An apparatus for studying the characteristics of enhancing gas convective heat transfer by acoustic vibration

Abstract

The present invention discloses a device for studying the characteristics of enhancing gas convective heat transfer by acoustic vibration. The heating part is designed as a smooth circular tube, and the thermal boundary condition is designed by means of electric heating for the circular tube. By arranging a sound source outside the pipe and designing an elliptical front obstacle inside the pipe, when the frequency of the sound source is the same as the shedding of fluid vortices at the front of the obstacle, acoustic resonance is excited. In this way, the characteristics and mechanism of enhancing gas convective heat transfer by acoustic vibration are studied. Axial sound sources and radial sound sources are respectively designed for this test bench, which can realize acoustic vibration under different conditions to study the enhancement mechanism of the sound field in different directions. A plurality of K-type thermocouples are installed in the wall of the test section, and the thermocouples are directly connected to electronic devices to display the wall temperature of the test section. A pressure oscilloscope, a pressure recorder and a thermometer are installed at the outlet of the test section to measure the fluid conditions after convective heat transfer of the fluid and to compare the enhancement results.

Description

Technical Field

[0001] The present invention belongs to the fields of fluid numerical calculation (CFD) and fluid acoustic calculation (ACC) experiments, and particularly relates to a device for studying the characteristics of acoustic vibration enhanced gas convective heat transfer. Background Art

[0002] Acoustic resonance is most likely to occur in structures with transverse gas flow. When the natural frequency of the sound wave is the same as the excitation frequency caused by vortex shedding or turbulence itself, acoustic resonance will occur, resulting in harsh noise. And all along, research on using sound fields to enhance heat transfer has been carried out. Sound waves can cause changes in the fluid flow structure, and can improve the heat and mass transfer ability of the fluid by reducing or destroying the fluid flow boundary layer. When the vibration frequency of the sound wave is the same as the excitation frequency caused by vortex shedding or turbulence itself, a frequency locking phenomenon will occur and resonance will occur. The sound field after resonance can cause the vibration of the solid structure pipe wall, destroying the boundary layer structure of the fluid and thus improving the heat transfer ability of the fluid. For gas-cooled microreactors, the method of using sound waves to enhance heat transfer is feasible. As mentioned above, acoustic resonance is most likely to occur during the transverse flow of gas media. At the same time, during the turbulent flow of gas, due to flow instability, a quadrupole sound source can be formed to propagate sound waves. If obstacles are set in the flow pipeline and acoustic resonance is formed under the excitation of sound waves, causing wall vibration, the gas flow boundary layer can be destroyed and the heat transfer effect of the fluid can be improved. A large number of studies have been carried out on this heat transfer enhancement method.

[0003] For example, in the early 1960s, foreign scholars J.R. McCarthy and H. Wolf found in the process of studying the flow heat transfer of hydrogen and helium in a smooth round tube heated by electricity that in the experimental results of some experiments in multiple groups, the temperature of the heated pipe wall decreased significantly. Combining on-site observations of the experiment, they believed that it might be caused by the increased heat transfer ability due to acoustic vibration. After that, they specifically conducted experimental research on the effect of longitudinal acoustic vibration on gas convective heat transfer and concluded that acoustic vibration can double the gas flow heat transfer ability in the round tube in some cases. However, the authors of this literature did not give a specific explanation of how acoustic resonance affects heat transfer. Moreover, due to the early time, the design of this experimental bench inevitably has some inevitable problems such as complex design and backward equipment.

[0004] For example, in the 1990s, M.C. Welsh and K. Hourigan wrote the paper "Acoustics and Experimental Methods: The Influence of Sound on Flow and Heat Transfer". This literature combined the experiments conducted by many predecessors and the experiments designed by the authors themselves to explore the mechanism of how sound affects the heat transfer ability, and described the working principles under different working conditions through experiments, such as the noise generated by the flow in the air duct, the generation of noise in the open jet wind tunnel, and the influence of noise in the water pipe. However, the model of flow heat transfer with a heated wall surface was not considered in this literature.

[0005] Another example is that in recent years, the literature "Heat Transfer Implications of Acoustic Resonances in Turbine Internal Cooling Channels" studied the heat transfer significance of acoustic resonances in turbine internal cooling channels. This literature first obtained the approximate range distribution of the sound field frequency and sound pressure through software simulation, and then designed these parameters in specific experiments. In the test bench provided by this literature, the arrangement of the sound source was achieved by installing a loudspeaker outside the test section, proving that the method of arranging the sound source in the present invention is feasible. However, the model design of this experiment was the internal cooling channel of the turbine, with limitations of the model.

