Temperature control using applied electromagnetic fields

Abstract

A technique for characterizing a product based on a reactance signal and a resistance signal exhibited by the product in an electromagnetic field is disclosed.

Description

TECHNICAL FIELD

[0001] The present invention relates to a non-invasive and non-contact method that can be used to determine the temperature of a product and determine the degree of freezing of a product, such as a food product. The present invention also relates to applying the method to control equipment, such as equipment for cooling and freezing, and applying the method to equipment with which the method can be implemented to control the operation of the equipment. BACKGROUND

[0002] In many fields, the ability to determine the temperature of an object or group of objects is important. This ability is useful for many reasons, such as maintaining or controlling conditions to which a product is exposed. Traditionally, the temperature of an object can be measured by bringing the object into direct contact with a thermometer or direct contact with a contact attached to a thermocouple. However, in many situations, such as in the food industry, a method that does not require contact with the product and is non-invasive would be preferred, but only if such a method can be found that is practical and reliable. Non-contact methods are known in the art, such as techniques using infrared temperature sensors, but they have many drawbacks. Typically, infrared sensors only provide a reading of the temperature of a surface point of an item, not a reading of the temperature of a larger surface or volume of the item. Also, the accuracy of the measurement depends on the actual measurement point size and the measurement distance, and even with all other locations equal, the accuracy is typically not as good as 3-4 °F for a relatively small target point. The small target area relative to the distance results in less accurate measurements. The temperature from the surface element being measured to the surface element of the item typically varies (top, bottom, edge, center, etc.). Furthermore, if the item is undergoing a phase change during freezing, small temperature variations can mean large freezing degree variations. In the frequent case where the object being measured has internal temperature variations, infrared temperature sensors cannot reliably detect the internal or average temperature. For example, during a continuous freezing process, there is a temperature gradient within the food, where the surface of the product is colder than the core of the product. The product can take some time after it leaves the freezer for the internal temperature gradient to disappear and for the entire product to reach an equilibrium temperature. Therefore, measuring the surface temperature at the time of leaving the freezer is not very useful because it is not well correlated to the final equilibrium temperature. On the other hand, when a temperature probe is inserted into a product with an internal temperature gradient, small variations in the penetration depth can result in significant inaccuracies.

[0003] U.S. Patent Application 2012 / 0237644 describes a method for controlling a cooking process based on measuring the electrical impedance of food items during cooking. The sensor probe is inserted into the food item for impedance measurement, which can damage, alter, harm, or destroy the shape of the food item. Furthermore, the sensor surface can pose food safety issues when in contact with one or more food items. Therefore, this contact measurement method is only suitable for random and occasional sampling of food items and is not a reliable method for determining food temperature in continuous production.

[0004] U.S. Patent Application 2017 / 0138661 discloses a method for automatically adjusting heat transfer to freeze food products to a selected temperature based on real-time measurements of the food product's physical properties. For example, the reference document suggests using infrared (IR) sensors for food product temperature measurement and freezer control. However, this has many drawbacks as discussed above, including that the surface temperature measured by the infrared sensor does not represent the average temperature of the product or its overall degree of freezing due to the temperature gradient within and on the surface of the food article during freezing. US2017 / 0138661 also describes a method for controlling the freezing process by continuously adjusting heat transfer. In many cases, continuous adjustment of operating parameters is not preferred. After parameter adjustments, the system requires time to reach stability, and additional adjustments within this response time can lead to significant instability in process control and thus poor product quality.

[0005] U.S. Patent No. 5,189,366 discloses a method and apparatus for determining the temperature of a material by passing a sample through a coil system that generates an electromagnetic field, wherein the conductivity of the material varies with temperature. If the reactance and resistance components are processed according to an expression (as described in the patent), the patent asserts that the measurement method is substantially independent of the cross-sectional area and dimensions of the product being tested.

[0006]

[0007] Where K rX is the calculated amplitude, R is the reactance signal, and α is the resistance signal, where α is the power varying between 0.5 and 1.0, depending on the geometry of the material. Specifically, this patent describes a trial-and-error method for pre-determining the value of α by running a series of test samples with the same known conductivity and different known cross-sections and finding the best-fit value for α. However, the inventors have determined that the results obtainable according to the teachings of this patent are not always independent of the size and dimensions of the product being measured, at least when the product is fully or partially frozen. In many commercial processes, there is variability in the quality, size, and shape of the products being processed. For example, in poultry processing, there are significant differences in the size, shape, and weight of individual chicken breasts being processed. If the size, shape, or weight of the chicken breast significantly affects K... r Reading the numbers will make it very difficult to derive K. r Does the change in the value represent a change in the product's average temperature, or only a change in the product's weight, size, and / or shape? This will make K... r Using readings as a means of measuring the average temperature of a product is impractical.

[0008] In contrast, this invention provides a reliable technique for assessing product temperature and determining the degree of freezing of partially or fully frozen products, in a manner independent of product size or shape, non-invasive, and requiring no contact with the product or physical penetration. This invention also provides a reliable technique for avoiding erroneous readings from other factors, such as high production throughput, where multiple product pieces may pass through the sensor simultaneously. These advantages make this invention highly applicable to a wide variety of applications, including but not limited to assessing food products that have been cooled, frozen, or heated. Summary of the Invention

[0009] One aspect of the present invention is a method for analyzing a product to determine its temperature, comprising:

[0010] (a) Providing a correlation between the actual temperature of a product having the composition of the product to be analyzed and the phase angle exhibited by the product having the composition of the product to be analyzed at two or more different actual temperatures, wherein the phase angle exhibited by a given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given strength and frequency applied to the given product.

[0011] (b) Applying an electromagnetic field of a given intensity and frequency to the product being analyzed, measuring the reactance and resistance signals exhibited by the product being analyzed in the electromagnetic field of the given intensity and frequency, and determining the phase angle exhibited by the product being analyzed based on the measured reactance and resistance signals; and

[0012] (c) Based on the correlation, determine the actual temperature of the product being analyzed based on the phase angle determined in step (b).

[0013] Another aspect of the present invention is a method for analyzing a product to determine the degree of freezing of the product, comprising:

[0014] (a) Providing a correlation between the degree of freezing of a product having the composition of the product to be analyzed and the phase angle exhibited by the product having the composition of the product to be analyzed at two or more different degrees of freezing, wherein the phase angle exhibited by a given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product.

[0015] (b) Applying an electromagnetic field of a given intensity and frequency to the product being analyzed, measuring the reactance and resistance signals exhibited by the product being analyzed in the electromagnetic field of the given intensity and frequency, and determining the phase angle exhibited by the product being analyzed based on the measured reactance and resistance signals; and

[0016] (c) Based on the correlation, determine the degree of freezing of the product being analyzed based on the phase angle determined in step (b).

[0017] Another aspect of the invention is a method of operating equipment, said equipment providing a product at an actual temperature within a desired range when the product leaves said equipment, said method comprising:

[0018] (a) To conduct the product into and through the equipment, the equipment being capable of subjecting the product within the equipment to at least one adjustable operating condition that can modify the temperature of the product within the equipment.

[0019] (b) Applying an electromagnetic field of a given intensity and frequency to the product at one or more of the following locations: (i) a location within the equipment, or (ii) a location where the product leaves the equipment, or (iii) a location where the product enters the equipment, measuring the reactance and resistance signals exhibited by the product in the applied electromagnetic field, and determining the phase angle exhibited by the product, wherein the phase angle exhibited by the given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product;

[0020] (c) Determining the actual temperature of the product based on the measured phase angle, according to a predetermined correlation between two or more different actual temperatures of the product and the phase angle exhibited by the product having the composition of the analyzed product as measured in the applied electromagnetic field of the given intensity and frequency; and

[0021] (d) When the difference between the actual temperature of the product determined in step (c) and the actual temperature of the product at a predetermined set point is greater than a predetermined difference, the difference is reduced by adjusting at least one adjustable operating condition in the equipment to modify the actual temperature of the product in the equipment, so that the actual temperature of the product when it leaves the preparation is within the desired range.

[0022] Another embodiment of the present invention is a method of operating equipment, said equipment providing a product at an actual temperature within a desired range when the product leaves said equipment, said method comprising:

[0023] (a) To conduct the product into and through the equipment, the equipment being able to subject the product within the equipment to at least one adjustable operating condition that can modify the temperature of the product within the equipment.

