A humidification system for a fuel cell test bench

Abstract

The present invention discloses a humidification system for a fuel cell test bench, which includes a humidifier capable of humidifying gas; the humidifier includes a humidification tank and a water circulation system disposed outside the humidification chamber; the gas coming out of the humidifier is successively connected to the fuel cell stack to be tested on the test bench via a second plate heat exchanger, a gas-water separator, and a pipeline heater; temperature sensors and humidity sensors are provided between any two adjacent ones of the humidifier, the second plate heat exchanger, the gas-water separator, and the test bench. By first cooling and then heating the gas coming out of the humidifier, the present invention enables precise control of the final gas humidity only by relatively precisely controlling the temperature of the gas in each link, and can reduce the difficulty of controlling the humidity of a large-flow gas. The humidity of the finally obtained large-flow gas can be stably maintained above 95%, showing obvious progress compared with the prior art humidity control scheme with high cost and only 90% humidity.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell testing, and particularly to a humidification system for a fuel cell test bench. Background Art

[0002] A fuel cell is a device that directly converts the chemical energy of a fuel into electrical energy through a non-combustion process. It can continuously convert the chemical energy of chemical reactions between fuels such as hydrogen and oxygen into electrical energy. And a fuel cell converts part of the Gibbs free energy in the chemical energy of the fuel into electrical energy through an electrochemical reaction. The reaction is not limited by the Carnot cycle and has extremely high efficiency.

[0003] In the process of the rapid development of fuel cells, a fuel cell test bench is an important device for evaluating the performance of fuel cells. It can meet a series of tests such as sensitivity testing, compression volume verification, vibration shock, thermal shock, cold start, and durability in the development and design stage of fuel cells; in the product engineering stage, it can test items such as the activation characteristics, polarization characteristic curves, rated output power, peak output power, and low-temperature cold start performance of fuel cells and can meet the test requirements of fuel cells under different working conditions and simulation functions. For a fuel cell test bench, accurate flow control, temperature, and humidity control systems are essential. Flow control is relatively easy to achieve, but temperature and humidity control under high power, variable load, and different working condition requirements are a difficult problem. For a polymer electrolyte membrane fuel cell (PEMFC), the electrolyte needs to be in a hydrated state to maintain high ionic conductivity. For performance optimization, a more accurate humidification system for the fuel cell test bench is essential.

[0004] For traditional fuel cell test benches, most of them adopt ordinary bubbling humidifier humidification systems or spray humidifier humidification systems. For the large gas flow rate under high power, the humidification system cannot accurately control the temperature and humidity. For example, Patent CN209357839U discloses a scheme for auxiliary humidification of the waste heat of a fuel cell stack using a bubbling humidifier. It sequentially arranges an air inlet pipe, an air lift pipe filled with corrugated packing, and a demister from bottom to top in the humidifier housing. A heating rod is provided between the air lift pipe and the inner wall of the humidifier housing. After dry air enters the humidifier, the dry air will be humidified under the action of the corrugated packing and the demister. Patent CN114883603A discloses a spray humidification device applied to fuel cell test equipment, which includes a humidification tank main body. A water leakage partition is provided in the humidification tank main body, and the water leakage partition divides the humidification tank main body into upper and lower layers. The humidification tank main body is provided with a dry gas inlet, a wet gas outlet, and a liquid outlet. Gas humidification packing is provided inside the upper layer of the humidification tank main body. The spray humidification device also includes a spray head connecting pipe and an inserted spray assembly. A hollow interlayer is provided outside the upper layer of the humidification tank main body. One end of the interlayer is provided with a liquid inlet, and the other end is connected to the spray head connecting pipe. The inserted spray assembly includes one or more connecting pipelines located inside the upper layer of the humidification tank main body. Each connecting pipeline is provided with a plurality of spray heads, and the connecting pipeline accesses the spray head connecting pipe through the side wall of the humidification tank main body. In actual use, both of the above two humidification systems have the characteristics of slow humidification and low efficiency, and there are limitations to the gas humidity, making it difficult to reach a humidity of 95% or even higher.

[0005] In addition, Patent CN109713332A discloses an intake air cooling and humidifying system for fuel cells, which can generate ultrasonic waves to turn liquid water into tiny liquid water mist. The low-temperature liquid water mist exchanges heat with high-temperature air, and according to the change of the temperature inside the fuel cell stack, through the adjustment of the control unit, the intake air temperature of the fuel cell is reduced and the humidity is increased. In this patent, on the one hand, it is difficult to meet the humidification requirements of large-throughput gas, and on the other hand, a large amount of water droplets are entrained in the gas, which does not meet the gas supply requirements of the test bench in this application.

