KR100774572B1 - Heat exchanger for solid oxide fuel cell power generation system - Google Patents

Abstract

A heat exchanger for a solid oxide fuel cell generation system is provided to allow the system to be operated without the additional supply of heat after the supply of air having heat source initially. A heat exchanger comprises a first cover(110) which has a plurality of channels at one end and a plurality of rectangular opened parts connected with the channels at the other end; a nozzle(120) which is connected with the opened parts and has a plurality of round holes for the uniform distribution of the fluid flown from the channels; a manifold(130) which is provided with a groove capable of mounting the nozzle and is joined with the first cover; a plurality of laminated metal plates(140) which are joined with the manifold and are provided with a plurality of rectangular opened parts and a microchannel connected with the opened parts for the exchange of heat; and a second cover(150) which is joined with the last metal plate of the laminated metal plates and is provided with a discharge hole.

Description

Heat Exchanger for Solid Oxide Fuel Cell Power Generation System

1 is a conceptual diagram of power generation of a solid oxide fuel cell system.

2 is a schematic diagram of a solid oxide fuel cell power generation system for an auxiliary power supply unit.

3 is an exploded perspective view of a heat exchanger for a solid oxide fuel cell power generation system according to an embodiment of the present invention.

Figure 3a is a schematic diagram showing the flow of the flow path of the heat exchanger for a solid oxide fuel cell power generation system according to an embodiment of the present invention.

4 is a front view and a cross-sectional view of a first cover of a heat exchanger for a solid oxide fuel cell power generation system according to an embodiment of the present invention.

5A and 5B are front views of a nozzle of a heat exchanger for a solid oxide fuel cell power generation system according to an embodiment of the present invention.

6 is a front view of a manifold of a heat exchanger for a solid oxide fuel cell power generation system according to an embodiment of the present invention.

7 is a front view of a metal plate of the heat exchanger for a solid oxide fuel cell power generation system according to an embodiment of the present invention.

8 is a front view and a sectional view of a second cover of a heat exchanger for a solid oxide fuel cell power generation system according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

20: fuel cell stack 21: fuel electrode

22: air cathode 30: reformer

40: after combustor 50: heat exchanger

60 valve 80 fuel supply unit

90: air supply unit 110: first cover

120: nozzle 130: manifold

140: metal plate 150: second cover

The present invention relates to a structure of a heat exchanger in a solid oxide fuel cell (SOFC) power generation system.

Depending on the type of electrolyte used, the type of fuel cell includes phosphate (PAFC, Phosphoric Acid Fuel Cell), molten carbonate (MCFC, Molten Carbonate Fuel Cell), solid oxide type (SOFC, Solid Oxide Fuel Cell), and solid polymer type. (PEMFC, Proton Exchange Membrane Fuel Cell)

1 is a conceptual diagram of power generation of a solid oxide fuel cell system among the fuel cells.

As shown in the figure, a solid oxide fuel cell converts chemical energy of hydrogen and oxygen directly into electrical energy by an electrochemical reaction, and is a high efficiency, pollution-free power generation apparatus. The anode 21 is supplied with hydrogen to generate electricity by electrochemical reaction by reverse electrolysis of water.

The operation principle of the solid oxide fuel cell is to produce water by the oxygen ion generated by the reduction reaction of oxygen in the cathode moves to the anode through the electrolyte and reacts with hydrogen supplied to the anode again. In the air electrode, electrons are consumed, so when two electrodes are connected to each other, electricity flows.

Meanwhile, various methods have been proposed to commercialize the solid oxide fuel cell, and a method of using the same as a power source of a vehicle has been proposed. In order to be used as the main power source of a vehicle, a maximum output of about 50 kW is required, and the fuel cell system of this capacity is limited in weight or volume in order to be mounted in the engine room of the vehicle, and even considering the maximum power reported by the SOFC, It is true that there is a difficulty in commercialization since there must be a stacked stack.

Recently, however, studies are being actively conducted to utilize such a solid oxide fuel cell as an Auxiliary Power Unit (APU) before using it as a main power source for automobiles.

2 shows a schematic diagram of a solid oxide fuel cell power generation system for an auxiliary power supply unit.

