A multi-stage heat dissipation battery pack thermal management system for solid-liquid hybrid phase change

Abstract

A multi-stage heat dissipation battery pack thermal management system for solid-liquid mixed phase change, belonging to the field of power battery thermal management systems, includes a battery pack. A plurality of battery cells are provided in the battery pack and filled with a fluorinated liquid. A plurality of heating units are provided on the bottom side of the inner cavity of the battery pack. A plurality of composite phase change blocks are also provided in the inner cavity of the battery pack between the plurality of heating units and the lower partition plate. The medium inlet on the bottom side and the medium outlet on the top side of the battery pack are respectively connected to the first channel of a plate heat exchanger. The second channel of the plate heat exchanger is connected to a heat dissipation circulation loop. Through the heat dissipation circulation loop, the heat dissipation medium can flow into the second channel to facilitate cooling of the fluorinated liquid in the first channel. A temperature sensor and a pressure sensor are provided in the battery pack. The medium outlet is also connected to a pressure relief pipeline through a pressure relief valve. The side wall of the battery pack is connected to a first liquid replenisher through a liquid replenishment port, improving the adverse effects of low-temperature starting problems and thermal overshoot problems of the vehicle on the battery life and safety.

Description

Technical Field

[0001] The present invention relates to the field of power battery thermal management systems, and particularly to a multi-stage heat dissipation battery pack thermal management system with solid-liquid hybrid phase change. Background Art

[0002] With the rapid development of electric vehicles, lithium batteries, as their core power sources, have their performance, lifespan, and safety highly dependent on the operating temperature. Whether the temperature is too high or too low, it will have a significant impact on the charge and discharge efficiency of the battery, and may even cause serious safety hazards such as thermal runaway. Therefore, developing an efficient thermal management system has become one of the key technologies in the field of electric vehicles.

[0003] Currently, the mainstream thermal management technologies mainly include air cooling, liquid cooling, phase change materials (PCM), and heat pipes, etc. Among them, although the air cooling system has a simple structure, its heat dissipation efficiency is limited and it is difficult to meet the heat dissipation requirements of high-power battery packs; the liquid cooling system achieves efficient heat dissipation through the circulation of coolant, but its structure is complex and the cost is high, and there is also a potential risk of liquid leakage; phase change materials utilize their heat absorption and heat release characteristics during the phase change process to regulate the temperature, which can effectively alleviate temperature fluctuations, but face great challenges in material selection and system design; heat pipe technology achieves rapid heat transfer through efficient heat conduction, especially suitable for high-power battery packs, but its design and manufacturing costs are high. In addition, thermoelectric cooling (TEC) technology has also been gradually introduced, using the thermoelectric effect to achieve rapid temperature control, but its energy consumption is high, which limits its wide application. And with the continuous increase in the capacity of battery cells, the heat generation of battery cells has increased exponentially, and traditional single heat dissipation methods can no longer meet the growing heat dissipation requirements. Summary of the Invention

[0004] The purpose of the present invention is to provide a multi-stage heat dissipation battery pack thermal management system with solid-liquid hybrid phase change, which can effectively control the temperature and temperature difference of the battery pack within a reasonable range, and improve the adverse effects of problems such as low-temperature startup and thermal overshoot of the vehicle on the battery life and safety.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a multi-stage heat dissipation battery pack thermal management system of solid-liquid hybrid phase change, including a battery pack, a plurality of battery cells are arranged in the battery pack and filled with fluoride liquid, an upper partition and a lower partition are installed inside the battery pack, a plurality of battery cells are distributed parallel to each other between the upper partition and the lower partition, the upper and lower ends of the battery cells are respectively clamped on the upper partition and the lower partition, the upper partition and the lower partition are both provided with a plurality of medium holes for the circulation of fluoride liquid, a plurality of heating units are arranged on the bottom side of the inner cavity of the battery pack, which are used to heat the fluoride liquid to the normal working temperature range of the battery cells, and a plurality of composite phase change blocks are also arranged in the inner cavity of the battery pack between the plurality of heating units and the lower partition, and the composite phase change blocks are of size A spherical body or block that is larger than the medium hole, the outside of the composite phase change block is wrapped and sealed by an aluminum-diamond composite high thermal conductivity material, the inside is filled with an inorganic hydrated salt phase change material, and the melting point of the phase change material is higher than the normal operating temperature range of the battery cell. The medium inlet on the bottom side of the battery pack and the medium outlet on the top side are respectively connected to the first channel of the plate heat exchanger, and the second channel of the plate heat exchanger is connected to the heat dissipation circulation loop. The heat dissipation medium can flow into the second channel through the heat dissipation circulation loop to cool the fluorinated liquid in the first channel. A temperature sensor and a pressure sensor are provided in the battery pack, and the medium outlet is also connected to the pressure relief pipeline through a pressure relief valve, and the side wall of the battery pack is connected to the first refiller through the refill port.