[0006] In the prior art, the temperature of the gas to be humidified can be accurately controlled, but the control of humidity is relatively difficult. In many cases, after passing through the humidifier, the gas temperature and humidity do not reach the set temperature and humidity. Then, through the heat preservation of the heating tape and the heating of the pipeline heater, although the generation of liquid water is prevented, the temperature and humidity control is not so accurate. After the temperature reaches the standard through regulation, the humidity may only be 90%. Summary of the Invention

[0007] Object of the Invention: In order to overcome the deficiencies in the prior art, the present invention provides a humidification system for a fuel cell test bench that can stably control the humidity of a large flow rate of gas.

[0008] Technical solution: To achieve the above object, the humidification system of the fuel cell test bench of the present invention includes a humidifier that can humidify gas; the humidifier includes a humidification tank and a water circulation system disposed outside the humidification chamber; the gas coming out of the humidifier is successively connected to the fuel cell stack to be tested on the test bench via a second plate heat exchanger, a gas-liquid separator, and a pipeline heater; temperature sensors and humidity sensors are provided between any two adjacent ones of the humidifier, the second plate heat exchanger, the gas-liquid separator, and the test bench.

[0009] Further, the humidification tank has a humidification chamber, a first heater is installed in the humidification chamber, and a gas distributor, a filler, a diverter, and a demisting net are also installed in a layout from bottom to top in sequence; the gas distributor is connected to an intake pipeline, and a mass flow controller and a one-way valve are installed on the intake pipeline;

[0010] The humidification chamber is connected to a water replenishing pipeline, and a first regulating valve is installed on the water replenishing pipeline; and a liquid level gauge is installed on the humidification tank;

[0011] The water circulation system includes a circulation pipeline, and a circulation water pump, a first plate heat exchanger, a flow switch, and a fifth temperature sensor are provided on the circulation pipeline; a second regulating valve is provided at the cooling water inlet of the first plate heat exchanger;

[0012] A sixth temperature sensor for detecting the temperature inside it and a first pressure sensor for detecting the air pressure inside it are installed on the humidification tank.

[0013] Further, a safety valve is provided at the top of the humidification tank, and a patch ceramic switch is provided on the outer wall of the humidification tank.

[0014] Further, both the first regulating valve and the second regulating valve are pneumatic angle valves.

[0015] Further, the gas distributor is a shower-shaped jet device with dense pores.

[0016] Further, the gas-liquid separator has a separation chamber and spiral blades disposed in the separation chamber, and the central axis of the spiral blades is vertically arranged.

[0017] Further, the bottom of the humidification tank is connected to the drain of the humidifier through a first solenoid valve.

[0018] Further, heat insulation layers are provided on the pipelines connecting the humidifier, the second plate heat exchanger, the gas-liquid separator, and the test bench, and heating tapes are installed in at least part of the heat insulation layers of the pipelines.

[0019] Beneficial effects: The humidification system of the fuel cell test bench of the present invention has the following beneficial effects:

[0020] (1) By cooling the gas coming out of the humidifier first and then heating it, only the temperature of the gas in each link needs to be precisely controlled to achieve precise control of the final gas humidity. This can reduce the difficulty of humidity control for large-flow gases, save costs, and improve the accuracy of experiments. The humidity of the final large-flow gas can be stably maintained above 95%, showing obvious progress compared with the high-cost humidity control scheme with only 90% in the prior art.

[0021] (2) The humidifier combines the advantages of a bubbling humidifier and a spray humidifier, which can effectively improve the humidification efficiency.

[0022] (3) Each safety measure such as the temperature switch and safety valve of the humidification tank in the main body of the present invention ensures the safety of the system under high temperature and high pressure.

[0023] (4) The whole-process heat preservation and heat tracing measures ensure less loss of gas temperature, and the pipeline heating and heat tracing before entering the fuel cell prevent the entry of liquid water, extending the life of the fuel cell while ensuring accurate temperature and humidity.

