EP0069155A1 - Méthode pour faire fonctionner un générateur de vapeur d'eau - Google Patents

Méthode pour faire fonctionner un générateur de vapeur d'eau Download PDF

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Publication number
EP0069155A1
EP0069155A1 EP81105016A EP81105016A EP0069155A1 EP 0069155 A1 EP0069155 A1 EP 0069155A1 EP 81105016 A EP81105016 A EP 81105016A EP 81105016 A EP81105016 A EP 81105016A EP 0069155 A1 EP0069155 A1 EP 0069155A1
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EP
European Patent Office
Prior art keywords
water
predetermined
cycles
frequency
current
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP81105016A
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German (de)
English (en)
Inventor
Michael Howard-Leicester
Siegbert Gundacker
Larry James Moffatt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Condair AG
Original Assignee
Condair AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Condair AG filed Critical Condair AG
Priority to EP81105016A priority Critical patent/EP0069155A1/fr
Publication of EP0069155A1 publication Critical patent/EP0069155A1/fr
Withdrawn legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/28—Methods of steam generation characterised by form of heating method in boilers heated electrically
    • F22B1/30—Electrode boilers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F6/00—Air-humidification, e.g. cooling by humidification
    • F24F6/02—Air-humidification, e.g. cooling by humidification by evaporation of water in the air
    • F24F6/025—Air-humidification, e.g. cooling by humidification by evaporation of water in the air using electrical heating means