[0024] (b) Applying an electromagnetic field of a given intensity and frequency to the product at one or more of the following locations: (i) a location within the equipment, or (ii) a location where the product leaves the equipment, or (iii) a location where the product enters the equipment, measuring the reactance and resistance signals exhibited by the product in the applied electromagnetic field, and determining the phase angle exhibited by the product, wherein the phase angle exhibited by the given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product;

[0025] (c) Determine the difference between the phase angle exhibited by the product as measured in step (b) and the predetermined phase angle setpoint; and

[0026] (d) When the difference measured in step (c) is greater than a predetermined difference, the difference is reduced by adjusting at least one adjustable operating condition within the equipment to modify the temperature of the product in the equipment, so that the actual temperature of the product when it leaves the preparation is within the desired range.

[0027] Another aspect of the invention is a method of operating equipment, said equipment providing a product at a desired degree of freezing when the product leaves said equipment, said method comprising:

[0028] (a) To transfer the product into and through the equipment, the equipment being capable of subjecting the product within the equipment to at least one adjustable operating condition that can modify the degree of freezing of the product within the equipment.

[0029] (b) Applying an electromagnetic field of a given intensity and frequency to the product at one or more of the following locations: (i) a location within the equipment, or (ii) a location where the product leaves the equipment, or (iii) a location where the product enters the equipment, measuring the reactance and resistance signals exhibited by the product in the applied electromagnetic field, and determining the phase angle exhibited by the product, wherein the phase angle exhibited by the given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product;

[0030] (c) Determining the degree of freezing of the product based on the measured phase angle, according to a predetermined correlation between two or more different actual degrees of freezing of the product and the phase angle exhibited by the product having the composition of the analyzed product as measured in the applied electromagnetic field of the given intensity and frequency; and

[0031] (d) When the difference between the degree of freezing of the product determined in step (c) and the degree of freezing of the product at a predetermined set point is greater than a predetermined difference, the difference is reduced by adjusting at least one adjustable operating condition in the equipment to modify the degree of freezing of the product in the equipment, so that the degree of freezing of the product when it leaves the preparation is within the desired range.

[0032] Another aspect of the present invention is an apparatus capable of modifying the temperature of a product within the apparatus, comprising:

[0033] A housing having a channel extending through the housing from an inlet to an outlet, a first means for moving a product through the channel from the inlet to the outlet, and one or more outlets within the housing from which a liquid or gaseous heat transfer medium can be transferred to the channel to establish an environment in which the product is exposed within the housing, wherein at least one condition in which the product is exposed within the housing is adjustable to modify the temperature of the product within the channel.

[0034] A second device, located in one or more of the following positions: (i) within the housing, (ii) at an outlet of the housing, or (iii) at an entrance of the housing, capable of applying an electromagnetic field to the product.

[0035] A third device, operably connected to the second device and capable of measuring the reactance signal and the resistance signal exhibited by the product in the electromagnetic field, and calculating the phase angle exhibited by the product based thereon;

[0036] A fourth device, operatively connected to the third device and capable of determining the difference between a predetermined setpoint phase angle exhibited by the product and the phase angle exhibited by the product passing through its channel, and

[0037] A fifth device, operatively connected to the fourth device and capable of adjusting at least one operating condition of the product within the housing to reduce the difference in response to the difference.

[0038] Alternative embodiments of the present invention include:

[0039] An apparatus capable of modifying the temperature of a product within the apparatus, comprising:

[0040] A housing having a channel extending through the housing from an inlet to an outlet, a first means for moving a product through the channel from the inlet to the outlet, and one or more outlets within the housing from which a liquid or gaseous heat transfer medium can be transferred to the channel to establish an environment in which the product is exposed within the housing, wherein at least one condition in which the product is exposed within the housing is adjustable to modify the temperature of the product within the channel.

[0041] A second device, located within the housing and / or at an outlet exiting the housing and / or at an inlet entering the housing, is capable of applying an electromagnetic field to the product.

[0042] A third device, operably connected to the second device and capable of measuring the reactance signal and the resistance signal exhibited by the product in the electromagnetic field, and calculating the phase angle exhibited by the product based thereon;

[0043] A fourth device, operatively connected to the third device and capable of determining, based on a predetermined correlation between the temperature of a reference product having the same composition as the product passing through the channel and its phase angle, the difference between a predetermined setpoint temperature of the product and the temperature of the product corresponding to a calculated phase angle of the product; and

[0044] A fifth device, operatively connected to the fourth device and capable of adjusting at least one operating condition of the product within the housing to reduce the difference in response to the difference.

[0045] Other alternative embodiments of the present invention include an apparatus capable of modifying the degree of freezing of a product within the apparatus, comprising:

[0046] A housing having a channel extending through the housing from an inlet to an outlet, a first means for moving a product through the channel from the inlet to the outlet, and one or more outlets within the housing from which a liquid or gaseous heat transfer medium can be transferred to the channel to establish an environment in which the product is exposed within the housing, wherein at least one condition of the product exposure within the housing is adjustable to modify the degree of freezing of the product within the channel.

[0047] A second device, located within the housing and / or at an outlet exiting the housing and / or at an inlet entering the housing, is capable of applying an electromagnetic field to the product.

[0048] A third device, operably connected to the second device and capable of measuring the reactance signal and the resistance signal exhibited by the product in the electromagnetic field, and calculating the phase angle exhibited by the product based thereon;

[0049] A fourth device, operatively connected to the third device and capable of determining, based on a predetermined correlation between the degree of freezing of a reference product having the same composition as the product passing through the channel and its phase angle, the difference between the degree of freezing of the product and the degree of freezing of the product corresponding to a calculated phase angle of the product; and

[0050] A fifth device, operatively connected to the fourth device and capable of adjusting at least one operating condition of the product within the housing to reduce the difference in response to the difference.

[0051] Another aspect of the invention is a method of operating equipment, said equipment providing a product that exhibits selected physical characteristics within a desired range when leaving said equipment, said method comprising:

[0052] (a) To conduct the product into and through the equipment, the equipment being capable of subjecting the product within the equipment to at least one adjustable operating condition that can modify selected physical properties of the product within the equipment.

[0053] (b) Applying an electromagnetic field of a given intensity and frequency to the product at one or more of the following locations: (i) a location within the equipment, or (ii) a location where the product leaves the equipment, or (iii) a location where the product enters the equipment, measuring the reactance and resistance signals exhibited by the product in the applied electromagnetic field, and determining the phase angle exhibited by the product, wherein the phase angle exhibited by the given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product;

[0054] (c) Determine the difference between the phase angle exhibited by the product as measured in step (b) and a predetermined phase angle setpoint corresponding to the desired value of the selected physical characteristic; and

[0055] (d) When the difference measured in step (c) is greater than a predetermined difference, the difference is reduced by adjusting at least one adjustable operating condition within the equipment to modify a selected physical characteristic of the product in the equipment, such that the selected physical characteristic of the product when it leaves the preparation is within the desired range.

[0056] The equipment according to the present invention is used to perform the above-described method and is capable of modifying selected characteristics of a product within the equipment, including...

[0057] A housing having a channel extending through the housing from an inlet to an outlet, a first means for moving a product through the channel from the inlet to the outlet, and one or more outlets within the housing from which a liquid or gaseous heat transfer medium can be transferred to the channel to establish an environment in which the product is exposed within the housing, wherein at least one condition of the product exposure within the housing is adjustable to modify selected characteristics of the product within the channel.

[0058] A second device, located at one or more of the following positions: (i) within the housing, (ii) at an outlet of the housing, or (iii) at an entrance of the housing, capable of applying an electromagnetic field to the product.

[0059] A third device, operably connected to the second device and capable of measuring the reactance signal and the resistance signal exhibited by the product in the electromagnetic field, and calculating the phase angle exhibited by the product based thereon;

[0060] A fourth device, operatively connected to the third device and capable of determining the difference between a predetermined setpoint phase angle corresponding to a desired value of the selected physical characteristic and the phase angle exhibited by the product passing through its channel, and

[0061] A fifth device, operatively connected to the fourth device and capable of adjusting at least one operating condition of the product within the housing to reduce the difference in response to the difference.

[0062] As used in this article:

[0063] "Actual temperature" refers to the average product temperature over the entire mass of the product.

