A novel phase change material lithium-ion battery pack cooling system, method, and medium

Abstract

The application discloses a novel phase change material lithium ion battery pack cooling system, method and medium, relates to the battery thermal management technical field, and solves the problem that the phase change material is not fully utilized in the traditional scheme. The technical scheme points are that: in the case that the battery is in the non-charging and non-discharging state, the coolant is input into the first cooling channel in the metal fin directly contacted with the phase change material, and the phase change material is solidified. The coolant flowing in the first cooling channel in the metal fin can make the phase change material completely solidify after the discharge / charge stage of the battery, so that the latent heat of the phase change material can be repeatedly and fully utilized to absorb the heat of the battery heat dissipation, the use of the cooling unit is reduced, the energy is saved, and the lower operation cost is ensured.

Description

Technical Field

[0001] This invention relates to the field of battery thermal management technology, and in particular to a novel phase change material lithium-ion battery pack cooling system, method, and storage medium. Background Technology

[0002] In recent years, lithium batteries have become an important component of the new energy field due to their low self-discharge, high energy density, high capacity, and good cycle life. These superior properties have led to their widespread use in new energy storage systems and portable electronic devices. However, when the temperature of a lithium battery module is too low, it slows down the ion mobility, reducing battery capacity and power, thus requiring special thermal management. The battery thermal management system should be able to keep the battery cell temperature within the optimal operating temperature range. Otherwise, high temperatures will accelerate the aging and capacity loss of lithium-ion batteries. The capacity decay of a lithium-ion battery system depends on the total number of charge / discharge cycles, battery chemistry, battery purity, operating temperature, and charge / discharge rate. Furthermore, batteries inevitably generate heat during charging and discharging. If this heat is not effectively controlled, it can lead to increased internal temperature and pressure, resulting in increased internal pressure, causing overpressure devices to open or the battery casing to burst. The dense packaging of batteries means that thermal runaway from one battery can easily propagate to neighboring batteries, ultimately leading to a fire. Therefore, ensuring that heat transfer within the battery module is within a controllable range is crucial. The ideal temperature range is 15°C to 60°C. This not only helps prevent thermal runaway or thermal instability in the battery, but also significantly improves the overall performance of the battery, maintains the battery's operational balance, and thus extends the battery's health and cycle life.

[0003] Therefore, the role of the battery management system, especially the battery thermal management system, is particularly important to achieve this temperature control. The battery thermal management system monitors and regulates the battery's current and temperature to ensure they remain within a safe and efficient operating range, typically requiring a temperature difference of less than 6°C. Temperature control methods for battery thermal management systems include air cooling, liquid cooling, nanofluidic systems, and thermoelectric cooling, as well as heat pipe systems and phase change material solutions as passive technologies.

[0004] Currently, phase change material (PCM) cooling systems using passive control strategies do not fully utilize the latent heat potential of PCMs to absorb heat, and these systems require large amounts of PCM, resulting in high costs. At present, there is no comprehensive control strategy based on the entire charging and discharging process of PCMs.

[0005] Therefore, there is a need for a novel phase change material lithium-ion battery pack cooling system, method, and storage medium. Summary of the Invention

[0006] To address the problem of insufficient utilization of phase change materials in existing technologies, this invention provides a novel cooling system, method, and storage medium for lithium-ion battery packs using phase change materials. This system effectively utilizes phase change materials to cool the battery, thereby reducing the amount of phase change materials used in the cooling system and lowering costs. The specific technical solution is as follows:

[0007] In a first aspect, embodiments of this application provide a novel phase change material lithium-ion battery pack cooling system. The system includes: a battery, a control unit, a cooling unit, a cooling frame, and at least one cooling plate. The frame includes a base plate and a side plate. The cooling plate is connected to the base plate and the side plate respectively, forming a groove for accommodating the battery. The size of the groove is adapted to the size of the battery. The cooling plate is filled with phase change material, and metal fins are disposed within the cooling plate, directly contacting the phase change material. The metal fins are provided with a first cooling channel for coolant flow. The side plate includes a second cooling channel, which is connected to both the cooling unit and the first cooling channel.