Definitions

  • This invention relates to humidifiers and wore particularly to the electrode type steam generating humidifiers.
  • Such humidifiers in which a current is passed-between spaced electrodes in a water-carrying vessel are well-known.
  • the current causes heating of the water and subsequently generation of steam which is passed into the air space, the moisture content of which is to be controlled.
  • the magnitude of the current and hence the steam generating ability is dependent on the voltage applied to the electrodes, the size, shape and spacing of the electrodes, the depth of immersion of the electrodes and the conductivity and volume of the water.
  • a serious problem which has been recognised is that the conductivity of a water supply can vary by as much as 10:1 depending on the geological conditions of the source and also the conductivity of a particular water supply can vary daily in the same range (10:1) depending on variables such as interconnections in the water main and switching and/or mixing of the sources and the season of the year.
  • the magnitude of the current between the electrodes is measured continuously and the actual time taken for the current to drop between two predetermined values is compared with the calculated time required for the current to drop between those two values when the conductivity of the water is at the designed value. If the actual time measured is shorter, some of the water is flushed from the vessel, as this represents an unacceptably high conductivity.
  • the present invention involves obtaining a measure of the frequency of two or more cycles, each cycle containing a boil and fill leg, and, if the measure of the frequency increases above a predetermined value corresponding to a desired, i.e. design, frequency, causing water to be discharged-.
  • the frequency can be determined in various ways, such as by measuring the time to count a predetermined plurality of cycles, or by counting the number of cycles in a predetermined duration.
  • the frequency of the fill legs or the boil legs can be used as a measure of the cycle frequency in which case the time to measure a predetermined plurality of fill legs or boil legs is obtained or the number of fill legs or boil legs in a predetermined duration is counted.
  • the accumulated boil time over two or more cycles or the accumulated fill time over two or more cycles may be measured and this also would give a measure or indication of the cycle frequency.
  • the drain leg can be adjusted directly by time so that the higher the frequency measured the longer the drain leg.
  • the drain leg can be arranged to continue until the current reaches- a threshold value, the higher the frequency the lower the threshold value selected.
  • the invention By concentrating on measuring the frequency of two or more cycles, the invention has the effect of minimizing the possibility of obtaining an incorrect indication of contained water conductivity which could arise due to spurious or transient factors and thereby minimizing the possibility of ordering a flush cycle needlessly.
  • a feedback control can be built in which has the effect of altering the requirements for a particular group of cycles depending upon the frequency measured for the immediately preceding group of cycles.
  • the measured frequency is compared with a variable frequency which is weighted in relation to the frequency measured for the preceding group.
  • the predetermined frequency is decreased and if the frequency measured for the previous cycles was low, the predetermined frequency is increased. The effect of this is to stabilize the water level substantially at one point with respect to the electrodes whether the mains supply is of high or low conductivity.
  • a vaporization container contains two or more electrodes which heat water in the container to boiling point and as water is boiled off and replenished with "fresh" mains water the concentration of minerals in the container water gradually increases causing a corresponding increase in the conductivity of the water. It is necessary to flush out some of the container water from time to time to maintain the water conductivity around the value for which the unit was designed. Figure 1 explains how this may be accomplished according to the present invention.
  • Figure la is a plot of the electrode current, expressed as a percentage of the rated or designed value, against time, this shows fill, boil and drain cycles of the vaporization vessel.
  • the point A represents the end of a fill portion of a cycle near start-up of the whole operation, i.e. before the container water has become very concentrated. It could, in fact, be the end of the very first fill leg beginning from empty. From the point A the next three (for example) complete boil/fill cycles are counted and this occurs at point B.
  • the design frequency i.e. the frequency which would occur if the contained water conductivity were at the desired or designed value, can be established theoretically or experimentally and this would give a duration C-D for three complete cycles. If the measured frequency of the three cycles from A - B differs from the design frequency it can be determined whether the conductivity is too high or too low.
  • the first three cycles from A - B last longer than C - D, i.e. the measured frequency is less than the design frequency, for three complete cycles assuming the water is at the desired conductivity. This means that the water conductivity is less than the desired value and no drain cycle is initiated.
  • the end of the very next fill portion at which the 105% current level is reached is designated E and the next three complete boil/fill cycles ending at point F are counted and it is noted that the frequency from E - F is greater than the design frequency indicated by C - D corresponding to the desired conductivity.
  • the three cycles have elapsed some 4 units before C - D and so at point F a drain cycle is initiated to flush out some of the concentrated water.
  • the drain cycle continues to the point G at which the electrode current is a predetermined percentage of the rated current, e.g. 80%.
  • the length of the drain cycle depends on how much greater the actual frequency is than the design frequency. If the actual frequency is very high, this indicates that the water conductivity is very high and so the drain cycle should be correspondingly long.
