Novel phase change material lithium ion battery pack cooling system, method and medium

Abstract

The invention discloses a novel phase change material lithium ion battery pack cooling system and method and a medium, relates to the technical field of battery thermal management, and solves the problem that a phase change material is not fully utilized in a traditional scheme. According to the technical scheme, under the condition that the battery is in a non-charging and non-discharging state, a cooling agent is input through a first cooling channel in a metal fin in direct contact with a phase change material, and the phase change material is cured. According to the invention, the phase change material can be completely cured after the discharging / charging stage of the battery through the coolant flowing in the first cooling channels in the metal fins, so that the latent heat of the phase change material can be repeatedly and fully utilized to absorb the heat radiated by the battery, the use of a cooling unit is reduced, the energy is saved, and the lower operation cost is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of battery thermal management, and particularly to a novel phase change material lithium-ion battery pack cooling system, method and storage medium. Background Art

[0002] In recent years, lithium batteries have become an important part of the new energy field due to their low self-discharge, high energy density, high capacity and good cycle life. These superior performances have made lithium batteries widely used in applications such as new energy energy storage systems and portable electronic devices. However, when the temperature of the lithium battery module is too low, the ion migration rate of the battery will slow down, reducing the battery capacity and power. Therefore, special thermal management is required. The battery thermal management system should be able to keep the battery cell temperature within the optimal operating temperature range. Otherwise, high temperature will accelerate the aging and capacity loss of lithium-ion batteries. The capacity attenuation of the lithium-ion battery system depends on the total number of charge / discharge cycles, battery chemical composition, battery purity, operating temperature and charge / discharge rate. In addition, heat is inevitably generated during the charge and discharge process of the battery. If this heat is not effectively controlled, it may lead to an increase in internal temperature and pressure, an increase in the internal pressure of the battery, resulting in the opening of the overpressure device or the bursting of the battery case. The dense packaging of the batteries makes it very likely that the thermal runaway of one battery will spread to adjacent batteries, eventually leading to battery fires. Therefore, it is crucial to ensure that the heat transfer in the battery module is within a controllable range. The ideal temperature range is 15°C to 60°C, which not only helps to prevent the battery from experiencing thermal runaway or thermal instability, but also significantly improves the overall performance of the battery, maintains the operating balance of the battery, and thus extends the health state and cycle life of the battery.

[0003] Therefore, in order to achieve this temperature control, the role of the battery management system, especially the battery thermal management system, is particularly important. The battery thermal management system monitors and adjusts the current and temperature of the battery to ensure that they remain within a safe and efficient operating range, usually requiring a temperature difference of less than 6°C. The temperature control methods of the battery thermal management system include air cooling, liquid cooling, nanofluid systems and thermoelectric cooling, as well as heat pipe systems and phase change material solutions as passive technology attempts.

[0004] Currently, the phase change material cooling system controlled by passive strategies does not fully utilize the latent heat potential of the phase change material to absorb heat, and more phase change materials are required for the cooling system, resulting in higher costs. At present, there is no overall control strategy based on the entire charge and discharge working process of the phase change material.

[0005] In view of this, a novel phase change material lithium-ion battery pack cooling system, method and storage medium are needed. Summary of the Invention

[0006] In view of the problem that phase change materials are not fully utilized in the prior art, the present invention provides a novel phase change material lithium-ion battery pack cooling system, method and storage medium, which can make full use of phase change materials to cool the battery, thereby reducing the amount of phase change materials in the cooling system and lowering the cost. The specific technical solutions are as follows:

[0007] In a first aspect, an embodiment of the present application provides a novel phase change material lithium-ion battery pack cooling system, which includes: a battery, a control unit, a cooling unit, a cooling frame and at least one cooling plate. The frame includes a bottom plate and side plates; the cooling plates are respectively connected to the bottom plate and the side plates to form a groove for accommodating the battery, and the size of the groove is adapted to the size of the battery; the cooling plates are filled with phase change materials, and metal fins are arranged in the cooling plates. The metal fins are in direct contact with the phase change materials, and the metal fins are provided with a first cooling channel for the coolant to flow through; the side plates include a second cooling channel, and the second cooling channel is respectively communicated with the cooling unit and the first cooling channel;

[0008] The control unit is used to obtain the charge and 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 state or a discharging state; the control unit is further 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 fins are horizontally arranged, the first cooling channel is a circular channel, and the first cooling channel horizontally penetrates the metal fins.

