JP2004156881A

JP2004156881A - Structure of heat exchanger using porous metal

Info

Publication number: JP2004156881A
Application number: JP2002325045A
Authority: JP
Inventors: Hideo Kawamura; 英男河村
Original assignee: Ship and Ocean Foundation; Fuji Cera Tech Co Ltd
Current assignee: Ship and Ocean Foundation; Fuji Cera Tech Co Ltd
Priority date: 2002-11-08
Filing date: 2002-11-08
Publication date: 2004-06-03

Abstract

<P>PROBLEM TO BE SOLVED: To remarkably improve the heat exchanging efficiency by internally joining metallic porous members mounted on a heat receiving area and a heat radiating area, and a partition defining both areas in a structure of a heat exchanger. <P>SOLUTION: In this structure of the heat exchanger wherein the heat is moved from the heat receiving area 7 where the fluids GA, GB of different temperatures flow, to the heat radiating area 8, both areas 7, 8 are respectively shielded from each other by the partition 2, the heat receiving area 7 and the heat radiating area 8 are respectively provided with the metallic porous members 1, the surface layers of the metallic porous members 1 are respectively provided with joint layers 9, 10 formed by burying the plate-shaped paste prepared by kneading metallic powder and a brazing filler metal, the joint layers 9, 10 are closely kept into contact with the partition 2, and the metallic porous members 1 and the partition 2 are joined to each other by sintering the joint layers 9, 10. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
この発明は，流体間での熱交換に適用でき，例えば，天然ガスを熱分解して改質燃料に改質したり，水を水蒸気に変換したり，使用済みの水蒸気を水に復水させたり，オイルの温度を上昇させるため，排気ガス等が有する熱エネルギーを利用して熱交換することができる多孔質金属を用いた熱交換器の構造に関する。
【０００２】
【従来の技術】
従来，熱交換器において，ガス通路にセラミック製多孔質部材を配置したものが知られている。該熱交換装置は，エンジンからの排気ガスで蒸気を加熱する排気通路に設けられた第１段熱交換器と第２段熱交換器から成る。第１段熱交換器は，第１ケーシング内に配置された蒸気が流れる蒸気通路と，蒸気通路に配置された排気ガスが流れる排気ガス通路とから構成されている。第２段熱交換器は，第１ケーシングの下方に設けられた第２ケーシング内に配置された水を貯留できる水・蒸気通路と，水・蒸気通路の周りに配置された排気ガスが流れる排気ガス通路とから構成されている。各通路には，多孔質セラミック部材が配置されている（例えば，特許文献１参照）。
【０００３】
また，熱交換器を天然ガス改質装置に適用したものが知られている。該天然ガス改質装置は，天然ガス主成分のＣＨ_４をＣＯとＨ_２の改質燃料に熱分解するものであり，熱効率を改善すると共に排気ガス中のＣＯ_２を熱分解に使用して放出する排気ガス中のＣＯ_２含有量を低減するものである。天然ガス改質装置は，排気ガスパイプ内に排気ガス通路を形成する排気ガス通路体を配置し，排気ガスパイプの外側にガス燃料が流れるガス燃料ケースを配置し，ガス燃料ケース内にガス燃料通路を形成する多孔質セラミックスから成る多孔質部材を配置し，多孔質部材の表面にＣＨ_４とＣＯ_２をＣＯとＨ_２の改質燃料に変換させる作用を有する触媒を被覆し，更にガス燃料パイプの外周に断熱材を配置したものである（例えば，特許文献２参照）。
【０００４】
また，天然ガス改質装置を備えたガスエンジンが知られている。該ガスエンジンは，天然ガス主成分のＣＨ_４をＣＯとＨ_２の改質燃料に熱分解して発熱量をアップし，排気ガス中のＣＯ_２を熱分解に使用してＣＯ_２の含有量を低減すると共にＮＯ_Ｘの発生を抑制する。ガスエンジンは，ＣＨ_４にＣＯ_２を混合して排気通路に配置された触媒反応器に送り込み，排気ガスの熱エネルギで熱分解させて改質燃料に変換させる。ＣＯ_２分離膜で排気ガスからＣＯ_２を取り込んで触媒反応器へ送り込む。排気ガスが有する熱エネルギは，ターボチャージャで回収されると共に，第１熱交換器及び第２熱交換器によって高温蒸気に変換され，該高温蒸気で蒸気タービンを駆動して電気エネルギとして回収される（例えば，特許文献３参照）。
【０００５】
【特許文献１】
特開平１１−６６０１号公報（第１頁，図１）
【特許文献２】
特開平１１−９３７７７号公報（第１頁，図１）
【特許文献３】
特開平１１−１３５４７号公報（第１頁，図１）
【０００６】
【発明が解決しようとする課題】
ところで，多孔質構造を持つ熱交換器をセラミックスで作製した場合，セラミックスは，衝撃荷重に弱いので，複雑な形状の熱交換器として使用することが困難であるため，金属を用いた多孔質材の熱交換器の出現が望まれていた。しかるに，金属多孔質部材と平板の接合ができず，その実現ができなかった。エンジンから排出される排気ガスが有する熱エネルギーを回収するシステムは，高効率の熱交換器を用いることが有効である。即ち，燃料を天然ガスとした遮熱形ターボコンパウンドエンジンでは，燃焼室を遮熱構造とした場合に，該エンジンにおいて，燃料エネルギーを最大限に動力に変換して利用するには，排気ガスの熱エネルギーを最大限に活用し，動力に変換しなければならない。熱交換器として，作動流体間での熱交換では，その熱交換効率が重要であり，熱交換効率が良いほど熱の利用率がよく，全体の熱効率も良くなる。熱交換器の性能では，作動流体の熱伝達率と熱伝導率とが影響し，スムーズに熱を移動させるためには，その抵抗が小さい方が良い。
【０００７】
近年，耐熱金属を発泡体とし，熱伝導率の大きい金属多孔質部材を形成する研究が進み，その用途として，フィルタ用等が良いとして，多くの研究が進んでいる。金属多孔質部材は，三次元的に金属が絡まって交差しているがジャングルジム状に連続しているので，同一体積あたりの外表面積はフィンに比較し，６倍程度大きく，１ブロック毎に連続しているので，熱流体として適したものである。そこで，金属多孔質部材を２つの作動流体を分離する隔壁の金属平板に接合し，隔壁によって受熱領域と放熱領域とに区画し，受熱領域に一方のガス等の作動流体を通過させれば，作動流体は多孔質材料の隙間をその面に衝突接触しながら通過し，流体が持つ熱を金属多孔質部材の固体に伝達する。固体に伝達された熱は隔壁の金属平板に伝導され，他方の作動流体に熱を移動させることになる。多孔体のエレメントである足と隔壁は確実に接合されているので，熱流はスムーズに受熱側から放熱側に移動される。
【０００８】
そこで，熱交換器において，流体通路に多孔質金属部材を配設し，多孔質金属部材を熱交換面に持つことにより，高効率の熱交換器が構成される。エンジンの排気ガスの熱エネルギを再利用するために，排気ガスの熱エネルギを蒸気に変換したり，使用済みの蒸気を水に戻したりするためには，効率の良い熱交換器が必要である。熱交換器の伝熱について，理論的に考察すると，高温ガスから固体への熱移動は，ガス体の熱伝達率が大きい程，多量の熱が伝熱される。ガス体の熱伝達率は，流速と動粘度の関数であるレイノルズ数，ガス物性値特性を示すプラントル数，熱伝導率，レイノルズ数の関数であるヌセルト数によって決まる。
これを数式で示すと，次の通りである。
αｇ１＝Ｎｕ・λ／Ｘ
Ｎｕ＝Ｋ・Ｒｅ^ｍ・Ｐｒ^ｎ
Ｒｅ＝Ｕ・Ｘ／ν
但し，αｇ１：熱伝達率，Ｎｕ：ヌセルト数，λ：熱伝導率，Ｋ：定数，Ｒｅ：レイノルズ数，Ｐｒ：プラントル数，Ｕ：代表速度，ν：動粘度，Ｘ：代表長さ。
ここで，熱伝達率を数式で考えると，最も大きな影響を与える要素は，レイノルズ数であり，レイノルズ数は，速度の関数であると言って差し支えない。固体表面に流れる流体では，固体の表面の流れがゼロであり，固体の表面から遠くなるに従って流体の流速が大きくなるので，固体表面の近傍の流量特性を関数として，レイノルズ数が決まる。
【０００９】
また，気体から固体への熱伝達を増加させるには，次の条件が考えられる。
１．気体と固体との間で，固体の気体への接触面積を増加させること。
２．気体流れの中に固体が広く分散し，網目状に分布していること。
３．集熱部分から伝熱される熱伝導部分は，熱伝導率の大きな材料で構成され，多くの熱を熱交換器の流体間の隔壁に伝熱されること。
４．集熱材と隔壁は固体として確実に接合され，熱を効果的に伝熱すること。
５．伝熱された熱は，固体の熱放散体を通って効果的に熱放散すること。
上記１〜上記５の条件を満たす構造を概念図で示すと，図１に示すような原理図になる。
【００１０】
熱伝達・伝導体では，気体の速度を大きくして，レイノルズ数を大きくし，伝熱量を増大させるよりは，気体の速度を余り上げずに，固体の伝達面積を大きくした方が熱を大きく移動させることができる。
図１及び図２を参照して，熱交換器における受熱と放熱とを伝達計算で求めると，次のとおりである。
図２に示すように，フィン３を備えた円形の管４で形成される通路を備えた熱交換器における熱伝達量Ｑは，次の式のように熱通過率Ｋ（単位：Ｗ／ｍ^２・Ｋ）に関係している。
Ｑ＝Ｋ・Ａｒ・ΔＴ
但し，Ｑ：熱伝達量，Ｋ：熱通過率，Ａｒ：基準面積，ΔＴ：温度差。
【００１１】
また，図２に示すように，フィン３を備えた管４の内外に形成された受熱側と放熱側との通路が形成されている熱交換器における熱通過率Ｋは，次の一般式１で示される。