  • the drain cycle may be arranged to last a time proportional to the difference between the actual frequency and the design frequency or, as is preferred, the drain cycle is arranged so that it shuts off when a predetermined value of current is reached this value being proportional to the frequency difference.
  • the point G at which the drain cycle ceases corresponds to 80% current
  • the point H (which is the drain shut-off point after the next three cycles) corresponds to 90% current and so on.
  • Figure la has been drawn for the case where the conductivity of the replenishing water is low and Figure lb represents the case where the replenishing water is much higher in conductivity. It can be seen that the predetermined number of cycles is counted much more quickly, i.e. the actual frequency is much higher, and correspondingly lower values of current are reached before the drain cycles are ceased in the case of Figure lb.
  • Figure 2 is a schematic diagram of an embodiment of the invention.
  • a vaporization container or vessel 1, constructed of a non-corrosive and non-conductive material contains a plurality (two in the embodiment shown) of electrodes 2.
  • the electrodes may be concentric cylindrical tubes or spaced plates and in the embodiment shown are spaced plates vertically disposed and of constant cross-section throughout their height.
  • the electrodes are constructed of a non-corrosive electrically conductive material.
  • the vessel 1 has an opening 3 at the top thereof-for communication with a steam-carrying conduit (not shown) for conveying steam to a space the moisture content or humidity of which is to be controlled.
  • the vessel I has an opening at its bottom, the opening communicating by means of a pipe 5 with a drain valve (solenoid operated in this embodiment) 6.
  • a branch pipe 7 connects opening 4 to a solenoid operated fill valve 8 for supplying replenishing mains water to the vessel.
  • the electrodes 2 are connected to an electrical supply source 8 by means of lead wires 9a and 9b.
  • a current sensing means typically a current transformer 10 or an electrical resistor, is provided in line 9b.
  • the transformer outputs are connected by lead wires lla and llb to a transducer 12 which processes the signals from the current transformer into control signals proportional to the electrode current.
  • the current transformer and transducer together form a measuring device for the current passing between the electrodes.
  • a manual or automatically adjusting variable resistor 13 is provided in line lla so as to permit regulation of the magnitude of the control signal.
  • the output of the transducer 12 is connected via lead 14 to a fill threshold switch 15 which contains a changeover switch having three contacts 15a, 15b and 15c and a movable contact 15a which is movable from the position shown in the solid line to the position shown in the broken line.
  • the threshold switch 15 is constructed so that the movable contact 15d moves to the position shown in solid when the control signal reaches or exceeds a predetermined maximum value fixed in the threshold switch and switches back to the broken line position when the control signal drops to or below a predcternined minimum value fixed in the threshold switch.
  • the value of the control signal is determined by the setting of variable resistor 13 and corresponds to the value of the current which should flow through the electrodes 2 and thus is also a measure of the value of the vaporizing capacity. Since the relationship between the electrode current and the magnitude of the control signal can be set by adjusting the variable resistor 13, the response values of the threshold switch 15 can be adjusted over a wide capacity range of the vaporizer. Whatever the actual current values chosen, typically the maximum and minimum values at which the threshold switches cause changeover of contact 15d represent, respectively, 105% and 95% of the rated or designed current value.
  • transducer 12 is also connected through lead wire 16, an extension of lead 14, to drain thresholds 17a - 17e which are, respectively, fixed to turn off when the control signal drops below a value corresponding to 95%, 90%, 85%, 80%, 75% of the rated electrode current.
  • drain thresholds 17a - 17e which are, respectively, fixed to turn off when the control signal drops below a value corresponding to 95%, 90%, 85%, 80%, 75% of the rated electrode current.
  • additional drain thresholds going down to 40% or so, as necessary, would also be incorporated in the circuit but it is unnecessary to show all of these.
  • a control voltage source 20 is connected via a line 21,22 to contact 15a of the changeover switch.
  • Contact 15b is connected to a cycle counter 23 via line 24 which branches via line 25 to a' start activator 26 which is also connected directly via line 21 to voltage source 20.
  • the start actuator output is connected to the start input of a count down sequencer 27 via lines 28 and 29 and to the reset input of cycle counter 23 via lines 28 and 30.
  • the cycle counter 23 has an output which is connected via line 32 to a series of switches 33a-33f of which switches 33b-33f correspond, respectively to drain thresholds 17a-17e and are shown connected via lines 34.
  • An output line 35 from switch 33a is connected back to the start input of sequencer 27 and the reset input of counter 23.
  • switches 33 and thresholds 17 are shown separately, they may be combined as relays each when energised via line 32 passing a drain opening signal when the predetermined threshold is reached. Accordingly, hereinafter switches 33 will be referred to as relays and it will be understood that thresholds 17 are not separate physical elements but represent preset thresholds of the relays.
  • a line 36 is connected from line 21 to the relays 33 (shown connected to drain thresholds 17) and an output line 37 is connected from the relays 22 (shown connected to the drain thresholds 17a-17e) to a relay 38 which has a normally open contact arranged 38a in the line 37 between the drain thresholds and the solenoid drain valve 6.
  • Relay 38 also has a normally closed contact 38b arranged in a line 40 which connects contact 15c of the changeover switch to solenoid fill valve 8.