[0006] Another example is that in recent years in China, Lv Ping et al. in the "Experimental Study on the Influence of Vibration on Convective Heat Transfer of Fluid in a Pipe" used a spring installed outside the heat exchange pipe to apply vibration to study the influence of vibration on the flow heat transfer in the pipe. However, this test bench had problems such as large losses and being restricted by the fixity of the bench. Summary of the Invention

[0007] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a device for studying the enhancement of gas convective heat transfer characteristics by acoustic vibration. This device forms a thermal boundary condition by setting an electric heating wire L on the test section N to heat the pipeline; controls the inlet conditions of the flowing gas through a pressure control valve B and a gas preheating device E;; improves the accuracy of the experimental results by setting a pipeline silencer F; records experimental data by setting a thermometer, a pressure gauge, a thermocouple K, and a pressure oscilloscope O; sets longitudinal sound field conditions and transverse sound field conditions through an axial loudspeaker G and a radial loudspeaker M respectively, and there are obstacles designed in the adiabatic section. When the frequency of the loudspeaker is consistent with the frequency of vortex shedding generated when the fluid flows through the obstacle, acoustic resonance will be induced to form a stronger sound field, and the sound field will cause the solid wall surface to vibrate, thereby achieving the purpose of affecting convective heat transfer. Furthermore, it studies the simulation of the influence of the sound field on the convective heat transfer behavior of the gas in the pipe.

[0008] The object of the present invention is achieved by the following technical solutions:

[0009] A device for studying the characteristics of enhanced gas convective heat transfer by acoustic vibration includes a gas supply device A. The outlet pipe of the gas supply device A is connected to a pressure control valve B and a gas flow meter C. A gas preheating device E is connected downstream of the gas flow meter C. The downstream pipe of the gas preheating device E must be set in an "L" shape, and a loudspeaker, denoted as an axial loudspeaker G, is arranged in the direction of the test section at the corner to provide a longitudinal sound field. The axial loudspeaker G is placed in a hexahedron device with five-sided sound insulation, and the remaining side is closely attached to the pipe wall to reduce the energy loss during the propagation of sound into the pipe; A pipe muffler F is installed upstream of the axial loudspeaker G. On the one hand, the pipe muffler F prevents the sound from interfering with the gas heat transfer in the gas preheating device E, ensuring that the gas maintains the set inlet temperature when entering the test section, and at the same time, it can also prevent the noise in the upstream pipe from interfering with the downstream sound field setting; A fluid inlet press H is arranged downstream of the axial loudspeaker G. The fluid inlet press H is sequentially connected to an adiabatic section I and a test section N downstream; The gas develops a stable temperature field and flow velocity through sufficient flow in the adiabatic section I. An inlet fluid thermometer J is installed on the adiabatic section I; In the part of the adiabatic section behind the installation position of the inlet fluid thermometer, smooth obstacles with elliptical fronts are added inside the pipe to stimulate the acoustic resonance phenomenon; A thermocouple K and an electric heating wire L are installed on the test section N. The thermocouple K is installed on the test section according to the test design, and the electronic equipment is used to visually display the change of the test section wall temperature along the way; A radial loudspeaker M is also installed on the side wall of the test section N. The installation method of the radial loudspeaker M is the same as that of the axial loudspeaker G, and the orientation of the radial loudspeaker M is consistent with the radial direction of the test section, which is used to simulate the transverse sound field during the gas flow process; A pressure oscilloscope O, an outlet pressure gauge P, and an outlet thermometer Q are sequentially installed downstream of the test section N; The pressure oscilloscope O is used to measure the vibration frequency of the fluid under the action of the sound field; A gas cooler R, a pressure control valve S, and a gas discharge treatment device T are sequentially installed downstream of the outlet thermometer Q;

[0010] When it is necessary to simulate the propagation of the longitudinal sound field along the gas flow direction, induce acoustic resonance and affect the forced convection heat transfer behavior in the test section, at the beginning of the experiment, adjust the pressure control valve B to control the gas to flow out according to the experimental design conditions, flow through the gas preheater E, be heated to the experimental design temperature in the gas preheater E and then flow out, flow through the "L"-shaped pipe, and after fully flowing in the adiabatic section I to form a stable flow field, flow into the test section N. The electric heating wire L is energized to heat the pipe wall to form forced convection heat transfer to the gas. The wall temperature is measured by the thermocouple K installed on the wall, and the fluid outlet temperature is measured by the outlet thermometer Q; after completing the first group of forced convection heat transfer without the action of the longitudinal sound field, record the experimental data and draw a graph, then only turn on the axial speaker G, set multiple groups of experiments, set different sound intensities and frequencies for each group of experiments, record the experimental data and draw a graph for comparison; by adjusting the frequency of the sound source, when the frequency of the sound wave is the same as the frequency of the vortex shedding on the obstacle in the adiabatic section under the condition that the flow has been established, acoustic resonance is excited. At this time, record the data and compare and summarize the action mechanism of acoustic resonance on convective heat transfer;