但し，ｈｉ：内径側熱伝達率（Ｗ／ｍ^２・Ｋ），ｈｏ：外径側熱伝達率（Ｗ／ｍ^２・Ｋ），λ：管の熱伝導率（Ｗ／ｍ・Ｋ），ｄｉ：管の内径（ｍ），ｄｏ：管の外径（ｍ），Ａｆ：管の内側のフィン部面積（ｍ^２），φｆ：フィン効率，Ａｂ：フィン間の外周面積（ｍ^２），Ａｒ：基準面積（フィンの１ピッチ間の外周面積，ｍ^２），ｌｎ：ｎａｔｕｒａｌｌｏｇａｒｉｔｈｍ．。
また，上記式１において，ｌｎ（ｄｏ／ｄｉ）の項は，管４のｄｏとｄｉとが大きく異なる場合に，〔ｄｉ／２〕ｌｎ（ｄｏ／ｄｉ）で修正している。また，フィン付き管４では，ｄｉ／ｄｏ（Ａｆ φｆ＋Ａｂ）／Ａｒで修正している。その理由は，伝熱面積が基準に対して大幅に変化するからである。
また，管４のｄｏとｄｉとが余り変わらない場合には，熱通過率Ｋは，次の一般式２で示される。

【００１２】
上記のことから，熱交換効率の基本的な原理を図１を参照して説明すると，次のとおりである。図１では，熱交換器を構成する受熱領域７と放熱領域８とが隔壁２で区画され，受熱領域７には高温ガスＧＡが流れ，放熱領域８には低温ガスＧＢが流れるように構成されている。受熱領域７と放熱領域８には，隔壁２に接合層９によって一体構造に接合された１本の足部５に複数の枝部６が一体構造に構成されており，これらの足部５と枝部６が複雑に多数集まって金属多孔質部材１が構成されるものである。通常，熱通過率Ｋは，伝熱側，受熱側の熱伝達率の係数で決まるが，作動流体を分離する隔壁２の外面にフィン３（図２），金属多孔質部材１等を付けた熱交換器では，面積効果を考慮して計算すると，実験値と一致する。従って，熱交換器において，受熱側，放熱側の面積を増加するように，図１に示す基本原理の構造を用いると，１本の足部５に対して，四方に拡散されている枝部６が受熱面積となり，熱通過率は３〜５倍に増加させることができる。従って，熱交換器において，熱通過率をアップさせるため，流体が接触する面積を如何に大きくし，特に，流体を区画した隔壁との接合に如何に一体構造に構成するかの課題がある。
【００１３】
【課題を解決するための手段】
この発明の目的は，上記の課題を解決するため，金属多孔質部材を構成する１本１本の足部を隔壁に金属体として一体構造に接続させ，金属多孔質部材と隔壁とを物理的に連続して接合することによって，受熱領域で受熱した熱エネルギを放熱領域に伝達させて放熱させ，熱通過率を３〜５倍に増加させるものであり，具体的には，流体が流れる受熱領域と放熱領域との間の隔壁と両領域に配設された金属多孔質部材とを接合するに当たって，金属多孔質部材と隔壁との接合を接合層を介して一体構造に構成し，熱遮断部の存在を無くして熱交換効率をアップさせ，エンジンから排出される排気ガス等の熱エネルギの熱交換効率を向上させ，例えば，天然ガスをＣＯとＨ_２との改質燃料に改質する燃料改質装置に適用したり，水を水蒸気に変換したり，オイルの温度を上昇させたりする装置等に適用される熱交換器の構造を提供することである。
【００１４】
この発明は，温度の互いに異なる流体がそれぞれ流れる受熱領域と放熱領域とを有し，前記受熱領域から前記放熱領域へ熱移動させる熱交換器において，前記受熱領域と前記放熱領域との間は隔壁によって互いに遮蔽され，前記受熱領域と前記放熱領域とに金属多孔質部材がそれぞれ配設され，前記金属多孔質部材の表層には金属粉末とろう材とを練り合わせた板状ペーストから成る接合層が形成され，前記金属多孔質部材のエレメントに前記接合層が密着接合し，更に前記隔壁にも密接して接合され，前記接合層の溶着によって前記金属多孔質部材と前記隔壁とが互いに導体接合されていることを特徴とする熱交換器の構造に関する。
【００１５】
前記金属多孔質部材はニッケル，ニッケルクロム合金，銅，アルミニウム等の金属から成り，前記隔壁はニッケル，ニッケルクロムと銅等の金属から成り，前記金属粉末は銀，ニッケル，銅，亜鉛等の耐熱性で高熱伝導率の金属から成るものである。
【００１６】
前記接合層は，前記隔壁を挟んで一方の前記金属多孔質部材に埋め込まれた高温耐熱性の第１接合層と，他方の前記金属多孔質部材に埋め込まれた前記第１接合層より１００℃以上低い溶融温度の第２接合層とから構成され，前記第１接合層は前記第２接合層より溶融温度が高くなるように接合層材料が選択されているものである。また，前記金属多孔質部材の前記接合層では，前記金属多孔質部材の足部が該足部の断面直径以上に埋設しているか又は円錐形状に取り巻かれた状態で接合されている。
【００１７】
前記金属多孔質部材の表面には，熱伝導率の大きい銅，アルミニウム，銀等のメッキ又はデッピング，蒸着等のコーティングが施されている。また，前記接合面とは反対側の前記金属多孔質部材の表面には，前記流体の流れに沿って溝が設けられている。
【００１８】
前記金属多孔質部材の表面にはアルミナ，ジルコニア等のセラミックスがコーティングされ，前記セラミックスの表面にはプラチナ，パナジウム，ニッケル，ロジウム，ルテニウム，酸化セリウム等の触媒が付着されている。
【００１９】
前記金属多孔質部材の表層には，熱伝導率の大きい銅，銀，アルミニウム等のメッキ層が施され，前記メッキ層の厚さが前記接合層において徐々に変化している。
【００２０】
前記金属多孔質部材への前記メッキ層の厚さは，前記金属多孔質部材をメッキ槽に浸漬する所要時間を変えて徐々に変化させることができる。
【００２１】
前記金属多孔質部材の表面にアルミニウムコーティングを行ってアルミニウム層を形成し，前記アルミニウム層を熱処理してαアルミナを析出させたものである。
【００２２】
この熱交換器の構造は，上記のように，熱交換器の隔壁に接合するフィン即ち金属多孔質部材を隔壁の表面層に接合しているので，熱交換効率を向上させることができる。
【００２３】
【発明の実施の形態】
以下，図面を参照して，この発明による熱交換器の構造の実施例を説明する。図３〜図５を参照して，この発明による熱交換器の基本的な構成について説明する。図３はこの発明による熱交換器の構造を説明するための熱移動モデル，図４は放熱側モデルが示され，図５は放熱側モデルのメッキ層の厚さの変化が示され，また，図６は受熱側熱流モデルがそれぞれ示されている。
【００２４】
この熱交換器の構造は，図３に示すように，温度の互いに異なる流体，即ち，高温の流体ＧＡが受熱領域７を流れ，低温の流体ＧＢが放熱領域８を流れ，受熱領域７から放熱領域８へ熱移動させるものであり，例えば，流体ＧＡは，エンジンや燃焼器（図示せず）から放出された高温の排気ガスであり，また，流体ＧＢは，熱分解して改質燃料に変換される低温の天然ガスである。
【００２５】
この発明による熱交換器の構造は，図３に示されるように，受熱領域７と放熱領域８とが金属製隔壁２によって互いに遮蔽され，受熱領域７と放熱領域８とがに金属多孔質部材１１，１２（総称の場合は符号１）が配設されている。金属多孔質部材１は，金属多孔質部材１の多数の足部５を通じて接合層９，１０を介して熱伝導率の良好な金属製の隔壁２に接合されている。足部５には，図４に示すように，多数の枝部６が一体構造に分岐している。足部５の断面積Ａｘ，Ａは，受熱領域７側と放熱領域８側とで変更させることができる。
【００２６】
この熱交換器の構造は，特に，金属多孔質部材１の表層には，金属粉末とろう材とを練り合わせた板状ペーストを埋め込んで形成された接合層９，１０が形成され，金属多孔質部材１に設けられた接合層９，１０が隔壁２上に密接して配設され，金属多孔質部材１と隔壁２とが接合層９，１０が焼結されることによって互いに接合されていることを特徴としている。ここで，板状ペーストを構成する金属粉末は，銀，ニッケル，銅，亜鉛，アルミニウム等の高熱伝導率を有し，耐腐食性，耐熱性に富んだ金属材料である。
【００２７】
金属多孔質部材１は，ニッケル，銅，アルミニウム等の金属から成る。また，隔壁２は，ニッケル，銅等の高熱伝導率の金属から成る。更に，接合層９，１０に含有された金属粉末は，銀，ニッケル，銅，亜鉛等の耐熱性で高熱伝導率の金属から成る。また，接合層９，１０は，隔壁２を挟んで一方の金属多孔質部材１１に埋め込まれた高温耐熱性の第１接合層９と，他方の金属多孔質部材１２に埋め込まれ且つ第１接合層９より１００℃程低い温度の耐熱性の第２接合層１０とから構成され，そのため，第１接合層９は，第２接合層１０より焼結温度が高くなるように材料が選択されている。隔壁２への金属多孔質部材１１，１２との接合は，まず，金属多孔質部材１１に押し込んだ第１接合層９を隔壁２に密接して配置し，第１接合層９を高い温度で焼結することによって金属多孔質部材１１と隔壁２とを焼結された第１接合層９で接合し，次いで，金属多孔質部材１２に押し込んだ第２接合層１０を隔壁２に密接して配置し，第２接合層１０を低い温度で焼結することによって，焼結された第１接合層９を破壊することなく，金属多孔質部材１２と隔壁２とを焼結された第２接合層１０で接合することができる。場合によっては，隔壁２の両側に金属多孔質部材１を密接して配置し，同一の焼結温度によって同時に接合することもできる。その際には，第１接合層９と第２接合層１０とは，同程度の温度の耐熱性の材料，或いは同一材料で作製することも可能である。
【００２８】
金属多孔質部材１１の表面には，熱伝導率の大きい銅，銀，アルミニウム等の金属がメッキ又はデッピング，蒸着等のコーティングによって施されている。また，金属多孔質部材１２の表面には，例えば，天然ガスを熱分解するため，アルミナ，ジルコニア等のセラミックスがコーティングされ，また，セラミックスの表面にはプラチナ，パナジウム，ニッケル，ロジウム，ルテニウム，酸化セリウム等の触媒が付着されて触媒層１３が設けられている。
【００２９】
