CN100595963C - Cooling airflow control method for direct air-cooled hydrogen stack - Google Patents

Abstract

The invention discloses a cooling air control method for an air direct cooling hydrogen cell stack, which is characterized in that in the hydrogen cell stack system an air resistance distribution control board is added and an air return method is used, wherein, the air resistance distribution control board refers to the honeycomb panel of metal material with an insulating layer and/ or the honeycomb panel of a polymer with insulating property, a honeycomb through hole is arranged on the honeycomb panel, the through hole can have a shape of a triangle, a quadrangle, a circular and /or a hexagon, and the thickness of the panel can be adjusted by thinning processing according to cooling effect; the air return method refers to adding the air return pathway of cooling air to the hydrogen cell stack, part or all of the cooling air heated by the hydrogen cell stack are returned through one channel and /or a plurality of channels with control valve plates, and are absorbed in from the front end of a fan so as to be mixed with fresh cooling air, and then the hydrogen cell stack is cooled. The cooling air control method of the invention has the advantages of decreasing the weight, the volumeand the production cost of a fuel cell system, increasing the starting speed of the hydrogen cell stack, and reducing the antifreeze difficulty of the system.

Description

Cooling airflow control method for direct air-cooled hydrogen stack

technical field

The invention relates to a cooling airflow control method for an air direct cooling type hydrogen proton exchange membrane fuel cell stack, which is used for the direct air cooling stack.

Background technique

The rated operating temperature of the hydrogen proton exchange membrane fuel cell stack (hereinafter referred to as the hydrogen stack) increases with the improvement of the membrane electrode technology. When the rated operating temperature of the stack is above 100°C, the water cooling method must consider the water cooling method. The problem of dealing with the system pressure, or changing to other liquid-based heat carriers, such as high-boiling ethylene glycol. However, in the liquid cooling method of heat carriers represented by water and ethylene glycol, at least one of the problems such as antifreeze, anticorrosion, and boiling point will become a technical obstacle in use. In addition, liquid is used as a heat carrier. Generally speaking, air is still required to use air as a heat sink for hydrogen stacks when it is used in water and/or in a specific environment, especially for mobile applications, such as those driven by hydrogen stacks. Cars, it all comes down to air cooling in the end. After all, the volume and weight of the liquid-cooled stack system is larger than that of the direct air-cooled stack system.

Due to the increase of the rated operating temperature of the stack, the air flow used for direct cooling of the air will decrease rapidly, and the resistance of the cooling air will decrease faster, even more than linearly. Therefore, as the flow rate of the cooling air decreases, the power of the fan delivering the cooling air decreases more than linearly, and the diameter of the cooling channel can also decrease.

Compared with the liquid cooling method, the air direct cooling method has the advantages of light system weight, anti-freezing, easy corrosion protection and fast system start-up. The disadvantage is that the uniformity of cooling is relatively poor; there are many difficulties in the design of stack design and bipolar plate combination design, as well as the flow channel design of cooling air.

Contents of the invention

The purpose of the present invention is to provide a cooling air flow control method for a direct air-cooled hydrogen stack, aiming at cooling the hydrogen stack in a balanced manner by controlling the cooling air flow rate and return air ratio of the cooling channel on the hydrogen stack.

To achieve the above object, the technical solution adopted in the present invention is:

A method for controlling the cooling air flow of a direct air-cooled hydrogen stack, characterized in that: an air resistance distribution control board is added to the hydrogen stack system and a return air method is used. For the blow-in cooling method, the resistance plate is located at Between the fan and the hydrogen stack or after the hydrogen stack; for the suction cooling method, the resistance plate is located before the hydrogen stack or between the hydrogen stack and the fan; where:

The air resistance distribution control panel is a metal material with an insulating layer or a honeycomb panel with an insulating polymer, with honeycomb through holes on it, and the through holes can be triangular, quadrilateral, circular and/or hexagonal. The geometry of the polygon; the thickness of the plate can be adjusted as follows:

(1) First calculate or measure the distribution of the wind speed of the fan on the airflow section without hydrogen stack and/or with hydrogen stack;

(2) After the hydrogen stack, press the original plate of the resistance plate with uniform thickness close to the stack, and the opening of the resistance plate and the through hole of the hydrogen stack may be consistent or inconsistent;

(3) Under the specific ambient temperature and rated working conditions, measure the airflow temperature of each cooling air channel of the hydrogen stack with and/or without the resistance plate and/or measure the temperature distribution of the cooling air flowing out of the resistance plate;

(4) According to step (1) and step (3), thinning is carried out to the resistance plate of the position of air flow temperature; The side of described thinning is the surface of resistance plate away from the hydrogen stack;

