GB2404727A

GB2404727A - Heat exchanger

Info

Publication number: GB2404727A
Application number: GB0318360A
Authority: GB
Inventors: Tak Ming William Tsui
Original assignee: Falmer Investments Ltd
Current assignee: Falmer Investments Ltd
Priority date: 2003-08-05
Filing date: 2003-08-05
Publication date: 2005-02-09
Anticipated expiration: 2023-08-05
Also published as: CN1580682A; HK1072290A1; GB2404727B; GB0318360D0

Abstract

A heat exchanger 1 comprises concentric primary 3 and secondary 8 heat exchange units in fluid communication. Primary unit 3 may comprises a tube 15 which may receive dye liquor from a textile processing machine through a tapered inlet 2 and passes through a conical filter 10 to an outlet end 16. The dye liquor may then be guided by a toroidal shaped reversal device 4 so that it reverses back on itself and enters the secondary unit 8, which may comprise a plurality of tubes 6 and an outer passage 5, and exits via an elbow 9. Heat exchange fluid, which maybe steam or oil, enters the heat exchanger 1 via an inlet 11 and flows though a passage 18 between the tube 15 and a concentric tube 17 of the secondary unit 8, flows around the tubes 6 and exits via an outlet 12. Tube 15 and tubes 6 may have any suitable cross sectional shape, and tubes 6 may themselves have the same or different cross sectional area.