As shown in the figure, the reformed gas is supplied to the fuel electrode of the fuel cell stack 20 and air is supplied to the cathode, and the reformed gas passes through the reformer 30 and enters the stack 20. However, in order for the fuel to be reformed, the reformer 30 must be above an appropriate temperature, so for this purpose, the reformer 30 must first be preheated as hot air, which is possible because the air is preheated through the preheater and then passed through the reformer 30. Done. In addition, since the reformed gas and the preheated air are introduced into the fuel cell stack 20, the power generation is possible.

In order to achieve the above development, it is necessary to go through four steps of operation.

Reformer preheating stage (first stage) to preheat the reformer with hot air, reformer operation stage (second stage) through reformer fuel supply, post combustor operation through reformed gas supply to post combustor and fuel using preheated air The cell stack preheating step (third step) and the reformed gas are supplied to the fuel cell stack via a switching valve and the preheated air is supplied to the fuel cell stack (fourth step).

In the one-step start operation mode, fuel is not supplied, and after the air supplied through the air supply unit 90 is preheated in the preheater, the air is supplied to the heat exchanger 50, and the air passing through the heat exchanger 50 is After entering the reformer 30 to preheat the reformer 30, again passing through the heat exchanger 50, then passing through the combustor 40, and then again passing through the heat exchanger 50 to be discharged to the outside. to be.

In the second stage start-up operation mode, fuel supply is added, but the reformed gas is not supplied to the fuel cell stack 20 to perform normal operation. In the two-stage mode, fuel is supplied to introduce fuel into the reformer 30 to operate the reformer 30. The reformed gas is fed to a post combustor 40 via a heat exchanger 50. The air supplied from the air supply unit 90 branches into two lines so that a part of the air is introduced into the reformer 30 through the heat exchanger 50 to maintain the reformer 30 temperature.

In the third stage start-up operation mode, a part of the branched air passing through the heat exchanger 50 is sent to the fuel cell stack 20 for preheating, and the reformed gas from the reformer outlet is sent to the post combustor 40. The combustor 40 is operated. To this end, the switching valve 61 located at the reformer outlet is adjusted to send the reformed gas to the heat exchanger 50 rather than to the fuel cell stack 20.

 That is, in the two-stage and three-stage start-up operation mode, the reformer 30 is operated by supplying fuel to the reformer 30 (step 2), and the after-burner 40 is operated (step 3). It is not necessary to operate the preheater, etc. In addition, the time difference of 2-3 steps is about 2 minutes.

Lastly, the fourth stage operation mode is a mode in which the internal temperature of the fuel cell stack 20 is preheated to about 650 to 700 degrees, and the SOFC power generation system is normally operated.

In the four-stage operation mode, the reformed gas, which was supplied to the combustor 40 after the heat exchanger 50 in the second and third stages, is supplied to the fuel cell stack 20 through the switching valve 61. In the fuel cell, the generated reformed fuel and air react with each other to generate power, and some of the generated water vapor and the reacted gas are branched back to the reformer 30, and the branched gas is reacted with the post combustor 40. After being introduced and burned, it is discharged through the heat exchanger 50 to the exhaust part.

As a result, the reformed gas is supplied to the fuel cell so that the reformer 30 operates normally to generate power.

That is, in the fuel cell power generation system, heat exchange is continuously performed according to each power generation stage. For this purpose, after one heat source is supplied, a heat exchanger that performs its own heat exchange without power supply should be provided. do.

The present invention is to provide a heat exchanger in the solid oxide fuel cell power generation system, after the air provided with the heat source in the initial start-up stage is supplied to the heat exchanger does not require additional heat exchange from the outside by its own heat exchange.

In addition, an object of the present invention is to provide a heat exchanger in which fluids do not mix with each other in a complex heat exchange in which a plurality of flow paths are formed.

The present invention relates to a structure of a heat exchanger in a solid oxide fuel cell power generation system.

That is, a first cover having a plurality of flow path pipes formed at one end and a plurality of rectangular openings connected to the flow path pipes at the other end thereof; A nozzle connected to the opening and having a plurality of round holes for uniform distribution of the fluid introduced from the flow path tube; A manifold having a groove for mounting the nozzle and joined to the first cover; A plurality of alternately stacked metal plates joined to the manifold and having a plurality of rectangular openings through which the fluid passes and microchannels connected to the openings to exchange heat between the fluids; And a second cover bonded to the last metal plate of the stacked metal plates and having an outlet. It relates to a heat exchanger for a solid oxide fuel cell power generation system comprising a.

