Battery thermal management system

Abstract

The invention provides a battery thermal management system. Comprising a compressor, a first heat exchanger, an expansion valve, a first distributor, a battery heat exchange assembly, a second distributor and a control device, and in a refrigeration mode, a refrigerant sequentially passes through an outlet of the compressor, the first heat exchanger, the expansion valve, the first distributor, the battery heat exchange assembly, the second distributor and an inlet of the compressor; the control device synchronously adjusts the opening degree of the distribution port of the first distributor according to the rotating speed of the compressor. The first distributor is provided with the distribution piece capable of synchronously adjusting the opening degree of the distribution ports, the opening degree of each distribution port in the first distributor is adjusted while the rotating speed of the compressor is reduced by the system, the pipe resistance of the whole distribution pipeline is improved, and then the influence of gravity resistance on the total resistance is reduced; the flow distribution uniformity of the whole battery energy storage system is ensured, and the temperature control effect of the battery heat management system is improved.

Description

Technical Field

[0001] The invention relates to the technical field of battery energy storage, in particular to a battery thermal management system. Background Art

[0002] A battery energy storage system has multiple battery packs. Multiple branch pipes need to be provided in the circulation pipeline of the thermal management system to direct the refrigerant to each battery pack. If a flow control valve is installed on each branch pipeline, the flow rate can be ensured to be uniform, but multiple flow control valves will make the structure of the circulation pipeline complex and the equipment cost high. Therefore, in the existing circulation pipeline, the flow rate of each branch pipeline is generally distributed through a distributor.

[0003] Since the heights of each battery pack are different, the gravity pressure drops from the liquid outlet of the distributor to each battery pack are not the same, and accordingly, the gravity resistances in each distribution pipeline are different. When the rotational speed of the compressor decreases, the pipe resistance of each distribution pipeline also decreases correspondingly, and the contribution of the gravity resistance to the total resistance becomes larger, further making the flow distribution of the entire battery energy storage system more uneven, which is not conducive to the overall temperature control. Therefore, it is necessary to provide a battery thermal management system to overcome the above-mentioned defects. Summary of the Invention

[0004] The purpose of the invention is to provide a battery thermal management system.

[0005] According to one aspect of the invention, there is provided a battery thermal management system, comprising: a compressor; a first heat exchanger, the inlet of the first heat exchanger being connected to the outlet of the compressor; an expansion valve, one end of the expansion valve being connected to the outlet of the first heat exchanger; a battery heat exchange assembly, the battery heat exchange assembly comprising at least two cold plate units located at different heights, the cold plate units performing heat transfer with energy storage batteries; a first distributor, the first distributor being connected to the inlet of the battery heat exchange assembly, the first distributor comprising a confluence port, distribution ports and a distribution member, the confluence port being connected to the other end of the expansion valve, the distribution ports corresponding to the cold plate units one by one and being connected through distribution pipelines, the distribution member being capable of synchronously adjusting the opening degrees of the distribution ports; a second distributor, the second distributor being connected to the outlet of the battery heat exchange assembly, the battery heat exchange assembly being connected to the inlet of the compressor through the second distributor; a control device, the control device being in signal connection with the compressor and the first distributor. In the refrigeration mode, the refrigerant sequentially passes through the outlet of the compressor, the first heat exchanger, the expansion valve, the first distributor, the battery heat exchange assembly, the second distributor and the inlet of the compressor, and the control device synchronously adjusts the opening degrees of the distribution ports of the first distributor according to the rotational speed of the compressor.

[0006] Preferably, it also includes: a third pressure sensor, which is arranged on the confluence pipe of the second distributor and is connected to the control device by signal; in the cooling mode, the control device obtains the pressure P at the outlet of the battery heat exchange assembly 3 , the control device is at pressure P 3 The corresponding saturation temperature T P3 When the compressor speed is maintained within the third preset range, the pressure P 3 The corresponding saturation temperature T P3 When the pressure P is greater than the upper limit of the third preset range, the compressor speed is increased. 3 The corresponding saturation temperature T P3 When the speed is less than the lower limit of the third preset range, the compressor speed is reduced or even shut down.

[0007] Preferably, in the cooling mode, the control device obtains the maximum temperature T of the energy storage battery in the current state. max and the minimum temperature T min , the control device is at the maximum temperature T max and the minimum temperature T min The difference is greater than the fourth threshold T d In the case of max The size of the ratio determines the opening of the distribution port.

[0008] Preferably, the control device is configured to control the current rotation speed V and the maximum rotation speed V max When the ratio of the current rotation speed V to the maximum rotation speed V is less than the lower limit of the fourth preset range, the opening of the first distributor is adjusted to the first state, and the control device adjusts the opening of the first distributor to the first state when the current rotation speed V is less than the maximum rotation speed V max When the ratio of the current rotation speed V to the maximum rotation speed V is within the fourth preset range, the opening of the first distributor is adjusted to the second state. max When the ratio of is greater than the upper limit of the fourth preset range, the opening of the first distributor is adjusted to the third state and the maximum temperature T of the energy storage battery in the current state is re-acquired. max and the minimum temperature T min , the opening degree of the distribution port of the first distributor gradually decreases in the first state, the second state and the third state.

[0009] Preferably, it also includes: a third temperature sensor, which is arranged on the confluence pipe of the second distributor and is connected to the control device by signal; in the cooling mode, the control device obtains the pressure P at the outlet of the battery heat exchange component 3 and temperature T 3 , the control device is at temperature T 3 With pressure P 3 The corresponding saturation temperature T P3When the difference between them is within the first preset range, maintain the current opening degree of the expansion valve. When the temperature T 3 and the pressure P 3 corresponding saturation temperature T P3 When the difference between them is greater than the upper limit value of the first preset range, increase the opening degree of the expansion valve. When the temperature T 3 and the pressure P 3 corresponding saturation temperature T P3 When the difference between them is less than the lower limit value of the first preset range, decrease the opening degree of the expansion valve.

[0010] Preferably, it further includes: a first pressure sensor, the first pressure sensor is arranged at the outlet of the compressor and is in signal connection with the control device; in the refrigeration mode, the control device obtains the pressure P at the outlet of the compressor 1 , and when the pressure P 1 corresponding saturation temperature T P1 is greater than the upper limit value of the second preset range, turn on the fan equipped with the first heat exchanger. When the pressure P 1 corresponding saturation temperature T P1 is less than the lower limit value of the second preset range, turn off the fan equipped with the first heat exchanger.