[0024] (5) The circulation pump in the system of the present invention uses a permanent magnet synchronous water pump with low noise, high stability, long life, and more precise adjustment performance; the regulating valve is a pneumatic angle valve with sensitive reaction and accurate action, which can meet the requirements of precise gas flow regulation, water replenishment regulation, etc., making the control accuracy more precise. Brief description of the drawings

[0025] Figure 1 It is a system schematic diagram of the humidification system of the fuel cell test bench;

[0026] Figure 2 It is a three-dimensional structure diagram of the humidification system of the fuel cell test bench;

[0027] Figure 3 It is an external structure diagram of the humidification tank;

[0028] Figure 4 It is an internal structure diagram of the humidification tank;

[0029] Figure 5 It is a first state diagram of the gas distributor;

[0030] Figure 6 It is a second state diagram of the gas distributor;

[0031] Figure 7 It is a preferred structure diagram of the humidification tank part.

[0032] In the figure: 1 - intake pipe; 2 - mass flow controller; 3 - one-way valve; 4 - gas distributor; 5 - liquid level gauge; 6 - diverter; 7 - sixth temperature sensor; 8 - demister; 9 - safety valve; 10 - first temperature sensor; 11 - first humidity sensor; 12 - tracing heater; 13 - second plate heat exchanger; 14 - proportional regulating valve; 15 - second temperature sensor; 16 - second humidity sensor; 17 - gas-liquid separator; 18 - third temperature sensor; 19 - third humidity sensor; 20 - pipeline heater; 21 - fourth temperature sensor; 22 - fourth humidity sensor; 23 - second pressure sensor; 24 - second solenoid valve; 25 - separator drain; 26 - fifth temperature sensor; 27 - flow switch; 28 - first plate heat exchanger; 29 - second regulating valve; 30 - first pressure sensor; 31 - packing; 32 - patch ceramic switch; 33 - circulating water pump; 34 - first solenoid valve; 35 - humidifier drain; 36 - first heater; 37 - first regulating valve; 38 - make-up water pipeline; 39 - humidifying tank; 40 - chuck; 41 - container; 41a - first gas outlet; 41b - second gas outlet; 42 - adjusting plate; 42a - third gas outlet; 42b - fourth gas outlet; 50 - gas circulation pump; 61 - box body; 62 - plate body. Detailed implementation manner

[0033] The present invention will be further described in detail below with reference to the accompanying drawings.

[0034] As Figure 1-2 shown in the fuel cell test bench humidification system, which includes a humidifier that can humidify gas; the humidifier includes a humidifying tank 39 and a water circulation system disposed outside the humidification chamber; the humidifying tank 39 is composed of multiple parts, and each part is connected by a chuck 40; the gas coming out of the humidifier is sequentially connected to the fuel cell stack to be tested on the test bench after passing through the second plate heat exchanger 13, the gas-liquid separator 17, and the pipeline heater 20; temperature sensors and humidity sensors are provided between any two adjacent ones of the humidifier, the second plate heat exchanger 13, the gas-liquid separator 17, and the test bench. Specifically, a first temperature sensor 10 and a first humidity sensor 11 are provided between the humidifier and the second plate heat exchanger 13; a second temperature sensor 15 and a second humidity sensor 16 are provided between the second plate heat exchanger 13 and the gas-liquid separator 17; a third temperature sensor 18 and a third humidity sensor 19 are provided between the gas-liquid separator 17 and the pipeline heater 20; a fourth temperature sensor 21 and a fourth humidity sensor 22 are provided between the pipeline heater 20 and the test bench, and a second pressure sensor 23 is also installed.

[0035] In the above system, the temperature of the gas after humidification and temperature increase by the humidifier is higher than the temperature of the gas that finally reaches the fuel cell to be tested. After the gas coming out of the humidifier passes through the second plate heat exchanger 13, the water molecules in the gas can reach the saturation state and water droplets are separated out. The gas-water separator 17 separates the water droplets entrained in the gas, and the pipeline heater 20 heats the gas to the target temperature again. In this way, precise control of the humidity of a large-flow gas can be achieved.

[0036] Specifically, the temperature of the deionized water in the humidifier should be set 3 - 5 °C higher than the temperature required for the test to meet the subsequent temperature adjustment process and consider heat loss. The humidity of the gas coming out of the humidifier is not less than 90%, generally between 90% - 92%. After the gas passes through the second plate heat exchanger 13, its temperature drops by 1 - 2 °C to increase the humidity by 10% to reach the saturation state. The pipeline heater 20 is the last step of temperature and humidity adjustment for the incoming gas before it enters the fuel cell. It cooperates with the temperature sensor and humidity sensor after the gas-water separator to perform heat preservation and heating treatment on the gas, so that its humidity is maintained above 95%.