更に，金属多孔質部材１１，１２の表層には，熱伝導率の大きい銅，銀，アルミニウム等のメッキ層が施され，該メッキ層の厚さが接合層９，１０において徐々に変化している。更に，金属多孔質部材１１，１２へのメッキ層２０の厚さは，図５に示すように，金属多孔質部材１１，１２をメッキ槽に浸漬する所要時間を変えて徐々に変化させることで変化させることができる。また，金属多孔質部材１１，１２の表面にアルミニウムコーティングを行って，アルミニウム層を形成した場合には，アルミニウム層を熱処理し，結晶相としてのコランダムであるαアルミナを析出させる。それによって，金属多孔質部材１１，１２は，強度をアップし，耐酸化性を向上させると共に，表面に多数の凹凸や気孔を形成して表面積を増大させ，熱交換効率をアップする。
【００３０】
図４には，放熱領域８における金属多孔質部材１２の１単位，即ち，隔壁２に接合された１本の足部５と足部５から分岐する多数の枝部６が示されている。金属多孔質部材１２の接合層１０では，金属多孔質部材１２の足部５は，その断面直径Ｄ以上の長さＬに埋設した状態で隔壁２に接合されている。また，受熱領域７においても，図４に示すものと同様に，金属多孔質部材１１の接合層９では，金属多孔質部材１１の足部５は，その断面直径Ｄ以上の長さＬにわたって埋設した状態で接合されている。金属多孔質部材１１，１２は，隔壁２に多数の足部５が接合層９，１０によって接合され，図６に示すように，多数の枝部６が絡み合って接合された構造に形成されており，多数の枝部６間の隙間がオープンポア１４に形成され，オープンポア１４を流体ＧＡ，ＧＢがスムーズに流れる多孔体に構成されている。金属多孔質部材１１，１２では，上記の構造を持つことによって，受熱領域７では，受熱面積を大幅に拡大し，また，放熱領域８では，放熱面積を大幅に拡大した状態になっている。
【００３１】
この熱交換器の構造において，高温側の接合層９の隔壁２の面とは反対側の隔壁２の表面には，流体ＧＢの流れに沿って溝（図示せず）が設けることもできることは勿論である。
【００３２】
この熱交換器の構造は，例えば，図７に示すように，燃料改質装置に適用することができる。図７には，この熱交換器の構造が適用された燃料改質装置の１例が示されている。図７に示すように，燃料改質装置１５は，外筒１８内に同一の構造を有する一対の熱交換部１６，１７が配設されている。熱交換部１６，１７は，一方が天然ガスの改質側であり，他方が炭酸ガス捕集側であり，両部が順次に繰り返して排気ガスの熱エネルギによって天然ガスを炭酸ガスの存在下で熱分解するものである。熱交換部１６と熱交換部１７とは，断熱遮蔽層１９で互いに分離されている。また，熱交換部１６，１７は，排気ガスが流れる受熱領域７と天然ガスが流れる放熱領域８とに隔壁２で区画されて積層構造にそれぞれ構成されている。放熱領域８に配設された金属多孔質部材１２には，例えば，天然ガスが流れる際に，天然ガスの熱分解を助けるための触媒層１３が表面にコーティングされている。また，受熱領域８に配設された金属多孔質部材１１には，例えば，低温の排気ガスが流れる際に，天然ガスを熱分解するのに必要な炭酸ガスを捕捉するために，ゼオライト，リチウムジルコネート等の吸着剤が表面にコーティングされている。
【００３３】
燃料改質装置１５は，詳細には図示されていないが，例えば，エンジンの排気管の下流に設けられた天然ガスを触媒の存在下でエンジンに排気ガスエネルギーによって改質させて改質燃料に変換するものであり，ハウジング内には回転軸に取り付けられた外筒１８が外側にガス通路を形成するように配設され，外筒１８が断熱遮蔽層１９で熱交換部１６と熱交換部１７とに分離されている。熱交換部１６，１７は，仕切板となる隔壁２によって受熱領域７と放熱領域８とに分割されている。受熱領域７にはガス通路の上流側から流入させた高温の排気ガスを通過させて下流側から放出し，また，触媒が配置された放熱領域８にはガス通路の上流側から流入させた天然ガス，空気及び水蒸気を通過させる。天然ガスは，触媒の存在下で改質され，ガス通路の下流側から改質燃料を送り出すように構成されている。
【００３４】
また，燃料改質装置１５では，天然ガスの熱分解に必要な炭酸ガスを低温の炭酸ガスから金属多孔質部材１２に吸着捕捉するため，まず，一方の熱交換部１６における受熱領域７に位置する金属多孔質部材１１を通過して冷却された低温の前記排気ガスを，他方の熱交換部１７おける放熱領域８に位置する金属多孔質部材１２に通過させ，排気ガス中の炭酸ガスを金属多孔質部材１２の表面のゼオライトに吸着及び／又はリチウムジルコネートに反応吸着して捕捉する。次いで，外筒１８を半回転させ，他方の熱交換部１７における受熱領域７に位置する金属多孔質部材１１に高温の排気ガスを流入させると共に，熱交換部１７における放熱領域８に位置する金属多孔質部材１２に天然ガス（場合によっては，天然ガスに加えて水蒸気及び排気ガス）を流入させ，それによって，受熱領域７を通る排気ガスの熱エネルギによって放熱領域８を通る天然ガスを水素と一酸化炭素とから成る改質燃料に変換する。燃料改質装置１５は，上記の工程を繰り返して天然ガスを改質燃料に連続して改質するものである。
【００３５】
燃料改質装置１５は，上記のように構成されているので，受熱領域７と放熱領域８とに充填された金属多孔質部材１が加熱により輻射熱を発生し，熱交換効率をアップし，排気ガスが有する熱エネルギを天然ガスの改質に有効に利用し，天然ガスの主成分であるＣＨ_４をＣＯとＨ_２とに改質し，改質において排気ガス中のＣＯ_２を捕捉して排気ガスの温度が高い状態でＣＯ_２を利用して天然ガスを改質することを可能にしたものである。
【００３６】
【発明の効果】
この発明による熱交換器の構造は，上記のように，金属多孔質部材が接合層によって隔壁に一体構造として互いに接合されているので，隔壁と金属多孔質部材との接合面で熱遮断面が発生することがなく，両者間の熱伝導率が向上し，流体間の熱交換効率が大幅にアップする。また，受熱領域と放熱領域とにそれぞれ配設された金属多孔質部材に，天然ガス，排気ガス等の流体が流れることにより，流体が金属多孔質部材に接触する面積が大幅に増大し，熱交換効率を大幅にアップさせることができる。
【図面の簡単な説明】
【図１】この発明による熱交換器の構造の基本的原理を説明するための概念図である。
【図２】円形の管についての熱通過率を説明するための概念図である。
【図３】この発明による熱交換器の構造を説明するための熱移動モデルを示す概略説明図である。
【図４】この発明による熱交換器の構造を説明するための放熱側モデルを示す概略説明図である。
【図５】この発明による熱交換器の構造を説明するための放熱側モデルのメッキ層の厚さの状態を示す概略説明図である。
【図６】この発明による熱交換器の構造を説明するための受熱側熱流モデルを示す概略説明図である。
【図７】この発明による熱交換器の構造を燃料改質装置に適用した場合のモデルを示す概略説明図である。
【符号の説明】
１，１１，１２金属多孔質部材
２隔壁
３フィン
４管
５足部
６枝部
７受熱領域
８放熱領域
９第１接合層
１０第２接合層
１３触媒層
１４オープンポア
１５燃料改質装置
１６，１７熱交換部
１８外筒
１９断熱遮蔽層
ＧＡ，ＧＢ流体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is applicable to heat exchange between fluids. For example, natural gas is pyrolyzed to reform fuel, reformed water is converted to steam, and used steam is returned to water. The present invention relates to a structure of a heat exchanger using a porous metal capable of exchanging heat by using heat energy of exhaust gas or the like to raise the temperature of oil.
[0002]
[Prior art]
Conventionally, a heat exchanger in which a ceramic porous member is arranged in a gas passage is known. The heat exchanger includes a first-stage heat exchanger and a second-stage heat exchanger provided in an exhaust passage for heating steam with exhaust gas from an engine. The first-stage heat exchanger includes a steam passage arranged in the first casing and through which steam flows, and an exhaust gas passage arranged in the steam passage and through which exhaust gas flows. The second-stage heat exchanger includes a water / steam passage disposed in the second casing provided below the first casing and capable of storing water, and an exhaust gas disposed around the water / steam passage through which exhaust gas flows. And a gas passage. A porous ceramic member is disposed in each passage (for example, see Patent Document 1).
