JP4476522B2

JP4476522B2 - Evaporator with defrost heater and refrigerator using the evaporator

Info

Publication number: JP4476522B2
Application number: JP2001246595A
Authority: JP
Inventors: 悟平國; 章西澤; 嘉裕隅田
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2001-08-15
Filing date: 2001-08-15
Publication date: 2010-06-09
Anticipated expiration: 2021-08-15
Also published as: JP2003056971A

Description

【０００１】
【発明の属する技術分野】
本発明は、オゾン層破壊や地球温暖化などの地球環境に悪影響を与えることの少ない、又熱効率を改善した冷蔵庫及び該冷蔵庫等に使われる蒸発器に関するものである。
【０００２】
【従来の技術】
現在、冷凍冷蔵庫の冷媒には、主にフロン系冷媒が用いられている。フロン系冷媒の中でもCFC系およびHCFC系冷媒は大気へ放出された場合、オゾン層を破壊するため、塩素を含まないHFC系冷媒への移行が進められている。家庭用冷蔵庫ではHFC系冷媒であるR134aが広く用いられている。
【０００３】
図１５、図１６は従来の冷凍冷蔵庫の一例として特開平８‐２８５４４０号公報に示された、家庭用冷蔵庫の側断面図および冷媒回路構成図である。
図において、1は圧縮機、２は凝縮器、３は絞り装置である毛細管、４は蒸発器、５は負荷変動時などに発生する余剰冷媒をためるヘッダーであり、これらは順次配管で接続され、冷凍サイクルを形成している。
【０００４】
また、１０は冷凍室内温度検出手段、１１は庫内に空気を循環する空気循環手段、１２は冷凍室への冷気循環をダンパ−で制御する冷凍室の空気循環制御手段、１３は冷蔵室への冷気循環を制御する冷蔵室の空気循環制御手段、１５は冷凍室、１６は冷蔵室、２１は冷蔵室内温度検出手段である。
また、４０は蒸発器４に付着する霜を溶かすために蒸発器４の下方に設置された除霜用電気ヒ−タ、４１は冷却システムＯＮ時間検出手段、４２は除霜タイマ−で圧縮機１の運転時間を積算するためのものである。
さらに、４４は冷凍室空気吸込み口、４８は冷蔵室空気吸込み口である。
【０００５】
次に、従来のフロン系冷媒を用いた冷蔵庫の除霜動作について説明する。冷凍室内温度検出手段１０が予め設定された温度に到達した時点で圧縮機１を停止させる。次に、除霜タイマ−４２が積算した冷却システムＯＮ時間（圧縮機運転時間）を冷却システムＯＮ時間検出手段４１において、予め設定された設定値と比較し、設定値より短い場合は、冷凍室の空気循環制御手段１２のダンパ−を閉じ、空気循環手段１１をそのまま通電した状態で引き続き送風を行う。
【０００６】
従って、空気循環手段１１により送風された空気は冷凍室の空気循環制御手段１２により冷凍室１５には流れ込まず、冷蔵室の空気循環制御手段１３の側面の開口部から冷蔵室ダクト４６を経て冷蔵室１６に流れ込む。そして冷蔵室１６内を冷却した上で５〜７℃程度の温度となり冷蔵室空気吸込み口４５から蒸発器４に戻り、蒸発器４で熱交換を行い、付着した霜を溶かす。
【０００７】
一方、除霜タイマ−４２が積算した冷却システムＯＮ時間（圧縮機運転時間）を冷却システムＯＮ時間検出手段４１において、予め設定された設定値と比較し、設定値より長い場合は冷凍室の空気循環制御手段１２のダンパ−を閉じ、空気循環手段１１を停止させ除霜用電気ヒ−タ４０を通電し、このヒ−タにより加熱された空気が上方へ自然対流により上昇し、蒸発器４に付着した霜を溶かす。
これらの動作により、冷蔵庫の蒸発器４に付着した霜を取り除き効率良く冷蔵庫を運転している。
【０００８】
また、HFC系冷媒は大気放出された場合、地球温暖化を促進する物質であり、地球環境を悪化させない炭化水素系冷媒やアンモニアなどの自然冷媒を冷蔵庫の冷媒として用いることが検討されている。
自然冷媒を用いた冷蔵庫としては、例えば特開平８−１７８４８１号公報に示されたものがある。この冷凍冷蔵庫の冷媒は、地球温暖化に対する影響は非常に小さいが、可燃性を示すプロパンやブタンなどの炭化水素系冷媒が用いられている。
【０００９】
【発明が解決しようとする課題】
上記のような従来の冷蔵庫に地球温暖化への影響か小さい可燃性冷媒を用いる場合、まず可燃性に対する安全性の確保が最重要課題であり、万一冷媒が漏れても発火しないシステムを構築することが重要である。
【００１０】
さらに、地球温暖化を抑制するために、地球温暖化への影響が小さい可燃性冷媒を用いることのみならず冷凍冷蔵庫のエネルギ−効率を向上させるべく、電気ヒ−タによる除霜方法を改善することも重要な課題となる。
【００１１】
この発明は、上記のような問題を解決するためになされたもので、地球環境に対して悪影響の非常に小さい冷媒の除霜時の安全性を改善し、また、除霜時のエネルギ−効率を向上させ、地球温暖化を抑制する冷蔵庫及び冷蔵庫等に使用する蒸発器を得ることを目的とする。
【００１２】
【課題を解決するための手段】
本発明に係わる除霜ヒ−タ付き蒸発器は、可燃性冷媒を使用し、表面温度が前記可燃性冷媒の発火温度より低い温度となるように設定される除霜ヒ−タを備えた蒸発器であって、伝熱管が貫通し、所定の間隔で配列した複数のプレ−トフィンと、被冷却空気が流れる方向と平行な方向で、プレ−トフィンと直交し、かつその端部と接触するように配置した面状の除霜ヒ−タとを備え、複数のプレ−トフィンの端部はプレ−トフィンごとに面状の除霜ヒ−タと接触するもの及び両者間に間隙を設けて非接触としたものがあるものである（請求項１）。
面状の除霜ヒ−タはヒ−タ表面積が大きくでき、ヒ−タ入力を大きくしても、ヒ−タ表面温度を可燃性冷媒の発火温度より低くできる。また、除霜ヒ−タを蒸発器の構成部材と接触させることで、熱の伝達効率が良くなる。そこで、除霜ヒ−タの表面温度が可燃性冷媒の発火温度より低い温度とでき、冷媒が漏れて除霜ヒ−タに接触しても発火、燃焼しない。また、面状の除霜ヒ−タとプレ−トフィンの両者間に設けた間隙により、着霜しても風路が塞がれない。そこで、熱交換能力が確保できる。
【００１５】
また、前記プレ−トフィンの両側の端部に面状の除霜ヒ−タを接触するように配置し、さらに、前記プレ−トフィンの配列の両外側に面状の除霜ヒ−タを配置した除霜ヒ−タ付き蒸発器である（請求項２）。
面状の除霜ヒ−タで風路を形成でき、除霜がより確実にできる。
【００１９】
また、圧縮機、凝縮器、絞り装置及び前記記載のいずれかの除霜ヒ−タ付き蒸発器を有する冷凍サイクルを備えた冷蔵庫である（請求項３）。
