WO1993004421A1 - Temperature control in an ohmic process - Google Patents

Temperature control in an ohmic process Download PDF

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Publication number
WO1993004421A1
WO1993004421A1 PCT/GB1992/001446 GB9201446W WO9304421A1 WO 1993004421 A1 WO1993004421 A1 WO 1993004421A1 GB 9201446 W GB9201446 W GB 9201446W WO 9304421 A1 WO9304421 A1 WO 9304421A1
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WIPO (PCT)
Prior art keywords
outlet
temperature
electrodes
elements
inlet
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Application number
PCT/GB1992/001446
Other languages
French (fr)
Inventor
Jonathan Yniol Hauser
Original Assignee
Sous Chef Limited
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Filing date
Publication date
Application filed by Sous Chef Limited filed Critical Sous Chef Limited
Publication of WO1993004421A1 publication Critical patent/WO1993004421A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
    • A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
    • A23L3/005—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by heating using irradiation or electric treatment
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D23/00—Control of temperature
    • G05D23/19—Control of temperature characterised by the use of electric means
    • G05D23/1917—Control of temperature characterised by the use of electric means using digital means

Definitions

  • This invention relates to controlling temperature in an ohmic heating process and has particular but not exclusive application to preparation of foodstuffs.
  • An ohmic heating process for foodstuffs preparation is knovm from UK Patent Specification Nos. 2067390 and 2068199, and as shown in Figure 1, an electrically conductive fluid such as foodstuffs, which may contain particulate solids, is pumped on a continuous basis through a duct 1 that contains first and second electrodes 2,3 connected to an AC power source (not shown).
  • the duct has an inlet 4 and an outlet 5.
  • the temperature to which the fluid is heated can be controlled.
  • the relationship between the temperature of the inlet and outlet 4,5 and the applied Power P is given as follows:
  • Tout Process outlet temperature (°C)
  • Tin Process inlet temperature (°C)
  • outlet temperature Tout it is desirable to control the outlet temperature Tout.
  • a continuous flow of product enters the inlet 4 and is preheated by the electrodes 2, 3 to an outlet temperature Tout selected to achieve sterilization. If the outlet temperature falls below a minimum level, sterile conditions downstream of the ohmic heater are lost and the process must be shut down to enable sterile conditions to be re-established. This is costly in terms of production down time and product loss. Temperatures above a particular outlet temperature are also undesirable since this leads to deterioration of product quality.
  • the outlet temperature Tout falls in response to the power reduction and thereafter returns to the its previous constant level when product between the electrodes 2, 3 is flushed through the outlet 5.
  • the present invention provides a method of controlling temperature in an ohmic heating process wherein an electrically conductive fluid is pumped from an inlet to an outlet past spaced apart electrodes that receive electrical power thereby heating the fluid during is passage from the inlet to the outlet, wherein the outlet temperature is controlled to tend to lie within predetermined range, by repeatedly considering the fluid between the electrodes to comprise a series of elements moving from the inlet to the outlet and predicting the outlet temperature that will occur for each of the elements upon reaching the outlet, and adjusting the power level applied to the electrodes if any of the predicted outlet temperatures for the elements falls outside of said predetermined range.
  • the invention also includes ohmic heating apparatus configured to perform the aforesaid method.
  • the outlet temperature is controlled in such a way that it tends to minimise the likelihood of fluid between the electrodes from failing to achieve a desired outlet temperature.
  • Figure 1 is a schematic view of a known ohmic heating apparatus
  • Figure 2 is a graph illustrative of power applied to the electrodes of Figure 1, and the resulting outlet temperature, produced in response to a step change in inlet temperature, as a function of time;
  • Figure 3 is a schematic diagram of an apparatus configured to perform a method in accordance with the invention, and;
  • Figure 4 is a schematic sectional view of fluid in the duct 1, when considered to be formed of a plurality of equal volume elements.
  • the ohmic heating apparatus is similar to that described with reference to Figure 1 and the same reference numbers have been used to identify like component parts.
  • the duct 1 includes electrodes 2, 3 and fluid to be heated e.g. foodstuffs pumped at a flow rate Q from an inlet 4 to an outlet 5.
  • the inlet temperature Tin is sensed by a sensor 8 connected to a processor unit 9.
  • the temperature upstream of the inlet is sensed by a sensor 11 also connected to the processor unit 9.
  • a flow rate detector 12, shown schematically, provides data indicative of the product flow rate Q to the processor unit 9.
  • the processor unit may comprise a personal computer PC or a programmable process control unit specifically configured to carry out the inventive method.
  • the unit 9 controls operation of a power supply controller 10 which controls the level of AC Power P applied to the electrodes 2, 3.
