Spray heat dissipation system for fuel cell vehicle and control method thereof

Abstract

The invention discloses a spraying heat dissipation system for a fuel cell vehicle. The spraying heat dissipation system comprises a spraying device, a heat dissipation device and a controller. The spraying device and the heat dissipation device are arranged adjacent to each other. And the spraying device and the heat dissipation device are connected to the fuel cell. The spraying device is arranged to be not in direct heat conduction with the heat dissipation device. The spraying device is arranged to recycle water in waste gas of the fuel cell and spray the water to the heat dissipation device as a spraying medium, so that heat dissipation is performed on the heat dissipation device by means of phase change of the spraying medium. The heat dissipation device comprises a heat dissipation device with the angle adjustable relative to the spraying device, and the heat dissipation power is changed by changing the angle of the heat dissipation device. And the controller is electrically connected to the spraying device and the heat dissipation device. The invention further discloses a control method for the spray heat dissipation system.

Description

Technical Field

[0001] The present application relates to the field of fuel cells, and particularly relates to a spray cooling system for a fuel cell vehicle and a control method for the spray cooling system. Background Art

[0002] Fuel cell vehicles (FCVs) have inherent advantages such as short charging (e.g., hydrogen refueling) time, high energy density, strong adaptability to low-temperature environments, and large amount of waste heat utilization. However, their development still faces numerous obstacles. With the rapid development of fuel cell technology, higher-power fuel cells will be applied to vehicles, which will pose a huge challenge to the thermal management of FCVs.

[0003] In a proton exchange membrane fuel cell vehicle, approximately 95% of the heat generated by the stack needs to be taken away by the cooling medium. Since the operating temperature of the fuel cell is not much different from the ambient temperature, compared with traditional vehicles, an FCV of the same power level requires a larger radiator.

[0004] Currently, most of the cooling systems for FCVs adopt the forced air cooling (convective heat transfer) method. By increasing the air volume of the fan, the flow rate of the coolant, and adding air deflectors, the heat dissipation capacity of the vehicle can be improved. However, increasing the rotational speeds of the water pump and the fan will also increase the power and noise of the accessories; for a vehicle with a determined structure, adding air deflectors cannot significantly improve the heat dissipation capacity. Therefore, it is necessary to introduce a new cooling method to improve the heat dissipation capacity.

[0005] As a powerful and effective cooling method, spray cooling is widely used in large heat exchange equipment such as steel rolling, turbines, and high heat flux electronic devices (such as computer chips, sensors, and lasers). For traditional vehicles using spray cooling, the problems of how to replenish and recycle the spray liquid will be faced. In contrast, the working product of an FCV is water, which means that the spray cooling system can be designed as an open system. For an FCV, extreme operating conditions (such as climbing a slope in a high-temperature environment) must be considered when designing the thermal management system. In this case, the fuel cell generates a large amount of heat, more water is generated at the cathode, and at the same time the vehicle speed is low, resulting in it being difficult for the FCV to be cooled by the traditional convective heat dissipation method. Therefore, spray cooling is particularly suitable for such FCVs. Summary of the Invention

[0006] To solve the above technical problems, the present application proposes a spray cooling system for a fuel cell vehicle. Compared with the convective heat exchange system used in the prior art, the spray cooling system further improves the heat dissipation effect of the fuel cell vehicle. The present application also proposes a control method for the spray cooling system. The control method obtains a greater heat dissipation power by controlling the spray cooling system to spray in an intermittent manner, and at the same time can save the consumption of the spray medium. The control method also solves the problem of easily forming a water film between the fins of the radiator during the spraying process by co-controlling the spray interval time and the windward angle of the radiator.

[0007] The present application discloses a spray cooling system for a fuel cell vehicle. The fuel cell vehicle includes a fuel cell. Wherein, the spray cooling system includes a spray device, a heat dissipation device and a controller. It is characterized in that the spray device and the heat dissipation device are arranged adjacent to each other. Among them, the spray device and the heat dissipation device are connected to the fuel cell, and the spray device is arranged not to conduct direct heat conduction with the heat dissipation device; the spray device is configured to recover water in the exhaust gas of the fuel cell and spray it onto the heat dissipation device as a spray medium, so as to dissipate heat from the heat dissipation device by means of the phase change of the spray medium; the heat dissipation device includes a radiator whose angle is adjustable relative to the spray device, and is configured to change the heat dissipation power by changing the angle of the radiator; and the controller is electrically connected to the spray device and the heat dissipation device.