前記の除霜ヒ−タの特徴を有する冷蔵庫が得られる。
【００２０】
【発明の実施の形態】
実施の形態１．
図1は、本発明の実施の形態１の冷凍冷蔵庫の側断面図、図２は、冷凍冷蔵庫の冷媒回路を示す図、図３は、面状の除霜ヒ−タ付き蒸発器の斜視図、図４は、図３の横断面図である。
図において、従来技術と同じもの又は相当するものは、同一番号を付し、その説明を省略する。即ち、１は圧縮機、２は凝縮器、３は絞り装置である毛細管、４は蒸発器、５はヘッダ−、１０は冷凍室温度検出手段、１１は空気循環手段、１２は冷凍室の空気循環制御手段、１３は冷蔵庫の空気循環制御手段、１５は冷凍室、１６は冷蔵室、２１は冷蔵室庫内温度検出手段である。
【００２１】
この冷凍冷蔵庫の冷媒には地球温暖化に非常に影響が小さい炭化水素系冷媒R600aを用いている。
図において、７は蒸発器４のプレ−トフィンで、７ａの幅広フィンと７ｂの幅狭フィンからなる。８は蒸発器４の伝熱管、８ａは伝熱管のＵ字管部である。
また、１７は冷凍室空気吸込み口、１８は冷蔵室空気吹き出し口であり、１８ａ、１８ｂ、１８ｃ、１８ｄと複数開口し、冷蔵室送風ダクト１９から空気を冷蔵室１６へ吹出す。２０は野菜室、２５は冷蔵室空気吸いこみ口であり、２５ａ、２５ｂと冷蔵室１６の空気を吸込む。２６は野菜室空気吹き出し口であり、２６ａ、２６ｂ、２６ｃと冷蔵室吸込み口２５からの空気を冷凍室１５に吹出す。２７は野菜室空気吸込み口であり、野菜室２０からの空気を吸込む。２８は空気の野菜室から蒸発器への戻りダクトである。
３０ａは、蒸発器４の側面に配置された除霜ヒ−タである面状の除霜ヒ−タであり、除霜ヒ−タ３０の１例である。
図３に示すように、プレ−トフィン７（幅広フィン７ａ幅狭フィン７ｂ）、伝熱管８（伝熱管のＵ字管部８ａ）及び面状の除霜ヒ−タ３０ａ等で除霜ヒ−タ付き蒸発器６を構成する。
本除霜ヒ−タ付き蒸発器６は、図１に示すように冷凍室１５内に設置される。
【００２２】
冷蔵室の空気循環制御手段１３は、冷蔵室１６内に設置された冷蔵室庫内温度検知手段２１により検知された冷蔵室１６の庫内温度が予めコントロ−ラ２３内に記憶されている設定値より高い場合にダンパ−を開け、冷蔵室１６に蒸発器４からの空気を冷蔵室送風ダクト１９、冷蔵室空気吹出し口１８を経て導入可能とする。また、設定値より低い場合は、ダンパ−を閉じ、蒸発器４から冷蔵室１６への空気の導入を遮断する。
【００２３】
冷凍室の空気循環制御手段１２も冷蔵室の空気循環制御手段１３と同様に、冷凍室１５内に設置された冷凍室庫内温度検知手段１０により検知された冷凍室１５の庫内温度が予めコントローラ２３内に記憶されている設定値より高い場合にダンパ−を開け冷凍室１５に蒸発器４からの空気を導入可能とする。また、設定値より低い場合はダンパ−を閉じ蒸発器４から冷凍室１５への空気の導入を遮断する。
【００２４】
圧縮機１は冷凍室１５内に設置された、冷凍室庫内温度検出手段１０により検知された庫内温度が、コントロ−ラ２３内に記憶されている設定値より高くなった場合に運転させ、設定値以下になったら停止する。
【００２５】
空気循環手段１１は、冷凍室の空気循環制御手段１２のダンパ−及び冷蔵室の空気循環制御手段１３のダンパ−のどちらか一方が開いた場合に通電され作動し、両方のダンパ−が閉じた場合に停止する。
【００２６】
通常冷凍冷蔵庫内の冷却運転では冷蔵室の空気循環制御手段１２のダンパ−及び冷凍室の空気循環制御手段１３のダンパ−は両方共に開の状態であり、圧縮機１及び空気循環手段１１とも運転を行っており、冷凍室１５、冷蔵室１６及び野菜室２０とも冷却されている。冷蔵庫庫内の空気の流れを図１中に矢印で示す。
【００２７】
その間、蒸発器４には霜が付着成長している。冷蔵庫庫内の空気の流れは空気循環手段１１から吹出された空気は冷蔵室１６と冷凍室１５に分かれる。冷蔵室の空気循環制御手段１２を通過した空気は冷蔵室用ダクト１９を通過し、冷蔵室吹出し口１８a、１８b、１８c、１８dから−１５℃程度で冷蔵室１５に吹出す。吹出された空気は冷蔵室内を３〜５℃程度に冷却しながら、冷蔵室吸込み口２５a、２５bに流れ込み、野菜室吹出し口２６a、２６b、２６cから野菜室２０に吹出される。
【００２８】
さらに、野菜室を５〜７℃程度に冷却し、蒸発器４への戻りダクト２８を通過して５〜７℃程度の温度で蒸発器４に流れ込む。−３０℃程度の蒸発器４と熱交換を行いながら空気中の水分を蒸発器に奪われ、−２７℃程度の空気となって再び蒸発器４から吹出される。
【００２９】
一方、冷凍室の空気循環制御手段１３の開いたダンパ−を通過した空気は−２７℃程度で冷凍室１５に吹出され冷凍室１５を冷却し、冷凍室１５下部の冷凍室空気吸込み口１７から−２０℃程度で蒸発器４へ流れ込む。
【００３０】
圧縮機１の積算運転時間が予め記憶された設定値に達した場合、及び冷凍室庫内温度検知手段１０により検知された冷凍室１５の庫内温度が予め記憶された設定値より高く、かつ、ヘッダ−の温度検知手段により検知されたヘッダ−温度が予め記憶された設定値より低い場合に面状の除霜ヒ−タ３０ａに通電し蒸発器４に付着した霜を溶かすための除霜運転を行う。
除霜ヒ−タ３０に通電しての除霜運転は、圧縮機１を止め、空気循環手段１１を停止させ、冷凍室の空気循環制御手段１２及び冷蔵室の空気循環手段１３のダンパ−を閉じて行う。両ダンパ−を閉じることにより、余計な熱が冷凍室及び冷蔵室に伝わるのを防止する。
【００３１】
次に、面状の除霜ヒ−タ３０ａの大きさ及び表面温度の設定方法について説明する。
冷媒としてR600aを使用する場合、面状の除霜ヒ−タ３０ａの表面温度はR600aの発火下限温度494℃より低い温度に設計し、制御する。例えば、100℃ほど低い、394℃以下になるように設計、制御する。
例えば、ヒ−タ入力 A[W]、蒸発器表面温度255.15[K]、ヒ−タ表面温度667.15[K]、ヒ−タ表面積 B[m²]、ヒ−タ効率 η[-]、ヒ−タと蒸発器間の熱伝達率K [W/m²K]とした場合、次式により面状の除霜ヒ−タ３０ａの加熱面のヒ−タ表面積を決定する。
B×η≧A/{Ｋ×(ヒ−タ表面温度−蒸発器表面温度)} [m²]
但し、この場合の、ヒ−タ表面温度−蒸発器表面温度＝４１２
【００３２】
本算式により、ヒ−タ表面積を決定するため、表面温度は394℃以下になるように設計することが可能である。即ち、除霜ヒ−タ３０として、面状の除霜ヒ−タ３０ａを用いるので、表面積を大きくでき、除霜効果が得られるヒ−タ入力を与えてもヒ−タ表面温度を下げることができ、可燃性冷媒の発火温度より低く（100℃低く）できる。
さらに、面状の除霜ヒ−タ３０ａの表面に温度検知手段を設置して、予め設定された温度になると、面状の除霜ヒ−タ３０ａへの通電を停止するように制御しているので、表面温度は394℃以下に制御できる。
【００３３】
