FR2694388A1 - Heat exchanger with a water tube layer, especially for a condensing boiler. - Google Patents

Abstract

A plurality of separators (12) each covering a sector of several water tubes (1) are regularly distributed inside and around the entire periphery of an upper distributor ring (2) and a lower distributor ring between which the water rises and falls in the adjacent tube bundles. Each separator isolates its sector from the neighboring sector not provided with a separator. The water inlet pipe (10) and the water outlet pipe (11) are mounted diametrically opposed on this upper distributor ring (2). Application to condensing boiler heat exchangers.

Description

Heat exchanger with a layer of water tubes, especially for

condensing boiler.

  The invention, which relates to a heat exchanger, in particular for a condensing boiler, relates more precisely to the distribution of the flow rates inside the sheet of water tubes which constitute the cylindrical exchanger. The cylindrical exchangers of the condensing type boilers are usually made in the form of a sheet of water tubes which are distributed vertically - evenly around a central burner and which

  delimit a combustion chamber.

  The cylindrical sheet is wrapped with a leaktight shell intended to collect the products of combustion which escape through a chimney This arrangement allows a partial or total recovery of the latent heat of condensation of the water vapor contained in the combustion gases , thanks to the large exchange surfaces provided between the water tubes and these gases These exchange surfaces result from a particular profile of each water tube, preferably of oblong section and fairly flattened In this type of known exchanger , the heating water circulates in the tubes of the tablecloth by going up by some neighboring tubes forming a bundle, and then down by a bundle

neighbor, and so on.

  This upward and downward circulation is between a lower distribution ring and an upper distributor ring, one of the two receiving a supply duct and a water outlet duct. In each distribution ring are provided baffles which isolate between them the In each sector, this leads to a bundle of upright tubes and a bundle of down tubes. In this way, the water makes several "round trips" from one ring to the other, between the feed pipe and the outlet duct The baffles in question constitute partition walls between the sectors and they must be sufficiently sealed so that said sectors are perfectly isolated from each other. This is even more important for the baffle which is in a distribution ring, between the supply duct and the water outlet duct F at least a portion of the water flow is passed to the outlet In order to avoid this, it is necessary to check the quality of the seals of the baffles. If brazing is required for this, this requires expensive machining operations. and this does not exclude the need to carry out subsequent rework in the workshop if leakage defects are still observed during use Although it has been thought to use removable baffles of particular conformation that fit directly into the tubes of water without requiring welding and which are capped with a seal, as described in FR-A 2 508 157 in the name of the Applicant, but the seal of the joints is sometimes also doubtful

  after a long period of use.

  This flow distribution system, apart from the aforementioned difficulties related to the existence of these baffles,

has other disadvantages.

  Indeed, it has been found that in each sector of the distribution rings o, as we know, the water undergoes a sudden change of direction between the rising tube bundle and the descending beam, there is not a homogeneous distribution of the flow in each tube of the same beam. The heterogeneities of water velocities in each of them and the swirling effects in the sectors result in irregularities in the tube temperatures and internal clogging of some of them, resulting from the irregular precipitation of the particles in

suspended in water.

  The invention therefore proposes a water tube web heat exchanger which overcomes the aforementioned drawbacks, by not using the usual baffles, said exchanger allowing a distribution

  better flow rates, with low pressure drop.

  A main object of the invention is therefore a cylindrical heat exchanger of water tubes arranged around a central burner and which open into lower and upper distribution rings between which the water performs several reversals of direction of flow up and down successively in the adjacent bundles of tubes, exchanger according to which a plurality of separators each capping a sector of several water tubes are regularly distributed inside and around the entire periphery of each distribution ring and isolate their sector of the neighboring sector not provided with a separator, the separators of the upper distributor ring and those of the lower distribution ring being offset relative to one another and the inlet pipe and the water outlet pipe being mounted diametrically opposite on one and the same

splitter ring.

  According to a particular characteristic of the invention, the separators of the upper splitter ring cover an odd number of water tubes and the water inlet and outlet pipes take on the upper splitter ring each in a sector comprising a

  even number of water tubes, without separator.

  In the upper distribution ring, the number of water tubes in the water inlet sector is different from

that of the departure of water.

  Finally all sectors of the lower splitter ring, those wearing a separator and those that are not have an odd number and identical tubes, and in line with the water inlet and outlet two pipes. separators are placed at the limit of the diameter of the ring,

to the right of said conduits.

