RU181270U1 - GAS TEMPERATURE STRATIFICATION DEVICE - Google Patents

Abstract

The utility model relates to industrial heat engineering and can be used to create refrigeration and heating devices, which are based on the mechanism of machine-less separation of a gas stream with an initial excess pressure on the cooled and heated flows at the outlet. The technical result achieved by using the claimed utility model is to reduce the initial pressure level due to the absence of the need to provide a supersonic flow regime at the device inlet. In addition, the device provides a reduction in the total pressure loss of one of the separated streams, and also has smaller dimensions in comparison with devices of a similar purpose. The technical result is achieved due to the fact that in the device for temperature stratification of the gas stream containing a separation chamber, including internal and external channels, the outlets of which are connected to the corresponding flues to output the separated heated and cooled gases, a narrowing nozzle that allows acceleration of the gas stream supplied to the device to the speed of sound, and a supersonic diffuser located at the output of the internal channel and providing braking of the heated gas, according to In accordance with the technical solution, the tapering nozzle is located at the inlet of the inner channel, while the output diameter of the tapering nozzle is equal to the input diameter of the inner channel, the inner and outer channels are coaxial, while the walls of the inner channel are at least partially permeable, and the walls of the outer channel are impermeable, from a material with a low coefficient of thermal conductivity and equipped with external thermal insulation. The length of the permeable section of the inner channel of the separation chamber is at least 4 calibers. 2 s.p. f-ly, 2 ill.

Description

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

State of the art

A device for temperature gas stratification is known, which is based on the vortex effect (Rank-Hills tube). The principle of operation of the device is to supply compressed air tangentially into a cylindrical or conical 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.

A device based on the resonant method of temperature stratification in gas flows (Hartmann-Sprenger pipe) is known. In accordance with this solution, the gas jet is directed into the tube with the plugged end face, the temperature of the end surface under certain conditions can be several times higher than the initial temperature of the flow inhibition. 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).

A device for the temperature stratification of gas (Leontief pipe), comprising a housing made in the form of a pipe, with a separation chamber for receiving the processed gas and with ducts for outputting cold and hot gases (RU 2106581 C1, class F25B 9/02, publ. 23.05. 1996) [3]. The housing is equipped with an additional pipe of a heat-conducting material of smaller diameter with a profiled supersonic nozzle and a supersonic diffuser mounted coaxially in the first pipe.

The disadvantage of this technical solution 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.

The closest in technical essence to the claimed utility model is the stratification device disclosed in the publication [4] (Vinogradov Yu.A., Zditovets A.G., Strongin M.M. “An experimental study of the temperature stratification of an air stream flowing through a supersonic channel, with a central body in the form of a porous permeable tube "// Fluid and gas mechanics. No. 5, 2013, pp. 134-145). A device for temperature gas stratification comprises a receiver, a housing, inside of which a dividing wall, a supersonic nozzle, and a supersonic diffuser are placed. The operation of the device consists in supplying gas to the separation chamber, the discharge of cold and hot gases through separate flues, similarly to the basic concept implemented in the Leontief pipe, while a porous permeable surface is used as the separation chamber (wall). The supersonic flow regime in the described experiment was organized in an external annular channel, and the central body was a cylindrical channel made of permeable material (sintered electrocorundum). The publication results indicate that the air stream entering the inner cylindrical channel, by the beginning of the porous permeable section, was accelerated to sound speed due to the work of friction forces. At the exit from the central porous channel, the flow due to the expenditure effect (suction) had a supersonic speed and a higher braking temperature than in the receiver, and a subsonic flow and a slight difference in the braking temperature from the initial temperature in the receiver were recorded at the exit from the annular channel.

The disadvantage of this technical solution is the fact that for the implementation of temperature stratification in this configuration, it is necessary to provide a supersonic flow regime in the external annular channel, which requires excess pressure at the inlet, while the resulting gas injection from the internal channel leads to significant loss of total pressure, disruption of the supersonic flow conditions and reduce heating of a supersonic flow at the exit of the annular channel.

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.

Utility Model Disclosure

The technical result achieved by using the claimed utility model is to reduce the initial pressure level due to the absence of the need to provide a supersonic flow regime at the device inlet. In addition, the device provides a reduction in the total pressure loss of one of the separated streams, and also has smaller dimensions in comparison with devices of a similar purpose.

The technical result is achieved due to the fact that in the device for temperature stratification of the gas stream containing a separation chamber, including internal and external channels, the outlets of which are connected to the corresponding flues to output the separated heated and cooled gases, a narrowing nozzle that allows acceleration of the gas stream supplied to the device up to speed, and a supersonic diffuser located at the outlet of the internal channel and providing braking of the heated gas, according to the technical To the solution, the tapering nozzle is located at the inlet of the inner channel, while the output diameter of the tapering nozzle is equal to the diameter of the inner channel, the inner and outer channels are coaxial, while the walls of the inner channel are at least partially permeable, and the walls of the outer channel are impermeable, from material with a low coefficient of thermal conductivity and equipped with external thermal insulation. The length of the permeable section of the inner channel of the separation chamber is at least 4 calibers.

