RU2612540C1 - Device for preventing deposit formation in heat exchanger - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: device for preventing deposit formation in a heat exchanger comprises a device receiving signals from a temperature sensor mounted on the outlet pipe line of the heat exchanger second stage, a control device which determines operation of a mechanical oscillation unit and a unit that impacts on the heat-carrying medium. Unit that impacts on the heat-carrying medium is mounted on the outlet pipe line of the heat exchanger first stage comprises a housing with a passage opening for the heat-carrying medium passage. Sleeve of insulating material is rigidly connected to the housing. Two solenoid windings are fixed on the sleeve. Each winding is equipped with a current sensor. There is a hollow rod inside the insulating sleeve. Rod consists of two parts: a ferromagnetic and a diamagnetic. Rod has ability to move horizontally under the impact of electromagnetic winding fields inside the sleeve in opposite directions so that the diamagnetic rod part opened or overlapped the through opening of the housing.

EFFECT: reduction of generated capacity and reduction of windings heating.

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Description

The invention relates to heat engineering, is intended to prevent the formation of deposits in heat exchangers, regulate temperature conditions and during operation of heat exchangers in closed heat supply circuits.

A device is known for preventing the formation of deposits in the heat exchanger, the efficiency of which is achieved by supplying the first stage of the heat exchanger with hydraulic pulses with a change in the speed of the coolant from the rest state to the maximum possible, with synchronously intermittent supply of pulsed mechanical vibrations, resonant frequency, directly to the metal structure of the heat exchanger .

This device has options for nodes affecting the coolant. A variant of the assembly based on a ball valve, which is coaxially mounted on the outlet pipe of the first stage of the heat exchanger. Outside, on the axis of the ball valve, a gear driven by a worm is rigidly fixed. The gear wheel is equipped with a motor stop sensor. The electric motor by the "command" of the control device drives or stops the worm pair. And the ball valve gets the opportunity to pass the coolant through the unit with hydraulic pulses (see p. RU 2496073 C2, paragraph 2. IPC F28G 7/00).

The disadvantage of this option is that modern ball valves have a large moment of resistance when turning, so there is a need to install a powerful electric motor. It is also necessary to introduce an additional support for the worm so that the worm shaft is connected to the motor shaft through an additionally installed special spring coupling. This coupling after stopping the motor should turn the motor rotor in the opposite direction by about one revolution. So that the next time you start the electric motor, the resistance to rotation of its shaft is close to zero and grows to a maximum at the moment when the rotor gains inertia of motion. In view of the foregoing, this node impacts on the coolant is inefficient to use for the operation of hot water heat exchangers with a small diameter of the pipeline.

The closest technical solution to the declared one is the variant of the node of the impact on the coolant based on the solenoid. This assembly, mounted on the outlet pipe of the first stage of the heat exchanger, comprises a housing with a through hole that is aligned with the pipe. An insulating sleeve is rigidly connected to the body, the axis of which is perpendicular to the axis of the body through hole. A solenoid winding is connected to the insulating sleeve, which is connected to the control device. Inside the sleeve is a rod made of ferromagnetic material. The rod is hollow and has the ability to move in the vertical direction and thereby allow or prohibit the passage of the coolant through the node (see p. RU 2496073 C2, paragraph 1. IPC F28G 7/00).

This option has a number of disadvantages. At the moment the current passes through the solenoid winding, a large consumption of electricity occurs, which is spent inefficiently, since it is necessary to hold the rod in the upper position for a long time to pass the coolant. As a result, significant power is released on the solenoid winding, which leads to a strong heating of the winding. In this regard, it is difficult to choose the material for the insulating sleeve, since the material must have high heat resistance. In practice, only ceramics are suitable, and this is also a drawback, since it is difficult to manufacture the structure. The disadvantage is that the unit begins to work unsatisfactorily even at medium pressure drops, this is due to the fact that there is not enough force developed by the solenoid to lift the rod. To lift the rod up, the solenoid winding must develop a force equal to the product of the cross-sectional area of the coolant passage passageway by the pressure drop and the friction coefficient plus the rod weight:

F = S⋅ΔP⋅k + G (or approximately F≈2G),

where F is the pulling force of the solenoid winding;

S is the cross-sectional area of the through hole;

ΔР - differential pressure (the difference between the pressures of the coolant in the supply and return piping);

k is the coefficient of friction between the materials used;

G - rod weight

(Archimedean force can be neglected due to its weak influence).

It can be seen from the formula that the retracting force of the solenoid winding can be reduced (the current in the winding and its heating can be reduced), as well as the rod weight, due to the use of materials with a low coefficient of friction, and this is difficult, since the construction material used must have, first of all, high heat resistance.