[0006] Preferably, a plurality of micro-fin structures are provided on the outer cylindrical surface of the battery core, the micro-fin structures are sheet-like protrusions extending along the length direction of the battery core, and the plurality of micro-fin structures are spaced apart along the circumference of the battery core. The height of the micro-fin structure extending outward from the outer cylindrical surface of the battery core is 100-200 μm, the thickness of the micro-fin structure is 30-60 μm, and the spacing between two adjacent micro-fin structures is 50-80 μm. The interior of the micro-fin structure is a metal substrate formed by surface laser micro-melting treatment, and the surface of the micro-fin structure is a vaporized and deposited graphene surface layer with a thickness of 3-5 μm.

[0007] Preferably, the upper partition and the lower partition are both provided with a plurality of stepped through holes, the upper and lower ends of the battery cell are respectively clamped at the large ends of the stepped through holes, and the upper and lower ends of the battery cell can respectively contact the fluorinated liquid through the small ends of the stepped through holes.

[0008] Preferably, the battery pack includes a shell of a rectangular structure, an upper cover is provided on the top side of the shell, the medium inlet is located on the bottom surface of the shell, the liquid replenishing port is located on one side of the shell, and the medium outlet is located on the upper cover.

[0009] Preferably, the heating unit is a PTC heater or a resistance wire, and a plurality of heating units are arranged in an array on the bottom side of the inner cavity of the battery pack.

[0010] Preferably, the heat dissipation medium is tetrafluoroethane. A compressor, a condenser, and a throttle valve are sequentially arranged on the heat dissipation circulation loop. The compressor can transport the compressed high-temperature and high-pressure gaseous tetrafluoroethane to the condenser. A cooling fan is arranged on one side of the condenser to facilitate the condensation of the gaseous tetrafluoroethane into medium-temperature and high-pressure liquid tetrafluoroethane. The throttle valve can reduce the pressure of the liquid tetrafluoroethane to facilitate the formation of a low-temperature and low-pressure tetrafluoroethane liquid-gas mixture through the evaporation of part of the liquid tetrafluoroethane. The low-temperature and low-pressure tetrafluoroethane liquid-gas mixture can flow into the second channel of the plate heat exchanger and absorb the heat of the gaseous fluorinated liquid. After complete evaporation, the low-temperature and low-pressure gaseous tetrafluoroethane can flow back to the compressor.

[0011] Preferably, a second liquid replenisher is also connected to one side of the heat dissipation circulation loop.

[0012] According to the above technical solution, the beneficial effects of the present invention are as follows:

[0013] In the present invention, heat exchange is carried out by contacting the fluorinated liquid with the battery cell. When the temperature of the battery cell is low, such as when the vehicle starts, the battery cell can be quickly heated by heating the fluorinated liquid through the heating unit. When the heat dissipation of the system fails and the temperature of the battery cell is too high, the solid composite phase change material and liquid phase change material with different phase change points in the composite phase change block can jointly absorb the heat of the fluorinated liquid to carry out emergency refrigeration of the battery cell, and then the gaseous fluorinated liquid sent out by the battery pack is continuously cooled through plate heat exchange and the heat dissipation circulation loop. Finally, the temperature and temperature difference of the battery pack can be effectively controlled within a reasonable range. The temperature and pressure inside the battery pack can be monitored through sensors. When the temperature of the battery cell rises sharply due to a fault, the pressure relief valve can be opened in time as the pressure rises due to the large-scale gasification of the fluorinated liquid, and the battery pack can be supplemented with relatively low-temperature fluorinated liquid through the first liquid replenisher. This not only improves the adverse effects of low-temperature starting problems and thermal overshoot problems of the vehicle on the battery life and safety, but also effectively avoids the rapid thermal runaway and damage of the battery pack, winning a relatively sufficient escape time for the driver and passengers and ensuring the safety of the driver and passengers. In addition, a micro-rib structure is provided on the surface of the battery cell. Through the graphene deposited on the surface of the micro-rib structure, the temperature uniformity of the battery cell can be improved, and the micro-rib structure increases the contact area between the battery cell and the fluorinated liquid, greatly increasing the heat exchange area and improving the heat exchange efficiency. Description of the Drawings

[0014] Figure 1 is a schematic diagram of the system of the present invention;

[0015] Figure 2 is an internal structure diagram of the battery pack;

[0016] Figure 3 is a partial three-dimensional view of the upper separator - battery cell - lower separator;

[0017] Figure 4It is a partial cross-sectional view of the upper separator-battery core-lower separator;

[0018] Figure 5 is a schematic diagram of a battery cell;

[0019] Figure 6 Schematic diagram of the micro-fin structure on the surface of the battery cell.

