JP3856538B2

JP3856538B2 - Refrigeration equipment

Info

Publication number: JP3856538B2
Application number: JP23806697A
Authority: JP
Inventors: 直彦山下; 隆夫山本
Original assignee: Air Liquide Japan GK
Current assignee: Air Liquide Japan GK
Priority date: 1997-09-03
Filing date: 1997-09-03
Publication date: 2006-12-13
Anticipated expiration: 2017-09-03
Also published as: JPH1183219A

Description

【０００１】
【発明の属する技術分野】
本発明は、供給された第１熱媒体を気化させることにより対象物の冷却を行う冷却部と、その冷却部で気化した前記第１熱媒体を導いてほぼ一定の入口温度で圧縮を行う低温圧縮機と、その低温圧縮機で圧縮された前記第１熱媒体を導いて、第２熱媒体との熱交換により前記第１熱媒体を冷却する第１熱交換器と、その第１熱交換器で冷却された前記第１熱媒体を導いて、その第１熱媒体を膨張させた後、その第１熱媒体を再び前記冷却部に供給しうる膨張弁とを具備して冷凍機サイクルを構成すると共に、前記第１熱交換器へ前記第２熱媒体を導いて、その第１熱交換器にて前記第１熱媒体との熱交換により前記第２熱媒体を加熱した後、前記第２熱媒体を排出する第２熱媒体流通路を設けてある冷凍装置に関する。
【０００２】
【従来の技術】
従来、この種の冷凍装置は、低温熱媒体（例えば液化天然ガス）の寒冷を利用して、より低温の冷凍を行うものであるが、例えば冷凍庫や石油化学の分野で用いられている。その際、冷凍負荷が変化した時に、装置の冷凍能力を変化させる必要があるが、通常は低温圧縮機単独の能力調整によって行われていた。
【０００３】
例えば、低温圧縮機が定容積式低温圧縮機である場合、アンローダ弁、クリアランス弁、バイパス弁などによる調整が行われてきた。アンローダ弁による調整は、シリンダーの一部を機能しないようにする方法であり、クリアランス弁による調整は、シリンダー内の死容積を調整する方法であり、また、バイパス弁による調整は、定容積式低温圧縮機の入口側と出口側との間に弁を有するバイパスを設けて、弁の開度を調整する方法である。
【０００４】
【発明が解決しようとする課題】
しかしながら、アンローダ弁またクリアランス弁による調整では、能力の調整が段階的になるために、冷凍装置の安定的な制御がしづらいという欠点があった。
【０００５】
一方、バイパス弁による調整では、低温圧縮機の入口側と出口側とでは温度差が大きく、そのまま入口側に戻すと低温圧縮機の運転温度が変動し、冷凍装置の制御が複雑・困難になる。このため、低温熱媒体との熱交換により低温圧縮機の入口側の温度まで冷却することも考えられるが、付加設備が必要になり経済的でない。
【０００６】
そして、上記のような定容積式低温圧縮機の出口圧力を一定にした場合には、例えば冷凍負荷が減少して、低温圧縮機の入口側の圧力が低下した場合に、圧縮比が大きくなるため、温度上昇、ピストン等の構造体に加わる不平衡力の増大、容積効率の異常低下による不安定化などが生じる。
一方、遠心式低温圧縮機を用いる場合においても、低風量域でサージ現象により動作が不安定となる。入口圧力が変化する場合、その限界値は圧縮比の上限で規定されるので定容積式低温圧縮機と同様に問題となる。
【０００７】
従って、本発明の目的は、上記に鑑みて、簡易な装置構成によって、冷凍負荷が変化した時に、自動で装置の冷凍能力を広範囲に調整でき、しかも安定な動作が可能な冷凍装置を提供することにある。
【０００８】
【課題を解決するための手段】
上記目的を達成するための本発明の特徴構成は、供給された第１熱媒体を気化させることにより対象物の冷却を行う冷却部と、その冷却部で気化した前記第１熱媒体を導いてほぼ一定の入口温度で圧縮を行う低温圧縮機と、その低温圧縮機で圧縮された前記第１熱媒体を導いて、第２熱媒体との熱交換により前記第１熱媒体を冷却する第１熱交換器と、その第１熱交換器で冷却された前記第１熱媒体を導いて、その第１熱媒体を膨張させた後、その第１熱媒体を再び前記冷却部に供給しうる膨張弁とを具備して冷凍機サイクルを構成すると共に、前記第１熱交換器へ前記第２熱媒体を導いて、その第１熱交換器にて前記第１熱媒体との熱交換により前記第２熱媒体を加熱した後、前記第２熱媒体を排出する第２熱媒体流通路を設けてある冷凍装置において、前記低温圧縮機の入口側と出口側とに、それぞれの圧力を検出する入口圧検出器と出口圧検出器とを設けると共に、前記入口圧検出器の出力に基づいて、予め定めた関係式を用い、前記低温圧縮機の望ましい出口圧力の設定値を算出する手段を有し、前記出口圧検出器の出力が前記設定値になるよう、前記膨張弁の開度を調整する制御手段を設けてある点にある。ここで、望ましい出口圧力とは、低温圧縮機の種類に応じて決定され、安全域とされる圧縮比を与えるための出口圧力を指す。
【０００９】
また、上記構成において、前記膨張弁と前記冷却部との間に、前記膨張弁にて膨張した前記第１熱媒体を導いて、その第１熱媒体の液体成分を貯留しつつ、その液体成分を前記冷却部に供給すると共に、前記第１熱媒体の気体成分を貯留しつつ、その気体成分を前記冷却部の下流側に供給する貯留槽を、更に設けてあることがより好ましい。
【００１０】
