EP0962695B1 - Steam generator with plate for direct evaporation - Google Patents

Description

The subject of the present invention is a steam generator with direct evaporation tray comprising a box inside which are arranged at least a first plate equipped with a resistance electric heater and a second plate kept applied against a first main face of the first plate by means of elastic return, means being provided for introducing water under pressure in the center of the steam generator in the interface between the first and second trays, and at least one steam outlet being housed in the housing.

We already know, in particular from document EP-A-0 023 855, direct evaporative steam generators in which liquid to evaporate is injected under pressure to create a laminar flow of very thin between the facing faces of a first plate fixed heater and a second mobile evaporator plate which cooperates with elastic return means intended to maintain the second plate at a short distance from the heating plate.

Tray steam generators of this type have however, a yield which is not optimized and consequently involves special precautions for use, especially in the case outside, taking into account heat losses notably by radiation.

We have also proposed, by document EP-A-0 651 202, a tray steam generator involving evaporation in two steps. Following a main evaporation achieved by the injection of water under pressure at the center of the steam generator, at the interface between the fixed heating plate and the mobile evaporator plate, the flow of primary steam created at the interface between the plates and the residual water droplets contained in this stream are returned to an annular free space outside the plates then projected onto the second side of the heating plate to create a secondary system additional evaporation which helps reduce losses thermal radiation. Such an achievement presents however some complexity due to the evaporation process in two steps, and does not optimize the steam generator or from the point of view of efficiency, neither from the point of view of space or the ease of manufacture or use.

We also know from document FR-A-2 581 442 a generator vapor with direct evaporation in which a stack of mobile evaporator trays. The water comes out in the center of the pile of movable plates which are drilled in the center and are applied one against the other pressing on the inner face of an outer casing, by through an undrilled plate and an elastic return means. An electrical resistance is embedded in the outer casing. The distance of the electrical resistance from the plates does not optimize the transmission of energy and limits performance. Through elsewhere, a steam generator of this type lacks compactness.

The present invention aims to remedy the aforementioned drawbacks and to make an improved tray steam generator which both compact and easy to manufacture and use and improves performance and safety of the steam generator.

These aims are achieved by means of a steam generator with a direct evaporation plate comprising a box inside of which are disposed at least a first plate equipped with an electrical heating resistance and a second plate maintained applied against a first main face of the first plate by elastic return means, means being provided for introducing pressurized water into the center of the steam generator in the interface between the first and second plates, and at least one steam outlet orifice being provided in The box,
characterized in that it comprises a third plate maintained applied against a second main face of the first plate by said elastic return means, which interact between the second and third plates between which the first plate is sandwiched to constitute a mechanically closed system on itself and in that the means for introducing pressurized water also open into the interface between the first and third plates.

Thanks to the presence of mobile evaporator trays on both sides on the other side of the heating body, the two main faces of the first plate fixed forming heating bodies are used to cause a direct primary evaporation, which helps improve yield and minimizes radiation losses.

The fact that all of the three trays of the central module of steam production incorporates elastic return means acting between the second and third plates avoids contact of these means of recall with the external casing so that the manufacture of this one is simplified and safety is reinforced during use.

Preferably, all of the first, second and third trays is thermally insulated from the housing by a porous insulating material lining which is vapor permeable while constituting a trap for residual water.

The presence of a porous body such as rock wool around of the central module thus contributes not only to isolate the housing outside in relation to the central steam generator module and focus heat energy, but also to retain and contribute also evaporate any residual water droplets.

According to a particular embodiment, the second and third trays are kept pressed against the first heating plate by flange systems cooperating with said return means elastic.

According to an exemplary embodiment, the first heating plate basically has the shape of a disc and the second and third trays have geometric shapes that extend slightly beyond the heating plate to form at least part flange systems.

Flange systems can be incorporated into the second and third trays or may include first and second stirrups located outside the second and third plates.

According to a particular characteristic of the steam generator according to the invention, the means for introducing pressurized water include an external connector in which is fixed an injector which is arranged essentially inside the housing, crosses the wall thereof by an orifice thermally insulated by a seal and, is fixed in the first tray to be in communication by a conduit with a central orifice application of pressurized water in the interfaces between the first tray and respectively the second and third trays.

A thermostat for controlling the heating resistance of the first plate is disposed on the body of said external connector water supply.

