JP2013088080A

JP2013088080A - Binary refrigerating device

Info

Publication number: JP2013088080A
Application number: JP2011230759A
Authority: JP
Inventors: Tomotaka Ishikawa; 智隆石川; So Nomoto; 宗野本; Tetsuya Yamashita; 哲也山下; Takashi Ikeda; 隆池田
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2011-10-20
Filing date: 2011-10-20
Publication date: 2013-05-13
Anticipated expiration: 2031-10-20
Also published as: JP5409747B2

Abstract

PROBLEM TO BE SOLVED: To provide a binary refrigerating device capable of obtaining energy-saving effect throughout the year by controlling the amount of radiation from an auxiliary radiator.SOLUTION: This binary refrigerating device includes a high-stage refrigerating cycle 20 forming a high-stage side circuit for circulating a refrigerant by connecting a high-stage side compressor 21 and the like by piping, a low-order side refrigerating cycle 10 forming a low-stage side refrigerant circuit for circulating a refrigerant by connecting a low-stage side compressor 11, the auxiliary radiator 15, a low-stage side condenser 12, a low-stage side expansion valve 13 and a low-stage side evaporator 14 by piping, a cascade condenser C exchanging heat between the refrigerants, an auxiliary radiator fan 16 through which the outdoor air is passed to exchange heat with the refrigerant flowing in the auxiliary radiator 15, and a control device 30 reducing an air volume of the auxiliary radiator fan 16 when it is determined that a temperature of the outdoor air passing through the auxiliary radiator fan 15 is higher than a condensation temperature in the low-order refrigerating cycle 10.

Description

本発明は二元冷凍装置に関するものである。特に低元冷凍サイクル側に補助放熱器を備えた二元冷凍装置に関するものである。 The present invention relates to a binary refrigeration apparatus. In particular, the present invention relates to a binary refrigeration apparatus provided with an auxiliary radiator on the low-source refrigeration cycle side.

従来より、マイナス数十度の低温度の冷却を行うための装置として、高温側冷媒を循環するための冷凍サイクル装置である高元冷凍サイクルと低温側冷媒を循環するための冷凍サイクル装置である低元冷凍サイクルとを有する二元冷凍装置が使用されている。例えば、二元冷凍装置では、低元冷凍サイクルにおける低元側凝縮器と高元冷凍サイクルにおける高元側蒸発器とを熱交換できるように構成したカスケードコンデンサによって低元冷凍サイクルと高元冷凍サイクルとを連結している。 Conventionally, as a device for cooling at a low temperature of minus several tens of degrees, a high-source refrigeration cycle that is a refrigeration cycle device for circulating a high-temperature side refrigerant and a refrigeration cycle device for circulating a low-temperature side refrigerant A binary refrigeration device having a low refrigeration cycle is used. For example, in a binary refrigeration system, a low-source refrigeration cycle and a high-source refrigeration cycle are configured by a cascade condenser configured to exchange heat between a low-source side condenser in a low-source refrigeration cycle and a high-source side evaporator in a high-source refrigeration cycle. Are linked.

そして、このような二元冷凍装置には、例えば低元冷凍サイクルにおいてカスケードコンデンサの前段に補助放熱器を設置し、低温側圧縮機から吐出された吐出冷媒を補助放熱器で放熱させて冷却することで運転効率の向上を図っているものがある（例えば、特許文献１参照）。 In such a binary refrigeration apparatus, for example, an auxiliary radiator is installed in the preceding stage of the cascade condenser in the low refrigeration cycle, and the discharged refrigerant discharged from the low-temperature side compressor is radiated by the auxiliary radiator and cooled. In some cases, the driving efficiency is improved (see, for example, Patent Document 1).

特許第３６０４９７３号公報（第２頁、第３頁、図１）Japanese Patent No. 3606043 (2nd page, 3rd page, FIG. 1)

上記の特許文献１の二元冷凍装置は、低元冷凍サイクルにおいて吐出冷媒を冷却する補助放熱器の放熱量を増大させることで、高元冷凍サイクルの冷却能力を低減して運転効率を向上するものである。ここで、補助放熱器の放熱量をどの程度まで増大できるかは、例えば屋外の空気（外気）の温度などの放熱を行う対象によって異なる。 The above-described binary refrigeration apparatus of Patent Literature 1 increases the heat radiation amount of the auxiliary radiator that cools the discharged refrigerant in the low-source refrigeration cycle, thereby reducing the cooling capacity of the high-source refrigeration cycle and improving the operation efficiency. Is. Here, the extent to which the heat radiation amount of the auxiliary radiator can be increased depends on the object to be radiated, such as the temperature of outdoor air (outside air).

