FR2521809A1 - MICROWAVE BOILER FOR THE PRODUCTION OF HOT FLUID FOR DOMESTIC, INDUSTRIAL OR HEATING OF PREMISES, AND METHOD USED BY THIS BOILER - Google Patents

Abstract

1. A microwave boiler producing hot fluids for domestic or industrial use or for room heating, comprising a metallic conducting and/or absorbing chamber (7) containing a fluid to be heated (6), a source of microwave energy (2) of the klystron or magnetron type, a device (3) of the waveguide, coaxial cable or similar type, transmitting said energy from the source (2) to the chamber (7) and a diffuser (5) which is fluid-tight and permeable to the waves, characterised in that, the fluid to be heated being a particular fluid among a plurality of fluids - particularly industrial oils -, between said device (3) of the waveguide type and said chamber (7) is interposed an applicator device (4) which co-operates with said chamber (7) in such a manner that it enables said microwave energy to be applied to said particular fluid (6) at a frequency corresponding to the natural frequency of relaxation oscillation of the particular fluid in question at a given temperature, said applicator device (4) being closed by said diffuser (5) which is fluid-tight and permeable to the waves, said applicator device (4) radiating said microwave energy towards said particular fluid (6) to be heated.

Description

252 1809

  The present invention relates to the field of heating fluids for domestic use, industrial, or space heating, and relates to a boiler

  microwaves for this purpose.

  The subject of the invention is also a method of

  fluid heating by means of this boiler.

  Currently, the heating of hot fluids for domestic use, industrial, or space heating, is mainly achieved by means of boilers for liquid fuel, gaseous, or solid, of dimensions

appropriate to the needs.

  These existing boilers generally have

  acceptable thermal efficiencies and are of a

  relatively simple and therefore inexpensive truction.

  because of the scarcity of sources of supply.

  fuel costs and the rapid rise in the price of these fuels, the operating cost of these known boilers is increasing rapidly, and other energy sources are becoming competitive for fluid heating. energy application

  electricity has become commonplace, especially

  this energy by means of heating resistors

or by means of heat pumps.

  However, this method of heating a fluid by means of electrical energy does not allow optimal exploitation of the latter, and therefore a

  satisfactory overall energy balance.

  The present invention aims to overcome these disadvantages. It relates, in fact, to a microwave boiler for producing a hot fluid for domestic, industrial or space heating purposes, characterized in that it essentially consists of a device for application of microwave energy supplied by a microwave power source of the klystron or magnetron type, by a device for transporting said waveguide type energy, coaxial cable, or the like, by an applicator device coupled with the source of microwave energy, radiating said energy towards the fluid to be heated, closed by a fluid-tight and wave-permeable diffuser, and which cooperates with the cylindrical, parallelepipedic, or spherical metallic conductor and / or absorber, or another form, defining the heat treatment zones of the fluid, and by safety elements preventing the flow of microwaves out of the enclosure

of the boiler.

  The subject of the invention is also a method of

  production of hot fluid implemented in the heat

  characterized in that it consists in applying microwave energy radiation to a fluid at a frequency corresponding to the relaxation frequency of the fluid considered at a given temperature, inside a conductive and absorbent envelope thermally and electromagnetically isolated, by means of a microwave source whose power wave is transmitted via a waveguide and / or an applicator to the medium to be heated, the heating of the fluid s effected by convection or conduction and by use of its dielectric properties, especially dielectric losses

and / or by relaxation.

  The invention will be better understood thanks to the description

  Hereinafter, which relates to preferred embodiments, given by way of non-limiting examples, and explained with reference to the accompanying diagrammatic drawings, in which: FIG. 1 is a sectional view of a boiler according to FIG. FIGS. 2 and 3 show, in sectional views, respectively the mounting of the boiler in a heating circuit and the detail of the control and regulation device. FIG. 4 shows the variation of the constant.

  dielectric of water with the frequency at a temperature

  25 ° C, Figure 5 shows the curve of the optimum power dissipated in water as a function of frequency and

  Figures 6 to 12 show other variants of

of the invention.

