JP2018204824A - Waste heat recovery device - Google Patents

Abstract

To provide a waste heat recovery device high in anticorrosion against combustion exhaust gas, and having a heat exchanger with high heat exchange efficiency.SOLUTION: A waste heat recovery device is configured to recover waste heat with heat exchange between combustion exhaust gas and liquid. The waste heat recovery device comprises: a microchannel heat sink including a liquid flow passage where liquid flows; and a pair of flat exhaust gas pipes formed of stainless steel, each including an exhaust gas flow passage where combustion exhaust gas flows, and holding the microchannel heat sink with flat surfaces.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an exhaust heat recovery apparatus that recovers exhaust heat by exchanging heat between combustion exhaust gas and liquid.

  Conventionally, as this type of exhaust heat recovery apparatus, a plurality of stainless steel plate fins arranged in parallel between stainless steel side plates and a plurality of stainless steel sheaths provided in parallel so as to penetrate the side plates and the plate fins The thing provided with the heat exchanger comprised by the pipe and the U-shaped copper water flow pipe inserted in the sheath pipe used as a pair is proposed (for example, refer to patent documents 1). This heat exchanger is made by providing an opening with burring on the plate fin, passing the sheath tube through the opening, inserting a water pipe into the inner passage of the sheath pipe, and expanding the water pipe Is done. An exhaust heat recovery apparatus equipped with such a heat exchanger guides combustion exhaust so that it passes between the side plates, receives the heat of the combustion exhaust with the plate fins and the sheath tube, and exchanges heat with the water flowing in the water flow tube. Recover waste heat.

JP 2005-297497 A

  In the exhaust heat recovery device described above, the heat transfer efficiency is improved by improving the adhesion of the plate fin, the sheath tube and the water flow tube, and the condensation of the combustion exhaust is formed by forming the plate fin and the sheath tube from stainless steel. We are trying to improve the corrosion resistance against water. However, in order to increase the adhesion between the sheath pipe and the water pipe, it is necessary to expand all the water pipes, resulting in variations in the adhesion between the sheath pipe and the water pipe, and the heat transfer efficiency is deteriorated. There is a case.

  The main purpose of the exhaust heat recovery apparatus of the present invention is to provide an exhaust heat recovery apparatus having a heat exchanger that has high corrosion resistance to combustion exhaust gas and high heat exchange efficiency.

  The exhaust heat recovery apparatus of the present invention employs the following means in order to achieve the main object described above.

The first exhaust heat recovery device of the present invention comprises:
An exhaust heat recovery device that recovers exhaust heat by heat exchange between combustion exhaust gas and liquid,
A microchannel heat sink having therein a liquid flow path through which the liquid flows;
A pair of flat exhaust gas pipes formed of stainless steel, each having an exhaust gas flow path through which the combustion exhaust gas flows, sandwiching the microchannel heat sink between flat surfaces,
It is a summary to provide.

  The first exhaust heat recovery apparatus of the present invention is configured by sandwiching a microchannel heat sink having a liquid channel inside a pair of flat exhaust gas pipes having an exhaust gas channel inside. Since the exhaust gas piping is formed flat with stainless steel, it has high corrosion resistance and low pressure loss. In addition, heat exchange efficiency can be improved because heat exchange is performed by bringing a microchannel heat sink having a high heat transfer coefficient into contact with the surface (uneven plane) of the exhaust gas pipe. Further, since the high-temperature combustion exhaust gas does not directly hit the heat sink, the corrosion resistance against the combustion exhaust gas on the heat sink can be increased. As a result, it is possible to provide an exhaust heat recovery apparatus having a heat exchanger with high corrosion resistance against combustion exhaust gas and high heat exchange efficiency.

  In the first exhaust heat recovery apparatus of the present invention, the exhaust gas flow path is a flow path provided in the vertical lower part of the exhaust gas pipe from a flow path inlet provided in the vertical upper part of the exhaust gas pipe. The straight portion and the folded portion may be formed in a meandering manner toward the outlet, and the straight portion may be formed to be inclined obliquely downward. By so doing, it is possible to further improve the exhaustability of moisture in the combustion exhaust gas generated by heat exchange with the liquid.