例えば、二元冷凍装置に対しては、年間を通して高い運転効率での運転ができることが望まれている。よって、空冷式の補助放熱器を備えた二元冷凍装置においても、例えば年間を通した外気温度変化を踏まえた上で、高い運転効率によって省エネルギーを図ることができるように補助放熱器の放熱量を制御することが望まれる。しかし、従来の二元冷凍装置において、この点については検討されているものはなかった。 For example, it is desired that a binary refrigeration apparatus can be operated with high operational efficiency throughout the year. Therefore, even in a binary refrigeration system equipped with an air-cooled auxiliary radiator, for example, the amount of heat released from the auxiliary radiator can be saved with high operating efficiency, taking into account changes in the outside air temperature throughout the year. It is desirable to control. However, none of the conventional binary refrigeration apparatuses has been studied in this regard.

本発明はこのような点に鑑みなされたもので、補助放熱器の放熱量を制御し、例えば、年間を通して省エネルギー効果を得ることが可能な二元冷凍装置を提供することを目的とする。 This invention is made | formed in view of such a point, and it aims at providing the binary refrigeration apparatus which can control the thermal radiation amount of an auxiliary heat radiator, and can obtain the energy saving effect throughout the year, for example.

本発明に係る二元冷凍装置は、高元側圧縮機、高元側凝縮器、高元側絞り装置及び高元側蒸発器を配管接続し、冷媒を循環させる高元側冷媒回路を形成する高元冷凍サイクルと、低元側圧縮機、補助放熱器、低元側凝縮器、低元側絞り装置及び低元側蒸発器を配管接続し、冷媒を循環させる低元側冷媒回路を形成する低元冷凍サイクルと、高元側蒸発器と低元側凝縮器とにより構成し、高元側冷媒回路を流れる冷媒と低元側冷媒回路を流れる冷媒との間の熱交換を行うカスケードコンデンサと、補助放熱器を流れる冷媒と熱交換させるための屋外空気を補助放熱器に通過させる送風機と、低元冷凍サイクルにおける凝縮温度よりも、補助放熱器を通過させる屋外空気の温度の方が高いと判断すると、送風機の風量を減少させる制御を行う制御装置とを備えるものである。 A binary refrigeration apparatus according to the present invention connects a high-side compressor, a high-side condenser, a high-side throttle device, and a high-side evaporator to form a high-side refrigerant circuit that circulates refrigerant. The high-source refrigeration cycle is connected to the low-side compressor, auxiliary radiator, low-side condenser, low-side expansion device, and low-side evaporator to form a low-side refrigerant circuit that circulates the refrigerant. A cascade condenser configured by a low-source refrigeration cycle, a high-side evaporator and a low-side condenser, and performing heat exchange between the refrigerant flowing through the high-side refrigerant circuit and the refrigerant flowing through the low-side refrigerant circuit; When the temperature of the outdoor air passing through the auxiliary radiator is higher than the blower that passes outdoor air to exchange heat with the refrigerant flowing through the auxiliary radiator and the condensation temperature in the low-source refrigeration cycle If judged, control to reduce the air volume of the blower It is intended and a location.

本発明によれば、二元冷凍装置において、低減冷凍サイクルに補助放熱器と放熱器に屋外空気を流す送風機を備え、制御装置が、低元冷凍サイクルにおける凝縮温度よりも屋外空気の温度の方が高いと判断すると送風機の風量を減少させるようにしたので、例えば、空気の温度変化を踏まえた上で運転を制御することができ、高い運転効率を達成し、省エネルギーを図ることができる。例えば屋外空気に放熱を行う際には、年間を通して高い運転効率を達成することができる。 According to the present invention, in the dual refrigeration apparatus, the reduced refrigeration cycle includes an auxiliary radiator and a blower that causes outdoor air to flow to the radiator, and the control device has a higher outdoor air temperature than the condensation temperature in the low refrigeration cycle. If it is determined that the air flow is high, the air volume of the blower is reduced. For example, it is possible to control the operation in consideration of the temperature change of the air, achieve high operation efficiency, and save energy. For example, when heat is radiated to outdoor air, high operating efficiency can be achieved throughout the year.