In addition, the nozzle includes a plurality of holes formed in a row, but a small hole in the middle of the plurality of holes and a larger hole toward the edge, or a plurality of holes of the same size formed in a row in the nozzle It is provided with a method in which the spacing between holes decreases toward the edge to allow the fluid to pass evenly through the fine channels.

In addition, the rectangular opening formed in the metal plate forms two openings on each side, but is formed by connecting the microchannels between the opposing openings, and the two openings formed on one surface are configured differently from each other. It is also possible to improve the efficiency of heat exchange depending on the amount of fluid.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is an exploded perspective view of a heat exchanger in a solid oxide fuel cell power generation system according to an embodiment of the present invention, and FIG. 3A is a schematic diagram showing a flow path of a heat exchanger for a solid oxide fuel cell power generation system.

As shown in the drawing, a heat exchanger for a solid oxide fuel cell power generation system includes a first cover 110 having a plurality of flow path tubes, a nozzle 120 having a plurality of holes mounted in an inner portion of the first cover, The manifold 130 is coupled to the nozzle and connects the nozzle and the metal plate so that the fluid can be moved to the metal plate, dozens of alternating metal plates 140 between the manifold and the second cover and the last part of the metal plate. And a second cover 150 having a discharge pipe for guiding the fluid flowing out to the outside.

The first cover 110 is provided with a rectangular opening 112 that can be sent to the inside of the heat exchanger through the flow pipes 111 together with the plurality of flow pipes 111, from the air supply device. The passage A through which the preheated air is supplied, the passage A 'through which the air passes after the heat exchanger, and the reformed gas passing through the reformer are passed through the reformer in a stack preheating step before being supplied to the stack. A passage B through which a reformed gas flows in, a passage B ′ through which the gas passes through a heat exchanger, and a passage C through which unheated air supplied from an air supply device flows in, and the air flows out The passage C ', and finally the passage D through which the gas after the reaction passes through the after-burner is provided.

A manifold 130 is formed between the first cover 110 provided with the flow path tube 111 and the metal plate 140 provided with the microchannels. Serves to move to the metal plate 140 having the microchannels.

The second cover 150 is provided with a discharge pipe D ′ through which the gas after the reaction passed through the post combustor flows into the heat exchanger and is discharged.

The nozzle 120 is coupled between the manifold 130 and the A, B, C, and D portions of the first cover 110 so that the air flowing from the portions is uniformly distributed into the fine channels of the metal plate 140. Refers to a metal having a plurality of holes.

The metal plate is coupled to the manifold 131 and directs fluid from the flow path tubes into the plurality of channels for substantial heat exchange. As the material of the metal plate 140, a material having excellent thermal conductivity is used so that heat exchange can occur quickly. In order to increase the effect of heat exchange, the metal plate has a very thin thickness. Preferably, the material is made of a material such as aluminum, aluminum silicon alloy or copper alloy, the thickness of the plate can be formed to be 3mm or less.

In addition, since the heat exchange is performed by stacking dozens of metal plates 140, the channel is formed in a flat surface without protruding or recessing the microchannel portion. Therefore, in joining the metal plate 140 and the metal plate 140, no additional member is required, thereby improving the efficiency of heat exchange. Bonding of the metal plate and the metal plate is by a brazing joining method.

The metal plate 140 should be laminated by stacking a plurality of metal sheets alternately in a horizontal and vertical direction. This is because a plurality of flow paths required by the solid oxide fuel cell are required, and the properties of the fluids coming from these flow paths are different from each other.

Due to the above characteristics, the metal plates 140 are alternately stacked, and two metal passages and outlets are formed in each metal plate to prevent the incoming fluid from mixing with each other.

After stacking all of the metal plates 140, the second cover 150 including the discharge pipe 151 is coupled to the last portion of the heat exchanger. The discharge pipe 151 is to serve to recover the heat of the gas before the gas is discharged out after the reaction passing through the after-burner.

Each corner of the first cover 110, the manifold 130, the metal plate 140, and the second cover 150 is provided with a round hole 160, and then a fastener 152 is connected to the heat exchanger as a whole. Do not disassemble and bond firmly.

