EP0508942B1 - Verfahren und Einrichtung zur Regelung eines Dampferzeugers - Google Patents

Verfahren und Einrichtung zur Regelung eines Dampferzeugers Download PDF

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Publication number
EP0508942B1
EP0508942B1 EP19920810152 EP92810152A EP0508942B1 EP 0508942 B1 EP0508942 B1 EP 0508942B1 EP 19920810152 EP19920810152 EP 19920810152 EP 92810152 A EP92810152 A EP 92810152A EP 0508942 B1 EP0508942 B1 EP 0508942B1
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EP
European Patent Office
Prior art keywords
current
water
standardised
time
calculated
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.)
Expired - Lifetime
Application number
EP19920810152
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German (de)
English (en)
French (fr)
Other versions
EP0508942A2 (de
EP0508942A3 (en
Inventor
Heiner Grieder
Rudolf Fackler
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
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Condair AG
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Publication of EP0508942A2 publication Critical patent/EP0508942A2/de
Publication of EP0508942A3 publication Critical patent/EP0508942A3/de
Application granted granted Critical
Publication of EP0508942B1 publication Critical patent/EP0508942B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • F24F6/18—Air-humidification, e.g. cooling by humidification by injection of steam into the air

Definitions

  • the invention relates to a method for controlling a steam generator used in particular for air humidification according to the preamble of claim 1, and to a device for carrying out the method according to the preamble of claim 7.
  • evaporator also called an electrode evaporator
  • a single or multi-phase alternating current is passed through the water via two or more electrodes and the water itself is used as a heating resistor for generating the heat required for the evaporation.
  • the evaporated amount of water is automatically replaced by fresh water at certain intervals.
  • the steam output is determined in normal operation, i.e. apart from starting processes and other malfunctions and special cases, and for a given geometry of the steam generator by the heating current. This depends primarily on two parameters: the immersion length of the electrodes and the electrical conductivity of the water.
  • the known electrode evaporators use an intermittent cycle of filling and draining Water to regulate these two quantities that determine the current strength. During the evaporation process, the water level drops and the current strength decreases according to a certain characteristic.
  • the immersion length of the electrodes can be brought to a desired value in a simple manner by filling in fresh water at certain time intervals and, if appropriate, by draining water. Mastering the conductivity of the water is more difficult. This must be adjustable for two reasons.
  • the water composition especially the mineral salt content, and thus the conductivity, varies greatly from place to place.
  • the constituents determining conductivity are not also evaporated, so that their concentration increases continuously in the course of the evaporation process, which continuously increases the conductivity. This increase is desirable if the conductivity of the fresh water is too low, but it also leads to undesirably high conductivity.
  • part of the water enriched with conductivity-determining constituents is therefore also drained off at certain time intervals and replaced with fresh water. In continuous operation, this results in a repeated sequence of filling phase, steam phase and, if necessary, drain phase, the devices being designed in such a way that steam is also generated during the filling and drain phases.
  • a drainage duration is calculated from the remaining time span while the water is being drained off.
  • Another method can be found in Swiss Patent Specification No. 672 015.
  • the fact is taken advantage of that the heating current increases a little further after the end of the filling, before it drops again, and that the shape of the "current peak" thus formed depends on the conductivity of the water.
  • water is drained off when a characteristic parameter, preferably the duration of the current peak, exceeds a predetermined limit value.
  • the clocked direct control of the heating current intensity used according to the invention achieves a significantly faster and more precise control of the steam output than is possible with controls via the level control of the water level according to the prior art.
  • the response time is determined by the period of the clock signal, which will generally be from about 100 milliseconds to one second.
  • control dynamics are additionally blocked for a period of time required to determine the conductivity, usually in the order of magnitude of 10 to 100 seconds, while in contrast to this
  • the method according to the invention can be used for continuous control.
  • a steam generator is shown schematically in FIG. 1, together with a block diagram of a control and regulating device according to the invention.
  • the Container 2 is filled to an indicated level with water.
  • a pair of electrodes 4 are partially immersed in the water.
  • the electrodes can be connected to an electrical AC voltage network via lines 6.
  • the connection is usually made via a switching element (not shown), for example via a contactor.
  • a combined inlet / outlet 8 This comprises a feed line 10 and a drain line 12.
  • the feed line can be connected, for example, to a water supply network, and the discharge line, for example, to a sewage line that leads into the public sewage system or a any wastewater reservoir opens out.
