WO2012098183A1 - Procédé pour fournir de l'énergie thermique directe et homogène à un substrat fluide - Google Patents

Procédé pour fournir de l'énergie thermique directe et homogène à un substrat fluide Download PDF

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Publication number
WO2012098183A1
WO2012098183A1 PCT/EP2012/050770 EP2012050770W WO2012098183A1 WO 2012098183 A1 WO2012098183 A1 WO 2012098183A1 EP 2012050770 W EP2012050770 W EP 2012050770W WO 2012098183 A1 WO2012098183 A1 WO 2012098183A1
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WO
WIPO (PCT)
Prior art keywords
substrate
fluid
irradiation chamber
flow
fluid substrate
Prior art date
Application number
PCT/EP2012/050770
Other languages
English (en)
Inventor
Nils Kongmark
Laurent Selles
Original Assignee
Creative Heating Services Sa
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Creative Heating Services Sa filed Critical Creative Heating Services Sa
Publication of WO2012098183A1 publication Critical patent/WO2012098183A1/fr

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/70—Feed lines
    • H05B6/707—Feed lines using waveguides
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
    • A23L3/005—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by heating using irradiation or electric treatment
    • A23L3/01—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by heating using irradiation or electric treatment using microwaves or dielectric heating
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/80—Apparatus for specific applications
    • H05B6/802—Apparatus for specific applications for heating fluids

