RU2076468C1 - Electric steam heater - Google Patents

Abstract

FIELD: electric-heated steam heaters and evaporators, can be used in light and food industries, public utilities sphere, agriculture and everyday life. SUBSTANCE: electric steam heater uses an induction steam heater with secondary winding, steam superheater with secondary winding in the form of a coil pipe, casing partially filled with evaporated liquid, ferromagnetic core with primary winding built in it and connected to the power mains. The secondary windings of the steam heater and superheater are positioned on the ferromagnetic core; the secondary winding of the steam generator is made in the form of a closed lattice metal structure, which is partially dipped in the liquid being evaporated. EFFECT: enhanced power factor. 2 cl, 2 dwg

Description

 The invention relates to electrical engineering, in particular to the designs of steam generators and evaporators with electric heating and can be used in light and food industries, services, agriculture and household appliances.

 Known electric steam heaters for various purposes with steam generators in which tubular electric heaters (TENs) are used for vaporization, for example a heating device (application N 4038695, Germany, MKI F 28 D 1/00).

The main disadvantages of such electric heaters are:
increased thermal inertia and, as a result, increased time for heating the evaporated water due to the small contact surface of tubular electric heaters (TENOV) and evaporated water;
the practical impossibility of conducting conductive heating of evaporated water due to the inability to directly contact this water with a heating resistor (whose temperature in the heating elements is hundreds of degrees Celsius), as well as due to the appearance in this case of the electric potential of the supply network (220/380 V) directly on water, significantly reducing the electrical safety of the device;
scale formation on the surface of the heating elements, significantly increasing the thermal tension of the heating resistor due to an increase in its temperature (in the presence of scale) by 20-30% or more, which reduces the durability of such electric steam generators, and in case of accidents (for example, the appearance of cracks in the shell of the heating elements) reduce the electrical safety of the device.

 Electric steam heaters based on electrode devices with direct heating of evaporated water when electric current flows through it under the influence of a network voltage (including high, several kV) between the electrodes located in the evaporated water and acting as a current supply are also known. water specified parameters of the electric field of conductivity. For example, the steam electrode boiler of the Sulzer type jet or the domestic electrode steam boiler EEP-160 and 1 designed by VNIITO and others (Fig. 2 and 9, Vinokurov M. Kh. Romanov V.F. Khrushcheva T.P. Yanevsky G. D. Electric steam and hot water boilers, Review TSNIITENtyazhmash, M. 1991, Power engineering, series 3, issue 3).

These devices provide sufficient thermal and speed (short warm-up time), however:
the disadvantages associated with electrical safety remain and are amplified, since the evaporated and heating water is always under the potential of a network of low (220/380 V) or high voltage (more than 1000 V). That is why devices with electrode heating of water by the current rules are forbidden to be used in livestock farms, bathhouses, laundries, showers, at home, etc. and in other cases it is recommended to install them in separate rooms;
there is corrosive wear of the elements of the electrode group and scale formation intensified by the electric field on the internal surfaces in the zone of electrode heating of water, which reduces the durability of the structural elements of such electric steam generators;
the operation of steam generators and water-heating devices with electrode heating is complicated, since it requires maintaining an appropriate level of electrical conductivity of water, regular preventive examinations of steam generating constructs, relatively frequent current repairs of elements of the electrode group to clean them of scale and corrosion products, and regular replacement of electrodes.

 In addition, both of the above analogues cannot be used for vaporization in open water bodies.

 According to the level of electrical safety, durability and ease of operation, in comparison with the listed analogues, an induction electric steam generator is preferred (US patent 5237144, MKI N 05 B 6/36, NKI 219-10, 79), adopted as a prototype, which is designed to generate low pressure steam using induction-conductive heating of the evaporated liquid at an industrial frequency of alternating current (60 Hz).

 The prototype consists of a steam generator and a superheater connected to its output. In the lower part of the steam generator tank, a U-shaped steel ferromagnetic core with a primary winding connected to an alternating current main is installed; on the rods of the U-shaped core there is a massive metal plate of the object to be heated. The latter is irrigated with water from the sprayer located above it, and the steam generated in this case through the separator enters the superheater. In the latter, a primary winding (inductor) is wound on a rod of a U-shaped magnetic circuit and a coil of at least one turn of a metal tube is wound on top of it. The conclusions of the coil are shorted by a jumper so that it is a short-circuit winding of a heating transformer.

The disadvantages of the prototype include:
low power factor (cos Φ) due to the relatively large magnetic fluxes of dissipation resulting from counteraction to the main flow in the U-shaped core of eddy currents in a massive plate lying on this core;
the practical impossibility of the direct use of the prototype steam generator in open waters (in particular for the evaporation of sea water) without the use of special devices for forced (requiring additional energy) irrigation of the steam generating plate, which narrows the scope.