前記制御手段による制御としては種々の方法を採用することができるが、前記制御手段が、前記入口圧検出器の出力に基づいて、その出力値が既定値以下となる場合に、前記低温圧縮機による圧縮比が既定値をほぼ維持するように、前記膨張弁を開度調整するものであることがより好ましい。
【００１１】
前記低温圧縮機としては、種々の形式のものが採用できるが、定容積式圧縮機の場合には、その流量がほぼ入口条件で決まり、入口温度がほぼ一定のとき入口の絶対圧力にほぼ比例するので流量特性を予測しやすいとの長所がある。
【００１２】
前記第１熱媒体と前記第２熱媒体との組み合わせとしては、種々のものが採用できるが、前記第１熱媒体が窒素であり、かつ前記第１熱交換器へ導く前記第２熱媒体が液化天然ガスである組み合わせが一般によく用いられる。
【００１３】
また、上記目的を達成するための本発明の他の特徴構成は、供給された第１熱媒体を気化させることにより対象物の冷却を行う冷却部と、その冷却部で気化した前記第１熱媒体を導いてほぼ一定の入口温度で圧縮を行う低温圧縮機と、その低温圧縮機で圧縮された前記第１熱媒体を導いて、第２熱媒体との熱交換により前記第１熱媒体を冷却する第１熱交換器と、その第１熱交換器で冷却された前記第１熱媒体を導いて、その第１熱媒体を膨張させた後、その第１熱媒体を再び前記冷却部に供給しうる膨張弁とを具備して冷凍機サイクルを構成すると共に、前記第１熱交換器へ前記第２熱媒体を導いて、その第１熱交換器にて前記第１熱媒体との熱交換により前記第２熱媒体を加熱した後、前記第２熱媒体を排出する第２熱媒体流通路を設けてある冷凍装置において、前記低温圧縮機の出口側にその圧力を検出する出口圧検出器を設けると共に、前記冷却部と低温圧縮機との間に、第１熱媒体の流量を検出する流量検出器を設けて、その流量検出器の出力に基づいて、予め定めた関係式を用い、前記低温圧縮機の望ましい出口圧力の設定値を算出する手段を有し、前記出口圧検出器の出力が前記設定値になるよう、前記膨張弁の開度を調整する制御手段を設けてある点にある。
【００１４】
〔作用効果〕
本発明による冷凍装置、つまり、第２熱媒体の寒冷で第１熱媒体を第１熱交換器で冷却し膨張弁で膨張する方式の冷凍装置では、一般的に、第１熱交換器における第１熱媒体の圧力（低温圧縮機の出口側の圧力）がある程度高いほど冷凍能力が大きくなる。また、自明のことであるが、第１熱媒体の流量に比例して冷凍能力が変化する。
そして、本発明の上記特徴構成によれば、前記低温圧縮機の入口側と出口側とに、それぞれの圧力を検出する入口圧検出器と出口圧検出器とを設けてあるため、それらの出力より入口側と出口側の圧力及び圧縮比を求めることができる。そして、制御手段が、前記入口圧検出器の出力に基づいて、前記低温圧縮機の出口圧力が望ましい値になるように、前記膨張弁を開度調整するため、例えば冷凍負荷が減少して、低温圧縮機の入口側の圧力が低下した場合に、膨張弁の開度をそのままにしておくと低温圧縮機の出口圧力が下がって第１熱交換器が機能しなくなるのを避けるため、膨張弁の開度を閉じる方へ調節することによって出口側の圧力を制御し、圧縮比を安全域に自動で維持することができる。また、この操作は、同時に前記膨張弁を通過する第１熱媒体の流量を減少させ延いては液化効率の低下をもたらし、冷凍能力の調整にも寄与することができる。しかも、検出器等は安価であり装置構成も単純である。
その結果、簡易な装置構成によって、冷凍負荷が変化した時に、自動で装置の冷凍能力を広範囲に調整でき、しかも安定な動作が可能な冷凍装置を提供することができる。
【００１５】
前記膨張弁と前記冷却部との間に、前記膨張弁にて膨張した前記第１熱媒体を導いて、その第１熱媒体の液体成分を貯留しつつ、その液体成分を前記冷却部に供給すると共に、前記第１熱媒体の気体成分を貯留しつつ、その気体成分を前記冷却部の下流側に供給する貯留槽を、更に設けてある場合、
冷凍負荷の変化に対して貯留槽がバッファータンクの役割をすると共に、気液分離器の機能を有するため、液体成分のみを前記冷却部に供給して、効率よく冷却を行うことが可能になると共に、気体成分はサイクル中に戻して第１熱媒体として再利用することができる。
【００１６】
前記制御手段が、前記入口圧検出器の出力に基づいて、その出力値が既定値以下となる場合に、前記低温圧縮機による圧縮比が既定値をほぼ維持するように、前記膨張弁を開度調整するものである場合、
入口圧検出器からの出力値が既定値以下になると、圧縮比が大きくなるので、これを抑える必要があり、圧縮比をほぼ設定値に維持すれば、運転に問題が生じず、動作が安定化する。この方式による場合、第１熱交換器に於ける第１、第２熱媒体の運転圧力を定格点近くでほぼ一定にでき、より安定な運転が出来、かつ制御系が簡略になるとの利点がある。
【００１７】
前記低温圧縮機が定容積式低温圧縮機である場合、前述のように圧縮機の風量特性が予測しやすく、制御方式が決定しやすいとの利点がある。
【００１８】
前記第１熱媒体が窒素であり、かつ前記第１熱交換器へ導く前記第２熱媒体が液化天然ガスである場合、
液化天然ガスは、輸送の為に加圧液化されているため、その寒冷の有効利用が望まれており、また窒素は空気中に多量に含有される成分であり、沸点が液化天然ガスの供給温度より低いため、本発明の冷凍機サイクルに好適に用いられる。
【００１９】
本発明の他の特徴構成によると、前記冷却部と低温圧縮機との間に、第１熱媒体の流量を検出する流量検出器を設けてあるため、その出力から冷凍負荷の変化を知ることができる。そして、その冷凍負荷の変化を圧力の推定値として算出することができる一方、制御手段が、その流量検出器の出力に基づいて、予め定めた関係式を用い、前記低温圧縮機の望ましい出口圧力の設定値になるように、前記膨張弁の開度を調整するため、例えば冷凍負荷が減少して、低温圧縮機の入口側の流量が低下した場合に、膨張弁の開度をそのままにしておくと低温圧縮機の出口圧力が下がって第１熱交換器が機能しなくなるのを避けるため、膨張弁の開度を閉じる方へ調節することによって出口側の圧力を制御し、圧縮比を安全域に自動で維持することができる。また、この操作は、同時に前記膨張弁を通過する第１熱媒体の流量を減少させ延いては液化効率の低下をもたらし、冷凍能力の調整にも寄与することができる。しかも、検出器等は安価であり装置構成も単純である。