  • Both Zuals and derivation are each provided with an electrically controllable valve 14 and 16.
  • a steam outlet 18 In the ceiling of the container 2 there is a steam outlet 18, via which the generated steam exits directly or via a distribution system or via an air conditioning system into a room to be humidified, such as a common room for people, a highly air-conditioned production system, a laboratory or an air-conditioned equipment cabinet can.
  • the electrodes 6 are connected to the AC voltage via a power controller 20 which can be controlled by a clock signal and with which the current in the electrodes can be controlled in a clocked manner.
  • the power controller 20 is preferably a power semiconductor component, for example a triac. This type of power control is known in principle, the use according to the invention is discussed in more detail below.
  • the current flowing in the electrodes is included a current sensor 22, for example a current transformer.
  • a request signal y which represents a steam output setpoint and is generated, for example, by a moisture measuring and control device or according to a fixed program, serves as a reference variable for the current control.
  • An electronic current control device 24 has a control logic part 26, a device adaptation part 28 and a clock generator 30.
  • the clock generator 30 is electrically connected to the power controller 20 and the current sensor 22 to the control logic part 26.
  • the request signal y is introduced into the device adaptation part 28.
  • An electronic water control device 32 has a current normalization part 34, a demand standardization part 36 and a drain / fill control 38.
  • the current normalization part 34 is electrically connected to the control logic part 26.
  • the controllable valves 14 and 16 of the supply and discharge for the water are electrically connected to the drain / fill control 38.
  • the current control and water regulation device are provided with a parameter input device 40 and a display device 42.
  • the function of the current control device 24 and the water control device 32 is explained below. These devices can be implemented electronically in a variety of configurations known to the person skilled in the art. Digital components are preferably used, in particular an appropriately programmed microprocessor.
  • FIG. 2 two diagrams a) and b) can be seen, both of which show the profile of an alternating current i and an associated clock signal s.
  • the above-mentioned power controller 20 is controlled with the clock signal, so that it passes the current during the pulse duration and blocks during the remaining time.
  • An effective average current I d per pulse period is therefore dependent on the duty cycle and can be controlled by changing this duty cycle.
  • Diagram a) shows a longer duty cycle and diagram b) shows a shorter one.
  • the peak value of the alternating current is not influenced in this type of control, the peak values are drawn differently in the two diagrams.
  • semiconductor components are preferably used as the power controller 20, which only switch after the clock signal has been switched on or off close to the subsequent zero crossing of the alternating current.
  • half-wave packet control a single current packet always consists of a number of whole half-waves (cf. FIG. 2).
  • the clock signal s is preferably controlled such that always two successive half-wave packets form a common control packet in which both half-wave packets have the same number of half-waves, but the second half-wave packet is antisymmetric with respect to the first axis with respect to the zero axis. 2, the first two half-wave packets each form such a control packet.
  • the direct current components are formed into low-frequency alternating current components that cannot have any adverse effects.
  • there are indications that such low-frequency alternating currents can delay or even prevent the formation of limescale in tap water systems, which would advantageously extend the operating life and service life of steam generators according to the invention.
  • the required steam power that is to say the required effective average current I d in the electrodes
  • the request signal y is processed in the device adaptation part 28 taking into account the system boundary conditions (mains voltage, device type, possible limitations, etc.) and then fed to the control logic part 26.
  • the control variable, the alternating current in the electrodes is determined by the current sensor 22 as real current, rectified and also supplied to the control logic part 26 as an electrical signal.
  • the control logic part calculates the acting average current by integrating this signal over each pulse period T, prepares it for one the value comparable to the request signal y and calculates a newly adapted duty cycle V for the clock signal s from the deviation.
  • the clock 30 is operated with the new duty cycle V, and this controls the power controller 20 with a correspondingly adapted clock signal s.
  • the control logic part 26 also ensures that the control packets mentioned above are each generated with two antisymmetric half-wave packets.
  • the control of the current according to the invention has two objectives compared to the prior art.
  • First, the current change occurring during the filling phase-vapor phase-drain phase by changing the water level should be compensated for and secondly, the current should be controlled practically continuously according to the request signal y. 3 serves to explain the compensation of the current change caused by the changing water level.
