WO2011087969A1 - Humidity analyzer in a food processing device and associated method - Google Patents

Humidity analyzer in a food processing device and associated method Download PDF

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Publication number
WO2011087969A1
WO2011087969A1 PCT/US2011/020621 US2011020621W WO2011087969A1 WO 2011087969 A1 WO2011087969 A1 WO 2011087969A1 US 2011020621 W US2011020621 W US 2011020621W WO 2011087969 A1 WO2011087969 A1 WO 2011087969A1
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WO
WIPO (PCT)
Prior art keywords
tube
working cavity
exiting
temperature
liquid
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Application number
PCT/US2011/020621
Other languages
French (fr)
Inventor
Luca Gemelli
Alessandro Rigo
Original Assignee
Premark Feg L.L.C.
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Publication date
Application filed by Premark Feg L.L.C. filed Critical Premark Feg L.L.C.
Publication of WO2011087969A1 publication Critical patent/WO2011087969A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/56—Investigating or analyzing materials by the use of thermal means by investigating moisture content
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/6447—Method of operation or details of the microwave heating apparatus related to the use of detectors or sensors
    • H05B6/6458—Method of operation or details of the microwave heating apparatus related to the use of detectors or sensors using humidity or vapor sensors

Definitions

  • the present invention relates to a humidity analyzer in a food processing device, such as for example a combined oven, and to an associated method for monitoring the humidity .
  • the present invention thus relates to a humidity analyzer in a food processing device, e.g. a combined oven, as defined in claim 1.
  • the invention further relates to a method for monitoring the humidity value present, in use, in an air flow circulating within a working cavity of a food processing device, e.g. a combined oven, according to claim 8.
  • the humidity analyzer comprises, in combination: a tube arranged within the working cavity of the food processing device, e.g. consisting of a food cooking chamber, so as to be exposed in use to a flow of air circulating within the working cavity; means for feeding a controlled flow of liquid, e.g. water, through the tube, the flow being such that the temperature of the liquid exiting from the tube is never higher than the boiling temperature; means for measuring the temperature of the liquid entering in and exiting from the tube; and a control unit provided with memory means, comparator means for detecting the temperature difference of the liquid entering in and exiting from the tube, processing means and means for detecting the temperature inside the working cavity.
  • a tube arranged within the working cavity of the food processing device, e.g. consisting of a food cooking chamber, so as to be exposed in use to a flow of air circulating within the working cavity
  • the analyzer further comprises means for collecting and holding the liquid entering in and exiting from the tube, arranged outside the working cavity and made so that the flow of liquid flowing therethrough is under steady state conditions.
  • the means for measuring the temperature of the liquid entering in and exiting from the tube are further arranged within the collecting and holding means.
  • FIG. 1 diagrammatically shows an axonometric, three- quarters rear view of an oven provided with a humidity analyzer provided according to the invention
  • FIG. 4 shows a graph of the calculated and measured humidity pattern inside the oven according to time.
  • numeral 1 indicates as a whole a humidity analyzer intended to be used in a food processing device 2, e.g. a (known) combined oven, only partially and diagrammatically shown by the dashed line in figure 1.
  • Oven 2 comprises an internal working cavity 3, consisting of the cooking chamber, adapted to contain in use the food to be cooked, which is introduced therein through a front opening 4 thereof, normally closed by a pivoting door (known and not shown for simplicity) ; at the rear, the working cavity 3 may be provided with a service compartment 5, e.g. accommodating heating means of one or more different types and one or more fans for the forced circulation of air in cavity 3 (known and not shown for simplicity) .