[0008] The present application also discloses a control method for the spray cooling system. The control method includes the following steps: S101: Calculate the spray duration according to the inlet temperature, outlet temperature and coolant flow rate of the radiator of the heat dissipation device, the ambient temperature and ambient relative humidity of the air system, the spray medium temperature, spray medium flow rate and spray medium liquid film coverage rate of the spray device, and the vehicle speed V from the controller area network of the fuel cell vehicle; and S102: When the outlet temperature of the radiator exceeds the maximum coolant inlet temperature of the fuel cell stack of the fuel cell vehicle, start the spray device and adjust the windward angle of the radiator, and then stop the spray device when the running time of the spray device exceeds the spray duration; wherein, the windward angle is obtained according to the spray duration and the vehicle speed V from the controller area network of the fuel cell vehicle.

[0009] The spray cooling system for a fuel cell vehicle according to the present application sprays a spray medium onto the radiator through the spray device and uses the phase change of the spray medium to dissipate heat. Compared with the forced convective heat exchange used in the prior art, the phase change heat dissipation further improves the heat dissipation effect.

[0010] The control method for the spray cooling system according to the present application calculates the spray interval time and the spray duration based on the relevant parameters of the spray cooling system and other components of the fuel cell, and causes the spraying device to spray at the specific spray interval time and spray duration. Compared with continuous spraying, intermittent spraying can utilize the latent heat of evaporation of the liquid film during the spray interval time to obtain a greater cooling power, and at the same time can also save the consumption of the spray medium.

[0011] When the radiator adopts a plate-fin radiator, due to the narrow fin spacing of the radiator, it is very easy to form a water film between the fins of the radiator during the spraying process, which will reduce the air intake of the radiator. The control method for the spray cooling system according to the present application solves this problem by coordinately controlling the spray interval time and the windward angle of the radiator. Description of the Drawings

[0012] The foregoing and other aspects of the present application can be more comprehensively understood from the following detailed description in conjunction with the accompanying drawings below. It should be noted that the scales of the various drawings may be different for the purpose of clear illustration, but this will not affect the understanding of the present application.

[0013] Figure 1 is a schematic diagram of a spray cooling system for a fuel cell vehicle according to the present application.

[0014] Figure 2 is Figure 1 a schematic diagram of the heat dissipation device of the spray cooling system of Detailed Embodiments

[0015] The exemplary embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present application can be more thoroughly understood and the scope of the present application can be completely conveyed to those skilled in the art.

[0016] It should be understood that the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, the meanings of "a plurality" and "several" are two or more, unless otherwise specifically defined.

[0017] It should be noted that the terms "installation", "connection", and "coupling" 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 an indirect connection through an intermediate medium, and it can be the communication inside two components.

[0018] Figure 1 It is a schematic diagram of a spray cooling system for a fuel cell vehicle according to the present application. The fuel cell vehicle includes a spray cooling system, a fuel cell 4, and a load 5. The fuel cell 4 is connected to the load 5 to supply energy thereto. The spray cooling system is connected to the fuel cell 4 to cool it. The fuel cell 4 includes a fuel cell stack 40 having a cathode and an anode (for example, a proton exchange membrane PEM type fuel cell stack), an anode circulation device 41 connected to the anode of the fuel cell stack 40, and a cathode circulation device 42 connected to the cathode of the fuel cell stack 40. The anode circulation device 41 humidifies the air containing oxygen and introduces it into the inlet of the anode of the fuel cell stack 40, and recovers the exhaust gas from the outlet of the anode of the fuel cell stack 40, dehumidifies the exhaust gas and sends it back to the inlet of the anode, and discharges the water in the exhaust gas. The cathode circulation device 42 introduces hydrogen into the inlet of the cathode of the fuel cell stack 40, and recovers the hydrogen from the outlet of the cathode of the fuel cell stack 40 and sends it back to the inlet of the cathode.