[0010] Preferably, the cooling plate includes a phase change material chamber for filling the phase change material, and the phase change material chamber is an enclosed 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 material of the metal fins is 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; 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 temperature of the battery 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 the latent heat value of the phase change material; calculate the height of the phase change material chamber based on the volume and the width of the metal fin.

[0015] In a second aspect, an embodiment of the present application provides a novel phase change material lithium-ion battery pack cooling method, which is applied to the control unit of the system in the first aspect. The method includes:

[0016] The control unit is used to obtain the charge and discharge state of the battery; when the battery is in a charging state or a 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] In a third aspect, a computing device includes: a memory for storing a program; a processor for loading the program to execute the method as described in the second aspect.

[0018] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium. The computer-readable storage medium includes a stored program, wherein when the program runs, it controls the device where the computer-readable storage medium is located to execute the method as 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 fin of the present invention can completely solidify the phase change material 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 dissipated by the battery, reduce the use of the cooling unit to save energy, and ensure a lower operating cost. Description of the Drawings

[0020] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. 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 It is a schematic structural diagram of a novel phase change material lithium-ion battery pack cooling system provided by an embodiment of the present invention;

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

[0023] Figure 3 Schematic diagram of the structure of a cooling plate provided by an embodiment of the present invention;

[0024] Figure 4 Numerical verification flowchart of an electrical and thermal behavior model of a battery provided by an embodiment of the present invention;

[0025] Figure 5 Schematic diagram of an equivalent circuit of a battery provided by an embodiment of the present invention;

[0026] Figure 6 Graph of the maximum heat and maximum temperature rise generated during battery charging and discharging provided by an embodiment of the present invention; where (a) is the charging process and (b) is the discharging process;

[0027] Figure 7 Graph of the temperature field change process during the discharging process of a battery provided by an embodiment of the present invention;

[0028] Figure 8 Data schematic diagram during the charge-discharge cycle operation of a battery provided by an embodiment of the present invention, where (a) is the voltage; (b) is the generated heat; (c) is the maximum temperature of the battery; (d) is the liquid phase fraction;

[0029] Figure 9 Flow schematic diagram of a cooling method for a new type of phase change material lithium-ion battery pack provided by an embodiment of the present invention;

[0030] Figure 10 Schematic diagram of the structure of a computing device provided by an embodiment of the present invention. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

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

[0033] It should also be understood that the terms used in the specification of the present invention are merely for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

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

[0035] To solve the problem that phase change materials are not fully utilized in the prior art, the present invention provides a novel phase change material lithium-ion battery pack cooling system, method, computing device and storage medium, which can make full use of the phase change material to cool the battery, thereby reducing the amount of phase change material in the cooling system and lowering the cost.

[0036] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of a novel phase change material lithium-ion battery pack cooling system provided by an embodiment of the present application. As Figure 1 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. In Figure 1 a specific example, the system 10 includes 3 batteries 11 and 4 cooling plates 15. It can be understood that in actual applications, the system 10 may include more or fewer batteries 11 and cooling plates 15 (at least one), and the present application does not make specific limitations in this regard.

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

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

[0039] Among them, the cooling frame 14 includes a bottom plate and side plates (not shown in the figure); the cooling plates 15 are respectively connected to the bottom plate and the side plates to form a groove for accommodating the battery 11, and the size of the groove is adapted to the size of the battery 11. Specifically, please refer to Figure 2 , Figure 2 which is a schematic diagram of a cooling frame and a battery provided by an embodiment of the present application. Preferably, as Figure 2 shown, in Figure 2In a specific example, the cooling frame 14 and the cooling plate 15 can be integrally formed.

[0040] Among them, the system 10 can connect a group of identical lithium-ion batteries 11 in series. A plurality of cooling plates 15 are connected to the cooling frame 14 at equal intervals, thereby forming grooves corresponding to the size of the battery 11. The battery 11 can be inserted into the grooves, and the cooling frame 14 and the cooling plate 15 cool down the battery 11.

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

[0042] Optionally, the side surface of the cooling frame 14 can include 2 long side surfaces, or a combination of 2 long side surfaces and 2 short side surfaces.