  • each of the elements El - En is for a particular time t attributed a different temperature Tl - Tn dependent upon the power P to which it has been subjected so far during its time of residency between the electrodes 2,3. A prediction is then made for each element of the temperature it will achieve at the outlet 5 on the basis of a projection of future inlet conditions and power requirements.
  • the power level P is then adjusted, if necessary, so that a satisfactory oulet temperature will be achieved for each of the elements El - En.
  • consideration is given to the temperature of fluid between the electrodes 2,3 when a rapid change of inlet temperature occurs.
  • Step 1 Establish initial state of the system
  • the ohmic heating apparatus shown in Figure 3 is brought into a nominally steady state condition in which it may be assumed that the relationship between applied power P, Tout and Tin is in acccordance with equation (2) given hereinbefore.
  • the microprocessor 9 can compute a value of Tout.
  • Tout Referring to Figure 4, on the basis of Tin and Tout, it is possible to attribute a temperature to each of the elements El - En. It will be appreciated that element El has been heated for only a short period whereas element En has been heated for the longest period and hence will achieve the highest temperature.
  • the intermediate elements will achieve a temperature which is a function of their residence time between the electrodes 2,3.
  • the microprocessor 9 can attribute a temperature Tl - Tn to each of the elements El - En.
  • the level of sophistication of the algorithm will depend upon the degree of accuracy required and should take into account factors such as electrical resistance of the fluid (which is a function of temperature) and its specific heat, the flow rate Q and the applied power P.
  • Step 2 Collect input data for current time increments .
  • the micro ⁇ processor 9 notes the current measured values of Tin, Q and P.
  • the values for inlet C and Tout are
  • the sensor 11 senses the temperature of the fluid in the conduit upstream of the heating apparatus.
  • the resulting sequence of temperature values from sensor 11 serve as a look-up table for the microprocessor 9 to predict Tin values for n At in step 4 hereinafter.
  • Step 3 Calculate state of system at end of £_. t.
  • the microprocessor 9 uses the data obtained in step 2 in order to compute the value of Tl - Tn attributable to each of the elements El - En at the end of time increment ⁇ t.
  • Step 4 Collect input data for projected residence
  • the microprocessor 9 considers the number of time increments that it will take for the fluid in each element El - En to exit from the column i.e. pass to the outlet 5 ( Figure 3). Thus, referring to Figure 4, the fluid in element El will take n A t time increments to reach the outlet 5. The projected inlet conditions are determined for this period from the look up table generated in Step 2 and are used in a subsequent forward prediction of Tout in Step 5
  • Step r 5 Predict forward Toutn.
  • the microprocessor computes the likely temperature Tout that will be achieved by the fluid
  • Step 4 Computation is performed on the basis of the projected inlet conditions determined by Step 4.
  • the power input during this period may be set in a number of ways.
  • the current power input could be held constant or alternatively the power may respond to the projected inlet conditions as specified in equation (2) .
  • This step is effectively the repeated calculation of the real time status of the heating process as described in Step 1 hereinbefore projected into the future for n At.
  • the output from this calculation is an array of values Tout, - Tout which corresponds to the predicted outlet
  • Step 6 Find maximum (Tout (max)) and minimum
  • each of the elements El - En are scanned by the microprocessor 9 to determine the maximum and minimum values thereof Tout (max) and Tout (min) .
  • Step 7 Adjust Power Level P.
  • Tout (max) and Tout (min) are compared with a predetermined range of desired output temperatures. If Tout (max) and Tout (min) lie outside of the predetermined range, the power level is adjusted with a view to making sure that the outlet temperature for the fluid in all of the elements does not fall outside of the predetermined range.
  • the temperature at outlet 5 will have a desired set point with associated upper and lower acceptable limits.
  • the power level P can be adjusted in a number of different ways and three examples will be given below. In the examples, the following temperature definitions will be utilized:
  • Q is the current inlet conditions and is the assigned heat capacity for the element for which the adjustment is being made.
  • the function F(e) is a factor selected to take into account the position of the element E associated with either Tout (min) or Tout (max) .
  • F(e) can be expressed as follows:
  • Step 8 Transmit power of set point to power control (10).
  • the microprocessor 9, in this step, adjusts the power set point by the amount ⁇ P computed in step 7.
  • Step 9 Go back to Step 2.
  • the process is repeated for the next time interval A t.
  • the fluid in each element has moved on by one position in the column thereof shown in Figure 4 and the process is then repeated.
  • the temperature at the outlet 5 is controlled in such a way that in response to an inlet temperature change, the outlet temperature is maintained within upper and lower limits Tout (LL) and Tout (UL) .
  • the present invention has been described with reference to a simple ohmic heater employing only two electrodes.
  • the present invention is equally applicable to heaters employing multiple electrodes.
  • the apparatus for performing the present invention has been described in an embodiment using a single processor unit, the apparatus may also be embodied using a multiprocessor unit carrying out parallel processing.

