Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
  • G06Q10/00—Administration; Management
  • G06Q10/06—Resources, workflows, human or project management; Enterprise or organisation planning; Enterprise or organisation modelling
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
  • F25D29/00—Arrangement or mounting of control or safety devices
  • F25D29/001—Arrangement or mounting of control or safety devices for cryogenic fluid systems
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
  • F25D3/00—Devices using other cold materials; Devices using cold-storage bodies
  • F25D3/10—Devices using other cold materials; Devices using cold-storage bodies using liquefied gases, e.g. liquid air
  • F25D3/11—Devices using other cold materials; Devices using cold-storage bodies using liquefied gases, e.g. liquid air with conveyors carrying articles to be cooled through the cooling space
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
  • F25D2400/00—General features of, or devices for refrigerators, cold rooms, ice-boxes, or for cooling or freezing apparatus not covered by any other subclass
  • F25D2400/30—Quick freezing
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
  • F25D2500/00—Problems to be solved
  • F25D2500/04—Calculation of parameters
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
  • F25D2700/00—Means for sensing or measuring; Sensors therefor
  • F25D2700/16—Sensors measuring the temperature of products

Definitions

• the present invention relates to a method for predicting the temperature of articles undergoing thermal cooling.
• the invention applies for example to installations for freezing food articles.
• Known deep-freezing installations comprise, for example, an enclosure or tunnel, of deep-freezing crossed right through by a belt conveyor on which the articles to be frozen are deposited, the conveyor circulating continuously or sequentially through the deep-freezing tunnel.
• a cryogenic tunnel uses an inert fluid at low temperature which exchanges heat directly by contact with the products to be frozen.
• a cryogenic tunnel uses either dry ice (-80 ° C), or liquid air, or liquid nitrogen (-196 ° C) as a vector of cold.
• Dry ice allows the transport of fresh or frozen products without fear of breaking the cold chain.
• Nitrogen and liquid air allow either individual freezing of food products or the hardening of fragile, deformable or sticky products (such as ice cream ).
• the production rate which, for a given loading rate, implies a variation of the time of stay in the enclosure
• the flow rate of the fluid which acts on the temperature profile
• the inlet temperature of the product the convective profile of the enclosure
• the loading rate the production rate which, for a given loading rate, implies a variation of the time of stay in the enclosure
• the flow rate of the fluid which acts on the temperature profile
• the inlet temperature of the product the convective profile of the enclosure
• the main difficulty in correcting setpoint deviations is related to the fact that there is no commercially available sensor capable of continuously measuring the internal temperature of products today.
• the operating conditions and regulation instructions are defined in recipes created experimentally.
• a recipe memorizes the tuning parameters for a given production.
• the present invention aims to remedy these problems. To this end, it relates to a method for predicting the temperature of articles passing from an inlet to an outlet, an enclosure of a cooling installation, which uses a cooling fluid, which method comprises a step of predicting of the temperature of articles leaving said enclosure, characterized in that said prediction is calculated on the basis of operating characteristic quantities of said enclosure, of thermodynamic and physical characteristics of said enclosure and of thermodynamic and physical characteristics of said articles.
