JP7369030B2

JP7369030B2 - Refrigeration system and refrigeration system control method

Info

Publication number: JP7369030B2
Application number: JP2019236355A
Authority: JP
Inventors: 昌樹片岡
Original assignee: Mayekawa Manufacturing Co
Current assignee: Mayekawa Manufacturing Co
Priority date: 2019-12-26
Filing date: 2019-12-26
Publication date: 2023-10-25
Anticipated expiration: 2039-12-26
Also published as: JP2021105474A

Description

本開示は、冷凍システム及び該冷凍システムの制御方法に関する。 The present disclosure relates to a refrigeration system and a method of controlling the refrigeration system.

冷凍サイクルを構成する冷凍システムにおいて、凝縮器と蒸発器との間の冷媒流路に気液分離器を設け、凝縮器から出た冷媒を膨張弁で減圧し、気液混合となった冷媒を気液分離器で気相部と液相部とに分離し、気液分離器内の気相部のガス冷媒を蒸発器をバイパスして圧縮機に供給することが行われている。これによって、高圧冷媒用の耐圧配管を配置する領域を少なくし、低コスト化を図ることができる。特許文献１及び２にはこのような冷凍システムが開示されている。特に、特許文献２に記載された冷凍システムは、冷媒として超臨界状態で高圧となるＣＯ_２を用いるため、このような措置が有効である。 In the refrigeration system that constitutes the refrigeration cycle, a gas-liquid separator is installed in the refrigerant flow path between the condenser and the evaporator, and the refrigerant coming out of the condenser is depressurized by an expansion valve, and the refrigerant becomes a gas-liquid mixture. A gas-liquid separator separates the refrigerant into a gas phase and a liquid phase, and the gas refrigerant in the gas phase in the gas-liquid separator bypasses the evaporator and is supplied to the compressor. As a result, the area in which pressure-resistant piping for high-pressure refrigerant is arranged can be reduced, and costs can be reduced. Patent Documents 1 and 2 disclose such refrigeration systems. In particular, such a measure is effective because the refrigeration system described in Patent Document 2 uses CO ₂ that is under high pressure in a supercritical state as a refrigerant.

特許文献１では、保冷庫外の外気温度が低下すると、気液分離器内の中間圧力が低下して、中間圧力と蒸発圧力との圧力差が減少すると、蒸発器に流入する冷媒の循環量が減少し、冷凍システムの冷凍能力が低下するために、該中間圧力を制御して冷凍能力の低下を防止するようにしている。特許文献２では、蒸発器の冷却負荷の変動によって必要冷媒量が変動しても、気液分離器に液冷媒を一次貯留し、かつ気液分離器の気相部を圧縮機に直接供給することで、必要冷媒量の変動に対応している。 In Patent Document 1, when the outside air temperature outside the cold storage box decreases, the intermediate pressure inside the gas-liquid separator decreases, and when the pressure difference between the intermediate pressure and the evaporation pressure decreases, the circulating amount of refrigerant flowing into the evaporator decreases. , and the refrigerating capacity of the refrigeration system decreases, so the intermediate pressure is controlled to prevent the refrigerating capacity from decreasing. In Patent Document 2, even if the required amount of refrigerant changes due to changes in the cooling load of the evaporator, the liquid refrigerant is primarily stored in the gas-liquid separator, and the gas phase part of the gas-liquid separator is directly supplied to the compressor. This accommodates fluctuations in the amount of refrigerant required.

特開平０９－２２９４９７号公報Japanese Patent Application Publication No. 09-229497 特開２００７－２６３４８７号公報JP2007-263487A

冷凍システムにおいては、圧縮機に液冷媒が吸入される、所謂液バックを防止する必要があると共に、圧縮機の入口におけるガス冷媒の異常過熱に起因した圧縮機モータ等の故障を回避する必要がある。特に、冷媒として超臨界状態で高圧となるＣＯ_２冷媒を用いる場合、異常過熱が起こりやすい。気液分離器内の冷媒は飽和状態となっているので、圧力と温度とは一義的に対応し、蒸発器で冷却される冷却負荷側の温度は、気液分離器内の冷媒の圧力又は温度によって支配される。Ｃ級温度帯（－２０～＋１０℃）の冷凍庫の場合、Ｆ級温度帯（－２０℃以下）の冷凍庫と比べて、冷却負荷側の温度帯が高いため、蒸発器を経た冷媒の過熱度を十分に取ることができない。そのため、圧縮機の液バックを回避するため、気液分離器内の圧力調整が必要となってくる。また、気液分離器内の圧力は外気温度によっても影響を受ける。このように、圧縮機の液バックや異常過熱を回避するために、冷凍システムの運転可能な温度範囲が制約を受けるという問題がある。 In refrigeration systems, it is necessary to prevent liquid refrigerant from being sucked into the compressor, so-called liquid back-up, and it is also necessary to avoid failure of the compressor motor, etc. due to abnormal overheating of the gas refrigerant at the inlet of the compressor. be. In particular, when a CO ₂ refrigerant that reaches high pressure in a supercritical state is used as a refrigerant, abnormal overheating is likely to occur. Since the refrigerant in the gas-liquid separator is in a saturated state, pressure and temperature are uniquely related, and the temperature on the cooling load side cooled by the evaporator depends on the pressure of the refrigerant in the gas-liquid separator or Governed by temperature. In the case of a freezer in the C-class temperature range (-20 to +10°C), compared to a freezer in the F-class temperature range (-20°C or less), the temperature range on the cooling load side is higher, so the degree of superheating of the refrigerant passing through the evaporator is lower. I can't get enough of it. Therefore, in order to avoid liquid back in the compressor, it is necessary to adjust the pressure inside the gas-liquid separator. The pressure inside the gas-liquid separator is also affected by the outside temperature. As described above, there is a problem in that the operating temperature range of the refrigeration system is restricted in order to avoid liquid backflow and abnormal overheating of the compressor.

本開示は、上述する問題点に鑑みてなされたもので、圧縮機の液バック及び異常過熱を回避しながら、冷凍システムの運転適用範囲を拡大可能にすることを目的とする。 The present disclosure has been made in view of the above-mentioned problems, and aims to make it possible to expand the operational range of a refrigeration system while avoiding liquid back-up and abnormal overheating of the compressor.

上記目的を達成するため、本開示に係る冷凍システムは、気相部および液相部を有する気液分離器と、前記気液分離器の前記液相部からの冷媒が導かれる蒸発器と、前記蒸発器を通過後の冷媒を圧縮するための圧縮機と、前記蒸発器と前記圧縮機とを接続する第１冷媒流路と、前記気液分離器の前記気相部と前記第１冷媒流路とを接続するための第２冷媒流路と、前記気液分離器の前記液相部と前記蒸発器を経た前記冷媒とを熱交換するための熱交換器と、前記第２冷媒流路に設けられる第１膨張弁と、前記蒸発器における前記冷媒の蒸発温度と相関のある圧力又は温度を検出するためのセンサと、前記センサの検出結果に基づいて設定される前記気液分離器の目標圧力に基づいて、前記第１膨張弁の開度制御を行うための制御部と、を備える。 In order to achieve the above object, a refrigeration system according to the present disclosure includes: a gas-liquid separator having a gas phase part and a liquid phase part; an evaporator into which refrigerant from the liquid phase part of the gas-liquid separator is guided; a compressor for compressing the refrigerant after passing through the evaporator; a first refrigerant flow path connecting the evaporator and the compressor; and the gas phase part of the gas-liquid separator and the first refrigerant. a second refrigerant flow path for connecting the flow path; a heat exchanger for exchanging heat between the liquid phase part of the gas-liquid separator and the refrigerant that has passed through the evaporator; and a second refrigerant flow path. a first expansion valve provided in the duct, a sensor for detecting a pressure or temperature correlated with the evaporation temperature of the refrigerant in the evaporator, and the gas-liquid separator that is set based on the detection result of the sensor. a control section for controlling the opening degree of the first expansion valve based on the target pressure of the first expansion valve.