(5) Measure the airflow temperature of each cooling air channel of the resistance plate thinned through step (4) and/or measure the temperature distribution of the cooling air flowing out of the resistance plate under specific ambient temperature and rated working condition;

(6) According to step (5), thinning is carried out again on the resistance plate at the position where the air flow temperature is relatively high; the surface of the thinning process is still the surface of the resistance plate away from the hydrogen stack;

(7) Step (5) and step (6) are repeated until the measured temperature distribution is relatively uniform and meets the conditions for the stable operation of the hydrogen stack;

(8) If the thinned part of the original plate of the resistance plate is close to its full plate thickness, increase the thickness of the original plate or reduce the aperture of the through hole, and continue the steps (2) to (7) after increasing the thickness and reducing the aperture at the same time, until The temperature difference condition of step (7) is satisfied;

The air return method is to add cooling air return air path in the hydrogen stack, through a single channel and/or multiple channels, and the control valve with cut-off, opening, and flow control will pass through the hydrogen stack The heated cooling air returns part or all of it to the front end of the hydrogen stack, and is sucked by the fan through the front end to mix with the new cooling air to cool the hydrogen stack. The temperature can be close to the above-mentioned specific temperature to prevent air cooling The hydrogen stack produces freezing; the process steps are as follows:

(1) The above return air control is based on the temperature of the mixed cooling air discharged from the hydrogen stack. If the temperature of the discharged cooling air is lower than the temperature set by the system, the return air valve will be opened to reduce the intake of fresh air. The return air temperature of the hydrogen stack is close to the set temperature of the system, and then the fresh air is turned on;

(2) For starting in a low temperature environment, the system judges that if the hydrogen stack freezes according to the detected hydrogen stack and ambient temperature, it will first use the complete return air, and at the same time turn on the heater in the return air path, when the return air When the temperature reaches the set value of the system, the hydrogen stack is allowed to start generating electricity and stop heating.

The beneficial effects of the present invention are:

It is beneficial to reduce the weight, volume and cost of the entire fuel cell system, improves the start-up speed of the hydrogen stack and reduces the difficulty of antifreezing of the system.

Description of drawings

Fig. 1 is the basic structural representation of the present invention when using the original plate of the resistance plate without thickness correction;

Figure 2 is a schematic diagram of gradually modifying the original plate of the resistance plate under rated conditions for the case of no return air;

Fig. 3 is a schematic diagram of forming a resistance plate template under rated conditions in the case of no return air;

Figure 4 is a schematic diagram of using the thickness-corrected resistance plate or the finished resistance plate and using partial return air conditions under the non-rated working conditions of the hydrogen stack;

Figure 5 is a schematic diagram of the hydrogen stack when the hydrogen stack uses the full return air condition for the use of the thickness-corrected resistance plate or the finished resistance plate;

In the figure: 1. Cooling fan, 2. Thermocouple for measuring the mixed air inlet temperature, 3. Hydrogen stack, 4. Resistance plate, 5. Thermocouple for measuring the air outlet temperature of each channel of the resistance plate, 6. Return air Inlet, 7. Return air channel shell, 8. Return air flow control valve, 9. Return air channel, 10. Heater, 11. Return air outlet, 12. Fresh air control valve, 13. Thinned resistance plate Curved surfaces, 14. Thermocouples for measuring the mixing temperature at the cooling air outlet.

Detailed ways

A direct air-cooled hydrogen stack system as shown in Figures 1 to 5, consists of a fresh air control valve 12, a thermocouple 2 for measuring the temperature of the mixed inlet air, a bipolar plate and an end plate, and a stack 3, Resistance plate 4, thermocouple 14 for measuring the mixed temperature of cooling air outlet, return air inlet 6, return air channel shell 7, return air flow control valve plate 8, return air channel 9, heater 10, and return air outlet 11.

There is an air resistance distribution control panel throughout the system. For the blow-in cooling method with the fan before the stack, the resistance plate is located between the fan and the hydrogen stack or after the hydrogen stack; for the suction cooling mode with the fan behind the hydrogen stack, the resistance plate is located before the hydrogen stack Or between the hydrogen stack and the fan. The resistance plate is a honeycomb panel with uniform or uneven hole diameter and uneven or uniform thickness, or a thin plate with uneven hole diameter, or a mixture of these methods.

Use resistance plates with a certain thickness and the same aperture shape, and adopt honeycomb through-holes with uniform distribution. The through-holes can be triangular, quadrilateral, circular, hexagonal and other geometric shapes that are convenient for processing. The thickness of the board needs to be adjusted, the adjustment method is as follows:

1. First calculate or measure the distribution of the wind speed of the fan on the airflow section under the two conditions of no hydrogen stack and hydrogen stack. Or do not perform this step.