  • a service compartment 5 e.g. accommodating heating means of one or more different types and one or more fans for the forced circulation of air in cavity 3 (known and not shown for simplicity) .
  • the humidity analyzer 1 works in an indirect manner as illustrated below and comprises in combination: a tube 10 arranged within the working cavity 3 of the food processing device 2 so as to be exposed in use to an air flow 11 (represented by the arrow in figure 2) circulating within the working cavity 3, e.g. coming from the rear compartment 5; means 12 for feeding a controlled liquid flow F, e.g. water, through tube 10, of such a flow rate that the temperature of the liquid exiting from tube 10 is never higher than the boiling temperature of the liquid itself; and means 13,14 for measuring the temperature of the liquid entering in and exiting from tube 10.
  • a controlled liquid flow F e.g. water
  • analyzer 1 also comprises a control unit 15 provided with memory means 16, comparator means 17 for detecting the temperature difference of the liquid entering in and exiting from tube 10, processing means 18, and means 19 for detecting the temperature within the working cavity 3, including a specific (known) temperature probe 20 located inside cavity 3.
  • control unit 15 provided with memory means 16, comparator means 17 for detecting the temperature difference of the liquid entering in and exiting from tube 10, processing means 18, and means 19 for detecting the temperature within the working cavity 3, including a specific (known) temperature probe 20 located inside cavity 3.
  • the means for feeding a controlled liquid flow F consist in network water feeding means having a predetermined flow rate, e.g. including a pump and/or a solenoid valve with a flow rate limiter, diagrammatically shown by a block identified by reference number 21 (figure 2) . It is apparent that these means 21 for feeding a controlled liquid flow F may be adapted to feed both a single, predetermined liquid flow rate Ql (during the step of designing the oven) , and a plurality of mutually different flow rates Ql, Q2, Q3, ...Qn, all known as they are predetermined during the step of designing the oven, which may be used in the same oven according to its conditions of use, e.g. of the predetermined cooking program. Such a possibility may be easily implemented, e.g. by using a multiple-way solenoid valve provided with a plurality of calibrated outlet tubes.
  • analyzer 1 further comprises means 22,23 for collecting and temporary holding the liquid entering in and exiting from tube 10, which are arranged outside the working cavity 3 and made so that the liquid flow F flowing therethrough is under steady state conditions, e.g. laminar motion without accelerations/decelerations or sudden changes of direction; moreover, according to the invention, means 13,14 for measuring the temperature of the liquid entering in and exiting from tube 10 are arranged within the collecting and holding means 22,23.
  • means 22,23 for collecting and holding the liquid entering in and exiting from tube 10 consist of a first box 24 and a second box 25, both preferably made of metal, each comprising (with reference also to figure 3, which illustrates box 25 in detail and on an enlarged scale) a chamber 26 delimited by the box 24 or 25 and accommodating a temperature thermocouple probe 13 or 14 therein, carried so as to overhangingly protrude into chamber 26 from a side wall 27 of the chamber 26 itself.
  • probes 13 and 14 are each arranged close to a bottom wall 28 of the respective chamber 26, parallel thereto.
  • Boxes 24,25 further comprise a first tube section 29 carried by the bottom wall 28 so as to overhangingly protrude into chamber 26 and arranged on the side opposite to the side wall 27, carrying the temperature probe 13 or 14; and a second tube section 30 carried by an upper wall 31 of chamber
  • the tube section 30 is however arranged on the side of the side wall
  • Boxes 24 and 25 differ from each other in that the first tube section 29 and the second tube section 30 of box 24 are connected to means 12 for feeding the controlled liquid flow F (section 29) and to an inlet end 40 of tube 10 (section 30), respectively, while the first tube section 29 and the second tube section 30 of box 25 are connected to a drain 41 (figure 2) for the liquid (section 29) and to an outlet end 42 of tube 10 (section 30) , respectively.