[0011] Preferably, a liquid receiver is further arranged between the expansion valve and the first distributor, and the liquid inlet and the liquid outlet of the liquid receiver are both arranged at the bottom of the liquid receiver.

[0012] Preferably, the lengths and cross-sectional areas of the distribution pipelines are the same, the distribution pipelines have the same number and type of elbow structures, and the difference in the total resistance of each distribution pipeline at the maximum flow rate is controlled within 5%.

[0013] Preferably, it further includes: a second heat exchanger, the inlet of the second heat exchanger is connected to the outlet of the compressor, and the outlet of the second heat exchanger is connected to the confluence port of the second distributor; a fourth heat exchanger, the fourth heat exchanger includes a first passage and a second passage that are independent of each other and can exchange heat with each other; the inlet of the first passage is connected to the outlet of the first heat exchanger, the outlet of the first passage is connected to one end of the expansion valve, the inlet of the second passage is connected to the confluence port of the second distributor, and the outlet of the second passage is connected to the outlet of the compressor; a third heat exchanger, the third heat exchanger is an electric heating device, the inlet of the third heat exchanger is connected to the inlet of the first passage, and the outlet of the second heat exchanger is connected to the inlet of the compressor.

[0014] Preferably, in the heating mode, the refrigerant sequentially passes through the outlet of the compressor, the second heat exchanger, the second distributor, the battery heat exchange component, the first distributor, the liquid accumulator, the expansion valve, the fourth heat exchanger, the third heat exchanger, and the inlet of the compressor; in the cooling mode, the refrigerant sequentially passes through the outlet of the compressor, the first heat exchanger, the first passage of the fourth heat exchanger, the expansion valve, the first distributor, the battery heat exchange component, the second distributor, the second passage of the fourth heat exchanger, and the inlet of the compressor.

[0015] Preferably, it further includes: a second pressure sensor, which is arranged at the inlet of the compressor and is signal-connected to the control device; a second temperature sensor, which is arranged at the inlet of the compressor and is signal-connected to the control device; in the heating mode, the control device obtains the pressure P of the intake air of the compressor 2 and the temperature T 2 , the control device, when the difference between the temperature T 2 and the saturation temperature T corresponding to the pressure P 2 is within the fifth preset range, maintains the current opening degree of the expansion valve; when the difference between the temperature T P2 and the saturation temperature T corresponding to the pressure P 2 is greater than the upper limit value of the fifth preset range, increases the opening degree of the expansion valve; when the difference between the temperature T 2 and the saturation temperature T corresponding to the pressure P P2 is less than the lower limit value of the fifth preset range, reduces the rotational speed of the compressor or even closes the opening degree of the expansion valve. 2 and the saturation temperature T corresponding to the pressure P 2 is less than the lower limit value of the fifth preset range, reduces the rotational speed of the compressor or even closes the opening degree of the expansion valve. P2 is less than the lower limit value of the fifth preset range, reduces the rotational speed of the compressor or even closes the opening degree of the expansion valve.

[0016] Preferably, it further includes: a first temperature sensor, which is arranged at the outlet of the compressor and is signal-connected to the control device; a third temperature sensor, which is arranged on the confluence pipeline of the second distributor and is signal-connected to the control device; a third pressure sensor, which is arranged on the confluence pipeline of the second distributor and is signal-connected to the control device; in the heating mode, the control device obtains the pressure T at the outlet of the compressor 1、 the pressure P at the inlet of the battery heat exchange component 3 and the temperature T 3 , when the pressure T 1 is greater than the sixth threshold and the difference between the temperature T 3 and the saturation temperature T corresponding to the pressure P 3 is greater than the upper limit value of the sixth preset range, the fan equipped with the second heat exchanger is turned on; when the pressure T P3 is less than the seventh threshold or the temperature T 1 is less than the seventh threshold or the temperature T 3 and the saturation temperature T corresponding to the pressure P3 The corresponding saturation temperature T P3 When the difference is less than the lower limit value of the sixth preset range, the fan equipped with the second heat exchanger is turned off.

[0017] Compared with the prior art, the battery thermal management system provided by the invention has the following beneficial effects: By providing a distributor on the first distributor that can synchronously adjust the opening degree of the distribution ports, when the system reduces the rotational speed of the compressor, the opening degrees of the distribution ports in the first distributor are adjusted simultaneously, increasing the pipe resistance of the entire distribution pipeline, thereby reducing the influence of gravity resistance on the total resistance, ensuring the uniformity of the flow distribution of the entire battery energy storage system, and improving the temperature control effect of the battery thermal management system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention will be further described in detail below in conjunction with the drawings and specific embodiments:

[0019] Figure 1 It is a schematic diagram of the principle of the battery thermal management system in Embodiment 1 of the invention;

[0020] Figure 2 It is a schematic diagram of the structure of the first distributor and the first structure of the distribution pipeline in Embodiment 1 of the invention;

[0021] Figure 3 It is a schematic diagram of the structure of the second structure of the first distributor and the distribution pipeline in the invention;

[0022] Figure 4 It is a schematic diagram of the second structure of the distribution pipeline in the invention ( Figure 3 partial enlarged view at A in

[0023] Figure 5 It is a schematic diagram of the first structure of the first distributor in the invention;

[0024] Figure 6 It is a schematic diagram of the second structure of the first distributor in the invention;

[0025] Figure 7 It is a schematic diagram of the internal structure of the second structure of the first distributor in the invention;

[0026] Figure 8 It is a schematic diagram of the principle of the battery thermal management system in Embodiment 2 of the invention;

[0027] Figure 9 It is a schematic diagram of the principle of the battery thermal management system in Embodiment 2 of the invention in the refrigeration mode;

[0028] Figure 10 It is a schematic diagram of the principle of the battery thermal management system in Embodiment 2 of the invention in the heating mode;

[0029] Figure 11 It is a schematic structural diagram of the mode switching unit in Embodiment 2 of the invention.