The technical result of the claimed solution is to increase work efficiency due to energy savings, the ability to work with a large pressure drop, reducing the requirements for heat resistance of materials, which allows the use of less expensive, easily processed materials with a low coefficient of friction. The technical result is achieved by the fact that the device for preventing the formation of deposits in the heat exchanger contains receiving signals from a temperature sensor installed on the output pipe of the second stage of the heat exchanger, a control device that determines the operation of the unit of mechanical vibrations and the site of exposure to the coolant. The mechanical vibration unit interacting with the heat exchanger body transfers to the case body bundles of mechanical pulse vibrations close to the natural resonant frequency of the heat exchanger. The node for influencing the heat carrier mounted on the outlet pipe of the first stage of the heat exchanger comprises a housing in which a passage hole is made for passage of the heat carrier. A sleeve of insulating material is rigidly connected to the housing. The axis of the sleeve approximately perpendicular to the axis of the through hole. Two (opening and closing) solenoid windings are stationary mounted on the sleeve. Each winding is equipped with a current sensor. Inside the insulating sleeve is a rod made hollow. The stem consists of two parts: ferromagnetic and diamagnetic. The rod has the ability under the action of electromagnetic fields of the windings to move horizontally inside the sleeve in opposite directions. This allows the diamagnetic part of the stem to fully open or completely close the passage opening of the housing and thereby allow or prohibit the passage of the coolant through the assembly.

Moving the ferromagnetic part of the rod inside the solenoid winding changes the inductance of this winding. If, for example, the ferromagnetic part of the rod is outside the winding, then the inductance of the winding is minimal, when the ferromagnetic part is completely in the winding, then the inductance is maximum. The total resistance of the winding is equal to the square root of the sum of the squares of the active and reactive resistance; where reactance is equal to the product of the angular frequency and inductance:

,

,

where Rпол. - impedance of the winding;

Ract. - active resistance of the winding;

- угловая частота промышленного тока;

- angular frequency of industrial current;

L is the inductance of the winding.

It can be seen from the formula that the impedance of the solenoid winding depends on the inductance of this winding (in practice, the impedance, depending on the position of the rod, varies by about 2.1-2.4 times). The industrial alternating electric current passing through the winding, according to Ohm's law, depends on the impedance of the solenoid winding. The current sensor, fixing the magnitude of this winding current, determines the position of the ferromagnetic part of the rod in the winding, and therefore, determines when the diamagnetic part of the rod opened (or closed) the passage hole in the housing through which the coolant passes. Information from the current sensor that the passage hole is open (or blocked) enters the control device.

In FIG. Figure 1 shows a section of an assembly for influencing a coolant, comprising a housing (1) with a through hole (2), an insulating sleeve (3) with a closing solenoid winding (4) and an opening solenoid winding (5) fixed to it, a rod (6) consisting of the ferromagnetic part (6.1) and the diamagnetic part (6.2), and the cover (7). In FIG. 2 shows an example of a current sensor circuit for explaining the operation of the device.

The site of influence on the coolant installed on the outlet pipe of the first stage of the heat exchanger, operates as follows. For example, at a certain moment, a temperature sensor installed on the outlet pipe of the second stage of the heat exchanger detects a temperature drop and transmits this information to the control device. The control device following the thermal regime connects to the power network the opening solenoidal winding (5) of the node for influencing the coolant. The ferromagnetic part (6.1) of the rod (6) in the horizontal direction under the influence of an electromagnetic field, moving in the insulating sleeve (3), begins to be drawn into the opening winding, and the diamagnetic part (6.2) begins to open the passage hole (2) of the housing (1), through which coolant enters the first stage of the heat exchanger. At the moment when the passage hole is fully open, and the ferromagnetic part of the rod is in the opening winding (the inductance of this winding has reached its maximum value), the current strength in the winding decreases. The current sensor with which this winding is equipped detects this decrease in current and reports this to the control device. The control device disconnects from the power network the opening solenoid winding of the unit. In this case, the rod does not change its position (the through hole is open) and the coolant enters the first stage of the heat exchanger. This occurs until, as a result of the heat exchange process, the temperature at the outlet pipe of the second stage of the heat exchanger rises to the required value. A temperature sensor installed on this pipeline detects this change and transfers it to the control device. Now the control device connects to the power network a closing solenoid winding (4) of the assembly, the ferromagnetic part of the rod is drawn in by the electromagnetic field of this winding. The rod moves in the opposite direction, blocks the passage opening of the housing with its diamagnetic part and closes the passage to the coolant. Now the ferromagnetic part of the rod is in the closing winding. The current passing through this winding decreases. This current reduction fixes the current sensor, which is equipped with a closing winding, and reports this to the control device. The control device disconnects the closing solenoid winding of the unit from the power network, while the rod does not change its position - the passage to the coolant is closed. The process is then repeated.

