EP0451416B1 - Ohmscher Erhitzer - Google Patents

Ohmscher Erhitzer Download PDF

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Publication number
EP0451416B1
EP0451416B1 EP90314168A EP90314168A EP0451416B1 EP 0451416 B1 EP0451416 B1 EP 0451416B1 EP 90314168 A EP90314168 A EP 90314168A EP 90314168 A EP90314168 A EP 90314168A EP 0451416 B1 EP0451416 B1 EP 0451416B1
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EP
European Patent Office
Prior art keywords
electrodes
vessel
ohmic heater
electrically conductive
fluid
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
EP90314168A
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English (en)
French (fr)
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EP0451416A1 (de
Inventor
David Preston Dr. Simpson
Robert Dr. Stirling
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.)
EA Technology Ltd
Original Assignee
EA Technology Ltd
Electricity Association Services Ltd
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Publication date
Application filed by EA Technology Ltd, Electricity Association Services Ltd filed Critical EA Technology Ltd
Priority to AT90314168T priority Critical patent/ATE93605T1/de
Publication of EP0451416A1 publication Critical patent/EP0451416A1/de
Application granted granted Critical
Publication of EP0451416B1 publication Critical patent/EP0451416B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
    • F24H1/10—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium
    • F24H1/101—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium using electric energy supply
    • F24H1/106—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium using electric energy supply with electrodes

