JP4690574B2 - Control method and control device for expansion valve in refrigerator - Google Patents

Control method and control device for expansion valve in refrigerator Download PDF

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JP4690574B2
JP4690574B2 JP2001117690A JP2001117690A JP4690574B2 JP 4690574 B2 JP4690574 B2 JP 4690574B2 JP 2001117690 A JP2001117690 A JP 2001117690A JP 2001117690 A JP2001117690 A JP 2001117690A JP 4690574 B2 JP4690574 B2 JP 4690574B2
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expansion valve
refrigerator
temperature
refrigerant
opening degree
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憲治 上田
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Mitsubishi Heavy Industries Ltd
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Description

【０００１】
【発明の属する技術分野】
本発明は冷凍機における膨張弁の制御方法及び制御装置に関し、特に各種の物理量に基づき循環冷媒量を演算し、この循環冷媒量に対応する最適な開度指令を生成して膨張弁を制御する場合に適用して有用なものである。
【０００２】
【従来の技術】
図３はターボ冷凍機を示すブロック図である。同図に示すように、当該ターボ冷凍機では、蒸発器１において負荷に供給する冷水により吸熱されて気化した冷媒を、ターボ圧縮機２で圧縮して高温・高圧の冷媒ガスとする。この高温・高圧の冷媒ガスは、凝縮器３で冷却水により冷却されて凝縮し、液化して冷媒液となる。その後、この冷媒液は、膨張弁４に至り、この膨張弁４で膨張されて低圧となり蒸発器１に至る。蒸発器１では、冷媒液が冷水と熱交換することにより蒸発して上述の如き冷凍サイクルが繰り返される。
【０００３】
ここで、当該ターボ冷凍機においては、負荷に供給する冷水の温度、すなわち冷水出口温度が設定値になるようにその温度制御を行う必要がある。かかる冷水の温度制御は、一般に、ターボ圧縮機２のベーン２ａの開度を電動機２ｂで調整し、吸入冷媒量を制御することにより行っている。
【０００４】
一方、膨張弁４の開度も冷媒の循環量に応じて適切に制御する必要がある。そこで、ターボ冷凍機等の大型冷凍機では、膨張弁４の上流側（凝縮器、中間冷却器、受液器）の冷媒液の液面を一定に保つ液面制御により膨張弁４の弁開度制御を実施している。
【０００５】
【発明が解決しようとする課題】
上述の如き冷媒液の液面制御による膨張弁４の弁開度制御において、制御対象となる膨張弁４は、電動機４ａの回転で弁開度を制御する電動機駆動の電磁制御弁が通常用いられている。このため、冷水温度を設定値に保持すべく行うターボ圧縮機２の吸入冷媒量の制御に対して膨張弁４の弁開度制御の遅れを生起する。冷媒液の液面の変動に対して電動機駆動による膨張弁４の開閉を追従させることができないからである。かかる制御遅れは、膨張弁４の上流側の冷媒液の液面の上昇及び蒸発器１内の圧力の異常低下の原因等となって冷凍機の運転を不安定なものとする。
【０００６】
そこで、かかる不安定要素を除去すべく、従来の冷凍機においては、膨張弁４の弁開度制御の精度を落としていた。すなわち、当該弁開度制御のパラメータを厳密なものとせず、膨張弁４の弁開度がその最適値よりも若干開き気味になるような制御を行っている。ところが、これは負荷が変動した場合（ターボ圧縮機２で吸入冷媒量の制御を行う場合）に膨張弁４を介して蒸発器１内に冷媒ガスが流入するのを許容することともなる。ところが、蒸発器１内に混入した冷媒ガスは冷水の冷却には寄与しない。したがって、蒸発器１内に冷媒ガスが混入した場合には、混入した分、当該ターボ冷凍機の運転効率が低下する。すなわち、冷媒ガスが１％混入すれば、当該冷凍機の運転効率も１％低下する。
【０００７】
一方、冷水温度制御に伴うターボ圧縮機２の吸入冷媒量の制御に対する膨張弁４の弁開度制御の遅れの低減は、この膨張弁４を動作速度が速い空気圧駆動又は油圧駆動のシリンダー駆動弁で形成することによりある程度緩和し得る。ところが、このシリンダー駆動弁は大嵩であるばかりでなく高価であり、コストの高騰を招来するという問題がある。
【０００８】
なお、上述の如き問題は、ターボ冷凍機に固有のものではなく、圧縮機が異なる他の種類の冷凍機でも、一般に発生する。
【０００９】
本発明は、上記従来技術の問題点に鑑み、通常の電動制御弁を膨張弁とする場合でも、上流側に冷媒液の液面を常に作り、凝縮器で凝縮しない冷媒ガスが循環することを防止し、冷凍機効率の低下を防止し得る冷凍機における膨張弁の制御方法及び制御装置を提供することを目的とする。
【００１０】
【課題を解決するための手段】
上記目的を達成する本発明の構成は次の点を特徴とする。
【００１１】
１） 凝縮器から蒸発器に至る管路の途中に配設されて冷媒を膨張させるための膨張弁の制御方法において、
蒸発器における流入冷水又は流入ブラインの温度と、流出冷水又は流出ブラインの温度との差に基づいて演算により得る当該冷凍機の第１の冷凍能力を媒介として、当該冷凍機における冷媒の第１の循環量を演算し、さらにこの第１の循環量と、膨張弁の上流側の圧力及び下流側の圧力とに基づく演算により膨張弁の開度を制御するための第１の開度指令を形成する一方、
前記蒸発器における流入冷水又は流入ブラインの温度と、流出冷水又は流出ブラインの設定温度に基づいて予め設定した設定温度との差に基づいて演算により得る当該冷凍機の第２の冷凍能力を媒介として、当該冷凍機における冷媒の第２の循環量を演算し、さらにこの第２の循環量と、膨張弁の上流側の圧力及び下流側の圧力とに基づく演算により膨張弁の開度を制御するための第２の開度指令を形成し、
前記第１の開度指令及び第２の開度指令のうち、大きい開度指令を選択し、このようにして選択した第１の開度指令又は第２の開度指令で膨張弁の開度を制御するようにしたこと。
【００１２】
２） 上記１）に記載する冷凍機における膨張弁の制御方法において、
流出冷水又は流出ブラインの設定温度に基づいて予め設定する設定温度は、圧縮機の吸入冷媒量又は吐出冷媒量を調整して制御する当該冷凍機の前記流出冷水又は流出ブラインの設定温度としたこと。
【００１３】
３） 凝縮器から蒸発器に至る管路の途中に配設されて冷媒を膨張させるための膨張弁の制御装置において、
流入温度検出手段が検出する、蒸発器における流入冷水又は流入ブラインの流入温度と、出口温度検出手段が検出する、前記流出冷水又は流出ブラインの流出温度とに基づき両者の温度差を演算するとともに、この温度差に基づき当該冷凍機の第１の冷凍能力を演算し、さらにこの第１の冷凍能力を媒介として当該冷凍機における冷媒の第１の循環量を演算するとともに、前記第１の循環量と、膨張弁の上流側の圧力及び下流側の圧力とに基づく演算により膨張弁の開度を制御するための第１の開度指令を形成する第１の開度指令生成手段と、
前記入口温度検出手段が検出する前記入口温度と、前記流出冷水又は流出ブラインの設定温度に基づいて予め設定した設定温度との温度差を演算するとともに、この温度差に基づき当該冷凍機の第２の冷凍能力を演算し、さらにこの第２の冷凍能力を媒介として当該冷凍機における冷媒の第２の循環量を演算するとともに、前記第２の循環量と、膨張弁の上流側の圧力及び下流側の圧力とに基づく演算により膨張弁の開度を制御するための第２の開度指令を形成する第２の開度指令生成手段と、
前記第１の開度指令及び第２の開度指令のうち、大きい開度指令を選択し、このようにして選択した第１の開度指令又は第２の開度指令で膨張弁の開度を制御する開度指令手段とを有すること。
【００１４】
４） 上記３）に記載する冷凍機における膨張弁の制御装置において、
流出冷水又は流出ブラインの設定温度に基づいて予め設定する設定温度は、圧縮機の吸入冷媒量又は吐出冷媒量を調整して制御する当該冷凍機の前記流出冷水又は流出ブラインの設定温度としたこと。
【００１５】
５） 上記３）又は４）に記載する冷凍機における膨張弁の制御装置において、
膨張弁は、ターボ圧縮機のベーンの開度を調整して吸入冷媒量を調整することにより流出冷水又は流出ブラインの温度が設定温度になるように制御するターボ冷凍機の膨張弁であること。
【００１６】
６） 上記３）乃至５）の何れか一つに記載する冷凍機における膨張弁の制御装置において、
膨張弁は、凝縮器から蒸発器に至る管路の途中であって、且つ凝縮器から中間冷却器に至る管路の途中に配設されており、中間冷却器に流入する冷媒を膨張させる多段圧縮冷凍機の膨張弁であること、
中間冷却器は、中間冷却器から一部の冷媒を、多段圧縮冷凍機の多段圧縮機の２段目以降に戻すものであること。
【００１７】
７） 上記３）乃至５）の何れか一つに記載する冷凍機における膨張弁の制御装置において、
膨張弁は、凝縮器から蒸発器に至る管路の途中であって、凝縮器から流出する冷媒を過冷却するサブクーラと中間冷却器との間に配設されており、サブクーラで過冷却され、且つ中間冷却器に流入する冷媒を膨張させる多段圧縮冷凍機の膨張弁であること、
中間冷却器は、中間冷却器から一部の冷媒を、多段圧縮冷凍機の多段圧縮機の２段目以降に戻すものであること。
【００１８】
８） 上記３）乃至５）の何れか一つに記載する冷凍機における膨張弁の制御装置において、
膨張弁は、凝縮器から蒸発器に至る管路の途中であって、凝縮器から流出する冷媒を過冷却するサブクーラの下流側に配設されており、サブクーラで過冷却され、蒸発器に流入する冷媒を膨張させる冷凍機の膨張弁であること。
【００１９】
【発明の実施の形態】
以下本発明の実施の形態を図面に基づき詳細に説明する。
【００２０】
近年、冷凍機、特に大型のターボ冷凍機の中には、マイクロ・コンピュータ制御盤（以下、マイコン制御盤と称す。）を具備し、各種の物理量を取り込んで所定の演算を行う演算機能を有するものが開発され、実用に供されている。本形態も、かかるマイコン制御盤を具備する冷凍機に適用するものである。すなわち、本形態に係る膨張弁の制御装置は、上述の如きマイコン制御盤を利用することにより好適に構成することができる。だだ、これに限るものではない。また、本形態に係る制御装置は、図３に示すターボ冷凍機に適用するものとして説明する。そこで、図３と同一部分には同一番号を付し、重複する説明は省略する。
