Open cathode PEMFC electric pile temperature adjusting system and adjusting method

Abstract

The invention belongs to the field of fuel cell temperature control equipment, and particularly discloses an open cathode PEMFC electric pile temperature adjusting system and method, the system comprises a first airflow conveying mechanism and a second airflow conveying mechanism which are symmetrically arranged on the two sides of an electric pile body, the first airflow conveying mechanism comprises a plurality of first fans arranged in the vertical direction, and the second airflow conveying mechanism comprises a plurality of second fans arranged in the vertical direction; the second airflow conveying mechanism comprises a plurality of second fans arranged in the vertical direction, the airflow directions of the first fans and the airflow directions of the second fans are parallel to a cathode runner of the electric pile body, and the airflow directions of the first fans and the airflow directions of the second fans are the same or opposite. The first fan and the second fan can generate airflow in the same or opposite directions, heat dissipation in the cathode flow channel is enhanced so as to reduce the temperature, or an airflow stagnation point is located in the cathode flow channel so as to maintain the temperature and realize temperature rise, so that temperature adjustment of the galvanic pile body is realized, and relatively good use performance of the galvanic pile body is maintained.

Description

Technical Field

[0001] The present application belongs to the field of fuel cell temperature control equipment, and more specifically, to an open cathode PEMFC stack temperature regulation system and regulation method. Background Art

[0002] Proton exchange membrane fuel cell (PEMFC) is an important carrier for the application of hydrogen energy technology. It has the advantages of high efficiency, fast start-up and zero emissions. It has broad application prospects in transportation, fixed power stations and portable power sources.

[0003] An open cathode proton exchange membrane fuel cell is a type of proton exchange membrane fuel cell. In existing open cathode air-cooled fuel cells, the cathode flow channel and the cooling channel are the same channel, or the cooling channel and the cathode flow channel are separated, and a fan is installed at the inlet side of the cathode flow channel. The fan blows in air to provide reaction gas to the stack through the cathode flow channel while cooling the stack. The membrane electrode of the open cathode air-cooled fuel cell is directly exposed to the air by passing through the open cathode flow channel, and its performance will be affected when used in high and low temperature environments.

[0004] The temperature of an open cathode proton exchange membrane fuel cell is of great significance to the efficiency and service life of the fuel cell. If the temperature of an open cathode proton exchange membrane fuel cell is too low, the liquid water produced during the electrochemical reaction will undergo a phase change at an extremely low temperature, condense into ice, and destroy the membrane electrode structure, causing irreversible damage to the battery. However, excessively high temperatures can cause the internal temperature of the battery to be too high, thermal management to be out of control, local overheating, and even membrane electrode sintering. Therefore, an open cathode PEMFC stack temperature regulation system and regulation method are urgently needed. Summary of the invention

[0005] In view of the defects of the prior art, the present application provides an open cathode PEMFC stack temperature regulation system and regulation method, aiming to solve the problem that open cathode proton exchange membrane fuel cells are prone to damage when used in high or low temperature environments.

[0006] The present application provides an open cathode PEMFC stack temperature regulation system, which specifically includes a first airflow conveying mechanism and a second airflow conveying mechanism symmetrically arranged on both sides of the stack body, wherein the first airflow conveying mechanism includes a plurality of first fans arranged in a vertical direction, and the second airflow conveying mechanism includes a plurality of second fans arranged in a vertical direction, and the airflow directions of the first fan and the second fan are both parallel to the cathode flow channel of the stack body, and the airflow directions of the first fan and the second fan are the same or opposite.

[0007] Through the above technical scheme conceived by the present application, compared with the prior art, since starting the first fan and the second fan can generate airflows in the same or opposite directions, the airflows enter the cathode flow channel. In a high temperature environment, when the airflow directions are the same, the wind pressure and airflow velocity in the cathode flow channel are increased, the heat dissipation is improved, and the temperature of the battery stack body is reduced; in a low temperature environment, when the airflow directions are opposite, the stagnation points of the two airflows are located in the cathode flow channel, so that oxygen is supplied to the cathode of the battery stack body while keeping the heat of the battery stack from being lost, so as to maintain the temperature of the battery stack body or increase the temperature, thereby realizing temperature regulation of the battery stack body and maintaining its good performance when used in high or low temperature environments.

