes or to complement helical grooved tubes. This is achievable by the inducement of a suitably developed helical vortex flow upon the inlet fluid which is sustainable along the total length of the tube. Therefore, the overall heat transfer process is also enhanced resulting in improved efficiency performance heat exchangers. The vortex flow inducer promotes improved flow dynamic efficiency at the tube inlet area and provides improved tube-side cleanliness. The vortex flow inducer is designed to be used in conjunction with and is more accommodating towards the use of in-service mechanical tube-side cleaning systems than previously proposed inducer methods. The vortex flow inducer is more versatile than previously proposed inducer methods as it can be conveniently located into existing heat exchangers without requiring significant modification to then.

Claims

A vortex flow inducer comprises of a member which can be either constant cylindrical or tapered shaped or comprise of both a cylindrical and tapered section together with a helical projection on the inner surface of the member, an peripheral fluid inlet arrangement and a central outlet arrangement from which the fluid can exhaust.

2. A vortex flow inducer, according to claim 1, in which the helical projection may extend radially inwards and cease axially at a diameter to reveal a bore hole extending along the entire length of the member. Alternatively, the helical projection may extend radially inwards fully so as to meet at the centre-line of the member.

3. A vortex flow inducer, according to claims 1 and 2, in which the helical projection is generally provided as a scroll and can be single or multi-start, can divide or merge, can vary in cross-section between the peripheral inlet and central outer arrangements, can split or cease and then continue in a different orientation and/or geometry along the axial length of the member.

4. A vortex flow inducer, according to any one of the proceeding claims, in which the included angle of the tapered section of the member is in excess of OC and no greater than 180.

6 5. A vortex flow inducer, according to any one of the proceeding claims, which can be located individually inside the fluid inlet section of a heat exchanger with the peripheral inlet arrangement facing into the fluid inlet section whilst the central outlet arrangement locates adjacent to the tube inlet end and on the same axial plane. Alternatively, several members can be coupled together in a configuration which corresponds with all or part of the heat exchanger tube nest atrangement geometry.

6. A vortex flow inducer, according to any one of the proceeding claims, in which the shape and geometry can vary to suat the particular heat exchanger design for which it is being intended, the type of in-service cleaning service employed, the heat transfer fluid characteristics and dynamics and the operational/ environmental parameters which exist.