A microwave deicing system and method for asphalt pavement based on high-temperature liquid water induction

Abstract

The present invention discloses a microwave deicing system and method for asphalt pavement based on high-temperature liquid water induction, which relates to the technical field of microwave deicing. The system includes a spraying system, a microwave heating system, a high-temperature liquid water supply system, a liquid water collection system, a road drying system and a water purification system; the spraying system is located in the microwave heating system, and is connected to the high-temperature liquid water supply system, the water purification system and the liquid water collection system through pipelines to form a water circulation system; the microwave heating system is located above the ice melting area; the road drying system is located on one side of the liquid water collection system to process the road surface after deicing; the system is mounted on a vehicle, and a suitable vehicle speed is selected to form a high-speed mobile deicing system. The present invention utilizes the principle that liquid water has a higher absorption rate of microwaves than ice layers and road surfaces, and is matched with a vehicle-mounted system to achieve high-efficiency mobile deicing. Compared with traditional microwave deicing, it reduces energy waste, improves deicing efficiency and is more environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave deicing, and in particular to a microwave deicing system and method for an asphalt pavement based on high-temperature liquid water induction. Background Art

[0002] In winter in my country, road icing is particularly common. Road icing can greatly reduce the friction coefficient between vehicle tires and the road surface, which can easily cause serious traffic accidents. In order to reduce such safety hazards, road deicing is particularly important. At present, there are three main methods for road deicing. The first is the mechanical method, which mainly uses a deicing machine or manual to crush the ice layer and remove it from the road surface. This deicing method is the most common method for road deicing because it is simple and easy to operate, but it will cause damage to the surface structure of the road surface, thereby affecting the service life of the road. The second is to deicing by spreading salt on the ice layer or spreading anti-freezing chemical materials on the road to accelerate the melting of the ice layer or inhibit its freezing, but high concentrations of chloride ions will corrode asphalt pavement and corrode curbstones, etc., seriously causing deformation of roads and bridges, and destroying roadside guardrails and vegetation. The third is to heat the road surface. There are two ways to heat the road surface. One is to bury a heating device under the road, and the other is to heat the asphalt pavement by microwaves. These two ways of heating the road surface have their own shortcomings. One is to consume a lot of financial resources and have complicated technology, and the other is to be inefficient and easy to cause microwave leakage.

[0003] The patent with publication number CN101483330A proposes a microwave superheated steam deicing device and deicing method. This technology uses the energy generated by microwaves to heat the water in the heating kettle to generate superheated steam, and de-ices through different steam injection methods, namely, steam ice cutting knife cutting ice and steam ice melting device melting ice. It is more flexible, accurate and efficient to deal with the on-site environment of steam deicing.

[0004] Patent publication number CN103031819A proposes a technology for heating a de-icing vehicle with microwave radiation. This technical solution utilizes the fact that the road surface has a stronger ability to absorb microwaves than the ice layer, and uses microwaves to heat the ground, so that the ice layer close to the road surface melts, eliminating the bonding force between the ice layer and the road surface, and then uses an ice crushing device to break up the ice layer. This not only improves the efficiency of ice crushing, but also reduces damage to the road surface, and can greatly save the energy consumption of the ice crushing device and extend the service life of the device.

[0005] The deicing technology and principle of the microwave deicing system and method for high-speed movement of asphalt pavement induced by high-temperature liquid water in the present application are quite different from those proposed previously. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a road deicing system that is more environmentally friendly, more efficient and does not damage the road surface. This asphalt pavement microwave deicing system based on high-temperature liquid water induction greatly improves the efficiency of microwave heating, reduces the loss of microwave energy, and avoids damage to the road surface and the surrounding environment.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A microwave deicing system for asphalt pavement based on high-temperature liquid phase water induction, characterized in that: the system includes a spraying system, a microwave heating system, a high-temperature liquid phase water supply system, a liquid water collection system, a road drying system and a water purification system;

[0009] The microwave heating system includes a plurality of first microwave generators and a metal microwave isolation cover, wherein the metal microwave isolation cover is located above the deicing area, and the first microwave generator is located on the metal microwave isolation cover; the spraying system is inside the metal microwave isolation cover and is connected to a positive pressure water barrier through a wave-isolating and heat-insulating hose, the other end of the positive pressure water barrier is connected to a high-temperature liquid water supply system, and the water inlet of the high-temperature liquid water supply system is connected to the water outlet of a water purification system; the water inlet of the water purification system is connected to a liquid water collection system through a negative pressure water pumping barrier; the bottom of the liquid water collection system is close to the ground to recover liquid water; a road drying system for drying the road surface after deicing is located on one side of the liquid water collection system.