図３の面状の除霜ヒ−タ付き蒸発器の斜視図及び図４のその横断面図に示すように、本実施の形態の蒸発器４において、伝熱管８が貫通しているプレ−トフィン７は幅広フィン７ａと幅狭フィン７ｂが所定の間隔をもって、１枚ごとに交互に設置され、面状の除霜ヒ−タ３０ａがプレ−トフィン７と平行に、幅広フィン７ａのみとその一方の端部７ｃにおいて接触するように配置されている。従って、蒸発器４の片側に面状の除霜ヒ−タ３０ａを接触するように設置しても、蒸発器４内を通過する空気の流れに影響を及ぼすことはない。なお、この蒸発器の被冷却空気の流れる方向は図の上下方向である。
即ち、面状の除霜ヒ−タ３０ａと幅狭フィン７ｂ間に間隙が生じる。そこで、プレ−トフィン７、伝熱管８に着霜しても目詰まりにより風路が塞がれることが防止でき、冷却能力の低下を防止できる。
【００３４】
また、面状の除霜ヒ−タ３０ａを蒸発器4のプレ−トフィン７と接触させて設置しているので、面状の除霜ヒータ３０ａからの熱が効率的に蒸発器４に伝わり、低入力で除霜が可能となる。従って、除霜運転時の入力は低減され、さらに必要以上に冷蔵庫庫内に熱負荷をかけることもないため、除霜運転後の圧縮機１による冷却運転時も短時間で終了することが可能となり、低消費電力量を実現できる。
【００３５】
更に、可燃性冷媒であるR600aが冷蔵庫内に漏れた場合でも、面状の除霜ヒ−タ３０ａの表面温度が発火下限温度より低いため、漏れたR600a冷媒が面状の除霜ヒ−タ３０ａに接触しても、R600aは発火温度に達せず、発火、燃焼することはない。そこで、安全に除霜運転を行うことができる。
【００３６】
当然ながら、プレ−トフィン７の幅広フィン７ａ及び幅狭フィン７ｂの配置は1枚ごとに交互に設置せずに、幅広フィン７ａの配列に適当な割合で幅狭フィン７ｂを混入させてもよい。要するに、着霜により風路が塞がれなければよい。
また、面状の除霜ヒ−タ３０ａの大きさも、プレ−トフィン７の片側の端部７ｃすべてに接触する大きさでなくてもよい。即ち、前記の算出式によりヒ−タ表面積Ｂを算出し、この大きさに合せて適当にプレ−トフィン７の端部７ｃに接触させればよい。
【００３７】
さらに、面状の除霜ヒ−タ３０ａのその他の例を図５、図６、図７および図８に示す。図５、図６は、それぞれ、面状の除霜ヒ−タ付き蒸発器の斜視図、その横断面図であり、図７、図８は、それぞれ、別の面状の除霜ヒ−タ付き蒸発器の斜視図、その横断面図である。
【００３８】
図５の例では、除霜ヒ−タ３０を図３の面状の除霜ヒ−タ３０ａに加えて、プレ−トフィン７の配列の両外側に、面状の除霜ヒ−タ３０ｂ、３０ｃと、それぞれ1枚づつ設置している。
この場合、図３の場合に比べて、さらに除霜ヒ−タ３０の加熱面が広くなるため、除霜ヒ−タ３０の表面温度を低くすることが可能となる。また、両外側の除霜フィルタ−３０ｂ、３０ｃは蒸発器４の伝熱管８のＵ字管部８ａと接触させなくてもよいが、接触させるように設置することにより、さらに効率良く蒸発器の除霜が可能となる。
【００３９】
また、図７の例では、蒸発器４の周囲に面状の除霜ヒ−タ３０ａ、３０ｂ、３０ｃ、３０ｄを設置している。そこで、前記の図３や図５の例よりもさらに、除霜ヒ−タの表面積が大きく取れるため、表面温度を低くすることが可能となり、より安全性に優れる。
また、面状の除霜ヒ−タ３０ａ、３０ｂ、３０ｃ、３０ｄにより蒸発器４の風路を形成するため、蒸発器４のみならず風路の除霜も同時に確実に行うことができ、信頼性の高い冷蔵庫を提供することが可能となる。
さらに、各部の面状の除霜ヒ−タ３０ａ、３０ｂ、３０ｃ、３０ｄは電気的に並列に接続されるため、仮にその中の何れかが、何らかの原因で動作しなくとも残りの除霜ヒ−タ３０で除霜することができ、信頼性の高い冷蔵庫を提供することが可能である。
また、効率は悪くなるが、面状の除霜ヒ−タ３０ａ、３０ｂ、３０ｃ、３０ｄは設置の都合等でプレ−トフィン７、伝熱管８のＵ字管部８ａに接触させなくてもよい。当然選択的に接触させてもよい。
【００４０】
実施の形態２．
図９は、本発明の実施の形態２の冷凍冷蔵庫の除霜ヒ−タ付き蒸発器の側断面図、図１０は、シ−ズヒ−タを設置した伝熱管の断面図である。
この冷凍冷蔵庫の冷凍サイクルの冷媒には地球温暖化に非常に影響が小さい炭化水素系冷媒R600aを用いている。
図において、３０ｅは伝熱管８内に設置された除霜ヒ−タ３０であるシ−ズヒ−タである。その他の構成は、前記の実施の形態１と同じであり、又冷凍冷蔵庫の冷却運転動作および除霜運転等についても実施の形態１と同様なので説明を省略する。
【００４１】
冷凍サイクル内には殆ど酸素（空気）が存在せず、従って、蒸発器４の伝熱管８にも殆ど酸素（空気）が存在しない。そこで、このように蒸発器４の伝熱管８内にシ−ズヒ−タ３０ｅを設置すれば、シ−ズヒ−タ３０ｅ表面温度がいくら上昇しても可燃性冷媒に発火することはない。
また、冷凍サイクル内に空気が混入すると、冷媒の圧縮機吐出温度が通常より上昇する。そこで、圧縮機温度検知手段により圧縮機１の吐出温度を測定し、所定の温度より高くなると、冷蔵冷凍庫の運転を停止させる。従って、除霜運転も実行されないため、冷媒R600ａに発火することはなく、安全な冷蔵冷蔵庫を提供することができる。
なお、図９では、プレ−トフィン７を幅広フィン７ａ及び幅狭フィン７ｂとしているが、同形状のフィンでもよい。
【００４２】
実施の形態３．
図１１は、本発明の実施の形態３の冷凍冷蔵庫の除霜ヒ−タ付き蒸発器の側断面図であり、図１２は、除霜ヒ−タ付き蒸発器の伝熱管に鋳込んだシ−ズヒ−タを示す伝熱管の断面図である。
本冷凍冷蔵庫の冷凍サイクルの冷媒には地球温暖化に非常に影響が小さい炭化水素系冷媒R600aを用いている。
図において、除霜ヒ−タ３０であるシ−ズヒ−タ３０ｅは、伝熱管８の一部に鋳込んで設置されている。その他及び冷蔵庫の冷却運転動作等については実施の形態１と同様なので省略する。
【００４３】
このように、蒸発器４の伝熱管８の一部に直接シ−ズヒ−タ３０ｅを設置しているため、除霜ヒ−タ３０の発熱が効率よく蒸発器４全体に伝わるため、除霜ヒ−タ３０の表面温度はR600aの発火温度より低く制御されても、十分に蒸発器４の霜を溶かすことができる。さらに、除霜ヒ−タ３０の表面温度をR600ａの発火温度より低く、例えば、100℃低い394℃に制御されているため、R600aに発火することはなく、安全な冷蔵庫を提供することが出来る。
なお、図１１では、プレ−トフィン７を幅広フィン７ａ及び幅狭フィン７ｂとしているが、同形状のフィンでもよい。
【００４４】
実施の形態４．
図１３は、本発明の実施の形態４の冷凍冷蔵庫の除霜ヒ−タ付き蒸発器の斜視図であり、図14は、環状シ−ズヒ−タを示す斜視図である。
この冷凍冷蔵庫の冷凍サイクルの冷媒には地球温暖化に非常に影響が小さい炭化水素系冷媒R600aを用いている。