As shown in FIG. 3A, the fluid entering A through the flow channel is discharged only to A ′ after heat exchange through the microchannels, and the same is true of B, C, and D. This is to prevent fluids from mixing with each other in a power generation system having a complicated flow path.

The size of A, B, C, and D can be determined according to the problem of the relative flow depending on the amount of fluid flow or the operation process of the solid oxide fuel cell power generation system. That is, a large rectangular opening is formed in a place where the flow of fluid is large, and passes through a plurality of channels of the channel of the metal plate, and a small rectangular opening is formed in a place where the fluid flow is small, so that a small number of channels of the channel of the metal plate are formed. Pass through to increase the efficiency of heat exchange.

If the flow rate of fuel flowing into the fuel cell power generation system is Mf, the flow rate of preheated air is M1, the flow rate of general air is M2, and the flow rate of oxygen ions transferred from the cathode to the anode through the electrolyte in the fuel cell stack is Mt. The information on fluid and flow rate for each stage is as follows.

Reformer Preheating Step (Step 1)

Line A B C D Matter air air Inactive air flux M1 M1 M1 Inlet temperature To 500 degrees ~ 200 degrees Outlet temperature 20 degrees

Reformer operating stage (second stage) and afterburner operation and fuel cell stack preheating stage (third stage)

Line A B C D Matter air Reformed gas air Reformed Gas and Air flux M1 M1 + Mf M2 M1 + M2 + Mf Inlet temperature To 500 degrees To 800 degrees 20 degrees To 800 degrees Outlet temperature

Normal operation stage (fourth stage)

Line A B C D Matter air Inactive air Gas after reaction flux M1 M2 M1 + M2 + Mf Inlet temperature 20 degrees 20 degrees To 800 degrees Outlet temperature

That is, the power generation system can be operated smoothly only when the type and temperature of the fluid passing through each flow path of each stage heat exchanger are different and the passage through which the fluid passes is constant.

4 is a front view and a cross-sectional view of a first cover of a heat exchanger for a solid oxide fuel cell power generation system according to an embodiment of the present invention.

As shown in FIG. 3, the first cover 110 is provided with a plurality of flow path tubes that allow the fluid coming from the different flow pipes 111 to go out to the designated flow path without mixing, as illustrated in FIG. 3.

The fluid flowing from each flow pipe 111 is heat exchanged from the flow pipe 111 through the rectangular opening of the first cover 110 and through the fine channel of the nozzle and the metal plate to distribute the fluid evenly. It is discharged through the pipe 111 or the discharge pipe.

In the drawing, the size of the flow path tube 111 is provided different, which can be adjusted by varying the size according to the amount of fluid generated in the operation of the fuel cell power generation system.

In addition, circular holes are formed at each corner of the first cover so that the elements constituting the heat exchanger can be firmly supported using fasteners.

5A and 5B show front views of nozzles of a heat exchanger for a solid oxide fuel cell power generation system according to an embodiment of the present invention, and FIG. 6 shows front views of a manifold of a heat exchanger for a solid oxide fuel cell power generation system.

5A is connected to portions A and D in FIG. 3A, and the diagram shown in FIG. 5B is connected to portions B and C, with FIG. 5A connected to 131a and FIG. 5B connected to 131b, respectively. In addition, the nozzle 120 is coupled to and mounted in the groove portions 131a and 131b of the manifold 130. The nozzle 120 is a device for allowing the fluid flowing into the heat exchanger to be evenly dispersed.

The plurality of holes 121 formed in the nozzle 120 may be formed by varying sizes and intervals of the holes 121 according to portions A, B, C, and D into which fluid is introduced. That is, the hole 121 in the middle portion may be formed to be smaller and form a larger hole 121 toward the outside, or may be uniformly distributed in a manner that narrows the formation interval of the hole 121.

That is, as shown in the drawing, the diameter of the center hole (Ø ₁ ) is formed to be smaller than the diameter of the edge part (Ø ₂ ), or the distance (L ₁ ) between the center hole and the next hole with the hole of the edge. It is possible to form larger than the distance L ₂ .

Preferably, nine holes are formed in the nozzle 120 coupled to the A and D portions, and the size of the center hole is 4 pi (Ø), but the remaining eight holes are 5 pi (Ø). It is possible to form the gap between the holes on both sides by 11mm and reduce it by 1mm toward the edge.