その結果、簡易な装置構成によって、冷凍負荷が変化した時に、自動で装置の冷凍能力を広範囲に調整でき、しかも安定な動作が可能な冷凍装置を提供することができる。
【００２０】
【発明の実施の形態】
以下に本発明の実施の形態を図面に基づいて説明する。
本発明の冷凍装置は、例えば図１に示すように、供給された第１熱媒体Ｍ１を気化させることにより対象物の冷却を行う冷却部８と、その冷却部８で気化した第１熱媒体Ｍ１を導いてほぼ一定の入口温度で圧縮を行う低温圧縮機１と、その低温圧縮機１で圧縮された第１熱媒体Ｍ１を導いて、第２熱媒体Ｍ２との熱交換により第１熱媒体Ｍ１を冷却する第１熱交換器Ｅ１と、その第１熱交換器Ｅ１で冷却された第１熱媒体Ｍ１を導いて、その第１熱媒体Ｍ１を膨張させた後、その第１熱媒体Ｍ１を再び冷却部８に供給しうる膨張弁５とを具備して冷凍機サイクルを構成してある。
【００２１】
本実施形態では、膨張弁５と冷却部８との間に、膨張弁５にて膨張した第１熱媒体Ｍ１を導いて、その第１熱媒体Ｍ１の液体成分を貯留しつつ、その液体成分を冷却部８に供給すると共に、第１熱媒体Ｍ１の気体成分を貯留しつつ、その気体成分を冷却部８の下流側に供給する貯留槽６を設けてある例を示す。
【００２２】
冷凍機サイクルの構成をより具体的に説明すると、以下のようになる。
冷却部８は、経路Ｐ７を経て供給された第１熱媒体Ｍ１を気化させることにより対象物の冷却を行うための各種冷却槽やガス製造装置のコンデンサー等であり、多管式やジャケット式のものなどが用いられる。図１には槽の周囲にジャケット８ａを有する冷却槽を示してある。冷却部８で気化した第１熱媒体Ｍ１は、経路Ｐ８を経て熱交換器４に供給される。経路Ｐ８には圧力調整弁９，１０が設けられている。なお、経路Ｐ８の温度と圧力を例示すると、例えば約−１７５℃，約３．１ｋｇ／ｃｍ²ｇである。
【００２３】
熱交換器４では、膨張弁５で膨張させる前の第１熱媒体Ｍ１による加熱が行われ、経路Ｐ９を経て低温圧縮機１に供給される。なお、経路Ｐ９の温度と圧力を例示すると、例えば約−１４０℃，約３ｋｇ／ｃｍ²ｇである。
【００２４】
低温圧縮機１は経路Ｐ９を経て導かれた第１熱媒体Ｍ１の圧縮を行うものであり、圧縮された第１熱媒体Ｍ１は、経路Ｐ４を経て熱交換器２に供給される。低温圧縮機１としては、定容積式低温圧縮機や遠心式低温圧縮機等が用いられるが、本実施形態では前者を用いた場合を示す。なお、経路Ｐ４の温度と圧力を例示すると、例えば約１００℃，約６０ｋｇ／ｃｍ²ｇである。経路Ｐ４には水冷等による冷却器を設けてもよい。
【００２５】
熱交換器２は熱交換器３と共に、第１熱交換器Ｅ１を構成するものであり、熱交換器２は気体状の第２熱媒体Ｍ２との熱交換を行い、熱交換器３は液体状の第２熱媒体Ｍ２との熱交換を行う。従って、両者は１つの熱交換器で構成することも可能である。熱交換器２と熱交換器３とは経路Ｐ５で接続され、熱交換器３の出口側には経路Ｐ６が接続されている。なお、経路Ｐ５の温度と圧力を例示すると、例えば約−２６℃，約６０ｋｇ／ｃｍ²ｇであり、経路Ｐ６の温度と圧力を例示すると、例えば約−１３８℃，約６０ｋｇ／ｃｍ²ｇである。
【００２６】
熱交換器４では、冷却部８で気化した第１熱媒体Ｍ１による冷却が行われ、冷却した第１熱媒体Ｍ１は膨張弁５に供給される。膨張弁５では第１熱媒体Ｍ１の膨張が行われ、その冷却効果により一部液化が生じながら、貯留槽６に供給される。なお、熱交換器４は、被冷却部の必要温度レベルに対して第１熱交換器による冷却で十分であれば、特に設ける必要はない。
【００２７】
貯留槽６は、第１熱媒体Ｍ１の液体成分を貯留しつつ、その液体成分を経路Ｐ７を経て冷却部８に供給すると共に、第１熱媒体Ｍ１の気体成分を貯留しつつ、その気体成分を冷却部８の下流側に位置する経路Ｐ８に供給する。経路Ｐ８への供給路には圧力調整弁１１が設けられており、貯留槽６内の圧力がほぼ一定に維持されている。また、貯留槽６には、第１熱媒体Ｍ１の液体成分の貯留量をほぼ一定範囲に維持するため、排出経路Ｐ１０と開閉弁１４、および、外部タンク１２と供給経路Ｐ１１と開閉弁１３が設けられている。
【００２８】
そして、第２熱媒体Ｍ２は経路Ｐ１を経て熱交換器３へ導かれるが、経路Ｐ１には、経路Ｐ６の温度がほぼ一定になるように供給量を調節すべく、流量調整弁１５が設けてある。その結果、熱交換器４の能力を充分にしておけば、経路Ｐ６つまり低温圧縮機の入口温度をほぼ一定に保つことができる。なお、経路Ｐ１の温度と圧力を例示すると、例えば約−１５３℃，約３０ｋｇ／ｃｍ²ｇである。
【００２９】
熱交換器３と熱交換器２の間は経路Ｐ２で接続され、更にその経路Ｐ２には気液分離槽１６が設けられている。気液分離槽１６からは気体成分のみが熱交換器２に供給され、液体成分は気液分離槽１６に貯留される。その際、第２熱媒体Ｍ２の液体成分の貯留量をほぼ一定範囲に維持するため、排出経路Ｐ１２と開閉弁１７が設けられている。熱交換器３と熱交換器２とで構成される第１熱交換器Ｅ１では、第１熱媒体Ｍ１との熱交換により第２熱媒体Ｍ２が加熱され、その後、第２熱媒体流通路Ｐ３を経て排出される。
なお、第１熱媒体Ｍ１と第２熱媒体Ｍ２の組み合わせによっては、気液分離槽１６を設ける必要がない場合もある。
【００３０】
