JP3675498B2

JP3675498B2 - Heat absorption tube for absorption refrigerator

Info

Publication number: JP3675498B2
Application number: JP17517694A
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: 1994-07-27
Filing date: 1994-07-27
Publication date: 2005-07-27
Anticipated expiration: 2020-07-27
Also published as: JPH0835739A

Description

【０００１】
【技術分野】
本発明は、吸収式冷凍機（吸収式ヒートポンプを含む。以下、同じ）に用いられる伝熱管であって、特に、冷媒が管内に導かれる一方、該外面に複数のフィンが装着されて冷却空気や被冷却流体が接触せしめられる、吸収器や蒸発器に用いられる吸収式冷凍機用伝熱管に関するものである。
【０００２】
【背景技術】
従来から、吸収式冷凍機における蒸発器としては、一般に、伝熱管内に冷媒を流通せしめる一方、該伝熱管の外面に複数のフィンを装着して空気やブライン等の被冷却流体を接触せしめるようにした構造のものが採用されており、また、吸収式冷凍機における吸収器としても、伝熱管外表面を流下せしめられる吸収液を管内に流通せしめられる冷却水で冷却するようにした従来の水冷式のものに代えて、近年、吸収液を伝熱管内に流通せしめる一方、該伝熱管の外面に複数のフィンを装着して冷却空気を接触せしめるようにした空冷式のものが検討されており、空冷式にすることによって小型化が可能であることから、家庭用の小型冷房機等への適用も考えられている。
【０００３】
ところで、このような蒸発器や空冷式の吸収器における伝熱管の如く、伝熱管内に冷媒や吸収液を流通せしめるに際しては、かかる冷媒等の流通性や熱交換効率を有利に確保するために、複数本の伝熱管を鉛直方向にまたは所定角度傾斜して配管し、それら伝熱管の内面に沿って冷媒や吸収液を流下させることが望ましい。
【０００４】
ところが、このように鉛直配管または傾斜配管される伝熱管として、従来から水平配管される吸収器用伝熱管等として一般に用いられている内外面が平滑な円形断面を有する平滑管を採用すると、冷媒や吸収液が直線的に流下してしまって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や熱交換効率を得ることが難しいという問題があった。なお、このような問題に対処するために、特開平４−１５１４７３号公報に開示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も提案されているが、未だ、管周方向への広がりを充分に得ることが出来ず、冷媒や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り、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、冷媒や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の断面形状となるために、突起表面に膜切れが生じ易いことに加えて、螺旋状溝部と突起との境界部分に存在する不連続な屈曲点に液膜が偏るために、溝部中央の平坦部分に膜切れが生じ易く、冷媒や吸収液の液膜の厚さに大きな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】
【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、鉛直配管乃至は傾斜配管した場合でも、管内を流通せしめられる冷媒や吸収液が管内表面において有利に広げられて、液膜の著しい偏りを生ずることなく濡れ面積を有利に得ることが出来ると共に、液膜の滞留時間が有利に確保されて伝熱性能の向上が達成され得る吸収式冷凍器用伝熱管を提供することにある。
【０００７】
【解決手段】
そして、かかる課題を解決するために、本発明の特徴とするところは、冷媒が管内に導かれる一方、管外面に複数のフィンが装着される吸収式冷凍機用伝熱管において、５〜５０°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０．３〜５．０mmのピッチで形成すると共に、該凸部の該凹部に対する突出高さを０．３〜０．６mmとする一方、かかる管周方向で交互に位置する凹部および凸部の断面形状を実質的な不連続部を有しない連続面としたことにある。
【０００８】
また、本発明は、管内に導かれる冷媒を溶解する吸収液が管内周面に沿って流下せしめられる一方、管外面に複数のフィンが装着されて冷却空気が接触せしめられる吸収器に用いられる吸収式冷凍機用伝熱管において、５〜５０°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、該凸部の該凹部に対する突出高さを０．３〜０．６mmとする一方、かかる管周方向で交互に位置する凹部および凸部の断面形状を実質的な不連続部を有しない連続面としたことも、特徴とする。
【０００９】
更にまた、本発明は、冷媒が管内周面に沿って流下せしめられる一方、管外面に複数のフィンが装着されて被冷却流体が接触せしめられる蒸発器に用いられる吸収式冷凍機用伝熱管において、５〜５０°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０．３〜０．６mmのピッチで形成すると共に、該凸部の該凹部に対する突出高さを０．３〜０．６mmとする一方、かかる管周方向で交互に位置する凹部および凸部の断面形状を実質的な不連続部を有しない連続面としたことをも、特徴とする。
【００１０】
そこにおいて、本発明に従う構造とされた吸収式冷凍機用伝熱管における凹部および凸部の断面形状は、実質的な不連続部を有しない連続面である限り、具体的に限定されるものでなく、直線部分を含むものであっても良いが、好ましくは、円や楕円，放物線等の湾曲面形状とされる。なお、断面形状が実質的な不連続部を有しない連続面であるとは、断面上の何れの点においても接線が複数となる屈曲点や、曲率半径が極めて小さい曲部の如く実質的に屈曲点と見なし得る点を実質的に持たない面であることをいう。