[0008] The control unit is used to obtain the charge / discharge state of the battery; the control unit is used to control the cooling unit to stop outputting the coolant to the second cooling channel when the battery is in a charging or discharging state; the control unit is also used to control the cooling unit to output the coolant to the second cooling channel to solidify the phase change material when the battery is in a non-charging and non-discharging state.

[0009] Preferably, the metal fin is horizontally arranged, and the first cooling channel is a circular channel that horizontally penetrates the metal fin.

[0010] Preferably, the cooling plate includes a phase change material chamber for filling with the phase change material, and the phase change material chamber is a sealed space formed by the inner wall of the cooling plate and the metal fins.

[0011] Preferably, the phase change material is n-octadecane.

[0012] Preferably, the metal fins are made of aluminum, and the coolant is a mixture of water and ethylene glycol.

[0013] Preferably, the metal fins are 2 mm high and 7 mm wide; the diameter of the circular channel is 1 mm; and the coolant is a mixture of 50% water and 50% ethylene glycol.

[0014] Preferably, the method for calculating the height of the phase change material chamber is as follows: establish an electrical and thermal behavior model of the battery; calculate the expected heat generated after the battery temperature exceeds a preset temperature threshold based on the model; calculate the volume of the phase change material required to absorb the expected heat based on the expected heat, the strength value and latent heat value of the phase change material; and calculate the height of the phase change material chamber based on the volume and the width of the metal fins.

[0015] Secondly, embodiments of this application provide a novel cooling method for a phase change material lithium-ion battery pack, applied to the control unit of the system described in the first aspect. The method includes:

[0016] The control unit is used to obtain the charge / discharge state of the battery; when the battery is in a charging or discharging state, the control unit controls the cooling unit to stop outputting the coolant to the second cooling channel; when the battery is in a non-charging and non-discharging state, the control unit controls the cooling unit to output the coolant to the second cooling channel to solidify the phase change material.

[0017] A third aspect is a computing device, comprising: a memory for storing a program; and a processor for loading the program to execute the method as described in the second aspect.

[0018] Fourthly, embodiments of this application provide a computer-readable storage medium including a stored program, wherein, when the program is executed, it controls the device where the computer-readable storage medium is located to perform the method described in the second aspect.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: the coolant flowing through the first cooling channel in the metal fins can completely solidify the phase change material after the battery discharge / charge stage, thereby enabling repeated and full utilization of the latent heat of the phase change material to absorb the heat dissipated by the battery, reducing the use of cooling units, saving energy, and ensuring lower operating costs. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0021] Figure 1 This is a schematic diagram of the structure of a novel phase change material lithium-ion battery pack cooling system provided in an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of a cooling frame and a battery provided in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of a cooling plate provided in an embodiment of the present invention;

[0024] Figure 4 A flowchart illustrating the numerical verification of an electrical and thermal behavior model of a battery, provided for an embodiment of the present invention.

[0025] Figure 5 This is a schematic diagram of a battery equivalent circuit provided in an embodiment of the present invention;

[0026] Figure 6 The diagram shows the maximum heat generated during battery charging and discharging, as provided in an embodiment of the present invention; where (a) represents the charging process and (b) represents the discharging process.

[0027] Figure 7 A temperature field change process diagram during battery discharge is provided as an embodiment of the present invention;

[0028] Figure 8 This is a schematic diagram of data during a battery charge-discharge cycle provided in an embodiment of the present invention, wherein (a) is voltage; (b) is heat generated; (c) is the highest temperature of the battery; and (d) is the liquid phase fraction.

