JP4258030B2

JP4258030B2 - Refrigerant circulation device

Info

Publication number: JP4258030B2
Application number: JP30844897A
Authority: JP
Inventors: 浩招牧野; 浩司山下
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1997-01-20
Filing date: 1997-11-11
Publication date: 2009-04-30
Anticipated expiration: 2017-11-11
Also published as: JPH10259960A

Description

【０００１】
【発明の属する技術分野】
冷媒として例えば一部にＨＦＣ（ハイドロフルオロカーボン）系冷媒、冷凍機油としてアルキルベンゼン系等の油を使用する様な冷媒に溶解しにくい冷凍機油を使用する冷媒循環装置に関するものである。
【０００２】
【従来の技術】
従来の、冷媒としてＨＦＣ（ハイドロフルオロカーボン）系冷媒、冷凍機油としてアルキルベンゼン系の油を使用する冷媒循環システムの一例を図８に示す。１は冷媒ガスを圧縮する圧縮機、２は冷媒の流れ方向を切り替える機能を有する四方弁であり、３は圧縮機１から吐出された高圧冷媒ガスを凝縮させる凝縮器、４は蒸発器、５は減圧装置、８０は冷媒量調整機能を有するアキュムレータである。この冷媒循環システムで使用するアルキルベンゼン系の油はＨＦＣ（ハイドロフルオロカーボン）系冷媒に対して、凝縮圧力および凝縮温度条件下における液冷媒への冷凍機油の重量溶解率が0.5〜７％の溶解性を有し、かつ、蒸発圧力および蒸発温度条件下における液冷媒への重量溶解率が０〜２％の非相溶性もしくは微弱な溶解性を有するとともに、その比重量が−２０℃〜＋６０℃の温度域において、同一温度とその飽和蒸気圧下における液冷媒の比重量よりも、小さな値となる。
【０００３】
次に、冷凍機油の挙動について説明する。圧縮機１により圧縮された高圧冷媒ガスは、凝縮器３に吐出される。この際、冷媒との重量比で言うと０．３〜２．０％程度の冷凍機油が冷媒と共に圧縮機１から吐出される。冷媒ガスの流れる凝縮器３の管径は、冷媒ガス流速が冷凍機油を下流へ搬送するのに十分な流速を確保するよう設定されている。凝縮器３の出口付近では大部分の冷媒は液化し管内流速は著しく低下するが、冷凍機油は凝縮液冷媒に対し弱い溶解性を有するので、液冷媒に溶解して減圧装置５から搬送される。減圧装置５の下流域では冷媒の温度と圧力は著しく低下し、冷凍機油は液冷媒に対し非相溶性もしくは微弱な溶解性に転じる。
【０００４】
しかし、減圧装置５の下流域で生じる液冷媒の一部のガス化により冷媒流速は急激に増加し、続く蒸発器４の管径は冷媒ガス流速が冷凍機油を下流へ搬送するのに十分な流速を確保するよう設定されているため、冷凍機油はアキュムレータ８０へ搬送される。冷凍機油は液冷媒より比重が小さく、蒸発圧力および蒸発温度条件下において、液冷媒への溶解性が無いかもしくは微弱なため、アキュムレータ８０内で冷凍機油は液冷媒の上方に分離層を形成する。アキュムレータ内にあって冷媒を外部へ導く導出管８１には、アキュムレータ下端８０ａからの高さが異なる複数の油戻し穴８２ａ、８２ｂ、８２ｃ、８２ｄが設けられており、アキュムレータ８０内の冷凍機油はこれらの油戻し穴を通り圧縮機１へ戻る。
【０００５】
【発明が解決しようとする課題】
従来の、冷媒としてＨＦＣ（ハイドロフルオロカーボン）系冷媒、冷凍機油としてアルキルベンゼン系の油を使用する様な冷媒循環システムは以上のように構成されているが、アキュムレータ８０内に多量の余剰冷媒が貯留され液冷媒層の液面が高くなった場合において、以下のような問題があった。まず、液冷媒層の液面が高くなると導出管８１の複数個の油戻し穴から液冷媒が吸い込まれるため、圧縮機１に多量の液冷媒が戻り、圧縮室内に非圧縮性の液冷媒が供給されることによる圧縮室内の急激な圧力上昇を引き起こしたり、また圧縮室から吐出された液冷媒が圧縮機密閉容器内に溜まることにより、冷凍機油に代わって液冷媒が潤滑要素部へ供給されて圧縮機１の軸受、圧縮要素摺動部の焼き付き等、信頼性の低下を招くおそれがあった。次に、圧縮機１に多量の液冷媒が戻らないよう油戻し穴の径を小さく設定すると、冷凍機油も同様に戻らずアキュムレータ８０内に多量に溜まってしまい、圧縮機１内の冷凍機油が枯渇するおそれがある上、回路内のゴミ、不純物等が油戻し穴につまりやすくなるおそれがあった。
【０００６】
この発明は、上記の問題点を解決するためになされたもので、圧縮機に多量の液冷媒を戻すことなく余剰液冷媒を貯留でき、かつ冷凍機油を確実に圧縮機に戻すことで、信頼性の高い冷媒循環装置を提供することを目的とする。また、この発明は簡単な構成で安価な信頼性の高い装置を得ることにある。
【０００７】
【課題を解決するための手段】
この発明に関わる冷媒循環装置は、冷媒を圧縮して吐出する圧縮機と、この圧縮機から吐出された高圧冷媒ガスを凝縮させる凝縮器と、この凝縮器にて凝縮された液冷媒を減圧する減圧装置と、この減圧装置で減圧された冷媒を蒸発させる蒸発器と、これらを順次接続し冷媒回路を形成する冷媒配管と、凝縮圧力および凝縮温度条件下における液冷媒への重量溶解率が弱溶解性を有し、かつ、蒸発圧力および蒸発温度条件における液冷媒への重量溶解率が非溶解性もしくは弱溶解性を有する冷凍機油と、を備え、減圧装置が、冷凍機油の冷媒への溶解限界が冷媒とともに圧縮機から吐出された冷凍機油の冷媒との重量比である油循環率未満とならない範囲に圧力を低下させる第一の減圧装置と、この第一の減圧装置の下流に配置され冷媒を蒸発圧力まで減圧させる第二の減圧装置とに分割されて構成されるとともに、これら二つの減圧装置の間に冷媒回路の余剰冷媒を貯留する液溜容器が接続され、液溜容器に冷媒とともに第一の減圧装置を通過して搬入された冷凍機油が、冷媒から分離することなく冷媒に溶解したまま液溜容器から流出し、冷媒配管を通って第二の減圧装置および蒸発器を通過して、圧縮機まで搬送されるものである。
【００１０】
またこの発明に関わる冷媒循環装置は、前記蒸発器の配管径が、蒸発器を流れる冷媒の流速が液溜容器から流出した冷凍機油を下流へ搬送できる流速となるように設定されたものである。
【００１４】
またこの発明に関わる冷媒循環装置は、冷凍機油が凝縮圧力及び凝縮温度条件下における液冷媒への重量溶解率が０．５−７％の弱溶解性を有し、かつ、蒸発圧力及び蒸発温度条件における液冷媒への重量溶解率が０−２％の非溶解性もしくは弱溶解性を有するものである。
【００１５】
【発明の実施の形態】
実施の形態１．
以下、本発明に対応する実施の形態１を図１、図２に基づいて説明する。図１は空調機に適用される冷媒循環装置の一例であり、図１において１は冷媒ガスを圧縮する圧縮機、４は圧縮機１から吐出された高圧冷媒ガスを凝縮させる室外熱交換器、３は室内熱交換器、５は減圧装置、６は余剰冷媒を貯留する液溜容器である。また、図２は液溜容器の構造を示したもので、７は液溜容器本体、８は入口配管で容器の下側に接続しており、９は出口配管で容器の上側に接続している。１６、１７は室内及び室外熱交換器用の送風機である。
【００１６】
次に冷媒および冷凍機油の挙動を冷媒が矢印の向きに流れる場合について説明する。圧縮機１により圧縮された高圧冷媒ガスが、冷媒との重量比で２．０％の冷凍機油と共に吐出され冷媒を凝縮する凝縮器である室外熱交換器４へ入る。冷凍機油は十分な流速を持った冷媒ガスによって搬送され、室外熱交換器４の出口付近では液化した液冷媒中に一部は溶解し、残りは油滴となって冷媒とともに液溜容器６へ搬送される。流路面積が大きくなる液溜容器本体部７では液冷媒の流速が低下し、油滴となった冷凍機油は冷媒よりも比重が小さく容器上方に浮き上がる。しかし、冷凍機油が浮き上がる方向は図の矢印の如く冷媒の流れと同じで、容器本体部７は起動直後（５分程度）を除いては通常満液状態のため、容器内に滞留することなく出口配管９から容器外へ搬送される。従って、冷凍機油が液溜容器本体７内に溜まることはなく、減圧装置５まで搬送される。減圧装置５によって必要な圧力まで減圧されて液冷媒の一部がガス化することにより、液で存在する冷媒量が減少するため、ガス化した液冷媒に溶解していた冷凍機油は分離して油滴となる。しかし、液冷媒の一部のガス化により冷媒流速は急激に増加し、続く冷媒を蒸発させる蒸発器である室内熱交換器３の管径は冷媒ガス流速が冷凍機油を下流へ搬送するのに十分な流速を確保するよう設定されているため、冷凍機油は室内熱交換器内を搬送され圧縮機１に戻る。このように、圧縮機から流出した冷凍機油を確実に圧縮機に戻すことができ、圧縮要素部の正常な潤滑およびシール機能が維持されるため、圧縮機の信頼性の高い装置が得られる。また、構造が簡単で生産性、コストパフォーマンスに優れ、ゴミの詰まりなどによる性能低下も起こさない。
【００１７】
実施の形態２．
以下、本発明に対応する実施の形態２を図２、図３に基づいて説明する。図３は空調機に適用される冷媒循環装置の一例であり、図３において１は冷媒ガスを圧縮する圧縮機、２は冷媒の流れ方向を切り替える機能を持つ四方弁、１８は室内機と室外機を接続する延長配管、３は室内熱交換器、４は室外熱交換器、５は減圧装置、６は余剰冷媒を貯留する液溜容器である。また、図２は液溜容器の構造を示したもので、７は液溜容器本体、８は入口配管で容器の下側に接続しており、９は出口配管で容器の上側に接続している。
【００１８】