本発明の実施の形態１における二元冷凍装置の構成を表す図である。It is a figure showing the structure of the binary refrigeration apparatus in Embodiment 1 of this invention. 本発明の実施の形態１の二元冷凍装置におけるエンタルピと飽和温度との関係を示す図である。It is a figure which shows the relationship between enthalpy and saturation temperature in the binary refrigeration apparatus of Embodiment 1 of this invention. 低元側凝縮温度と圧縮機入力との関係を示す図である。It is a figure which shows the relationship between the low original side condensing temperature and a compressor input. 低元側凝縮温度が外気温度よりも低い場合と高い場合の放熱量について説明するための図である。It is a figure for demonstrating the thermal radiation amount in the case where the low element side condensing temperature is lower than outside temperature, and when it is high. 補助放熱器１５の放熱量とＣＯＰとの関係を説明するための図である。It is a figure for demonstrating the relationship between the heat dissipation of the auxiliary radiator 15, and COP. 本発明の実施の形態２における二元冷凍装置の構成を表す図である。It is a figure showing the structure of the binary refrigeration apparatus in Embodiment 2 of this invention.

以下、本発明に係る二元冷凍装置の好適な実施の形態について図面を参照して説明する。 Hereinafter, a preferred embodiment of a binary refrigeration apparatus according to the present invention will be described with reference to the drawings.

実施の形態１．
図１は本発明の実施の形態１における二元冷凍装置の構成を表す図である。図１に示すように、本実施の形態における二元冷凍装置は、低元冷凍サイクル１０と高元冷凍サイクル２０とを有し、それぞれ独立して冷媒を循環させる冷媒回路を構成する。そして、２つの冷媒回路を多段構成するために、高元側蒸発器２４と低元側凝縮器１２とを、それぞれ通過する冷媒間での熱交換を可能に結合させて構成したカスケードコンデンサ（冷媒間熱交換器）Ｃを設けている。また、二元冷凍装置全体の運転制御を行う制御装置３０を有する。ここで、温度、圧力等の高低については、特に絶対的な値との関係で高低等が定まっているものではなく、システム、装置等における状態、動作等において相対的に定まるものとする。 Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration of a binary refrigeration apparatus according to Embodiment 1 of the present invention. As shown in FIG. 1, the binary refrigeration apparatus in the present embodiment includes a low-source refrigeration cycle 10 and a high-source refrigeration cycle 20, and configures a refrigerant circuit that circulates refrigerant independently of each other. In order to configure the two refrigerant circuits in multiple stages, a cascade condenser (refrigerant) in which the high-side evaporator 24 and the low-side condenser 12 are coupled so as to enable heat exchange between the refrigerants passing therethrough is possible. An intermediate heat exchanger (C) is provided. Moreover, it has the control apparatus 30 which performs operation control of the whole binary refrigeration apparatus. Here, the levels of temperature, pressure, and the like are not particularly determined in relation to absolute values, but are relatively determined in terms of the state and operation of the system, apparatus, and the like.

図１において、低元冷凍サイクル１０は、低元側圧縮機１１と、補助放熱器１５と、低元側凝縮器１２と、低元側膨張弁１３と、低元側蒸発器１４とを順に冷媒配管で接続して冷媒回路（以下、低元側冷媒回路という）を構成している。一方、高元冷凍サイクル２０は、高元側圧縮機２１と、高元側凝縮器２２と、高元側膨張弁２３と、高元側蒸発器２４とを順に冷媒配管で接続して冷媒回路（以下、高元側冷媒回路という）を構成している。 In FIG. 1, the low-source refrigeration cycle 10 includes a low-side compressor 11, an auxiliary radiator 15, a low-side condenser 12, a low-side expansion valve 13, and a low-side evaporator 14 in order. A refrigerant circuit (hereinafter referred to as a low-side refrigerant circuit) is configured by connecting with refrigerant piping. On the other hand, the high-source refrigeration cycle 20 includes a high-side compressor 21, a high-side condenser 22, a high-side expansion valve 23, and a high-side evaporator 24 connected in order through a refrigerant pipe. (Hereinafter referred to as a high-side refrigerant circuit).