【００１１】
また、本発明に従う構造とされた吸収式冷凍機用伝熱管においては、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。
【００１２】
更にまた、本発明に従う構造とされた吸収式冷凍機用伝熱管においては、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。
【００１３】
【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式冷凍機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、例えば図４に示されているように、適当な長さに切断した複数本を互いに並列的に配管し、それらの外周面に多数枚のプレートフィン１２を装着せしめて一体的に組み付けることにより、吸収器乃至は蒸発器を構成するようになっている。そして、各伝熱管１０の中心軸が鉛直方向乃至は鉛直方向に対して所定角度だけ傾斜した方向に延びる状態で吸収器または蒸発器内に配設されることとなり、吸収器においては、管内面に沿って吸収液１４が流下されて管内に導かれた冷媒が該吸収液１４に吸収されると共に、管外面に冷却空気が接触せしめられて溶解熱乃至は希釈熱や潜熱による吸収液の温度上昇が抑えられる一方、蒸発器においては、管内に導かれて管内面に沿って流下せしめられる液状の冷媒１４が蒸発することにより、冷媒の蒸発による冷凍作用によって、管外面に接触せしめられる空気等の被冷却流体が冷却されることとなる。
【００１４】
ここにおいて、伝熱管１０の材質は、管内に導かれる冷媒や吸収液に対する耐蝕性の他、伝熱性や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。
【００１５】
これら凹部１８と凸部２０は、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０．３〜５．０mm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１２〜１５０条となるように設定することが望ましい。
【００１６】
けだし、かかるピッチ：ｐが、０．３mmより小さいと、凹部１８の幅が小さくなり過ぎて、凹部１８内に冷媒や吸収液が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、０．３〜５．０mm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や凸部２０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。
【００１７】
また、特に、吸収器用伝熱管として用いる場合には、上記ピッチ：ｐを、１．０〜５．０mmとすることが望ましい。けだし、吸収器用伝熱管では、一般に、臭化リチウム水溶液等の粘性の高い吸収液が管内面を流下せしめられるために、ピッチ：ｐを１．０mmよりも小さくすると、吸収液が凹部１８内に充分に流れ込みにくくなるからである。一方、蒸発器用伝熱管として用いる場合には、上記ピッチ：ｐを、０．３〜０．６mmとすることが望ましい。けだし、蒸発器用伝熱管では、一般に、管内に導かれる冷媒の粘性がそれ程大きくないことから、ピッチ：ｐを０．６mm以下とすることによって、伝熱面積の増加が極めて有利に達成され得るからである。
【００１８】
また、これら凹部１８と凸部２０は、伝熱管１０の全長に亘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５〜５０°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（巻き方向の直線）と、管軸に直角な平面とがなす角度をいう。
【００１９】
けだし、リード角：αが５０°より大きいと、伝熱管１０を吸収器または蒸発器に組み付けた際に、凹部１８に沿う冷媒や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、凹部１８および凸部２０による伝熱面積の増大効果が有効に発揮され難くなるからであり、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１２および凸部１４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、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、流体距離が実質的に増大されて、冷媒や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。
【００２０】
なお、蒸発器や吸収器において、伝熱管１０が傾斜配管される場合には、その傾斜角度をも考慮して、凹部１８および凸部２０のリード角：αを決定することが望ましく、具体的には、リード角：αを、鉛直方向に対する伝熱管の配管傾斜角度以上に設定することが望ましい。それによって、伝熱管１０の配管時にも、伝熱管の軸方向下方に向かって螺旋条に延びる凹部１８および凸部２０の傾斜が部分的に上方に向かうことが防止されて、凹部１８および凸部２０に沿った冷媒や吸収液の下方に向かう流れが有利に生ぜしめられる得ることとなる。
【００２１】
さらに、伝熱管１０の内周面に形成された凹部１８および凸部２０は、それらの断面の全体に亘って実質的な不連続部を有しない連続面とされている。なお、実質的な不連続部を有しない連続面とは、接線が複数となる屈曲点や、曲率半径が極めて小さい曲部の如く実質的に屈曲点と見なし得る点を持たない面であることをいう。
【００２２】