図において、３０ｆは、除霜ヒ−タ３０である環状シ−ズヒ−タであり、環状シ−ズヒ−タ３０ｆは除霜ヒ−タ付き蒸発器６のプレ−トフィンの配列の外側の伝熱管８の曲がり部である伝熱管のＵ字部８ａに設置されている。
その他の構成は、実施の形態１と同じであり、冷凍冷蔵庫の冷却運転動作および除霜運転についても実施の形態１と同じなので説明を省略する。
【００４５】
このように、蒸発器４の伝熱管のＵ字部８ａに環状シ−ズヒ−タ３０ｅを設置しているので、除霜ヒ−タ３０の発熱が効率よく蒸発器４全体に伝わる。そこで、ヒ−タ表面温度はR600aの発火温度より低く設定、制御されても、十分に蒸発器の霜を溶かすことができる。さらに、ヒ−タの表面温度をR600ａの発火温度より低く、例えば、100℃低い、394℃に設定、制御するので、R600aが漏れても、R600aに発火、燃焼することはなく、安全な除霜ヒ−タ付き冷蔵庫６を提供することができる。
又、設置箇所が蒸発器４の配列プレ−トフィン７の外側の伝熱管のＵ字部８ａであるため、新たに蒸発器４を開発せずとも、従来の蒸発器４に簡単に取り付け可能であり、安価に除霜ヒ−タ付き蒸発器６を有する冷凍冷蔵庫を提供することが可能となる。
【００４６】
なお、図１３では環状シ−ズヒ−タ３０ｅを伝熱管のＵ字部８ａの全てに取付けているが、全てでなく、必要に応じて適当数の取付けでよい。
又、図１３では、プレ−トフィン７を幅広フィン７ａ及び幅狭フィン７ｂとしているが、同形状のフィンでもよい。
【００４７】
前記の実施の形態１〜実施の形態４では、冷媒として炭化水素冷媒R600a(イソブタン)を用いた場合について説明したがこれに限ることなく、R600（ブタン）やR290（プロパン）などの炭化水素冷媒やアンモニアなどの自然冷媒、あるいはこれらの混合冷媒であってもよい。また、R134a、R32やR152aなどの地球温暖化係数の小さなHFC系フロン冷媒、あるいはそれらの混合冷媒であってもよい。
【００４８】
又、前記の実施の形態１〜実施の形態４では、絞り装置を毛細管を用いた場合の例で説明したが、これに限るものではなく、電気信号により開度を任意に調整できる電子式膨張弁でもよい。
【００４９】
また、前記の実施の形態では、冷凍機油について特に明示していないが、鉱油及びアルキルベンゼン、エステル油、エ−テル油、PAG油などの合成油が使用される。
【００５０】
また、前記の実施の形態では、圧縮機について特に明示していないが、レシプロ式、ロータリー式、スクロール式などであればよく、圧縮機内の圧力を高圧に保持した高圧シェルタイプもしくは圧縮機内の圧力を低圧に保持した低圧シェルタイプのいずれのタイプでもよい。
【００５１】
また、前記の実施の形態で用いられている凝縮器について、特に明示していないが、冷蔵庫の側壁に埋め込まれた銅配管と外板が接触した自然対流式や送風手段を用いた強制対流式のいずれのタイプでもよい。
【００５２】
さらに、前記実施の形態１〜実施の形態４に記載の除霜ヒ−タ付き蒸発器６は、冷蔵庫のみでなく、冷凍機、空気調和機等の冷凍サイクルに広く使用できる。
【００５３】
【発明の効果】
本発明に係わる除霜ヒ−タ付き蒸発器は、可燃性冷媒を使用し、表面温度が前記可燃性冷媒の発火温度より低い温度となるように設定される除霜ヒ−タを備えた蒸発器であって、伝熱管が貫通し、所定の間隔で配列した複数のプレ−トフィンと、被冷却空気が流れる方向と平行な方向で、プレ−トフィンと直交し、かつその端部と接触するように配置した面状の除霜ヒ−タとを備え、複数のプレ−トフィンの端部はプレ−トフィンごとに面状の除霜ヒ−タと接触するもの及び両者間に間隙を設けて非接触としたものがあるものとした（請求項１）。このため、面状の除霜ヒ−タはヒ−タ加熱面の表面積を大きくでき、除霜効果が得られるヒ−タ入力を与えても表面温度を可燃性冷媒の発火温度より低くできる。また、除霜ヒ−タを蒸発器の構成部材と接触させるため、熱が効率的に蒸発器に伝わる。そこで、除霜効果が得られるとともに、万一冷媒が漏れ除霜ヒ−タに触れても発火、燃焼を防止できる。また、前記の面状の除霜ヒ−タの効果及び除霜ヒ−タを蒸発器に接触させた効果に加えて、蒸発器に着霜しても目詰まりにより風路が塞がれることがなく、熱交換の能力が確保できる。
【００５６】
また、前記プレ−トフィンの両側の端部に面状の除霜ヒ−タを接触するように配置し、さらに、前記プレ−トフィンの配列の両外側に面状の除霜ヒ−タを配置した除霜ヒ−タ付き蒸発器とした（請求項２）ので、前記の効果に加えて、面状の除霜ヒ−タで風路を形成でき、除霜がより確実に行われる。
【００６０】
また、圧縮機、凝縮器、絞り装置及び前記記載のいずれかの除霜ヒ−タ付き蒸発器を有する冷凍サイクルを備えた冷蔵庫とした（請求項３）ので、除霜ヒ−タ付き蒸発器が前記の各効果を有する冷蔵庫が得られる。
【図面の簡単な説明】
【図１】本発明の実施の形態１の冷凍冷蔵庫の側断面図である。
【図２】本発明の実施の形態１の冷凍冷蔵庫の冷媒回路図である。
【図３】本発明の実施の形態１の冷凍冷蔵庫の面状の除霜ヒ−タ付き蒸発器の斜視図である。
【図４】図３の除霜ヒ−タ付き蒸発器の横断面図である。
【図５】本発明の実施の形態１の別の面状の除霜ヒ−タ付き蒸発器の斜視図である。
【図６】図５の横断面図である。
【図７】本発明の実施の形態１のさらに別の面状の除霜ヒ−タ付き蒸発器の斜視図である。
【図８】図７の横断面図である。
【図９】本発明の実施の形態２の冷凍冷蔵庫の除霜ヒ−タ付き蒸発器の側断面図である。
【図１０】本発明の実施の形態２のシ−ズヒ−タを設置した伝熱管の断面図である。
【図１１】本発明の実施の形態３の冷凍冷蔵庫の除霜ヒ−タ付き蒸発器の側断面図である。
【図１２】本発明の実施の形態３のシ−ズヒ−タを鋳込んだ伝熱管の断面図である。
【図１３】本発明の実施の形態４の冷凍冷蔵庫の除霜ヒ−タ付き蒸発器の斜視図である。
【図１４】本発明の実施の形態４の環状シ−ズヒ−タを示す斜視図である。
【図１５】従来の冷凍冷蔵庫の側断面図である。
【図１６】従来の冷凍冷蔵庫の冷媒回路図である。
【符号の説明】
１圧縮機、２凝縮器、３絞り装置、４蒸発器、６除霜ヒ−タ付き蒸発器、7 プレ−トフィン、７ｃプレ−トフィンの端部、８伝熱管、８ａ伝熱管のＵ字管部、３０除霜ヒ−タ、３０ａ３０ｂ、３０ｃ、３０ｄ面状の除霜ヒ−タ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a refrigerator that has less adverse effects on the global environment such as ozone layer destruction and global warming, and that has improved thermal efficiency, and an evaporator used in the refrigerator.