[0010] Preferably, the spraying system includes a plurality of atomizing nozzles, and is connected to a small water tank in the high-temperature liquid water supply system through a positive pressure water barrier with the aid of a wave-isolating and heat-insulating hose.

[0011] Preferably, the microwave heating system includes a plurality of first microwave generators and a metal microwave isolation cover; the first microwave generator includes a magnetron, a waveguide and a radiation cavity; the metal microwave isolation cover is sealed with metal wave-isolating materials on all sides and on the top, and the metal microwave isolation cover is close to the ground with a flexible wave-isolating metal wire fabric.

[0012] Preferably, the high-temperature liquid water supply system includes a small water tank, a second microwave generator, a water level probe, a water tank level controller, a water barrier for controllable water absorption and discharge, and a large water tank; the second microwave generator for heating the liquid water in the small water tank is located on the small water tank; the small water tank is connected to the water barrier for controllable water absorption and discharge through a wave-isolating and heat-insulating hose, and the other end of the water barrier for controllable water absorption and discharge is connected to the large water tank; the water tank level controller obtains water level information through the water level probe located in the small water tank, thereby controlling the water barrier for controllable water absorption and discharge through electric wires; the second microwave generator includes a magnetron, a waveguide and a radiation cavity.

[0013] Preferably, the liquid water collection system is made of flexible material at the position where it contacts the ground, and a filter screen capable of filtering out large impurities is provided at the front end; a filter element is used in the water purification system to prevent fine impurities from clogging the atomizing nozzle.

[0014] Preferably, the road drying system includes a high-temperature powerful blower.

[0015] The present invention provides a microwave deicing method for asphalt pavement based on high-temperature liquid water induction. The method is completed by means of the above-mentioned deicing system. The key technology thereof is: comprising the following steps:

[0016] 1) Liquid water preheating stage: using the second microwave generator to heat the liquid water in the small water tank;

[0017] 2) Water film spraying stage: Turn on the positive pressure water pump to drive the high-temperature liquid phase water to flow through the wave-isolating and heat-insulating hose to the multiple atomizing nozzles of the spraying system;

[0018] 3) Microwave heating and ice melting stage: During the water film spraying stage, all first microwave generators are turned on, and their magnetrons generate microwave beams of specific frequency and power. Since the water film has a stronger absorption capacity for microwaves than solid water and asphalt pavement, it quickly absorbs microwave energy and heats up, and efficiently transfers heat to the solid water through the dual mechanisms of heat conduction and heat convection;

[0019] 4) Liquid water recovery and reuse stage: The liquid water collection system uses negative pressure to pump water onto the road surface to create a negative pressure zone, recover the liquid water generated by ice melting, and transport the recovered liquid water to the water purification system through the wave-proof and heat-insulating hose. The purified liquid water enters the high-temperature liquid water supply system through the wave-proof and heat-insulating hose, forming a liquid water efficient circulation system;

[0020] 5) Road surface drying treatment stage: The road surface after liquid water recovery is dried by the high-temperature and powerful blower of the road drying system.

[0021] The benefits of adopting the present invention are:

[0022] The microwave deicing method proposed in the present invention uses microwaves to heat liquid water. Compared with traditional mechanical and chemical deicing methods, it can effectively avoid damage and corrosion to the road surface, extend the service life of the road surface, and reduce damage to the ecological environment of roadside plants.

[0023] The microwave deicing method proposed in the present invention utilizes the induction mechanism of liquid phase water. The principle is based on the characteristics that the dielectric constant of liquid phase water is much greater than that of asphalt pavement and solid phase water. Under these three materials, most of the microwave energy is absorbed by liquid phase water, and a small part of the microwave energy is absorbed by asphalt pavement and solid phase water. Therefore, microwaves can quickly heat liquid phase water, so that liquid phase water and solid phase water undergo heat exchange to achieve a rapid ice melting effect. In the ice melting process, since the asphalt pavement absorbs less microwave energy, the solid phase water has melted before the asphalt pavement is heated, thereby reducing the waste of microwave energy and improving the efficiency of asphalt pavement deicing.

[0024] The liquid water collection system and road surface drying system in the microwave deicing system proposed in the present invention recycle the liquid water after deicing and perform hot air drying on the water film adsorbed on the road surface that is difficult to recover, thereby saving water resources and reducing the risk of "black ice" forming again on the road surface.