This particular arrangement of the thermostat makes it possible to anticipate the switching on the heating when cold water is injected and increases the amount of steam produced compared to others arrangements where the thermostat cooperates with the heating body by example.

Advantageously, all of the first, second and third trays equipped with the heating element and an injector water supply constitutes a modular assembly removable by report to the housing.

In this case, the water supply injector can play the role of positioner of the removable modular assembly relative to the housing.

According to a particular embodiment, the housing has a prismatic shape with two main planar faces and faces flat side panels of low height on which the fittings are located power supply to the heating element, the fitting water supply and a removable cover for the introduction or removal of all of the first, second and third trays.

• la figure 1 est une vue en coupe selon la ligne I-I de la figure 2, d'un exemple de générateur de vapeur à plateau selon l'invention,
• la figure 2 est une vue en coupe selon la ligne ll-ll de la figure 1,
• la figure 3 est une vue de dessus d'un étrier coopérant avec les plateaux évaporateurs selon un mode de réalisation de l'invention,
• la figure 4 est une vue en coupe selon la ligne IV-IV de la figure 1, d'un module évaporateur incorporé dans le générateur de vapeur de la figure 1,
• la figure 5 est une vue de dessus d'un exemple de plateaux évaporateurs superposés selon l'invention et destinés à recevoir entre eux un plateau chauffant,
• la figure 6 est une vue d'une face latérale du boítier d'un exemple de générateur de vapeur selon l'invention, la face présentant une ouverture d'introduction d'un module évaporateur, et
• la figure 7 est une vue de détail montrant un exemple d'injecteur d'eau pouvant être utilisé dans un générateur de vapeur selon l'invention.

Other characteristics and advantages of the invention will emerge from the following description of particular embodiments, given by way of examples, with reference to the appended drawings, in which:

• FIG. 1 is a sectional view along line II of FIG. 2, of an example of a tray steam generator according to the invention,
• FIG. 2 is a sectional view along the line II-II of FIG. 1,
• FIG. 3 is a top view of a stirrup cooperating with the evaporator plates according to an embodiment of the invention,
• FIG. 4 is a sectional view along line IV-IV of FIG. 1, of an evaporator module incorporated in the steam generator of FIG. 1,
• FIG. 5 is a top view of an example of stacked evaporator trays according to the invention and intended to receive between them a heating plate,
• FIG. 6 is a view of a side face of the case of an example of a steam generator according to the invention, the face having an opening for introducing an evaporator module, and
• FIG. 7 is a detail view showing an example of a water injector that can be used in a steam generator according to the invention.

If we mainly refer to Figures 1, 2 and 4, we see a example of direct evaporation tray steam generator according to the invention comprising an outside housing 110 inside which is placed, without direct contact with this housing 110, a set modular evaporation essentially comprising a central plate or heating body 30 sandwiched between two trays evaporators 10, 20. The modular assembly 10, 20, 30 is isolated from the housing 110 by a lining of a porous thermal insulating material 90, such as rock wool which prevents heat from radiating to the housing 110.

The central plate 30 can be produced for example in the form of a disc having two main faces 31, 32 which can be flat, as shown in the drawings, to increase the compactness, but can also be slightly curved if necessary having a spherical or conical shape so as to increase the exchange surface. The fixed central plate 30 is equipped with a resistance electric 60 integrated by overmolding. Electric resistance 60 has connection ends 61, 62 which pass through the material porous 90 and sections 117, 116 of the side wall of the housing 110 in being isolated from the housing 110 for example by silicone tubes 63, 64 which help to ensure not only electrical insulation but above all a seal preventing steam from escaping from the housing 110 at level of these electrical connections 61, 62, or comes into contact with the connection pins.

Pressurized water E can be injected in the center of the tray central 30 by an injector 80 which includes a fitting element disposed outside the housing 110, at a lateral face 117, and comprising a body 81 and a fitting proper 82. The injector itself, an example of which is illustrated on the Figure 7, comprises a body 85 provided with a collar 85a, extended by side by a threaded tubular part 84 intended to be fixed in the body 81 of the connector, and on the other side by a threaded tubular part 86 which is screwed into the central plate 30 and is extended by a channel 87 which is formed in this central plate 30 and opens into an orifice central 88 cooperating with recesses 88a, 88b allowing a injection of pressurized water on either side of the central plate 30 (see Figures 1 and 2). A seal 83 also playing the role of insulator, which can be for example PTFE, provides insulation of the injector 80 relative to the housing 110 and prevents steam leakage at the orifice for the passage of the injector 80 through the housing 110.