[0037] In the above system, by first cooling and then heating the gas coming out of the humidifier, only the temperature of the gas in each link needs to be precisely controlled to achieve precise control of the humidity of the final gas, which can reduce the difficulty of humidity control for a large-flow gas, save costs, and improve the accuracy of the experiment.

[0038] Preferably, as Figure 4 shown, the humidifying tank 39 has a humidifying chamber. A first heater 36 is installed in the humidifying chamber, and a gas distributor 4, a packing 31, a diverter 6, and a demisting net 8 are also installed in sequence from bottom to top; the gas distributor 4 is connected to an intake pipeline 1, and a mass flow controller 2 and a one-way valve 3 are installed on the intake pipeline 1;

[0039] The humidifying chamber is connected to a water replenishing pipeline 38, and a first regulating valve 37 capable of adjusting the water flow is installed on the water replenishing pipeline 38; and a liquid level gauge 5 is installed on the humidifying tank 39; the liquid level gauge 5 is an external liquid level gauge, which is a non-contact liquid level gauge using frequency conversion ultrasonic technology. There is a side-pass reserved port at the vertical height position of the humidifying tank 39 to connect a transparent heat-resistant and pressure-resistant PU pipe, and the liquid level height in the tank can be directly observed.

[0040] The water circulation system includes a circulation pipeline, and a circulation water pump 33, a first plate heat exchanger 28, a flow switch 27, and a fifth temperature sensor 26 are arranged on the circulation pipeline; a second regulating valve 29 is arranged at the cooling water inlet of the first plate heat exchanger 28;

[0041] As Figure 3As shown, a sixth temperature sensor 7 for detecting the temperature inside the humidifying tank 39 and a first pressure sensor 30 for detecting the air pressure inside it are installed on the humidifying tank 39.

[0042] Based on the above structure, the control system can control the opening and closing of the first regulating valve 37 based on the liquid level value in the humidifying tank 39 detected by the liquid level gauge 5, so as to maintain the liquid level of deionized water in the humidifying tank 39 within a specific range. In addition, based on the temperature data collected by the sixth temperature sensor 7, the control system can control the first heater 36 and the first plate heat exchanger 28 to regulate the temperature of deionized water in the humidifying chamber. When the water temperature needs to be reduced, the flow rate of the cooling water in the first plate heat exchanger 28 can be regulated by adjusting the second regulating valve 29 to achieve cooling of the water temperature. The temperature data collected by the fifth temperature sensor 26 can monitor the temperature of the deionized water returning to the humidifying chamber through the circulation pipeline, and the control system can further adjust the opening degree of the second regulating valve 29 accordingly. By using the coordinated control of the above components and sensors, the circulation of deionized water in the humidifier can be realized to ensure that the temperature of deionized water at different positions in the tank is consistent.

[0043] Based on the pressure value detected by the first pressure sensor 30, the pressure inside the tank can be monitored. When the pressure is too high, the safety valve 9 can be actively opened for pressure relief. In addition, based on the humidity data of the gas collected by the first humidity sensor 11, the control can adjust the opening degree of the flow switch 27 to speed up or reduce the water circulation rate to regulate the gas humidity. Based on the temperature data collected by the first temperature sensor 10, the above first heater 36 and first plate heat exchanger 28 can be further optimized for control, so that the temperature and humidity of the gas output from the humidifying tank 39 both meet the requirements. The overall control logic of the above various adjustment and control methods is based on PID adjustment.

[0044] It can be seen that based on the coordinated control of the above sensors and actuating components, the temperature and humidity of the gas output from the humidifying tank 39 can be effectively maintained.

[0045] Preferably, the top of the humidifying tank 39 is provided with a safety valve 9. When the temperature and pressure in the humidifying chamber are too high and out of adjustment, the safety valve can be opened for air release and pressure relief to ensure safety. In addition, a patch ceramic switch 32 is arranged on the outer wall of the humidifying tank 39, and the system is powered off when the temperature is too high to ensure safety.

[0046] Preferably, both the first regulating valve 37 and the second regulating valve 29 are pneumatic angle valves, which have more precise regulation performance and can meet the precise flow regulation requirements.

[0047] Preferably, the gas distributor 4 is a shower-shaped jet device with dense pores, and its pore diameter is about 1 mm.

[0048] Preferably, the gas-water separator 17 has a separation chamber and a spiral blade disposed in the separation chamber. The central axis of the spiral blade is vertically arranged, the air inlet is located at the bottom of the separation chamber, and the air outlet is located at the top of the separation chamber.

