JP3617538B2

JP3617538B2 - Heat exchanger tube for absorber

Info

Publication number: JP3617538B2
Application number: JP09838694A
Authority: JP
Inventors: 直栄佐々木; 嘉弘西本
Original assignee: Sumitomo Light Metal Industries Ltd
Current assignee: Sumitomo Light Metal Industries Ltd
Priority date: 1994-05-12
Filing date: 1994-05-12
Publication date: 2005-02-09
Anticipated expiration: 2020-02-09
Also published as: JPH07305918A

Description

【０００１】
【技術分野】
本発明は、吸収式冷凍器や吸収式ヒートポンプ等の吸収器内に配管される伝熱管であって、特に、略鉛直方向に配管されて管内面に沿って吸収液が流下せしめられる一方、管外面に複数の冷却フィンが装着されて冷却空気が接触せしめられる空冷式の吸収器に用いられる伝熱管に関するものである。
【０００２】
【背景技術】
吸収式冷凍器や吸収式ヒートポンプ等の吸収器としては、従来から、一般に、管内に冷却水を流通せしめて、管外表面を流下せしめられる吸収液を冷却するようにした水冷式のものが採用されているが、近年、小型化を図るために空冷式の吸収器が研究されており、家庭用の小型冷房機等への適用も検討されている。
【０００３】
ところで、空冷式の吸収器においては、冷却効率や吸収液の流通性の確保等の観点から、複数本の伝熱管を略鉛直方向に配管して、その管内面に沿って吸収液を流下させる一方、管外面に複数の冷却フィンを装着して冷却空気を接触せしめる構造が、好適に採用される。
【０００４】
ところが、かくの如き空冷式の吸収器においては、従来の水冷式の吸収器に用いられている内外面が平滑な円形断面の平滑管を伝熱管として採用すると、吸収液が直線的に流下してしまい液膜が充分に広がらず、液膜の滞留時間も短くなるために充分な伝熱性能を得ることが難しい。そこで、特開平４−１５１４７３号公報に記載されているように平滑管の内表面を切削工具等で切り起こして局部的な突起を形成したり、管内表面に濡れ性向上のための表面処理を施したりすることが提案されているが、未だ、管周方向への広がりを充分に得ることができず、吸収液の滞留時間や管内表面の濡れ面積を確保することも難しいために、満足できる伝熱性能を得ることが困難であった。
【０００５】
また、平滑管の内表面を切削工具で切り起こして管長手方向に連続して螺旋状に延びる突起を形成することによって、管内表面に螺旋状に延びる溝部を形成することも考えられるが、このような構造のものにあっては、吸収液が螺旋状の溝部に沿って管周方向に案内されて広げられるものの、切起しによって形成された突起が、鋭角的な頂角を有する略三角形の断面形状となるために、突起の表面に膜切れが生じ易く、液膜の厚さに偏りが生じて液膜の広がりが充分でなくなり、その結果、螺旋状の突起の形成によって管内表面積が増大されるにも拘わらず、全体としての伝熱性能の向上は余り望めなかったのである。
【０００６】
或いはまた、管内にコイル部材を挿入して管内周面に密接配置することによって、管内表面に螺旋状に延びる溝部を形成することも考えられるが、このような構造のものにあっては、コイル部材の管内表面への密着性を安定して得難いために、性能の安定性や耐久性に問題があり、しかも、管内にコイル部材を配設するには、伝熱管とは別途コイル部材を準備し、それを伝熱管内に挿入した後、かかるコイル部材を管内表面に密接させる加工をしなければならないために、製造が極めて面倒であるという問題もあった。
【０００７】
【解決課題】
ここにおいて、本発明は、上述の如き事情を背景として為されたものであって、その解決課題とするところは、略鉛直方向に配管した場合でも、管内を流下せしめられる吸収液の滞留時間を充分に得ることができると共に、管内表面において液膜の著しい偏りを生ずることなく有効な濡れ面積を確保することができ、有効伝熱面積が増加されて伝熱性能の向上が達成され得る吸収器用伝熱管を提供することにある。
【０００８】
【解決手段】
そして、かかる課題を解決するために、本発明は、略鉛直方向に配管されて吸収液が管内面に沿って流下せしめられる一方、管外面に複数の冷却フィンが装着されて冷却空気が接触せしめられる空冷式の吸収器用伝熱管において、５〜７５°のリード角で管内面を管長手方向に向かって螺旋状に延びる凹部と凸部を、管周方向で交互に位置するように、それぞれ管周方向で１．０〜５．０ｍｍのピッチで形成すると共に、該凸部の凹部に対する突出高さを０．２〜０．６ｍｍとする一方、かかる凸部の表面を湾曲断面形状とし、且つ凹部の底部を実質的な不連続部を有する断面形状としたことを、特徴とするものである。
【０００９】
そこにおいて、凸部の断面形状としては、半円形状や半楕円形状，放物線形状等が何れも採用され得る。また、そのような凸部を、管軸方向一方の側に傾斜して設けるようにしても良い。
【００１０】
さらに、凹部および凸部のリード角よりも小さなリード角を有するコイル部材を管内に挿入し、該コイル部材を管内周面に密接させて配設することも可能である。
【００１１】
【発明の具体的構成】