  • This represents a schematic current-time diagram over a cycle of filling phase of a duration T E , vapor phase of a duration T D , discharge phase of a duration T A , in which as An example of a possible process profile is an uncontrolled current profile 44 and a current profile 46 controlled according to a constant request signal of 100%.
  • the uncontrolled current profile 44 basically follows the water level, that is to say it rises during the filling phase, then decreases as evaporation progresses during the vapor phase and falls further during the draining phase until it rises again during the subsequent filling phase.
  • these changes are compensated for by appropriate adaptation of the pulse duty factor of the clock signal, so that the average current to for small deviations consistently 100%.
  • the circled slots in the figure show the associated clock signal and the pulse duty factor (in percent) for characteristic points.
  • the duty cycle corresponding to a requirement of 100% must be less than 100%; it is therefore chosen, for example, as shown in FIG. 3, that 100% requirement corresponds to 80% duty cycle.
  • FIG. 5 shows a current curve 48 controlled according to a variable request signal in a current-time diagram similar to FIG. 3.
  • a controlled current flow cannot be used directly to regulate the water balance, that is to say to regulate the filling and draining phases, as is the case with the methods according to the prior art, since it is precisely the influences of the quantities to be regulated and the water level and electrical conductivity can be compensated.
  • the invention therefore uses its own procedure to calculate a current profile normalized to uncontrolled operation from the controlled current profile.
  • Curve 52 in FIG. 5 shows such a normalized current profile with a start at the beginning of the vapor phase T D.
  • the normalized current profile corresponds to a fictitious uncontrolled current profile and can therefore be used to determine the water level and electrical conductivity, for example using one of the known methods .
  • the start of the normalized current flow does not necessarily have to be at the beginning of the vapor phase, but can be freely selected depending on the method used.
  • the normalized current profile is calculated in the current normalization part 34, which receives the information required for this from the control logic part 26 about the measured average current and the clock signal.
  • the invention proposes in a preferred embodiment a new method for determining the suitable length of the steam and discharge phase. This method is based on the idea of comparing the measured sequence represented by the normalized current profile with a theoretical sequence calculated from the profile of the request signal.
  • the theoretical process describes how the evaporation process should take place under ideal conditions, i.e. with ideal electrical conductivity of the water and without disturbing influences such as limescale deposits on the electrodes, blistering in the heated water, etc.
  • An ideal average pulse duration t e is used for the theoretical sequence id of the clock signal, which is matched to a request of 100%, weighted with the respective value y i of the request signal y, that is to say an ideal time t id is calculated by summing up the values y i multiplied by the ideal pulse duration.
  • the ideal pulse duration is a theoretical mean value over the entire dynamic range related to the water balance and can be determined for each specific type of steam generator. 3, for example, the ideal pulse duration would be 80% of the clock period.
  • the regulation of the water balance can proceed as follows, for example.
  • the (increasing) normalized current is monitored, and as soon as this reaches a first predetermined value I 1, the filling is ended, so that the pure vapor phase begins.
  • the calculation of the standardized time t n and the ideal time t id is started.
  • the normalized current drops in a manner dependent on the current control and the electrical conductivity of the water.
  • the calculation of the normalized and the ideal time is stopped. Between the start and the stop of the calculation, a certain number of m clock periods have expired. This results in two time periods, namely a standardized time period and an ideal length of time
  • the difference between these two time periods can be used to calculate the length of the drain phase necessary to reset the electrical conductivity of the water, based on a function optimized for the steam generator type. If the standardized time period corresponded to the ideal time period, if the evaporation process had run ideally, no water would have to be drained off and the next filling phase could be started directly.
  • the method just described is implemented by the water control device 32.
  • the current normalization part 34 takes care of the calculation of the normalized current and the normalized time.
  • the calculation of the ideal time from the respective value of the request signal is carried out by the request normalization part 36.
  • the drain / fill control 38 controls the valves 14 and 16. It receives the respectively calculated value of the normalized current from the current normalization part 34. As soon as this reaches the value I 1 during the filling phase, the drain / filling control 32 closes the valve 14 and starts the calculation of normalized and ideal time periods T n and T id .
  • the drain / fill control stops the calculation of the normalized and ideal time period, determines a drainage period from the difference between these time periods, opens during this drainage period Valve 16 and then begins the next filling phase with the opening of valve 14, with which the next water balance cycle begins.