  According to the invention, and as shown more particularly by way of example, FIG. 1 of the accompanying drawings, the microwave boiler for

  production of a hot fluid for domestic use,

  triel, or heating premises, is constituted by a microwave energy application device 1 powered by a microwave energy source 2 of the klystron or magnetron type, by a device 3 for transporting energy, of the waveguide type, coaxial cable, or the like, and by an applicator device 4 coupled with the energy source 2, which radiates said energy towards the fluid to be heated 6, and which is closed by a fluid-tight diffuser and permeable to the waves 5 and / or to the cylindrical shaped conducting and / or absorbent metal enclosure 7 which delimit the treatment zones

thermal fluid.

  The enclosure 7 may also have a shape

  parallelepipedic, spherical, or other.

  The applicator 4 may advantageously be completed by at least one radiating antenna 8 whose elements have an effective electrical length equal to an integer representing one quarter of the length

  of the frequency of the radiated energy This application

  4 and / or the antenna 8 radiate the micro-energy

  waves in the chamber 7 of the fluid to be heated 6 so that is obtained an optimal yield of said energy. The types of applicators can be arbitrary, so that any volume of fluid can be treated. Similarly, the dimensions of the enclosure are provided.

  to match the frequency used.

  The microwave boiler according to the invention is -unie of a conducting and / or absorbent enclosure 7 provided with a protective envelope 12, a heat insulation 7 ', and at least one inspection hatch 9 provided with a closure device 10 in a conductive and / or absorbent material for stopping the microwaves and having a sealing device 11 for the fluid and allowing

  stopping the microwave radiation.

  The boiler is further provided with openings 13

  to 16 allowing the flow of fluid 6 to the canali-

  of the energy distribution network and the

  radiators and the filling or emptying of the

  by means of pipes 17 and 18, these openings 13 to 16 each housing a microwave stop device 19 to 22 for the reflection and / or absorption of said microwaves and thus preventing the leakage of the latter through said pipes and the various auxiliaries

23 to 25 connected to the boiler.

  The shape of the stop devices 19 to 22 is a function of the diameter of the openings 13 to 16 and the wavelength of the microwaves used, and these devices are provided.

  each of one or more openings allowing the flow of

  of the fluid 6 while preventing the passage of the mlcro-

* waves.

  It is also possible, according to another characteristic

  the invention, to realize the pipes as conductive and / or absorbent elements, so that the microwave stop devices become unnecessary. The boiler is further provided with at least one safety device against the overheating of the enclosure 7, not shown, in the form of a lack of water detector, an energy measuring device microwave, or the like, of at least one thermocouple 26, of a table

  27 control and operation of the boiler pre-

  indicating control and signaling members 28, a manometer 29, a control device 30 and

  regulation of the micro-energy application device 1

  cooperating with one or more thermal controllers

31.

  The walls of the enclosure 7 are advantageously made of any conductive material for stopping electromagnetic radiation and / or the absorption of this radiation, for example by blackbody effect, these materials being able to be metals and light alloys such as aluminum alloys,

or stainless steel.

  As shown in FIG. 2, the boiler according to the invention can be used for continuous direct heating of a fluid by microwaves, this fluid circulating in a thermal energy distribution network.

  such network is constituted by the boiler described above.

  above and designated by reference 32, by channeling

  arrival 33 and starting 34 of the treated fluid, connected to a use circuit having radiating elements such as radiators, and by 36 control members

of the circulation of the fluid.

  The device 30 for controlling and regulating the device 1 for applying microwave energy (FIG. 3)

  directly affects the emission of electromagnetic radiation

  tick, which is subjected to the fluid 6 inside the chamber 7, thus allowing to bring to the temperature

  said fluid, which is constituted by a receiver

  electric power source 37 connected to the hyperfre-

  2 through a static converter 38, or the like, acting on the supply circuit

  39 of source 2, and by a micro-processing unit

  processor 40, or other electronic device, ensuring the regulation and the operational safety of the entire boiler as well as auxiliaries 23 to 25, and to which are connected the thermal controller 31, the thermostat

  26, temperature sensors 41 and safety devices

  42 43, the device 30 being further provided with

  of a cooling circuit 2 'of the microwave source.

  wave 2, so that calories can be recovered

  to improve the efficiency of the boiler.