[0030] Figure 12 It is a control logic diagram of the battery thermal management system in the refrigeration mode in Embodiment 3 of the invention;

[0031] Figure 13 It is a control logic diagram of the mode switching unit in the refrigeration mode in Embodiment 3 of the invention;

[0032] Figure 14 It is a control logic diagram of the battery thermal management system in the heating mode in Embodiment 3 of the invention.

[0033] Explanation of reference numerals:

[0034] 10. Compressor; 11. Gas-liquid separator;

[0035] 20. Mode switching unit; D. First valve port; C. Second valve port; S. Third valve port; E. Fourth valve port;

[0036] 31. First heat exchanger; 32. Second heat exchanger; 33. Third heat exchanger; 34. Fourth heat exchanger; 341. First passage; 342. Second passage;

[0037] 40. Expansion valve; 41. First filter; 42. Second filter;

[0038] 50. Receiver;

[0039] 60. Battery heat exchange assembly; 61. Cold plate unit; 62. Energy storage battery;

[0040] 70. First distributor; 71. Mixing chamber; 711. Arc structure; 72. Confluence port; 721. Jet ring; 73. Distribution port; 74. Distributor; 741. Tapered valve core; 742a. Arc-shaped pipe; 742b. Distribution hole; 75. Actuator; 76. Distribution pipeline; 761. First pipeline; 762. Second pipeline; 763. Third pipeline; 764. First elbow; 765. Second elbow;

[0041] 80. Second distributor;

[0042] 910. Solenoid valve; 921. First stop valve; 922. Second stop valve; 931. First check valve; 932. Second check valve; 933. Third check valve; 934. Fourth check valve;

[0043] P1, the first pressure sensor; P2, the second pressure sensor; P3, the third pressure sensor; P4, the fourth pressure sensor; T1, the first temperature sensor; T2, the second temperature sensor; T3, the third temperature sensor; T4, the fourth temperature sensor; T5, the fifth temperature sensor; T6, the sixth temperature sensor. Detailed implementation mode

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0045] To make the drawings concise, only the parts related to the invention are schematically shown in each drawing, and they do not represent the actual structure of the product. Additionally, to make the drawings concise and easy to understand, in some drawings, components with the same structure or function are only schematically shown for one of them, or only one of them is marked. In this article, "one" not only means "only this one", but also means "more than one" situation.

[0046] It should also be further understood that the term "and / or" used in the description of this application 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.

[0047] In this article, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0048] In addition, in the description of this application, the terms "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the invention or the prior art, the following will describe the specific implementation mode of the invention with reference to the drawings. Obviously, the drawings in the following description are only some embodiments of the invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings, and other implementation modes can also be obtained.

[0050] Embodiment 1

[0051] See Figure 1 , this embodiment discloses a battery thermal management system, including: a compressor 10, a first heat exchanger 31, an expansion valve 40, a liquid storage tank 50, a first distributor 70, a battery heat exchange assembly 60 and a second distributor 80.

[0052] The inlet of the first heat exchanger 31 is connected to the outlet of the compressor 10, one end of the expansion valve 40 is connected to the outlet of the first heat exchanger 31, the battery heat exchange assembly 60 includes a plurality of cold plate units 61 located at different heights, the cold plate units 61 transfer heat with the energy storage battery 62, the first distributor 70 is connected to the inlet of the battery heat exchange assembly 60, the first distributor 70 includes a confluence port 72, a plurality of distribution ports 73 and a distribution member 74, the confluence port 72 is connected to the other end of the expansion valve 40, the distribution ports 73 are in one-to-one correspondence with the cold plate units 61 and are connected through distribution pipelines 76, the distribution member 74 can synchronously adjust the opening degrees of the distribution ports 73, the second distributor 80 is connected to the outlet of the battery heat exchange assembly 60, and the battery heat exchange assembly 60 is connected to the inlet of the compressor 10 through the second distributor 80.

[0053] In the refrigeration mode, the low-temperature and low-pressure gaseous refrigerant (10°C to 30°C) outputs a high-temperature and high-pressure gaseous refrigerant (45 to 100°C) after the work of the compressor 10, condenses through the first heat exchanger 31, and converts the incoming high-temperature and high-pressure gaseous refrigerant into a medium-temperature and high-pressure liquid refrigerant (30°C to 60°C). Then, the pressure energy of the refrigerant is converted into kinetic energy through the expansion valve 40 to obtain a low-temperature and low-pressure two-phase refrigerant (10°C to 25°C). The low-temperature and low-pressure two-phase refrigerant is evenly distributed to each cold plate unit 61 through the first distributor 70. The low-temperature and low-pressure two-phase refrigerant evaporates in the cold plate unit 61 and absorbs the heat generated by the energy storage battery 62, becoming a low-temperature and low-pressure gaseous refrigerant (10°C to 25°C). The low-temperature and low-pressure gaseous refrigerant is discharged from the cold plate unit 61 and re-enters the compressor 10 through the second distributor 80 to complete the refrigeration cycle.

[0054] It can be understood that the gravity resistance is one of the total resistances of each distribution pipeline 76. The gravity resistance of the distribution pipeline 76 of the lowermost cold plate unit 61 is the smallest, and the corresponding total resistance is also smaller than the total resistances of other distribution pipelines 76. When the rotational speed of the compressor 10 is reduced, the pipe resistance of the distribution pipeline 76 is also correspondingly reduced, and the influence of the gravity resistance in the distribution pipeline 76 on the total resistance is increased.

[0055] In this embodiment, reducing the rotational speed of the compressor 10 synchronously adjusts the opening degrees of the distribution ports 73 in the first distributor 70. By adjusting the opening degrees of the distribution ports 73, the pipe resistance of the entire distribution pipeline 76 is increased, thereby reducing the influence of the gravity resistance on the total resistance, ensuring the flow distribution uniformity of the entire battery energy storage system, and improving the temperature control effect of the battery thermal management system.

[0056] Refer to the appendix Figure 1 Figure 1 , a liquid receiver 50 is further provided between the expansion valve 40 and the first distributor 70, and the liquid inlet and the liquid outlet of the liquid receiver 50 are both provided at the bottom of the liquid receiver 50. After the low-temperature and low-pressure two-phase refrigerant enters the liquid receiver 50, more low-temperature liquid refrigerant will accumulate in the lower part, and more low-temperature liquid refrigerant is introduced from the outlet of the liquid receiver 50 into the confluence port 72 of the first distributor 70, which is beneficial to the uniform distribution of the first distributor 70 and improves the temperature control effect of the battery thermal management system.