[0008] As further preferred, the number of the first fans is the same as the number of the second fans, and the position of each of the first fans corresponds to that of the second fans.

[0009] By adopting the above technical solution, the airflows generated by the first fan and the second fan can correspond to each other, so that the two corresponding airflows can form a stagnation point inside the cathode flow channel, or can improve the effect of increasing the wind pressure and airflow velocity in the cathode flow channel, thereby improving the temperature regulation effect of the battery stack body.

[0010] As a further preference, a plurality of the first fans and the second fans are evenly and equidistantly arranged.

[0011] By adopting the above technical solution, the airflow generated by the first fan and the second fan is evenly distributed, and the airflow can evenly enter the cathode flow channel of the fuel cell stack, so that the temperature regulation effect of the fuel cell stack is better.

[0012] As a further preference, at least three of the first fans and the second fans are provided and are respectively located at the top, middle and bottom of the side of the stack body.

[0013] By adopting the above technical solution, the layout of the first fan and the second fan can generate the same or relative airflow at the top, middle and bottom of the side of the battery stack body, further achieving uniform distribution of the airflow.

[0014] As further preferred, the temperature regulation system further includes a temperature sensing module and a control module, and the temperature sensing module and the first fans and second fans are electrically connected to the control module.

[0015] By adopting the above technical solution, after the temperature sensing module monitors the temperature, the control module can automatically control the first fan and the second fan according to the monitored temperature data to change the airflow direction and wind speed, thereby achieving temperature regulation of the battery stack body and improving the automation of the system.

[0016] A method for regulating the temperature of an open cathode PEMFC stack is implemented using the above-mentioned temperature regulation system, and comprises the following steps:

[0017] S1: starting a plurality of first fans and a second fan to allow air flow to enter the cathode flow channel;

[0018] S2: adjusting the airflow directions of the first fan and the second fan according to the use environment of the battery stack body;

[0019] If the use environment is a low temperature environment, adjusting the airflow directions of the first fan and the second fan to be opposite;

[0020] If the use environment is a normal temperature or high temperature environment, adjust the airflow directions of the first fan and the second fan to be the same;

[0021] S3: adjusting the wind speeds of the first fan and the second fan according to the temperature of the use environment to achieve temperature regulation of the fuel cell stack body.

[0022] As further preferred, in step S2, the temperature of the low temperature environment is X, and X≤0°C.

[0023] By adopting the above technical solution, in a low temperature environment of 0°C or below, in order to ensure the normal use of the fuel cell stack, the airflow directions of the first fan and the second fan are adjusted to be relative to each other so that the airflow stagnation point is located inside the cathode flow channel, so that the temperature of the fuel cell stack body is increased, thereby being able to maintain the temperature required for normal operation.

[0024] As further preferred, in step S2, the temperature of the high temperature environment is Y, and Y≥30°C, and the temperature of the normal temperature environment is Z, and 30°C>Z>0°C.

[0025] By adopting the above technical solution, in a high temperature environment of 30°C or above, in order to accelerate the heat dissipation of the battery stack body, the airflow directions of the first fan and the second fan are adjusted to be the same, the wind pressure in the cathode flow channel is superimposed, the airflow velocity is increased, the heat in the cathode flow channel can be dissipated quickly, and the temperature of the battery stack body is reduced.

[0026] As further preferred, in step S3, when the temperature T of the use environment is less than -10°C, the wind speeds of the first fans or the second fans are equal, and there is a wind speed difference between the wind speed of the first fan and the wind speed of the second fan;

[0027] When the temperature of the use environment is 0℃≥T≥-10℃, the wind speed of the first fan is equal to the corresponding second fan, and the wind speed of the first fan or the second fan located in the middle position is greater than the wind speed of the first fan or the second fan located at the top and bottom.