  The fluid to be heated 6, present in the enclosure

  and subjected to microwave radiation, undergoes a warm-up

  under very fast conditions controlled by

the processing unit 40.

  Thus the fluids or mixtures used in the

  most of them have sufficient loss factors

  large enough to allow them to heat up with high HF currents. As a result, the higher this factor of

  losses is low, the warmer is the slow

  l O tre more this factor is high, plus HF currents

  will have a fast action In reality, this unit of

  control the treatment of the fluid that is heated by

  dielectric losses and / or relaxation losses.

  The main characteristics of this regulation are translated by the power factor of the product to be heated since it is of its value that the possiblity depends

to heat a certain product.

  The active power consumed in the boiler, inside the enclosure 7 is in all approximation equal to the real value of the complex power P = WSE of E ek C &) This expression is more conne in the form Pa = kf E 2 V ú tg J with E: the electric field V: is the volume of the fluid to be treated k: is a coefficient ú 'tg S: is the loss factor f: is the frequency of the microwave source This expression makes appear that the power dissipated in the fluid 6, is proportional to the square of the electric field The loss factor ú tg & is a function of the frequency due to the fact that various electric charges are affected by the electric fields

  at very specific wavelengths.

  I is the absolute value of the permittivity of the dielectrics

  that Knowing that the permittivity of a material is a complex value, it can be put in the form highlighting the phase shift between the field E and the induction D, related to braking of the orientation of the

dipoles under the action of the field.

  The variations of E and Eq as a function of the frequency characterize a material and its behavior as a function of the frequency If the dipolar relaxation is of the type of DEBEYE, LU takes a maximum value at a frequency f D called frequency of DEBEYE; this frequency corresponds

  the maximum heat dissipation in the dielectric.

  This frequency f D is a characteristic of the material.

  Also the process used in the microwave boiler according to the invention makes it possible to implement this principle

  physical figure shown in Figure 4 for the case of water.

  FIG. 4 represents, by way of example, the variation of the dielectric constant of water with the frequency at the temperature of 250 C. The values of ú 'and ú change with temperature, and the same is true of

of the frequency of DEBEYE.

  The experimental results indicate that by using a microwave source operating at the frequency of 2450 MHz, a frequency commonly used in microwave ovens, one liter of water can be heated to 65 ° C in six minutes with a cooling device. Maximum power of 1200 WA as a comparison with a resistor

  electrical power of the same power, we put a dozen of

  the high efficiency of this heating process.

  Indeed, instead of using the slow process of conducting

  The microwaves produce heat simultaneously throughout the material. They constitute a heating system.

  direct and intense with a dissipation in volume, instan-

  and avoid the heating of the treatment chamber and the corresponding losses, which leads to

  considerable reduction in the duration of heat treatment

  and therefore very significant energy savings. Figure 5 shows the optimal power dissipated in the water according to the frequency and the volume for a microwave boiler of 1200 W of installed nominal power The efficiency obtained with the frequency of DEBEYE is very important since it indicates that to warm

  a volume of 1 liter of water at 60 C, the heating time

  fage will be much lower than that of the frequency of

2,450 GHz.

  It can therefore be affirmed that when a fluid and / or a material is subjected to a high frequency electric field, it absorbs a certain amount of energy.

  electromagnetic which is found in the form of heat.

  This absorbed energy is proportional to the loss factor of the fluid and / or the material E tg produced in which ú denotes the dielectric coefficient and tgi,

  the tangent of the loss angle of the body considered.

  Thus according to the invention, the microwave boiler

  which uses the optimal performance of the electromagnetic waves

  tromagnetic and the physical properties of absorption of the fluids to be heated, allows to see its implementation in applications as diverse as the heating of premises of any kind in the residential, tertiary, industrial and other sectors, because the fluid temperature level to heat (air or water from 50 O to 70 OC) is close to the best performance coefficients of this principle

  heating at appropriate frequencies.

  The subject of the invention is also the method implemented by the boiler described above, which consists in the use of the thermal agitation generated by the excitation states of the molecules to be heated by said fluid.

  contained in a conductive and / or absorbent enclosure.

  The method according to the invention uses one of the fundamental mechanisms of interaction of microwaves with a fluid, at the molecular level, which is the

  rotation of the polar molecules induced in the field.