  • the tube sections 29 and 30 of the second box 25 are arranged so as to leave an empty space of height Z in chamber 26 therebetween, which avoids a siphon from being formed in box 25. Therefore, in this box, the liquid exiting from tube 10 will drip from the top through the tube segment 30 into chamber 26, thus only partially filling it with a head of liquid L of height H equal to the length by which the tube segment 29 overhangingly protrudes into chamber 26 from the bottom wall 28; indeed, arriving at such a height, the liquid exits from chamber 26 through the tube segment 29, which acts as spillway.
  • chamber 26 of box 24 where the liquid arrives from the bottom through the tube section 29 and exits from the top through the tube section 30, is completely filled with liquid.
  • Tube 10 overhangingly extends into the working cavity 3, from an inner wall 45 thereof, in this case (as shown in figure 1) the side wall of the cavity 3 itself, and is preferably U-shaped, so as to have (figure 2) a transversal rectilinear branch 46 and two rectilinear end branches 47,48 connected to each other by the transversal branch 46 and ending, on the side opposite to the branch 46, with the inlet end 40 and outlet end 42 of tube 10; with respect to the branch 46, branches 47,48 are perpendicularly arranged and are fluid-tightly mounted through the inner wall 45 of cavity 3, so that the transversal branch 46 remains arranged at a predetermined distance from the wall 45 itself and preferably oriented parallel to wall 45, so that the section 46 may be better lapped in use by the air flow 11 circulating in cavity 3.
  • tube 10 is preferably preassembled, e.g. by welding, on a flange (not shown for simplicity) which is then fixed in use, in any appropriate manner, so as to be fluid-tightly integral with wall 45, e.g. by means of screws and an appropriate seal.
  • the memory means 16 contain a plurality of humidity values of the air flow 11 normally circulating in the working cavity 3, which have been previously measured, and a plurality of temperature difference values of the liquid entering in and exiting from tube 10, also previously measured and correspondingly generated by the stored humidity values, at different internal temperatures of the working cavity 3.
  • the processing means 18 are then adapted to read in use the temperature differences generated by the comparator means 17 and to calculate by interpolation, by using the memory means 16 and the means 19 for detecting the temperature inside the working cavity 3, the corresponding theoretical values of humidity in the air flow 11 circulating in the working cavity 3.
  • control unit 15 implements a method for monitoring the humidity value present in use in the air flow 11 circulating in the working cavity 3 of the food processing device 2 comprising the steps of:
  • the step of measuring the temperature difference of the liquid entering in and exiting from tube 10 is preferably carried out outside the working cavity 3 , within the chambers 26 connected to an inlet end 40 and an outlet end 42 of tube 10, respectively, and made so that the controlled liquid flow F therein is under steady state conditions.
  • a step of testing is carried out on one or more ovens in which the humidity of the air flow 11 circulating in the cavity 3 is known beforehand and is however measured outside the cavity 3 prior to being fed into the same.
  • a practically dry air flow is firstly used and humidity is gradually increased over time; for each measured humidity value, the temperature difference of the liquid entering in and exiting from tube 10 is also measured, thus maintaining it relatively cold as compared to the temperature within oven 2, and these values of humidity and corresponding temperature difference are stored in the control unit 15. This is repeated at the various operating temperatures of oven 2.
  • control unit 15 is able to determine, directly or by interpolation, the corresponding humidity values according to the values measured and stored during the step of testing.
  • the solid line indicates the pattern of real humidity over time, i.e. measured directly and/or known beforehand, while the dashed line indicates the pattern over time of the humidity calculated by the control unit 15, according to the readings of the temperature difference of the liquid entering in and exiting from tube 10.
  • the line representing the calculated humidity perfectly follows the pattern of the line which represents the real humidity.

