LNG (Liquefied Natural Gas) cold energy recovery heat exchanger with thermal pressurization function

Abstract

The invention relates to an LNG (Liquefied Natural Gas) cold energy recovery heat exchanger with a thermal pressurization function, and belongs to the technical field of heat exchangers. The input end of the LNG heat exchanger is provided with an LNG inlet pipe, the output end of the LNG heat exchanger is provided with an NG outlet pipe, the LNG inlet pipe is connected with an LNG gas cylinder, the NG outlet pipe is connected with an external heat exchanger, an NG coil pipe is arranged in the external heat exchanger, one end of the NG coil pipe is communicated with the NG outlet pipe, and the other end of the NG coil pipe is provided with an NG gas supply pipe used for being connected with an engine; the input end of the secondary refrigerant heat exchanger is provided with a secondary refrigerant inlet pipe, the output end of the secondary refrigerant heat exchanger is provided with a secondary refrigerant outlet pipe, the output end of the secondary refrigerant outlet pipe is connected with the refrigerating device, the input end of the secondary refrigerant inlet pipe is communicated with the interior of the external heat exchanger, and the external heat exchanger is provided with a secondary refrigerant outer inlet pipe. According to the LNG cold energy recycling system, the LNG cold energy is recycled in a stepped mode, and the recycling efficiency of the cold energy can be improved; and by arranging the coolant circulating pump and the heating device, the device has the effect of heating and pressurizing the LNG cylinder.

Description

Technical Field

[0001] This application relates to the field of heat exchangers, and more particularly to an LNG cold energy recovery heat exchanger with thermal pressurization. Background Technology

[0002] LNG, as a fuel, boasts advantages such as low price, high calorific value, low exhaust pollution after combustion, and environmental friendliness, and is currently widely used in various sectors of the national economy. LNG has a temperature of approximately -162℃ at atmospheric pressure and is typically stored in cryogenic storage tanks. Before combustion, LNG needs to be heated and vaporized into natural gas. This vaporization process releases a large amount of cold energy, which is usually directly released into the atmosphere, resulting in significant waste of cooling capacity.

[0003] LNG cold energy recovery is highly valued abroad, especially in Japan, and has been widely applied in engineering practice. However, due to the relatively late start of my country's LNG industry, research on LNG cold energy recovery technology has only just begun, particularly in small-scale LNG equipment. Currently, some experts and scholars from universities and research institutes have proposed automotive air conditioning systems based on LNG cold energy recovery. However, these systems all use direct heat exchange between the refrigerant and LNG. Due to the large temperature difference between the two, LNG air conditioning systems are prone to refrigerant freezing and poor heat exchange, making continuous and stable operation impossible, and resulting in low cold energy recovery efficiency.

[0004] Chinese patent CN110802996A discloses an LNG air conditioning refrigeration system that uses a refrigerant as an intermediate heat exchange medium. This solves the problems of continuous operation of the LNG air conditioning system, low heat exchange efficiency, and significant cooling loss caused by the freezing of the refrigerant during high-temperature heat exchange between LNG and the refrigerant. However, compared to the refrigerant, the liquid phase temperature of the refrigerant is lower, and the NG temperature (approximately -10°C) after utilizing the LNG's cold energy through the aforementioned heat exchanger is also lower, resulting in a small amount of cooling loss. Furthermore, during the LNG supply process, the liquid level in the LNG storage tank continuously decreases, leading to a drop in the pressure of the LGN gas phase space, which in turn causes insufficient LNG supply to the storage tank. Summary of the Invention

[0005] To further improve the efficiency of cold energy recovery and utilization and the heat exchange efficiency, this application provides an LNG cold energy recovery heat exchanger with thermal pressurization.

[0006] This application provides an LNG cold energy recovery heat exchanger with thermal pressurization, which adopts the following technical solution:

[0007] An LNG cold energy recovery heat exchanger with thermal pressurization includes:

[0008] A storage tank for storing a cold storage agent, which has gas-liquid conversion characteristics and its freezing point is lower than that of LNG. The cold storage agent exists in a gas-liquid coexistence state inside the storage tank.

[0009] An LNG heat exchanger is located in the gas phase space inside a storage tank. The LNG heat exchanger has an LNG inlet pipe at its input end and an NG outlet pipe at its output end. The LNG inlet pipe is connected to an LNG cylinder, and the NG outlet pipe is connected to an external heat exchanger. An NG coil is installed inside the external heat exchanger. One end of the NG coil is connected to the NG outlet pipe, and the other end is connected to an NG gas supply pipe.

[0010] A refrigerant heat exchanger is located in the liquid phase space inside a storage tube. The refrigerant heat exchanger has a refrigerant inlet pipe at its input end and a refrigerant outlet pipe at its output end. The output end of the refrigerant outlet pipe is connected to a refrigeration device. The input end of the refrigerant inlet pipe is connected to the interior of an external heat exchanger. The external heat exchanger is equipped with an external refrigerant inlet pipe.