本開示に係る冷凍システムの制御方法は、気相部および液相部を有する気液分離器と、前記気液分離器の前記液相部からの冷媒が導かれる蒸発器と、前記蒸発器を通過後の冷媒を圧縮するための圧縮機と、前記蒸発器と前記圧縮機とを接続する第１冷媒流路と、前記気液分離器の前記気相部と前記第１冷媒流路とを接続するための第２冷媒流路と、前記気液分離器の前記液相部と前記蒸発器を経た前記冷媒とを熱交換するための熱交換器と、前記第２冷媒流路に設けられる第１膨張弁と、前記蒸発器における前記冷媒の蒸発温度と相関のある圧力又は温度を検出するためのセンサと、前記センサの検出結果に基づいて設定される前記気液分離器の目標圧力に基づいて、前記膨張弁の開度制御を行うための制御部と、を備える冷凍システムの制御方法であって、前記蒸発器における冷媒の蒸発温度と相関のある検出値を検出する検出ステップと、前記検出値に基づいて前記気液分離器の圧力が目標圧力となるように前記第１膨張弁を制御する制御ステップと、を備える。 A method for controlling a refrigeration system according to the present disclosure includes: a gas-liquid separator having a gas phase part and a liquid phase part; an evaporator to which refrigerant from the liquid phase part of the gas-liquid separator is guided; a compressor for compressing the refrigerant after passing through; a first refrigerant flow path connecting the evaporator and the compressor; and the gas phase part of the gas-liquid separator and the first refrigerant flow path. a second refrigerant flow path for connection, a heat exchanger for exchanging heat between the liquid phase part of the gas-liquid separator and the refrigerant that has passed through the evaporator; and a heat exchanger provided in the second refrigerant flow path. a first expansion valve; a sensor for detecting a pressure or temperature correlated with the evaporation temperature of the refrigerant in the evaporator; and a target pressure of the gas-liquid separator that is set based on the detection result of the sensor. A control method for a refrigeration system, comprising: a control unit for controlling the opening degree of the expansion valve; and a control step of controlling the first expansion valve so that the pressure of the gas-liquid separator becomes a target pressure based on the detected value.

本開示に係る冷凍システム及び冷凍システムの制御方法によれば、圧縮機への液バックや圧縮機の異常過熱を回避しながら、冷凍システムの運転適用範囲を広げることができ、これによって、冷凍システムの用途を拡大できる。 According to the refrigeration system and the refrigeration system control method according to the present disclosure, it is possible to expand the operational range of the refrigeration system while avoiding liquid back to the compressor and abnormal overheating of the compressor. The usage of can be expanded.

一実施形態に係る冷凍システムを示す系統図である。FIG. 1 is a system diagram showing a refrigeration system according to an embodiment. 一実施形態に係る冷凍システムのモリエル線図である。It is a Mollier diagram of a refrigeration system concerning one embodiment. 一実施形態に係る制御部の記憶部に記憶されるマップを示す図表である。It is a chart showing a map stored in a storage part of a control part concerning one embodiment. 一実施形態に係る気液分離器の目標圧力を示すグラフである。It is a graph showing target pressure of a gas-liquid separator concerning one embodiment. 一実施形態に係る冷凍システムの制御方法を示す工程図である。FIG. 2 is a process diagram showing a method of controlling a refrigeration system according to an embodiment.

以下、添付図面を参照して本発明の幾つかの実施形態について説明する。ただし、実施形態として記載され又は図面に示されている構成部品の寸法、材質、形状、その相対的配置等は、本発明の範囲をこれに限定する趣旨ではなく、単なる説明例にすぎない。
例えば、「ある方向に」、「ある方向に沿って」、「平行」、「直交」、「中心」、「同心」或いは「同軸」等の相対的或いは絶対的な配置を表す表現は、厳密にそのような配置を表すのみならず、公差、若しくは、同じ機能が得られる程度の角度や距離をもって相対的に変位している状態も表すものとする。
例えば、「同一」、「等しい」及び「均質」等の物事が等しい状態であることを表す表現は、厳密に等しい状態を表すのみならず、公差、若しくは、同じ機能が得られる程度の差が存在している状態も表すものとする。
例えば、四角形状や円筒形状等の形状を表す表現は、幾何学的に厳密な意味での四角形状や円筒形状等の形状を表すのみならず、同じ効果が得られる範囲で、凹凸部や面取り部等を含む形状も表すものとする。
一方、一つの構成要素を「備える」、「具える」、「具備する」、「含む」、又は「有する」という表現は、他の構成要素の存在を除外する排他的な表現ではない。 Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, and are merely illustrative examples.
For example, expressions expressing relative or absolute positioning such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""centered,""concentric," or "coaxial" are strictly In addition to representing such an arrangement, it also represents a state in which they are relatively displaced with a tolerance or an angle or distance that allows the same function to be obtained.
For example, expressions such as "same,""equal," and "homogeneous" that indicate that things are in an equal state do not only mean that things are exactly equal, but also have tolerances or differences in the degree to which the same function can be obtained. It also represents the existing state.
For example, expressions expressing shapes such as squares and cylinders do not only refer to shapes such as squares and cylinders in a strict geometric sense, but also include uneven parts and chamfers to the extent that the same effect can be obtained. Shapes including parts, etc. shall also be expressed.
On the other hand, the expressions "comprising,""comprising,""comprising,""containing," or "having" one component are not exclusive expressions that exclude the presence of other components.

図１は、一実施形態に係る冷凍システムを示す系統図である。冷凍システム１０は、
冷媒循環路１２（第１冷媒流路）に、圧縮機１４と、気液分離器１６と、蒸発器１８とが設けられている。気液分離器１６で冷媒の気相部及び液相部が分離され、気液分離器１６の液相部から冷媒が冷媒循環路１２を通って蒸発器１８に導かれ、蒸発器１８を通過後の冷媒は圧縮機１４で圧縮される。気液分離器１６の気相部と圧縮機１４の入口側とはバイパス路２４（第２冷媒流路）で接続されている。冷媒循環路１２には、気液分離器１６の液相部と蒸発器１８を経た冷媒とを熱交換するための熱交換器２０が設けられ、バイパス路２４に膨張弁２６（第１膨張弁）が設けられている。 FIG. 1 is a system diagram showing a refrigeration system according to one embodiment. The refrigeration system 10 is
A compressor 14, a gas-liquid separator 16, and an evaporator 18 are provided in the refrigerant circulation path 12 (first refrigerant flow path). The gas-liquid separator 16 separates the refrigerant into a gas phase and a liquid phase, and the refrigerant is guided from the liquid phase of the gas-liquid separator 16 to the evaporator 18 through the refrigerant circulation path 12 and passes through the evaporator 18. The latter refrigerant is compressed by the compressor 14. The gas phase portion of the gas-liquid separator 16 and the inlet side of the compressor 14 are connected through a bypass path 24 (second refrigerant flow path). The refrigerant circulation path 12 is provided with a heat exchanger 20 for exchanging heat between the liquid phase part of the gas-liquid separator 16 and the refrigerant that has passed through the evaporator 18. ) is provided.