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Abstract

A humidity analyzer (1) including a tube (10) arranged within a working cavity (3), typically a cooking chamber, of a food processing device (2), typically a combined oven, so as to be exposed in use to a flow (11) of air circulating within the working cavity, means (12) for feeding a controlled flow of water through the tube so that the temperature of the water exiting from the tube is never higher than the boiling temperature, means (22,23) for collecting and holding the water entering in and exiting from the tube (10), which are made so that the flow of water flowing therethrough is under steady state conditions, means (13,14) for measuring the temperature of the water entering in and exiting from the tube, arranged within said collecting and holding means, and a control unit (15) provided with memory means (16), comparator means (17) for detecting the temperature difference of the water entering in and exiting from the tube (10), processing means (18), and means (19) for detecting the temperature inside the working chamber.

Description

HUMIDITY ANALYZER IN A FOOD PROCESSING
DEVICE AND ASSOCIATED METHOD
The present invention relates to a humidity analyzer in a food processing device, such as for example a combined oven, and to an associated method for monitoring the humidity .
The use of different or multiple cooking technologies, such as combined steam and/or microwave and/or traditional cooking modes, is known in modern combined ovens for professional use, e.g. to be used in cafeterias, restaurants and communities. In order to ensure the best possible cooking results, it would be useful to continuously monitor not only the temperature inside the oven, which is easily achieved by means of one more temperature probes, but also the humidity content of the air flow which moves by either natural or forced convection in the internal working cavity of the oven, consisting of the cooking chamber.
Unfortunately, directly measuring the amount of steam present in the working cavity in use is either impossible or otherwise implies problems which are difficult to be solved.
It is an object of the present invention to overcome such a drawback, by providing a humidity analyzer adapted to be employed in a food processing device, such as for example a combined oven, which is simple and cost-effective to be implemented, reliable and small in size, in particular within the working cavity. The present invention thus relates to a humidity analyzer in a food processing device, e.g. a combined oven, as defined in claim 1.
The invention further relates to a method for monitoring the humidity value present, in use, in an air flow circulating within a working cavity of a food processing device, e.g. a combined oven, according to claim 8.
In particular, the humidity analyzer according to the invention comprises, in combination: a tube arranged within the working cavity of the food processing device, e.g. consisting of a food cooking chamber, so as to be exposed in use to a flow of air circulating within the working cavity; means for feeding a controlled flow of liquid, e.g. water, through the tube, the flow being such that the temperature of the liquid exiting from the tube is never higher than the boiling temperature; means for measuring the temperature of the liquid entering in and exiting from the tube; and a control unit provided with memory means, comparator means for detecting the temperature difference of the liquid entering in and exiting from the tube, processing means and means for detecting the temperature inside the working cavity.
According to an aspect of the invention, the analyzer further comprises means for collecting and holding the liquid entering in and exiting from the tube, arranged outside the working cavity and made so that the flow of liquid flowing therethrough is under steady state conditions. The means for measuring the temperature of the liquid entering in and exiting from the tube are further arranged within the collecting and holding means.
Thereby, instead of directly measuring the humidity present in the air flow which circulates in the working cavity and laps on the tube, an indirect measurement is made by reading the temperature difference of the water entering in and exiting from the tube which, with the other parameters being equal, depends only on the temperature inside the oven and on the amount of humidity which, by condensing in use on the tube, kept at a relatively cold temperature (as compared to the temperature inside the oven) by the circulation of liquid also kept under the boiling point, gives condensation heat to the liquid circulating in the tube, thus correspondingly contributing to determine the temperature difference between the tube inlet and outlet.