[0057] Refer to the appendix Figure 2 、 3 3 , in order to ensure the consistency of the total resistance of each distribution pipeline 76, the length and cross-sectional area of the distribution pipeline 76 are the same, so that the pipe resistance in each distribution pipeline 76 is basically equal, thereby improving the uniformity of the refrigerant flow rate.

[0058] The length of the distribution pipeline 76 is positively correlated with the height difference between the uppermost cold plate unit 61 and the lowermost cold plate unit 61. According to the friction coefficient between the refrigerant and the wall of the distribution pipeline 76 and the height difference between the uppermost cold plate unit 61 and the lowermost cold plate unit 61, the minimum length of the distribution pipeline 76 can be calculated. By extending the length of each distribution pipeline 76, the total resistance of the distribution pipeline 76 is increased, so that the difference in the total resistance of each distribution pipeline 76 at the maximum flow rate is controlled within 5%, thereby improving the uniformity of the refrigerant flow rate.

[0059] Refer to the appendix Figure 2 Figure 2 , the distribution pipeline 76 includes a first pipeline 761 connected to the cold plate unit 61 and horizontally arranged, a second pipeline 762 connected to the distribution port 73 and vertically arranged, and a third pipeline 763 connecting the first pipeline 761 and the second pipeline 762. Since the first distributor 70 is located at the upper part of the entire energy storage system, in the distribution pipeline 76 at the lowermost layer, the first pipeline 761 extends downward along the distribution port 73, then bends horizontally to form the first pipeline 761, and is connected to the cold plate unit 61 through the first pipeline 761. In the distribution pipeline 76 at other layers, the first pipeline 761 extends downward along the distribution port 73, first bends upward according to the height of the cold plate unit 61 to form the third pipeline 763, then bends horizontally to form the first pipeline 761, and is connected to the cold plate unit 61 through the first pipeline 761.

[0060] Refer to the appendix Figure 3 、 4In another embodiment, the distribution pipelines 76 have the same number and type of elbow structures, a first elbow 764 with a 180° angle is formed between the second pipeline 762 and the third pipeline 763 in all the distribution pipelines 76, a second elbow 765 with a 90° angle is formed between the second pipeline 762 and the first pipeline 761, the first elbow 764 forms the third pipeline 763 through the first elbow 764 according to the height position of the cold plate unit 61, and then the third pipeline 763 forms the second pipeline 762 through the second elbow 765 at a position flush with the cold plate unit 61, ensuring that each distribution pipeline 76 has the same first elbow 764 and second elbow 765 under the premise of having the same length, so that the local pipe resistance in each distribution pipeline 76 is basically equal, further improving the uniformity of the refrigerant flow.

[0061] This embodiment provides two exemplary structures of the distribution member 74. In the first structure, refer to the attached Figure 5 The distribution member 74 includes a plurality of conical valve cores 741 which are arranged at the distribution port 73 and partially inserted into the distribution port 73. The distributor is transmission-connected to the actuator 75. The actuator 75 drives the conical valve core 741 to move relative to the distribution port 73. The opening of the distribution port 73 is adjusted by controlling the gap between the conical valve core 741 and the distribution port 73.

[0062] In the second structure, see Appendix Figure 6 , 7 A mixing chamber 71 is formed inside the first distributor 70, and the confluence port 72 and the distribution port 73 are connected to the mixing chamber 71. The distribution member 74 is arranged in the mixing chamber 71. The inner surface of the first distributor 70 is an arc structure 711, and the distribution ports 73 are arranged side by side on the arc structure 711. The distribution member 74 includes an arc surface pipe 742a that fits the arc structure 711, and a plurality of distribution holes 742b that are arranged on the arc surface pipe 742a and correspond to the distribution ports 73 one by one. The distribution member 74 is connected to the actuator 75 in a transmission manner. The actuator 75 drives the arc surface pipe 742a to rotate relative to the distribution port 73, and adjusts the opening of the distribution port 73 by controlling the overlap between the distribution holes 742b and the distribution port 73.

[0063] See attached Figure 7 A jet ring 721 is provided on the confluence port 72. The aperture of the jet ring 721 is smaller than that of the confluence port 72. The flow channel area is reduced by the jet ring 721 structure, and the flow velocity of the low-temperature and low-pressure two-phase refrigerant entering the mixing chamber 71 is increased. The gas-liquid two-phase flow is more likely to form a symmetrically distributed annular flow, thereby improving the uniformity of the diversion.

[0064] When the rotational speed of the compressor 10 changes, the control method of the system includes the following steps: S1. Obtain the highest temperature and the lowest temperature of the current state of the energy storage battery 62, and obtain the current rotational speed of the compressor 10; S2. Calculate whether the difference between the highest temperature and the lowest temperature is greater than a first threshold. If so, execute step S3; if not, maintain the current state; S3. Determine whether the current rotational speed of the compressor 10 is less than a second threshold. If so, adjust the opening degree of the first distributor 70 to a first state; if not, execute step S4; S4. Determine whether the current rotational speed of the compressor 10 is less than a third threshold, where the third threshold is greater than the second threshold. If so, adjust the opening degree of the first distributor 70 to a second state; if not, adjust the opening degree of the first distributor 70 to a third state and return to step S1; the opening degrees of the first distributor 70 in the first state, the second state, and the third state gradually decrease.

[0065] Embodiment 2

[0066] Embodiment 1 provides a battery thermal management system, mainly introducing the refrigeration mode. In actual use, the system needs to be used in combination with the heating mode. Embodiment 2 provides a battery thermal management system on the basis of Embodiment 1, and the system includes a heating mode and a refrigeration mode.

[0067] Refer to the appendix Figures 8 to 10 In this embodiment, a battery thermal management system is disclosed, including: a compressor 10, a mode switching unit 20, a gas-liquid separator 11, a first heat exchanger 31, a second heat exchanger 32, a third heat exchanger 33, a fourth heat exchanger 34, an expansion valve 40, a liquid storage tank 50, a first distributor 70, a second distributor 80, and a battery heat exchange assembly 60.