Definitions

  • This invention relates to an ohmic heater, which heats a fluid by passing an electric current through the fluid.
  • This type of heater is used for fluids which require heating but which might foul or block conventional heaters.
  • transverse ohmic heaters in which the current is passed between electrodes transversely, or perpendicular to the flow of the fluid.
  • some of the current may flow to earthed components in the apparatus such as the ends of the connecting pipes to and from the heater. This is termed a leakage current, and can give rise to unacceptably high levels of electrolytic corrosion or fouling of the pipe ends which carry these currents.
  • FR 964733 discloses an ohmic heater for heating a fluid which has three electrodes equally spaced about the axis of flow of fluid. The electrodes are connected to separate phases of a three phase supply in order to heat the fluid ohmically.
  • the present invention provides an ohmic heater for heating a fluid
  • a vessel having inlet and outlet ports arranged at opposite ends of said vessel and between which said fluid flows when in use, along an axis; at least two electrodes arranged to be equally spaced about said axis of flow and contained within said vessel; and means to supply electric power to said electrodes such that the electric potential at any time on said axis is substantially zero relative to earth; characterised in that said inlet and outlet ports are arranged to lie on said axis, and an electrically conductive guard ring is positioned around the periphery of each of said ports, and exposed to the flow of fluid in use; said electrically conductive guard ring being connected to earth or a neutral point in use.
  • the present invention provides further a method of operating an ohmic heater according to claim 14.
  • This arrangement has the advantage in that the fluid along the axis of flow is maintained at or near earth potential, so that current leakage to pipe ends is significantly reduced.
  • the vessel is electrically insulating and said electrodes are adjacent to the walls of the vessel.
  • Said electrodes may be arranged to extend parallel to said axis of said fluid flow where electrical conductivity of the fluid remains relatively constant along the length of the electrodes, in the flow direction, in order to provide a uniform current density over the length.
  • said electrodes may be arranged such that their separation transverse to said axis increases along said axis in the direction of flow of said fluid. This arrangement compensates for the linear increase in conductivity with temperature by increasing the separation of the electrodes, thus maintaining a uniform current density over the length.
  • FIG. 1 and 2 illustrate an embodiment of the present invention in which electrodes 1 are arranged to be parallel to the flow of the fluid to be heated.
  • the vessel 2 comprises three parts:- a cylindrical main body 2a, a top end plate 2b and a bottom end plate 2c.
  • the top end plate 2b has a flange 3a which is connected to an upper flange 3b of the cylindrical main body 2a, by bolts.
  • the bottom end plate 2c has a flange 3d that is connected to a lower flange 3c of the cylindrical main body 2a, also by bolts.
  • the vessel 2 is constructed from a suitable electrically-insulating material and of such wall thickness as to adequately withstand the internal pressures applied or generated in the heater - for example by any tendency for the heated fluid to boil.
  • the top end plate 2b has a outlet port 4 in the centre.
  • the internal surface of the top end plate 2b tapers from the internal diameter of the cylindrical main body 2a to the diameter of the outlet port 4.
  • the outlet port 4 is arranged to form a connection with an output pipe 5 by the coupling of flanges 6 and 7 of the outlet port 4 and the output pipe 5 respectively.
  • a guard ring 8 Surrounding the outlet port 4 within the flange 6, there is a guard ring 8 which is electrically connected to earth by a metallic gasket 9.
  • top end plate 2b At regular spacings around the upper surface of the top end plate 2b, upper ends of three rod shaped electrodes 1 project through the top end plate 2b into the vessel 2.
  • the electrodes 1 and the top end plate 2b are sealed to prevent fluid loss from the vessel 2 by seals 17.
  • the electrodes 1 extend parallel to the axis of the vessel 2 and have opposite ends located in bores drifted in the interior face of the bottom and plate 2c. When in use, the electrodes 1 are electrically connected by wires 10 to a three-phase power supply (not shown).
  • the electrodes 1 are equally spaced and in Figure 2, they can be seen to lie at the apices of an equilateral triangle, wherein the centroid of the equilateral triangle falls at the axis of the vessel 2, which is also the axis of flow of the fluid to be heated.
  • the bottom end plate 2c is of similar shape to the top end plate 2a and comprises an inlet port 12 with a guard ring 13, a metallic gasket 14 and a flange 15.
  • the inlet port 12 is connected to an input pipe 11 by the connection of flanges 15 and 16 of the inlet port 12 and input pipe 11 respectively.
  • a fluid to be heated When in operation, a fluid to be heated is passed into the input pipe 11 and flows through the vessel 2 to the output pipe 5.
  • the direction of flow of the fluid is indicated in the drawings by arrows.
  • the electrical conductivity of the fluid In order to heat the fluid uniformly, the electrical conductivity of the fluid must be relatively uniform over the length of the electrodes 1. This can be achieved either by selecting a fluid to be heated for which the electrical conductivity does not change very much over a wide temperature variation or by limiting the temperature range over which the fluid is heated, such that the change in electrical conductivity is small.
