JP4258241B2

JP4258241B2 - Heat pump system, heat pump water heater

Info

Publication number: JP4258241B2
Application number: JP2003083506A
Authority: JP
Inventors: 宗野本; 史武畝崎; 昌之角田; 慎一若本; 寿彦榎本
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2002-03-28
Filing date: 2003-03-25
Publication date: 2009-04-30
Anticipated expiration: 2023-03-25
Also published as: JP2004003825A

Description

【０００１】
【発明の属する技術分野】
この発明は、二酸化炭素等の超臨界サイクルを形成する冷媒を用いたヒートポンプシステムおよびヒートポンプ式給湯機に関するものである。
【０００２】
【従来の技術】
従来の超臨界サイクルを形成する蒸気圧縮式回路は、直列に連結した圧縮器と、放熱器と、膨張弁と、蒸発器と、アキュムレータを備え、圧縮機で超臨界圧力まで圧縮された冷媒による超臨界サイクル装置の能力調整は、放熱器出口の冷媒状態を変動させることで制御される。この超臨界サイクルにおいては、超臨界状態の冷媒は凝縮されず、放熱器にて温度が低下することが特徴的であり、放熱器出口の冷媒温度は、冷媒と空気又は水の流れが対向している場合、空気又は水温より数℃高くなり、この温度は高圧圧力レベルと無関係に一定となる。したがって、放熱器における加熱能力の調整は、放熱器出口の冷媒温度をほぼ一定の状態として、高圧圧力を変動することにより達成される。冷媒の臨界点付近での等温線カーブは、圧力によるエンタルピーの変動をもたらし、圧力を変動させるには、高圧における冷媒の質量を変動させることが必要であり、アキュムレータのような緩衝装置にて処理されなければならない。つまり、アキュムレータに貯留する冷媒量を制御することで加熱能力を制御できる（例えば、特許文献１参照）。また、超臨界サイクルでは最大エネルギ効率を得る高圧圧力が存在することが知られている。蒸気圧縮回路の最大エネルギ効率を維持するために、所定の高圧に調整する必要があるが、膨張装置を制御し、アキュムレータの冷媒量を制御することで高圧を制御できる。
【０００３】
【特許文献１】
特公平７−１８６０２号公報（第３−５頁、第２図）
【０００４】
【発明が解決しようとする課題】
このような超臨界サイクルを形成する蒸気圧縮回路を熱源として用いた給湯機において、タンク下部の低温水を加熱し、タンク上部へ高温水を戻して沸き上げる積層沸き上げを行なった場合、貯湯タンク内は上部に高温水が、下部に低温水が貯留することになる。そして、高温水と低温水の間に温度勾配を持った混合層が生ずる。沸き上げ終了に近づくにつれて混合層が貯湯タンク下部より供給されるため、熱源機への供給水温が上昇する。よって放熱器で熱交換するために流入する被加熱流体の流入温度が上昇すると、冷媒と被加熱流体の流れが対向している場合、放熱器出口の被加熱流体の温度も上昇するため高圧側の冷媒量が減少する。したがって、供給水温が高温になると余剰冷媒が生じ、アキュムレータによる貯留が必要となる。ところが、アキュムレータは気体と液体を分離する機能を持っているため、その容積が大きくなり、装置が大きくなる問題点があった。
【０００５】
また、被加熱流体である給湯用流体が高温になると、加熱能力が低下し、成績係数が低下する問題点もあった。冷凍能力の低下は、高圧圧力を上げて抑えることもできるが、その場合には装置の耐圧を上げる必要があり、装置が大型化する問題点もある。
【０００６】
この発明は上記のような問題点を解消するためになされたもので、アキュムレータのような余剰冷媒を調整する容器を不要とし、装置を小型化することを目的とする。また、放熱器に流入する被加熱流体である給湯用流体が高温になったとき、装置の耐圧を変えることなく、加熱能力の低下を抑えて、成績係数の低下を抑えることを目的とする。
【０００７】
【課題を解決するための手段】
この発明に係るヒートポンプシステムは、冷媒を超臨界圧力まで圧縮する圧縮機、前記圧縮機から吐出した冷媒と被加熱流体とを熱交換する放熱器、冷媒を臨界圧力以下に減圧する膨張弁および蒸発器を順次接続して冷媒が循環する基本冷媒回路と、前記放熱器に流入する前記被加熱流体を冷却する冷却器と、前記放熱器と前記膨張弁の間から、または、前記蒸発器と前記圧縮機の間から、または、前記膨張弁と前記蒸発器の間のいずれかから分岐し、前記冷却器を介して前記圧縮機の吸入側へ合流するバイパス回路と、前記バイパス回路を流通する冷媒の流量を調整する流量調整手段と、前記放熱器の出口側冷媒配管に冷媒温度センサを備え、前記冷媒温度センサにより検出する冷媒温度を、冷媒の温度上昇にともない密度変化が急に減少する特異温度以下となるように前記流量調整手段を制御することによって前記冷却器の熱交換量を調整するものである。
【０００８】
【発明の実施の形態】
実施の形態１．
図１はこの発明の実施の形態１におけるヒートポンプシステムの冷媒回路図を示すものであり、一例としてヒートポンプ式給湯機を取り上げ、冷媒系統および被加熱流体を水とする給湯水系統の回路図である。図において、冷媒系統は、圧縮機５、放熱器４、膨張弁（減圧手段）６および蒸発器７を順次配管で接続し、冷媒として二酸化炭素を用いた冷凍サイクルを形成する。また、給湯水系統は、貯湯タンク１の下部から低温水をポンプ２で搬送し、冷却器３から前記放熱器４を順次通過して高温の冷媒と熱交換して高温水となって貯湯タンク１の上部から戻る循環回路と、前記冷却器３へ第２のポンプ１０により冷水槽９で冷却された冷却流体を循環させる回路から構成されている。なお、放熱器４では冷媒の流れと給湯水の流れが対向するように構成された、例えば二重管熱交換器を用いている。また、給湯水系統回路における放熱器４への被加熱流体の流入温度を検出するために放熱器４入口側配管に水温センサ１１を設け、一方冷媒系統回路における放熱器４からの冷媒流出温度を検出するために放熱器４の出口側冷媒配管に冷媒温度センサ１２を設けている。
【０００９】
まず、貯湯タンク側の積層沸上げの動作について説明する。貯湯タンク１には低温水が充満しており、低温水をポンプ２で貯湯タンク１下方部から冷却器３へ導く。後述する動作により、放熱器４で所定温度に加熱された高温水は貯湯タンク１上方部から流入し、上部から徐々に蓄熱される。通常、貯湯タンク１上部の高温水と貯湯タンク１下部の低温水は温度差が大きいため、その密度差も大きく、成層化が保たれる。しかし、時間経過により、その境界層は水の熱伝導により熱が伝わり、混合層と呼ばれる温度勾配を生じる。
【００１０】
次に、被加熱流体である供給水温が低い場合の冷凍サイクルの動作について説明する。圧縮機５で圧縮されて吐出した二酸化炭素冷媒は、臨界圧力を超えた超臨界状態の高温高圧となり、放熱器４に流入して被加熱流体、例えば水と熱交換して、冷媒は放熱し等圧冷却され依然として超臨界状態にあり、水は加熱される。放熱器４から流出した冷媒は膨張弁（減圧手段）６を通過して減圧され湿り蒸気の状態となり、その後蒸発器７でファン８によって送られる空気からの吸熱作用によって等圧加熱され蒸発して飽和蒸気となり、圧縮機５へと循環する冷凍サイクルを形成する。
【００１１】
次に被加熱流体の供給水温が上昇した場合の冷凍サイクルの動作について説明する。通常時は、一定温度の低温水が放熱器４に供給され、安定した冷凍サイクルの運転状態が続くが、時間が経過し、貯湯タンク１が満蓄に近づくと、温度勾配を持った混合層の水が放熱器４に供給される。つまり、放熱器４には高温水が供給されることになる。
【００１２】
ここで、放熱器４へ供給される水温が低温時と高温時の場合の冷媒状態について、図２を用いて説明する。図２は二酸化炭素のモリエル線図であり、縦軸は圧力、横軸はエンタルピーを示している。図２において、例えば、給湯水側の沸上げ温度９０℃における、放熱器４から流出する冷媒が２５℃の冷凍サイクル状態Ｘを図中の実線で示し、放熱器流出冷媒温度が５０℃の冷凍サイクル状態Ｙを図中の点線で示す。放熱器４で冷凍サイクルの冷媒と給湯水系統の水が対向した流れで熱交換すると、放熱器４出口の冷媒温度は、放熱器４入口の水温よりやや高い温度となる。ここで、放熱器４から流出する出口冷媒温度と放熱器４へ流入する被加熱流体の流入水温の差が一定値、例えば１０ｄｅｇになるように給湯水系統の流量を制御した場合、放熱器４に供給される水温が１５℃の場合、放熱器４出口の冷媒温度は２５℃となり、冷凍サイクル状態Ｘ（図中のＡ−Ｂ−Ｃ−Ｄ点）となる。一方、放熱器４に供給される水温が４０℃の場合、放熱器４出口の冷媒温度は５０℃となり、冷凍サイクル状態Ｙ（図中のＡ−Ｂ−Ｃ’−Ｄ’点）となる。冷凍サイクル状態Ｙでは冷凍サイクル状態Ｘと比較して、放熱器４出口の冷媒状態は等圧のエンタルピーが高い方へ移動して冷媒密度が減少するため、放熱器４における冷媒量が減少する。したがって、放熱器４に供給される給湯水系統の水温が上昇することにより、冷凍サイクルにおける放熱器４からの流出冷媒が低密度状態となり、上記の冷凍サイクル状態Ｙでは冷媒が余ることとなる。なお、図２中のＡ，Ｂ，Ｃ，Ｄ点は、それぞれ図１の冷媒回路上に示したＡ，Ｂ，Ｃ，Ｄ点位置の冷媒状態に対応している。
【００１３】
またさらに、放熱器４に供給される給湯水系統の水温が４０℃、つまり放熱器４出口の冷媒温度が５０℃で、かつ冷媒量が変わらない場合には、放熱器４出口の冷媒密度は、等密度線上を移動して冷凍サイクルの状態Ｃ点と同じ密度、つまり状態Ｃ’’点になる。したがって、冷凍サイクル状態Ｚ（図中のＡ−Ｂ’’−Ｃ’’−Ｄ’’点を通る破線表示）となり高圧が上昇し、サイクル効率が低下することとなる。
【００１４】
図３は、冷媒として二酸化炭素を用いた冷凍サイクルにおける放熱器４出口の冷媒温度が等圧変化したときの放熱器４における冷媒量を、放熱器４出口の冷媒温度が１５℃時の冷媒量を基準にその冷媒量比を実線で示し、縦軸に放熱器冷媒量比、横軸に放熱器出口冷媒温度［℃］としている。この図の実線で示す特性値より、放熱器４出口冷媒温度が３５℃付近で急激に冷媒量比が小さくなる特異温度点が存在することが分かる。したがって、二酸化炭素を冷媒として成績係数がほぼ所定値となる圧力においては、放熱器４出口の冷媒温度が３５℃以下であれば、冷媒量比の低下が少ないため、大幅な余剰冷媒の発生を抑えることができる。
【００１５】