[0002]
[Prior art]
Currently, chlorofluorocarbon refrigerants are mainly used as refrigerants in refrigerators and refrigerators. Among CFC-based refrigerants, CFC-based refrigerants and HCFC-based refrigerants are being transferred to HFC-based refrigerants that do not contain chlorine in order to destroy the ozone layer when released to the atmosphere. R134a, which is an HFC refrigerant, is widely used in household refrigerators.
[0003]
FIGS. 15 and 16 are a side sectional view and a refrigerant circuit configuration diagram of a household refrigerator disclosed in Japanese Patent Laid-Open No. 8-285440 as an example of a conventional refrigerator-freezer.
In the figure, 1 is a compressor, 2 is a condenser, 3 is a capillary tube which is a throttling device, 4 is an evaporator, 5 is a header for accumulating surplus refrigerant generated when the load fluctuates, etc., which are sequentially connected by piping. Forming a refrigeration cycle.
[0004]
Reference numeral 10 denotes a freezer temperature detecting means, 11 an air circulating means for circulating air into the refrigerator, 12 a freezer air circulation control means for controlling cold air circulation to the freezer room by a damper, and 13 to a refrigerator room. Refrigeration room air circulation control means for controlling the cold air circulation, 15 is a freezing room, 16 is a refrigeration room, and 21 is a temperature detection means for the refrigeration room.
In addition, 40 is an electric heater for defrosting installed below the evaporator 4 in order to melt frost adhering to the evaporator 4, 41 is a cooling system ON time detection means, 42 is a defrost timer, and a compressor This is for accumulating the operation time of 1.
Furthermore, 44 is a freezer compartment air inlet, and 48 is a refrigerator compartment air inlet.
[0005]
Next, a defrosting operation of a refrigerator using a conventional chlorofluorocarbon refrigerant will be described. The compressor 1 is stopped when the freezer compartment temperature detecting means 10 reaches a preset temperature. Next, the cooling system ON time (compressor operating time) accumulated by the defrost timer -42 is compared with a preset set value in the cooling system ON time detection means 41. The air circulation control means 12 is closed and the air circulation means 11 is continuously energized as it is.
[0006]
Accordingly, the air blown by the air circulation means 11 does not flow into the freezer compartment 15 by the air circulation control means 12 of the freezer compartment, but is refrigerated from the opening on the side surface of the air circulation control means 13 of the refrigerating compartment through the refrigerator compartment duct 46. It flows into the chamber 16. And after cooling the inside of the refrigerator compartment 16, it becomes temperature of about 5-7 degreeC, it returns to the evaporator 4 from the refrigerator inlet air inlet 45, heat exchange is performed by the evaporator 4, and the adhering frost is melted.
[0007]
On the other hand, the cooling system ON time (compressor operating time) accumulated by the defrosting timer -42 is compared with a preset set value in the cooling system ON time detecting means 41, and if it is longer than the set value, the air in the freezer compartment The damper of the circulation control means 12 is closed, the air circulation means 11 is stopped, the defrosting electric heater 40 is energized, the air heated by this heater rises upward by natural convection, and the evaporator 4 Melt frost on the surface.
By these operations, the frost adhered to the evaporator 4 of the refrigerator is removed and the refrigerator is operated efficiently.
[0008]
In addition, HFC-based refrigerants are substances that promote global warming when released into the atmosphere, and the use of natural refrigerants such as hydrocarbon refrigerants and ammonia that do not deteriorate the global environment as refrigerator refrigerants has been studied.
An example of a refrigerator using a natural refrigerant is disclosed in Japanese Patent Laid-Open No. 8-178481. The refrigerant of this refrigerator-freezer has a very small influence on global warming, but a hydrocarbon-based refrigerant such as propane or butane that exhibits flammability is used.
[0009]
[Problems to be solved by the invention]
When using a flammable refrigerant that has little impact on global warming in the conventional refrigerator as described above, first of all, securing safety against flammability is the most important issue, and a system that does not ignite even if the refrigerant leaks is built It is important to.
[0010]
Furthermore, in order to suppress global warming, not only the use of a flammable refrigerant that has a small impact on global warming but also the improvement of the defrosting method using electric heaters in order to improve the energy efficiency of the refrigerator-freezer. This is also an important issue.
[0011]
The present invention has been made to solve the above-described problems, and improves the safety at the time of defrosting of a refrigerant having a very small adverse effect on the global environment, and further improves the energy efficiency at the time of defrosting. It aims at obtaining the evaporator used for a refrigerator, a refrigerator, etc. which improve global warming and suppress global warming.
[0012]
[Means for Solving the Problems]
  The evaporator with a defrost heater according to the present invention is:An evaporator using a flammable refrigerant and having a defrost heater that is set so that the surface temperature is lower than the ignition temperature of the flammable refrigerant, the heat transfer tube passing through, and a predetermined interval A plate-shaped defrosting heater arranged so as to be orthogonal to the plate fin and in contact with the end portion in a direction parallel to the direction in which the air to be cooled flows. The end portions of the plurality of plate fins are in contact with the planar defrost heater for each plate fin, and there are those in which a gap is provided between them to make no contact between them.(Claim 1).
  The planar defrost heater can increase the heater surface area, and even if the heater input is increased, the heater surface temperature can be lower than the ignition temperature of the flammable refrigerant.Moreover, heat transfer efficiency improves by making a defrost heater contact the structural member of an evaporator.Therefore, the surface temperature of the defrost heater can be made lower than the ignition temperature of the combustible refrigerant, and even if the refrigerant leaks and contacts the defrost heater, it does not ignite or burn.Further, the air path is not blocked even if frost is formed by the gap provided between the planar defrost heater and the plate fin. Therefore, heat exchange capability can be secured.
[0015]
  Further, a planar defrost heater is disposed so as to contact the end portions on both sides of the plate fin, and further, a planar defrost heater is disposed on both outer sides of the array of the plate fins. An evaporator with a defrost heater (claim)2).
  An air path can be formed with a planar defrost heater, and defrosting can be performed more reliably.
[0019]
  Moreover, it is a refrigerator provided with the refrigerating cycle which has a compressor, a condenser, an expansion apparatus, and the evaporator with a defrost heater in any one of the said description.3).
  A refrigerator having the characteristics of the defrost heater is obtained.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
1 is a side sectional view of a refrigerator-freezer according to Embodiment 1 of the present invention, FIG. 2 is a diagram showing a refrigerant circuit of the refrigerator-freezer, and FIG. 3 is a perspective view of an evaporator with a planar defrost heater. 4 is a cross-sectional view of FIG.
In the figure, the same or corresponding parts as those of the prior art are denoted by the same reference numerals, and the description thereof is omitted. That is, 1 is a compressor, 2 is a condenser, 3 is a capillary tube as a throttling device, 4 is an evaporator, 5 is a header, 10 is a freezer temperature detecting means, 11 is an air circulation means, and 12 is air in the freezer room. Circulation control means, 13 is an air circulation control means of the refrigerator, 15 is a freezer compartment, 16 is a refrigerator compartment, and 21 is a temperature detection means in the refrigerator compartment.