[0003]
Further, there is known a heat exchanger applied to a natural gas reformer. The natural gas reforming apparatus is to thermally decompose CH ₄ to the reforming fuel CO and H ₂ in the natural gas main component, the CO ₂ in the exhaust gas as well as improving the thermal efficiency by using the thermal decomposition It is to reduce the CO ₂ content in the exhaust gas to be released. The natural gas reformer has an exhaust gas passage body that forms an exhaust gas passage in an exhaust gas pipe, a gas fuel case in which gas fuel flows outside the exhaust gas pipe, and a gas fuel passage in the gas fuel case. A porous member made of porous ceramics to be formed is arranged, a surface of the porous member is coated with a catalyst having an action of converting CH ₄ and CO ₂ into a reformed fuel of CO and H ₂ , and a gas fuel pipe is formed. A heat insulating material is arranged on the outer periphery (for example, see Patent Document 2).
[0004]
Further, a gas engine equipped with a natural gas reforming device is known. The gas engine, the content of natural gas mainly composed of CH ₄ and is thermally decomposed in the reforming fuel CO and H ₂ and up the calorific value, the CO ₂ in the exhaust gas by using the thermal decomposition CO ₂ And the generation of NO _X is suppressed. The gas engine mixes CO ₂ with CH ₄ and sends it to a catalytic reactor arranged in an exhaust passage, where it is thermally decomposed by the thermal energy of the exhaust gas and converted into reformed fuel. CO ₂ fed from the separation membrane in the exhaust gas to the catalytic reactor takes in CO _2. The heat energy of the exhaust gas is recovered by the turbocharger, converted into high-temperature steam by the first heat exchanger and the second heat exchanger, and driven by the steam turbine to be recovered as electric energy. (For example, see Patent Document 3).
[0005]
[Patent Document 1]
JP-A No. 11-6601 (page 1, FIG. 1)
[Patent Document 2]
JP-A-11-93777 (page 1, FIG. 1)
[Patent Document 3]
JP-A-11-13547 (page 1, FIG. 1)
[0006]
[Problems to be solved by the invention]
By the way, when a heat exchanger having a porous structure is made of ceramics, it is difficult to use ceramics as a heat exchanger having a complicated shape because the ceramics are vulnerable to impact load. The advent of a heat exchanger was desired. However, it was not possible to join the metal porous member and the flat plate, and the realization was not possible. It is effective to use a high-efficiency heat exchanger for the system that recovers the thermal energy of the exhaust gas discharged from the engine. That is, in a heat shield type turbo compound engine using natural gas as a fuel, when the combustion chamber has a heat shield structure, in order to maximize the use of the fuel energy by converting it to power in the engine, the exhaust gas We must make the most of heat energy and convert it to power. In the heat exchange between working fluids as a heat exchanger, the heat exchange efficiency is important. The higher the heat exchange efficiency, the better the heat utilization rate and the better the overall heat efficiency. The performance of the heat exchanger is affected by the heat transfer coefficient and the heat conductivity of the working fluid, and it is better that the resistance is small in order to smoothly transfer heat.
[0007]
