RU2672457C1 - Method of temperature gas stratification - Google Patents

Abstract

FIELD: heating equipment.

SUBSTANCE: invention relates to industrial heat engineering and can be used in construction of refrigeration and heating apparatus. Method of temperature stratification of gas includes supplying initial gas stream with excess pressure to inlet of internal channel of separation chamber, ensuring its acceleration and heating. Gas flow is supplied to external channel of separation chamber to cool it. Heated and cooled gas streams are removed from internal and external channels of separation chamber through separate flues. Gas flow to outer channel of separation chamber is effected through permeable walls of inner channel, while at the entrance to inner channel, flow of velocity equal to or greater than speed of sound is achieved.

EFFECT: technical result is separation of flow by allowing gas to be extracted from feed stream through device permeable wall.

4 cl, 2 dwg

Description

Technical field

The invention relates to industrial heat engineering and can be used to create refrigeration and heating devices, the basis of which is the mechanism of machine-less separation of the gas stream with an initial excess pressure on the cooled and heated flows at the outlet.

State of the art

A known method of temperature gas stratification based on the vortex effect (Rank-Hills tube). The principle of operation of the device is to supply compressed air tangentially into the cylindrical chamber through the nozzle inlet, the formation of a swirling flow in the pipe and the selection of the hot air stream from the peripheral section, and the cold stream through the central hole in the pipe (A. Merkulov, “Vortex effect and its application in technology ”/ Samara: Optima, 1997. 346 p. [1]).

The main disadvantages of the known technical solutions are low thermodynamic efficiency (less than 30%) and large losses of total pressure in both cold and hot flows.

The known resonant method of temperature stratification in gas flows (Hartmann-Sprenger pipe). In accordance with the known method, a gas jet is directed into a tube with a plugged end face, the surface temperature of the end face under certain conditions can be several times (up to 4) higher than the initial flow inhibition temperature. In this case, the temperature of the gas flowing out of the tube with the closed end decreases (Burtsev SA, Leontiev AI “Investigation of the influence of dissipative effects on the temperature stratification in gas flows (review)” // Thermophysics of high temperatures. V. 52, No. 2, 2014. S. 310-322. [2]).

The main disadvantages of the known solutions are large losses of the total pressure of the gas stream and low efficiency of cooling the stream (less than 10 degrees).

The closest in technical essence to the claimed invention is a method of temperature stratification of gas using a Leontief pipe, comprising supplying gas to the separation chamber, the discharge of cold and hot gases through separate gas ducts, while the gas stream after the separation chamber is directed through the inner pipe and the outer annular channel, in this case, gas is accelerated through a profiled nozzle to a supersonic speed through a profiled nozzle, gas is passed through an external annular channel at a subsonic speed (p RF patent No. 2106581). The wall separating the channels is made of a heat-conducting material, through which heat transfer occurs from a subsonic flow to a supersonic one.

The disadvantage of this method is the operation due to the provision of supersonic flow rates, which requires additional overpressure at the inlet. The presence of thermal resistance in the form of an impermeable partition between subsonic and supersonic flows reduces the effectiveness of this method of temperature stratification. Also, the presence of two streams exchanging heat at the inlet increases the dimensions of the device.

A technical problem is the need to provide a large initial gas pressure in order to achieve supersonic speeds in devices of this type, as well as the significant total pressure loss associated with the subsequent gas flow inhibition.

Disclosure of the invention

The technical result achieved by using the claimed invention is the separation of the stream by allowing suction of gas from the original stream through the permeable wall of the device. In addition, the method can be implemented in a device with smaller dimensions compared to devices of a similar purpose by supplying gas to the separation chamber through a single gas duct, and by ensuring the separation of the stream by suctioning the gas from the original stream through a permeable wall.