次に室内機にて暖房を行う冷媒および冷凍機油の挙動を冷媒が矢印の向きに流れる場合について説明する。圧縮機１により圧縮された高圧冷媒ガスが、冷媒との重量比で２．０％の冷凍機油と共に吐出され四方弁２を通って凝縮器である室内熱交換器３へ入る。冷凍機油は十分な流速を持った冷媒ガスによって搬送され、室内熱交換器３の出口付近では液化した液冷媒中に一部は溶解し、残りは油滴となって冷媒とともに液溜容器６へ搬送される。流路面積が大きくなる液溜容器本体部７では液冷媒の流速が低下し、油滴となった冷凍機油は冷媒よりも比重が小さく容器上方に浮き上がる。しかし、冷凍機油が浮き上がる方向は図の矢印の如く冷媒の流れと同じで、容器本体部７は起動直後（５分程度）を除いては通常満液状態のため、容器内に滞留することなく出口配管９から容器外へ搬送される。従って、冷凍機油が液溜容器本体７内に溜まることはなく、減圧装置５まで搬送される。減圧装置５によって必要な圧力まで減圧されて液冷媒の一部がガス化することにより、液で存在する冷媒量が減少するため、ガス化した液冷媒に溶解していた冷凍機油は分離して油滴となる。しかし、液冷媒の一部のガス化により冷媒流速は急激に増加し、続く蒸発器である室外交換器４の管径は冷媒ガス流速が冷凍機油を下流へ搬送するのに十分な流速を確保するよう設定されているため、冷凍機油は室外熱交換器内を搬送され圧縮機１に戻る。
【００１９】
暖房の場合一般に室内熱交換器を室外熱交換器に比べ小さくしているから冷媒量が冷房に比べ少なくて済むので余剰冷媒が発生しやすい。
一方、四方弁２を切り換えることによって冷媒を逆方向に流し室内機にて冷房を行う場合、室外、室内熱交換器の凝縮と蒸発の役割が変わり、減圧装置５で減圧されて一部ガス化して液とガスが混合された冷媒が出口配管９から容器本体部７に流れ込むが、冷媒は容器の上から下へ流れるため、液冷媒が滞留することなく入口配管８から容器外へ搬送される。このため冷媒量を多く使う冷房の場合、液溜容器としての機能は無くなるがこの必要性もなく、冷媒とともに搬送される冷凍機油も容器内に滞留すること無く搬送される。このため、圧縮機１から吐出された冷凍機油はサイクル中に滞留せず圧縮機１に戻る。
【００２０】
以上により、流れ方向によって必要冷媒量が異なる場合でも、余剰冷媒を貯留することができるため、流れ方向によらず効率的な運転ができ、かつ、圧縮機から流出した冷凍機油を確実に圧縮機に戻すことができ、圧縮要素部の正常な潤滑およびシール機能が維持されるため、圧縮機の信頼性の高い装置が得られる。
【００２１】
実施の形態３．
以下、本発明に対応する実施の形態３を図４に基づいて説明する。図４は空調機に適用される冷媒循環装置の一例であり、図４において１は冷媒ガスを圧縮する圧縮機、２は冷媒の流れ方向を切り替える機能を持つ四方弁、４は室外熱交換器、１６は室内送風機、３は室内熱交換器、１７は室外送風機、５ａおよび５ｂは減圧装置、６は余剰冷媒を貯留する液溜容器である。
【００２２】
次に冷媒および冷凍機油の挙動について説明する。圧縮機１により圧縮された高圧冷媒ガスは、冷媒との重量比で例えば１．０％の冷凍機油と共に吐出され四方弁２を通って凝縮器である室内熱交換器３へ入る。冷凍機油は十分な流速を持った冷媒ガスによって搬送され、室内熱交換器３の出口付近では液化した液冷媒中に完全に溶解する。ただし、アルキルベンゼン系油は、凝縮圧力および凝縮温度条件下での冷凍機油の冷媒への溶解限界は１．５％程度である。そして、冷媒とともに減圧装置５ｂを通過し液溜容器６へ搬送される。減圧装置５ａでの圧力と温度の低下を溶解限界が１％未満にならない範囲に設定することにより、冷凍機油は液溜容器６内で冷媒から分離すること無く、冷媒に溶解したまま容器外へ搬送される。したがって、冷凍機油は液溜容器６内に溜まることなく、減圧装置５ｂまで搬送される。減圧装置５ｂでは必要な圧力まで減圧されて温度が急激に低下するため、冷凍機油の液冷媒への溶解限界が０．５％に減少し、液冷媒中に溶解しきれない冷凍機油は分離して油滴となる。さらに、室外熱交換器４では大半の冷媒がガス化して液状態で存在する冷媒量が減少するため、溶解できなくなった冷凍機油が分離する。しかし、減圧装置をでた後では冷媒のガス化により冷媒の流速は分離した冷凍機油を下流へ搬送するために十分な流速になるため、冷凍機油は圧縮機１まで搬送される。また、四方弁２によって逆方向に流した場合も同様である。
【００２３】
一般に冷媒回路に液だめ部を設けると例えばハイドロフルオロカーボンを使用した冷媒に溶解しにくい冷凍機油、例えばＨＦＣ系冷媒に対して凝縮圧力及び凝縮温度条件下における液冷媒への重量溶解率が０．５−７．０％、また蒸発圧力及び蒸発温度条件下における液冷媒への重量溶解率が０−２．０％の非溶解性もしくは微弱な溶解性を有する冷凍機油、アルキルベンゼン、鉱油、エステル油、エーテル油、等を使用すると、冷媒の移動速度が遅くなる液だめ部、すなわち余剰冷媒を貯留するための液だめ容器を有する冷媒回路において、この容器内に冷媒と一緒に混合してきた油が溜まることになる。
冷媒への油の重量溶解率は先ず冷媒と油の種類によって変化する。例えばＨＦＣ系冷媒である液冷媒Ｒ４０７ＣへのＨＡＢ油である冷凍機油アルキルベンゼン（粘度グレードＶＧ＝８−３２）の溶解率、及び油循環率と圧縮機周波数の関係では、凝縮温度範囲の液冷媒に対し１．０−４．０ｗｔ％の溶解率を示すが、蒸発温度範囲の液冷媒に対しては０．２−１．８ｗｔ％の微小な溶解率となる。この溶解率は各種の冷媒と各種の油の組み合わせにより変化する。
一般には圧縮機から冷媒とともに流出する冷凍機油の冷媒との重量比である油循環率は
０．３−２．０ｗｔ％程度の値となり圧縮機周波数の上昇と共に増加する傾向にある。
冷媒回路内にはこの油循環率で示される量の冷凍機油が循環しており、特に液だめ容器内に溜まりやすく、容器内の液冷媒中にはその温度における溶解率の範囲内で冷凍機油が溶解している。しかし冷媒が存在する箇所での運転条件において油循環率が液冷媒への冷凍機油の溶解率を上回った場合、循環する冷凍機油の量は液冷媒への許容溶解量を超えてしまうため、冷凍機油は液冷媒と分離し、例えば液だめ容器内で油滴或いは油層の状態となり、液だめ容器内に溜まり、圧縮機に戻らないことになる。これに対し、例えば容器内の液冷媒の温度をサーミスタで検知し、冷媒の温度が油の溶解に必要な温度より低くなった場合に減圧装置５ａを閉じる方向へ動かして設定することにより、油を溶解させることが出来る。
もちろん減圧装置として制御可能な電動式膨張弁のようなものでなく、キャピラリチューブを使用し各種運転状況において液だめ容器内にて温度の下限や圧力の下限を一定値に抑えるようにはじめから設定しておいても良い。
【００２４】
以上の説明はＨＦＣ系冷媒を例として説明したがこれに限られることが無く、ＨＣ系冷媒を使用しても冷媒に溶けにくい冷凍機油を使う場合には同様な効果を生ずることは明らかである。
圧縮機の運転周波数が低い場合、凝縮温度が低下し、冷凍機油の冷媒への溶解度が低下するが、同時に圧縮機から吐出される冷凍機油の量も減少するために、循環する冷凍機油は液溜め容器６で全て冷媒に溶解することが出来る。
以上により、冷房、暖房のどちらの流れ方向においても余剰冷媒を液溜めに溜めることが出来るため、効率的な運転を行うことが出来、かつ、液溜め容器に冷凍機油が滞留すること無く圧縮機に戻すことが出来るため、圧縮機の信頼性の高い装置を得ることが出来る。
特に、複数の室内機を持ち、冷房・暖房の各運転状態で室内機の運転台数により必要冷媒量が大きく変化するマルチタイプの空調装置に有効である。
【００２５】
実施の形態４．
以下本発明に対する実施の形態４を、図４、図５、図６に基づいて説明する。図５は液溜容器の構造を表し、液溜容器１０の下面から入口配管１１、出口配管１２が容器内に挿入されており、容器の上方に向かって開口している。また、入口配管１１、出口配管１２の容器内への入り込み長さは５ｍｍで配管の外径はともに９．５２ｍｍである。
【００２６】
次に冷媒および冷凍機油の挙動について説明する。圧縮機１により圧縮された高圧冷媒ガスは、定常時には冷媒との重量比で例えば１．０％の冷凍機油と共に吐出され四方弁２を通って凝縮器である室内熱交換器３へ入る。冷凍機油は十分な流速を持った冷媒ガスによって搬送され、室内熱交換器３の出口付近では液化した液冷媒中に完全に溶解する。これに対して、圧縮機１の起動時には一時的に２％以上の冷凍機油が冷媒ガスとともに吐出される場合がある。この場合、室内熱交換器３で液冷媒に溶解されなかった冷凍機油は油滴となって液冷媒とともに液溜容器６に搬送される。ただし、凝縮圧力および凝縮温度条件下での冷凍機油の冷媒への溶解限界は１．５％程度である。入口配管１１から容器１０に流れ込んだ液冷媒は容器１０内で流速が低下するため、液冷媒とともに容器内に流入した油滴は浮き上がって油層１４を形成する。そして、運転状態が安定し冷凍機油の吐出量が容器１０での圧力および温度条件下での冷凍機油の冷媒への溶解量以下まで減少すると、油層１４の油が容器内の冷媒１３に溶解し、徐々に油層１４の厚さが減少する。圧縮機起動後の油層１４の厚さの変化を図６に示す。この際、容器１０内の液冷媒１０内には冷凍機油の溶解濃度に分布が生じ、油層１４に近いほど濃度が高くなる。これに対して、容器の下部に設けた入口配管１１は油層１４の方向に向かって下から上へ開口しているため、流れ込んだ冷媒の流速は油層１４の下面を打ち、油層１４は冷媒１３と攪拌され、同時に冷媒１３も攪拌される。このため、油層１４に接する冷媒１３での冷凍機油の濃度が減少し、油層１４の冷凍機油の冷媒１３への溶解が促進される。溶解した油は、容器の下部に設けた出口配管から冷媒とともに容器外へ搬送され圧縮機に戻る。