[0064] For the purposes of this invention, the "actual temperature" can be determined by any of many different methods, provided that in any given specific embodiment of this invention, the foregoing association and determination are relative to the same method. When a product has no internal temperature gradient, determining the actual temperature is easily accomplished by bringing a thermometer into contact with the surface of the product or by inserting a thermometer into the product, or in some cases by using an infrared temperature sensor. However, in many industrial applications, a product leaving a temperature control device (e.g., a continuous cooler) will have an internal temperature gradient. In this case, different techniques familiar to those skilled in the art are used to determine the actual, average, or equilibrium temperature of the product. One approach is to place the product in a well-insulated container that does not allow heat leakage. Once the internal temperature gradient disappears, the above procedure using a thermometer can be used to determine the actual temperature of the product. Another way to measure the actual or average temperature of a product with an internal temperature gradient is to use methods such as hydrocalorimetry. In hydrocalorimetry, a known mass of a product with an internal temperature gradient is immersed in a known amount of liquid (preferably water) at a known initial temperature. The liquid and the product are in contact in a well-insulated container to prevent heat leakage from or to the environment. Once the temperature of the liquid-product mixture stabilizes, this final mixture temperature is used to determine the actual temperature of the product, which is then immersed in the liquid using an energy balance equation. Those skilled in the art will recognize that many variations of the above-described technique exist. For example, instead of water, the product can be immersed in a boiling liquid (such as liquid nitrogen). In this case, the amount of vaporized liquid nitrogen is used in the energy balance equation to measure the actual temperature of the product.

[0065] The "degree of freezing" of a product refers to the portion of all normally liquid materials present in the product in a solid phase relative to the total amount of all normally liquid materials present in the product in a solid or liquid phase, where "normally liquid material" is a material that is liquid at 25°C and one atmosphere. Water is an example of a normally liquid material. If some, but not all, of the normally liquid materials present in the product are solid, the product is considered to be "partially frozen." If all the normally liquid materials present in the product are solid, the product is considered to be "completely frozen" or "fully frozen."

[0066] "Cooling" a product means removing heat from the product, thereby reducing the temperature of the product; "cooling" includes removing heat from the product without freezing any of the normally liquid materials in the product, and includes removing heat from the product and causing some of the normally liquid materials to freeze, or all of the normally liquid materials in the product to freeze.

[0067] "Conductive" means that a product is electrically conductive, electromagnetically conductive, or both, at least to the extent that it emits signals when in an electromagnetic field. A product can be "conductive" if it contains water (whether liquid, solid, or a mixture of liquid and solid) or one or more substances that enable it to conduct. Examples of such substances include ions formed by the ionization of organic or inorganic ionic compounds in water, and include dissociated organic and inorganic acids or salts. Other materials within the product that enable its electromagnetic conduction may also be replaced by water.

[0068] "Phase angle" refers to a specific characteristic property exhibited by a product in an electromagnetic field, as defined in equation (1) of this paper. To further explain how important this equation is, when an alternating electromagnetic field is applied to an electromagnetically conducted product, a separate alternating field is generated within the product itself. In this case, the phase angle is defined as the shift or delay between the applied and induced alternating electromagnetic fields. This shift or delay, or phase angle, is due to the product's reactance (X). product ) and resistance (R) product And mathematically equal to X product and R product The arctangent of the ratio In commercially available metal detector equipment, when a product passes through the electromagnetic field generated by the metal detector, the reactance signal (X) is measured by the detector's electronics. signal ) and resistance signal (R) signal These signals are related to X. product and R product The same or related factors. The difference between actual reactance and resistance and those measured by electronic devices can be due to several factors, including the distance of the measuring coil and the distance between the product and the measuring coil. The phase angle found to be used in this invention is preferably defined as the arctangent of the ratio of the measured reactance signal to the resistance signal. Although, as a general case, the phase angle can also be modified by shifting any of the aforementioned mathematical functions by a constant, for example, shifting the phase angle by 90 degrees. Furthermore, as a general case, the phase angle can be X. product R product X signal R signal Any mathematical function that satisfies the following criteria: (a) normalizes reactance and resistance values ​​to reduce the influence of product mass, size, and dimensions and amplifies the influence of temperature; (b) then applies a suppression function to further reduce the influence of mass, size, and dimensions at all temperatures of interest; and (c) the mathematical function should be monotonic with respect to temperature, preferably at least at all temperatures of interest; the phase angle of equation (1) in this paper has been found to satisfy all these considerations. Attached Figure Description

[0069] Figure 1A This is a flowchart of the temperature determination method according to the present invention.

[0070] Figure 1B This is a flowchart of a method for determining the degree of freezing according to the present invention.

[0071] Figure 1C It is a representative curve of the enthalpy relative temperature of the product, extending from the point where the product is not frozen to the point where the product is completely frozen.

[0072] Figure 1D This is a flowchart of another method according to the present invention for achieving a desired value of a selected characteristic.

[0073] Figure 2 This is a cross-sectional view of an apparatus that can be used to implement the present invention.

[0074] Figure 3 This is a schematic representation of the connection used to implement the present invention.

[0075] Figure 4A and Figure 4B This is a representative graph showing the application of normalization and suppression functions to the phase angle to obtain temperature-sensitive accuracy independent of mass, size, shape, or dimensions. Detailed Implementation

[0076] This invention is applicable to any physical application in which it is desired to determine the actual temperature of a product or the degree of freezing of a product. Numerous examples exist in commercial methods for manufacturing, processing, heating, or cooling products. Preferred examples are in the cooling of food products, such as through the use of equipment for cooling or freezing food products (this refers to fully edible products, as well as edible products contained in packaging, the packaging itself of which may not be considered edible). The following description will refer to the cooling (or freezing) of food products to illustrate the invention, but is not intended to limit the applicability of the invention to such applications. Examples of food products in which the invention can be implemented include water, aqueous beverages, fruits, vegetables (whole or sliced), seafood, poultry, meat other than seafood and poultry, ready-to-eat foods, food ingredients, and baked goods.

[0077] This invention utilizes previously unrecognized relationships between the phase angle exhibited by a product as defined herein and the actual temperature of the product, and between the phase angle exhibited by a product as defined herein and the degree of freezing of the product. Based on the detection of the electromagnetic field emitted by the product when exposed to an external electromagnetic field, the phase angle is correlated with the degree of freezing or a determined (or equilibrium) temperature of the product. Such products exhibit a combination of resistive and reactive characteristics, where the combination is referred to as impedance. Specifically, resistance originates from ions in the product (such as in food products), while reactance is driven by the capacitive characteristics of the product. Both characteristics are affected by the actual temperature of the product and its composition.

[0078] When a product is exposed to an external (primary) electromagnetic field, eddy currents are induced within the product. These eddy currents generate a secondary electromagnetic field, which is measured as a complex signal. This complex signal is further decomposed by a detector into resistance and reactance signals. A shift or delay exists between the primary applied field and the secondary generated field. This shift or delay is sometimes referred to as the phase angle. The amplitude, frequency, and phase angle of the secondary complex signal are influenced by the product's resistance and reactance, as well as by the amplitude and frequency of the primary field. The preferred frequency of the primary electromagnetic field is between 100 kHz and 1 MHz, but frequencies in a wider range between 50 kHz and 1000 kHz can also be used. As is known in the art, the desired frequency of the electromagnetic field is provided by applying an alternating current with the desired frequency. (Although direct current can be used to establish the electromagnetic field, alternating current is preferred.) In particular, the phase angle of the secondary complex signal, the resistance signal (R or R), and the phase angle of the secondary complex signal are all related to the primary electromagnetic field. signal The amplitude and reactance signal (X or X) signal The amplitude of the wave is strongly correlated with the resistance and capacitance of the product. The phase angle θ is determined according to equation (1):

[0079] (1) θ = arctan(reactance signal / resistance signal)

[0080] As further described below, it has been found that both the resistance and reactance signals, and therefore the phase angle of a given product, are affected by temperature, phase transitions during freezing, and the degree of freezing of the product. The reactance and resistance signals mentioned above can be fundamental characteristics of the product under a given primary field at a given temperature, or they can be functions of such fundamental characteristics, as measured by equipment detecting the secondary inductive field. The phase angle can also be a modification of Equation 1, for example, shifting the phase angle by 90 degrees.

[0081] Typically, the phase angle can also be defined as any mathematical function of reactive and resistive signals that satisfies the following criteria.

[0082] i. Applying a normalization function to reactance and resistance signals, N(X,R), reduces the influence of product mass, size, and shape, but amplifies the contrast between temperature effects and size / shape effects. Some examples of normalization functions are... Where α and β are constants.

[0083] ii. In some cases, it is also necessary to apply the suppression function D(N(X,R)) to the normalization function to further suppress the size / magnitude effect for temperature control. Some examples of suppression functions are Arctan(N) and Arctan(N)+A, where A is constant.