Description

HEAT EXCHANGER The present invention relates to heat exchangers, in particular, although not exclusively for use in the textile industry. Many industries including the textile industry use heat exchangers to heat or cool fluids during or after processing. Generally a heat exchanger will comprises a passage through which the fluid to be cooled or heated passes, which passage comprises come means of heating or cooling the fluid in the passage. For example, the passage carrying the fluid may be an inner passage surrounded by a concentric outer passage, which outer passage contains a heating or cooling medium. In the textile processing industry it is common to use processing fluids such as dye liquor, which processing fluids are often required to be heated in order to enhance chemical reactions during processing. Heat exchangers used in the textile industry, particularly with dyeing machines, are usually single-pass, steam-condense heat exchangers. A single-pass, steam-condense heat exchanger involves passing dye liquor through an interior tube and passing steam, or the like, flow through an outer jacket, which surrounds and is concentric with the inner tube. Fresh stream continuously enters the outer jacket while condensate drains out of the jacket. Therefore, a substantially constant amount of heat energy is available in the jacket for transfer to the processing fluid in the inner tube. This type of heat exchanger is highly effective for heating dye liquor, or the like.However, an unacceptably large amount of heat energy is wasted by loss to the surrounding atmosphere. Preferred embodiments of the present invention seek to provide an improved heat exchanger. The present invention provides a heat exchanger comprising a primary heat exchange unit in fluid flow communication with a secondary heat exchange unit, the secondary heat exchange unit being substantially concentric with the primary heat exchange unit. Suitably, the primary heat exchange unit comprises a single tube. The tube may have any suitable cross-sectional shape. Suitably, the secondary heat exchange unit comprises a plurality of tubes. The tubes may have any suitable cross-sectional shape. Suitably, the tubes are aligned substantially parallel to one another. The tubes may all have substantially the same cross-sectional area. Alternatively, one or more of the plurality of tubes may have a different cross-sectional area from others of the plurality of tubes. Preferably, each of the plurality of tubes of the secondary heat exchange unit has a smaller cross-sectional area than the tube of the primary heat exchange unit. Suitably, the secondary heat exchange unit encloses the primary heat exchange unit. The secondary heat exchange unit may additionally comprise a passage enclosing the plurality of tubes, which passage is also in fluid flow communication with the primary heat exchange unit. Preferably, the heat exchanger comprises an inner tube, a mid-tube and an outer tube concentrically arranged about one another. Suitably, the inner tube provides the single tube of the primary heat exchange unit. Suitably, the mid-tube and the outer tube provide, in conjunction with the inner tube, the secondary heat exchange unit. The plurality of tubes of the secondary heat exchange unit are suitably located between the exterior surface of the inner tube and the interior surface of the mid-tube. The plurality of tubes of the secondary heat exchange unit is suitably arranged substantially co-axial with the longitudinal axes of the inner tube, the mid-tube and the outer tube. A space between the interior face of the outer passage and the exterior face of the mid-passage suitably provides a passage of the secondary heat exchange unit enclosing the plurality of tubes. Suitably, the heat exchanger further comprises a heat exchange fluid inlet and a heat exchange fluid outlet. Suitably, the heat exchange fluid inlet and the heat exchange fluid outlet are arranged such that heat exchange fluid flowing through the heat exchanger during use thereof simultaneously provides a heating or cooling source for both the primary heat exchange unit and the secondary heat exchange unit. Preferably, the heat exchange fluid inlet opens into the space between the inner tube and the mid-tube. Preferably, the heat exchange fluid outlet opens out from the space between the inner tube and the mid-tube. With this arrangement, the heat exchange fluid advantageously simultaneously heats or cools processing fluid inside the inner tube, or primary heat exchange unit, processing fluid within the plurality of tubes of the secondary heat exchange unit, and processing fluid within the passage of the heat exchange unit surrounding the plurality of tubes of the secondary heat exchange unit. The heat exchanger may be used with any suitable heat exchange fluid, for example, steam or oil. The heat exchanger suitably further comprises flow reversal means to direct, in use, processing fluid flow from the primary heat exchange unit into the secondary heat exchange unit. Suitably, the flow reversal means extends across the processing fluid outlet of the primary heat exchange unit and the processing fluid inlet of the secondary heat exchange unit. Suitably, the flow reversal means comprises a substantially toroidal surface substantially opposite the processing fluid outlet of the primary heat exchange unit and the processing fluid inlet of the secondary heat exchange unit, to facilitate flow reversal of the processing fluid in use. The heat exchanger may further comprise a filter. The filter may be located in either or both of the primary and secondary heat exchange units, but is preferably located in the primary heat exchange unit. The filter suitably extends across the full width of the single tube of the primary heat exchange unit. The filter is preferably conical. The conical filter is suitably arranged with the point of the cone nearest the processing fluid inlet of the primary heat exchange unit and the base of the cone nearest the processing fluid outlet of the primary heat exchange unit. The filter advantageously removes large particles, including, loose fabric or fibres from the processing fluid flow. A conical filter advantageously reduces the resistance to flow of the processing fluid passing through the filter and thereby minimises the pressure loss in the processing fluid flow. The processing fluid inlet of the primary heat exchange unit may comprise an expansion tube at the inlet thereof, arranged such that the cross-sectional area of flow into the single tube of the primary heat exchange unit increases. The expansion tube is preferably provided by an extension of the single tube of the primary heat exchange unit. The expansion tube preferably tapers outwardly from the processing fluid inlet. Increasing the cross-sectional area of fluid flow into the primary heat exchange unit advantageously reduces the speed of the processing fluid flowing