【００２１】
図１は本実施の形態に係る制御装置を、これを適用するターボ冷凍機とともに示すブロック線図である。同図において、一点鎖線で囲んだ部分が本形態に係る制御装置であり、上述の如く、これはマイコン制御盤で実現している。同図に示すように、流入温度検出器１１は、蒸発器１内に流入して冷媒と熱交換を行うことにより冷却される流入冷水（又は流入ブライン；以下同じ。）の流入温度Ｔi を検出してこれを表す入口温度信号Ｓ１を送出する。流出温度検出器１２は、蒸発器１内で冷却されてこの蒸発器１から流出する流出冷水（又は流出ブライン；以下同じ。）の流出温度Ｔo を検出してこれを表す出口温度信号Ｓ２を送出する。この流出冷水が負荷に供給される。したがって、当該ターボ冷凍機の運転の際の設定温度Ｔs とは、流出冷水の設定温度をいう。また、当該ターボ冷凍機は、そのターボ圧縮機２のベーン２ａの開度を電動機２ｂで調整することにより吸入冷媒量を調整し、前記流出冷水が設定温度Ｔs になるように制御するものとする。さらに詳言すると、電動機２ｂはベーン開度制御部１３の出力信号である開度指令信号Ｓ３で駆動制御され、さらにこのベーン開度制御部１３は、出口温度信号Ｓ２と、流出冷水の設定温度Ｔs を表す設定温度信号Ｓ４とに基づき両者の偏差を演算し、この偏差に応じてベーン２ａの最適開度を指示する。設定温度Ｔs は負荷側の要求に応じた温度で、温度設定部１４に予め設定してある。
【００２２】
上流側圧力検出器１５は膨張弁４の上流側の圧力、例えば凝縮器３内の圧力を検出してこれを表す上流側圧力信号Ｓ５を送出する。下流側圧力検出器１６は膨張弁４の下流側の圧力、例えば蒸発器１内の圧力を検出してこれを表す下流側圧力信号Ｓ４を送出する。
【００２３】
第１の開度指令生成部１７は、先ず上記流入温度信号Ｓ１及び出口温度信号Ｓ２に基づき流入冷水と流出冷水との温度差を演算するとともに、この温度差に基づき当該ターボ冷凍機の第１の冷凍能力Ｑ1 を演算する。ここで、第１の冷凍能力Ｑ1 は、次式（１）で与えられる。
Ｑ1 ＝（Ｔi −Ｔo ）・ｇ・γ・Ｋ ・・・・・（１）
ここで、Ｔi は流入温度、Ｔo は流出温度、ｇは冷水流量、γは冷水の比重、Ｋは冷水の比熱である。
【００２４】
次に、第１の開度指令生成部１７は、第１の冷凍能力Ｑ1 を媒介として当該ターボ冷凍機における冷媒の第１の循環量ＧＲ1 を演算する。具体的には、冷媒の循環量が当該ターボ冷凍機の冷凍能力と比例関係にある点を利用して求める。すなわち、第１の冷凍能力Ｑ1 と第１の循環量ＧＲ1 とは比例関係にあるので、第１の冷凍能力Ｑ1 に所定のパラメータを乗じて第１の循環量ＧＲ1 を演算する。このときの第１の循環量ＧＲ1 は、現時点の流入冷水の温度Ｔi と現時点の流出冷水の温度Ｔo との温度差を反映したものとなっている。換言すれば、流入冷水と流出冷水の現時点の温度差を維持するための冷媒量を表している。
【００２５】
最後に、第１の開度指令生成部１７は、上流側圧力検出器１５が検出する膨張弁４の上流側圧力Ｐ1 及び下流側圧力検出部１６が検出する膨張弁４の下流側圧力Ｐ2 と、上記第１の循環量ＧＲ1 に基づき膨張弁４の開度を演算し、その演算結果を第１の開度指令とする。この第１の開度指令の演算は、第１の循環量ＧＲ1 、上流側圧力Ｐ1 及び下流側圧力Ｐ2 に、冷水流量ｇ、冷水の比重γ、冷水の比熱Ｋ及び膨張弁４の口径等のパラメータを乗じて演算する。この場合の演算は、厳密なパラメータを用いて行う。すなわち、負荷に応じた最適の冷媒循環量とするための膨張弁４の最適開度を開度指令とする。このように、パラメータを厳密に設定することにより、負荷の変動があっても膨張弁４における冷媒ガスの漏れを可及的に低減し得る。この結果、第１の指令信号Ｓ７を得る。
【００２６】
第２の開度指令部１８は、流出温度Ｔo の代わりに設定温度Ｔs を用いる点が異なるだけで第１の開度指令部１７と全く同様の演算を行う。すなわち、次式（２）に基づき第２の冷凍能力Ｑ2 を演算する。
Ｑ2 ＝（Ｔi −Ｔs ）・ｇ・γ・Ｋ ・・・・・（２）
ここで、Ｔi は流入温度、Ｔs は設定温度、ｇは冷水流量、γは冷水の比重、Ｋは冷水の比熱である。
【００２７】
次に、第２の冷凍能力Ｑ2 を媒介として当該ターボ冷凍機における冷媒の第２の循環量ＧＲ2 を演算する。このときの第２の循環量ＧＲ2 は、現時点の流入冷水の温度Ｔi と設定温度Ｔs との温度差を反映したものとなっている。換言すれば、流入冷水を冷却して設定温度Ｔs の流出冷水とするのに必要な冷媒量を表している。
【００２８】
最後に、第２の開度指令部１８は、第１の循環量ＧＲ1 と上流側圧力Ｐ1 及び下流側圧力Ｐ2 と、に基づき膨張弁４の開度を演算し、その演算結果を第２の開度指令とする。この第２の開度指令の演算は、第１の開度指令生成部１７における第１の循環量ＧＲ1 の代わりに第２の循環量ＧＲ2 を用いるだけで、第１の開度指令生成部１７における演算と同様の手法により行う。したがって、この演算も、第１の開度指令生成部１７におけるのと同様の厳密なパラメータを用いて行う。すなわち、負荷に応じた最適の冷媒循環量とすべるための膨張弁４の最適開度を確保するための開度指令とする。かくして、第２の指令信号Ｓ８を得る。
【００２９】
なお、上記第２の開度指令生成部１８における演算に用いる設定温度は、負荷に供給する流出流水の設定温度Ｔs としたが、この設定温度Ｔs に基づく温度であれば、これに限るものではない。すなわち、設定温度Ｔs よりも高い温度を設定温度とすることも、また低い温度を設定温度とすることも可能である。
【００３０】
開度指令部１９は、第１の開度指令信号Ｓ７及び第２の開度指令信号Ｓ８のうち、大きい開度指令を選択し、このようにして選択した第１の開度指令信号Ｓ７又は第２の開度指令信号Ｓ８で膨張弁４の開度を制御するようその電動機４ａを駆動制御する。かくして、膨張弁４は、何れも厳密な制御パラメータを用いて演算した２種類の開度指令のうち、大きい開度指令に応じてその開度が決定される。この点の制御的な意味を図２に基づき詳細に説明する。
【００３１】
図２は上述の如き制御装置による膨張弁４の制御の態様を説明するための温度特性図で、（ａ）は流入冷水の流入温度Ｔi が高温側に急変した場合、（ｂ）は低温側に急変した場合である。
【００３２】
先ず、高温側に急変した場合について説明する。図２（ａ）に示すように、流出温度Ｔo が設定温度Ｔs となっており、且つ流入温度Ｔi （例えば１１°Ｃ）と流出温度Ｔo （例えば７°Ｃ）との温度差（Ｔi −Ｔo ）が一定で安定している定常状態（このときターボ圧縮機２のベーン２ａの開度及び膨張弁４の開度は一定）で、ある時刻ｔ1 において流入温度Ｔi が急変した場合（例えば１２°Ｃに変化した場合）、温度差（Ｔi −Ｔo ）に基づく第１の開度指令よりも温度差（Ｔi −Ｔs ）に基づく第２の開度指令の方が大きい。したがって、この場合は、第２の指令信号Ｓ８で膨張弁４の開度が制御される。すなわち、膨張弁４の開度は、冷水温度の急変により増加させるべき冷媒の循環量を先取りして制御される。
【００３３】
ちなみに、本形態と同様の厳密な制御パラメータ及び温度差（Ｔi −Ｔo ）を用いて一種類の開度指令（第１の開度指令）のみで、当該開度制御を行う場合には、冷水温度が急変しても温度差（Ｔi −Ｔo ）は変化しないので、膨張弁４の開度も変化しない。膨張弁４は現時点の循環量の冷媒を流すべく制御されるからである。一方、ターボ圧縮機２は、上昇した流出温度Ｔo を設定温度Ｔs に戻すべく、そのベーン２ａの開度が制御される。この場合には開く方向に制御される。したがって、膨張弁４の下流側で冷媒が不足し、蒸発器１内の液面が低下するが、この異常低下が検出されて始めて膨張弁４の開度を開く制御が行なわれる。すなわち、この場合には、流入温度Ｔi の急変時刻ｔ1 から点線で示すような温度変化を経て設定温度Ｔs に落ちつくが、その間当該ターボ冷凍機の運転が不安定になる。したがって、温度差（Ｔi −Ｔo ）を用いて一種類の開度指令（第１の開度指令）のみで膨張弁４の開度制御を行う場合には、制御パラメータを厳密に設定することができず、循環冷媒量に対する最適開度よりも若干開き気味の制御を行う必要がある。このため、定常状態における冷媒ガスの蒸発器１側への若干の漏れは許容せざるを得ないような制御となっている。
【００３４】
これに対して、本形態では、流入温度Ｔi の急変によりこれから必要になる冷媒の循環量を予測して膨張弁４の開度を制御しているので、厳密な制御パラメータを設定した場合でも、十分良好な追従制御を行うことができる。
【００３５】
次に、流入温度Ｔi が低温側に急変した場合について説明する。図２（ｂ）に示すように、図２（ａ）に示す場合と同様の定常状態で、ある時刻ｔ1 において流入温度Ｔi が急変した場合（例えば１１°Ｃから１０°Ｃに変化した場合）、温度差（Ｔi −Ｔs ）に基づく第１の開度指令の方が温度差（Ｔi −Ｔs ）に基づく第２の開度指令よりも大きい。したがって、この場合は、第１の指令信号Ｓ７で膨張弁４の開度が制御される。すなわち、膨張弁４の開度は、冷水温度の急変によっても変化せず、現時点の開度が保持されるように制御される。
【００３６】
ちなみに、本形態と同様の厳密な制御パラメータ及び温度差（Ｔi −Ｔs ）を用いて一種類の開度指令（第２の開度指令）のみで、当該開度制御を行う場合には、冷水温度が急変して温度差（Ｔi −Ｔs ）が縮小した場合、膨張弁４の開度は閉じる方向に制御される。すなわち、図中に点線で示す設定温度Ｔs との差に応じた循環冷媒量とするべく膨張弁４を閉じる。一方、ターボ圧縮機２は、低下する流出温度Ｔo を設定温度Ｔs に戻すべく、そのベーン２ａの開度が制御され、この場合には閉じる方向に制御される。ただ、このベーン２ａの開度制御により当該ターボ冷凍機の系統が落ちつく迄には一定の時間を要する。したがって、このように膨張弁４の開度を先行して閉じた場合には、膨張弁４の下流側で冷媒が不足する等、当該ターボ冷凍機の不安定な運転の原因となる。
【００３７】
これに対して、本形態では、温度差（Ｔi −Ｔo ）に応じて膨張弁４の開度をそのまま維持しているので、厳密な制御パラメータを設定した場合でも、流出温度Ｔo は、一旦、設定温度Ｔs に対して低温側にオーバシュートしても当該ターボ冷凍機の運転を不安定にすることはなく、ターボ圧縮機２のベーン２ａの開度制御により設定温度Ｔs に戻すことができる。
【００３８】
なお、上記実施の形態における膨張弁４は、ターボ冷凍機における膨張弁４について説明したが、この場合の冷凍機の種類には特別な限定はない。ただ、負荷に応じて変化する冷水の温度制御を圧縮機の吸入冷媒量又は吐出冷媒量を調整することにより制御する冷凍機に適用して好適なものとなる。
【００３９】
