ES2237785T3 - APPARATUS AND PROCEDURE FOR HEATING OBJECTS WITH MICROWAVES. - Google Patents

Abstract

A METHOD IS PRESENTED TO HEAT FLAT AND NON-FLAT OBJECTS USING MICROWAVE, THE METHOD INCLUDES: THE SUPPLY OF AT LEAST TWO RAYS OF MOVING MICROWAVES FROM A COHERENT MICROWAVE SOURCE (4); THE ADDRESS OF EACH RAY OF MICROWAVES IN MOVEMENT IN SEPARATE ARMS (8,10) OF A WAVE GUIDE (6); THE ISOLATION OF THE MOVING MICROWAVE RAY IN EACH ARM USING A MICROWAVE CIRCULATOR (12); THE FORMATION OF A SEASONAL WAVE FROM THE MOVING WAVES IN THE WORK AREA (14) WHERE THE ARMS ARE FOUND; AND THE VARIATION IN PHASE OF AT LEAST A RAY OF MICROWAVES IN MOVEMENT THROUGH THE ALTERATION OF THE LENGTH OF THE MICROWAVE TRAJECTORY IN THE WAVE GUIDE TO MOVE THE STATIONARY WAVE. AN OBJECT THAT PASSES THROUGH THE WORK AREA IS IRRADIATED BY THE MICROWAVES, GENERATING IN THIS FORM COMPLEX INTERFERENCE MODELS ON THE OBJECT. THE CONTROL CHANGES TO THE PHASES OF THE CHANGES OF THE INCIDENT MICROWAVES AND CONTROLS THE COMPOSED TIME SUPERPOSITION OF THE INTERFERENCE MODELS, FACILITATING THE EFFECTIVE VOLUMETRIC HEATING OF THE OBJECT.

Description

Apparatus and procedure for heating objects with microwave.

Field of the Invention

The present invention relates to an apparatus and to a procedure for heating objects, such as products Food, with microwave.

Prior art

It is well known to use microwave radiation for heating purposes. A problem that comes long has been the non-uniform spatial distribution of the energy of microwave in a heating cavity, which causes points Hot and cold in different places in the cavity. Known procedures to remove these hot spots and Colds include the use of an agitator in electromagnetic wave mode to change the radiation reflection patterns and / or place the object to be heated on a rotary table in the cavity, ostensibly passing the object through the hot spots and cold Non-uniform heating may also be due to dielectric and thermal properties of the object to be heated, together with Its size and geometry.

US 4464554 (General Electric Co.) describes an excitation system for a microwave oven; be facilitate means to change the phase of a wavefield pattern stationary in a waveguide between a first relationship of phases and a second phase relationship, thereby improving the uniformity of a distribution of energy averaged over time in the oven cavity.

EP 136453, US 4775770, US 4866233 and US 4952763 (Snowdrift Corp.) provide procedures for the microwave controlled heating of packaged objects sealed; microwaves emanate well from a microwave emitter subdivided into two, well, preferably, of two emitters of microwave. The two resulting energy distributors are overlap in a sum field, at least when the averaged time and the object is placed in a region of maximum field strength of the microwave sum field, thus achieving a default temperature distribution in the object, the distribution a scalar sum of two or more independent fields of temperature.

Document FR 2523797 ( Center National de la Recherche Scientifique ) describes means for heating objects with large slenderness ratios, such as paper, where the object passes consecutively through grooves in two waveguide arms. The waveguide fields in the arms are standing waves displaced transversely with respect to the direction of propagation of the object by the length of the waveguide divided by four. EP 446114 and US 5278375 ( Microondes Energie Systemes ) describe similar means for heating sheet-shaped objects passed through grooves in a waveguide.

Mexatas, AC & Meredith, RJ (1983) in " Industrial Microwave Heating ", published by Peter Peregrinus Ltd., London, UK (reprinted in 1993) pp. 170-1 treats the quarter-wave displacement between electric fields in two cavities to uniformly heat a flat object. They affirm that this procedure can only be used to heat sheet-shaped materials, where the thickness is a small fraction of the width, otherwise the material experiences large field variations along its length.

In US 4 378 806 (Henley-Cohn), describes an apparatus and a procedure for raising the temperature of a tumor due to hyperthermia without unduly heating healthy tissue that surrounds the tissue that contains the tumor.