[0021]
The refrigerant of this refrigerator-freezer is a hydrocarbon refrigerant R600a that has a very small effect on global warming.
In the figure, reference numeral 7 denotes a plate fin of the evaporator 4, which includes a wide fin 7a and a narrow fin 7b. 8 is a heat transfer tube of the evaporator 4, and 8a is a U-shaped tube portion of the heat transfer tube.
Reference numeral 17 denotes a freezer compartment air inlet, and 18 denotes a refrigerator compartment air outlet, which opens a plurality of openings 18 a, 18 b, 18 c, and 18 d and blows air from the refrigerator compartment air duct 19 to the refrigerator compartment 16. Reference numeral 20 denotes a vegetable room, and 25 denotes a refrigeration room air intake, which sucks air from 25a and 25b and the refrigeration room 16. Reference numeral 26 denotes a vegetable room air outlet, which blows air from 26 a, 26 b, 26 c and the refrigerator compartment inlet 25 into the freezer compartment 15. Reference numeral 27 denotes a vegetable room air inlet, which sucks air from the vegetable room 20. Reference numeral 28 denotes a return duct from the air vegetable compartment to the evaporator.
Reference numeral 30 a denotes a planar defrost heater that is a defrost heater disposed on the side surface of the evaporator 4, and is an example of the defrost heater 30.
As shown in FIG. 3, the plate fin 7 (the wide fin 7a and the narrow fin 7b), the heat transfer tube 8 (the U-shaped tube portion 8a of the heat transfer tube), the planar defrost heater 30a, etc. The evaporator 6 is provided.
This evaporator 6 with a defrost heater is installed in the freezer compartment 15 as shown in FIG.
[0022]
The air circulation control means 13 in the refrigerating room is set so that the internal temperature of the refrigerating room 16 detected by the refrigerating room internal temperature detecting means 21 installed in the refrigerating room 16 is stored in the controller 23 in advance. When the value is higher than the value, the damper is opened so that the air from the evaporator 4 can be introduced into the refrigerating room 16 through the refrigerating room air duct 19 and the refrigerating room air outlet 18. If it is lower than the set value, the damper is closed and the introduction of air from the evaporator 4 to the refrigerator compartment 16 is shut off.
[0023]
Similarly to the air circulation control means 13 in the freezer compartment, the freezer compartment air circulation control means 12 has the internal temperature of the freezer compartment 15 detected by the freezer compartment temperature detection means 10 installed in the freezer compartment 15 in advance. When the value is higher than the set value stored in the controller 23, the damper is opened so that the air from the evaporator 4 can be introduced into the freezer compartment 15. If the value is lower than the set value, the damper is closed and the introduction of air from the evaporator 4 to the freezer compartment 15 is shut off.
[0024]
The compressor 1 is operated when the internal temperature detected by the freezer compartment internal temperature detecting means 10 installed in the freezer compartment 15 becomes higher than the set value stored in the controller 23. Stop when the set value is reached.
[0025]
The air circulation means 11 is energized when one of the damper of the air circulation control means 12 in the freezer compartment and the damper of the air circulation control means 13 in the refrigerator compartment is opened, and both dampers are closed. If you want to stop.
[0026]
Normally, in the cooling operation in the refrigerator, both the damper of the air circulation control means 12 in the refrigerator compartment and the damper of the air circulation control means 13 in the freezer compartment are open, and both the compressor 1 and the air circulation means 11 are operated. The freezer compartment 15, the refrigerator compartment 16, and the vegetable compartment 20 are also cooled. The flow of air in the refrigerator is shown by arrows in FIG.
[0027]
In the meantime, frost grows on the evaporator 4. As for the air flow in the refrigerator compartment, the air blown out from the air circulation means 11 is divided into a refrigerator compartment 16 and a freezer compartment 15. The air that has passed through the refrigerating room air circulation control means 12 passes through the refrigerating room duct 19 and blows out from the refrigerating room outlets 18a, 18b, 18c, 18d to the refrigerating room 15 at about -15 ° C. The blown air flows into the refrigerator compartment suction ports 25a and 25b while cooling the refrigerator compartment to about 3 to 5 ° C., and is blown out to the vegetable compartment 20 from the vegetable compartment outlets 26a, 26b and 26c.
[0028]
Furthermore, the vegetable room is cooled to about 5 to 7 ° C., passes through the return duct 28 to the evaporator 4, and flows into the evaporator 4 at a temperature of about 5 to 7 ° C. While exchanging heat with the evaporator 4 at about −30 ° C., moisture in the air is taken away by the evaporator, becoming air at about −27 ° C. and blown out from the evaporator 4 again.
[0029]
On the other hand, the air that has passed through the open damper of the air circulation control means 13 in the freezer compartment is blown out to the freezer compartment 15 at about −27 ° C. to cool the freezer compartment 15, and from the freezer compartment air intake port 17 below the freezer compartment 15. It flows into the evaporator 4 at about -20 ° C.
[0030]
When the accumulated operation time of the compressor 1 reaches a preset value stored in advance, and the internal temperature of the freezer compartment 15 detected by the freezer compartment internal temperature detection means 10 is higher than the preset value stored, and Defrosting for energizing the planar defrosting heater 30a to melt the frost adhering to the evaporator 4 when the header temperature detected by the header temperature detecting means is lower than a preset stored value. Do the driving.
In the defrosting operation with the defrost heater 30 energized, the compressor 1 is stopped, the air circulation means 11 is stopped, and the dampers of the air circulation control means 12 in the freezer compartment and the air circulation means 13 in the refrigerator compartment are turned on. Close and do. By closing both dampers, excess heat is prevented from being transmitted to the freezer compartment and the refrigerator compartment.
[0031]
Next, a method for setting the size and the surface temperature of the planar defrost heater 30a will be described.
When R600a is used as a refrigerant, the surface temperature of the planar defrost heater 30a is designed and controlled to be lower than the ignition minimum temperature 494 ° C. of R600a. For example, the temperature is designed and controlled so that it is lower than 394 ° C. by about 100 ° C.
For example, heater input A [W], evaporator surface temperature 255.15 [K], heater surface temperature 667.15 [K], heater surface area B [m²], Heater efficiency η [-], heat transfer coefficient between heater and evaporator K [W / m²K], the heater surface area of the heating surface of the planar defrost heater 30a is determined by the following equation.
B × η ≧ A / {K × (heater surface temperature−evaporator surface temperature)} [m²]
However, in this case, the heater surface temperature−the evaporator surface temperature = 412
[0032]
Since the heater surface area is determined by this formula, the surface temperature can be designed to be 394 ° C. or lower. That is, since the planar defrost heater 30a is used as the defrost heater 30, the surface area can be increased, and the heater surface temperature can be lowered even when a heater input that provides a defrost effect is given. It can be lower than the ignition temperature of the combustible refrigerant (100 ° C lower).
Further, a temperature detecting means is installed on the surface of the sheet-shaped defrost heater 30a, and control is performed to stop energization of the sheet-shaped defrost heater 30a when the temperature reaches a preset temperature. Therefore, the surface temperature can be controlled to 394 ° C. or lower.
[0033]
As shown in the perspective view of the planar defroster-equipped evaporator in FIG. 3 and the transverse cross-sectional view in FIG. 4, in the evaporator 4 of the present embodiment, the pre-passage through which the heat transfer tube 8 passes. The wide fins 7a and the narrow fins 7b are alternately installed one by one with a predetermined interval, and the planar defrost heater 30a is parallel to the plate fins 7, only the wide fins 7a and It arrange | positions so that it may contact in one edge part 7c. Therefore, even if it installs so that the planar defrost heater 30a may contact one side of the evaporator 4, it does not affect the flow of the air which passes through the inside of the evaporator 4. The direction in which the air to be cooled flows in this evaporator is the vertical direction in the figure.