  Placed in an electric field, molecules such as water are subjected to a torque 4 which tends to align them with the field, so as to reduce as much as possible the potential energy of the dipoles When the polarity or the direction of the field changes, reorientation

  cyclic dip 8 depends on energy dissipation

  viscous tick to which the molecule is subjected.

  A polar molecule therefore has a critical absorption frequency, called the relaxation frequency, which is a function of the characteristics of the molecule,

  the viscosity of the fluid and the temperature.

  At the critical frequency of rotation, the field transmits the maximum energy to the molecule and the energy of

  rotation is transformed into thermal energy.

  This mode of interaction explains the behavior of the permittivity as a function of the frequency In the spectral segment of the microwaves (10 M Hz to 300 G Hz),

  several modes of molecular movements are

  For example, the water that can constitute the heating element has a frequency of relaxation whose

  peak absorption is in the frequencies 2 to 80 GHz.

  Practically, the interactions radiation molecules integrate into the electrical permittivity of the material

  and the energy absorbed by said fluid becomes calculable

  by the equations of energy conservation

  and the equations of the so-called equations of Maxwell's equations.

  Figures 6 to 18 give as non-limiting examples various possible applications of the method

  and the microwave boiler according to the invention.

  Figure 6 represents a variant of

  According to the invention, a device for applying microwave energy 1 is placed in a radiator element 44 and constitutes an autonomous convection heating system with a single and closed circuit. small footprint. It is also possible to integrate this device -5 i in-an accumulation circuit 45 (Figure 7), or in a heater 46 (Figure 8), in a form and to

any locations.

  Figure 9 represents another example of application

  invention, in which the application device

  microwave energy cation 1 is mounted on a channel

  conduct 47 of a power distribution network

  geothermal energy 48 in which circulates or parks a

  fluid, devices 49 for stopping the micro-radiation

  waves being provided within the network 48, from

  and other of the source 2, and the possible antenna 8.

  It is also possible to carry out an assembly - in series or in parallel of a number of boilers

  or microwave sources of the type described above.

  Thus, as shown in FIG. 10, a mixed microwave boiler 50 can be provided simultaneously for the space heating and the production of domestic hot water, the microwave energy required for heating the two speakers 51 let 52 can be provided

  by a single source or by several sources.

  FIGS. 11 and 12 represent two other possible applications of the microwave boiler, on the one hand, by adaptation to a conventional electric boiler heating circuit 53 (FIG. 11), in FIG.

  which fluid contained in the heat exchanger 54 of the

  dière 53 is heated inside the boiler at

  microwaves 56, the radiators 57 being heated directly

  and, on the other hand, by adaptation in a conventional heating circuit whose fluid is heated

  inside the boiler 58.

  Thanks to the invention, it is possible to achieve a direct heating of fluids, such as water, air, oil, etc., for example to achieve heating

of premises.

  The method and the boiler according to the invention allow, for example, a production of hot water with a yield higher than that produced by traditional solutions with a lower energy consumption. It follows therefore that the heating provided by these radiations is direct and intense, and the heating of the usual treatment chamber in most traditional systems is avoided and thus

  the corresponding losses are saved.

  The power used is therefore generally

  less than that required for a conventional heating system, especially since the precise location of the zone of action of radiation in the core of the material can lead to a reduction in the volume to be heated because the treatment time is extremely low, so that significant energy savings can be

to be realized.

  Other uses may be envisaged, in particular in industrial, agricultural, agro-food heating applications for heating water, steam and other fluids or mixtures, as well as for heating.

  pools with high efficiency.

  The microwave boilers according to the invention can also complement or completely replace conventional boiler devices with gas, fuel oil, electric, heat pumps They are interesting for geothermal, solar thermal and heat.

  in addition to solar energy devices.

  Of course, the invention is not limited to

  Embodiments described and shown in the accompanying drawings Modifications are possible, particularly from the point of view of the constitution of the various elements or by substitution of technical equivalents, without leaving

  for all that the field of protection of the invention.