以上のことから、冷水槽９から第２のポンプ１０で冷却水を冷却器３に流入させて高温水を冷却し、放熱器４冷媒側出口の冷媒温度センサ１２により検知される冷媒温度が３５℃以下、例えば２５℃となるよう制御することで、上記図２に示す冷凍サイクル状態Ｙ（点線）を冷凍サイクル状態Ｘ（実線）に戻るように制御して、余剰冷媒の発生を抑えることができる。このため、アキュムレータのような余剰冷媒を調整する容器が不要となり、装置を小型化できる。
【００１６】
また、図４は二酸化炭素を冷媒とした冷凍サイクルの高圧圧力における放熱器４出口の冷媒温度に対する加熱能力の特性を表し、実線が冷却器なしの場合、点線が冷却器ありの場合を示してあり、縦軸に加熱能力［ｋＷ］、横軸に放熱器出口冷媒温度［℃］をとっている。給湯水系統回路に被加熱流体を冷却する冷却器３がない場合、放熱器４に流入する水温が上昇すると、放熱器４出口の冷媒温度も上昇して加熱能力が低下する。一般的に空調や給湯で利用する場合、二酸化炭素を冷媒とした冷凍サイクルの高圧圧力は概ね１０ＭＰａ程度であり、この圧力近傍で運転する時の放熱器４出口の冷媒温度が３０℃以下では、温度変化に対するエンタルピー変化はほぼ比例関係にあるが、３０〜５０℃付近で温度変化に対するエンタルピー変化が大きくなる。つまり、加熱能力は、冷媒流量が一定であれば放熱器４のエンタルピー差に比例するため、放熱器４出口の冷媒温度が３０℃以下では温度変化に対して比例減少し、水流量も一定となるが、３０〜５０℃付近では温度変化に対して急激に減少することになる。よって、図４に示すように、放熱器４出口の冷媒温度が３０℃以上になると急激な加熱能力の低下を起し、それに伴い水流量が減少することとなる。
【００１７】
次に被加熱流体を冷却する冷却器３がある場合の動作について説明する。前述のとおり、冷凍系統回路の放熱器４出口における冷媒温度と給湯水系統回路の放熱器４入口の被加熱流体の水温との差が一定値、例えば１０ｄｅｇになるように第２のポンプ１０の搬送量を制御した場合、放熱器４出口に設けた冷媒温度センサ１２により検出する冷媒温度は、給湯水系統回路の放熱器４入口側配管に設けた水温センサ１１により検出する水温より１０ｄｅｇ高くなる。例えば、第２のポンプ１０の搬出流量を調整して水温センサ１１による検出水温が１５℃となるように制御すると、放熱器４に流入する水温が１５℃になるので、それに伴い放熱器４出口の冷媒温度は２５℃になる。給湯水系統回路における放熱器４出口の水温を第１のポンプ２で所定値、例えば９０℃に制御した場合、水流量が一定であれば放熱器４に流入する水温に比例して加熱能力が変化する。
【００１８】
ここで、放熱器４に流入する水温が１５℃から２０℃に上がると、放熱器４出口の冷媒温度は２５℃から３０℃になる。そこで、第２のポンプ１０による冷却水の搬送流量を多くなるように制御して水温センサ１１で検知する水温が１５℃となるように制御すると、冷却器３では水温を２０℃から１５℃に冷却し、それに対応して冷媒系統回路における放熱器４出口の冷媒温度は３０℃から２５℃になる。このとき、上記放熱器４では被加熱流体の水温を１５℃から９０℃に加熱するが、被加熱流体の水流量が一定であるため、冷却器３で２０℃から１５℃まで降温する冷却能力と、放熱器４で１５℃から２０℃まで昇温する加熱能力は等しく、したがって、冷却器３なしで２０℃から９０℃に昇温する加熱能力と等しくなる。つまり、加熱能力が放熱器４出口の冷媒温度に比例して変化する範囲（放熱器４出口の冷媒温度が３０℃以下）では水流量が一定であり、実質の加熱能力は冷却器３の有無でほとんど変わらない。
【００１９】
ところが、放熱器４に流入する水温が１５℃から４０℃に上がると、それに伴い放熱器４出口冷媒温度は２５℃から５０℃になる。そこで、第２のポンプ１０の流量を制御して水温センサ１１による検知水温が１５℃となるように制御すると、冷却器３では水温を４０℃から１５℃に冷却し、放熱器４出口の冷媒温度は５０℃から２５℃になる。前述のとおり、放熱器４出口の冷媒温度が３０℃以上では冷媒温度変化に対して加熱能力が激減し、水流量が減少する。したがって、水温が１５℃から４０℃に上がると水流量が減少するので、４０℃から９０℃まで昇温する加熱能力より、水温センサ１１による検知水温が１５℃となるように制御して水流量を減少させずに放熱器４で４０℃から９０℃まで昇温する加熱能力の方が大きくなる。つまり、冷却器３なしで放熱器４出口の冷媒温度が３０℃以上となる場合には、冷却器３の作用によって加熱能力の低下が抑えられ、サイクルの成績係数が改善される。
【００２０】
以上の説明では、放熱器４入口の水温センサ１１による検知水温が所定値以下（ここでは１５℃）となるように制御した場合の説明を行なったが、放熱器４出口の冷媒温度センサ１２による検知冷媒温度が所定値以下（例えば上記の例では２５℃）となるように制御しても同様の制御が可能であるのは明らかである。
【００２１】
ここでは冷却器３で高温水を冷却するための冷熱源として冷水槽９を用いたが、当然これに限定したものではなく、氷蓄熱槽や水道水など、給湯水系統回路の被加熱流体の水より低温の熱源であればよい。また、例としてヒートポンプ給湯機を取り上げたがこれに限定されるものではなく、空気調和機でも良く同様の効果が得られる。さらには被加熱流体を水として説明したが、当然これに限定されるものではなく、ブラインやオイルを用いても同様の効果が得られる。
【００２２】
また、この発明の別の例の冷凍サイクルを図５で説明する。図５は別のヒートポンプシステムの冷媒回路図であり、貯湯タンク１、ポンプ２、冷却器３、放熱器４を順次接続して被加熱流体（例えば、水）が循環する貯湯タンク側の積層沸上げの動作については前述と同様なので省略する。冷凍サイクルは、二酸化炭素を冷媒として、圧縮機５、放熱器４、膨張弁（減圧手段）６、蒸発器７を順次配管で接続した基本冷媒回路の冷凍サイクルに放熱器４と膨張弁６の間から分岐して圧縮機５の吸入側へ合流するバイパス回路に第２の膨張弁（減圧手段）１３および冷媒と貯湯タンク側の水である被加熱流体の間で熱交換させる冷却器３を備えた冷凍サイクルから構成されている。また、貯湯タンク側の水回路における放熱器４への流入温度を検出するために放熱器４と冷却器３を接続する配管の放熱器７入口側に水温センサ１１が設けられるとともに、冷凍サイクル側の放熱器４からの流出温度を検出するために放熱器４に接続した出口側冷媒配管に冷媒温度センサ１２を備えている。
【００２３】
次に、この冷凍サイクルの動作について説明する。圧縮機５から吐出した高温高圧の冷媒は、放熱器４で被加熱流体、例えば水と熱交換して、冷媒は放熱し、水は加熱される。さらに膨張弁（減圧手段）６で減圧された冷媒は蒸発器７へ、そして第２の膨張弁（減圧手段）１３で減圧された冷媒は冷却器３へと適当な流量比で分配される。冷却器３に流入した冷媒は、冷却器３で水と熱交換して蒸発し、圧縮機５へと循環する。また、蒸発器７に流入した冷媒も、蒸発器７でファン８によって送られる空気によって蒸発し、圧縮機５へと循環して冷凍サイクルを形成する。このような構成においても第２の膨張弁１３でバイパス回路を流通する冷媒の流量および温度を変化させて、水温センサ１１により検知する被加熱流体の放熱器４への流入温度あるいは冷媒温度センサ１２により検知する放熱器４から流出する出口冷媒温度が所定値以下となるように制御でき、図１の冷凍サイクルを用いた上述と同様の動作を行わせることができる。また、この図５に示す冷凍サイクルでは分流してバイパス回路へも冷媒を流すので蒸発器７に循環する冷媒量が減少し、外気から奪う熱量が少なくなるため、それに応じて外気を蒸発器７へ送風するファン８の回転数を低くして入力を低減することができ、成績係数が向上する効果もある。
【００２４】
また、この発明のさらに別の冷凍サイクルを図６で説明する。図６はさらに別のヒートポンプシステムの冷媒回路図であり、貯湯タンク１、ポンプ２、冷却器３、放熱器４を順次接続して被加熱流体（例えば、水）が循環する貯湯タンク側の積層沸上げの動作については前述と同様なので省略する。冷凍サイクルは、二酸化炭素を冷媒として、圧縮機５、放熱器４、膨張弁（減圧手段）６、蒸発器７および流量調整手段１４を順次配管接続した基本冷媒回路の冷凍サイクルに、前記流量調整手段１４から冷媒を分流して被加熱流体と熱交換させる冷却器３を介して圧縮機５の吸入側へ合流するバイパス回路を備えた冷凍サイクルから構成されている。また、図５と同様に、貯湯タンク側の水（被加熱流体）回路の放熱器４入口側配管に水温センサ１１を、そして放熱器４出口側冷媒配管に冷媒温度センサ１２をそれぞれ備えている。
【００２５】
次に、この冷凍サイクルの動作について説明する。圧縮機５から吐出した高温高圧冷媒は、放熱器４で被加熱流体、例えば水と熱交換して、冷媒は放熱し、水は加熱される。さらに膨張弁（減圧手段）６で減圧された冷媒は、蒸発器７でファン８によって送られる空気によって蒸発して蒸発器７から流出した後、流量調整手１４へ流入する。この流量調整手段１４において、冷却器３へ流入するバイパス回路と圧縮機５へ流入する流路に適当な流量比で分配される。流量調整手段１４は、例えば流量調整可能な三方弁、あるいは分配されたいずれかの配管上に設けられた二方弁などである。そして流量調整手段１４にて分流され冷却器３に流入した冷媒は、冷却器３で被加熱流体と熱交換して蒸発し、圧縮機５の吸入側へ合流して循環する冷凍サイクルを形成する。
【００２６】
このような構成においても流量調整手段１４での基本冷媒回路と冷却器３へ流れるバイパス回路との流量比を調整することで、水温センサ１１により検知する被加熱流体の放熱器４への流入温度あるいは冷媒温度センサ１２により検知する放熱器出口冷媒温度が所定値以下となるように制御でき、図１で説明した同様の動作を行わせることができる。また、冷却器３は蒸発器７の下流側に設置されているので、圧縮機５に流入する冷媒を過熱ガスにでき、液圧縮を避けられることから圧縮機の入力が下がり性能が向上する効果がある。さらには、蒸発器７に流入する冷媒の乾き度が小さくでき、液相の比率が増えて蒸発器７で複数の経路へ均一に分配できるため性能向上の効果もある。さらには、冷媒の二酸化炭素はドライアウトが早く、蒸発器７の伝熱性能がよくなるため性能が向上する効果もある。
【００２７】
また、前記流量調整手段１４の代わりに、図７に示すように、蒸発器７を流出した冷媒を分岐して冷却器３へ流れるバイパス回路の配管上に設けられた流量調整弁１８を用いても良く、貯湯タンク側の動作及び冷凍サイクルの動作及び効果については前記と同様の効果が得られる。
【００２８】