[0019] The spray cooling system includes a spray device 1, a cooling device 2, and a controller 3. The spray device 1 and the cooling device 2 are arranged adjacent to each other. The spray device 1 is used to spray a spray medium onto the cooling device 2 to cool the cooling device 2 by means of the phase change (such as evaporation) of the spray medium. The spray device 1 and the cooling device 2 are connected to the fuel cell stack 4, but not directly connected to each other. In other words, the spray device 1 is arranged not to conduct heat directly with the cooling device 2 to prevent the reduction of the phase change cooling efficiency due to the increase in the temperature of the spray medium in the spray device 1. The controller 3 is electrically connected to the spray device 1 and the cooling device 2 to control the spray device 1 and the cooling device 2. Optionally, the controller 3 supports at least three ADC inputs, two switch signal outputs, and two PWM signal outputs.

[0020] Figure 2 is Figure 1 A schematic diagram of the cooling device of the spray cooling system, showing a part of the cooling device. The cooling device 2 includes a rotating shaft 20, a radiator frame 21, a radiator 22 (see Figure 1 , omitted in Figure 2 for clarity), a fan 23 (see Figure 1 ), a motor (not shown), and a coolant sensor 25 (see Figure 1)。The rotating shaft 20 is fixed in the power compartment of the fuel cell vehicle. The radiator frame 21 is rotatably mounted at both of its ends in the rotating shaft 20. The radiator frame 21 includes a rack 210 at its edge. The rack 210 extends in a direction perpendicular to the rotation axis of the radiator frame 21. The radiator 22 is fixed in the radiator frame 21 and is connected to the fuel cell stack through a coolant pipeline so that the coolant of the fuel cell stack is dissipated heat through the radiator 22. The radiator 22 can adopt a plate-fin radiator, including a plurality of heat dissipation plates arranged in parallel with each other. The heat dissipation plates include internal pipelines to allow the coolant to flow through them. The fan 23 is arranged near the radiator 22 to provide an air flow to the radiator 22, assisting the phase change (such as evaporation) of the spray medium on the radiator 22 to dissipate heat, and at the same time assisting the radiator 22 to dissipate heat through air convection. The motor is connected (such as meshed) to the rack 210 of the radiator frame 21 by means of a gear thereon to control the windward angle of the radiator 22 through the rotation angle of the motor. The coolant sensor 25 is connected to the coolant pipeline. The coolant sensor 25 includes a temperature sensor and a pressure sensor to measure the temperature and pressure of the coolant entering and leaving the radiator 22.

[0021] Return Figure 1, the spraying device 1 includes a recovery water tank 10, a water pump 11, a throttle valve 12, a diverter 13, a nozzle 14, a filter 15, a buffer 16, a solenoid valve 17, and a spraying medium sensor 18. The recovery water tank 10 is connected to the drain outlet of the anode circulation device 41 to recover the water in the exhaust gas of the fuel cell stack 40 processed by the anode circulation device 41 and use it as the spraying medium. The water pump 11 is connected to the recovery water tank 10. The throttle valve 12 is connected to the water pump 11 to adjust the flow rate of the spraying medium, thereby adjusting the spraying intensity. The diverter 13 is connected to the water pump 11 via a spraying medium pipeline and the throttle valve 12. A plurality of nozzles 14 are connected to the diverter 13 to spray the spraying medium onto the heat dissipation device 2. Since the spraying area of a single nozzle is limited, different numbers of nozzles need to be configured for radiators of different sizes. The diverter 13 is used to distribute (e.g., equally divide) the spraying medium to each nozzle 14 to achieve full coverage of the radiator with spraying. The filter 15 is disposed in the spraying medium pipeline downstream of the water pump 11 to filter the spraying medium and prevent the nozzle 14 from being blocked. The buffer 16 is connected to the spraying medium pipeline between the filter 15 and the diverter 13. The buffer 16 generally consists of a hydraulic cylinder and a spring or an airbag. When the spraying medium in the spraying medium pipeline flows, the buffer 16 can absorb or release energy by adjusting the piston position of the hydraulic cylinder, thereby balancing the pressure change in the spraying medium pipeline. The function of the buffer 16 is to protect the spraying medium pipeline and equipment from damage caused by hydraulic shock and improve the stability and safety of the spraying medium pipeline. The solenoid valve 17 is disposed in the spraying medium pipeline, specifically between the connection point of the buffer 16 to the spraying medium pipeline and the diverter 13, and is used to adjust the on / off of the spraying, that is, to adjust the spraying interval time and the spraying duration. The spraying medium sensor 18 is connected to the spraying medium pipeline, specifically between the buffer 16 and the diverter 13. The spraying medium sensor 18 can include a temperature sensor, a flow sensor, and a pressure sensor, and is used to monitor the temperature, flow rate, and pressure of the spraying medium.