That is, a gap is generated between the planar defrost heater 30a and the narrow fin 7b. Therefore, even if the plate fins 7 and the heat transfer tubes 8 are frosted, the air passage can be prevented from being blocked by clogging, and the cooling capacity can be prevented from being lowered.
[0034]
Moreover, since the planar defrost heater 30a is installed in contact with the plate fin 7 of the evaporator 4, heat from the planar defrost heater 30a is efficiently transmitted to the evaporator 4, Defrosting is possible with low input. Therefore, the input during the defrosting operation is reduced, and further, no heat load is applied to the refrigerator cabinet more than necessary, so that the cooling operation by the compressor 1 after the defrosting operation can be completed in a short time. Thus, low power consumption can be realized.
[0035]
Further, even when R600a, which is a flammable refrigerant, leaks into the refrigerator, the surface temperature of the sheet-shaped defrost heater 30a is lower than the ignition lower limit temperature, so that the leaked R600a refrigerant is a sheet-shaped defrost heater. Even if it contacts 30a, R600a does not reach the ignition temperature and does not ignite or burn. Therefore, the defrosting operation can be performed safely.
[0036]
Naturally, the arrangement of the wide fins 7a and the narrow fins 7b of the plate fins 7 may be mixed with the narrow fins 7b at an appropriate ratio in the arrangement of the wide fins 7a without being alternately arranged for each sheet. . In short, it is sufficient that the air path is not blocked by frost formation.
Further, the size of the planar defrost heater 30a may not be a size that contacts all the end portions 7c on one side of the plate fin 7. That is, the heater surface area B is calculated by the above calculation formula, and it may be brought into contact with the end portion 7c of the plate fin 7 appropriately according to the size.
[0037]
Furthermore, the other example of the planar defrost heater 30a is shown in FIG.5, FIG.6, FIG.7 and FIG. 5 and 6 are a perspective view and a cross-sectional view of an evaporator with a planar defrost heater, respectively, and FIGS. 7 and 8 are different planar defrost heaters, respectively. It is a perspective view of an attached evaporator, and its cross-sectional view.
[0038]
In the example of FIG. 5, the defrost heater 30 is added to the planar defrost heater 30 a of FIG. 3, and the planar defrost heater 30 b, on both outer sides of the array of plate fins 7, 30c, one for each.
In this case, since the heating surface of the defrost heater 30 is further widened compared to the case of FIG. 3, the surface temperature of the defrost heater 30 can be lowered. Further, the defrosting filters 30b and 30c on both the outer sides need not be in contact with the U-shaped tube portion 8a of the heat transfer tube 8 of the evaporator 4, but by installing the defrosting filters 30b and 30c in contact with each other, the evaporator can be more efficiently installed. Defrosting is possible.
[0039]
In the example of FIG. 7, planar defrost heaters 30 a, 30 b, 30 c, and 30 d are installed around the evaporator 4. Therefore, since the surface area of the defrost heater can be made larger than in the examples of FIGS. 3 and 5, the surface temperature can be lowered and the safety is further improved.
Further, since the air passage of the evaporator 4 is formed by the planar defrost heaters 30a, 30b, 30c, and 30d, not only the evaporator 4 but also the air passage can be defrosted reliably and reliably. It becomes possible to provide a highly efficient refrigerator.
Further, since the planar defrost heaters 30a, 30b, 30c, and 30d of each part are electrically connected in parallel, even if any of them does not operate for some reason, the remaining defrost heaters -It is possible to defrost with the cover 30, and it is possible to provide a highly reliable refrigerator.
Further, although the efficiency is deteriorated, the planar defrost heaters 30a, 30b, 30c, and 30d may not be brought into contact with the plate fin 7 and the U-shaped tube portion 8a of the heat transfer tube 8 for the convenience of installation. . Of course, you may contact selectively.
[0040]
Embodiment 2. FIG.
FIG. 9 is a side sectional view of an evaporator with a defrost heater of a refrigerator / refrigerator according to Embodiment 2 of the present invention, and FIG. 10 is a sectional view of a heat transfer tube provided with a sheath heater.
The refrigerant of the refrigerating cycle of this refrigerator / freezer is a hydrocarbon refrigerant R600a that has a very small influence on global warming.
In the figure, reference numeral 30e denotes a sheath heater, which is a defrost heater 30 installed in the heat transfer tube 8. Other configurations are the same as those in the first embodiment, and the cooling operation and defrosting operation of the refrigerator-freezer are the same as those in the first embodiment, and thus the description thereof is omitted.
[0041]
There is almost no oxygen (air) in the refrigeration cycle, and therefore there is almost no oxygen (air) in the heat transfer tube 8 of the evaporator 4. Therefore, if the sheath heater 30e is installed in the heat transfer tube 8 of the evaporator 4 in this way, no matter how much the sheath heater 30e surface temperature rises, the combustible refrigerant will not ignite. .
Moreover, if air mixes in the refrigeration cycle, the compressor discharge temperature of the refrigerant rises more than usual. Therefore, the discharge temperature of the compressor 1 is measured by the compressor temperature detecting means, and when the temperature becomes higher than a predetermined temperature, the operation of the refrigerated refrigerator is stopped. Therefore, since the defrosting operation is not executed, the refrigerant R600a is not ignited and a safe refrigerated refrigerator can be provided.
In FIG. 9, the plate fins 7 are the wide fins 7a and the narrow fins 7b, but they may be the same shape.
[0042]
Embodiment 3 FIG.
FIG. 11 is a side cross-sectional view of an evaporator with a defrost heater of a refrigerator / refrigerator according to Embodiment 3 of the present invention. FIG. 12 shows a sheet cast into a heat transfer tube of the evaporator with a defrost heater. -It is sectional drawing of the heat exchanger tube which shows a heater.
The refrigerant of the refrigerating cycle of this refrigerator / freezer is a hydrocarbon refrigerant R600a which has a very small influence on global warming.
In the figure, a sheath heater 30 e which is a defrost heater 30 is installed by being cast into a part of the heat transfer tube 8. Others and the cooling operation of the refrigerator are the same as those in the first embodiment, and are omitted.
[0043]
In this way, since the sheath heater 30e is directly installed on a part of the heat transfer tube 8 of the evaporator 4, the heat generated by the defrost heater 30 is efficiently transmitted to the entire evaporator 4; Even if the surface temperature of the frost heater 30 is controlled to be lower than the ignition temperature of R600a, the frost of the evaporator 4 can be sufficiently melted. Furthermore, since the surface temperature of the defrost heater 30 is controlled to be 394 ° C., which is lower than the ignition temperature of R600a, for example, 100 ° C., R600a is not ignited and a safe refrigerator can be provided. .
In FIG. 11, the plate fins 7 are the wide fins 7a and the narrow fins 7b, but they may be the same shape.
[0044]
Embodiment 4 FIG.
FIG. 13 is a perspective view of an evaporator with a defrost heater of a refrigerator / refrigerator according to Embodiment 4 of the present invention, and FIG. 14 is a perspective view showing an annular seed heater.
The refrigerant of the refrigerating cycle of this refrigerator / freezer is a hydrocarbon refrigerant R600a that has a very small influence on global warming.
In the figure, reference numeral 30f denotes an annular sheet heater which is a defrosting heater 30, and the annular sheet heater 30f is outside the plate fin arrangement of the evaporator 6 with the defrosting heater. It is installed in the U-shaped portion 8a of the heat transfer tube, which is a bent portion of the heat transfer tube 8.