For this purpose, the following steps are carried out in accordance with the method of the invention:
- within the working cavity, placing a tube arranged so as to be exposed in use to the air flow;
- passing a controlled flow of a liquid through the tube so that the liquid never boils, and measuring the temperature difference of the liquid entering in and exiting from the tube ;
during a step of testing, measuring the humidity present in the air flow at different internal temperatures of the working cavity by means of a suitable external instrument and the corresponding temperature differences detected in the liquid entering in and exiting from the tube;
storing the humidity values and the corresponding values of temperature difference of the liquid entering in and exiting from the tube and of the temperature inside the working cavity, measured during the step of testing;
- by reading the values previously stored during the step of testing, calculating in use by interpolation the current humidity values of the air flow theoretically corresponding to current measured values of the temperature difference detected in the liquid entering in and exiting from the tube and of the temperature inside the working cavity .
Further features and advantages of the present invention will be apparent from the following description of a preferred embodiment, merely provided by way of non- limitative example, with reference to the accompanying drawings, in which:
- figure 1 diagrammatically shows an axonometric, three- quarters rear view of an oven provided with a humidity analyzer provided according to the invention;
- figures 2 and 3 show a cross section view on enlarged scale of some details of the main components of the analyzer in figure 1; and
- figure 4 shows a graph of the calculated and measured humidity pattern inside the oven according to time.
With reference to figures from 1 to 4, numeral 1 indicates as a whole a humidity analyzer intended to be used in a food processing device 2, e.g. a (known) combined oven, only partially and diagrammatically shown by the dashed line in figure 1.
Oven 2 comprises an internal working cavity 3, consisting of the cooking chamber, adapted to contain in use the food to be cooked, which is introduced therein through a front opening 4 thereof, normally closed by a pivoting door (known and not shown for simplicity) ; at the rear, the working cavity 3 may be provided with a service compartment 5, e.g. accommodating heating means of one or more different types and one or more fans for the forced circulation of air in cavity 3 (known and not shown for simplicity) .
The humidity analyzer 1 according to the invention works in an indirect manner as illustrated below and comprises in combination: a tube 10 arranged within the working cavity 3 of the food processing device 2 so as to be exposed in use to an air flow 11 (represented by the arrow in figure 2) circulating within the working cavity 3, e.g. coming from the rear compartment 5; means 12 for feeding a controlled liquid flow F, e.g. water, through tube 10, of such a flow rate that the temperature of the liquid exiting from tube 10 is never higher than the boiling temperature of the liquid itself; and means 13,14 for measuring the temperature of the liquid entering in and exiting from tube 10.
Furthermore, analyzer 1 also comprises a control unit 15 provided with memory means 16, comparator means 17 for detecting the temperature difference of the liquid entering in and exiting from tube 10, processing means 18, and means 19 for detecting the temperature within the working cavity 3, including a specific (known) temperature probe 20 located inside cavity 3.
The means for feeding a controlled liquid flow F consist in network water feeding means having a predetermined flow rate, e.g. including a pump and/or a solenoid valve with a flow rate limiter, diagrammatically shown by a block identified by reference number 21 (figure 2) . It is apparent that these means 21 for feeding a controlled liquid flow F may be adapted to feed both a single, predetermined liquid flow rate Ql (during the step of designing the oven) , and a plurality of mutually different flow rates Ql, Q2, Q3, ...Qn, all known as they are predetermined during the step of designing the oven, which may be used in the same oven according to its conditions of use, e.g. of the predetermined cooking program. Such a possibility may be easily implemented, e.g. by using a multiple-way solenoid valve provided with a plurality of calibrated outlet tubes.
