Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B1/00—Methods of steam generation characterised by form of heating method
  • F22B1/28—Methods of steam generation characterised by form of heating method in boilers heated electrically
  • F22B1/287—Methods of steam generation characterised by form of heating method in boilers heated electrically with water in sprays or in films
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B1/00—Methods of steam generation characterised by form of heating method
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B1/00—Methods of steam generation characterised by form of heating method
  • F22B1/28—Methods of steam generation characterised by form of heating method in boilers heated electrically
  • F22B1/284—Methods of steam generation characterised by form of heating method in boilers heated electrically with water in reservoirs
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F6/00—Air-humidification, e.g. cooling by humidification
  • F24F6/02—Air-humidification, e.g. cooling by humidification by evaporation of water in the air
  • F24F6/04—Air-humidification, e.g. cooling by humidification by evaporation of water in the air using stationary unheated wet elements
  • F24F6/043—Air-humidification, e.g. cooling by humidification by evaporation of water in the air using stationary unheated wet elements with self-sucking action, e.g. wicks

Definitions

• the present invention relates to a method and a device for vaporizing a liquid. It is known that, to vaporize a liquid, it is possible to use an electrical resistance immersed in a relatively large water depth. By this design, the heating time of the liquid necessary to vaporize it is relatively long and the vaporization yield is poor, especially in sequential regime. This is for example the case of a number of steam boilers using combustion gases.
• At least one porous substrate that is to say with capillary property exposed to a determined ambient pressure
• At least one energy source for heating at least one vaporization zone of said substrate located downstream of the upstream portion, and the liquid which charges it, so that at least part of this liquid is vaporized there,
• FIG. 4 of this patent shows the advantage that there may be to use several feeding trays arranged at different elevation levels, the highest placing the substrate horizontally. Tests carried out with such a device however show that the yield remains poor, and that the quantity of liquid in the vaporization zone is quickly too low, that the time of arrival of the liquid in this vaporization zone is often too long.
• the device of DE-C-158 050 is also bulky, not conducive to industrial achievements Today (high efficiency, compactness, low manufacturing cost for large series, reliability over time ).
• the object of the invention is to provide a solution to many of the above-mentioned drawbacks and in particular proposes a process which can be industrially implemented under commercially attractive conditions, without exorbitant manufacturing and / or maintenance costs and also offers flexibility of use, performance and reliability adapted to current needs.
• the solution of the invention consists in particular, for a given vaporization regime corresponding to determined energy supply conditions, in establishing in the substrate ("capillary") a liquid inlet flow rate greater than the inlet flow rate of liquid induced in the same substrate, in the position then assumed to be horizontal thereof, by the capillarity and vaporization of the liquid only, (the position of the first cited substrate not necessarily being horizontal).
• the device of the invention provides that the means for supplying liquid to the substrate in question must include means for pressurizing the liquid in order to establish a pressure therein greater than ambient pressure.
• FIG. 1 we have shown in FIG. 1 the manner in which we will advantageously proceed to measure the induced flow rate as indicated above, "in the same substrate, by capillarity and vaporization only (of course for the same conditions of supply of energy), in the position then assumed to be horizontal of the substrate ".
• the knowledge, for a given time interval, of the quantity Q 2 or of the weight of liquid which has entered the substrate (and which therefore has left the container) will make it possible to have the "induced flow" of liquid entering the substrate.
• Another solution can also consist:
• the additional pressure can in particular be created by a pump.
• this substrate has a porosity of between approximately 5% and 90%, and a substrate will be used comprising empty volumes of liquid retention, so that this liquid can occupy between approximately 5% and 100% of said volumes empty.
• the use of a substrate which is almost like a thin porous film offers the advantage that the heat flux generated does not face it.
• a characteristic of the invention also provides for increasing the flow rate range of liquid to be vaporized, by supersaturating the substrate in such a way that part of the liquid s 'flows on a free external surface thereof, being held against this substrate by interfacial tension.
• a simple way to adjust the flow rate of liquid in the substrate is to tilt it relative to the horizontal. We can then create, as indicated above, a water column in the substrate area directly exposed to the heating flow and possibly above it, in order to take advantage of the effect of gravity. When the liquid flow rate is greater than the density of the thermal flow, the excess liquid flowing out of the lower part of the substrate can be recovered, to reinject it into its upper part.