[0068] Refer to the appendix Figure 11 In this embodiment, the mode switching unit 20 selects a four-way valve. The four-way valve changes the flow direction of the refrigerant, thereby realizing a convenient switch between the refrigeration function and the heating function of the energy storage thermal management system. Specifically, the four-way valve includes a first valve port D, a second valve port C, a third valve port S, and a fourth valve port E. In the heating mode, the first valve port D is communicated with the fourth valve port E, and the second valve port C is communicated with the third valve port S; in the refrigeration mode, the first valve port D is communicated with the second valve port C, and the fourth valve port E is communicated with the third valve port S.

[0069] The inlet of the compressor 10 is connected to the third valve port S, the outlet of the compressor 10 is communicated with the first valve port D, and a gas-liquid separator 11 is provided between the compressor 10 and the third valve port S. The compressor 10 is used to pressurize the refrigerant and discharge high-temperature and high-pressure gaseous refrigerant. The gas-liquid separator 11 is used to separate gas from liquid.

[0070] The inlet of the first heat exchanger 31 is connected to the second valve port C, and the outlet of the first heat exchanger 31 is connected to the first channel. A blower is provided outside the first heat exchanger 31. Driven by the blower, the relatively low-temperature outdoor air will flow through the outside of the pipes of the first heat exchanger 31 and exchange heat with the high-temperature refrigerant inside the first heat exchanger 31.

[0071] The inlet of the second heat exchanger 32 is connected to the fourth valve port E, and the outlet of the second heat exchanger 32 is connected to the second channel. Similarly, a blower is provided outside the second heat exchanger 32. Driven by the blower, the relatively low-temperature outdoor air will flow through the outside of the pipes of the second heat exchanger 32 and exchange heat with the high-temperature refrigerant inside the second heat exchanger 32.

[0072] The fourth heat exchanger 34 includes a first passage 341 and a second passage 342 that are independent of each other and can exchange heat with each other. Specifically, the inlet of the first passage 341 is connected to the outlet of the first heat exchanger 31, the outlet of the first passage 341 is connected to one end of the expansion valve 40, the inlet of the second passage 342 is connected to the confluence port 72 of the second distributor 80, and the outlet of the second passage 342 is connected to the outlet of the compressor 10.

[0073] In the refrigeration mode, the low-temperature and low-pressure gaseous refrigerant passing through the second passage 342 is used to cool the medium-temperature and high-pressure liquid refrigerant in the first channel, and at the same time, complete evaporation of itself is achieved, avoiding the residue of liquid refrigerant and preventing the hydraulic refrigerant from entering the inside of the compressor 10.

[0074] The inlet of the third heat exchanger 33 is connected to the first passage 341, and the outlet of the third heat exchanger 33 is connected to the second valve port C, that is, the third heat exchanger 33 is arranged in parallel with the first heat exchanger 31, reducing the system resistance, thereby reducing the power consumption of the whole machine.

[0075] The third heat exchanger 33 is an electric heating device, which integrates a refrigerant flow channel, an electric heater, and a spoiler. After the refrigerant absorbs the heat of the electric heating, it transfers the heat to the battery, and there is no need for defrosting, avoiding the phenomenon of frosting on the evaporator during operation at low temperatures. The heating capacity is stable, not affected by the ambient temperature, and can stably heat at extremely low ambient temperatures, and the lowest ambient temperature can be as low as -40°C.

[0076] The battery heat exchange assembly 60 includes a plurality of cold plate units 61 located at different heights, and the cold plate units 61 transfer heat to and from the energy storage battery 62. The distribution port 73 of the first distributor 70 is connected to the inlet of the battery heat exchange assembly 60, and the confluence port 72 of the first distributor 70 is connected to the expansion valve 40. The distribution port 73 of the second distributor 80 is connected to the outlet of the battery heat exchange assembly 60. In the refrigeration mode, the confluence port 72 of the second distributor 80 is connected to the second channel, and in the heating mode, the confluence port 72 of the second distributor 80 is connected to the second heat exchanger 32.

[0077] The first distributor 70 can adjust the opening degree or the main pipe resistance entering each cold plate unit 61 according to the rotational speed of the compressor 10. For the specific structure of the first distributor 70, refer to Embodiment 1 and will not be elaborated here. There is no such requirement for the second distributor 80.

[0078] The expansion valve 40 and the accumulator 50 are both arranged on the pipeline between the first passage 341 and the battery heat exchange assembly 60. The expansion valve 40 is located between the first passage 341 and the accumulator 50. A first filter 41 and a second filter 42 are respectively arranged on both sides of the expansion valve 40 to prevent impurities from entering the expansion valve 40 and blocking the expansion valve 40 in the refrigeration mode or the heating mode.

[0079] Both the liquid inlet and the liquid outlet of the accumulator 50 are arranged at the bottom of the accumulator 50. After the low-temperature and low-pressure two-phase refrigerant enters the accumulator 50, more low-temperature liquid refrigerant will accumulate in the lower part. More low-temperature liquid refrigerant is introduced from the outlet of the accumulator 50 into the confluence port 72 of the first distributor 70, which is beneficial to the uniform distribution of the first distributor 70 and improves the temperature control effect of the battery thermal management system.

[0080] To realize the switching between the heating mode and the refrigeration mode, there is a solenoid valve 910 between the inlet of the first heat exchanger 31 and the third valve port S. A first one-way valve 931 that only allows the refrigerant to flow unidirectionally from the first heat exchanger 31 to the first passage 341 is arranged at the inlet of the first heat exchanger 31. A second one-way valve 932 that only allows the refrigerant to flow unidirectionally to the cold plate unit is arranged at the outlet of the second heat exchanger 32. A third one-way valve 933 that only allows the refrigerant to flow unidirectionally to the mode switching unit 20 is arranged at the outlet of the third heat exchanger 33. A fourth one-way valve 934 that only allows the refrigerant to flow unidirectionally to the mode switching unit 20 is arranged on the pipeline between the second passage 342 and the fourth valve port E. A first stop valve 921 is arranged on the pipeline between the refrigerant end of the heat exchange module and the accumulator 50. A second stop valve 922 is arranged on the overlapping pipeline between the second heat exchanger 32, the second passage 342 and the hot end of the cold plate unit.