すなわち、このように凹部１８および凸部２０を、それらの断面の全体に亘って実質的な不連続部を有しない連続面をもって形成すれば、谷状の屈曲点（不連続部）への液膜の集中や、峰状の屈曲点における液膜の切れが何れも有利に防止され得て、凹部１８における局部的な液膜厚さの偏りが軽減されると共に、凸部２０の表面にも液膜が有利に広げられることとなり、その結果、凹部１８の平坦部や凸部２０の頂部及び下面等で生じ易かった液切れ（渇き面の発生）が効果的に防止され得て、液膜による濡れ面積の増大が図られ、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。
【００２３】
なお、凹部１８および凸部２０の具体的な断面形状は、何等限定されるものでなく、半円形状や半楕円形状，放物線形状などの湾曲断面形状の他、一部に直線部分を有する断面形状も採用され得る。具体的には、図１〜３に示された形状の他、図５に示されているように両側面が略平行とされた形状の凸部２０を形成したり、図６に示されているように凹部１８の両側から覆いかぶさるように張り出した先太形状の凸部２０を形成したり、或いは図７のように配管時に上方となる管軸方向一方の側に傾斜した凸部２０を形成することも出来、それによって、管内面に沿って流下せしめられる冷媒や吸収液を凸部２０によって受ける形となることから、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こととなる。
【００２４】
また、好適には、凹部１８および凸部２０は、何れも湾曲断面形状をもって形成される。なお、湾曲断面形状とは、単一の若しくは連接された複数の湾曲面によって形成された断面形状をいい、直線的な断面部分を含まない形状をいう。即ち、このような湾曲断面形状をもって形成すれば、冷媒や吸収液の凸部２０の表面上への広がりも一層スムーズとなり、凹部１８および凸部２０の表面における液膜厚さの均一化が、表面張力の作用によって一層有利に図られ得るのであり、液膜厚さの大きな偏りによる部分的な熱伝導の低下が防止されて、有効伝熱面積の増加による伝熱性能向上効果が一層効果的に達成され得るのである。尤も、本発明においては、凹部１８および凸部２０が、実質的な不連続部を有しない断面形状をもって形成されることから、凹部１８の底部中央を略平坦面としても、凹部１８の幅方向両側への液膜の著しい偏りが防止されて、かかる平坦面における液切れ等の発生が防止され得、有効な伝熱性能が発揮され得ることとなる。
【００２５】
さらに、凸部２０は、凹部１８の底面からの突出高さが０．３〜０．６mmとなるように形成される。けだし、凸部２０の突出高さが０．３mmより低いと、冷媒や特に比重が大きい臭化リチウム溶液等の吸収液を凹部１８内に有効に保持することが難しく、結果的に、凹部１８に沿った液膜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、０．３〜０．６mm、好ましくは０．５〜０．６mm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。
【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条のコイル部材を挿入し、凹部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、冷媒や吸収液の一部がコイル部材に沿って管周方向に導かれることにより、液膜の滞留時間の更なる増大が図られ得ることとなる。
【００２７】
なお、コイル部材は、伝熱管１０と同様、冷媒や吸収液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を形成された伝熱管１０内に挿入せしめた後、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、上述の如き、本発明に従う構造とされた伝熱管１０は、例えば目的とする凹部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８〜１０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２５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、有利に製造されることとなる。
【００３０】
なお、ロール２６としては、例えば、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。なお、図６に示されている如き、先端部が膨らんだ断面形状の凸部２０は、例えば、先端部が膨らんでいない断面形状の凸部を形成した後、管内に拡管プラグを挿入して凸部の先端部を押し潰すこと等によって、製作することが可能である。
【００３２】
そして、このようにして製作された伝熱管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１２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等によって、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は、言うまでもないところである。
【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８〜１０に示されている如き転造加工を施して、管内面にそれぞれ曲率半径が略一定の円弧状断面を有する凹部および凸部を形成することにより、それぞれ、図１〜３に示されている如き形状とされた蒸発器用伝熱管および吸収器用伝熱管を得た。それら蒸発器用伝熱管および吸収器用伝熱管の諸元を、下記表１に示す。また、蒸発器用伝熱管の比較例として、図１１に示されているように、凹部３２の底面が平坦面とされて該凹部３２の幅方向両側端部に実質的な屈曲部３４，３４が形成されてなる断面形状を有する伝熱管を製造すると共に、吸収器用伝熱管の比較例として、図１２に示されているように、螺旋状に連続して延びる凸部としての切起し突起３６が管内周面に形成されて該凸部の頂点と凹部の幅方向両側端部にそれぞれ実質的な屈曲部３８が形成されてなる断面形状を有する伝熱管を製造した。これら比較例としての蒸発器用伝熱管および吸収器用伝熱管の諸元も、下記表１に併せ示す。
【００３５】
【表１】