 Analysis of the prior art indicates its feasibility of creating an electric steam heater with a higher power factor and wider scope.

 This is achieved by the fact that in an electric steam heater containing an induction steam generator with a secondary winding, a steam heater with a secondary winding in the form of a tubular coil, a housing partially filled with evaporated liquid, a ferromagnetic core with a primary winding connected to the network, secondary windings of the steam generator and a steam superheater are integrated in it located on the specified ferromagnetic core, and the secondary winding of the steam generator is made in the form of a closed lattice metal structure, which partially immersed in a vaporized liquid.

 An electric steam heater can be equipped with float chambers, and holes are made in the bottom of the housing.

 In FIG. 1 presents a structural diagram of the proposed electric heater; in FIG. 2 diagram of a similar electric heater intended for use in open water. The proposed electric heater (Fig. 1) contains a housing 1 made of heat-insulating material. In the upper part of the housing 1, a lined core, for example, a three-core core 2, with waterproof housing insulation 3 is integrated, on the middle core of which there is a primary winding 4 connected to an alternating current network, and on the upper core a tubular coil of electrically conductive material is wound, short-circuited and representing secondary winding of the superheater 5. In the lower zone of the housing 1 there is a closed cavity 6, partially filled with vaporized liquid 7, the level of which is maintained in the cavity 6 in the tank 6 yannym (external system of known type, FIG. 1, not shown). On the lower rod, in vertical yokes of core 2, lattices 8 of electrically conductive plates are mounted, short-circuited by lateral electrically conductive shells adjacent to the walls of the cavity of the reservoir 6. These lattice structures, being a secondary short-circuited winding of the steam generator, are partially immersed in the evaporated liquid 7 and partially protrude above its surface . The upper part of the cavity of the tank 6, free from the evaporated liquid, is connected to the superheater 5 by a tube 9, and a tube 10 is provided for steam to exit the superheater.

 In the electric heater (Fig. 2), mainly low pressure, intended for use in open water, for example for evaporating sea water, the presence of a superheater is optional, and holes are made in the bottom of the housing 1. The superheater is equipped with float chambers 12.

 The proposed electric heater (Fig. 1) operates as follows.

After filling the tank 6 with the evaporated liquid to a certain level (which is further maintained constant), the electric heater is connected to the AC network. Primary winding 4 streamlined by alternating current creates an alternating magnetic flux in core 2, which induces sufficiently large currents in short-circuited secondary circuits
lattice structures 8 partially immersed in the evaporated liquid and a short-circuited coil of the superheater 5. These currents create predetermined temperature regimes of both the lattice structures 8 and the superheater 5. Lattice structures 8 located in the upper layers of evaporated liquid 7 and partially protruding above the surface of the latter, are sources of vaporization, the intensity of which is determined (and therefore can be controlled) by many factors: the geometry of the gratings, the difference in their temperatures and the evaporated liquid, the magnitude of the induced current, etc. The steam formed in the upper part of the tank cavity 6 rushes through the pipe 9 into the superheater 5 and after passing it is supplied to the consumer through the outlet with the appropriate parameters (temperature and pressure) handset 10.

 The electric heater (Fig. 2) when used in open water for the production of low pressure steam functions similarly, but can be without a superheater. An appropriate level of liquid (for example, sea water) is maintained in the vaporization zone (where the secondary winding of the steam generator is located in the form of closed lattice structures 9) automatically using float chambers 12. The holes 11 in the bottom of the housing 1 are designed for the evaporation of liquid from the reservoir.

The technical efficiency of the proposed electric heater in comparison with the prototype is that:
As a result of using a lined closed core 1 in a transformer operating practically on a resistive load (secondary closed windings in the form of lattice structures 8 and a tubular coil 5), the power factor of the electric heater (cos Φ) is quite high and approaches unity;
an electric heater equipped with float chambers 12 (Fig. 2) with holes 11 in the bottom of the housing 1 can be effectively used in open water bodies, in particular during evaporation or desalination of sea water.

Claims (2)

 1. An electric steam heater comprising an induction steam generator with a secondary winding, a superheater with a secondary winding in the form of a tubular coil, a housing partially filled with vaporized liquid, a ferromagnetic core integrated in it with a primary winding connected to the network, characterized in that the secondary windings of the steam generator and superheater located on the specified ferromagnetic core, and the secondary winding of the steam generator is made in the form of a closed lattice metal structure, which partially immersed in the evaporable liquid.  2. The steam heater according to claim 1, characterized in that it is equipped with float chambers, and holes are made in the bottom of the housing.

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