また、膨張弁４は単段の冷凍機に適用するものとして説明したが、当然これに限るものでもない。冷凍機の中には、凝縮器と蒸発器との間に中間冷却器を有し、この中間冷却器から一部の冷媒を圧縮機の２段目以降に戻してやる多段圧縮機を有する多段冷凍機があるが、これにも適用し得る。この場合、膨張弁４は、凝縮器から蒸発器に至る管路の途中であって、且つ凝縮器から中間冷却器に至る管路の途中に配設されて中間冷却器に流入する冷媒を膨張させるように構成される。また、さらに凝縮器から流出する冷媒を過冷却するサブクーラを有する冷凍機もあるが、これにも適用し得る。この場合、膨張弁４は、凝縮器から蒸発器に至る管路の途中であって、凝縮器から流出する冷媒を過冷却するサブクーラと中間冷却器との間に配設され、サブクーラで過冷却され、且つ中間冷却器に流入する冷媒を膨張させるように構成される。さらに、サブクーラのみを有する単段の冷凍機にも適用し得る。この場合、膨張弁４は、凝縮器から蒸発器に至る管路の途中であって、凝縮器から流出する冷媒を過冷却するサブクーラの下流側に配設され、サブクーラで過冷却され、蒸発器に流入する冷媒を膨張させるように構成される。
【００４０】
【発明の効果】
以上実施の形態とともに具体的に説明した通り、〔請求項１〕に記載する発明は、凝縮器から蒸発器に至る管路の途中に配設されて冷媒を膨張させるための膨張弁の制御方法において、蒸発器における流入冷水又は流入ブラインの温度と、流出冷水又は流出ブラインの温度との差に基づいて演算により得る当該冷凍機の第１の冷凍能力を媒介として、当該冷凍機における冷媒の第１の循環量を演算し、さらにこの第１の循環量と、膨張弁の上流側の圧力及び下流側の圧力とに基づく演算により膨張弁の開度を制御するための第１の開度指令を形成する一方、前記蒸発器における流入冷水又は流入ブラインの温度と、流出冷水又は流出ブラインの設定温度に基づいて予め設定した設定温度との差に基づいて演算により得る当該冷凍機の第２の冷凍能力を媒介として、当該冷凍機における冷媒の第２の循環量を演算し、さらにこの第２の循環量と、膨張弁の上流側の圧力及び下流側の圧力とに基づく演算により膨張弁の開度を制御するための第２の開度指令を形成し、前記第１の開度指令及び第２の開度指令のうち、大きい開度指令を選択し、このようにして選択した第１の開度指令又は第２の開度指令で膨張弁の開度を制御するようにしたので、
流入冷水の流入温度が高温側に急変した場合には、第２の循環量に基づく第２の開度指令により、この急変により必要になる冷媒量を予測して膨張弁の開度を制御することができる。また、流入冷水の流入温度が低温側に急変した場合には、第１の循環量に基づく第１の開度指令により、現時点の冷媒循環量を維持すべく膨張弁の開度を制御することができる。すなわち、第２の開度指令で、当該冷凍系統の冷水温度制御に先行して膨張弁を閉じることはない。
この結果、厳密な制御パラメータを設定して膨張弁の最適開度制御を行っても当該冷凍機の運転を不安定にすることはない。したがって、蒸発器側への冷媒ガスの漏れを可及的に低減して高効率で当該冷凍機の運転を行うことができる。さらに、当該冷凍機の起動時に冷媒液の液面が上昇する方向にオーバシュートすることなく、最適な液面に落ちつくため、起動から冷水温度制御が安定する迄の時間が最短となる。また、制御の追従性に起因する低圧トリップを最小限に抑えることもできる。
【００４１】
〔請求項２〕に記載する発明は、〔請求項１〕に記載する冷凍機における膨張弁の制御方法において、流出冷水又は流出ブラインの設定温度に基づいて予め設定する設定温度は、圧縮機の吸入冷媒量又は吐出冷媒量を調整して制御する当該冷凍機の前記流出冷水又は流出ブラインの設定温度としたので、
負荷に供給する流出冷水の設定温度を基準として〔請求項１〕に記載する発明と同様の制御を行うことができ、同様の作用・効果を得る。
【００４２】
〔請求項３〕に記載する発明は、凝縮器から蒸発器に至る管路の途中に配設されて冷媒を膨張させるための膨張弁の制御装置において、流入温度検出手段が検出する、蒸発器における流入冷水又は流入ブラインの流入温度と、出口温度検出手段が検出する、前記流出冷水又は流出ブラインの流出温度とに基づき両者の温度差を演算するとともに、この温度差に基づき当該冷凍機の第１の冷凍能力を演算し、さらにこの第１の冷凍能力を媒介として当該冷凍機における冷媒の第１の循環量を演算するとともに、前記第１の循環量と、膨張弁の上流側の圧力及び下流側の圧力とに基づく演算により膨張弁の開度を制御するための第１の開度指令を形成する第１の開度指令生成手段と、前記入口温度検出手段が検出する前記入口温度と、前記流出冷水又は流出ブラインの設定温度に基づいて予め設定した設定温度との温度差を演算するとともに、この温度差に基づき当該冷凍機の第２の冷凍能力を演算し、さらにこの第２の冷凍能力を媒介として当該冷凍機における冷媒の第２の循環量を演算するとともに、前記第２の循環量と、膨張弁の上流側の圧力及び下流側の圧力とに基づく演算により膨張弁の開度を制御するための第２の開度指令を形成する第２の開度指令生成手段と、前記第１の開度指令及び第２の開度指令のうち、大きい開度指令を選択し、このようにして選択した第１の開度指令又は第２の開度指令で膨張弁の開度を制御する開度指令手段とを有するので、
流入冷水の流入温度が高温側に急変した場合には、第２の循環量に基づく第２の開度指令により、この急変により必要になる冷媒量を予測して膨張弁の開度を制御することができる。また、流入冷水の流入温度が低温側に急変した場合には、第１の循環量に基づく第１の開度指令により、現時点の冷媒循環量を維持すべく膨張弁の開度を制御することができる。すなわち、第２の開度指令で、当該冷凍系統の冷水温度制御に先行して膨張弁を閉じることはない。
この結果、厳密な制御パラメータを設定して膨張弁の最適開度制御を行っても当該冷凍機の運転を不安定にすることはない。したがって、蒸発器側への冷媒ガスの漏れを可及的に低減して高効率で当該冷凍機の運転を行うことができる。さらに、当該冷凍機の起動時に冷媒液の液面が上昇する方向にオーバシュートすることなく、最適な液面に落ちつくため、起動から冷水温度制御が安定する迄の時間が最短となる。また、制御の追従性に起因する低圧トリップを最小限に抑えることもできる。
【００４３】
〔請求項４〕に記載する発明は、〔請求項３〕に記載する冷凍機における膨張弁の制御装置において、流出冷水又は流出ブラインの設定温度に基づいて予め設定する設定温度は、圧縮機の吸入冷媒量又は吐出冷媒量を調整して制御する当該冷凍機の前記流出冷水又は流出ブラインの設定温度としたので、
負荷に供給する流出冷水の設定温度を基準として〔請求項３〕に記載する発明と同様の制御を行うことができ、同様の作用・効果を得る。
【００４４】
〔請求項５〕に記載する発明は、〔請求項３〕又は〔請求項４〕に記載する冷凍機における膨張弁の制御装置において、膨張弁は、ターボ圧縮機のベーンの開度を調整して吸入冷媒量を調整することにより流出冷水又は流出ブラインの温度が設定温度になるように制御するターボ冷凍機の膨張弁であるので、
〔請求項３〕及び〔請求項４〕に記載する発明と同様の作用・効果をターボ冷凍機で得ることができる。
【００４５】
〔請求項６〕に記載する発明は、〔請求項３〕乃至〔請求項５〕の何れか一つに記載する冷凍機における膨張弁の制御装置において、膨張弁は、凝縮器から蒸発器に至る管路の途中であって、且つ凝縮器から中間冷却器に至る管路の途中に配設されており、中間冷却器に流入する冷媒を膨張させる多段圧縮冷凍機の膨張弁であり、中間冷却器は、中間冷却器から一部の冷媒を、多段圧縮冷凍機の多段圧縮機の２段目以降に戻すものであるので、
〔請求項３〕乃至〔請求項５〕に記載する発明と同様の作用・効果を多段冷凍機で得ることができる。
【００４６】
〔請求項７〕に記載する発明は、〔請求項３〕乃至〔請求項５〕の何れか一つに記載する冷凍機における膨張弁の制御装置において、膨張弁は、凝縮器から蒸発器に至る管路の途中であって、凝縮器から流出する冷媒を過冷却するサブクーラと中間冷却器との間に配設されており、サブクーラで過冷却され、且つ中間冷却器に流入する冷媒を膨張させる多段圧縮冷凍機の膨張弁であり、中間冷却器は、中間冷却器から一部の冷媒を、多段圧縮冷凍機の多段圧縮機の２段目以降に戻すものであるので、
〔請求項３〕乃至〔請求項５〕に記載する発明と同様の作用・効果をサブクーラを有する多段冷凍機で得ることができる。
【００４７】
〔請求項８〕に記載する発明は、〔請求項３〕乃至〔請求項５〕の何れか一つに記載する冷凍機における膨張弁の制御装置において、膨張弁は、凝縮器から蒸発器に至る管路の途中であって、凝縮器から流出する冷媒を過冷却するサブクーラの下流側に配設されており、サブクーラで過冷却され、蒸発器に流入する冷媒を膨張させる冷凍機の膨張弁であるので、
〔請求項３〕乃至〔請求項５〕に記載する発明と同様の作用・効果をサブクーラを有する冷凍機で得ることができる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る制御装置を、これを適用するターボ冷凍機とともに示すブロック線図である。
【図２】図１に示す制御装置による膨張弁の制御の態様を説明するための温度特性図である。
【図３】従来技術に係る一般的なターボ冷凍機を示すブロック線図である。
【符号の説明】
１ 蒸発器
２ ターボ圧縮機
２ａ ベーン
３ 凝縮器
４ 膨張弁
１１ 流入温度検出器
１２ 流出温度検出器
１４ 温度設定部
１５ 上流側圧力検出器
１６ 下流側圧力検出器
１７ 第１の指令生成部
１８ 第２の指令生成部
１９ 開度指令部
Ｔi 流入温度
Ｔo 流出温度[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an expansion valve control method and control apparatus for a refrigerator, and more particularly, calculates a circulating refrigerant amount based on various physical quantities, generates an optimal opening degree command corresponding to the circulating refrigerant quantity, and controls the expansion valve. It is useful to apply to cases.
[0002]
[Prior art]