さらに、蒸発器１８における冷媒の蒸発温度と相関のある圧力又は温度を検出するためのセンサ２８が設けられている。センサ２８の検出値は制御部３０に送られ、制御部３０は、センサ２８の検出値に基づいて気液分離器１６の目標圧力を設定する。冷媒が飽和状態にあるとき、飽和圧力と飽和温度とは一義的に対応する。従って、冷媒の飽和圧力を検出すれば、冷媒の飽和温度を求めることができる。この目標圧力は、冷凍システム１０の運転条件下で、圧縮機１４の液バックや異常過熱が起らない圧力値として設定される。制御部３０は、気液分離器１６が目標圧力の圧力値になるように膨張弁２６の開度制御を行う。 Furthermore, a sensor 28 is provided for detecting pressure or temperature that correlates with the evaporation temperature of the refrigerant in the evaporator 18. The detected value of the sensor 28 is sent to the control section 30, and the control section 30 sets the target pressure of the gas-liquid separator 16 based on the detected value of the sensor 28. When the refrigerant is in a saturated state, the saturation pressure and saturation temperature uniquely correspond. Therefore, by detecting the saturation pressure of the refrigerant, the saturation temperature of the refrigerant can be determined. This target pressure is set as a pressure value that does not cause liquid back-up or abnormal overheating of the compressor 14 under the operating conditions of the refrigeration system 10. The control unit 30 controls the opening degree of the expansion valve 26 so that the pressure value of the gas-liquid separator 16 reaches the target pressure.

このような構成によれば、蒸発器１８を経た冷媒は、熱交換器２０で気液分離器１６の液相部の冷媒と熱交換して加熱されるため、過熱度不足を解消できる。従って、冷却負荷が例えばＣ級温度帯の冷凍倉庫であっても、圧縮機の液バックを抑制できる。また、蒸発器１８の蒸発温度を低く設定すると、熱交換器２０の出口側で過熱度が過剰になるが、膨張弁２６の開度を制御し、気液分離器１６の冷媒圧力を圧縮機の液バック及び異常過熱が起きない目標圧力に制御するため、液バックや異常過熱を回避しながら、冷却負荷の冷却温度など、冷凍システム１０の運転適用範囲を拡大できる。 According to such a configuration, the refrigerant that has passed through the evaporator 18 is heated by exchanging heat with the refrigerant in the liquid phase portion of the gas-liquid separator 16 in the heat exchanger 20, so that insufficient superheating can be resolved. Therefore, even if the cooling load is, for example, in a refrigerated warehouse in the C-class temperature range, liquid backflow in the compressor can be suppressed. Furthermore, if the evaporation temperature of the evaporator 18 is set low, the degree of superheating will be excessive at the outlet side of the heat exchanger 20. Since the target pressure is controlled to a target pressure that does not cause liquid back-up and abnormal overheating, it is possible to expand the operational range of the refrigeration system 10, such as the cooling temperature of the cooling load, while avoiding liquid back-up and abnormal overheating.

一実施形態では、圧縮機１４の出口側に凝縮器３２が設けられ、圧縮機１４から吐出されたガス冷媒は凝縮器３２で冷却媒体ｗ１と熱交換して冷却される。凝縮器３２で冷却された冷媒は膨張弁３４を通って減圧された後、気液分離器１６に送られ気相と液相に分離される。気液分離器１６で分離されたガス冷媒は、バイパス路２４を経て圧縮機１４に送られる。気液分離器１６内の液相部を形成する液冷媒は、気液分離器１６から出て、熱交換器２０で蒸発器１８で蒸発した低温のガス冷媒と熱交換して該ガス冷媒を加熱する。気液分離器１６から熱交換器２０に送られた液相部は、熱交換器２０を出て膨張弁２２を経て減圧され、蒸発器１８で被冷却媒体ｗ２（冷却負荷）を冷却し、自身は蒸発する。 In one embodiment, a condenser 32 is provided on the outlet side of the compressor 14, and the gas refrigerant discharged from the compressor 14 is cooled by exchanging heat with the refrigerant w1 in the condenser 32. The refrigerant cooled in the condenser 32 is depressurized through the expansion valve 34 and then sent to the gas-liquid separator 16 where it is separated into a gas phase and a liquid phase. The gas refrigerant separated by the gas-liquid separator 16 is sent to the compressor 14 via a bypass path 24. The liquid refrigerant forming the liquid phase in the gas-liquid separator 16 exits from the gas-liquid separator 16 and exchanges heat with the low-temperature gas refrigerant evaporated in the evaporator 18 in the heat exchanger 20 to convert the gas refrigerant into Heat. The liquid phase portion sent from the gas-liquid separator 16 to the heat exchanger 20 exits the heat exchanger 20, passes through the expansion valve 22, is depressurized, cools the medium to be cooled w2 (cooling load) in the evaporator 18, itself evaporates.

気液分離器１６は、フラッシュタンク、アキュムレータ、又はレシーバ等であってもよく、要は、供給された冷媒を気液分離する機能があればよい。また、冷媒としてＣＯ_２が用いられる場合、凝縮器３２はガスクーラとして作動する。 The gas-liquid separator 16 may be a flash tank, an accumulator, a receiver, or the like, as long as it has the function of separating the supplied refrigerant into gas and liquid. Additionally, when CO ₂ is used as the refrigerant, the condenser 32 operates as a gas cooler.

図２は、冷凍システム１０がＣ級（冷却温度－２０℃～＋１０℃）の温度帯を有し、かつ冷媒としてＣＯ_２を用いたときの冷凍システム１０のモリエル線図の一例を示す。図２において、Ｋ点はＣＯ_２の臨界点であり、Ｋ点より左側のラインＸは飽和液線であり、Ｋ点より右側のラインＹは飽和蒸気線である。ａ点は圧縮機１４の出口における冷媒の状態量であり、ｂ点は凝縮器３２としてのガスクーラの出口における冷媒の状態量であり、ｃ点は気液分離器１６で気液混合状態の冷媒の状態量であり、ｄ点は気液分離器１６で気液分離された後の気相部の状態量であり、ｅ点は気液分離器１６の液相部の状態量を示している。ｆ点は膨張弁２６の出口、ｇ点は膨張弁２２の出口側（蒸発器１８の入口側）、ｉ点は蒸発器１８の出口における夫々の冷媒の状態量を示している。ｊ点において、冷媒循環路１２にバイパス路２４が合流すると、合流後のエンタルピｈは、ｉ点より下がったガス冷媒となり、その後、圧縮機１４に吸引され圧縮される。なお、理解の便宜のため、図１中の同一の場所にも符号ａ～ｊを付している。 FIG. 2 shows an example of a Mollier diagram of the refrigeration system 10 when the refrigeration system 10 has a temperature range of class C (cooling temperature -20° C. to +10° C.) and uses CO ₂ as a refrigerant. In FIG. 2, point K is the critical point of _CO2 , line X to the left of point K is a saturated liquid line, and line Y to the right of point K is a saturated vapor line. Point a is the state quantity of the refrigerant at the outlet of the compressor 14, point b is the state quantity of the refrigerant at the outlet of the gas cooler as the condenser 32, and point c is the state quantity of the refrigerant at the outlet of the gas-liquid separator 16. Point d is the state quantity of the gas phase after gas-liquid separation in the gas-liquid separator 16, and point e indicates the state quantity of the liquid phase part of the gas-liquid separator 16. . Point f indicates the state quantity of the refrigerant at the outlet of the expansion valve 26, point g indicates the outlet side of the expansion valve 22 (inlet side of the evaporator 18), and point i indicates the state quantity of the refrigerant at the outlet of the evaporator 18. When the bypass path 24 joins the refrigerant circulation path 12 at point j, the enthalpy h after the joining becomes a gas refrigerant lower than that at point i, and is then sucked into the compressor 14 and compressed. Note that for convenience of understanding, the same locations in FIG. 1 are also labeled with symbols a to j.