The problem is solved in that in the method of temperature stratification of gas, including supplying an initial gas stream with excess pressure to the inlet of the internal channel of the separation chamber to ensure its acceleration and heating, supplying a gas stream to the external channel of the separation chamber to ensure its cooling, output of the heated and cooled gas flows from the internal and external channels of the separation chamber, respectively, through separate gas ducts, according to the technical solution, the gas flow in The external channel of the separation chamber is carried out through the permeable walls of the internal channel, while at the entrance to the internal channel the flow reaches a speed equal to or greater than the speed of sound, while the pressure of the gas stream at the input of the internal channel provides at least 190 kPa. Achieving the speed of sound by the flow can be achieved by working the friction forces by directing the initial gas flow into a constant-cross-section channel in front of the separation chamber or by geometrically affecting the flow in a tapering or tapering-expanding nozzle.

As the initial gas stream, a two-phase stream with liquid or solid particles dissolved in it can be used, and the effect of temperature stratification increases due to condensation falling on the channel wall of the separation chamber.

In other words, the technical result is achieved due to the available pressure of the initial flow of at least 190 kPa, which allows the flow to be accelerated to a speed equal to or greater than the speed of sound, to ensure the redistribution of the braking temperature in the boundary layer and the formation of a cooled wall gas layer, which is then sucked out through the permeable wall and organize, thus, a secondary stream of chilled gas, while increasing the mass-average temperature of the initial stream.

Brief Description of the Drawings

In FIG. 1 schematically shows a device for temperature gas stratification.

In FIG. 2 schematically reflects the principle of operation of a temperature stratification device that implements the inventive method, showing the distribution of the braking temperature in the boundary layer of a high-speed stream of compressible gas when flowing around a permeable wall.

The positions in the drawing indicate:

1 - receiver with compressed gas having a pressure of at least 190 kPa;

2 - tapering nozzle;

3 - the internal channel of the separation chamber with permeable (porous) walls;

4 - external (annular) channel of the separation chamber;

5 - external thermal insulation of the separation chamber and exhaust gas ducts;

6 - output supersonic diffuser for braking the heated stream leaving the inner tube of the separation chamber;

7 - chimney gas collection duct;

8 - a flue for collecting heated gas;

9 - source gas flow with excess pressure supplied to the separation chamber and having an inlet velocity equal to the speed of sound (M = 1);

10 - permeable (porous) wall of the separation chamber;

11 - impermeable wall of the separation chamber;

12 - chilled stream leaving the separation chamber;

13 - heated stream exiting the separation chamber.

The implementation of the invention

The invention is illustrated as follows.

The braking temperature in the boundary layer of the compressible gas is not evenly distributed. The temperature inside the boundary layer is lower, and in the outer part it is higher than the stagnation temperature in the flow core (with the Prandtl number of the working fluid less than 1, which is typical for most gases). The temperature determining the heat flux in this case is the adiabatic wall temperature

- начальная температура торможения потока, K;Where:

- initial flow inhibition temperature, K;

k is the adiabatic index of the working fluid (k = 1.4 for air);

M is the Mach number in the stream;

r is the coefficient of temperature recovery.

The parameter r exerts the greatest influence on the adiabatic temperature of the wall and shows the fraction of the energy of the flow that goes into heat on the wall. The temperature recovery coefficient is most dependent on the type of gas - the Prandtl number for the working medium - Pr:

where n = 1/2 (laminar flow regime), n = 1/3 (turbulent regime - most often implemented in practice).

For air (Pr = 0.7), the temperature recovery coefficient r for a continuous turbulent continuous flow around a flat wall (as well as cylindrical and conical in the longitudinal direction), according to experimental data [4] - (Schlichting G. “Theory of the boundary layer” // M: Science, 1974, 711 p.) Is equal to 0.885 ± 0.01. For gas mixtures helium-xenon, helium-argon, argon-hydrogen, hydrogen-xenon, etc. (Pr = 0.1-0.4) the value of r can decrease to 0.3-0.4. Accordingly, according to (1), the adiabatic wall temperature decreases and, thus, the temperature stratification potential of the gas increases.