[0020] Markings in the figure: 1. battery pack, 2. first refiller, 3. pressure relief valve, 4. plate heat exchanger, 5. compressor, 6. condenser, 7. cooling fan, 8. second refiller, 9. throttle valve, 10. upper partition, 11. battery cell, 12. lower partition, 13. shell, 14. composite phase change block, 15. heating unit, 16. fluorinated liquid, 17. upper cover. DETAILED DESCRIPTION

[0021] With reference to the accompanying drawings, the specific implementation is as follows:

[0022] like Figure 1 As shown, a multi-stage heat dissipation battery pack thermal management system with solid-liquid mixed phase change includes a battery pack 1, such as Figure 2 As shown, the battery pack 1 includes a housing 13 of a rectangular structure, a top cover 17 is provided on the top side of the housing 13, a plurality of battery cells 11 are provided in the battery pack 1 and are filled with a fluorine liquid 16, an upper partition 10 and a lower partition 12 are installed inside the battery pack 1, and the plurality of battery cells 11 are distributed parallel to each other between the upper partition 10 and the lower partition 12, as shown in FIG. Figure 3 , 4 As shown, the upper partition 10 and the lower partition 12 are both provided with a plurality of medium holes for the circulation of the fluorinated liquid 16. The upper partition 10 and the lower partition 12 are also both provided with a plurality of stepped through holes. The upper and lower ends of the battery cell 11 are respectively clamped at the large ends of the stepped through holes, and the upper and lower ends of the battery cell 11 can respectively contact with the fluorinated liquid 16 through the small ends of the stepped through holes.

[0023] like Figure 2 As shown, a plurality of heating units 15 are provided on the bottom side of the inner cavity of the battery pack 1. The heating units 15 are PTC heaters or resistance wires. The plurality of heating units 15 are arranged in an array on the bottom side of the inner cavity of the battery pack 1 to heat the fluoride liquid 16 to the normal working temperature range of the battery cell 11. A plurality of composite phase change blocks 14 are also provided in the inner cavity of the battery pack 1 between the plurality of heating units 15 and the lower partition 12. The composite phase change blocks 14 are spherical or blocky bodies with a size larger than the medium pores. The outer side of the composite phase change block 14 is wrapped and sealed by an aluminum-diamond composite high thermal conductivity material with a thermal conductivity of 500-800W / (m·K). The inner side is filled with an inorganic hydrated salt phase change material with a melting point of 58°C, which is higher than the normal working temperature range of the battery cell 11. The latent heat of phase change is 230kJ / kg. After the phase change occurs, a large amount of heat can be taken, and the volume change is small.

[0024] The bottom surface of the housing 13 is provided with a medium inlet, the upper cover 17 is provided with a medium outlet, and a liquid replenishing port is also provided on one side of the housing 13, as Figure 1 shown. The medium inlet and the medium outlet are respectively connected to the first channel of the plate heat exchanger 4. The second channel of the plate heat exchanger 4 is connected to the heat dissipation circulation loop. Through the heat dissipation circulation loop, the heat dissipation medium can flow into the second channel to facilitate the cooling of the fluorinated liquid 16 in the first channel. The battery pack 1 is provided with a temperature sensor and a pressure sensor. The medium outlet is also connected to a pressure relief pipeline through a pressure relief valve 3, and the liquid replenishing port is connected to the first liquid replenisher 2.

[0025] As Figure 5 , 6 shown, a plurality of micro-rib structures are provided on the outer cylindrical surface of the battery cell 11. The micro-rib structures are sheet-like protrusions extending along the length direction of the battery cell 11. The plurality of micro-rib structures are circumferentially spaced along the battery cell 11. The height h of the micro-rib structure extending outward from the outer cylindrical surface of the battery cell 11 is 100-200 μm, the thickness s of the micro-rib structure is 30-60 μm, the spacing t between adjacent two micro-rib structures is 50-80 μm. The inside of the micro-rib structure is a metal substrate formed by surface laser micro-melting treatment, and the surface of the micro-rib structure is a graphene surface layer with a thickness of 3-5 μm formed by vapor deposition. The graphene has extremely high thermal conductivity, which can improve the temperature uniformity of the battery cell, and the micro-rib structure increases the contact area between the battery cell and the fluorinated liquid, greatly increasing the heat exchange area and improving the heat exchange efficiency.