【００３６】
そして、これら実施例および比較例としての蒸発器用伝熱管および吸収器用伝熱管を各１本用いて、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、蒸発器用伝熱管および吸収器用伝熱管の各々について、下記表２に示す条件下に冷房能力および冷媒吸収能力を測定した。その結果を、下記表３に示す。なお、かかる測定に際しては、冷媒として水を用いると共に、吸収液として臭化リチウム水溶液を用いた。また、冷媒吸収能力の評価は、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行った。
【００３７】
【表２】

【００３８】
【表３】

【００３９】
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、吸収式冷凍機における蒸発器に用いることによって優れた冷房能力が発揮され得ると共に、空冷式吸収器に用いることによって優れた水蒸気の吸収能力が発揮され得ることが、明らかである。
【００４０】
【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式冷凍機用伝熱管においては、管長手方向に螺旋状に延びる凹部と凸部が管内周面に形成されており、鉛直配管乃至は傾斜配管された際、管内面を流下せしめられる冷媒や吸収液が凹部に沿って導かれることにより、液膜が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得、しかも、それら凹部と凸部の断面形状が連続面とされていることから、凹部における局部的な液膜の偏りが防止されると共に、凸部の表面にも液膜が有利に広げられて、全体として略均一な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得るのであり、それによって、優れた伝熱性能が発揮され得るのである。
【００４１】
そして、特に、本発明に従う構造とされた吸収器用の伝熱管においては、優れた水蒸気の吸収能力が発揮され得るのであり、また一方、本発明に従う構造とされた蒸発器用の伝熱管においては、優れた冷却能力が発揮され得るのである。
【００４２】
また、凸部を管軸方向の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冷媒や吸収液を、かかる凸部によって受ける形とすることができ、それによって、液膜が凹部内に一層有利に保持され得て、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。
【００４３】
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も図られ得る。
【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】本発明に従う構造とされた伝熱管の更に別の具体例を示す、図２に対応する断面説明図である。
【図７】本発明に従う構造とされた伝熱管の更に別の具体例を示す、図２に対応する断面説明図である。
【図８】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９】図８に示された伝熱管の製造装置の正面説明図であって、図８におけるIX−IX断面に相当する図である。
【図１０】図８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１１】伝熱性能の実験において比較例として用いた蒸発器用伝熱管を示す、図２に対応する断面説明図である。
【図１２】伝熱性能の実験において比較例として用いた吸収器用伝熱管を示す、図２に対応する断面説明図である。
【符号の説明】
１０伝熱管
１８凹部
２０凸部[0001]
【Technical field】
The present invention relates to a heat transfer tube used in an absorption refrigerator (including an absorption heat pump; hereinafter the same), and in particular, a refrigerant is led into the tube, and a plurality of fins are attached to the outer surface of the heat transfer tube. It is related with the heat exchanger tube for absorption refrigerators used for an absorber and an evaporator with which a to-be-cooled fluid is made to contact.
[0002]
[Background]
Conventionally, as an evaporator in an absorption chiller, generally, a refrigerant is circulated in a heat transfer tube, while a plurality of fins are attached to the outer surface of the heat transfer tube so that a fluid to be cooled such as air or brine is brought into contact therewith. In addition, as an absorber in an absorption refrigerator, a conventional water-cooling system in which the absorbing liquid that flows down the outer surface of the heat transfer tube is cooled with cooling water that is circulated in the tube. In recent years, an air-cooled type in which the absorption liquid is circulated in the heat transfer tube while a plurality of fins are attached to the outer surface of the heat transfer tube so that the cooling air is brought into contact has been studied. Since it is possible to reduce the size by air cooling, it is also considered to be applied to a small air conditioner for home use.
[0003]
By the way, when circulating a refrigerant or an absorbent in a heat transfer tube, such as a heat transfer tube in such an evaporator or an air-cooled absorber, in order to advantageously ensure the flowability and heat exchange efficiency of such a refrigerant. It is desirable that a plurality of heat transfer tubes be piped in the vertical direction or inclined at a predetermined angle, and the refrigerant and the absorbing liquid flow down along the inner surfaces of the heat transfer tubes.
[0004]
However, when a smooth tube having a circular cross section with a smooth inner and outer surface, which is generally used as a heat transfer tube for an absorber that has been conventionally horizontal, is adopted as a heat transfer tube that is vertically or inclinedly piped in this way, There is a problem that it is difficult to obtain sufficient heat transfer performance and heat exchange efficiency because the absorbing film flows down linearly and the liquid film does not spread sufficiently and the residence time of the liquid film is shortened. In order to cope with such a problem, as disclosed 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 a local protrusion, or the inner surface of the tube It has also been proposed to apply surface treatment to improve wettability, but it is still not possible to obtain sufficient spread in the pipe circumferential direction, and the residence time of the refrigerant and absorption liquid and the wetness of the pipe inner surface Since it is difficult to secure the area, it has been difficult to obtain satisfactory 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, although the refrigerant and the absorbing liquid are guided and expanded in the pipe circumferential direction along the spiral groove portion, the protrusion formed by cutting and raising has an acute apex angle. In addition to being prone to film breakage on the protrusion surface due to the triangular cross-sectional shape, the liquid film is biased at discontinuous bending points existing at the boundary between the spiral groove and the protrusion. Film breakage is likely to occur in the flat part, and the liquid film thickness of the refrigerant or the absorbing liquid is largely biased, so that the liquid film does not spread sufficiently. As a result, the surface area in the tube is increased by the formation of the spiral protrusion. Nevertheless, the overall heat transfer performance Is did not expect too much.
[0006]
[Solution]
Here, the present invention has been made in the background as described above, and the problem to be solved is that the refrigerant and the absorbing liquid that can be circulated in the pipe even when the pipe is a vertical pipe or an inclined pipe. Absorption that can be advantageously widened on the inner surface of the tube to advantageously obtain a wetted area without causing a significant deviation of the liquid film, and can advantageously improve the heat transfer performance by ensuring the liquid film residence time. The object is to provide a heat transfer tube for a refrigerator.
[0007]
[Solution]