先ず、図１〜３には、本発明に従う構造とされた吸収器用伝熱管の一具体例が示されている。かかる伝熱管１０は、全体として円形断面の直管形状を有しており、図４に示されているように、適当な長さに切断されて複数本が互いに所定距離を隔てて配管されると共に、それらの外周面にプレートフィン１２が装着されて一体的に組み付けられることにより、空冷式の吸収器を構成するようになっている。そして、各伝熱管１０の軸心が略鉛直方向に延びる状態で吸収器内に配設され、管内面に沿って吸収液１４が流下されることにより、管内に導かれた冷媒が吸収液に吸収されるようにする一方、管外面およびプレートフィン１２に冷却空気が接触せしめられて、冷媒の吸収液への溶解によって生ずる溶解熱乃至は希釈熱や潜熱による温度上昇が抑えられることにより、吸収器として機能せしめられるようになっている。
【００１２】
ここにおいて、伝熱管１０の材質は、従来と同様、使用する冷媒および吸収剤に対する耐蝕性や伝熱性，加工性等を考慮して選定されることとなり、例えば、水を冷媒とし、臭化リチウムを吸収剤とする場合には、銅管が好適に採用され得る。また、この伝熱管１０は、図１中のＡ部の拡大図および横断面拡大図が図２および図３に示されているように、外周面１６が平滑面とされている一方、内周面に対して、それぞれ管長手方向に螺旋状に延びる複数条の凹部１８と凸部２０が、管周方向で交互に位置して互いに略平行に形成されている。
【００１３】
これら凹部１８と凸部２０は、図面上に明示されてはいないが、管周方向におけるピッチ：ｐ（図３参照）、換言すれば管軸に直角な断面において周方向で隣接位置する凹部１８と凹部１８および凸部２０と凸部２０の間隔が、何れも１．０〜５．０ｍｍとなるように設定される。具体的には、例えば、φ１９．０５ｍｍの銅管であれば、凹部１８および凸部２０の数が、それぞれ、一周当たり１２〜４８条となるように設定されることとなる。
【００１４】
けだし、かかるピッチ：ｐが、１．０ｍｍより小さいと、凹部１８の幅が小さくなり過ぎて、臭化リチウム水溶液等の粘性の高い溶液が凹部１８内に充分に流れ込みにくくなり、凹部１８に沿った管周方向への液膜の広がりが充分に期待できなくなるからであり、一方、ピッチ：ｐが、５．０ｍｍより大きいと、管内面に形成される凹凸が少なくなって有効な伝熱面積の増加が実現され難くなるからである。即ち、凹部１８および凸部２０の管周方向におけるピッチ：ｐを、１．０〜５．０ｍｍとすることにより、それら凹部１８および凸部２０の形成による管内面の伝熱面積の増加と、凹部１８の案内作用による管周方向への液膜の広がりの促進とが、共に有利に達成されて、有効伝熱面積の拡大が効果的に図られ得るのである。
【００１５】
また、これら凹部１８と凸部２０は、伝熱管１０の全長に渡って一定のリード角で形成されていても、或いは部分的にリード角が変化させられていても良いが、かかるリード角：αが、何れの部位においても５〜７５°の範囲内となるように、好ましくは５〜３０°の範囲内となるように設定される。なお、リード角：αとは、図１に示されているように、凹部１２または凸部１４の接線と、管軸に直角な平面とがなす角度をいう。
【００１６】
けだし、リード角：αが７５°より大きいと、伝熱管１０を吸収器に組み付けた際に、凹部１８に沿う吸収液の流下速度が大きくなって、管内面における液膜の滞留時間を充分に確保することが難しくなるからであり、一方、リード角：αが５°より小さいと、伝熱管１０の内周面における凹部１８および凸部２０の形成が困難となるからである。即ち、凹部１８および凸部２０のリード角：αを、５〜５０°とすることにより、より好ましくは５〜３０°とすることにより、製作性の著しい低下を伴うことなく、管内面を流下せしめられる液膜が凹部１８に沿って管周方向に導かれて液膜の流下速度が効果的に抑えられると共に、流下距離が実質的に増大されて、吸収液の滞留時間を有利に確保することができるのである。
【００１７】
さらに、凹部１８には、その断面において、実質的な不連続部２２が底部に形成されている。この不連続部２２は、凹部１８の横断面において、共通接線を持たない交点で連接された屈曲点状の連接部として形成され、或いは、曲率半径が３．５ｍｍ以下である湾曲面や、幅が２．５ｍｍ以下である平坦面の如く、実質的に屈曲点とみなし得る連接部として形成される。
【００１８】
すなわち、このような実質的な不連続部２２を凹部１８の底部に形成すれば、かかる凹部１８の底部において、伝熱管１０の長手方向に向かって螺旋状に延びる筋状の細溝が構成されることとなり、その結果、管内面を流下せしめられる吸収液が、その表面張力等に基づく毛細管現象によって、かかる細溝に沿って凹部１８内を管周方向に螺旋状に広がるのであり、その結果、吸収液の凹部１８および凸部２０に沿った管周方向への流れが促進されて、液膜の管周方向への広がりや滞留時間の延長が図られ、有効伝熱面積、延いては伝熱性能が有利に向上され得るのである。
【００１９】
なお、かかる凹部１８の底部は、その断面形状において、実質的な不連続部２２を挟んだ両側内面の交角を２０〜９０°とすることが望ましい。それによって、毛細管現象による吸収液の管周方向への広がりの促進効果が一層有利に発揮され得るのである。
【００２０】
また、凸部２０は、湾曲断面形状をもって形成されている。即ち、かかる凸部２０の表面は、その横断面の全体に渡って曲率半径が一定である必要はないが、連続しており、例えば、半円形状や半楕円形状，放物線形状などの断面形状が好適に採用され得る。
【００２１】
すなわち、凸部２０を、このような湾曲断面形状をもって形成すれば、吸収液が凸部２０を乗り越えて鉛直下方に流下する際にも、その流れがスムーズで、表面張力の作用によって略均一の厚さの液膜が有利に形成されて、部分的な膜厚の偏りや渇き面（液切れ）の発生が効果的に防止され得るのであり、その結果、濡れ面積が有利に確保されると共に、液膜厚さの大きな偏りによる部分的な熱伝導の低下が回避されて、有効伝熱面積の増加による伝熱性能の向上がより有効に達成され得るのである。
【００２２】