into the primary heat exchange unit. The heat exchange may further comprises a reducing tube at the outlet of the secondary heat exchange unit, arranged such that the cross-sectional area of flow out of the secondary heat exchange unit decreases. The reducing tube is preferably provided by an extension of the outer tube of the secondary heat exchange unit. The reducing tube preferably tapers inwardly from the processing fluid outlet. Decreasing the cross-sectional area of fluid flow out of the secondary heat exchange unit advantageously increases the speed of the processing fluid flowing out of the secondary heat exchange unit. The reducing tube may be bent to provide an elbow and advantageously direct the flow of fluid to exit sideways out of the heat exchanger. The elbow is suitably designed to change the direction of the flow of processing fluid by about 90[deg]. The elbow is suitably tapered to effect an increase of speed of the processing fluid passing through the elbow. The use of a plurality of smaller diameter tubes in the secondary heat exchange unit advantageously provides an increase contact area with the heat exchange fluid. The concentric design of the primary and secondary heat exchange units advantageously provides a more compact heat exchanger. In addition, the location of the outer passage about the mid-passage though which the heat exchange fluid flows in use, facilitates a more efficient use of the heat transfer properties of the heat exchange fluid. Less heat is lost to or absorbed from the surrounding atmosphere into the heat exchange fluid. Inclusion of a filter inside the pipework of the heat exchanger also provides a more compact heat exchanger and avoids the need for separate pipework to support the filter. The toroidal design of the flow reversal device, particularly if used with a curved outlet end of the primary heat exchange unit tube, advantageously provides for reversal of flow direction of the processing fluid without significant pressure loss. Furthermore, the toroidal shape of the flow reversal device advantageously facilitates even distribution of the processing fluid across the plurality of tubes and passage of the secondary heat exchange unit. The present invention will now be explained, by way of example only, with reference to the following schematic drawings, in which:- Figure 1 is a cross-sectional side-view of a heat exchanger, and Figure 2 is a section along A-A of figure 1. Figure 1 shows a heat exchanger 1 comprising a primary heat exchange unit 3 and a secondary heat exchange unit 8. The primary heat exchange unit 3 comprises a tube 15, having an inlet 2 and an outlet 16. The inlet 2 tapers outwardly such that the cross-sectional area for fluid flow through the tube 15 increases as processing fluid enters the tube 15 in use. As can be seen from figure 1, the majority of the tube 15 has a substantially uniform crosssection with a substantially constant cross-sectional area. The outlet end 16 of the tube 15 may curve outwardly as shown in figure 1. The secondary heat exchange unit 8 encloses the tube 15 of the primary heat exchange unit 3. The secondary heat exchange unit 8 comprises a plurality of tubes 6, arranged between the tube 15 of the primary heat exchange unit 3 and a concentric tube 17 of the secondary heat exchange unit 8. The space between the tube 15 and the concentric tube 17 provides a passage 18, in which passage 18 the plurality of tubes 6 are located. The secondary heat exchange unit 8 additionally comprises a further concentric tube 19, which further concentric tube 19 encloses the concentric tube 17. An outer passage 5 is formed between the concentric tube 17 and the further concentric tube 19. The outlet end 16 of the tube 15 of the primary heat exchange unit 3 opens into a pear-shaped flow reversal device 4. The pear-shaped flow reversal device 4 is connected to the exterior surface of the further concentric tube 19. The heat exchanger 1 further comprises a heat exchange fluid inlet 11 and a heat exchange fluid outlet 12. The heat exchange fluid inlet 11 opens into the passage 18 between the tube 15 and the concentric tube 17, and the heat exchange fluid outlet 12 opens outwards from the passage 18 between the tube 15 and the concentric tube 17. The heat exchanger 1 also comprises a conical filter 10. In this embodiment the conical filter 10 is arranged in the tube 15 of the primary heat exchange unit 3. In addition, the heat exchanger 1 comprises a elbow 9 attached to the processing fluid outlet end of the further concentric tube 19 of the secondary heat exchange unit 8. The elbow 9 is shaped to change the flow of processing fluid exiting the secondary heat exchange unit 8 by about 90[deg], such that the processing fluid exits the heat exchanger 1 sideways. The elbow 9 is tapered inwardly to effect an increase in speed of the processing fluid as it passes through the elbow. In use of the heat exchanger 1 to heat dye liquor of a textile processing machine (not shown), dye liquor to be heated enters the primary heat exchange unit 3 through the tapered inlet 2. The tapering causes the speed of the liquor entering the tube 15 to be reduced. The dye liquor flows through the tube 15 of the primary heat exchange unit 3, wherein it passes through the conical filter 10 and any particulate material in the dye liquor is retained by the filter. The dye liquor exits the tube 15 through the outlet end 16 and is guided by the pear-shaped flow reversal device such that the fluid flow reverses back on itself and enters the secondary heat exchange unit 8. The dye liquor passes through the plurality of tubes 6 and the outer passage 5 of the secondary heat exchange unit 8 and exits the secondary heat exchange unit through the elbow 9. The elbow 9 alters the direction of flow of the dye liquor by about 90[deg]. The arrows indicate the flow of dye liquor through the heat exchanger. It can be seen from figure 1 that the dye liquor passes twice through the heat exchanger 1. Thereby optimising the heat transfer from the heat exchange fluid to the dye liquor. The heat exchange fluid (steam) enters the heat exchanger 1 through the inlet 11 and flows through the passage 18 between the tube 15 of the primary heat exchange unit 3 and the concentric tube 17 of the secondary heat exchange unit 8. The steam flows around the plurality of tubes 6 of the secondary heat exchange unit 8. Steam then exits the heat exchanger 1 through the outlet 12 as condensate (water). Steam is continuously pumped through the heat exchanger during use at an appropriate rate to provide a continuous heating effect on the dye liquor flowing through the heat exchanger 1. The steam simultaneously passes heat to the dye liquor through the wall of the tube 15 of the primary heat exchange unit 3, through the walls of the plurality of tubes 6 of the secondary heat exchange unit 8 and through the wall of the outer passage 5 provided by the concentric tube 17.