低元冷凍サイクル１０の低元側圧縮機１１は、冷媒を吸入し、圧縮して高温・高圧の状態にして吐出する。ここでは、例えばインバータ回路等により回転数を制御し、高元側冷媒の吐出量を調整できるタイプの圧縮機で構成する。 The low-source side compressor 11 of the low-source refrigeration cycle 10 sucks the refrigerant, compresses it, and discharges it in a high temperature / high pressure state. Here, for example, it is configured by a compressor of a type that can control the number of revolutions by an inverter circuit or the like and adjust the discharge amount of the high-side refrigerant.

補助放熱器１５は、例えばガスクーラ等として機能し、屋外の空気（外気）との熱交換により低元側圧縮機１１が吐出したガス冷媒を冷却する。ここで、本実施の形態における二元冷凍装置は、補助放熱器１５における外気と冷媒との熱交換を促すための送風機である補助放熱器ファン１６を有しているものとする。補助放熱器ファン１６は補助放熱器１５に空気を通過させる流れを形成する。例えばインバータ回路等により回転数を制御し、風量を調整できるタイプのファンで構成する。 The auxiliary radiator 15 functions as a gas cooler, for example, and cools the gas refrigerant discharged by the low-source compressor 11 by heat exchange with outdoor air (outside air). Here, the binary refrigeration apparatus in the present embodiment includes an auxiliary radiator fan 16 that is a blower for promoting heat exchange between the outside air and the refrigerant in the auxiliary radiator 15. The auxiliary radiator fan 16 forms a flow that allows air to pass through the auxiliary radiator 15. For example, it is configured with a fan of a type that can adjust the air volume by controlling the rotation speed by an inverter circuit or the like.

また、低元側凝縮器１２は、補助放熱器１５を通過した冷媒との間で熱交換を行い、冷媒を凝縮させて液状の冷媒にする（凝縮液化させる）ものである。例えば、ここではカスケードコンデンサＣにおいて低元側冷媒回路を流れる冷媒が通過する伝熱管等が低元側凝縮器１２となって、高元側冷媒回路を流れる冷媒との熱交換が行われるものとする。 Further, the low-side condenser 12 exchanges heat with the refrigerant that has passed through the auxiliary radiator 15 to condense the refrigerant into a liquid refrigerant (condensate liquid). For example, in this case, in the cascade condenser C, a heat transfer tube or the like through which the refrigerant flowing through the low-side refrigerant circuit passes becomes the low-side condenser 12, and heat exchange with the refrigerant flowing through the high-side refrigerant circuit is performed. To do.

減圧装置、絞り装置等となる低元側膨張弁１３は、低元側冷媒回路を流れる冷媒を減圧して膨張させるものである。例えば電子式膨張弁等の流量制御手段、毛細管（キャピラリ）、感温式膨張弁等の冷媒流量調節手段等で構成する。低元側蒸発器１４は、例えば冷却対象との熱交換により低元冷媒回路を流れる冷媒を蒸発させて気体（ガス）状の冷媒にする（蒸発ガス化させる）ものである。冷媒との熱交換により、冷却対象は、直接又は間接に冷却されることになる。 The low-side expansion valve 13 serving as a decompression device, a throttle device, or the like decompresses the refrigerant flowing through the low-side refrigerant circuit and expands it. For example, the flow rate control means such as an electronic expansion valve, a capillary (capillary), a refrigerant flow rate control means such as a temperature-sensitive expansion valve, and the like are used. The low element side evaporator 14 evaporates the refrigerant flowing through the low element refrigerant circuit, for example, by heat exchange with the object to be cooled, and converts it into a gas (gas) refrigerant (evaporated gas). The object to be cooled is cooled directly or indirectly by heat exchange with the refrigerant.