• At least part of said quantities characteristic of the operation of said installation is entered manually; - At least part of said quantities characteristic of the operation of said installation is automatically detected;
• thermodynamic characteristics of said cooling fluid and said thermodynamic and physical characteristics of said enclosure are used to make a prediction of the behavior of said enclosure based on the resolution of thermal balances on elementary slices of the volume of said enclosure;
• thermodynamic and physical characteristics of said articles are used to make a prediction of the behavior of said articles based on the resolution of the discretized heat conservation equation and applied to a network of spatial and temporal points constituting a mesh of said articles; said prediction of the behavior of said articles also uses said quantities characteristic of the operation of said installation;
• - Said quantities characteristic of the operation of said installation include the temperature of said articles entering said enclosure; - Said prediction of the behavior of said articles is optimized by calculations of modification of said mesh of said articles according to mathematical sequences;
• said prediction of the behavior of said articles is optimized by removing prediction calculations for spatial and temporal points of said mesh of said articles for which the enthalpy variations are less than a predetermined threshold;
• the present invention also relates to a method for cooling articles passing from an inlet to an outlet, an enclosure of a plant for cooling said articles (P) which uses a cooling fluid, characterized in that it includes a step of predicting the temperature of said articles according to the invention;
• said prediction is carried out by a reiteration of the prediction of the behavior of said enclosure and the prediction of the behavior of said articles, said method comprising a step of modifying at least one of the parameters chosen in the group consisting of:
• the present invention also relates to a device for predicting the temperature of articles passing through an installation, comprising a cooling enclosure which uses a cooling fluid comprising means for predicting this temperature, characterized in that said predicting means comprise calculation means which use quantities characteristic of the operation of the installation, thermodynamic and physical characteristics of said enclosure and thermodynamic and physical characteristics of said articles.
• the present invention also relates to an installation for cooling articles comprising an enclosure for cooling said articles which uses a cooling fluid, characterized in that it comprises a device for predicting the temperature of said articles according to the invention. According to other characteristics of the invention:
• cooling fluid circulates in a heat exchange device included in said enclosure, and indirectly exchanges heat with said articles through said heat exchange device.
• - Fig.1 shows a block diagram illustrating an installation implementing a method according to the invention
• - Fig.4 shows the flowchart of the coupling of the enclosure model and the items model.
• FIG 1 there is shown a food article processing installation equipped to implement a method according to the invention.
• This installation comprises a cryogenic enclosure or tunnel 2, of the conventional type, allowing the freezing of food articles P by bringing them into contact with a cryogenic fluid 4 conveyed by a supply line 5, from any source.
• tunnel 2 has the shape of a rectangular parallelepiped.
• cryogenic fluid 4 used can be, for example, dry ice or liquid nitrogen.
• This tunnel 2 is associated with a conveyor 6 of the conventional type, allowing the articles P to be introduced into the enclosure 2 and their extraction and operating either sequentially or continuously.
• the installation is equipped with measuring means 8 of characteristics relating thereto. They deliver for example the temperature profile in enclosure 2 and the conveyor unwinding speed 6. This last piece of information linked to the length of enclosure 2 makes it possible to obtain the residence time of the products P in enclosure 2.
• the installation is furthermore equipped with input means 10 by an operator of operating parameters, such as for example the temperature of entry into the enclosure 2 of the products P.
• the cited operating parameters namely the temperature profile, the residence time or the unwinding speed, and the inlet temperature of the products P, are distributed differently between the measurement. and manual entry.
• the installation finally comprises means 12 for controlling the quantity of cryogenic fluid 4 injected into the enclosure 2.
• These means 12 comprise means 14 for controlling the flow of cryogenic fluid 4.
• the control means 14 are constituted by solenoid valve systems or proportional valves of the conventional type, arranged on the cryogenic fluid supply line 5.
• the fluid 4 is injected at one or more places in the enclosure 2.
• the control means 14 are controlled by the output of comparison means 16, which are connected as input to input means 18 of a setpoint relating to the temperature of the articles leaving the enclosure 2 and to means 20 for predicting this temperature.
• Control of the flow rate of cryogenic fluid 4 injected into an installation such as that described, on the basis of a comparison between a setpoint and a prediction of the outlet temperature of the articles, is considered to be known and will not be described further. in detail.
• the installation also includes a gas ventilation system controlling the gas flows and the ventilation of the atmosphere of the enclosure 2.
• this system is made up of specific fans enabling gas to speed up, fans controlling gas recirculation and a combination of fans and movable doors controlling the balance between air inlets and outlets. gas.
• the means 20 for predicting the temperature of the articles P at the outlet of the enclosure 2 comprise means for predicting or predicting 22 the behavior of the enclosure 2, and means for predicting or predicting 24 of the behavior of the articles P.
