RU2263863C2 - Method of cooling a temperature of water in the heat-mass exchange aggregates, for example in cooling towers - Google Patents

Abstract

FIELD: cooling towers and systems of water recirculation of industrial enterprises.

SUBSTANCE: the invention is pertaining to the method of cooling a temperature of water in the heat-exchange aggregates, for example, in cooling towers and may be used in the systems of water recirculation of industrial enterprises. The method of cooling a temperature of water in the heat-exchange aggregates provides for the action by airflows on an evaporated surface of water. At that the surface of water in addition is exposed to a high-frequency ultrasonic action using the frequencies corresponding or multiple to the frequencies of the natural thermal oscillations of molecules of water: V_A = V_nto·n and V_A = V_nto /n, where: V_A - frequency of acoustic oscillations; V_nto - frequency of natural thermal oscillations:

where: i - average number of the intermolecular spacing intervals passed by a molecule or a particle till their concussion; L - a distance between the centers of molecules; d - a diameter of a molecule; k - Boltzmann constant; T-thermodynamic temperature of water; m - a molecular (corpuscle) mass; n - an integer 1,2,3,4,5, etc., at that with an amplitude of an oscillation displacement of the acoustic waves, equal or exceeding the value of the intermolecular spacing interval, at which the forces of attraction between the molecules of the water are insignificantly small: A ≥ l, where: A - is an amplitude of an oscillation displacement of the acoustic waves; l - a spacing interval between molecules of water, at which forces of attraction between them are insignificantly small: l ≈ 10^-9 m. The high-frequency acoustic action on the evaporated surface is conducted simultaneously in two mutually intersecting directions. At that one of the directions is tangential to the evaporated surface. The high-frequency acoustic action on the evaporated surface is conducted mainly in the direction of motion of the aerodynamic airflows of the cooling tower. The evaporated surface is exposed to the high-frequency acoustic action frontally with an intensity level ≥ 145 dB, and tangentially - with a level of intensity ≥ 120 dB. The invention allows to raise intensity of cooling of water.

EFFECT: the invention ensures an increase of intensity of cooling of water.

4 cl, 3 dwg

Description

The invention relates to a power system, in particular to cooling towers, and can be used in circulating water systems of industrial enterprises.

BACKGROUND

Known spray basin (see patent of the Russian Federation No. 2168133, IPC F 28 C 1/00, 2001), containing a pressure header with groups of spray nozzles in the form of rows, in the lower part of which are connected pipelines with ejectors, on the inner surface of the expanding part of each which have helical grooves, and the ejector is mounted on a float and is connected to the riser by means of a flexible corrugated insert, in addition, the ejector is connected to the pulsator by its mixing chamber, and T-resonators are installed at the bottom of the pool azine form, consisting of a vertical elastic plate fixed in the lower part to the pedestal, and in the upper part movably connected to the propeller-float, made in the form of a spiral vibrator.

The disadvantage of this technical solution is the low efficiency of water cooling due to the reduction of heat and mass transfer in the entire space of the spray pool, due to the lack of organized natural ascending air flows. The interaction of air with water organized only above the surface of the pool water mirror by means of ejectors with the aim of generating waves and thereby increasing the heat and mass transfer surface is not sufficiently effective in comparison with the cooling effect created by the organized natural air flow interacting with the entire evaporated surface of the falling water droplets and the surface pool water mirrors of heat exchangers, such as cooling towers.

There is a method of lowering the temperature of water in heat exchangers, for example in cooling towers, providing for the impact of air flows on the surface of the water (see. Farforovsky B.S. Coolers of circulating water of thermal power plants. L .: Energy, 1972, p.45 p.4- 1, p. 70-76 p. 4-7).

The disadvantage of this method is the low efficiency of heat and mass transfer, due to the low speed of the air supplied to the tower, providing separation of a relatively small number of water molecules from the evaporated surface (films, drops), which does not allow intensive cooling. Increasing the speed of the supplied air, for example, due to the use of fans, leads to a significant increase in the cost of the process and loss of water to the atmosphere due to an increase in the entrainment of small drops of water.

SUMMARY OF THE INVENTION

The objective of the claimed technical solution is the creation of such a method that would increase the number of detached water molecules from the evaporated surface without increasing the speed of air flows and, thereby, increase the intensity of its cooling with minimal loss of water into the atmosphere.