なお冷媒より重い油を使用しても、上記の説明の構成や攪拌動作により、油を冷媒に溶解させることが出来、圧縮機への油の戻りに有効であることは当然である。
【００２７】
実施の形態５．
この発明の別の実施形態を図７を用いて説明する。図７は本発明の一実施例を示す冷媒循環装置の概略構成を示す図で、図７において１は冷媒ガスを圧縮する圧縮機、２は冷媒の流れ方向を切り替える機能を持つ四方弁で暖房運転の位置、４は圧縮機１から吐出された高圧冷媒ガスを凝縮させる室外熱交換器、１６は室内送風機、３は室内熱交換器、１７は室外送風機、５ａおよび５ｂは減圧装置、６は余剰冷媒を貯留する液溜容器、１８は室内機と室外機を接続する延長配管、１９は圧力検知手段、２０は室内熱交換器の出口温度を検知する温度検知手段、２１は室外熱交換器の入口温度を検知する温度検知手段、２２は圧縮機吸入温度を検知する温度検知手段、２３は１９から２２の検知手段の検知データに基づき減圧装置１５ａ，１５ｂの開口面積を制御する演算・制御装置である。
【００２８】
本発明における冷媒循環装置において、減圧装置１５ａと１５ｂがある開口面積に制御され液溜め容器６には液冷媒が溜り、その溜まった液面が安定した状態を保っているとする。この時減圧装置１５ａと１５ｂの間の液溜め容器を含む流路内の冷媒圧力は凝縮圧力と蒸発圧力の間の圧力、いわば中圧となっており液溜め容器６内に溜まった液冷媒は飽和液状態となっている。
【００２９】
なお、圧縮機吸入冷媒過熱度は圧縮機吸入冷媒温度検知手段２２及び室外熱交換器入口温度検知手段２１がそれぞれ検知した温度からその偏差値を、演算・制御装置２３が演算して求める。なお、この偏差値を過熱度と呼ぶ。
また、室内熱交換器出口過冷却度は、圧力検知手段１９が検知した圧力と対応した冷媒の飽和温度と室内熱交換器出口冷媒温度検知手段２０が検知した検知温度との差を、演算・制御装置２３が演算して求める。なお、この偏差値を過冷却度と呼ぶ。
なお、室内熱交換器出口冷媒の過冷却度に相当する過冷却特性を検知する過冷却検知手段としては、室内熱交換器出口冷媒温度を検知する検知手段２０と、圧力検知手段１９が検知した圧力と対応した冷媒の飽和温度に相当する室内熱交換器中央付近の温度を検知する室内外熱交換器中央温度検知手段（図示せず）との組み合わせからなり、室内熱交換器中央付近の冷媒温度と室内熱交換器出口冷媒温度との偏差値を過冷却度としても良い。
また、圧縮機冷媒の吸入冷媒の過熱度に相当する過熱特性値を検知する過熱度検知手段としては、室外熱交換器出口冷媒温度を検知する室外熱交換器出口温度検知手段（図示せず）と、室外熱交換器入口冷媒温度を検知する室外熱交換器入口温度検出手段２１との組み合わせからなり、この室外熱交換器の出入口温度の偏差値を過熱度としてもよい。
【００３０】
ここで、高圧側減圧装置１５ａを絞ると減圧装置１５ａの出口では圧力が下がり、冷媒は気・液二相の状態となって液溜め容器６へ流入する。このとき、液溜め容器６では重力の作用により、ガス冷媒は上部に、液冷媒は下部に分離される為、液溜め容器６の入口管・出口管ともに液溜め容器の下部に配置しておけば、減圧装置１５ｂへは常に液冷媒のみが送られる。また、冷媒の気・液二相化により、気化した冷媒が液溜め容器６内の液冷媒を減少させ、液面を低下させる。
そして、液溜め容器６から冷凍サイクル中に放出された液冷媒は室内熱交換器３の出口に溜まるため、冷凍サイクルにおける過冷却度が大きくなる。
このため、液溜容器６内の冷媒の温度が低下し、冷凍機油の冷媒への溶解度は減少する。
また、逆に、高圧側減圧装置１５ａを開くと、絞った場合の逆の変化が起き、液面が上昇するとともに、液溜容器６内の冷媒の温度が上昇し、冷凍機油の冷媒への溶解度は増加する。このように運転状況や周囲環境により設定される目標値、すなわち外気温度や室内の設定温度に応じて、空調機の性能をフルに発揮できるように設定された過冷却度の目標設定値に応じて高圧側弁装置の開口面積を増減させればよい。
このように、高圧側減圧装置１５ａを制御することにより過冷却度および液溜め容器内の冷媒の温度を制御することが出来る。
【００３１】
実施の形態６．
一方、低圧側減圧装置１５bを開くと、高圧側減圧装置１５ａの出口では圧力が下がり、冷媒は気・液二相の状態となって液溜め容器６へ流入する。このとき、液溜め容器６では重力の作用により、ガス冷媒は上部に、液冷媒は下部に分離される為、液溜め容器６の入口管・出口管ともに液溜め容器の下部に配置しておけば、減圧装置１５ｂへは常に液冷媒のみが送られる。また、冷媒の気・液二相化により、気化した冷媒が液溜め容器６内の液冷媒を減少させ、液面を低下させる。
そして、低圧側減圧装置１５ｂの出口での冷媒流量が増加するため、圧縮機吸入での過熱度が低下する。
逆に、低圧側減圧装置１５ｂを絞ると、圧縮機吸入での過熱度が増加する。このように運転状況や周囲環境により設定される目標値、すなわち外気温度や室内の設定温度に応じて、空調機の性能をフルに発揮できるように設定された過過熱度の目標設定値に応じて低圧側弁装置の開口面積を増減させればよい。
このように、低圧側減圧装置１５ｂを制御し、圧縮機吸入での過熱度、すなわち乾き度を最適な値に制御するこで、利用できる圧力と温度を一層拡大することが出来、効率の良い装置とすることができ、エネルギーの少ない運転状態を保つことが出来る。
【００３２】
実施の形態７．
さらに、高圧側減圧装置１５ａと低圧側減圧装置１５ｂを連動して制御することにより、過冷却度と過熱度を同時に所定の値に制御することで入力エネルギーが小さい状態の運転状態を保つことが出来る。これは与えられた条件で最小のエネルギーの運転となり得る。
【００３３】
実施の形態８．
以下にこの発明の別の実施の形態を、図５、図７に基づいて説明する。減圧装置１５ａ、１５ｂとして図７に示すようにマイコンにより制御される電動式膨張弁を使用する。そして、液溜容器部の圧力と温度の状態が飽和状態になるように制御し、この状態から、入口側膨張弁１５ａの開口面積を小さく、出口側膨張弁１５ｂの開口面積を大きくするように制御すると図５に示す入口配管１１を通過する冷媒の状態が飽和液から気液二相状態へと変化する。このため、入口配管１１から気泡が発生し、発生した気泡は容器内の冷媒１３中を上昇しながら、冷媒１３を攪拌し、油層１４に到達すると油層１４と冷媒１３を攪拌する。
この状態を続けると容器内に溜める冷媒量が減少するため、ある時間経過後に膨張弁１５ａ，１５ｂの開口面積を入口配管１１での冷媒の状態が過冷却液となるように制御する。
このように容器内に気泡を発生させ、気泡により冷媒１３および油層１４を攪拌することにより、滞留した冷凍機油の冷媒への溶解を促進する。なお、気泡を発生させて攪拌する説明をしたが、圧力変化に伴う流速の変化によって攪拌させてもよい。この制御は運転中例えば一定時間毎や所定の圧縮機運転時間毎のように適宜実施してもよいし、油が容器内に溜まったことを容器の高さ方向の温度を検出して行ってもよい。
なおこの冷媒に与える変化として、減圧装置で行うことを説明したが入り口配管の出口部に切り換え回路を設けオリフィスによる圧力変化を繰り返し与えるなどの各種方法により冷媒の状態を変化させても良い。
【００３４】
実施の形態９．
以下に別の発明の実施の形態を図５、図７に基づいて説明する。減圧装置１５ａ、１５ｂとして図７に示すようにマイコンにより制御される電動式膨張弁を使用する。そして、液溜容器部の圧力と温度の状態が飽和状態になるように制御する。この状態から、入口側膨張弁１５ａの開口面積を小さく、出口側膨張弁の開口面積を大きくするように制御すると図５に示す入口配管１１を通過する冷媒の状態が飽和液から気液二相状態へと変化する。この状態では容器内の冷媒１３は徐々に減少し、冷媒１３が無くなるまでこの状態を継続する。その後、再度冷媒を貯留する為に入り口配管１１での冷媒の状態が過冷却液となるように膨張弁を制御する。冷媒１３の液面が無くなることにより油層１４は出口配管１２から容器外へ搬送される。そして、冷凍機油を容器外へ搬送したところで、容器に冷媒を貯留するための制御を行う。この制御を圧縮機の起動後の容器内に油層厚さが厚い条件の時に１度行うことにより、容器内に滞留した冷凍機油を容器外に搬送し、圧縮機に返すことができる。直江鬼面の有無については容器の高さ方向の温度を検知することなどにより行うことが出来る。
【００３５】
以上のようにこの発明では冷媒へ溶解しにくい油を使用して、かつ、液だめ容器であるレシーバーやアキュムレーター、ヘッダーなとを冷媒回路に設けても容器内に油を滞留させない、回路や制御方法が可能となる。この結果液だめ容器内に多量の油を溜めることなく確実に圧縮機へ戻すことが出来、圧縮機内の正常な潤滑やシール機能が維持できる都道時に冷媒回路内の余剰冷媒を貯めて負荷状態に適した性能を確実に維持できる。さらに装置の冷媒の流れる方向に応じて余剰冷媒を貯めることができ、装置の能力をフルに活用できると共にフレキシブルな運転が可能となり、また圧縮機によけいな冷媒を流さずに済み圧縮機の信頼性を向上させることが出来る。
【００３６】
また本発明は冷媒の流れ方向に関係なく、油を溜めずに液冷媒を液だめに溜めたり、液だめから空にすることが出来、圧縮機の信頼性を維持したまま起動時や負荷状態の変化に対応して最適な運転状態を設定できる。さらに一時的に油が液だめ容器内に滞留しても、急速に圧縮機へ戻すことも、また運転性能へ影響を与えず徐々に油を冷媒に溶解させて滞留量を減少させることも可能である。流入する冷媒の速度を利用して容器内の冷媒を攪拌して冷媒への溶解を促進でき圧縮機の信頼性を損なわずに変油を確実に出来る。