Low values of the temperature recovery coefficient (up to zero) are realized when condensate falls onto a wall streamlined by a high-speed stream of a two-phase working fluid (for example, moist air or natural gas). During high-speed flow, the Sefman lifting force leads to the deposition of droplets on a solid wall. In [5] (Leont'ev AI, Osiptsov AN, Rybdylova OD “The boundary layer on a flat plate in a supersonic gas-droplet flow. The effect of evaporating droplets on the temperature of the adiabatic wall” // Thermal physics of high temperatures. T. 53, No. 6, 2015. S. 910-917) it is shown that the presence of even a very low concentration of drops can lead to a significant decrease in the adiabatic temperature of the wall.

For the implementation of temperature stratification of gas, it is necessary to first accelerate the flow to a speed not lower than the speed of sound. According to the theory of thermodynamics of gas flows [6] - (L. Vulis “Thermodynamics of gas flows” / Gosenergoizdat, Moscow, 1950, 304 pp.), In the presence of a geometric effect in the form of a narrowing of the channel or the work of friction forces in the constant section channel, an accelerated gas movement up to a critical state (speed of sound). In the internal channel of a separation chamber with permeable walls, a stream moving at the speed of sound or at a supersonic speed experiences a expenditure effect - suction through the permeable wall under the condition of lower pressure from the back of the wall (for example, atmospheric pressure). In this case, the separation chamber is a supersonic section of the flow nozzle in which the wall cooled gas layer is released (suction) through the permeable channel walls. According to the law of conservation of energy, the mass-average temperature of the rest of the gas rises. The length of the channel and the porosity of the wall material is limited only by the value of the working pressure at the inlet to the device and by ensuring the required margin of safety. In this case, effective braking of the supersonic flow exiting from the internal channel with permeable walls may allow maintaining the full pressure of the heated flow.

Also, as follows from (1), with an increase in the total free-stream temperature, the difference between the temperature in the flow core and the adiabatic wall temperature (the temperature of the wall layers of the gas) increases. Thus, the potential for the implementation of temperature stratification and, accordingly, the difference between the temperatures of the heated and cooled flows at the outlet of the separation chamber are increased.

The implementation of the proposed method of temperature gas stratification is shown by the example of the operation of the device shown in FIG. 1. The device contains a tapering nozzle 2, a separation chamber that provides reception and temperature separation of gas flows, and flues 7 and 8 for outputting the flows of cooled and heated gases. The separation chamber consists of an internal (cylindrical) 3 and an external (annular) 4 channels. The tapering nozzle is designed to accelerate to the speed of sound of the supplied gas stream and is located at the inlet of the separation chamber so that its output is the input of the internal channel. Accordingly, the output diameter of the nozzle 2 is equal to the diameter of the inner channel 3 of the chamber. The inner channel 3 is connected to the duct 8 of the outlet of the heated gas, and the outer 4 is connected to the duct 7 of the outlet of the cooled gas. The inner 3 and outer 4 channels are placed coaxial to each other. The internal channel 3 is designed to supply gas to the separation chamber. The external channel 4 serves to collect the chilled gas taken from the internal channel 3. The walls 10 of the internal channel 3 are permeable (porous). At the output of the internal channel is placed a supersonic diffuser 6, designed to inhibit the heated stream. The outer walls of the external channel 4 are impermeable from a material with a low coefficient of thermal conductivity, for example, stainless steel (λ = 16 W / (mK)), which is often used in the manufacture of pipelines. The outer surface of the separation chamber and the exhaust ducts 7 and 8 are provided with a layer of thermal insulation 5.

и соответствующим массовым расходом G₀ (определяемым критическим сечением сопла) подают, например, из ресивера 1 в заявляемое устройство через сужающееся сопло 2, которое переходит во внутренний цилиндрический канал 3 с пористыми стенками 10. Для обеспечения звуковой скорости потока 9 на выходе из сопла 2 необходим запас полного давления

в ресивере 1 не меньше 190 кПа (при атмосферном давлении на выходе из установки и во внешнем кольцевом канале 4). При этом в пристенной области высокоскоростного потока формируется искривленный профиль температуры торможения Т^*. Под воздействием диссипативных процессов в пограничном слое адиабатная температура стенки

