JP2007303774A - Water evaporator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water evaporator capable of securing a stable evaporation behavior, improving evaporation efficiency, and being optimum for a fuel battery device. <P>SOLUTION: This evaporator includes a water storing tank and a heat exchange core, wherein a piezoelectric element is disposed at the base of the water storing tank, the piezoelectric element is utilized to put water in a mist state, and the water in the mist state is supplied to a heat exchange core. The evaporator includes a gas humidifying part and a heat exchange core, wherein a piezoelectric element is disposed at the base of the gas humidifying part, the piezoelectric element is utilized to put the water in the mist state, and further gas is made to flow into the gas humidifying part to be mixed with the water in the mist state, and after that, the mixed gas is supplied to the heat exchange core. These processes are optimum for use in modifying the fuel battery device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water evaporator that can be applied to fuel reforming of a fuel cell. More specifically, by supplying water in a mist state using a piezoelectric element into the water evaporator, the evaporation efficiency is improved and a small size is achieved. The present invention relates to a water evaporator capable of ensuring stable evaporation behavior by reducing flow rate fluctuation accompanying pressure fluctuation.

  Many water evaporators are used in processes for evaporating water and obtaining superheated steam in industrial equipment in a wide technical field such as heat exchangers, fuel cell devices, and hydrogen production devices.

  In the water evaporator, water is vaporized and vaporized in the water evaporator, so that there are always two gas-liquid phases in the water evaporator. Usually, when water vapor generated by the water evaporator is supplied to the next process, the water vapor is superheated and supplied as superheated steam so that the water vapor does not return to the liquid again.

  As described above, there are always two phases of liquid and gas mixed in the water evaporator, and the heat mass differs greatly between liquid and gas, so the temperature rises rapidly when water evaporates and becomes water vapor. However, temperature fluctuations occur inside the water evaporator. For this reason, thermal stress is always generated inside the water evaporator, and the water evaporator is easily damaged.

  In addition, when bumping occurs when water evaporates, not only temperature fluctuations associated therewith but also water evaporation behavior due to pressure fluctuations becomes a problem. When water evaporates, the volume rapidly expands to about 1000 times. As a result, the pressure fluctuation increases with the occurrence of bumping, and the evaporation behavior becomes unstable. If the evaporation behavior becomes unstable, the supply of water vapor to the next process is not stable.

  For example, in a fuel cell device, a water evaporator is used for hydrogenation of natural gas or hydrogen reforming of methanol for producing fuel to be used. As described above, when the evaporation behavior in the water evaporator is not stable, the supply amount of water vapor becomes unstable, and the mixing of the water vapor and the mixed gas becomes non-uniform. The mixed gas supply amount fluctuates, and the power generation amount of the fuel cell becomes unstable.

  Further, in the water evaporator employed in the fuel cell device, the flow rate of water may be relatively small. Therefore, even if a nozzle or the like is used when flowing water into the water evaporator, the passage of the water evaporator It is difficult to distribute evenly inside. For this reason, water tends to flow directly under the nozzle, and the water evaporation behavior may become unstable due to insufficient heat exchange.

  In addition, when water is flowed into the water evaporator using a nozzle, it is necessary to manage the cleanliness of the fuel cell device because the nozzle may be clogged if the cleanliness of the water is poor. This increases the running cost.

  The fuel cell uses waste heat such as high-temperature exhaust gas, and when the unvaporized liquid comes out of the water evaporator and is supplied to the fuel reforming of the next process, the part where the unvaporized liquid is supplied As a result, the heat of vaporization is lost, the temperature drops, and an effective reforming reaction is not performed.

  For this reason, in the fuel cell device, the evaporation technology in the water evaporator is an important development factor, and the performance of the water evaporator, that is, the improvement of the evaporation efficiency is improved, and the pressure fluctuation accompanying the evaporation of the liquid is suppressed and stabilized. By securing the evaporation behavior, it is particularly desirable to supply stable water vapor for the reforming process in the next step.

