EP1010937A1 - Mikroprozessor gesteuerter elektrischer Dampferzeuger ohne separate Sensoren - Google Patents

Mikroprozessor gesteuerter elektrischer Dampferzeuger ohne separate Sensoren Download PDF

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Publication number
EP1010937A1
EP1010937A1 EP99204312A EP99204312A EP1010937A1 EP 1010937 A1 EP1010937 A1 EP 1010937A1 EP 99204312 A EP99204312 A EP 99204312A EP 99204312 A EP99204312 A EP 99204312A EP 1010937 A1 EP1010937 A1 EP 1010937A1
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EP
European Patent Office
Prior art keywords
heating element
steam
temperature
water
flow heater
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.)
Granted
Application number
EP99204312A
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English (en)
French (fr)
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EP1010937B1 (de
Inventor
Bernardus Johannes Maria Leerkotte
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Nederlandsche Apparatenfabriek NEDAP NV
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Nederlandsche Apparatenfabriek NEDAP NV
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Publication of EP1010937A1 publication Critical patent/EP1010937A1/de
Application granted granted Critical
Publication of EP1010937B1 publication Critical patent/EP1010937B1/de
Anticipated expiration legal-status Critical
Expired - Fee Related 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
    • F22B1/288—Instantaneous electrical steam generators built-up from heat-exchange elements arranged within a confined chamber having heat-retaining walls