本実施形態では、第１熱媒体が窒素であり、かつ第１熱交換器へ導く第２熱媒体が液化天然ガスである例を示すが、本発明はこれに限定されるものではない。
【００３１】
以下、本発明の特徴構成に係る制御に関して説明する。
低温圧縮機１の入口側と出口側に相当する経路Ｐ９，Ｐ４には、それぞれの圧力を検出する入口圧検出器Ｓ１と出口圧検出器Ｓ２とが設けられている。検出器には種々の圧力センサ等が用いられ、また、検出器の設置位置は、経路Ｐ９の代わりに経路Ｐ８であってもよく、経路Ｐ４の代わりに経路Ｐ５，Ｐ６であってもよい。入口圧検出器Ｓ１と出口圧検出器Ｓ２の出力信号は、制御手段Ｃに接続されている。
【００３２】
制御手段Ｃは、入口圧検出器Ｓ１の出力に基づいて、予め定めた関係式を用い、前記低温圧縮機１の望ましい出口圧力の設定値を算出する手段を有し、出口圧検出器Ｓ２の出力が前記設定値になるよう膨張弁５を開度調整する。具体的な制御回路構成としては、入口圧力検出器Ｓ１の出力信号を所謂“折れ線演算回路”で変換後、出口圧力検出器Ｓ２と膨張弁５による圧力調節器の設定信号として入力するカスケード制御回路で実現できる。
具体的な例としては、入口圧検出器Ｓ１の出力に基づいて、その出力値が既定値以下となる場合に、低温圧縮機１による圧縮比が既定値をほぼ維持するように、膨張弁５の開度を調整すればよい。
また、入口圧力検出器Ｓ１の出力の全域に対して、圧縮比をほぼ維持するように、開度調整を行う方式も場合により考えられる。
【００３３】
〔別実施形態〕
以下、本発明の他の実施形態について説明する。
【００３４】
〈１〉先の実施形態では、低温圧縮機の入口側に入口圧検出器を設けて、その出力による制御を行う例を示したが、図２に示すように、前記冷却部８と低温圧縮機１との間に、第１熱媒体Ｍ１の流量を検出する流量検出器Ｓ３を設けて、その出力による制御を行うように構成してもよい。
その場合、前記低温圧縮機１の出口側にその圧力を検出する出口圧検出器Ｓ２を設けると共に、前記冷却部８と低温圧縮機１との間に、第１熱媒体の流量を検出する流量検出器Ｓ３を設けて、その流量検出器Ｓ３の出力に基づいて、予め定めた関係式を用い、前記低温圧縮機１の望ましい出口圧力の設定値を算出する手段を有し、前記出口圧検出器Ｓ２の出力が前記設定値になるよう、前記膨張弁５の開度を調整する制御手段Ｃを設けて構成する。この点以外は、先の実施形態の説明と同様であるため、相違点のみについて説明する。
流量検出器Ｓ３としては、気体用の流量センサ等が用いられその出力信号は、制御手段Ｃに接続されている。流量検出器Ｓ３の出力と入口圧との関係を求めておき、その関係から得られる値に基づいて、先の実施形態と同様の制御を行うことができる。
【００３５】
〈２〉先の実施形態では、各経路の温度と圧力を例示したが、これは本発明の理解を容易にするために示したものであり、運転条件や各部の設計、熱媒体の種類や量などによって変化しうるため、本発明は例示した値によってなんら制限を受けるものではない。
【図面の簡単な説明】
【図１】冷凍装置の一例を示す模式構成図
【図２】別実施形態の冷凍装置を示す模式構成図
【符号の説明】
１低温圧縮機
５膨張弁
６貯留槽
８冷却部
Ｍ１第１熱媒体
Ｍ２第２熱媒体
Ｅ１第１熱交換器
Ｓ１入口圧検出器
Ｓ２出口圧検出器
Ｓ３流量検出器
Ｃ制御手段[0001]
BACKGROUND OF THE INVENTION
The present invention performs compression at a substantially constant inlet temperature leading a cooling unit for cooling the object, the first heat medium is vaporized in the cooling section by vaporizing the first heat medium supplied A low-temperature compressor, a first heat exchanger that guides the first heat medium compressed by the low-temperature compressor and cools the first heat medium by heat exchange with the second heat medium, and the first heat An refrigeration machine cycle comprising: an expansion valve capable of guiding the first heat medium cooled by the exchanger and expanding the first heat medium and then supplying the first heat medium to the cooling unit again The second heat medium is guided to the first heat exchanger, and the second heat medium is heated by heat exchange with the first heat medium in the first heat exchanger, The present invention relates to a refrigeration apparatus provided with a second heat medium flow passage for discharging the second heat medium.