[0029] Figure 9 A schematic flowchart illustrating a novel phase change material lithium-ion battery pack cooling method provided in an embodiment of the present invention;

[0030] Figure 10 This is a schematic diagram of the structure of a computing device provided in an embodiment of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0033] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0034] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0035] To address the problem of insufficient utilization of phase change materials in existing technologies, this invention provides a novel phase change material lithium-ion battery pack cooling system, method, computing device, and storage medium that can fully utilize phase change materials to cool the battery, thereby reducing the amount of phase change materials used in the cooling system and lowering costs.

[0036] Please see Figure 1 , Figure 1 This is a schematic diagram of a novel phase change material lithium-ion battery pack cooling system provided in an embodiment of this application. Figure 1 As shown, the novel phase change material lithium-ion battery pack cooling system 10 includes a battery 11, a control unit 12, a cooling unit 13, a cooling frame 14, and at least one cooling plate 15. Figure 1 In a specific example, the system 10 includes three batteries 11 and four cooling plates 15. It is understood that in practical applications, the system 10 may include more or fewer batteries 11 and cooling plates 15 (at least one), and this application does not make any specific limitation in this regard.

[0037] The battery 11 is used to power electrical equipment or components inside or outside the system 10. The battery 11 can be electrically connected to and power the control unit 12 and the cooling unit 13 respectively. Optionally, the control unit 12 and the cooling unit 13 can be powered by other power sources.

[0038] The control unit 12 is connected to the cooling unit and is used to control the cooling unit 13 to output cooled coolant to the cooling frame 14. The cooling unit 13 is used to cool the coolant.

[0039] The cooling frame 14 includes a base plate and side plates (not shown in the figure); the cooling plate 15 is connected to the base plate and the side plates respectively, forming a groove for accommodating the battery 11, the size of which is adapted to the size of the battery 11. See details in [reference needed]. Figure 2 , Figure 2 This is a schematic diagram of a cooling frame and a battery provided for an embodiment of this application. Preferably, as... Figure 2 As shown, in Figure 2In a specific example, the cooling frame 14 and the cooling plate 15 can be integrally formed.

[0040] In this system 10, a group of identical lithium-ion batteries 11 are connected in series. Multiple cooling plates 15 are connected to the cooling frame 14 at equal intervals to form grooves corresponding to the size of the batteries 11. The batteries 11 can be inserted into the grooves, and the cooling frame 14 and the cooling plates 15 cool the batteries 11.

[0041] The base plate of the cooling frame 14 is insulated, while the top of the cooling frame 14 is in contact with ambient air at 25°C. Each cooling plate 15 is vertically connected to the base plate, and the vertical plane where the center of each cooling plate 15 is located can be called a plane of symmetry, because two adjacent cooling plates 15 can be considered symmetrical with respect to the battery 11 in between. This helps reduce the computational complexity of the model after modeling. For a single battery 11, we will focus on its two adjacent planes of symmetry, that is... Figure 2 The area defined by the dashed line is because this control volume represents the behavior of the entire battery pack.

[0042] Optionally, the sides of the cooling frame 14 may include two long sides, or a combination of two long sides and two short sides.

[0043] The main dimensions of the battery can be labeled Lx, Ly, and Lz.

[0044] The cooling plate 15 is filled with a phase change material, and metal fins are disposed within the cooling plate 15. These metal fins are in direct contact with the phase change material, and the metal fins have a first cooling channel for the flow of coolant. For details, please refer to [reference needed]. Figure 3 , Figure 3 A perspective view and a cross-sectional view of the cooling plate provided in the embodiments of this application.

[0045] like Figure 3 As shown, preferably, the metal fins are arranged horizontally, the first cooling channel is a circular channel that runs horizontally through the metal fins, and the first cooling channel allows liquid coolant to flow to promote rapid curing of PCM.

[0046] The diameter of the circular channel can be set based on the height and width of the metal fins. Furthermore, it can also be set in conjunction with the heat dissipation requirements of system 10, as well as the flow rate and heat absorption efficiency of the coolant.