Definitions

  • the invention relates to an electronic, microcontroller-controlled apparatus whereby, par unit of time, a specific amount of steam is procuced. Depending on the type of the apparatus, this invention enables controlling the pressure and the humidity of the egressing steam.
  • the non-evaporated water is entrained in the water vapor to the outlet of the steam generator.
  • the water/steam ratio determines the humidity.
  • steam generators consisting of a boiler having a content of from half a liter to a few liters. At the bottom of the boiler, an electric heating element is located. With these steam generators, the energy supply to the heating element is switched off by means of a pressure sensor when the pressure of the boiler exceeds a particular value or when the temperature becomes too high. Most types involve an open communication with the outside air.
  • the invention provides a solution to the above-mentioned drawbacks by using a through-flow heater having a small volume and a great electric power density for transferring the required energy to the water in the form of heat.
  • the mass of the through-flow heater is small, so that little energy is required for heating up the through-flow heater itself to the required temperature.
  • the resistance in which the electric energy supplied is converted into heat is so arranged that the available heat can be transferred to the water very directly.
  • Fig. 1 shows the principle of an electric through-flow heater based on a heating element utilizing a dissipating resistance designed in thick-film technology, enabling the heat generated to be transferred to the rest of the element very directly.
  • Fig. 2 shows the block diagram of an electronic circuit with which the principle of temperature measurement and the operation of the control of the steam generator will be explained.
  • Fig. 3 shows the setup of a steam generator which draws the water to be evaporated from a pressureless reservoir.
  • Fig. 4 shows a circuit wherein the feed to the heating element is switched off in the event of a failure of the microcontroller or the electric control of the heating element is interrupted if an error occurs in said circuit.
  • Fig. 5 shows the side of a heating element on which a resistance track is provided between thin insulating and protective layers.
  • Fig. 6 shows a spiral-shaped labyrinth in which the water flows while it is being heated up by the underlying heating element.
  • Fig. 7 shows the side of a heating element on which a resistance track is provided between thin insulating and protective layers as in Fig. 5, but here, the resistance track is spiral-shaped.
  • Fig. 8 shows a spiral-shaped labyrinth in which the water flows while it is being heated up by the underlying heating element which, in contrast with Fig. 6, is spiral-shaped.
  • Fig. 9 shows graphs of the temperature distribution of the water in the through-flow heater at four different pumping rates as a function of the position in the spiral-shaped labyrinth.
  • Fig. 10 shows a graph of the increase in resistance relative to the resistance of a specific heating element at 0°C as a function of the optimal flow (F) at which all the water pumped in is precisely entirely evaporated at the outlet of the through-flow heater.
  • a heating element (2) on the basis of thick-film technology is used. With this type of heating elements, it is presently possible to dissipate powers up to about 60 watt per cm 2 .
  • the thick-film resistance (23) (Fig. 5) is thermally and mechanically coupled to a slightly spherical support (2) (Fig. 1), which may be of stainless steel (SS) design.
  • the thickness of the SS is about 1 mm.
  • the electric connection to the heating element is effected by means of an adapter (6) (Fig. 1), which establishes the connection to the ends of the heating track (24) (Fig. 5) by means of spring contacts.
  • the supply voltage is connected to the terminals (7) (Fig. 1).
  • the through-flow heater (Fig.
  • a spiral-shaped object of a high melting point and a high thermal resistance and a low specific heat can be fitted in this space, which object provides that the water supplied at (1) (see also 26 (Fig. 6) or 28 (Fig. 8)) flows along the outer side of this spiral in a spiral-shaped labyrinth towards the center and can leave the outlet (5) (see also 27 (Fig. 6) or 29 (Fig. 8)) in the form of steam and together with any unevaporated water.
  • An advantage of the use of a spiral is that the through-flow heater can also be used at an angle of inclination of more than 45° without there being formed unduly hot spots on the heating element.
  • the spiral-shaped labyrinth (25) (Fig. 6) mentioned may form an integral part of a plastic cover for forming the through-flow heater (Fig. 1) together with the heating element (2).
  • the current through the heating element (15) is measured by converting the current through the low-ohmic measuring resistance (14) into a voltage.
  • This measured AC voltage is fed to the electronic circuit (12) which amplifies the measured voltage slightly and subsequently converts it into a DC voltage which is proportional to the AC current through the measuring resistance (14).
  • the current through measuring resistance (14) is influenced by the temperature variation over the heating track (11) of the heating element (15), which is the result of the positive temperature coefficient of the resistance material of the heating track.
  • the desired temperature can be set and, by the control, be maintained.
  • V ref reference voltage
  • a user interface consisting of a few keys and a display, which are connected to the microcontroller (not shown), specific settings (such as pressure, steam humidity and flow) can be effected and it can be checked, via the display, what is the status of the apparatus.
  • the microcontroller (8) can maintain the temperature by controlling the pump capacity to a lower value. Due to the above-mentioned control properties of the invention, the system recognizes within a few tenths of a second that the water supply stagnates due to a defective pump or pump control, or simply because the water has run out. Upon the consequently detected rise of the temperature, the microcontroller will stop the current supply to the heating element (15) by means of triac Trl. Hence, this provides a very fast boiling-dry protection. In the control system described so far, the temperature cannot be measured after switching off of the heating element (15).
  • the microcontroller can switch the water pump (16) on and off in fast alternation to control the water flow at the inlet (1) (Fig. 1).
  • triac Tr1 (and also triac Tr2) is controlled by the microcontroller (8) in such a manner that after a control interruption, a positive half period of the sine voltage (0-180°) is succeeded by a negative half period (180-360°) and vice versa, so that line interference is prevented.
  • the measured voltage on the measuring resistance (14) will not be an uninterrupted sine shape.
  • circuit (12) uses the amplitude of the voltage, the temperature measurement can be continued normally, with the understanding that due to the time constant for smoothing the signal from the rectifier of circuit (12), this output voltage will decrease, which will have to be corrected in the software.