[0011] When it is necessary to simulate the influence behavior of the transverse sound field on the forced convection heat transfer ability of the gas in the pipe, the setting steps after the start of the experiment are the same as those of the longitudinal sound field. After completing the forced convection heat transfer experiment without the action of the sound field, turn on the radial speaker M to create a transverse sound field. The position of the radial speaker M is parallel to the position of the thermocouple K on the test section to more intuitively show the influence of the transverse sound field on gas convection heat transfer; similarly, design multiple groups of experiments respectively, and design different frequencies and sound intensities for each group of experiments; draw a graph for each group of experimental results and conduct an intuitive comparison to realize the simulation of the working conditions of the influence of the transverse sound field on gas flow heat transfer.

[0012] The test section N adopts a smooth inner wall circular pipe.

[0013] An axial speaker G is designed in the device. On the one hand, it realizes the study of the influence of the longitudinal sound field on the gas flow heat transfer ability; on the other hand, it realizes the simulation of the influence of the fluid vibration induced by the turbulent sound during the gas flow process on the gas flow heat transfer ability.

[0014] The gas supply device A replaces different gases according to the experimental requirements to study the changes in the flow heat transfer characteristics of different gas fluids under the action of the sound field.

[0015] A plurality of thermocouples K are equidistantly installed on the wall surface of the test section pipe. At the same time, the thermocouple K is connected to the computer, and the wall temperature distribution of the heating pipe during convective heat transfer can be directly obtained, and the distribution of the wall temperature under the convective heat transfer working condition can be obtained.

[0016] The present invention has the following advantages and beneficial effects:

[0017] 1. The device is designed with sound sources in two directions, which can simulate the sound field under different conditions and effectively simulate the changes in the convective heat transfer characteristics of fluids under different sound fields.

[0018] 2. The device is designed with internal obstacles in the adiabatic section, which can be used to study the influence of self-excited sound in the pipe on the flow structure.

[0019] 3. The device has a high degree of integration, can collect multi-point signals using a computer, and has a relatively fast data monitoring and processing speed.

[0020] 4. The main working medium of this device is gas, and the conclusions can be used to study the enhanced heat transfer design in gas-cooled microreactors.

[0021] 5. This device can produce vibration effects with lower energy consumption. At the same time, using sound field vibration can reduce the loss of bench equipment and materials compared to externally applied vibration, and has better durability and economy.

[0022] 6. The model selected for the test section of this device is the most basic smooth inner wall circular pipe, which can be used for the research of various test models. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the experimental device bench.

[0024] Figure 2 It is a schematic diagram of the obstacle setting in the adiabatic section. Detailed Implementation Modes

[0025] The present invention will be further described in detail below with reference to the drawings.

[0026] Such as Figure 1As shown in the figure, a device for studying the characteristics of enhancing gas convective heat transfer by acoustic vibration is characterized in that: it includes a gas supply device A. The outlet pipe of the gas supply device A is connected to a pressure control valve B and a gas flow meter C. A gas preheating device E is connected downstream of the gas flow meter C. The downstream pipe of the gas preheating device E must be set in an "L" shape, and a loudspeaker is arranged at the corner facing the test section, denoted as the axial loudspeaker G, to provide a longitudinal sound field. The axial loudspeaker G is placed in a hexahedron device with five-sided sound insulation, and the remaining side is closely attached to the pipe wall to reduce the energy loss during the propagation of sound into the pipe; A pipe muffler F is installed upstream of the axial loudspeaker G. On the one hand, the pipe muffler F can prevent the sound from interfering with the gas heat transfer in the gas preheating device E, ensuring that the gas can maintain the set inlet temperature when entering the test section, and at the same time, it can also prevent the noise in the upstream pipe from interfering with the downstream sound field setting; A fluid inlet press H is arranged downstream of the axial loudspeaker G. Downstream of the fluid inlet press H are successively connected an adiabatic section I and a test section N; The gas develops a stable temperature field and flow velocity after sufficient flow in the adiabatic section I. An inlet fluid thermometer J is installed on the adiabatic section I; As Figure 2 shown, in the adiabatic section, in the part behind the installation position of the inlet fluid thermometer, smooth obstacles with an elliptical front are added inside the pipe to stimulate the acoustic resonance phenomenon; A thermocouple K and an electric heating wire L are installed on the test section N. The thermocouple K is installed on the test section according to the test design, and the electronic equipment is used to visually display the change of the wall temperature of the test section along the way; A radial loudspeaker M is installed on the side wall of the test section N. The installation method of the radial loudspeaker M is the same as that of the axial loudspeaker G. The orientation of the radial loudspeaker M is the same as the radial direction of the test section, and a transverse sound field during the gas flow can be simulated; A pressure oscilloscope O, an outlet pressure gauge P and an outlet thermometer Q are successively installed downstream of the test section N; The pressure oscilloscope O can measure the vibration frequency of the fluid under the action of the sound field; Downstream of the outlet thermometer Q are successively installed a gas cooler R, a pressure control valve S and a gas discharge treatment device T.

