WO2005066573A1

WO2005066573A1 - Heat exchanger comprising cleaning means

Info

Publication number: WO2005066573A1
Application number: PCT/FR2004/003130
Authority: WO
Inventors: Thierry Hyest
Original assignee: Technos Et Compagnie
Priority date: 2003-12-12
Filing date: 2004-12-06
Publication date: 2005-07-21
Also published as: US20070163752A1; EP1704379A1; FR2863697A1; FR2863697B1

Abstract

The invention relates to a heat exchanger comprising: a chamber (1) which is fitted with a plurality of tubes (2) through which a heat-transfer fluid flows, said fluid conveying cleaning balls (8); an outlet manifold (5) which is connected to the chamber (1) and which is used to release the heat-transfer fluid from same, said manifold (5) comprising a single piece; and a device (13) which is disposed in the manifold (5) in order to separate the cleaning balls (8) from the fluid conveying same.

Description

Heat exchanger provided with cleaning means.

The present invention relates to heat exchangers, also called condensers, and more particularly to their cleaning. A condenser comprises an enclosure furnished with a plurality of tubes inside which circulates a heat transfer fluid which performs a heat exchange with a warmer surrounding medium (generally water vapor coming from a turbine of a power plant and which, in contact with the colder tubes, condenses on them to be then routed to a collection well). The heat transfer fluid transports spherical cleaning bodies, hereinafter called balls, which clean the internal walls of the condenser tubes to avoid fouling due to the deposition of impurities present in the fluid (generally river water, sea water , or from cooling towers or other sources). Generally, two collectors, respectively for supplying heat transfer fluid and for discharging the fluid, are connected to the enclosure on either side, and connect the latter to a circuit for supplying heat transfer fluid. The balls are separated from the fluid after passing through the evacuation collector and then reinjected towards the supply collector by means of a recycling device arranged in the vicinity of the enclosure. To illustrate this type of condenser, one can in particular refer to the French patent application published under the number FR-A-2 438 815 or to its American equivalent bearing the number US-4 283 807. If this type of condenser gives whole satisfaction from the point of view of its operation, it however poses problems of congestion, in particular because of the arrangement of the device for recycling the balls under the enclosure. The invention aims to solve this drawback in particular by proposing a condenser which has a reduced bulk, and whose installation is simplified. To this end, the invention provides a heat exchanger comprising: an enclosure provided with tubes in which circulates a heat transfer fluid transporting cleaning balls, an outlet manifold connected on the one hand to said enclosure for the evacuation of the heat transfer fluid in coming from the latter, and on the other hand to a circuit for evacuating the heat-transfer fluid, this collector being produced in one piece, and a device arranged in said collector for separating the cleaning balls from the fluid which transports them. The balls being separated from the fluid in the immediate vicinity of the enclosure, directly in the collector, it is possible to save on long evacuation pipes, and thus guarantee a better compactness of the installation. In particular, it is possible to place the exchanger in a lower position than usual. In this way, the heat exchanger can be placed in places where the lack of space would have forced the architects to choose a heat exchanger devoid of cleaning means, to the detriment of the good flow of the coolant and, ultimately , the quality of the cooling. According to one embodiment, the outlet manifold has a first portion forming a convergent, as well as a second portion forming a tube which is connected to said convergent (for example at right angle), and in which the separation device is placed. According to one embodiment, the separation device comprises a plurality of grids arranged across said tubing, associated in pairs to form a filtering structure with a W-profile converging on the side opposite to said enclosure towards a device disposed in the elbow to recover the cleaning balls separated from the heat transfer fluid by the separation device. Each grid comprises, for example, a row of parallel braced blades, preferably mounted on a common axis extending across the manifold. Each grid can be rotatably mounted around its axis, to allow its own cleaning. The exchanger may, in this case, include a device for measuring a difference in fluid pressure on either side of the grids, connected to a system provided for controlling the rotation of the grids when this pressure difference is greater than a value predetermined. The exchanger may further include a ball recycling circuit, connecting the ball recovery device to a supply manifold connected to the enclosure for supplying the latter with heat transfer fluid, supply manifold through which the balls are reinjected into the enclosure. Other characteristics and advantages of the invention will appear during the following description of one of its embodiments, given by way of nonlimiting example, with reference to the accompanying drawings, in which:

- Figure 1 is a sectional elevation view of a condenser according to the invention;

- Figure 2 is a sectional elevation view of a detail of Figure 1, illustrating an elbow outlet manifold; and - Figure 3 is a perspective view in partial cutaway illustrating the collector of Figure 2. In Figure 1 is shown a heat exchanger, also called condenser, comprising an enclosure 1 furnished with a plurality of tubes 2 in which circulates a heat transfer fluid (in this case water) for the condensation of steam coming for example from a turbine of a power plant (not shown). The heat transfer fluid is brought to the enclosure 1 by a supply manifold (also called a “water box”) 3 connected to the enclosure 1 by a first side wall 4, on which the tubes 2 end and on the side of which the fluid enters the enclosure 1 to then circulate in the tubes 2. The fluid is evacuated from the enclosure 1 by an outlet manifold (also called “water box”) 5 connected to the enclosure 1 by a second wall lateral 6, opposite to the first 4, on which the tubes 2 end and on the side of which the fluid leaves the enclosure 1 after having circulated in the tubes 2 which constitute the place of a heat exchange between the heat transfer fluid and the water vapor, this being condensed on the external walls of the tubes 2 to then flow towards a collection basin 7 located under the enclosure 1. As can be seen in FIG. 1, the heat transfer fluid carries cleaning balls 8 d aligned in an elastic, compressible material which, carried by the fluid, pass with it through the tubes 2. The diameter of the balls 8 is greater than the internal diameter of the tubes 2, so that, by traversing the latter, the balls 8 ^" scrape their internal walls which it cleans of impurities which, carried by the heat transfer fluid, have accumulated there. The tubes 2 extend parallel to each other along a horizontal X axis perpendicular to the side walls 4, 6, which in this case are vertical. By convention, it is assumed that the heat transfer fluid circulates from the first side wall 4 to the second 6 - that is to say, in Figure 1, from left to right, as indicated by the arrow F. The outlet manifold 5 has an upstream mouth 9, by which it is connected to the enclosure 1, and a downstream mouth 10, by which it is connected to a pipe (not shown) for evacuating the heat-transfer fluid, the section of the upstream mouth 9 here being greater than that of the downstream mouth 10. As shown in FIG. 3, the outlet manifold 5 comprises, from upstream to downstream, a first portion 11 which forms a convergent ( in this case with rectangular section, although any other section could be envisaged), as well as a second portion 12 with a substantially constant section (here circular) connected to the convergent 11 in one piece, the manifold 5 thus forming a part piece. According to an embodiment illustrated in the figures, the convergent 11 and the tubing 12 form a bend substantially at right angles, so as to deflect downward the flow leaving horizontally from the enclosure 1, the tubing 12 extending along a substantially vertical Y axis. This provision, given by way of example, is in no way restrictive, since it aims to channel the flow towards a recovery zone imposed by the configuration of the premises. Thus, the tubing could extend along the axis X, or form with it any angle between

0 ° and 90 °. As can be seen in Figure 2, a device

13 provided for separating the balls 8 from the fluid which transports them is disposed in the outlet manifold 5 and, more precisely, in the tubing 12. This device 13 comprises a plurality of grids 14,