なお、凸部２０の表面を、その全体に渡って、変曲点を有しない断面形状とすると共に、そのような断面形状をもって形成されて隣接位置せしめられた凸部２０，２０の表面を、実質的な不連続部２２によって直接的に接続せしめてなる断面形状とすることも可能である。そして、凹部１８および凸部２０を、このような断面形状をもって形成すれば、凹部１８の底部に沿った吸収液の管周方向への広がりと、凸部２０の表面における略均一な液膜の形成とが、何れも、極めて有効に達成され得るのこととなる。
【００２３】
さらに、凸部２０は、凹部１８の底面からの突出高さが０．２〜０．６ｍｍとなるように形成される。
【００２４】
けだし、凸部２０の突出高さが０．２mmより低いと、臭化リチウム溶液等の比重が大きい吸収液を凹部１８内に有効に保持することが難しく、結果的に、凹部１８に沿った吸収液の管周方向への広がり効果が低下してしまうからであり、一方、凸部２０の突出高さが０．６mmより高いと、伝熱管１０の内周面における凹部１８および凸部２０の形成が困難となるからである。即ち、凸部２０の突出高さを、０．２〜０．６mm、好ましくは０．３〜０．４mmとすることにより、良好なる製作性を確保しつつ、凹部１８に沿った管周方向への液膜の広がりの促進による有効伝熱面積の拡大が効果的に図られ得るのである。
【００２５】
なお、吸収液を凹部１８内に有利に保持せしめて、吸収液の凹部１８に沿った管周方向への広がりを促進するためには、図５に示されているように、凸部２０を、管軸方向一方の側に傾斜して突出形成することも有効である。即ち、かくの如き傾斜した凸部２０を形成し、かかる凸部２０が鉛直上方に向かって傾斜するように伝熱管１０を配管すれば、管内面に沿って流下せしめられる吸収液を凸部２０が受ける形となるのであり、それ故、液膜が凹部１８内に有利に保持されて、凹部１８に沿った液膜の管周方向への広がりや滞留時間の延長が、一層効果的に達成され得るのである。
【００２６】
また、図面上に明示はされていないが、上述の如き凹部１８と凸部２０が形成された伝熱管１０に対して、凹部１８および凸部２０のリード角：αよりも小さなリード角を有する螺旋状のコイル部材を挿入し、凸部２０に密接させて配設することも可能である。このようなコイル部材を配設することにより、伝熱面積の更なる増大が図られ得ると共に、吸収液がコイル部材に沿って管周方向に導かれることにより吸収液の滞留時間の更なる増大が図られ得るのである。
【００２７】
なお、かかるコイル部材は、伝熱管１０と同様、冷媒や吸収剤に対する耐蝕性等を考慮して材質が選定されることとなり、例えば、凹部１８および凸部２０が形成された伝熱管１０内に挿入された後、拡管プラグ等を挿入して、コイル部材を伝熱管１０の内周面に圧接固定すること等によって、伝熱管１０に組み付けられる。
【００２８】
ところで、このような伝熱管１０は、内外周面が平滑な素管に対して、目的とする凹部１８および凸部２０に対応した螺旋状の凹凸が外周面に付されたプラグを用い、引抜加工を施すこと等によっても製造することが可能であるが、特に、転造加工によって有利に製造され得る。
【００２９】
具体的には、例えば、図６〜８に示されているように、内外周面が平滑な素管２４の内部に、目的とする凹部１８および凸部２０に対応した螺旋状の凹凸が外周面に付されたプラグ２６を挿入配置すると共に、素管２４の外部に３つのロール２６を配設せしめて、それらロール２６によって素管２４の外周面に圧力を加え、素管２４を回転させながら軸方向に移動させて管内周面に凹凸加工を施すことにより、目的とする伝熱管１０が製造されることとなる。
【００３０】
なお、ロール２６としては、外周面が平滑な異径のディスク２８の複数枚を軸方向に重ね合わせてロッド３０に装着したものが好適に用いられ、一般的な転造加工と同様、ロッド３０の軸が管軸に対して所定角度：βだけ傾斜した状態で配設される。このようなロール２６を採用すれば、各種サイズの伝熱管の転造加工に、容易に対応することができるのである。
【００３１】
すなわち、上述の如き構造の伝熱管１０にあっては、転造加工等によって容易に製造することができるのであり、それ故、従来の切起し突起を設けた伝熱管に比べて、製造性およびコスト性が大幅に向上されるといった利点も有しているのである。
【００３２】
そして、上述の如き伝熱管１０は、図４に示されているように、アルミニウム合金等で形成された多数枚のプレートフィン１２の装着孔に挿通固定されることにより、それらのプレートフィンが伝熱管１０の外周面に装着されると共に、複数本が並列的に配置された状態でプレートフィン１２によって一体的に組み付けられることとなる。なお、かかるプレートフィン１２の装着は、例えば、伝熱管１０に多数枚のプレートフィン１２を挿通せしめた後、伝熱管１０内に拡管プラグを挿入して拡径し、プレートフィン１２の装着孔に嵌着せしめることによって行われることとなる。
【００３３】
以上、本発明の構成について、図面を参照しつつ詳細に説明したが、本発明は、図示された具体例や上述の具体的構成例、或いは以下の実施例の記載によって限定的に解釈されるものではなく、当業者の知識に基づいて種々なる変更，修正，改良等を加えた態様において実施され得るものであり、また、そのような実施態様が、本発明の趣旨を逸脱しない限り、何れも、本発明の範囲内に含まれるものであることが、理解されるべきである。
【００３４】
【実施例】
ＪＩＳＨ３３００の銅管（外径：φ１９．０５ｍｍ，肉厚：０．７ｍｍ）を素管として用い、図６〜８に示されている如き転造加工を施して、管内面に凹部および凸部を形成することにより、図１〜３に示されている如き構造の伝熱管を得た。なお、かかる伝熱管における凹部および凸部の数はそれぞれ一周当たり２４条で、ピッチ：ｐを略２．５ｍｍとし、リード角：αを１５°，凹部の底面に対する凸部の高さを略０．３ｍｍとした。また、凸部を、曲率半径が２．２ｍｍの略半円形の断面形状とすると共に、凹部の底部に曲率半径が０．１ｍｍである実質的な不連続部を形成し、かかる不連続部によって、隣接する両側凸部が直接に接続されてなる断面形状を採用した。なお、凸部は管軸方向に傾斜させず、管内へのコイル部材の配設も行わなかった。