  In the first exhaust heat recovery apparatus of the present invention, the exhaust gas pipe is formed in a substantially rectangular box shape, and the exhaust gas flow path is formed from one side surface to the other side surface of the exhaust gas pipe. The first and second ribs are formed in a meandering shape including a straight portion and a folded portion by a first rib extending to the front of the side surface and a second rib extending to the front of the one side surface from the other side surface. The channel width of the straight portion may be formed so as to gradually widen from the upstream side to the downstream side. If it carries out like this, the combustion exhaust gas which flows through the linear part of an exhaust-gas flow path will be made to collide with the side surface of the exhaust-gas piping in a pushing-back part, a turbulent flow will be caused, and heat transfer can be accelerated | stimulated.

  Furthermore, in the first exhaust heat recovery apparatus of the present invention, the exhaust gas pipe may be joined to the microchannel heat sink by diffusion joining. In this way, it is possible to increase the bonding strength and further increase the corrosion resistance without the need for brazing that causes corrosion.

The second exhaust heat recovery apparatus of the present invention is
An exhaust heat recovery device that recovers exhaust heat by heat exchange between combustion exhaust gas and liquid,
A microchannel heat sink having therein a liquid flow path through which the liquid flows;
An exhaust gas pipe formed of stainless steel and having a plurality of tubes extending in parallel through which the combustion exhaust gas flows;
A metal member formed of a metal having high thermal conductivity and provided to cover the microchannel heat sink and the exhaust gas pipe;
It is a summary to provide.

  In the second exhaust heat recovery apparatus of the present invention, a microchannel heat sink having a liquid flow path and an exhaust gas pipe in which a plurality of tubes (exhaust gas flow paths) extend in parallel are covered with a metal member having a high thermal conductivity. Configured. Since the heat of the combustion exhaust gas in the exhaust gas pipe is transmitted to the microchannel heat sink via the metal member, the heat transfer efficiency can be improved. Further, since the exhaust gas pipe is made of stainless steel, it has high corrosion resistance. Further, since the high-temperature combustion exhaust gas does not directly hit the heat sink, the corrosion resistance against the combustion exhaust gas on the heat sink can be increased. As a result, it is possible to provide an exhaust heat recovery apparatus having a heat exchanger with high corrosion resistance against combustion exhaust gas and high heat exchange efficiency.

  In such a second exhaust heat recovery apparatus of the present invention, the tube meanders by a straight portion and a folded portion from a flow path inlet provided at the upper part in the vertical direction to a flow path outlet provided at the lower part in the vertical direction. The linear portion may be formed to be inclined obliquely downward. By so doing, it is possible to further improve the exhaustability of moisture in the combustion exhaust gas generated by heat exchange with the liquid.

It is a block diagram which shows the outline of a structure of the fuel cell system 10 including the waste heat recovery apparatus 30 of this embodiment. 2 is a perspective view of a heat exchanger 40. FIG. 3 is a side view of the heat exchanger 40. FIG. It is explanatory drawing which shows the exhaust gas flow path 45 of the exhaust gas piping. It is a perspective view of the heat exchanger 140 of a modification. 3 is a side view of the inside of a heat exchanger 140. FIG. It is explanatory drawing which shows the tubes 145A-145D of the exhaust gas piping 144. FIG.

  DESCRIPTION OF EMBODIMENTS Embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram showing an outline of the configuration of a fuel cell system 10 including an exhaust heat recovery device 30 of the present embodiment, FIG. 2 is a perspective view of a heat exchanger 40, and FIG. 3 is a diagram of the heat exchanger 40. It is a side view. As shown in FIG. 1, the fuel cell system 10 includes a power generation module 20 including a fuel cell 24, and an exhaust heat recovery device 30 that recovers exhaust heat generated with power generation by the power generation module 20.