• the predictive means 22 of the behavior of the enclosure 2 make it possible to predict by calculation, as described below with reference to FIG. 3, the theoretical profile of the temperatures of the cryogenic fluid 4 to inside the enclosure 2.
• the results delivered by the prediction means 22 depend on the thermodynamic characteristics of the cryogenic fluid 4, on the convective characteristics of the enclosure 2, as well as on the characteristics of the means for injecting the cryogenic fluid 4 into the enclosure 2, on the characteristics of the system. ventilation and physical characteristics of the enclosure 2.
• the prediction means 20 also include means 26 for correcting the predictor 22 of the behavior of the enclosure 2.
• correction means 26 make it possible to take into account, in the calculations of the predictor 22, elements characteristic of the operation of the installation, such as for example the speed of the conveyor 6, temperature readings inside the enclosure 2, the temperature of the cryogenic fluid 4 recovered after the treatment of articles P, or the thermal losses of enclosure 2.
• the data injected into the predictor 22 using the correction means 26 can be entered manually through the means of input 10 or measured by the measurement means 8. For example, there is a series of probes inside the enclosure 2 which make it possible to establish an experimental profile of the temperatures of the cryogenic fluid 4 in the enclosure 2 .
• the means 24 of predicting the behavior of the articles P make it possible to determine by calculation, as described below with reference to FIG. 2, the variations in enthalpy of the articles P as a function of their external environment and their initial temperature .
• the results delivered by the predictor 24 depend on the physical and thermodynamic characteristics of the P products.
• the prediction means 20 also include means 28 for optimizing the predictor 24 calculations of the behavior of the products P, the operation of which is described below with reference to FIG. 2.
• Coupling means 30, described in more detail with reference to FIG. 4, make it possible to link the results delivered by the predictor 22 of the behavior of the enclosure 2 and those delivered by the predictor 24 of the behavior of the articles P and to deliver a theoretical temperature of the items P leaving the enclosure 2.
• the prediction implemented by the means 20 for predicting the temperature of the articles P leaving the enclosure 2 takes into account the thermodynamic and physical characteristics of the enclosure 2 and of the products P, as well as the quantities characteristics of the operation of the installation.
• the determination of the temperature of the articles P at the outlet of the enclosure 2 is dynamic, easily configurable and easily adaptable to the operating conditions of the installation.
• thermodynamic and physical characteristics of the articles P are taken into account in the cooling process by the predictor 24 of the behavior of the articles P, and is based on a modeling of the articles P to which the heat conservation equation is applied. discrete.
• the method used consists in discretizing this equation so that it is solved only on spatial and temporal points called nodes and designated by the general reference 32.
• X, Y and Z are axes defining an orthonormal spatial reference frame around the article P.
• T is the temperature of the article P expressed in kelvin (K), and C its specific heat expressed in watt per kilogram and by Kelvin (W / (Kg * K)).
• Food items P that are frozen are generally made up of different bodies.
• phase change is accompanied by a temperature variation and that the heat conservation equation can still apply.
• the discretization is made thanks to the mathematical method of the finite differences in variable mode.
• the first, implicit discretization has the advantage of being stable whatever the spatial and temporal configuration. At a given instant, it makes it possible to determine the temperature of a node 32 as a function of the temperature of the neighboring nodes at the same instant. However, it implies constant boundary conditions and a matrix resolution of the equation system formed by each of the nodes 32.
• the second, explicit discretization makes it possible to directly determine the temperature of a node 32 at an instant T + ⁇ T d ' after the conditions at time T. The result is immediate, on the other hand, it is necessary to choose a suitable time step so as to avoid the instability of the model.
• the first method is recommended in the case where it is sought mainly to obtain the surface temperature of a product, which corresponds to the operation commonly called the "crusting" operation.
• the second is recommended when you want to freeze and know the core temperature of a product.