また、この発明のさらに別の冷凍サイクルを図８で説明する。図８はさらに別のヒートポンプシステムの冷媒回路図であり、貯湯タンク１、ポンプ２、冷却器３、放熱器４を順次接続して被加熱流体（例えば、水）が循環する貯湯タンク側の積層沸上げの動作については前記と同様なので省略する。冷凍サイクルは、圧縮機１、放熱器４、膨張弁（減圧手段）６、蒸発器７を順次配管接続した基本冷媒回路の冷凍サイクルに、膨張弁６と蒸発器７の間から冷媒を分岐して被加熱流体と熱交換させる冷却器３を介して蒸発器７の流入側配管に合流するバイパス回路を備えた冷凍サイクルに二酸化炭素を冷媒として循環させるように構成されている。また、図５と同様に、貯湯タンク側の水（被加熱流体）回路の放熱器４入口側配管に水温センサ１１を、そして放熱器４出口側冷媒配管に冷媒温度センサ１２をそれぞれ備えている。
【００２９】
次に、上記冷凍サイクルの動作について説明する。圧縮機５から吐出した高温高圧の二酸化炭素の冷媒は、放熱器４で被加熱流体、例えば水と熱交換し、冷媒は放熱され、水は加熱される。さらに膨張弁（減圧手段）６で減圧された低温の冷媒は、その後流量調整手段１４にて冷却器３へ流入するバイパス回路と直接蒸発器７へ流入する流路に適当な流量比で分配される。この流量調整手段１４は、例えば流量調整可能な三方弁、あるいは分配されたいずれかの配管上に設けられた二方弁などである。上記流量調整手段１４により分流されて冷却器３に流入した低温の冷媒は、この冷却器３で被加熱流体と熱交換して蒸発し、冷却器３を流出した後蒸発器７の入口側に合流して蒸発器７へと循環する冷凍サイクルを形成する。
【００３０】
このような構成においても、流量調整手段１４での基本冷媒回路とバイパス回路への冷媒の流量比を調整することで、水温センサ１１により検知される被加熱流体の放熱器４への流入温度あるいは冷媒温度センサ１２により検知される放熱器出口冷媒温度が所定値以下となるように制御でき、図１の冷凍サイクルを用いた上述と同様の動作を行わせることができる。
【００３１】
また、前記流量調整手段１４の代わりに、図９に示すように、膨張弁６で減圧された冷媒が分岐されて冷却器３へ流入するバイパス回路の配管上に設けられた流量調整弁１８を用いても良く、貯湯タンク側の動作及び冷凍サイクルの動作及び効果については前記と同様の効果が得られる。
【００３２】
実施の形態２．
この発明の別の実施の形態を図１０から図１２を用いて説明する。ここでは一例としてダクト空調を取り上げる。
図１０は、ヒートポンプシステムを示す冷媒回路図および冷却水回路図であり、圧縮機５、放熱器４、膨張弁（減圧手段）６および蒸発器７を順次配管で接続して二酸化炭素を冷媒として循環させる基本冷媒回路と、蓄冷されて冷水が貯留した冷水槽９、第２のポンプ１０、冷却器３を順次接続した冷却水回路と、下流側に冷却器３およびその送風用ファン８と上流側に前記放熱器４を内部に配置した送風用ダクト１９から構成されている。また、放熱器４からの流出する冷媒の温度を検知するために放熱器出口側の冷媒配管に冷媒温度センサ１２を備えるとともに、前記送風用ダクト内の放熱器４に流入する空気の温度を検出するために、放熱器４の空気上流側に空気温度センサ１５を備えている。
【００３３】
次に、上記冷媒回路における冷凍サイクルの動作について説明する。圧縮機５から吐出した高温高圧の冷媒は、放熱器４で被加熱流体、例えば空気と熱交換して、冷媒は放熱し、空気は加熱される。さらに膨張弁６で減圧された冷媒は、蒸発器７に流入しファン８によって送られる外気等の空気によって蒸発して、その後圧縮機５へ流入循環する冷凍サイクルを形成する。また、冷水槽９から第２のポンプ１０で冷却水を冷却器３に流入させて送風用ダクト１９への戻り空気を冷却する。そして、この冷却された空気が同じ送風用ダクト内の上流側に設けられた放熱器４を通過して高温の冷媒と熱交換し、冷媒を冷却させる。
【００３４】
このような構成においても、冷却水回路の第２のポンプ１０による冷水の吐出流量を調整して、空気温度センサ１５により検知される放熱器４への流入空気温度あるいは冷媒温度センサ１２により検知される放熱器出口冷媒温度が所定値以下となるように制御でき、図１の冷凍サイクルを用いた上述と同様の動作を行なわせることができる。
【００３５】
また、この発明の別の例を図１１で説明する。図１１は別のヒートポンプシステムの冷媒回路図であり、二酸化炭素を冷媒として、圧縮機５、放熱器４、膨張弁（減圧手段）６、蒸発器７を順次配管で接続した基本冷媒回路に、放熱器４と膨張弁６の間から分岐して第２の膨張弁（減圧手段）１３と冷却器３を順に配設したバイパス回路が圧縮機５の吸入側に合流接続する冷凍サイクルから構成されている。そして、下流側に前記冷却器３およびその送風用ファン８と上流側に前記放熱器４を内部に配置する形態の送風用ダクト１９を備えている。また、放熱器４からの流出する冷媒の温度を検知するために放熱器出口側の冷媒配管に冷媒温度センサ１２を備えるとともに、前記送風用ダクト内の放熱器４に流入する空気の温度を検出するために、放熱器４の空気上流側に空気温度センサ１５を備えている。
【００３６】
次に、冷凍サイクルの動作について説明する。圧縮機５から吐出した高温高圧の冷媒は、放熱器４で被加熱流体、例えば空気と熱交換して、冷媒は放熱し、空気は加熱される。さらに膨張弁（減圧手段）６で減圧された冷媒は蒸発器７へ、そして第２の膨張弁１３で減圧された冷媒は冷却器３へと適当な流量比で分配される。第２の膨張弁（減圧手段）１３を介して冷却器３に流入した冷媒は、冷却器３でファン１６によって送られる空気によって蒸発し、蒸発した冷媒は再び圧縮機５へ戻り循環する。また、蒸発器７に流入した冷媒も、蒸発器７の近傍に設けられたファン８によって送られる空気によって蒸発し、圧縮機５へと循環する冷凍サイクルを形成する。冷却器３では第２の膨張弁１３で減圧された低温の冷媒によりダクト戻り空気を冷却するが、この第２の膨張弁１３における冷媒絞り量の変更で冷媒温度センサ１２により検知される放熱器４出口冷媒温度あるいは空気温度センサ１５により検知される放熱器流入空気温度が所定値以下となるように制御でき、同様の動作を行なわせることができる。また、ここでは放熱器４の出口側配管を分岐して蒸発器７と冷却器３へ分配しているが、前述の図６あるいは図８に示すように蒸発器７の上流側で膨張弁６との間もしくは蒸発器７の下流側に、流量調整手段１４を配置して冷却器３へ冷媒を分岐流入させることもでき、同様の動作を行なわせることができる。
【００３７】
また、この発明の別の例を図１２で説明する。図１２は別のヒートポンプシステムの冷媒回路図であり、二酸化炭素を冷媒として、圧縮機５、放熱器４、膨張弁（減圧手段）６、蒸発器７を順次配管で接続した冷凍サイクルに、下流側に前記冷却器３およびその送風用ファン８と上流側に前記放熱器４を内部に直列配置するとともに、前記冷却器７と放熱器４の間の風路に風量調整手段１７を有した分岐風路、例えば室内空間との空気流通可能とされた風路ダクトが接続された形態の送風用ダクト１９を備えている。また、放熱器４からの流出する冷媒の温度を検知するために放熱器出口側の冷媒配管に冷媒温度センサ１２を備えるとともに、前記送風用ダクト内の放熱器４に流入する空気の温度を検出するために、放熱器４の空気上流側に空気温度センサ１５を備えている。
【００３８】
次に、冷凍サイクルの動作について説明する。圧縮機５から吐出した高温高圧の冷媒は、放熱器４で被加熱流体、例えば空気と熱交換して、冷媒は放熱し、空気は加熱される。さらに膨張弁６で減圧された冷媒は蒸発器７でファン８によって送られる空気によって蒸発し、圧縮機５へと循環する冷凍サイクルを形成する。ここでは、蒸発器７が上述図１１での冷却器３の役割をも成し、また送風用ダクト１９内に配設された風量調整手段１７は蒸発器７を通過した空気を放熱器４と室内へバイパスする経路に分配、もしくは蒸発器７を通過した空気と室内から取り込んだ空気を放熱器４へと導くように作動する。この風量調整手段１７は例えば、電動可変ダンパなどである。このような構成においても、風量調整手段１７の風路流通開度を調整して、空気温度センサ１５により検知される放熱器４流入空気温度あるいは冷媒温度センサ１２により検知される放熱器出口冷媒温度が所定値以下となるように制御でき、同様の動作を行なわせることができる。
【００３９】
この発明は以上説明したように、冷媒を超臨界圧力まで圧縮する圧縮機、前記圧縮機から吐出した冷媒と被加熱流体とを熱交換する放熱器、冷媒を臨界圧力以下に減圧する膨張弁および蒸発器を順次接続して冷媒が循環する基本冷媒回路と、前記放熱器に流入する前記被加熱流体を冷却する冷却器と、前記放熱器と前記膨張弁の間から、または、前記蒸発器と前記圧縮機の間から、または、前記膨張弁と前記蒸発器の間のいずれかから分岐し、前記冷却器を介して前記圧縮機の吸入側へ合流するバイパス回路と、前記バイパス回路を流通する冷媒の流量を調整する流量調整手段と、前記放熱器の出口側冷媒配管に冷媒温度センサを備え、前記冷媒温度センサにより検出する冷媒温度を、冷媒の温度上昇にともない密度変化が急に減少する特異温度以下となるように前記流量調整手段を制御することによって前記冷却器の熱交換量を調整するので、冷却器の冷却量を制御することで放熱器出口冷媒温度を調整でき、冷却器の冷媒量をほぼ一定にすることができるため、アキュムレータのような余剰冷媒を調整する容器が不要となり、装置を小型化できる。また、加熱能力の低下を抑えることができ、成績係数をさらに向上することができる。
【図面の簡単な説明】
【図１】この発明の実施の形態１によるヒートポンプシステムを示す冷媒回路図である。
【図２】この発明の実施の形態１に係りヒートポンプシステムの運転状態を示すモリエル線図である。
【図３】この発明の実施の形態１に係り放熱器出口冷媒温度に対する放熱器の冷媒量変化を示す図である。
【図４】この発明の実施の形態１に係り放熱器出口冷媒温度に対する加熱能力変化を示す図である。
【図５】この発明の実施の形態１に係るヒートポンプシステムを示す別の冷媒回路図である。
【図６】この発明の実施の形態１に係るヒートポンプシステムを示すさらに別の冷媒回路図である。
【図７】この発明の実施の形態１に係るヒートポンプシステムを示す別の冷媒回路図である。
【図８】この発明の実施の形態１に係るヒートポンプシステムを示す別の冷媒回路図である。
【図９】この発明の実施の形態１に係るヒートポンプシステムを示す別の冷媒回路図である。
【図１０】この発明の実施の形態２によるヒートポンプシステムを示す別の冷媒回路図である。
【図１１】この発明の実施の形態２に係るヒートポンプシステムを示す別の冷媒回路図である。
【図１２】この発明の実施の形態２に係るヒートポンプシステムを示すさらに別の冷媒回路図である。
【符号の説明】