一方、高元冷凍サイクル２０の高元側圧縮機２１は、高元側冷媒回路を流れる冷媒を吸入し、その冷媒を圧縮して高温・高圧の状態にして吐出する。高元側圧縮機２１についても、例えばインバータ回路等を有し、冷媒の吐出量を調整できるタイプの圧縮機で構成する。高元側凝縮器２２は、例えば、空気、ブライン等と高元側冷媒回路を流れる冷媒との間で熱交換を行い、冷媒を凝縮液化させるものである。ここで、本実施の形態では、外気と冷媒との熱交換を行うものとし、熱交換を促すための高元側凝縮器ファン２５を有しているものとする。高元側凝縮器ファン２５についても風量を調整できるタイプのファンで構成する。 On the other hand, the high-side compressor 21 of the high-side refrigeration cycle 20 sucks the refrigerant flowing through the high-side refrigerant circuit, compresses the refrigerant, and discharges it in a high temperature / high pressure state. The high-side compressor 21 is also composed of a compressor of a type that has an inverter circuit or the like and can adjust the refrigerant discharge amount. The high-side condenser 22 performs heat exchange between, for example, air, brine, and the refrigerant flowing through the high-side refrigerant circuit to condense and liquefy the refrigerant. Here, in the present embodiment, heat exchange between the outside air and the refrigerant is performed, and the high-side condenser fan 25 for promoting heat exchange is provided. The high-end side condenser fan 25 is also composed of a fan of a type that can adjust the air volume.

減圧装置、絞り装置等となる高元側膨張弁２３は、高元側冷媒回路を流れる冷媒を減圧して膨張させるものである。例えば前述した電子式膨張弁等の流量制御手段、毛細管等の冷媒流量調節手段で構成する。高元側蒸発器２４は、熱交換により高元側冷媒回路を流れる冷媒を蒸発ガス化するものである。例えば、ここではカスケードコンデンサＣにおいて高元側冷媒回路を流れる冷媒が通過する伝熱管等が高元側蒸発器２４となって、低元側冷媒回路を流れる冷媒との熱交換が行われるものとする。 The high-side expansion valve 23 serving as a decompression device, a throttling device, or the like decompresses the refrigerant flowing through the high-side refrigerant circuit and expands it. For example, the flow rate control means such as the electronic expansion valve described above and the refrigerant flow rate control means such as a capillary tube are used. The high element side evaporator 24 evaporates the refrigerant flowing through the high element side refrigerant circuit by heat exchange. For example, in this case, in the cascade condenser C, a heat transfer tube or the like through which the refrigerant flowing through the high-side refrigerant circuit passes becomes the high-side evaporator 24, and heat exchange with the refrigerant flowing through the low-side refrigerant circuit is performed. To do.

また、カスケードコンデンサＣは、前述した高元側蒸発器２４と低元側凝縮器１２との機能を有し、高元側冷媒と低元側冷媒とを熱交換可能にする冷媒間熱交換器である。カスケードコンデンサＣを介して高元側冷媒回路と低元側冷媒回路とを多段構成にし、冷媒間の熱交換を行うようにすることで、独立した冷媒回路を連携させることができる。また、制御装置３０は、二元冷凍装置を構成する各機器の動作制御等を行う。外気温度検出手段３１は外気温度を検出するための温度センサーである。以下、外気温度は、外気温度検出手段３１の検出に係る温度であるものとする。 Further, the cascade condenser C has the functions of the high-end side evaporator 24 and the low-end side condenser 12 described above, and the inter-refrigerant heat exchanger enables heat exchange between the high-end side refrigerant and the low-end side refrigerant. It is. By configuring the high-side refrigerant circuit and the low-side refrigerant circuit in multiple stages via the cascade capacitor C and performing heat exchange between the refrigerants, independent refrigerant circuits can be linked. Moreover, the control apparatus 30 performs operation control etc. of each apparatus which comprises a binary refrigeration apparatus. The outside air temperature detecting means 31 is a temperature sensor for detecting the outside air temperature. Hereinafter, it is assumed that the outside air temperature is a temperature related to the detection by the outside air temperature detection means 31.