  According to another particular characteristic of the invention, each separator consists of a folded sheet forming a bridge over several adjacent tubes, the two vertical flanks of the separator converging towards the center of the ring bearing against the base of the splitter ring, between two neighboring tubes. Other special features and

  advantages of the invention will emerge from the description which

  FIG. 1 is a general perspective view of the heat exchanger; FIG. 1 is a general perspective view of the heat exchanger; Figure 2 a diametrical vertical sectional view of said exchanger; Figure 3 a perspective view of the separator and Figure 4 said separator mounted above several water tubes; FIGS. 5 and 6 are plan views respectively of the upper distributor ring and the lower distributor ring whose covers have been removed; figure 7 a schematic view in elevation

half of the heat exchanger.

  Referring to FIGS. 1 and 2, it can be seen that the exchanger consists of a cylindrical sheet of water tubes 1 which connect an upper distributor ring 2 and a lower distributor ring 3 The tubes 1 delimit a combustion chamber 4 inside which is disposed a radial burner not shown The upper distribution ring 2 is closed by an annular cover 5 and the lower ring 3 also by another cover 6 The combustion chamber 4 is closed, at the

  level of the lower distributor ring by a bottom 7.

  The upper distribution ring 2 is secured to a support plate 8 by means of which the heat exchanger is held in place in the appliance. On this plate are provided hooking lugs 9 for the burner. The upper distribution ring 2 communicates with the water inlet and outlet ducts respectively via a supply connection and an outlet connection 11, the two connections being

  diametrically opposite on the ring.

  A plurality of separators 12, the profile and mounting of which are better seen in FIGS. 3 and 4, are placed inside each distribution ring. Each separator

  12 consists of a folded sheet, forming a bridge 15 to

  above several adjacent tubes 1 and the two vertical flanks 13 of the separator which converge towards the center of the ring bear against the base of the distribution ring, between two adjacent tubes The central portion of the separator 12 forms a slight elevation 14 relative to the bridge 15 and bears against the annular cover 5 or 6 of the distribution ring in question, to which it is brazed The separator is thus perfectly held in place It will be noted that the vertical flanks of each separator are spaced apart by a distance corresponding

nine tubes 1.

  FIG. 5 illustrates the place occupied by the separators 12 inside the upper distributor ring 2. In this figure, we see the regular distribution of the seventy-two tubes 1 which constitute the exchanger. The dotted line is shown in FIG. water and the water outlet 11 which are on the same

  diameter AA ', on each side of the splitter ring.

  On the side of the water inlet 10, eight tubes, that is,

  say four on each side of the diameter AA 'are supplied with water and are not capped by a separator On the other hand, by cons, nine adjacent tubes are capped by a separator 12; the tubes then appear in dashed lines in the figure Then the nine neighboring tubes are open and the following capped with a separator and so on It will be noted that the sector of the water outlet tube 11 is - as the sector of the tube of water inlet 10 devoid of separator Each separator therefore covers a sector of nine water tubes, an odd number of tubes, and isolates

  of the neighboring sector not provided with separator.

  Figure 5 shows that there are four sectors with separator, capping 36 tubes Between each sector equipped with separator, there is one sector which is not It has been seen that the sector of entry occupied eight tubes The intermediate sectors On the other hand, the outlet sector on the side of the duct 11, on the diameter AA 'relates to tubes. There is thus between the inlet zone and the outlet water zone a difference in the number of tubes of interest. will appear further Thus the inlet ducts 10 and 11 start on the upper distribution ring in a sector with a number

  pair of water tubes, devoid of separator.

  FIG. 6 shows that the space occupied by the separators 12 inside the lower distribution ring 3 With respect to the same diameter AA 'of the exchanger, it can be seen that the separators are offset with respect to the separators of FIG. and at the limit of said diameter Thus on the water inlet side 10 a vertical flank 13 of the separator 12 is on the diameter AA ', that is to say that the separator is shifted by four tubes relative to that of the upper distribution ring This shift is found on the side of the water outlet 11 A vertical flank of the separator is also on the diameter AA ', but this time it is offset by five tubes compared to that of the upper splitter ring It will be noted that the eight sectors of the lower splitter ring, the four which are capped with a splitter and the four which are not,

all cover 9 tubes each.