[0025] The microwave deicing system proposed by the present invention uses a liquid water collection system and a water purification system to form a cycle of recycling and utilizing liquid water, thereby improving the utilization rate of water resources and being more green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a system diagram of the asphalt pavement microwave deicing system of the present invention;

[0027] Description of Reference Numerals

[0028] 1. Magnetron, 2. Waveguide, 3. Radiation cavity, 4. Atomizing nozzle, 5. Metal microwave isolation cover, 6. Flexible wave-isolating metal wire fabric, 7. First microwave generator, 8. Water film, 9. Positive pressure water barrier, 10. Water level probe, 11. Small water tank, 12. Water tank level controller, 13. Electric wire, 14. Water barrier with controllable water absorption and discharge, 15. Large water tank, 16. Wave-isolating and heat-insulating hose, 17. Water purification system, 18. Negative pressure water pumping barrier, 19. Liquid water collection system, 20. Road drying system, 21. Solid water, 22. Asphalt pavement, 23. Second microwave generator. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the technical scheme in the embodiments of the present invention will be clearly and completely described below in combination with the drawings and specific implementation methods in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] like Figure 1The present invention is based on a microwave deicing system for an asphalt pavement induced by high-temperature liquid water, which includes a spraying system, a microwave heating system, a high-temperature liquid water supply system, a liquid water collection system 19, a road drying system 20 and a water purification system 17.

[0031] The atomizing nozzle 4 in the spraying system is located inside the microwave heating system and is connected to the small water tank 11 in the high-temperature liquid water supply system through a wave-isolating and heat-insulating hose 16. The atomizing nozzle 4 sprays the liquid water in the small water tank 11 in the high-temperature liquid water supply system evenly on the solid water 21 on the road surface through a positive pressure water barrier 9, forming a water film 8 required for subsequent microwave heating. The spray effect of the atomizing nozzle 4 can ensure that the liquid water is evenly distributed on the road surface. The wave-isolating and heat-insulating hose 16 ensures that the temperature and state of the liquid water are stable during transportation, preventing the liquid water from freezing during transportation and causing pipeline blockage, while reducing heat dissipation and improving subsequent de-icing efficiency.

[0032] The function of the microwave heating system is to provide heat for the sprayed liquid water, causing it to heat up and exchange heat with the solid water 21. The microwave heating device is composed of a plurality of first microwave generators 7 and a metal microwave isolation cover. The metal microwave isolation cover 5 is composed of a metal copper seal with wave-isolating material on all sides and the top. The function is to prevent microwave leakage and prevent heat dissipation in the metal cover. The bottom of the metal microwave isolation cover 5 is composed of a flexible wave-isolating metal wire fabric 6. The purpose is to be in close contact with the road surface without damaging the road surface. The first microwave generator 7 includes a magnetron 1, a waveguide 2 and a radiation cavity 3. The parameters such as the generated microwave frequency and power match the heating requirements of the liquid water to ensure fast and efficient heating.

[0033] The high-temperature liquid phase water supply system is responsible for providing sufficient high-temperature liquid phase water to the spraying system and storing and recovering excess liquid phase water. The high-temperature liquid phase water supply system includes a small water tank 11 and a large water tank 15 for storing liquid phase water, a water level probe 10 for controlling the water level of the small water tank, a water tank liquid level controller 12 and a water dam 14 for controlling water absorption and discharge, and a second microwave generator 23 for heating the liquid phase water in the small water tank 11. The second microwave generator 23 includes a magnetron 1, a waveguide 2 and a radiation cavity 3; wherein the small water tank 11 is connected to the large water tank 15 through the water dam 14 for controlling water absorption and discharge, and the small water tank 11 and the large water tank 15 are connected to the water dam 14 for controlling water absorption and discharge through a wave-isolating and heat-insulating hose 16; the water level probe 10, the water tank liquid level controller 12 and the water dam 14 for controlling water absorption and discharge The coordinated work of the water tank 14 for releasing water ensures that the water level in the small water tank is stable within an appropriate range. The amount of water in the small water tank 11 is controlled by the water tank level controller 12 according to the water level probe 10, which is specifically manifested as follows: when the water level probe 10 detects that the water level in the small water tank 11 is insufficient, the water tank level controller 12 controls the water tank 14 for controlling water absorption and release through the wire 13 to absorb water with the large water tank 15; when the water level probe 10 detects that the water level is too high, the water tank level controller 12 controls the water tank 14 for controlling water absorption and release through the wire 13 to release water into the large water tank 15, ensuring that the amount of water in the small water tank 11 is sufficient for the use of the spraying system without overflowing, and ensuring that the second microwave generator 23 can quickly heat the water in the small water tank 11. The specific amount of water is sufficient for the early operation of the system according to the specific situation, and is sufficient for the operation of the spraying system when the liquid water collected by the liquid water collection system 19 cannot be used by the spraying system; because the water collected by the liquid water collection system 19 is much larger than the liquid water consumed by the spraying device, the small water tank 11 is generally drained to the large water tank 15, and the drainage relationship between the small water tank 11 and the large water tank 15 ensures the early operation of the system and the recycling of the overall water. The water in the small water tank 11 is heated by the second microwave generator 23 to prevent the water sprayed by the spraying system from freezing directly on the road surface due to the low external temperature, and is heated in advance. At the same time, the heated liquid water can increase the temperature difference, which also improves the subsequent ice melting efficiency.