  Therefore, in order to reduce the temperature fluctuation and pressure fluctuation inside the water evaporator that occurs during the water evaporation process, conventionally, a method of providing a water storage tank for increasing the amount of liquid in the water evaporator and water into the water evaporator are used. A method of uniformly distributing and flowing in has been studied.

  FIG. 1 is a diagram showing a configuration example in which a water storage tank is provided in a conventionally used water evaporator to ensure stable evaporation behavior. FIG. 2 is a diagram showing a partial configuration of a sparge pipe which is a water distribution method conventionally used in water evaporators.

  As shown in FIG. 1, a separate water tank 2 is provided as the water evaporator 1, and water is supplied to the water tank 2. The water supplied to the water storage tank 2 is caused to flow into the water evaporator 1 installed at a position higher than the water storage tank 2 using the water head pressure of the water evaporator 1. The water that has flowed into the water evaporator 1 is evaporated and vaporized by exchanging heat with the high-temperature gas, and supplied to the reformer in the next step, which is omitted in FIG.

  By increasing the amount of circulating fluid, the temperature distribution in the water evaporator 1 is stabilized, and it becomes possible to suppress damage to the water evaporator 1 due to thermal stress. However, in the configuration example shown in FIG. 1, since it is necessary to provide the water reservoir 2, there is a restriction that an installation space for the reservoir 2 must be secured.

  Moreover, the sparge pipe 3 shown in FIG. 2 is built in, for example, a header tank of a water evaporator, and is provided with pores 3a that uniformly distribute water and introduce it into the passage. By allowing water to flow from the sparge pipe 3 into the respective passages through the pores 3a, it becomes possible to uniformly distribute the water.

  However, in the sparge pipe, as shown in FIG. 2, the basic structure is to arrange the pores 3a for uniformly distributing the low-temperature fluid into the pipe 3 and introducing it into the passage, and the water distribution performance is improved. As a result, the structure of the component parts becomes complicated, which deteriorates maintainability such as part replacement and increases the manufacturing cost.

  Furthermore, Patent Document 1 proposes a gas humidifier provided with an injection tube. In the basic configuration proposed in Patent Document 1, an injection tube inserted substantially horizontally along the tube plates on both sides is arranged on the upper part of the flow passage in order to uniformly disperse the liquid as the vapor source in the flow passage. The cryogenic fluid in the header can be uniformly distributed and introduced into the cryogenic fluid passage.

  However, as in the basic configuration proposed in Patent Document 1, it is necessary to attach a large number of injection tubes to the header. For this reason, even when the injection tube is employed, as in the case of the use of the sparge pipe, the maintainability such as the replacement of parts in the evaporator is deteriorated and the manufacturing cost is greatly increased.

  Moreover, in the prior art shown above, all use water in a liquid state as a premise, and examination about making water flow into an evaporator as a mist state is not made | formed.

JP 2004-53101 A

  As described above, water evaporators, particularly water evaporators used in fuel cell devices, need to stabilize the evaporation behavior of water and supply a stable amount of water vapor to the reforming process in the next step. is there. Moreover, it is necessary to suppress temperature fluctuations in the water evaporator and to suppress damage to the water evaporator due to thermal stress caused by the temperature fluctuations.

  The present invention has been made in view of the above situation, and by making water into a mist state using a piezoelectric element and supplying the water into the water evaporator, the evaporation behavior of water is stabilized and stabilized to the next step. It is possible to secure and supply water vapor, and further suppress the temperature fluctuation in the water evaporator, suppress the damage of the water evaporator due to the thermal stress caused by the temperature fluctuation, and improve the evaporation efficiency An object of the present invention is to provide a miniaturized water evaporator.

  In order to solve the above-described problems, the present inventor has made various studies on a method of supplying water into the water evaporator. As a result, the knowledge shown in the following (a) to (c) was obtained by supplying water into the water evaporator as a mist state.