And in order to solve such a subject, the feature of the present invention is that in the heat transfer tube for an absorption refrigeration machine in which a plurality of fins are mounted on the outer surface of the tube while the refrigerant is guided into the tube, the angle is 5 to 50 °. The inner surface of the tube is formed with a pitch of 0.3 to 5.0 mm in the tube circumferential direction so as to be alternately located in the tube circumferential direction so that the inner surface of the tube spirally extends in the longitudinal direction of the tube at a lead angle of In addition, the protrusion height of the convex portion with respect to the concave portion is set to 0.3 to 0.6 mm, while the sectional shape of the concave portion and the convex portion alternately located in the pipe circumferential direction has a substantially discontinuous portion. There is a continuous surface.
[0008]
The present invention also provides an absorption liquid used for an absorber in which a cooling liquid introduced into a pipe is allowed to flow down along the inner peripheral surface of the pipe, and a plurality of fins are attached to the outer surface of the pipe and cooling air is brought into contact therewith. In the heat transfer pipe for a refrigerator, the concave and convex portions extending spirally toward the longitudinal direction of the pipe at a lead angle of 5 to 50 ° are arranged in the pipe circumferential direction so as to be alternately positioned in the pipe circumferential direction. Are formed at a pitch of 1.0 to 5.0 mm, and the protrusion height of the protrusion with respect to the recess is 0.3 to 0.6 mm, while the recess and the protrusion are alternately positioned in the pipe circumferential direction. It is also a feature that the cross-sectional shape is a continuous surface having no substantial discontinuity.
[0009]
Furthermore, the present invention relates to a heat transfer tube for an absorption refrigeration machine used in an evaporator in which a refrigerant is allowed to flow down along an inner peripheral surface of a tube, and a plurality of fins are attached to the outer surface of the tube to contact a fluid to be cooled. The recesses and projections that spirally extend on the inner surface of the tube in the longitudinal direction of the tube at a lead angle of 5 to 50 ° are 0.3 to 0.00 mm in the tube circumferential direction so that they are alternately positioned in the tube circumferential direction. While forming at a pitch of 6 mm and setting the projection height of the projections to the recesses to be 0.3 to 0.6 mm, the cross-sectional shapes of the recesses and projections alternately located in the pipe circumferential direction are substantially It is also characterized by having a continuous surface that does not have discontinuous portions.
[0010]
Therefore, the cross-sectional shape of the concave portion and the convex portion in the heat exchanger tube for an absorption refrigeration machine structured according to the present invention is specifically limited as long as it is a continuous surface having no substantial discontinuous portion. However, a curved surface shape such as a circle, an ellipse, or a parabola is preferable. Note that a cross-sectional shape that is a continuous surface having no substantial discontinuity is substantially a bending point where a plurality of tangents are present at any point on the cross-section, or a curved portion having a very small radius of curvature. A surface that does not substantially have a point that can be regarded as a bending point.
[0011]
Further, in the heat transfer tube for an absorption refrigeration machine structured according to the present invention, the convex portion may be provided to be inclined toward one side in the tube axis direction.
[0012]
Furthermore, in the heat exchanger tube for an absorption refrigeration machine structured according to the present invention, a coil member having a lead angle smaller than the lead angle of the concave and convex portions is inserted into the tube, and the coil member is placed on the inner peripheral surface of the tube. It is also possible to arrange them closely.
[0013]
Specific Configuration of the Invention
First, FIGS. 1 to 3 show a specific example of a heat transfer tube for an absorption refrigeration machine having a structure according to the present invention. Such a heat transfer tube 10 has a straight tube shape with a circular cross section as a whole. For example, as shown in FIG. By attaching a large number of plate fins 12 to the outer peripheral surface and assembling them integrally, an absorber or an evaporator is configured. The central axis of each heat transfer tube 10 extends in a vertical direction or a direction inclined by a predetermined angle with respect to the vertical direction, and is disposed in the absorber or the evaporator. As the absorbent 14 flows down along the line, the refrigerant introduced into the pipe is absorbed by the absorbent 14 and the cooling air is brought into contact with the outer surface of the pipe so that the temperature of the absorbent due to the heat of dissolution or the heat of dilution or latent heat. On the other hand, in the evaporator, in the evaporator, the liquid refrigerant 14 that is guided into the pipe and allowed to flow down along the inner surface of the pipe evaporates, whereby the air that is brought into contact with the outer surface of the pipe by the refrigeration action due to the evaporation of the refrigerant, etc. The to-be-cooled fluid is cooled.
[0014]
Here, the material of the heat transfer tube 10 is selected in consideration of the heat resistance, workability, and the like in addition to the corrosion resistance to the refrigerant and absorption liquid introduced into the tube. 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 that extend in a spiral shape in the longitudinal direction of the pipe are alternately positioned in the circumferential direction of the pipe and are formed substantially parallel to the surface.
[0015]
The recesses 18 and the projections 20 have a pitch p in the pipe circumferential direction (see FIG. 3), in other words, the