Document FR 2 128 936 (Thomson - CSF) describes improvements in high heating devices frequency for sheet-shaped dielectric materials thin

These known heating procedures of Microwave objects are based on averaged overlay over time of scalar heating patterns. This is translates into a certain number of restrictions during use, such as a limited distance over which the heating procedure to obtain uniform heating, limited control of the distribution of the heating pattern and effective heating only with objects that have large slenderness relationships, such as flat goals, for example paper or cookies, (as the overlay procedure averaged over time of scalar heating patterns is not can use to produce three-dimensional uniform heating in objects that are not flat).

The present invention seeks to provide a improved apparatus and procedure for heating objects using microwave.

Summary of the invention

In accordance with the present invention, provides an apparatus for heating objects using microwaves, comprising the device:

a work area to place an object;

elongated microwave transmission members first and second, each having an end located in the area of work;

a single microwave source or a plurality of coherent microwave sources;

a means to provide a first beam of microwave and a second microwave beam from the energy of microwave output from the source or microwave sources;

a means to couple the first microwave beam to the end of the first remote microwave transmission member of the work area and a means to couple the second beam of microwave at the end of the second microwave transmission away from the work area; Y

a means to vary the microwave phase in the first and / or second microwave transmission member;

in which the apparatus is arranged in such a way that the first microwave beam enters the work zone according to a first direction, and the second microwave beam enters the work area according to a second direction, and the angle between First and second directions is not orthogonal;

characterized in that the apparatus comprises, in addition, a medium associated with each transmission member of microwave to insulate the microwave inside to prevent, in this way, substantial crosstalk.

The microwaves that propagate in each member of microwave transmission, from the microwave source or sources, They meet in the work area. The microwaves that spread in the first microwave transmission member and the microwaves that propagate in the second microwave transmission member are consistent and mutually exclusive. Therefore, the vector sum of microwave electric fields are produced to form a interference pattern, or standing wave, in the work area. When no object is present in the work area, the interference pattern has a simple sinusoidal shape. The phase This standing wave can be varied. This is called control. per phase

In contrast, in the prior art, the Used microwaves are not consistent and mutually exclusive; by this produces the scalar sum (instead of the vector sum) of microwave electric fields to form a wave stationary climb in the work area. The phase of this wave stationary varies continuously, so you cannot control.

In the present invention, when an object is partially or completely present in the work area, such as when the object is passed through the work area, the object is irradiated by microwaves that propagate in each microwave transmission member. A new pattern of complex interference within the object by vector sum of the Microwave incident electric fields.

The initial phase of microwaves is important, and may vary according to the object.

The microwave phase in at least one of the microwave transmission members can be varied, generating, therefore, different interference patterns in the object (in relationship with the spatial distribution of the microwave field). The overlap averaged over time of the patterns of interference within the object can result in a rapid heating, averaged over time, of the object up to three dimensions; hot and cold spots can be remove effectively.

The heating depth can also be control using phase control to select patterns of interference that, for example, direct microwave energy away from incident surfaces. This is only possible. when the microwaves in each transmission member are consistent and mutually exclusive (that is, when the crosstalk between microwave in each transmission member is substantially avoided to maintain the average consistency over time) of such so that interference patterns can be generated from destructive and constructive microwave interference.

On the other hand, in the prior art, you cannot destructive and constructive interference occur because both without microwave coherent or mutually exclusive, it is only possible the scalar sum of energy distributions, and not the vector sum of electric fields as in the current invention. Therefore, in the prior art, microwaves are also they add where they meet in the object; this is contrary to the present invention, where the selected areas of the object are they can take as target to not make any warming, be which is.

It is well known that the power absorbed by a dielectric material is proportional to the square of the field electric. In the case of coherent microwave signals and mutually exclusive of equal breadth, as in the present invention, electric fields are added so that the distribution of resulting power is proportional to four times the amplitude of either of the two microwave signals. In the scalar sum, it add the power distribution configured by each field electric, not by the electric field itself, so that the distribution of the resulting field is proportional to twice the amplitude of any one of the two microwave signals (the electrical fields interfere continuously, constructively and destructively on time scales in nanoseconds, so that the distribution of energy averaged over time is simply the average intensity of the electric field in the object, which is twice the amplitude of any of the two signals of microwave). Therefore, an additional advantage of the invention current is that more intense heating is possible from it power source

In addition, the effective depth can be increased heating with the use of phase control. When selecting interference patterns that target the energy in the center (or any other predetermined position) within a object, and exploit the increased heating intensity that is possible, as explained above, can be set to readiness at greater depths more energy not absorbed from microwaves, compared with procedures during the technique above, for significant heating.