Claims

1. A heat exchanger comprising a primary heat exchange unit in fluid flow communication with a secondary heat exchange unit, the secondary heat exchange unit being substantially concentric with the primary heat exchange unit.

2. A heat exchanger according to claim 1, wherein the primary heat exchange unit comprises a single tube.

3. A heat exchanger according to claim 2, wherein the cross-sectional area of the tube increases at an inlet end.

4. A heat exchanger according to claim 2 or 3, wherein the tube curls outwardly at an outlet end.

5. A heat exchanger according to any one of the preceding claims, wherein the secondary heat exchange unit comprises a plurality of tubes.

6. A heat exchanger according to claim 5 as dependent on any one of claims 2 to 4, wherein each of the plurality of tubes of the secondary heat exchange unit has a smaller cross-sectional area than the single tube of the primary heat exchange unit.

7. A heat exchanger according to claim 5 or 6, wherein the secondary heat exchange unit further comprises a passage enclosing the plurality of tubes, which passage is also in fluid flow communication with the primary heat exchange unit.

8. A heat exchanger according to any one of the preceding claims, wherein the secondary heat exchange unit encloses the primary heat exchange unit.

9. A heat exchanger according to claim 7, wherein the passage is provided by a space between two concentric tubes.

10. A heat exchanger according to any one of the preceding claims, comprising a heat exchange fluid inlet and a heat exchange fluid outlet.

11. A heat exchanger according to claim 10, wherein the heat exchange fluid inlet and outlet are arranged such that, in use, heat exchange fluid flowing through the heat exchanger simultaneously provides a heating or cooling source for both the primary heat exchange unit and the secondary heat exchange unit.

12. A heat exchanger according to claim 10 or 11, wherein the heat exchange fluid inlet opens into the secondary heat exchange unit such that the heat exchange fluid flows around the plurality of tubes of the secondary heat exchange unit.

13. A heat exchanger according to any one of the preceding claims, comprising a flow reversal device arranged to direct, in use, fluid from the primary heat exchange unit into the secondary heat exchange unit.

14. A heat exchanger according to claim 13, wherein the flow reversal device comprises a substantially toroidal surface to guide the processing fluid flow in use.

15. A heat exchanger according to any one of the preceding claims, comprising a filter.

16. A heat exchanger according to claim 15, wherein the filter is a conical filter.

17. A heat exchanger according to claim 15 or 16, wherein the filter is located in the primary heat exchange unit.

18. A heat exchanger according to any one of the preceding claims, comprising an inwardly tube of decreasing cross-sectional area located at the processing fluid outlet of the secondary heat exchange unit.

19. A heat exchanger according to claim 18, wherein the reducing tube is curved to alter the direction of flow of the processing fluid exiting the heat exchanger.

20. A heat exchanger substantially as described herein and with reference to the drawings hereof.