According to a useful aspect of the invention, analyzer 1 further comprises means 22,23 for collecting and temporary holding the liquid entering in and exiting from tube 10, which are arranged outside the working cavity 3 and made so that the liquid flow F flowing therethrough is under steady state conditions, e.g. laminar motion without accelerations/decelerations or sudden changes of direction; moreover, according to the invention, means 13,14 for measuring the temperature of the liquid entering in and exiting from tube 10 are arranged within the collecting and holding means 22,23.
In the non-limitative example shown, means 22,23 for collecting and holding the liquid entering in and exiting from tube 10 (figure 2) consist of a first box 24 and a second box 25, both preferably made of metal, each comprising (with reference also to figure 3, which illustrates box 25 in detail and on an enlarged scale) a chamber 26 delimited by the box 24 or 25 and accommodating a temperature thermocouple probe 13 or 14 therein, carried so as to overhangingly protrude into chamber 26 from a side wall 27 of the chamber 26 itself. In particular, probes 13 and 14 are each arranged close to a bottom wall 28 of the respective chamber 26, parallel thereto.
Boxes 24,25 further comprise a first tube section 29 carried by the bottom wall 28 so as to overhangingly protrude into chamber 26 and arranged on the side opposite to the side wall 27, carrying the temperature probe 13 or 14; and a second tube section 30 carried by an upper wall 31 of chamber
26 so as to be hydraulically in communication with the chamber 26 itself, such as the tube section 29, and possibly overhangingly protruding into chamber 26 from wall 31, which is opposite to and facing the bottom wall 27; the tube section 30 is however arranged on the side of the side wall
27 and, therefore, on the side opposite to the tube section 29, so that two tube sections 29 and 30 are divided from each other by nearly the whole extension of each chamber 26 in length . Boxes 24 and 25 differ from each other in that the first tube section 29 and the second tube section 30 of box 24 are connected to means 12 for feeding the controlled liquid flow F (section 29) and to an inlet end 40 of tube 10 (section 30), respectively, while the first tube section 29 and the second tube section 30 of box 25 are connected to a drain 41 (figure 2) for the liquid (section 29) and to an outlet end 42 of tube 10 (section 30) , respectively.
Furthermore, according to an aspect of the invention (figure 3), the tube sections 29 and 30 of the second box 25 are arranged so as to leave an empty space of height Z in chamber 26 therebetween, which avoids a siphon from being formed in box 25. Therefore, in this box, the liquid exiting from tube 10 will drip from the top through the tube segment 30 into chamber 26, thus only partially filling it with a head of liquid L of height H equal to the length by which the tube segment 29 overhangingly protrudes into chamber 26 from the bottom wall 28; indeed, arriving at such a height, the liquid exits from chamber 26 through the tube segment 29, which acts as spillway. In contrast, chamber 26 of box 24, where the liquid arrives from the bottom through the tube section 29 and exits from the top through the tube section 30, is completely filled with liquid.
The presence of an empty space full of air in chamber 26 of box 25, which separates the two tube segments 29 and 30 is fundamental for ensuring a correct measurement of the temperature of the liquid exiting from tube 10. Tube 10 overhangingly extends into the working cavity 3, from an inner wall 45 thereof, in this case (as shown in figure 1) the side wall of the cavity 3 itself, and is preferably U-shaped, so as to have (figure 2) a transversal rectilinear branch 46 and two rectilinear end branches 47,48 connected to each other by the transversal branch 46 and ending, on the side opposite to the branch 46, with the inlet end 40 and outlet end 42 of tube 10; with respect to the branch 46, branches 47,48 are perpendicularly arranged and are fluid-tightly mounted through the inner wall 45 of cavity 3, so that the transversal branch 46 remains arranged at a predetermined distance from the wall 45 itself and preferably oriented parallel to wall 45, so that the section 46 may be better lapped in use by the air flow 11 circulating in cavity 3.
For assembly simplicity, tube 10 is preferably preassembled, e.g. by welding, on a flange (not shown for simplicity) which is then fixed in use, in any appropriate manner, so as to be fluid-tightly integral with wall 45, e.g. by means of screws and an appropriate seal.