[0084] The primary purpose of normalization and suppression functions is to ensure that the final mathematical function representing the phase angle is substantially independent of product quality, size, and dimensions without sacrificing the ability to detect changes in product temperature. The following factors must be considered in the selection of normalization and suppression functions: application factors include food temperature, the required accuracy of food temperature readings, food size / dimensions, and potential variations in food size / dimensions. A single normalization function ( Figure 4A ) or standardization and suppression function ( Figure 4B Together, it should be ensured that phase angle variations from dimensions / size / shape are within the requirements for temperature measurement accuracy. Figure 4A and Figure 4B In this diagram, square, star, and circle symbols represent food items at a set temperature, a set temperature plus accuracy (δ), and a set temperature minus accuracy, respectively. For example, five square symbols represent five food items of different sizes / dimensions at the set temperature. Ideally, the phase angle should be completely independent of size / dimension, so symbols with the same temperature should form a [phase angle]. Figure 4B The horizontal line in the diagram. In temperature control applications, if the phase angle values ​​of food items at different temperatures do not overlap, a normalization and suppression function can be selected. Specifically, the maximum phase angle from the square group is less than the minimum from the circle group, and the minimum phase angle from the square group is greater than the maximum from the star group. exist Figure 4A The above requirements are not met because a single normalization function cannot eliminate the influence of size / dimension. In this case, both normalization and suppression functions are necessary for the definition of the phase angle in order to measure the temperature. The final mathematical function should also be monotonic with respect to the product temperature. This is to ensure that the function does not lose its ability to identify differences in product temperature. However, for the purposes of this invention, it has been determined that the definition of equation (1) satisfies all these considerations and provides the phase angle after all such normalization and suppression have been implemented; that is, after the phase angle has been determined according to equation (1), no normalization or suppression of the phase angle value is required. Furthermore, it will be appreciated that the ratio of (reactance signal) to (resistance signal) is independent of the specific unit of each signal, provided that the value of each signal is determined in the same unit.

[0085] Now for reference Figure 1A A flowchart is shown illustrating the steps that can be performed according to the present invention to determine the actual temperature of a product.

[0086] Element 201 represents the method step of applying an electromagnetic field to the product. Element 202 represents the step in which the reactance and resistance signals of the product induced in response to the applied electromagnetic field are measured, and the phase angle is determined according to equation (1) based on the amplitudes of the reactance and resistance signals measured in this step. A preferred embodiment is to provide a plurality of coils and pass the product through the coils while simultaneously passing an alternating current through one of the coils to establish an electromagnetic field through which the product passes. The other coils of the plurality of coils are used to detect secondary complex signals emitted by the product after it passes through the electromagnetic field of the first coil. The resistance and reactance components of the secondary complex signals are determined by detectors. Devices for performing these functions are known. The phase angle is preferably determined based on a portion of the signal that appears as a flat “tail,” thereby ignoring (or filtering, visually or electronically) any peaks that are correctly characterized as “noise.”

[0087] It will be recognized, of course, that in order for a secondary signal to be detectable from the product, the corresponding coils will need to be positioned close enough to each other (taking into account relevant factors such as the strength of the electromagnetic field through which the product passes, the speed at which the product moves through the first coil and toward the detection coil, and the ability of the product to continue emitting its electromagnetic field after it has passed through the first coil) so that the signal emitted by the product can be detected by the detection coil.

[0088] Element 203 represents the correlation between the actual temperature of a separately established reference product (which has the same composition as the product being analyzed) and the phase angle it exhibits in an electromagnetic field of the same strength and frequency as the electromagnetic field applied to the product in step 201, as determined. The correlation is preferably established by subjecting the reference product, which has the same composition as the product being analyzed, to electromagnetic fields of the same strength and frequency as the product being analyzed at different actual temperatures (preferably at least two different actual temperatures, and more preferably two to ten different actual temperatures), and by measuring resistance and reactance signal values ​​and calculating the phase angle according to equation (1) or any other function of the reactance and resistance signals as previously described, to determine the phase angle exhibited by each sample of the reference product at each corresponding temperature. This correlation will generally be different for each product or product type being subjected to the invention. As described herein, different actual temperatures of the product have been found to correspond to different phase angles obtained.

[0089] As indicated, the aforementioned correlation between the actual temperature of the product being analyzed and the phase angle exhibited by the product being analyzed can be directly established, i.e., by actually testing a reference product having the same composition as the product being analyzed. However, the present invention can also achieve this correlation indirectly, i.e., by establishing a first correlation (through actual testing) between the phase angle exhibited by a product having the same composition as the product being analyzed and a reference product having a different composition, and a second correlation between the phase angle exhibited by the reference product and the actual temperature of a product having the same composition as the product being analyzed. In this way, in practicing the present invention, a reference product that differs from the product being analyzed by only a few percentage points (at most 5% or even up to 10%) in one or more component components can be used. Therefore, it is not always necessary for the composition of the reference product to be the same as that of the product being analyzed. For example, the survey (Husak, Ryan Lon, “A survey of commercially available broilers originating from organic, free-range and conventional production systems for cooked meat yields, meat composition and relative value” (2007), retrospective dissertation and topical paper, 14523) showed that the average moisture level in commercially available broiler leg meat in the United States had a mean standard error (SEM) of 1%. In this case, a reference product can be selected as long as its composition differs from that of the product to be analyzed by only a few percentage points (up to 10%) in one or more component components. Alternatively, the U.S. Department of Agriculture has established a food composition database that records the composition of food products with different Universal Product Codes (UPCs). The reference product should have the same UPC number as the product to be analyzed.

[0090] Element 204 represents the following step: wherein, for the product being processed, the actual temperature of the product that has undergone steps 201 and 202 is determined by finding the actual temperature corresponding to the phase angle determined due to the execution of steps 201 and 202 in the above association (in element 203).

[0091] Optional element 205 indicates the use of the determined actual temperature for any of a number of functional purposes (such as the operation of a device for controlling the processing or handling of a product whose actual temperature is determined). The description herein of the control of a food cooling device is an example of such use of the actual temperature determined according to the invention.

[0092] Now for referenceFigure 1B A flowchart is shown illustrating the steps that can be performed according to the present invention to determine the degree of freezing of a product.

[0093] Figure 1B Elements 201 and 202 in the text represent, as described above, relative to... Figure 1A The same method and steps as described above.

[0094] Figure 1B Element 206 in the equation represents the correlation established individually between the degree of freezing of the treated product and its phase angle exhibited in an electromagnetic field having the same strength and frequency as the electromagnetic field applied to the product in step 201, as determined according to equation (1). The correlation is typically established by subjecting a reference sample of the product to an electromagnetic field of the strength and frequency of the present invention at different actual degrees of freezing (preferably at least two different actual degrees of freezing, and more preferably two to ten different actual degrees of freezing), and by determining the phase angle exhibited by each sample of the product at each corresponding degree of freezing by measuring resistance and reactance signal values ​​and calculating the phase angle according to equation (1) or any other function of the reactance and resistance signals as previously described. This correlation will generally be different for each product or product type undergoing the present invention. The following is relative to... Figure 1C A method for determining the degree of freezing is described.

[0095] Figure 1B Element 207 in the text represents the following step: wherein, for the product being tested, the actual degree of freezing of the product that has undergone steps 201 and 202 is determined by finding, in the above association (in element 206), the actual degree of freezing corresponding to the phase angle determined by performing steps 201 and 202.

[0096] Figure 1B 208 optional elements (similar) Figure 1A Optional element 205) indicates the use of the determined degree of freezing for any of a number of functional purposes (such as the operation of a device for controlling the processing or handling of a product at a determined temperature). The description herein of the control of a food cooling device is an example of such use of the temperature determined according to the invention.

[0097] Now for reference Figure 1D The flowchart shows the steps of an apparatus that can be used to control the operation of a product whose temperature is determined.

[0098] Figure 1D Elements 201 and 202 in the text represent, as described above, relative to... Figure 1A The same method and steps as described above.

[0099] Figure 1D Element 209 (similar)Figure 1A Element 205) represents the use of the phase angle determined by steps 201 and 202 for any of a number of functional purposes (such as the operation of a device for controlling the processing or handling of a product whose phase angle is determined). The predetermined setpoint phase angle corresponds to a desired value for a selected physical characteristic of the product. The description herein of the control of a food cooling device is an example of such use of the temperature determined according to the invention.

[0100] Go to Figure 1C The solid line extending between points A and D represents an idealized relationship between the enthalpy of a pure liquid (such as water) and its temperature. In the region at point A, the pure liquid is completely liquid. As heat is removed from the liquid and its enthalpy decreases, the liquid cools and its temperature decreases, as shown in the segment from region A to point B. Point B represents the initial onset of freezing of the pure liquid.