[0011] By adopting the above technical solution, LNG cylinders are used to supply LNG, which enters the LNG heat exchanger through the LNG inlet pipe. The LNG heat exchanger exchanges heat with the gaseous refrigerant in the storage tank. The temperature of the LNG in the tube side increases due to heat absorption, and it continuously vaporizes into NG. At the same time, the refrigerant undergoes the first stage of cold energy recovery and storage through condensation. After the first stage of cold energy recovery, the NG enters the external heat exchanger through the NG outlet pipe. The NG exchanges heat with the refrigerant flowing into the inner cavity of the external heat exchanger through the NG coil. The refrigerant performs the second stage of cold energy recovery on the NG in the NG coil. The temperature difference between the NG after the first stage of cold energy recovery and the refrigerant is not too large, ensuring that the refrigerant is not frozen after heat exchange in the external heat exchanger. After recovering this portion of the cold energy directly, the refrigerant enters the refrigerant heat exchanger through the refrigerant inlet pipe. There, it exchanges heat with the refrigerant that has undergone the first stage of cold energy recovery, achieving secondary cascade cooling. The cooled refrigerant then enters the corresponding refrigeration unit through the refrigerant outlet pipe, realizing the function of reusing LNG cold energy. By recovering LNG cold energy in stages, cold energy loss is reduced, and the efficiency of cold energy recovery and utilization is improved. During the heat exchange process with the refrigerant, the refrigerant absorbs heat and vaporizes, generating a large number of bubbles. These bubbles create convective disturbances within the refrigerant, increasing its turbulence and thus improving the heat exchanger's efficiency.

[0012] Optionally, the storage tank is provided with a refrigerant inlet pipe, and the storage tank is provided with a refrigerant circulation pump for pumping the refrigerant out of the storage tank. The output end of the refrigerant circulation pump is provided with a refrigerant outlet pipe, and the refrigerant inlet pipe is connected to the inner cavity of the storage tank.

[0013] By adopting the above technical solution and setting up a refrigerant circulation pump, on the one hand, a circulating refrigerant is provided to the storage tank to ensure that the heat exchanger can continuously and stably recover the cold energy of LNG; on the other hand, the turbulence of the refrigerant in the storage tank can be improved to ensure that it has a high heat exchange efficiency.

[0014] Optionally, the end of the refrigerant outlet pipe away from the refrigerant circulation pump is connected to a first return pipe and a second return pipe via a cryogenic combined pressure regulating valve. A heating device is provided on the second return pipe. The ends of the first and second return pipes away from the cryogenic combined pressure regulating valve are connected to a confluence pipe via a three-way pipe. An internal diversion pipe is provided in the jacket of the LNG cylinder. Both ends of the internal diversion pipe extend out of the jacket of the LNG cylinder. The end of the confluence pipe away from the first return pipe is connected to one end of the internal diversion pipe, and the other end of the internal diversion pipe is connected to the refrigerant inlet pipe.

[0015] By adopting the above technical solution, when the pressure inside the LNG cylinder is too low, the refrigerant is controlled to enter the second return pipe. The refrigerant is heated by the heating device. After vaporization, the refrigerant is condensed and liquefied before flowing back to the storage tank, thereby pressurizing the LNG cylinder and avoiding insufficient NG gas supply due to excessively low internal pressure of the LNG cylinder, which would affect the engine's power performance.

[0016] Once the pressure in the LNG cylinder is within a safe range, the heat exchanger can continue to provide cooling. The cryogenic combination pressure regulating valve controls the flow of the refrigerant into the first return pipe, and then through the confluence pipe into the LNG cylinder for heat exchange. After releasing heat, the refrigerant flows back to the storage tank, thus achieving refrigerant circulation. Furthermore, since the refrigerant stores a large amount of cold energy, the coolant can absorb cold energy from the liquid-phase refrigerant through the coolant heat exchanger. Therefore, when the LNG cylinder stops supplying LNG to the LNG inlet pipe, i.e., when there is no need for the NG gas supply pipe to provide NG gas, the refrigeration unit can still perform cooling operations, providing a micro-powered circulating cooling function. When this heat exchanger is applied to LNG vehicles, it can achieve the function of "parking cooling".

[0017] Optionally, a condenser heat exchanger is provided on the inner branch pipe.

[0018] By adopting the above technical solution, during the thermal pressurization process, the refrigerant circulation pump pumps the refrigerant to the second return pipe. Through the heating effect of the heating device, the refrigerant vaporizes, and the heat energy it carries quickly heats and pressurizes the LNG liquid, ensuring the engine's gas supply pressure. Then, it enters the condenser heat exchanger, where the refrigerant condenses and liquefies, and the LNG cylinder can be rapidly heated, thereby achieving rapid pressurization of the LNG cylinder and improving the response efficiency of the LNG cylinder thermal pressurization.