  • the electrodes 1 Whilst the fluid is passing the electrodes 1, the electrodes 1 are energised by connection to a three-phase power supply (not shown).
  • a convenient voltage to use may be 415 V. Given that the electrical conductivity of the fluid to be heated is substantially constant over any planar section of the heated volume taken at right angles to the axis of the vessel 2, equal phase to phase electrical currents will be maintained between these three electrodes 1 since they are disposed at equal separations. This provides balanced phase currents as required for a three-phase power supply.
  • a major advantage of this geometry is that the centroid of the equilateral triangle formed by the three electrodes 1 will always be maintained at or very near the common electrically neutral voltage level of the three electrical phase voltages applied to the electrodes 1, if a current balance is maintained between them, in the manner explained above.
  • the input and output pipes 11 and 5 are provided at each end of the vessel 2, co-axial with the vessel 2 and the centroid of the electrodes 1 and hence the axes of these pipes 5 and 11 will also lie along lines of zero net voltage or electrical potential relative to earth
  • thermocouple can be used in the outlet stream.
  • the dimensions of the apparatus are such that the mutual separation of the electrodes 1 in their triangular disposition is substantially greater than the diameters of the input and output pipes 11 and 5 and hence it is apparent that the voltage level corresponding to the periphery of these pipes 5 and 11 will be very low compared to the electrode voltages, and may, by suitable choice of dimensions, be reduced to an insignificant value.
  • a small or even negligible leakage current could be constrained to flow to the pipes 5 and 11 in the end plates 2b and 2c of the vessel 2 from each electrode 1 as its voltage varies sinusoidally in time about a mean (zero) level corresponding to the axial voltage value of the vessel 2.
  • guard rings 8 and 13 of suitable material - which may be the same material used to form the electrodes of the heater - may be mounted over the end of each pipe 5 and 11 in such a way as to shield or screen the pipe material from carrying any current at all; all the leakage current flowing to the guard rings 8 and 13. It must be appreciated that with perfect phase-balance between the three main electrodes 1 of the ohmic heater and identical electrode 1 to guard ring 8 and 13 distances, achieved by suitable ohmic heater geometry, any leakage current from each electrode 1 to the guard rings 8 and 13 at either end of the vessel 2 will be exactly equal in peak amplitude to that from any other electrode 1.
  • the electrodes 1 and guard rings 8 and 13 may be made from any suitable material which is compatible with the chemical and electrochemical properties of the fluid to be heated. In general there will be an upper limit to the current density which any particular electrode material/working fluid will withstand without either damaging the current-carrying portion of the electrode or causing the fluid to decompose or otherwise react at the electrode surface and form a fouling deposit on the surface thus adversely affecting the operation of the ohmic heater.
  • the dimensions of the ohmic heater, and in particular the mutual electrode 1 spacings and the electrode 1 to guard rings 8 and 13 distances will need to be chosen in such a way as to limit the currents flowing to levels which the electrode/fluid combination will withstand. Suitable electrode materials which will operate successfully with wide range of industrial fluids have been found to be platinized titanium and various graphite-based materials.
  • suitable dimensions for the ohmic heater components may be electrode diameters of approximately 50 mm, at a mutual spacing of 100 mm between centres.
  • the electrodes 1 might be contained in a tubular insulating housing some 200 mm in diameter and 1000mm long. Pipes 5 and 11 to the ends of the heater of 25 mm diameter might be used, recessed approximately 50 mm into the insulating end plates 2b and 2c of the ohmic heater to reduce leakage currents.
  • Such an ohmic heater would draw a balanced three-phase power totalling some 10 kW.
  • the guard rings 8 and 13 at either end of the vessel 2 may be simply connected to earth by means of suitably shaped metallic gasket 9 and 14 interposed between the guard rings 8 and 13 and the pipe flanges 6, 7, 15 and 16 at either end of the vessel.
  • the three parts forming the vessel 2 may be constructed from suitable plastic material which will withstand the temperature and pressure conditions within the vessel, as well as any corrosive action of the heated fluid, or alternatively they may be constructed from glass or enamel lined steel in the case of particularly arduous operating conditions.
  • FIG. 3 An example of another embodiment of the present invention is shown in Figure 3. Many of the components of this embodiment are similar to those already described herein above for the previous embodiment.
  • the vessel 20 comprises only two parts, an upper end plate 20a and a tapered main body 20b, joined together by bolts through flanges 22 and 23.
  • the separation of the three electrodes is increased as the heated fluid passes through the vessel 20 from bottom to top. In this way the current density at any point along the length of each electrode 21 can be maintained at the constant desired level even if the electrical conductivity of the heated fluid increases during its passage through the heater.