なお液だめ容器を狭く深い形にして攪拌しやすい構造としても良い。
【００３７】
さらに容器へ流入する冷媒の流速が遅く、攪拌効果が小さい場合には容器内の冷媒の状態を変化させて油の冷媒への溶解を促進することもできる。
【００３８】
【発明の効果】
この発明に関わる冷媒循環装置は、冷媒を圧縮して吐出する圧縮機と、この圧縮機から吐出された高圧冷媒ガスを凝縮させる凝縮器と、この凝縮器にて凝縮された液冷媒を減圧する減圧装置と、この減圧装置で減圧された冷媒を蒸発させる蒸発器と、これらを順次接続し冷媒回路を形成する冷媒配管と、凝縮圧力および凝縮温度条件下における液冷媒への重量溶解率が弱溶解性を有し、かつ、蒸発圧力および蒸発温度条件における液冷媒への重量溶解率が非溶解性もしくは弱溶解性を有する冷凍機油と、を備え、減圧装置が、冷凍機油の冷媒への溶解限界が冷媒とともに圧縮機から吐出された冷凍機油の冷媒との重量比である油循環率未満とならない範囲に圧力を低下させる第一の減圧装置と、この第一の減圧装置の下流に配置され冷媒を蒸発圧力まで減圧させる第二の減圧装置とに分割されて構成されるとともに、これら二つの減圧装置の間に冷媒回路の余剰冷媒を貯留する液溜容器が接続され、液溜容器に冷媒とともに第一の減圧装置を通過して搬入された冷凍機油が、冷媒から分離することなく冷媒に溶解したまま液溜容器から流出し、冷媒配管を通って第二の減圧装置および蒸発器を通過して、圧縮機まで搬送されるようにしたので、第一の減圧装置を液溜容器内にて冷凍機油が冷媒から分離することなく冷媒に溶解するように設定することで、液溜容器内に冷凍機油が溜まることがなく、冷凍機油を確実に圧縮機に戻すことができ、圧縮機の信頼性を高めることが出来る。
【００４１】
またこの発明に関わる冷媒循環装置は、蒸発器の配管径が、蒸発器を流れる冷媒の流速が液溜容器から流出した冷凍機油を下流へ搬送できる流速となるように設定されるので、蒸発器で大半の冷媒がガス化して溶解できなくなった冷凍機油が分離するが、ガス化した冷媒の流速が分離した冷凍機油を下流へ搬送するために十分な流速になることで冷凍機油を確実に圧縮機まで搬送することができ、圧縮機の信頼性を高めることが出来る。
【００４９】
またこの発明に関わる冷媒循環装置は、冷媒に対する所定の条件下で非溶解性もしくは弱溶解性を有する冷凍機油を使用しても、冷凍機油を確実に圧縮機に戻すことができるので、圧縮機の高い信頼性が得られるとともに、メインテナンスの容易な装置が得られる。
【図面の簡単な説明】
【図１】この発明の実施の形態１を示す冷媒循環装置の概念図である。
【図２】この発明の実施の形態１及び２を示す液溜容器の概念図である。
【図３】この発明の別の実施の形態を示す冷媒循環装置の概念図である。
【図４】この発明の別の実施の形態を示す冷媒循環装置の概念図である。
【図５】この発明の別の実施の形態を示す液溜容器の概念図である。
【図６】この発明の起動後の液溜容器内の油の滞留状態の変化を表す図である。
【図７】この発明の別の実施の形態を示す冷媒循環装置の概念図である。
【図８】従来の冷媒循環システムを表す図である。
【符号の説明】
１圧縮機、２四方弁、３室内熱交換器、４室外熱交換器、５減圧装置、５ａ前段減圧装置、５ｂ後段減圧装置、６液溜容器、７液溜容器、８液溜容器入口配管、９液溜容器出口配管、１０液溜容器、１１液溜容器入口配管、１２液溜容器出口配管、１３冷媒、１４冷凍機油、１５ａ前段側電動膨張弁、１５ｂ後段側電動膨張弁、１６室内送風機、１７室外送風機、８０アキュムレータ、８１導出管、８２油戻し穴。[0001]
BACKGROUND OF THE INVENTION
For example, the present invention relates to a refrigerant circulation apparatus that uses a refrigerating machine oil that is difficult to dissolve in a refrigerant, for example, an HFC (hydrofluorocarbon) type refrigerant as a refrigerant and an alkylbenzene oil as a refrigerating machine oil.
[0002]
[Prior art]
An example of a conventional refrigerant circulation system using an HFC (hydrofluorocarbon) refrigerant as a refrigerant and an alkylbenzene oil as a refrigerating machine oil is shown in FIG. 1 is a compressor for compressing refrigerant gas, 2 is a four-way valve having a function of switching the flow direction of refrigerant, 3 is a condenser for condensing high-pressure refrigerant gas discharged from the compressor 1, 4 is an evaporator, 5 Is a decompressor, and 80 is an accumulator having a refrigerant amount adjusting function. Alkylbenzene oil used in this refrigerant circulation system has a solubility of 0.5 to 7% by weight of refrigerating machine oil in liquid refrigerant under condensing pressure and condensing temperature conditions with respect to HFC (hydrofluorocarbon) refrigerant. And having an incompatible or weak solubility of 0 to 2% by weight in the liquid refrigerant under the conditions of the evaporation pressure and the evaporation temperature, and a specific weight of −20 ° C. to + 60 ° C. In the region, the value is smaller than the specific weight of the liquid refrigerant at the same temperature and its saturated vapor pressure.
[0003]
Next, the behavior of refrigeration oil will be described. The high-pressure refrigerant gas compressed by the compressor 1 is discharged to the condenser 3. At this time, in terms of the weight ratio to the refrigerant, about 0.3 to 2.0% of the refrigerating machine oil is discharged from the compressor 1 together with the refrigerant. The tube diameter of the condenser 3 through which the refrigerant gas flows is set so that the refrigerant gas flow rate is sufficient to transport the refrigerating machine oil downstream. Near the outlet of the condenser 3, most of the refrigerant is liquefied and the flow velocity in the pipe is remarkably reduced. However, since the refrigeration oil has a weak solubility in the condensate refrigerant, it is dissolved in the liquid refrigerant and conveyed from the decompression device 5. . In the downstream area of the decompression device 5, the temperature and pressure of the refrigerant are remarkably reduced, and the refrigerating machine oil turns into incompatible or weak solubility in the liquid refrigerant.