[0034] The liquid water collection system 19 forms negative pressure at the position where the liquid water collection system 19 contacts the road surface through the negative pressure pump 18, so as to collect the liquid water generated after the road surface melts. The part of the liquid water collection system 19 in contact with the ground uses flexible materials to ensure that it is close to the ground while preventing damage to the ground; a filter is set at the front end of the liquid water collection system 19 to prevent large foreign objects from entering the pipeline, clogging the pipeline, and damaging the equipment; a water purification system 17 is connected between the liquid water collection system 19 and the high-temperature liquid water supply system through a wave-isolating and heat-insulating hose 16, and the water purification system 17 purifies the recovered liquid water. The water purification system 17 uses a medium-efficiency filter element, which mainly filters Dust particles larger than 1 μm are prevented to prevent small foreign objects in the water from clogging the atomizing nozzle 4 after entering the spraying system; the liquid water collected from the road surface is filtered and re-input into the small water tank 11, and the spraying system, high-temperature liquid water supply system, liquid water collection system 19, and water purification system 17 are connected as a loop to realize the recycling of water resources and reduce the waste of water resources. The negative pressure of the negative pressure water pump 18 can be adjusted according to the road conditions, ice melting speed and moving speed to ensure the collection efficiency and recycling effect. Too small negative pressure will cause the accumulation of liquid water on the road surface, and the subsequent drying treatment cannot completely remove it, which is easy to form secondary ice. Too large negative pressure will waste energy.

[0035] The road drying system 20 is located on one side of the liquid water collection system 19, and dries the road surface after the ice melts to prevent the residual liquid water adsorbed on the road surface from freezing again, thereby improving the road safety.

[0036] All systems work together to achieve efficient and rapid de-icing. The entire system can be installed on a vehicle. The on-board design ensures that all systems operate stably while on the move and can adapt to different road conditions and de-icing operation requirements.

[0037] See attached Figure 1 The present invention is based on the microwave deicing method of asphalt pavement induced by high-temperature liquid water. A layer of water film 8 is directly added above the solid water 21, and the process of first heating the asphalt pavement 22 with microwaves and then exchanging heat with the solid water 21 on the asphalt pavement 22 to melt into liquid water is directly omitted. Since the wave absorption capacity of the asphalt pavement 22 is poor, this process takes a long time. A layer of water film 8 is directly added above as a fast heat absorption medium to exchange heat with the solid water 21 to make it undergo phase change, and then microwaves heat the upper water film 8 to increase its temperature, and then heat is exchanged with the solid water 21 from top to bottom to achieve phase change of all the solid water 21. The specific steps are as follows:

[0038] 1) Liquid phase water preheating stage: using the second microwave generator 23 to heat the liquid phase water in the small water tank 11;

[0039] 2) Water film 8 spraying stage: Turn on the positive pressure water barrier 9 to drive the high-temperature liquid phase water to flow to the multiple atomizing nozzles 4 of the spraying system through the wave-isolating and heat-insulating hose 16. The pressure of the positive pressure water barrier 9 can be adjusted according to the road conditions, ice thickness and the number of atomizing nozzles equipped;

[0040] 3) Microwave heating and ice melting stage: During the water film 8 spraying stage, all first microwave generators 7 are turned on, and their magnetrons 1 generate microwave beams of specific frequency and power. Since the water film 8 has a stronger ability to absorb microwaves than the solid water 21 and the asphalt pavement 22, it quickly absorbs microwave energy to heat up, and efficiently transfers heat to the solid water 21 through the dual mechanisms of heat conduction and heat convection. A metal microwave isolation cover 5 is set in the area of ​​the microwave-heated ice surface to reduce the dissipation of microwave energy. A flexible wave-isolating metal wire fabric 6 is used at the metal microwave isolation cover 5 close to the ground to prevent damage to the ground.

[0041] 4) Liquid water recovery and reuse stage: The liquid water collection system 19 uses negative pressure pumping 18 to create a negative pressure zone on the road surface, recover the liquid water generated by melting ice, and transport the recovered liquid water to the water purification system 17 through the wave-proof insulation hose 16. The purified liquid water enters the high-temperature liquid water supply system through the wave-proof insulation hose 16 to form a liquid water efficient circulation system. The negative pressure pump 18 adjusts the pressure based on the thickness of the ice layer on the road surface, the deicing speed and the forward speed to ensure the pumping speed and pumping effect;

[0042] 5) Road surface drying treatment stage: The road surface after liquid water recovery is dried by multiple high-temperature and powerful hair dryers of the road drying system 20 to ensure that the residual water on the road surface evaporates quickly to prevent the risk of secondary freezing of the road surface. The deployment of the hair dryers is selected based on the road width and the depth of water accumulation after ice melting.