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  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Nutrition Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Food Science & Technology (AREA)
  • Polymers & Plastics (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Control Of Resistance Heating (AREA)

Abstract

An ohmic heating process in which liquid foodstuffs material is pumped from an inlet (4) to an outlet (5) past electrodes (2, 3) that receive ac power to heat the liquid, and the outlet temperature is controlled within a predetermined range using a microprocessor (9) that operates a power supply controller (10). The processor (9) considers the liquid between the electrodes (2, 3) to comprise a series of elements moving from the inlet to the outlet and predicts the outlet temperature that will occur for each of the elements upon reaching the outlet. The power level applied to the electrodes (2, 3) is adjusted if any of the predicted outlet temperatures for the elements falls outside of a predetermined range.

Description

TEMPERATURE CONTROL IN AN OHMIC PROCESS
DESCRIPTION
FIELD OF THE INVENTION
This invention relates to controlling temperature in an ohmic heating process and has particular but not exclusive application to preparation of foodstuffs.
EACKGROUND OF THE INVENTION
An ohmic heating process for foodstuffs preparation is knovm from UK Patent Specification Nos. 2067390 and 2068199, and as shown in Figure 1, an electrically conductive fluid such as foodstuffs, which may contain particulate solids, is pumped on a continuous basis through a duct 1 that contains first and second electrodes 2,3 connected to an AC power source (not shown). The duct has an inlet 4 and an outlet 5. The heat input to the fluid between the electrodes is proportional to the electrical power consumed, which is given as follows: Power P = V^. 1^; (1)
Where V = RMS AC Voltage
IRMS = RMS AC current
By controlling the Power P, the temperature to which the fluid is heated can be controlled. The relationship between the temperature of the inlet and outlet 4,5 and the applied Power P is given as follows:
P Q.Cρ.(Tout-Tin) (2) where P = Power (kW)
Q = Flow rate between electrodes (kg/sec)
C = Product heat capacity (KJ/Kg.K)
Tout = Process outlet temperature (°C) Tin = Process inlet temperature (°C)
Often, it is desirable to control the outlet temperature Tout. For example, in the preparation of food products, a continuous flow of product enters the inlet 4 and is preheated by the electrodes 2, 3 to an outlet temperature Tout selected to achieve sterilization. If the outlet temperature falls below a minimum level, sterile conditions downstream of the ohmic heater are lost and the process must be shut down to enable sterile conditions to be re-established. This is costly in terms of production down time and product loss. Temperatures above a particular outlet temperature are also undesirable since this leads to deterioration of product quality.
It will be seen from equation (2) that the Power P can be continuously calculated by a computer from the input parameters. C and Tout have in the past been set
manually or by a suitable programmed computer whereas Q and Tin are measured in real time. The resulting power level or set point thus calculated is transmitted to an electrical control system which controls the power level applied to the electrodes 2, 3.
However, a disadvantage of the known power control system is that it is unable to provide constant outlet temperature conditions when there is a significant fluctuation in the inlet temperature. The control function given in equation (2) takes no account of the product which is in the heater at any given time. Thus, a rapid increase in inlet temperature Tin will cause an immediate power reduction according to equation (2) . Product in the heater between the electrodes 2, 3 will consequently be subjected to less power than that required to cause it to reach a desired outlet temperature. Consequently, the outlet temperature will fall until the product between the electrodes 2, 3 flows through the outlet 5. This is shown in detail in Figure 2, where it can be seen that a rapid rise in inlet temperature 6 results in a corresponding rapid reduction in power P, referenced 7, according to equation (2). However, the outlet temperature Tout falls in response to the power reduction and thereafter returns to the its previous constant level when product between the electrodes 2, 3 is flushed through the outlet 5. An inverse situation arises when the inlet temperature suddenly falls and overheating of the product between the electrodes 2, 3 can occur.