[0022] Optionally, the spraying device 1 may include a spraying medium recovery box and a recovery and filtration device (not shown). The spraying medium recovery box is disposed below the heat dissipation device 2 and is open upward to recover the liquid spraying medium that has not evaporated and has fallen from the heat dissipation device 2. The spraying medium recovery box is disposed above the recovery water tank 10 and is connected to the recovery water tank 10 via a pipeline so that the recovered liquid spraying medium flows back to the recovery water tank 10 under the action of gravity for reuse. The recovery and filtration device is disposed in this pipeline to filter the recovered liquid spraying medium before it enters the recovery water tank 10.

[0023] Alternatively, the water pump 11 can be a centrifugal pump with adjustable speed to adjust the speed according to the heat dissipation demand, thereby changing the flow rate of the spray medium and adjusting the spray intensity. In this case, the throttle valve 12 can be omitted. The flow divider 13 is directly connected to the water pump 11 via the spray medium pipeline.

[0024] Alternatively, the water pump 11 can be a controlled start-stop pump to start and stop according to the calculated spray interval time and spray duration. In this case, the solenoid valve 17 can be omitted.

[0025] The control method for the spray cooling system according to the present application is described in detail below. The method comprises the following steps:

[0026] S101: According to the inlet temperature T of the radiator 22 from the radiator 2 in , outlet temperature T out and coolant flow M coolant , ambient temperature T from the air system env and ambient relative humidity H env , the spray medium temperature T from the spray device 1 spray , spray medium flow rate M spray The spray duration t is calculated based on the spray medium film coverage η and the vehicle speed V from CAN. spray ;as well as

[0027] S102: At the outlet temperature T of the radiator 22 out When the maximum coolant inlet temperature of the fuel cell stack is exceeded, the spray device 1 is started and the windward angle of the radiator 22 is adjusted. Then, when the operation time of the spray device 1 exceeds the spray duration t spray The spray device 1 is shut down.

[0028] In the above steps, the windward angle is determined according to the spray duration t spray And the vehicle speed V from the CAN signal is obtained.

[0029] In the above steps, the windward angle of the radiator 22 is adjusted by operating the motor at a specific duty cycle. The duty cycle is determined according to the spray duration t spray And the vehicle speed V from the CAN signal is obtained.

[0030] Optionally, the spray duration t spray The calculation is performed in the following manner. First, the outlet temperature T of the radiator 22 is obtained. out , the maximum coolant inlet temperature of the fuel cell T FCmax and coolant flow Calculate the heat dissipation power P required by the radiator rad :

[0031]

[0032] Next, assume that the total heat dissipation power P of the spraying process spray is equal to the heat dissipation power P required by the radiator rad :

[0033] P spray = P rad (2)

[0034] According to the working principle of the spray heat dissipation system, the total heat dissipation power P of the spraying process spray multiplied by the total duration of the spraying process (i.e., the sum of the spraying duration t spray and the spraying interval time t evapor ) is the total heat exchange amount Q of the spraying process:

[0035] Q = P spray (t spray + t evapor ) (3)

[0036] The total heat exchange amount Q of the spraying process consists of the sensible heat transfer amount Q spray of the droplets on the radiator 22 and the latent heat transfer amount Q evapor of the liquid film on the radiator 22:

[0037] Q = Q spray + Q evapor (4)

[0038] The sensible heat transfer amount Q spray is calculated by the following formula:

[0039]

[0040]

[0041] where c p is the specific heat capacity of the spraying medium. Since the spraying medium is water in the exhaust gas of the fuel cell stack, c p is taken as 4.2 J / (g·°C); T spray is the temperature of the spraying medium, in °C; T wall is the average wall temperature of the radiator 22, and its value can be replaced by the average of the inlet temperature T in and the outlet temperature T out of the radiator 22, in °C.