このような構成の二元冷凍装置においては、低元冷凍サイクル１０の一部の機器（例えば低元側蒸発器１４）を、例えばスーパーマーケットのショーケースなどの室内の負荷装置が有していることがある。例えば、ショーケースを配置換えなどして配管の接続変更などを行って冷媒回路が開放されると、冷媒漏れが発生する可能性が多くなる。そこで、ここでは、低元冷凍サイクル１０の低元側冷媒回路を循環させる冷媒として、冷媒漏れを考慮し、地球温暖化に対する影響が小さいＣＯ₂（二酸化炭素）を用いる。一方、高元冷凍サイクル２０に用いる冷媒は、高元冷凍サイクル２０は冷媒回路が開放されることがないため、例えば地球温暖化係数の高いＨＦＣ冷媒などを用いることができる。それでも、例えば、ＨＦＯ冷媒（ＨＦＯ１２３４ｙｆ、ＨＦＯ１２３４ｚｅ等）、ＨＣ冷媒、ＣＯ₂、アンモニア、水などの地球温暖化に対する影響が小さい冷媒を用いることが望ましい。そこで、本実施の形態では、高元冷凍サイクル２０の高元側冷媒回路を循環させる冷媒としてＨＦＯ冷媒を用いる。 In the binary refrigeration apparatus having such a configuration, a part of the low refrigeration cycle 10 (for example, the low original evaporator 14) is included in an indoor load device such as a supermarket showcase. There is. For example, if the refrigerant circuit is opened by changing the connection of pipes by rearranging the showcase or the like, the possibility of refrigerant leakage increases. Therefore, here, CO ₂ (carbon dioxide) having a small influence on global warming is used as the refrigerant circulating in the low-side refrigerant circuit of the low-source refrigeration cycle 10 in consideration of refrigerant leakage. On the other hand, since the refrigerant circuit used in the high refrigeration cycle 20 does not open the refrigerant circuit in the high refrigeration cycle 20, for example, an HFC refrigerant having a high global warming potential can be used. Nevertheless, it is desirable to use a refrigerant having a small influence on global warming, such as HFO refrigerant (HFO1234yf, HFO1234ze, etc.), HC refrigerant, CO ₂ , ammonia, water, and the like. Therefore, in the present embodiment, an HFO refrigerant is used as a refrigerant that circulates in the high-side refrigerant circuit of the high-source refrigeration cycle 20.

以上のような二元冷凍装置の冷却運転における各構成機器の動作等を、各冷媒回路を循環する冷媒の流れに基づいて説明する。まず、高元冷凍サイクル２０の動作について説明する。高元側圧縮機２１は、ＨＦＯ冷媒を吸入し、圧縮して高温・高圧の状態にして吐出する。吐出した冷媒は高元側凝縮器２２へ流入する。高元側凝縮器２２は、高元側凝縮器ファン２５から供給される外気とＨＦＯ冷媒との間で熱交換を行い、ＨＦＯ冷媒を凝縮液化する。凝縮液化した冷媒は高元側膨張弁２３を通過する。高元側膨張弁２３は凝縮液化した冷媒を減圧する。減圧した冷媒は高元側蒸発器２４（カスケードコンデンサＣ）に流入する。高元側蒸発器２４は、低減側凝縮器１２を通過する冷媒との熱交換により冷媒を蒸発ガス化する。蒸発ガス化したＨＦＯ冷媒を高元側圧縮機２１が吸入する。 The operation | movement of each component apparatus in the cooling operation of the above binary refrigeration apparatuses is demonstrated based on the flow of the refrigerant | coolant which circulates through each refrigerant circuit. First, the operation of the high-source refrigeration cycle 20 will be described. The high-end compressor 21 sucks in the HFO refrigerant, compresses it, and discharges it in a high temperature / high pressure state. The discharged refrigerant flows into the high-side condenser 22. The high-side condenser 22 performs heat exchange between the outside air supplied from the high-side condenser fan 25 and the HFO refrigerant, and condenses and liquefies the HFO refrigerant. The condensed and liquefied refrigerant passes through the high-side expansion valve 23. The high-side expansion valve 23 depressurizes the condensed and liquefied refrigerant. The decompressed refrigerant flows into the high-side evaporator 24 (cascade capacitor C). The high-side evaporator 24 evaporates the refrigerant by heat exchange with the refrigerant passing through the reduction-side condenser 12. The high-end compressor 21 sucks the evaporated HFO refrigerant.