• Another means of supplying liquid consists in injecting it under pressure into all or part of the passage section of the substrate. It is thus possible to arrange the substrate so that it bathes at two opposite ends (between which the liquid to vaporize flows along it), in a tube where said liquid will be brought by means of forced circulation. This could also be the case, for example, if the device was operated with substrates then arranged horizontally.
• drop-by-drop means for example taking advantage of capillary pumping by immersing an additional porous body in a suitable reservoir.
• a spray nozzle which sends the liquid to be vaporized onto the substrate, or even immerse the porous substrate directly, at least part of which receives the flow of heating energy, in a sheet of water which can be vary the level.
• a pump to circulate the liquid under pressure in a locally bent pipe between two of the branches of which the porous substrate has been previously disposed, so that its ends are immersed in the liquid of the tube.
• the vaporization of the liquid contained in the substrate can be obtained in particular by all or part of the following three heat transfer modes: radiation, conduction or convection originating both from combustion gases and from an electrical source, for example, this under operating conditions which can be both at lower pressure and at pressure greater than or equal to atmospheric pressure, the vaporization of a number of different liquids, such as water, alcohol, liquid petroleum or the like being able to be considered.
• porous substrate of the invention could be produced from cotton fibers or threads, or even mineral fibers, such as for example glass or quartz fibers, or even metallic fibers, such as for example steel wires.
• mineral fibers such as for example glass or quartz fibers
• metallic fibers such as for example steel wires.
• a substrate formed like a canvas permeable flexible fibrous fabric, or a plate with a more rigid structure.
• the device of the invention may advantageously comprise two hollow boxes delimiting between them a chimney in which the combustion products of the burner will then circulate, these boxes each containing at least one substrate.
• FIG. 2 shows a possible structure of the substrate in accordance with the invention
• FIG. 3 is a perspective view of an assembly for measuring the flow rate in porous substrate, as a function of the height of its supply water body
• FIG. 4 is a diagram showing the variation of the water flow rate of a porous substrate according to the invention as a function of the height of its water level
• FIG. 5 is a side view (arrow V) of the generator shown in partial perspective, with cutaway
• Figure 6 Figure 7 is a diagram showing, for an installation of the type of that of Figures 5 and 6, the variation of the vaporization yield as a function of the heating power generated , this for several heights of water available and for two different thicknesses of porous substrates
• FIG. 1 is a perspective view of an assembly for measuring the flow rate in porous substrate, as a function of the height of its supply water body
• FIG. 4 is a diagram showing the variation of the water flow rate of a porous substrate according to the invention as a function of the height of its water level
• FIG. 8 is a diagram showing, as a function of the power injected, the influence of the thickness of the substrate on the outlet temperature of the gases for a e installation still in accordance with that of FIGS. 5 and 6,
• FIG. 9 is a perspective view with cutaway of a steam boiler using an electrical resistance of cartridge type
• FIGS. 10 and 11 are sectional views (respectively according to lines XI-XI and XX) of an electric vaporization device equipped with two porous substrates bathing locally in a pipe where circulates water to vaporize injected by means of a pump
• FIG. 12 is a partial perspective view with cutaway of the drip feed of a device according to the invention
• FIG. 13 is also a partial perspective view with cutaway of another generator producing vapor by thermal radiation of a resistance.
• FIG. 2 represents an example of design of a porous "film” 1 with capillary property, made of cotton, type “honeycomb” with square mesh 2 of approximately 30 to 50 mm.
• the latter therefore has a structure integrating empty volumes for retaining the liquid to be vaporized, these volumes being here constituted by the spaces between the wires of the mesh and by the structural empty volumes of the wires themselves same.
• the central part of the substrate 1 illustrated is a weaving of threads of different thicknesses according to the choice of the desired flow capacity. Peripherally, this substrate here consists of wicks three times thicker than those of the central part. Thus, a peripheral buffer for the reserve and diffusion of water is created towards the central parts of the mesh.
• the choice of the permeable substrate is important. In what follows, it will be seen that its thickness will always be between approximately 0.05 mm and 5 mm, with a porosity to the liquid to be vaporized between approximately 5 and 90%.
• FIG. 3 is an example of an experimental device for feeding by pumping a fine porous substrate in the height of a body of water.