[0101] As additional heat is removed from the liquid, its enthalpy continues to decrease. In an idealized setting, the temperature of the pure liquid will remain constant until point C is reached, which represents the point where the pure liquid is completely frozen. Ideally, the line connecting points B and C is perpendicular, and the point where this line intersects the temperature axis is considered the freezing point of the pure liquid. Then, as additional heat is removed from the now completely frozen product, the enthalpy of the product continues to decrease toward the region of point D.

[0102] When the product is a mixture containing liquids and solids, as well as other components some of which are soluble in the liquids or solids, removing heat and enthalpy from the product after the enthalpy has decreased to reach point B will cause the product temperature to rise along... Figure 1C The path shown by the dashed line gradually decreases. As more and more liquid in the product gradually freezes, the decreasing temperature corresponds to a decrease in the product's freezing point caused by other components present in the product. Therefore, for any enthalpy content H2 in the product, there exists a corresponding temperature T2. This also means that enthalpy can be used to replace actual temperature throughout the document.

[0103] The degree of freezing of any given product can be determined as follows: by establishing a reference curve for the product in question (i.e., Figure 1C The curve (displayed as a dashed line) is determined by performing a series of temperature T2 measurements corresponding to a series of different enthalpy values ​​for the product between H1 (the enthalpy value at point B where freezing first occurs) and H3 (the enthalpy value at which no more liquid in the product can be frozen). The degree of freezing of the product is then determined as the value of (H1-H2) / (H1-H3), expressed as a percentage.

[0104] These functions can be performed using the device in any of several different ways. That is, the device receiving input from the coil can measure and provide the user with values ​​of reactance and resistance signals, based on which the user determines the phase angle and, depending on the predetermined correlation between the phase angle and the actual temperature or degree of freezing, determines the actual temperature or degree of freezing independently (or manually) based on the phase angle. Alternatively, the device can receive input from the coil and directly determine and provide the user with the phase angle (i.e., based on the measured reactance and resistance signals), and the user can, depending on the aforementioned correlation, determine the actual temperature or degree of freezing independently (or manually) based on the phase angle. Alternatively, the device can receive input from the coil, directly determine the phase angle (i.e., based on the measured reactance and resistance signals), and, depending on the aforementioned correlation already included in the device, directly determine and provide the user with the actual temperature or degree of freezing. Another alternative is for the user to receive the values ​​of reactance and resistance signals from the device and then input those values ​​into the device that directly determines the phase angle, determining the actual temperature or degree of freezing based on the correlation already included in the device.

[0105] Any of these implementations can be combined with (even within the same device) controls for controlling conditions within the equipment used to process the product in question, such that conditions are adjusted and controlled based on reactance and resistance signals and temperature or degree of freezing values ​​determined by phase angle. The invention is described in further detail with reference to its application to an apparatus in which food products can be cooled and, if necessary, frozen. Experiments have determined that (a) there is a reliable and reproducible correlation between the actual temperature of the product (and its degree of freezing) and the phase angle it exhibits at different temperatures; and (b) the correlation exists regardless of whether the moisture in the product is completely unfrozen, partially frozen, or completely frozen, allowing for the determination of the degree of freezing of the moisture; and (c) the correlation is independent of the product's mass, size, and dimensions, thereby greatly enhancing the ability of the method of the invention to determine actual temperature while allowing for comparison of results across different product samples.

[0106] refer to Figure 2 The present invention is illustrated with a typical apparatus for cooling or freezing food or heating products (if modified as described herein) and implementing the present invention.

[0107] A device 10 for cooling, freezing, or heating products includes a housing 12 formed by a top wall 14a and a plurality of side walls 14, which define an internal chamber 16 therein. An inlet 18 is disposed through one of the side walls 14, while an outlet 20 is disposed in the other side wall, typically located at the end of the housing 12 opposite to the inlet 18. The inlet 18 and outlet 20 provide communication between the chamber 16 and an area outside the device 10. A transport component (such as a conveyor belt 22) moves through the chamber 16 and conveys food products 24 from the inlet 18 through the chamber 16 to the outlet 20. The conveyor belt 22 can be of any known type of construction, such as a stainless steel mesh belt. The belt 22 is propelled by any conventional equipment, such as in Figure 2 The drive motor is represented as 42 in the diagram.

[0108] To cool product 24 in device 10, a sufficiently cold atmosphere is established in chamber 16 to cool or (if necessary) freeze product 24. Some embodiments employ the injection of cold gas or refrigerant, which refers to a liquid or solid substance that is gaseous at 32°F and one atmosphere; examples include liquid nitrogen and solid carbon dioxide particles (“dry ice”). As is known in the art, liquid carbon dioxide passing from the outlet into the channel causes the liquid carbon dioxide to solidify, i.e., the aforementioned dry ice. This is considered in the practice of the invention as a liquid heat transfer medium passing from the outlet. Refrigerant may be introduced into chamber 16 via conduit 26. Conduit 26 may include valves 28 (such as regulating control valves) to control or limit the amount of refrigerant introduced into chamber 16 of device 10. Refrigerant conduit 26 is in fluid communication with a remote source of refrigerant (not shown), which may be, for example, nitrogen, liquid nitrogen (LIN), or liquid carbon dioxide. The end 30 of the conduit 26 in chamber 16 is branched or split into multiple sections 32 or portions to provide a spray bar including multiple nozzles 34, which serves as a distribution arm or manifold for refrigerant supplied from the conduit. The sections 32 may also be provided with at least one, and for most applications, multiple nozzles 34, which distribute or spray a spray 36 of refrigerant onto the food product 24 passing on the conveyor belt 22. The refrigerant spray 36 is typically in the form of LIN or solid carbon dioxide snow to absorb heat from the food product passing below the nozzles 34.

[0109] In an alternative embodiment, a cold atmosphere is established in chamber 16 by a refrigeration unit 48, which draws in the atmosphere (cold air) from chamber 16 into unit 48 and across pipes, fins, or other metal surfaces (which are cooled by a liquid coolant or refrigerant passing through them), and discharges the cooled atmosphere from an outlet in unit 48 back into chamber 16. Unit 48 may rely on the removal of refrigerant, in which case pipes 26 and sections 32 and nozzles 34 are not required, or unit 48 may be used in conjunction with a device for applying refrigerant.

[0110] The housing 12 is also provided with at least one, and for most applications, multiple motors 38, each of which is connected to and drives a corresponding fan 40. This fan circulates and moves the refrigerant product 36 or the cold atmosphere provided by the refrigeration unit 48 within the chamber 16, as appropriate, and maintains the atmosphere in the chamber 16 at a desired cooling temperature that will reduce the product temperature. It will be appreciated that, depending on the cooling technology used, the atmosphere can be isothermal or co-current (temperature profile in the same direction as the product's movement within the refrigeration atmosphere) or counter-current (temperature profile in the opposite or dissimilar direction), and can utilize impingement, convection, or contact cooling. The movement of the fan 40 provides distribution of cold atmosphere across the chamber 16, causing the food product 24 entering at the inlet 18 to begin undergoing heat transfer and thus cooling and / or freezing. The motors 38 can be mounted externally to the housing 12 such that heat from the motors has minimal impact on the atmosphere in the chamber 16. The conveyor belt 22 is configured as a straight belt with single or multiple passes.

[0111] The equipment includes one or more units 46 that enable the product 24 to be subjected to an electromagnetic field and, in response to the electromagnetic field, to measure the product's resistance and reactance signals. Units 46 may be located at one or more of the following locations, all of which are in... Figure 2 As shown in the diagram (although unit 46 does not necessarily need to be located in...) Figure 2 (i) at all locations shown); and / or (ii) at outlet 20; and / or (iii) at inlet 18. One or more units 46 may also be separate units placed before or after unit 10 in a conveyor, and for measuring and / or controlling communication with unit 10. In some cases, only unit 46 at inlet 18 may be used, especially if the shape, size, and dimensions of each product are constant and the only variation for the product is its inlet temperature. Unit 46 may include or be connected to any combination of devices having the capabilities described above.

[0112] In an alternative embodiment, device 10 may be having, in relation to, the present invention, Figure 2 The enclosed housing describes all the aforementioned features, but in which the belt follows a curved path within the device between the inlet and outlet, and in which the belt repeatedly passes over itself in a vertical stack of rows around a central axis, thus forming a spiral or helical shape. Examples of such devices, known as spiral refrigerators, are found in numerous patents, such as U.S. Patent Nos. 5,398,521, 6,912,869, and 4,953,365.