The problem is achieved in that in a method of lowering the temperature of water in heat-exchange units, for example in cooling towers, providing for the action of air flows on the evaporated surface of the water, it is additionally subjected to high-frequency acoustic exposure with frequencies corresponding to or multiple of the frequencies of natural thermal vibrations of water molecules

ν _A = ν _stk · n;

ν _A = ν _stk / n ,

where ν _A is the frequency of acoustic vibrations;

ν _stk - the frequency of natural thermal vibrations

where i is the average number of intermolecular distances traveled by a molecule or particle before a collision;

L is the distance between the centers of the molecules;

d is the diameter of the molecules;

k is the Boltzmann constant;

T is the thermodynamic temperature of water;

m is the mass of the molecule;

n is an integer 1, 2, 3, 4, 5, etc.,

with an amplitude of the vibrational displacement of the acoustic waves equal to or greater than the intermolecular distance at which the attractive forces between the water molecules are negligible

A≥l,

where A is the amplitude of the vibrational displacement of the acoustic waves;

l is the distance between water molecules at which the attractive forces between them are negligible

l≈10 ^-9 m

(see Trofimov T.I. Physics in tables and formulas. M: Drofa, 2002, p.112).

In addition, according to claim 2, the high-frequency acoustic effect on the evaporated surface can be carried out simultaneously in two mutually intersecting directions, one of which is tangential to the evaporated surface.

In addition, according to claim 3, the high-frequency acoustic effect on the evaporated surface can be carried out mainly in the direction of movement of the aerodynamic air flows of the tower.

In addition, according to claim 4, the evaporated surface can be subjected to high-frequency acoustic exposure in the frontal direction with an intensity level of ≥145 dB, and tangential with an intensity level of ≥120 dB.

The action of high-frequency acoustic vibrations on the evaporated surface by frequencies corresponding to or multiples of the intrinsic thermal vibrations of the water molecules excites resonance and, thereby, increases the amplitude of their own thermal vibrations to extraordinary values due to breaking or weakening of intermolecular bonds. From physics it is known (see. "The Great Encyclopedic Dictionary" edited by Prokhorov AM M., scientific publishing house "Big Russian Encyclopedia", 1998, p.235 "Evaporation") that the breaking of bonds between liquid molecules, in particular water, accompanied by a decrease in temperature. The energy of breaking intermolecular bonds during acoustic exposure is equivalent to the magnitude of thermal energy with the opposite sign, capable of providing a similar gap. Thus, with its non-thermal - dynamic breaking or weakening of intermolecular bonds, a thermal energy deficit is created numerically equal to q = 2258.5 KJ per kilogram of evaporated moisture (water) (see Losev KS Voda. L .: Gidrometeoizdat, 1989 city, p. 125, 126), which leads to an instantaneous decrease in the temperature of the split molecules by a value corresponding to a given energy. Water molecules with broken or weakened bonds are easily captured and carried by the air flows of the cooling tower, where by means of diffusive heat and mass transfer during their (molecules) autonomous state, air flows are substantially cooled. Interacting with the evaporated surface of the water, the cooled air flows, in turn, intensively cool it (water), while continuing to capture (demolish) other molecules whose intermolecular bonds are broken or weakened by high-frequency acoustic exposure. Due to the fact that the temperature of the water molecules of the evaporated surface along the front of the high-frequency acoustic exposure is different and has a range of values from T ₁ to T ₂ , high-frequency acoustic exposure must be carried out simultaneously in the corresponding frequency range.

The high-frequency acoustic effect on the evaporated surface with vibrational displacement amplitudes A exceeding the intermolecular distance allows one to obtain, with the help of resonant frequency superposition, the vibration amplitudes of water molecules of the order of 10 ^-9 m or more, at which the mutual attraction forces between them are negligible or are absent. This significantly reduces the energy consumption for separation and removal of water molecules from the evaporated surface, thereby increasing the fraction of non-thermal evaporation, which increases the cooling efficiency of the air flow of the cooling tower at minimum speeds, which, in turn, significantly reduces the loss of water into the atmosphere.