  • the count down sequencer 27 is arranged to step through relays 33n to 33a in that order as it counts down from the preset value, for example 20.
  • solenoid fill valve 8 is open to fill or partially fill the vessel 1.
  • the threshold switch 15 causes the changeover switch to move to the position shown in full from the broken line position thus immediately closing the fill valve.
  • the fill threshold switch 15 changes the changeover switch back to the broken line position and fill valve 8 opens again to replenish the vessel with mains water. Again the 105% value is reached and the changeover switch reverts to the solid line position signalling to cycle counter 23 one complete cycle.
  • this signal energises that relay which causes a signal to pass from voltage source 20 to relay 38. This corresponds to point F on Figure la.
  • the cycle counter output signal energises this relay (thus energising from voltage source 20 relay 38) until the current value drops to 80%. It can be seen from Figure la that this current value corresponds to the step (4) to which the sequencer has progressed.
  • the energising of relay 38 causes contact 38a to close thus activating drain valve 6 and causing water to drain from vessel 1.
  • relay 38 could be dispensed with so that when the current value dropped to 95% the fill threshold switch 15 would energise the fill valve 8.
  • relay 38 could be adapted by replacing normally closed contact 38b with a normally open contact connected directly between voltage source 20 and fill solenoid valve 8 so that as soon as drain valve 6 was opened the fill valve would also open.
  • Figure 3 illustrates a modification of the basic techniques described with reference to Figure I.
  • the value to which the count down sequencer 27 is reset depends upon the duration of the previous three cycles.
  • Figure 3a illustrates the case where the mains water is of low conductivity and Figure 3b where the mains water is of high conductivity.
  • the drain cycle is carried out over portion M-N until a threshold current value corresponding to the step to which the sequencer has progressed is reached.
  • the count down sequencer is reset by adding a predetermined number of steps to the steps left on the sequencer at point M.
  • Figure 4a illustrates diagrammatically the difference in water levels inside the vessel for mains water of high conductivity (I) and for mains water of low conductivity (II) using a fixed number of count down steps as explained with reference to Figure 1 and Figures 4b(I) and 4b(II) illustrate the same thing but using a "weighted" number of count down steps.
  • reference numeral 40 indicates the water level in the high conductivity case at which the current is 100% of designed value and the same current value is achieved at water level 41 when the conductivity is low. It can be seen that there is a considerable difference in these levels.
  • the levels 40' and 41' representing the high conductivity and low conductivity levels, respectively, for 100% current are virtually identical and so the vessel can be designed so that this level is near the bottom of the electrodes 2. This is desirable because in this way, the bottom of the electrodes is used first and as this becomes encrusted with deposits the level moves up bringing into use fresh surface portions of the electrodes.
  • a low water level means that the current is passed between a small surface area of the electrodes and the relatively high current density enables great penetration of the build-up of deposits on the electrodes. Thus, the deposits can build-up to a considerable thickness before the current flow is seriously curtailed which means a longer cylinder life.
  • a reset corrector 45 shown in phantom in Figure 2 This has an input connected to relays 33 and an output connected to count down sequencer 27.
  • Reset corrector operates to add to a fixed value (e.g. 15 minutes) in the count down timer 27 the value in minutes corresponding to the relay 33 which has previously been stepped by the count down timer 27 while the cycle counter gave out its output signal.
  • a fixed value e.g. 15 minutes
  • Figure 5 illustrates a variant of the technique shown in Figure 1.
  • the total number of cycles in a predetermined time interval is counted and compared to the number of cycles that would occur in that same time if contained water was at design conductivity.
  • the first interval Tg four cycles are counted and this number has been previously determined as the correct number in the particular time period to give the required conductivity level.
  • the conductivity increases, five cycles are counted in the next interval Tg and a drain cycle is initiated, the extent of the drain cycle depending on the number of counted cycles by which the predetcrnined number, namely 4, is exceeded.
  • the third interval Tg shown the number of cycles counted is 6 and the drain cycle is correspondingly longer. Again, the length of the drain cycle can be made time dependent or can be determined by a current threshold.
  • Figure 6 illustrates a variant of the basic technique shown in Figure 3.
  • the frequency of occurence of a particular leg of the cycles e.g. the boil leg or the fill leg.
  • the boil legs RS, R'S', R"S” etc. or fill legs TR, SR', S'R” etc. are counted in the predetermined duration Tg.
  • the number of boil legs (or fill legs) is the same as the number of cycles, again we are comparing the actual frequency of the cycles with the design frequency.
  • the actual accumulated duration of all the boil legs could be obtained as a measure of the cycle frequency (The accumulated time is, of course, inversely proportional to the frequency). This then would be compared with a value corresponding to the accumulated boil (or fill) time which would be expected for a design frequency.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Life Sciences & Earth Sciences (AREA)
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  • Sustainable Energy (AREA)
  • Physics & Mathematics (AREA)
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  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
EP81105016A 1981-06-29 1981-06-29 Méthode pour faire fonctionner un générateur de vapeur d'eau Withdrawn EP0069155A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP81105016A EP0069155A1 (fr) 1981-06-29 1981-06-29 Méthode pour faire fonctionner un générateur de vapeur d'eau