  (A) Compared with the case where water is directly flowed into the water evaporator, the surface area ratio (surface area / volume) of water is large and the heat transfer area is increased, so that the evaporation efficiency can be improved.

  (B) The water distribution performance can be improved, and the fluctuation in the supply amount accompanying the fluctuation in the water flow rate can be suppressed.

  (C) Since water in a mist state behaves like a gas, the gas and water can be mixed uniformly.

This invention is completed based on the knowledge of said (a)-(c), and makes it a summary to the water evaporator described to following (1)-(3).
(1) An evaporator comprising a water storage tank section and a heat exchange core, wherein a piezoelectric element is arranged on the bottom surface of the water storage tank section, and water is supplied using high-frequency vibration generated by applying a voltage to the piezoelectric element. The water evaporator is characterized by being in a mist state and supplying the water in the mist state to the heat exchange core part (hereinafter referred to as “first water evaporator”).
(2) An evaporator composed of a gas humidification unit having a water storage tank and a heat exchange core, wherein a piezoelectric element is arranged on the bottom surface of the water storage tank and a high frequency vibration is generated by applying a voltage to the piezoelectric element. The water is made into a mist state by using the gas, and further, after the gas flowing into the gas humidifying unit and the water in the mist state are mixed, the mixed gas is supplied to the heat exchange core. Evaporator (hereinafter referred to as “second water evaporator”).
(3) The first and second water evaporators are preferably used for the reforming process of the fuel cell device. Furthermore, the heat exchange cores in the first and second water evaporators can be of the plate fin type in which the passage of the high temperature fluid and the passage of the low temperature fluid are adjacent to each other through the partition plate.

  According to the water evaporator of the present invention, since water is supplied into the water evaporator as a mist state using a high frequency vibration using a piezoelectric element, stable evaporation behavior can be ensured and evaporation efficiency can be ensured. The water evaporator can be reduced in size. Further, damage to the water evaporator due to thermal stress caused by temperature fluctuations in the water evaporator can be suppressed, and fluctuations in the amount of water supplied due to flow rate fluctuations can be suppressed.

  The water evaporator of the present invention stabilizes the evaporation behavior of water and improves the evaporation efficiency by supplying water into the water evaporator by using a piezoelectric element to make high-frequency vibrations into a mist state. Can be achieved.

  FIG. 3 is a diagram showing a configuration example of the “first water evaporator” of the present invention. As shown in FIG. 3, the 1st water evaporator 1 is comprised by the water storage tank part 1a and the heat exchange core 1b, and the piezoelectric element 4 is distribute | arranged to the bottom face of the water storage tank part 1a. The water stored in the water storage tank 1a is supplied to the water storage tank 1a via a solenoid valve 5 interlocked with a liquid level gauge not shown in FIG. The mist is made into a mist state, floats in the water evaporator, is heated by exchanging heat with the high-temperature gas, generates an updraft, and is supplied to the next process.

  When water is made into a mist state using the piezoelectric element 4, the amount of mist generated is controlled by the supply voltage to the piezoelectric element 4. Therefore, there is little influence of flow rate fluctuations due to water pressure fluctuations during evaporation, which is a problem when using a conventional spray nozzle or the like, and troubles due to nozzle clogging can be avoided.

  Furthermore, since water can be uniformly distributed to the heat exchange core by making the water into a mist state, the sparge pipes and injection tubes that have been used to improve the water distribution performance are no longer necessary. The manufacturing cost of the water evaporator can be reduced.

  Furthermore, the water in the mist state has a large surface area ratio (surface area / volume) and the heat transfer area increases, so that the evaporation efficiency can be improved and the water evaporator can be downsized.