  • the ratio of the pitch circle diameters of the upper and lower ends of the electrodes 21 should generally be equal to the ratio of the initial and final conductivities of the heated fluid, it being understood that the conductivity of fluids generally increases linearly with temperature so that the linearly-increasing spacing of the electrodes exactly compensates for this effect.
  • the temperature of the heated fluid increases more or less linearly with distance during its passage along the length of the vessel 20.
  • FIG. 4 A further embodiment of the present invention, where the conductivity changes significantly during the heating cycle is shown in Figure 4.
  • two vessels 30 and 31 of the same general type as shown in Figure 1 but of different diameters to cope with the change in conductivity, are connected together by means of an adaptor plate 32 constructed from some suitable insulating material. If the geometrically correlating electrodes 33a and 33b in the two parts of the ohmic heater are connected to the same phase of the electrical supply, there will be no need to provide a guard ring at the adapter plate 32, since the current densities flowing in each part of the ohmic heater will be largely unaffected by the electrical conditions in the other part.
  • Figure 4 shows alternative means 34 and 35 of making the electrical connection to the lower electrodes 33b, and of sealing these connections against fluid leakage.
  • Connecting pins 34 penetrate the bottom end plate 37 to connect perpendicularly with the lower end of the electrodes 33b.
  • the head of the connecting pin 34 is connected to wires 36 to provide electrical continuity between the wires 36 and the electrodes 33b.
  • the connecting pins 34 and the lower end plate 37 are sealed to prevent fluid loss by seal 35.
  • the adaptor plates 32 may also be shaped as described above in such a manner as to promote the egress of evolved gases or prevent the accumulation of solids at these plates 32.
  • FIG. 5 shows a still further embodiment of the present invention.
  • the versatility of the invention is illustrated in that the heater is used as a heater for tanks of liquid, as used in plating or phosphating baths. Conventionally heat exchanges are used for this application but these are subject to considerable fouling.
  • the vessel 42 is composed of a vessel body 42a and a vessel top plate 42b, and is suspended in a tank 49 of liquid.
  • the electrodes 41 project through the top plate 42b into the vessel 42, and are connected to a three phase power supply (not shown) by wires 45.
  • guard rings 43 and 44 In the outlet pipe 48 and the inlet port 50 two sets of guard rings are provided 43 and 44.
  • the guard rings nearest the electrodes are the neutral guard rings 43 whilst those furthest away are the earth guard rings.
  • the provision of two sets of guard rings allows for the leakage current to be measured and hence monitored by subtracting the neutral return current from the sum of the line phase currents in a sensitive transformer.
  • the total leakage current was found to be well below 1mA, thereby supporting the claim that the leakage current to the earthed parts of the equipment via the heater fluid is negligible using the design.
  • circulation of the fluid is provided for by thermal siphoning, in that the circulation occurs due to the decrease in density of the fluid as its temperature rises. Therefore as the temperature of the fluid in the vessel increases it rises up to the outlet pipe 48 and is replaced at the inlet port 50 by cooler fluid.
  • An earthed metal clad thermocouple 47 is ued to measure the temperature of the fluid leaving the heater. The use of this is possible since the axis at the outlet pipe 48 is maintained at or near earth potential as hereinbefore mentioned.
  • Figure 5 also shows thet electrode current adjusting insulating sleeves 46 as hereinbefore mentioned. The movement of these sleeves up or down the length of the electrodes 41 varies the electrode currents.
  • the electrodes have been shown to lie within the vessel cavity, where viscous fluids are to be heated it may be advantageous to mount the electrodes against the insulating wall of the vessel. This is advantageous in that no area is provided behind the electrodes in which particulate matter in the fluid can be trapped.
  • Figure 6 illustrates such an arrangement using a cross-sectional view similar to Figure 2.
  • the cross-section of the electrodes 54 is shaped such that their back face lies flush with the vessel wall 52. 53 denotes the input port.
  • this arrangement it may be more convenient to make electrical connections to the electrodes to the back face of the electrodes through the vessel wall; with suitable sealing arrangements. This allows for a smoother surface transition between the inlet and outlet ports and reduces the possibility of solids in suspension lodging around the electrodes. This is clearly of paramount importance with viscous or solid-bearing fluids.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Thermal Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Instantaneous Water Boilers, Portable Hot-Water Supply Apparatuses, And Control Of Portable Hot-Water Supply Apparatuses (AREA)
  • Resistance Heating (AREA)
  • Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
  • Control Of Resistance Heating (AREA)
  • Heat-Pump Type And Storage Water Heaters (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)