• the mesh of the product P is a crucial problem. On this directly depends the simplicity of further processing and the accuracy of the results.
• one solution is to distribute nodes in each direction of space using for example a geometric progression , as shown in Figure 2.
• ⁇ x the value of the first term which corresponds to the abscissa of the first node
• r the reason, different from 1, of the geometric sequence set implemented.
• the value of the n th term is: ⁇ x * r n "1. , This corresponds to the position on the X axis of the n th node.
• the sum of the first n terms is: î -"
• Another possible optimization method consists in reducing the processing time by omitting certain calculations.
• the treatment is broken down by no longer summing up the heat fluxes on each face, but in each direction.
• ⁇ T the equations with the nodes while going from the border towards the heart, until the va- enthalpy is considered to be negligible because it is below a predetermined threshold.
• the article P In the case where the article P is of complex shape, it can be broken down into a set of elementary forms to which the mesh defined above or any other mesh adapted to the shape of the article P is applied.
• the means 24 for predicting the behavior of the articles P as well as the means 28 for optimizing the calculations are, for example, implemented by software means.
• FIG 3 there is shown schematically the enclosure for processing food articles.
• thermodynamic and physical characteristics of the enclosure 2 are taken into account in the cooling process by the predictor 22 of the behavior of the enclosure 2, and is based on a modeling of the enclosure 2 in the form of elementary slices .
• the cooling enclosure 2 is associated with a conveyor 6. It is supplied with cryogenic fluid 4 via a supply line 5.
• the enclosure 2 is assimilated to a rectangular parallelepiped.
• the method implemented by the predictor 22 of the behavior of the enclosure 2 consists in carrying out a succession of local heat balances.
• thermodynamic system of tunnel 2 in steady state, in the form of elementary sections 34 ⁇ to 34 n , perpendicular to the length of the enclosure 2.
• the sum of these elementary sections 34 ⁇ to 34 n represents the internal volume of enclosure 2.
• the balance of the heat transfers is carried out in order to determine the enthalpy of the fluid 4 and therefore its temperature.
• m corresponds to the enthalpy of the cryogenic fluid 4 at the outlet of the elementary section 34j expressed in joules per kilogram (J / Kg);
• H M e corresponds to the enthalpy of the cryogenic fluid 4 at the input of the elementary section 34j expressed in joules per kilogram (J / Kg); corresponds to the liquid enthalpy of the cryogenic fluid 4 injected expressed in joules per kilogram (J / Kg);
• H corresponds to the enthalpy of the article P at the outlet of the section
• ⁇ ⁇ corresponds to the heat exchange coefficient of tunnel 2 with the outside expressed in watt per square meter and per kelvin (W / (m 2 K));
• m __ corresponds to the mass flow rate of cryogenic fluid 4 vaporized in section 34j expressed in kilograms per second (Kg / s);
• j jl corresponds to the mass flow rate of cryogenic fluid 4 entering the section 34 ⁇ expressed in kilograms per second (Kg / s);
• YYl corresponds to the mass flow rate of products to be treated expressed in kilograms per second (Kg / s); 1 Amb corresponds to the ambient temperature expressed in kelvin; and y corresponds to the temperature of the cryogenic fluid 4 at the input of the unit 34
• FIG. 3 also shows the heat flows: th r H t is represented P ar ' a letter A;
• rh m H M O is re BSB has P ar the l ⁇ ttre B: H m m m is represented by the letter C;
• cryogenic liquid 4 injected is only partially vaporized and a fraction of the liquid flows towards the inlet. of enclosure 2.
• an enthalpy of the limiting fluid is designated, below which a liquid content will appear.
• fj J m corresponds to the limit enthalpy of formation of a liquid title in an elementary section of the tunnel 2.
• FIG. 4 shows the operation of the means 20 for predicting the temperature of the articles P at the outlet of the enclosure 2.
• the cooling process involves predicting the behavior of enclosure 2 implemented by the predictor 22 of the behavior of enclosure 2 and the prediction of the behavior of the articles implemented by the predictor 24 of the behavior of the articles P.