[0019] Optionally, both the LNG heat exchanger and the refrigerant heat exchanger are finless microchannel heat exchangers.

[0020] By adopting the above technical solution, on the one hand, the finless microchannel heat exchanger has a microchannel structure, a large heat transfer area, and can reduce the flow resistance of the fluid. At the same time, the eddies and turbulence inside the microchannel can increase the turbulence of the fluid inside, further enhancing the heat transfer effect and improving the heat transfer efficiency. On the other hand, its compact structure and short flow path of the heat transfer medium result in fast heat transfer speed and rapid thermal response. In addition, its small size and finless structure can further reduce the space occupied in the storage tank, reduce the flow resistance to the gas-liquid two-phase flow of the refrigerant, and ensure high heat transfer efficiency.

[0021] Optionally, the external heat exchanger is located outside the storage tank.

[0022] By adopting the above technical solution, since the storage tank is a sealed structure, the external heat exchanger is independently set outside the storage tank. On the one hand, this reduces the space occupied inside the storage tank, thereby reducing the flow obstruction to the refrigerant; on the other hand, it facilitates the inspection and maintenance of the external heat exchanger, which helps to extend the service life of the heat exchanger.

[0023] Optionally, the storage tank is equipped with a distributor, and the LNG inlet pipe, NG outlet pipe, refrigerant inlet pipe and refrigerant outlet pipe are respectively connected to the distribution port of the distributor.

[0024] By adopting the above technical solution, the distributor can control the on / off state of the LNG inlet pipe, NG outlet pipe, refrigerant inlet pipe and refrigerant outlet pipe and adjust the fluid flow rate, which facilitates the arrangement of pipe bundles and reduces the number of valves used.

[0025] Optionally, the storage tank includes a tank body, a front end cap, and a rear end cap, wherein the front end cap and the rear end cap are respectively welded to both ends of the tank body, the tank body is cylindrical, and the front end cap and the rear end cap are both dome-shaped with outward protrusions.

[0026] By adopting the above technical solution, the refrigerant absorbs heat from the coolant, causing its temperature to rise and generating a large number of bubbles on the outer wall of the coolant heat exchanger. As these bubbles rise from the outer wall of the coolant heat exchanger, they create intense turbulence within the liquid-phase refrigerant and exchange heat with the cooler refrigerant. The bubbles gradually shrink, and those that have not fully exchanged heat enter the upper part of the storage tank, becoming gaseous refrigerant. The pressure inside the storage tank gradually increases as the gaseous refrigerant accumulates. Therefore, the tank body is cylindrical, with the front and rear end caps being outwardly convex domes. This design evenly distributes the pressure inside the storage tank and ensures a larger pressure contact area under the same volume conditions, thereby improving the storage tank's pressure resistance and deformation resistance.

[0027] Optionally, the tank body is provided with a support plate, the two ends of which are fixed to the inner wall of the tank body, and the LNG heat exchanger, NG outlet pipe, refrigerant heat exchanger and refrigerant inlet pipe are fixed to the support plate.

[0028] By adopting the above technical solution, the support plate serves two purposes: firstly, it arranges and fixes the LNG heat exchanger, NG outlet pipe, refrigerant heat exchanger, and refrigerant inside the storage tank; secondly, it supports the tank body, improving the structural strength of the storage tank. Furthermore, the expansion and contraction caused by temperature changes inside the storage tank are addressed by the support plate, which further enhances the tank's resistance to deformation under temperature loads.

[0029] In summary, this application includes at least one of the following beneficial technical effects:

[0030] 1. By setting up storage tanks, LNG heat exchangers, refrigerant heat exchangers, and external heat exchangers, the cold energy of LNG is recovered in stages, reducing cold energy loss and improving the efficiency of cold energy recovery and utilization. During the heat exchange process between the refrigerant and the refrigerant, the refrigerant absorbs heat and vaporizes, generating a large number of bubbles, which form convection disturbances inside, increasing the turbulence of the refrigerant and thus improving the heat exchange efficiency of the heat exchanger.

[0031] 2. By setting up a refrigerant circulation pump, after the refrigerant in the storage tank absorbs a large amount of cold energy, it is pumped to the refrigerant outlet pipe. The refrigerant enters the first return pipe through the cryogenic combination pressure regulating valve, and then enters the inner diversion pipe of the bottom jacket of the LNG cylinder through the confluence pipe for heat exchange. After releasing some heat, it flows back to the storage tank through the refrigerant inlet pipe, thus realizing the circulation of the refrigerant.