[0028] By adopting the above technical scheme, in a low temperature environment of 0℃~-10℃, the operating temperature of the battery stack body presents a distribution with high in the middle and low at both ends, and the wind speed of the first fan or the second fan at the top and the bottom is lower than the wind speed of the first fan or the second fan at the middle position. Since the wind speed at the top and the bottom is relatively low, the cold air carried by the airflow blown in by the fan is not enough to resist the along-the-way loss in the cathode flow channel, and at the same time, the heat inside the cathode flow channel will not cause heat loss with the flow of the airflow, so that the airflow stagnation point position of the first fan and the second fan can be heated up; since the wind speed in the middle is relatively high, more cold air enters the cathode flow channel, and an airflow stagnation point is formed in the middle, so that the airflow stagnation point position can be cooled, so that the overall temperature of the battery stack body presents a relatively uniform distribution, avoiding local overheating and local hypothermia;

[0029] In a low temperature environment below -10°C, the airflow generated by the first fan and the airflow generated by the second fan form a stagnation point inside the cathode flow channel, and due to the wind speed difference between the first fan and the second fan, the positions of the airflow stagnation points are different. The airflow with a higher wind speed has a longer stroke, and the cold air blown in is used to resist the loss along the way, so that the airflow stagnation point position inside the battery stack body is heated up. By adjusting the wind speed of the first fan and the wind speed of the second fan, different positions can be heated evenly, achieving a dynamic balance of heat, thereby improving the normal operation efficiency of the battery stack body.

[0030] As further preferred, in the step S3, when the temperature of the use environment is 30°C>T>0°C, the wind speeds of the first fan and the second fan are uniform;

[0031] When the temperature T of the use environment is ≥30° C., the wind speeds of the first fan and the second fan increase as the temperature rises.

[0032] By adopting the above technical solution, under normal temperature environment, the first fan and the second fan rotate at a uniform speed so that the airflow passes through the cathode flow channel to meet the heat dissipation of the battery stack body. When the temperature rises to 30°C or above, the wind speed of the first fan and the second fan rises and increases with the temperature, thereby increasing the airflow velocity to accelerate the heat dissipation of the battery stack body.

[0033] In general, the above technical solutions conceived by this application have the following technical advantages compared with the prior art:

[0034] 1. Since starting the first fan and the second fan can generate airflows in the same or opposite directions, the airflows enter the cathode flow channel. In a high temperature environment, when the airflow directions are the same, the wind pressure and airflow velocity in the cathode flow channel are increased, heat dissipation is improved, and the temperature of the battery stack body is reduced; in a low temperature environment, when the airflow directions are opposite, the stagnation points of the two airflows are located in the cathode flow channel, so that oxygen is supplied to the cathode of the battery stack body while keeping the heat of the battery stack from being lost, so as to maintain the temperature of the battery stack body or increase the temperature, thereby achieving temperature regulation of the battery stack body and maintaining its good performance when used in high or low temperature environments.

[0035] 2. In the present application, when in a low temperature environment of 0℃~-10℃, since the operating temperature of the battery stack body is high in the middle and low at both ends, the wind speed of the first fan or the second fan at the top and the bottom is lower than the wind speed of the first fan or the second fan in the middle. Since the wind speed at the top and the bottom is relatively low, the cold air carried by the airflow blown in by the fan is not enough to resist the along-the-way loss in the cathode flow channel. At the same time, the heat inside the cathode flow channel will not cause heat loss with the flow of the airflow, and the airflow stagnation point of the first fan and the second fan can be heated up. Since the wind speed in the middle is relatively high, more cold air enters the cathode flow channel and an airflow stagnation point is formed in the middle, which can cool the airflow stagnation point and make the overall temperature of the battery stack body more evenly distributed, thus avoiding local overheating and local hypothermia.