[0026] As Figure 1 shown, the heat dissipation medium is tetrafluoroethane. A compressor 5, a condenser 6 and a throttle valve 9 are sequentially provided on the heat dissipation circulation loop. The compressor 5 can transport the compressed high-temperature and high-pressure gaseous tetrafluoroethane to the condenser 6. A cooling fan 7 is provided on one side of the condenser 6 to facilitate the condensation of the gaseous tetrafluoroethane into medium-temperature and high-pressure liquid tetrafluoroethane. The throttle valve 9 can reduce the pressure of the liquid tetrafluoroethane to facilitate the formation of a low-temperature and low-pressure tetrafluoroethane liquid-gas mixture through the evaporation of part of the liquid tetrafluoroethane. The low-temperature and low-pressure tetrafluoroethane liquid-gas mixture can flow into the second channel of the plate heat exchanger 4 and absorb the heat of the gaseous fluorinated liquid 16. After complete evaporation, the low-temperature and low-pressure gaseous tetrafluoroethane can flow back to the compressor 5. A second liquid replenisher 8 is also connected to one side of the heat dissipation circulation loop, which can replenish liquid tetrafluoroethane into the heat dissipation circulation loop.

[0027] The normal working mode is as follows: In the startup phase, when the external temperature is too low, the heater in the battery pack heats the fluorinated liquid and the battery cells to an appropriate temperature to ensure the normal operation of the battery cells. During operation, when the temperature of the battery cells rises and reaches the vaporization point of the fluorinated liquid, the fluorinated liquid starts to vaporize and takes away the heat of the battery cells. Due to the large latent heat of phase change of the fluorinated liquid, the surface temperature of the battery cells can be maintained near 47°C during the vaporization process. The vaporized gaseous fluorinated liquid enters the plate heat exchanger and exchanges heat with the low-temperature tetrafluoroethane from the heat dissipation circulation loop. After releasing heat, the gaseous fluorinated liquid cools down and condenses into a liquid fluorinated liquid, which then flows back to the bottom of the battery pack and undergoes the vaporization and heat absorption cycle again. The normal operation of this cycle can control the temperature of the battery cells within a small temperature range, and the working efficiency of the battery cells is high.

[0028] The first failure mode is: When a failure occurs in the heat dissipation circulation loop, the gaseous fluorinated liquid cannot be effectively cooled in the plate heat exchanger, resulting in the inability of the gaseous fluorinated liquid to condense into a liquid or the temperature after condensation being too high. At this time, the fluorinated liquid with too high a temperature enters the bottom of the battery pack, and the composite phase change block starts to undergo a phase change and absorbs a large amount of heat from the high-temperature fluorinated liquid. The melting point of the composite phase change block at the bottom of the battery pack is slightly higher than the phase change temperature of the fluorinated liquid, which is 58°C. Therefore, it can reduce the overall temperature of the fluorinated liquid, avoid the rapid increase in the overall temperature of the fluorinated liquid in the battery pack, and prevent the battery pack from heating up quickly.

[0029] The second failure mode is: When a failure occurs in the battery cells, the heat generation of the battery cells increases and the temperature rises rapidly and abnormally. A large amount of the liquid fluorinated liquid vaporizes, and the temperature and pressure increase rapidly. At this time, the composite phase change block at the bottom of the battery pack undergoes a phase change and absorbs a large amount of heat from the high-temperature fluorinated liquid, which can play a role in suppressing the rapid increase in the overall temperature of the battery pack and prevent rapid thermal runaway. The pressure sensor will monitor that the pressure in the battery pack rises sharply, and the pressure relief valve opens to quickly reduce the pressure inside the battery pack. After the pressure in the battery pack cavity drops, the first liquid replenisher can supplement the fluorinated liquid with a relatively low temperature, further reducing the overall temperature level of the fluorinated liquid, avoiding excessive pressure in the battery pack and causing it to burst, and winning more sufficient escape time for the driver and passengers to ensure their safety.