[0043] This new de-icing method that uses microwaves to heat the water film 8 to quickly exchange heat with the solid water 21 is more efficient than traditional microwave de-icing and more energy-saving and environmentally friendly than other de-icing methods.

[0044] Next, the feasibility of the present invention is discussed in theory:

[0045] Table 1 Dielectric constant and dielectric loss tangent of materials

[0046] Material Dielectric constant Dielectric loss tangent Liquid water (20℃) 76.7 0.157 Asphalt concrete (-20℃) 4.5-6.5 0.015-0.036 Solid water (ice) (-20℃) 3.2 0.009

[0047] As shown in Table 1, the rate of microwave heating of an object is proportional to the dielectric constant and dielectric loss tangent of each material. The principle of traditional microwave deicing is to utilize the fact that the wave absorption performance of the asphalt pavement 22 is greater than that of the solid phase water 21. The asphalt pavement 22 is heated by microwaves and then the solid phase water 21 on the asphalt pavement 22 is melted by the temperature difference between the asphalt pavement 22 and the solid phase water 21. In essence, since the wave absorption performance of the asphalt pavement 22 is better than that of the solid phase water 21, the temperature of the asphalt pavement 22 is first increased. After reaching a temperature above 0°C, the solid phase water 21 in contact with the asphalt pavement 22 begins to melt into liquid phase water. Since the wave absorption performance of the liquid phase water is better than that of the asphalt pavement 22 and the solid phase water 21, the temperature of the liquid phase water heated by microwaves rises faster, and it can exchange heat with the solid phase water 21 faster, so that the solid phase water 21 undergoes a phase change, and finally the solid phase water 21 is completely heat exchanged and converted into liquid phase water. Therefore, the present invention can improve the deicing efficiency and reduce energy waste compared with the traditional deicing method by using the form of spraying water film 8.

[0048] The asphalt pavement microwave deicing system based on high-temperature liquid water induction proposed by the present invention is verified at the experimental level as follows:

[0049] 1. Experimental Setup

[0050] 1. Set up an experimental group and prepare an asphalt mixture rutting plate specimen to simulate the road surface. Freeze a solid phase water 21 with a diameter of 5 cm and a thickness of 2 cm on the rutting plate in an environment of -20°C (refrigerator). Heat it in a microwave environment with a power of 6000 watts. During the melting process, the ice layer melts slowly. After 85 seconds, all the ice melts. At this time, touch the surface of the rutting plate with your hand and you can clearly feel the temperature.

[0051] 2. Set up a control group. Also take an asphalt mixture rutting plate specimen to simulate the road surface. Freeze a solid phase water 21 with a diameter of 5 cm and a thickness of 2 cm on the rutting plate in an environment of -20°C (refrigerator), and spray a layer of water film 8 with a temperature of 40°C on the ice surface. Heat the experiment in a microwave environment with a power of 6000 watts. After 16 seconds, check the ice. It is found that the ice has gradually melted about 2 / 3 of its volume. Push the ice gently with your hand and find that it has not moved. Then continue to heat it until it is completely melted in 23 seconds. At this time, touch the surface of the rutting plate with your hand and no obvious temperature can be felt.

[0052] 2. Experimental Conclusion

[0053] 1. Comparison of ice melting progress. Under the same microwave environment, when the experimental group and the control group were subjected to microwave heating at the same time, an obvious phenomenon was observed: the time it took for the ice layer in the experimental group to completely melt was much longer than that in the control group. This indicates that after spraying a water film on the ice layer, the ice melting speed was significantly improved by microwave heating. This preliminarily proves that the new microwave heating deicing method (accelerating ice melting by adding a layer of water film on the ice layer) is feasible and efficient.

[0054] 2. Verification of ice melting position and induction mechanism. During the ice melting process, it was found in the control group that when 2 / 3 of the ice was melted, it would not move when pushed by hand, indicating that the ice started to melt from the surface. Moreover, by comparing the experimental group and the control group, it was found that when all the ice was melted in the experimental group, the rutting plate could obviously feel the temperature, indicating that the rutting plate absorbed most of the microwave energy, while the rutting plate in the control group did not obviously feel the temperature after all the ice was melted, indicating that the rutting plate absorbed very little microwave energy. Judging from the melting time of the ice in the control group, it was shown that warm water absorbed most of the microwave energy. These phenomena show that it is feasible to add a layer of water film on the ice layer as the "induction factor" in the induction mechanism.