[0047] Preferably, the cooling plate 15 includes a phase change material chamber for filling the phase change material. The phase change material chamber is a sealed space formed by the inner wall of the cooling plate 15 and the metal fins.

[0048] The side panel includes a second cooling channel, which is connected to the cooling unit 13 and the first cooling channel.

[0049] Preferably, the phase change material is n-octadecane.

[0050] Preferably, the metal fins are made of aluminum, and the coolant is a mixture of water and ethylene glycol. It is understood that other common liquid coolants besides the mixture of water and ethylene glycol can also be used, and this application does not specifically limit the use of any particular coolant.

[0051] Preferably, the metal fins are 2 mm high and 7 mm wide; the diameter of the circular channel is 1 mm; and the coolant is a mixture of 50% water and 50% ethylene glycol.

[0052] The control unit 12 is used to obtain the charging and discharging state of the battery 11; the control unit 12 is used to control the cooling unit 13 to stop outputting the coolant to the second cooling channel when the battery 11 is in a charging or discharging state; the control unit 12 is also used to control the cooling unit 13 to output the coolant to the second cooling channel to solidify the phase change material when the battery 11 is in a non-charging and non-discharging state.

[0053] During charging and discharging, the battery 11 continuously generates heat. The phase change material in the cooling plate 15 absorbs this heat and melts, maintaining the battery's operating temperature within a preset range. In this case, cooling via the cooling unit 13 is unnecessary. When the battery 11 is neither charging nor discharging, the cooling unit 13 outputs cooled coolant to the second cooling channel. This cooled coolant then enters the first cooling channel of the metal fins, where it solidifies the phase change material through direct contact with the metal fins. This allows the phase change material to absorb heat again when the battery 11 releases heat. The metal fins, on the one hand, solidify the phase change material through the first cooling channel, repeatedly utilizing the latent heat of the phase change material to cool the battery 11, reducing the operating time of the cooling unit 13 and making the system 10 more energy-efficient and environmentally friendly. On the other hand, they also prevent the ineffective solidification of phase change materials with poor thermal conductivity.

[0054] The present invention allows the coolant flowing through the first cooling channel within the metal fins to completely solidify the phase change material after the battery's discharge / charge phase. This enables repeated and full utilization of the latent heat of the phase change material to absorb heat dissipated by the battery, reducing the use of cooling units, saving energy, and ensuring lower operating costs.

[0055] Furthermore, to ensure that the heat absorption capacity of the phase change material is sufficient to keep the operating temperature of the battery 11 within a preset range, the volume of the phase change material needs to be determined based on the heat generated by the battery 11. Assuming that the density of the phase change material remains constant and the bottom area of ​​the phase change material chamber is the same as the bottom area of ​​the cooling plate 15, this can also be considered as determining the height of the phase change material.

[0056] Preferably, the method for calculating the height of the phase change material chamber is as follows: establish an electrical and thermal behavior model of the battery 11; calculate the expected heat generated after the temperature of the battery 11 exceeds a preset temperature threshold based on the model; calculate the volume of the phase change material required to absorb the expected heat based on the expected heat, the strength value and latent heat value of the phase change material; and calculate the height of the phase change material chamber based on the volume and the width of the metal fins.

[0057] It is understood that this calculation method can be executed by any electronic device with computing capabilities; the following explanation uses a computing device executing this calculation method as an example.

[0058] Please refer to Figure 4 ,like Figure 4 As shown, the computing device can first establish an electrical and thermal behavior model of battery 11 and collect relevant data of battery 11 under experimental conditions; then verify whether the running data of the model is consistent with the experimental data, and adjust the model until convergence based on the verification results; after the model converges and can accurately represent the electrical and thermal behavior of battery 11, the computing device calculates the height of the phase change material cavity based on the model; then updates the height into the model to verify the cooling effect.

[0059] First, the heat generated by a single cell 11 can be calculated. The energy balance equation for a single cell describes the generation and transfer of heat within the cell.