According to one of the aspects of the invention, the memory means 16 contain a plurality of humidity values of the air flow 11 normally circulating in the working cavity 3, which have been previously measured, and a plurality of temperature difference values of the liquid entering in and exiting from tube 10, also previously measured and correspondingly generated by the stored humidity values, at different internal temperatures of the working cavity 3. The processing means 18 are then adapted to read in use the temperature differences generated by the comparator means 17 and to calculate by interpolation, by using the memory means 16 and the means 19 for detecting the temperature inside the working cavity 3, the corresponding theoretical values of humidity in the air flow 11 circulating in the working cavity 3.
In practice, according to the description, the control unit 15 implements a method for monitoring the humidity value present in use in the air flow 11 circulating in the working cavity 3 of the food processing device 2 comprising the steps of:
within the working cavity 3, placing a tube 10 arranged so as to be exposed in use to the air flow 11;
- passing a controlled liquid flow F (i.e. of known, constant flow rate) within tube 10 so that the liquid never boils, and measuring the temperature difference of the liquid entering in and exiting from tube 10;
during a step of testing, measuring the humidity present in the air flow 11 at different internal temperatures of the working cavity 3 by means of a suitable external instrument and the corresponding temperature differences detected in the liquid entering in and exiting from tube 10 by using the comparator means 17 and the temperature probes 13 and 14;
- storing the previously measured humidity values and the corresponding values of temperature difference of the liquid entering in and exiting from tube 10 and of the temperature inside the working cavity 3 , also previously measured during the same step of testing;
- calculating in use by interpolation, according to the current values (i.e. the values measured instant-by-instant) of the temperature difference detected in the liquid entering in and exiting from tube 10 and of the temperature inside the working cavity 3 detected by probe 20, by reading the values previously stored during the step of testing, the current humidity values of the air flow 11 theoretically corresponding to the current values of the temperature difference measured in the liquid entering in and exiting from tube 10 and of the temperature inside cavity 3 .
The step of measuring the temperature difference of the liquid entering in and exiting from tube 10 is preferably carried out outside the working cavity 3 , within the chambers 26 connected to an inlet end 40 and an outlet end 42 of tube 10, respectively, and made so that the controlled liquid flow F therein is under steady state conditions.
In practice, for each model of oven 2, a step of testing is carried out on one or more ovens in which the humidity of the air flow 11 circulating in the cavity 3 is known beforehand and is however measured outside the cavity 3 prior to being fed into the same. In practice, a practically dry air flow is firstly used and humidity is gradually increased over time; for each measured humidity value, the temperature difference of the liquid entering in and exiting from tube 10 is also measured, thus maintaining it relatively cold as compared to the temperature within oven 2, and these values of humidity and corresponding temperature difference are stored in the control unit 15. This is repeated at the various operating temperatures of oven 2.
Therefore, in use, according to the values of the temperature difference in the liquid circulating in tube 10 and of the temperature within oven 2 only, the control unit 15 is able to determine, directly or by interpolation, the corresponding humidity values according to the values measured and stored during the step of testing.
This is due to the fact that in the dynamic system consisting of analyzer 1, with the other parameters being equal, the temperature difference between the liquid entering in tube 10 and that exiting therefrom is only proportional to the humidity of the air flow 11 which laps on the tube 10.
Such a proportional relationship has been experimentally demonstrated and is shown in figure 4. In the figure, the solid line indicates the pattern of real humidity over time, i.e. measured directly and/or known beforehand, while the dashed line indicates the pattern over time of the humidity calculated by the control unit 15, according to the readings of the temperature difference of the liquid entering in and exiting from tube 10. As apparent, in spite of a zigzag pattern, the line representing the calculated humidity perfectly follows the pattern of the line which represents the real humidity.