[0036] 3. In the present application, when in a low temperature environment below -10°C, the airflow generated by the first fan and the airflow generated by the second fan form a stagnation point inside the cathode flow channel, and due to the wind speed difference between the wind speed of the first fan and the wind speed of the second fan, the positions of the airflow stagnation points are different. The airflow with a higher wind speed has a longer stroke, and the cold air blown in is used to resist the loss along the way, so that the airflow stagnation point position inside the battery stack body is heated up. By adjusting the wind speed of the first fan and the wind speed of the second fan, different positions can be heated evenly, achieving a dynamic balance of heat, thereby improving the normal operation efficiency of the battery stack body. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the overall structure of the temperature adjustment system provided in the embodiment of the present application;

[0038] Figure 2 It is a schematic diagram of the overall structure of the first fan and the second fan provided in the embodiment of the present application, in which the airflow directions of the first fan and the second fan are opposite and the wind speeds are the same;

[0039] Figure 3 It is a schematic diagram of the overall structure in which the airflow directions of the first fan and the second fan provided in the embodiment of the present application are opposite and there is a wind speed difference;

[0040] Figure 4is a schematic diagram of an overall structure in which the first fan and the second fan provided in an embodiment of the present application have the same airflow direction;

[0041] Figure 5 It is a flow chart of the temperature adjustment method provided in the embodiment of the present application.

[0042] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0043] 1. Battery stack body; 11. Cathode flow channel; 2. First airflow conveying mechanism; 21. First fan; 3. Second airflow conveying mechanism; 31. Second fan. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0045] Reference Figure 1 An open cathode PEMFC stack temperature regulation system disclosed in the present application includes a first airflow conveying mechanism 2, a second airflow conveying mechanism 3, a temperature sensing module and a control module, wherein the first airflow conveying mechanism 2 and the second airflow conveying mechanism 3 are symmetrically arranged on both sides of the stack body 1 with a cylindrical structure, specifically, they are respectively located at the inlet and outlet of the cathode flow channel on the stack body 1, the first airflow conveying mechanism 2 includes a plurality of first fans 21 arranged in a vertical direction, the second airflow conveying mechanism 3 includes a plurality of second fans 31 arranged in a vertical direction, the airflow directions of the first fan 21 and the second fan 31 are both parallel to the cathode flow channel 11 of the stack body 1, and the airflow directions of the first fan 21 and the second fan 31 are the same or opposite. When the stack body 1 is located in a high-temperature environment, the airflow directions are the same, increasing the wind pressure and airflow velocity in the cathode flow channel 11, improving heat dissipation, and reducing the temperature of the stack body 1; when the stack body 1 is in a low-temperature environment, the airflow directions are opposite, and the stagnation points of the two airflows are located in the cathode flow channel 11, so as to supply oxygen to the cathode of the stack body 1 while keeping the heat of the stack from being lost, so as to maintain the temperature of the stack body 1 or increase the temperature, thereby achieving temperature regulation of the stack body 1.

[0046] Specifically, the number of first fans 21 and the number of second fans 31 are the same, and the positions of each first fan 21 and the second fan 31 correspond to each other, that is, one first fan 21 corresponds to one second fan 31 in the horizontal direction, and the first fans 21 and the second fans 31 are evenly arranged at equal distances.

[0047] More specifically, at least three first fans 21 and second fans 31 are provided, and in the present embodiment, four are provided. One first fan 21 is located at the top of one side of the stack body 1, two first fans 21 are located in the middle of one side of the stack body 1, one first fan 21 is located at the bottom of one side of the stack body 1, and four second fans 31 are provided on the other side of the stack body 1 and correspond to the positions of the first fans 21.

[0048] Furthermore, the temperature sensing module and the first fans 21 and the second fans 31 are electrically connected to the control module. After the temperature sensing module monitors the temperature, the control module can automatically control the first fans 21 and the second fans 31 according to the monitored temperature data to change the airflow direction and wind speed of the first fans 21 and the second fans 31, thereby realizing automatic temperature adjustment of the battery stack body 1. The temperature sensing module and the control module adopt temperature sensors and controllers commonly used in this field.