[0113] In other alternative embodiments, device 10 is an open or closed trough or U-shaped container or vessel or tubular jacketed device (such as a scraping surface heat exchanger), through which food product 24 is moved forward by the action of an auger or one or more rotating paddles mounted on a motor-driven shaft.

[0114] In addition to continuous cooling or heating processes and equipment, batch processes and systems (such as cabinet freezers or batch meat mixers) can also benefit from this invention. Product samples can be manually or automatically removed from the interior of the chamber or mixing vessel using a sampling system, measured using the methods of the invention described above, and the necessary residence time and operating conditions can be manually or automatically set to achieve the desired actual temperature or degree of freezing of the product.

[0115] In some commercially used equipment where product temperature is altered or controlled, the product can be a single piece passing through, arranged in columns aligned along the direction of product movement, with gaps between the pieces in the columns. In many cases, the pieces are also arranged in rows perpendicular to the direction of product movement, such that multiple pieces in a given row pass through simultaneously, sometimes touching each other or having small gaps between them at other times. For example, when beef patties are formed and frozen in a food processing facility, it is typical to provide a row of four to six patties arranged along the width of a conveyor belt passing through the freezer. There are usually gaps of a few inches or less between the patties in the same row.

[0116] When operating the invention with respect to multiple product parts, it is desirable to obtain reliable readings for each product part without erroneous readings, such as those that may be caused by interference between the response of a given part to an electromagnetic field and the responses of any other part also being analyzed in the field. It is believed that the risk of such erroneous readings due to interference between the responses of multiple product parts can be reduced or avoided by providing sufficient spacing between the product parts as the multiple product parts pass through a given electromagnetic field. The spacing to be provided will include the distance between the parts in the direction in which the parts move through the field, and may also include the distance between the parts in the direction perpendicular to the direction in which the parts move through the field. For any given device and product set, the distance between the parts sufficient to avoid interference can be readily determined experimentally, for example, by subjecting a single part to the field and determining the phase angle (or determining a characteristic such as actual temperature based on the phase angle), and then repeating this step with respect to that part and one or more additional parts present at a measured distance from the first part; and then determining the distance from the first part where the reading (such as phase angle or temperature) obtained using the single part is seen to change; and then operating the invention with respect to multiple parts spaced apart by a distance greater than the distance at which the reading of the first part is seen to change.

[0117] A measure of the appropriate distance (where multiple product pieces pass through the electromagnetic field as a column aligned in the direction of movement through the field) is to maintain a sufficient distance along the direction of movement such that at most one product in the column is subjected to the electromagnetic field at any given time; that is, a product piece enters the field only after the piece immediately in front of it has left the field. In applications, gaps between product pieces in a column can be addressed by adjusting the conveyor belt speed to be faster than the upstream operation, thereby creating gaps between the product pieces.

[0118] Device 10 and similar equipment can be used to heat product 24 instead of cooling it, in which case, instead of refrigerant or cooling air, hot air or a hot gaseous composition such as steam is fed into housing 16 from unit 48 or nozzle 34. Heating can be performed to simply raise the temperature of the product, or to cook the product, or to thaw it from a fully or partially frozen state.

[0119] Now for reference Figure 3 The controller 52 processes real-time inputs from one or more units 46, corresponding to reactance and resistance signals detected by each unit 46, and determines a phase angle based on the reactance and resistance signal inputs. The controller 52 determines the actual temperature corresponding to the phase angle based on its correlation with the actual temperature previously provided to the controller. The controller 52 then compares the thus determined actual temperature with a predetermined setpoint actual temperature and determines the difference (if any) between the determined actual temperature and the setpoint actual temperature, and the direction of the difference (i.e., the difference indicates whether the determined actual temperature is higher or lower than the setpoint actual temperature). It is advantageous to perform these measurements and comparisons intermittently, such as every 0.1 to 20 seconds, rather than continuously. An equivalent method is suitable for measuring and controlling the degree of freezing of a product compared to the actual temperature.

[0120] Controller 52 is connected to one or more of the operating components of device 10 that affect the device's ability to remove heat from the product (or heat the product, as appropriate) to provide control over the operation of such components. Such components include, but are not limited to:

[0121] The speed of the motor 42, through which the belt moves through the housing 16, can increase or decrease the length of time the product is exposed to cooling or heating conditions in the chamber 16.

[0122] Adjust the rate at which the temperature and / or cooling or heating atmosphere circulates through unit 48, thereby enabling control over the temperature of the cooling or heating atmosphere to which the product is exposed.

[0123] The rate at which a gaseous heat transfer medium (e.g., a refrigerant or cold air for cooling the product, or hot air or steam for heating the product) is fed into chamber 16 or product 24 (e.g., by adjusting valve 28) makes it possible to control how much of such heat transfer medium is available to be applied to product 24.

[0124] The temperature of the heat transfer medium fed into the chamber 16 is such that the rate at which the heat transfer medium cools or heats the product 24 can be controlled.

[0125] The speed of the motor 38 of the rotating fan 40 enables control over the rate at which the heat transfer atmosphere circulates within the chamber 16 and propels toward the product 24.

[0126] When desired by the operator, controller 52 can be connected to any one or more of the aforementioned operating components of device 10 to control the operation of the device when adjusting the temperature within the device.

[0127] The interconnection between unit 46 and one or more operating components allows device 10 to operate to automatically control and optimize food cooling, freezing, or heating, and also provides feedback to the operator to allow for more precise monitoring and control of other processes located upstream and downstream of device 10.

[0128] Each unit 46 measures the product phase angle exhibited by each product in the electromagnetic field passing through unit 46. For the detected phase angle exhibited by the product, the actual temperature of the product is determined according to a predetermined phase angle-actual temperature correlation and compared with the desired temperature. If the actual temperature of the product is higher than the desired setpoint, this means that the product will require further cooling before reaching an acceptable limit, and a rejection / rework condition may be triggered. Furthermore, the controller 52 will use the difference between the actual temperature and the desired temperature to determine whether any changes to the unit operating parameters are needed to ensure that the product leaves at the desired equilibrium temperature. Unit operating parameters include setpoint temperature, conveyor belt speed, fan speed, number of operating fans (if more than one), refrigerant control valve opening percentage, and other parameters. In this example, the product is under-frozen. This will trigger the refrigeration unit to reduce its gas temperature setpoint. Another possibility is to reduce the belt speed (to increase residence time) or increase the fan speed. Of course, any combination of these operating parameters can be adjusted together. On the other hand, if the detected actual temperature of the product is lower than the desired setpoint temperature, this indicates that the product is over-frozen. The refrigeration unit will similarly alter its operating parameters to reduce its cooling capacity, thereby ensuring that the product leaves the refrigeration unit at the desired actual temperature. This approach results in reduced refrigeration unit operating costs.

[0129] The phase angle values ​​exhibited by food products passing through unit 46 are collected and stored every 0.1 to 20 seconds (preferably within the range of 0.5 to 3 seconds). Phase angles can also be collected each time a new product passes through the electromagnetic field. The number of phase angle values ​​collected for statistical analysis can be 20-2000 (preferably within the range of 50-500). If the value is reached before time has elapsed, the oldest phase angle is eliminated once a new phase angle is collected. The sample set is statistically analyzed every 1 to 300 seconds (preferably within the range of 10-100 seconds) and compared with a predefined target phase angle. If the difference is greater than a predetermined difference, one or more of the operating parameters are adjusted. While the invention can be practiced by continuously measuring reactance and resistance signals and continuously determining and processing phase angles, discontinuous measurement, determination, and processing are preferred. When adjusting the operating conditions of the freezer, there is always a lag time for the modified operating conditions to reach a steady-state value. If subsequent changes to the operating conditions are made before the previous changes have a chance to reach a steady state, the freezer operation may become unstable. For this reason, it is preferable to continuously change the operation of the refrigeration unit. Preferably, the change in the operation of the refrigeration unit is made no more than once every 1 second, more preferably no more than once every 100 seconds, and most preferably no more than once every 300 seconds.

[0130] Compared to other techniques for determining actual temperature, the main benefit of this invention and its dependence on phase angle is that the parameters detected, determined, and utilized in this invention are independent of the quality, size, and dimensions of the product whose phase angle is determined, regardless of whether the product is frozen. Below is an example of measuring the actual temperature of a beef patty using the method outlined in this invention. For comparison, the actual temperature of the product is also measured following the description outlined in U.S. Patent No. 5,189,366.