As a result, the solenoidal windings of the coolant impact unit work in turn, for a short period of time, only at the moment of opening or closing the passage opening. This leads to energy savings, a reduction in power output and a significant reduction in the heating of the windings from the current passing through them. Reducing heating reduces the requirements for materials for heat resistance, which allows the use of technological materials with a low coefficient of friction, for example caprolon, which is used in shipbuilding for the manufacture of sliding bearings of propeller and stern shafts. Horizontal movement of the rod is necessary, first, so that after opening or closing the passage opening of the housing, the rod does not spontaneously change its position in the insulating sleeve without the “command” of the control device. Secondly, the retracting force of the opening solenoid winding is not spent on lifting the rod weight (as with vertical movement), but is almost completely used to overcome the pressure drop. Rational use of the retracting force (with horizontal movement of the rod) and the use of materials with a low coefficient of friction allowed the impact unit on the coolant to work at large pressure drops.

The current sensor may be different in design, for example, any optocoupler pair, low-current winding and Hall sensor or reed switch, current transformer, and so on. The parameters of the opening and closing solenoid windings are identical, and the current sensors with which these windings are equipped are also the same (interchangeable).

The diagram (see Fig. 2) shows a possible example of a current sensor, which operates as follows. Through a power connector (XP1) at a certain point in time, the control device connects to the power network any solenoid winding (Y). In series with this winding, an exemplary powerful resistor (R1) is included, which must be active, that is, not have a reactive component. As the ferromagnetic part of the rod is pulled into the winding, the current strength in the series circuit (Y, R1) will fall. The current drop leads to a decrease in the voltage across the model resistor, this voltage is removed by the diode bridge (VDI-VD4). Next, the rectified pulsating voltage enters the filter chain (R2, C, R3), where; a resistor (R2) limits the input current through an optocoupler (U), a trimming resistor (R3) controls the strength of this input current, a capacitor (C) smoothes the voltage ripple. A couple is working in the optocoupler; LED (HL) and phototransistor (VT). Such a choice of optocouplers gives sufficient slope; that is, a small change in the voltage on the LED leads to a sharp change in the current through the phototransistor. The voltage reduction at the model resistor (R1) is transmitted to the input of the optocoupler (C, HL); LED emission drops, which leads to the closure of the phototransistor. As a result, a logical “one” appears on the load of the phototransistor resistor (R4) and the output (1) of the low-current connector (XP2). This "unit" informs the control device about the moment of disconnection of the solenoid winding from the power circuit. The moment of closing the phototransistor and the appearance of a logical “unit” on its collector is regulated by a trimming resistor (R3).

The site of exposure to the coolant is assembled as follows. An insulating sleeve with solenoidal windings mounted on it is installed on the housing. A rod is inserted into the sleeve, with a diamagnetic part towards the passage hole. Then the cover (7) is mounted on the insulating sleeve. Next, the current sensors of each winding are adjusted. The tuning resistors (R3) of both sensors are set so that their resistance is minimal (the tuning engine is in the extreme left position on the diagram). Then, for example, the opening solenoid winding through the connector (XP1) is connected to the power network, the ferromagnetic part of the rod is drawn into the winding and abuts against the cover. Moving the slider (to the right according to the diagram) of the trimming resistor of the opening current sensor, increase the resistance of this resistor until a logical “one” appears on the terminal (1) of the adjustable current sensor connector (XP) and gives a signal to disconnect the connected solenoid winding. For reliable operation, the resistance of the tuning resistor needs to be slightly increased so that the opening winding is turned off a little earlier (before the stem and cover touch); An insignificant distance the rod passes by inertia. Similarly adjust the current sensor of the closing solenoid winding. This winding is connected to the power network and after the diamagnetic part of the rod rests against the body, the resistance of the corresponding trimming resistor is changed until a logical “one” appears on the output of the current sensor. The coolant impact unit is ready for use. It is rational to locate the current sensors of the solenoid windings directly in the housing of the control device.

Claims (1)

A device for preventing the formation of deposits in the heat exchanger, containing receiving signals from a temperature sensor installed on the output pipe of the second stage of the heat exchanger, a control device, a supply unit for intermittent pulsed mechanical vibrations connected to the control device, interacting with the heat exchanger body at the natural resonant frequency of the heat exchanger, in addition mounted on the outlet pipe of the first stage of the heat exchanger and connected to the control unit l impact on the coolant containing the housing with a through hole, an insulating sleeve rigidly connected to the housing with a hollow rod located inside the sleeve, characterized in that two solenoidal windings are fixed to the sleeve, each winding is equipped with a current sensor, the rod consisting of two parts : ferromagnetic and diamagnetic, has the ability to move horizontally and with its diamagnetic part open or close the passage opening of the housing.

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