【００３５】
また、かくの如き本実施例の伝熱管と比較するために、同一の素管の内周面を切起し加工することにより、図９に示されているように、螺旋条に連続して延びる切起し突起３２を管内周面に設けた比較例としての伝熱管３４を得た。なお、かかる伝熱管３４における切起し突起３２の数（ピッチ）やリード角、突出高さは、何れも、上記本実施例の伝熱管における凸部と同一に設定した。
【００３６】
そして、これら本実施例および比較例の伝熱管を各１本用い、それぞれ、管外周面にアルミニウムフィンを装着せしめて鉛直方向に配管し、濃度：６４重量％，飽和圧力：８．９ｍｍＨｇの臭化リチウム水溶液を、管内周面に沿わせて６０ｃｃ／分の流量で流下させる一方、３５℃（入口温度）の冷却空気をアルミニウムフィンに連続的に接触させて冷却せしめつつ、伝熱管内に水蒸気を導いて水蒸気の吸収能力を測定した。かかる測定結果を、冷房能力が２．２ｋＷ時の発生蒸気を完全に吸収した場合の吸収能力に対する比率で表した結果が、下記「表１」に示されている。
【００３７】

【００３８】
かかる比較実験結果からも、本発明に従う構造とされた伝熱管が、優れた伝熱性能を有しており、空冷式吸収器に用いた場合に優れた水蒸気の吸収能力を発揮し得ることが明らかである。
【００３９】
【発明の効果】
上述の説明から明らかなように、本発明に従う構造とされた吸収器用伝熱管においては、凹部の底部が管長手方向に螺旋状に延びる筋状の細溝形状をもって形成されていることから、鉛直方向に配管された際、管内面を流下せしめられる液膜が凹部に沿って導かれることにより、管周方向に広げられて流下距離が長くされると共に、流下速度が抑えられて滞留時間が有利に確保されるのであり、しかも、凸部の表面にも略均一な膜厚さで広げられることから、液膜が広い面積で形成されて有効伝熱面積が効果的に確保されるのであり、それによって、優れた伝熱性能が発揮され得るのである。
【００４０】
また、凸部を管軸方向一方の側に傾斜させれば、配管時に、管内面に沿って流下せしめられる吸収液を、かかる凸部によって受ける形とすることができるのであり、それによって、液膜が凹部内に有利に保持されて、液膜の管周方向への広がりや滞留時間の延長が、より効果的に図られ得る。
【００４１】
更にまた、伝熱管の内部にコイル部材を密接配置すれば、伝熱面積の更なる増大が図られると共に、吸収液の滞留時間の更なる延長が図られ得る。
【図面の簡単な説明】
【図１】本発明に従う構造とされた伝熱管の具体例を示す一部切欠正面図である。
【図２】図１におけるＡ部を拡大して示す断面説明図である。
【図３】図１に示された伝熱管の横断面を拡大して示す説明図である。
【図４】図１に示された伝熱管に対するプレートフィンの組付状態を示す説明図である。
【図５】本発明に従う構造とされた伝熱管の別の具体例を示す、図２に対応する断面説明図である。
【図６】図１に示された伝熱管の製造装置の一例を説明するための縦断面説明図である。
【図７】図６に示された伝熱管の製造装置の正面説明図であって、図６におけるＶＩＩ−ＶＩＩ断面に相当する図である。
【図８】図６に示された伝熱管の製造装置におけるロールの配設状態を示す説明図である。
【図９】伝熱性能の実験において比較例として用いた伝熱管を示す、図２に対応する断面説明図である。
【符号の説明】
１０伝熱管
１２プレートフィン
１４吸収液
１６外周面
１８凹部
２０凸部
２２不連続部[0001]
【Technical field】
The present invention is a heat transfer pipe that is piped in an absorber such as an absorption refrigerating machine or an absorption heat pump. In particular, the pipe is piped in a substantially vertical direction, and the absorption liquid flows down along the inner surface of the pipe. The present invention relates to a heat transfer tube used in an air-cooled absorber in which a plurality of cooling fins are mounted on the outer surface and cooling air is brought into contact therewith.
[0002]
[Background]
Conventionally, water-cooled type absorbers such as absorption refrigerators and absorption heat pumps have been adopted, in which cooling water is circulated in the tube to cool the absorption liquid that can flow down the outer surface of the tube. However, in recent years, air-cooled absorbers have been studied in order to reduce the size, and application to a small air-conditioner for home use is also being studied.