１貯湯タンク、２ポンプ、３冷却器、４放熱器、５圧縮機、６膨張弁、７蒸発器、８ファン、９冷水槽、１０第２のポンプ、１１水温センサ、１２冷媒温度センサ、１３第２の膨張弁、１４流量調整手段、１５空気温度センサ、１６ファン、１７
風量調整手段、１８流量調整弁、１９送風用ダクト。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat pump system and a heat pump water heater using a refrigerant that forms a supercritical cycle such as carbon dioxide.
[0002]
[Prior art]
A conventional vapor compression circuit that forms a supercritical cycle includes a compressor connected in series, a radiator, an expansion valve, an evaporator, and an accumulator, and is based on refrigerant compressed to a supercritical pressure by the compressor. The capacity adjustment of the supercritical cycle device is controlled by changing the refrigerant state at the radiator outlet. In this supercritical cycle, the refrigerant in the supercritical state is not condensed, and the temperature is lowered by the radiator. The refrigerant temperature at the radiator outlet is such that the refrigerant and the flow of air or water face each other. The temperature is a few degrees higher than the air or water temperature, and this temperature is constant regardless of the high pressure level. Therefore, the adjustment of the heating capacity in the radiator is achieved by changing the high pressure while setting the refrigerant temperature at the outlet of the radiator to a substantially constant state. The isotherm curve near the critical point of the refrigerant causes fluctuations in enthalpy due to pressure, and in order to fluctuate the pressure, it is necessary to fluctuate the mass of the refrigerant at high pressure, and it is processed by a buffer device such as an accumulator. It must be. That is, the heating capacity can be controlled by controlling the amount of refrigerant stored in the accumulator (see, for example, Patent Document 1). It is also known that there is a high pressure to obtain maximum energy efficiency in the supercritical cycle. In order to maintain the maximum energy efficiency of the vapor compression circuit, it is necessary to adjust to a predetermined high pressure, but the high pressure can be controlled by controlling the expansion device and the amount of refrigerant in the accumulator.
[0003]
[Patent Document 1]
Japanese Patent Publication No. 7-18602 (page 3-5, Fig. 2)
[0004]
[Problems to be solved by the invention]
In a hot water heater that uses a vapor compression circuit that forms such a supercritical cycle as a heat source, when low-temperature water at the bottom of the tank is heated and the high-temperature water is returned to the top of the tank and boiled up, the hot water storage tank Inside, hot water is stored in the upper part and low-temperature water is stored in the lower part. And the mixed layer with a temperature gradient arises between high temperature water and low temperature water. Since the mixed layer is supplied from the lower part of the hot water storage tank as the boiling end is approached, the temperature of the water supplied to the heat source device rises. Therefore, when the inflow temperature of the heated fluid that flows in to exchange heat with the radiator increases, the temperature of the heated fluid at the radiator outlet also increases when the flow of the refrigerant and the heated fluid is opposed to each other. The amount of refrigerant decreases. Therefore, when the supply water temperature becomes high, surplus refrigerant is generated and storage by an accumulator is required. However, since the accumulator has a function of separating gas and liquid, there is a problem that the volume of the accumulator increases and the apparatus becomes large.
[0005]
In addition, when the hot water supply fluid, which is a fluid to be heated, becomes high temperature, there is a problem that the heating ability is lowered and the coefficient of performance is lowered. The decrease in the refrigerating capacity can be suppressed by increasing the high pressure, but in that case, it is necessary to increase the pressure resistance of the apparatus, and there is a problem that the apparatus becomes large.
[0006]
The present invention has been made to solve the above-described problems, and an object of the present invention is to eliminate the need for a container for adjusting excess refrigerant such as an accumulator and to reduce the size of the apparatus. Another object of the present invention is to suppress a decrease in the coefficient of performance by suppressing a decrease in heating capacity without changing the pressure resistance of the apparatus when the hot water supply fluid that is a fluid to be heated flowing into the radiator becomes high temperature.
