EP0913651B1 - High efficiency heat exchanger element for building a heating element in a sectional boiler - Google Patents

Abstract

The heat exchanger, having projecting studs (4) on its lateral surfaces (2,3), has an inner chamber with a chicane for the heat-carrying fluid formed by lower (30) and upper (31) deflectors and lower (26) and upper (26) partitions. The partitions stop short of the end walls of the heat exchanger and form restricted passages (27,28) for the heat carrying fluid passing through them. The two deflectors are inclined upwards in relation to the flow of fluid between the inlet (21) and outlet (22) of the heat exchanger.

Description

Underfloor heating and certain elements water circulation heaters for rooms and premises allow to use water for heating so-called low temperature lying in the range 20 ° C-35 ° C.

The ideal in terms of yield is to directly use the water coming out of the boiler brought to these temperatures considered low in the field of heating.

Boilers serving water at such low temperature condense in the downstream part of the path combustion gases causing the disadvantages that we know: corrosion by acid condensates causing deterioration of the exchanger elements, difficulties in collecting and disposing of condensates.

To increase the efficiency of the elements sectional boiler exchangers, spikes protruding from flat surfaces opposite two successive exchanger elements, the structures overlap each other to achieve a suitable deceleration of gases and fumes from burning that get rid of their calories as they progress along the elements exchangers.

Another feature known for increase the efficiency of these exchanger elements concerns the presence of an interior chicane materialized by two offset transverse walls which are each integral with the adjacent wall of the element exchanger.

These exchanger elements are produced usually foundry cast iron causing the making fairly complex foundry molds with use of sand cores for the formation of hollow body.

These interior walls complicate the realization of the foundry sand core and constitute hollow transverse zones which weaken. So the risk of rupture, of deterioration or simply deformation of the nuclei is important. This risk leads to the increase the number of defective parts to be discarded or scrap. In addition, the presence of these walls forming a baffle obstructs the evacuation of the sand after constitution of the part. Indeed, the sand pours out wrong to the only existing exits from the room interior which are the holes provided for the entrance and the outlet of the heat transfer fluid. Even more problematic, the junction angle between each wall transverse forming the baffle and the wall of the exchanger element is re-entrant, forming a true difficult sand retention trap to dislodge from these places.

This has been remedied by realizing sand discharge openings to the right of compartments delimited by the transverse walls of chicanery. The sand is evacuated almost completely by these holes and this solution is satisfactory on this point. However, the orifices must be filled to allow the technical use of the exchanger element. We are therefore led to carry out additional mechanical filling work. We performs this recapping frequently by tapping the walls of the orifices then closing them with threaded plugs. We understand that these works significantly increase the price of the exchanger element and increase its duration by manufacturing while complicating it technically and mechanically weakening it.

We also know an exchanger, described in patent application DE 3622 266 in the name of VAILLANT, which has in its interior room deflectors of small dimensions which are not contact with the side walls of the exchanger.

It is a classic spike exchanger exterior with two inclined deflectors slightly fan-shaped. Because of their location and their short length they provide simply an overall hydrodynamic effect in preferably directing the flow upwards and towards the opposite wall.

The two deflectors do not constitute actually a chicane. They just orient slightly the flow in order to decrease the areas dormant. They do not lengthen the course enormously of fluid, a large majority of the flow can even go directly from the inlet to the go out without being diverted. The improvement of heat exchange is therefore very low.

The object of the invention is to remedy these disadvantages by making an element by foundry heat exchanger with baffle at low risk of manufacturing and free of sand residue after its evacuation phase, exchanger element which presents plus a high heat exchange efficiency.

As already indicated the new core of sand ensures low-risk industrial manufacturing fault (s) resulting from deterioration or rupture of the sand core.

To this end, the invention relates to a high efficiency exchanger element for boiler sectionable with an internal structure of baffle bounded by two transverse structures each consisting of an oblique transverse plane and an inclined deflector distant from each other to form a deflector means and a secondary baffle.

Thanks to this structure, the invention allows after molding to completely evacuate through the orifices existing nucleus residues lodged in re-entrant angles at the ends of the deflectors near the element body exchanger.

In addition, the yield is further increased general of the exchanger element by lengthening the path of water inside the room and removing the sleeping areas at the baffle walls.

As already indicated, the removal of the walls long baffle crosses and joined with the exchanger body provides the core sufficient mechanical strength to guarantee industrial manufacturing without interior defect (s).

The core reinforced by fasteners which improve its cohesion systematically resists different constraints of molding.