以下、冷凍システム１０がＣ級の冷却温度帯を有する冷凍システムであり、かつ冷媒ととしてＣＯ_２を用いたときの気液分離器１６の圧力と冷凍システム１０の運転条件との関連につき幾つかの事例を説明する。気液分離器１６で冷媒ｒは飽和状態となっており、気液分離器１６の飽和圧力が４．８ＭＰａのとき飽和温度は１２．６℃であり、飽和圧力が４．３ＭＰａのとき飽和温度は８．１℃であり、飽和圧力が３．７ＭＰａのとき飽和温度は２．２℃である。 Below, some information regarding the relationship between the pressure of the gas-liquid separator 16 and the operating conditions of the refrigeration system 10 when the refrigeration system 10 is a refrigeration system having a C-class cooling temperature range and uses CO ₂ as a refrigerant will be described. An example of this will be explained. The refrigerant r is in a saturated state in the gas-liquid separator 16, and when the saturation pressure of the gas-liquid separator 16 is 4.8 MPa, the saturation temperature is 12.6°C, and when the saturation pressure is 4.3 MPa, the saturation temperature is is 8.1°C, and when the saturation pressure is 3.7 MPa, the saturation temperature is 2.2°C.

ケース１；冷却庫内の冷却負荷温度を０℃とし、気液分離器１６の圧力（飽和圧力）を４．３ＭＰａ（飽和温度８．１℃）とし、蒸発器１８の蒸発温度Ｔｅを－５℃、蒸発器１８の出口側冷媒の過熱度ＳＨを５℃と設定した場合
気液分離器１６から熱交換器２０に供給される液冷媒の温度は８．１℃であり、一方、蒸発器１８から熱交換器２０に供給されるガス冷媒は０℃となる。両者の温度差が十分あるので、十分熱交換が可能であり、該ガス冷媒は６℃に加熱されて圧縮機１４に吸引されるため、液バック及び異常過熱が起こるおそれはない。 Case 1: The cooling load temperature in the refrigerator is 0°C, the pressure (saturation pressure) of the gas-liquid separator 16 is 4.3 MPa (saturation temperature 8.1°C), and the evaporation temperature Te of the evaporator 18 is -5°C. ℃, and the degree of superheating SH of the refrigerant on the outlet side of the evaporator 18 is set to 5℃.The temperature of the liquid refrigerant supplied from the gas-liquid separator 16 to the heat exchanger 20 is 8.1℃; The gas refrigerant supplied from 18 to the heat exchanger 20 has a temperature of 0°C. Since there is a sufficient temperature difference between the two, sufficient heat exchange is possible, and since the gas refrigerant is heated to 6° C. and sucked into the compressor 14, there is no risk of liquid backflow or abnormal overheating.

ケース２；冷却庫内の冷却温度を０℃とし、気液分離器１６の圧力（飽和圧力）を３．９ＭＰａ（飽和温度２．２℃）とし、蒸発器１８の蒸発温度Ｔｅを－５℃、蒸発器１８の出口側冷媒の過熱度ＳＨを５℃と設定した場合
気液分離器１６から熱交換器２０に供給される液冷媒の温度は２．２℃であり、一方、蒸発器１８から熱交換器２０に供給されるガス冷媒は０℃であるので、両者は十分に熱交換できず、過熱度ＳＨを十分に取ることができない。従って、０℃の冷媒が圧縮機１４に送られることになるので、液バックが起こるおそれがある。 Case 2: The cooling temperature in the refrigerator is 0°C, the pressure (saturation pressure) of the gas-liquid separator 16 is 3.9 MPa (saturation temperature 2.2°C), and the evaporation temperature Te of the evaporator 18 is -5°C. When the degree of superheating SH of the refrigerant on the outlet side of the evaporator 18 is set to 5°C, the temperature of the liquid refrigerant supplied from the gas-liquid separator 16 to the heat exchanger 20 is 2.2°C; Since the gas refrigerant supplied from the refrigerant to the heat exchanger 20 has a temperature of 0° C., the two cannot sufficiently exchange heat, and a sufficient degree of superheat SH cannot be obtained. Therefore, since 0° C. refrigerant is sent to the compressor 14, there is a possibility that liquid backflow may occur.

ケース３；冷却庫内の冷却温度を０℃と設定し、気液分離器１６の目標圧力（飽和圧力）を４．８ＭＰａ（飽和温度１２．６℃）とし、蒸発器１８の蒸発温度Ｔｅを－１５℃、蒸発器１８の出口側冷媒の過熱度ＳＨを５℃と設定した場合
気液分離器１６から熱交換器２０に供給される液冷媒の温度は１２．６℃であり、一方、蒸発器１８から熱交換器２０に供給されるガス冷媒は－１０℃であるので、両者の熱交換量が多大となり、過熱されたガス冷媒が圧縮機１４に送られることになる。圧縮機１４に吸入される吸入ガスの温度が１００～１５０℃を超えると異常過熱となり、モータなどが故障するおそれがある。 Case 3: The cooling temperature in the refrigerator is set to 0°C, the target pressure (saturation pressure) of the gas-liquid separator 16 is 4.8 MPa (saturation temperature 12.6°C), and the evaporation temperature Te of the evaporator 18 is set to When the superheating degree SH of the refrigerant on the outlet side of the evaporator 18 is set to -15°C and 5°C, the temperature of the liquid refrigerant supplied from the gas-liquid separator 16 to the heat exchanger 20 is 12.6°C, and on the other hand, Since the gas refrigerant supplied from the evaporator 18 to the heat exchanger 20 has a temperature of -10° C., the amount of heat exchanged between the two becomes large, and the superheated gas refrigerant is sent to the compressor 14. If the temperature of the suction gas taken into the compressor 14 exceeds 100 to 150° C., abnormal overheating may occur, which may cause the motor or the like to malfunction.

ケース１～３から、気液分離器１６の圧力を、ケース１のように、圧縮機の液バックや異常過熱を回避可能な目標圧力に制御すれば、これらの現象を抑制できることがわかる。 From Cases 1 to 3, it can be seen that these phenomena can be suppressed by controlling the pressure of the gas-liquid separator 16 to a target pressure that can avoid liquid back and abnormal overheating of the compressor, as in Case 1.

一実施形態では、図１に示すように、センサ２８（２８ａ、２８ｂ、２８ｃ、２８ｄ又は２８ｅ）は、膨張弁２２の出口側と圧縮機１４の入口側との間の冷媒循環路１２に設けられ、この領域の冷媒循環路１２を流れる冷媒の圧力又は温度を検出する。この領域の冷媒圧力又は冷媒温度を検出すれば、設定された蒸発器１８の運転条件などから圧縮機入口の冷媒圧力又は冷却温度を演算できる。従って、センサ２８の検出値に基づいて、気液分離器１６の目標圧力を設定し、気液分離器１６の圧力が目標圧力となるよう膨張弁２６の開度を制御すれば、圧縮機１４の液バックや異常過熱を回避できる。そのため、圧縮機１４の液バックや異常過熱を回避しながら、冷凍システム１０の運転適用範囲を広げることができる。
なお、図１に示す実施形態では、センサ２８（２８ａ、２８ｃ）は圧力センサであり、センサ２８（２８ｂ、２８ｄ、２８ｅ）は温度センサである。 In one embodiment, as shown in FIG. The pressure or temperature of the refrigerant flowing through the refrigerant circulation path 12 in this area is detected. If the refrigerant pressure or refrigerant temperature in this region is detected, the refrigerant pressure or cooling temperature at the compressor inlet can be calculated from the set operating conditions of the evaporator 18 and the like. Therefore, if the target pressure of the gas-liquid separator 16 is set based on the detected value of the sensor 28 and the opening degree of the expansion valve 26 is controlled so that the pressure of the gas-liquid separator 16 becomes the target pressure, the compressor 14 liquid back-up and abnormal overheating can be avoided. Therefore, the range of operation of the refrigeration system 10 can be expanded while avoiding liquid backflow and abnormal overheating of the compressor 14.
Note that in the embodiment shown in FIG. 1, the sensors 28 (28a, 28c) are pressure sensors, and the sensors 28 (28b, 28d, 28e) are temperature sensors.