  The power generation module 20 includes a module case 21 formed of a heat insulating material that accommodates each component, a vaporizer 22 that evaporates reformed water to generate water vapor, and raw fuel gas (for example, natural gas or LP gas). ) And steam to generate a fuel gas (reformed gas) containing hydrogen by a steam reforming reaction, and supply of the fuel gas and air (oxidant gas) to generate power by an electrochemical reaction Fuel cell 24, combustion section 25 that burns exhaust gas (off-gas) from fuel cell 24 to heat vaporizer 22 and reformer 33, ignition heater 26 that ignites the exhaust gas, and water that stores reformed water A tank 27 and a reforming water pump 28 that supplies the reforming water in the water tank 27 to the vaporizer 22 are provided. The combustion exhaust gas generated by the combustion in the combustion unit 25 is supplied to the heat exchanger 40 via the combustion catalyst 29. The combustion catalyst 29 is an oxidation catalyst that causes the fuel gas left unburned in the combustion section 25 to be reburned by the catalyst.

  As shown in the figure, the exhaust heat recovery device 30 connects a heat exchanger 40 to which combustion exhaust gas is supplied, a hot water storage tank 31 for storing hot water (water), a heat exchanger 40 and the hot water storage tank 31. And a circulation pump 33 for circulating the hot water in the circulation pipe 32, and the hot water is stored by heat exchange between the combustion exhaust gas and the hot water by the heat exchanger 40. The hot water is stored in the hot water storage tank 31. The combustion exhaust gas supplied to the heat exchanger 40 is condensed with water vapor components by heat exchange with the hot water, and the condensed water (condensed water) is purified by a water purifier (not shown) and collected in the water tank 27. The Further, the remaining exhaust gas (gas component) is discharged to the outside air.

  2 and 3, the heat exchanger 40 is a rectangular plate-like microchannel having a water inlet 42i for inputting hot water from the hot water storage tank 31 and a water outlet 42o for discharging the hot water to the hot water storage tank 31. A heat sink 42, two flat exhaust gas pipes 44 and 46 sandwiching the microchannel heat sink 42 with a flat surface, and an exhaust gas inlet 48i for inputting combustion exhaust gas from the combustion section 25 are input. And a distribution pipe 48 that distributes to each of the two exhaust gas pipes 44 and 46.

  The microchannel heat sink 42 is a heat sink that uses a microchannel having a cross section of 1 μm to 1 mm formed in a rectangular shape with a metal having a high heat transfer coefficient such as copper or aluminum, and has a low pressure loss, It has excellent characteristics such as low thermal resistance, high pressure resistance, thin and light weight.

  The exhaust gas pipes 44 and 46 are made of stainless steel into a substantially rectangular flat box shape, and in this embodiment, the flat surfaces are joined to the microchannel heat sink 42 by diffusion bonding. Here, diffusion bonding is performed by pressurizing and heating the bonded materials to each other using the diffusion of atoms generated on the bonding surface. The bonding strength is higher than brazing and brazing. There are no problems such as corrosion from the parts (brazing material). Hereinafter, details of the exhaust gas pipe 44 will be further described. However, since the two exhaust gas pipes 44 and 46 have the same configuration, a detailed description of the configuration of the exhaust gas pipe 46 is omitted.

  FIG. 4 is an explanatory view showing the exhaust gas passage 45 of the exhaust gas pipe 44. The exhaust gas pipe 44 includes a plurality of left ribs 44lr extending linearly from the left side 44ls to the front of the right side 44rs, and a plurality of right ribs 44rr extending linearly from the right side 44rs to the front of the left side 44ls. Have. The left ribs 44lr and the right ribs 44rr are provided so as to be alternately arranged in the vertical direction, and partition the internal space of the box-shaped exhaust gas pipe 44 to thereby meandering exhaust gas including the straight portion 45s and the folded portion 45t. A flow path 45 is formed. In the present embodiment, the left rib 44lr is inclined toward the lower right in the drawing, and the right rib 44rr is inclined toward the upper left in the drawing. In addition, an inclination angle can be 10 to 15 degree | times with respect to a horizontal surface, for example. An exhaust gas introduction portion 44 i for introducing the combustion exhaust gas from the distribution pipe 48 into the exhaust gas passage 45 is provided at the upper part in the vertical direction (upper left in the figure) of the exhaust gas pipe 44. In order to discharge the combustion exhaust gas (condensed water) that has passed through the exhaust gas passage 45 (straight line portion 45s, folded portion 45t) to the outside (water tank 27, etc.) Exhaust gas outlet 44o is provided.