[0003]
By the way, in the air-cooled absorber, from the viewpoint of ensuring the cooling efficiency and the flowability of the absorption liquid, a plurality of heat transfer pipes are piped in a substantially vertical direction, and the absorption liquid flows down along the inner surface of the pipe. On the other hand, a structure in which a plurality of cooling fins are attached to the outer surface of the pipe and the cooling air is brought into contact is preferably employed.
[0004]
However, in such air-cooled absorbers, when a smooth tube with a circular cross section with a smooth inner and outer surface used in conventional water-cooled absorbers is used as the heat transfer tube, the absorbing liquid flows down linearly. As a result, the liquid film does not spread sufficiently and the residence time of the liquid film is shortened, so that it is difficult to obtain sufficient heat transfer performance. Therefore, as described in JP-A-4-151473, the inner surface of the smooth tube is cut and raised with a cutting tool or the like to form local protrusions, or surface treatment for improving wettability is performed on the inner surface of the tube. However, it is still satisfactory because it is not possible to obtain sufficient spread in the pipe circumferential direction, and it is difficult to secure the retention time of the absorbing liquid and the wet area of the pipe inner surface. It was difficult to obtain heat transfer performance.
[0005]
It is also conceivable to form a groove extending spirally on the inner surface of the tube by cutting and raising the inner surface of the smooth tube with a cutting tool and forming a protrusion extending spirally continuously in the longitudinal direction of the tube. In the case of such a structure, the absorbing liquid is guided and expanded in the pipe circumferential direction along the spiral groove portion, but the projection formed by cutting and raising has a substantially triangular shape having an acute apex angle. Therefore, the surface of the projection is likely to be cut off, the thickness of the liquid film is uneven, and the liquid film does not spread sufficiently. As a result, the formation of the spiral projection increases the surface area in the tube. Despite the increase, the improvement of the overall heat transfer performance could not be expected much.
[0006]
Alternatively, it is conceivable to form a groove extending spirally on the inner surface of the tube by inserting a coil member into the tube and placing it closely on the inner peripheral surface of the tube. Since it is difficult to stably obtain the adhesion of the member to the inner surface of the tube, there is a problem in the stability and durability of the performance. In addition, to arrange the coil member in the tube, a coil member is prepared separately from the heat transfer tube However, after inserting the coil member into the heat transfer tube, the coil member must be processed so as to be in close contact with the inner surface of the tube.
[0007]
[Solution]
Here, the present invention has been made in the background as described above, and the problem to be solved is that the residence time of the absorbing liquid that can flow down in the pipe even when piped in a substantially vertical direction. For absorbers that can be obtained sufficiently and that an effective wetting area can be secured without causing a significant deviation of the liquid film on the inner surface of the pipe, and that the effective heat transfer area can be increased to achieve improved heat transfer performance The purpose is to provide a heat transfer tube.
[0008]
[Solution]
In order to solve such a problem, the present invention is arranged in a substantially vertical direction so that the absorption liquid flows down along the inner surface of the pipe, while a plurality of cooling fins are mounted on the outer surface of the pipe so that the cooling air comes into contact therewith. In the air-cooled absorber heat transfer tubes, the pipes are respectively arranged so that the concave portions and the convex portions that spirally extend in the pipe longitudinal direction at a lead angle of 5 to 75 ° are alternately arranged in the pipe circumferential direction. While forming at a pitch of 1.0 to 5.0 mm in the circumferential direction and setting the protrusion height of the protrusion to the recess to 0.2 to 0.6 mm, the surface of the protrusion has a curved cross-sectional shape, and It is characterized in that the bottom of the recess has a cross-sectional shape having a substantially discontinuous portion.
[0009]
In this case, any of a semicircular shape, a semi-elliptical shape, a parabolic shape, and the like can be adopted as the cross-sectional shape of the convex portion. Moreover, you may make it provide such a convex part incline in the one side of a pipe-axis direction.
[0010]
Furthermore, it is also possible to insert a coil member having a lead angle smaller than the lead angle of the concave portion and the convex portion into the pipe and arrange the coil member in close contact with the inner peripheral surface of the pipe.
[0011]
Specific Configuration of the Invention
First, FIGS. 1 to 3 show a specific example of a heat transfer tube for an absorber having a structure according to the present invention. The heat transfer tube 10 has a straight tube shape with a circular cross section as a whole, and is cut into an appropriate length and a plurality of tubes are piped at a predetermined distance from each other as shown in FIG. At the same time, plate fins 12 are attached to the outer peripheral surfaces of the plate fins 12 and integrally assembled to form an air-cooled absorber. Then, the heat transfer tube 10 is disposed in the absorber with the axial center of the heat transfer tube 10 extending in a substantially vertical direction, and the absorbent 14 flows down along the inner surface of the tube, so that the refrigerant introduced into the tube becomes the absorbent. On the other hand, the cooling air is brought into contact with the outer surface of the tube and the plate fin 12 to suppress the heat of dissolution caused by dissolution of the refrigerant in the absorption liquid, or the temperature rise due to dilution heat or latent heat, thereby absorbing the absorption. It is designed to function as a vessel.
[0012]
Here, the material of the heat transfer tube 10 is selected in consideration of the corrosion resistance, heat transfer property, workability, etc. with respect to the refrigerant and absorbent used as in the conventional case. For example, water is used as the refrigerant, and lithium bromide is used. When using as an absorbent, a copper tube can be suitably employed. Further, the heat transfer tube 10 has an outer peripheral surface 16 as a smooth surface, as shown in FIGS. 2 and 3 in an enlarged view and a cross-sectional enlarged view of a portion A in FIG. A plurality of concave portions 18 and convex portions 20 respectively extending in a spiral shape in the longitudinal direction of the tube with respect to the surface are alternately positioned in the circumferential direction of the tube and are formed substantially parallel to each other.