膨張弁２２の出口側と圧縮機１４の入口側との間の領域は、図２のエンタルピｈのｇ点からｉ点までの領域に相当する。この領域は、飽和蒸気線のラインＹより右側を除いて飽和領域であり、この領域の温度又は圧力を検出することで、一義的に蒸発温度を求めることができる。ｇ点及びｊ点においても過熱度がわかれば、蒸発圧力から容易に蒸発温度を求めることができる。こうして求めた蒸発温度に基づいて気液分離器１６の圧力を目標圧力に制御することで、圧縮機１４の液バックや異常過熱を回避しながら、冷凍システム１０の運転適用範囲を広げることができる。 The area between the outlet side of the expansion valve 22 and the inlet side of the compressor 14 corresponds to the area from point g to point i of enthalpy h in FIG. This region is a saturated region except for the region to the right of line Y of the saturated vapor line, and by detecting the temperature or pressure in this region, the evaporation temperature can be uniquely determined. If the degree of superheating at points g and j is known, the evaporation temperature can be easily determined from the evaporation pressure. By controlling the pressure of the gas-liquid separator 16 to the target pressure based on the evaporation temperature determined in this way, it is possible to widen the operational range of the refrigeration system 10 while avoiding liquid back in the compressor 14 and abnormal overheating. .

一実施形態では、図１に示すように、センサ２８（２８ａ、２８ｂ、２８ｃ又は２８ｄ）は、熱交換器２０の出口側と圧縮機１４の入口側との間の冷媒循環路１２に設けられ、この領域の冷媒圧力又は温度を検出する。センサ２８によって、上記領域の冷媒循環路１２における冷媒圧力又は冷媒温度を検出するため、設定された蒸発器１８の運転条件などから、圧縮機入口の冷媒圧力又は冷却温度を演算できる。従って、上記検出値に基づいて、膨張弁２６の開度を制御し、気液分離器１６の圧力を設定された目標圧力に制御すれば、圧縮機１４の液バックや異常過熱を回避できる。そのため、圧縮機１４の液バックや異常過熱を回避しながら、冷凍システム１０の運転適用範囲を広げることができる。 In one embodiment, as shown in FIG. 1, the sensor 28 (28a, 28b, 28c or 28d) is provided in the refrigerant circuit 12 between the outlet side of the heat exchanger 20 and the inlet side of the compressor 14. , detect the refrigerant pressure or temperature in this area. Since the sensor 28 detects the refrigerant pressure or refrigerant temperature in the refrigerant circuit 12 in the above region, the refrigerant pressure or cooling temperature at the compressor inlet can be calculated from the set operating conditions of the evaporator 18 and the like. Therefore, by controlling the opening degree of the expansion valve 26 and controlling the pressure of the gas-liquid separator 16 to the set target pressure based on the detected value, liquid back and abnormal overheating of the compressor 14 can be avoided. Therefore, the range of operation of the refrigeration system 10 can be expanded while avoiding liquid backflow and abnormal overheating of the compressor 14.

一実施形態では、図１に示すように、センサ２８（２８ａ又は２８ｂ）は、バイパス路２４と冷媒循環路１２とが合流する合流点（ｊ点）と圧縮機１４の入口との間の冷媒循環路１２に設けられ、この領域の冷媒循環路１２を流れる冷媒の温度又は圧力を検出する。膨張弁２６によって減圧されたバイパス路２４の冷媒が冷媒循環路１２に合流することで、冷媒のエンタルピｈが変動する（図２；ｉ点→ｊ点）。本実施形態によれば、このエンタルピｈの変動後の検出値が得られるので、該変動を加味した演算を必要としない。そのため、気液分離器１６の目標圧力の設定が容易になる。 In one embodiment, as shown in FIG. It is provided in the circulation path 12 and detects the temperature or pressure of the refrigerant flowing through the refrigerant circulation path 12 in this region. When the refrigerant in the bypass path 24 whose pressure has been reduced by the expansion valve 26 joins the refrigerant circulation path 12, the enthalpy h of the refrigerant changes (FIG. 2; from point i to point j). According to the present embodiment, a detected value after the enthalpy h fluctuates is obtained, so there is no need to perform calculations that take this fluctuation into account. Therefore, the target pressure of the gas-liquid separator 16 can be easily set.

一実施形態では、図１に示すように、センサ２８（２８ｅ）は、蒸発器１８の入口の冷媒循環路１２に設けられ、この領域の冷媒循環路１２を流れる冷媒の圧力又は温度を検出する。蒸発器１８の入口における冷媒の圧力又は温度を検出することで、これらの検出値と、設定された蒸発器１８の運転条件などとから、圧縮機入口の冷媒圧力又は冷却温度を演算できる。こうして、得られた演算値に基づいて気液分離器１６の目標圧力を設定することで、圧縮機１４の液バックや異常過熱を回避しながら、冷凍システム１０の運転適用範囲を広げることができる。 In one embodiment, as shown in FIG. 1, a sensor 28 (28e) is provided in the refrigerant circuit 12 at the inlet of the evaporator 18 to detect the pressure or temperature of the refrigerant flowing through the refrigerant circuit 12 in this region. . By detecting the pressure or temperature of the refrigerant at the inlet of the evaporator 18, the refrigerant pressure or cooling temperature at the compressor inlet can be calculated from these detected values and the set operating conditions of the evaporator 18. In this way, by setting the target pressure of the gas-liquid separator 16 based on the calculated value obtained, it is possible to widen the operational range of the refrigeration system 10 while avoiding liquid back and abnormal overheating of the compressor 14. .

一実施形態では、図１に示すように、制御部３０は、気液分離器１６の目標圧力とセンサ２８の検出値との相関関係を記憶した記憶部３６を備えている。制御部３０は、センサ２８の検出値及び上記相関関係に基づいて、気液分離器１６の目標圧力を設定し、気液分離器１６の圧力が目標圧力となるように膨張弁２６の開度を制御する。この実施形態によれば、過去のデータから、圧縮機１４の液バックや異常過熱を回避可能な気液分離器１６の目標圧力を精度良く設定できる。 In one embodiment, as shown in FIG. 1, the control unit 30 includes a storage unit 36 that stores the correlation between the target pressure of the gas-liquid separator 16 and the detected value of the sensor 28. The control unit 30 sets the target pressure of the gas-liquid separator 16 based on the detected value of the sensor 28 and the above correlation, and adjusts the opening degree of the expansion valve 26 so that the pressure of the gas-liquid separator 16 reaches the target pressure. control. According to this embodiment, the target pressure of the gas-liquid separator 16 that can avoid liquid backflow and abnormal overheating of the compressor 14 can be set with high accuracy from past data.

図３は、記憶部３６に記憶されたマップの一例を示す。ｇ点からｉ点の間の領域で冷媒は飽和状態であるので、センサ２８の検出値から一義的に蒸発温度を求めることができる。しかし、ｉ点及びｊ点は過熱領域であるので、センサ２８の検出値に基づいて過熱度を加味した演算を行って蒸発温度を求める必要がある。なお、図３のモリエル線図上では、ｇ点から飽和蒸気線Ｙまでが飽和状態である。 FIG. 3 shows an example of a map stored in the storage unit 36. Since the refrigerant is saturated in the region between point g and point i, the evaporation temperature can be uniquely determined from the detected value of sensor 28. However, since the i point and the j point are in the overheating region, it is necessary to calculate the evaporation temperature based on the detected value of the sensor 28 and taking into account the degree of superheating. In addition, on the Mollier diagram of FIG. 3, the saturated state is from point g to saturated vapor line Y.