Description of drawings

In FIG. 1 schematically shows the inventive device for temperature stratification of gas.

In FIG. 2 schematically reflects the principle of operation of the inventive temperature stratification device, 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 are indicated

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 - the source gas stream 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.

Utility Model Implementation

The essence of the utility model is explained as follows.

The braking temperature of the compressible gas is distributed unevenly in the boundary layer. For near-wall gas layers, it turns out to be lower, and for more distant ones it is higher than the stagnation temperature in the flow core (with a Prandtl number of gas less than 1). The temperature determining the heat flux in this case is the temperature of the wall layers of the gas or the adiabatic wall temperature T _w ^* :

,

,

where T ₀ ^* is the 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 undisturbed flow; 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 kind of gas - the Prandtl number of the working fluid - 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 continuous turbulent continuous flow around a flat, cylindrical and conical surface, according to experimental data [5] - (Schlichting G. “Theory of the boundary layer” // M: Nauka, 1974. 711 s) is 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.

The temperature stratification of a stream depends on its speed and becomes noticeable at flow rates not lower than the speed of sound. According to the theory of thermodynamics of gas flows [6] - (6. Vulis L.A. “Thermodynamics of gas flows” / Gosenergoizdat, Moscow. 1950. 304 p.), In the presence of a geometric effect in the form of a narrowing of the channel, accelerated gas movement up to a critical state (speed of sound). In this case, the necessary supply of gas pressure to achieve the speed of sound (M = 1) depends on the type of gas (adiabatic index):

,

,

where P ₀ ^* , P ₁ ^* is the total pressure at the inlet and at the outlet of the installation, Pa; k is the adiabatic exponent of the working fluid.

For air (k = 1.4), in accordance with (3), the pressure drop is about 1.89. Accordingly, at atmospheric pressure at the outlet of the installation in the receiver at the inlet, it is necessary to maintain a pressure of at least 190 kPa.

In the channel of the separation chamber with permeable walls, a stream moving with the speed of sound, with a sufficient initial overpressure, experiences a expenditure effect - suction through the wall. According to the law of conservation of energy, the mass-average temperature of the rest of the gas rises. As experience shows, to obtain a significant effect of temperature stratification of the gas, the length of the permeable section of the inner channel of the separation chamber must be at least 4 calibers (the ratio of the length of the inner channel to its diameter). 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 in the diffuser located at the outlet of the central channel with permeable walls allows the total pressure of the heated flow to be maintained.

Also, as follows from (1), with an increase in the total gas temperature at the device inlet, the difference between the temperature in the flow core and the adiabatic wall temperature (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 device are increased.

The inventive device for temperature gas stratification comprises a tapering nozzle 2, a separation chamber for receiving and temperature separation of gas streams, and gas ducts 7 and 8 for outputting cooled and heated gas streams. 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 is used to collect cold gas taken from the internal channel 3. The walls 10 of the internal channel 3 are made permeable (porous), while the length of the permeable section of the inner channel of the separation chamber must be at least 4 calibers. To provide a greater effect of temperature stratification, the walls of the inner channel can be made porous along the entire length of the channel. 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, ebonite, λ = 0.16 W / (mK). The outer surface of the separation chamber and the exhaust gas ducts 7 and 8 are provided with a layer of thermal insulation 5. To ensure the operation of the device, it can be connected to a compressor, high pressure pipe, receiver, prechamber or any other tank with compressed gas with a pressure of at least 190 kPa.

The inventive device operates as follows.

. Пристенный слой высокоскоростного потока газа, имеющий более низкую температуру, за счет имеющегося избыточного давления отсасывается через проницаемую стенку 10 (dG_хол) и формирует с другой стороны стенки вторичный поток суммарным расходом G_хол с температурой Т_хол ^* 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_гор=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 the initial braking pressure P _o ^* and the corresponding mass flow rate G ₀ (determined by the critical nozzle diameter) is supplied, 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 flow rate 9 at the exit of the nozzle 2 requires a margin of total pressure P ₀ ^* in the receiver 1 of at least 190 kPa (at atmospheric pressure at the outlet of the installation and in the external 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 T _w ^* is lower than the mass average stagnation temperature

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

Thus, the claimed utility model is a device with a smaller design in comparison with analogues due to the presence of only one gas stream at the inlet of the device. Moreover, the device provides the ability to reduce the total pressure loss of one of the gas flows due to the absence of gas injection into the high-speed stream, and the possibility of its subsequent effective braking in the diffuser. In addition, due to the lack of need for a supersonic flow regime at the inlet of the device, less initial overpressure is required for its operation.

Example.

The inventive device is implemented as part of a model experiment with the following characteristics. The material of the porous tube (inner channel) is sintered electrocorundum (λ = 40 W / (m⋅K), open porosity of 37-38%, pore diameter 60-65 μm, density 2210 kg / m ^3. The length of the porous tube is 150 mm or about 42 calibers. Thus, the walls of the inner channel are made porous for the entire length. The output diameter of the nozzle - 3.5 mm - is equal to the diameter of the inner channel of the tube, the outer diameter of the tube is 10 mm, the inner diameter of the outer annular channel is 20 mm. Part of the gas through the permeable walls the tube flows into the annular external channel (4), and the remainder enters the outlet one diffuser (6) and further into the flue gas collecting duct for heated gas (8).