[0007]
[Means for Solving the Problems]
A heat pump system according to the present invention includes a compressor that compresses a refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and a fluid to be heated, an expansion valve that depressurizes the refrigerant below a critical pressure, and evaporation A basic refrigerant circuit in which the refrigerant is circulated by sequentially connecting the units, and a cooler for cooling the heated fluid flowing into the radiator Branching from between the radiator and the expansion valve, from the evaporator and the compressor, or from between the expansion valve and the evaporator, and via the cooler A bypass circuit that joins to the suction side of the compressor, a flow rate adjusting means that adjusts the flow rate of the refrigerant flowing through the bypass circuit, and a refrigerant temperature sensor in the outlet-side refrigerant pipe of the radiator With By controlling the flow rate adjusting means so that the refrigerant temperature detected by the refrigerant temperature sensor is equal to or lower than a specific temperature at which the density change suddenly decreases as the refrigerant temperature rises. The heat exchange amount of the cooler is adjusted.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 shows a refrigerant circuit diagram of a heat pump system according to Embodiment 1 of the present invention, which is a circuit diagram of a hot water supply system that takes a heat pump hot water supply as an example and uses a refrigerant system and a fluid to be heated as water. . In the figure, the refrigerant system connects a compressor 5, a radiator 4, an expansion valve (decompression unit) 6 and an evaporator 7 in order by a pipe to form a refrigeration cycle using carbon dioxide as a refrigerant. Further, the hot water supply system transports low temperature water from the lower part of the hot water storage tank 1 with a pump 2 and sequentially passes through the radiator 4 from the cooler 3 to exchange heat with high temperature refrigerant to form high temperature water. 1, and a circuit for circulating the cooling fluid cooled in the cold water tank 9 by the second pump 10 to the cooler 3. The radiator 4 uses, for example, a double pipe heat exchanger configured such that the flow of the refrigerant and the flow of hot water supply are opposed to each other. Further, in order to detect the inflow temperature of the fluid to be heated to the radiator 4 in the hot water system circuit, a water temperature sensor 11 is provided on the inlet side pipe of the radiator 4, while the refrigerant outflow temperature from the radiator 4 in the refrigerant system circuit is set. In order to detect, the refrigerant | coolant temperature sensor 12 is provided in the exit side refrigerant | coolant piping of the heat radiator 4. FIG.
[0009]
First, the operation of stacking and boiling on the hot water storage tank side will be described. The hot water storage tank 1 is filled with low temperature water, and the low temperature water is guided from the lower part of the hot water storage tank 1 to the cooler 3 by the pump 2. By the operation described later, the high-temperature water heated to a predetermined temperature by the radiator 4 flows from the upper part of the hot water storage tank 1 and is gradually stored from the upper part. Usually, the high temperature water at the upper part of the hot water storage tank 1 and the low temperature water at the lower part of the hot water storage tank 1 have a large temperature difference. However, as time passes, heat is transferred to the boundary layer by heat conduction of water, and a temperature gradient called a mixed layer is generated.
[0010]
Next, the operation of the refrigeration cycle when the supply water temperature as the fluid to be heated is low will be described. The carbon dioxide refrigerant compressed and discharged by the compressor 5 becomes a supercritical high temperature and high pressure exceeding the critical pressure, flows into the radiator 4 and exchanges heat with the fluid to be heated, for example, water, and the refrigerant dissipates heat. Isobaric cooled and still in a supercritical state, the water is heated. The refrigerant flowing out of the radiator 4 passes through the expansion valve (decompression means) 6 and is reduced in pressure to become wet steam. Thereafter, the evaporator 7 is heated at an equal pressure by the endothermic action from the air sent by the fan 8 and evaporated. A refrigeration cycle that forms saturated steam and circulates to the compressor 5 is formed.
[0011]
Next, the operation of the refrigeration cycle when the supply water temperature of the fluid to be heated rises will be described. In normal times, low-temperature water at a constant temperature is supplied to the radiator 4 and the operation state of the stable refrigeration cycle continues. However, as time passes and the hot water storage tank 1 approaches full storage, a mixed layer having a temperature gradient Water is supplied to the radiator 4. That is, high-temperature water is supplied to the radiator 4.
[0012]
Here, the refrigerant | coolant state in case the water temperature supplied to the heat radiator 4 is a low temperature and a high temperature is demonstrated using FIG. FIG. 2 is a Mollier diagram of carbon dioxide, in which the vertical axis represents pressure and the horizontal axis represents enthalpy. In FIG. 2, for example, a refrigeration cycle state X in which the refrigerant flowing out from the radiator 4 is 25 ° C. at a boiling temperature of 90 ° C. on the hot water supply side is indicated by a solid line in the drawing, and The cycle state Y is indicated by a dotted line in the figure. When heat is exchanged in the radiator 4 in a flow in which the refrigerant in the refrigeration cycle and the water in the hot water supply system face each other, the refrigerant temperature at the outlet of the radiator 4 becomes slightly higher than the water temperature at the inlet of the radiator 4. Here, when the flow rate of the hot water supply system is controlled so that the difference between the outlet refrigerant temperature flowing out of the radiator 4 and the inflowing water temperature of the heated fluid flowing into the radiator 4 becomes a constant value, for example, 10 deg. When the water temperature supplied to the refrigerant is 15 ° C., the refrigerant temperature at the outlet of the radiator 4 is 25 ° C., which is the refrigeration cycle state X (A-B-C-D point in the figure). On the other hand, when the temperature of the water supplied to the radiator 4 is 40 ° C., the refrigerant temperature at the outlet of the radiator 4 is 50 ° C., and the refrigeration cycle state Y (A-B-C′-D ′ point in the figure) is achieved. In the refrigeration cycle state Y, compared to the refrigeration cycle state X, the refrigerant state at the outlet of the radiator 4 moves toward the higher isobaric enthalpy and the refrigerant density decreases, so the amount of refrigerant in the radiator 4 decreases. Therefore, when the water temperature of the hot water supply system supplied to the radiator 4 rises, the refrigerant flowing out of the radiator 4 in the refrigeration cycle is in a low density state, and the refrigerant remains in the refrigeration cycle state Y described above. Note that points A, B, C, and D in FIG. 2 correspond to the refrigerant states at the points A, B, C, and D shown on the refrigerant circuit in FIG. 1, respectively.
[0013]
Furthermore, when the water temperature of the hot water supply system supplied to the radiator 4 is 40 ° C., that is, the refrigerant temperature at the outlet of the radiator 4 is 50 ° C. and the amount of refrigerant does not change, the refrigerant density at the outlet of the radiator 4 is , It moves on the isodensity line and becomes the same density as the state C point of the refrigeration cycle, that is, the state C ″ point. Therefore, the refrigeration cycle state Z (indicated by the broken line passing through the points AB ″ -C ″ -D ″ in the figure) is reached, and the high pressure increases, and the cycle efficiency decreases.
[0014]
FIG. 3 shows the amount of refrigerant in the radiator 4 when the refrigerant temperature at the outlet of the radiator 4 in the refrigeration cycle using carbon dioxide as the refrigerant changes at the same pressure, and the amount of refrigerant when the refrigerant temperature at the outlet of the radiator 4 is 15 ° C. As a reference, the refrigerant amount ratio is indicated by a solid line, the vertical axis is the radiator refrigerant amount ratio, and the horizontal axis is the radiator outlet refrigerant temperature [° C.]. From the characteristic value shown by the solid line in this figure, it can be seen that there is a singular temperature point where the refrigerant amount ratio suddenly decreases when the refrigerant temperature at the outlet of the radiator 4 is around 35 ° C. Therefore, if the refrigerant temperature at the outlet of the radiator 4 is 35 ° C. or less at a pressure at which the coefficient of performance is almost a predetermined value using carbon dioxide as the refrigerant, the refrigerant amount ratio will not decrease much, so that a large excess refrigerant is generated. Can be suppressed.
[0015]
From the above, cooling water is allowed to flow from the cold water tank 9 into the cooler 3 by the second pump 10 to cool the high temperature water, and the refrigerant temperature detected by the refrigerant temperature sensor 12 at the radiator 4 refrigerant side outlet is 35. By controlling the temperature to be equal to or lower than, for example, 25 ° C., the refrigeration cycle state Y (dotted line) shown in FIG. 2 is controlled to return to the refrigeration cycle state X (solid line), thereby suppressing the generation of excess refrigerant. it can. For this reason, the container which adjusts surplus refrigerant | coolants like an accumulator becomes unnecessary, and an apparatus can be reduced in size.
[0016]
FIG. 4 shows the characteristics of the heating capacity with respect to the refrigerant temperature at the outlet of the radiator 4 at the high pressure of the refrigeration cycle using carbon dioxide as a refrigerant. The solid line indicates the case without a cooler, and the dotted line indicates the case with a cooler. Yes, the vertical axis represents the heating capacity [kW], and the horizontal axis represents the radiator outlet refrigerant temperature [° C.]. When there is no cooler 3 for cooling the heated fluid in the hot water system circuit, when the temperature of the water flowing into the radiator 4 rises, the refrigerant temperature at the outlet of the radiator 4 also rises and the heating capacity is lowered. In general, when used in air conditioning or hot water supply, the high pressure of the refrigeration cycle using carbon dioxide as a refrigerant is approximately 10 MPa, and when the refrigerant temperature at the outlet of the radiator 4 when operating near this pressure is 30 ° C. or less, Although the enthalpy change with respect to the temperature change has a substantially proportional relationship, the enthalpy change with respect to the temperature change becomes large in the vicinity of 30 to 50 ° C. In other words, the heating capacity is proportional to the enthalpy difference of the radiator 4 if the refrigerant flow rate is constant. Therefore, when the refrigerant temperature at the outlet of the radiator 4 is 30 ° C. or less, the heating capacity decreases proportionally to the temperature change, and the water flow rate is also constant. However, in the vicinity of 30 to 50 ° C., it rapidly decreases with respect to the temperature change. Therefore, as shown in FIG. 4, when the refrigerant temperature at the outlet of the radiator 4 becomes 30 ° C. or higher, the heating capacity is suddenly lowered, and the water flow rate is reduced accordingly.