一実施形態では、気液分離器１６の目標圧力は、圧縮機１４の異常過熱を起こさず、かつ圧縮機１４への液バックを起さない範囲に設定される。図４は、気液分離器１６の目標圧力の一例を示すグラフである。図４に示すように、目標圧力は、センサ２８により検出された圧力又は温度の検出値と共に増加する可変範囲内に設定される。図４において、領域Ａは、圧縮機に異常過熱を引き起こす領域であり、領域Ｂは、圧縮機に吸引される冷媒の温度が不足して液バックを起こすおそれがある領域である。範囲Ｃは、センサ２８の検出値と共に増加する上記問題を起さない可変範囲であり、可変範囲Ｃの中で例えばラインＤ上に目標圧力が設定される。目標圧力を可変範囲Ｃの中に設定することで、圧縮機１４の異常過熱や圧縮機への液バックを回避できる目標圧力を設定できる。 In one embodiment, the target pressure of the gas-liquid separator 16 is set within a range that does not cause abnormal overheating of the compressor 14 and does not cause liquid back to the compressor 14. FIG. 4 is a graph showing an example of the target pressure of the gas-liquid separator 16. As shown in FIG. 4, the target pressure is set within a variable range that increases with the pressure or temperature detected by the sensor 28. In FIG. 4, region A is a region that causes abnormal overheating in the compressor, and region B is a region where the temperature of the refrigerant sucked into the compressor is insufficient, which may cause liquid back. The range C is a variable range that does not cause the above problem and increases with the detection value of the sensor 28, and the target pressure is set, for example, on the line D within the variable range C. By setting the target pressure within the variable range C, it is possible to set a target pressure that can avoid abnormal overheating of the compressor 14 and liquid backflow to the compressor.

一実施形態では、図１に示すように、冷凍システム１０は気液分離器１６の上流側の冷媒循環路１２に膨張弁３４を備えている。膨張弁３４によって、気液分離器１６の圧力を一次制御できる。膨張弁３４の一次制御と膨張弁２６の二次制御（精密制御）との組み合わせによって、気液分離器１６の圧力を目標圧力に精度良く制御できる。 In one embodiment, as shown in FIG. 1, the refrigeration system 10 includes an expansion valve 34 in the refrigerant circuit 12 upstream of the gas-liquid separator 16. The pressure in the gas-liquid separator 16 can be primarily controlled by the expansion valve 34 . By combining the primary control of the expansion valve 34 and the secondary control (precision control) of the expansion valve 26, the pressure of the gas-liquid separator 16 can be accurately controlled to the target pressure.

一実施形態に係る冷凍システム１０の制御方法は、図５に示すように、蒸発器１８における冷媒の蒸発温度と相関のある検出値を検出する検出ステップＳ１０と、検出ステップＳ１０で検出された検出値に基づいて気液分離器１６の目標圧力を設定し、気液分離器１６が該目標圧力となるように膨張弁２６を制御する制御ステップＳ１２と、を備える。これによって、気液分離器１６の圧力を圧縮機１４の液バックや異常過熱が起きない目標圧力に制御できるため、圧縮機１４の液バックや異常過熱を回避しながら、冷却負荷の冷却温度など、冷凍システム１０の運転適用範囲を拡大できる。 As shown in FIG. 5, the method for controlling the refrigeration system 10 according to one embodiment includes a detection step S10 for detecting a detection value correlated with the evaporation temperature of the refrigerant in the evaporator 18, and a detection value detected in the detection step S10. A control step S12 is provided, in which a target pressure of the gas-liquid separator 16 is set based on the value, and the expansion valve 26 is controlled so that the gas-liquid separator 16 reaches the target pressure. As a result, the pressure in the gas-liquid separator 16 can be controlled to a target pressure that does not cause liquid backflow or abnormal overheating of the compressor 14, so that the cooling temperature of the cooling load can be adjusted while avoiding liquid backflow or abnormal overheating of the compressor 14. , the operational range of the refrigeration system 10 can be expanded.

上記各実施形態に記載の内容は、例えば以下のように把握される。 The contents described in each of the above embodiments can be understood as follows, for example.

（１）一つの態様に係る冷凍システムは、気相部および液相部を有する気液分離器と、前記気液分離器の前記液相部からの冷媒が導かれる蒸発器と、前記蒸発器を通過後の冷媒を圧縮するための圧縮機と、前記蒸発器と前記圧縮機とを接続する第１冷媒流路（例えば、図１に示す冷媒循環路１２）と、前記気液分離器の前記気相部と前記第１冷媒流路とを接続するための第２冷媒流路（例えば、図１に示すバイパス路２４）と、前記気液分離器の前記液相部と前記蒸発器を経た前記冷媒とを熱交換するための熱交換器と、前記第２冷媒流路に設けられる第１膨張弁（例えば、図１に示す膨張弁２６）と、前記蒸発器における前記冷媒の蒸発温度と相関のある圧力又は温度を検出するためのセンサ（例えば、図１に示すセンサ２８）と、前記センサの検出結果に基づいて設定される前記気液分離器の目標圧力に基づいて、前記第１膨張弁の開度制御を行うための制御部（例えば、図１に示す制御部３０）と、を備える。 (1) A refrigeration system according to one aspect includes a gas-liquid separator having a gas phase part and a liquid phase part, an evaporator to which refrigerant from the liquid phase part of the gas-liquid separator is guided, and the evaporator a first refrigerant flow path (for example, the refrigerant circulation path 12 shown in FIG. 1) connecting the evaporator and the compressor, and the gas-liquid separator. A second refrigerant flow path (for example, the bypass path 24 shown in FIG. 1) for connecting the gas phase portion and the first refrigerant flow path, and a second refrigerant flow path for connecting the gas phase portion and the first refrigerant flow path, and the liquid phase portion of the gas-liquid separator and the evaporator. a heat exchanger for exchanging heat with the refrigerant, a first expansion valve (for example, the expansion valve 26 shown in FIG. 1) provided in the second refrigerant flow path, and an evaporation temperature of the refrigerant in the evaporator. A sensor (for example, sensor 28 shown in FIG. 1) for detecting a pressure or temperature correlated with 1. A control unit (for example, the control unit 30 shown in FIG. 1) for controlling the opening degree of the expansion valve.

このような構成によれば、上記熱交換器を備えるため、蒸発器を経た冷媒をこの熱交換器で加熱することで、該冷媒の過熱度不足を解消できるため、冷却負荷がＣ級温度帯であっても、圧縮機の液バックを抑止できる。蒸発器の蒸発温度を低く設定すると、熱交換器の出口側で過熱度が過剰になるが、第１膨張弁の開度を制御し、気液分離器内の冷媒圧力を圧縮機の液バック及び異常過熱が起きない目標圧力に制御するため、液バックや異常過熱を回避しながら、冷却負荷の冷却温度など、冷凍システムの運転適用範囲を拡大できる。 According to such a configuration, since the heat exchanger is provided, the refrigerant that has passed through the evaporator is heated by the heat exchanger, so that insufficient superheating of the refrigerant can be resolved, so that the cooling load is in the C class temperature range. However, liquid backflow in the compressor can be suppressed. If the evaporation temperature of the evaporator is set low, the degree of superheating will be excessive at the outlet side of the heat exchanger, but by controlling the opening degree of the first expansion valve, the refrigerant pressure in the gas-liquid separator is adjusted to the liquid back of the compressor. Since the pressure is controlled to a target pressure that does not cause abnormal overheating, it is possible to expand the scope of operation of the refrigeration system, such as the cooling temperature of the cooling load, while avoiding liquid back-up and abnormal overheating.