Claims (8)

-R E V E N D I C AT IO N S-   1 Microwave boiler for the production of a   hot fluid for domestic, industrial, or heating purposes   building, characterized in that it is essen-   actually constituted by a device (1) for applying microwave energy supplied by a microwave energy source (2) of the klystron or magnetron type, by a device (3) for transporting said energy of the guide type wave, coaxial cable, or the like, by an applicator device (4) coupled to the microwave energy source (2), radiating said energy to the fluid to be heated (6), closed by a fluid-tight and permeable diffuser to the waves (5), and which co-operates with the cylindrical, parallelepipedic, or spherical, or other form, conducting and / or absorbent metallic enclosure delimiting the thermal treatment zones of the fluid, and by elements (19 to 22) preventing the flow of   microwave out of the boiler enclosure.   Boiler according to claim 1, characterized   characterized in that the applicator (4) is advantageously completed by at least one radiating antenna (8) whose elements have an effective electrical length equal to an integer representing one quarter of the   wavelength of the frequency of the radiated energy.   3 Boiler according to claim 1, characterized   characterized in that it is provided with a conductive and / or absorbent enclosure (7) provided with a protective envelope (12), a thermal insulation (7 '), and at least one is a inspection hatch (9) provided with a closure device (10) of a conductive and / or absorbent material for stopping the microwaves and having a sealing device (11) for the fluid and for stopping the radiation   microwaves, and the walls of the enclosure (7) are   tageusement made of any conductive material for stopping electromagnetic radiation and / or the absorption of these radiations, for example by blackbody effect, these materials being able to be   light metals and alloys such as aluminum alloys minium, or stainless steel.   Boiler according to any one of Claims 1 and 3, characterized in that it is provided with   in addition, openings (13 to 16) allowing the circulation   fluid flow (6) to the pipes of the energy distribution network and radiators and the filling or emptying of the enclosure by means of pipes (17 and 18), these openings (13 to 16) accommodating each a microwave stop device (19 to 22) for reflecting and / or absorbing said microwaves and thereby preventing leakage of these microwaves;   past through these channels and the different   Auxiliary devices (23 to 25) connected to the boiler.   Boiler according to any one of claims 1 and 4, characterized in that the pipes are in the form of conductive and / or absorbent elements, so that the shut-off devices microwaves become useless.   6 boiler, according to any of the claims   dications 1 and 3 to 5, characterized in that it is provided with at least one safety device against the overheating of the enclosure (7), in the form of a lack of water detector, a device measuring the microwave energy, or the like, of at least one thermocouple (26), a board (27) for controlling and operating the boiler having control and signaling members (28), a pressure gauge (29), a device (30) for controlling and regulating the device (1) for applying microwave energy cooperating with one or   several thermal controllers (31).   Boiler according to claim 6, characterized   in that the device (30) for controlling and regulating the energy application device (1) 7 'v 1 R (9 microwaves acts directly on the emission of the electromagnetic radiation to which the fluid is subjected (6) inside the enclosure (7), thereby enabling said fluid to be brought to the desired temperature, and which consists of an electrical receiver (37) connected to the   source of microwave energy (2) via   a static converter (38), or the like, acting on the supply circuit (39) of the   source (2), and by a micro-processing unit   processor (40), or other electronic device, providing regulation and operational safety of the entire boiler as well as auxiliaries (23 to 25), and   which are connected the thermal controller (31), the.   :; thermostat (26), temperature sensors (41) and operating safeties (42 43), the device (30) being further provided with a cooling circuit (2 ') from the microwave source (2).   Boiler according to claim 1, characterized   it is integrated in an accumulation heating circuit, in a heater, in a conventional heating network, or connected in parallel or in series with other boilers of the same type, or in a network of,   geothermal energy distribution.   9 Process for producing a hot fluid for domestic, industrial, or space heating purposes,   by the boiler according to any one of the   1 to 8, characterized in that it consists in applying a microwave energy radiation to a fluid at a frequency corresponding to the relaxation frequency of the fluid considered at a given temperature, within a thermally insulating and electrically insulating conducting and absorbent envelope, by means of a microwave source whose power wave is transmitted via a waveguide and / or an applicator to the medium to be heated, the fluid heating being effected by   convection or by conduction and by the use of its   dielectric properties, including dielectric losses and / or by relaxation. t ,, j