[0004]
However, due to the gasification of a part of the liquid refrigerant generated in the downstream region of the decompression device 5, the refrigerant flow rate rapidly increases, and the tube diameter of the subsequent evaporator 4 is sufficient for the refrigerant gas flow rate to convey the refrigerating machine oil downstream. Since the flow rate is set to ensure, the refrigeration oil is conveyed to the accumulator 80. Refrigerating machine oil has a specific gravity smaller than that of liquid refrigerant and has no or weak solubility in liquid refrigerant under the conditions of evaporation pressure and evaporation temperature. Therefore, in the accumulator 80, the refrigerating machine oil forms a separation layer above the liquid refrigerant. . A plurality of oil return holes 82a, 82b, 82c, and 82d having different heights from the lower end 80a of the accumulator are provided in the outlet pipe 81 that leads the refrigerant to the outside in the accumulator, and the refrigerating machine oil in the accumulator 80 is It returns to the compressor 1 through these oil return holes.
[0005]
[Problems to be solved by the invention]
A conventional refrigerant circulation system using an HFC (hydrofluorocarbon) refrigerant as a refrigerant and an alkylbenzene oil as a refrigerating machine oil is configured as described above, but a large amount of excess refrigerant is stored in the accumulator 80. When the liquid level of the liquid refrigerant layer becomes high, there are the following problems. First, when the liquid level of the liquid refrigerant layer becomes higher, the liquid refrigerant is sucked from the plurality of oil return holes of the outlet pipe 81, so that a large amount of liquid refrigerant returns to the compressor 1, and incompressible liquid refrigerant flows into the compression chamber. Liquid refrigerant is supplied to the lubrication element instead of refrigeration oil by causing a sudden pressure increase in the compression chamber due to the supply or liquid refrigerant discharged from the compression chamber collecting in the compressor sealed container. Further, there is a risk that reliability may be reduced, such as seizure of the bearing of the compressor 1 and the sliding portion of the compression element. Next, if the diameter of the oil return hole is set small so that a large amount of liquid refrigerant does not return to the compressor 1, the refrigerating machine oil does not return in the same manner and accumulates in the accumulator 80 in a large amount, and the refrigerating machine oil in the compressor 1 does not return. There is a risk of exhaustion, and dust, impurities, etc. in the circuit may become clogged easily in the oil return hole.
[0006]
The present invention has been made to solve the above-described problems, and can store excess liquid refrigerant without returning a large amount of liquid refrigerant to the compressor and reliably return the refrigeration oil to the compressor. It aims at providing a highly reliable refrigerant circulation device. Another object of the present invention is to obtain an inexpensive and highly reliable apparatus with a simple configuration.
[0007]
[Means for Solving the Problems]
The refrigerant circulation device according to the present invention includes a compressor that compresses and discharges the refrigerant, a condenser that condenses the high-pressure refrigerant gas discharged from the compressor, and a liquid refrigerant condensed by the condenser. Press A pressure reducing device, an evaporator for evaporating the refrigerant depressurized by the pressure reducing device, a refrigerant pipe that sequentially connects them to form a refrigerant circuit, and a weight dissolution rate in a liquid refrigerant under condensing pressure and condensing temperature conditions. It has weak solubility, and its weight dissolution rate in liquid refrigerant under evaporation pressure and evaporation temperature conditions is insoluble or weakly soluble Cold With freezer oil The Prepared, The decompressor is Refrigeration oil of Refrigerant To Dissolution The limit was discharged from the compressor along with the refrigerant Refrigerator oil refrigerant A first pressure reducing device that reduces the pressure within a range that does not become less than the oil circulation rate, and a second pressure reducing device that is arranged downstream of the first pressure reducing device and depressurizes the refrigerant to the evaporation pressure. In addition to being divided, the surplus refrigerant in the refrigerant circuit is stored between these two decompression devices. Liquid reservoir Is connected to the liquid storage container through the first decompression device together with the refrigerant. Brought in Refrigerating machine oil remains dissolved in refrigerant without separation from refrigerant Leaked from ,cold Through the medium pipe Second It passes through the decompression device and the evaporator and is conveyed to the compressor.
[0010]
The refrigerant circulation device according to the present invention is the above-mentioned Evaporator The pipe diameter of the refrigerant is set so that the flow rate of the refrigerant flowing through the evaporator becomes a flow rate at which the refrigerating machine oil flowing out of the liquid storage container can be conveyed downstream. .
[0014]
Ma The In the refrigerant circulation device according to the present invention, refrigeration oil is used. To liquid refrigerant under condensing pressure and condensing temperature conditions Heavy Volume dissolution rate is 0.5-7% Weakness of It has solubility, and has a non-solubility or weak solubility with a weight dissolution rate of 0-2% in a liquid refrigerant under conditions of evaporation pressure and evaporation temperature.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
A first embodiment corresponding to the present invention will be described below with reference to FIGS. 1 is an example of a refrigerant circulation device applied to an air conditioner. In FIG. 1, 1 is a compressor that compresses refrigerant gas, 4 is an outdoor heat exchanger that condenses high-pressure refrigerant gas discharged from the compressor 1, 3 is an indoor heat exchanger, 5 is a pressure reducing device, and 6 is a liquid reservoir for storing excess refrigerant. FIG. 2 shows the structure of a liquid storage container. 7 is a liquid storage container body, 8 is an inlet pipe connected to the lower side of the container, and 9 is an outlet pipe connected to the upper side of the container. Yes. 16 and 17 are blowers for indoor and outdoor heat exchangers.
[0016]
Next, the behavior of the refrigerant and the refrigerating machine oil will be described when the refrigerant flows in the direction of the arrow. The high-pressure refrigerant gas compressed by the compressor 1 is discharged together with 2.0% refrigerant oil by weight with respect to the refrigerant, and enters the outdoor heat exchanger 4 which is a condenser that condenses the refrigerant. The refrigerating machine oil is transported by a refrigerant gas having a sufficient flow rate, and in the vicinity of the outlet of the outdoor heat exchanger 4, a part of the refrigerant is dissolved in the liquefied liquid refrigerant, and the rest becomes oil droplets together with the refrigerant to the liquid storage container 6. Be transported. The flow rate of the liquid refrigerant is reduced in the liquid reservoir main body 7 where the flow path area is large, and the refrigerating machine oil that has become oil droplets has a lower specific gravity than the refrigerant and floats above the container. However, the direction in which the refrigerating machine oil rises is the same as the flow of the refrigerant as shown by the arrow in the figure, and the container body 7 is normally full except for immediately after startup (about 5 minutes), so it does not stay in the container. It is conveyed out of the container from the outlet pipe 9. Accordingly, the refrigerating machine oil is not accumulated in the liquid reservoir main body 7 and is conveyed to the decompression device 5. Since the pressure of the pressure reducing device 5 is reduced to a necessary pressure and a part of the liquid refrigerant is gasified, the amount of the refrigerant existing in the liquid is reduced. Therefore, the refrigerating machine oil dissolved in the gasified liquid refrigerant is separated. It becomes oil droplets. However, the refrigerant flow rate rapidly increases due to the gasification of a part of the liquid refrigerant, and the pipe diameter of the indoor heat exchanger 3, which is an evaporator for evaporating the subsequent refrigerant, allows the refrigerant gas flow rate to convey the refrigeration oil downstream. Since it is set to ensure a sufficient flow rate, the refrigeration oil is conveyed through the indoor heat exchanger and returned to the compressor 1. In this way, the refrigeration oil that has flowed out of the compressor can be reliably returned to the compressor, and the normal lubrication and sealing function of the compression element is maintained, so that a highly reliable device of the compressor is obtained. In addition, it has a simple structure, excellent productivity and cost performance, and does not cause performance degradation due to clogging.
[0017]
Embodiment 2. FIG.
A second embodiment corresponding to the present invention will be described below with reference to FIGS. FIG. 3 shows an example of a refrigerant circulation device applied to an air conditioner. In FIG. 3, 1 is a compressor for compressing refrigerant gas, 2 is a four-way valve having a function of switching the flow direction of refrigerant, 18 is an indoor unit and an outdoor unit. An extension pipe for connecting the machine, 3 is an indoor heat exchanger, 4 is an outdoor heat exchanger, 5 is a decompression device, and 6 is a liquid storage container for storing excess refrigerant. FIG. 2 shows the structure of a liquid storage container. 7 is a liquid storage container body, 8 is an inlet pipe connected to the lower side of the container, and 9 is an outlet pipe connected to the upper side of the container. Yes.
[0018]
Next, the behavior of the refrigerant that heats the indoor unit and the refrigeration oil will be described when the refrigerant flows in the direction of the arrow. The high-pressure refrigerant gas compressed by the compressor 1 is discharged together with 2.0% refrigeration oil by weight with respect to the refrigerant, passes through the four-way valve 2 and enters the indoor heat exchanger 3 which is a condenser. The refrigerating machine oil is conveyed by a refrigerant gas having a sufficient flow rate, and in the vicinity of the outlet of the indoor heat exchanger 3, a part of the refrigeration oil is dissolved in the liquefied liquid refrigerant, and the rest becomes oil droplets together with the refrigerant to the liquid storage container 6. Be transported. The flow rate of the liquid refrigerant is reduced in the liquid reservoir main body 7 where the flow path area is large, and the refrigerating machine oil that has become oil droplets has a lower specific gravity than the refrigerant and floats above the container. However, the direction in which the refrigerating machine oil rises is the same as the flow of the refrigerant as shown by the arrow in the figure, and the container body 7 is normally full except for immediately after startup (about 5 minutes), so it does not stay in the container. It is conveyed out of the container from the outlet pipe 9. Accordingly, the refrigerating machine oil is not accumulated in the liquid reservoir main body 7 and is conveyed to the decompression device 5. Since the pressure of the pressure reducing device 5 is reduced to a necessary pressure and a part of the liquid refrigerant is gasified, the amount of the refrigerant existing in the liquid is reduced. Therefore, the refrigerating machine oil dissolved in the gasified liquid refrigerant is separated. It becomes oil droplets. However, due to the gasification of a part of the liquid refrigerant, the refrigerant flow rate rapidly increases, and the tube diameter of the subsequent outdoor exchanger 4 as an evaporator ensures a sufficient flow rate for the refrigerant gas flow rate to convey the refrigeration oil downstream. Therefore, the refrigerating machine oil is conveyed through the outdoor heat exchanger and returned to the compressor 1.