[0055] (I) Analysis of heat transfer mode

[0056] 1. Heat conduction and heat convection act at the same time. In the process of microwave heating of liquid water and solid water for heat exchange, the heat exchange and transfer is achieved simultaneously through heat conduction and heat convection. Heat conduction is like the slow transfer of heat inside an object or between objects in contact with each other, just like when one end of an iron rod is heated, the heat will gradually transfer along the iron rod to the other end. Heat convection is the transfer of heat driven by the flow of liquid or gas. For example, when boiling water, the water rises due to the heat, and the surrounding colder water falls, forming convection, making the whole pot of water hot. In this ice melting process, heat conduction and heat convection occur at the same time. Their combined effect causes the solid water to undergo a phase change, and this synergistic effect makes the time for the solid water to undergo a phase change shorter than when there is only a single heat conduction or heat convection method.

[0057] (II) Calculation and analysis of heat conduction time

[0058] 1. Calculation basis of heat transfer rate: For heat conduction between liquid water and solid water, the heat transfer rate (Q V The law involves several key factors, such as the thermal conductivity of ice (K, about 2.2 watts per meter Kelvin, which reflects the ability of ice to conduct heat. The larger the value, the faster the heat conduction), the contact area between solid water and liquid water (A, the larger the contact area, the more channels for heat transfer), the temperature difference (solid water 21 temperature (T 固 ) and liquid water temperature (T 液) and the thickness of the solid water layer (H f ). According to Fourier's law, the heat transfer rate Qv is calculated as

[0059] ;

[0060] 2. Calculation of heat conduction time and influencing factors. Knowing the heat transfer rate of heat conduction, combined with the latent heat of phase change of solid water, the time required for heat conduction between the solid water layer and the liquid water can be calculated:

[0061] ;

[0062] During the calculation process, it was found that the time for heat conduction melting is proportional to the square of the thickness of the solid water layer, that is, the thicker the solid water layer, the longer the time required for heat conduction, and the time increases rapidly; at the same time, the heat conduction time is inversely proportional to the temperature difference between the two. The greater the temperature difference, the faster the heat conduction, because a larger temperature difference provides a stronger driving force for heat transfer.

[0063] (III) Calculation and analysis of thermal convection time

[0064] 1. Calculation basis of heat transfer rate of convection: for heat convection between solid water and liquid water, the heat transfer rate (Q W The formula involves the convection heat transfer coefficient (h, about 1000 watts per square meter Kelvin, which reflects the strength of convection heat transfer), the contact area between solid water and liquid water (A), and the temperature difference between liquid water and solid water (T 液 -T 固 ). According to the convective heat transfer formula, the heat transfer rate Q W The calculation formula is

[0065] ;

[0066] 2. Calculation of heat convection time and influencing factors. Combining the latent heat of phase change of solid water and the heat transfer rate of heat convection, the time for convection heat exchange between solid water and liquid water can be calculated:

[0067] ;

[0068] The results show that the time of thermal convection is proportional to the thickness of the solid water layer, that is, the thicker the solid water layer, the longer the time required for thermal convection; the thermal convection time is inversely proportional to the temperature difference, the greater the temperature difference, the faster the thermal convection, which is similar to the law of heat conduction.

[0069] (IV) Summary

[0070] Factors affecting the speed of ice melting. Through the analysis of heat conduction and convection, it can be seen that the melting of the solid water layer by high-temperature liquid water is mainly related to the thickness of the solid water layer. The thicker the solid water layer, the longer it takes to complete the heat exchange and make the solid water change phase, whether it is heat conduction or heat convection, especially the heat conduction rate is more affected by the thickness; the temperature difference is also one of the main factors affecting the speed of ice melting, so increasing the power of microwaves and accelerating the rise of liquid water temperature can effectively increase the speed of new microwave deicing. In addition, since heat conduction and heat convection exist simultaneously in the process of microwave heating liquid water to melt the solid water layer, the actual ice melting rate is much less than the time it takes for these two to act alone.

[0071] Based on the corresponding relationship between the amount of liquid water sprayed and the thickness of the ice layer, the energy analysis of the water film melting the ice layer is carried out:

[0072] 1. Calculation of ice mass: For solid water 21 (including the ice layer of the experimental group and the control group), its mass can be calculated based on density and volume. For objects of a certain shape, the volume can be calculated by parameters such as radius and height (thickness), and then multiplied by the density of ice to get the mass of solid water 21; the mass of water film 8 is obtained by the density and thickness of water and the radius of the beaker. The absorption and transfer of heat are closely related to mass, so the mass of solid water 21 is very important for the subsequent calculation of the heat absorbed by solid water 21 and the heat exchange with water film 8.