[0027] As Figure 1As shown, when it is necessary to simulate the propagation of the longitudinal sound field along the gas flow direction, induce vibration and affect the forced convection heat transfer behavior in the test section, at the beginning of the experiment, adjust the pressure control valve B to control the gas to flow out according to the experimental design conditions, flow through the gas preheater E, be heated to the experimental design temperature in the gas preheater and then flow out, flow through the "L"-shaped pipe, and after fully flowing in the adiabatic section I to form a stable flow field, flow into the test section. The electric heating wire L is energized to heat the pipe wall to form forced convection heat transfer to the gas. The wall temperature is measured by the thermocouple K installed on the wall, and the fluid outlet temperature is measured by the outlet thermometer Q. After completing the first group of forced convection heat transfer without the action of the longitudinal sound field, after using computer software to record the wall temperature distribution in the test section, the fluid inlet and outlet temperatures, the gas inlet and outlet pressures, the sound source frequency, the sound source intensity and drawing a graph, only turn on the speaker G, set multiple groups of experiments, and set different sound intensities and frequencies for each group of experiments. Record the wall temperature distribution in the test section, the fluid inlet and outlet temperatures, the gas inlet and outlet pressures, the sound source frequency, the sound source intensity and draw a graph for comparison. The main comparison is the along-wall temperature distribution in the test section, the temperature rise at the fluid inlet and outlet, and the fluid pressure drop after the fluid flows through the test section at different frequencies and different sound intensities, and summarize the influence of the sound field on the forced convection heat transfer of the gas. The axial speaker can also simulate the influence of the gas-fluid vibration induced by the turbulent sound generation during the gas flow process on the forced convection heat transfer performance of the gas in the circular pipe.

[0028] When it is necessary to simulate the influence behavior of the transverse sound field on the forced convection heat transfer capacity of the gas in the circular pipe, the setting steps after the start of the experiment are the same as those of the longitudinal sound field. After completing the forced convection heat transfer experiment without the action of the sound field, turn on the radial speaker M to create a transverse sound field. The position of the radial speaker M is parallel to the position of the thermocouple K on the test section to more intuitively show the influence of the transverse sound field on the gas convection heat transfer. Similarly, multiple groups of experiments are designed respectively, and different frequencies and sound intensities are designed for each group of experiments. After using computer software to draw a graph of the results of each group of experiments for intuitive comparison, the simulation of the working conditions of the influence of the transverse sound field on the gas flow heat transfer is realized.

[0029] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited thereto. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the patent protection scope determined by the claims submitted by the present invention.

