An experimental system for liquid evaporation heat transfer in a nanopore under non-condensable gas condition

Abstract

An experimental system for liquid evaporation heat transfer in nano-pores with non-condensable gas is provided, which is used for research in the fields of energy, chemical industry and environment, and comprises a non-condensable gas providing unit, a liquid providing unit and a liquid evaporation unit. The liquid providing unit delivers liquid to the liquid evaporation unit by steam heating expansion and extrusion, the non-condensable gas providing unit delivers non-condensable gas to the evaporation chamber in the liquid evaporation unit by a hierarchical delivery mode, and a buffer tank is used to ensure that the mass and concentration of the non-condensable gas component are accurately controllable. The platinum deposition layer on the surface of the nano-pore structure in the evaporation unit is connected to a direct current power supply for heating and temperature measurement, and the evaporation rate and temperature data are obtained. The experimental system has the characteristics of precise temperature measurement, accurate control of non-condensable gas content, smooth gas-liquid delivery and adjustable nano-pore structure parameters, and provides a reliable reference scheme for experimental research on the evaporation mechanism of liquid in nano-pores with non-condensable gas.

Description

Technical Field

[0001] This invention belongs to the field of evaporative heat transfer of nanoporous materials and is commonly used in chemical, energy and environmental fields. It involves the exploration of the influence mechanism of liquid evaporation under conditions containing non-condensable gases. Background Technology

[0002] Liquid evaporation heat transfer within nanoporous structures offers advantages such as low thermal resistance, high efficiency, and stable operation, making it a promising area for engineering applications. While significant research has been conducted on the selection of new materials and micro / nano fabrication in nanoporous evaporation studies, the fundamental laws and theoretical research on liquid evaporation heat transfer within nanopores have received relatively little attention. The liquid evaporation mechanism under non-condensable gas conditions is crucial for technologies such as heat pipes, vapor chambers, and photothermal interface evaporation. The interfacial transport and gas diffusion processes involved are complex and require specialized mechanistic elucidation at the molecular level. Current research on liquid evaporation mechanisms within nanopores is often limited to the evaporation of single components, with insufficient research on evaporation under non-condensable gas conditions, and the development of related experimental systems is lagging behind.

[0003] Research on the heat transfer mechanism of liquid evaporation within nanopores under conditions containing non-condensable gases can promote the development and maturation of new technologies such as nanoporous thin-film heat sinks in engineering, meeting the needs of key areas such as renewable energy utilization, chemical engineering, and the environment. Academically, the heat transfer characteristics of liquid evaporation within nanopores are at the forefront and a hot topic in multiphase flow physics, and can contribute to the development of the discipline.

[0004] This invention addresses the study of liquid evaporation under conditions containing non-condensable gases. It proposes an experimental system design that can reveal the heat transfer mechanism of liquid evaporation within nanopores under such conditions and study the distribution characteristics of non-condensable gases and their influence on the liquid evaporation rate. Utility Model Content

[0005] This invention innovatively establishes an experimental system that can solve the experimental research problem of liquid evaporation under conditions containing non-condensable gases, and reveals the influence mechanism of the component diffusion effect of non-condensable gases on the flow resistance and liquid evaporation rate in the transition zone.

[0006] This invention designs a liquid evaporation system under conditions containing non-condensable gases, characterized in that: the overall system of this invention is as follows... Figure 1 As shown, it includes a non-condensable gas supply unit, such as Figure 2 Liquid supply unit, such as Figure 3 Liquid evaporation unit, such as Figure 4 .

[0007] like Figure 2As shown, the non-condensable gas supply unit adopts a staged delivery of non-condensable gas. The non-condensable gas cylinder (3) is connected to the non-condensable gas buffer tank (4) via the first valve (2). The first heating device (5) is set below the non-condensable gas buffer tank (4) to heat the non-condensable gas buffer tank (4). The non-condensable gas buffer tank (4) is connected to the evaporation chamber (15) via the second valve (6) to fill the evaporation chamber (15) with non-condensable gas. An independent evaporation device (12) is provided in the evaporation chamber (15). The evaporation device (12) has a rectangular cavity structure. One side wall of the evaporation device (12) is provided with a window with a nanoporous structure that can be embedded.