recesses

18 and 18 that are adjacent to each other in the circumferential direction in a cross section perpendicular to the tube axis. The intervals of 20 are all set to be 0.3 to 5.0 mm. Specifically, for example, in the case of a copper pipe with a diameter of 19.05 mm, it is desirable to set the number of the concave portions 18 and the convex portions 20 to be 12 to 150 per round.
[0016]
However, if the pitch p is smaller than 0.3 mm, the width of the recess 18 becomes too small, and it becomes difficult for the refrigerant and the absorbent to flow into the recess 18 sufficiently. This is because the spread of the liquid film cannot be expected sufficiently. On the other hand, if the pitch: p is larger than 5.0 mm, the unevenness formed on the inner surface of the tube is reduced and it is difficult to realize an effective increase in the heat transfer area. Because it becomes. That is, by increasing the pitch p of the concave portion 18 and the convex portion 20 in the pipe circumferential direction to 0.3 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 concave portion 18 and the convex portion 20 can be advantageously achieved, and the effective heat transfer area can be effectively increased.
[0017]
In particular, when used as a heat transfer tube for an absorber, the pitch: p is preferably set to 1.0 to 5.0 mm. However, in the absorber heat transfer tube, generally, a highly viscous absorbing liquid such as a lithium bromide aqueous solution is allowed to flow down the inner surface of the tube. Therefore, when the pitch p is smaller than 1.0 mm, the absorbing liquid enters the recess 18. This is because it becomes difficult to flow in sufficiently. On the other hand, when used as a heat transfer tube for an evaporator, the pitch: p is preferably set to 0.3 to 0.6 mm. However, in the evaporator heat transfer tube, since the viscosity of the refrigerant led into the tube is generally not so large, the increase of the heat transfer area can be achieved very advantageously by setting the pitch: p to 0.6 mm or less. It is.
[0018]
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 to be within a range of 5 to 50 °, preferably within a range of 5 to 30 °, at any part. As shown in FIG. 1, the lead angle refers to an angle formed by a tangent line (a straight line in the winding direction) of the concave portion 12 or the convex portion 14 and a plane perpendicular to the tube axis.
[0019]
However, if the lead angle: α is larger than 50 °, when the heat transfer tube 10 is assembled to the absorber or the evaporator, the flow rate of the refrigerant or the absorbing liquid along the concave portion 18 increases, and the liquid film on the inner surface of the tube increases. This is because it is difficult to secure a sufficient residence time, and the effect of increasing the heat transfer area by the concave portion 18 and the convex portion 20 is hardly exhibited. On the other hand, if the lead angle: α is smaller than 5 °, the heat transfer tube This is because it becomes difficult to form the concave portions 12 and the convex portions 14 on the inner peripheral surface of the tenth. That is, by setting the lead angle α of the concave portion 18 and the convex portion 20 to 5 to 50 °, preferably 5 to 30 °, the inner surface of the pipe can be allowed to flow down without significant deterioration in manufacturability. The liquid film is guided along the concave portion 18 in the pipe circumferential direction, and the flow speed of the liquid film is effectively suppressed, and the fluid distance is substantially increased to advantageously secure the residence time of the refrigerant and the absorbing liquid. It can be done.
[0020]
In addition, in the evaporator or the absorber, when the heat transfer tube 10 is inclined, it is desirable to determine the lead angle: α of the concave portion 18 and the convex portion 20 in consideration of the inclination angle. For this, it is desirable to set the lead angle: α to be equal to or greater than the pipe inclination angle of the heat transfer tube with respect to the vertical direction. Thereby, even when the heat transfer tube 10 is piped, the inclination of the concave portion 18 and the convex portion 20 extending in the spiral direction downward in the axial direction of the heat transfer tube is prevented from partially moving upward, and the concave portion 18 and the convex portion are prevented. Thus, the downward flow of the refrigerant and the absorbent along the line 20 can be advantageously generated.
[0021]
Furthermore, the recessed part 18 and the convex part 20 which were formed in the internal peripheral surface of the heat exchanger tube 10 are made into the continuous surface which does not have a substantial discontinuous part over the whole those cross sections. Note that a continuous surface having no substantial discontinuous portion is a surface that does not have a point that can be regarded as a substantially bending point, such as a bending point having a plurality of tangents or a bending portion having a very small radius of curvature. Say.
[0022]
That is, if the concave portion 18 and the convex portion 20 are formed with a continuous surface that does not have a substantial discontinuous portion over the entire cross section, the liquid to the valley-shaped bending point (discontinuous portion) is formed. Concentration of the film and breakage of the liquid film at the ridge-like bending point can be advantageously prevented, the local unevenness of the liquid film thickness in the concave portion 18 is reduced, and the surface of the convex portion 20 is also reduced. As a result, the liquid film is advantageously widened, and as a result, liquid breakage (occurrence of a thirsty surface) that easily occurs at the flat portion of the concave portion 18 and the top and bottom surfaces of the convex portion 20 can be effectively prevented. As a result, the wetted area can be increased, and the effective heat transfer area and thus the heat transfer performance can be advantageously improved.
[0023]