[0019]
In the case of heating, since the indoor heat exchanger is generally smaller than the outdoor heat exchanger, the amount of refrigerant is smaller than that of cooling, so that excess refrigerant is likely to be generated.
On the other hand, when the refrigerant is caused to flow in the reverse direction by switching the four-way valve 2 and cooling is performed in the indoor unit, the roles of condensation and evaporation of the outdoor and indoor heat exchangers change, and the pressure is reduced by the decompression device 5 and partially gasified. The refrigerant in which the liquid and gas are mixed flows from the outlet pipe 9 into the container main body 7. However, since the refrigerant flows from the top to the bottom of the container, the liquid refrigerant is conveyed from the inlet pipe 8 to the outside of the container without stagnation. . For this reason, in the case of cooling that uses a large amount of refrigerant, the function as a liquid storage container is lost, but this is not necessary, and the refrigerating machine oil conveyed with the refrigerant is also conveyed without staying in the container. For this reason, the refrigerating machine oil discharged from the compressor 1 returns to the compressor 1 without staying in the cycle.
[0020]
As described above, even when the required amount of refrigerant varies depending on the flow direction, the surplus refrigerant can be stored, so that efficient operation can be performed regardless of the flow direction, and the refrigeration oil flowing out from the compressor can be reliably Since the normal lubrication and sealing function of the compression element portion is maintained, a highly reliable apparatus for the compressor can be obtained.
[0021]
Embodiment 3 FIG.
A third embodiment corresponding to the present invention will be described below with reference to FIG. FIG. 4 is an example of a refrigerant circulation device applied to an air conditioner. In FIG. 4, 1 is a compressor for compressing refrigerant gas, 2 is a four-way valve having a function of switching the flow direction of refrigerant, and 4 is an outdoor heat exchanger. , 16 is an indoor blower, 3 is an indoor heat exchanger, 17 is an outdoor blower, 5a and 5b are decompression devices, and 6 is a reservoir for storing excess refrigerant.
[0022]
Next, the behavior of the refrigerant and the refrigerating machine oil will be described. The high-pressure refrigerant gas compressed by the compressor 1 is discharged together with, for example, 1.0% refrigeration oil in a weight ratio with respect to the refrigerant, passes through the four-way valve 2 and enters the indoor heat exchanger 3 that is a condenser. The refrigerating machine oil is conveyed by a refrigerant gas having a sufficient flow rate, and is completely dissolved in the liquefied liquid refrigerant in the vicinity of the outlet of the indoor heat exchanger 3. However, the solubility limit of the refrigeration oil in the refrigerant under the conditions of the condensation pressure and the condensation temperature of the alkylbenzene oil is about 1.5%. Then, the refrigerant passes through the decompression device 5 b and is conveyed to the liquid reservoir 6. By setting the decrease in pressure and temperature in the decompression device 5a within a range in which the solubility limit does not become less than 1%, the refrigerating machine oil is not separated from the refrigerant in the liquid reservoir 6 and remains out of the container while being dissolved in the refrigerant. Be transported. Therefore, the refrigerating machine oil is transported to the decompression device 5b without accumulating in the liquid storage container 6. In the decompression device 5b, the pressure is reduced to a necessary pressure and the temperature rapidly decreases. Therefore, the solubility limit of the refrigeration oil in the liquid refrigerant is reduced to 0.5%, and the refrigeration oil that cannot be completely dissolved in the liquid refrigerant is separated. Oil droplets. Furthermore, in the outdoor heat exchanger 4, most of the refrigerant is gasified and the amount of refrigerant existing in the liquid state decreases, so that the refrigerating machine oil that cannot be dissolved is separated. However, after exiting the decompression device, the refrigerant flow rate becomes sufficient to convey the separated refrigerating machine oil downstream due to the gasification of the refrigerant, so that the refrigerating machine oil is conveyed to the compressor 1. The same applies to the case where the four-way valve 2 flows in the reverse direction.
[0023]
In general, when a liquid reservoir is provided in a refrigerant circuit, for example, a refrigerating machine oil that is difficult to dissolve in a refrigerant using hydrofluorocarbon, such as an HFC refrigerant, has a weight dissolution rate of 0.5 in a liquid refrigerant under condensation pressure and condensation temperature conditions. -7.0%, a refrigerating machine oil having an insoluble or weak solubility of 0 to 2.0% by weight in a liquid refrigerant under conditions of evaporation pressure and temperature, alkylbenzene, mineral oil, ester oil, When ether oil or the like is used, in the refrigerant circuit having a liquid reservoir portion where the moving speed of the refrigerant becomes slow, that is, a liquid reservoir container for storing excess refrigerant, oil mixed with the refrigerant is collected in the container. It will be.
The weight dissolution rate of oil in the refrigerant first varies depending on the type of refrigerant and oil. For example, the refrigerating machine oil alkylbenzene (viscosity grade VG = 8-32), the HAB oil, is dissolved in the liquid refrigerant R407C, which is an HFC refrigerant, and the relationship between the oil circulation rate and the compressor frequency is the liquid refrigerant in the condensation temperature range. On the other hand, it shows a dissolution rate of 1.0 to 4.0 wt%, but it is a minute dissolution rate of 0.2 to 1.8 wt% for liquid refrigerant in the evaporation temperature range. This dissolution rate varies depending on the combination of various refrigerants and various oils.
In general, the oil circulation rate, which is the weight ratio of refrigeration oil flowing out of the compressor together with the refrigerant, is
It becomes a value of about 0.3-2.0 wt% and tends to increase with an increase in the compressor frequency.
The amount of refrigerating machine oil indicated by this oil circulation rate circulates in the refrigerant circuit, and in particular, the refrigerating machine oil easily accumulates in the liquid reservoir, and the refrigerating machine oil in the liquid refrigerant in the container is within the range of the dissolution rate at that temperature. Is dissolved. However, if the oil circulation rate exceeds the dissolution rate of the refrigeration oil in the liquid refrigerant under the operating conditions where the refrigerant is present, the amount of refrigeration oil circulating will exceed the allowable dissolution amount in the liquid refrigerant. The machine oil is separated from the liquid refrigerant, and becomes, for example, an oil droplet or an oil layer in the liquid reservoir, and accumulates in the liquid reservoir and does not return to the compressor. On the other hand, for example, the temperature of the liquid refrigerant in the container is detected by a thermistor, and when the temperature of the refrigerant becomes lower than the temperature necessary for dissolving the oil, the pressure reducing device 5a is moved and set in the closing direction, Can be dissolved.
Of course, it is not like an electric expansion valve that can be controlled as a pressure reducing device, but it is set from the beginning to use a capillary tube to keep the lower limit of temperature and lower limit of pressure in the reservoir in various operating situations. You can keep it.
[0024]
Although the above description has been given by taking the HFC refrigerant as an example, the present invention is not limited to this, and it is obvious that the same effect is produced when using refrigeration oil that is hardly soluble in the refrigerant even if the HC refrigerant is used. .
When the operating frequency of the compressor is low, the condensation temperature decreases and the solubility of the refrigeration oil in the refrigerant decreases, but at the same time the amount of refrigeration oil discharged from the compressor also decreases. All can be dissolved in the refrigerant in the reservoir 6.
As described above, surplus refrigerant can be accumulated in the liquid reservoir in both the cooling and heating flow directions, so that efficient operation can be performed and the compressor oil is not retained in the liquid reservoir. Therefore, a highly reliable device of the compressor can be obtained.
In particular, the present invention is effective for a multi-type air conditioner having a plurality of indoor units and in which the required refrigerant amount varies greatly depending on the number of indoor units operated in each cooling and heating operation state.
[0025]
Embodiment 4 FIG.
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIGS. 4, 5, and 6. FIG. FIG. 5 shows the structure of the liquid storage container. An inlet pipe 11 and an outlet pipe 12 are inserted into the container from the lower surface of the liquid storage container 10 and open toward the upper side of the container. The length of entry of the inlet pipe 11 and the outlet pipe 12 into the container is 5 mm, and the outer diameters of the pipes are both 9.52 mm.