Claims (18)

  1. Ohmsches Heizgerät zum Erwärmen eines Fluids umfassend einen Behälter (2,20,30,42) mit Einlaß- und Auslaßöffnungen (12,3,48,50), die an entgegengesetzten Enden des Behälters (2,20,30,42) angeordnet sind und zwischen welchen das Fluid im Betrieb entlang einer Achse strömt; wenigstens zwei Elektroden (1,21,33,41), die mit gleichem Abstand um die Achse der Strömung angeordnet sind und im Behälter (2,20,30,42) enthalten sind; und Mittel (10,45) um die Elektroden (1,21,33,41) mit elektrischer Leistung derart zu versorgen, daß das elektrische Potential auf der Achse bezüglich Massepotential in jedem Zeitpunkt im wesentlichen Null ist;
    dadurch gekennzeichnet, daß
    die Einlaß- und Auslaßöffnungen (12,4,48,50) auf der Achse liegend angeordnet sind und ein elektrisch leitender Schutzring (8,13,43,44) um den Umfang jeder der Öffnungen (12,4,48,50) angeordnet ist und im Betrieb der Fluidströmung ausgesetzt ist; wobei der elektrisch leitende Schützring (8,13,43,44) in Betrieb mit Massepotential oder einem neutralen Punkt verbunden ist.
  2. Ohmsches Heizgerät nach Anspruch 1, bei dem der Behälter elektrisch isolierend ist.
  3. Ohmsches Heizgerät nach Anspruch 1 oder Anspruch 2, bei dem die Elektroden sich parallel zu der Strömungsachse erstreckend angeordnet sind.
  4. Ohmsches Heizgerät nach Anspruch 1 oder Anspruch 2, bei dem die Elektroden derart angeordnet sind, daß ihr Abstand quer zur Achse entlang der Achse in der Strömungsrichtung des Fluids zunimmt.
  5. Ohmsches Heizgerät nach Anspruch 2, 3 oder 4, bei dem jede Elektrode eine an die Wand des Behälters angrenzende Rückseite aufweist.
  6. Ohmsches Heizgerät nach einem der vorhergehenden Ansprüche, umfassend drei der Elektroden, wobei jede der Elektroden im Betrieb eine einzelne Phase einer Drei-Phasen-Stromversorgung empfängt.
  7. Ohmsches Heizgerät nach Anspruch 6, umfassend erste und zweite elektrisch leitende Schutzringe (43,44), die um den Umfang jeder der Öffnungen (48,50) angeordnet sind; wobei jeder der ersten elektrisch leitenden Schutzringe (43) in Betrieb mit einem neutralen Punkt verbunden ist und näher an den Elektroden (41) angeordnet ist als ein entsprechender der zweiten elektrisch leitenden Schutzringe (44), wobei der zweite elektrisch leitende Schutzring (44) in Betrieb mit Massepotential verbunden ist.
  8. Ohmsches Heizgerät nach Anspruch 7, umfassend Mittel zum Messen eines Leckstroms zwischen den ersten elektrisch leitenden Schutzringen (43) und einem neutralen Punkt der Mittel zur Versorgung mit elektrischer Leistung (45).
  9. Ohmsches Heizgerät nach einem der vorhergehenden Ansprüche, bei dem die Fläche der Einlaß- und Auslaßöffnungen eine wesentlich kleiner ist als die Querschnittsfläche des Behälters.
  10. Ohmsches Heizgerät nach einem der vorergehenden Ansprüche, bei dem die Oberfläche eines Teilbereichs jeder der Elektroden mit einem bewegbaren, isolierenden Material bedeckt ist.
  11. Ohmsches Heizgerät nach einem der vorhergehenden Ansprüche, bei dem der Behälter derart angeordnet ist, daß das Fluid gegen die Schwerkraft strömt.
  12. Ohmsches Heizgerät nach einem der vorhergehenden Ansprüche, umfassend wenigstens zwei der Behälter, die koaxial gekoppelt sind, wobei der Abstand der Elektroden in entlang der Strömungsrichtung des Fluids folgenden der Behälter größer ist.
  13. Ohmsches Heizgerät nach Anspruch 12, bei dem Elektroden in geometrisch äquivalenten Positionen in jedem der Behälter elektrisch miteinander verbunden sind.
  14. Verfahren zum Betreiben eines Ohmschen Heizgeräts nach einem der Ansprüche 1 bis 13, umfassend die Schritte des Durchführens eines zu erwärmenden Fluids entlang einer Strömungsachse durch einen Behälter (2,20,30,42) und des Versorgens von Elektroden (1,21,33,41) mit Energie, welche um die Achse derart angeordnet sind, daß das elektrische Potential auf der Achse bezüglich Massepotential in jedem Zeitpunkt im wesentlichen Null ist.
  15. Verfahren zum Betreiben eines Ohmschen Heizgeräts nach Anspruch 14, bei dem der Strom zwischen den Elektroden (1,21,33,41) durch das Einstellen der Position eines die Oberfläche der Elektroden (1,21,33,41) teilweise bedeckenden isolierenden Materials (46) variiert werden kann.
  16. Verfahren zum Betreiben eines Ohmschen Heizgeräts nach Anspruch 14 oder Anspruch 15, bei dem elektrisch leitende Schutzringe (8,13,43,44) um den inneren Umfang einer Einlaßöffnung (12,50) und einer Auslaßöffnung (4,48) des Ohmschen Heizgeräts positioniert sind, welches Verfahren den Schritt des Verbindens der elektrisch leitenden Schutzringe (8,13,43,44) mit Massepotential oder einem neutralen Punkt beinhaltet.
  17. Verfahren zum Betreiben eines Ohmschen Heizgeräts nach Anspruch 16, bei dem das Ohmsche Heizgerät erste und zweite elektrisch leitende Schutzringe (43,44) in jeder der Öffnungen (48,50) umfaßt, wobei jeder der ersten elektrisch leitenden Schutzringe (43) näher an den Elektroden (41) angeordnet ist als ein entsprechender der zweiten elektrisch leitenden Schutzringe (44), wobei das Verfahren die Schritte des Verbindens der ersten elektrisch leitenden Schutzringe (43) mit einem neutralen Punkt und des Verbindens der zweiten elektrisch leitenden Schutzringe (44) mit Massepotential umfaßt.
  18. Verfahren zum Betreiben eines Ohmschen Heizgeräts nach Anspruch 17, umfassend den Schritt des Messens des Leckstroms zwischen den ersten elektrisch leitenden Schutzringen (43) und einem neutralen Punkt einer Stromversorgung.
EP90314168A 1990-04-10 1990-12-21 Ohmscher Erhitzer Expired - Lifetime EP0451416B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT90314168T ATE93605T1 (de) 1990-04-10 1990-12-21 Ohmscher erhitzer.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9008095A GB2243064A (en) 1990-04-10 1990-04-10 An ohmic heater
GB9008095 1990-04-10