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

[0044] Among them, the cooling plate 15 is filled with a phase change material, and metal fins are arranged inside the cooling plate 15. The metal fins are in direct contact with the phase change material, and the metal fins are provided with a first cooling channel for the coolant to flow through. For details, please refer to Figure 3 , Figure 3 which is the perspective view and cross-sectional view of the cooling plate provided by the embodiment of the present application.

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

[0046] Among them, the diameter of the circular channel can be set based on the height and width of the metal fins. Further, it can also be set in combination with the heat dissipation requirements of the system 10 and 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 closed space formed by the inner wall of the cooling plate 15 and the metal fins.

[0048] Among them, the side plate includes a second cooling channel, and the second cooling channel is respectively communicated with the cooling unit 13 and the first cooling channel.

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

[0050] Preferably, the material of the metal fins is aluminum, and the coolant is a mixture of water and ethylene glycol. It can be understood that, in addition to the mixture of water and ethylene glycol, other common liquid coolants can also be used, and the embodiments of the present application do not make specific limitations in this regard.

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

[0052] The control unit 12 is configured to obtain the charge and discharge state of the battery 11; the control unit 12 is configured to control the cooling unit 13 to stop outputting the coolant to the second cooling channel when the battery 11 is in a charging state or a discharging state; the control unit 12 is further configured 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] Among them, the battery 11 continuously generates heat during the charge and discharge process. The phase change material in the cooling plate 15 can absorb this heat and melt to keep the working temperature of the battery within a preset range. At this time, it is not necessary to cool down through the cooling unit 13; when the battery 11 is in a non-charging and non-discharging state, the cooling unit 13 outputs the cooled coolant to the second cooling channel, so that the cooled coolant can enter the first cooling channel of the metal fins, and the phase change material is solidified through the metal fins in direct contact with the phase change material, so that the phase change material can absorb heat again when the battery 11 generates heat next time. The setting of the metal fins can, on the one hand, solidify the phase change material through the first cooling channel therein, thereby repeatedly using the latent heat of the phase change material to cool the battery 11, reducing the working time of the cooling unit 13, and making the system 10 more energy-saving and environmentally friendly; on the other hand, it can also avoid the situation where the phase change material with poor thermal conductivity cannot be effectively solidified.

[0054] In the present invention, the coolant flowing through the first cooling channel in the metal fins can completely solidify the phase change material 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 dissipated by the battery, reduce the use of the cooling unit, save energy, and ensure a lower operating cost.

[0055] Further, in order to ensure that the heat absorption capacity of the phase change material can keep the operating temperature of the battery 11 within a preset range, it is also necessary to determine the volume of the phase change material based on the heat generation of the battery 11. Assuming that the density of the phase change material remains unchanged and the bottom area of the phase change material chamber is the same as that of the cooling plate 15, it can also be regarded as determining the height of the phase change material.

[0056] Preferably, the calculation method for 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 the preset temperature threshold based on this model; calculate the volume of the phase change material required to absorb this expected heat based on this expected heat, the strength value and latent heat value of the phase change material; calculate the height of the phase change material chamber based on this volume and the width of the metal fin.

[0057] It can be understood that this calculation method can be executed by any electronic device with computing power. Here, the case where a computing device executes this calculation method is taken as an example for illustration.

[0058] For reference, Figure 4 , such as Figure 4 shown, the computing device can first establish an electrical and thermal behavior model of the battery 11 and collect relevant data of the battery 11 under experimental conditions; then verify whether the operation data of this model is consistent with the experimental data, and adjust this model according to the verification result until it converges; after this model converges and can accurately represent the electrical and thermal behavior of the battery 11, the computing device then calculates the height of the phase change material cavity based on this model; then update this height into this model and verify the cooling effect.

[0059] First, the heat of a single battery 11 can be calculated. Through the energy balance equation of a single battery, the heat generation and transfer inside the battery are described;

[0060] An electrical equivalent circuit model is established through the change of state of charge, voltage relationship and voltage change of the RC network to describe the behavior of the battery cell.

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

[0062]

[0063] Among them, ρ is the density of the battery cell, C p is its heat capacity, T is the temperature, k is the thermal conductivity tensor of the battery cell, is the generated volumetric heat. The three major heat generation topics are respectively related to the electrical and electrochemical states of the outer shell: Joule heating, entropy heat or reversible heating, and irreversible heating. The present invention uses an electrical equivalent circuit model to describe the behavior of the battery cell.