The injector 80 makes it possible to position the central plate 30 by compared to the housing 110 without there being any other contact between these two elements that the seal 83 or the insulating tubes 63, 64 arranged around the electrical connections 61, 62 of the resistor 60.

According to an important aspect of the present invention, trays mobile evaporators 10, 20 are arranged on either side of the plate central 30 and are kept applied against the two main faces 31, 32 of the central plate 30 by the action of springs such as 71, 72, against the pressure of the water injected through the orifice 88 and the recesses 88a, 88b at level of the interfaces between the central heating plate 30 and the plates evaporators 10, 20. The sides of the evaporator plates 10, 20 facing the central plate 30 have geometric shapes complementary to those of the main faces 31, 32 of the plate central, that is to say are planar if the main faces 31, 32 are planar, and concave if the main faces 31, 32 are convex, so that ensure a laminar flow of water in the interfaces between the trays 10, 30 and 20, 30. The presence of evaporator trays 10, 20 sandwiching the central heating plate 30 allows use at maximum heat energy supplied by the central plate 30 using all this heat energy to effect a primary evaporation of the water injected into the center of the steam generator and preventing the central plate 30 radiates towards the housing 110. The presence of the lining 90 made of porous material and the absence of contact between on the one hand the evaporator plates 10, 20 and their elastic return means 71, 72 and on the other hand the box 110, allows to increase the quantity of steam produced with reduced power for example of the order of 2 kW which is suitable for household appliances.

In general, the housing 110, which is without direct contact with the evaporator module consisting of the three plates 10, 20, 30, is not not subjected to excessive temperature and can be made in one economical material, such as metallic material such as aluminum or a molded plastic. Safe operation of the steam generator can thus be improved while the cost of manufacturing is reduced. The evaporator plates 10, 20 can be made for example of aluminum.

In addition, the water injected into the center of the steam generator through orifice 88 is distributed on each main face of the central plate 30, so that the amount of water to be evaporated on each side is not not excessive, which limits the risk of residual water being present in the steam produced. In addition, any residual water, appearing by example at the end of use when the temperature of the heating body 30 decreases, is trapped by the porous material 90 which absorbs by capillary water not evaporated and thus serves as a filter allowing only steam, so that even after use, the steam generator can produce unsaturated vapor free from water droplets. Furthermore, the water droplets trapped in the porous material 90 also end up being vaporized within this porous material 90 whose temperature is intermediate between that of the evaporator module 10, 20, 30 and that of the housing 110.

Advantageously, a thermostat 89 is arranged on the room water supply 80 thermally insulated from the housing 110. The thermostat 89 can thus be arranged for example on the metal body 81 of the fitting 81, 82 into which the injector body 85 is screwed. The thermostat 89 controls the supply of the resistor 60 as soon as water is injected, so that the heating of the central tray 30 is started done early, which increases the amount of steam produced. During operation of the steam generator, the thermostat 89 remains sensitive, via the metal injector 80, to variations in temperature of the central plate 30, and can thus control the power supply of resistor 60 to maintain sufficient heat production at the tray heating 30.

The housing 110 comprises two main faces 111, 112 advantageously flat. Face 111 can be used as a lower face constituting the base of the generator while the upper face 112 is provided with one or more steam outlet orifices 91. Box 110 may for example have a prismatic shape with faces flat side 113 and 118 of low height on some of which (faces 116 and 117 for example) are located the connections 61, 62 electric supply of the heating resistor 60 and the connector 81, 82 water supply. In the embodiment shown in the drawing, one of the flat side faces (face 115) has an opening 122 closed by a cover 119 fixed for example by engaged screws in nuts 121 integral with the circumference of the face 115. The opening 122 allows the insertion and removal of the removable assembly consisting of trays 10, 20, 30 and the injector 80, as well as the introduction or the exchange of porous material 90. A flat seal, simple to arrange and of relatively short length, is interposed between the flat cover 119 and the periphery of the flat face 115 around opening 122. Other embodiments without removable module evaporator are possible as will be explained below.

According to an important aspect of the invention, the evaporator trays mobile 10, 20 which enclose the central heating plate 30 fixed are kept applied against the main faces 31, 32 of the central plate against the force exerted by the pressurized water introduced by the orifice 88, under the action of at least two springs 71, 72 which act directly between the two evaporator plates 10, 20, so as to cause a crushing of water droplets in laminar flow at the level interfaces between the plates 30, 10 and 30, 20 and thus cause a primary evaporation reducing the risk of heat build-up.