Publications (2)

Publication Number Publication Date
EP0451416A1 EP0451416A1 (de) 1991-10-16
EP0451416B1 true EP0451416B1 (de) 1993-08-25

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EP90314168A Expired - Lifetime EP0451416B1 (de) 1990-04-10 1990-12-21 Ohmscher Erhitzer

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EP (1) EP0451416B1 (de)
JP (1) JPH05322308A (de)
AT (1) ATE93605T1 (de)
DE (1) DE69002936T2 (de)
ES (1) ES2045827T3 (de)
GB (1) GB2243064A (de)
PT (1) PT97083A (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2389169A (en) * 2002-05-28 2003-12-03 Rosecharm Ltd Electric flow boiler
KR100778461B1 (ko) * 2007-04-04 2007-11-21 윤정수 전기장 차폐 기능을 갖는 온수매트의 가열장치
CN102563879A (zh) * 2012-01-02 2012-07-11 萧志杰 电热丝浸入水中发热都不漏电的热水器
DE102018121466A1 (de) * 2018-09-03 2020-03-05 Enas Ag Inverter-Wellengenerator zur Temperierung von Wasser und Verfahren zur Temperierung eines Temperiermediums

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR964733A (de) * 1950-08-23
GB234087A (en) * 1924-05-16 1925-10-22 British Thomson Houston Co Ltd Improvements in and relating to electric steam generators
GB389571A (en) * 1931-01-26 1933-03-23 Widerstand A G Fur Elektro War Improvements in or relating to electric boilers
DE909379C (de) * 1941-06-12 1954-04-15 Rheinisch Westfaelisches Elek Elektroden-Durchlauferhitzer
US2663788A (en) * 1949-11-28 1953-12-22 G W B Electric Furnaces Ltd Temperature control apparatus for electrode type boilers
US3488474A (en) * 1967-10-20 1970-01-06 Fred Q Saunders Electric steam generator
US3520979A (en) * 1968-02-26 1970-07-21 Penelectro Ltd Electrode circuit for hex electric furnace

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Publication number Publication date
JPH05322308A (ja) 1993-12-07
PT97083A (pt) 1993-04-30
GB2243064A (en) 1991-10-16
EP0451416A1 (de) 1991-10-16
ATE93605T1 (de) 1993-09-15
GB9008095D0 (en) 1990-06-06
ES2045827T3 (es) 1994-01-16
DE69002936D1 (de) 1993-09-30
DE69002936T2 (de) 1994-01-13

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