SUMMARY OF THE INVENTION
With a view to overcoming these problems and difficulties, the present invention provides a method of controlling temperature in an ohmic heating process wherein an electrically conductive fluid is pumped from an inlet to an outlet past spaced apart electrodes that receive electrical power thereby heating the fluid during is passage from the inlet to the outlet, wherein the outlet temperature is controlled to tend to lie within predetermined range, by repeatedly considering the fluid between the electrodes to comprise a series of elements moving from the inlet to the outlet and predicting the outlet temperature that will occur for each of the elements upon reaching the outlet, and adjusting the power level applied to the electrodes if any of the predicted outlet temperatures for the elements falls outside of said predetermined range.
The invention also includes ohmic heating apparatus configured to perform the aforesaid method.
In accordance with the invention, the outlet temperature is controlled in such a way that it tends to minimise the likelihood of fluid between the electrodes from failing to achieve a desired outlet temperature. BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be more fully understood, an embodiment thereof will now be described by way of example, reference being made to the accompanying drawings wherein
Figure 1 is a schematic view of a known ohmic heating apparatus;
Figure 2 is a graph illustrative of power applied to the electrodes of Figure 1, and the resulting outlet temperature, produced in response to a step change in inlet temperature, as a function of time;
Figure 3 is a schematic diagram of an apparatus configured to perform a method in accordance with the invention, and;
Figure 4 is a schematic sectional view of fluid in the duct 1, when considered to be formed of a plurality of equal volume elements.
DESCRIPTION OF EMBODIMENT
Referring to Figure 3, the ohmic heating apparatus is similar to that described with reference to Figure 1 and the same reference numbers have been used to identify like component parts. Thus, the duct 1 includes electrodes 2, 3 and fluid to be heated e.g. foodstuffs pumped at a flow rate Q from an inlet 4 to an outlet 5. The inlet temperature Tin is sensed by a sensor 8 connected to a processor unit 9. The temperature upstream of the inlet is sensed by a sensor 11 also connected to the processor unit 9. A flow rate detector 12, shown schematically, provides data indicative of the product flow rate Q to the processor unit 9. The processor unit may comprise a personal computer PC or a programmable process control unit specifically configured to carry out the inventive method. The unit 9 controls operation of a power supply controller 10 which controls the level of AC Power P applied to the electrodes 2, 3.
The fluid between the electrodes 2, 3, can be considered as a column of n equal volume elements El-En as shown in Figure 4. If each element is assumed to have a volume Ve, for a flow rate Q, the elements will move from one position to the next in time increments t = Ve x fluid bulk average density/Q In accordance with the method of the invention, each of the elements El - En is for a particular time t attributed a different temperature Tl - Tn dependent upon the power P to which it has been subjected so far during its time of residency between the electrodes 2,3. A prediction is then made for each element of the temperature it will achieve at the outlet 5 on the basis of a projection of future inlet conditions and power requirements. The power level P is then adjusted, if necessary, so that a satisfactory oulet temperature will be achieved for each of the elements El - En. Thus, in accordance with the method of the invention, consideration is given to the temperature of fluid between the electrodes 2,3 when a rapid change of inlet temperature occurs. An example of a method in accordance with the invention will now be given in more detail.