2. After the hydrogen stack, press the original plate of the resistance plate with uniform thickness close to the stack. The opening of the resistance plate and the through hole of the hydrogen stack may be consistent or inconsistent. The resistance plate must not affect the conductive properties of the hydrogen stack, and the contact point with the stack must be non-conductive, and it must be made of metal material with an insulating layer or an insulating polymer.

3. At a specific ambient temperature, measure the airflow temperature of each cooling air channel after the hydrogen stack without adding resistance plates and adding resistance plates under rated working conditions. When there is a resistance plate, the temperature distribution of the cooling air flowing out of the resistance plate can be determined. All cooling air channels can be measured in whole or in intervals.

4. According to steps 1 and 3, thin the resistance plate at the part where the airflow temperature is relatively high. After thinning, the airflow resistance of the channel with relatively high airflow temperature will decrease, the proportion of the cooling air flow in the corresponding part to the total flow will increase, the temperature of the cooling air flowing out will decrease, and the cooling air flow in the part without thinning will account for the total flow ratio will decrease. The thinned side is the side of the resistance plate away from the hydrogen stack.

5. At a specific ambient temperature, measure the airflow temperature of each cooling air hole behind the hydrogen stack under rated working conditions using the thinned resistance plate, or measure the temperature distribution of the cooling air flowing out of the resistance plate. Can be measured entirely or intermittently.

6. According to step 5, carry out thinning processing on the resistance plate at the part where the air flow temperature is relatively high. The thinned side is the side of the resistance plate away from the hydrogen stack.

7. Repeat steps 5 and 6 until the measured temperature distribution is relatively uniform and meets the conditions for the stable operation of the hydrogen stack, which is determined by the specific hydrogen stack. For example, when the ambient temperature is 20°C and the outlet cooling air mixing temperature is 90°C, if the temperature difference between the cooling air flowing out of the individual cooling air channels required by the hydrogen stack is at most less than 10%, then the temperature difference is 7°C, then according to 7 °C to determine the stop of the thinning process.

8. If the thinned part of the original plate of the resistance plate has been thinned to almost completely cut off all the thickness of the part, then improve the original plate of the resistance plate, increase the thickness of the original plate, or reduce the aperture of the through hole, or use both increased thickness and reduced via aperture method. Then continue the steps from 2 to 7 on the basis of the original thinning data until the temperature difference condition of 7 is satisfied.

9. Use the resistance board obtained by the above method as a template to produce the actual resistance board. The production methods include injection molding, molding, stamping and other conventional methods. The resistance board can be a single whole board, or a combination of multiple boards, plugging, layering pressure way.

10. The honeycomb aperture of the resistance plate is in an appropriate range, for example, between 1/3 and 2/3 of the aperture size of the cooling air channel of the hydrogen stack, and the thickness is between 1/2 and 1 of the length of the cooling channel of the hydrogen stack /4, which should be determined according to the specific structural size of the hydrogen stack, and then adjusted.

In order to adapt to start-up, especially low-temperature start-up and other conditions below the rated temperature (such as 20-40°C), the system uses the return air method to solve the corresponding problems. The return air method is as follows:

1. Add cooling air return air path in the system, return part or all of the cooling air heated by the hydrogen stack, back to the front of the hydrogen stack, mix with supplementary fresh cooling air, or not supplement, the hydrogen power The stack can be cooled through a single channel or multiple channels, and the cross-section can be in any form that is convenient for installation, including uniform and variable cross-sections, or it can be in the form of a shell borrowed from a hydrogen stack, including all surrounding components. Return air and partial return air. And there are control valves for cutting off, opening and controlling the flow. According to the shape of the hydrogen stack, the space arrangement requirements and the specific setting of the return air passage, there can be multiple valves, and the valves can be installed in any convenient installation position. Because the system allows a certain deviation for the cooling air outlet temperature of the hydrogen stack, the control of the valve plate allows a certain deviation. The return air is sucked by the fan at the front end of the fan and mixed with the new cooling air. The temperature can be close to the above-mentioned specific temperature, for example, 20°C. The inlet temperature of the cooling air of the hydrogen stack can be guaranteed to be above the freezing point to prevent wind cooling in an environment below 0°C. Occurrence of freezing on hydrogen stacks.