[0073] 2. Calculation of heat absorption when solid water 21 is heated (from -20℃ to 0℃) First, calculate the amount of heat that solid water 21 needs to absorb when it rises from -20℃ to 0℃. We know that the amount of heat absorbed or released by an object (represented by Q) is related to the specific heat capacity (c, where the specific heat capacity of ice at -20℃ is a specific value), mass (m, which is the mass of the ice cube calculated earlier), and temperature difference (∆T, which is the difference from -20℃ to 0℃, i.e. 20K). According to the principles of thermodynamics, heat is expressed as the product of specific heat capacity, mass, and temperature difference. For the ice cubes in the experimental group and the control group, this method can be used to calculate the amount of heat absorbed when the temperature rises from -20℃ to 0℃. In this process, the temperature of the ice cube gradually rises after absorbing heat, but there is no phase change from solid to liquid.

[0074] 3. Calculation of latent heat of phase change of solid water 21 (solid to liquid at 0℃). When the temperature of solid water 21 rises to 0℃, ice needs to absorb some heat to change from solid to liquid. This heat is called latent heat. The calculation of latent heat is related to the mass of ice (m) and a specific melting latent heat value. The melting latent heat value of water is 334,000 joules / kilogram. The calculation of latent heat is specifically expressed as the product of mass and melting latent heat value. From this, the latent heat required for a certain mass of ice to change from solid to liquid at 0℃ can be calculated. This part of latent heat needs to be calculated for the ice in both the experimental group and the control group, because this is the additional heat that must be absorbed for the ice to completely melt into water.

[0075] 4. Calculation of total heat and analysis of heat exchange with water film 8. Add the heat absorbed by solid phase water 21 from -20℃ to 0℃ and the latent heat absorbed by phase change at 0℃ to get the total heat absorbed by solid phase water 21 to melt into liquid state. Then according to the principle of energy conservation, to melt all solid phase water 21, the same amount of heat needs to be exchanged with it. For the water film 8 in the control group (mass m 2 ), it will release heat during the cooling process. We can calculate the heat capacity and mass (m 2 ) and the temperature change range (from 100°C to 0°C) to calculate how much heat the water film 8 can release. Here, because the mass of the water film 8 is small, the microwave heating speed of the water film to 100°C is very fast, so the calculation is based on 100°C. The specific expression is as follows:

[0076] ;

[0077] Among them, c 水 is the specific heat capacity of water. 冰 is the specific heat capacity of ice, is the temperature of water from 100℃ to 0℃, For ice temperatures from -20°C to 0°C, is the latent heat of melting, and the mass of melted ice is m x .

[0078] By comparing the heat released by the water film 8 and the total heat required to melt the solid water 21, it is possible to calculate how much -20°C ice the water film 8 can melt under ideal conditions (without considering microwave heating energy loss), thereby deriving the quality relationship between water and ice in terms of heat exchange.

[0079] Through the above analysis, it can be concluded that the thickness of the water film 8 required to melt a certain thickness of solid water 21 is required, which provides a reference for the amount of liquid water sprayed according to the thickness of the solid water 21 in actual applications, to prevent the water film 8 from being too thin, which leads to a decrease in the rate of thermal convection and heat exchange, thereby slowing down the ice melting efficiency; or the water film 8 is too thick, which leads to a decrease in the microwave heating rate of the water film, a decrease in the temperature difference, and a slowdown in the ice melting rate.

[0080] Confirmation of the de-icing vehicle speed is an important part of actual use.

[0081] ;

[0082] Where L is the length of the metal microwave isolation cover, V is the speed of the deicing vehicle. The microwave deicing time is first estimated by the thermal convection rate and the thermal conduction rate according to the thickness of the solid water layer. At the same time, the deicing vehicle is running, and the speed of the deicing vehicle is adjusted based on the actual deicing time and deicing effect.

[0083] Efficient ice-melting solution: When the ice layer is thick, it will seriously affect the rate of heat conduction and heat convection, resulting in a longer microwave deicing time. It is appropriate to use multiple deicing vehicles to work together. In theory, the thickness of the solid phase water 21 is divided into multiple layers and melted by different deicing vehicles respectively. This can increase the speed of the deicing vehicle and prevent the deicing work from being difficult to advance due to the influence of road traffic in actual work. The specific method is that when melting the thick solid phase water 21 on the road section, the solid phase water 21 is divided into multiple layers of thinner solid phase water 21, thereby estimating the speed of the deicing vehicle, and then determining the number of deicing vehicles according to the number of layers; the deicing rate of the deicing vehicle can also be increased by lengthening the length of the metal microwave isolation cover 5, adding the first microwave generator 7, increasing the power of the second microwave generator 23, or increasing the temperature of the water in the small water tank 11.