[0049] Reference Figure 5 The present application discloses an open cathode PEMFC stack temperature regulation method, comprising the following steps:

[0050] S1: Simultaneously start a plurality of first fans 21 and second fans 31 on both sides of the stack body 1 to allow airflow to enter the cathode flow channel 11;

[0051] S2: adjusting the airflow directions of the first fan 21 and the second fan 31 according to the use environment of the fuel cell stack body 1;

[0052] Reference Figure 2-3 If the use environment is a low temperature environment, the airflow directions of the first fan 21 and the second fan 31 are adjusted to be opposite; specifically, the temperature of the low temperature environment is X, and X≤0°C;

[0053] Reference Figure 4 If the operating environment is a normal temperature environment or a high temperature environment, adjust the airflow directions of the first fan 21 and the second fan 31 to be the same; specifically, the temperature of the high temperature environment is Y, and Y≥30°C, the temperature of the normal temperature environment is Z, and 30°C>Z>0°C, the airflow directions of the first fan 21 and the second fan 31 are the same, the wind pressure in the cathode flow channel 11 is superimposed, the airflow velocity is increased, the heat in the cathode flow channel 11 can be quickly dissipated, and the stack body 1 is cooled.

[0054] S3: Adjust the wind speed of the first fan 21 and the second fan 31 according to the ambient temperature to achieve temperature regulation of the stack body 1; for details, refer to Figure 3When the temperature T of the operating environment is less than -10°C, the wind speeds of the first fans 21 or the second fans 31 are equal, and there is a wind speed difference between the wind speed of the first fan 21 and the wind speed of the second fan 31. The airflow generated by the first fan 21 and the airflow generated by the second fan 31 form a stagnation point inside the cathode flow channel 11. Since there is a wind speed difference between the wind speed of the first fan 21 and the wind speed of the second fan 31, the positions of the airflow stagnation points are different. The airflow with a higher wind speed has a longer stroke, and the cold air blown in is used to resist the loss along the way, so that the airflow stagnation point position inside the battery stack body 1 is heated up. By adjusting the wind speed of the first fan 21 and the wind speed of the second fan 31, different positions can be evenly heated, and the dynamic balance of the heat of the battery stack body 1 can be achieved.

[0055] Reference Figure 2 When the temperature of the operating environment is 0℃≥T≥-10℃, since the operating temperature of the battery stack body 1 is high in the middle and low at both ends, the wind speed of the first fan 21 is equal to the corresponding second fan 31, and the wind speed of the two first fans 21 or the second fans 31 located in the middle is greater than the wind speed of the first fan 21 or the second fan 31 located at the top and the bottom. Since the wind speed at the top and the bottom is relatively low, the cold air carried by the airflow blown in by the fan is not enough to resist the along-the-way loss in the cathode flow channel 11. At the same time, the heat inside the cathode flow channel 11 will not cause heat loss with the flow of the airflow, so that the airflow stagnation point position of the first fan 21 and the second fan 31 can be heated up; since the wind speed in the middle is relatively high, more cold air enters the cathode flow channel 11, and an airflow stagnation point is formed in the middle, which can cool the airflow stagnation point position, so that the overall temperature of the battery stack body 1 is relatively evenly distributed, avoiding local overheating and local hypothermia.

[0056] When the temperature of the operating environment is a normal temperature environment of 30℃>T>0℃, the wind speeds of the first fan 21 and the second fan 31 are uniform, and the airflow passing through the cathode flow channel can meet the heat dissipation of the battery stack body; when the temperature of the operating environment T≥30℃, the wind speeds of the first fan 21 and the second fan 31 increase with the increase in temperature, thereby increasing the airflow velocity to accelerate the heat dissipation of the battery stack body.