Compressed air with braking parameters (Т _o ^* = 22.4 ° С, Р _o ^* = 2 ÷ 10 atm) comes from the receiver (1) into the narrowing nozzle (2), which smoothly passes into the tube with porous permeable walls (3) (Fig. . one). A receiver is located in the receiver for measuring the flow inhibition pressure P _o ^* . Temperature measurements were carried out with chromel-alumel thermocouples at the following points: there were four flow braking temperature receivers T _o ^* in the receiver, a probe coordinate device made it possible to measure the braking temperature profile T ^* in the heated gas receiver at the outlet of the diffuser. At the first stage of the experiment, the outer annular channel was absent, and the temperature of the outer surface of the porous permeable tube was measured by the non-contact method using a ThermaCAM SC3000 thermal imager. At the second stage, an external channel was used and chilled gas was collected with its flowmeter measured by a rotameter and temperature using a thermocouple in the chilled gas collection duct (7). During the experiment, the braking temperature in the receiver (1) was maintained equal to the ambient temperature. The absolute error in measuring the braking temperature in the receiver was ± 0.3 ° С, the braking temperature in the ducts for collecting heated and cooled gas ± 0.4 ° С, and the temperature of the outer surface of the porous tube when measured with a thermal imager ± 0.5 ° С.

The experiment was carried out as follows. Using a valve in the receiver, the required flow braking pressure was set, and using an electric heater, the temperature of the stream in the receiver was set equal to the ambient temperature. Upon reaching the stationary state, measurements were made of the profile of the braking temperature in the diffuser, the wall temperature of the porous tube (at the 1st stage) or the flow rate and air temperature in the chilled gas collection duct (at the 2nd stage). Data was stored on a PC and further processed.

As a result of the first part of the experiment, using a thermal imager, it was obtained that with increasing braking pressure in the receiver, the surface temperature of the porous wall decreases. Thus, assuming that the temperature of the porous wall is equal to the temperature of the air flowing through it, we can conclude that the air flowing through the porous wall has a temperature lower than the temperature of the air in the receiver. With increasing pressure in the receiver, the mass-average temperature of air braking at the outlet of the internal channel of the porous permeable tube increases. As a result of the second part of the experiment, the effect of temperature stratification was obtained in the form of heating the flow in the inner porous tube and cooling the flow in the external annular channel. With an increase in pressure from 2 to 10 atm, the ratio of gas flow in the external annular channel to the flow through the internal channel increased from 0.4 to 1.5, while the integral effect of temperature stratification (the difference between the flow temperatures at the outlet of the device) increased from 4 to 11 degrees. Compared with the Joule-Thomson effect at corresponding pressure drops, the obtained effect of cooling the flow in the external annular channel ranged from 2.5 to 14 times depending on the initial pressure in the receiver.

Bibliography

1. Merkulov A.P. “Vortex effect and its application in technology” / Samara: Optima, 1997. 346 p.

2. Burtsev S.A., Leontiev A.I. “Investigation of the influence of dissipative effects on temperature stratification in gas flows (review)” // Thermophysics of high temperatures. T. 52, No. 2, 2014.S. 310-322.

3. The method of temperature stratification of gas and a device for its implementation (Leontief pipe). RU 2106581 C1 (CL F25B 9/02, published 05/23/1996)

4. Vinogradov Yu.A., Zditovets A.G., Strongin M.M. “An experimental study of the temperature stratification of an air stream flowing through a supersonic channel with a central body in the form of a porous permeable tube” // Fluid and Gas Mechanics. No. 5, 2013, p. 134-145.

5. Schlichting G. "Theory of the boundary layer" // M: Nauka, 1974. 711 p.

6. Vulis L.A. “Thermodynamics of gas flows” / Gosenergoizdat, Moscow. 1950. 304 p.

Claims (3)

1. A device for temperature stratification of a gas stream, comprising a separation chamber configured to communicate with a reservoir of compressed gas, and including internal and external channels, the outlets of which are connected to the corresponding flues to output the separated heated and cooled gases, a tapering nozzle, which allows acceleration of the feed from the reservoir to the gas flow device to the speed of sound, and a supersonic diffuser located at the outlet of the internal channel and providing braking heated gas, characterized in that the possibility of communication of the separation chamber with the reservoir is provided through a tapering nozzle, the output of which is the input of the separation chamber, which is the input of the internal channel of the separation chamber, while the output diameter of the tapering nozzle is equal to the input diameter of the internal channel, while the channels are inner designed for the selection of heated gas, and the external, designed for the selection of chilled gas, are located coaxially, the walls of the internal channel, at least th least partially made permeable and outer channel walls are impermeable. 2. The device according to claim 1, characterized in that the length of the permeable portion of the inner channel of the separation chamber is at least 4 calibers. 3. The device according to p. 1, characterized in that the walls of the external channel are made of material with a low coefficient of thermal conductivity and are equipped with external thermal insulation.

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