[0131] Example

[0132] 6-ounce beef patties (80% lean / 20% fat) with a thickness of 0.5 inches were used in this study. The patties were stored overnight in a temperature-controlled chamber. The temperature for the first experiment was set at 0℉ (almost completely frozen) and the temperature for the second experiment was set at 35℉ (above freezing). The temperature of the patties was measured in two ways: using a thermometer inserted into each patty and using the hydrocalorimetry method described above, to account for any potential internal temperature gradients. The patties were then passed through a commercially available metal detector (Thermo Fisher APEX 500 High Performance) utilizing a field frequency of 300 kHz. The patties were arranged in different configurations to vary the size, dimensions, and shape of the product. Reactance (X) and resistance (R) signals were measured from the metal detector. The determination was performed following the instructions in U.S. Patent No. 5189366. The ratio (where α varies between 0.5 and 1). Similarly, following the invention, according to... The phase angle was calculated. The results and comparisons are shown in Table 1 below. At a temperature of 35℉ (unfrozen), both U.S. Patent No. 5,189,366 and the method of this invention provide a measure of temperature that is relatively independent of mass, shape, and size. However, at 0℉ (almost completely frozen), The height depends on the mass, size, and dimensions. On the other hand, at 0℉, the phase angle is independent of the mass, size, and dimensions.

[0133] In commercial meat patty freezing operations, 0℉ is the temperature at which most meat patties are frozen for long-term storage. Therefore, 0℉ is a commercially relevant temperature. In most commercial continuous freezing applications, there are multiple meat patty forming lines that form a feeder to a freezer. Therefore, multiple meat patties are arranged in a line along the width of the conveyor at the freezer's inlet and outlet. If a coil used to establish an electromagnetic field is located at the freezer's outlet to detect the actual temperature of the frozen meat patties, multiple meat patties will enter the field at a given time. If one or more of the meat patty forming lines malfunction due to damage or another reason (which is known to occur in commercial facilities), the number of meat patties entering the freezer and the field will change. If the operator is using the method of U.S. Patent No. 5,189,366, this change in the number of meat patties on the conveyor can be interpreted as a significant change in the product temperature, due to… The ratio depends on the quality, size, and dimensions of the product. However, the phase angle method of this invention will not produce the same error.

[0134] Table 1

[0135]

[0136] The method of the present invention can be used to ensure that a product leaves the device 10 at a desired value or at an actual temperature within the desired actual temperature range. In such applications, the actual temperature of the product leaving the device 10 can be determined by any conventional technique (in... Figure 2 The measurement is performed using a thermocouple, thermometer, or other temperature measuring device (represented by 50). For example, if the product is at an actual temperature that is too high or too low when it leaves, the operator can simply adjust the operating conditions in device 10 such that the actual temperature within the device, determined based on its relationship with the phase angle of the product using any of the methods described herein, decreases or increases, respectively.

[0137] The method of the present invention can also be implemented using the correlation between actual temperature and phase angle, as described herein, but does not specifically include the step of determining the actual temperature. That is, the apparatus for practicing the present invention (such as relative to...) Figure 2The setpoint for the operation of the described device can be established based on the above-mentioned correlation between the actual temperature and the phase angle, but the setpoint is the actual phase angle value; and then the operating status of the device is adjusted in response to detecting the difference between the phase angle setpoint and the measured phase angle.

[0138] Furthermore, just as the actual temperature or degree of freezing of the product upon leaving device 10 is a useful guide for determining whether the conditions within device 10 need to be adjusted, alternatively, other physical characteristics of the product upon leaving device 10 may be relied upon. Examples of such other physical characteristics include the product's visual appearance, surface texture, or internal stickiness or viscosity, which may affect the product's handleability in subsequent processing steps. In such cases, the phase angle setpoint on which the operation of the present invention is based is the phase angle exhibited by the product exhibiting the desired characteristics upon leaving the device (as defined and determined herein). The operator may modify the operating conditions of device 10 to achieve the desired state or condition of the product leaving device 10, establish the corresponding phase angle exhibited by the product, and simply use this phase angle as the setpoint of device 10, including an acceptable range of variability in the phase angle.

Claims

1. A method for analyzing a product to determine its temperature, comprising: (a) Providing a correlation between the actual temperature of the product having the composition of the product being analyzed and the phase angle exhibited by the product having the composition of the product being analyzed at two or more different actual temperatures, wherein the phase angle exhibited by a given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product, wherein the reactance signal and the resistance signal of the given product are decomposed from the secondary electromagnetic field generated by eddy currents induced in the given product; (b) Apply an electromagnetic field of a given intensity and frequency to the product being analyzed, measure the reactance signal and the resistance signal exhibited by the product being analyzed in the electromagnetic field of the given intensity and frequency, and determine the phase angle exhibited by the product being analyzed based on the measured reactance signal and resistance signal of the product being analyzed; as well as (c) Based on the correlation, determine the actual temperature of the product being analyzed based on the phase angle determined in step (b).

2. A method for analyzing a product to determine the degree of freezing of the product, comprising: (a) Providing a correlation between the degree of freezing of the product having the composition of the product being analyzed and the phase angle exhibited by the product having the composition of the product being analyzed at two or more different degrees of freezing, wherein the phase angle exhibited by a given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product, wherein the reactance signal and the resistance signal of the given product are decomposed from the secondary electromagnetic field generated by eddy currents induced in the given product; (b) Apply an electromagnetic field of a given intensity and frequency to the product being analyzed, measure the reactance signal and the resistance signal exhibited by the product being analyzed in the electromagnetic field of the given intensity and frequency, and determine the phase angle exhibited by the product being analyzed based on the measured reactance signal and resistance signal of the product being analyzed; as well as (c) Based on the correlation, determine the degree of freezing of the product being analyzed based on the phase angle determined in step (b).

3. A method of operating equipment, said equipment providing a product at a temperature within a desired range when the product leaves said equipment, said method comprising: (a) To conduct the product into and through the equipment, the equipment being capable of subjecting the product within the equipment to at least one adjustable operating condition that can modify the temperature of the product within the equipment. (b) Applying an electromagnetic field of a given intensity and frequency to the product at one or more of the following locations: (i) a location within the equipment, or (ii) a location where the product leaves the equipment, or (iii) a location where the product enters the equipment, measuring the reactance and resistance signals exhibited by the product in the applied electromagnetic field, and determining the phase angle exhibited by the product, wherein the phase angle exhibited by the given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product, wherein the reactance signal and the resistance signal of the given product are decomposed from the secondary electromagnetic field generated by eddy currents induced in the given product; (c) Determining the actual temperature of the product based on the measured phase angle, according to a predetermined correlation between two or more different actual temperatures of the product and the phase angle exhibited by the product having the composition of the analyzed product as measured in the applied electromagnetic field of the given intensity and frequency; and (d) When the difference between the actual temperature of the product determined in step (c) and the predetermined set point temperature of the product is greater than a predetermined difference, the difference is reduced by adjusting at least one adjustable operating condition in the equipment to modify the temperature of the product in the equipment, so that the temperature of the product when it leaves the equipment is within the desired range.

4. A method of operating equipment, said equipment providing a product at a temperature within a desired range when the product leaves said equipment, said method comprising: (a) To conduct the product into and through the equipment, the equipment being capable of subjecting the product within the equipment to at least one adjustable operating condition that can modify the temperature of the product within the equipment. (b) Applying an electromagnetic field of a given intensity and frequency to the product at one or more of the following locations: (i) a location within the equipment, or (ii) a location where the product leaves the equipment, or (iii) a location where the product enters the equipment, measuring the reactance and resistance signals exhibited by the product in the applied electromagnetic field, and determining the phase angle exhibited by the product, wherein the phase angle exhibited by the given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product, wherein the reactance signal and the resistance signal of the given product are decomposed from the secondary electromagnetic field generated by eddy currents induced in the given product; (c) Determine the difference between the phase angle exhibited by the product as measured in step (b) and the predetermined phase angle setpoint; and (d) When the difference measured in step (c) is greater than a predetermined difference, the difference is reduced by adjusting at least one adjustable operating condition within the equipment to modify the temperature of the product in the equipment, so that the temperature of the product when it leaves the equipment is within the desired range.

5. The method of claim 4, wherein the predetermined phase angle setpoint is determined based on the expected actual temperature of the product and a predetermined correlation between two or more different actual temperatures of a product having the same composition as the product passing through the equipment and the phase angle of the product measured at the electromagnetic field of the given intensity and frequency.