[0064] In the embodiments of the present application, an electrical equivalent circuit model is used to describe the behavior of the battery cell. As Figure 5 shown, the electrical equivalent circuit model is an initial resistance (Ro) in series with double equipotential resistors - capacitors (R1 - C1 and R2 - C2). The time variation of the state of charge (soc) of the battery is as follows:

[0065]

[0066] where Q n is the nominal capacity and I(t) is the current.

[0067] In the embodiments of the present application, the voltage change V(t) and the open - circuit voltage (Uoc) are interrelated by the following relational equation:

[0068] V(t) = φ + - φ - = U oc (soc) - R 0 (soc)I(t) - V 1 (t) - V 2 (t) (3)

[0069] In the embodiments of the present application, the voltages of V1 and V2 are from:

[0070]

[0071] where i = 1, 2.

[0072] In the embodiments of the present application, the entropy of the heat generated by the battery and the irreversible heat effect are expressed by the following equations:

[0073]

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

[0075]

[0076] where σ + and σ - are the effective electrical conductivities of the positive and negative electrodes. The current balance provides a relationship between the volume shunt density and the phase potential expressed as:

[0077]

[0078] After the above - mentioned modeling of the single battery 11 is completed, its boundary conditions can be set as follows: the bottom is insulated, and all other surfaces are in contact with the environment at a temperature of 25 °C. Except for the natural convection generated around the battery, there is no air flow, so the convective heat transfer coefficient is h = 12.8 W / m 2K. The initial temperature of the battery is also 25 °C. The system of equations, together with the initial conditions and boundary conditions, is solved using the fusion method. By using a simple numerical model, the time step is 1 s, and the number of iterations for each time step is 20 times. When the difference between each time step is less than 10, the continuity equation, momentum equation, and energy equation all reach convergence.

[0079] After the modeling is completed and it is determined that the model is consistent with the experimental data, the computing device can further calculate the height of the phase change material cavity; calculating this height requires first calculating the volume of the phase change material, and calculating this volume requires first calculating the heat generation of the battery.

[0080] In the embodiment of the present application, thermal management is based on the balance between the heat generated during charging / discharging and the heat absorption of the phase change material in the aluminum shell. Considering between soc = 60% and full discharge, the energy balance of the phase change material melting is expressed as:

[0081] Q = ρ PCM L f V PCM (10)

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

[0083]

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

[0085]

[0086] In the embodiment of the present application, the system of equations in the heat generated by a single battery is completed by the energy conservation equation of the fin, and the energy conservation of the metal fin is expressed as:

[0087]

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

[0089] ΔH = βL f (14)

[0090] Where βL fis the liquid volume fraction, defined as follows:

[0091]

[0092] Wherein, 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 embodiment of the present application, the mass conservation is expressed as:

[0093]

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

[0095]

[0096] In the embodiment of the present application, the energy conservation equation is expressed as:

[0097]

[0098] Among them, S represents The viscosity constant is A mush =10 5 .

[0099] It should be noted that the phase change material wrapped around the vertical faces 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 charge / discharge process).

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

[0101] In order to better illustrate the method provided in the embodiments of the present application, a specific embodiment will be described below.

[0102] Step 1: Connect a group of identical lithium-ion battery cells in series. The cooling frame and the cooling plates with equal spacing form grooves corresponding to the battery size, and the batteries can be inserted into the grooves; the bottom plate of the cooling frame is insulated, while the top is in contact with the ambient air at 25°C, such as Figure 2 Each symmetry plane 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 focus, as this control volume represents the behavior of the entire battery pack.

[0103] Among them, the nominal capacity of each lithium-ion battery is 115 Ah, and the nominal voltage is 3.74 V. The main dimensions of the battery are (Lx = 220 mm) x (Ly = 33.2 mm) x (Lz = 102.5 mm). As shown in Table 1, the thermal characteristics of the battery are listed. The state of charge of the battery is between 1% and 97%, and the maximum voltage and cut-off voltage are 4.3 V and 2.8 V respectively.