[0032] 3. By using a cryogenic combined pressure regulating valve, when the pressure inside the LNG cylinder is too low, the valve controls the refrigerant to enter the second return pipe. The refrigerant is then heated by a heating device. The vaporized refrigerant first enters the inner distribution pipe in the bottom jacket of the LNG cylinder to exchange heat with the LNG and condense, achieving LNG saturation and pressurization. This prevents insufficient NG gas supply due to excessively low internal pressure in the LNG cylinder, which would affect the power performance of the NG gas supply pipe output. Once the cylinder pressure reaches the rated value, the cryogenic combined pressure regulating valve disconnects the refrigerant outlet pipe from the second return pipe, stopping the thermal pressurization. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of an LNG cold energy recovery heat exchanger with thermal pressurization according to an embodiment of this application.

[0034] Figure 2 This is a schematic diagram illustrating the internal structure of the storage tank in the embodiments of this application.

[0035] Figure 3This is a schematic diagram illustrating the switching between cooling and heating / pressurization in the embodiments of this application.

[0036] Explanation of reference numerals in the attached drawings: 1. Storage tank; 11. Tank body; 111. First pressure gauge; 112. Pressure relief valve; 113. Support plate; 12. Front end cap; 13. Rear end cap; 14. Refrigerant inlet pipe; 15. Refrigerant circulation pump; 151. Refrigerant outlet pipe; 152. Low-temperature combined pressure regulating valve; 16. First reflux pipe; 17. Second reflux pipe; 171. Heating device; 18. Combination pipe; 181. Thermometer; 19. 1. External distribution pipe; 2. LNG heat exchanger; 21. LNG inlet pipe; 22. NG outlet pipe; 3. Refrigerant heat exchanger; 31. Refrigerant inlet pipe; 32. Refrigerant outlet pipe; 4. LNG cylinder; 41. Second pressure gauge; 42. Internal distribution pipe; 421. Condensing heat exchanger; 5. External heat exchanger; 51. NG coil; 511. NG gas supply pipe; 52. Refrigerant external inlet pipe; 6. Refrigeration unit; 7. Distributor. Detailed Implementation

[0037] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail below.

[0038] Example:

[0039] This application discloses an LNG cold energy recovery heat exchanger with thermal pressurization. (Refer to...) Figure 1 and Figure 2 An LNG cold energy recovery heat exchanger with thermal pressurization includes a storage tank 1, an LNG heat exchanger 2 installed inside the storage tank 1, and a refrigerant heat exchanger 3. The storage tank 1 stores a refrigerant with gas-liquid conversion characteristics and a freezing point lower than that of LNG. After absorbing heat, the refrigerant vaporizes into refrigerant vapor gas. The refrigerant exists in a gas-liquid coexistence state inside the storage tank 1, and its function is to efficiently transfer the cold energy of LNG to the refrigerant. The LNG heat exchanger 2 is located in the gas phase space within the storage tank 1, and the refrigerant heat exchanger 3 is located in the liquid phase space within the storage tank 1.

[0040] By introducing a cold storage agent as an intermediate heat transfer medium, the gaseous and liquid phases of the cold storage agent in storage tank 1 can be interconverted. Its freezing temperature is lower than that of LNG, meaning it will not freeze under any circumstances due to absorbing the cold energy of LNG. The cold storage agent has a high liquefaction temperature and a low liquefaction pressure, meaning that the pressure inside the cavity will not be too high at high temperatures. The cold storage agent has a high thermal conductivity in both gaseous and liquid states and a large latent heat of vaporization. In the inner cavity of storage tank 1, the gaseous cold storage agent is located above the liquid cold storage agent, and the temperature of the gaseous cold storage agent is higher than that of the liquid cold storage agent. The gaseous cold storage agent can liquefy into a liquid cold storage agent by absorbing the cold energy of LNG, and the liquid cold storage agent can vaporize into a gaseous cold storage agent by absorbing heat.

[0041] Reference Figure 1-3 The LNG heat exchanger 2 has an LNG inlet pipe 21 connected to its input end and an NG outlet pipe 22 connected to its output end. The LNG inlet pipe 21 has an LNG cylinder 4 for supplying LNG connected to its input end. An external heat exchanger 5 is installed at the output end of the NG outlet pipe 22. An NG coil 51 is installed inside the external heat exchanger 5. One end of the NG coil 51 is connected to the NG outlet pipe 22, and the other end is connected to the NG gas supply pipe 511.

[0042] The input end of the refrigerant heat exchanger 3 is connected to the refrigerant inlet pipe 31, and the output end is connected to the refrigerant outlet pipe 32. The output end of the refrigerant outlet pipe 32 is connected to the refrigeration device 6. The input end of the refrigerant inlet pipe 31 is connected to the interior of the external heat exchanger 5. The external heat exchanger 5 is provided with a refrigerant external inlet pipe 52 for replenishing refrigerant into its interior.