  As described above, the heat exchanger 40 is configured by sandwiching the microchannel heat sink 42 between the flat surfaces of the two exhaust gas pipes 44 and 46, and the stored hot water from the hot water storage tank 31 is input to the microchannel heat sink 42. The exhaust gas pipes 44 and 46 receive the combustion exhaust gas from the combustion section 25 via the distribution pipe 48. Then, the combustion exhaust gas input to the exhaust gas pipe 44 passes through the meandering exhaust gas passage 45 formed in the exhaust gas pipe 44, and the water flow formed in the microchannel heat sink 42. Heat is transferred to the hot water stored in the passage and discharged from the exhaust gas outlet 44o. On the other hand, the combustion exhaust gas input to the exhaust gas pipe 46 passes through the meandering exhaust gas flow path formed inside the exhaust gas pipe 46, and the water flow path formed inside the microchannel heat sink 42. Heat is transferred to the hot water passing through the exhaust gas and discharged from the exhaust gas outlet 46o.

  In the present embodiment, the exhaust gas passage 45 of the exhaust gas pipe 44 has a left rib 44lr and a right rib 44rr that are inclined toward the lower right and the upper left in FIG. The condensed water generated by heat exchange with the gas flows along the inclination of the ribs (left rib 44lr, right rib 44rr) and is easily discharged to the exhaust gas outlet 44o. Since the exhaust gas flow path of the exhaust gas pipe 46 is similarly configured, the condensed water generated by heat exchange with the hot water of the combustion exhaust gas is easily discharged to the exhaust gas outlet 46o.

  In the present embodiment, the exhaust gas passage 45 of the exhaust gas pipe 44 has a left rib 44lr and a right rib 44rr that are inclined toward the lower right and the upper left, respectively. The channel width is formed so as to gradually widen. Therefore, the combustion exhaust gas flowing from the straight portion 45s of the exhaust gas flow channel 45 to the downstream folded portion 45t collides with the side surface (the left side surface 44ls or the right side surface 44rs), and part of the combustion exhaust gas goes downstream and the other part. As a result, the heat transfer is promoted. Since the exhaust gas flow path of the exhaust gas pipe 46 is similarly configured, heat transfer is promoted.

  The heat exchanger 40 of the exhaust heat recovery apparatus 30 of the present embodiment described above is configured such that the microchannel heat sink 42 through which hot water flows flows is sandwiched between the flat surfaces of a pair of exhaust gas pipes 44 and 46 through which combustion exhaust gas flows. The Since the exhaust gas pipes 44 and 46 are formed flat by stainless steel, they have high corrosion resistance and low pressure loss. In addition, since heat exchange is performed by bringing the microchannel heat sink 42 having a high heat transfer coefficient into contact with the surfaces (flat surfaces) of the exhaust gas pipes 44 and 46, the heat transfer coefficient can be improved. Further, since the high-temperature combustion exhaust gas does not directly hit the microchannel heat sink 42, the corrosion resistance against the combustion exhaust gas on the heat sink side can be improved. As a result, it is possible to improve the corrosion resistance against the combustion exhaust gas and improve the heat exchange efficiency.

  Further, the heat exchanger 40 of the exhaust heat recovery apparatus 30 of the present embodiment forms the exhaust gas flow path 45 in a meandering manner by partitioning the internal space of the exhaust gas pipe 44 with ribs (left rib 44lr, right rib 44rr). Then, the straight portion 45s of the exhaust gas passage 45 is formed so as to be inclined obliquely downward. Thereby, the condensed water produced | generated by heat exchange with the hot water of combustion exhaust gas can be discharged | emitted along the inclination of the exhaust gas flow path 45, and the discharge property of condensed water can be improved more. Further, similarly, the exhaust performance of the condensed water can be further improved with respect to the exhaust gas flow path of the exhaust gas pipe 46.

  In the embodiment, the straight portion 45s of the meandering exhaust gas passage 45 is formed so as to be inclined obliquely downward, but is not limited thereto, and is a direction orthogonal to the vertical direction. It may be formed so as to extend in the (horizontal direction). Further, the exhaust gas pipe 46 may be configured similarly.

  In the embodiment, the straight portion 45s of the meandering exhaust gas passage 45 is formed so that the passage width gradually increases from the upstream side to the downstream side, but the passage width may be constant. . The same may be applied to the exhaust gas pipe 46.