[0104] Component <![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 Table 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, and all other surfaces are in contact with the environment at a temperature of 25 °C. There is no air flow except for natural convection generated around the battery, so the convective heat transfer coefficient is h = 12.8 W / m 2 K. The initial temperature of the battery is also 25 °C. The system of equations together with the initial conditions and boundary conditions is solved using the fusion method. By using a simple numerical model, the time step is 1 s, and the number of iterations for each time step is 20 times. When the difference between each time step is less than 10, the continuity equation, momentum equation, and energy equation all reach convergence. Structured grids are used on the battery components. A grid sensitivity study is carried out to ensure grid independence. As Figure 6 shown, Figure 6 (a) and (b) respectively show the maximum heat and maximum temperature rise generated during battery charging and discharging. The abscissa represents the state of charge. Specifically, Figure 7 shows the change in the temperature field of the battery from the start to the end of discharge.

[0107] Step 3: In terms of battery thermal management, the standard adopted in the present invention is to maintain a certain absolute temperature range of 15 °C ≤ T ≤ 35 °C, and the maximum relative temperature difference of the battery, △Tmax ≤ 5 °C. Only when the state of charge drops to -60%, the battery temperature will rise by 10 °C and reach the threshold of 35 °C. When the battery is half discharged, the relative temperature difference inside the battery will be greater than 5 °C. At the end of the discharge process, the hot spot is near the expected positive and negative electrodes. This is also the position with the highest temperature gradient inside the battery. Therefore, the present invention will calculate the required volume of the phase change material based on the heat generated by the battery during the process of discharging from 60% state of charge of the battery to the end of discharge, so that the corresponding phase change material can keep the working temperature of the battery below 35 °C under the condition of sufficient heat absorption.

[0108] Since the thermal conductivity of the phase change material is often low, horizontal metal fins with a thickness of 2 mm and a length of 7 mm are inserted into the phase change material (see Figure 3)。Although this configuration allows for the effective melting of the phase change material, the surface of the phase change material-based cooling system is mainly sandwiched in the middle and cannot solidify quickly, limiting the heat exchange with different environments. Therefore, each fin along the xy plane contains a horizontal coolant channel with a diameter of 1 mm (see Figure 3 ), and the coolant circulates after the end of discharge and before charging, and 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 properties of the corresponding materials are shown in Table 2. In addition, the latent heat of the phase change material is 241,360 J / kg, the solid phase temperature is = 300 K, and the liquid temperature is = 301 K. As shown in Table 3, the initial values and boundary conditions are provided.

[0110]

[0111] Table 2 Thermophysical properties of materials

[0112]

[0113] Table 3 Initial conditions and boundary conditions

[0114] Among them, h(T - Tamb) refers to the temperature difference between the real-time temperature of the system and the ambient temperature; P gauge refers to the gauge pressure; R e refers to the Reynolds number, n is the fluid flow rate, and q” is the fluid flow rate.

[0115] Step 4: During continuous discharge (and charging), the liquid cooling is turned off, and the thermal management is only caused by the phase change in the phase change material stage. The highest temperature reached in the battery is 34.8 °C, so it is still below the critical value. The maximum temperature difference during the entire cycle is 3.7 °C, and the error is also within the allowable 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 is discharged at a rate of 2C and then charged at the same rate. The charging and discharging are separated by 12 minutes, during which the coolant circulation is activated. Figure 8 a shows the voltage change during the process cycle, and the generated heat is as Figure 8 shown in b. The highest temperature change and the liquid phase fraction during the entire cycle are shown in Figure 8 c and Figure 8 d respectively. The thermal management strategy of the present invention keeps the battery temperature within a predetermined range.

[0117] The experimental results show that the integration of phase change material and liquid cooling can reduce the total energy consumption by 54.9% (from 0.4406 kJ to 0.1963 kJ). Therefore, the thermal management system of this solution can not only save energy but also ensure low operating costs.

[0118] The above describes the system provided by the embodiments of the present application. Next, the novel phase change material lithium-ion battery pack cooling method provided by the embodiments of the present application will be described. Please refer to Figure 9 , Figure 9 which is a schematic flowchart of a novel phase change material lithium-ion battery pack cooling method provided by the embodiments of the present application. This method is applied to the control unit of the above system and specifically includes:

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

[0120] Step 902: When the battery is in the charging state or the 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 state of neither charging nor discharging, the control unit controls the cooling unit to output the coolant to the second cooling channel to solidify the phase change material.