  FIG. 4 is a diagram showing a configuration example of the “second water evaporator” of the present invention. As shown in FIG. 4, the 2nd water evaporator 1 is comprised by the gas humidification part 7 provided with the water storage tank part 1a, and the heat exchange core 1b. The water stored in the water storage tank 1a is supplied to the water storage tank 1a via a solenoid valve 5 interlocked with a liquid level gauge (not shown in the figure), and a high frequency generated by applying a voltage to the piezoelectric element 4. Mist state is caused by vibration.

  Gas (for example, fuel gas in the fuel cell device) is supplied to the gas humidification unit 7 via the gas solenoid valve 6, mixed with water in the mist state, supplied to the water evaporator, and exchanges heat with the high-temperature gas. And is supplied to the fuel reforming of the next step, which is omitted in the drawing.

  By making water into a mist state, the water behaves like a gas and it becomes easy to mix with the gas uniformly. Moreover, since the water made into the mist state by the piezoelectric element does not have the driving force, it can be used as the driving force of the water in the mist state by the fuel gas injection.

  As a method of mixing water and fuel gas in the mist state in the gas humidification unit 7, for example, the fuel gas is vigorously flowed into a passage narrowed at the center, and the passage is communicated with the gas humidification unit 7; The effect can be utilized. The apparatus structure when using the Venturi effect is simple and the number of components is small, so that troubles caused by parts damage and the like can be suppressed, and the manufacturing cost of the water evaporator can be reduced.

  Furthermore, by mixing mist water and fuel gas and supplying them to the water evaporator, it is possible to superheat water vapor and preheat the fuel gas. Compared to the conventional method, the energy efficiency of the water evaporator Can be improved.

  The “first water evaporator” and the “second water evaporator” of the present invention are preferably used for the reforming process of the fuel cell device. As described above, in a water evaporator used for hydrogenation of natural gas or hydrogen reforming of methanol to produce fuel for fuel cell devices, particularly fuel cells, the amount of steam supplied affects the amount of power generated by the fuel cell. Therefore, it is necessary to ensure a stable evaporation behavior.

  In particular, the “second water evaporator” of the present invention ensures stable evaporation behavior and can mix water and fuel gas and supply them to the heat exchange core, so that fuel gas is preheated along with the generation of water vapor. It is possible to improve the energy efficiency of the water evaporator as compared with the prior art, and it is optimal to use it for the reforming process of the fuel cell device.

  The heat exchange core in the “first water evaporator” and “second water evaporator” of the present invention adopts a plate fin type in which the passage of the high-temperature fluid and the passage of the low-temperature fluid are adjacent to each other through the partition plate. It is desirable to do. By miniaturizing the water evaporator and ensuring excellent evaporation efficiency.

  Further, when the water evaporator of the present invention described above is in a mist state, it is desirable to use fine water particles having a mist state water particle diameter of about several microns.

  Since the water microparticles in the mist state also have mass, the water microparticles in the mist state will fall if there is no driving force (for example, rising air flow). When the particle size of water is large, the mass of the particle becomes heavier and inevitably descends quickly, and depending on the temperature of the air, the floor and the wall may be moistened shortly before vaporization.

  On the other hand, when the particle size of water is small, the water particles become light and difficult to descend, reach every corner of the space, and easily vaporize even in a room set at a relatively low temperature. Therefore, in general, the smaller the water particle size, the easier it is to maintain a uniform humidity environment. Therefore, in the water evaporator according to the present invention, when water is in a mist state, the use of fine water particles having a particle diameter of about several microns can exhibit high performance and excellent durability. .

  The effect of the “first water evaporator” of the present invention will be described below. The water vapor generator is designed to have a water vapor generation rate of 1000 cc / hr, the water inlet temperature is room temperature (20 ° C.), the outlet temperature is 350 ° C., and is installed in the fuel cell device. The performance of the "first water evaporator" was compared.

  FIG. 5 is a diagram showing a specific configuration example and external dimensions of a water evaporator conventionally used in a fuel cell device. On the other hand, FIG. 6 is a diagram showing a specific configuration example and external dimensions of the “first water evaporator” used in the examples.