（２）一態様に係る冷凍システムでは、（１）に記載の冷凍システムであって、前記熱交換器と前記蒸発器との間に設けられた第２膨張弁（例えば、図１に示す膨張弁２２）を備え、前記センサは、前記第２膨張弁の出口側と前記圧縮機の入口側との間の前記第１冷媒流路に設けられる。 (2) In the refrigeration system according to one embodiment, the refrigeration system according to (1) is provided with a second expansion valve (for example, an expansion valve shown in FIG. 1) provided between the heat exchanger and the evaporator. valve 22), and the sensor is provided in the first refrigerant flow path between the outlet side of the second expansion valve and the inlet side of the compressor.

このような構成によれば、第２膨張弁と圧縮機との間の領域の冷媒圧力又は冷媒温度を検出すれば、設定された蒸発器の運転条件などから圧縮機入口の冷媒圧力又は冷却温度を演算できる。従って、上記検出値に基づいて、第１膨張弁の開度を制御し、気液分離器の圧力を設定された目標圧力に制御すれば、圧縮機の液バックや異常過熱を回避できる。そのため、圧縮機の液バックや異常過熱を回避しながら、冷凍システムの運転適用範囲を広げることができる。 According to such a configuration, if the refrigerant pressure or refrigerant temperature in the area between the second expansion valve and the compressor is detected, the refrigerant pressure or cooling temperature at the compressor inlet can be determined based on the set operating conditions of the evaporator. can be calculated. Therefore, by controlling the opening degree of the first expansion valve and controlling the pressure of the gas-liquid separator to the set target pressure based on the detected value, liquid backflow and abnormal overheating of the compressor can be avoided. Therefore, the range of operation of the refrigeration system can be expanded while avoiding liquid backflow and abnormal overheating of the compressor.

（３）別な態様に係る冷凍システムでは、（１）又は（２）に記載の冷凍システムであって、前記センサは、前記熱交換器の出口側と前記圧縮機の入口側との間の前記第１冷媒流路に設けられる。 (3) In the refrigeration system according to another aspect, in the refrigeration system according to (1) or (2), the sensor is located between the outlet side of the heat exchanger and the inlet side of the compressor. Provided in the first refrigerant flow path.

このような構成によれば、上記センサによって、熱交換器の出口側と圧縮機の入口側との間の冷媒の圧力又は温度を検出するため、設定された蒸発器の運転条件などから圧縮機入口の冷媒圧力又は冷却温度を演算できる。従って、上記検出値に基づいて、第１膨張弁の開度を制御し、気液分離器の圧力を設定された目標圧力に制御すれば、圧縮機の液バックや異常過熱を回避できる。そのため、圧縮機の液バックや異常過熱を回避しながら、冷凍システムの運転適用範囲を広げることができる。 According to such a configuration, since the sensor detects the pressure or temperature of the refrigerant between the outlet side of the heat exchanger and the inlet side of the compressor, the pressure or temperature of the refrigerant is determined based on the set operating conditions of the evaporator, etc. The inlet refrigerant pressure or cooling temperature can be calculated. Therefore, by controlling the opening degree of the first expansion valve and controlling the pressure of the gas-liquid separator to the set target pressure based on the detected value, liquid backflow and abnormal overheating of the compressor can be avoided. Therefore, the range of operation of the refrigeration system can be expanded while avoiding liquid backflow and abnormal overheating of the compressor.

（４）さらに別な態様に係る冷凍システムでは、（３）に記載の冷凍システムであって、前記センサは、前記第１冷媒流路と前記第２冷媒流路とが合流する合流点（例えば、図１に示すｊ点）と前記圧縮機の入口側との間の前記第１冷媒流路に設けられる。 (4) In the refrigeration system according to yet another aspect, in the refrigeration system according to (3), the sensor is configured to detect a confluence point (for example, , point j shown in FIG. 1) and the inlet side of the compressor.

このような構成によれば、上記合流点で第２冷媒流路から第１冷媒流路に流入するガス冷媒による温度又は圧力の変動後の検出値が得られるので、該変動を加味した演算を必要としない。そのため、気液分離器の目標圧力の設定が容易になる。 According to such a configuration, since a detected value after fluctuations in temperature or pressure due to the gas refrigerant flowing from the second refrigerant flow path into the first refrigerant flow path at the above-mentioned confluence point is obtained, calculations that take into account the fluctuations are performed. do not need. Therefore, it becomes easy to set the target pressure of the gas-liquid separator.

（５）さらに別な態様に係る冷凍システムは、（２）に記載の冷凍システムであって、前記センサは、前記蒸発器の入口側の前記第１冷媒流路に設けられ、前記冷媒の圧力又は温度を検出するように構成される。 (5) A refrigeration system according to still another aspect is the refrigeration system according to (2), in which the sensor is provided in the first refrigerant flow path on the inlet side of the evaporator, and the sensor is provided at the refrigerant pressure or configured to detect temperature.

このような構成によれば、蒸発器入口側の第１冷媒流路における冷却温度の検出値と、蒸発器の運転条件とから、圧縮機入口の冷媒圧力又は冷却温度を演算できる。こうして、得られた演算値に基づいて気液分離器の目標圧力を設定することで、圧縮機の液バックや異常過熱を回避しながら、冷凍システムの運転適用範囲を広げることができる。 According to such a configuration, the refrigerant pressure or cooling temperature at the compressor inlet can be calculated from the detected value of the cooling temperature in the first refrigerant flow path on the evaporator inlet side and the operating conditions of the evaporator. In this way, by setting the target pressure of the gas-liquid separator based on the calculated value obtained, it is possible to widen the operational range of the refrigeration system while avoiding liquid backflow and abnormal overheating of the compressor.

（６）さらに別な態様に係る冷凍システムは、（１）乃至（５）の何れかに記載の冷凍システムであって、前記制御部は、前記気液分離器の目標圧力と前記検出値との相関関係を記憶した記憶部（例えば、図１に示す記憶部３６）を有し、前記制御部は、前記検出値及び前記相関関係に基づいて前記気液分離器の目標圧力を設定し、前記気液分離器の圧力が前記目標圧力となるように前記第１膨張弁の開度を制御するように構成される。 (6) A refrigeration system according to yet another aspect is the refrigeration system according to any one of (1) to (5), in which the control unit is configured to adjust the target pressure of the gas-liquid separator and the detected value. The controller has a storage unit (for example, the storage unit 36 shown in FIG. 1) that stores a correlation, and the control unit sets a target pressure of the gas-liquid separator based on the detected value and the correlation; The opening degree of the first expansion valve is controlled so that the pressure of the gas-liquid separator becomes the target pressure.

このような構成によれば、過去のデータから、圧縮機への液バックや圧縮機の異常過熱を回避可能な気液分離器の目標圧力を精度良く設定できる。 With this configuration, it is possible to accurately set the target pressure of the gas-liquid separator that can avoid liquid backflow to the compressor and abnormal overheating of the compressor, based on past data.

（７）さらに別な態様に係る冷凍システムは、（１）乃至（６）の何れかに記載の冷凍システムであって、前記目標圧力は、前記センサにより検出された温度又は圧力の検出値と共に増加する可変範囲（例えば、図４に示す可変範囲Ｃ）である。 (7) A refrigeration system according to yet another aspect is the refrigeration system according to any one of (1) to (6), wherein the target pressure is together with a detected value of temperature or pressure detected by the sensor. This is an increasing variable range (for example, variable range C shown in FIG. 4).

このような構成によれば、気液分離器の目標圧力を上記可変範囲とすることで、圧縮機の液バックや異常過熱を回避できる目標圧力に設定できる。 According to such a configuration, by setting the target pressure of the gas-liquid separator within the above variable range, it is possible to set the target pressure to a value that can avoid liquid back and abnormal overheating of the compressor.