  • Fig. 3 schematically represents a possible application of the invention, which could be used in a steam cleaner, sauna or any other apparatus requiring a stable supply of steam for a proper operation.
  • the apparatus provides a pump (18) controlled by the electronics (21) and capable of building up sufficient pressure for supplying water also if the steam pressure rises, the through-flow heater (19) and, when this is desired in the apparatus, an electronically settable excess pressure valve (20), whereby it is achieved that through a further rise of temperature, the pressure in the through-flow heater (19) will increase to a value equal to the set pressure value of the excess pressure valve, as a result of which the excess pressure valve will open and steam will egress at an increased pressure. Because of the distribution in the resistance values of the different heating elements produced, this invention provides a system for automatically performing a calibration of the temperature during the operative mode of the apparatus, for instance each time at the startup. For this, use is made of the boiling point of water under atmospheric conditions. To this end, the excess pressure valve (20), if present in the apparatus, is fully opened electronically.
  • the pump (18) is set in operation by the electronics (21) for so long that the through-flow heater of Fig. 1 is filled with water for more than 50%, so that the hollow heating element is entirely filled. After that, electric energy is transmitted at maximal power to the through-flow heater (19). By the manner of temperature measuring described, it will be detected that the temperature of the heating element (2) (Fig. 1) will rise.
  • the derived measuring value is stored in a nonvolatile memory and can thereafter be used as reference point to enable measuring other temperatures as well through calculation, since the properties of the heating element are known after that. Because said calibration is also performed during the testing of the apparatus in the factory, a temperature determination can already be performed within one second after the heating element has been switched on. The result of this measurement is a good approximation for the water temperature in the reservoir (17) (Fig. 3). Because the energy required for heating 1 gram of water from 20°C to 100°C is only 334 Joule ( ⁇ 12.9%), while said heating and evaporating (at 100°C) of this quantity requires 2590 Joule of energy, an error of 10°C in the determination of water temperature in the reservoir (17) (Fig.
  • said temperature measurement/pressure determination is also possible with conventional heating elements in a boiler (see present state of the art), in respect of which allowance should be made for the longer response times and, accordingly, the possible occurrence of dangerous situations.
  • said through-flow heater and electronics it is possible to generate steam of a predetermined mass per unit of time, a predetermined humidity and a predetermined pressure.
  • the pump (16 (Fig. 2) and 18 (Fig. 3)) will pump a specific amount of water per minute into the through-flow heater. This water will be passed via the spiral-shaped labyrinth (Figs. 6 and 8) to the center of the heating element.
  • Figs. 5 and 7 show two embodiments of the thick-film resistances on the heating element.
  • the track of the heating element of Fig. 7 has a longer lifetime. If the pump (16 (Fig. 2) and 18 (Fig. 3)) at a given power pumps too little water into the through-flow heater, all the water will already be converted into steam before reaching the outlet (see 5 (Fig. 1), 27 (Fig. 6) and 29 (Fig. 8)). Because the heat transfer to steam is much poorer than to water, the temperature of the heating element will rise substantially at those locations. The resistance of the heating track is in fact determined by three temperature areas (Fig. 9):
  • Graph B is the graph where the amount of water pumped into the through-flow heater (Fig. 1) has precisely evaporated when reaching the outlet (5).
  • the heating up to this boiling point takes 12.9% of the available power. This power is used in the first 13% of the passage through the spiral labyrinth.
  • the flow is lower by a factor of 2, so that the path in the labyrinth in which the water boils is reduced to half the path in graph B.
  • the resistance of the heating element is the result of the sum of the resistances of the three temperature areas mentioned.
  • Fig. 10 shows how the resistance, relative to the resistance at 0°C, represented by the vertical axis, depends on the flow and the prevailing pressure (at atmospheric pressure or during the use of an electronically controlled excess pressure valve (20) (Fig. 3)), at a constant power.
  • the heating track at a given position is at approximately the same temperature as the water flowing past on the other side of the heating element.
  • a graph as shown in Fig. 10 can be derived.
  • 'optimal flow (F)' is understood to mean the through-flow at which all the supplied water, during its complete course through the spiral labyrinth, has precisely evaporated completely.
  • the resistance calculated by the microcontroller can be related to the steam humidity of 0% at a boiling point associated with the prevailing atmospheric pressure.
  • the microcontroller can increase the steam humidity by increasing the pump power, or by reducing the power to the heating element.
  • the power is reduced, less water can be converted into steam, as a result of which the control is no longer at a point of optimal flow of a graph.
  • a halving of the supplied power to the heating element will shift the working point of the control to the point 2x the optimal flow (F).
  • Deviations relative to the theory here described in a specific embodiment of an apparatus caused by the differences in resistance occurring in the hoses and accessories connected to the outlet (5) (Fig. 1), are corrected by software per type of apparatus by means of measurements of the properties of the relevant type of apparatus.
  • Relay RY1 (Fig. 4) has a make-contact whereby, in cases of failure, the heating element (15) (Fig. 2) can be switched off.
  • the relay will de-energize if the program in the microcontroller is not or no longer properly performed. In that case, the lower terminal pin of capacitor C1 will no longer be provided with a block-shaped signal. Accordingly, transistor T3 will start to block, so that C2 will start to charge itself to such an extent that the base current from transistor T1 becomes so low that this transistor starts to block as well. As a result, the relay RY1 will de-energize and contact ryl is opened.
EP19990204312 1998-12-15 1999-12-15 Mikroprozessor gesteuerter elektrischer Dampferzeuger ohne separate Sensoren Expired - Fee Related EP1010937B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL1010813A NL1010813C2 (nl) 1998-12-15 1998-12-15 Een microcontroller gestuurd apparaat dat door middel van elektriciteit op een beheerste wijze stoom genereert zonder gebruikmaking van afzonderlijke sensoren.
NL1010813 1998-12-15