[0043] When using this heat exchanger, LNG enters the LNG heat exchanger 2 through the LNG inlet pipe 21. It exchanges heat with the refrigerant in the storage tank 1 through the LNG heat exchanger 2. The LNG absorbs heat and its temperature rises, continuously vaporizing into NG. At the same time, the refrigerant undergoes the first stage of cold energy recovery and storage. After the first stage of cold energy recovery, the NG enters the external heat exchanger 5 through the NG outlet pipe 22. The NG exchanges heat with the refrigerant flowing into the inner cavity of the external heat exchanger 5 through the NG coil 51. The refrigerant performs the second stage of cold energy recovery on the NG in the NG coil 51. The temperature difference between the NG after the first stage of cold energy recovery and the refrigerant is not too large, ensuring that the refrigerant after heat exchange in the external heat exchanger 5 is not frozen. After recovering this portion of the cold energy directly, the refrigerant enters the refrigerant heat exchanger 3 through the refrigerant inlet pipe 31. There, it exchanges heat with the refrigerant that has undergone the first stage of cold energy recovery, achieving secondary cascade cooling. The cooled refrigerant then enters the corresponding refrigeration unit 6 through the refrigerant outlet pipe 32, realizing the function of LNG cold energy reuse. By recovering LNG cold energy in stages, cold energy loss is reduced, and the efficiency of cold energy recovery and utilization is improved. During the heat exchange process with the refrigerant, the refrigerant absorbs heat and vaporizes, generating a large number of bubbles. These bubbles create convective disturbances within the refrigerant, increasing its turbulence and thus improving the heat exchange efficiency of the heat exchanger.

[0044] Reference Figure 1 and Figure 2 A distributor 7 is fixed on the storage tank 1. The LNG inlet pipe 21, NG outlet pipe 22, refrigerant inlet pipe 31, and refrigerant outlet pipe 32 are respectively connected to the distribution port of the distributor 7. In this way, the distributor 7 can control the on / off state of the LNG inlet pipe 21, NG outlet pipe 22, refrigerant inlet pipe 31, and refrigerant outlet pipe 32 and adjust the fluid flow rate, which facilitates the arrangement of the pipe bundle.

[0045] Reference Figure 1 and Figure 2The storage tank 1 includes a tank body 11, a front end cap 12, and a rear end cap 13. The front end cap 12 and the rear end cap 13 are welded to both ends of the tank body 11, respectively. The tank body 11 is cylindrical, and both the front end cap 12 and the rear end cap 13 are dome-shaped structures that bulge outwards. A first pressure gauge 111 and a pressure relief valve 112 are installed at the upper end of the tank body 11. The detection end of the first pressure gauge 111 is located in the upper part of the inner cavity of the tank body 11 and is used to detect the internal pressure of the storage tank 1. After absorbing heat from the coolant, the temperature of the refrigerant rises, and a large number of bubbles are generated on the outer wall of the coolant heat exchanger 3. As the bubbles detach from the outer wall of the coolant heat exchanger 3 and float upwards, they generate a violent turbulence in the liquid phase refrigerant and exchange heat with the coolant at a lower temperature. The bubbles gradually shrink, and the bubbles that have not completely exchanged heat enter the upper part of the storage tank 1 and become gaseous refrigerant. At this time, the LNG heat exchanger 2 is located in the gas phase space inside the storage tank 1, exchanging heat with the gas phase refrigerant. While vaporizing the LNG, it reduces the pressure inside the storage tank 1, expands the temperature difference between the gas and liquid phases of the refrigerant, accelerates the gas-liquid phase heat exchange efficiency, and also benefits the heat exchange of the refrigerant. In case of an accident, the pressure inside the storage tank 1 will gradually increase as the gas phase refrigerant accumulates. When the pressure value inside the storage tank 1 exceeds the safety value preset by the first pressure gauge 111, the pressure relief valve 112 will open, realizing the function of automatically relieving pressure when the internal pressure of the storage tank 1 exceeds the standard, ensuring the safety of the heat exchanger.

[0046] By setting the tank body 11 as a cylinder and the front end cap 12 and the rear end cap 13 as outwardly protruding dome shapes, the pressure inside the storage tank 1 can be evenly distributed, and a larger pressure contact area can be ensured under the same volume conditions, thereby improving the pressure resistance and deformation resistance of the storage tank 1.