（８）一つの態様に係る冷凍システムの制御方法は、気相部および液相部を有する気液分離器と、前記気液分離器の前記液相部からの冷媒が導かれる蒸発器と、前記蒸発器を通過後の冷媒を圧縮するための圧縮機と、前記蒸発器と前記圧縮機とを接続する第１冷媒流路と、前記気液分離器の前記気相部と前記第１冷媒流路とを接続するための第２冷媒流路と、前記気液分離器の前記液相部と前記蒸発器を経た前記冷媒とを熱交換するための熱交換器と、前記第２冷媒流路に設けられる第１膨張弁と、前記蒸発器における前記冷媒の蒸発温度と相関のある圧力又は温度を検出するためのセンサと、前記センサの検出結果に基づいて設定される前記気液分離器の目標圧力に基づいて、前記膨張弁の開度制御を行うための制御部と、を備える冷凍システムの制御方法であって、前記蒸発器における冷媒の蒸発温度と相関のある検出値を検出する検出ステップと、前記検出値に基づいて前記気液分離器の圧力が目標圧力となるように前記第１膨張弁を制御する制御ステップと、を備える。 (8) A method for controlling a refrigeration system according to one embodiment includes: a gas-liquid separator having a gas phase part and a liquid phase part; an evaporator to which refrigerant from the liquid phase part of the gas-liquid separator is guided; a compressor for compressing the refrigerant after passing through the evaporator; a first refrigerant flow path connecting the evaporator and the compressor; and the gas phase part of the gas-liquid separator and the first refrigerant. a second refrigerant flow path for connecting the flow path; a heat exchanger for exchanging heat between the liquid phase part of the gas-liquid separator and the refrigerant that has passed through the evaporator; and a second refrigerant flow path. a first expansion valve provided in the duct, a sensor for detecting a pressure or temperature correlated with the evaporation temperature of the refrigerant in the evaporator, and the gas-liquid separator that is set based on the detection result of the sensor. A control method for a refrigeration system, comprising: a control unit for controlling the opening degree of the expansion valve based on a target pressure of the evaporator, the method comprising: detecting a detected value correlated with the evaporation temperature of the refrigerant in the evaporator; The method includes a detection step, and a control step of controlling the first expansion valve so that the pressure of the gas-liquid separator becomes a target pressure based on the detected value.

このような方法によれば、気液分離器の圧力を圧縮機の液バックや異常過熱が起きない目標圧力に制御できるため、圧縮機の液バックや異常過熱を回避しながら、冷却負荷の冷却温度など、冷凍システムの運転適用範囲を拡大できる。 According to this method, the pressure in the gas-liquid separator can be controlled to a target pressure that does not cause liquid backflow or abnormal overheating of the compressor, so it is possible to cool the cooling load while avoiding liquid backflow or abnormal overheating of the compressor. The operating range of the refrigeration system can be expanded, such as temperature.

１０冷凍システム
１２冷媒循環路
１４圧縮機
１６気液分離器
１８蒸発器
２０熱交換器
２２膨張弁（第２膨張弁）
２４バイパス路
２６膨張弁（第１膨張弁）
２８（２８ａ、２８ｂ、２８ｃ、２８ｄ、２８ｅ）センサ
２８（２８ａ、２８ｃ）圧力センサ
２８（２８ｂ、２８ｄ、２８ｅ）温度センサ
３０制御部
３２凝縮器
３４膨張弁
３６記憶部
Ｋ臨界点
Ｘ飽和液線
Ｙ飽和蒸気線
ｗ１冷却媒体
ｗ２被冷却媒体 10 Refrigeration system 12 Refrigerant circuit 14 Compressor 16 Gas-liquid separator 18 Evaporator 20 Heat exchanger 22 Expansion valve (second expansion valve)
24 Bypass path 26 Expansion valve (first expansion valve)
28 (28a, 28b, 28c, 28d, 28e) Sensor 28 (28a, 28c) Pressure sensor 28 (28b, 28d, 28e) Temperature sensor 30 Control section 32 Condenser 34 Expansion valve 36 Memory section K Critical point X Saturated liquid line Y Saturated steam line w1 Cooling medium w2 Medium to be cooled

Claims

a gas-liquid separator having a gas phase part and a liquid phase part;
an evaporator to which refrigerant from the liquid phase part of the gas-liquid separator is guided;
a compressor for compressing the refrigerant after passing through the evaporator;
a first refrigerant flow path connecting the evaporator and the compressor;
a second refrigerant flow path for connecting the gas phase part of the gas-liquid separator and the first refrigerant flow path;
a heat exchanger for exchanging heat between the liquid phase part of the gas-liquid separator and the refrigerant that has passed through the evaporator;
a first expansion valve provided in the second refrigerant flow path;
a sensor for detecting pressure or temperature correlated with the evaporation temperature of the refrigerant in the evaporator;
a control unit for controlling the opening degree of the first expansion valve based on a target pressure of the gas-liquid separator that is set based on a detected value of the sensor;
Equipped with
The second refrigerant flow path is connected to a portion of the first refrigerant flow path where the refrigerant after passing through the evaporator flows from the heat exchanger toward the compressor,
The control unit is configured to control the opening degree of the first expansion valve provided in the second refrigerant flow path so that the pressure of the gas-liquid separator becomes the target pressure.
refrigeration system.

a second expansion valve provided between the heat exchanger and the evaporator;
The refrigeration system according to claim 1, wherein the sensor is provided in the first refrigerant flow path between the outlet side of the second expansion valve and the inlet side of the compressor.

The refrigeration system according to claim 1 or 2, wherein the sensor is provided in a portion of the first refrigerant flow path where the refrigerant after passing through the evaporator flows from the heat exchanger toward the compressor.

The refrigeration system according to claim 3, wherein the sensor is provided in the first refrigerant flow path between a confluence point where the first refrigerant flow path and the second refrigerant flow path merge and an inlet side of the compressor. system.

The refrigeration system according to claim 2, wherein the sensor is provided in the first refrigerant flow path on the inlet side of the evaporator and configured to detect the pressure or temperature of the refrigerant.

The control unit includes a storage unit that stores a correlation between the target pressure of the gas-liquid separator and the detected value,
The control unit sets a target pressure of the gas-liquid separator based on the detected value and the correlation, and adjusts the opening degree of the first expansion valve so that the pressure of the gas-liquid separator reaches the target pressure. The refrigeration system according to any one of claims 1 to 5, configured to control.

The refrigeration system according to any one of claims 1 to 6, wherein the target pressure has a variable range that increases with the temperature or pressure detected by the sensor.

A gas-liquid separator having a gas phase part and a liquid phase part, an evaporator to which refrigerant from the liquid phase part of the gas-liquid separator is guided, and a compressor for compressing the refrigerant after passing through the evaporator. a first refrigerant flow path connecting the evaporator and the compressor; a second refrigerant flow path connecting the gas phase part of the gas-liquid separator and the first refrigerant flow path; a heat exchanger for exchanging heat between the liquid phase part of the gas-liquid separator and the refrigerant that has passed through the evaporator; a first expansion valve provided in the second refrigerant flow path; A sensor for detecting pressure or temperature correlated with the evaporation temperature of the refrigerant, and an opening degree of the first expansion valve based on a target pressure of the gas-liquid separator that is set based on the detection result of the sensor. a control unit for performing control, and the second refrigerant flow path is configured such that the refrigerant in the first refrigerant flow path after passing through the evaporator is directed from the heat exchanger to the compressor. A method for controlling a refrigeration system connected to a flowing part , the method comprising:
a detection step of detecting a detected value correlated with the evaporation temperature of the refrigerant in the evaporator;
A control step of controlling the first expansion valve provided in the second refrigerant flow path so that the pressure of the gas-liquid separator becomes a target pressure based on the detected value. Method.