  In the embodiment, the meandering exhaust gas passage 44c is formed in the internal space of the exhaust gas pipe 44. However, the present invention is not limited to this, and a plurality of exhaust gas passages extending in parallel in a straight shape are used. It is good also as what forms. The same may be applied to the exhaust gas pipe 46.

  In the embodiment, the heat exchanger 40 includes the two flat exhaust gas pipes 44 that sandwich the microchannel heat sink 42 between the flat surfaces. However, the heat exchanger 40 is not limited to this, and the heat of the modified example of FIG. As shown in the exchanger 140, a metal member 149 such as an aluminum casting that covers the microchannel heat sink 142 in a state of being sandwiched between two exhaust gas pipes 144 and 146 may be provided. The microchannel heat sink 142 is configured in the same manner as the microchannel heat sink 42 of the embodiment, and has a water inlet 142i to which hot water is input and a water outlet 142o from which the hot water is discharged. FIG. 6 is a side view of the inside of the heat exchanger 140, and FIG. 7 is an explanatory diagram showing the tubes 145 </ b> A to 145 </ b> D of the exhaust gas pipe 144. As shown in FIG. 7, the exhaust gas pipe 144 has a plurality (four in this example) of stainless steel tubes 145 </ b> A to 145 </ b> D extending in parallel. Each of the tubes 145A to 145D extends in parallel in a meandering shape including a straight portion and a folded portion. The straight portions of the tubes 145A to 145D are formed so as to be inclined obliquely downward (for example, inclined by 10 to 15 degrees with respect to the horizontal plane). The exhaust gas pipe 146 has the same configuration as that of the exhaust gas pipe 144, and a description thereof will be omitted because it is redundant. The distribution pipe 148 has an exhaust gas inlet 148i to which combustion exhaust gas is input, and an exhaust gas inlet 144i that connects the input combustion exhaust gas to the plurality of tubes 145A to 145D of the exhaust gas pipe 144 and the exhaust gas pipe 146 Each is distributed to an exhaust gas inlet (not shown) connected to a plurality of tubes (not shown).

  In the heat exchanger 140 of the modified example thus configured, the microchannel heat sink 142 is covered with the tubes 145A to 145D in a state where the microchannel heat sink 142 is sandwiched between the tubes 145A to 145D of the pair of exhaust gas pipes 144 and 146. The stored hot water is input to the microchannel heat sink 142, and the combustion exhaust gas is input to the exhaust gas pipes 144 and 146 through the distribution pipe 148. The combustion exhaust gas input to the tubes 145A to 145D of the exhaust gas pipe 144 passes through water channels formed inside the microchannel heat sink 142 while passing through the tubes 145A to 145D in a meandering manner. Heat is transferred to the hot water and discharged from the exhaust gas outlet 144o. On the other hand, the combustion exhaust gas input to each tube of the exhaust gas pipe 146 transfers heat to the hot water stored in the microchannel heat sink 142 while passing through the tube in a meandering manner. The exhaust gas is discharged from the exhaust gas outlet 146o.

  In the present embodiment, each of the tubes 145A to 145D of the exhaust gas pipe 144 has a straight portion inclined obliquely downward, so that the condensed water generated by heat exchange with the hot water of the combustion exhaust gas is in the straight portion. It flows along the inclination and is easily discharged to the exhaust gas outlet 144o. Since each tube of the exhaust gas pipe 146 is similarly configured, the condensed water generated by heat exchange with the hot water of the combustion exhaust gas is easily discharged to the exhaust gas outlet 146o. Thereby, the condensed water produced | generated by heat exchange with the hot water storage water of combustion exhaust gas can be discharged | emitted along the inclination of tubes 145A-145D, and the discharge property of condensed water can be improved more.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problems will be described. In the embodiment, the exhaust heat recovery device 30 including the heat exchanger 40 corresponds to the “exhaust heat recovery device”, the microchannel heat sink 42 corresponds to the “microchannel heat sink”, and the exhaust gas pipes 44 and 46 correspond to “exhaust gas”. The exhaust gas flow path 145 (ribs 44lr, 44rr) corresponds to the “exhaust gas flow path”. The exhaust heat recovery device including the heat exchanger 140 corresponds to the “exhaust heat recovery device”, the microchannel heat sink 142 corresponds to the “microchannel heat sink”, and the exhaust gas pipes 144 and 146 become the “exhaust gas pipe”. The tubes 145A to 145D correspond to “tubes”, and the metal member 149 corresponds to “metal members”.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem is the same as that of the embodiment described in the column of means for solving the problem. Therefore, the elements of the invention described in the column of means for solving the problems are not limited. That is, the interpretation of the invention described in the column of means for solving the problem should be made based on the description of the column, and the embodiment of the invention described in the column of means for solving the problem is described. It is only a specific example.