In recent years, research on forming a porous metal member having a high thermal conductivity by using a heat-resistant metal as a foam has been advanced. The metal porous member is three-dimensionally entangled and intersected by the metal, but is continuous in the form of a jungle gym. Therefore, the outer surface area per unit volume is about six times larger than that of the fin. Because it is continuous, it is suitable as a thermal fluid. Therefore, if the metal porous member is joined to the metal plate of the partition wall that separates the two working fluids, the partition wall is divided into a heat receiving area and a heat radiating area, and the working fluid such as one gas passes through the heat receiving area. The working fluid passes through the gap between the porous materials while colliding and contacting the surface thereof, and transfers the heat of the fluid to the solid of the metal porous member. The heat transferred to the solid is transmitted to the metal plate of the partition wall and transfers the heat to the other working fluid. Since the feet and the partition walls, which are porous elements, are securely joined, the heat flow can be smoothly moved from the heat receiving side to the heat radiating side.
[0008]
Therefore, in a heat exchanger, a high-efficiency heat exchanger is configured by disposing a porous metal member in a fluid passage and having the porous metal member on a heat exchange surface. Efficient heat exchangers are needed to convert the heat energy of exhaust gas to steam and to return used steam to water in order to reuse the heat energy of engine exhaust gas. . Considering the heat transfer of the heat exchanger theoretically, in the heat transfer from the hot gas to the solid, the larger the heat transfer coefficient of the gas is, the more heat is transferred. The heat transfer coefficient of a gaseous body is determined by the Reynolds number, which is a function of flow velocity and kinematic viscosity, the Prandtl number, which indicates gas properties, the thermal conductivity, and the Nusselt number, which is a function of Reynolds number.
This is represented by the following equation.
αg1 = Nu · λ / X
Nu = K ・ Re ^m・ Pr ⁿ
Re = U · X / ν
Here, αg1: heat transfer coefficient, Nu: Nusselt number, λ: thermal conductivity, K: constant, Re: Reynolds number, Pr: Prandtl number, U: representative speed, ν: kinematic viscosity, X: representative length.
Here, when the heat transfer coefficient is considered by an equation, the factor that has the greatest influence is the Reynolds number, and the Reynolds number can be said to be a function of speed. In a fluid flowing on a solid surface, the flow on the surface of the solid is zero, and the flow velocity of the fluid increases as the distance from the surface of the solid increases. Therefore, the Reynolds number is determined as a function of the flow characteristics near the solid surface.
[0009]
In order to increase the heat transfer from gas to solid, the following conditions can be considered.
1. To increase the contact area of a solid with a gas between the gas and the solid.
2. Solids are widely dispersed and distributed in a gas flow.
3. The heat conducting part transferred from the heat collecting part is made of a material with high thermal conductivity, and much heat is transferred to the partition between the fluids of the heat exchanger.
4. The heat collecting material and the partition walls must be securely joined as a solid and transfer heat effectively.
5. The heat transferred shall be effectively dissipated through the solid heat dissipator.
When a structure satisfying the above conditions 1 to 5 is shown in a conceptual diagram, a principle diagram as shown in FIG. 1 is obtained.
[0010]
In heat transfer / conductors, increasing the velocity of the gas, increasing the Reynolds number, and increasing the amount of heat transfer, rather than increasing the velocity of the gas, increasing the solid's transfer area increases the heat. Can be moved.
With reference to FIG. 1 and FIG. 2, heat reception and heat dissipation in the heat exchanger are obtained by transfer calculation as follows.
As shown in FIG. 2, the heat transfer amount Q in a heat exchanger having a passage formed by a circular tube 4 having fins 3 is represented by a heat transfer rate K (unit: W / m) as shown in the following equation. ² · K).
Q = K ・ Ar ・ ΔT
Here, Q: heat transfer amount, K: heat transmittance, Ar: reference area, ΔT: temperature difference.
[0011]
As shown in FIG. 2, the heat transfer coefficient K in the heat exchanger having a passage between the heat receiving side and the heat radiating side formed inside and outside the tube 4 having the fins 3 is represented by the following general formula 1. Indicated by

