RU2667515C1 - Induction fluid heater - Google Patents

Abstract

FIELD: electrical equipment.

SUBSTANCE: invention relates to electrical equipment. Induction fluid heater includes a single- or three-phase transformer with O-shaped toroidal ferromagnetic core (1), with primary winding of bifilar type (4) with parallel resonant capacitor connected to it, connected to the alternating current network, and secondary electrically conductive winding (2), which is a heat exchanger for a heated fluid, consisting of one or more turns of a thick-walled copper tube, preferably of the type M1, electrically connected among themselves along the entire length of the welding seam to form a short-circuited coil.

EFFECT: increase the efficiency and power factor of the heater and ensure the possibility of its use in systems with natural circulation, and also when the fluids with forced circulation are heated to high temperatures.

5 cl, 2 dwg

Description

The invention relates to the field of electrical engineering, namely to induction fluid heaters.

Known three-phase electric heating device of the transformer type (certificate for utility model RU No. 2692, IPC6 H05B 6/10, publ. 08/16/96). The electric heater contains a flat lined rod core with a three-phase primary winding and a short-circuited secondary winding. The secondary winding consists of three cylinders concentrically covering the primary windings, sidewalls covering all three rods with windings, and two ends - the upper and lower, and the secondary winding is simultaneously part of the tank. The disadvantage of this device is the low efficiency and high metal consumption.

Known induction fluid heater (certificate for utility model RU No. 21709, IPC6 H05B 6/10, publ. January 27, 2002). The induction fluid heater contains a three-phase transformer with a ferromagnetic core, with a primary winding and a secondary winding located on the rods, which is a heating chamber, made hollow with inlet and outlet pipes for the passage of the heated fluid, in which there are through channels with electrically conductive walls, each of which contains transformer rod. The heating chamber is equipped with jumpers of electrically conductive material located between the through channels electrically connecting opposite walls of the heating chamber and forming short-circuited contours around the core rods. The disadvantage of the heater is insufficient heat removal, which leads to overheating of the primary winding at the extreme terminals, the lack of symmetry of the power factors in phases, the chamber is not able to hold high pressure.

Known induction fluid heater (Patent RU No. 2074529, IPC6 H05B 6/10, publ. 02.27.97), which contains a housing, a transformer with a multi-rod ferromagnetic core, located on the rods with a multiphase primary winding connected to an AC network current, and the secondary winding, which is a heat exchanger. The heat exchanger is made in the form of a hollow chamber with one lower inlet and one upper outlet nozzles for the passage of the heated fluid. The chamber has through vertical channels with electrically conductive walls, in each of which transformer core rods are installed with a gap. The disadvantage of this device is the design complexity and not high enough efficiency of the device, as it gives off heat not only to the heated fluid, but also dissipates it into the environment.

Known inductive conductive fluid heater (Patent RU No. 2301507, IPC H05B 6/10, publ. 06/20/2007), containing a transformer with a ferromagnetic core, located on the core rods of the primary winding and the secondary winding, which is a heating chamber made hollow with inlet and outlet nozzles for the passage of a heated fluid, in which there are through channels with electrically conductive walls, in each of which a transformer core rod is installed with a gap. The heating chamber is divided into identical parts according to the number of rods of the core of the transformer, the indicated input and output pipes and the through channel with the core of the transformer installed in it are located in each part of the heating chamber. The heater allows to reduce material consumption and conduct simultaneous heating of two or more liquids, since the nozzles for supplying fluid and the output of the heated fluid are made in each separate chamber and are not interconnected. The disadvantage of this heater is the insufficiently high service life due to salt deposition, as well as the high material consumption due to the separate supply of different liquids to each chamber, which reduces the efficiency of the heater. A three-phase core made of ferromagnetic material with a primary winding located on the rods connected to an AC network and a secondary electrically conductive winding, which is a heat exchanger for a heated fluid, with nozzles for entering and leaving the fluid.

The closest technical solution is an induction fluid heater (Application RU No. 2006121117, IPC H05B 6/10, published January 10, 2008), comprising a lined three-phase core made of ferromagnetic material with a primary winding located on the rods connected to an alternating current main, and a secondary electrically conductive winding, which is a heat exchanger for a heated fluid, with nozzles for the inlet and outlet of the fluid. The heat exchanger consists of three chambers for heating the fluid, each of which is made of two cylinders of different diameters, mounted concentrically one in the other, connected at the top and bottom by end caps to form a sealed hollow chamber for heating the fluid in it, inside which rods with primary winding, the turns of which are located in a horizontal plane with an air gap with the formation of a closed loop around the corresponding core core, each chamber has nozzles for ode and exit fluid. The nozzles of all three chambers for fluid inlet are connected in parallel to the common pipeline for supplying one fluid to all three chambers, and the nozzles of the outlet are connected in parallel to the pipeline for exiting the heated fluid. The disadvantage of this heater is not a high efficiency.

Common to the prototype and the claimed invention are

- the presence of a transformer with a lined core of ferromagnetic material with a primary winding connected to an alternating current network;

- a secondary electrically conductive winding, which is a heat exchanger for a heated fluid, with nozzles for the inlet and outlet of the fluid.

The problem solved by the invention is to increase the efficiency and power factor of the induction heater.