[0084] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A microwave deicing system for asphalt pavement based on high-temperature liquid water induction, characterized in that: The system comprises a spraying system, a microwave heating system, a high-temperature liquid water supply system, a liquid water collection system (19), a road drying system (20) and a water purification system (17); The microwave heating system comprises a plurality of first microwave generators (7) and a metal microwave isolation cover (5), wherein the metal microwave isolation cover (5) is located above the deicing area, and the first microwave generator (7) is located on the metal microwave isolation cover (5); the spraying system is inside the metal microwave isolation cover (5) and is connected to a positive pressure water wall (9) through a wave-isolating and heat-insulating hose (16); the other end of the positive pressure water wall (9) is connected to a high-temperature liquid phase water supply system, and the water inlet of the high-temperature liquid phase water supply system is connected to the water outlet of a water purification system (17); the water inlet of the water purification system (17) is connected to a liquid water collection system (19) through a negative pressure pumping wall (18); the bottom of the liquid water collection system (19) is close to the ground to recover liquid phase water; a road drying system (20) for drying the road surface after deicing is located on one side of the liquid water collection system (19); The microwave heating system comprises a plurality of first microwave generators (7) and a metal microwave isolation cover (5); the first microwave generator (7) comprises a magnetron (1), a waveguide (2) and a radiation cavity (3); the metal microwave isolation cover (5) is sealed around and on the top with a metal wave-isolating material, and the metal microwave isolation cover (5) is provided with a flexible wave-isolating metal wire braid (6) at a position close to the ground; The high-temperature liquid phase water supply system comprises a small water tank (11), a second microwave generator (23), a water level probe (10), a water tank liquid level controller (12), a water dam (14) for controlling water absorption and discharge, and a large water tank (15); the second microwave generator (23) for heating liquid water in the small water tank (11) is located on the small water tank (11); the small water tank (11) is connected to the water dam (14) for controlling water absorption and discharge through a wave-proof heat-insulating hose (16), and the other end of the water dam (14) for controlling water absorption and discharge is connected to the large water tank (15); the water tank liquid level controller (12) obtains water level information through the water level probe (10) located in the small water tank (11), thereby controlling the water dam (14) for controlling water absorption and discharge through an electric wire (13); the second microwave generator (23) comprises a magnetron (1), a waveguide (2), and a radiation cavity (3); The spraying system comprises a plurality of atomizing nozzles (4) and is connected to a small water tank (11) in a high-temperature liquid phase water supply system via a wave-isolating and heat-insulating hose (16) through a positive pressure water barrier (9).

2. The asphalt pavement microwave deicing system based on high temperature liquid water induction according to claim 1 is characterized in that: The liquid water collection system (19) is made of flexible material at the position where it contacts the ground, and a filter screen capable of filtering large impurities is arranged at the front end; a filter element is used in the water purification system (17) to prevent fine impurities from clogging the atomizing nozzle (4).

3. The asphalt pavement microwave deicing system based on high temperature liquid water induction according to claim 1 is characterized in that: The road drying system (20) comprises a high-temperature powerful blower.

4. A microwave deicing method for asphalt pavement based on high temperature liquid water induction, the method is accomplished by means of a deicing system as claimed in any one of claims 1 to 3, characterized in that: The steps include: 1) Liquid phase water preheating stage: using a second microwave generator (23) to heat the liquid phase water in the small water tank (11); 2) Water film (8) spraying stage: opening the positive pressure water barrier (9) to drive the high-temperature liquid phase water to flow to the multiple atomizing nozzles (4) of the spraying system through the wave-isolating and heat-insulating hose (16); 3) Microwave heating and ice melting stage: During the water film (8) spraying stage, all first microwave generators (7) are turned on, and their magnetrons (1) generate microwave beams of specific frequency and power. Since the water film (8) has a stronger ability to absorb microwaves than the solid water (21) and the asphalt pavement (22), it quickly absorbs microwave energy and heats up, and efficiently transfers heat to the solid water (21) through the dual mechanisms of heat conduction and heat convection; 4) Liquid phase water recovery and reuse stage: The liquid phase water collection system (19) uses negative pressure pumping (18) to create a negative pressure zone on the road surface to recover the liquid phase water generated by melting ice. The recovered liquid phase water is transported to the water purification system (17) through the wave-isolating and heat-insulating hose (16). The purified liquid phase water enters the high-temperature liquid phase water supply system through the wave-isolating and heat-insulating hose (16), forming a liquid phase water efficient circulation system; 5) Road surface drying treatment stage: The road surface after liquid phase water recovery is dried by a high-temperature and powerful blower of the road drying system (20).

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