[0081] In the heating mode, refer to the appendix Figure 9 , the refrigerant sequentially passes through the outlet of the compressor 10, the mode switching unit 20 (the first valve port D and the fourth valve port E are conducted), the second heat exchanger 32, the battery heat exchange assembly 60, the accumulator 50, the expansion valve 40, the fourth heat exchanger 34, the third heat exchanger 33, the mode switching unit 20 (the second valve port C and the third valve port S are conducted), and the inlet of the compressor 10.

[0082] In the refrigeration mode, refer to the appendix Figure 10, the refrigerant sequentially passes through the outlet of the compressor 10, the mode switching unit 20 (the first valve port D is communicated with the second valve port C), the first heat exchanger 31, the first passage 341 of the fourth heat exchanger 34, the expansion valve 40, the liquid storage device 50, the battery heat exchange assembly, the second passage 342 of the fourth heat exchanger 34, the mode switching unit 20 (the fourth valve port E is communicated with the third valve port S), and the inlet of the compressor 10.

[0083] Embodiment 3

[0084] To ensure the stable operation of the system, based on Embodiment 2, this system is also provided with a plurality of temperature sensors and a plurality of pressure sensors, and the pressure sensors and temperature sensors are electrically connected or signal-connected to the control device of the system. A first temperature sensor T1 is provided at the outlet of the compressor 10, a second temperature sensor T2 is provided at the inlet of the gas-liquid separator 11, a third temperature sensor T3 is provided between the connection of the second heat exchanger 32 and the second passage 342 of the fourth heat exchanger 34 and the second shut-off valve 922, a fourth temperature sensor T4 is provided between the liquid storage device 50 and the first shut-off valve 921, a fifth temperature sensor T5 is provided near the first heat exchanger 31, and a sixth temperature sensor T6 is provided on the third heat exchanger 33.

[0085] A first pressure sensor P1 is provided at the outlet of the compressor 10, a second pressure sensor P2 is provided at the inlet of the gas-liquid separator 11, a third pressure sensor P3 is provided between the connection of the second heat exchanger 32 and the second passage 342 and the second shut-off valve 922, and a fourth pressure sensor P4 is provided between the liquid storage device 50 and the first shut-off valve 921.

[0086] The first temperature sensor T1 and the first pressure sensor P1 are respectively used to detect the exhaust temperature and pressure of the compressor 10, the second temperature sensor T2 and the second pressure sensor P2 are respectively used to detect the intake temperature and pressure of the compressor 10, the third temperature sensor T3 and the third pressure sensor P3 are respectively used to detect the refrigerant temperature and pressure at the outlet of the cold plate in the refrigeration mode, the fourth temperature sensor T4 and the fourth pressure sensor P4 are respectively used to detect the refrigerant temperature and pressure at the inlet of the cold plate in the refrigeration mode, the fifth temperature sensor T5 is used to detect the ambient temperature; the sixth temperature sensor T6 is used to detect the temperature of the third heat exchanger 33 to prevent the third heat exchanger 33 from having a thermal runaway due to excessive temperature.

[0087] Refer to the appendix Figure 12 , the control device communicates with the upper computer through R485 to collect the highest temperature T max and the lowest temperature T min , the control device when the highest temperature T max is greater than the first threshold and the lowest temperature T minWhen it is greater than the second threshold, the control mode switching unit turns on the heating mode and turns on the compressor 10. Among them, both the first threshold and the second threshold are empirical values, which are set according to the appropriate operating temperature of the energy storage battery.

[0088] In the refrigeration mode, the control device obtains the pressure P at the outlet of the battery heat exchange component 60 3 and the temperature T 3 . When the difference between the temperature T 3 and the saturation temperature T 3 corresponding to the pressure P P3 is within the first preset range, the current opening of the expansion valve 40 is maintained. When the difference between the temperature T 3 and the saturation temperature T 3 corresponding to the pressure P P3 is greater than the upper limit value of the first preset range, the opening of the expansion valve 40 is increased. When the difference between the temperature T 3 and the saturation temperature T 3 corresponding to the pressure P P3 is less than the lower limit value of the first preset range, the opening of the expansion valve 40 is decreased. In this embodiment, the first preset range is an empirical value, and the first preset range is (-1, 1].

[0089] In the refrigeration mode, the control device obtains the pressure P at the outlet of the compressor 10 1 . When the saturation temperature T 1 corresponding to the pressure P P1 is greater than the upper limit value of the second preset range, the fan equipped with the first heat exchanger 31 is turned on, and the adjustment of the fan speed is realized through PID control. When the saturation temperature T 1 corresponding to the pressure P P1 is less than the lower limit value of the second preset range, the fan equipped with the first heat exchanger 31 is turned off. In this embodiment, the second preset range is an empirical value, and the second preset range is [28, 35].

[0090] In the refrigeration mode, the control device obtains the pressure P at the outlet of the battery heat exchange component 60 3 . When the saturation temperature T 3 corresponding to the pressure P P3 is within the third preset range, the rotation speed of the compressor 10 is maintained. When the saturation temperature T 3 corresponding to the pressure P P3 is greater than the upper limit value of the third preset range, the rotation speed of the compressor 10 is increased. When the saturation temperature T 3 corresponding to the pressure P P3When the value is less than the lower limit of the third preset range, the rotational speed of the compressor 10 is decreased or the compressor 10 is even turned off. In this embodiment, the third preset ranges are all empirical values, and the third preset range is [13, 15]. Additionally, a third threshold is also set below the lower limit of the third preset range. When the pressure P 3 corresponding saturation temperature T P3 is less than the third threshold, the compressor is turned off, and the third threshold is 10.

[0091] Refer to the attached Figure 13 , in the refrigeration mode, the control device acquires the highest temperature T max and the lowest temperature T min of the current state of the energy storage battery. When the difference between the highest temperature T max and the lowest temperature T min is greater than the fourth threshold T d , the control device determines the opening degree of the distribution port according to the ratio of the current rotational speed V of the compressor 10 to the maximum rotational speed V max .