FIG. 3 is a block diagram showing a turbo refrigerator. As shown in the figure, in the turbo refrigerator, the refrigerant absorbed by the cold water supplied to the load in the evaporator 1 and vaporized is compressed by the turbo compressor 2 into a high-temperature and high-pressure refrigerant gas. This high-temperature and high-pressure refrigerant gas is cooled and condensed by the cooling water in the condenser 3 and is liquefied to become a refrigerant liquid. Thereafter, the refrigerant liquid reaches the expansion valve 4, is expanded by the expansion valve 4, becomes a low pressure, and reaches the evaporator 1. In the evaporator 1, the refrigerant liquid evaporates by exchanging heat with cold water, and the refrigeration cycle as described above is repeated.
[0003]
Here, in the turbo refrigerator, it is necessary to control the temperature so that the temperature of the cold water supplied to the load, that is, the cold water outlet temperature becomes a set value. The temperature control of the cold water is generally performed by adjusting the opening of the vane 2a of the turbo compressor 2 with the electric motor 2b and controlling the amount of refrigerant sucked.
[0004]
On the other hand, the opening degree of the expansion valve 4 needs to be appropriately controlled according to the circulation amount of the refrigerant. Therefore, in a large refrigerator such as a turbo refrigerator, the expansion valve 4 is opened by liquid level control that keeps the liquid level of the refrigerant liquid upstream of the expansion valve 4 (condenser, intermediate cooler, receiver). The degree control is implemented.
[0005]
[Problems to be solved by the invention]
In the valve opening control of the expansion valve 4 by the liquid level control as described above, the expansion valve 4 to be controlled is usually an electric motor-driven electromagnetic control valve that controls the valve opening by the rotation of the electric motor 4a. ing. For this reason, the valve opening degree control of the expansion valve 4 is delayed with respect to the control of the intake refrigerant amount of the turbo compressor 2 performed to keep the cold water temperature at the set value. This is because the opening and closing of the expansion valve 4 driven by the electric motor cannot follow the fluctuation of the liquid level of the refrigerant liquid. Such a control delay causes an increase in the liquid level of the refrigerant liquid on the upstream side of the expansion valve 4 and an abnormal decrease in the pressure in the evaporator 1 and makes the operation of the refrigerator unstable.
[0006]
Therefore, in order to eliminate such unstable elements, the accuracy of the valve opening degree control of the expansion valve 4 has been lowered in the conventional refrigerator. That is, the valve opening control parameter is not strictly set, and control is performed such that the valve opening of the expansion valve 4 is slightly opened from its optimum value. However, this also allows refrigerant gas to flow into the evaporator 1 via the expansion valve 4 when the load fluctuates (when the amount of refrigerant sucked is controlled by the turbo compressor 2). However, the refrigerant gas mixed in the evaporator 1 does not contribute to cooling of the cold water. Therefore, when refrigerant gas is mixed in the evaporator 1, the operation efficiency of the turbo refrigerator is reduced by the amount of the mixed gas. That is, if 1% of the refrigerant gas is mixed, the operating efficiency of the refrigerator is also reduced by 1%.
[0007]
On the other hand, a reduction in the valve opening control delay of the expansion valve 4 with respect to the control of the intake refrigerant amount of the turbo compressor 2 in accordance with the cold water temperature control is achieved by a pneumatically driven or hydraulically driven cylinder driven valve. Can be relaxed to some extent. However, this cylinder-driven valve is not only bulky but also expensive, and there is a problem that the cost increases.
[0008]
Note that the above-described problems are not unique to turbo refrigerators, and generally occur in other types of refrigerators with different compressors.
[0009]
In view of the above-mentioned problems of the prior art, the present invention makes it possible to always create a liquid surface of the refrigerant liquid on the upstream side and circulate refrigerant gas that does not condense in the condenser even when an ordinary electric control valve is used as an expansion valve. It is an object of the present invention to provide an expansion valve control method and a control device for a refrigerator that can prevent and prevent a decrease in refrigerator efficiency.
[0010]
[Means for Solving the Problems]
The configuration of the present invention that achieves the above object is characterized by the following points.