[0060] By analyzing changes in state of charge, voltage relationships, and RC network voltage variations, an electrical equivalent circuit model is established to describe the behavior of the battery cell.

[0061] In this embodiment of the application, the energy balance within a single battery is expressed as:

[0062]

[0063] Where ρ is the cell density, C p Let T be its heat capacity, T be its temperature, and k be its thermal conductivity tensor of the battery cell. This refers to the volumetric heat generated. The three main heat generation themes relate to the electrical and electrochemical states of the casing: Joule heating, entropy heating or reversible heating, and irreversible heating. This invention uses an electrical equivalent circuit model to describe the behavior of the battery cell.

[0064] In this application embodiment, an electrical equivalent circuit model is used to describe the behavior of the battery cell. For example... Figure 5 As shown, the electrical equivalent circuit model uses an initial resistance (Ro) of two equal-voltage resistors and capacitors (R1-C1 and R2-C2) connected in series. The time-varying state of charge (SOC) of the battery is as follows:

[0065]

[0066] Among them, Q n I(t) represents the nominal capacity, and I(t) represents the current.

[0067] In this embodiment, the voltage change V(t) and the open-circuit voltage (Uoc) are related by the following equation:

[0068] V(t)=φ + -φ - =U oc (soc)-R0(soc)I(t)-V1(t)-V2(t) (3)

[0069] In this embodiment of the application, the voltages of V1 and V2 come from:

[0070]

[0071] Where i = 1, 2.

[0072] In this embodiment of the application, the entropy of the heat generated by the battery and the irreversible thermal effect are expressed by the following formula:

[0073]

[0074] Where j represents the current density. The heat generated by the Joule effect is expressed as:

[0075]

[0076] Where, σ + and σ - The effective conductivity of the positive and negative electrodes. Current balance provides the relationship between volumetric shunt density and phase potential, expressed as:

[0077]

[0078] After completing the above modeling of a single battery 11, its boundary conditions can be set as follows: the bottom is insulated, while all other surfaces are in contact with the environment at a temperature of 25°C. There is no airflow except for natural convection around the battery; therefore, the convective heat transfer coefficient is h = 12.8 W / m. 2K. The initial temperature of the battery is also 25℃. The equations, along with the initial and boundary conditions, are solved using a fusion method. A simple numerical model is used, with a time step of 1s and 20 iterations per time step. When the difference between each time step is less than 10, the continuity equation, momentum equation, and energy equation all converge.

[0079] After the modeling is completed and confirmed to be consistent with the experimental data, the computing device can further calculate the height of the phase change material cavity; however, calculating this height requires first calculating the volume of the phase change material, which in turn requires first calculating the heat generation of the battery.

[0080] In this embodiment, thermal management is based on the balance between the heat generated during charging / discharging and the heat absorbed by the phase change material in the aluminum casing. Considering the melting energy balance of the phase change material between SOC = 60% and full discharge, it is expressed as follows:

[0081] Q = ρ PCM L f V PCM (10)

[0082] Where, ρ PCM For the strength of phase change materials, L f For the latent heat of phase change materials, V PCM Let represent the corresponding volume of the phase change material. The required height δ of the phase change material for complete melting was estimated using proportional analysis. The energy balance at the liquid-solid interface of the phase change material is expressed as:

[0083]

[0084] Where ΔT represents the temperature change experienced by the phase change material, and k represents the thermal conductivity. Assuming the density of the phase change material remains constant, the change in height of the phase change material over time is expressed as:

[0085]

[0086] In this embodiment, the equations governing the heat generated by a single battery are resolved by the energy conservation equations for the fins. The energy conservation of the metal fins is expressed as:

[0087]

[0088] In this embodiment, the behavior of the phase change material is modeled using the enthalpy-porosity method, considering the total specific enthalpy H = h + Δh, where h represents the explicit enthalpy and Δh represents the latent enthalpy. The relationship between latent enthalpy and liquid volume fraction is expressed as:

[0089] ΔH=βL f (14)

[0090] Among them, βL fThe volume fraction of a liquid is defined as follows:

[0091]

[0092] Where T-solidus is the solid-state temperature of the phase change material, and T-liquidus is the liquid-state temperature of the phase change material. In the embodiments of this application, mass conservation is expressed as:

[0093]

[0094] In this embodiment of the application, the momentum equation is expressed as:

[0095]

[0096] In this embodiment, the energy conservation equation is expressed as:

[0097]

[0098] Where S represents The viscous region constant is A. mush =10 5 .

[0099] It should be noted that the phase change material wrapped around the vertical surface of the battery, combined with the horizontal metal fins, can effectively melt while absorbing the heat generated by the battery. The spacing between the fins must be selected based on the development of the molten layer within the time frame required for thermal management (from reaching the critical battery temperature to the end of the charging / discharging process).

[0100] Based on the above model and related formulas, the height of the phase change material cavity can be calculated. It is understandable that, based on the proportional analysis method, the calculation device can obtain the height of one or more phase change material cavities, ensuring that the phase change material cavities are reasonably distributed to absorb heat from various parts of the battery 11 while the phase change material filled within them can fully melt.

[0101] To better illustrate the method provided in the embodiments of this application, a specific embodiment will be described below.

[0102] Step 1: Connect a group of identical lithium-ion battery cells in series. A cooling frame and equally spaced cooling plates form grooves corresponding to the battery size, into which the batteries can be inserted. The bottom plate of the cooling frame is insulated, while the top is in contact with ambient air at 25°C. Figure 2 As shown. Each plane of symmetry is a vertical plane located at the center of the cooling plate between every two adjacent cells. For a single cell, the area delineated by the dashed line will be of particular interest, as this control volume represents the behavior of the entire battery pack.

[0103] Each lithium-ion battery has a nominal capacity of 115 Ah and a nominal voltage of 3.74 V. The main dimensions of the battery are (Lx = 220 mm) x (Ly = 33.2 mm) x (Lz = 102.5 mm). Table 1 lists the battery's thermal characteristics. The battery's state of charge ranges between 1% and 97%, with a maximum voltage of 4.3 V and a cutoff voltage of 2.8 V.

[0104] Components <![CDATA[Density (Kg / m 3 )]]> Heat capacity (J / Kg*K) Thermal conductivity (w / m*K) battery cell 2404 1132 <![CDATA[K x =20,K y =3.8,K z =13.1]]> Negative electrode (copper) 8978 381 202 Positive electrode (aluminum) 2719 871 387.6

[0105] Table 1 Thermal characteristics of lithium-ion batteries

[0106] Step 2: When modeling the behavior of the battery during 2C charge and discharge, the boundary conditions are as follows: the bottom is insulated, while all other surfaces are in contact with the environment at 25°C. There is no airflow except for natural convection around the battery; therefore, the convective heat transfer coefficient is h = 12.8 W / m. 2 K. The initial temperature of the battery is also 25℃. The equations, along with the initial and boundary conditions, are solved using a fusion method. A simple numerical model is used with a time step of 1 s and 20 iterations per time step. The continuity, momentum, and energy equations converge when the difference between each time step is less than 10. A structured mesh is used on the battery assembly. Mesh sensitivity studies are conducted to ensure mesh independence. Figure 6 As shown, Figure 6 (a) and (b) show the maximum heat and maximum temperature rise generated during battery charging and discharging, respectively, with the horizontal axis representing the state of charge. Specifically, Figure 7 It shows the temperature field changes of the battery from the start of discharge to the end of discharge.