Definitions

  • the invention refers to methods and techniques suitable for providing direct microwave heating of fluids, especially fluids such as liquid food products or beverages moving in a continuous flow.
  • Heat energy is a favorite means for performing sterilization of various compositions of matter like e.g. beverages, food products, medicaments or the like and related techniques are currently widely applied in the industry.
  • Aseptic packaging of food products is indeed a real challenge for sterilization because sensitive food material cannot last for too long at the required temperature or cannot be heated beyond a limit unless a severe loss of quality is observed.
  • Homogeneous distribution of heat energy throughout the entire mass subject to sterilization, within the time frame set for the above reasons, is also an issue which depends, namely, on the nature of the food or beverage material, its specific absorption coefficient, its water or salt content, its dimensions, etc. This is particularly crucial when continuous processing is applied industrially.
  • Continuous flow microwave heating seemed to represent a promising alternative to conventional heating for aseptic processing of semi-fluid food products like e.g. vegetable purees. Indeed a rapid and uniform heating associated with microwaves should be ideal for aseptic processing.
  • trials performed at laboratory or even at pilot scale have clearly thought that non-uniform temperature distribution and insufficient control of processing parameters are still the major hurdles in the industrial implementation of continuous microwave (electromagnetic) heating.
  • Factors responsible for non-uniform distribution of heat energy within the food product include differences in dielectric and thermo physical properties of the food material, non- homogenous distribution of electromagnetic filed or e.g. the magnitude of the diameter of the applicator tube. Additional issues associated with the scale-up of a microwave process to industrial scale include tight control of numerous processing parameters such as microwave power, flow rate, temperature, pressure, etc.
  • a method and device for providing as far as possible a direct and uniform energy distribution throughout the whole mass of a food substrate has already been proposed in e.g. US 4,775,770.
  • the latter is making use of dual high frequency irradiation generated in a mono mode way, as opposed to the multiple mode way used in a classical oven, by means of a microwave transmitter comprising at least two guiding devices and an irradiation chamber: it is dedicated, however, to the heating of sealed food packages as opposed to food fluids moving in a continuous flow.
  • US 4,775,770 discloses a microwave heating system provided as a continuous furnace comprising a tube for guiding the objects (sealed food packages) to be heated as well as several microwaves transmitters disposed next to each other in the transport direction.
  • a metal tube is provided with entrance openings for the microwaves and, inside, a coaxial plastic tube is provided for pressure sealing of the entrance openings and receiver containers are provided for the food packages to be heated and transported.
  • CHSD technique offers to the skilled artisan the means which are necessary for the adequate control and monitoring of microwave heating, especially when applied to heat sterilization of fluid material such as homogenous or heterogeneous liquid food products and beverages moving in a continuous flow.
  • the invention refers to a method for providing direct and homogeneous energy distribution throughout the whole mass of a fluid substrate flow by means of dual high frequency irradiation generated in a mono mode way by a "Magic T" microwave transmitter comprising a torus shaped guiding device wherein each of the two electromagnetic waves progress along each branch of the guiding device to reach the corresponding end of an irradiation chamber which is located inside the guiding device and opposite to the "Magic T" transmitter, which comprises the following steps: a) positioning the fluid substrate flow inside the irradiation chamber the configuration and dimensions of which are defined as follows: the fields are TEio and form standing waves
  • the standing waves end at the irradiation chamber at a knot
  • the width of chamber is defined by the penetration depth when the two fields overlap and their added amplitudes correspond to the necessary field intensity in order to reach the set temperature in the center of the irradiation chamber the heat energy distribution is controlled at any point in the mass of the substrate following the substrate's dielectric and thermal properties for the set ⁇ ⁇ ; b) subjecting the fluid substrate flow exposed to the two microwave trains of opposite direction which each depart from at least two opposite ends of the irradiation chamber; c) steering and monitoring the two microwave trains in such a way that they superpose inside the fluid substrate flow to form a sum field, wherein the configuration and dimensions of the guiding devices are defined as follows: the TEio field is guided either by an H-bend or an E-bend
  • the waveguide wave length is defined by the dimensioning of the section of both aside and b-side defining the fields' guide-wave-lengths (kg) so that the irradiation chamber' s dimensions correspond to the fluid substrate flow physical dimensions; wherein the fluid substrate flow is positioned symmetrically inside the irradiation chamber; and
  • ⁇ ' is the dielectric constant of the substrate (expressing the substrate's energy absorption) and ⁇ " is the loss factor (expressing the substrate's ability to convert the absorbed energy to heat energy) of the substrate
  • q is a constant which depends on the pressure drop inside the irradiation chamber, the fluid substrate viscosity and the thermal diffusivity of the fluid substrate; by applying separate equations for defining electromagnetic heating, with the exception of the attenuation and calculating waveguide dimensions based on the fluid substrate flow' s need of dimensions of the irradiation chamber so that the said fluid substrate flow represents the region where applies the maximum of standing wave of the field; and d) monitoring the energy (P) transferred to the irradiation chamber and absorbed by the fluid substrate flow using the time of exposure to the overlapping two fields in relation to the intensity of the injected energy, as expressed in the following equation
  • the core of the invention is based on the adequate and precise monitoring of the attenuation distances of the two overlapping fields in the fluid substrate flow, which are generated by the two identical fields meeting head on in an irradiation chamber (or applicator) where the fluid substrate to heat is flowing, e.g. the food material.
  • the global performance of the CHSD technique namely the yield of conversion of the energy input (microwave irradiation) into heat inside the selected fluid substrate flow is controlled by several parameters which depend on the physical or construction characteristics of the device used like microwave transmitter, microwave guide, dimensions or shape of the irradiation chamber, etc. and the intrinsic characteristics of the substrate as well: all these parameters have first to be identified, measured and subsequently applied by means of one or more specific mathematical formulations for defining the configuration of the microwave guides - see Fig. 1, 2 and 3 - and for monitoring adequately the microwave irradiation of the selected substrate.
  • Fig. 1 is a schematic representation of a system suitable for microwave heating wherein A represents the portion of the fluid flow subject to microwave irradiation; B is the applicator (e.g. a tube), C is the waveguide, D is the magnetron, E represents a switch mode power supply and F represents a monitoring tool, e.g. a computer, "a” and “b” each represent a dimension characterizing the waveguide, in cross section. Parameters "a” and "b” are necessary for the calculation of the appropriate wave length in the waveguide C.
  • Fig. 2 is a schematic representation of an "E-bend” wave guide i.e. wherein a > b.
  • Fig. 3 is a schematic representation of an "H-bend” wave guide i.e. wherein a ⁇ b.
  • a condition for adequately using a system as illustrated in Fig. 1, which exposes a fluid flow to two microwave trains of opposite direction which each depart from two opposite ends of the irradiation chamber, is that no energy transmission occurs from either side, i.e. that all the energy injected has to be absorbed by the fluid substrate moving in a continuous flow.
  • a system as illustrated in Fig. 1 requires mastering and monitoring several physical variables every second to perform as needed and the invention is providing the exhaustive inventory of the numerous and significant parameters one has to take into consideration.
  • the invention furthermore, is setting-up a unique sequence of mathematical equations that has to apply to the parameters (variables) so selected for achieving the desired technical effect, e.g. sterilizing in an optimal way a fluid flow of food material such as that defined here above. That sequence is namely provided by claim.
  • the rule is that the penetration length should be slightly sorter that the said pipe diameter to avoid any energy transmission which would damage the microwaves emitters.
  • D is the pipe diameter in meter
  • v is the flow velocity in m/s
  • p is the density in kg/m 3
  • ⁇ is the roughness of piping in kg/m/s (the irradiation chamber is usually a pipe);
  • a vertical reactor is moving the treated fluid mass upwards and the flow is given by the Reynolds and Nusselt numbers.
  • the field inlet window into the pipe and the b-side define the irradiation chamber.
  • the flow has at each applicator an inlet temperature and an exit temperature forming the delta T for the applicator.
  • these values should be constant and will together form the final flow conditions.
  • the gravity should also be taken into account.
  • the attenuation and the penetration factor of the microwaves inside the fluid flow is further depending on the selection of magnetron power: for example, at equal other factors, the penetration can increase by a factor 5 when moving from a 1KW magnetron to a 5 KW magnetron; and the attenuation length is increasing from 55 mm for a 1 KW magnetron to a 5 KW magnetron.
  • the distilled water has a Cp of 4 and the ⁇ is fixed at 25°C (140 - 115°), a dielectric constant of 52 at 125 °C and a loss factor of 1.6. It is also understood that the CHSD attenuation formula is valid for temperatures over 100°C and at pressures set for avoiding the liquid to evaporate. b) To calculate the dimensions of a e.g. UHT- sterilization one makes use of the results by coming out of the following CHSD attenuation formula:
  • the model calculation here above can be adjusted to food fluids definitely more complex than distilled water, for example fruits or vegetable juices, soups or bouillons or sauces, vegetable or meat purees or even food fluids like soups or sauces comprises solid or semi-solids pieces like e.g. beans, peas', vegetable pieces like carrot or onion pieces, or meat pieces or meat balls.
  • the skilled artisan shall first select from the text books available the values of the numerous variables listed here above, then he shall apply them to each of the mathematical formulae provided in claim 1 to obtain the adequate values which shall allow him to 1) properly design and dimension the wave guides and the applicator - see C and B in Fig.
  • heat energy is provided to the fluid substrate in such a way to perform e.g. cooking, pasteurizing or sterilizing