[0008] The liquid storage tank (7) contains liquid. A pipeline is connected from the liquid inside the liquid storage tank (7) through the third valve (10) and the flow meter (9) to the upper part of the evaporation device (12) to fill the evaporation device with liquid. The upper part of the liquid storage tank (7) is connected to the evaporation chamber (15) through the fourth valve (11) to fill the evaporation chamber (15).

[0009] The nanopore structure (20) is a plate-like structure with an array (preferably a single row or single column) of nanopores to be measured (19). When embedded in the sidewall of the evaporation device (12), the nanopore axis is horizontal. A platinum or / and gold deposition layer (18) is deposited on the plate surface facing the evaporation chamber (15). The platinum or / and gold deposition layer retains pores that are coaxial with and the same size as the nanopores (19). Wires are led out from both ends of the platinum or / and gold deposition layer (18) along the arrangement direction of the nanopores (19) and connected to a DC power supply (13). The DC power supply (13) is equipped with a data acquisition device (14) for recording current and voltage.

[0010] The vacuum pump (16) is connected to the evaporation chamber (15) via a valve;

[0011] The evaporation chamber (15), liquid storage tank (7), and non-condensable gas buffer tank (4) are all equipped with pressure detection devices and temperature detection devices; the pressure detection device and temperature detection device of the liquid storage tank (7) are used to detect the pressure and temperature of the gas above the liquid in the liquid storage tank.

[0012] The bottom of the evaporation device (12) is provided with a switchable liquid outlet.

[0013] The evaporation chamber (15) is a visual evaporation chamber, or it is equipped with a visual observation window (17).

[0014] The gas cylinder (3) is equipped with a pressure relief valve (1).

[0015] Heating devices include, but are not limited to, heating plates, heating wires, etc.

[0016] After the non-condensable gas flows out of the gas cylinder (3), it is not directly delivered to the liquid evaporation unit. Instead, it is buffered by the non-condensable gas buffer tank (4) as an intermediate stage to prevent the gas flow rate delivered to the evaporation chamber (15) from being too fast and causing interference. Furthermore, the amount of non-condensable gas cannot be precisely controlled. In order to accurately calculate the content of non-condensable gas in the system, a first heating device (5) is installed below the buffer tank (4) to measure the temperature and pressure inside the buffer tank (4) under closed conditions. Then, the density and mass of the non-condensable gas inside the tank can be calculated according to the gas state equation.

[0017] Liquid supply unit such as Figure 3 As shown, since the experiment requires a small liquid supply and to ensure a slow liquid supply speed, a mechanical pump or other means of supplying liquid were not used. Instead, a second heating device (8) was used to heat the liquid, and the liquid was transported by the thermal expansion of the steam above the liquid surface.

[0018] Two pipes are connected from the top of the liquid storage tank (7) to the evaporation chamber (15). One is a liquid delivery pipe, which is equipped with a flow meter (9) to record and monitor the liquid flow rate in real time. The other is a gas connection pipe, which allows the air in the evaporation chamber (15) and the liquid storage tank (7) to be extracted together by a vacuum pump (16) before the experiment begins.

[0019] like Figure 4 In the liquid evaporation unit shown in this invention, after the interfering gas in the visualization evaporation chamber (15) is purged by a vacuum pump (16), the liquid working fluid is transported from the liquid storage tank (7) to the evaporation device (12), and the non-condensable gas is transported from the non-condensable gas buffer tank (4) to the visualization evaporation chamber (15), ultimately forming a stable evaporation of the liquid into the non-condensable gas environment. The mass fraction of non-condensable gas in the gas can be precisely controlled. The liquid evaporation unit is equipped with a visualization observation window (17) to facilitate the photographing and observation of the liquid evaporation process.

[0020] like Figure 5 As shown, the evaporation device (12) is a cavity structure with an opening at the top. The opening at the top connects to the liquid storage tank (7), and the bottom has a switchable liquid outlet. Furthermore, there is another opening on the left side of the cavity, where a nanoporous membrane is installed. The liquid inside the cavity of the evaporation device enters the nanopores (19) and absorbs heat to evaporate, and the steam enters the space of the evaporation chamber (15).