Other configurations are the same as those in the first embodiment, and the cooling operation and the defrosting operation of the refrigerator-freezer are also the same as those in the first embodiment, so that the description thereof is omitted.
[0045]
Thus, since the annular sheath heater 30e is installed in the U-shaped portion 8a of the heat transfer tube of the evaporator 4, the heat generated by the defrost heater 30 is efficiently transmitted to the entire evaporator 4. Therefore, even if the heater surface temperature is set and controlled lower than the ignition temperature of R600a, the evaporator frost can be sufficiently melted. Furthermore, since the heater surface temperature is set and controlled to be lower than the ignition temperature of R600a, for example, 100 ° C lower, 394 ° C, even if R600a leaks, it will not ignite or burn to R600a. The refrigerator 6 with a frost heater can be provided.
Moreover, since the installation location is the U-shaped portion 8a of the heat transfer tube outside the array plate fin 7 of the evaporator 4, it can be easily attached to the conventional evaporator 4 without developing the evaporator 4 anew. It is possible to provide a refrigerator-freezer having the evaporator 6 with a defrost heater at low cost.
[0046]
In FIG. 13, the annular sheathed heater 30e is attached to all of the U-shaped portion 8a of the heat transfer tube, but an appropriate number may be attached if necessary.
In FIG. 13, the plate fins 7 are the wide fins 7a and the narrow fins 7b, but they may be the same shape.
[0047]
In the first to fourth embodiments, the case where the hydrocarbon refrigerant R600a (isobutane) is used as the refrigerant has been described. However, the present invention is not limited thereto, and hydrocarbon refrigerants such as R600 (butane) and R290 (propane) are used. Or a natural refrigerant such as ammonia or a mixed refrigerant thereof. Further, it may be an HFC-based chlorofluorocarbon refrigerant having a small global warming potential such as R134a, R32 or R152a, or a mixed refrigerant thereof.
[0048]
In the first to fourth embodiments described above, the example in which the capillary device is used as the throttle device has been described. However, the present invention is not limited to this, and the electronic expansion allows the opening degree to be arbitrarily adjusted by an electric signal. A valve may be used.
[0049]
In the above embodiment, the refrigeration oil is not particularly specified, but mineral oil and synthetic oils such as alkylbenzene, ester oil, ether oil, and PAG oil are used.
[0050]
In the above embodiment, the compressor is not particularly specified, but it may be a reciprocating type, a rotary type, a scroll type or the like, and a high pressure shell type or a pressure in the compressor that keeps the pressure in the compressor high. Any type of low-pressure shell type in which is held at a low pressure may be used.
[0051]
In addition, the condenser used in the above embodiment is not particularly specified, but the natural convection type in which the copper pipe embedded in the side wall of the refrigerator and the outer plate are in contact with each other or the forced convection type using a blowing means Any type of
[0052]
Furthermore, the evaporator 6 with a defrost heater described in the first to fourth embodiments can be widely used not only in a refrigerator but also in a refrigeration cycle such as a refrigerator or an air conditioner.
[0053]
【The invention's effect】
  The evaporator with a defrost heater according to the present invention is:An evaporator using a flammable refrigerant and having a defrost heater that is set so that the surface temperature is lower than the ignition temperature of the flammable refrigerant, the heat transfer tube passing through, and a predetermined interval A plate-shaped defrosting heater arranged so as to be orthogonal to the plate fin and in contact with the end portion in a direction parallel to the direction in which the air to be cooled flows. Provided, and the end portions of the plurality of plate fins are in contact with the planar defrost heater for each plate fin, and there are those in which a gap is provided between them to make no contact(Claim 1). For this reason,The planar defrost heater can increase the surface area of the heater heating surface, and the surface temperature can be made lower than the ignition temperature of the flammable refrigerant even when a heater input that provides a defrosting effect is given.Further, since the defrost heater is brought into contact with the constituent members of the evaporator, heat is efficiently transmitted to the evaporator.Thus, a defrosting effect can be obtained, and even if a refrigerant leaks and touches the defrosting heater, ignition and combustion can be prevented.In addition to the effect of the above-mentioned planar defrost heater and the effect of bringing the defrost heater into contact with the evaporator, the air path is blocked by clogging even if the evaporator is frosted. No heat exchange capacity can be secured.
[0056]
  Further, a planar defrost heater is disposed so as to contact the end portions on both sides of the plate fin, and further, a planar defrost heater is disposed on both outer sides of the array of the plate fins. And an evaporator with a defrost heater (claim)2Therefore, in addition to the above-described effect, the air passage can be formed with a planar defrost heater, and defrosting is performed more reliably.
[0060]
  Moreover, it was set as the refrigerator provided with the refrigerating cycle which has a compressor, a condenser, an expansion device, and the evaporator with a defrost heater in any one of the said description.3Therefore, a refrigerator in which the evaporator with a defrost heater has the above-described effects can be obtained.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a refrigerator-freezer according to Embodiment 1 of the present invention.
FIG. 2 is a refrigerant circuit diagram of the refrigerator-freezer according to the first embodiment of the present invention.
FIG. 3 is a perspective view of a planar defroster-equipped evaporator of the refrigerator-freezer according to Embodiment 1 of the present invention.
4 is a cross-sectional view of the evaporator with a defrost heater of FIG.
FIG. 5 is a perspective view of another planar defroster-equipped evaporator according to the first embodiment of the present invention.
6 is a cross-sectional view of FIG.
FIG. 7 is a perspective view of still another planar evaporator with a defrost heater according to the first embodiment of the present invention.
8 is a cross-sectional view of FIG.
FIG. 9 is a side sectional view of an evaporator with a defrost heater of the refrigerator-freezer according to the second embodiment of the present invention.
FIG. 10 is a cross-sectional view of a heat transfer tube provided with a sheath heater according to a second embodiment of the present invention.
FIG. 11 is a side sectional view of an evaporator with a defrost heater of a refrigerator-freezer according to Embodiment 3 of the present invention.
12 is a cross-sectional view of a heat transfer tube in which a seed heater according to a third embodiment of the present invention is cast. FIG.
FIG. 13 is a perspective view of an evaporator with a defrost heater of a refrigerator / freezer according to Embodiment 4 of the present invention.
FIG. 14 is a perspective view showing an annular seed heater according to a fourth embodiment of the present invention.
FIG. 15 is a side sectional view of a conventional refrigerator-freezer.
FIG. 16 is a refrigerant circuit diagram of a conventional refrigerator-freezer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Compressor, 2 Condenser, 3 Throttling device, 4 Evaporator, 6 Evaporator with defrost heater, 7 Plate fin, 7c End of plate fin, 8 Heat transfer tube, 8a U-shaped tube of heat transfer tube Part, 30 defrost heater, 30a30b, 30c, 30d Planar defrost heater.

Claims

An evaporator including a defrost heater that uses a flammable refrigerant and has a surface temperature set to be lower than an ignition temperature of the flammable refrigerant,
A plurality of plate fins through which the heat transfer tubes pass and arranged at predetermined intervals;
In a direction parallel to the direction in which the air to be cooled flows, the pre - Tofin and orthogonal, and their ends contact to such an arrangement the planar Joshimohi - e Bei a motor,
Wherein the plurality of pre - end of Tofin the pre - the planar Joshimohi per Tofin - you characterized in that there is that the non-contact is provided a gap between those in contact with the motor and both divided Evaporator with frost heater.

Arranged so that planar defrost heaters are in contact with both end portions of the plate fins, and further, planar defrost heaters are disposed on both outer sides of the plate fin arrangement. evaporator with data - Joshimohi of claim 1, wherein.

A refrigerator comprising a compressor, a condenser, a throttling device, and an evaporator with a defrost heater according to claim 1 or 2 .