The problem is solved using an induction fluid heater containing a one- or three-phase transformer with an O-shaped lined toroidal core made of ferromagnetic material, consisting of flat closed rings, with a bifilar type primary winding with a resonant capacitor connected to it in parallel, connected to an alternating network current; a secondary winding consisting of one or more turns of a thick-walled copper pipe, which is a heat exchanger for a heated fluid; nozzles for fluid inlet and outlet. Moreover, if there are several turns of the secondary winding, then they are electrically interconnected along the entire length of the weld with the formation of a short-circuited coil; as a secondary winding use a copper pipe brand M1; as a ferromagnetic material using magnetically soft isotropic sheet electrical steel; a heating fluid supply pipe is installed at the bottom of the induction heater, and a fluid outlet pipe is installed at the top of the induction heater.

The invention is illustrated by drawings, where in FIG. 1 shows top and side views of the heater; FIG. 2 - table of the calculated parameters of the induction heater.

The proposed induction heater contains an O-shaped lined toroidal core 1 of ferromagnetic material, consisting of flat closed rings, on which a bifilar-type primary winding coil 4 is wound. As a ferromagnetic material using magnetically soft isotropic sheet electrical steel, for example, grade 2421 according to GOST 21427.3-83; the thickness of the sheets and the brand are selected according to the operating frequency; values of induction, depending on the magnetic field strength of the mode to saturation of at least 1.4 T. A resonant capacitor (not shown in the images) is connected in parallel to the coil, forming a parallel oscillatory circuit with it. The O-shaped core is proposed based on the requirements for the durability of the heater (15-20 years) and the resonant mode of operation. Other types of cores (U-shaped, W-shaped, etc.) do not meet these requirements. Providing electrically closed rings in the O-shaped core along the lines of force of the magnetic field increases the efficiency of the device.

The electric capacity (C) of the formed oscillatory circuit is calculated from the frequency value f = 50 Hz for the resonant circuit according to the formula:

where L is the inductance, H;

C - capacity, F.

The oscillating circuit is connected to an AC source.

The application of the bifilar method of winding the primary winding 4 increases the coupling coefficient between the turns of the primary winding (k = 1) and thereby increases its overall inductance

where ω is the angular frequency, rad * Hz;

S is the cross-sectional area of the core, m ² ;

l is the length of the midline of the core, m;

μ is the absolute magnetic permeability of the core.

The values of magnetic permeability, magnetic resistance and other parameters for the corresponding material are selected from reference books or other regulatory documents, for example GOST 21427.2-83. The choice is determined by the need to obtain high inductance values.

The magnetic flux (Ф) in the core 1 is determined as the ratio of the magnetizing force to the magnetic resistance of the core and is determined by the formula:

Thus, the required amount of energy is concentrated in a magnetic field, calculated by the formula:

used to generate the required amount of thermal energy in the secondary winding that performs the function of a heat exchanger. Secondary winding 2 is a heat exchanger for heating a fluid, which is made in the form of turns of a thick-walled copper pipe, for example, with a wall thickness of 7 ~ 10 mm, preferably of the M1 grade, electrically connected together along the entire length of the weld with the formation of a short-circuited coil. The wall thickness of the pipe is determined by the requirement to reduce the resistance of the secondary winding by increasing the cross-sectional area of the conductor, therefore 7 mm is the optimal minimum wall thickness, 10 mm is the optimal maximum thickness, because its increase is limited by the technological difficulties of winding. Since all turns of the secondary winding 2 are interconnected shortly along the entire length, when calculating the number of turns of the secondary winding is taken to be unity, which reduces the mutual inductance between the secondary winding 2 and the primary winding and considers it equal to zero. Thread 3 (Fig. 1) is used to connect the induction heater to the heating system.

An example of calculating the generation of heat generated by an induction heater.

The calculation is made from the determination of the useful amount of heat necessary to increase the temperature of the heated material to a given value without taking into account heat loss

where m is the mass of the heated material, kg;

t _to , t _n - final and initial temperature, ° C;

s - specific heat of the material, kJ \ (kg⋅С °)

Having determined the useful amount of heat, we determine the total amount of heat, taking into account the radiation of heat into the environment,

where μ is the efficiency of the induction heater.

The power of the heater is determined by the formula:

where k is the coefficient of radiation efficiency,

t is the heating time, h

The calculation results obtained on the basis of data from the experimental heater are shown in the table (Fig. 2).

The efficiency of the invention and power factor will be higher than in known analogues. This became possible due to the use of resonance arising in a parallel oscillatory circuit formed by the primary winding of the heater and the resonant capacitor. The invention provides the possibility of using a heater in systems with natural circulation, as well as when heating to high temperatures fluids with forced circulation.

Claims (5)

1. An induction fluid heater comprising a transformer with a lined core of ferromagnetic material with a primary winding connected to an AC network; a secondary electrically conductive winding, which is a heat exchanger for a heated fluid, with nozzles for fluid inlet and outlet, characterized in that they use an O-shaped toroidal core consisting of flat closed rings, with a bifilar type primary winding with a resonant capacitor connected to it in parallel, plugged into AC power; a secondary winding consisting of one or more turns of a thick-walled copper pipe. 2. An induction fluid heater according to claim 1, characterized in that the turns of the copper pipe of the secondary winding are electrically interconnected along the entire length of the weld with the formation of a short-circuited coil. 3. An induction fluid heater according to claim 1, characterized in that a magnetically soft isotropic sheet steel is used as the ferromagnetic material. 4. An induction fluid heater according to claim 1 or 2, characterized in that a Ml grade copper pipe is used as the secondary winding. 5. An induction fluid heater according to claim 1, characterized in that the fluid supply pipe for heating is installed at the bottom of the induction heater, and the fluid outlet pipe is installed at the top of the induction heater.

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