[0030] Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Claims

1. A multi-stage heat dissipation battery pack thermal management system for solid-liquid mixed phase change, characterized in that: The battery pack (1) comprises a battery pack (1), wherein a plurality of battery cells (11) are arranged inside the battery pack (1) and are filled with a fluoride liquid (16), an upper partition (10) and a lower partition (12) are installed inside the battery pack (1), the plurality of battery cells (11) are arranged parallel to each other and spaced apart between the upper partition (10) and the lower partition (12), the upper and lower ends of the battery cells (11) are respectively clamped on the upper partition (10) and the lower partition (12), the upper partition (10) and the lower partition (12) are both provided with a plurality of medium holes for the fluoride liquid (16) to flow, a plurality of heating units (15) are provided on the bottom side of the inner cavity of the battery pack (1) for heating the fluoride liquid (16) to a normal operating temperature range of the battery cells (11), a plurality of composite phase change blocks (14) are further provided in the inner cavity of the battery pack (1) between the plurality of heating units (15) and the lower partition (12), and the composite phase The phase change block (14) is a spherical body or a block having a size larger than the medium hole. The outer side of the composite phase change block (14) is sealed by an aluminum-diamond composite high thermal conductivity material, and the interior is filled with an inorganic hydrated salt phase change material, and the melting point of the phase change material is higher than the normal working temperature range of the battery cell (11). The medium inlet on the bottom side and the medium outlet on the top side of the battery pack (1) are respectively connected to the first channel of the plate heat exchanger (4), and the second channel of the plate heat exchanger (4) is connected to the heat dissipation circulation loop. The heat dissipation medium can flow into the second channel through the heat dissipation circulation loop, so as to cool the fluorinated liquid (16) in the first channel. The battery pack (1) is provided with a temperature sensor and a pressure sensor. The medium outlet is also connected to the pressure relief pipeline through a pressure relief valve (3). The side wall of the battery pack (1) is connected to the first refiller (2) through the refill port. A plurality of micro-fin structures are provided on the outer cylindrical surface of the battery core (11), the micro-fin structures are sheet-like protrusions extending along the length direction of the battery core (11), the plurality of micro-fin structures are spaced apart along the circumference of the battery core (11), the height of the micro-fin structures extending outward from the outer cylindrical surface of the battery core (11) is 100-200 μm, the thickness of the micro-fin structures is 30-60 μm, the spacing between two adjacent micro-fin structures is 50-80 μm, the interior of the micro-fin structures is a metal substrate formed by surface laser micro-melting treatment, and the surface of the micro-fin structures is a graphene surface layer with a thickness of 3-5 μm deposited by vaporization.

2. The multi-stage heat dissipation battery pack thermal management system for solid-liquid hybrid phase change according to claim 1, characterized in that: The upper partition (10) and the lower partition (12) are both provided with a plurality of stepped through holes, and the upper and lower ends of the battery cell (11) are respectively clamped at the large ends of the stepped through holes, and the upper and lower ends of the battery cell (11) can respectively contact the fluorinated liquid (16) through the small ends of the stepped through holes.

3. The multi-stage heat dissipation battery pack thermal management system for solid-liquid hybrid phase change according to claim 1, wherein: The battery pack (1) comprises a shell (13) of a rectangular structure, an upper cover (17) is provided on the top side of the shell (13), a medium inlet is located on the bottom surface of the shell (13), a liquid replenishing port is located on one side of the shell (13), and a medium outlet is located on the upper cover (17).

4. A multi-stage heat dissipation battery pack thermal management system for solid-liquid hybrid phase change, characterized in that: The heating unit (15) is a PTC heater or a resistance wire, and a plurality of heating units (15) are arranged in an array on the bottom side of the inner cavity of the battery pack (1).

5. A multi-stage heat dissipation battery pack thermal management system for solid-liquid hybrid phase change according to claim 1, characterized in that: The heat dissipation medium is tetrafluoroethane. A compressor (5), a condenser (6) and a throttle valve (9) are successively arranged on the heat dissipation circulation loop. The compressor (5) can transport the compressed high-temperature and high-pressure gaseous tetrafluoroethane to the condenser (6). A cooling fan (7) is arranged on one side of the condenser (6) to facilitate the condensation of the gaseous tetrafluoroethane into a medium-temperature and high-pressure liquid tetrafluoroethane. The throttle valve (9) can reduce the pressure of the liquid tetrafluoroethane to facilitate the formation of a low-temperature and low-pressure tetrafluoroethane liquid-vapor mixture through the evaporation of part of the liquid tetrafluoroethane. The low-temperature and low-pressure tetrafluoroethane liquid-vapor mixture can flow into the second channel of the plate heat exchanger (4) and absorb the heat of the gaseous fluorinated liquid (16). After complete evaporation, the low-temperature and low-pressure gaseous tetrafluoroethane can flow back to the compressor (5).

6. The multi-stage heat dissipation battery pack thermal management system for solid-liquid hybrid phase change according to claim 5, characterized in that: A second liquid replenisher (8) is also connected to one side of the heat dissipation circulation loop.

Images