оказывается ниже среднемассовой температуры торможения

. Пристенный слой высокоскоростного потока газа, имеющий более низкую температуру, за счет имеющегося избыточного давления отсасывается через проницаемую стенку 10 (dG_хол) и формирует с обратной стороны стенки вторичный поток суммарным расходом G_хол с температурой

ниже исходной температуры

. Данный вторичный поток выходит по отдельному газоходу 7, образуя отводимый охлажденный поток газа 12. При этом среднемассовая температура первичного потока

становится выше исходной температуры

, а его массовый расход становится равным G_гop=G₀-G_хол. За счет расходного воздействия (отсос через проницаемую стенку 10) газ разгоняется по ходу движения по внутреннему каналу 3 до сверхзвуковых скоростей. Подогретый в центральном канале газ поступает в выходной сверхзвуковой диффузор 6 и далее отводится через отдельный газоход 8, образуя выходящий подогретый поток 13.Compressed gas with initial braking pressure

and the corresponding mass flow rate G ₀ (determined by the critical section of the nozzle) is fed, for example, from the receiver 1 to the inventive device through a tapering nozzle 2, which passes into the inner cylindrical channel 3 with porous walls 10. To ensure the sound velocity of the stream 9 at the exit of the nozzle 2 full pressure reserve required

in receiver 1 not less than 190 kPa (at atmospheric pressure at the outlet of the installation and in the outer annular channel 4). Moreover, in the near-wall region of the high-speed flow, a curved stagnation temperature profile T ^{* is formed} . Under the influence of dissipative processes in the boundary layer, the adiabatic wall temperature

turns out to be lower than the average mass braking temperature

. The near-wall layer of a high-speed gas stream having a lower temperature is sucked out through the permeable wall 10 (dG _chamber ) due to the available excess pressure and forms a secondary stream on the back side of the wall with the total flow rate G _chamber with temperature

below initial temperature

. This secondary stream exits through a separate gas duct 7, forming a discharged cooled gas stream 12. In this case, the mass-average temperature of the primary stream

gets higher than the initial temperature

, and its mass flow rate becomes equal to G _gop = G ₀ -G _hol . Due to the expenditure effect (suction through the permeable wall 10), the gas accelerates along the internal channel 3 to supersonic speeds. The gas heated in the central channel enters the supersonic outlet diffuser 6 and is then discharged through a separate gas duct 8, forming an outgoing heated stream 13.

The inventive method can be implemented by any other device that allows the suction of the wall layer of a high-speed gas stream through the permeable walls of the channel of the separation chamber.

Thus, the claimed method allows for temperature stratification of the gas and to obtain two flows at the outlet - a cooled gas stream, sucked out through the permeable wall, and a heated initial stream, accelerated to supersonic speed. The method of temperature stratification requires for effective functioning a smaller margin of initial overpressure due to the absence of the need for a supersonic flow regime at the inlet of the device. In addition, the method can be implemented in a device with smaller dimensions compared to devices of similar purpose by supplying gas to the separation chamber through one gas duct and providing separation of the stream by suctioning the gas from the primary stream through the permeable wall.

Claims (4)

1. The method of temperature stratification of gas, including supplying an initial gas stream with excess pressure to the inlet of the internal channel of the separation chamber to ensure its acceleration and heating, supplying a gas stream to the external channel of the separation chamber to ensure its cooling, output of the heated and cooled gas flows from the internal and external channels of the separation chamber, respectively, through separate gas ducts, characterized in that the gas stream is supplied to the external channel of the separation chamber through the permeable walls of the inner channel, while at the entrance to the inner channel ensure that the flow reaches a speed equal to or greater than the speed of sound. 2. The method according to p. 1, characterized in that the flow reaches the speed of sound due to the work of the friction forces by directing the original gas stream into the channel of constant cross section in front of the separation chamber. 3. The method according to p. 1, characterized in that the flow reaches a speed equal to or greater than the speed of sound, provide by directing the original gas stream into a tapering or tapering-expanding nozzle. 4. The method according to p. 1, characterized in that the source gas stream using a two-phase stream with dissolved in it liquid or solid particles.

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