  Referring also to Figure 7, we now describe how water flows in the exchanger

between the entrance 10 and the exit 11.

  The water admitted through the inlet 10 into the upper distribution ring 2 will go down into the eight tubes of the sector considered. A deflector, not shown, is advantageously placed in the supply connector 10.

  so that the water is distributed in the eight starting tubes.

  The vertical portions 13 of the two separators (FIG. 5) isolate the eight tubes from their neighbors. The downward water in these eight tubes reaches the lower distribution ring 3 Due to the partition constituted by the vertical flank 13 of the separator located as shown in FIG. 'saw, on the diameter AA', that is to say in the middle of the sector of the eight tubes, the descending water will be distributed on both sides of this partition and go up in the neighboring tubes We see that this first downward flow will be split on either side of the diameter AA 'This means that the flow of water will be from the inlet 10 to the outlet 11, on both sides of the exchanger which decreases considerably

  the pressure losses compared to a single circulation.

  FIG. 7 schematically shows one half of the exchanger in view unwound between the water inlet 10 and the outlet 11. The water admitted at 10 thus descends through the eight starting tubes and then separates to ascend through five neighboring tubes before to redecend by four and so on until the exit 11 This alternation of five and four tubes can be explained as follows The downward water in the first four tubes has five adjacent tubes capped by the same separator to go back to

the upper splitter ring.

  This rising water then has four adjacent tubes capped by the same separator of the upper distribution ring to descend to the lower distribution ring and so on The indication in Figure 7 of the four down tubes and five upright tubes and the marking by arrows of the circulation of water, illustrates this process of operation. Because of this particular provision that the number of rising water tubes differs from the number of down tubes, at the change of direction of the water under the separator, a certain turbulence is created which avoids the formation of water nets. continuous water between a rising tube and a down tube All tubes are supplied with water with substantially equivalent flow rates The absence of heterogeneities in the flow velocities eliminates the risk of localized overheating and internal clogging of the tubes. this fact, it is no longer necessary to use bridges to favor

  the distribution of fluids in the distribution rings.

  It has been seen that moving the water supply pipe away from the outlet pipe, and distributing the flow of water circulating on both sides of the heat exchanger, reduces the pressure losses. advantage that in the event of leakage at the level of the separators and more precisely of their partitions, the small water leak that results does not affect the operation of the exchanger, and in any case there is no no more direct bipass between entry and exit since the

  two corresponding conduits are distant from each other.

Claims (5)

  1 Heat exchanger with cylindrical sheet of water tubes arranged around a central burner and which open into lower and upper distribution rings between which the water performs several reversals of flow direction up and down successively in bundles of adjacent tubes characterized in that a plurality of separators (12) each capping a sector of several water tubes (1) are regularly distributed inside and around the entire periphery of each distribution ring and isolate their sector of the neighboring sector not provided with a separator, in that the separators of the upper distributor ring (2) and those of the lower distributor ring (3) are offset relative to one another and in that the water inlet duct (10) and the water outlet duct (11) are mounted diametrically   opposite on the same splitter ring.   2 heat exchanger according to claim 1 characterized in that the separators (12) of the upper distributor ring (2) cover an odd number of water tube (1) and in that the inlet ducts (10) and water outlet (11) take on the upper distribution ring each in a sector having an even number   of water tubes, without separator.   3 heat exchanger according to claim 2 characterized in that, in the upper distribution ring (2), the number of water tubes (1) of the arrival sector   water (10) is different from that of the water outlet (11).   4 heat exchanger according to claim 1 characterized in that all sectors of the lower distribution ring (3), those capped with a separator (3) and those which are not, have an odd number and identical tubes 1.   Heat exchanger according to claims 1   and 4 characterized in that in the lower distributor ring (3), in line with the inlet ducts (10) and water outlet (11), two separators (12) are placed at the limit of the diameter AA 'of the ring to the right of said conduits. 6 heat exchanger according to claim 1 characterized in that each separator (12) consists of a folded sheet forming a bridge (15) above several tubes (1) neighbors and in that the two vertical flanks (13) ) of the separator converging towards the center of the ring abut against the base of the ring   distributor, between two neighboring tubes.   7 heat exchanger according to claim 6 characterized in that the central separator portion (12) forms an elevation (14) relative to the bridge (15) and abuts against the cover (5, 6) of the ring dispatcher considered.