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP81105016A EP0069155A1 (fr) 1981-06-29 1981-06-29 Méthode pour faire fonctionner un générateur de vapeur d'eau

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EP0069155A1 true EP0069155A1 (fr) 1983-01-12

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0207804A2 (fr) * 1985-07-04 1987-01-07 S.D.I. Water Technology Limited Traitement de l'eau dans les systèmes à recirculation
EP0453384A1 (fr) * 1990-04-18 1991-10-23 Industrielle Du Ponant Sa Générateur de vapeur
JP2017106708A (ja) * 2015-12-07 2017-06-15 荏原冷熱システム株式会社 吸収ヒートポンプ
CN109974249A (zh) * 2019-04-08 2019-07-05 广东美的暖通设备有限公司 加湿器的控制方法、加湿器及空调系统

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3269364A (en) * 1964-03-03 1966-08-30 Bradley C Higgins Automatic adjustable electric control of mineral contents for blowdown in a boiler
US3682141A (en) * 1970-09-02 1972-08-08 Birton Klima Og Koleteknik As Steam generators
FR2186117A5 (fr) * 1972-05-23 1974-01-04 Ozonair Procede
US3937920A (en) * 1973-03-09 1976-02-10 Plascon Ag. Method of operating an electrode-type water-vapor generator
FR2279448A1 (fr) * 1974-07-25 1976-02-20 Luquet Sa H Et A Humidificateur
GB1555502A (en) * 1976-07-22 1979-11-14 Williams Sa Electrode boilers
US4262191A (en) * 1979-03-28 1981-04-14 Wehr Corporation Digital electronic steam humidifier control

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3269364A (en) * 1964-03-03 1966-08-30 Bradley C Higgins Automatic adjustable electric control of mineral contents for blowdown in a boiler
US3682141A (en) * 1970-09-02 1972-08-08 Birton Klima Og Koleteknik As Steam generators
FR2186117A5 (fr) * 1972-05-23 1974-01-04 Ozonair Procede
US3937920A (en) * 1973-03-09 1976-02-10 Plascon Ag. Method of operating an electrode-type water-vapor generator
FR2279448A1 (fr) * 1974-07-25 1976-02-20 Luquet Sa H Et A Humidificateur
GB1555502A (en) * 1976-07-22 1979-11-14 Williams Sa Electrode boilers
US4262191A (en) * 1979-03-28 1981-04-14 Wehr Corporation Digital electronic steam humidifier control

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0207804A2 (fr) * 1985-07-04 1987-01-07 S.D.I. Water Technology Limited Traitement de l'eau dans les systèmes à recirculation
EP0207804A3 (en) * 1985-07-04 1988-07-20 Sdi Water Tech Ltd The management of water in recirculatory water systems
EP0453384A1 (fr) * 1990-04-18 1991-10-23 Industrielle Du Ponant Sa Générateur de vapeur
FR2661233A1 (fr) * 1990-04-18 1991-10-25 Ponant Ind Generateur de vapeur.
JP2017106708A (ja) * 2015-12-07 2017-06-15 荏原冷熱システム株式会社 吸収ヒートポンプ
CN109974249A (zh) * 2019-04-08 2019-07-05 广东美的暖通设备有限公司 加湿器的控制方法、加湿器及空调系统

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Inventor name: MOFFATT, LARRY JAMES

Inventor name: HOWARD-LEICESTER, MICHAEL

Inventor name: GUNDACKER, SIEGBERT