In addition, the concrete cross-sectional shape of the recessed part 18 and the convex part 20 is not limited at all, In addition to curved cross-sectional shapes, such as a semicircle shape, a semi-elliptical shape, and a parabola shape, the cross section which has a linear part in part. Shapes can also be employed. Specifically, in addition to the shape shown in FIGS. 1 to 3, as shown in FIG. 5, a convex portion 20 having both sides substantially parallel to each other is formed, or as shown in FIG. 6. As shown in FIG. 7, a thick convex portion 20 that protrudes from both sides of the concave portion 18 is formed, or a convex portion 20 that is inclined to one side in the tube axial direction, which is upward during piping, as shown in FIG. The liquid film is advantageously held in the concave portion 18, so that the liquid film is advantageously held in the concave portion 18. The spread of the liquid film in the pipe circumferential direction and the extension of the residence time can be achieved more effectively.
[0024]
Preferably, both the concave portion 18 and the convex portion 20 are formed with a curved cross-sectional shape. The curved cross-sectional shape refers to a cross-sectional shape formed by a plurality of curved surfaces that are single or connected and does not include a straight cross-sectional portion. That is, if it is formed with such a curved cross-sectional shape, the refrigerant and the absorbing liquid spread more smoothly on the surface of the convex portion 20, and the liquid film thickness on the surface of the concave portion 18 and the convex portion 20 is made uniform. It can be achieved more advantageously by the action of surface tension, preventing a partial decrease in heat conduction due to a large deviation in the liquid film thickness, and improving the heat transfer performance by increasing the effective heat transfer area. Can be achieved. However, in the present invention, since the concave portion 18 and the convex portion 20 are formed with a cross-sectional shape that does not have a substantial discontinuous portion, the width direction of the concave portion 18 even if the bottom center of the concave portion 18 is a substantially flat surface. A significant deviation of the liquid film on both sides can be prevented, the occurrence of liquid breakage on the flat surface can be prevented, and effective heat transfer performance can be exhibited.
[0025]
Furthermore, the convex part 20 is formed so that the protrusion height from the bottom face of the concave part 18 is 0.3 to 0.6 mm. However, if the protruding height of the convex portion 20 is lower than 0.3 mm, it is difficult to effectively hold the refrigerant or an absorbent such as a lithium bromide solution having a large specific gravity in the concave portion 18, and as a result, the concave portion 18. If the projecting height of the convex portion 20 is higher than 0.6 mm, the concave portion 18 on the inner peripheral surface of the heat transfer tube 10 and This is because it becomes difficult to form the convex portion 20. That is, by setting the protruding height of the convex portion 20 to 0.3 to 0.6 mm, preferably 0.5 to 0.6 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.
[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 spiral coil member and place it in close contact with the recess 20. By disposing such a coil member, the heat transfer area can be further increased, and a part of the refrigerant or the absorbing liquid is guided along the coil member in the pipe circumferential direction, thereby A further increase in residence time can be achieved.
[0027]
The material of the coil member is selected in consideration of the corrosion resistance against the refrigerant and the absorbing liquid, as in the case of the heat transfer tube 10. For example, the coil member is inserted into the heat transfer tube 10 in which the concave portion 18 and the convex portion 20 are formed. After the caulking, the tube is assembled to the heat transfer tube 10 by inserting a tube expansion plug or the like and pressing and fixing the coil member to the inner peripheral surface of the heat transfer tube 10.
[0028]
By the way, the heat transfer tube 10 having the structure according to the present invention as described above is subjected to drawing using a plug in which spiral irregularities corresponding to the target concave portions 18 and convex portions 20 are attached to the outer peripheral surface, for example. However, it can be advantageously produced by a rolling process.
[0029]
Specifically, for example, as shown in FIGS. 8 to 10, spiral irregularities corresponding to the target concave portion 18 and convex portion 20 are provided on the outer periphery of the raw tube 24 whose inner and outer peripheral surfaces are smooth. The plug 25 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 advantageously manufactured by moving it in the axial direction and subjecting the inner peripheral surface of the tube to uneven processing.
[0030]
In addition, as the roll 26, for example, a roll having a plurality of discs 28 having different diameters with a smooth outer peripheral surface and being attached to the rod 30 in an axial direction is preferably used. The rod 30 is disposed in a state where the axis of the rod 30 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. As shown in FIG. 6, the convex portion 20 having a cross-sectional shape in which the tip portion swells is formed, for example, by forming a convex portion having a cross-sectional shape in which the tip portion is not bulged, and then inserting a tube expansion plug into the tube. It can be manufactured by crushing the tip of the convex portion.
[0032]
And the heat exchanger tube 10 manufactured in this way is inserted and fixed in the mounting holes of a large number of plate fins 12 formed of aluminum alloy or the like, as shown in FIG. The plate fins 12 are attached to the outer peripheral surface of the heat transfer tube 10 and are assembled integrally by the plate fins 12 in a state where a plurality of the plate fins 12 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 is performed by fitting it.
[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. However, it goes without saying that it is included in 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. By forming a concave portion and a convex portion having a substantially constant arc-shaped cross section, an evaporator heat transfer tube and an absorber heat transfer tube each having a shape as shown in FIGS. The specifications of these evaporator heat transfer tubes and absorber heat transfer tubes are shown in Table 1 below. Further, as a comparative example of the evaporator heat transfer tube, as shown in FIG. 11, the bottom surface of the recess 32 is a flat surface, and substantial