[0013]
Although these recesses 18 and projections 20 are not clearly shown on the drawing, the pitch in the tube circumferential direction: p (see FIG. 3), in other words, the recesses 18 adjacent in the circumferential direction in a cross section perpendicular to the tube axis. And the interval between the concave portion 18 and the convex portion 20 and the convex portion 20 are set to be 1.0 to 5.0 mm. Specifically, for example, in the case of a copper tube having a diameter of 19.05 mm, the number of the concave portions 18 and the convex portions 20 is set to be 12 to 48 per round, respectively.
[0014]
However, if the pitch: p is less than 1.0 mm, the width of the recess 18 becomes too small, and a highly viscous solution such as an aqueous solution of lithium bromide is difficult to flow into the recess 18. This is because the spread of the liquid film in the circumferential direction of the pipe cannot be sufficiently expected. On the other hand, when the pitch: p is larger than 5.0 mm, the unevenness formed on the inner surface of the pipe is reduced and the effective heat transfer area is reduced. This is because it is difficult to realize the increase in That is, by increasing the pitch p of the concave portion 18 and the convex portion 20 in the pipe circumferential direction to 1.0 to 5.0 mm, an increase in the heat transfer area of the inner surface of the tube due to the formation of the concave portion 18 and the convex portion 20; Both the promotion of the spread of the liquid film in the pipe circumferential direction by the guiding action of the recess 18 can be advantageously achieved, and the effective heat transfer area can be effectively increased.
[0015]
Moreover, although these recessed part 18 and the convex part 20 may be formed with the fixed lead angle over the full length of the heat exchanger tube 10, or the lead angle may be partially changed, such lead angle: α is set so as to be in the range of 5 to 75 °, preferably in the range of 5 to 30 °, in any part. As shown in FIG. 1, the lead angle α is an angle formed by a tangent line of the concave portion 12 or the convex portion 14 and a plane perpendicular to the tube axis.
[0016]
However, if the lead angle α is greater than 75 °, the flow rate of the absorbed liquid along the concave portion 18 increases when the heat transfer tube 10 is assembled to the absorber, and the residence time of the liquid film on the inner surface of the tube is sufficient. On the other hand, if the lead angle α is smaller than 5 °, it is difficult to form the recesses 18 and the protrusions 20 on the inner peripheral surface of the heat transfer tube 10. That is, by setting the lead angle α of the concave portion 18 and the convex portion 20 to 5 ° to 50 °, more preferably 5 ° to 30 °, the inner surface of the pipe flows down without significant deterioration in manufacturability. The liquid film to be squeezed is guided in the pipe circumferential direction along the recess 18 to effectively suppress the flow speed of the liquid film, and the flow distance is substantially increased, so that the residence time of the absorbing liquid is advantageously secured. It can be done.
[0017]
Furthermore, a substantially discontinuous portion 22 is formed at the bottom of the recess 18 in its cross section. The discontinuous portion 22 is formed as a bent point-like connecting portion connected at an intersection having no common tangent in the cross section of the concave portion 18, or a curved surface having a curvature radius of 3.5 mm or less, or a width As a flat surface having a thickness of 2.5 mm or less, it is formed as a connecting portion that can be substantially regarded as a bending point.
[0018]
That is, if such a substantially discontinuous portion 22 is formed at the bottom of the recess 18, a streak-like narrow groove extending spirally toward the longitudinal direction of the heat transfer tube 10 is formed at the bottom of the recess 18. As a result, the absorption liquid that can flow down the inner surface of the tube spreads spirally in the circumferential direction of the recess 18 along the narrow groove due to a capillary phenomenon based on the surface tension and the like. Further, the flow of the absorbing liquid in the pipe circumferential direction along the concave portion 18 and the convex portion 20 is promoted, the liquid film is spread in the pipe circumferential direction and the residence time is extended, and the effective heat transfer area, Heat transfer performance can be advantageously improved.
[0019]
In addition, as for the bottom part of this recessed part 18, it is desirable for the cross-sectional shape to make the intersection angle of the both inner surfaces which pinched | interposed the substantially discontinuous part 22 into 20-90 degrees. Thereby, the effect of promoting the spread of the absorbing liquid in the tube circumferential direction by capillary action can be exhibited more advantageously.
[0020]
Moreover, the convex part 20 is formed with the curved cross-sectional shape. That is, the surface of the convex portion 20 need not have a constant radius of curvature over the entire cross section, but is continuous, for example, a cross sectional shape such as a semicircular shape, a semielliptical shape, or a parabolic shape. Can be suitably employed.
[0021]
That is, if the convex part 20 is formed with such a curved cross-sectional shape, even when the absorbing liquid flows over the convex part 20 and flows downward vertically, the flow is smooth and substantially uniform by the action of the surface tension. A liquid film having a thickness can be advantageously formed, and partial film thickness unevenness and thirsty surfaces (liquid running out) can be effectively prevented. As a result, a wet area is advantageously ensured. Thus, a partial decrease in heat conduction due to a large deviation in liquid film thickness is avoided, and an improvement in heat transfer performance due to an increase in effective heat transfer area can be achieved more effectively.
[0022]
In addition, while making the surface of the convex part 20 into the cross-sectional shape which does not have an inflection point over the whole, the surface of the

convex parts

20 and 20 formed with such a cross-sectional shape and positioned adjacently, It is also possible to have a cross-sectional shape that is directly connected by the substantial discontinuous portion 22. And if the recessed part 18 and the convex part 20 are formed with such a cross-sectional shape, the absorption liquid will spread in the pipe circumferential direction along the bottom part of the recessed part 18, and the substantially uniform liquid film on the surface of the convex part 20 Both formations can be achieved very effectively.