[0002]
[Prior art]
Conventionally, this type of refrigeration apparatus performs refrigeration at a lower temperature by utilizing the coldness of a low-temperature heat medium (for example, liquefied natural gas), and is used in, for example, the freezer and petrochemical fields. At that time, when the refrigeration load changes, it is necessary to change the refrigeration capacity of the apparatus, but it is usually performed by adjusting the capacity of the low-temperature compressor alone.
[0003]
For example, when the low-temperature compressor is a constant displacement type low-temperature compressor, adjustment using an unloader valve, a clearance valve, a bypass valve, and the like has been performed. Adjustment with the unloader valve is a method to prevent a part of the cylinder from functioning, adjustment with the clearance valve is a method to adjust the dead volume in the cylinder, and adjustment with the bypass valve is a constant volume low temperature. In this method, a bypass having a valve is provided between the inlet side and the outlet side of the compressor to adjust the opening of the valve.
[0004]
[Problems to be solved by the invention]
However, the adjustment by the unloader valve or the clearance valve has a drawback that it is difficult to control the refrigeration apparatus stably because the adjustment of the capacity becomes stepwise.
[0005]
On the other hand, in the adjustment by the bypass valve, there is a large temperature difference between the inlet side and the outlet side of the low-temperature compressor. . For this reason, although cooling to the temperature of the inlet side of a low-temperature compressor is also considered by heat exchange with a low-temperature heat medium, additional equipment is needed and it is not economical.
[0006]
And, when the outlet pressure of the constant displacement low-temperature compressor as described above is made constant, for example, when the refrigeration load decreases and the pressure on the inlet side of the low-temperature compressor decreases, the compression ratio increases. For this reason, the temperature rises, the unbalance force applied to the structure such as the piston increases, and the volume efficiency becomes unstable due to an abnormal decrease.
On the other hand, even when a centrifugal low-temperature compressor is used, the operation becomes unstable due to a surge phenomenon in a low air volume region. When the inlet pressure changes, the limit value is defined by the upper limit of the compression ratio, so that it becomes a problem as in the case of the constant displacement cryogenic compressor.
[0007]
Therefore, in view of the above, an object of the present invention is to provide a refrigeration apparatus that can automatically adjust the refrigeration capacity of the apparatus over a wide range and can operate stably when the refrigeration load changes with a simple apparatus configuration. There is.
[0008]
[Means for Solving the Problems]
The characteristic configuration of the present invention for achieving the above object is to introduce a cooling unit that cools an object by vaporizing the supplied first heat medium, and the first heat medium vaporized by the cooling unit. A low-temperature compressor that compresses at a substantially constant inlet temperature and a first heat medium that is guided by the low-temperature compressor and that cools the first heat medium by exchanging heat with the second heat medium. The heat exchanger and the first heat medium cooled by the first heat exchanger are guided to expand the first heat medium, and then the first heat medium can be supplied to the cooling unit again. A refrigerating machine cycle comprising the valve, guiding the second heat medium to the first heat exchanger, and exchanging the first heat medium with the first heat medium by the first heat exchanger. Refrigeration provided with a second heat medium flow passage for discharging the second heat medium after heating the two heat medium In addition, an inlet pressure detector and an outlet pressure detector for detecting respective pressures are provided on the inlet side and the outlet side of the low-temperature compressor, and predetermined based on the output of the inlet pressure detector. Control means for adjusting the opening of the expansion valve so as to calculate a desired outlet pressure set value of the low-temperature compressor using a relational expression so that the output of the outlet pressure detector becomes the set value It is in the point which is provided. Here, the desirable outlet pressure refers to an outlet pressure that is determined according to the type of the low-temperature compressor and that provides a compression ratio that is within a safe range.
[0009]
In the above configuration, the liquid component of the first heat medium is introduced between the expansion valve and the cooling unit while guiding the first heat medium expanded by the expansion valve and storing the liquid component of the first heat medium. It is more preferable to further provide a storage tank that supplies the gas component to the downstream side of the cooling unit while supplying the gas component to the cooling unit and storing the gas component of the first heat medium.
[0010]
Various methods can be adopted as the control by the control means. When the output of the control means is lower than a predetermined value based on the output of the inlet pressure detector, the low-temperature compressor is used. More preferably, the opening of the expansion valve is adjusted so that the compression ratio of the above substantially maintains a predetermined value.
[0011]
Various types of low-temperature compressors can be adopted. In the case of a constant displacement compressor, the flow rate is determined almost by the inlet conditions, and is substantially proportional to the absolute pressure at the inlet when the inlet temperature is substantially constant. Therefore, there is an advantage that it is easy to predict the flow characteristics.
[0012]
Various combinations of the first heat medium and the second heat medium can be adopted. However, the first heat medium is nitrogen, and the second heat medium leading to the first heat exchanger is A combination that is liquefied natural gas is commonly used.
[0013]
Another feature of the present invention for achieving the above object is that a cooling unit that cools an object by vaporizing the supplied first heat medium, and the first heat vaporized by the cooling unit. A low-temperature compressor that guides the medium and compresses at a substantially constant inlet temperature, guides the first heat medium compressed by the low-temperature compressor, and exchanges the first heat medium by heat exchange with the second heat medium. The first heat exchanger to be cooled and the first heat medium cooled by the first heat exchanger are guided to expand the first heat medium, and then the first heat medium is returned to the cooling unit again. And an expansion valve that can be supplied to constitute a refrigerator cycle, guide the second heat medium to the first heat exchanger, and heat the first heat medium with the first heat exchanger. A second heat medium flow passage is provided for discharging the second heat medium after heating the second heat medium by replacement. In a certain refrigeration apparatus, an outlet pressure detector for detecting the pressure is provided on the outlet side of the low-temperature compressor, and a flow rate detector for detecting a flow rate of the first heat medium between the cooling unit and the low-temperature compressor. And a means for calculating a desired outlet pressure set value of the low-temperature compressor using a predetermined relational expression based on the output of the flow rate detector, and the output of the outlet pressure detector is The control means for adjusting the opening degree of the expansion valve is provided so as to be a set value.