[0021] In this invention, the temperature measurement method is non-invasive. For example... Figure 5As shown, a platinum and / or gold deposition layer (18) is deposited on the surface of the nanoporous membrane as a heating film and electrode. The positive and negative terminals of a DC power supply (13) are connected to the two ends of the heating film to provide voltage and current. A data acquisition device (14) records and stores the data. The DC power provided by the DC power supply (13) serves as the energy source for liquid evaporation, while the resistance-temperature relationship of platinum is used to measure and characterize the temperature of the liquid inside the nanopore.

[0022] In this invention, the inner wall of the nanopore (19) can be coated with a hydrophobic coating to prevent liquid from wetting, thereby allowing precise control of the position and depth of the liquid meniscus within the pore.

[0023] This invention quantitatively controls the mass fraction of non-condensable gas components in the evaporation chamber (15) using the following method: First, a vacuum pump (16) is used to remove residual air from each container. Then, a heating device (8) is used to maintain the evaporation chamber (15) in a saturated state of liquid working fluid. The density and mass of the saturated steam are calculated using temperature and pressure values. After the non-condensable gas buffer tank (4) is filled with non-condensable gas, it is sealed. Its density and mass are also calculated using temperature and pressure values. Finally, the valve (6) is opened to allow the non-condensable gas to enter the evaporation chamber. Once the non-condensable gas and saturated steam are mixed evenly, the mass fraction of each component can be calculated.

[0024] The non-condensable gas in this invention can be any inert gas such as nitrogen (not limited to), and the liquid working fluid can also be any liquid such as deionized water (not limited to). The heating device can be a heating plate, heating wire, or other forms of heating.

[0025] The advantages and effects of this utility model are as follows:

[0026] 1. This utility model can accurately measure the temperature and evaporation rate of the liquid inside the nanopore by using a DC power supply and a data acquisition device.

[0027] 2. After the non-condensable gas flows out of the gas cylinder (3), it passes through the non-condensable gas buffer tank (4) and then flows into the evaporation chamber (15). The above-mentioned method of providing non-condensable gas in stages can prevent the non-condensable gas from flowing into the buffer chamber at too fast a flow rate, which may affect the experimental results. At the same time, the method of providing non-condensable gas in stages can also better control the mass fraction of gas components and improve the experimental accuracy.

[0028] 3. The evaporation device of this invention can change the size and shape of the pores, and adjust the pore gap, porosity, and Knudsen number. The position of the liquid meniscus inside the nanopores can be freely changed, thereby allowing the study of the influence of various geometric parameters on liquid evaporation and revealing the intrinsic relationship between non-condensable gas diffusion and factors such as nanopore morphology, porosity, and Knudsen number.

[0029] 4. The liquid supply unit adopts the principle of thermal expansion and contraction. By heating the liquid storage tank (7), the internal vapor expands and squeezes the liquid working medium into the evaporation device (12), ensuring that the liquid flow is smooth and stable.

[0030] 5. This utility model can accurately control the mass fraction percentage of the mixture of steam and non-condensable gas in the evaporation chamber (15), calculate the density and mass of the gas in the saturated steam and non-condensable gas buffer tank (4) according to the gas state equation, and finally make the two gases mix evenly to reach equilibrium, thereby calculating the component concentration of non-condensable gas. Attached Figure Description

[0031] Figure 1 This is an overall system diagram of this utility model.

[0032] Figure 2 Provides units for non-condensable gases;

[0033] In the diagram: 1. Pressure relief valve, 2. First valve, 3. Non-condensable gas cylinder, 4. Non-condensable gas buffer tank, 5. First heating device, 6. Second valve;

[0034] Figure 3 Provides units for liquids;

[0035] In the diagram: 7. Liquid storage tank, 8. Second heating device, 9. Flow meter, 10. Third valve, 11. Fourth valve.

[0036] Figure 4 This is an evaporation unit;

[0037] In the diagram: 12. Evaporation device, 13. DC power supply, 14. Data acquisition unit, 15. Visual evaporation chamber, 16. Vacuum pump, 17. Observation window.

[0038] Figure 5 This invention relates to a nanoporous membrane.

[0039] In the figure: 18, platinum and gold deposition layer; 19, nanopores. Detailed Implementation

[0040] The system will be further explained below with reference to the accompanying drawings.

[0041] This utility model discloses an experimental system, referring to... Figure 1 This experimental system is arranged and installed in three units. The non-condensable gas supply unit, such as... Figure 2 Liquid supply unit, such as Figure 3 Liquid evaporation unit, such as Figure 4 .