In this way the apparatus and the procedure of the present invention provide control per phase which, in the control direction per phase, can vary and select patterns heating for directed or uniform heating of an object averaged over time. The effective depth and directed or uniform heating intensity can also be increase.

The control per phase can be applied in one, two or three dimensions in order to achieve uniform heating averaged over time in one, two or three dimensions, respectively. Alternatively, if phase control is applied in one dimension, other means can be used to achieve the uniform heating averaged over time in another dimension; for example, the object to be heated moves in a address that is perpendicular to the control direction per phase, or the work area is altered by having fitted walls, coated with dielectric or narrow.

In prior art procedures, only averaged overlap is possible along the time of scalar heating patterns, as the sources of Microwaves are neither coherent nor mutually exclusive.

Provide a certain number of beams of microwave from a single microwave source ensures that Beams are consistent. A plurality of microwave sources with Phase lock are also consistent.

The angle between the corresponding directions of the first and second beams is preferably from 0 to 30, 150 to 210 or 330 to 360 degrees. Preferably, the angle is 180 degrees.

The microwave transmission member can be a hollow waveguide, a coaxial cable, flat microwave line or any other means to transmit microwaves.

Microwave transmission members first and second may be the first and second arms of a single guide of waves, which is in the form of a loop.

The work area can be formed by the meeting of two waveguides or waveguide arms, so that The object is in an area limited by walls. An alternative is that the work area can be located between two antennas parallels that are mutually coupled via an object to be heated, so that the object is in a work area not limited by walls.

Preferably, the means for varying the phase of a microwave in the microwave transmission member first and / or second comprises means to alter the path length of a microwave in a microwave transmission member. In a example, a sliding short circuit is used to vary the length of the electrical path of a microwave beam on an arm of microwave. Short circuit branches can also be used sliders, an adjustable branch or other means to change the effective waveguide length; for example, the introduction of all or part of a dielectric material in the arm of transmission of a waveguide to change the length of the original trajectory

The medium associated with each transmission member microwave to insulate microwaves inside you can comprise an insulator, such as a microwave circulator.

According to an additional aspect of the invention, a method for heating objects is provided using microwave, understanding the procedure:

provide at least two microwave beams progressive from a single microwave source or from a plurality of coherent microwave sources;

direct each progressive microwave beam to inside of a different microwave transmission member;

isolate the progressive microwave beam in each microwave transmission member;

form a standing wave from the progressive waves in a work zone that is there where gather microwave transmission members to locate a object to be heated;

and vary the phase of at least one microwave beam progressive in order to shift the standing wave.

The present invention provides, however, a dynamic phase control system for heating uniform or directed non-flat objects in up to three dimensions.

Detailed description of the invention

Next, examples of the apparatus and methods of the invention to illustrate, but not to limit the invention, referring to the drawings which are accompanied, in which:

Figure 1 is a diagrammatic representation of a first embodiment of the apparatus;

Figure 2 is a diagrammatic representation of a second embodiment of the apparatus;

Figure 3 is a perspective view of a work area and the ends of the waveguides;

Figure 4 is a plan view of a tray;

Figure 4b is a side view of a tray;

Figure 5 is a perspective view of a work area containing a tray of food material supported on a block;

Figure 6a is a series of images of temperature distribution;

Figure 6b is a series of images of Energy Distribution;

Figure 7a is a series of images of temperature distribution;

Figure 7b is a series of images of Energy Distribution;

Figure 8a is a distribution image of Energy; Y

Figure 8b is a distribution image of Energy.

Referring to figures 1 and 2, the apparatus 2 comprises a microwave generator 4 that is coupled to a waveguide 6, which is divided via an E junction at T 7 in a first arm 8 and in a second arm 10. The T is tuned to such that the energy introduced into any arm of the T is divide in such a way that half of the energy goes out for the others two arms of the T. The microwave generator is, for example, a magnetron or a progressive wave tube. A circulator 12 (or other means to isolate) is associated with each arm.

The circulators are three devices ports of ferrite which are labeled as follows in the figures 1 and 2:

- microwaves entering through port A and leaving by port B

- microwaves that enter through port B and exit by port C

- microwaves that enter through port C and exit by port A.