And five holes are formed in the nozzle 120 coupled to the B and C portions, the size of the hole in the center portion is 3 pi (Ø) and the remaining four holes are composed of 4 pi (Ø), It is also possible to form the gap between the holes on both sides by 7mm and to reduce the gap by 1mm toward the edge.

At each corner of the manifold, a circular hole is formed so that the elements constituting the heat exchanger can be firmly supported using fasteners.

7 is a front view of a metal plate of a heat exchanger for a solid oxide fuel cell power generation system according to an embodiment of the present invention.

As shown in the drawing, each corner of the metal plate 140 having the microchannel 141 is provided with a circular hole 160 through which a fastener penetrates to fix the heat exchanger, and an edge thereof is connected to the first cover. Eight rectangular openings 142 through which the fluid coming from the flow pipe can enter are provided, and channels 141 which are fine and long holes connected between the openings 142 are provided. The number of channels 141 is determined according to the size of the rectangular opening 142, preferably 28 channels in A and D, 11 channels in B and C can be provided.

The metal plate 140 may be heat exchanged well, and a material having little change due to heat may be used, and preferably, a material of aluminum, aluminum silicon alloy, or copper alloy may be used. In addition, as described in FIG. 3, since the metal plate 140 is alternately stacked with the metal plate 140 and the metal plate 140, the metal plate 140 has a square shape.

8 is a front view and a cross-sectional view of a second cover of a heat exchanger for a solid oxide fuel cell power generation system according to an embodiment of the present invention.

 As shown in the figure, each corner of the second cover 150 is formed with a hole 160 for fastening the respective components of the heat exchanger, the fastener is coupled to the hole is fixed to the heat exchanger.

In addition, the fluid coming from the outlet to the after-burner enters the D portion and then passes through the metal plate provided with the fine channel and is discharged to D '. A discharge pipe 151 is formed to be discharged to the outside in connection with the D'. .

What has been described above is only one embodiment of a heat exchanger for a solid oxide fuel cell power generation system according to the present invention, and the present invention is not limited to the above embodiment, and as claimed in the following claims, Without departing from the gist of the present invention, one of ordinary skill in the art will have the technical idea of the present invention to the extent that various modifications can be made.

According to the present invention, after the initial supply of air having a heat source in a solid oxide fuel cell power generation system, a heat exchanger capable of operating the system without supplying an additional heat source can be provided.

In addition, a plurality of flow paths may be formed to provide a heat exchanger capable of heat exchange without mixing for each type of fluid entering the heat exchanger.

Claims (7)

A first cover having a plurality of flow path pipes formed at one end thereof and a plurality of rectangular openings connected to the flow path pipes at the other end thereof; A nozzle connected to the opening and having a plurality of round holes for uniform distribution of the fluid introduced from the flow path tube; A manifold having a groove for mounting the nozzle and joined to the first cover; A plurality of alternately stacked metal plates joined to the manifold and having a plurality of rectangular openings through which the fluid passes and microchannels connected to the openings to exchange heat between the fluids; And A second cover bonded to a last metal plate of the stacked metal plates and having an outlet; Heat exchanger for solid oxide fuel cell power generation system comprising a. The method of claim 1, The nozzle is provided with a plurality of holes formed in a row, a heat exchanger for a solid oxide fuel cell power generation system, characterized in that it has a small hole in the middle of the plurality of holes, the hole having a larger size toward the edge. The method of claim 1, The nozzle is provided with a plurality of holes of the same size formed in a row, the heat exchanger for a solid oxide fuel cell power generation system, characterized in that the gap between the holes decreases toward the edge. The method of claim 1, Each corner of the first cover, the manifold, the metal plate and the second cover further comprises a circular hole for fastening, and the heat exchanger for a solid oxide fuel cell power generation system, characterized in that is fastened and coupled using a fastener. The method of claim 1, And a rectangular opening formed in the metal plate, having two openings on each side thereof, wherein the openings are connected to each other by the microchannels. The method of claim 5, And two openings formed on one surface of the metal plate are different in size from each other. The method of claim 1, Bonding between the metal plate is a heat exchanger for a solid oxide fuel cell power generation system, characterized in that by the brazing bonding method.

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