Here, hi: heat transfer coefficient on the inner diameter side (W / m ² · K), ho: heat transfer coefficient on the outer diameter side (W / m ² · K), λ: heat conductivity of the tube (W / m · K), di: inner diameter of the pipe (m), do: outer diameter of the pipe (m), Af: fin area inside the pipe (m ² ), φf: fin efficiency, Ab: outer circumference area between fins (m ² ), Ar: reference area (peripheral area of one fin pitch, m ² ), ln: natural logarithm. .
In the above equation 1, the term ln (do / di) is corrected by [di / 2] ln (do / di) when do and di of the tube 4 are significantly different. In the case of the finned tube 4, the correction is made as di / do (Afφf + Ab) / Ar. The reason for this is that the heat transfer area greatly changes with respect to the standard.
When do and di of the tube 4 do not change much, the heat transmission coefficient K is represented by the following general formula 2.

[0012]
From the above, the basic principle of the heat exchange efficiency will be described with reference to FIG. In FIG. 1, a heat receiving area 7 and a heat radiating area 8 constituting the heat exchanger are partitioned by the partition 2, and the high temperature gas GA flows through the heat receiving area 7 and the low temperature gas GB flows through the heat radiating area 8. ing. In the heat receiving area 7 and the heat radiating area 8, a plurality of branches 6 are integrally formed on one foot 5 joined to the partition 2 by a bonding layer 9 in an integrated structure. The metal porous member 1 is constituted by a multiplicity of branch portions 6 gathering in a complicated manner. Normally, the heat transfer coefficient K is determined by the coefficient of heat transfer coefficient on the heat transfer side and the heat transfer side. The fins 3 (FIG. 2), the metal porous member 1 and the like are attached to the outer surface of the partition wall 2 for separating the working fluid. For the heat exchanger, the calculated values take into account the area effect, which agrees with the experimental values. Therefore, in the heat exchanger, if the structure of the basic principle shown in FIG. 1 is used so as to increase the areas on the heat receiving side and the heat radiating side, the branch portion diffused in all directions with respect to one foot 5 6 is the heat receiving area, and the heat transmission rate can be increased 3 to 5 times. Therefore, in the heat exchanger, there is a problem of how to increase the area in contact with the fluid in order to increase the heat transfer rate, and in particular, how to form an integral structure for joining with the partition partitioning the fluid.
[0013]
[Means for Solving the Problems]
An object of the present invention is to solve the above problems by connecting each foot constituting the metal porous member to the partition wall as a metal body in an integrated structure, and physically connecting the metal porous member and the partition wall. In this way, the heat energy received in the heat receiving area is transmitted to the heat radiating area to dissipate heat, thereby increasing the heat transmission rate by 3 to 5 times. In joining the partition between the area and the heat dissipation area and the porous metal members arranged in both areas, the joining of the porous metal member and the partition is made into an integral structure via a bonding layer, and the heat is blocked. The heat exchange efficiency is improved by eliminating the existence of the part, and the heat exchange efficiency of heat energy such as exhaust gas discharged from the engine is improved. For example, natural gas is reformed into a reformed fuel of CO and H _2. It can be applied to fuel reformers or convert water to steam. It is an object of the present invention to provide a structure of a heat exchanger applied to a device for changing the temperature or raising the temperature of oil.
[0014]
The present invention provides a heat exchanger having a heat receiving area and a heat radiating area through which fluids having different temperatures flow, and transferring heat from the heat receiving area to the heat radiating area, wherein a partition is provided between the heat receiving area and the heat radiating area. A metal porous member is disposed in each of the heat receiving area and the heat radiating area, and a bonding layer made of a plate-like paste obtained by kneading a metal powder and a brazing material is provided on a surface layer of the metal porous member. The joining layer is tightly joined to the element of the metal porous member, and is also closely joined to the partition, and the metal porous member and the partition are conductively joined to each other by welding of the joining layer. The present invention relates to a structure of a heat exchanger.
[0015]
The metal porous member is made of a metal such as nickel, nickel chromium alloy, copper, aluminum, etc., the partition is made of a metal such as nickel, nickel chrome and copper, and the metal powder is a heat resistant material such as silver, nickel, copper, zinc or the like. It is made of a metal having high thermal conductivity.
[0016]
The bonding layer is 100 ° C. higher than the first bonding layer embedded in one of the metal porous members with the high temperature and heat resistance embedded between the partition walls and the other of the first bonding layer embedded in the other metal porous member. And a second bonding layer having a lower melting temperature, wherein the first bonding layer is made of a bonding layer material selected to have a higher melting temperature than the second bonding layer. Further, in the joining layer of the porous metal member, the foot portion of the porous metal member is buried in a section having a diameter equal to or greater than the cross-sectional diameter of the foot portion or is joined in a conical shape.
[0017]
The surface of the metal porous member is coated with plating, dipping, vapor deposition, or the like of copper, aluminum, silver, or the like having high thermal conductivity. Further, a groove is provided on the surface of the metal porous member opposite to the joining surface along the flow of the fluid.
[0018]
Ceramics such as alumina and zirconia are coated on the surface of the metal porous member, and a catalyst such as platinum, panadium, nickel, rhodium, ruthenium and cerium oxide is attached to the surface of the ceramics.
[0019]
A plating layer of copper, silver, aluminum or the like having a high thermal conductivity is applied to a surface layer of the porous metal member, and the thickness of the plating layer is gradually changed in the bonding layer.
[0020]
The thickness of the plating layer on the metal porous member may be gradually changed by changing a time required for dipping the metal porous member in a plating bath.
[0021]
The surface of the metal porous member is coated with aluminum to form an aluminum layer, and the aluminum layer is heat-treated to precipitate α-alumina.
[0022]
In the structure of the heat exchanger, as described above, the fins, which are bonded to the partition of the heat exchanger, that is, the metal porous members are bonded to the surface layer of the partition, so that the heat exchange efficiency can be improved.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a structure of a heat exchanger according to the present invention will be described with reference to the drawings. The basic structure of the heat exchanger according to the present invention will be described with reference to FIGS. FIG. 3 shows a heat transfer model for explaining the structure of the heat exchanger according to the present invention, FIG. 4 shows a heat radiation side model, FIG. 5 shows a change in the thickness of the plating layer of the heat radiation side model, FIG. 6 shows heat receiving side heat flow models.
[0024]
As shown in FIG. 3, the structure of the heat exchanger is such that fluids having different temperatures, that is, a high-temperature fluid GA flows through the heat-receiving region 7, a low-temperature fluid GB flows through the heat-radiating region 8, and heat is radiated from the heat-receiving region 7. For example, the fluid GA is high-temperature exhaust gas discharged from an engine or a combustor (not shown), and the fluid GB is thermally decomposed into reformed fuel. Low temperature natural gas that is converted.
[0025]
As shown in FIG. 3, the structure of the heat exchanger according to the present invention is such that the heat receiving area 7 and the heat radiating area 8 are shielded from each other by the metal partition 2, and the heat receiving area 7 and the heat radiating area 8 are formed of a metal porous member. Reference numerals 11 and 12 (in the case of a generic name, reference numeral 1) are provided. The metal porous member 1 is joined to the metal partition wall 2 having good thermal conductivity through the bonding layers 9 and 10 through the many feet 5 of the metal porous member 1. As shown in FIG. 4, a large number of branch portions 6 are branched from the foot portion 5 into an integral structure. The cross-sectional area Ax, A of the foot 5 can be changed between the heat receiving area 7 side and the heat radiating area 8 side.
[0026]
The structure of this heat exchanger is such that joining