[0107] Step 3: Regarding battery thermal management, the standard adopted in this invention is to maintain a certain absolute temperature range of 15℃ ≤ T ≤ 35℃, and the maximum relative temperature difference of the battery, ΔTmax ≤ 5℃. The battery temperature will only rise by 10℃ and reach the 35℃ threshold when the state of charge drops to -60%. When the battery is half-discharged, the relative temperature difference within the battery will be greater than 5℃. At the end of the discharge process, the hot spot is near the expected positive and negative electrodes. This is also the location with the highest temperature gradient within the battery. Therefore, this invention calculates the required volume of the phase change material based on the heat generated by the battery during the discharge process from 60% SOC to complete discharge, so that the corresponding phase change material can maintain the battery's operating temperature below 35℃ while fully absorbing heat.

[0108] Because phase change materials often have low thermal conductivity, horizontal metal fins with a thickness of 2 mm and a length of 7 mm are inserted into the phase change material (see reference). Figure 3While this configuration allows for efficient melting of the phase change material, the surface of the phase change material-based cooling system is primarily sandwiched in the middle, preventing rapid solidification and limiting heat exchange with different environments. Therefore, each fin along the xy plane contains a horizontal coolant channel with a diameter of 1 mm (see [reference]). Figure 3 The coolant circulates after the discharge ends and before charging, and then solidifies the phase change material again.

[0109] The phase change material is n-octadecane, the fins are made of aluminum, and the coolant is a mixture of 50% water and ethylene glycol. The corresponding material properties are shown in Table 2. Furthermore, the latent heat of the phase change material is 241,360 d / kg, the solid phase temperature is 300 K, and the liquid phase temperature is 301 K. Initial values ​​and boundary conditions are provided in Table 3.

[0110]

[0111] Table 2. Thermophysical properties of materials

[0112]

[0113] Table 3 Initial Conditions and Boundary Conditions

[0114] Where h(T-Tamb) refers to the temperature difference between the system's real-time temperature and the ambient temperature; P gauge This refers to gauge pressure; R e "It refers to the Reynolds number, n is the fluid velocity, and q" is the fluid flow rate.

[0115] Step 4: During continuous discharge (and charging), liquid cooling is off, and thermal management is only due to the phase change of the phase change material stage. The highest temperature reached in the battery is 34.8°C, which is still below the critical value. The maximum temperature difference throughout the cycle is 3.7°C, which is within the acceptable range. At the end of discharge, 84.1% of the phase change material has melted.

[0116] Figure 8 The results of a complete cycle are shown: the battery was discharged at a rate of 2C and then charged at the same rate. There was a 12-minute interval between charging and discharging, during which coolant circulation was activated. Figure 8 a gives the voltage change during the cycle of this process, and the heat generated, such as Figure 8 As shown in b. The highest temperature changes and liquid fractions for the entire cycle are shown in [Figure 1]. Figure 8 c and Figure 8 d. The thermal management strategy of the present invention maintains the battery temperature within a predetermined range.

[0117] Experimental results show that the integrated phase change material-liquid cooling system can reduce total energy consumption by 54.9% (from 0.4406 kJ to 0.1963 kJ). Therefore, the thermal management system of this scheme can save energy and ensure low operating costs.

[0118] The system provided in the embodiments of this application has been described above. The following will describe the cooling method for a novel phase change material lithium-ion battery pack provided in the embodiments of this application. Please refer to... Figure 9 , Figure 9 This application provides a flowchart illustrating a novel phase change material lithium-ion battery pack cooling method, which is applied to the control unit of the aforementioned system and specifically includes:

[0119] Step 901: The control unit is used to obtain the charge / discharge status of the battery.

[0120] Step 902: When the battery is in a charging or discharging state, the control unit controls the cooling unit to stop outputting the coolant to the second cooling channel.

[0121] Step 903: When the battery is in a non-charging and non-discharging state, the control unit controls the cooling unit to output the coolant to the second cooling channel to solidify the phase change material.

[0122] The methods provided in this application can be understood by referring to the relevant content in the foregoing system embodiment section, and will not be repeated here.