[0023]
Furthermore, the convex part 20 is formed so that the protrusion height from the bottom face of the concave part 18 is 0.2 to 0.6 mm.
[0024]
However, if the protruding height of the convex portion 20 is lower than 0.2 mm, it is difficult to effectively hold an absorbing liquid having a large specific gravity such as a lithium bromide solution in the concave portion 18, and consequently, along the concave portion 18. This is because the effect of spreading the absorbing liquid in the pipe circumferential direction is reduced. On the other hand, when the protruding height of the convex portion 20 is higher than 0.6 mm, the concave portion 18 and the convex portion on the inner peripheral surface of the heat transfer tube 10 are obtained. It is because formation of 20 becomes difficult. That is, by setting the protruding height of the convex portion 20 to 0.2 to 0.6 mm, preferably 0.3 to 0.4 mm, the pipe circumferential direction along the concave portion 18 while ensuring good manufacturability. The effective heat transfer area can be effectively expanded by promoting the spread of the liquid film.
[0025]
In order to favorably hold the absorbent in the recess 18 and promote the spread of the absorbent in the pipe circumferential direction along the recess 18, as shown in FIG. It is also effective to form the projection so as to incline toward one side in the tube axis direction. That is, if the heat transfer pipe 10 is piped so that such a convex part 20 is formed and the convex part 20 is inclined upward in the vertical direction, the absorbing liquid that is allowed to flow down along the inner surface of the pipe is formed. Therefore, the liquid film is advantageously held in the recess 18, and the liquid film along the recess 18 extends in the pipe circumferential direction and the residence time is more effectively achieved. It can be done.
[0026]
Although not clearly shown in the drawings, the lead angle of the concave portion 18 and the convex portion 20 is smaller than the lead angle α of the heat transfer tube 10 in which the concave portion 18 and the convex portion 20 are formed as described above. It is also possible to insert a helical coil member and arrange it in close contact with the convex portion 20. By arranging such a coil member, the heat transfer area can be further increased, and the absorption time of the absorption liquid can be further increased by guiding the absorption liquid along the coil member in the pipe circumferential direction. Can be achieved.
[0027]
In addition, like the heat transfer tube 10, the material of the coil member is selected in consideration of the corrosion resistance with respect to the refrigerant and the absorbent, and for example, in the heat transfer tube 10 in which the concave portion 18 and the convex portion 20 are formed. After being inserted, a tube expansion plug or the like is inserted, and the coil member is assembled to the heat transfer tube 10 by pressing and fixing the coil member to the inner peripheral surface of the heat transfer tube 10.
[0028]
By the way, such a heat transfer tube 10 is drawn out by using a plug in which spiral irregularities corresponding to the intended concave portion 18 and convex portion 20 are attached to the outer peripheral surface with respect to the elementary tube having a smooth inner and outer peripheral surface. Although it is possible to produce by processing, etc., it can be advantageously produced particularly by rolling.
[0029]
Specifically, for example, as shown in FIGS. 6 to 8, spiral irregularities corresponding to the target concave portion 18 and convex portion 20 are provided on the outer periphery of the raw tube 24 having a smooth inner and outer peripheral surface. The plug 26 attached to the surface is inserted and arranged, and three rolls 26 are disposed outside the raw tube 24, and pressure is applied to the outer peripheral surface of the raw tube 24 by these rolls 26 to rotate the raw tube 24. However, the target heat-transfer tube 10 is manufactured by moving it in the axial direction and applying irregularities to the inner peripheral surface of the tube.
[0030]
In addition, as the roll 26, a plurality of discs 28 having different diameters with smooth outer peripheral surfaces, which are overlapped in the axial direction and mounted on the rod 30, is preferably used. Is arranged in a state where it is inclined by a predetermined angle β with respect to the tube axis. If such a roll 26 is employ | adopted, it can respond easily to the rolling process of the heat exchanger tube of various sizes.
[0031]
That is, the heat transfer tube 10 having the above-described structure can be easily manufactured by rolling or the like, and therefore, the productivity is higher than that of a conventional heat transfer tube provided with a raised and raised protrusion. In addition, there is an advantage that the cost is greatly improved.
[0032]
Then, as shown in FIG. 4, the heat transfer tube 10 as described above is inserted and fixed in the mounting holes of a large number of plate fins 12 formed of aluminum alloy or the like, so that these plate fins are transferred. It is attached to the outer peripheral surface of the heat tube 10 and is assembled integrally by the plate fins 12 in a state in which a plurality are arranged in parallel. For example, the plate fins 12 are mounted by, for example, inserting a large number of plate fins 12 into the heat transfer tube 10 and then inserting a tube expansion plug into the heat transfer tube 10 to expand the diameter thereof, so that the plate fins 12 are mounted in the mounting holes. It will be done by fitting.
[0033]
The configuration of the present invention has been described in detail with reference to the drawings. However, the present invention is limitedly interpreted by the illustrated specific examples, the above-described specific configuration examples, or the following examples. However, the present invention can be implemented in a mode in which various changes, modifications, improvements and the like are added based on the knowledge of those skilled in the art, and such a mode is not limited as long as it does not depart from the spirit of the present invention. Should also be understood to be included within the scope of the present invention.