[0017]
Next, an operation in the case where there is a cooler 3 that cools the fluid to be heated will be described. As described above, the second pump 10 is configured so that the difference between the refrigerant temperature at the outlet of the radiator 4 of the refrigeration system circuit and the water temperature of the fluid to be heated at the inlet of the radiator 4 of the hot water system circuit becomes a constant value, for example, 10 deg. When the transport amount is controlled, the refrigerant temperature detected by the refrigerant temperature sensor 12 provided at the outlet of the radiator 4 is 10 degrees higher than the water temperature detected by the water temperature sensor 11 provided in the radiator 4 inlet side piping of the hot water supply system circuit. . For example, when the discharge flow rate of the second pump 10 is adjusted to control the water temperature detected by the water temperature sensor 11 to be 15 ° C., the water temperature flowing into the radiator 4 becomes 15 ° C. The refrigerant temperature becomes 25 ° C. When the water temperature at the outlet of the radiator 4 in the hot water system circuit is controlled to a predetermined value, for example, 90 ° C. by the first pump 2, the heating capacity is proportional to the water temperature flowing into the radiator 4 if the water flow rate is constant. Change.
[0018]
Here, when the temperature of the water flowing into the radiator 4 rises from 15 ° C. to 20 ° C., the refrigerant temperature at the outlet of the radiator 4 becomes 25 ° C. to 30 ° C. Therefore, when the cooling water conveyance flow rate by the second pump 10 is controlled to be increased so that the water temperature detected by the water temperature sensor 11 is 15 ° C., the water temperature is changed from 20 ° C. to 15 ° C. in the cooler 3. In response to the cooling, the refrigerant temperature at the outlet of the radiator 4 in the refrigerant system circuit is changed from 30 ° C. to 25 ° C. At this time, in the radiator 4, the water temperature of the heated fluid is heated from 15 ° C. to 90 ° C., but since the water flow rate of the heated fluid is constant, the cooling ability to lower the temperature from 20 ° C. to 15 ° C. in the cooler 3. Thus, the heating capability for raising the temperature from 15 ° C. to 20 ° C. with the radiator 4 is equal, and therefore the heating capability for raising the temperature from 20 ° C. to 90 ° C. without the cooler 3 is equal. That is, the water flow rate is constant in the range in which the heating capacity changes in proportion to the refrigerant temperature at the outlet of the radiator 4 (the refrigerant temperature at the outlet of the radiator 4 is 30 ° C. or less). Almost no change.
[0019]
However, when the temperature of the water flowing into the radiator 4 rises from 15 ° C. to 40 ° C., the refrigerant temperature at the outlet of the radiator 4 becomes 25 ° C. to 50 ° C. accordingly. Therefore, when the flow rate of the second pump 10 is controlled so that the water temperature detected by the water temperature sensor 11 is 15 ° C., the cooler 3 cools the water temperature from 40 ° C. to 15 ° C., and the refrigerant at the outlet of the radiator 4 The temperature goes from 50 ° C to 25 ° C. As described above, when the refrigerant temperature at the outlet of the radiator 4 is 30 ° C. or higher, the heating capacity is drastically reduced with respect to the refrigerant temperature change, and the water flow rate is reduced. Therefore, since the water flow rate decreases when the water temperature rises from 15 ° C. to 40 ° C., the water flow rate is controlled by controlling the water temperature detected by the water temperature sensor 11 to be 15 ° C. from the heating capability of raising the temperature from 40 ° C. to 90 ° C. The heating ability to raise the temperature from 40 ° C. to 90 ° C. with the radiator 4 without decreasing the temperature becomes larger. That is, when the refrigerant temperature at the outlet of the radiator 4 is 30 ° C. or higher without the cooler 3, the cooling capacity is reduced by the action of the cooler 3, and the coefficient of performance of the cycle is improved.
[0020]
In the above description, the case where the water temperature detected by the water temperature sensor 11 at the inlet of the radiator 4 is controlled to be equal to or lower than a predetermined value (here, 15 ° C.) has been described, but the refrigerant temperature sensor 12 at the outlet of the radiator 4 is used. It is obvious that the same control can be performed even if the detected refrigerant temperature is controlled to be equal to or lower than a predetermined value (for example, 25 ° C. in the above example).
[0021]
Here, the chilled water tank 9 is used as a cold heat source for cooling the high-temperature water by the cooler 3, but it is not limited to this. Naturally, it is not limited to this. Any heat source lower than water may be used. Moreover, although the heat pump water heater was taken up as an example, it is not limited to this, An air conditioner may be used and the same effect is acquired. Furthermore, although the fluid to be heated has been described as water, it is naturally not limited to this, and the same effect can be obtained by using brine or oil.
[0022]
Moreover, the refrigeration cycle of another example of this invention is demonstrated in FIG. FIG. 5 is a refrigerant circuit diagram of another heat pump system, in which a hot water storage tank 1, a pump 2, a cooler 3, and a radiator 4 are connected in order to circulate a heated fluid (for example, water) on the hot water storage tank side. Since the raising operation is the same as described above, the description thereof is omitted. The refrigeration cycle uses carbon dioxide as a refrigerant, the compressor 5, the radiator 4, the expansion valve (decompression unit) 6, and the evaporator 7 connected to the refrigeration cycle of the basic refrigerant circuit in order by piping. The second expansion valve (decompression means) 13 and the cooler 3 that exchanges heat between the refrigerant and the heated fluid that is water on the hot water storage tank side are connected to the bypass circuit that branches from the middle and joins to the suction side of the compressor 5. It consists of a refrigeration cycle equipped. In addition, a water temperature sensor 11 is provided on the inlet side of the radiator 7 of the pipe connecting the radiator 4 and the cooler 3 in order to detect the inflow temperature to the radiator 4 in the water circuit on the hot water storage tank side, and the refrigeration cycle side The refrigerant temperature sensor 12 is provided in the outlet side refrigerant piping connected to the radiator 4 in order to detect the temperature of the outflow from the radiator 4.
[0023]
Next, the operation of this refrigeration cycle will be described. The high-temperature and high-pressure refrigerant discharged from the compressor 5 exchanges heat with a fluid to be heated, for example, water, in the radiator 4, and the refrigerant dissipates heat and the water is heated. Further, the refrigerant decompressed by the expansion valve (decompression unit) 6 is distributed to the evaporator 7, and the refrigerant decompressed by the second expansion valve (decompression unit) 13 is distributed to the cooler 3 at an appropriate flow ratio. The refrigerant flowing into the cooler 3 evaporates by exchanging heat with water in the cooler 3 and circulates to the compressor 5. The refrigerant that has flowed into the evaporator 7 is also evaporated by the air sent by the fan 8 in the evaporator 7 and circulates to the compressor 5 to form a refrigeration cycle. Even in such a configuration, the flow rate and temperature of the refrigerant flowing through the bypass circuit are changed by the second expansion valve 13, and the inflow temperature of the heated fluid detected by the water temperature sensor 11 or the refrigerant temperature sensor 12 is detected. The outlet refrigerant temperature flowing out from the radiator 4 detected by the above can be controlled to be a predetermined value or less, and the same operation as described above using the refrigeration cycle of FIG. 1 can be performed. Further, in the refrigeration cycle shown in FIG. 5, since the refrigerant is diverted and flows also to the bypass circuit, the amount of refrigerant circulating to the evaporator 7 is reduced and the amount of heat taken from the outside air is reduced. The number of rotations of the fan 8 that blows air can be lowered to reduce the input, and the coefficient of performance is improved.
[0024]
Still another refrigeration cycle of the present invention will be described with reference to FIG. FIG. 6 is a refrigerant circuit diagram of still another heat pump system, in which a hot water storage tank 1, a pump 2, a cooler 3, and a radiator 4 are sequentially connected to stack a hot water storage tank side in which a fluid to be heated (for example, water) circulates. Since the boiling operation is the same as described above, the description is omitted. The refrigeration cycle uses the carbon dioxide as the refrigerant, the flow rate adjustment to the refrigeration cycle of the basic refrigerant circuit in which the compressor 5, the radiator 4, the expansion valve (decompression means) 6, the evaporator 7 and the flow rate adjustment means 14 are connected in order by piping. The refrigeration cycle is provided with a bypass circuit that joins the suction side of the compressor 5 via the cooler 3 that diverts the refrigerant from the means 14 and exchanges heat with the fluid to be heated. Similarly to FIG. 5, the water temperature sensor 11 is provided in the radiator 4 inlet-side piping of the water (heated fluid) circuit on the hot water storage tank side, and the refrigerant temperature sensor 12 is provided in the radiator 4 outlet-side refrigerant piping. .
[0025]
Next, the operation of this refrigeration cycle will be described. The high-temperature and high-pressure refrigerant discharged from the compressor 5 exchanges heat with a fluid to be heated, for example, water, in the radiator 4, and the refrigerant dissipates heat and the water is heated. Further, the refrigerant depressurized by the expansion valve (decompression unit) 6 evaporates by the air sent by the fan 8 in the evaporator 7 and flows out of the evaporator 7, and then flows into the flow rate adjusting hand 14. In the flow rate adjusting means 14, the flow rate is distributed to the bypass circuit flowing into the cooler 3 and the flow path flowing into the compressor 5 at an appropriate flow rate ratio. The flow rate adjusting means 14 is, for example, a three-way valve capable of adjusting the flow rate, or a two-way valve provided on any distributed pipe. Then, the refrigerant divided by the flow rate adjusting means 14 and flowing into the cooler 3 evaporates by exchanging heat with the fluid to be heated in the cooler 3 and joins and circulates to the suction side of the compressor 5 to form a refrigeration cycle. .