Step 1 Establish initial state of the system
In this step, the ohmic heating apparatus shown in Figure 3 is brought into a nominally steady state condition in which it may be assumed that the relationship between applied power P, Tout and Tin is in acccordance with equation (2) given hereinbefore. Thus, the microprocessor 9 can compute a value of Tout. Referring to Figure 4, on the basis of Tin and Tout, it is possible to attribute a temperature to each of the elements El - En. It will be appreciated that element El has been heated for only a short period whereas element En has been heated for the longest period and hence will achieve the highest temperature. The intermediate elements will achieve a temperature which is a function of their residence time between the electrodes 2,3. Thus, with an appropriate algorithm, the microprocessor 9 can attribute a temperature Tl - Tn to each of the elements El - En. The level of sophistication of the algorithm will depend upon the degree of accuracy required and should take into account factors such as electrical resistance of the fluid (which is a function of temperature) and its specific heat, the flow rate Q and the applied power P. When step 1 is completed, the microprocessor 9 defines a start time t = 0. Step 2 Collect input data for current time increments .
At the end of a time increment Δt, the micro¬ processor 9 notes the current measured values of Tin, Q and P. The values for inlet C and Tout are
also noted as these may also have been changed by an operator or by a computer following a separate process algorithm.
The sensor 11 senses the temperature of the fluid in the conduit upstream of the heating apparatus. The resulting sequence of temperature values from sensor 11 serve as a look-up table for the microprocessor 9 to predict Tin values for n At in step 4 hereinafter.
Values of C may also be determined and similarly
incorporated in a look-up table.
Step 3 Calculate state of system at end of £_. t.
The microprocessor 9 uses the data obtained in step 2 in order to compute the value of Tl - Tn attributable to each of the elements El - En at the end of time increment Δ t.
Step 4 Collect input data for projected residence
Figure imgf000013_0001
In this step, the microprocessor 9 considers the number of time increments that it will take for the fluid in each element El - En to exit from the column i.e. pass to the outlet 5 (Figure 3). Thus, referring to Figure 4, the fluid in element El will take n A t time increments to reach the outlet 5. The projected inlet conditions are determined for this period from the look up table generated in Step 2 and are used in a subsequent forward prediction of Tout in Step 5
described hereinafter.
Stepr 5 Predict forward Toutn.
In this step, the microprocessor computes the likely temperature Tout that will be achieved by the fluid
in each of the elements by the time that it reaches the outlet 5. Computation is performed on the basis of the projected inlet conditions determined by Step 4. The power input during this period may be set in a number of ways. For example, the current power input could be held constant or alternatively the power may respond to the projected inlet conditions as specified in equation (2) . This step is effectively the repeated calculation of the real time status of the heating process as described in Step 1 hereinbefore projected into the future for n At.
The output from this calculation is an array of values Tout, - Tout which corresponds to the predicted outlet
temperature of the fluid originating in elements El - En at the start of Step 1.
Step 6 Find maximum (Tout (max)) and minimum