[0123] like Figure 10 As shown, Figure 10 This is a schematic diagram of a possible logical structure of a computing device provided in an embodiment of this application. The computing device 1000 includes a processor 1001, a communication interface 1002, a memory 1003, and a bus 1004. The processor 1001, communication interface 1002, and memory 1003 are interconnected via the bus 1004. In an embodiment of this application, the processor 1001 is used to control and manage the operation of the computing device 1000; for example, the processor 1001 is used to execute... Figure 9 The steps in the embodiments and / or other processes used in the techniques described herein. Communication interface 1002 is used to support communication by computing device 1000. Memory 1003 is used to store program code and data of computing device 1000.

[0124] The processor 1001 can be a central processing unit, a general-purpose processor, a digital signal processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a digital signal processor and a microprocessor, etc. The bus 1004 can be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 10 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0125] In another embodiment of this application, a computer-readable storage medium is also provided, the computer-readable storage medium including instructions that, when executed on a computer, cause the computer to perform the above-described... Figure 9 The method described in the embodiments.

[0126] Those skilled in the art will recognize that the units of the various examples described in connection with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of the invention.

[0127] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0128] In the embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0129] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0130] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0131] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A novel phase change material lithium-ion battery pack cooling system, characterized in that, The system includes: a battery, a control unit, a cooling unit, a cooling frame, and at least one cooling plate. The cooling frame includes a base plate and a side plate. The cooling plate is connected to the base plate and the side plate respectively, forming a groove for accommodating the battery. The size of the groove is adapted to the size of the battery. The cooling plate is filled with a phase change material, and metal fins are disposed within the cooling plate. The metal fins are in direct contact with the phase change material, and the metal fins are provided with a first cooling channel for coolant flow. The side plate includes a second cooling channel, which is connected to the cooling unit and the first cooling channel respectively. The control unit is used to obtain the charge / discharge state of the battery; The control unit is also configured to control the cooling unit to stop outputting the coolant to the second cooling channel when the battery is in a charging or discharging state; The control unit is also configured to control the cooling unit to output the coolant to the second cooling channel to solidify the phase change material when the battery is in a non-charging and non-discharging state; The metal fins are arranged parallel to the ground, and the first cooling channel is a circular channel that runs horizontally through the metal fins. The cooling plate includes a phase change material chamber, which is used to fill the phase change material. The phase change material chamber is a closed space formed by the inner wall of the cooling plate and the metal fins. The method for calculating the height of the phase change material chamber is as follows: Establish electrical and thermal behavior models for the battery; Based on the model, the expected heat generated when the battery temperature exceeds a preset temperature threshold is calculated. Based on the expected heat, the strength value and latent heat value of the phase change material, the volume of the phase change material required to absorb the expected heat is calculated. The height of the phase change material chamber is calculated based on the volume and the width of the metal fins.

2. The system according to claim 1, characterized in that, The cooling plate and the cooling frame are integrally formed.

3. The system according to claim 1, characterized in that, The phase change material is n-octadecane.

4. The system according to claim 1, characterized in that, The metal fins are made of aluminum, and the coolant is a mixture of water and ethylene glycol.

5. The system according to claim 4, characterized in that, The metal fins are 2mm high and 7mm wide; the diameter of the circular channel is 1mm; the coolant is a mixture of 50% water and 50% ethylene glycol.

6. A novel cooling method for lithium-ion battery packs using phase change materials, characterized in that, The method, applied to a control unit of the system according to any one of claims 1 to 5, comprises: The control unit acquires the charging and discharging status of the battery in the system; When the battery is in a charging or discharging state, the control unit controls the cooling unit to stop outputting the coolant to the second cooling channel; When the battery is in a non-charging and non-discharging state, the control unit controls the cooling unit to output the coolant to the second cooling channel to solidify the phase change material.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored program, wherein, when the program is executed, it controls the device on which the computer-readable storage medium is located to perform the method of claim 6.

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