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Health & Medical Sciences (AREA)
  • Nutrition Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Food Science & Technology (AREA)
  • Polymers & Plastics (AREA)
  • Food Preservation Except Freezing, Refrigeration, And Drying (AREA)
  • Constitution Of High-Frequency Heating (AREA)

Abstract

La présente invention concerne un procédé pour fournir une distribution d'énergie directe et homogène dans la totalité de la masse d'un écoulement de substrat fluide au moyen d'une double irradiation à haute fréquence générée de façon monomodale par un émetteur à micro-ondes « Magic T ». Ce dernier comprend un dispositif guide de forme toroïdale dans lequel chacune des ondes électromagnétiques progresse le long de chaque branche du dispositif guide pour atteindre l'extrémité correspondante d'une chambre d'irradiation qui se trouve à l'intérieur du dispositif guide et en face de l'émetteur « Magic T ». La présente invention est fondée sur la surveillance adéquate et précise des distances d'atténuation des deux champs à micro-ondes, qui se chevauchent, dans l'écoulement du substrat fluide. D'habitude, le substrat fluide à chauffer est un matériau alimentaire liquide.
PCT/EP2012/050770 2011-01-21 2012-01-19 Procédé pour fournir de l'énergie thermique directe et homogène à un substrat fluide WO2012098183A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201161435014P 2011-01-21 2011-01-21
US61/435,014 2011-01-21

Publications (1)

Publication Number Publication Date
WO2012098183A1 true WO2012098183A1 (fr) 2012-07-26

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4064791A1 (fr) * 2021-03-22 2022-09-28 Ultra High Temperature Processes Ltd Dispositif et procédé de transformation d'un matériau

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3120900A1 (de) * 1981-05-26 1983-06-16 Karl Dr. 7800 Freiburg Fritz Mikrowellen-arbeitsraum
US4775770A (en) 1983-08-10 1988-10-04 Snow Drift Corp. N.V. System for heating objects with microwaves
US5834744A (en) * 1997-09-08 1998-11-10 The Rubbright Group Tubular microwave applicator
EP1018856A1 (fr) * 1999-01-06 2000-07-12 Snowdrift Corp. N.V. Installation micro-onde à deux magnétrons au moins et procédé de contrôle d'une telle installation
US20090101639A1 (en) * 2006-03-13 2009-04-23 Creative Heating Services Sa Microwave heating method and device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3120900A1 (de) * 1981-05-26 1983-06-16 Karl Dr. 7800 Freiburg Fritz Mikrowellen-arbeitsraum
US4775770A (en) 1983-08-10 1988-10-04 Snow Drift Corp. N.V. System for heating objects with microwaves
US5834744A (en) * 1997-09-08 1998-11-10 The Rubbright Group Tubular microwave applicator
EP1018856A1 (fr) * 1999-01-06 2000-07-12 Snowdrift Corp. N.V. Installation micro-onde à deux magnétrons au moins et procédé de contrôle d'une telle installation
US20090101639A1 (en) * 2006-03-13 2009-04-23 Creative Heating Services Sa Microwave heating method and device

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
BAUM C.E.: "Impedance-matched Magic Tee", March 2006 (2006-03-01), XP002675941, Retrieved from the Internet <URL:http://www.ece.unm.edu/summa/notes/CESDN/CESDN51.pdf> [retrieved on 20120511] *
GORDON J LAUGHLIN: "A New Impedance-Matched Wide-Band Balun and Magic Tee", IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES,, vol. MTT-24, no. 3, 1 March 1976 (1976-03-01), pages 135 - 141, XP001368513 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4064791A1 (fr) * 2021-03-22 2022-09-28 Ultra High Temperature Processes Ltd Dispositif et procédé de transformation d'un matériau
WO2022200133A3 (fr) * 2021-03-22 2022-11-03 Ultra High Temperature Processes Ltd Dispositif et procédé de transformation d'un matériau

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