Publications (2)

Publication Number Publication Date
EP1010937A1 true EP1010937A1 (de) 2000-06-21
EP1010937B1 EP1010937B1 (de) 2003-09-03

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EP19990204312 Expired - Fee Related EP1010937B1 (de) 1998-12-15 1999-12-15 Mikroprozessor gesteuerter elektrischer Dampferzeuger ohne separate Sensoren

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EP (1) EP1010937B1 (de)
DE (1) DE69910960D1 (de)
NL (1) NL1010813C2 (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1516632A1 (de) * 2003-09-16 2005-03-23 Scican, a division of Lux and Zwingenberger Ltd. Verfahren und Vorrichtung zur Dampfsterilisation
US7801424B2 (en) 2006-02-20 2010-09-21 Technical (Hk) Manufacturing Limited Steam generator
EP1484961B2 (de) † 2002-03-15 2016-09-07 DeLaval Holding AB Verfahren und anordnung in einem melkbetrieb
CN114263953A (zh) * 2021-12-29 2022-04-01 华帝股份有限公司 一种蒸汽清洗的恒蒸气量控制方法及应用其的吸油烟机

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3232169A1 (de) * 1982-08-30 1984-03-01 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Verfahren zum regeln einer widerstandslast mit temperaturkoeffizent und schaltung fuer die durchfuehrung des verfahrens
EP0333916A2 (de) * 1988-03-22 1989-09-27 Heraeus-Wittmann Gmbh Verfahren zur Temperaturregelung von Widerstandsheizleitern
EP0595292A1 (de) * 1992-10-28 1994-05-04 Planeta Hausgeräte GmbH & Co. Elektrotechnik KG Kombinierbarer Dampferzeuger
DE19509772C1 (de) * 1995-03-17 1996-07-11 Draegerwerk Ag Elektrisch beheizter Wärmetauscher
JPH109506A (ja) * 1996-06-20 1998-01-16 Juki Corp 蒸気発生装置

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3232169A1 (de) * 1982-08-30 1984-03-01 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Verfahren zum regeln einer widerstandslast mit temperaturkoeffizent und schaltung fuer die durchfuehrung des verfahrens
EP0333916A2 (de) * 1988-03-22 1989-09-27 Heraeus-Wittmann Gmbh Verfahren zur Temperaturregelung von Widerstandsheizleitern
EP0595292A1 (de) * 1992-10-28 1994-05-04 Planeta Hausgeräte GmbH & Co. Elektrotechnik KG Kombinierbarer Dampferzeuger
DE19509772C1 (de) * 1995-03-17 1996-07-11 Draegerwerk Ag Elektrisch beheizter Wärmetauscher
JPH109506A (ja) * 1996-06-20 1998-01-16 Juki Corp 蒸気発生装置

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 098, no. 005 30 April 1998 (1998-04-30) *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1484961B2 (de) † 2002-03-15 2016-09-07 DeLaval Holding AB Verfahren und anordnung in einem melkbetrieb
EP1815737B1 (de) 2002-03-15 2018-04-25 DeLaval Holding AB Anordnung für einen Milchwirtschaftsbetrieb
EP1516632A1 (de) * 2003-09-16 2005-03-23 Scican, a division of Lux and Zwingenberger Ltd. Verfahren und Vorrichtung zur Dampfsterilisation
US7476369B2 (en) 2003-09-16 2009-01-13 Scican Ltd. Apparatus for steam sterilization of articles
US7801424B2 (en) 2006-02-20 2010-09-21 Technical (Hk) Manufacturing Limited Steam generator
CN114263953A (zh) * 2021-12-29 2022-04-01 华帝股份有限公司 一种蒸汽清洗的恒蒸气量控制方法及应用其的吸油烟机
CN114263953B (zh) * 2021-12-29 2023-10-20 华帝股份有限公司 一种蒸汽清洗的恒蒸气量控制方法及应用其的吸油烟机

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Publication number Publication date
NL1010813C2 (nl) 2000-06-19
DE69910960D1 (de) 2003-10-09
EP1010937B1 (de) 2003-09-03

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