Claims

1. An apparatus for studying the characteristics of enhancing gas convective heat transfer by acoustic vibration, characterized in that: It includes a gas supply device (A). The outlet pipe of the gas supply device (A) is connected to a pressure control valve (B) and a gas flowmeter (C). A gas preheating device (E) is connected downstream of the gas flowmeter (C). The downstream pipe of the gas preheating device (E) must be set in an "L" shape. There is a loudspeaker, denoted as the axial loudspeaker (G), installed at the corner facing the test section direction to provide a longitudinal sound field. The axial loudspeaker (G) is placed in a five-sided sound-insulating hexahedron device, and the remaining side is closely attached to the pipe wall to reduce the energy loss during the propagation of sound into the pipe. A pipe muffler (F) is installed upstream of the axial loudspeaker (G). On the one hand, the pipe muffler (F) prevents the sound from interfering with the gas heat exchange in the gas preheating device (E), ensuring that the gas maintains the set inlet temperature when entering the test section. At the same time, it can also prevent the noise in the upstream pipe from interfering with the downstream sound field setting. A fluid inlet press (H) is arranged downstream of the axial loudspeaker (G). The fluid inlet press (H) is sequentially connected to an adiabatic section (I) and a test section (N) downstream. The gas develops a stable temperature field and flow velocity after sufficient flow in the adiabatic section (I). An inlet fluid thermometer (J) is installed on the adiabatic section (I). In a part of the adiabatic section behind the installation position of the inlet fluid thermometer, smooth obstacles with an elliptical front are added inside the pipe to stimulate the acoustic resonance phenomenon. A thermocouple (K) and an electric heating wire (L) are installed on the test section (N). The thermocouple (K) is installed on the test section according to the test design, and the electronic equipment is used to visually display the change of the wall temperature of the test section along the way. A radial loudspeaker (M) is installed on the side wall of the test section (N). The installation method of the radial loudspeaker (M) is the same as that of the axial loudspeaker (G). The orientation of the radial loudspeaker (M) is consistent with the radial direction of the test section, and it is used to simulate the transverse sound field during the gas flow process. A pressure oscilloscope (O), an outlet pressure gauge (P), and an outlet thermometer (Q) are sequentially installed downstream of the test section (N). The pressure oscilloscope (O) is used to measure the vibration frequency of the fluid under the action of the sound field. A gas cooler (R), a pressure control valve (S), and a gas discharge treatment device (T) are sequentially installed downstream of the outlet thermometer (Q). When it is necessary to simulate the propagation of the longitudinal sound field along the gas flow direction, induce acoustic resonance and affect the forced convection heat transfer behavior in the test section, at the beginning of the experiment, adjust the pressure control valve (B) to control the gas to flow out according to the experimental design conditions, flow through the gas preheater (E), be heated to the experimental design temperature in the gas preheater (E) and then flow out, flow through the "L"-shaped pipe, and after fully flowing in the adiabatic section (I) to form a stable flow field, flow into the test section (N). The tube wall is heated by the electric heating wire (L) to form forced convection heat transfer to the gas. The wall temperature is measured by the thermocouple (K) installed on the wall, and the fluid outlet temperature is measured by the outlet thermometer (Q); after completing the first group of forced convection heat transfer without the action of the longitudinal sound field, record the experimental data and draw a graph, then only turn on the axial loudspeaker (G), set multiple groups of experiments, set different sound intensities and frequencies for each group of experiments, record the experimental data and draw a graph for comparison; by adjusting the frequency of the sound source, when the frequency of the sound wave is the same as the frequency of the vortex shedding on the obstacle in the adiabatic section under the condition that the flow has been established, acoustic resonance is excited. At this time, record the data and compare and summarize the action mechanism of acoustic resonance on convective heat transfer. When it is necessary to simulate the influence of the transverse sound field on the forced convection heat transfer ability of the gas in the pipe, the setup steps after the start of the experiment are the same as those of the longitudinal sound field. After completing the forced convection heat transfer test without the action of the sound field, turn on the radial loudspeaker (M) to create a transverse sound field. The position of the radial loudspeaker (M) is parallel to the position of the thermocouple (K) on the test section to more intuitively show the influence of the transverse sound field on gas convection heat transfer; similarly, design multiple groups of experiments, and design different frequencies and sound intensities for each group of experiments; draw a graph for each group of test results for intuitive comparison to realize the simulation of the working conditions of the influence of the transverse sound field on gas flow heat transfer.

2. The device for studying the characteristics of enhancing gas convective heat transfer by acoustic vibration according to claim 1, characterized in that: The test section (N) uses a smooth inner wall circular tube.

3. The device for studying the characteristics of enhancing gas convective heat transfer by acoustic vibration according to claim 1, characterized in that: An axial loudspeaker (G) is designed in the device. On the one hand, it realizes the study of the influence of the longitudinal sound field on the gas flow heat transfer ability; on the other hand, it realizes the simulation of the influence of the fluid vibration induced by the turbulent sound generation during the gas flow process on the gas flow heat transfer ability.

4. The device for studying the characteristics of enhancing gas convective heat transfer by acoustic vibration according to claim 1, wherein: The gas supply device (A) replaces different gases according to the experimental requirements to study the changes in the flow heat transfer characteristics of different gas fluids under the action of the sound field.

5. The device for studying the characteristics of enhancing gas convective heat transfer by acoustic vibration as claimed in claim 1, wherein: A plurality of thermocouples (K) are equidistantly installed on the tube wall of the test section. At the same time, the thermocouple (K) is connected to a computer, and the wall temperature distribution of the heating tube during convective heat transfer can be directly obtained, and the distribution of the wall temperature under the convective heat transfer working condition can be obtained.

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