• this step is implemented by the coupling means 30.
• the predictor 22 After repeating this operation a certain number of times, we obtain the total thermal losses 44 as well as the profile 46 of the temperatures of the fluid 4 in the enclosure 2. To calculate the thermal balance of each slice, the predictor 22 requires the enthalpic variations of articles P. In fact, during the first iteration, the temperature profile of the fluid 4 in the enclosure 2 cannot be calculated, it is fixed arbitrarily.
• the predictor 24 of the behavior of the items P is then implemented during a step 50. This delivers the enthalpy 52 of the product P at the outlet of the enclosure 2, ie its temperature.
• the predictor 24 of the behavior of the articles P also delivers the enthalpy variations 54 of an article P for each elementary section of the enclosure 2.
• this information is returned to the behavior predictor 22 of the enclosure 2 which inserts it into the heat balance of each elementary section.
• the enthalpy 52 of the product P at the outlet of the enclosure 2 as well as the profile 46 of the temperatures of the fluid 4 in the enclosure 2 and the total thermal losses 44, are put in relation in order to determine the total flow rate of the fluid, at step 60.
• the flow rate 62 injected into each elementary section is also obtained.
• this information is returned to the behavior predictor 22 of the enclosure 2 which inserts it into the heat balance of each elementary section.
• step 80 It is then checked whether the temperature profile of the fluid 4 in the enclosure 2 is stable, in step 80.
• the profile of the fluid temperatures is considered to be stable if it meets the following criteria twice:
• dif_profil is a constant fixed by the operator.
• the profile On the first pass, the profile is considered unstable. As long as the profile is considered unstable, we return to step
• step 80 it is checked whether the setpoint entered by the input means 10 for a setpoint relating to the temperature of the products P at the outlet of the enclosure 2 has been reached, in step 80. If the setpoint has been reached, the last profile of the temperatures of the fluid 4 inside the enclosure 2 is implemented, in a conventional manner, by the control of the means 14 for controlling the flow of fluid 4, step 90.
• a correction 102 is applied to the flow rate of the fluid 4 before repeating the algorithm.
• a correction 104 is also applied directly to the temperature profile of the fluid 4, which is injected into the predictor 22 of the behavior of the enclosure 2.
• the prediction of the temperature of the articles leaving the enclosure is used to perform automated control of a cryogenic enclosure 2 by influencing the flow rate of the fluid 4 injected.
• the method of the invention is implemented in an installation having non-contact sensors for the temperature of the items being output, for example sensors based on thermal radiation or the infrared image, or even on a measurement by microwave thermometry (TMO), such as the sensor described in patent FR-A-2,771,552.
• TEO microwave thermometry
• results delivered by the means for predicting the temperature of the articles leaving the enclosure according to the invention are then cross-checked with the measurements delivered by these sensors.
• one or the other of the information is used to check the other, or an average of the two values for the operation of the installation.
• the information delivered by the sensor is used to correct the prediction.
• the measurement frequency is lower than the frequency of delivery of a prediction.
• the installation is equipped with means for determining the value representative of the quality and / or quantity of articles treated, which means are connected to the means for predicting the temperature of the articles leaving according to the invention.
• cooling method of the invention can also be applied in a mechanical cooling installation having an indirect heat exchange device.
• the invention has been described in the case of cooling food articles, however it can also be applied to other types of articles, in particular metallic articles.
• cooling also covers systems aimed at maintaining and controlling a temperature lower than the initial temperature of an article.
• the invention has been described in the context of a cooling installation.
• the temperature prediction method can be implemented independently of the enclosure control means, for example in the context of temperature control.
• the invention makes it possible in particular to ensure the traceability of the articles during acquisition and storage operations with a view to providing a quality guarantee.

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  • 2001-10-05 FR FR0112860A patent/FR2830608B1/fr not_active Expired - Fee Related
• 2002
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