[0092] When the ratio of the current rotational speed V to the maximum rotational speed V max is less than the lower limit of the fourth preset range, the control device adjusts the opening degree of the first distributor 70 to the first state. When the ratio of the current rotational speed V to the maximum rotational speed V max is within the fourth preset range, the control device adjusts the opening degree of the first distributor 70 to the second state. When the ratio of the current rotational speed V to the maximum rotational speed V max is greater than the upper limit of the fourth preset range, the control device adjusts the opening degree of the first distributor 70 to the third state and re-acquires the highest temperature T max and the lowest temperature T min of the current state of the energy storage battery. The fourth preset range is [0.5, 0.7], and the opening degrees of the distribution ports of the first distributor 70 in the first state, the second state, and the third state gradually decrease.

[0093] Refer to the attached Figure 14 , the control device communicates with the upper computer through R485, acquires the highest temperature T max and the lowest temperature T min of the current state of the energy storage battery. When the lowest temperature T min is less than the fifth threshold T c , the control mode switching unit and the solenoid valve turn on the heating mode and turn on the third heat exchanger and the compressor. The fifth threshold T c is set according to the operating temperature of the energy storage battery.

[0094] In the heating mode, the control device acquires the intake pressure P 2 and the temperature T 2, the control device is at temperature T 2 With pressure P 2 The corresponding saturation temperature T P2 When the difference between the values ​​of the expansion valve 40 and the expansion valve 40 is within the fifth preset range, the current opening of the expansion valve 40 is maintained. 2 With pressure P 2 The corresponding saturation temperature T P2 When the difference between the values ​​of the expansion valve 40 and the expansion valve 40 is greater than the upper limit of the fifth preset range, the expansion valve 40 is opened at the temperature T 2 With pressure P 2 The corresponding saturation temperature T P2 When the difference between the values ​​is less than the lower limit of the fifth preset range, the compressor speed is reduced or even the opening of the expansion valve 40 is closed. In this embodiment, the fifth preset range is a set range, for example, the fifth preset range is [-0.5, 0.5].

[0095] In the heating mode, the control device obtains the pressure T at the outlet of the compressor 10 1、 Pressure P at the inlet of the battery heat exchange component 3 and temperature T 3 , the control device is at pressure T 1 is greater than the sixth threshold and the temperature T 3 With pressure P 3 The corresponding saturation temperature T P3 When the difference between the pressure and the load is greater than the upper limit of the sixth preset range, the fan equipped with the second heat exchanger 32 is turned on, and the fan speed is adjusted through PID control. 1 Less than the seventh threshold or temperature T 3 With pressure P 3 The corresponding saturation temperature T P3 When the difference is less than the lower limit of the sixth preset range, the fan equipped with the second heat exchanger 32 is turned off. In this embodiment, the sixth threshold value, the seventh threshold value, and the sixth preset range are all empirical values, and the second threshold value is greater than the third threshold value. For example, the second threshold value is 30, the seventh threshold value is 25, and the sixth preset range can be the same as the first preset range. The sixth preset range is (-1, 1].

[0096] In the heating mode, the control device obtains the pressure P at the inlet of the battery heat exchange assembly 60 3 , the control device is at pressure P 3 The corresponding saturation temperature T P3 When the pressure is greater than the eighth threshold, the compressor 10 is shut down to protect the system. In this embodiment, the eighth threshold is an empirical value, for example, the eighth threshold is 40.

[0097] The system adjusts the rotational speed of the compressor 10, the opening degree of the distribution port 73 of the first distributor 70, the rotational speed of the blower, the opening degree of the expansion valve 40, and the power of the electric heating device according to the parameters detected by each sensor. Each of these parameters has a suitable stable operating range. Deviating from this range may cause damage to the system components. The control system continuously adjusts the rotational speed of the compressor 10, the rotational speed of the blower, the opening degree of the expansion valve 40, the on / off of the electric heating, etc. to maintain these parameters within the corresponding ranges.

[0098] It will be apparent to those skilled in the art that various modifications and variations can be made to the above-described exemplary embodiments of the invention without departing from the spirit and scope of the invention. Accordingly, it is intended that the invention cover modifications and variations of the invention falling within the scope of the appended claims and their equivalent technical solutions.

Claims

1. A battery thermal management system, characterized in that: include: compressor; a first heat exchanger, wherein an inlet of the first heat exchanger is connected to an outlet of the compressor; an expansion valve, one end of which is connected to an outlet of the first heat exchanger; A battery heat exchange assembly, the battery heat exchange assembly is connected to the other end of the expansion valve, the battery heat exchange assembly comprises at least two cold plate units located at different heights, the cold plate units and the energy storage battery realize heat transfer; a first distributor, the first distributor being connected to the inlet of the battery heat exchange assembly, the first distributor comprising a confluence port, a distribution port and a distribution member, the confluence port being connected to the other end of the expansion valve, the distribution port corresponding to the cold plate unit one by one and connected through a distribution pipeline, and the distribution member being capable of synchronously adjusting the opening of the distribution port; a second distributor, wherein the second distributor is connected to the outlet of the battery heat exchange assembly, and the battery heat exchange assembly is connected to the inlet of the compressor through the second distributor; A control device is connected to the compressor and the first distributor by signal. In the cooling mode, the refrigerant passes through the compressor outlet, the first heat exchanger, the expansion valve, the first distributor, the battery heat exchange component, the second distributor and the compressor inlet in sequence. The control device synchronously adjusts the distribution port opening of the first distributor according to the rotation speed of the compressor.

2. The battery thermal management system according to claim 1, characterized in that: Also includes: A third temperature sensor, which is disposed on the confluence pipe of the second distributor and is signal-connected to the control device; In the cooling mode, the control device obtains the pressure P3 and temperature T3 at the outlet of the battery heat exchange component, and the control device generates a saturation temperature T corresponding to the temperature T3 and the pressure P3. P3 When the difference between the values ​​of temperature T3 and pressure P3 is within the first preset range, the current opening of the expansion valve is maintained, and the saturation temperature T corresponding to the temperature T3 and the pressure P3 is maintained. P3 When the difference between the temperature T3 and the pressure P3 is greater than the upper limit of the first preset range, the expansion valve opening is increased, and the saturation temperature T corresponding to the temperature T3 and the pressure P3 is increased. P3 When the difference between the values ​​is less than the lower limit of the first preset range, the expansion valve opening is reduced.