[0014]
[Function and effect]
In the refrigeration apparatus according to the present invention, that is, the refrigeration apparatus of the type in which the first heat medium is cooled by the first heat exchanger and is expanded by the expansion valve in the cold of the second heat medium, the first heat exchanger is generally The higher the pressure of one heat medium (pressure on the outlet side of the low-temperature compressor) is, the higher the refrigeration capacity becomes. Further, as is obvious, the refrigerating capacity changes in proportion to the flow rate of the first heat medium.
And according to the above-mentioned characteristic configuration of the present invention, since the inlet pressure detector and the outlet pressure detector for detecting the respective pressures are provided on the inlet side and the outlet side of the low-temperature compressor, their outputs are provided. Further, the pressure and the compression ratio on the inlet side and the outlet side can be obtained. Then, the control means adjusts the opening of the expansion valve based on the output of the inlet pressure detector so that the outlet pressure of the low-temperature compressor becomes a desired value. When the pressure on the inlet side of the low-temperature compressor is reduced, if the opening of the expansion valve is left as it is, the outlet pressure of the low-temperature compressor is reduced to prevent the first heat exchanger from functioning. The pressure on the outlet side can be controlled by adjusting the opening degree of the valve to close the compression ratio, and the compression ratio can be automatically maintained within a safe range. In addition, this operation can simultaneously reduce the flow rate of the first heat medium passing through the expansion valve , thereby reducing the liquefaction efficiency and contributing to the adjustment of the refrigerating capacity. Moreover, the detector and the like are inexpensive and the apparatus configuration is simple.
As a result, a simple apparatus configuration can provide a refrigeration apparatus that can automatically adjust the refrigeration capacity of the apparatus over a wide range and can operate stably when the refrigeration load changes.
[0015]
The first heat medium expanded by the expansion valve is guided between the expansion valve and the cooling unit, and the liquid component of the first heat medium is stored and supplied to the cooling unit. And a storage tank for storing the gas component of the first heat medium while supplying the gas component to the downstream side of the cooling unit,
Since the storage tank functions as a buffer tank with respect to changes in the refrigeration load and has the function of a gas-liquid separator, only the liquid component can be supplied to the cooling unit to efficiently perform cooling. At the same time, the gaseous component can be returned to the cycle and reused as the first heat medium.
[0016]
Based on the output of the inlet pressure detector, the control means opens the expansion valve so that the compression ratio of the low-temperature compressor substantially maintains the predetermined value when the output value is equal to or lower than the predetermined value. If you want to adjust the degree,
When the output value from the inlet pressure detector falls below the default value, the compression ratio increases, so it is necessary to suppress this, and if the compression ratio is maintained at almost the set value, there is no problem in operation and the operation is stable. Turn into. In this system, the operating pressure of the first and second heat mediums in the first heat exchanger can be made almost constant near the rated point, more stable operation can be achieved, and the control system can be simplified. is there.
[0017]
When the low-temperature compressor is a constant displacement low-temperature compressor, there is an advantage that the air flow characteristics of the compressor can be easily predicted as described above, and the control method can be easily determined.
[0018]
When the first heat medium is nitrogen and the second heat medium leading to the first heat exchanger is liquefied natural gas,
Since liquefied natural gas is liquefied under pressure for transportation, effective use of its cold is desired, and nitrogen is a component contained in large quantities in the air, and its boiling point is the supply of liquefied natural gas. Since it is lower than the temperature, it is suitably used in the refrigerator cycle of the present invention.
[0019]
According to another characteristic configuration of the present invention, since a flow rate detector for detecting the flow rate of the first heat medium is provided between the cooling unit and the low-temperature compressor, the change in the refrigeration load is known from the output. Can do. And while the change of the refrigeration load can be calculated as an estimated value of pressure, the control means uses a predetermined relational expression based on the output of the flow rate detector, and the desired outlet pressure of the low-temperature compressor In order to adjust the opening degree of the expansion valve so as to become the set value, for example, when the refrigeration load is reduced and the flow rate on the inlet side of the low-temperature compressor is reduced, the opening degree of the expansion valve is left as it is. placing the order to avoid the first heat exchanger drops outlet pressure of the low-temperature compressor to fail to control the pressure at the outlet side by adjusting towards closing the opening of the expansion valve, safety compression ratio Can be automatically maintained in the area. In addition, this operation can simultaneously reduce the flow rate of the first heat medium passing through the expansion valve , thereby reducing the liquefaction efficiency and contributing to the adjustment of the refrigerating capacity. Moreover, the detector and the like are inexpensive and the apparatus configuration is simple.
As a result, a simple apparatus configuration can provide a refrigeration apparatus that can automatically adjust the refrigeration capacity of the apparatus over a wide range and can operate stably when the refrigeration load changes.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
For example, as shown in FIG. 1, the refrigeration apparatus of the present invention includes a cooling unit 8 that cools an object by vaporizing a supplied first heat medium M <b> 1, and a first heat medium vaporized by the cooling unit 8. A low-temperature compressor 1 that guides M1 and compresses at a substantially constant inlet temperature, a first heat medium M1 compressed by the low-temperature compressor 1 is guided, and the first heat is exchanged with the second heat medium M2. The first heat exchanger E1 that cools the medium M1 and the first heat medium M1 cooled by the first heat exchanger E1 are guided to expand the first heat medium M1, and then the first heat medium The refrigerating machine cycle is configured by including an expansion valve 5 that can supply M1 to the cooling unit 8 again.