[0047] Reference Figure 1 and Figure 2 The external heat exchanger 5 is a tubular heat exchanger located outside the storage tank 1. A support plate 113 is welded inside the tank body 11, with both ends of the support plate 113 fixed to the inner wall of the tank body 11. In this embodiment, two support plates 113 are provided, and the LNG heat exchanger 2, NG outlet pipe 22, refrigerant heat exchanger 3, and refrigerant inlet pipe 31 are fixed to the support plate 113. The support plate 113 serves two purposes: firstly, it arranges and fixes the LNG heat exchanger 2, NG outlet pipe 22, refrigerant heat exchanger 3, and refrigerant inside the storage tank 1; secondly, it provides support to the tank body 11, enhancing the structural strength of the storage tank 1. Furthermore, the expansion and contraction caused by temperature changes inside the storage tank 1, through the temperature load on the support plate 113, further improves its resistance to deformation.

[0048] Since the storage tank 1 is a sealed structure, the external heat exchanger 5 is independently set outside the storage tank 1. On the one hand, this reduces the space occupied inside the storage tank 1, thereby reducing the flow obstruction to the refrigerant; on the other hand, it facilitates the inspection and maintenance of the external heat exchanger 5, which helps to extend the service life of the heat exchanger.

[0049] Reference Figure 2 Both the LNG heat exchanger 2 and the refrigerant heat exchanger 3 are finless microchannel heat exchangers. This design is based on the following reasons: Firstly, the finless microchannel heat exchanger has a microchannel structure, resulting in a larger heat transfer area and reduced fluid flow resistance. Simultaneously, the eddies and turbulence within the microchannels enhance the internal fluid turbulence, further improving heat transfer efficiency. Secondly, its compact structure and short flow path for the heat transfer medium allow for rapid heat transfer and a quick thermal response. Furthermore, its small size and finless structure further reduce its footprint within the storage tank 1, minimizing flow obstruction to the gas-liquid two-phase flow of the refrigerant and ensuring high heat exchange efficiency.

[0050] Reference Figure 2 and Figure 3 The storage tank 1 is equipped with a refrigerant inlet pipe 14 and a refrigerant circulation pump 15. The refrigerant inlet pipe 14 is connected to the inner cavity of the storage tank 1, and the input end of the refrigerant circulation pump 15 is connected to the inner cavity of the storage tank 1, while the output end is connected to the refrigerant outlet pipe 151. The refrigerant circulation pump 15 serves two purposes: firstly, it provides circulating refrigerant to the storage tank 1, ensuring that the heat exchanger can continuously and stably recover LNG cold energy; secondly, it increases the turbulence of the refrigerant within the storage tank 1, ensuring high heat exchange efficiency.

[0051] Reference Figure 3 The end of the refrigerant outlet pipe 151 away from the refrigerant circulation pump 15 is connected to a first return pipe 16 and a second return pipe 17 via a low-temperature combined pressure regulating valve 152. A heating device 171 is installed on the second return pipe 17. The ends of the first return pipe 16 and the second return pipe 17 away from the low-temperature combined pressure regulating valve 152 are connected to a confluence pipe 18 via a three-way pipe. The confluence pipe is connected to the refrigerant inlet pipe 14. A thermometer 181 is installed on the confluence pipe 18. The detection end of the thermometer 181 extends into the cavity of the confluence pipe 18 to detect the real-time temperature of the refrigerant flowing through the confluence pipe 18.

[0052] Reference Figure 3A second pressure gauge 41 is installed on the LNG cylinder 4. The detection end of the second pressure gauge 41 is located in the upper part of the inner cavity of the LNG cylinder 4. An inner diversion pipe 42 is also fixed in the bottom interlayer of the LNG cylinder 4. Both ends of the inner diversion pipe 42 extend out of the bottom interlayer of the LNG cylinder 4. The end of the confluence pipe 18 away from the first return pipe 16 is connected to one end of the inner diversion pipe 42, and the other end of the inner diversion pipe 42 is connected to the refrigerant inlet pipe 14.

[0053] As LNG is supplied to the external power unit, the LNG inside LNG cylinder 4 is continuously consumed, causing a drop in the internal pressure of LNG cylinder 4. When the second pressure gauge 41 detects that the pressure inside LNG cylinder 4 is too low, the cryogenic combination pressure regulating valve 152 controls the refrigerant to enter the second return pipe 17. The refrigerant is heated by the heating device 171, and the vaporized refrigerant enters the inner distribution pipe 42 to exchange heat with LNG and condense, thereby pressurizing LNG cylinder 4. After liquefaction, it flows back to storage tank 1 through the refrigerant inlet pipe 14. By heating and pressurizing LNG cylinder 4, insufficient LNG supply caused by excessively low internal pressure is avoided, which would affect the engine's power performance.