During normal use, through port A enters energy from the microwave generator. The isolation of a circulator is usually defined as how efficient the device to divert energy entering through port B to port C; The more insulation, the more energy is diverted to port C. For the present invention, all circulators should have a insulation better than 10 dB, preferably better than 20 dB, optimally better than 30 dB, at the frequency (or over the band of frequencies) of microwave generator operation.

During normal use, a circulator immediately follow a microwave source, with a load 13 dummy fixed to port C. The reflected energy is diverted from port B to port C thus protecting the source. The dummy loads are usually chilled water, but they can be Cool using air or other refrigerants. Optimally, a load dummy is designed so that a circulator minimizes the lack of concordance in impedance.

As shown in figures 1 and 2, the guide waves is a rectangular loop, but it can also be, for example, a circular loop or a square loop. The end of each arm of the waveguide joins the end of the other arm. In the location of this union, a work zone 14 and two are defined opposite waveguide walls have openings 16 in their inside; The openings shown in Figure 3 are rectangular. Preferably, these walls do not cut any field lines of microwave. Openings provide means to pass an object to through the work area of the waveguide. Doing reference to figure 3, a food 17 extends outward from each opening 16 to provide a step to feed the object to work zone 14. Horizontal access is preferred to the work area as a belt conveyor can run through the work area, with bare objects or packed to be heated on the belt. You can use two sections 15 twisted 90 degrees, and are shown in both figures 1 and 2 to allow horizontal access to the work area. Others "Twisted" angles could also be used.

The work area can have total walls or partially coated with dielectric, and can also have fully or partially fitted walls to modify the pattern of electric field, and the indentations of the structures notches can be filled dielectrically.

In an alternative embodiment, both arms of the waveguide taper into the work area, as shown in figure 3, preferably over a distance of length waveguide waveguide divided by four, so that the Work area is narrowed. The tapered region 19 may be partially or completely filled with dielectric with, for example, polytetrafluoroethylene, or with different dielectric materials in each tapered region, to control that the impedance matches between the arms and the work area. This allows to control the electric field and / or microwave modes present in the zone of job.

The microwaves from the generator 4 are divided into two beams and are directed in opposite directions through the waveguide loop (ie, a beam in the first arm 8 and a beam in the second arm 10). The angle between the respective directions of the beams when entering the work area is 180 degrees. The circulators act to isolate the microwave energy propagated in one arm from the microwave energy propagated in the other arm. The waves that progress in each arm meet and generate a standing wave in the work zone and in the region of the waveguide loop limited by the circulators. Microwave energy in each arm is sufficiently isolated using two circulators with dummy loads to prevent substantial crosstalk between
they.

The first arm 8 has a length section of variable trajectory comprising a circulator and a sliding short circuit (instead of a dummy load). Port Power input B leaves port C until short circuit 18 slider The energy is reflected outside the sliding short circuit and re-enters port C but leaves it in port A. The short circuit moves to predetermined positions that alter the length of the electrical path of a microwave that is propagates in the arm, thus varying the phase of the wave stationary, when detected in any position, using, for example, a waveguide 21 with grooved line with detector appropriate (see figure 2). Therefore, the standing wave it can be moved in a controlled way in the region limited by two circulators 12. Microwaves from the second arm 10 that propagate through the work zone will enter the port A and leave port B that enters its length of section without to affect. The sliding short circuit is preferably motorized via a programmable computer control system, so that the microwave phase on the first arm 8 can be varied continually.

In the apparatus of Figure 2 a room is used Adjustable branch 19 to balance the amount of power in each arm. The grooved line waveguide 21 is also used for allow access to a probe that measures the relative phase of the wave stationary at any time. This measure can be part of a control system, for example, to allow control dynamic of the standing wave phase.

To allow the implementation of the control dynamic phase, the control system preferably comprises, a sliding short as an interface with a computer. The position and duration of the sliding short circuit over the heating duration an object can be preprogrammed from according to the type of object and the final heating profile required.

In an alternative example, the adjustable branch 19 can be used to vary the amplitude of microwave energy in each arm, allowing additional control of the distribution resulting from energy. Additionally, the E junction in T 7 can be adjust to unevenly divide arms 8 and 10 of power input, the resulting distribution of energy. By for example, for objects of variable thickness, for example objects with a tapered section along the control direction per phase, it may be preferred to impose a power distribution initial to assist in the phase control procedure.