[0049] Preferably, the bottom of the humidifying tank 39 is connected to the floor drain 35 of the humidifier through a first solenoid valve 34. When the water level in the humidifying tank 39 is too high, the first solenoid valve 34 is controlled to open to drain the excess water into the floor drain 35 of the humidifier. When the liquid level data detected by the liquid level gauge 5 meets the requirements, the first solenoid valve 34 is controlled to close.

[0050] Preferably, heat-insulating layers are provided on the pipes connecting the humidifier, the second plate heat exchanger 13, the gas-water separator 17 and the test bench, and heating tapes 12 are installed in at least part of the heat-insulating layers of the pipes. The heating tapes 12 can play a role in pipe heat preservation, prevent the gas from cooling to form liquid water during transmission, and facilitate more accurate temperature control.

[0051] When the above humidifying system operates, the gas undergoes the following treatment steps:

[0052] Step 1, air intake. The gas enters the humidifying tank 39 through the mass flow controller 2 and the one-way valve 3. The one-way valve 3 can prevent backwater and gas backflow. After the gas enters the humidifying tank 39, it first enters the gas distributor 4, and the gas is dispersed by the gas distributor 4 into dense and fine micro-bubbles.

[0053] Step 2, gas mass transfer and heat transfer. In Step 1, the micro-bubbles perform mass transfer and heat transfer with the deionized water at a set temperature in the humidifying chamber. After the gas in the bubbles leaves the water level of the deionized water, it continues to perform mass transfer and heat transfer with the deionized water flowing back in the packing 31. The deionized water in the packing 31 is provided by the flow divider 6. The flow divider 6 is connected to the water return port of the water circulation system. The flow divider 6 is in a box-like structure and has dense holes. These holes disperse the flowing-back deionized water and make it fall into the packing 31, so that the gas leaving the deionized water level can fully contact the dispersed deionized water in the packing 31 to continue to increase the humidity. The demisting net can remove the foam in the gas. Since the non-saturated gas needs to be cooled to saturation and then the saturated gas is heated and insulated for further temperature and humidity control in the subsequent process of this humidifying system, the temperature of the deionized water in the humidifier should be set 3 - 5 °C higher than the required test temperature to meet the subsequent temperature adjustment process. After passing through the demisting net 8 at the top of the humidifying chamber and being demisted, the gas enters the next stage after being detected by the first pressure sensor 30, the first temperature sensor 10 and the first humidity sensor 11. The above process of mass transfer and heat transfer combines the structural advantages of a bubbling humidifier and a spray humidifier, and can efficiently increase the humidity of the gas.

[0054] Step 3: Cooling treatment. After mass and heat transfer of the gas, under the condition of large flow rate, the humidifier cannot meet the set temperature and humidity. The temperature difference is relatively small, while the humidity difference is relatively large. During the cooling process of the second plate heat exchanger 13 after the gas passes through the humidifier, the gas temperature drops by 1-2 °C and the humidity increases by 10% or even reaches the saturation state. The gas in the second plate heat exchanger 13 is a high-temperature, high-pressure and high-flow gas provided by the air compressor. The cooling water in the second plate heat exchanger 13 is provided by the chiller, and the proportional regulating valve 14 cooperates with the first temperature sensor 10, the first humidity sensor 11, the second temperature sensor 15 and the second humidity sensor 16 to adjust the flow rate of the cooling water, so as to achieve more precise cooling. The saturated high-humidity gas after cooling enters the next unit. The proportional regulating valve 14 is also a pneumatic angle valve, through which the flow rate of the cooling water in the second plate heat exchanger 13 can be precisely adjusted to precisely adjust the cooling temperature.

[0055] Step 4: Gas-water separation. During the cooling process of the gas in the previous step, the humidity in the gas reaches the saturation state, and some water droplets will precipitate and flow along with the gas. After the gas enters the gas-water separator 17, the gas spirally climbs along the spiral blades. During this process, the water droplets settle and slide down along the spiral blades and converge to the bottom of the separation chamber. The bottom of the separation chamber is connected to the separator floor drain 25 through the second solenoid valve 24. Opening the second solenoid valve 24 can discharge the separated deionized water to the separator floor drain 25, so as to achieve gas-water separation. The gas is discharged from the top of the gas-water separator 17 and enters the next link.

[0056] Step 5: Pipe heating. The pipe heater 20 performs the last step of temperature and humidity adjustment on the gas, and cooperates with the fourth temperature sensor 21 and the fourth humidity sensor 22 to perform heat preservation and heating treatment on the gas, so that the humidity is maintained above 95%.