[0054] Once the pressure of LNG cylinder 4 is within a safe range, the heat exchanger can continue to be used for refrigeration. After the refrigerant in storage tank 1 absorbs a large amount of cold energy, it is pumped to the refrigerant outlet pipe 151 by the refrigerant circulation pump 15. The refrigerant is then controlled by the low-temperature combined pressure regulating valve 152 to enter the first return pipe 16 and enters the inner diversion pipe 42 of the bottom jacket of LNG cylinder 4 through the confluence pipe 18 for heat exchange. After releasing some heat, it flows back to storage tank 1 through the refrigerant inlet pipe 14, realizing the circulation of the refrigerant. Since the refrigerant stores a large amount of cold energy, the coolant can absorb cold energy from the liquid phase refrigerant through the coolant heat exchanger 3. Therefore, when LNG cylinder 4 stops outputting LNG to LNG inlet pipe 21, that is, when there is no need for NG gas supply pipe 511 to provide NG gas source, the refrigeration device 6 can still perform refrigeration operation, which has the function of micro-powered circulation refrigeration. When this heat exchanger is applied to LNG vehicles, it can realize the function of "parking refrigeration".

[0055] Reference Figure 3 A condenser heat exchanger 421 is installed on the inner distribution pipe 42. Thus, during the thermal pressurization process, the refrigerant circulation pump 15 pumps the refrigerant to the second return pipe 17. Heated by the heating device 171, the refrigerant vaporizes, and the heat it carries rapidly heats and pressurizes the LNG liquid in the LNG cylinder 4, ensuring the engine's gas supply pressure. It then enters the condenser heat exchanger 421 for condensation and liquefaction, and finally flows back to the storage tank 1. Through the condensation and heat transfer of the refrigerant, the LNG cylinder 4 can be rapidly heated, thereby achieving rapid pressurization of the LNG cylinder 4 and improving the response efficiency of the thermal pressurization of the LNG cylinder 4.

[0056] The implementation principle of an LNG cold energy recovery heat exchanger with thermal pressurization in this application embodiment is as follows: When using the heat exchanger, the on / off state of the LNG inlet pipe 21 is controlled by the distributor 7. When LNG enters the LNG heat exchanger 2 through the LNG inlet pipe 21, it exchanges heat with the refrigerant in the storage tank 1 through the LNG heat exchanger 2. The LNG absorbs heat and its temperature rises, continuously vaporizing into NG. At the same time, the refrigerant performs the first stage of cold energy recovery and storage. After the first stage of cold energy recovery, the NG enters the external heat exchanger 5 through the NG outlet pipe 22. The NG exchanges heat with the refrigerant flowing into the inner cavity of the external heat exchanger 5 through the NG coil 51. The refrigerant performs the second stage of cold energy recovery on the NG in the NG coil 51. The temperature difference between the NG after the first stage of cold energy recovery and the refrigerant is not too large, ensuring that the refrigerant after heat exchange in the external heat exchanger 5 is not frozen. After the refrigerant directly recovers this portion of the cold energy, it enters the refrigerant heat exchanger 3 through the refrigerant inlet pipe 31. Then, it exchanges heat with the refrigerant that has undergone the first stage of cold energy recovery through the refrigerant heat exchanger 3, realizing secondary cascade cooling. The cooled refrigerant enters the corresponding refrigeration device 6 through the refrigerant outlet pipe 32, realizing the function of LNG cold energy reuse.

[0057] By performing cascade recovery of LNG cold energy, the loss of cold energy is reduced and the efficiency of cold energy recovery and utilization is improved. During the heat exchange process between the cold storage agent and the heat transfer agent, the cold storage agent absorbs heat and vaporizes, generating a large number of bubbles. Convection disturbances are formed inside the cold storage agent, which increases the turbulence of the cold storage agent and thus improves the heat exchange efficiency of the heat exchanger.

[0058] As NG is supplied to the external power unit, the LNG inside LNG cylinder 4 is continuously consumed, causing a drop in the internal pressure of LNG cylinder 4. When the second pressure gauge 41 detects that the pressure inside LNG cylinder 4 is too low, the cryogenic combination pressure regulating valve 152 controls the refrigerant to enter the second return pipe 17. The refrigerant is heated by the heating device 171, and the vaporized refrigerant is condensed and liquefied, thereby pressurizing LNG cylinder 4. By heating and pressurizing LNG cylinder 4, insufficient NG supply caused by excessively low internal pressure is avoided, which would affect the power performance of the output end of NG supply pipe 511.

[0059] Once the pressure of LNG cylinder 4 is within a safe range, the heat exchanger can continue to provide cooling. After the refrigerant in storage tank 1 absorbs a large amount of cold energy, it is pumped to the refrigerant outlet pipe 151 by the refrigerant circulation pump 15. The refrigerant is then controlled by the cryogenic combination pressure regulating valve 152 to enter the first return pipe 16 and enters the inner diversion pipe 42 of the bottom jacket of LNG cylinder 4 through the confluence pipe 18 for heat exchange. After releasing some heat, it flows back to storage tank 1 through the refrigerant inlet pipe 14, thus realizing the circulation of the refrigerant. Since the refrigerant stores a large amount of cold energy, the coolant can absorb cold energy from the liquid phase refrigerant through the coolant heat exchanger 3. Therefore, when LNG cylinder 4 stops outputting LNG to LNG inlet pipe 21, that is, when there is no need for NG gas supply pipe 511 to provide NG gas source, the refrigeration device 6 can still perform refrigeration operation, which has the function of micro-powered circulating refrigeration. When this heat exchanger is applied to LNG vehicles, it can realize the function of "parking refrigeration".