The fact that the evaporator plates 10, 20 are pressed against the central heating plate 30 without any spring being supported on the outer casing 110 facilitates manufacturing and avoids thermal bridges between the central evaporator module 10, 20, 30 and the housing 110, so that the thermal insulation by the lining of porous material 90 can to be fully effective.

According to a particular embodiment, illustrated in Figures 1 to 5, the central plate 30 is produced in the form of a circular disc whose peripheral part is inscribed in a square. Trays evaporators 10, 20 are produced in the form of plates, the polygonal outline also fits into the same square. Each evaporator plate 10, 20 thus essentially has the form of a square plate with two large cut sides 11, 12 respectively 21, 22 in the vicinity of two angles located at a diagonal of the square. The other two angles of each square plate 10, 20 can if necessary also present a small cutaway 17, 18 27, 28 respectively but essentially define two ears 13, 14 respectively 23, 24 drilled with an orifice 15, 16 respectively 25, 26. The plates forming the evaporator plates 10, 20 are identical but are superimposed with an offset of 90 ° so that the large cut sides 11, 12 respectively 21, 22 of a tray 10 respectively 20 are located in the vicinity of the ears 23, 24 respectively 13, 14 of the other plate 20 respectively 10.

A bracket 40, respectively 50 is arranged on the outside of each evaporator plates 10, 20 so as to form flanges cooperating with the ears 23, 24 respectively 13, 14 of the other plate evaporator 20, 10. The stirrups 40, 50 are thus arranged in the two diagonals of the square in which the evaporator plates 10 are inscribed, 20.

Figures 3 and 4 show more particularly the stirrup 40 comprising a main branch 41 flattened on the plate evaporator 10, two portions 42, 44 folded at 90 ° and two legs end forming flanges 43, 45 pierced with orifices 46, 47 which come superimpose on the ears 23, 24 forming flanges of the evaporator plate 20. Return springs 71, 72 cooperating with screw-nut systems 73, 74 respectively 75, 76, keep the flanges 43, 45 tight the stirrup 40 against the ears 23, 24 of the plate 20 so that the two plates 10, 20 are kept assembled against the central plate 30. The stirrup 50 is produced in a manner identical to the stirrup 40. In the example shown, four return springs 71, 72 are thus arranged at vicinity of the ears 13, 14 and 23, 24 of the evaporator plates 10, 20 in the vicinity of the four angles of the square delimiting the evaporator module 10, 20, 30, and outside the central plate 30 inscribed in said square. The spring systems 71, 72 are essentially located in the thickness of the evaporator module 10, 20, 30 (Figure 4) and thus allow to make a very compact steam generator. Plating force trays 10, 20 on the heating body 30 may for example be around 20 to 30kg. The number of springs can naturally vary according to the embodiments. In general, a number of springs between 2 and 4 is satisfactory.

For example, the thickness of the evaporator module 10, 20, 30 can be between about 20 and 40 mm and the thickness of the case between 40 and 60 mm. The diameter of the central heating plate 30 is adapted to the needs. For example, a steam generator domestic according to the invention may include a central tray 30 of 160 mm in diameter and 12 mm thick and evaporator trays 10, 20 of the type described above, inscribed in a 160 mm square of side and each having a thickness of the order of 6 mm. In this case, the outer housing 110 may have main faces 111, 112 inscribed in a rectangle of for example 200 x 225 mm.

In the version shown in Figures 1, 2 and 6, the planar flange 115 of the side face of the housing 110 defining the opening 122 and receiving the cover 119 is provided with a flat seal. This joint simple in shape and reduced in length is located in one area of the housing exterior little subject to thermal shock, which improves safety. The only other generator sealing elements are the seal 83 located at the level of the water injector 80 and the insulating means such as silicone tubes 63, 64 located at the pins of connection 61, 62 of the electrical resistance 60. The overall construction is therefore very simple.

Naturally various modifications and additions can be made to the embodiments described.

Thus, the stirrups 40, 50 could be integrated into the plates 10, 20 respectively. In this case, the flanges such as 43, 45 of the caliper 40 and the portions 42, 44 would be formed in one piece with the plate evaporator 10, and the corresponding parts of the stirrup 50 would be formed in one piece with the plate 20.