Alternatively, the slotted line socks, power measurements on each transmission arm, measured in line of object temperature, etc. can provide control of Sliding short, adjustable branch and / or an E junction in T with feedback in advance.

The microwave frequency is between 0.4 and 10 GHz. Industrial frequencies are particularly preferred, Scientific and medical (ISM) 896, 915, 2450 and 5800 MHz.

An object to be heated is passed through the area 14 work. The waves that progress in each arm impact on opposite faces of the object. This generates an interference pattern within the object, the pattern being dependent on the permittivity complex of the object and the phase of the standing wave that is present and contiguous to the object in the work area. To the extent that object passes continuously, or in the traditional stage, through the working area, the sliding short circuit shifts to vary the length of the microwave path that propagates in the first arm, and therefore the phase of the standing wave. This generates at least another different interference pattern within the object.

Control the changes in the phases of incident microwave changes and controls the average overlay over time interference patterns facilitating a most efficient volumetric heating of the object in up to three dimensions.

In an alternative example, if the heating a target, or the initial temperature distribution of the object is not uniform, or the complex permittivity of the object change with temperature, or change the geometry of the object with the temperature, or additional procedures of phase-controlled heating such as the use of hot air, or any combination of these, a pattern of interference to achieve the desired heating pattern.

This invention therefore achieves a optimization of the overlap averaged over time interference patterns.

Optimization can translate into patterns of interference that have different residence times; the phases used to generate different interference patterns to Overlapping are not necessarily 180 degree phases. By cons, in the prior art, standing waves for the scalar sum to be superimposed are approximately 180 degrees phases.

Example

A waveguide circuit was configured as shown in figure 2. A waveguide was used that has a 248 x 124 mm internal cross section, together with a generator microwave with small curl 5 kW 896 MHz (less than 5%). Area working included a section of the waveguide with a lid articulated to facilitate easy removal of objects placed in its interior. The circulators had insulation characteristics better than 30 dB at 896 MHz.

Materials were placed in the work area model food in polyethylene trays, and heated. Model food materials were chosen to be representative of the dielectric properties of many products frozen foods (model 1), or non-food products frozen high moisture content (model 2). The properties of the model materials are detailed in the following table.

one

Model 1 was a soft plastic material called Plasticine ™ (available from Trylon Ltd., Northants, RU). Its analytical composition was 78.1% ash, 21.2% of oil and 0.7% water.

Model 2 was a mixture of 91% water and 9% of powder TX151 (TX151 is the product name of a powder hydrophilic available at Weatherford, Kirkhill Ind Est, Aberdeen, RU). Its analytical composition was 93.6% water, 3.7% of carbohydrate, 2.2% ash, 0.5% protein.

Complex permittivity was measured using a coaxial probe with open end (Hewlett model HP85070B Packard)

Referring to figures 4a and 4b, each polyethylene tray 22 has an upper edge that defines a open face having a width w of 122 mm and a length z of 171 mm; a base that has a width x of 100 mm and a length and 150 mm; a depth D of 35 mm; a corner radius r_ {1} greater than 30 mm, a corner radius R2 of horizontal base of 15 mm and a corner radius F of vertical base of 6 mm. The model materials completely filled the trays, but not they overflowed.

As shown in Figure 5, each tray 22 it was supported on a block 23 of polytetrafluoroethylene located in the center of a work zone 14 so that the plane horizontal of the tray at a medium depth was approximately coinciding with half the height of the waveguide. The block 23 had a width a of 34 mm, a height b of 42 mm and a length 72mm c The model materials were heated during a enough time to raise the temperature by a maximum of 20 ° C

After heating, images were taken thermal of the horizontal plane at medium depth of the material of the model using an infrared scanner (model 870 obtained in Agema, Sweden). To prevent excessive disturbance in the temperature distribution, for example, when slicing the material with a knife, a layer of bonded film of half-height polyethylene of the tray as the material of the model was prepared on the tray: be careful to exclude All the air bubbles. After heating, the film adhered and the top half of the model material just removed to expose the surface of the model material to the height of the semi depth.