[0060] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An LNG cold energy recovery heat exchanger with thermal pressurization, characterized in that, include: Storage tank (1) is used to store cold storage agent. The cold storage agent has gas-liquid conversion characteristics and its freezing point temperature is lower than that of LNG. The cold storage agent is in a state of gas-liquid coexistence inside the storage tank (1). An LNG heat exchanger (2) is located in the gas phase space inside the storage tank (1). The LNG heat exchanger (2) has an LNG inlet pipe (21) at its input end and an NG outlet pipe (22) at its output end. The LNG inlet pipe (21) is connected to an LNG cylinder (4). The NG outlet pipe (22) is connected to an external heat exchanger (5). The external heat exchanger (5) has an NG coil (51) inside. One end of the NG coil (51) is connected to the NG outlet pipe (22), and the other end is provided with an NG gas supply pipe (511) for connection to the engine. A refrigerant heat exchanger (3) is located in the liquid phase space inside the storage tank (1). The refrigerant heat exchanger (3) has a refrigerant inlet pipe (31) at its input end and a refrigerant outlet pipe (32) at its output end. The output end of the refrigerant outlet pipe (32) is connected to the refrigeration device (6). The input end of the refrigerant inlet pipe (31) is connected to the interior of the external heat exchanger (5). The external heat exchanger (5) is provided with an external refrigerant inlet pipe (52).

2. The LNG cold energy recovery heat exchanger with thermal pressurization according to claim 1, characterized in that: The storage tank (1) is provided with a cold storage inlet pipe (14), and the storage tank (1) is provided with a cold storage circulation pump (15) for pumping out the cold storage in the storage tank (1). The cold storage circulation pump (15) is provided with a cold storage outlet pipe (151) at its output end. The cold storage inlet pipe is connected to the inner cavity of the storage tank (1).

3. An LNG cold energy recovery heat exchanger with thermal pressurization according to claim 2, characterized in that: The end of the refrigerant outlet pipe (151) away from the refrigerant circulation pump (15) is connected to the first return pipe (16) and the second return pipe (17) through a low-temperature combined pressure regulating valve (152). The second return pipe (17) is equipped with a heating device (171). The ends of the first return pipe (16) and the second return pipe (17) away from the low-temperature combined pressure regulating valve (152) are connected to the confluence pipe (18) through a three-way pipe. The LNG cylinder (4) is provided with an inner diversion pipe (42) in the interlayer. The two ends of the inner diversion pipe (42) extend out of the interlayer of the LNG cylinder (4). The end of the confluence pipe (18) away from the first return pipe (16) is connected to one end of the inner diversion pipe (42), and the other end of the inner diversion pipe (42) is connected to the refrigerant inlet pipe (14).

4. An LNG cold energy recovery heat exchanger with thermal pressurization according to claim 3, characterized in that: A condenser heat exchanger (421) is provided on the inner branch pipe (42).

5. An LNG cold energy recovery heat exchanger with thermal pressurization according to claim 1, characterized in that: Both the LNG heat exchanger (2) and the refrigerant heat exchanger (3) are finless microchannel heat exchangers.

6. An LNG cold energy recovery heat exchanger with thermal pressurization according to claim 1, characterized in that: The external heat exchanger (5) is located outside the storage tank (1).

7. An LNG cold energy recovery heat exchanger with thermal pressurization according to claim 1, characterized in that: The storage tank (1) is equipped with a distributor (7), and the LNG inlet pipe (21), NG outlet pipe (22), refrigerant inlet pipe (31) and refrigerant outlet pipe (32) are respectively connected to the distribution port of the distributor (7).

8. An LNG cold energy recovery heat exchanger with thermal pressurization according to claim 1, characterized in that: The storage tank (1) includes a tank body (11), a front end cap (12) and a rear end cap (13). The front end cap (12) and the rear end cap (13) are respectively welded to the two ends of the tank body (11). The tank body (11) is cylindrical, and the front end cap (12) and the rear end cap (13) are both dome-shaped with outward protrusion.

9. An LNG cold energy recovery heat exchanger with thermal pressurization according to claim 8, characterized in that: The tank (11) is provided with a support plate (113), and the two ends of the support plate (113) are fixed to the inner wall of the tank (11). The LNG heat exchanger (2), NG outlet pipe (22), refrigerant heat exchanger (3) and refrigerant inlet pipe (31) are fixed on the support plate (113).

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