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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)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Air Humidification (AREA)
EP19920810152 1991-04-12 1992-03-02 Verfahren und Einrichtung zur Regelung eines Dampferzeugers Expired - Lifetime EP0508942B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH1096/91 1991-04-12
CH109691A CH682177A5 (enrdf_load_stackoverflow) 1991-04-12 1991-04-12

Publications (3)

Publication Number Publication Date
EP0508942A2 EP0508942A2 (de) 1992-10-14
EP0508942A3 EP0508942A3 (en) 1993-05-19
EP0508942B1 true EP0508942B1 (de) 1995-06-14

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EP19920810152 Expired - Lifetime EP0508942B1 (de) 1991-04-12 1992-03-02 Verfahren und Einrichtung zur Regelung eines Dampferzeugers

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EP (1) EP0508942B1 (enrdf_load_stackoverflow)
CH (1) CH682177A5 (enrdf_load_stackoverflow)
DE (1) DE59202490D1 (enrdf_load_stackoverflow)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000017575A1 (de) * 1998-09-22 2000-03-30 Axair Ag Dampferzeuger mit abnehmbarem kalkaufnahmebehälter
DE602004019658D1 (de) * 2004-11-19 2009-04-09 Whirlpool Co Dampferzeuger für Gargeräte
WO2010042461A1 (en) 2008-10-06 2010-04-15 Sharma Virender K Method and apparatus for tissue ablation
EP2226583A1 (en) * 2009-03-02 2010-09-08 Koninklijke Philips Electronics N.V. Electrical water heating system
RU2566846C2 (ru) 2010-07-22 2015-10-27 Конинклейке Филипс Электроникс Н.В. Предотвращение или уменьшение образования накипи на нагревательном элементе водонагревателя
AU2011374994B2 (en) * 2011-08-16 2017-04-20 Wood Stone Ideas Llc Steam generator system
CN113015494A (zh) * 2018-06-01 2021-06-22 圣安娜技术有限公司 多级蒸汽消融治疗方法以及蒸汽产生和输送系统
CN109882979B (zh) * 2019-01-30 2021-09-24 青岛海尔空调电子有限公司 一种加湿器及其控制方法、空调、存储介质
CN110260439B (zh) * 2019-05-23 2021-12-17 青岛海尔空调电子有限公司 加湿器、加湿器的控制方法和机房空调
BE1028883A9 (de) * 2020-12-14 2022-07-25 Miele & Cie Heizvorrichtung zum Erhitzen von Wasser sowie wasserführendes Gerät mit einer Heizvorrichtung

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4705936A (en) * 1985-01-17 1987-11-10 Masco Corporation Electronically controlled electric steam humidifier
CH672015A5 (en) * 1986-11-19 1989-10-13 Nordmann Engineering Ag Generating steam to moisture air - monitoring current to check conductivity of water and regulating top-up and drainage

Also Published As

Publication number Publication date
EP0508942A2 (de) 1992-10-14
CH682177A5 (enrdf_load_stackoverflow) 1993-07-30
DE59202490D1 (de) 1995-07-20
EP0508942A3 (en) 1993-05-19

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