(Tout (min) ) for the forward prediction.
The various values of Toutn calculated for the fluid in
each of the elements El - En are scanned by the microprocessor 9 to determine the maximum and minimum values thereof Tout (max) and Tout (min) .
Step 7 Adjust Power Level P.
In this step Tout (max) and Tout (min) are compared with a predetermined range of desired output temperatures. If Tout (max) and Tout (min) lie outside of the predetermined range, the power level is adjusted with a view to making sure that the outlet temperature for the fluid in all of the elements does not fall outside of the predetermined range.
Typically, the temperature at outlet 5 will have a desired set point with associated upper and lower acceptable limits. The power level P can be adjusted in a number of different ways and three examples will be given below. In the examples, the following temperature definitions will be utilized:
Process outlet temperature set point = Tout (SP) Process outlet temperature lower limit = Tout (LL) Process outlet temperature upper limit = Tout (UL) Predicted minimum outlet temperature = Tout (min) Predicted maximum outlet temperature = Tout (max)
Example (1) Tout (min) < Tout (LL) Power setpoint adjustment = AP ΔP = Q.C . (Tout (LL) - Tout (Min)).F(e)
Where Q is are the current inlet conditions and is the assigned heat capacity for the element for
Figure imgf000016_0001
which the adjustment is being made.
Example (2) Tout (max) > Tout (UL) AP = Q.C .(Tout (UL) - Tout (max)).F(e)
Example (3) Tout (max) > Tout (UL) Tout (min) > Tout (LL)
ΔPχ = Q.C .(Tout (UL) - Tout (max)).F(e)
P«- = Q.Cp.(Tout (min) - Tout (LL)).F(e)
A pi > APo (using absolute values)
In this situation adjusting the power by the amount of Δp ι would cause the temperature of one of the
elements (represented by Tout (min) to fall below Tout (LL) . Therefore power adjustment should be given by : , P_ to keep the outlet temperature above the lower
limit.
In the examples, the function F(e) is a factor selected to take into account the position of the element E associated with either Tout (min) or Tout (max) . In its simplest form F(e) can be expressed as follows:
Figure imgf000017_0001
where Ne = element number of elements E N = total number of elements E
This function accounts for the fact that the power input P is distributed over the entire column of elements E. Thus, if an element towards the outlet 5 requires a power change of A P to correct its temperature, then a greater value is required over the total number of elements. Step 8 Transmit power of set point to power control (10).
The microprocessor 9, in this step, adjusts the power set point by the amount Δ P computed in step 7.
Step 9 Go back to Step 2.
In this step, the process is repeated for the next time interval A t. Thus, it is assumed that the fluid in each element has moved on by one position in the column thereof shown in Figure 4 and the process is then repeated. In this way, the temperature at the outlet 5 is controlled in such a way that in response to an inlet temperature change, the outlet temperature is maintained within upper and lower limits Tout (LL) and Tout (UL) .
Thus, by means of the described method, it is possible to sterilize food in an ohmic heating apparatus in such a way that in response to a step change in the inlet temperature, the outlet temperature can be controlled to be maintained within the upper and lower limits. Accordingly, the likelihood of septic conditions developing are substantially reduced and accordingly, the process can be run for much longer periods than hitherto since production down time can be minimised.
In the aforegoing description the present invention has been described with reference to a simple ohmic heater employing only two electrodes. However, the present invention is equally applicable to heaters employing multiple electrodes. Furthermore, although the apparatus for performing the present invention, has been described in an embodiment using a single processor unit, the apparatus may also be embodied using a multiprocessor unit carrying out parallel processing.