A three-dimensional model of microwave in the finite element time domain (3D FETD) to simulate the heating of model materials. The Figure 5 shows the section of the waveguide modeled. The model microwave produced energy distributions in the same plane that measured temperature distributions to allow a qualitative comparison with thermal images. The properties of dielectric constant were assumed in the microwave model to reduce computer calculation times (increases in temperature in the experiments were maintained until no more than 20 ° C to minimize the effect of complex permittivity dependent on temperature).

For each experiment, a material of the model that contains a tray in constant phase condition, is say the sliding short remained in one position. He phase 0 status was arbitrarily defined as the position Initial sliding short circuit. For each experiment it was used a new tray of model material. Short circuit slider then moved a known distance to give a 30º movement in the standing wave pattern in the zone of work regarding the previous short circuit position. Of this mode, the heating pattern at the half height of the plane of the Tray was measured every 30º.

The FETD model was executed to simulate the experimental conditions of the foregoing. To compare the measured temperature distributions with distributions simulated energy, thermal imaging and distributions Simulated energy should have matching phases. For example, let's say that for a sliding short circuit position given the temperature distribution phase matched the simulated power distribution in 120º; when he moved the sliding short circuit a distance α, which is known as from the dimensions of the sliding short circuit to produce a phase change of 35º, the result of the simulation at 155º I should have agreed with the experimental result correspondent. NB: is the phase change between the two points what which is important and not the absolute phase of any one of they.

Experiment one

Material 1 of the model was heated in the tray; the direction of the energy flow, and therefore the control per phase, was parallel to the width w of the upper edge of the tray. Figure 6a shows the distribution images thermal measured at each phase change of 30º; the clearer they are The shadows, the higher the temperature. You can see that the "points hot "move through the material.

3D FETD simulations were performed. Figure 6b show simulated energy distribution images in each 30º phase change; The lighter the shadows, the greater it is energy.

In Figure 6b, you can see the edge profile top of the tray. In figure 6a, the images are of inside the tray. You can see that there is a very concordance narrow in the position and size of the distributions of the thermal images and FETD simulations in each condition of phase.

Experiment 2

Model material 2 was heated in the tray; the direction of the energy flow, and therefore the control per phase, was parallel to the width w of the upper edge of the tray. Figure 7a shows the thermal distribution images measured at each 30 ° phase change; The lighter the shadows, the higher the temperature. You can see that the "hot spots" travel through the material. For a comparison with Figure 6a, it can be seen that the thermal distributions for material 2 of the model were more complex than for material 1 of the
model.

3D FETD simulations were performed. Figure 7b show simulated energy distribution images in each 30º phase change; The lighter the shadows, the greater it is energy.

In Figures 7a and 7b, the images are of inside the tray. You can see that there is a very concordance narrow in the position and size of the distributions of the thermal images and FETD simulations; that is to say the same changes in the pattern of energy distribution and heating are you can see how the phase of the standing wave changes in the work zone.

Experiment comparative

To demonstrate the advantages of phase control in experiments 1 and 2, in which vector summing results, imposed scalar conditions on propagation waves in arms 8 and 10 of the waveguide loop to simulate scalar sum. Model materials from experiments 1 and 2 were used. Only energy distribution is possible under sum conditions climb; Therefore, only one heating pattern is possible. The images due to the scalar sum are shown in figures 8a (model 1) and 8b (model 2); again, the clearer the shadows, the greater the energy. The difference in the distributions of Power of the two materials is clear. As a result of the sum scalar, which provides only one power distribution, not any controlled heating or considering a White.

These examples demonstrate the principle of control heating per phase; show that the pattern of heating can be controlled so that areas within a material can be taken as white with microwave energy. The experimental conditions were designed in such a way that would produce complex heating patterns to demonstrate The principle of control by phase. By appropriate overlap averaged over time from interference patterns, they can be get desired heating patterns.

It is clear that the phase of the standing wave in the work area can be changed in a controlled way in a first direction to get the desired heating patterns in one dimension

To obtain the desired patterns of two-dimensional heating, phase control is applied in a first dimension and either phase control can be applied throughout the second dimension, or, more preferably, the object can be moved in a direction that is perpendicular to the first direction.

To obtain desired heating patterns in Three dimensions, the control by phase can be applied by all three dimensions; or the control by phase can be applied by all the two dimensions and the object can move in one direction that is perpendicular to it; or the control per phase can be apply for all two dimensions and the work area can have walls completely or partially with dielectric, or have walls completely or partially notched, or have width narrowed, as shown in figure 3, to modify the pattern electric field and / or modes present in the work area.