[0021]
In the present embodiment, the first heat medium M1 expanded by the expansion valve 5 is guided between the expansion valve 5 and the cooling unit 8, and the liquid component of the first heat medium M1 is stored while the liquid component is stored. The storage tank 6 which supplies the gas component to the downstream of the cooling unit 8 while supplying the gas component to the cooling unit 8 and storing the gas component of the first heat medium M1 is shown.
[0022]
The configuration of the refrigerator cycle will be described more specifically as follows.
The cooling unit 8 is a condenser of various cooling tanks or gas production apparatuses for cooling an object by vaporizing the first heat medium M1 supplied via the path P7, and is a multi-tube type or jacket type. Things are used. FIG. 1 shows a cooling tank having a jacket 8a around the tank. The first heat medium M1 vaporized by the cooling unit 8 is supplied to the heat exchanger 4 via the path P8. Pressure regulating valves 9 and 10 are provided in the path P8. For example, the temperature and pressure of the path P8 are about −175 ° C. and about 3.1 kg / cm ² g.
[0023]
In the heat exchanger 4, heating by the first heat medium M1 before the expansion by the expansion valve 5 is performed, and the heat is supplied to the low-temperature compressor 1 through the path P9. For example, the temperature and pressure of the path P9 are about −140 ° C. and about 3 kg / cm ² g.
[0024]
The low-temperature compressor 1 compresses the first heat medium M1 guided through the path P9, and the compressed first heat medium M1 is supplied to the heat exchanger 2 through the path P4. As the low-temperature compressor 1, a constant displacement low-temperature compressor, a centrifugal low-temperature compressor, or the like is used. In the present embodiment, the former is used. For example, the temperature and pressure of the path P4 are about 100 ° C. and about 60 kg / cm ² g. You may provide the cooler by water cooling etc. in the path | route P4.
[0025]
The heat exchanger 2 constitutes the first heat exchanger E1 together with the heat exchanger 3, and the heat exchanger 2 exchanges heat with the gaseous second heat medium M2, and the heat exchanger 3 is liquid. Heat exchange with the second heat medium M2. Therefore, both can be constituted by one heat exchanger. The heat exchanger 2 and the heat exchanger 3 are connected by a path P5, and a path P6 is connected to the outlet side of the heat exchanger 3. For example, the temperature and pressure of the path P5 are, for example, about −26 ° C. and about 60 kg / cm ² g, and the temperature and pressure of the path P6 are, for example, about −138 ° C. and about 60 kg / cm ² g. is there.
[0026]
In the heat exchanger 4, cooling by the first heat medium M <b> 1 vaporized by the cooling unit 8 is performed, and the cooled first heat medium M <b> 1 is supplied to the expansion valve 5. In the expansion valve 5, the first heat medium M1 is expanded and supplied to the storage tank 6 while being partially liquefied by the cooling effect. Note that the heat exchanger 4 is not particularly required as long as the cooling by the first heat exchanger is sufficient for the required temperature level of the part to be cooled.
[0027]
The storage tank 6 stores the liquid component of the first heat medium M1, supplies the liquid component to the cooling unit 8 via the path P7 , and stores the gas component of the first heat medium M1 while storing the gas component. Is supplied to a path P8 located downstream of the cooling unit 8. A pressure adjusting valve 11 is provided in the supply path to the path P8, and the pressure in the storage tank 6 is maintained almost constant. In addition, the storage tank 6 includes a discharge path P10 and an opening / closing valve 14, an external tank 12, a supply path P11, and an opening / closing valve 13 in order to maintain the storage amount of the liquid component of the first heat medium M1 within a substantially constant range. Is provided.
[0028]
The second heat medium M2 is guided to the heat exchanger 3 through the path P1, and the flow rate adjustment valve 15 is provided in the path P1 so as to adjust the supply amount so that the temperature of the path P6 becomes substantially constant. It is. As a result, if the capacity of the heat exchanger 4 is sufficient, the path P6, that is, the inlet temperature of the low-temperature compressor can be kept substantially constant. For example, the temperature and pressure of the path P1 are about −153 ° C. and about 30 kg / cm ² g.
[0029]
The heat exchanger 3 and the heat exchanger 2 are connected by a path P2, and a gas-liquid separation tank 16 is provided in the path P2. Only the gas component is supplied from the gas-liquid separation tank 16 to the heat exchanger 2, and the liquid component is stored in the gas-liquid separation tank 16. At that time, in order to maintain the storage amount of the liquid component of the second heat medium M2 in a substantially constant range, the discharge path P12 and the on-off valve 17 are provided. In the first heat exchanger E1 configured by the heat exchanger 3 and the heat exchanger 2, the second heat medium M2 is heated by heat exchange with the first heat medium M1, and then the second heat medium flow path P3. It is discharged through.
Depending on the combination of the first heat medium M1 and the second heat medium M2, the gas-liquid separation tank 16 may not be required.
[0030]
In the present embodiment, an example is shown in which the first heat medium is nitrogen and the second heat medium led to the first heat exchanger is liquefied natural gas, but the present invention is not limited to this.
[0031]
Hereinafter, the control according to the characteristic configuration of the present invention will be described.
In the paths P9 and P4 corresponding to the inlet side and the outlet side of the low-temperature compressor 1, an inlet pressure detector S1 and an outlet pressure detector S2 for detecting respective pressures are provided. Various pressure sensors or the like are used for the detector, and the installation position of the detector may be the path P8 instead of the path P9, or may be the paths P5 and P6 instead of the path P4. The output signals of the inlet pressure detector S1 and the outlet pressure detector S2 are connected to the control means C.