Claims

1. A method of controlling temperature in an ohmic heating process wherein electrically conductive fluid is pumped from an inlet to an outlet past spaced apart electrodes that receive electrical power thereby heating the fluid, wherein the outlet temperature is controlled to tend to lie within a predetermined range, by repeatedly; considering the fluid between the electrodes to comprise a series of elements moving from the inlet to the outlet and predicting the outlet temperature that will occur for each of the elements upon reaching the outlet, and adjusting the power level applied to the electrodes if any of the predicted outlet temperatures for the elements falls outside of predetermined range.
2. A method according to claim 1, including the steps of calculating the current temperature of each of the elements on the basis of the power level currently applied to the electrodes, performing said prediction of outlet temperatures that will occur for each of said elements on the basis of the current element temperatures and a projected power level, adjusting the current power level as a function of the difference between the predicted outlet temperatures and the predetermined temperature range, and repeating said steps after a predetermined time.
3. A method according to claim 1 or 2 including selecting the maximum and minimum values of said temperature predictions, comparing said maximum and minimum values with predetermined upper and lower limits for the outlet temperature, and adjusting said power level on the basis of said comparison.
4. A method according to claim 1, 2 or 3, wherein during the prediction of outlet temperatures, a parameter of the element closest to the inlet is determined by a prediction based on measurement of fluid parameters upstream of the heating apparatus.
5. Apparatus for controlling temperature in an ohmic heating process comprising an ohmic heater including a fluid flow duct having an inlet and an outlet, spaced electrodes within the duct, variable power supply means for adjustably supplying power to the electrodes, and processor means for controlling operation of the power supply means, said processor means being operative to treat the fluid between the electrodes as comprising a series of elements moving from the inlet to the outlet and to predict the outlet temperature that will occur for each of the elements upon reaching the outlet, for the power level currently being supplied to the electrodes, said processor means being configured to adjust the power level if any of the predicted outlet temperatures for the elements falls outside of said predetermined range.
6. Apparatus according to claim 5 wherein said processor means is operative to calculate the current temperature of each of the elements on the basis of the power level currently applied to the electrodes and to perform said prediction of the outlet temperatures that will occur for each of the elements on the basis of the current element temperatures and a projected power level.
7. Apparatus according to claim 6 wherein said processor means is operative to select values of said temperature predictions and to compare said maximum and minimum values with predetermined upper and lower limits for the outlet temperature.
8. Apparatus according to claim 5, 6 or 7, further comprising a temperature sensor, located upstream of the inlet to the duct, and wherein the microprocessor is operative to predict the temperature of the fluid at the inlet to the duct.
PCT/GB1992/001446 1991-08-13 1992-08-04 Temperature control in an ohmic process WO1993004421A1 (en)

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EP0654724A1 (en) * 1993-11-19 1995-05-24 Electricite De France Device and method for electric fluid heating in an electric-resistance pipe
US5741539A (en) * 1995-06-02 1998-04-21 Knipper; Aloysius J. Shelf-stable liquid egg
AU691591B2 (en) * 1994-06-01 1998-05-21 David Reznik Electroheating apparatus and methods
FR2818085A1 (en) * 2000-12-08 2002-06-14 Electricite De France Heating installation esp for viscous products comprises insulated pipe divided into sections by rotary disc electrodes linked to power supply
EP1367858A1 (en) * 2002-05-31 2003-12-03 Electricité de France Heating installation of products, particularly viscous
WO2003103340A1 (en) * 2002-05-31 2003-12-11 Electricite De France Product heating installation in particular for viscous products
FR2887392A1 (en) * 2005-06-20 2006-12-22 Electricite De France Fluid product e.g. agri-food product, ohmic heating device for e.g. physical treatment of fluid product, has phase electrode, detector to control product level, and ground electrode with ovoid portion such that product flows around portion
WO2007119217A1 (en) * 2006-04-17 2007-10-25 The Iams Company Food composition prepared by a sterilization process
WO2007119218A2 (en) * 2006-04-17 2007-10-25 The Iams Company Food composition prepared by a sterilization process
WO2007119216A1 (en) * 2006-04-17 2007-10-25 The Iams Company Food composition prepared by a sterilization process
EP2085715A1 (en) 2008-01-29 2009-08-05 Societe Des Produits Nestle S.A. System for changing fluid temperature and method for controlling such a system
US8834947B2 (en) 2010-04-27 2014-09-16 Conopco, Inc. In-line heating process
CN106440392A (en) * 2016-11-23 2017-02-22 张洛宁 Instantaneous-heating type electromagnetic water heater capable of automatically regulating temperature
EP3721678B1 (en) * 2017-12-04 2024-01-24 CFT S.p.A. Ohmic heater and method for operating