High-frequency acoustic action on the evaporated surface, carried out simultaneously in two mutually intersecting directions, one of which is tangential to the evaporated surface, in combination even with low dynamic air flows, significantly increases the intensity of non-thermal (e.g., acoustic) evaporation of water, and thereby increases the cooling ability cooling towers. Frontal high-frequency acoustic exposure is carried out mainly to break and reduce the intermolecular bonds of water molecules, tangential primarily to remove them from the evaporated surface and to laminate the movement of autonomous molecules within each wave of acoustic vibrations. This effect is achieved by the fact that the region of the pressure wave, like a scraper, blows autonomous water molecules from the evaporated surface, dragging them in front of them. The region of the wave with reduced pressure captures not only water molecules with weakened and broken bonds, but also those molecules of the evaporated surface whose amplitudes of thermal vibrations are only increased. Thus, in terms of the effectiveness of its effect on the evaporated surface, the region of the wave with reduced pressure is decisive in increasing the evaporative and, accordingly, cooling ability of the tower.

The high-frequency acoustic effect on the evaporated surface, carried out mainly in the direction of movement of the aerodynamic air flows of the tower, significantly increases their cooling ability, which is due to the fact that the tangential dynamic component of the air flow of the tower is supplemented and amplified by the vibrational effect of traveling acoustic waves having the nature of a sharp, short-term, equivalent pulsed, pressure changes from maximum to minimum. Water molecules cut off in this way by means of wave energy receive an impulse of directed energy, the magnitude of which somewhat orders the movement of molecules, reducing the probability of their mutual collision and premature collapse (condensation), thereby increasing the heat and mass transfer between autonomous molecules and the air flow. The more autonomous water molecules receive thermal energy from the air flow, the less likely they will collapse back and therefore, the higher the cooling efficiency of the tower as a whole.

The high-frequency acoustic effect on the evaporated surface of the tower in the frontal direction, carried out with an intensity level of ≥445 dB, makes it possible to destroy and reduce intermolecular bonds of water with a high probability and, thereby, create conditions for a significant increase in cooling capacity. High-frequency acoustic exposure with an intensity level <145 dB significantly reduces the cooling ability of the acoustic exposure.

The high-frequency acoustic effect on the evaporated surface in a tangential direction with an intensity level <120 dB causes a negative effect - premature collapse (condensation) of water molecules and, thereby, reduces the cooling ability of the tower.

The invention is illustrated by drawings - figure 1, 2, 3. Position 1 (see figure 1, 2) is the line of water temperature in the stand; position 2 (see figure 1, 2) - line cooling efficiency of the air flow; position 3 (see figure 1, 2) - line cooling efficiency when combined with the air flow and high-frequency acoustic effects; position a, b (see figure 1) - peaks of cooling efficiency at frequencies of 25.2 kHz and 50.4 kHz, multiple of the calculated value. Position 1a, 2a (see figure 3) is the line of tangential and frontal high-frequency acoustic impact, respectively.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

Also, experiments were conducted on the acoustic decrease in water temperature at t = 38 ° C (see Fig. 1, item 1) on a bench simulating the heat and mass transfer processes of a cooling tower, in which the effect on the evaporated surface by air flow (see Fig. 1, item. 2) was supplemented by high-frequency acoustic exposure with frequencies of 16.0 kHz; 22.4 kHz; 25.2 kHz; 28.0 kHz; 32.0 kHz; 42.0 kHz; 45.0 kHz; 50.4 kHz; 54.0 kHz (see figure 1, position 3).

(см. фиг.1). Однако использование акустических излучателей, работающих в диапазоне супервысоких частот экономически не целесообразно ввиду их высокой стоимости и относительно небольшого ресурса работы.As a result of the experiment, it was found that the maximum cooling efficiency peaks occur at frequencies of 25.2 kHz and 50.4 kHz (see Fig. 1, pos. A, b), which are approximately a multiple of the calculated value of the thermal vibrations of water molecules, and the total cooling efficiency grows with increasing frequency multiple of thermal vibrations of water molecules

(see figure 1). However, the use of acoustic emitters operating in the super-high frequency range is not economically feasible due to their high cost and relatively small service life.