[0011]
1) In the control method of the expansion valve for expanding the refrigerant disposed in the middle of the conduit from the condenser to the evaporator,
The first refrigerating capacity of the refrigerant in the refrigerator is mediated by the first refrigeration capacity of the refrigerator obtained by calculation based on the difference between the temperature of the inflow cold water or the inflow brine in the evaporator and the temperature of the outflow cold water or the outflow brine. A circulation amount is calculated, and a first opening degree command for controlling the opening degree of the expansion valve is formed by calculation based on the first circulation amount and the upstream pressure and downstream pressure of the expansion valve. While
Through the second refrigeration capacity of the refrigerator obtained by calculation based on the difference between the temperature of the inflow cold water or the inflow brine in the evaporator and the preset temperature set based on the set temperature of the outflow cold water or the outflow brine Then, the second circulation amount of the refrigerant in the refrigerator is calculated, and the opening degree of the expansion valve is controlled by calculation based on the second circulation amount, the upstream pressure and the downstream pressure of the expansion valve. Forming a second opening command for
A large opening command is selected from the first opening command and the second opening command, and the opening of the expansion valve is selected by the first opening command or the second opening command selected as described above. To control.
[0012]
2) In the control method of the expansion valve in the refrigerator described in 1) above,
The preset temperature set in advance based on the preset temperature of the chilled cold water or effluent brine is the preset temperature of the chilled cold water or effluent brine of the refrigerator that is controlled by adjusting the amount of refrigerant sucked or discharged from the compressor. .
[0013]
3) In the control device for the expansion valve arranged in the middle of the conduit from the condenser to the evaporator to expand the refrigerant,
While calculating the temperature difference between the inflow temperature of the inflow cold water or the inflow brine in the evaporator detected by the inflow temperature detection means and the outflow temperature of the outflow cold water or the outflow brine detected by the outlet temperature detection means, A first refrigeration capacity of the refrigerator is calculated based on the temperature difference, and a first circulation amount of the refrigerant in the refrigerator is calculated using the first refrigeration capacity as a medium, and the first circulation amount is calculated. And a first opening degree command generating means for forming a first opening degree instruction for controlling the opening degree of the expansion valve by calculation based on the pressure on the upstream side and the pressure on the downstream side of the expansion valve;
A temperature difference between the inlet temperature detected by the inlet temperature detection means and a preset temperature set based on the preset temperature of the chilled cold water or effluent brine is calculated, and the second temperature of the refrigerator is calculated based on the temperature difference. And the second circulation amount of the refrigerant in the refrigerator is calculated using the second refrigeration capability as a medium, and the second circulation amount, the pressure upstream of the expansion valve, and the downstream Second opening degree command generating means for forming a second opening degree command for controlling the opening degree of the expansion valve by calculation based on the pressure on the side,
A large opening command is selected from the first opening command and the second opening command, and the opening of the expansion valve is selected by the first opening command or the second opening command selected as described above. And an opening degree command means for controlling.
[0014]
4) In the control device for the expansion valve in the refrigerator described in 3) above,
The preset temperature set in advance based on the preset temperature of the chilled cold water or effluent brine is the preset temperature of the chilled cold water or effluent brine of the refrigerator that is controlled by adjusting the amount of refrigerant sucked or discharged from the compressor. .
[0015]
5) In the control device for the expansion valve in the refrigerator described in 3) or 4) above,
The expansion valve is an expansion valve of a turbo chiller that controls the temperature of the chilled cold water or effluent brine to be a set temperature by adjusting the amount of refrigerant sucked by adjusting the vane opening of the turbo compressor.
[0016]
6) In the control device for the expansion valve in the refrigerator described in any one of 3) to 5) above,
  The expansion valve is arranged in the middle of the pipeline from the condenser to the evaporator and in the middle of the pipeline from the condenser to the intermediate cooler, and expands the refrigerant flowing into the intermediate cooler. This is an expansion valve for a compression refrigerator.When,
  The intercooler shall return a part of the refrigerant from the intercooler to the second and subsequent stages of the multistage compressor of the multistage compression refrigerator.
[0017]
7) In the control device for the expansion valve in the refrigerator described in any one of 3) to 5) above,
  The expansion valve is disposed in the middle of the pipeline from the condenser to the evaporator, and is disposed between the subcooler and the intercooler that supercools the refrigerant flowing out of the condenser, and is subcooled by the subcooler, And an expansion valve of a multistage compression refrigerator that expands the refrigerant flowing into the intercooler.When,
  The intercooler shall return a part of the refrigerant from the intercooler to the second and subsequent stages of the multistage compressor of the multistage compression refrigerator.
[0018]
8) In the control device for the expansion valve in the refrigerator described in any one of 3) to 5) above,
The expansion valve is located in the middle of the pipe line from the condenser to the evaporator, and is arranged downstream of the subcooler that supercools the refrigerant flowing out of the condenser. The expansion valve is supercooled by the subcooler and flows into the evaporator. It is an expansion valve of a refrigerator that expands the refrigerant to be used.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0020]
In recent years, refrigerators, particularly large turbo refrigerators, have a microcomputer control panel (hereinafter referred to as a microcomputer control panel), and have a calculation function that takes various physical quantities and performs predetermined calculations. Things have been developed and put into practical use. This embodiment is also applied to a refrigerator having such a microcomputer control panel. That is, the control device for the expansion valve according to the present embodiment can be suitably configured by using the microcomputer control panel as described above. However, it is not limited to this. Moreover, the control apparatus which concerns on this form is demonstrated as what is applied to the turbo refrigerator shown in FIG. Therefore, the same parts as those in FIG.
[0021]
FIG. 1 is a block diagram showing a control device according to the present embodiment together with a turbo chiller to which the control device is applied. In the same figure, the part enclosed with a dashed-dotted line is the control apparatus which concerns on this form, and as above-mentioned, this is implement | achieved by the microcomputer control board. As shown in the figure, the inflow temperature detector 11 flows into the evaporator 1 and cools the inflow cold water (or inflow brine; the same applies hereinafter) cooled by exchanging heat with the refrigerant.iIs detected and an inlet temperature signal S1 indicating this is sent out. The outflow temperature detector 12 is cooled in the evaporator 1 and flows out of the outflow cold water (or outflow brine; the same shall apply hereinafter) outflow temperature T flowing out of the evaporator 1.oIs detected and an outlet temperature signal S2 representing this is sent out. This outflow cold water is supplied to the load. Therefore, the set temperature T during operation of the turbo chillersMeans the set temperature of the chilled cold water. Further, the turbo chiller adjusts the amount of refrigerant sucked by adjusting the opening degree of the vane 2a of the turbo compressor 2 with the electric motor 2b, and the chilled water flowing out is set at a set temperature T.sIt shall be controlled so that More specifically, the electric motor 2b is driven and controlled by an opening command signal S3 that is an output signal of the vane opening control unit 13. The vane opening control unit 13 further includes an outlet temperature signal S2 and a set temperature of the chilled cold water. TsIs calculated based on the set temperature signal S4 indicating the optimum opening degree of the vane 2a according to the deviation. Set temperature TsIs a temperature according to a request on the load side, and is preset in the temperature setting unit 14.
[0022]
The upstream pressure detector 15 detects the pressure on the upstream side of the expansion valve 4, for example, the pressure in the condenser 3, and sends an upstream pressure signal S5 representing this pressure. The downstream pressure detector 16 detects the pressure on the downstream side of the expansion valve 4, for example, the pressure in the evaporator 1, and sends a downstream pressure signal S4 representing this.
[0023]
The first opening degree command generation unit 17 first calculates the temperature difference between the inflowing chilled water and the outflowing chilled water based on the inflow temperature signal S1 and the outlet temperature signal S2, and based on the temperature difference, the first opening degree command generating unit 17 Refrigeration capacity Q1Is calculated. Here, the first refrigeration capacity Q1Is given by the following equation (1).
Q1= (Ti-To) ・ G ・ γ ・ K (1)
Where TiIs the inflow temperature, ToIs the outflow temperature, g is the cold water flow rate, γ is the specific gravity of the cold water, and K is the specific heat of the cold water.
[0024]
Next, the first opening degree command generation unit 17 has the first refrigeration capacity Q1The first circulation amount GR of the refrigerant in the turbo refrigerator1Is calculated. Specifically, it is determined by utilizing the fact that the circulation amount of the refrigerant is proportional to the refrigeration capacity of the turbo chiller. That is, the first refrigeration capacity Q1And the first circulation amount GR1Is proportional to the first refrigeration capacity Q1The first circulation amount GR is multiplied by a predetermined parameter.1Is calculated. First circulation amount GR at this time1Is the current inflow cold water temperature TiAnd the current temperature T of the chilled wateroIt reflects the difference in temperature. In other words, it represents the refrigerant amount for maintaining the current temperature difference between the inflowing cold water and the outflowing cold water.
[0025]
Finally, the first opening degree command generator 17 is configured to detect the upstream pressure P of the expansion valve 4 detected by the upstream pressure detector 15.1 And the downstream pressure P of the expansion valve 4 detected by the downstream pressure detector 162And the first circulation amount GR1Based on the above, the opening of the expansion valve 4 is calculated, and the calculation result is used as the first opening command. The calculation of the first opening degree command is performed by calculating the first circulation amount GR.1, Upstream pressure P1 And downstream pressure P2Is multiplied by parameters such as the cold water flow rate g, the specific gravity γ of the cold water, the specific heat K of the cold water and the diameter of the expansion valve 4. The calculation in this case is performed using strict parameters. That is, the optimum opening degree of the expansion valve 4 for setting the optimum refrigerant circulation amount according to the load is used as the opening degree command. In this way, by setting the parameters strictly, it is possible to reduce the leakage of the refrigerant gas in the expansion valve 4 as much as possible even if the load varies. As a result, a first command signal S7 is obtained.
[0026]
The second opening degree command unit 18 outputs the outflow temperature ToInstead of set temperature TsThe same calculation as that of the first opening degree command unit 17 is performed only by using a different point. That is, the second refrigeration capacity Q based on the following equation (2)2Is calculated.