The shape of the evaporator trays 10, 20 and that of the tray heater 30 may also be different from those described previously. However a heating plate 30 in the form of a pancake circular and evaporator plates 10, 20 covering the entire heating plate 30 and extending beyond only to form spring clamps 71, 72, outside the heating plate 30 and depending on the thickness of the evaporator module 10, 20, 30, allows have excellent compactness while keeping systems away from return spring 71, 72 from both the outer housing 110 and the plate heating 30.

Furthermore, the steam generator according to the invention lends itself well to a series production with a housing 110 which can be produced in plastic material.

In this case, the housing 110 can be fully sealed by welding or bonding for example, after the introduction of the module evaporator 10, 20, 30 and porous material 90, which gives a maximum tightness while facilitating manufacturing at lower cost.

The realization of an external housing 110 in plastic material molded allows a simple and reliable device to be produced in a simple manner expensive whose forms can be very diverse and can particular be essentially rounded. The number of games to assembling can be very reduced especially in the case where the housing 110 is for example made in two sealed parts free of screws, when the injector 80 comprises a body 84, 85 which is not screwed into the heating plate 30, by a threaded tubular part 86 but is formed in one piece with this plate 30, and when the fixing flanges of the springs 71, 72 are formed in one piece with the plates evaporators 10, 20.

Claims (10)

1. Steam generator with a direct evaporation plate comprising a housing (110) inside which are arranged at least one first plate (30) equipped with an electric heating resistor (60) and a second plate (10) kept pressed against a first main face (31) of the first plate (30) by elastic return means (71, 72), with means (80) being provided to introduce pressurised water into the centre of the steam generator in the interface between the first and second plates (30, 10) and at least one steam outlet (91) arranged in the housing (110),
   characterised in that it comprises a third plate (20) kept pressed against the second main face (32) of the first plate (30) by said elastic return means (71, 72), which interact between the second and third plates (10, 20) between which the first plate (30) is sandwiched to constitute a system which is mechanically closed on itself and in that the means (80) for introducing pressurised water also emerge in the interface between the first and third plates (30, 20).
2. Steam generator according to claim 1, characterised in that all the first, second and third plates (30, 10, 20) are thermally insulated from the housing (110) by a porous insulating packing material (90) which is permeable to steam whilst constituting a trap for the residual water.
3. Steam generator according to claim 1 or claim 2, characterised in that the second and third plates (10, 20) are kept pressed against the first heating plate (10) by flange systems (40, 50) co-operating with said elastic return means (71, 72).
4. Steam generator according to claim 3, characterised in that the first heating plate (30) is essentially disk-shaped and the second and third plates (10, 20) have geometrical shapes which extend slightly beyond the heating plate (30) to form at least a part of the flange systems (40, 50).
5. Steam generator according to claim 3 or claim 4, characterised in that the flange systems (40, 50) comprise first and second clamps located outside the second and third plates (10, 20).
6. Steam generator according to any of the claims 1 to 5, characterised in that the means of introducing pressurised water (80) comprise an external connector (81, 82) in which is fixed an injector (84, 85, 86) which is arranged essentially inside the housing (110), crosses the latter's wall through an orifice which is thermally insulated by a gasket (83) and, is fixed in the first plate (30) to communicate via a conduit (87) with a main orifice (88) for applying pressurised water in the interfaces between the first plate (30) and respectively the second and third plates (10, 20).
7. Steam generator according to claim 6, characterised in that a thermostat (89) for controlling the heating resistor (60) of the first plate (30) is arranged on the body (81) of said external water supply connector (81, 82).
8. Steam generator according to any of the claims 1 to 7, characterised in that the set of first, second and third plates (30, 10, 20) fitted with the heating resistor (60) and a water supply injector (84, 85, 86) constitutes a modular set which is movable in relation to the housing (110).
9. Steam generator according to claim 8, characterised in that the water supply injector (84, 85, 86) plays the role of a positioner for the modular set which is movable in relation to the housing.
10. Steam generator according to any of the claims 1 to 9, characterised in that the housing (110) presents a prismatic shape with two flat main faces (111, 112) and low flat lateral faces (113 to 118) on which are located the heating resistor's (60) power supply connectors, the water supply connector (81, 82) and a removable cover (119) to introduce or withdraw all the first, second and third plates (30, 10, 20).

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