• This device makes it possible to adjust the flow rate of the liquid flowing through the effect of gravity right out of the feed tray. It consists of a balance 3, a container 5 for collecting the water flowing from the porous "film” 7 and a water tank 9 in which the upper part 7a of the porous substrate is immersed. To obtain a constant and free flow throughout the width of the passage section of the porous film, the film was cut at 11 at its bottom.
• the flow measurement consists in varying the height h of the water level of the tank 9.
• the table below indicates the characteristics of use of three thicknesses of porous substrates which may be square mesh of the type illustrated in FIG. 2.
• Type of substrate thickness of storage capacity Density of the porous flow in cotton substrate of saturated water (g / cm2) for heating the substrate (W / cm2)
• FIG. 4 is a diagram which indicates the flow of water flowing in a vertical porous film with small meshes (that is to say of thickness ⁇ 1 mm, for a unitary surface of mesh of the order of 0, 05 mm 2 ) depending on the height of the water body.
• Curve (A) measures the flow of water which flows freely to the lower part of the substrate.
• Curve (B) measures the water flow when the same porous film is immersed at its bottom in 2 cm of water.
• Curve (C) measures the flow rate when the film is pressed against a metal wall without being immersed in its lower part.
• the flow rate of the liquid flowing therein can be varied in a ratio of 1 to 8 depending on the curve (A), in a ratio from 1 to 5, curve (B), and close to the latter, curve (C), when the porous film is pressed against an exchange wall.
• the steam boiler presented vaporizes water contained in porous films pressed against heat exchange walls 21.
• the heat transfer can take place, as well from a gas train type burner, such as 19, with atmospheric air supply, or with supply air, only from one or more radiant burners.
• the heat transfer is mainly carried out by convection, while in the second it is mainly carried out by radiation.
• each partition 21 has been internally fitted with three porous films 7a, 7b, 7c extending in perspective over approximately half the height of the exchange wall, over 3/4 of the remaining height, and on the 1/4 of the highest part.
• a mesh 33 with large open meshes at a rate of 90% with a mesh surface of 4 cm 2 to, on the one hand, ensure good thermal contact with the substrates and, on the other hand, leave a passage for the steam produced.
• Each enclosure 29 is also equipped with an upper tank 34 in which is immersed an "upstream" portion of the three porous films which are here of the same thickness. It will be noted that the porous film 7a, in order to reach the top part up to the tank 34, is kept apart from that marked 7b (space d).
• the entire column of water Cl stored on the thermally protected upper part of the film 7a will be used to feed under suitable pressure (higher than the ambient pressure prevailing in the enclosure considered) its lower part pressed against the partition 21, therefore fully active in terms of heat exchange and vaporization capacity. It is also the same for the film 7b, but with a column C2 of lesser height practically the entire column being here exposed to the heating flow.
• the water collected in an appropriate lower reservoir is shown, when the flow rate in the films is greater than that vaporizable by the heat flow. When this excess water reaches a predetermined level, it can be reinjected by a pump into the tanks 34.
• FIG. 7 is a diagram which shows the influence of the number of substrates and the height of water on the vaporization yield as a function of the power injected, with either a single porous film of the aforementioned type "with small meshes" replacing the two substrates 7a, 7b, or these substrates themselves.
• the measure consists in varying the height of the water level of the tank 34, it being specified that the tank has in this case been placed approximately 4/5 of the height of the exchange walls.
• the vaporization yield goes from 0.6 g / Wh to 0.8 g / Wh, ie a gain of 30% on the efficiency of the boiler. This gain is obtained when the water height is varied from H-2 mm to H-4 mm, then to H-9 mm.
• FIG. 8 shows the influence of the thickness of the substrate (s) on the temperature of the gases leaving the boiler, this depending on of the variation of its power.
• a porous film with "small meshes” gives a temperature difference of 120 ° C to 400 ° C while this difference is only from 300 ° C to 370 ° C for a porous mesh film thick.
• Figure 9 is a cutaway and perspective view of an alternative embodiment of a steam generator using an electrical resistance.
• a cartridge resistor 37 on the outside surface of which a fibrous substrate is applied and clamped, presenting itself as a flexible sleeve 39 sewn at 41 and 43 to form two half-surfaces 45a, 45b which extend towards the lower part of the enclosure 47 while being partially submerged in water in the upper part in an upper tank 49 the level of which could be varied (by a feed pump) and in the lower part in a lower collection tank 51.
• the enclosure 47 is also equipped at its upper part with an outlet for steam 53. With this type of electric resistance boiler, the same kinds of measurements were made as on the gas boiler in FIGS. 5 and 6.