[0042] During the heat dissipation process of the radiator 22, due to the droplet splash of the spray medium and the erosion of the liquid film on the windward surface of the radiator 22, some droplets cannot contact the radiator 22 to form a liquid film. Therefore, an effective spray coefficient η is introduced in this paper to calculate the amount of the liquid film on the radiator 22. The effective spray coefficient η can be determined by experiments. In this paper, the effective spray coefficient η can take a default value of 0.25.

[0043] Latent heat transfer amount Q evapor is calculated by the following formula:

[0044]

[0045] where, Δ vap H is the latent heat of vaporization of the droplets of the spray medium, with the unit of kJ / mol. In the spray heat dissipation system according to the present application, the spray medium is water. Therefore, the value of Δ vap H can be interpolated according to the latent heat of vaporization table of water (see Table 1 below); M is the molar mass of the spray medium (water), which is 18 g / mol.

[0046] Table 1: Latent heat of vaporization of water

[0047] Temperature (°C) <![CDATA[Δ vap H (kJ / mol)]]> 0 45.054 25 43.990 40 43.350 60 42.482 80 41.585

[0048]

[0049] Spray interval time t evapor is the liquid film evaporation time, which can be calculated by dividing the spray amount by the liquid film evaporation rate:

[0050]

[0051] where, w the is the liquid film evaporation rate, with the unit of g / s. It can be calculated according to the evaporation area of the liquid film on the radiator 22:

[0052]

[0053] where, A is the heat transfer area of the radiator 22, with the unit of m 2 ; ε is the coverage rate of the liquid film; W is the surface evaporation rate of water per unit area, with the unit of g·hr -1 cm -2 and it is calculated by the following formula:

[0054] W = at b p c v d H e (10)

[0055] Among them, t is the temperature, with the unit of °C; p is the pressure, with the unit of Pa; v is the air velocity, with the unit of m / s; H is the humidity, with the unit of %; a, b, c, d, and e are regression coefficients.

[0056] The evaporation rate of water is related to factors such as the temperature, humidity, wind speed, and pressure of the surrounding environment. Formula (10) refers to relevant literature (Geng Jiangtao, Li Xiangyi, Xing Guanglei, etc. Experimental study on the evaporation rate of water surface [J]. Power Supply Technology, 2010, 34(05): 470 - 472).

[0057] The previous description of the embodiments has been provided for illustrative and descriptive purposes. It is not intended to be exhaustive or to limit the embodiments to the described variations. Many modifications and variations are obvious to those skilled in the art. These embodiments are selected and described to best illustrate the principles and practical applications, enabling those skilled in the art to understand these embodiments from their various embodiments and the various modifications applicable to their intended uses. Within the framework of the embodiments, the above components and features can be combined between different embodiments.

Claims

1. A spray cooling system for a fuel cell vehicle, the fuel cell vehicle including a fuel cell (4), Among them, the spray cooling system including a spraying device (1), a cooling device (2) and a controller (3), characterized in that the spraying device (1) and the cooling device (2) are arranged adjacent to each other, wherein the spraying device (1) and the cooling device (2) are connected to the fuel cell (4), and the spraying device (1) is arranged not to conduct heat directly with the cooling device (2); the spraying device (1) is configured to recover water in the exhaust gas of the fuel cell (4) and spray it onto the cooling device (2) as a spray medium to cool the cooling device (2) by means of the phase change of the spray medium; the cooling device (2) includes a radiator (22) whose angle is adjustable relative to the spraying device (1), and is configured to change the cooling power by changing the angle of the radiator (22); and the controller (3) is electrically connected to the spraying device (1) and the cooling device (2).

2. The spray cooling system for a fuel cell vehicle according to claim 1, wherein the controller (3) is configured to support at least three-way ADC input, two-way switch signal output and two-way PWM signal output.