[0026]
Next, the behavior of the refrigerant and the refrigerating machine oil will be described. The high-pressure refrigerant gas compressed by the compressor 1 is discharged together with, for example, 1.0% refrigerating machine oil in a weight ratio with respect to the refrigerant, and passes through the four-way valve 2 and enters the indoor heat exchanger 3 which is a condenser. The refrigerating machine oil is conveyed by a refrigerant gas having a sufficient flow rate, and is completely dissolved in the liquefied liquid refrigerant in the vicinity of the outlet of the indoor heat exchanger 3. On the other hand, 2% or more of refrigerating machine oil may be temporarily discharged together with the refrigerant gas when the compressor 1 is started. In this case, the refrigerating machine oil that has not been dissolved in the liquid refrigerant in the indoor heat exchanger 3 becomes oil droplets and is conveyed to the liquid reservoir 6 together with the liquid refrigerant. However, the solubility limit of the refrigerating machine oil in the refrigerant under the conditions of the condensation pressure and the condensation temperature is about 1.5%. Since the liquid refrigerant flowing into the container 10 from the inlet pipe 11 has a reduced flow velocity in the container 10, the oil droplets that flow into the container together with the liquid refrigerant rise to form an oil layer 14. When the operating state is stabilized and the discharge amount of the refrigerating machine oil is reduced below the amount of refrigerating machine oil dissolved in the refrigerant under the pressure and temperature conditions in the container 10, the oil in the oil layer 14 is dissolved in the refrigerant 13 in the container. The thickness of the oil layer 14 gradually decreases. FIG. 6 shows a change in the thickness of the oil layer 14 after the compressor is started. At this time, a distribution occurs in the dissolved concentration of the refrigerating machine oil in the liquid refrigerant 10 in the container 10, and the concentration increases as the oil layer 14 is closer. On the other hand, since the inlet pipe 11 provided in the lower part of the container opens from the bottom to the top in the direction of the oil layer 14, the flow rate of the refrigerant that has flowed hits the bottom surface of the oil layer 14, and the oil layer 14 At the same time, the refrigerant 13 is also stirred. For this reason, the density | concentration of the refrigerator oil in the refrigerant | coolant 13 which contact | connects the oil layer 14 reduces, and melt | dissolution to the refrigerant | coolant 13 of the refrigerator oil of the oil layer 14 is accelerated | stimulated. The dissolved oil is transported out of the container together with the refrigerant from an outlet pipe provided in the lower part of the container and returns to the compressor.
Even if oil heavier than the refrigerant is used, the oil can be dissolved in the refrigerant by the above-described configuration and stirring operation, and it is natural that the oil returns to the compressor.
[0027]
Embodiment 5 FIG.
Another embodiment of the present invention will be described with reference to FIG. FIG. 7 is a diagram showing a schematic configuration of a refrigerant circulation apparatus showing an embodiment of the present invention. In FIG. 7, 1 is a compressor for compressing refrigerant gas, and 2 is a four-way valve having a function of switching the flow direction of refrigerant. Operation position, 4 is an outdoor heat exchanger for condensing the high-pressure refrigerant gas discharged from the compressor 1, 16 is an indoor fan, 3 is an indoor heat exchanger, 17 is an outdoor fan, 5a and 5b are decompressors, and 6 is A liquid storage container for storing excess refrigerant, 18 is an extension pipe connecting the indoor unit and the outdoor unit, 19 is a pressure detection unit, 20 is a temperature detection unit for detecting the outlet temperature of the indoor heat exchanger, and 21 is an outdoor heat exchanger. Temperature detecting means for detecting the inlet temperature of the compressor, 22 is a temperature detecting means for detecting the compressor intake temperature, and 23 is a calculation / control for controlling the opening areas of the pressure reducing devices 15a and 15b based on the detection data of the detecting means 19 to 22. Device.
[0028]
In the refrigerant circulation device according to the present invention, it is assumed that the decompression devices 15a and 15b are controlled to have an opening area and liquid refrigerant is accumulated in the liquid reservoir 6 and the accumulated liquid surface is kept stable. At this time, the refrigerant pressure in the flow path including the liquid storage container between the decompression devices 15a and 15b is a pressure between the condensing pressure and the evaporation pressure, that is, an intermediate pressure, and the liquid refrigerant stored in the liquid storage container 6 is It is in a saturated liquid state.
[0029]
Note that the degree of superheat of the refrigerant sucked by the compressor is obtained by the calculation / control device 23 calculating the deviation value from the temperatures detected by the refrigerant intake refrigerant temperature detection means 22 and the outdoor heat exchanger inlet temperature detection means 21. This deviation value is called the degree of superheat.
The degree of subcooling at the outlet of the indoor heat exchanger is calculated by calculating the difference between the saturation temperature of the refrigerant corresponding to the pressure detected by the pressure detector 19 and the detected temperature detected by the refrigerant temperature detector 20 at the outlet of the indoor heat exchanger. The controller 23 calculates and obtains it. This deviation value is called the degree of supercooling.
In addition, as the supercooling detection means for detecting the supercooling characteristic corresponding to the degree of supercooling of the refrigerant at the outlet of the indoor heat exchanger, the detection means 20 for detecting the refrigerant temperature at the outlet of the indoor heat exchanger and the pressure detection means 19 detected. Refrigerant in the vicinity of the center of the indoor heat exchanger, comprising a combination with an indoor / outdoor heat exchanger central temperature detecting means (not shown) that detects the temperature in the vicinity of the center of the indoor heat exchanger corresponding to the saturation temperature of the refrigerant corresponding to the pressure. A deviation value between the temperature and the indoor heat exchanger outlet refrigerant temperature may be set as the degree of supercooling.
Further, as the superheat degree detecting means for detecting the superheat characteristic value corresponding to the superheat degree of the suction refrigerant of the compressor refrigerant, an outdoor heat exchanger outlet temperature detecting means (not shown) for detecting the outdoor heat exchanger outlet refrigerant temperature. And the outdoor heat exchanger inlet temperature detection means 21 for detecting the refrigerant temperature at the inlet of the outdoor heat exchanger, and the deviation value of the inlet / outlet temperature of the outdoor heat exchanger may be set as the degree of superheat.
[0030]
Here, when the high-pressure side decompression device 15a is throttled, the pressure is reduced at the outlet of the decompression device 15a, and the refrigerant flows into the liquid reservoir 6 in a gas / liquid two-phase state. At this time, since the gas refrigerant is separated into the upper part and the liquid refrigerant is separated into the lower part by the action of gravity in the liquid storage container 6, both the inlet pipe and the outlet pipe of the liquid storage container 6 should be arranged at the lower part of the liquid storage container. For example, only the liquid refrigerant is always sent to the decompression device 15b. In addition, the vaporized refrigerant reduces the liquid refrigerant in the liquid storage container 6 and lowers the liquid level due to the vapor / liquid two-phase formation of the refrigerant.
And since the liquid refrigerant | coolant discharge | released during the refrigerating cycle from the liquid reservoir 6 accumulates in the exit of the indoor heat exchanger 3, the supercooling degree in a refrigerating cycle becomes large.
For this reason, the temperature of the refrigerant | coolant in the liquid storage container 6 falls, and the solubility to the refrigerant | coolant of refrigerating machine oil reduces.
Conversely, when the high-pressure side pressure reducing device 15a is opened, the reverse change occurs when the pressure is reduced, the liquid level rises, the temperature of the refrigerant in the liquid reservoir 6 rises, and the refrigerant oil into the refrigerant of the refrigerating machine oil is increased. Solubility increases. In this way, according to the target value set according to the operating conditions and the surrounding environment, that is, according to the target setting value of the degree of supercooling set so that the performance of the air conditioner can be fully exhibited according to the outside air temperature or the indoor set temperature. Thus, the opening area of the high pressure side valve device may be increased or decreased.
In this way, the degree of supercooling and the temperature of the refrigerant in the liquid reservoir can be controlled by controlling the high-pressure side pressure reducing device 15a.
[0031]
Embodiment 6 FIG.
On the other hand, when the low pressure side pressure reducing device 15b is opened, the pressure is reduced at the outlet of the high pressure side pressure reducing device 15a, and the refrigerant flows into the liquid storage container 6 in a gas / liquid two-phase state. At this time, since the gas refrigerant is separated into the upper part and the liquid refrigerant is separated into the lower part by the action of gravity in the liquid storage container 6, both the inlet pipe and the outlet pipe of the liquid storage container 6 should be arranged at the lower part of the liquid storage container. For example, only the liquid refrigerant is always sent to the decompression device 15b. In addition, the vaporized refrigerant reduces the liquid refrigerant in the liquid storage container 6 and lowers the liquid level due to the vapor / liquid two-phase formation of the refrigerant.
And since the refrigerant | coolant flow volume in the exit of the low voltage | pressure side pressure reduction apparatus 15b increases, the superheat degree by compressor suction | inhalation falls.
On the other hand, when the low-pressure side pressure reducing device 15b is throttled, the degree of superheat at the suction of the compressor increases. In this way, according to the target value set according to the operating conditions and the surrounding environment, that is, according to the target set value of the superheat degree set so that the performance of the air conditioner can be fully demonstrated according to the outside air temperature or the indoor set temperature. Thus, the opening area of the low pressure side valve device may be increased or decreased.
In this way, by controlling the low-pressure side pressure reducing device 15b and controlling the degree of superheat in the compressor suction, that is, the degree of dryness to an optimal value, the available pressure and temperature can be further expanded, and the efficiency is high. It can be set as a device, and an operation state with less energy can be maintained.
[0032]
Embodiment 7 FIG.
Further, by controlling the high pressure side pressure reducing device 15a and the low pressure side pressure reducing device 15b in conjunction with each other, it is possible to maintain the operating state with a small input energy by simultaneously controlling the degree of supercooling and the degree of superheat to predetermined values. I can do it. This can result in minimal energy operation at a given condition.
[0033]
Embodiment 8 FIG.
Hereinafter, another embodiment of the present invention will be described with reference to FIGS. As the decompression devices 15a and 15b, electric expansion valves controlled by a microcomputer are used as shown in FIG. And it controls so that the state of the pressure and temperature of a liquid reservoir part may be in a saturated state, and from this state, the opening area of the inlet side expansion valve 15a is made small, and the opening area of the outlet side expansion valve 15b is made large. When controlled, the state of the refrigerant passing through the inlet pipe 11 shown in FIG. 5 changes from a saturated liquid to a gas-liquid two-phase state. For this reason, bubbles are generated from the inlet pipe 11, and the generated bubbles are stirred in the refrigerant 13 while rising in the refrigerant 13 in the container. When the bubbles reach the oil layer 14, the oil layer 14 and the refrigerant 13 are stirred.