• Each of the tables below shows, at constant water flow rate, the vaporization yield by varying the density of thermal flux for four thicknesses of porous film.
• Vaporization efficiency 0.85 1.02 1.10 1.11 1.10 1.08
• the vaporization yield 20% for a thickness of 0.2 mm, of 40% for a thickness of 1 mm, of 30% for a thickness of 2 mm and 25% for a thickness of 4 mm.
• the vaporization means comprise a rectangular resistor 59 with a power of 270 Watts. On the resistance is applied and tightened a fabric forming a woven film 61 sewn at 63 and 65 to form a sleeve extending downward, housed and integral with the interior of the lower part 67 of the pipe 69. This sleeve s 'also extends inside the upper part 71 of the same pipe 69.
• the resistance is housed in an enclosure 73 of vaporization.
• the vaporization enclosure comprises an outlet tube 75 for the vapor and a tube 77 for evacuating the excess water when the flow of circulating water is too high and a flange 79 integral with the resistance to be fixed in 81 at the enclosure.
• the circulation of water is ensured by a pump 84 whose flow rate can be adjusted.
• the outlet 85 of the pipe is provided with a tap 86. This can ensure a slight overpressure in the pipe so that the liquid preferentially flows into the porous film.
• the substrate can also be oversaturated with liquid, by creating a film of water maintained on the surface by the interfacial tension of the liquid on the faces of the porous film.
• FIG. 12 is an example of a drip device for supplying a vaporization apparatus comparable to that of FIG. 8.
• a drip device for supplying a vaporization apparatus comparable to that of FIG. 8.
• a double woven substrate 111a, 111b surrounds, in pendant, a tubular electrical resistance 113, in the lower part of an evaporation enclosure 115.
• the upper part of the substrate is flared in "V" shape and rests on two supports. Its supply of liquid to be evaporated is therefore ensured by a drip, by means of two fine rectangular woven substrates 117, 119, hanging vertically and ending at their free lower end with fringes 120 favoring the drip and a good distribution of the liquid.
• the substrates 117, 119 are immersed in a liquid supply tank 121, of variable liquid height, filled with a supply not shown.
• a chimney 123 allows the steam to escape.
• FIG. 13 shows a device for vaporizing liquid using at least one 1 mm thick sintered stainless steel plate.
• the liquid is vaporized by thermal radiation from an electrical resistance.
• this vaporization element can also be supplied by the drip device of FIG. 12.
• the process of the invention and its exemplary embodiments find their applications in particular in products from the craft sectors, the general public, DIY as well as in the processing and agro-food industries.
• steam generators ranging from a few kg of steam / hour to more than a ton / hour.
• These generators can be used, for example, in catering ovens, in bakeries, in consumer gas cookers, in the biscuit and pre-baking industry, in the textile industry for fiber processing, or even, for example, for steam pressing plants, or even in biology laboratories for sterilization. It is also possible, for example, to produce steam generators for individual irons or with a steam generator, or even for floor and wall cleaning devices.
• the device of the invention to operate both at atmospheric pressure and at overpressure or under vacuum, only the pressurization of the liquid having to be provided to ensure the flow conditions sought in the substrate.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
• Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Commercial Cooking Devices (AREA)
• Chemical Vapour Deposition (AREA)
• Sorption Type Refrigeration Machines (AREA)
• Motor Or Generator Cooling System (AREA)

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• 1994
  • 1994-05-18 FR FR9406076A patent/FR2720143B1/fr not_active Expired - Fee Related
• 1995
  • 1995-05-18 US US08/583,121 patent/US5771845A/en not_active Expired - Fee Related
  • 1995-05-18 CA CA002167598A patent/CA2167598A1/en not_active Abandoned
  • 1995-05-18 DE DE69506669T patent/DE69506669T2/de not_active Expired - Fee Related
  • 1995-05-18 JP JP7529428A patent/JPH09500957A/ja active Pending
  • 1995-05-18 EP EP95918659A patent/EP0708900B1/de not_active Expired - Lifetime
  • 1995-05-18 WO PCT/FR1995/000656 patent/WO1995031674A1/fr not_active Ceased
  • 1995-05-18 ES ES95918659T patent/ES2128058T3/es not_active Expired - Lifetime
  • 1995-05-18 AT AT95918659T patent/ATE174680T1/de active

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