次に、低元冷凍サイクル１０の動作について説明する。低元側圧縮機１１は、ＣＯ₂冷媒を吸入し、圧縮して高温・高圧の状態にして吐出する。吐出した冷媒は補助放熱器１５で冷却されて低元側凝縮器１２（カスケードコンデンサＣ）へ流入する。低元側凝縮器１２は、高元側蒸発器２４を通過する冷媒との熱交換により冷媒を凝縮液化する。凝縮液化した冷媒は低元側膨張弁１３を通過する。低元側膨張弁１３は凝縮液化した冷媒を減圧する。減圧した冷媒は低元側蒸発器１４に流入する。低元側蒸発器１４は冷却対象との熱交換により冷媒を蒸発ガス化する。蒸発ガス化したＣＯ₂冷媒を高元側圧縮機２１が吸入する。 Next, the operation of the low-source refrigeration cycle 10 will be described. The low-source compressor 11 sucks CO ₂ refrigerant, compresses it, and discharges it in a high temperature / high pressure state. The discharged refrigerant is cooled by the auxiliary radiator 15 and flows into the low-side condenser 12 (cascade capacitor C). The low-side condenser 12 condenses and liquefies the refrigerant by heat exchange with the refrigerant passing through the high-side evaporator 24. The condensed and liquefied refrigerant passes through the low-side expansion valve 13. The low-side expansion valve 13 depressurizes the condensed and liquefied refrigerant. The decompressed refrigerant flows into the low-side evaporator 14. The low-source side evaporator 14 evaporates the refrigerant by heat exchange with the object to be cooled. The high-end compressor 21 sucks the CO ₂ refrigerant that has been vaporized.

本実施の形態の二元冷凍装置では、例えば、高元側圧縮機２１において、駆動するモータの周波数を制御し、高元冷凍サイクル２０における冷却能力を制御することにより低元側冷媒回路における吐出側の圧力（高圧）を調節する。この点について以下に詳述する。 In the binary refrigeration apparatus of the present embodiment, for example, in the high-side compressor 21, the frequency of the motor to be driven is controlled, and the cooling capacity in the high-side refrigeration cycle 20 is controlled, thereby discharging in the low-side refrigerant circuit Adjust the side pressure (high pressure). This point will be described in detail below.

図２は本発明の二元冷凍装置におけるエンタルピと飽和温度との関係を示す図である。本実施の形態の二元冷凍装置では、カスケードコンデンサＣにおいて、低元側凝縮温度と高元側蒸発温度との温度差ΔＴが生じるものとする。温度差ΔＴはカスケードコンデンサＣの熱交換量によって変化するが、ここでは例えば５℃程度とする。 FIG. 2 is a diagram showing the relationship between enthalpy and saturation temperature in the binary refrigeration apparatus of the present invention. In the binary refrigeration apparatus of the present embodiment, it is assumed that the cascade capacitor C has a temperature difference ΔT between the low-side condensation temperature and the high-side evaporation temperature. Although the temperature difference ΔT varies depending on the heat exchange amount of the cascade capacitor C, it is, for example, about 5 ° C. here.

例えば、ある運転状態から高元側圧縮機２１の運転周波数を上げて高元側の冷却能力を増大させると、高元側蒸発温度が低下する。低下した高元側蒸発温度との温度差ΔＴを維持することで低元側凝縮温度（低元側高圧）も低下する。逆に、高元側の冷却能力を低減すれば低元側高圧が上昇する。 For example, when the operating frequency of the high-side compressor 21 is increased from a certain operating state to increase the high-side cooling capacity, the high-side evaporation temperature decreases. By maintaining the temperature difference ΔT with the reduced high element side evaporation temperature, the low element side condensation temperature (low element side high pressure) also decreases. Conversely, if the cooling capacity on the high element side is reduced, the low element side high pressure will increase.