Q2= (Ti-Ts) ・ G ・ γ ・ K ・ ・ ・ ・ ・ (2)
Where TiIs the inflow temperature, TsIs the set temperature, g is the cold water flow rate, γ is the specific gravity of the cold water, and K is the specific heat of the cold water.
[0027]
Next, the second refrigeration capacity Q2As a medium, the second circulation amount GR of the refrigerant in the turbo refrigerator2Is calculated. Second circulation amount GR at this time2Is the current inflow cold water temperature TiAnd set temperature TsIt reflects the difference in temperature. In other words, the inflow cold water is cooled and the set temperature TsIt represents the amount of refrigerant required to make the outflow cold water.
[0028]
Finally, the second opening degree command unit 18 uses the first circulation amount GR.1And upstream pressure P1 And downstream pressure P2Based on the above, the opening of the expansion valve 4 is calculated, and the calculation result is used as the second opening command. The calculation of the second opening degree command is performed by the first circulation amount GR in the first opening degree command generating unit 17.1Instead of the second circulation amount GR2Is used in the same manner as the calculation in the first opening command generation unit 17. Therefore, this calculation is also performed using the same exact parameters as those in the first opening command generation unit 17. That is, the opening degree command is used to ensure the optimum opening degree of the expansion valve 4 for sliding with the optimum refrigerant circulation amount corresponding to the load. Thus, the second command signal S8 is obtained.
[0029]
The set temperature used for the calculation in the second opening command generation unit 18 is the set temperature T of the outflow water supplied to the load.sThe set temperature TsIf it is the temperature based on, it will not restrict to this. That is, the set temperature TsA higher temperature can be set as the set temperature, and a lower temperature can be set as the set temperature.
[0030]
The opening command unit 19 selects a large opening command from the first opening command signal S7 and the second opening command signal S8, and selects the first opening command signal S7 or The electric motor 4a is driven and controlled so as to control the opening of the expansion valve 4 with the second opening command signal S8. Thus, the opening degree of the expansion valve 4 is determined in accordance with a large opening degree command among two kinds of opening degree commands calculated using strict control parameters. The control meaning of this point will be described in detail with reference to FIG.
[0031]
FIG. 2 is a temperature characteristic diagram for explaining an aspect of control of the expansion valve 4 by the control device as described above. FIG.i(B) shows the case where it suddenly changes to the low temperature side.
[0032]
First, a case where the temperature is suddenly changed to the high temperature side will be described. As shown in FIG. 2 (a), the outflow temperature ToIs set temperature TsAnd the inflow temperature Ti(Eg 11 ° C) and outflow temperature To(Teg difference of 7 ° C) (Ti-To) Is constant and stable (at this time, the opening degree of the vane 2a of the turbo compressor 2 and the opening degree of the expansion valve 4 are constant) at a certain time t1Inflow temperature TiWhen the temperature changes suddenly (for example, when the temperature changes to 12 ° C), the temperature difference (Ti-To) Temperature difference (Ti-Ts) Based on the second opening degree command is larger. Therefore, in this case, the opening degree of the expansion valve 4 is controlled by the second command signal S8. That is, the opening degree of the expansion valve 4 is controlled by preempting the circulation amount of the refrigerant to be increased by a sudden change in the cold water temperature.
[0033]
By the way, the exact control parameters and temperature difference (Ti-To) Using only one kind of opening degree command (first opening degree command), and performing the opening degree control, the temperature difference (Ti-To) Does not change, so the opening of the expansion valve 4 does not change. This is because the expansion valve 4 is controlled to flow the current circulating amount of refrigerant. On the other hand, the turbo compressor 2 has an increased outflow temperature ToSet temperature TsThe opening degree of the vane 2a is controlled to return to. In this case, the opening direction is controlled. Accordingly, the refrigerant runs short on the downstream side of the expansion valve 4 and the liquid level in the evaporator 1 is lowered. However, the opening degree of the expansion valve 4 is controlled only when this abnormal drop is detected. That is, in this case, the inflow temperature TiSudden change time t1To the set temperature T through a temperature change as shown by the dotted linesIn the meantime, the operation of the centrifugal chiller becomes unstable. Therefore, the temperature difference (Ti-To) To control the opening of the expansion valve 4 with only one kind of opening command (first opening command), the control parameter cannot be set strictly, and the optimum for the circulating refrigerant amount It is necessary to control the opening slightly more than the opening. For this reason, the control is such that a slight leakage of the refrigerant gas to the evaporator 1 side in a steady state must be allowed.
[0034]
On the other hand, in this embodiment, the inflow temperature TiSince the opening amount of the expansion valve 4 is controlled by predicting the amount of refrigerant to be circulated due to this sudden change, sufficiently good follow-up control can be performed even when strict control parameters are set.
[0035]
Next, the inflow temperature TiA case where the temperature suddenly changes to the low temperature side will be described. As shown in FIG. 2B, at a certain time t in a steady state similar to that shown in FIG.1Inflow temperature TiWhen the temperature changes suddenly (for example, when the temperature changes from 11 ° C to 10 ° C), the temperature difference (Ti-Ts) Based on the first opening degree command, the temperature difference (Ti-Ts) Based on the second opening degree command. Therefore, in this case, the opening degree of the expansion valve 4 is controlled by the first command signal S7. That is, the opening degree of the expansion valve 4 is controlled so that the current opening degree is maintained without being changed by a sudden change in the cold water temperature.
[0036]
By the way, the exact control parameters and temperature difference (Ti-Ts) Using only one kind of opening degree command (second opening degree command), when the opening degree control is performed, the cold water temperature changes suddenly and the temperature difference (Ti-Ts) Is reduced, the opening of the expansion valve 4 is controlled in the closing direction. That is, the set temperature T indicated by a dotted line in the figure.sThe expansion valve 4 is closed to obtain a circulating refrigerant amount corresponding to the difference between the expansion valve 4 and the refrigerant. On the other hand, the turbo compressor 2 has a decreasing outflow temperature T.oSet temperature TsThe opening degree of the vane 2a is controlled so as to return to, and in this case, the closing direction is controlled. However, a certain time is required until the system of the turbo chiller is settled by the opening degree control of the vane 2a. Therefore, when the opening degree of the expansion valve 4 is closed in advance as described above, it causes unstable operation of the turbo chiller such as a lack of refrigerant on the downstream side of the expansion valve 4.
[0037]
On the other hand, in this embodiment, the temperature difference (Ti-To), The opening degree of the expansion valve 4 is maintained as it is, so even if a strict control parameter is set, the outflow temperature ToOnce set temperature TsHowever, even when overshooting to the low temperature side, the operation of the turbo chiller is not made unstable, and the set temperature T is controlled by the opening degree control of the vane 2a of the turbo compressor 2.sCan be returned to.
[0038]
In addition, although the expansion valve 4 in the said embodiment demonstrated the expansion valve 4 in a turbo refrigerator, there is no special limitation in the kind of refrigerator in this case. However, the temperature control of the chilled water that changes according to the load is preferably applied to a refrigerator that controls by adjusting the amount of refrigerant sucked or discharged from the compressor.
[0039]
Moreover, although the expansion valve 4 was demonstrated as applied to a single stage refrigerator, naturally it is not restricted to this. The refrigerator includes an intercooler between the condenser and the evaporator, and a multistage refrigerator having a multistage compressor that returns a part of the refrigerant from the intermediate cooler to the second and subsequent stages of the compressor. There is a machine, but it can be applied to this. In this case, the expansion valve 4 is arranged in the middle of the pipeline from the condenser to the evaporator and in the middle of the pipeline from the condenser to the intermediate cooler, and expands the refrigerant flowing into the intermediate cooler. Configured to let Further, there is a refrigerator having a subcooler for supercooling the refrigerant flowing out of the condenser, but this can also be applied to this. In this case, the expansion valve 4 is disposed in the middle of a pipeline from the condenser to the evaporator, and is disposed between the subcooler and the intermediate cooler that supercools the refrigerant flowing out of the condenser, and is subcooled by the subcooler. And configured to expand the refrigerant flowing into the intercooler. Furthermore, the present invention can be applied to a single-stage refrigerator having only a subcooler. In this case, the expansion valve 4 is disposed in the middle of the pipe line from the condenser to the evaporator, and is disposed on the downstream side of the subcooler that supercools the refrigerant flowing out of the condenser, and is subcooled by the subcooler. The refrigerant flowing into the tank is configured to expand.
[0040]
【The invention's effect】
As specifically described with the above embodiments, the invention described in [Claim 1] is an expansion valve control method for expanding a refrigerant that is disposed in the middle of a conduit from a condenser to an evaporator. In the above, the first refrigerating capacity of the refrigerating machine obtained by calculation based on the difference between the temperature of the inflow cold water or the inflow brine in the evaporator and the temperature of the outflow cold water or the outflow brine is used as a medium. A first opening degree command for controlling the opening degree of the expansion valve by calculation based on the first circulation amount and the upstream pressure and the downstream pressure of the expansion valve. While the temperature of the inflow cold water or inflow brine in the evaporator and the second temperature of the refrigerator obtained by calculation based on the difference between the preset temperature set based on the set temperature of the outflow cold water or outflow brine cold Using the capacity as a medium, the second circulation amount of the refrigerant in the refrigerator is calculated, and the expansion valve is opened by calculation based on the second circulation amount and the upstream pressure and downstream pressure of the expansion valve. A second opening degree command for controlling the degree is selected, a larger opening degree instruction is selected from the first opening degree instruction and the second opening degree instruction, and the first opening instruction thus selected is selected. Since the opening degree of the expansion valve is controlled by the opening degree instruction or the second opening degree instruction,
When the inflow temperature of the inflowing cold water suddenly changes to the high temperature side, the opening amount of the expansion valve is controlled by predicting the amount of refrigerant required by this sudden change by the second opening degree command based on the second circulation amount. be able to. Further, when the inflow temperature of the inflowing cold water suddenly changes to the low temperature side, the opening degree of the expansion valve is controlled to maintain the current refrigerant circulation amount by the first opening degree command based on the first circulation amount. Can do. That is, the second opening degree command does not close the expansion valve prior to the cold water temperature control of the refrigeration system.