[0042] like Figure 2As shown, the non-condensable gas cylinder 3 is connected to the non-condensable gas buffer tank 4 via a pipeline with a valve, and a heating device 5 is arranged below the non-condensable gas buffer tank. A pipeline is led out from the top of the non-condensable gas buffer tank and connected to the evaporation chamber 15, and thermometers and pressure gauges are placed in the non-condensable gas buffer tank 4 to monitor the status of the device.

[0043] like Figure 3 The liquid supply unit shown has two pipelines extending from the liquid storage tank 7. One pipeline connects the liquid in the liquid storage tank 7 to the evaporation device 12 in the evaporation chamber. The other pipeline connects the liquid storage tank from above to the evaporation chamber 15, ensuring that the state parameters of the vapor components in the liquid storage tank and the evaporation chamber are consistent. The flow rate of liquid entering the evaporation chamber is controlled by arranging a heating device 8 in the liquid storage tank 7, and the state inside the liquid storage tank is monitored in real time by installing thermometers and pressure gauges.

[0044] Liquid evaporation unit such as Figure 4 As shown, the evaporation device 12 is controlled by a DC power supply 13 and connected to a data acquisition unit 14. The evaporation chamber 15 is connected to a vacuum pump 16 and is equipped with a visual observation window 17 for photographing the interior. The evaporation chamber 15 is also equipped with a thermometer and a pressure gauge to monitor the state of the gas inside the chamber in real time.

[0045] The complete experimental system consists of three parts: a liquid supply unit, a non-condensable gas supply unit, and a liquid evaporation unit. This system addresses the limitations of research on micro- and nano-scale liquid evaporation under conditions containing non-condensable gases.

[0046] The following is an embodiment of this utility model: Before the experiment begins, open valves 6 and 11, close valves 2 and 10, and turn on vacuum pump 16 to extract residual air from evaporation chamber 15, non-condensable gas buffer tank 4, and liquid storage tank 7; after vacuuming is completed, close valve 6, slowly open valve 2 to allow non-condensable gas to enter buffer tank 4, close valve 2 after a period of time, turn on first heating device 5, and record temperature and pressure readings of buffer tank 4 in real time.

[0047] The mass m2 [kg] of non-condensable gas in buffer tank 4 is calculated according to the following formula:

[0048]

[0049] In the formula, P2 and T2 are the pressure [Pa] and temperature [K] of the buffer tank, respectively, and Z2 and R2 are the compressibility factor and gas constant [m] of the non-condensable gas, respectively. 2 / s 2 -K], V2 is the volume of buffer tank 4 [m 3 ].

[0050] Then, the second heating device 8 is activated to vaporize the liquid working medium in the liquid storage tank 7. The steam enters the evaporation chamber 15 along the pipeline until the liquid working medium reaches saturation in both the liquid storage tank and the evaporation chamber. The fourth valve 11 is then closed, and the temperature T1 and pressure P1 of the evaporation chamber 15 are recorded. The mass of steam in the evaporation chamber is calculated using the following formula:

[0051]

[0052] In the formula, Z1 and R1 are the compressibility factor and gas constant of the working fluid vapor, respectively, and V1 is the volume of evaporation chamber 15. Next, the second valve 6 is opened to allow the non-condensable gas to diffuse freely from buffer tank 4 to evaporation chamber 15 until equilibrium is reached. The final mass fraction of the non-condensable gas component is then...

[0053]

[0054] Open the third valve 10, keep the second heating device 8 working, and the liquid working medium in the liquid storage tank 7 flows into the evaporation device 12 under the action of the steam expansion and compression above. The flow meter 9 calculates that the liquid just fills the evaporation device 12. Turn on the DC power supply 13 and the data acquisition device 14 to record the voltage U and current I of the platinum deposition layer 18 on the nanopore surface under stable conditions.

[0055] In this invention, the final experimental data are the evaporation rate of the liquid within the nanopore and the temperature of the liquid, obtained as follows: Evaporation rate [kg / m 2 -s] is obtained by dividing the electric heating power UI by the latent heat of vaporization of the liquid, i.e.