bent portions

34, 34 are formed at both end portions in the width direction of the recess 32. As shown in FIG. 12, as a comparative example of the heat transfer tube for the absorber, a cut and raised protrusion 36 as a convex portion extending continuously in a spiral shape is manufactured as a heat transfer tube having a cross-sectional shape formed. Is formed on the inner peripheral surface of the tube, and a heat transfer tube having a cross-sectional shape in which a substantial bent portion 38 is formed at each of the apex of the convex portion and both end portions in the width direction of the concave portion was manufactured. The specifications of the evaporator heat transfer tubes and the absorber heat transfer tubes as comparative examples are also shown in Table 1 below.
[0035]
[Table 1]

[0036]
Then, using one each of the evaporator heat transfer tube and the absorber heat transfer tube as examples and comparative examples, aluminum pipes are attached to the outer peripheral surfaces of the tubes and piped in the vertical direction. For each of the heat transfer tubes for equipment, the cooling capacity and the refrigerant absorption capacity were measured under the conditions shown in Table 2 below. The results are shown in Table 3 below. In this measurement, water was used as the refrigerant, and an aqueous lithium bromide solution was used as the absorbing solution. In addition, the refrigerant absorption capacity was evaluated by the ratio to the absorption capacity when the generated steam was completely absorbed when the cooling capacity was 2.2 kW.
[0037]
[Table 2]

[0038]
[Table 3]

[0039]
Also from the results of such comparative experiments, the heat transfer tube having a structure according to the present invention has excellent heat transfer performance, and when used in an evaporator in an absorption chiller, excellent cooling capacity can be exhibited, It is clear that excellent water vapor absorption ability can be exhibited by using it in an air-cooled absorber.
[0040]
【The invention's effect】
As is apparent from the above description, in the heat exchanger tube for an absorption refrigeration machine structured according to the present invention, a concave portion and a convex portion extending spirally in the longitudinal direction of the tube are formed on the inner peripheral surface of the pipe. In addition, when the pipe is inclined, the coolant or absorption liquid that can flow down the inner surface of the pipe is guided along the recess, so that the liquid film is spread in the circumferential direction of the pipe and the flow distance is increased, and the flow speed is suppressed. The retention time can be advantageously ensured, and since the cross-sectional shape of the concave and convex portions is a continuous surface, local liquid film unevenness in the concave portion is prevented and the surface of the convex portion is prevented. In addition, the liquid film is advantageously widened, and a substantially uniform liquid film as a whole is formed with a large area, so that an effective heat transfer area can be effectively secured, thereby exhibiting excellent heat transfer performance. To get.
[0041]
And, in particular, in the heat transfer tube for an absorber having a structure according to the present invention, an excellent water vapor absorption capacity can be exhibited. On the other hand, in the heat transfer tube for an evaporator having a structure according to the present invention, Excellent cooling capacity can be exhibited.
[0042]
Further, if the convex portion is inclined to one side in the tube axis direction, the refrigerant or the absorbing liquid that flows down along the inner surface of the pipe can be received by the convex portion at the time of piping. The liquid film can be more 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.
[0043]
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 absorbing liquid 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.
FIG. 6 is a cross-sectional explanatory view corresponding to FIG. 2, showing still another specific example of the heat transfer tube structured according to the present invention.
FIG. 7 is a cross-sectional explanatory view corresponding to FIG. 2, showing still another specific example of a heat transfer tube structured according to the present invention.
8 is a longitudinal cross-sectional explanatory view for explaining an example of a heat transfer tube manufacturing apparatus shown in FIG. 1; FIG.
9 is an explanatory front view of the heat transfer tube manufacturing apparatus shown in FIG. 8 and corresponds to a cross section taken along line IX-IX in FIG. 8;
FIG. 10 is an explanatory diagram showing a roll arrangement state in the heat transfer tube manufacturing apparatus shown in FIG. 8;
FIG. 11 is a cross-sectional explanatory view corresponding to FIG. 2, showing an evaporator heat transfer tube used as a comparative example in an experiment of heat transfer performance.
12 is a cross-sectional explanatory view corresponding to FIG. 2, showing an absorber heat transfer tube used as a comparative example in a heat transfer performance experiment. FIG.
[Explanation of symbols]
10 Heat transfer tube 18 Concave portion 20 Convex portion

Claims

Absorption liquid for dissolving refrigerant introduced into the pipe is allowed to flow down along the inner peripheral surface of the pipe, while a plurality of fins are attached to the outer surface of the pipe and used for an absorber in which cooling air is contacted. Because
A concave portion and a convex portion that spirally extend on the inner surface of the tube in the longitudinal direction of the tube so that the lead angle, which is an angle formed with a plane perpendicular to the tube axis, is in the range of 5 to 50 °. While being formed at a pitch of 1.0 to 5.0 mm in the pipe circumferential direction so as to be alternately positioned, the protrusion height of the protrusion relative to the recess is set to 0.3 to 0.6 mm. A heat transfer tube for an absorption refrigeration machine, characterized in that the cross-sectional shapes of recesses and projections alternately located in the circumferential direction are continuous surfaces that do not have substantial discontinuities over the entire cross-section.

The heat exchanger tube for an absorption refrigeration machine according to claim 1, wherein cross-sectional shapes of the concave portion and the convex portion are curved surfaces.

The heat exchanger tube for an absorption refrigeration machine according to claim 1 or 2 , wherein the convex portion is provided to be inclined toward one side in the tube axis direction.

The heat exchanger tube for an absorption refrigerating machine according to any one of claims 1 to 3 , 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 pipe and is in close contact with the inner peripheral surface of the pipe. .