  As mentioned above, although the form for implementing this invention was demonstrated using embodiment, this invention is not limited to such embodiment at all, In the range which does not deviate from the summary of this invention, it is with various forms. Of course, it can be implemented.

  The present invention is applicable to the manufacturing industry of exhaust heat recovery devices.

  DESCRIPTION OF SYMBOLS 10 Fuel cell system, 20 Power generation module, 21 Module case, 22 Vaporizer, 23 Reformer, 24 Fuel cell, 25 Combustion part, 26 Ignition heater, 27 Water tank, 28 Reformed water pump, 29 Combustion catalyst, 30 Exhaust Heat recovery device, 31 hot water storage tank, 32 circulation piping, 33 circulation pump, 40,140 heat exchanger, 42,142 microchannel heat sink, 42i, 142i water inlet, 42o, 142o water outlet, 44,46,144,146 exhaust Gas piping, 44i, 144i Exhaust gas inlet, 44o, 46o, 144o, 146o Exhaust gas outlet, 44lr Left rib, 44rr Right rib, 44ls Left side, 44rs Right side, 45 Exhaust gas flow path, 45s Straight section, 45t Turn back Part, 48, 148 minutes piping, 48i, 148i Air gas inlet, 145A～145D tube, 149 metal member.

Claims (6)

An exhaust heat recovery device that recovers exhaust heat by heat exchange between combustion exhaust gas and liquid,
A microchannel heat sink having therein a liquid flow path through which the liquid flows;
A pair of flat exhaust gas pipes formed of stainless steel, each having an exhaust gas flow path through which the combustion exhaust gas flows, sandwiching the microchannel heat sink between flat surfaces,
An exhaust heat recovery apparatus comprising: The exhaust heat recovery apparatus according to claim 1,
The exhaust gas flow path meanders from a flow path inlet provided at the upper part in the vertical direction of the exhaust gas pipe to a flow path outlet provided at the lower part in the vertical direction of the exhaust gas pipe by a straight part and a folded part. Formed into a shape,
The linear portion is formed to be inclined obliquely downward.
Waste heat recovery device. The exhaust heat recovery apparatus according to claim 1 or 2,
The exhaust gas pipe is formed in a substantially rectangular box shape,
The exhaust gas flow path includes a first rib extending from one side surface of both sides of the exhaust gas pipe to the front of the other side surface, and a second rib extending from the other side surface to the front of the one side surface. Formed in a meandering shape including a straight portion and a folded portion,
The first and second ribs are formed so that the flow path width of the linear portion gradually widens from the upstream side to the downstream side,
Waste heat recovery device. The exhaust heat recovery apparatus according to any one of claims 1 to 3,
The exhaust gas pipe is joined to the microchannel heat sink by diffusion joining,
Waste heat recovery device. An exhaust heat recovery device that recovers exhaust heat by heat exchange between combustion exhaust gas and liquid,
A microchannel heat sink having therein a liquid flow path through which the liquid flows;
An exhaust gas pipe formed of stainless steel and having a plurality of tubes extending in parallel through which the combustion exhaust gas flows;
A metal member formed of a metal having high thermal conductivity and provided to cover the microchannel heat sink and the exhaust gas pipe;
An exhaust heat recovery apparatus comprising: The exhaust heat recovery apparatus according to claim 5,
The tube extends in a meandering manner by a straight part and a folded part from a flow path inlet provided in the vertical upper part toward a flow path outlet provided in the vertical lower part,
The linear portion is formed to be inclined obliquely downward.
Waste heat recovery device.

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