15, 16, 17 arranged transversely to the vertical axis Y of the second portion 12 of the outlet manifold 5, in this case near the downstream mouth 10. As can be seen in FIG. 3, each grid 14, 15, 16, 17 comprises a row of parallel blades 18, 19 held at equal distance from each other by means of a plurality of coaxial spacers 20 together forming an axis 21, 22, 23, 24 common support support the respective grid 14, 15, 16, 17, axis which extends across the manifold 12 of the manifold 5. Each blade 18, 19 has a substantially straight leading edge 25, inclined relative to the direction of the current, indicated in Figure 2 by arrow F ', at an angle between 15 ° and 30 °. Each blade 18, 19 also has an upstream end 26, 27 and a downstream end 28, 29 opposite. As can be seen in Figure 2, the grids

14, 15, 16, 17 are associated in pairs 14, 15 on the one hand and 16, 17 on the other hand, the axes 21, 22, 23, 24 of the grids 14, 15, 16, 17 being parallel two by two . Each grid 14, 15, 16, 17 is mounted for rotation about its respective support axis 21, 22, 23, 24, between a normal position of use, illustrated in solid lines in FIG. 2, in which the grids 14, 15

16, 17 of each pair 14, 15 and 16, 17 converge from upstream to downstream - that is to say on the side of the downstream ends 27 -, and a cleaning position, illustrated in dotted lines in the figure - 2, in which the grids 14,

15, 16, 17 of each pair 14, 15 and 16, 17 diverge on the contrary from upstream to downstream. According to an embodiment illustrated in FIG. 2, the separation device 13 comprises at least two pairs of grids 14, 15 on the one hand and 16, 17 on the other hand, each consisting of a central grid 15, 16, located near the axis Y of the second portion 12 of the outlet manifold 5, and whose blades 19 are relatively long, and a peripheral grid 14, 17, located near the wall of the manifold 5, and whose blades 18 are relatively shorter. In the normal position of use, in which each blade 18, 19 presents its leading edge 25 with current, the central grids 15, 16 are back-to-back, the upstream ends 27 of their respective blades 19 being in contact with two in pairs, while the peripheral grids 14, 17 are in contact with the wall of the collector 5, the upstream ends 26 of their blades 19 coming to bear against the internal wall of the collector 5. Thus, in the normal position of use , the grids 14, 15, 16, 17 together form a filtering structure with a W profile, each pair of grids 14, 15 and 16, 17 forming a funnel through which the balls 8 pass and defining, between the downstream ends 28 and 29 of their respective blades 18, 19, a gap 30, 31. The distance between two adjacent blades 18, 19 of the same grid 14, 15, 16, 17 is less than the diameter of the balls 8, so that a ball 8 cannot pass between two adjacent blades 18, 19. On the other hand, the width of the i nterstice 30, 31 between the downstream ends 28, 29 of the blades 18, 19 of the same pair of grids 14, 15 or 16, 17., is greater than the diameter of the balls 8. Also these, after having been guided by the leading edges 25 of the blades 18, 19, are they forced by the current to pass in the gap 30, 31. As there is for the balls 8 no other passage in the section of the outlet manifold 5 , these are thus separated from the fluid which transports them by the grids 14, 15, 16, 17. As illustrated in FIG. 2, a device 32 is arranged in the elbow 5 to collect the balls 8 at the outlet of the separation device 13. This device 32 comprises two receptacles 33, 34 each placed at the right of the gap 30, 31 of each pair of grids 14, 15 and 16, 17, and in which the balls 8 are received and then reused. To this end, a recycling circuit 35 of the balls is provided, which connects each receptacle 33, 34 of the recovery device 32 to the supply manifold 3 by which the balls 8 are reinjected into the enclosure 1. A pump (not shown) placed on the recycling circuit 35 sucks the balls 8 received in the receptacles 33, 34 to return them to the supply manifold 3. The impurities carried by the heat transfer fluid are gradually deposited on the leading edge 25 blades 18, 19. In order to ensure regular cleaning of the blades 18, 19, the grids 14 are periodically controlled,