A preferred option for heating three-dimensional is to apply control per phase in the first dimension, move the object to the second dimension and modify the area of I work in the third dimension.

It will be appreciated that, as long as the control per phase is apply in at least a first dimension, a variety of others means can be used to effect heating in a second and / or third dimension.

The apparatus and method of this invention they are suitable for averaged heating over time uniform or directed of a solid three-dimensional or solid object particulate, such as a packaged food product, in the address (s) of the control per phase, up to three dimensions. For example, the object may be breaded chicken, or Vegetables such as peas, broccoli, spinach and sweet corn. It can also be used to seal caps or heat plastics.

The object can be prepackaged in a container (for example a tray with a film cover; a bag or purse; a plastic can; a plastic can that has a part metal top and metal base). If the object is prepackaged, is preferably packaged with a means for minimize deformation of the package during heating and cooling (for example, using a rigid sleeve). If the object it must be heated above 100 ° C, then it can be applied external pressure

The food product may be initially at room temperature, refrigerated temperature or temperature of freezing. Typically, this invention is used to heat food products up to temperatures above 50ºC, particularly up to pasteurization temperatures (for example, 70 ° C) and up to sterilization temperatures (for example, more than 120 ° C). This invention is also suitable for tempering objects. frozen, such as poultry, where the object is at freezing temperatures and the temperature is raised so that it is just below its defrosting temperature.

For various food products components, the invention can provide controlled heating so that one component receives more energy than another.

Claims (13)

1. An apparatus for heating objects using microwave, including the device: a work zone (14) to position a object; elongated (8, 10) transmission members of microwave first and second, each having an end located in the work zone (14); a single microwave source (4) or a plurality of coherent microwave sources; a means (7) to provide a first beam of microwave and a second microwave beam from the energy of microwave output from the source or microwave sources; a means (7) for coupling the first beam of microwave at the end of the first transmission member (8) of microwave away from the work area, and a means to couple the second microwave beam at the end of the second member (10) of microwave transmission away from the work area; Y a means (18) for varying the microwave phase in the first and / or second microwave transmission member; in which the apparatus is arranged in such a way that the first microwave beam enters the work zone according to a first direction and the second microwave beam enters the work area according to a second direction, and the angle between First and second directions is not orthogonal; characterized in that the apparatus further comprises a means (12) associated with each microwave transmission member to isolate the microwaves therein, to thereby prevent substantial crosstalk. 2. An apparatus according to claim 1, in the which means (18) to vary the microwave phase in the first and / or second microwave transmission member comprises means to vary the length of a microwave's trajectory in a microwave transmission member. 3. An apparatus according to claim 2, in the which means (18) to vary the length of the path It comprises a sliding short circuit (18) and a circulator (12). 4. An apparatus as claimed in any of the preceding claims, wherein the medium (12) associated with each microwave transmission member to isolate the microwaves inside comprises a circulator of microwave. 5. An apparatus as claimed in any of the preceding claims, in which the angle between First and second directions of the beams is 180 degrees. 6. An apparatus as claimed in any of the preceding claims further comprising means to vary an electric field pattern in the work area. 7. An apparatus as claimed in any preceding claim, wherein the transmission members of Microwaves taper inward towards the work area. 8. A procedure for heating objects using microwave, comprising the procedure: provide at least two microwave beams of propagation from a single microwave source (4) or from a plurality of coherent microwave sources; direct each propagation microwave beam to inside of a microwave transmission member (8, 10) separated; isolate the microwave beam spread in each microwave transmission member; form a standing wave from the propagation waves in a work zone (14), which is where gather the microwave transmission members, to locate a object to be heated; and vary the phase of at least one microwave beam of propagation in order to displace the standing wave. 9. A method according to claim 8, in which varies the phase of at least one microwave beam of propagation using a sliding short circuit (18) and a circulator (12). 10. A method according to claim 8 or 9, in which the microwave beam spread in each member of microwave transmission is isolated using a circulator microwave. 11. A procedure according to any one of the claims 8 to 10, in which there are two microwave beams of propagation and the angle between the directions of the beams, when They meet in the work area, it is 180 degrees. 12. A procedure according to any one of the claims 8 to 11, further comprising means for varying an electric field pattern in the work area. 13. A procedure according to any one of the claims 8 to 12, wherein the transmission members of Microwaves taper inward toward the work area.