2. The basis for the above return air control is to measure the temperature of the mixed cooling air discharged from the hydrogen stack. When the hydrogen stack outputs electric energy, the fan continues to run and discharges cooling air. If the temperature of the discharged cooling air is lower than the temperature set by the specific system, for example, 90°C, the return air valve is opened, and at the same time, an additional fan can be installed at the fresh air inlet. Air intake control reduces the intake of fresh air, or even completely shuts down the intake of fresh air. Wait until the return air temperature of the hydrogen stack is close to the set temperature of the system, such as 20°C, and then open the intake of fresh air. And control the opening and ratio of fresh air and return air according to the ambient temperature, inlet temperature and outlet temperature, so that the inlet temperature and outlet temperature of the cooling air when the hydrogen stack is working are kept within the range set by the system, for example, the inlet temperature is set at 20°C to 40°C, the outlet temperature is 90°C to 100°C, and the specific temperature is set according to the characteristics of the specific hydrogen stack.

3. For the start-up in a low-temperature environment, according to the hydrogen stack detected by the system and the ambient temperature, it is automatically judged whether the hydrogen stack may freeze water. If there is a possibility of freezing, use full return air first, and at the same time turn on the heater in the return air path to heat the entire circuit, including the hydrogen stack. When the return air temperature reaches the system setting value, such as 20°C or 30°C, and the hydrogen stack plate or internal fuel and oxidant circulation temperature reaches 10°C or 20°C, the hydrogen stack is allowed to start generating power and stop heating. The heating of the return air system can be used in parallel with other heating measures of the hydrogen stack.

Claims (1)

1, a kind of method for controlling cooling airflow of air direct freezing type hydrogen electric stack is characterized in that: increase a flaps (4) and use return air method in described hydrogen electric stack system, for being blown into the formula type of cooling, flaps

(4) be positioned between fan (1) and the hydrogen electric stack (3) or after the hydrogen electric stack; For the suction-type type of cooling, flaps (4) is positioned at hydrogen electric stack (3) before or between hydrogen electric stack and the fan; Wherein:

Described flaps is the cellular board that cording has the polymer of the metal material of insulating barrier or insulation, has cellular through hole on it, and through hole is triangle, quadrangle, circle and/or hexagonal geometry; The thickness of plate is adjusted by following step:

(1.1) wind speed that calculates earlier or measure fan is not having hydrogen electric stack and/or distribution on the flow area under the hydrogen electric stack condition is being arranged;

(1.2) be close to pile behind hydrogen electric stack and press the uniform flaps raw sheet of thickness, the through hole of flaps can be consistent or inconsistent with the through hole that hydrogen electric stack is used for the cooling air duct;

(1.3) under specific environment temperature and rated condition, measure the Temperature Distribution that the hydrogen electric stack that flaps and/or non-resistance plate are arranged is used for the through hole gas flow temperature in cooling air duct and/or measures the cooling air that flows out on the flaps;

(1.4) according to step (1.1) and step (1.3) gas flow temperature is carried out attenuate processing than the flaps at higher position; The one side of described attenuate is the face that flaps deviates from hydrogen electric stack;

(1.5) measuring through the gas flow temperature of the passage that is used for the cooling air duct of the flaps of step (1.4) attenuate under specific environment temperature and the rated condition and/or measuring the Temperature Distribution of the cooling air that flows out on the flaps;

(1.6) according to step (1.5) gas flow temperature is carried out attenuate processing once more than the flaps at higher position; The face of described attenuate processing is still the face that flaps deviates from hydrogen electric stack;

(1.7) repeating step (1.5) and step (1.6), more even up to the Temperature Distribution of measuring, satisfy the condition of hydrogen electric stack steady operation;

(1.8) if the lightening holes of flaps raw sheet near its whole thicknesss of slab, then improve former plate thickness or reduce through-hole aperture and adopt to improve thickness simultaneously and reduce the aperture after continue the step of (1.2) to (1.7), be met up to the temperature difference condition of step (1.7);

Described return air method is to tie up to the return air path (9) that adds cooling air in the hydrogen electric stack, by an independent passage and/or many passages (7), and have that the control valve block (8) that blocks, opens, controls flow will return a part through the cooling air of hydrogen electric stack heating or they are whole, get back to the hydrogen electric stack front end, sucked by fan by front end by fan, mix with new cooling air, hydrogen electric stack is cooled off, temperature can be near above-mentioned specified temp, prevents that air-cooled hydrogen electric stack is produced from freezing; Its processing step is as follows:

(1.9) above-mentioned return air control is according to being the cooling air temperature through mixing that hydrogen electric stack is discharged, if the temperature of discharging cooling air is lower than the temperature of default, then open the valve block of return air, reduce entering of new wind, even close entering of new wind fully, treat the design temperature of hydrogen electric stack return air temperature, open entering of new wind again near system;

(1.10) for the startup under the low temperature environment, system is according to the hydrogen electric stack and the ambient temperature that detect, judge that hydrogen electric stack is if freeze, then use return air completely earlier, open the heater in the return air path simultaneously, when return air temperature reaches default value, then allow hydrogen electric stack to start generating, stop heating.

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