3. The spray cooling system for a fuel cell vehicle according to claim 1, wherein the cooling device (2) includes: a rotating shaft (20) fixed in the power compartment of the fuel cell vehicle; a radiator frame (21) rotatably mounted at both ends in the rotating shaft (20) and having a radiator (22) fixed therein; a fan (23) provided near the radiator (22) to provide an air flow to the radiator (22); and a motor connected to the radiator frame (21) to change the windward angle of the radiator (22); wherein the radiator (22) is connected to the fuel cell stack through a coolant pipeline to cool the coolant of the fuel cell stack.

4. The spray cooling system for a fuel cell vehicle according to claim 1, wherein the radiator frame (21) includes a rack (210) at the edge; and the rack (210) extends along a direction perpendicular to the rotation axis of the radiator frame (21) and meshes with a corresponding gear on the motor.

5. The spray cooling system for a fuel cell vehicle according to claim 1, wherein the fuel cell (4) includes a fuel cell stack (40) having a cathode and an anode, an anode circulation device (41) connected to the anode of the fuel cell stack (40), and a cathode circulation device (42) connected to the cathode of the fuel cell stack (40); the spraying device (1) includes: a recovery water tank (10) connected to the drain port of the anode circulation device (41) to recover water in the exhaust gas of the fuel cell stack (40) processed by the anode circulation device (41); a water pump (11) connected to the recovery water tank (11); a diverter (13) connected via a spray medium pipeline to the water pump (11); A plurality of spray nozzles (14), which are connected to a diverter (13) and are configured to spray a spray medium onto a heat dissipation device (2), wherein the flow rate of the spray medium received by each spray nozzle is distributed by the diverter (13); A filter (15), which is arranged in the spray medium pipeline downstream of a water pump (11) to filter the spray medium and prevent the spray nozzles (14) from being blocked; A buffer (16), which is connected to the spray medium pipeline between the filter (15) and the diverter (13); and A spray medium sensor (18), which is connected to the spray medium pipeline between the buffer (16) and the diverter (13) to measure the temperature, flow rate and pressure of the spray medium.

6. The spray heat dissipation system for a fuel cell vehicle according to claim 5, wherein, The spray device (1) includes: A throttle valve (12), which is connected between the water pump (11) and the filter (15) to adjust the flow rate of the spray medium; and A solenoid valve (17), which is arranged between the connection point of the buffer (16) to the spray medium pipeline and the diverter (13) to adjust the on / off of the spray.

7. The spray heat dissipation system for a fuel cell vehicle according to claim 5, wherein, The water pump (11) is a variable-speed centrifugal pump configured to adjust the rotational speed according to the heat dissipation requirement.

8. The spray heat dissipation system for a fuel cell vehicle according to claim 5, wherein, The water pump (11) is a control start-stop pump configured to perform start and stop according to the calculated spray interval time and spray duration.

9. The spray heat dissipation system for a fuel cell vehicle according to claim 5, wherein, The spray device (1) includes a spray medium recovery box and a recovery and filtration device; The spray medium recovery box is arranged below the heat dissipation device (2) and above a recovery water tank (10) and is connected to the recovery water tank (10) via a pipeline; and The recovery and filtration device is arranged in the pipeline.

10. A control method for a spray heat dissipation system according to any one of claims 1-9, the control method comprising the following steps: S101: Calculate the spray duration according to the inlet temperature, outlet temperature and coolant flow rate of a radiator (22) from the heat dissipation device (2), the ambient temperature and ambient relative humidity from an air system, the spray medium temperature, spray medium flow rate and spray medium liquid film coverage rate from the spray device (1), and the vehicle speed V from a controller area network of the fuel cell vehicle; And S102: When the outlet temperature of the radiator (22) exceeds the maximum coolant inlet temperature of the fuel cell stack of the fuel cell vehicle, start the spray device (1) and adjust the windward angle of the radiator (22), and then stop the spray device (1) when the running time of the spray device (1) exceeds the spray duration; wherein, the windward angle is obtained according to the spray duration and the vehicle speed V from a controller area network of the fuel cell vehicle.

Images