layers

9 and 10 formed by embedding a plate-like paste obtained by kneading a metal powder and a brazing material are formed on the surface layer of the metal porous member 1. The bonding layers 9 and 10 provided on the member 1 are closely arranged on the partition 2, and the metal porous member 1 and the partition 2 are bonded to each other by sintering the bonding layers 9 and 10. It is characterized by: Here, the metal powder constituting the plate-like paste is a metal material having high thermal conductivity, such as silver, nickel, copper, zinc, and aluminum, and having high corrosion resistance and heat resistance.
[0027]
The metal porous member 1 is made of a metal such as nickel, copper, and aluminum. The partition 2 is made of a metal having high thermal conductivity such as nickel and copper. Further, the metal powder contained in the bonding layers 9 and 10 is made of a metal having high heat conductivity and high heat conductivity such as silver, nickel, copper, and zinc. The bonding layers 9 and 10 are embedded in one of the metal porous members 11 with the partition wall 2 interposed therebetween, and the first bonding layer 9 with high heat resistance is embedded in the other metal porous member 12 and the first bonding layer 9 is embedded therein. The first bonding layer 9 is made of a material such that the sintering temperature is higher than that of the second bonding layer 10. I have. First, the first bonding layer 9 pressed into the metal porous member 11 is disposed in close contact with the partition 2, and the first bonding layer 9 is bonded at a high temperature. By sintering, the metal porous member 11 and the partition wall 2 are joined by the sintered first bonding layer 9, and then the second bonding layer 10 pushed into the metal porous member 12 is brought into close contact with the partition wall 2. By arranging and sintering the second joining layer 10 at a low temperature, the sintered second joining layer 9 is bonded to the metal porous member 12 without breaking the sintered first joining layer 9. The layers 10 can be joined. In some cases, the metal porous members 1 can be closely arranged on both sides of the partition wall 2 and can be simultaneously joined at the same sintering temperature. In this case, the first bonding layer 9 and the second bonding layer 10 can be made of a heat-resistant material having the same temperature or the same material.
[0028]
The surface of the metal porous member 11 is coated with a metal having high thermal conductivity, such as copper, silver, or aluminum, by coating such as plating or dipping or vapor deposition. Further, the surface of the metal porous member 12 is coated with ceramics such as alumina and zirconia to thermally decompose natural gas, and the surface of the ceramics is coated with platinum, panadium, nickel, rhodium, ruthenium, oxide, and the like. The catalyst layer 13 is provided by attaching a catalyst such as cerium.
[0029]
Further, a plating layer of copper, silver, aluminum or the like having a high thermal conductivity is applied to the surface layers of the

porous metal members

11 and 12, and the thickness of the plating layer gradually changes in the bonding layers 9 and 10. I have. Further, as shown in FIG. 5, the thickness of the plating layer 20 on the metal

porous members

11 and 12 is gradually changed by changing the time required for immersing the metal

porous members

11 and 12 in the plating tank. Can be changed. When the surfaces of the metal

porous members

11 and 12 are coated with aluminum to form an aluminum layer, the aluminum layer is heat-treated to precipitate α-alumina which is corundum as a crystal phase. Thereby, the metal

porous members

11 and 12 increase the strength, improve the oxidation resistance, and form many irregularities and pores on the surface to increase the surface area, thereby increasing the heat exchange efficiency.
[0030]
FIG. 4 shows one unit of the metal porous member 12 in the heat radiation area 8, that is, one foot 5 joined to the partition wall 2 and a number of branches 6 branched from the foot 5. In the bonding layer 10 of the metal porous member 12, the foot portion 5 of the metal porous member 12 is bonded to the partition wall 2 in a state where the foot portion 5 is embedded in a length L equal to or more than the cross-sectional diameter D. Also in the heat receiving region 7, the foot 5 of the metal porous member 11 is embedded in the bonding layer 9 of the metal porous member 11 over a length L equal to or more than the cross-sectional diameter D, as in the case shown in FIG. It is joined in the state where it was done. The metal

porous members

11 and 12 are formed in a structure in which a large number of feet 5 are joined to the partition walls 2 by joining

layers

9 and 10, and a large number of branches 6 are intertwined and joined as shown in FIG. In addition, gaps between the many branch portions 6 are formed in the open pores 14, and the open pores 14 are formed as porous bodies through which the fluids GA and GB flow smoothly. The metal

porous members

11 and 12 have the above-described structure, so that the heat receiving area 7 has a greatly increased heat receiving area, and the heat radiating area 8 has a greatly expanded heat radiating area.
[0031]
In the structure of the heat exchanger, a groove (not shown) may be provided on the surface of the partition wall 2 on the side opposite to the surface of the partition wall 2 of the joining layer 9 on the high temperature side along the flow of the fluid GB. Of course.
[0032]
The structure of this heat exchanger can be applied to a fuel reformer, for example, as shown in FIG. FIG. 7 shows an example of a fuel reformer to which the structure of the heat exchanger is applied. As shown in FIG. 7, the fuel reforming apparatus 15 includes a pair of

heat exchange units

16 and 17 having the same structure in an outer cylinder 18. One of the

heat exchange units

16 and 17 is on the natural gas reforming side, and the other is on the carbon dioxide gas collecting side. Is to be thermally decomposed. The heat exchange section 16 and the heat exchange section 17 are separated from each other by a heat insulating shielding layer 19. Further, the

heat exchange sections

16 and 17 are divided into a heat receiving area 7 through which the exhaust gas flows and a heat radiating area 8 through which the natural gas flows by the partition wall 2 to have a laminated structure. The surface of the metal porous member 12 disposed in the heat radiation region 8 is coated with a catalyst layer 13 for assisting thermal decomposition of the natural gas when the natural gas flows, for example. In addition, the metal porous member 11 disposed in the heat receiving region 8 has, for example, zeolite or lithium for capturing carbon dioxide necessary for thermally decomposing natural gas when low-temperature exhaust gas flows. An adsorbent such as zirconate is coated on the surface.
[0033]
Although not shown in detail, the fuel reforming device 15 reforms the natural gas provided downstream of the exhaust pipe of the engine with the exhaust gas energy in the presence of a catalyst to produce a reformed fuel. In the housing, an outer cylinder 18 attached to the rotation shaft is disposed inside the housing so as to form a gas passage on the outside, and the outer cylinder 18 is connected to the heat exchange section 16 and the heat exchange section by the heat insulating shielding layer 19. 17 are separated. The