[0057] It should be understood that expressions such as "include" and "may include" used in this application indicate the existence of the disclosed functions, operations or constituent elements, and do not limit one or more additional functions, operations and constituent elements. In this application, terms such as "include" and / or "have" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components or combinations thereof.

[0058] It should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0059] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0060] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like 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 a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0061] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. An open cathode PEMFC stack temperature control system, characterized in that: The invention comprises a first airflow conveying mechanism (2) and a second airflow conveying mechanism (3) which are symmetrically arranged on both sides of a battery stack body (1); the first airflow conveying mechanism (2) comprises a plurality of first fans (21) arranged in a vertical direction; the second airflow conveying mechanism (3) comprises a plurality of second fans (31) arranged in a vertical direction; the airflow directions of the first fan (21) and the second fan (31) are both parallel to the cathode flow channel (11) of the battery stack body (1); and the airflow directions of the first fan (21) and the second fan (31) are the same or opposite.

2. An open cathode PEMFC stack temperature regulation system as claimed in claim 1, characterized in that: The number of the first fans (21) and the number of the second fans (31) are the same, and the positions of each of the first fans (21) and the second fans (31) correspond to each other.

3. An open cathode PEMFC stack temperature regulation system as claimed in claim 2, characterized in that: A plurality of the first fans (21) and the second fans (31) are uniformly arranged at equal distances.

4. An open cathode PEMFC stack temperature regulation system as claimed in claim 2, characterized in that: At least three of the first fans (21) and the second fans (31) are provided and are respectively located at the top, middle and bottom of the side of the stack body (1).

5. An open cathode PEMFC stack temperature regulation system according to any one of claims 1 to 4, characterized in that: The temperature regulating system further comprises a temperature sensing module and a control module. The temperature sensing module and a plurality of the first fans (21) and the second fans (31) are all electrically connected to the control module.

6. A method for regulating the temperature of an open cathode PEMFC stack, implemented by using the temperature regulation system according to any one of claims 1 to 5, characterized in that: The steps include: S1: starting a plurality of first fans (21) and second fans (31) to allow airflow to enter the cathode flow channel (11); S2: adjusting the airflow directions of the first fan (21) and the second fan (31) according to the use environment of the battery stack body (1); If the use environment is a low temperature environment, the airflow directions of the first fan (21) and the second fan (31) are adjusted to be opposite; If the use environment is a normal temperature or high temperature environment, the airflow directions of the first fan (21) and the second fan (31) are adjusted to be the same; S3: adjusting the wind speed of the first fan (21) and the second fan (31) according to the temperature of the use environment, so as to achieve temperature regulation of the battery stack body (1).

7. An open cathode PEMFC stack temperature regulation system as claimed in claim 6, characterized in that: In step S2, the temperature of the low temperature environment is X, and X≤0°C.

8. An open cathode PEMFC stack temperature regulation system as claimed in claim 6, characterized in that: In step S2, the temperature of the high temperature environment is Y, and Y≥30°C, and the temperature of the normal temperature environment is Z, and 30°C>Z>0°C.

9. An open cathode PEMFC stack temperature regulation system as claimed in claim 6, characterized in that: In the step S3, when the temperature T of the use environment is less than -10°C, the wind speeds of the first fans (21) or the second fans (31) are all equal, and there is a wind speed difference between the wind speed of the first fan (21) and the wind speed of the second fan (31); When the temperature of the use environment is 0°C ≥ T ≥ -10°C, the wind speed of the first fan (21) is equal to the wind speed of the corresponding second fan (31), and the wind speed of the first fan (21) or the second fan (31) located in the middle is greater than the wind speed of the first fan (21) or the second fan (31) located at the top and the bottom.

10. An open cathode PEMFC stack temperature regulation system as claimed in claim 6, characterized in that: In the step S3, when the temperature of the use environment is 30°C>T>0°C, the wind speeds of the first fan (21) and the second fan (31) are uniform; When the temperature T of the use environment is ≥30°C, the wind speeds of the first fan (21) and the second fan (31) increase as the temperature rises.

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