15, 16, 17 around their respective axes 21, 22, 23, 24 to place them in the cleaning position (as shown in dotted lines in FIG. 2), the leading edge 25 thus being traversed in reverse by the current , which detaches the accumulated impurities. The gradual fouling of the blades 18 has the consequence of gradually reducing the cross section of the fluid at the grids 14, 15, 16, 17, and therefore of slowing down its free flow. This results in a difference in the fluid pressure between the upstream of the grids 14, 15,

16, 17 and their endorsement. Beyond a certain threshold, this pressure difference can cause deformation of the grids 14, 15, 16, 17, or even their breakage. It is therefore proposed to measure this pressure difference using appropriate means, and, when the pressure difference exceeds a predetermined threshold, deemed critical for the flow of the fluid, to control - and this automatically by means of a suitable control system to which the probes are connected - the rotation of the grids 14, 15, 16, 17 in order to allow their cleaning. As the grids 14, 15, 16, 17 are placed not far from a bent zone at the outlet of the enclosure 1, the flow of the fluid in the vicinity of the grids 14, 15,

16, 17, both upstream and downstream of these, is vortex, which makes a conventional pressure measurement difficult. In order to overcome this difficulty, provision is made to measure the fluid pressure, upstream and downstream of the grids 14, 15, 16, 17, by means of probes placed in hollow protective tubes provided with perforations (of a diameter included between 3 mm and 10 mm. Thanks to these perforations, the fluid is static in the tubes, which makes a reliable measurement of pression possible. As we have just seen, the separation device 13 is particularly compact. Placed directly in the evacuation manifold 5 of the heat transfer fluid, and, to be more precise, in the tubing 12 thereof, it makes it possible to reduce the overall size of the installation. Furthermore, the monobloc embodiment of the outlet manifold allows faster and more convenient mounting thereof, and therefore simplified installation of the condenser and its cleaning system.

Claims

1. Heat exchanger comprising: - an enclosure (1) furnished with a plurality of tubes (2) in which circulates a heat transfer fluid transporting cleaning balls (8), an outlet manifold (5) connected to the enclosure ( 1) for the evacuation of the heat transfer fluid from the latter, this collector (5) being made in one piece, and a device (13) disposed in said collector (5) for separating the cleaning balls (8) of the fluid that transports them.

2. Exchanger according to claim 1, in which the outlet manifold (5) has a first portion (11) forming a converging, as well as a second portion (12) forming a tube which is connected to said converging (11), and in which the separation device (13) is placed.

3. Exchanger according to claim 2, wherein said convergent (11) and said tube (12) form a bend substantially at right angles.

4. Exchanger according to claim 2 or 3, wherein the separation device (13) comprises a plurality of grids (14, 15, 16, 17) arranged across said tube (12), associated in pairs (14, 15 ; 16, 17) to form a filter structure with a W profile converging on the side opposite to said enclosure (1) towards a device (32) disposed in the elbow (5) for recovering the cleaning balls (8) separated from the heat transfer fluid by the separation device (13).

5. Exchanger according to claim 4, wherein each grid (14, 15, 16, 17) comprises a row of parallel braced blades (18, 19).

6. Exchanger according to claim 5, in which blades (18, 19) of each grid (14, 15, 16, 17) are mounted on a common axis (21, 22, 23, 24) extending across the manifold (12) of the manifold (5 ).

7. Exchanger according to claim 6, wherein each grid (14, 15, 16, 17) is rotatably mounted about its axis (21, 22, 23, 24).

8. Exchanger according to claim- 7, which comprises a device for measuring a difference in fluid pressure on either side of the grids (14, 15, 16, 17), connected to a system provided for controlling the rotation of the grids (14, 15, 16, 17) when this pressure difference is greater than a predetermined value.

9. Exchanger according to one of claims 4 to

8, which comprises a recycling circuit (35) of the balls (8), connecting the recovery device (32) of the balls (8) to a supply collector (3) connected to the enclosure (1) for the supply thereof with heat transfer fluid, supply manifold (3) by which the balls (8) are reinjected into said enclosure (1).