• la figure 1 est une vue en coupe verticale le long de la chambre intérieure d'un élément échangeur selon l'art antérieur ;
• la figure 2 est une vue en coupe verticale le long de la chambre intérieure d'un élément échangeur selon l'invention ;
• la figure 3 est une vue en coupe verticale le long de la chambre intérieure d'un élément échangeur selon l'invention montrant le trajet des courants d'eau entre l'orifice inférieur d'entrée et l'orifice supérieur de sortie ;
• la figure 4 est une vue schématique approximative et générale en perspective du noyau en sable de fonderie correspondant au corps creux de l'élément échangeur selon l'invention ;
• la figure 5 est une vue en plan d'un élément échangeur conforme à l'invention
• la figure 6 est une vue en coupe transversale verticale selon la ligne VI-VI de la figure 5 ;
• la figure 7 est une vue en coupe transversale horizontale de la partie basse de l'élément échangeur selon l'invention selon la ligne VII-VII de la figure 5 ;
• la figure 8 est une vue en coupe transversale horizontale selon un plan passant par les orifices de deux éléments échangeurs latéralement juxtaposés.

Other characteristics and advantages of the present invention are set out in the description which follows, given without limitation, with reference to the accompanying drawings in which:

• Figure 1 is a vertical sectional view along the inner chamber of an exchanger element according to the prior art;
• Figure 2 is a vertical sectional view along the inner chamber of an exchanger element according to the invention;
• FIG. 3 is a view in vertical section along the interior chamber of an exchanger element according to the invention showing the path of the water currents between the lower inlet orifice and the upper outlet orifice;
• Figure 4 is an approximate and general schematic perspective view of the foundry sand core corresponding to the hollow body of the exchanger element according to the invention;
• Figure 5 is a plan view of an exchanger element according to the invention
• Figure 6 is a vertical cross-sectional view along line VI-VI of Figure 5;
• Figure 7 is a horizontal cross-sectional view of the lower part of the exchanger element according to the invention along line VII-VII of Figure 5;
• Figure 8 is a horizontal cross-sectional view along a plane passing through the orifices of two laterally juxtaposed exchanger elements.

The exchanger element according to the invention is intended for sectional boilers in particular condensing type. However, any application to another type of boiler not under any effort additional inventive comes under the present invention.

An example will not be described below. limiting an exchanger element provided for a boiler sectionable with condensation and gas burner.

The exchanger element is in the form of a hollow body 1 of general shape approximately rectangular with two lateral faces exchange 2 and 3 provided with pins such as 4 in shape prismatic with rounded 5 end and cross section diamond 6.

These pins constitute protruding points of each exchange side face 2 and 3 arranged in successive transverse rows such as 7 as represented. These rows are offset from those on the exchange side face opposite the adjacent exchanger element and protrude sufficiently of the junction plane between two exchanger elements neighbors 8 and 9 (figure 8) to nest in the free spaces between pimples such as 10 and constitute a flat volume 11 for the passage of combustion gases occupied mainly by spikes. Free spaces 10 form as many passages 12 in chicane for the slowing the evacuation of combustion gases.

There are a majority of pins 4 of identical shape and size, a top line 13 smaller spikes and two columns end 14 and 15 formed by specific pins 16 of general shape in rectangular section arranged in alternating succession with symmetrical presentation.

The area of pins on each exchange face 2 and 3 is delimited laterally by two edges of junction 17 and 18 projecting including the edges define the junction plane and serve as support for homologous songs from the neighboring exchanger element with interposition of a gasket 19 during assembly-juxtaposition of the heating body (figure 8).

The flat passage volume 11 formed by the junction of two neighboring exchanger elements 8 and 9 serves as a downdraft chimney for combustion gases.

The opposite side face is of conformation identical as shown in Figures 7 and 8.

The exchanger element includes a chamber interior 20 representing a flat interior volume crossed by the heat transfer fluid between an orifice lower inlet 21 and an upper outlet port 22.

As part of the application used as example, the body of the exchanger element has a upper end 23 shaped as a recess 24. This cavity 24 occupying practically the entire width of the exchanger element between an extension of the side wall and the top port block of outlet 22 is intended, with the exchanger elements neighbors 8, 9 and others forming the heating body of the boiler, to constitute a closed hearth at its upper end by the gas burner (not represented).

The body of the exchanger element is open to its lower end at the side faces exchange 2,3 and put in communication with a condensate collection receptacle (not shown).

This arrangement is typical of a boiler gas condensing. It conveniently avoids dripping condensate on the burner.

To slow down and distribute the water flow to reheat from the lower inlet 21 located at the lower end, the interior volume of room 20 has a chicane structure materialized by two large walls slightly oblique one lower 25 and the other upper 26 not joining the wall of the adjacent lateral edge of junction 17 and 18 respectively of the element body exchanger. The proximal end of each large wall 25 or 26 is offset from the adjacent wall of the inner chamber 20 of a constituent interval a restricted passage 27 and 28 respectively.

These intervals allow as indicated above to make the foundry core more solid by preventing it from being split transversely on a too long as is the case in the prior art (Figure 1).

The large lower oblique walls 25 and upper 26 are slightly inclined rising in the direction of movement of the heat transfer fluid so to favor the passage of the fluid as for a divergent opening (figure 2). This is the case of the large lower wall 25 which delimits a compartment diverge from the lower inlet of the fluid, but also of the large upper wall 26 which does not cut the current, but forces it to a path elongated meander 29.