[0034]
【Example】
Using a JIS H3300 copper tube (outer diameter: φ19.05 mm, wall thickness: 0.7 mm) as a raw tube, the rolling process as shown in FIGS. The heat transfer tube having the structure as shown in FIGS. 1 to 3 was obtained. The number of recesses and projections in each heat transfer tube is 24, and the pitch: p is about 2.5 mm, the lead angle: α is 15 °, and the height of the projection with respect to the bottom surface of the recess is about 0. 3 mm. Further, the convex portion has a substantially semicircular cross-sectional shape with a curvature radius of 2.2 mm, and a substantially discontinuous portion with a curvature radius of 0.1 mm is formed at the bottom of the concave portion. The cross-sectional shape in which the adjacent convex portions on both sides are directly connected is adopted. The convex portion was not inclined in the tube axis direction, and the coil member was not disposed in the tube.
[0035]
Further, in order to compare with the heat transfer tube of this embodiment as described above, by cutting and processing the inner peripheral surface of the same raw tube, as shown in FIG. A heat transfer tube 34 as a comparative example in which extending and raising protrusions 32 were provided on the inner peripheral surface of the tube was obtained. The number (pitch), lead angle, and protrusion height of the cut and raised protrusions 32 in the heat transfer tube 34 were all set to be the same as the convex portions in the heat transfer tube of the present embodiment.
[0036]
Each of these heat transfer tubes of the present example and the comparative example was used, and each was fitted with aluminum fins on the outer peripheral surface of the tube and piped vertically. Concentration: 64 wt%, saturation pressure: 8.9 mmHg odor While the lithium bromide aqueous solution is caused to flow down along the inner peripheral surface of the tube at a flow rate of 60 cc / min, while cooling air of 35 ° C. (inlet temperature) is continuously brought into contact with the aluminum fins to cool the water, The water vapor absorption capacity was measured. The results of the measurement results expressed as a ratio to the absorption capacity when the generated steam is completely absorbed when the cooling capacity is 2.2 kW are shown in “Table 1” below.
[0037]

[0038]
Also from the results of such comparative experiments, the heat transfer tube structured according to the present invention has excellent heat transfer performance, and can exhibit excellent water vapor absorption ability when used in an air-cooled absorber. it is obvious.
[0039]
【The invention's effect】
As is clear from the above description, in the heat exchanger tube for an absorber having the structure according to the present invention, the bottom of the recess is formed with a streak-like narrow groove shape extending spirally in the longitudinal direction of the tube. When the pipe is laid in the direction, the liquid film that can flow down the inner surface of the pipe is guided along the concave portion, so that the flow distance is increased by extending in the pipe circumferential direction, and the flow speed is suppressed and the residence time is advantageous. In addition, since the surface of the convex portion is also spread with a substantially uniform film thickness, the liquid film is formed in a wide area, and an effective heat transfer area is effectively secured, Thereby, excellent heat transfer performance can be exhibited.
[0040]
Further, if the convex portion is inclined to one side in the tube axis direction, the absorbing liquid that flows down along the inner surface of the pipe during piping can be received by the convex portion. The film is advantageously held in the recess, and the liquid film can be spread more effectively in the pipe circumferential direction and the residence time can be extended more effectively.
[0041]
Furthermore, if the coil member is closely arranged inside the heat transfer tube, the heat transfer area can be further increased and the residence time of the absorbent can be further extended.
[Brief description of the drawings]
FIG. 1 is a partially cutaway front view showing a specific example of a heat transfer tube structured according to the present invention.
FIG. 2 is an enlarged cross-sectional explanatory view showing a portion A in FIG.
FIG. 3 is an explanatory view showing an enlarged cross section of the heat transfer tube shown in FIG. 1;
4 is an explanatory view showing a state in which plate fins are assembled to the heat transfer tube shown in FIG. 1; FIG.
FIG. 5 is a cross-sectional explanatory view corresponding to FIG. 2, showing another specific example of a heat transfer tube structured according to the present invention.
6 is a longitudinal cross-sectional explanatory diagram for explaining an example of a heat transfer tube manufacturing apparatus shown in FIG. 1. FIG.
7 is a front explanatory view of the heat transfer tube manufacturing apparatus shown in FIG. 6, corresponding to a VII-VII cross section in FIG. 6;
FIG. 8 is an explanatory diagram showing a roll arrangement state in the heat transfer tube manufacturing apparatus shown in FIG. 6;
9 is a cross-sectional explanatory view corresponding to FIG. 2, showing a heat transfer tube used as a comparative example in an experiment of heat transfer performance.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Heat transfer tube 12 Plate fin 14 Absorbing liquid 16 Outer peripheral surface 18 Concave part 20 Convex part 22 Discontinuous part

Claims

An air-cooled absorber heat transfer tube that is piped in a substantially vertical direction and allows the absorbing liquid to flow down along the inner surface of the tube, while a plurality of cooling fins are attached to the outer surface of the tube to contact the cooling air,
1.0 to 5.0 mm in the pipe circumferential direction so that the concave and convex portions extending spirally on the pipe inner surface in the pipe longitudinal direction at a lead angle of 5 to 75 ° are alternately located in the pipe circumferential direction. The projection height of the convex portion with respect to the concave portion is 0.2 to 0.6 mm, the surface of the convex portion has a curved cross-sectional shape, and the bottom portion of the concave portion is substantially incomplete. A heat transfer tube for an absorber, characterized by having a cross-sectional shape having a continuous portion.

The heat exchanger tube for an absorber according to claim 1, wherein the convex portion is provided to be inclined toward one side in the tube axis direction.

The heat transfer tube for an absorber according to claim 1 or 2, wherein a coil member having a lead angle smaller than the lead angle of the concave portion and the convex portion is inserted into the tube and is in close contact with the inner peripheral surface of the tube.

The bottom part of the said recessed part is comprised so that the crossing angle of the both-side inner surface which pinched | interposed the said substantially discontinuous part may be 20-90 degrees in the cross-sectional shape. Heat transfer tube for absorber.