heat exchange sections

16 and 17 are divided into a heat receiving area 7 and a heat radiating area 8 by the partition 2 serving as a partition plate. The high-temperature exhaust gas that has flowed in from the upstream side of the gas passage passes through the heat receiving region 7 and is discharged from the downstream side, and the natural gas that flows in from the upstream side of the gas passage into the heat radiation region 8 in which the catalyst is disposed. Allow gas, air and water vapor to pass. Natural gas is reformed in the presence of a catalyst, and is configured to deliver reformed fuel from a downstream side of the gas passage.
[0034]
In the fuel reformer 15, the carbon dioxide required for the thermal decomposition of natural gas is adsorbed and captured from the low-temperature carbon dioxide by the metal porous member 12. The low-temperature exhaust gas cooled by passing through the metal porous member 11 is passed through the metal porous member 12 located in the heat radiation area 8 in the other heat exchange section 17, and carbon dioxide gas in the exhaust gas is It is adsorbed on zeolite on the surface of the porous member 12 and / or reactively adsorbed on lithium zirconate and captured. Next, the outer cylinder 18 is rotated half a turn to allow the high-temperature exhaust gas to flow into the metal porous member 11 located in the heat receiving area 7 in the other heat exchange section 17 and the metal located in the heat radiation area 8 in the heat exchange section 17. Natural gas (in some cases, steam and exhaust gas in addition to natural gas) flows into the porous member 12, whereby natural gas passing through the heat dissipation region 8 is converted into hydrogen by heat energy of the exhaust gas passing through the heat receiving region 7. It is converted to reformed fuel consisting of carbon monoxide. The fuel reformer 15 continuously reforms natural gas into reformed fuel by repeating the above steps.
[0035]
Since the fuel reformer 15 is configured as described above, the metal porous member 1 filled in the heat receiving area 7 and the heat radiating area 8 generates radiant heat by heating, thereby increasing the heat exchange efficiency and exhausting. the heat energy possessed by the gas by effectively utilizing the reforming of natural gas, reforming CH _4, the main component of natural gas and CO and H _2, to capture CO ₂ in the exhaust gas in the reforming This makes it possible to reform natural gas using CO ₂ while the temperature of the exhaust gas is high.
[0036]
【The invention's effect】
In the structure of the heat exchanger according to the present invention, as described above, since the metal porous member is joined to the partition wall as an integral structure by the bonding layer, the heat shielding surface is formed at the joint surface between the partition wall and the metal porous member. This does not occur, the thermal conductivity between the two is improved, and the heat exchange efficiency between the fluids is greatly increased. In addition, since fluid such as natural gas and exhaust gas flows through the porous metal members provided in the heat receiving area and the heat radiating area, the area in which the fluid comes into contact with the porous metal member is greatly increased. The exchange efficiency can be greatly increased.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram for explaining a basic principle of a structure of a heat exchanger according to the present invention.
FIG. 2 is a conceptual diagram for explaining a heat transfer coefficient of a circular tube.
FIG. 3 is a schematic explanatory view showing a heat transfer model for explaining the structure of the heat exchanger according to the present invention.
FIG. 4 is a schematic explanatory view showing a heat radiation side model for explaining the structure of the heat exchanger according to the present invention.
FIG. 5 is a schematic explanatory view showing a state of a thickness of a plating layer of a heat radiation side model for explaining a structure of a heat exchanger according to the present invention.
FIG. 6 is a schematic explanatory view showing a heat-receiving-side heat flow model for explaining the structure of the heat exchanger according to the present invention.
FIG. 7 is a schematic explanatory view showing a model when the structure of the heat exchanger according to the present invention is applied to a fuel reformer.
[Explanation of symbols]
1, 11, 12 Metal porous member 2 Partition wall 3 Fin 4 Tube 5 Foot 6 Branch 7 Heat receiving area 8 Heat radiating area 9 First bonding layer 10 Second bonding layer 13 Catalyst layer 14 Open pore 15

Fuel reformer

16, 17 Heat exchange section 18 Outer cylinder 19 Heat insulation shielding layer GA, GB fluid

Claims

In a heat exchanger that has a heat receiving area and a heat radiating area through which fluids having different temperatures flow, and transfers heat from the heat receiving area to the heat radiating area, the heat receiving area and the heat radiating area are shielded from each other by a partition. A metal porous member is disposed in each of the heat receiving region and the heat radiating region, and a bonding layer made of a plate-like paste obtained by kneading a metal powder and a brazing material is formed on a surface layer of the metal porous member; The joining layer is tightly joined to the element of the metal porous member, and further closely joined to the partition, and the metal porous member and the partition are conductively joined to each other by welding of the joining layer. Characteristic heat exchanger structure.

The metal porous member is made of a metal such as nickel, nickel chromium alloy, copper, aluminum, etc., the partition is made of a metal such as nickel, nickel chrome and copper, and the metal powder is a heat resistant material such as silver, nickel, copper, zinc or the like. The heat exchanger structure according to claim 1, wherein the heat exchanger is made of a metal having high thermal conductivity.

The bonding layer is 100 ° C. higher than the first bonding layer embedded in one of the metal porous members with the high temperature and heat resistance embedded between the partition walls and the other of the first bonding layer embedded in the other metal porous member. And a second bonding layer having a lower melting temperature, wherein a material of the bonding layer is selected so that the first bonding layer has a higher melting temperature than that of the second bonding layer. 3. The structure of the heat exchanger according to 2.

In the joining layer of the porous metal member, the foot portion of the porous metal member is buried in a diameter equal to or greater than a cross-sectional diameter of the foot portion or is joined in a conical shape. The structure of the heat exchanger according to claim 1.

The surface of the metal porous member is plated with copper, aluminum, silver, or the like having a high thermal conductivity or coated by dipping, vapor deposition, or the like. The structure of the heat exchanger according to 1.

The heat-generating device according to any one of claims 1 to 5, wherein a groove is provided on a surface of the metal porous member opposite to the joining surface along a flow of the fluid. Exchanger structure.

The surface of the metal porous member is coated with a ceramic such as alumina or zirconia, and a catalyst such as platinum, panadium, nickel, rhodium, ruthenium or cerium oxide is attached to the surface of the ceramic. The structure of the heat exchanger according to claim 1.

A plating layer made of copper, silver, aluminum or the like having a high thermal conductivity is applied to a surface layer of the metal porous member, and a thickness of the plating layer is gradually changed in the bonding layer. The structure of the heat exchanger according to claim 1.

9. The heat exchanger according to claim 8, wherein the thickness of the plating layer on the metal porous member can be gradually changed by changing a required time for immersing the metal porous member in a plating bath. Vessel structure.

The heat exchanger structure according to claim 1, wherein an aluminum layer is formed by coating the surface of the metal porous member with aluminum, and α-alumina is deposited by heat-treating the aluminum layer.