[0026]
Even in such a configuration, the inflow temperature of the heated fluid detected by the water temperature sensor 11 to the radiator 4 is adjusted by adjusting the flow ratio of the basic refrigerant circuit in the flow rate adjusting means 14 and the bypass circuit flowing to the cooler 3. Alternatively, the radiator outlet refrigerant temperature detected by the refrigerant temperature sensor 12 can be controlled to be equal to or lower than a predetermined value, and the same operation as described in FIG. 1 can be performed. Moreover, since the cooler 3 is installed on the downstream side of the evaporator 7, the refrigerant flowing into the compressor 5 can be used as superheated gas, and liquid compression can be avoided, so that the input of the compressor is lowered and the performance is improved. There is. Furthermore, the dryness of the refrigerant flowing into the evaporator 7 can be reduced, the liquid phase ratio can be increased, and the evaporator 7 can be uniformly distributed to a plurality of paths. Furthermore, the carbon dioxide refrigerant has a fast dry out effect, and the heat transfer performance of the evaporator 7 is improved.
[0027]
Further, instead of the flow rate adjusting means 14, as shown in FIG. 7, a flow rate adjusting valve 18 provided on the bypass circuit pipe that branches the refrigerant flowing out of the evaporator 7 and flows to the cooler 3 is used. As for the operation on the hot water storage tank side and the operation and effect of the refrigeration cycle, the same effect as described above can be obtained.
[0028]
Further, another refrigeration cycle of the present invention will be described with reference to FIG. FIG. 8 is a refrigerant circuit diagram of still another heat pump system, in which a hot water storage tank 1, a pump 2, a cooler 3, and a radiator 4 are connected in sequence so that a heated fluid (for example, water) circulates. Since the boiling operation is the same as described above, the description is omitted. The refrigeration cycle branches the refrigerant from between the expansion valve 6 and the evaporator 7 to the refrigeration cycle of the basic refrigerant circuit in which the compressor 1, the radiator 4, the expansion valve (decompression unit) 6, and the evaporator 7 are sequentially connected by piping. Thus, carbon dioxide is circulated as a refrigerant in a refrigeration cycle having a bypass circuit that joins the inflow side piping of the evaporator 7 via the cooler 3 that exchanges heat with the fluid to be heated. Similarly to FIG. 5, the water temperature sensor 11 is provided in the radiator 4 inlet-side piping of the water (heated fluid) circuit on the hot water storage tank side, and the refrigerant temperature sensor 12 is provided in the radiator 4 outlet-side refrigerant piping. .
[0029]
Next, the operation of the refrigeration cycle will be described. The high-temperature and high-pressure carbon dioxide refrigerant discharged from the compressor 5 exchanges heat with a fluid to be heated, such as water, in the radiator 4, and the refrigerant is dissipated to heat the water. Further, the low-temperature refrigerant depressurized by the expansion valve (decompression unit) 6 is then distributed by the flow rate adjusting unit 14 to the bypass circuit flowing into the cooler 3 and the flow path directly flowing into the evaporator 7 at an appropriate flow rate ratio. The The flow rate adjusting means 14 is, for example, a three-way valve capable of adjusting the flow rate, or a two-way valve provided on any distributed pipe. The low-temperature refrigerant that is diverted by the flow rate adjusting means 14 and flows into the cooler 3 evaporates by exchanging heat with the fluid to be heated in the cooler 3, flows out of the cooler 3, and then enters the inlet side of the evaporator 7. A refrigeration cycle that joins and circulates to the evaporator 7 is formed.
[0030]
Even in such a configuration, by adjusting the flow rate ratio of the refrigerant to the basic refrigerant circuit and the bypass circuit in the flow rate adjusting means 14, the inflow temperature of the heated fluid detected by the water temperature sensor 11 to the radiator 4 or The radiator outlet refrigerant temperature detected by the refrigerant temperature sensor 12 can be controlled to be equal to or lower than a predetermined value, and the same operation as described above using the refrigeration cycle of FIG. 1 can be performed.
[0031]
Further, instead of the flow rate adjusting means 14, as shown in FIG. 9, a flow rate adjusting valve 18 provided on the bypass circuit pipe in which the refrigerant decompressed by the expansion valve 6 is branched and flows into the cooler 3 is provided. You may use, and the effect similar to the above is acquired about the operation | movement by the side of a hot water storage tank, and the operation | movement and effect of a refrigerating cycle.
[0032]
Embodiment 2. FIG.
Another embodiment of the present invention will be described with reference to FIGS. Here, duct air conditioning is taken as an example.
FIG. 10 is a refrigerant circuit diagram and a cooling water circuit diagram showing the heat pump system, in which the compressor 5, the radiator 4, the expansion valve (decompression unit) 6 and the evaporator 7 are sequentially connected by piping to use carbon dioxide as a refrigerant. A basic refrigerant circuit to be circulated, a chilled water tank 9 in which cold water is stored and stored chilled water, a second pump 10 and a cooler 3 are sequentially connected, and the cooler 3 and its blower fan 8 and upstream are connected downstream. It is comprised from the duct 19 for ventilation which has arrange | positioned the said heat radiator 4 inside by the side. Further, in order to detect the temperature of the refrigerant flowing out from the radiator 4, a refrigerant temperature sensor 12 is provided in the refrigerant pipe on the outlet side of the radiator, and the temperature of the air flowing into the radiator 4 in the air duct is detected. For this purpose, an air temperature sensor 15 is provided on the air upstream side of the radiator 4.
[0033]
Next, the operation of the refrigeration cycle in the refrigerant circuit will be described. The high-temperature and high-pressure refrigerant discharged from the compressor 5 exchanges heat with a fluid to be heated, for example, air, in the radiator 4, and the refrigerant dissipates heat, and the air is heated. Further, the refrigerant depressurized by the expansion valve 6 evaporates by air such as outside air that flows into the evaporator 7 and is sent by the fan 8, and then forms a refrigeration cycle that flows into the compressor 5 and circulates. Further, the cooling water is caused to flow into the cooler 3 by the second pump 10 from the cold water tank 9 to cool the return air to the air duct 19. And this cooled air passes the heat radiator 4 provided in the upstream in the same ventilation duct, heat-exchanges with a high temperature refrigerant | coolant, and cools a refrigerant | coolant.
[0034]
Even in such a configuration, the cooling water discharge flow rate by the second pump 10 of the cooling water circuit is adjusted, and the temperature of the air flowing into the radiator 4 detected by the air temperature sensor 15 or the refrigerant temperature sensor 12 is detected. The radiator outlet refrigerant temperature can be controlled to be equal to or lower than a predetermined value, and the same operation as described above using the refrigeration cycle of FIG. 1 can be performed.
[0035]
Another example of the present invention will be described with reference to FIG. FIG. 11 is a refrigerant circuit diagram of another heat pump system. A basic refrigerant circuit in which a compressor 5, a radiator 4, an expansion valve (decompression unit) 6, and an evaporator 7 are sequentially connected by piping using carbon dioxide as a refrigerant. A bypass circuit that branches from between the radiator 4 and the expansion valve 6 and in which a second expansion valve (decompression unit) 13 and a cooler 3 are arranged in order is composed of a refrigeration cycle that joins and connects to the suction side of the compressor 5. ing. The cooler 3 and its blower fan 8 are provided on the downstream side, and the blower duct 19 is provided on the upstream side with the radiator 4 disposed therein. Further, in order to detect the temperature of the refrigerant flowing out from the radiator 4, a refrigerant temperature sensor 12 is provided in the refrigerant pipe on the outlet side of the radiator, and the temperature of the air flowing into the radiator 4 in the air duct is detected. For this purpose, an air temperature sensor 15 is provided on the air upstream side of the radiator 4.
[0036]
Next, the operation of the refrigeration cycle will be described. The high-temperature and high-pressure refrigerant discharged from the compressor 5 exchanges heat with a fluid to be heated, for example, air, in the radiator 4, and the refrigerant dissipates heat, and the air is heated. Further, the refrigerant decompressed by the expansion valve (decompression means) 6 is distributed to the evaporator 7, and the refrigerant decompressed by the second expansion valve 13 is distributed to the cooler 3 at an appropriate flow ratio. The refrigerant that has flowed into the cooler 3 via the second expansion valve (decompression means) 13 is evaporated by the air sent by the fan 16 in the cooler 3, and the evaporated refrigerant returns to the compressor 5 and circulates again. The refrigerant flowing into the evaporator 7 is also evaporated by the air sent by the fan 8 provided in the vicinity of the evaporator 7 to form a refrigeration cycle that circulates to the compressor 5. In the cooler 3, the duct return air is cooled by the low-temperature refrigerant decompressed by the second expansion valve 13, and the radiator that is detected by the refrigerant temperature sensor 12 by changing the refrigerant throttle amount in the second expansion valve 13. It is possible to control the radiator outlet air temperature detected by the 4-outlet refrigerant temperature or the air temperature sensor 15 to be equal to or lower than a predetermined value, and the same operation can be performed. Here, the outlet side piping of the radiator 4 is branched and distributed to the evaporator 7 and the cooler 3, but the expansion valve 6 is upstream of the evaporator 7 as shown in FIG. 6 or FIG. The flow rate adjusting means 14 can be arranged between the two and the downstream side of the evaporator 7 to branch the refrigerant into the cooler 3, and the same operation can be performed.
[0037]
Another example of the present invention will be described with reference to FIG. FIG. 12 is a refrigerant circuit diagram of another heat pump system, in which a compressor 5, a radiator 4, an expansion valve (decompression means) 6, and an evaporator 7 are sequentially connected downstream by a pipe using carbon dioxide as a refrigerant. The cooler 3 and its blower fan 8 on the side and the radiator 4 on the upstream side are arranged in series inside, and a branch having an air volume adjusting means 17 in the air path between the cooler 7 and the radiator 4 The air duct 19 is provided with a blower duct 19 connected to an air duct that is capable of air circulation with, for example, an indoor space. Further, in order to detect the temperature of the refrigerant flowing out from the radiator 4, a refrigerant temperature sensor 12 is provided in the refrigerant pipe on the outlet side of the radiator, and the temperature of the air flowing into the radiator 4 in the air duct is detected. For this purpose, an air temperature sensor 15 is provided on the air upstream side of the radiator 4.