  As shown in FIG. 5, the conventional water evaporator allows liquid water to flow into the heat exchange core 1b from the bottom. The liquid water that has flowed into the heat exchange core 1b flows through the heat exchange core 1b while exchanging heat with the heating body, and is evaporated and vaporized to form water vapor and flow out of the water evaporator.

  Further, as shown in FIG. 6, the “first water evaporator” of the present invention is composed of a water storage tank 1a and a heat exchange core 1b, and a piezoelectric element 4 is arranged at the bottom of the water storage tank 1a to apply a voltage. It is possible to make water into a mist state.

  Further, the level of water is controlled by a liquid level meter, which is omitted in the figure, and the optimal level for the atomization efficiency of the piezoelectric element 4 is ensured.

  As shown in FIGS. 5 and 6, the water evaporator having a conventional structure has an outer dimension of 50 W × 100 H × 200 L and a weight of 5 kg, whereas the “first water evaporator” of the present invention has an outer shape. The dimensions are 50W x 50H x 175L and the weight is 3.5kg. By supplying water in the mist state to the heat exchange core 1b, it is possible to improve the evaporation efficiency of the water evaporator and downsize the water evaporator. And the weight of the water evaporator was reduced by 30%.

  In addition, the “first water evaporator” of the present invention has a uniform temperature supply to the heat exchange core compared to the conventional water evaporator, so that the temperature fluctuation of the heat exchange core is suppressed, As a result, stable evaporation behavior could be secured, and a stable amount of water vapor could be supplied to the reformer in the next step.

  The water evaporator according to the present invention can ensure a stable water evaporation behavior by supplying water in a mist state using a piezoelectric element into the water evaporator. It can be secured. In addition, by supplying water in the mist state into the water evaporator, the evaporation efficiency is improved. Further, by suppressing the temperature fluctuation in the water evaporator, the water due to the thermal stress caused by the temperature fluctuation is reduced. Damage to the evaporator can be suppressed. Thereby, it can apply widely for the fuel reforming of a fuel cell device.

It is a figure which shows the structural example which provided the water storage tank in the water evaporator used conventionally and ensured the stable evaporation behavior. It is a figure which shows the partial structure of the sparge pipe which is the distribution method of the water conventionally used for the water evaporator. It is a figure which shows the structural example of the "1st water evaporator" of this invention. It is a figure which shows the structural example of the "2nd water evaporator" of this invention. It is a figure which shows the specific structural example and external dimension of the water evaporator conventionally used for the fuel cell apparatus. It is a figure which shows the specific structural example and external dimension of the "1st water evaporator" used for the Example.

Explanation of symbols

1: water evaporator, 1a: water reservoir,
1b: heat exchange core, 2: water tank,
3: sparge pipe, 3a: hole,
4: Piezoelectric element, 5: Solenoid valve,
6: Gas solenoid valve, 7: Gas humidifier

Claims (4)

  An evaporator comprising a water storage section and a heat exchange core, wherein a piezoelectric element is disposed on the bottom surface of the water storage section, and water is made into a mist state by utilizing high frequency vibration generated by applying voltage to the piezoelectric element. The water evaporator is characterized in that the water in the mist state is supplied to the heat exchange core part.   An evaporator comprising a gas humidifying unit and a heat exchange core with a water storage tank, and a piezoelectric element is disposed on the bottom surface of the water storage tank, and a high frequency vibration generated by applying a voltage to the piezoelectric element is utilized. The water evaporator is characterized in that the water is made into a mist state, and further, the gas flowing into the gas humidifying unit and the water in the mist state are mixed, and then the mixed gas is supplied to the heat exchange core.   The water evaporator according to claim 1 or 2, wherein the water evaporator is used for a reforming process of a fuel cell device. The water evaporator according to any one of claims 1 to 3, wherein the heat exchange core is a plate fin type in which a passage of a high-temperature fluid and a passage of a low-temperature fluid are adjacent to each other through a partition plate.

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