[0122] The method provided by the embodiments of the present application can be understood by referring to the corresponding content in the foregoing system embodiment part, and will not be repeated here.

[0123] As Figure 10 shown, Figure 10 which is a possible logical structure schematic diagram of the computing device provided by the embodiments of the present application. The computing device 1000 includes: a processor 1001, a communication interface 1002, a memory 1003, and a bus 1004. The processor 1001, the communication interface 1002, and the memory 1003 are interconnected through the bus 1004. In the embodiments of the present application, the processor 1001 is used to control and manage the actions 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 for the technologies described herein. The communication interface 1002 is used to support the communication of the computing device 1000. The memory 1003 is used to store the program code and data of the computing device 1000.

[0124] Among them, the processor 1001 can be a central processing unit, a general-purpose processor, a digital signal processor, an application-specific integrated circuit, a field-programmable gate array 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 connection 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, and so on. 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 the sake of convenience of representation, Figure 10 only a thick line is used to represent it in Figure 10 , but it 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 further provided. The computer-readable storage medium includes instructions that, when run on a computer, cause the computer to execute the above Figure 9 method described in the embodiment.

[0126] Those of ordinary skill in the art can realize that the units of each example described in connection with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the components of each example have been generally described according to their functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0127] Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the systems, devices, and units described above can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0128] In several embodiments provided by the embodiments of the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection between each other can be through some interfaces. The indirect coupling or communication connection of the device or unit can be in an electrical, mechanical, or other form.

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

[0130] In addition, in each embodiment of the present invention, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0131] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of this 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 for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present invention. And the aforementioned storage medium includes: USB flash drives, read-only memories (ROMs), random access memories (RAMs), mobile hard disks, magnetic disks, or optical discs and other various media that can store program codes.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements 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 the description of the present invention.

Claims

1. A novel phase change material lithium ion battery pack cooling system, characterized in that: The system comprises: a battery, a control unit, a cooling unit, a cooling frame and at least one cooling plate, wherein the cooling frame comprises a bottom plate and a side plate; the cooling plates are respectively connected to the bottom plate and the side plates to form a groove for accommodating the battery, and the size of the groove is adapted to the size of the battery; the cooling plate is filled with a phase change material, and a metal fin is arranged inside the cooling plate, the metal fin is in direct contact with the phase change material, and the metal fin is provided with a first cooling channel for circulating a coolant; the side plate comprises a second cooling channel, and the second cooling channel is respectively connected to the cooling unit and the first cooling channel; The control unit is used to obtain the charging and discharging status of the battery; The control unit is further used to control the cooling unit to stop outputting the coolant to the second cooling channel when the battery is in a charging state or a discharging state; The control unit is further 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.

2. The system according to claim 1, characterized in that The metal fins are arranged parallel to the ground, the first cooling channel is a circular channel, and the first cooling channel horizontally penetrates the metal fins.

3. The system according to claim 1, characterized in that The cooling plate comprises a phase change material chamber, the phase change material chamber is used to fill the phase change material, and the phase change material chamber is a closed space formed by the inner wall of the cooling plate and the metal fins.

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

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

6. The system according to claim 3, characterized in that The height of the phase change material chamber is calculated as follows: Modeling the electrical and thermal behavior of the battery; Calculating, based on the model, an expected amount of heat generated when the temperature of the battery exceeds a preset temperature threshold; Based on the expected amount of heat, the strength value and the latent heat value of the phase change material, calculating the volume of the phase change material required to absorb the expected amount of heat; Based on the volume and the width of the metal fin, the height of the phase change material chamber is calculated.

7. The system according to claim 2, characterized in that The material of the metal fin is aluminum, and the coolant is a mixture of water and ethylene glycol.

8. The system according to claim 7, characterized in that The metal fin is 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.

9. A novel phase change material lithium ion battery pack cooling method, characterized in that: A control unit applied to the system according to any one of claims 1 to 7, the method comprising: The control unit obtains the charging and discharging status of the battery in the system; The control unit controls the cooling unit to stop outputting the coolant to the second cooling channel when the battery is in a charging state or a discharging state; The control unit controls 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.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute the method according to claim 9.

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