As a result, even if strict control parameters are set and optimal opening degree control of the expansion valve is performed, the operation of the refrigerator is not made unstable. Therefore, it is possible to reduce the leakage of the refrigerant gas to the evaporator side as much as possible and operate the refrigerator with high efficiency. Furthermore, since the refrigerant liquid falls to the optimum liquid level without overshooting in the direction in which the liquid level of the refrigerant rises when the refrigerator is started, the time from the start to the stabilization of the cold water temperature control is minimized. Moreover, the low pressure trip resulting from the control following ability can be minimized.
[0041]
The invention described in [Claim 2] is the expansion valve control method in the refrigerator described in [Claim 1], wherein the preset temperature set in advance based on the preset temperature of the chilled cold water or effluent brine is As the set temperature of the chilled water or bleed brine of the refrigerator to adjust and control the amount of refrigerant sucked or discharged refrigerant,
Control similar to that of the invention described in [Claim 1] can be performed with reference to the set temperature of the chilled cold water supplied to the load, and similar actions and effects are obtained.
[0042]
The invention described in [Claim 3] is an evaporator that is detected by inflow temperature detection means in an expansion valve control device that is arranged in the middle of a conduit from the condenser to the evaporator to expand the refrigerant. And calculating the temperature difference between the inflow cold water or the inflow brine in the inflow and the outflow temperature of the outflow cold water or the outflow brine detected by the outlet temperature detection means, and based on this temperature difference, 1 refrigeration capacity is calculated, and a first circulation amount of the refrigerant in the refrigerator is calculated using the first refrigeration capacity as a medium, and the first circulation amount, the pressure upstream of the expansion valve, and A first opening degree command generating means for forming a first opening degree instruction for controlling the opening degree of the expansion valve by a calculation based on the downstream pressure, and the inlet temperature detected by the inlet temperature detecting means; The cold outflow Alternatively, a temperature difference with a preset temperature is calculated based on the set temperature of the outflow brine, a second refrigeration capacity of the refrigerator is calculated based on the temperature difference, and the second refrigeration capacity is mediated. And calculating the second circulation amount of the refrigerant in the refrigerator and controlling the opening degree of the expansion valve by calculation based on the second circulation amount and the upstream pressure and the downstream pressure of the expansion valve. A second opening degree command generating means for forming a second opening degree instruction for the first opening degree command, and a larger opening degree instruction among the first opening degree instruction and the second opening degree instruction. Since it has an opening degree command means for controlling the opening degree of the expansion valve with the selected first opening degree command or the second opening degree instruction,
When the inflow temperature of the inflowing cold water suddenly changes to the high temperature side, the opening amount of the expansion valve is controlled by predicting the amount of refrigerant required by this sudden change by the second opening degree command based on the second circulation amount. be able to. Further, when the inflow temperature of the inflowing cold water suddenly changes to the low temperature side, the opening degree of the expansion valve is controlled to maintain the current refrigerant circulation amount by the first opening degree command based on the first circulation amount. Can do. That is, the second opening degree command does not close the expansion valve prior to the cold water temperature control of the refrigeration system.
As a result, even if strict control parameters are set and optimal opening degree control of the expansion valve is performed, the operation of the refrigerator is not made unstable. Therefore, it is possible to reduce the leakage of the refrigerant gas to the evaporator side as much as possible and operate the refrigerator with high efficiency. Furthermore, since the refrigerant liquid falls to the optimum liquid level without overshooting in the direction in which the liquid level of the refrigerant rises when the refrigerator is started, the time from the start to the stabilization of the cold water temperature control is minimized. Moreover, the low pressure trip resulting from the control following ability can be minimized.
[0043]
The invention described in [Claim 4] is the expansion valve control device in the refrigerator described in [Claim 3], wherein the preset temperature set in advance based on the preset temperature of the chilled cold water or the spilled brine is As the set temperature of the chilled water or bleed brine of the refrigerator to adjust and control the amount of refrigerant sucked or discharged refrigerant,
Control similar to that of the invention described in [Claim 3] can be performed with reference to the set temperature of the chilled cold water supplied to the load, and similar actions and effects are obtained.
[0044]
The invention described in [Claim 5] is the expansion valve control device in the refrigerator described in [Claim 3] or [Claim 4], wherein the expansion valve adjusts the opening degree of the vane of the turbo compressor. Because it is an expansion valve of a turbo chiller that controls the temperature of the outflow cold water or outflow brine to be the set temperature by adjusting the amount of refrigerant sucked,
The effect similar to that of the invention described in [Claim 3] and [Claim 4] can be obtained by the turbo refrigerator.
[0045]
  The invention described in [Claim 6] is the expansion valve control device in the refrigerator according to any one of [Claim 3] to [Claim 5], wherein the expansion valve is changed from the condenser to the evaporator. An expansion valve of a multistage compression refrigerator that is arranged in the middle of the pipe line that leads to the intermediate cooler and expands the refrigerant flowing into the intermediate cooler.Yes, the intercooler returns a part of the refrigerant from the intercooler to the second and subsequent stages of the multistage compressor of the multistage compression refrigerator.So
  The same operation and effect as the invention described in [Claim 3] to [Claim 5] can be obtained by the multistage refrigerator.
[0046]
  The invention described in [Claim 7] is the expansion valve control device in the refrigerator according to any one of [Claim 3] to [Claim 5], wherein the expansion valve is changed from the condenser to the evaporator. It is located in the middle of the pipe line, and is placed between the subcooler and the intercooler that supercools the refrigerant flowing out of the condenser, and expands the refrigerant that is supercooled by the subcooler and flows into the intercooler The expansion valve of the multistage compression refrigeratorYes, the intercooler returns a part of the refrigerant from the intercooler to the second and subsequent stages of the multistage compressor of the multistage compression refrigerator.So
  The same operation and effect as the invention described in [Claim 3] to [Claim 5] can be obtained by the multistage refrigerator having the subcooler.
[0047]
The invention described in [Claim 8] is the expansion valve control device in the refrigerator according to any one of [Claim 3] to [Claim 5], wherein the expansion valve is changed from the condenser to the evaporator. An expansion valve of a refrigerator that is disposed in the middle of the pipe line and downstream of the subcooler that supercools the refrigerant flowing out of the condenser and expands the refrigerant that is supercooled by the subcooler and flows into the evaporator So
The same operation and effect as the invention described in [Claim 3] to [Claim 5] can be obtained by the refrigerator having the subcooler.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a control device according to an embodiment of the present invention together with a turbo chiller to which the control device is applied.
FIG. 2 is a temperature characteristic diagram for explaining an aspect of control of the expansion valve by the control device shown in FIG. 1;
FIG. 3 is a block diagram showing a general turbo chiller according to the prior art.