The high-frequency acoustic effect on the evaporated surface with vibrational amplitude A≥10 ^-9 m allowed us to obtain stable values of cooling efficiency at a frequency of 25.2 kHz, which expands the possibilities of using this frequency range and, thereby, increases the economic effect of the use of acoustic exposure.

=8°С при скорости воздушного потока 0,2 м/сек; ν=25,2 кГц и

=10°С при скорости воздушного потока 0,2 м/сек; ν=50,4 кГц, при этом охлаждающая эффективность воздушного потока составила только ΔT₁≈2°С (см. фиг.2). Дальнейшее снижение скорости воздушного потока приводит к снижению суммарной охлаждающей эффективности.The high-frequency acoustic effect on the evaporated surface in two mutually intersecting directions: frontal and tangential, ensured the maintenance of the total cooling efficiency at the level

= 8 ° C at an air flow rate of 0.2 m / s; ν = 25.2 kHz and

= 10 ° C at an air flow rate of 0.2 m / s; ν = 50.4 kHz, while the cooling efficiency of the air flow was only ΔT ₁ ≈2 ° C (see figure 2). A further decrease in air flow rate leads to a decrease in overall cooling efficiency.

на каждой из кратных частот в среднем на 1,7°С. Боковое по отношению к аэродинамическому потоку высокочастотное акустическое воздействие позволило получить дополнительное приращение суммарной охлаждающей эффективности

на каждой из кратных частот в среднем около 2°С.The experiments on superimposing the effects of aerodynamic air flow and tangentially directed high-frequency acoustic effects (associated effects) made it possible to obtain an increment of the total cooling efficiency by 2.5 ° C. Counter exposure improves overall cooling efficiency

at each of multiple frequencies by an average of 1.7 ° C. The high-frequency acoustic impact, lateral with respect to the aerodynamic flow, made it possible to obtain an additional increment in the total cooling efficiency

at each of multiple frequencies an average of about 2 ° C.

As a result of the experiment, shown in figure 3, to determine the minimum sufficient level of intensity of high-frequency acoustic exposure in the frontal and tangential directions, it was found that a decrease in the intensity of high-frequency acoustic exposure at a frequency of 25.2 kHz in the frontal direction <145 dB leads to a significant decrease in cooling efficiency , which is consistent with the data (see. "Little Encyclopedia" Ultrasound "", edited by Golyamin I.P. M .: Soviet Encyclopedia, 1979, p.339). The high-frequency acoustic effect in the tangential direction in combination with the air flow showed that the threshold values of the acoustic intensity in this direction are slightly reduced and amount to 120 dB. High-frequency acoustic exposure with an intensity of <120 dB significantly reduces the cooling efficiency of acoustic exposure.

Claims (4)

1. A method of lowering the temperature of water in heat exchange units, for example in cooling towers, comprising exposing the water surface to an evaporated water surface, characterized in that the water surface is additionally subjected to high-frequency acoustic exposure with frequencies corresponding to or a multiple of the natural frequencies of the water molecules ν _A = ν _ctn ν _A = ν _stk / n where ν _A is the frequency of acoustic vibrations; ν _stk - the frequency of natural thermal vibrations,

where i is the average number of intermolecular distances traveled by a molecule or particle before a collision; L is the distance between the centers of the molecules; d is the diameter of the molecules; k is the Boltzmann constant; T is the thermodynamic temperature of water; m is the mass of the molecule (particle); n is an integer 1, 2, 3, 4, 5, etc., with an amplitude of the vibrational displacement of the acoustic waves equal to or greater than the intermolecular distance at which the attractive forces between the water molecules are negligible A≥l, where A is the amplitude of the vibrational displacement of the acoustic waves; l is the distance between water molecules at which the attractive forces between them are negligible, l≈10 ^-9 m. 2. The method according to claim 1, characterized in that the high-frequency acoustic effect on the evaporated surface is carried out simultaneously in two mutually intersecting directions, one of which is tangential to the evaporated surface. 3. The method according to claim 2, characterized in that the high-frequency acoustic effect on the evaporated surface is carried out mainly in the direction of movement of the aerodynamic air flows of the tower. 4. The method according to claim 3, characterized in that the evaporated surface is subjected to high-frequency acoustic impact frontally with an intensity level of ≥145 dB, and tangentially with an intensity level of ≥120 dB.

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