[0032]
The control means C includes means for calculating a desired outlet pressure set value of the low-temperature compressor 1 using a predetermined relational expression based on the output of the inlet pressure detector S1, and the control means C of the outlet pressure detector S2. The opening of the expansion valve 5 is adjusted so that the output becomes the set value. As a specific control circuit configuration, the output signal of the inlet pressure detector S1 is converted by a so-called “broken line arithmetic circuit” and then input as a setting signal for the pressure regulator by the outlet pressure detector S2 and the expansion valve 5. Can be realized.
As a specific example, when the output value is equal to or lower than a predetermined value based on the output of the inlet pressure detector S1, the expansion valve 5 is maintained so that the compression ratio by the low-temperature compressor 1 substantially maintains the predetermined value. What is necessary is just to adjust the opening degree.
Also, a method of adjusting the opening degree so as to substantially maintain the compression ratio over the entire output of the inlet pressure detector S1 may be considered in some cases.
[0033]
[Another embodiment]
Hereinafter, other embodiments of the present invention will be described.
[0034]
<1> In the previous embodiment, the example in which the inlet pressure detector is provided on the inlet side of the low-temperature compressor and the control is performed based on the output is shown. However, as shown in FIG. A flow rate detector S3 for detecting the flow rate of the first heat medium M1 may be provided between the machine 1 and the control based on the output thereof.
In that case, an outlet pressure detector S2 for detecting the pressure is provided on the outlet side of the low-temperature compressor 1, and a flow rate for detecting the flow rate of the first heat medium between the cooling unit 8 and the low-temperature compressor 1. A detector S3, and means for calculating a desired outlet pressure set value of the low-temperature compressor 1 using a predetermined relational expression based on the output of the flow rate detector S3; so that the output of the vessel S2 is the set value, it is constituted by providing a control unit C for adjusting the opening degree of the expansion valve 5. Other than this point, since it is the same as the description of the previous embodiment, only the differences will be described.
As the flow rate detector S3, a gas flow rate sensor or the like is used, and its output signal is connected to the control means C. A relationship between the output of the flow rate detector S3 and the inlet pressure is obtained, and control similar to that of the previous embodiment can be performed based on a value obtained from the relationship.
[0035]
<2> In the previous embodiment, the temperature and pressure of each path were exemplified, but this is shown for easy understanding of the present invention, and the operating conditions, the design of each part, the type of heat medium, The present invention is not limited by the exemplified values because it can vary depending on the amount.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an example of a refrigeration apparatus. FIG. 2 is a schematic configuration diagram illustrating a refrigeration apparatus according to another embodiment.
DESCRIPTION OF SYMBOLS 1 Low temperature compressor 5 Expansion valve 6 Storage tank 8 Cooling part M1 1st heat medium M2 2nd heat medium E1 1st heat exchanger S1 Inlet pressure detector S2 Outlet pressure detector S3 Flow rate detector C Control means

Claims

A cooling unit that cools the object by vaporizing the supplied first heat medium, a low-temperature compressor that guides the first heat medium vaporized in the cooling unit and compresses at a substantially constant inlet temperature, A first heat exchanger that guides the first heat medium compressed by the low-temperature compressor and cools the first heat medium by heat exchange with the second heat medium, and is cooled by the first heat exchanger. The first heat medium is guided to expand the first heat medium, and then an expansion valve that can supply the first heat medium to the cooling unit again constitutes a refrigerator cycle.
The second heat medium is guided to the first heat exchanger, and the second heat medium is heated by heat exchange with the first heat medium in the first heat exchanger. A refrigeration apparatus provided with a second heat medium flow passage for discharging,
An inlet pressure detector and an outlet pressure detector for detecting respective pressures are provided on the inlet side and the outlet side of the low-temperature compressor, and
Based on the output of the inlet pressure detector, it has means for calculating a desired outlet pressure set value of the low-temperature compressor using a predetermined relational expression, and the output of the outlet pressure detector is set to the set value. A refrigeration apparatus provided with control means for adjusting the opening degree of the expansion valve.

The first heat medium expanded by the expansion valve is guided between the expansion valve and the cooling unit, and the liquid component of the first heat medium is stored and supplied to the cooling unit. The refrigeration apparatus according to claim 1, further comprising a storage tank that stores the gas component of the first heat medium and supplies the gas component to the downstream side of the cooling unit.

Based on the output of the inlet pressure detector, the control means opens the expansion valve so that the compression ratio of the low-temperature compressor substantially maintains the predetermined value when the output value is equal to or lower than the predetermined value. The refrigeration apparatus according to claim 1 or 2, which adjusts the degree.

The refrigeration apparatus according to any one of claims 1 to 3, wherein the low-temperature compressor is a constant displacement low-temperature compressor.

5. The refrigeration apparatus according to claim 1, wherein the first heat medium is nitrogen and the second heat medium led to the first heat exchanger is liquefied natural gas.

A cooling unit that cools the object by vaporizing the supplied first heat medium, a low-temperature compressor that guides the first heat medium vaporized in the cooling unit and compresses at a substantially constant inlet temperature, A first heat exchanger that guides the first heat medium compressed by the low-temperature compressor and cools the first heat medium by heat exchange with the second heat medium, and is cooled by the first heat exchanger. The first heat medium is guided to expand the first heat medium, and then an expansion valve that can supply the first heat medium to the cooling unit again constitutes a refrigerator cycle.
The second heat medium is guided to the first heat exchanger, and the second heat medium is heated by heat exchange with the first heat medium in the first heat exchanger. A refrigeration apparatus provided with a second heat medium flow passage for discharging,
An outlet pressure detector for detecting the pressure on the outlet side of the low-temperature compressor is provided, and a flow rate detector for detecting the flow rate of the first heat medium is provided between the cooling unit and the low-temperature compressor,
Based on the output of the flow rate detector, it has means for calculating a desired outlet pressure set value of the low-temperature compressor using a predetermined relational expression, and the output of the outlet pressure detector becomes the set value. A refrigeration apparatus provided with control means for adjusting the opening of the expansion valve.