If this state is continued, the amount of refrigerant stored in the container decreases, so that the opening area of the expansion valves 15a and 15b is controlled so that the state of the refrigerant in the inlet pipe 11 becomes supercooled liquid after a certain period of time.
In this way, bubbles are generated in the container, and the refrigerant 13 and the oil layer 14 are agitated by the bubbles, thereby promoting the dissolution of the accumulated refrigerating machine oil in the refrigerant. In addition, although it demonstrated that a bubble was generated and stirred, you may make it stir by the change of the flow rate accompanying a pressure change. This control may be performed appropriately during operation, for example, every fixed time or every predetermined compressor operation time, or by detecting the temperature in the height direction of the container that oil has accumulated in the container. Also good.
As the change to be applied to the refrigerant, the description has been made with the decompression device. However, the state of the refrigerant may be changed by various methods such as providing a switching circuit at the outlet of the inlet pipe and repeatedly applying the pressure change by the orifice.
[0034]
Embodiment 9 FIG.
Another embodiment of the present invention will be described below with reference to FIGS. As the decompression devices 15a and 15b, electric expansion valves controlled by a microcomputer are used as shown in FIG. And it controls so that the state of the pressure and temperature of a liquid reservoir part may be saturated. From this state, when the control is performed so that the opening area of the inlet side expansion valve 15a is reduced and the opening area of the outlet side expansion valve is increased, the state of the refrigerant passing through the inlet pipe 11 shown in FIG. Change to state. In this state, the refrigerant 13 in the container gradually decreases, and this state is continued until the refrigerant 13 runs out. Thereafter, in order to store the refrigerant again, the expansion valve is controlled so that the state of the refrigerant in the inlet pipe 11 becomes the supercooled liquid. When the liquid level of the refrigerant 13 disappears, the oil layer 14 is conveyed from the outlet pipe 12 to the outside of the container. Then, when the refrigerating machine oil is conveyed out of the container, control for storing the refrigerant in the container is performed. By performing this control once when the oil layer thickness is thick in the container after starting the compressor, the refrigerating machine oil staying in the container can be conveyed outside the container and returned to the compressor. The presence or absence of the Naoe Demon plane can be determined by detecting the temperature in the height direction of the container.
[0035]
As described above, in the present invention, oil that does not easily dissolve in the refrigerant is used, and even if a receiver, accumulator, or header that is a reservoir is provided in the refrigerant circuit, the oil does not stay in the container. A control method is possible. As a result, it can be reliably returned to the compressor without accumulating a large amount of oil in the sump container, and the surplus refrigerant in the refrigerant circuit can be stored in a load state when normal lubrication and sealing functions in the compressor can be maintained. The performance suitable for can be reliably maintained. Furthermore, it is possible to store surplus refrigerant according to the direction of refrigerant flow in the equipment, making full use of the capacity of the equipment, enabling flexible operation, and eliminating the need for unnecessary refrigerant flow through the compressor. Can be improved.
[0036]
In addition, the present invention can store liquid refrigerant in a liquid reservoir without storing oil, or empty from the liquid reservoir regardless of the flow direction of the refrigerant. The optimal operating state can be set in response to changes in Furthermore, even if the oil temporarily stays in the sump container, it can be quickly returned to the compressor, or the oil can be gradually dissolved in the refrigerant without affecting the operating performance to reduce the amount of residence. It is. Utilizing the speed of the refrigerant flowing in, the refrigerant in the container is agitated to promote dissolution in the refrigerant, and oil change can be ensured without impairing the reliability of the compressor.
It is also possible to make the reservoir container narrow and deep so that it can be easily stirred.
[0037]
Further, when the flow rate of the refrigerant flowing into the container is slow and the stirring effect is small, the state of the refrigerant in the container can be changed to promote the dissolution of oil in the refrigerant.
[0038]
【The invention's effect】
The refrigerant circulation device according to the present invention includes a compressor that compresses and discharges the refrigerant, a condenser that condenses the high-pressure refrigerant gas discharged from the compressor, and a liquid refrigerant condensed by the condenser. Press A pressure reducing device, an evaporator for evaporating the refrigerant depressurized by the pressure reducing device, a refrigerant pipe that sequentially connects them to form a refrigerant circuit, and a weight dissolution rate in a liquid refrigerant under condensing pressure and condensing temperature conditions. It has weak solubility, and its weight dissolution rate in liquid refrigerant under evaporation pressure and evaporation temperature conditions is insoluble or weakly soluble Cold With freezer oil The Prepared, The decompressor is Refrigeration oil of Refrigerant To Dissolution The limit was discharged from the compressor along with the refrigerant Refrigerator oil refrigerant A first pressure reducing device that reduces the pressure within a range that does not become less than the oil circulation rate, and a second pressure reducing device that is arranged downstream of the first pressure reducing device and depressurizes the refrigerant to the evaporation pressure. In addition to being divided, the surplus refrigerant in the refrigerant circuit is stored between these two decompression devices. Liquid reservoir Is connected to the liquid storage container through the first decompression device together with the refrigerant. Brought in Refrigerating machine oil remains dissolved in refrigerant without separation from refrigerant Leaked from ,cold Through the medium pipe Second Since it was transported to the compressor through the decompression device and the evaporator, By setting the first decompression device so that the refrigerating machine oil dissolves in the refrigerant without being separated from the refrigerant in the liquid reservoir, the refrigerating machine oil does not accumulate in the liquid reservoir, Refrigerating machine oil can be reliably returned to the compressor, and the reliability of the compressor Can increase .
[0041]
Mako The refrigerant circulation device related to the invention of The pipe diameter of the evaporator should be such that the flow rate of the refrigerant flowing through the evaporator can flow the refrigerating machine oil flowing out of the liquid storage container downstream. Setting Is So The refrigerating machine oil, which has become unable to dissolve due to the gasification of most of the refrigerant in the evaporator, is separated, but the flow rate of the gasified refrigerant is sufficient to transport the separated refrigerating machine oil downstream. Refrigerating machine oil reliably compressor Transport to It is possible to improve the reliability of the compressor.
[0049]
Mako The refrigerant circulation device according to the invention is a predetermined condition for the refrigerant. Non-under Solubility or weak solubility Have Even if refrigeration oil is used, ensure that refrigeration oil is used. On the compressor Because you can return , A high reliability of the compressor can be obtained, and an apparatus that can be easily maintained can be obtained.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a refrigerant circulation device showing Embodiment 1 of the present invention.
FIG. 2 is a conceptual diagram of a liquid reservoir container showing Embodiments 1 and 2 of the present invention.
FIG. 3 is a conceptual diagram of a refrigerant circulation device showing another embodiment of the present invention.
FIG. 4 is a conceptual diagram of a refrigerant circulation device showing another embodiment of the present invention.
FIG. 5 is a conceptual diagram of a liquid reservoir container showing another embodiment of the present invention.
FIG. 6 is a diagram illustrating a change in the oil retention state in the liquid reservoir after activation according to the present invention.
FIG. 7 is a conceptual diagram of a refrigerant circulation device showing another embodiment of the present invention.
FIG. 8 is a diagram illustrating a conventional refrigerant circulation system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Compressor, 2 Four-way valve, 3 Indoor heat exchanger, 4 Outdoor heat exchanger, 5 Pressure reducing device, 5a Front pressure reducing device, 5b Rear pressure reducing device, 6 Liquid storage container, 7 Liquid storage container, 8 Liquid storage container inlet piping 9 Reservoir outlet pipe, 10 Reservoir container, 11 Reservoir inlet pipe, 12 Reservoir outlet pipe, 13 Refrigerant, 14 Refrigerating machine oil, 15a Front side electric expansion valve, 15b Rear side electric expansion valve, 16 Indoor Blower, 17 outdoor fan, 80 accumulator, 81 outlet pipe, 82 oil return hole.

Claims

A compressor that compresses and discharges the refrigerant;
A condenser for condensing the high-pressure refrigerant gas discharged from the compressor;
A decompression device for decompressing the liquid refrigerant condensed in the condenser;
An evaporator for evaporating the refrigerant decompressed by the decompression device;
Refrigerant piping that connects these sequentially to form a refrigerant circuit;
Refrigeration in which the weight dissolution rate in liquid refrigerant under condensation pressure and condensation temperature conditions is weakly soluble, and the weight dissolution rate in liquid refrigerant under evaporation pressure and evaporation temperature conditions is insoluble or weakly soluble With machine oil,
The pressure reducing device reduces the pressure to a range in which the solubility limit of the refrigerating machine oil in the refrigerant does not become less than the oil circulation rate which is the weight ratio of the refrigerating machine oil discharged from the compressor together with the refrigerant. And a second decompression device that is arranged downstream of the first decompression device and decompresses the refrigerant to the evaporating pressure, and is configured to be divided between these two decompression devices and surplus refrigerant in the refrigerant circuit The refrigerating machine oil that has passed through the first pressure reducing device together with the refrigerant flows out of the liquid reservoir while being dissolved in the refrigerant without being separated from the refrigerant. Then, the refrigerant circulating device is conveyed to the compressor through the second decompression device and the evaporator through the refrigerant pipe.

Pipe diameter of the evaporator, the flow rate of the refrigerant flowing through the evaporator of claim 1, characterized in that the refrigerating machine oil flowing out from the liquid reservoir container is set such that the flow rate can be transported to the downstream Refrigerant circulation device.

The refrigerating machine oil has a weak solubility of 0.5-7% in the liquid refrigerant under the condensing pressure and condensing temperature conditions, and the refrigerating machine oil in the liquid refrigerant under the evaporating pressure and evaporating temperature conditions. the refrigerant circulating apparatus according to claim 1 or claim 2 wt dissolution rate and having a non-soluble or slightly soluble 0-2% of.