6. The method of claim 4, wherein the predetermined phase angle setpoint is determined based on the desired degree of cooling of the product and a predetermined correlation between two or more different degrees of cooling of the product having the same composition as the product passing through the equipment and the phase angle of the product measured at the electromagnetic field of the given intensity and frequency.

7. The method of claim 4, wherein the predetermined phase angle setpoint is a phase angle exhibited by a reference product having the same composition as the product passing through the equipment, measured at the electromagnetic field of the given intensity and frequency, the product exhibiting desired specific physical characteristics as it leaves the equipment.

8. A method of operating equipment, said equipment providing said product at a desired degree of freezing when the product leaves said equipment, said method comprising: (a) To transfer the product into and through the equipment, the equipment being capable of subjecting the product within the equipment to at least one adjustable operating condition that can modify the degree of freezing of the product within the equipment. (b) Applying an electromagnetic field of a given intensity and frequency to the product at one or more of the following locations: (i) a location within the equipment, or (ii) a location where the product leaves the equipment, or (iii) a location where the product enters the equipment, measuring the reactance and resistance signals exhibited by the product in the applied electromagnetic field, and determining the phase angle exhibited by the product, wherein the phase angle exhibited by the given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product, wherein the reactance signal and the resistance signal of the given product are decomposed from the secondary electromagnetic field generated by eddy currents induced in the given product; (c) Determining the degree of freezing of the product based on the measured phase angle, according to a predetermined correlation between two or more different actual degrees of freezing in the actual temperature of the product and the phase angle exhibited by the product having the composition of the analyzed product as measured in the applied electromagnetic field of the given intensity and frequency; and (d) When the difference between the degree of freezing of the product determined in step (c) and the degree of freezing of the product at a predetermined set point is greater than a predetermined difference, the difference is reduced by adjusting at least one adjustable operating condition in the equipment to modify the degree of freezing of the product in the equipment, so that the degree of freezing of the product when it leaves the equipment is within the desired range.

9. The method according to claim 3, 4 or 8, wherein the at least one adjustable operating condition is any one of: the temperature of the gaseous atmosphere within the equipment, the rate at which the gaseous atmosphere circulates within the equipment; the rate at which the gaseous heat transfer medium is fed into the equipment; and the rate at which the product passes through the equipment.

10. An apparatus capable of modifying the temperature of a product within the apparatus, the apparatus comprising: A housing having a channel extending through the housing from an inlet to an outlet, a first means for moving a product through the channel from the inlet to the outlet, and one or more outlets within the housing from which a liquid or gaseous heat transfer medium can be transferred to the channel to establish an environment in which the product within the housing is exposed, wherein at least one condition in which the product within the housing is exposed is adjustable to modify the temperature of the product within the channel. A second device, located at one or more of the following positions: (i) within the housing, (ii) at an exit from the housing, or (iii) at an entrance to the housing, the second device being capable of applying an electromagnetic field to the product. A third device, operably connected to the second device and capable of measuring the reactance signal and the resistance signal exhibited by the product in the electromagnetic field, and calculating the phase angle exhibited by the product accordingly, wherein the phase angle exhibited by the given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product, wherein the reactance signal and the resistance signal of the given product are decomposed from the secondary electromagnetic field generated by eddy currents induced in the given product; A fourth device, operatively connected to the third device and capable of performing one or both of the following: (i) determining the difference between a predetermined setpoint phase angle exhibited by the product and the phase angle exhibited by the product passing through its channel; and (ii) determining the difference between a predetermined degree of freezing of the product and the degree of freezing of the product corresponding to a calculated phase angle of the product, based on a predetermined correlation between the degree of freezing of a reference product having the same composition as the product passing through the channel and its phase angle. and A fifth device, operatively connected to the fourth device and capable of adjusting at least one operating condition of the product within the housing to reduce the difference in response to the difference.

11. An apparatus capable of modifying the degree of freezing of a product within the apparatus, the apparatus comprising: A housing having a channel extending through the housing from an inlet to an outlet, a first means for moving a product through the channel from the inlet to the outlet, and one or more outlets within the housing from which a liquid or gaseous heat transfer medium can be transferred to the channel to establish an environment in which the product within the housing is exposed, wherein at least one condition in which the product within the housing is exposed is adjustable to modify the degree of freezing of the product within the channel. A second device, located within the housing and / or at an outlet exiting the housing and / or at an inlet entering the housing, is capable of applying an electromagnetic field to the product. A third device is capable of measuring the reactance signal and the resistance signal exhibited by the product in the electromagnetic field, and calculating the phase angle exhibited by the product based thereon, wherein the phase angle exhibited by the given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product, wherein the reactance signal and the resistance signal of the given product are decomposed from the secondary electromagnetic field generated by eddy currents induced in the given product; A fourth device is capable of determining the difference between a predetermined degree of freezing of the product and the degree of freezing of the product corresponding to a calculated phase angle of the product, based on a predetermined correlation between the degree of freezing of a reference product having the same composition as the product passing through the channel and its phase angle. and A fifth device is capable of adjusting at least one operating condition of the product within the housing to reduce the difference in response to the difference.

12. The apparatus according to claim 10 or 11, wherein the apparatus is capable of cooling the product within the apparatus, wherein a liquid or gaseous coolant is capable of being transferred from the one or more outlets into the channel, and the fifth device is capable of adjusting at least one operating condition within the housing to cool the product within the housing.

13. A method of operating equipment, said equipment providing a product that exhibits selected physical characteristics within a desired range when leaving said equipment, said method comprising: (a) To conduct the product into and through the equipment, the equipment being capable of subjecting the product within the equipment to at least one adjustable operating condition that can modify selected physical properties of the product within the equipment. (b) Applying an electromagnetic field of a given intensity and frequency to the product at one or more of the following locations: (i) a location within the equipment, or (ii) a location where the product leaves the equipment, or (iii) a location where the product enters the equipment, measuring the reactance and resistance signals exhibited by the product in the applied electromagnetic field, and determining the phase angle exhibited by the product, wherein the phase angle exhibited by the given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product, wherein the reactance signal and the resistance signal of the given product are decomposed from the secondary electromagnetic field generated by eddy currents induced in the given product; (c) Determine the difference between the phase angle exhibited by the product as measured in step (b) and a predetermined phase angle setpoint corresponding to the desired value of the selected physical characteristic; and (d) When the difference measured in step (c) is greater than a predetermined difference, the difference is reduced by adjusting at least one adjustable operating condition within the equipment to modify a selected physical characteristic of the product in the equipment, such that the selected physical characteristic of the product when it leaves the equipment is within the desired range.

14. The method according to claim 3, 4, 8 or 13, wherein the at least one adjustable environmental condition is any one of: the temperature of the gaseous atmosphere within the equipment, the rate at which the gaseous atmosphere circulates within the equipment, and the rate at which the product passes through the equipment.

15. The method of claim 1, 2, 3, 4, 8 or 13, wherein the plurality of products are analyzed by passing the plurality of products through the electromagnetic field, wherein the plurality of products are arranged in columns along the direction in which the plurality of products pass through the electromagnetic field and are spaced apart from each other in the columns, such that products do not enter the electromagnetic field until a product immediately in front of the product in the column has left the electromagnetic field.

16. An apparatus capable of modifying selected physical properties of a product within the apparatus, the apparatus comprising: A housing having a channel extending through the housing from an inlet to an outlet, a first means for moving a product through the channel from the inlet to the outlet, and one or more outlets within the housing from which a liquid or gaseous heat transfer medium can be transferred to the channel to establish an environment in which the product within the housing is exposed, wherein at least one condition in which the product within the housing is exposed is adjustable to modify selected physical properties of the product within the channel. A second device, located at one or more of the following positions: (i) within the housing, (ii) at an exit from the housing, or (iii) at an entrance to the housing, the second device being capable of applying an electromagnetic field to the product. A third device, operably connected to the second device and capable of measuring the reactance signal and the resistance signal exhibited by the product in the electromagnetic field, and calculating the phase angle exhibited by the product accordingly, wherein the phase angle exhibited by the given product is a function of the reactance signal and the resistance signal of the given product measured in an electromagnetic field of a given intensity and frequency applied to the given product, wherein the reactance signal and the resistance signal of the given product are decomposed from the secondary electromagnetic field generated by eddy currents induced in the given product; A fourth device, operatively connected to the third device and capable of determining the difference between a predetermined setpoint phase angle corresponding to a desired value of the selected physical characteristic and the phase angle exhibited by the product passing through its channel, and A fifth device, operatively connected to the fourth device and capable of adjusting at least one operating condition of the product within the housing to reduce the difference in response to the difference.

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