[0038]
Next, the operation of the refrigeration cycle will be described. The high-temperature and high-pressure refrigerant discharged from the compressor 5 exchanges heat with a fluid to be heated, for example, air, in the radiator 4, and the refrigerant dissipates heat, and the air is heated. Further, the refrigerant depressurized by the expansion valve 6 evaporates by the air sent by the fan 8 in the evaporator 7 and forms a refrigeration cycle that circulates to the compressor 5. Here, the evaporator 7 also serves as the cooler 3 in FIG. 11 described above, and the air volume adjusting means 17 disposed in the air duct 19 allows the air passing through the evaporator 7 to be exchanged with the radiator 4. The air is distributed to the path to be bypassed into the room, or the air that has passed through the evaporator 7 and the air taken in from the room are guided to the radiator 4. The air volume adjusting means 17 is, for example, an electric variable damper. Even in such a configuration, the air passage flow opening degree of the air volume adjusting means 17 is adjusted, and the radiator 4 inflow air temperature detected by the air temperature sensor 15 or the radiator outlet refrigerant temperature detected by the refrigerant temperature sensor 12. Can be controlled to be equal to or less than a predetermined value, and the same operation can be performed.
[0039]
As described above, the present invention includes a compressor that compresses a refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and a fluid to be heated, an expansion valve that depressurizes the refrigerant below a critical pressure, and A basic refrigerant circuit in which refrigerant is circulated by sequentially connecting evaporators, and a cooler for cooling the heated fluid flowing into the radiator Branching from between the radiator and the expansion valve, from the evaporator and the compressor, or from between the expansion valve and the evaporator, and via the cooler A bypass circuit that joins to the suction side of the compressor, a flow rate adjusting means that adjusts the flow rate of the refrigerant flowing through the bypass circuit, and a refrigerant temperature sensor in the outlet-side refrigerant pipe of the radiator With By controlling the flow rate adjusting means so that the refrigerant temperature detected by the refrigerant temperature sensor is equal to or lower than a specific temperature at which the density change suddenly decreases as the refrigerant temperature rises. Since the amount of heat exchange in the cooler is adjusted, the temperature of the radiator outlet refrigerant can be adjusted by controlling the amount of cooling in the cooler, and the amount of refrigerant in the cooler can be made almost constant. A container for adjusting the surplus refrigerant becomes unnecessary, and the apparatus can be miniaturized. Moreover, the fall of a heating capability can be suppressed and a coefficient of performance can be improved further.
[Brief description of the drawings]
FIG. 1 is a refrigerant circuit diagram showing a heat pump system according to Embodiment 1 of the present invention.
FIG. 2 is a Mollier diagram showing the operating state of the heat pump system according to Embodiment 1 of the present invention;
FIG. 3 is a diagram illustrating a refrigerant amount change of the radiator with respect to the radiator outlet refrigerant temperature according to the first embodiment of the present invention.
FIG. 4 is a diagram showing a change in heating capacity with respect to a radiator outlet refrigerant temperature according to the first embodiment of the present invention.
FIG. 5 is another refrigerant circuit diagram showing the heat pump system according to Embodiment 1 of the present invention.
FIG. 6 is still another refrigerant circuit diagram showing the heat pump system according to Embodiment 1 of the present invention.
FIG. 7 is another refrigerant circuit diagram showing the heat pump system according to Embodiment 1 of the present invention.
FIG. 8 is another refrigerant circuit diagram showing the heat pump system according to Embodiment 1 of the present invention.
FIG. 9 is another refrigerant circuit diagram showing the heat pump system according to Embodiment 1 of the present invention.
FIG. 10 is another refrigerant circuit diagram showing a heat pump system according to Embodiment 2 of the present invention.
FIG. 11 is another refrigerant circuit diagram showing a heat pump system according to Embodiment 2 of the present invention.
FIG. 12 is still another refrigerant circuit diagram showing the heat pump system according to Embodiment 2 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Hot water storage tank, 2 Pump, 3 Cooler, 4 Radiator, 5 Compressor, 6 Expansion valve, 7 Evaporator, 8 Fan, 9 Chilled water tank, 10 2nd pump, 11 Water temperature sensor, 12 Refrigerant temperature sensor, 13 Second expansion valve, 14 flow rate adjusting means, 15 air temperature sensor, 16 fan, 17
Air volume adjusting means, 18 flow rate adjusting valve, 19 air duct.

Claims

A compressor that compresses the refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and the fluid to be heated, an expansion valve that depressurizes the refrigerant below the critical pressure, and an evaporator are sequentially connected to form a refrigerant. A circulating basic refrigerant circuit, a cooler that cools the heated fluid flowing into the radiator, between the radiator and the expansion valve, or between the evaporator and the compressor, or A bypass circuit that branches from one of the expansion valve and the evaporator and joins to the suction side of the compressor via the cooler; and a flow rate adjusting means that adjusts the flow rate of the refrigerant flowing through the bypass circuit And a refrigerant temperature sensor on the outlet side refrigerant pipe of the radiator ,
The heat exchange amount of the cooler is adjusted by controlling the flow rate adjusting means so that the refrigerant temperature detected by the refrigerant temperature sensor is equal to or lower than a specific temperature at which the density change suddenly decreases as the refrigerant temperature rises. A heat pump system characterized by that.

A compressor that compresses the refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and the fluid to be heated, an expansion valve that depressurizes the refrigerant below the critical pressure, and an evaporator are sequentially connected to form a refrigerant. A circulating basic refrigerant circuit, a cooler that cools the heated fluid flowing into the radiator, between the radiator and the expansion valve, or between the evaporator and the compressor, or A bypass circuit that branches from one of the expansion valve and the evaporator and joins to the suction side of the compressor via the cooler; and a flow rate adjusting means that adjusts the flow rate of the refrigerant flowing through the bypass circuit And a heated fluid temperature sensor for detecting the temperature of the heated fluid flowing into the radiator ,
The heated fluid temperature detected by the heated fluid temperature sensor is set such that the temperature of the refrigerant flowing out of the radiator is equal to or lower than a singular temperature where the density change suddenly decreases with respect to the temperature rise of the refrigerant in a supercritical state. A heat pump system that controls the temperature of the fluid to be heated by controlling a flow rate adjusting means to adjust a heat exchange amount of the cooler.

The bypass circuit branches from between the radiator and the expansion valve of the basic refrigerant circuit and joins to the suction side of the compressor ,
The flow rate adjusting means, the heat pump system according to claim 1 or 2, characterized in that said cooler second expansion valve provided on the upstream side of the bypass circuit.

The bypass circuit, the suction of the evaporator and the compressor the refrigerant pipe branched from the flow rate adjusting means provided between the compressor through the cooler for cooling the heated fluid of the basic refrigerant circuit the heat pump system according to claim 1 or 2, characterized in that to join the side.

The bypass circuit, the suction of the expansion valve and the evaporator said compressor via said cooler refrigerant pipe branched from the flow rate adjusting means provided to cool the heated fluid between the basic refrigerant circuit the heat pump system according to claim 1 or 2, characterized in that to join the side.

The heat pump system according to any one of claims 1 to 5 , wherein carbon dioxide is used as the refrigerant.

A compressor that compresses the carbon dioxide refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and the fluid to be heated, an expansion valve that reduces the refrigerant below the critical pressure, and an evaporator are sequentially connected. A basic refrigerant circuit through which the refrigerant circulates, a lower part of the hot water storage tank for storing the heated fluid, a pump for conveying the heated fluid, a cooler for cooling the heated fluid, the radiator and the hot water storage tank A hot water supply circuit in which hot water is circulated by sequentially connecting the upper part thereof, between the radiator and the expansion valve, between the evaporator and the compressor, or between the expansion valve and the evaporator A bypass circuit that branches from any of the two and joins to the suction side of the compressor via the cooler, a flow rate adjusting means that adjusts a flow rate of refrigerant flowing through the bypass circuit, and an outlet of the radiator Side refrigerant distribution Includes a refrigerant temperature sensor,
The heat exchange amount of the cooler is adjusted by controlling the flow rate adjusting means so that the refrigerant temperature detected by the refrigerant temperature sensor is equal to or lower than a specific temperature at which the density change suddenly decreases as the refrigerant temperature rises. A heat pump type water heater characterized by that.

A compressor that compresses the carbon dioxide refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and the fluid to be heated, an expansion valve that reduces the refrigerant below the critical pressure, and an evaporator are sequentially connected. A basic refrigerant circuit through which the refrigerant circulates, a lower part of the hot water storage tank for storing the heated fluid, a pump for conveying the heated fluid, a cooler for cooling the heated fluid, the radiator and the hot water storage tank A hot water supply circuit in which hot water is circulated by sequentially connecting the upper part thereof, between the radiator and the expansion valve, between the evaporator and the compressor, or between the expansion valve and the evaporator A bypass circuit that branches from any of the two and joins to the suction side of the compressor via the cooler, a flow rate adjusting means that adjusts the flow rate of the refrigerant that flows through the bypass circuit, and flows into the radiator To do Comprising a heated fluid temperature sensor for detecting the temperature of the heating fluid,
The heated fluid temperature detected by the heated fluid temperature sensor is set such that the temperature of the refrigerant flowing out of the radiator is equal to or lower than a singular temperature where the density change suddenly decreases with respect to the temperature rise of the refrigerant in a supercritical state. A heat pump type hot water heater characterized by controlling the fluid temperature to be heated by controlling a flow rate adjusting means and adjusting a heat exchange amount of the cooler.