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GB2068199A (en) * 1980-01-21 1981-08-05 Electricity Council Apparatus for heating electrically conductive flowable media
DE3142992A1 (en) * 1980-11-08 1982-06-03 Mitsubishi Denki K.K., Tokyo METHOD FOR CONTROLLING A CONTINUOUS HEATER
EP0285297A2 (en) * 1987-04-02 1988-10-05 International Control Automation Finance S.A. Boiler steam temperature controller
GB2203320A (en) * 1987-04-08 1988-10-12 Creda Ltd Cooking ovens
EP0445966A1 (en) * 1990-02-28 1991-09-11 Gary L. Funk Control of fractional distillation process

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0654724A1 (en) * 1993-11-19 1995-05-24 Electricite De France Device and method for electric fluid heating in an electric-resistance pipe
FR2712762A1 (en) * 1993-11-19 1995-05-24 Electricite De France Device and method for heating by Joule effect of a fluid in a tube forming an electrical resistance.
AU691591B2 (en) * 1994-06-01 1998-05-21 David Reznik Electroheating apparatus and methods
US5741539A (en) * 1995-06-02 1998-04-21 Knipper; Aloysius J. Shelf-stable liquid egg
FR2818085A1 (en) * 2000-12-08 2002-06-14 Electricite De France Heating installation esp for viscous products comprises insulated pipe divided into sections by rotary disc electrodes linked to power supply
EP1367858A1 (en) * 2002-05-31 2003-12-03 Electricité de France Heating installation of products, particularly viscous
WO2003103340A1 (en) * 2002-05-31 2003-12-11 Electricite De France Product heating installation in particular for viscous products
FR2887392A1 (en) * 2005-06-20 2006-12-22 Electricite De France Fluid product e.g. agri-food product, ohmic heating device for e.g. physical treatment of fluid product, has phase electrode, detector to control product level, and ground electrode with ovoid portion such that product flows around portion
EP1737272A1 (en) * 2005-06-20 2006-12-27 Electricité de France Resistive heating cell
WO2007119218A2 (en) * 2006-04-17 2007-10-25 The Iams Company Food composition prepared by a sterilization process
WO2007119217A1 (en) * 2006-04-17 2007-10-25 The Iams Company Food composition prepared by a sterilization process
WO2007119216A1 (en) * 2006-04-17 2007-10-25 The Iams Company Food composition prepared by a sterilization process
WO2007119218A3 (en) * 2006-04-17 2007-12-27 Iams Company Food composition prepared by a sterilization process
AU2007237876B2 (en) * 2006-04-17 2012-08-16 Mars, Incorporated Food composition prepared by a sterilization process
US8771771B2 (en) 2006-04-17 2014-07-08 The Iams Company Food composition prepared by a sterilization process
EP2085715A1 (en) 2008-01-29 2009-08-05 Societe Des Produits Nestle S.A. System for changing fluid temperature and method for controlling such a system
US8118482B2 (en) 2008-01-29 2012-02-21 Nestec S.A System for changing fluid temperature and method for controlling such a system
US8834947B2 (en) 2010-04-27 2014-09-16 Conopco, Inc. In-line heating process
CN106440392A (en) * 2016-11-23 2017-02-22 张洛宁 Instantaneous-heating type electromagnetic water heater capable of automatically regulating temperature
EP3721678B1 (en) * 2017-12-04 2024-01-24 CFT S.p.A. Ohmic heater and method for operating

Also Published As

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AU2389192A (en) 1993-03-16

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