[0056]

[0057] In the formula, U and I represent the voltage [V] and current [A] passing through the deposition layer, respectively, and h evap The latent heat of vaporization of the liquid working fluid [J / kg], A p The total cross-sectional area of ​​the nanopores [m 2 The temperature of the liquid is obtained based on the resistance-temperature relationship of the metal deposition layer: Before the experiment, the heating film is calibrated, placed in different temperature environments, and the resistance (U / I) of the deposition layer is measured. Finally, the linear relationship between the resistance of the deposition layer and the temperature is expressed as follows:

[0058]

[0059] In the formula, β is the resistance-temperature linearity coefficient of the deposited layer used in the experiment [K / Ω]. In the experiment, the resistance of the heating film can be calculated by the voltage applied by the DC power supply (13) and the loop current, and then the temperature inside the nanopores can be obtained.

[0060] Based on the above data processing, further research was conducted on the nanopore evaporation rate m".evap With liquid temperature T L The study investigates the variation pattern of the temperature of the sediment layer and the temperature of the liquid after stabilization, and examines its evolution behavior under different non-condensable gas mass fractions ω.

[0061] After the experiment, disconnect the DC power supply 13 and the data acquisition device 14, turn off the first heating device 5 and the second heating device 8, remove the vacuum pump 16 and the connecting pipe to connect the evaporation chamber 15, the liquid storage tank 7 and the non-condensable gas buffer tank 4 to the outside air, and finally clean the experimental table.

[0062] In this invention, the preconditions such as nanopore size parameters, meniscus depth, and non-condensable gas mass fraction can be changed, and the operation of the embodiments can be repeated to explore the evaporation law and mechanism of liquid in nanopore into non-condensable gas environment under different working conditions.

[0063] The above are preferred embodiments and arrangements of this application, and are not intended to limit the scope of protection of this application. Therefore, any equivalent changes made based on the principle of this experimental system, arrangement method, working medium substitution, etc., should be covered within the scope of protection of this patent.

Claims

1. An experimental system for liquid evaporation and heat transfer within nanopores under conditions containing non-condensable gases, characterized in that: It includes a non-condensable gas supply unit, a liquid supply unit, and a liquid evaporation unit, with the following specific structure: Non-condensable gas is connected from gas cylinder (3) to non-condensable gas buffer tank (4) via first valve (2). A first heating device (5) is installed below non-condensable gas buffer tank (4) to heat non-condensable gas buffer tank (4). Non-condensable gas buffer tank (4) is connected to evaporation chamber (15) via second valve (6) to fill evaporation chamber (15) with non-condensable gas. An independent evaporation device (12) is provided in evaporation chamber (15). Evaporation device (12) has a rectangular cavity structure. One side wall of evaporation device (12) is provided with a window with a nanoporous structure that can be embedded. The liquid storage tank (7) contains liquid. A pipeline is connected from the liquid inside the liquid storage tank (7) to the upper part of the evaporation device (12) via the third valve (10) and the flow meter (9) to fill the evaporation device with liquid. The upper part of the liquid storage tank (7) is connected to the evaporation chamber (15) via the fourth valve (11) to fill the evaporation chamber (15). The device has a nanoporous structure (20): it is a plate-like structure with an array of nanopores (19) to be measured. The array of nanopores (19) to be measured is a single row or a single column. When embedded in the side wall of the evaporation device (12), the axis of the nanopores is horizontal. A platinum or / and gold deposition layer (18) is deposited on the plate surface facing the evaporation chamber (15). The platinum or / and gold deposition layer retains pores that are coaxial with the nanopores (19) and of the same size. Wires are led out from both ends of the platinum or / and gold deposition layer (18) along the arrangement direction of the nanopores (19) and connected to a DC power supply (13). The DC power supply (13) is equipped with a data acquisition device (14) for recording current and voltage. The vacuum pump (16) is connected to the evaporation chamber (15) via a valve; The evaporation chamber (15), liquid storage tank (7), and non-condensable gas buffer tank (4) are all equipped with pressure detection devices and temperature detection devices; the pressure detection device and temperature detection device of the liquid storage tank (7) are used to detect the pressure and temperature of the gas above the liquid in the liquid storage tank.

2. The experimental system according to claim 1, characterized in that: The bottom of the evaporation device (12) is provided with a switchable liquid outlet.

3. The experimental system according to claim 1, characterized in that: The evaporation chamber (15) is a visual evaporation chamber, or has a visual observation window (17).

4. The experimental system according to claim 1, characterized in that: The gas cylinder (3) is equipped with a pressure relief valve (1).

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