3. The battery thermal management system according to claim 2, characterized in that: Also includes: a first pressure sensor, the first pressure sensor being disposed at the compressor outlet and being signal-connected to the control device; In the cooling mode, the control device obtains the pressure P1 at the outlet of the compressor, and the control device controls the saturation temperature T corresponding to the pressure P1. P1 When the pressure P1 is greater than the upper limit of the second preset range, the fan equipped with the first heat exchanger is turned on, and the saturation temperature T corresponding to the pressure P1 is P1 When the temperature is less than the lower limit of the second preset range, the fan equipped with the first heat exchanger is turned off.

4. The battery thermal management system according to claim 3, characterized in that: Also includes: A third pressure sensor, which is disposed on the confluence line of the second distributor and is signal-connected to the control device; In the cooling mode, the control device obtains the pressure P3 at the outlet of the battery heat exchange component, and the control device controls the saturation temperature T corresponding to the pressure P3. P3 When the compressor speed is maintained within the third preset range, the saturation temperature T corresponding to the pressure P3 is P3 When the pressure P3 is greater than the upper limit of the third preset range, the compressor speed is increased, and the saturation temperature T corresponding to the pressure P3 is increased. P3 When the speed of the compressor is less than the lower limit of the third preset range, the compressor speed is reduced or the compressor is turned off.

5. The battery thermal management system according to claim 4, characterized in that: In the cooling mode, the control device obtains the maximum temperature T of the current state of the energy storage battery max and the minimum temperature T min , the control device is at the maximum temperature T max and the minimum temperature T min The difference is greater than the fourth threshold T d In the case of max The size of the ratio determines the opening of the distribution port.

6. The battery thermal management system according to claim 5, characterized in that: The control device is configured to control the current rotation speed V and the maximum rotation speed V max When the ratio of the current rotation speed V to the maximum rotation speed V is less than the lower limit of the fourth preset range, the opening of the first distributor is adjusted to the first state, and the control device adjusts the opening of the first distributor to the first state when the current rotation speed V is less than the maximum rotation speed V max When the ratio of the current rotation speed V to the maximum rotation speed V is within the fourth preset range, the opening of the first distributor is adjusted to the second state. max When the ratio of is greater than the upper limit of the fourth preset range, the opening of the first distributor is adjusted to the third state and the maximum temperature T of the energy storage battery in the current state is re-acquired. max and the minimum temperature T min , the opening degree of the distribution port of the first distributor gradually decreases in the first state, the second state and the third state.

7. The battery thermal management system according to claim 1, characterized in that: A liquid reservoir is further provided between the expansion valve and the first distributor, and a liquid inlet and a liquid outlet of the liquid reservoir are both provided at the bottom of the liquid reservoir.

8. The battery thermal management system according to claim 1, characterized in that: The distribution pipelines have the same length and cross-sectional area, have the same number and type of elbow structures, and the difference in total resistance of the distribution pipelines at maximum flow is controlled within 5%.

9. The battery thermal management system according to claim 1, characterized in that: Also includes: a second heat exchanger, wherein the inlet of the second heat exchanger is connected to the outlet of the compressor, and the outlet of the second heat exchanger is connected to the confluence port of the second distributor; a fourth heat exchanger, the fourth heat exchanger comprising a first passage and a second passage which are independent of each other and can exchange heat with each other; an inlet of the first passage is connected to an outlet of the first heat exchanger, an outlet of the first passage is connected to one end of the expansion valve, an inlet of the second passage is connected to a confluence port of the second distributor, and an outlet of the second passage is connected to an outlet of the compressor; a third heat exchanger, wherein the third heat exchanger is an electric heating device, an inlet of the third heat exchanger is connected to the inlet of the first passage, and an outlet of the second heat exchanger is connected to the inlet of the compressor; In the heating mode, the refrigerant passes through the outlet of the compressor, the second heat exchanger, the second distributor, the battery heat exchange assembly, the first distributor, the liquid reservoir, the expansion valve, the fourth heat exchanger, the third heat exchanger and the inlet of the compressor in sequence; In cooling mode, the refrigerant passes through the outlet of the compressor, the first heat exchanger, the first passage of the fourth heat exchanger, the expansion valve, the first distributor, the battery heat exchange assembly, the second distributor, the second passage of the fourth heat exchanger and the inlet of the compressor in sequence.

10. The battery thermal management system according to claim 9, characterized in that: Also includes: A second pressure sensor, the second pressure sensor is arranged at the compressor inlet and is signal-connected to the control device; A second temperature sensor, the second temperature sensor is arranged at the compressor inlet and is signal-connected to the control device; In the heating mode, the control device obtains the pressure P2 and temperature T2 of the intake air of the compressor, and the control device adjusts the saturation temperature T corresponding to the temperature T2 and the pressure P2. P2 When the difference between the values ​​of temperature T2 and pressure P2 is within the fifth preset range, the current opening of the expansion valve is maintained, and the saturation temperature T corresponding to the temperature T2 and the pressure P2 is maintained. P2 When the difference between the temperature T2 and the pressure P2 is greater than the upper limit of the fifth preset range, the expansion valve opening is increased, and the saturation temperature T corresponding to the temperature T2 and the pressure P2 is increased. P2 When the difference between the values ​​of the expansion valve and the speed of the compressor is smaller than the lower limit value of the fifth preset range, the compressor speed is reduced or the expansion valve opening is closed.

11. The battery thermal management system according to claim 10, characterized in that: Also includes: a first temperature sensor, the first temperature sensor being disposed at the compressor outlet and being signal-connected to the control device; A third temperature sensor, which is disposed on the confluence pipe of the second distributor and is signal-connected to the control device; A third pressure sensor, which is disposed on the confluence line of the second distributor and is signal-connected to the control device; In the heating mode, the control device obtains the pressure T at the compressor outlet 1、 The pressure P3 and temperature T3 at the inlet of the battery heat exchange component, the control device when the pressure T1 is greater than the sixth threshold and the temperature T3 is the saturation temperature T corresponding to the pressure P3 P3 When the difference between the pressure T1 and the temperature T3 is greater than the upper limit of the sixth preset range, the fan equipped with the second heat exchanger is turned on, and when the pressure T1 is less than the seventh threshold value or the temperature T3 is greater than the saturation temperature T corresponding to the pressure P3, the fan equipped with the second heat exchanger is turned on. P3 When the difference is less than the lower limit value of the sixth preset range, the fan equipped with the second heat exchanger is turned off.

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