To avoid excessive leakage from the running through restricted passages 27 and 28, has an inclined deflector in front of each of them amount respectively lower 30 and higher 31. These deflectors are small and are made in one piece with the adjacent side wall of the inner chamber 20. They make it possible to deflect locally the current of water to prevent its entry into restricted passages 27 and 28.

Each time we formed a chicane lower secondary 32 and upper 33 of which the only goal is to avoid or at least limit entry of the water current in the existing technical interval between the proximal end of each large wall and the adjacent wall of the interior chamber 20.

Note that the inclination of the deflector higher 31 is stronger. This is conditioned by the shape of the water current at this place coming from the lower part of the room and that it takes fold down so that it runs along the large wall 26.

We thus achieve a slowdown and a increased fluid path beneficial to heat exchange efficiency during path along the interior chamber during from which it heats up as shown in Figure 3 materializing the stream of water.

The great interest of the invention lies in being able to manufacture the exchanger element by a foundry technique with a core of sand mechanically strong ensuring repetitive quality in industrial manufacturing while improving advantages of the baffle structure interior.

Thus, as shown in Figure 4, the nucleus is produced in the form of a compact block 34 without large transverse notch (s).

There is a limited and inclined notch lower 35 and upper 36 corresponding to the walls 25 and 26 and two small oblique notches 37 and 38 offset corresponding to the deflectors 30 and 31 of the secondary baffles 32 and 33 delimiting bonds of material or attachments 39 and 40.

These material bonds or attachments 39 and 40 at the level of these secondary baffles bring the additional mechanical strength which the core lacked in the previous embodiments of the elements exchangers with baffle due to walls 41 and 42 of baffles made transverse and in one piece with the adjacent side wall of the chamber interior (Figure 1).

We notice in Figure 5 edges protruding cross sections such as 43 and 44 along joining edges. These transverse edges at number of at least two on each side edge of junction share length in intervals approximately the same length. They aim to play the role of a picot in order to occupy the space between two pins of an end column.

Note that the upper edge 43 at upper secondary baffle level 33 is placed in the space between the two deflectors.

To improve the circulation of combustion and therefore the exchange and to increase the duration life of the exchanger elements and facilitate cleaning, we plan to enamel the exchange surfaces side faces of the exchanger element.

The enamel layer provides protection against corrosion and smoothness on surfaces system improving the passage of combustion gases and avoiding the majority of incrustations and deposits.

Claims (6)

1. High-efficiency heat exchange element for sectionable boilers, in particular condensing boilers, having, on the one hand, raised portions (4) on lateral exchange faces (2, 3) thereof, which are each delimited by junction edges (17, 18), and, on the other hand, an internal chamber (20) in the form of a chicane, through which chamber (20) flows the liquid coolant, characterised in that the chicane comprises an upper structure (26, 31) and a lower structure (25, 30) serving as baffles, which are each formed by a first baffle plate (25, 26) and a second baffle plate (30, 31), the first baffle plate (25, 26) being separated from the adjacent lateral wall of the internal chamber (20) by a free interval which extends between the proximal end of the first baffle plate (25, 26) and the wall in order to form in each case a restricted passage (27, 28) and the second baffle plate (30, 31) being offset from the first baffle plate (25, 26) relative to the inlet of the liquid coolant in order to form in each case with the proximal end of the first baffle plate (25, 26) a lower (32) and upper (33) secondary chicane allowing connections (39, 40) of aggregated sand to be constituted in the core of the foundry mould, giving it additional mechanical strength and allowing simple, ready and complete removal of the moulding sand after moulding.
2. Exchange element according to claim 1, characterised in that the first baffle plates (25, 26) are inclined upwards in the direction of advance of the liquid coolant.
3. Exchange element according to claim 1 or 2, characterised in that the upper secondary chicane (33) is constituted by the proximal end of an upper wall (26) of the main chicane and by an oblique baffle plate (31) which is inclined upwards from the exchange element, which is of short length, which is located below the upper wall and which forms an integral part of the adjacent lateral wall of the internal chamber (20) in order to delimit with the proximal end of the upper wall (26) a bent lateral passage (28) close to the lateral wall of the chamber.
4. Exchange element according to the preceding claim, characterised in that the oblique baffle plate (31) is acutely inclined upwards.
5. Exchange element according to claim 1 or 2, characterised in that the lower secondary chicane (32) is constituted by the proximal end of a lower wall (25) of the main chicane and by a rising oblique baffle plate (30), which is of short length, which is located below the lower wall (25) and which forms an integral part of the wall of the internal chamber (20) in order to delimit a bent lateral passage (27) close to the wall of the internal chamber (20).
6. Exchange element according to any one of the preceding claims, characterised in that it is produced from a foundry mould with a sand core whose transverse notches (35, 36) and the adjacent small oblique notches (37, 38), which are intended to constitute the chicane structures (25, 26, 30, 31) of the internal chamber (20), delimit in each case a material connection (39, 40) between the central portion of the core and the lateral edges of the core with a view to improving the mechanical strength thereof.

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