[Explanation of symbols]
1 Evaporator
2 Turbo compressor
2a Vane
3 Condenser
4 Expansion valve
11 Inflow temperature detector
12 Outflow temperature detector
14 Temperature setting section
15 Upstream pressure detector
16 Downstream pressure detector
17 First command generator
18 Second command generator
19 Opening command section
Ti        Inflow temperature
To        Outflow temperature

Claims (8)

凝縮器から蒸発器に至る管路の途中に配設されて冷媒を膨張させるための膨張弁の制御方法において、
蒸発器における流入冷水又は流入ブラインの温度と、流出冷水又は流出ブラインの温度との差に基づいて演算により得る当該冷凍機の第１の冷凍能力を媒介として、当該冷凍機における冷媒の第１の循環量を演算し、さらにこの第１の循環量と、膨張弁の上流側の圧力及び下流側の圧力とに基づく演算により膨張弁の開度を制御するための第１の開度指令を形成する一方、
前記蒸発器における流入冷水又は流入ブラインの温度と、流出冷水又は流出ブラインの設定温度に基づいて予め設定した設定温度との差に基づいて演算により得る当該冷凍機の第２の冷凍能力を媒介として、当該冷凍機における冷媒の第２の循環量を演算し、さらにこの第２の循環量と、膨張弁の上流側の圧力及び下流側の圧力とに基づく演算により膨張弁の開度を制御するための第２の開度指令を形成し、
前記第１の開度指令及び第２の開度指令のうち、大きい開度指令を選択し、このようにして選択した第１の開度指令又は第２の開度指令で膨張弁の開度を制御するようにしたことを特徴とする冷凍機における膨張弁の制御方法。In the control method of the expansion valve for expanding the refrigerant disposed in the middle of the conduit from the condenser to the evaporator,
The first refrigerating capacity of the refrigerant in the refrigerator is mediated by the first refrigeration capacity of the refrigerator obtained by calculation based on the difference between the temperature of the inflow cold water or the inflow brine in the evaporator and the temperature of the outflow cold water or the outflow brine. A circulation amount is calculated, and a first opening degree command for controlling the opening degree of the expansion valve is formed by calculation based on the first circulation amount and the upstream pressure and downstream pressure of the expansion valve. While
Through the second refrigeration capacity of the refrigerator obtained by calculation based on the difference between the temperature of the inflow cold water or the inflow brine in the evaporator and the preset temperature set based on the set temperature of the outflow cold water or the outflow brine Then, the second circulation amount of the refrigerant in the refrigerator is calculated, and the opening degree of the expansion valve is controlled by calculation based on the second circulation amount, the upstream pressure and the downstream pressure of the expansion valve. Forming a second opening command for
A large opening command is selected from the first opening command and the second opening command, and the opening of the expansion valve is selected by the first opening command or the second opening command selected as described above. A control method for an expansion valve in a refrigerator, wherein the control is performed. 〔請求項１〕に記載する冷凍機における膨張弁の制御方法において、
流出冷水又は流出ブラインの設定温度に基づいて予め設定する設定温度は、圧縮機の吸入冷媒量又は吐出冷媒量を調整して制御する当該冷凍機の前記流出冷水又は流出ブラインの設定温度としたことを特徴とする冷凍機における膨張弁の制御方法。In the control method of the expansion valve in the refrigerator described in [Claim 1],
The preset temperature set in advance based on the preset temperature of the chilled cold water or effluent brine is the preset temperature of the chilled cold water or effluent brine of the refrigerator that is controlled by adjusting the amount of refrigerant sucked or discharged from the compressor. A control method for an expansion valve in a refrigerator. 凝縮器から蒸発器に至る管路の途中に配設されて冷媒を膨張させるための膨張弁の制御装置において、
流入温度検出手段が検出する、蒸発器における流入冷水又は流入ブラインの流入温度と、出口温度検出手段が検出する、前記流出冷水又は流出ブラインの流出温度とに基づき両者の温度差を演算するとともに、この温度差に基づき当該冷凍機の第１の冷凍能力を演算し、さらにこの第１の冷凍能力を媒介として当該冷凍機における冷媒の第１の循環量を演算するとともに、前記第１の循環量と、膨張弁の上流側の圧力及び下流側の圧力とに基づく演算により膨張弁の開度を制御するための第１の開度指令を形成する第１の開度指令生成手段と、
前記入口温度検出手段が検出する前記入口温度と、前記流出冷水又は流出ブラインの設定温度に基づいて予め設定した設定温度との温度差を演算するとともに、この温度差に基づき当該冷凍機の第２の冷凍能力を演算し、さらにこの第２の冷凍能力を媒介として当該冷凍機における冷媒の第２の循環量を演算するとともに、前記第２の循環量と、膨張弁の上流側の圧力及び下流側の圧力とに基づく演算により膨張弁の開度を制御するための第２の開度指令を形成する第２の開度指令生成手段と、
前記第１の開度指令及び第２の開度指令のうち、大きい開度指令を選択し、このようにして選択した第１の開度指令又は第２の開度指令で膨張弁の開度を制御する開度指令手段とを有することを特徴とする冷凍機における膨張弁の制御装置。In the control device for the expansion valve that is arranged in the middle of the conduit from the condenser to the evaporator and expands the refrigerant,
While calculating the temperature difference between the inflow temperature of the inflow cold water or the inflow brine in the evaporator detected by the inflow temperature detection means and the outflow temperature of the outflow cold water or the outflow brine detected by the outlet temperature detection means, A first refrigeration capacity of the refrigerator is calculated based on the temperature difference, and a first circulation amount of the refrigerant in the refrigerator is calculated using the first refrigeration capacity as a medium, and the first circulation amount is calculated. And a first opening degree command generating means for forming a first opening degree instruction for controlling the opening degree of the expansion valve by calculation based on the pressure on the upstream side and the pressure on the downstream side of the expansion valve;
A temperature difference between the inlet temperature detected by the inlet temperature detection means and a preset temperature set based on the preset temperature of the chilled cold water or effluent brine is calculated, and the second temperature of the refrigerator is calculated based on the temperature difference. And the second circulation amount of the refrigerant in the refrigerator is calculated using the second refrigeration capability as a medium, and the second circulation amount, the pressure upstream of the expansion valve, and the downstream Second opening degree command generating means for forming a second opening degree command for controlling the opening degree of the expansion valve by calculation based on the pressure on the side,
A large opening command is selected from the first opening command and the second opening command, and the opening of the expansion valve is selected by the first opening command or the second opening command selected as described above. And an opening degree commanding means for controlling the expansion valve. 〔請求項３〕に記載する冷凍機における膨張弁の制御装置において、流出冷水又は流出ブラインの設定温度に基づいて予め設定する設定温度は、圧縮機の吸入冷媒量又は吐出冷媒量を調整して制御する当該冷凍機の前記流出冷水又は流出ブラインの設定温度としたことを特徴とする冷凍機における膨張弁の制御装置。  In the expansion valve control apparatus for a refrigerator described in [Claim 3], the preset temperature set in advance based on the preset temperature of the chilled cold water or effluent brine is adjusted by adjusting the amount of refrigerant sucked or discharged from the compressor. A control device for an expansion valve in a refrigerator, wherein a set temperature of the chilled water or bleed brine of the refrigerator to be controlled is set. 〔請求項３〕又は〔請求項４〕に記載する冷凍機における膨張弁の制御装置において、
膨張弁は、ターボ圧縮機のベーンの開度を調整して吸入冷媒量を調整することにより流出冷水又は流出ブラインの温度が設定温度になるように制御するターボ冷凍機の膨張弁であることを特徴とする冷凍機における膨張弁の制御装置。In the control device for the expansion valve in the refrigerator according to [Claim 3] or [Claim 4],
The expansion valve is an expansion valve of a turbo chiller that controls the temperature of the chilled water or bleed brine to be the set temperature by adjusting the amount of refrigerant sucked by adjusting the opening of the vane of the turbo compressor. A control device for an expansion valve in a refrigerator. 〔請求項３〕乃至〔請求項５〕の何れか一つに記載する冷凍機における膨張弁の制御装置において、
膨張弁は、凝縮器から蒸発器に至る管路の途中であって、且つ凝縮器から中間冷却器に至る管路の途中に配設されており、中間冷却器に流入する冷媒を膨張させる多段圧縮冷凍機の膨張弁であること、
中間冷却器は、中間冷却器から一部の冷媒を、多段圧縮冷凍機の多段圧縮機の２段目以降に戻すものであること、
を特徴とする冷凍機における膨張弁の制御装置。In the control device for the expansion valve in the refrigerator according to any one of [Claim 3] to [Claim 5],
The expansion valve is arranged in the middle of the pipeline from the condenser to the evaporator and in the middle of the pipeline from the condenser to the intermediate cooler, and expands the refrigerant flowing into the intermediate cooler. that it is an expansion valve of the compression refrigeration machine,
The intercooler is to return a part of the refrigerant from the intercooler to the second and subsequent stages of the multistage compressor of the multistage compression refrigerator,
A control device for an expansion valve in a refrigerator. 〔請求項３〕乃至〔請求項５〕の何れか一つに記載する冷凍機における膨張弁の制御装置において、
膨張弁は、凝縮器から蒸発器に至る管路の途中であって、凝縮器から流出する冷媒を過冷却するサブクーラと中間冷却器との間に配設されており、サブクーラで過冷却され、且つ中間冷却器に流入する冷媒を膨張させる多段圧縮冷凍機の膨張弁であること、
中間冷却器は、中間冷却器から一部の冷媒を、多段圧縮冷凍機の多段圧縮機の２段目以降に戻すものであること、
を特徴とする冷凍機における膨張弁の制御装置。In the control device for the expansion valve in the refrigerator according to any one of [Claim 3] to [Claim 5],
The expansion valve is disposed in the middle of the pipeline from the condenser to the evaporator, and is disposed between the subcooler and the intercooler that supercools the refrigerant flowing out of the condenser, and is subcooled by the subcooler, that it is a and the expansion valve of the multi-stage compression refrigeration machine for expanding the refrigerant flowing into the intermediate cooler,
The intercooler is to return a part of the refrigerant from the intercooler to the second and subsequent stages of the multistage compressor of the multistage compression refrigerator,
A control device for an expansion valve in a refrigerator. 〔請求項３〕乃至〔請求項５〕の何れか一つに記載する冷凍機における膨張弁の制御装置において、
膨張弁は、凝縮器から蒸発器に至る管路の途中であって、凝縮器から流出する冷媒を過冷却するサブクーラの下流側に配設されており、サブクーラで過冷却され、蒸発器に流入する冷媒を膨張させる冷凍機の膨張弁であることを特徴とする冷凍機における膨張弁の制御装置。In the control device for the expansion valve in the refrigerator according to any one of [Claim 3] to [Claim 5],
The expansion valve is located in the middle of the pipe line from the condenser to the evaporator, and is arranged downstream of the subcooler that supercools the refrigerant flowing out of the condenser. The expansion valve is supercooled by the subcooler and flows into the evaporator. A control device for an expansion valve in a refrigerator, which is an expansion valve of a refrigerator for expanding a refrigerant to be cooled.
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JPH0275841A (en) * 1988-09-09 1990-03-15 Mitsubishi Electric Corp Multi-room type air-conditioning machine
JPH0599517A (en) * 1991-10-09 1993-04-20 Sharp Corp Air conditioner
JPH06323639A (en) * 1993-05-10 1994-11-25 Hitachi Ltd Method for controlling chilled water supplying device

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JPS6291167U (en) * 1985-11-29 1987-06-11
JPH0275841A (en) * 1988-09-09 1990-03-15 Mitsubishi Electric Corp Multi-room type air-conditioning machine
JPH0599517A (en) * 1991-10-09 1993-04-20 Sharp Corp Air conditioner
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