[0057] Preferably, as Figure 5-6 shown, the above-mentioned gas distributor 4 includes a container 41 with a cavity inside. The side wall of the container 41 has an air inlet, and its top has a first air outlet 41a and a second air outlet 41b arranged in an array respectively. The hollow area of the first air outlet 41a is larger than that of the second air outlet 41b. The gas distributor 4 further includes an adjusting plate 42 placed on the top of the container 41 and capable of sliding relative to the container 41. The adjusting plate 42 has a third air outlet 42a and a fourth air outlet 42b, and the third air outlet 42a and the fourth air outlet 42b are of the same specifications as the first air outlet 41a and the second air outlet 41b respectively. The adjusting plate 42 can be switched between a first state and a second state relative to the container 41, as Figure 5As shown, in the first state, the first air outlet 41a is completely aligned with the third air outlet 42a, and the second air outlet 41b is offset from the fourth air outlet 42b. The shaded area in the figure is the actual air outlet area, and the dashed line is the occluded contour; as Figure 6 shown, in the second state, the second air outlet 41b is completely aligned with the fourth air outlet 42b, and the first air outlet 41a is partially offset from the third air outlet 42a, so that the actual air outlet area of the first air outlet 41a is equal to the air outlet area of the second air outlet 41b. The shaded area in the figure is the actual air outlet area, and the dashed line is the occluded contour. Preferably, the shapes of all the above-mentioned air outlets are square, and the regulating plate 42 moves along the diagonal direction of the square. In this way, the bubble outlet specifications of the gas distributor 4 can be adjusted as required. In addition, as Figure 7 shown, the above-mentioned flow divider 6 is composed of a plurality of boxes 61, and a plurality of rotatable plates 62 are formed between the boxes 61. A pipeline leading to the gas distributor 4 is connected to the position below the flow divider 6 on the humidifying tank 39, and a gas circulation pump 50 is installed on the pipeline. With the above structure, when the first humidity sensor 11 detects that the humidity of the gas coming out of the humidifier is insufficient, the plate 62 can be controlled to rotate to reduce the opening degree, and the gas circulation pump 50 can be turned on. At the same time, the state of the regulating plate 42 in the gas distributor 4 is adjusted to the second state, so that the bubbles coming out of the gas distributor 4 are finer. In this way, the humidity can be effectively increased. The gas flow rate of the gas circulation pump 50 and the opening degree of the regulating plate 42 can be adjusted as required.

[0058] The above are only the preferred embodiments of the present invention. It should be noted that: for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A humidifier for a fuel cell, the humidifier comprising a humidification tank (39); Characterized in that, The humidification tank (39) has a humidification chamber therein, and a first heater (36) is installed in the humidification chamber. There is also installed a gas distributor (4), a packing (31), a diverter (6) and a demisting mesh (8) which are arranged in sequence from bottom to top; the gas distributor (4) is connected to an intake pipe (1), and a mass flow controller (2) and a check valve (3) are installed on the intake pipe (1); The gas distributor (4) includes a container (41) with a cavity inside. The side wall of the container (41) has an air inlet, and its top has a first air outlet (41a) and a second air outlet (41b) which are arranged in an array respectively. The hollow area of the first air outlet (41a) is larger than that of the second air outlet (41b). The gas distributor (4) further includes an adjusting plate (42) placed on the top of the container (41) and capable of sliding relative to the container (41). The adjusting plate (42) has a third air outlet (42a) and a fourth air outlet (42b), and the third air outlet (42a) and the fourth air outlet (42b) are of the same specification as the first air outlet (41a) and the second air outlet (41b) respectively; the adjusting plate (42) can switch between a first state and a second state relative to the container (41). In the first state, the first air outlet (41a) and the third air outlet (42a) are completely aligned, and the second air outlet (41b) and the fourth air outlet (42b) are offset; in the second state, the second air outlet (41b) and the fourth air outlet (42b) are completely aligned, and the first air outlet (41a) and the third air outlet (42a) are partially offset, so that the actual air outlet area of the first air outlet (41a) is equal to the air outlet area of the second air outlet (41b); the shapes of all the air outlets are square, and the adjusting plate (42) moves along the diagonal direction of the square; The diverter (6) is composed of a plurality of boxes (61), and a plurality of rotatable plates (62) are formed between the boxes (61). A pipe leading to the gas distributor (4) is connected to the position below the diverter (6) on the humidification tank (39), and a gas circulation pump (50) is installed on the pipe.

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