Claims

1. A humidity analyzer (1) in a food processing device (2), e.g. a combined oven, characterized in that it comprises, in combination: a tube (10) arranged within a working cavity (3) of the food processing device, consisting for example of a cooking chamber, so as to be exposed in use to a flow (11) of air circulating within the working cavity; means (12) for feeding a controlled flow of liquid through the tube so that the temperature of the liquid exiting from the tube is never higher than its boiling temperature; means (13,14) for measuring the temperature of the liquid entering in and exiting from the tube; and a control unit (15) provided with memory means (16), comparator means (17) for detecting the temperature difference of the liquid entering in and exiting from the tube (10), processing means (18), and means (19) for detecting the temperature inside the working cavity .
2. A humidity analyzer according to claim 1, characterized in that it further comprises means (22,23) for collecting and temporary holding the liquid entering in and exiting from the tube (10), which are arranged outside the working cavity (3) and made so that the flow of liquid flowing therethrough is under steady state conditions; said means (13,14) for measuring the temperature of the liquid entering in and exiting from the tube being arranged within said collecting and holding means (22, 23) .
3. A humidity analyzer according to claim 2, characterized in that said means (22,23) for collecting and holding the liquid entering in and exiting from the tube consist of first and second boxes (24,25), each comprising: a chamber (26) delimited by the box and accommodating a thermocouple temperature probe (13,14) therein, carried so as to overhangingly protrude within the chamber from a side wall (27) of the chamber itself and arranged close to a bottom wall (28) of the chamber, parallelly thereto; a first tube section (29) overhangingly protruding within the chamber from the bottom wall (28), arranged on the opposite side of the side wall (27) carrying the temperature probe; and a second tube section (30), possibly overhangingly protruding within the chamber from an upper wall (31) of the chamber itself, opposite to and facing the bottom wall (28), arranged on the side of the side wall (27) carrying the temperature probe; the first and second tube sections (28, 30) of the first box
(24) being connected to said means (12) for feeding a controlled flow of liquid and to an inlet end (40) of the tube, respectively, and the first and second tube sections (29, 30) of the second box (25) being connected to a drain (41) for the liquid and to an outlet end (42) of the tube, respectively, the tube sections (29, 30) of the second box
(25) being arranged so as to leave an empty space (Z) therebetween in the chamber (26), which avoids a siphon from being formed in the second box (25) .
4. A humidity analyzer according to one of the preceding claims, characterized in that said tube (10) overhangingly extends within said working cavity (3), from an inner wall (45) thereof, and is preferably U-shaped.
5. A humidity analyzer according to claim 4, characterized in that said tube (10) has a transversal rectilinear branch (46) and two rectilinear end branches (47,48) connected to each other by the transversal branch (46), with respect to which they are perpendicularly arranged and fluid-tightly mounted through the inner wall (45) so that the transversal branch (46) remains arranged at a predetermined distance from the inner wall (45) of the working cavity and preferably oriented parallel thereto.
6. A humidity analyzer according to one of the preceding claims, characterized in that said means (12) for feeding a controlled flow of liquid consist in means for feeding network water, having at least one predetermined flow rate .
7. A humidity analyzer according to one of the preceding claims, characterized in that said memory means
(16) contain a plurality of humidity values of the flow of air circulating in the working cavity (3) and a plurality of temperature difference values of the liquid entering in and exiting from the tube (10), previously measured and correspondingly generated by the stored humidity values, at different internal temperatures of the working cavity, said processing means (18) being adapted to read in use the temperature differences generated by the comparator means
(17) and to calculate by interpolation by means of the memory means (16) and the means (19) for detecting the temperature inside the working cavity the corresponding theoretical values of humidity in the flow (11) of air circulating in the working cavity.
8. A method for monitoring the value of humidity present in use in a flow (11) of air circulating in a working cavity (3) of a food processing device (2), e.g. a combined oven, characterized in that it comprises the steps of:
- within the working cavity (3), placing a tube (10) arranged so as to be exposed in use to said air flow (11);
- making a controlled flow (F) of a liquid pass into the tube (10) the flow being so that the liquid never boils, and measuring the temperature difference of the liquid entering in and exiting from the tube;
during a step of testing, measuring the humidity present in the air flow (11) at different internal temperatures of the working cavity (3) by means of a suitable external instrument and the corresponding temperature differences detected in the liquid entering in and exiting from the tube (10);
storing the humidity values and the corresponding values of temperature difference of the liquid entering in and exiting from the tube (10) and of the temperature inside the working cavity, measured during the step of testing;
- by reading the values previously stored during the step of testing, calculating in use by interpolation the current humidity values in the air flow (11) theoretically corresponding to current measured values of the temperature difference detected in the liquid entering in and exiting from the tube (10) and of the temperature inside the working cavity (3) .
9. A method according to claim 8, characterized in that said step of measuring the temperature difference of the liquid entering in and exiting from the tube (10) is carried out outside the working cavity (3), within chambers (26) connected to an inlet end (40) and an outlet end (42) of the tube (10), respectively, and made so that the controlled flow of liquid therein is under steady state conditions.
PCT/US2011/020621 2010-01-13 2011-01-10 Humidity analyzer in a food processing device and associated method WO2011087969A1 (en)

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ITTO2010A000015A IT1397778B1 (en) 2010-01-13 2010-01-13 HUMIDITY ANALYZER IN A PROCESSING DEVICE FOR FOOD AND ASSOCIATED METHOD

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5694835A (en) * 1994-09-09 1997-12-09 Zanussi Grandi Impianti S.P.A. Humidity measurement arrangement and cooking oven provided therewith
EP1193493A1 (en) * 2000-09-29 2002-04-03 Infineon Technologies SC300 GmbH & Co. KG Method and apparatus for measuring and controlling the water content of a water containing liquid mixture

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5694835A (en) * 1994-09-09 1997-12-09 Zanussi Grandi Impianti S.P.A. Humidity measurement arrangement and cooking oven provided therewith
EP1193493A1 (en) * 2000-09-29 2002-04-03 Infineon Technologies SC300 GmbH & Co. KG Method and apparatus for measuring and controlling the water content of a water containing liquid mixture

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IT1397778B1 (en) 2013-01-24

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