また、図２から明らかなように、高元側圧縮機２１の運転周波数を上げて低元冷凍サイクル１０の低元側高圧が低下すると、高元側圧縮機２１の入力（以下、高元側圧縮機入力という）は大きくなる（ＷＨ１＜ＷＨ２）のに対し、低元側圧縮機１１の入力（以下、低元側圧縮機入力という）は小さくなる（ＷＬ１＞ＷＬ２）。ここで、冷凍能力Ｑ＝ΔＨ（エンタルピ差）×Ｇｒ（冷媒流量）である。二元冷凍装置では、外気温度に応じて冷却負荷が変化し、冷却負荷に対して冷凍能力（低元冷凍サイクル１０側の蒸発能力に相当）を決定している。そして、決定した冷凍能力を一定に保つように低元側圧縮機１１によりＧｒ（冷媒流量）を制御している。例えば、ΔＨ（エンタルピ差）が一定であれば、Ｇｒ（冷媒流量）が一定となるように低元側圧縮機１１を制御する。 Further, as apparent from FIG. 2, when the operating frequency of the high-end compressor 21 is increased and the low-end side high pressure of the low-end refrigeration cycle 10 is lowered, the input (hereinafter referred to as the high-end side) of the high end compressor 21 is reduced. Compressor input) becomes larger (WH1 <WH2), while the low-end compressor 11 input (hereinafter referred to as low-end compressor input) becomes smaller (WL1> WL2). Here, the refrigerating capacity Q = ΔH (enthalpy difference) × Gr (refrigerant flow rate). In the two-way refrigeration apparatus, the cooling load changes according to the outside air temperature, and the refrigeration capacity (corresponding to the evaporation capacity on the low-source refrigeration cycle 10 side) is determined for the cooling load. Then, Gr (refrigerant flow rate) is controlled by the low-side compressor 11 so as to keep the determined refrigeration capacity constant. For example, if ΔH (enthalpy difference) is constant, the low-source compressor 11 is controlled so that Gr (refrigerant flow rate) is constant.

例えば、本実施の形態の二元冷凍装置において、低元冷凍サイクル１０に使用されるＣＯ₂冷媒は、高元冷凍サイクル２０で用いられるＨＦＯ冷媒に比べて冷凍効果が小さい。そのため、大きな圧縮機動力が必要となり、高元冷凍サイクル２０で用いているＨＦＯ冷媒に比べて運転効率が低くなる。そこで、高元側圧縮機２１の容量を増大させて、低元側高圧を低下させることにより、低元冷凍サイクル１０側の消費電力を小さくする。そして、運転効率が高いＨＦＯ冷媒を用いた高元冷凍サイクル２０側の消費電力が大きくなったとしても高元冷凍サイクル２０側の仕事量を増やすことで、二元冷凍装置全体の運転効率を向上させる。このように、高効率な高元冷凍サイクル２０の消費電力比率を大きくすることで、二元冷凍装置全体の運転効率を最適とすることができる。このため、低元冷凍サイクル１０の低元側高圧は、ＣＯ₂が超臨界状態にならないことが多くなり、低元側凝縮器１２において相変化が生じる飽和温度（低元側凝縮温度）が決まっている。 For example, in the binary refrigeration apparatus of the present embodiment, the CO ₂ refrigerant used in the low refrigeration cycle 10 has a smaller refrigeration effect than the HFO refrigerant used in the high refrigeration cycle 20. Therefore, a large compressor power is required, and the operation efficiency is lower than that of the HFO refrigerant used in the high-source refrigeration cycle 20. Therefore, the power consumption on the low-source refrigeration cycle 10 side is reduced by increasing the capacity of the high-source side compressor 21 and decreasing the low-source side high pressure. And even if the power consumption on the high refrigeration cycle 20 side using the HFO refrigerant having high operating efficiency increases, the operation efficiency of the entire dual refrigeration system is improved by increasing the work amount on the high refrigeration cycle 20 side. Let Thus, by increasing the power consumption ratio of the high-efficiency high-source refrigeration cycle 20, it is possible to optimize the operation efficiency of the entire binary refrigeration apparatus. For this reason, in the low-source side high pressure of the low-source refrigeration cycle 10, CO ₂ often does not enter a supercritical state, and a saturation temperature (low-source side condensation temperature) at which phase change occurs in the low-source side condenser 12 is determined. ing.

図３は低元側凝縮温度と圧縮機入力との関係を示す図である。図３において、横軸は低元側凝縮温度であり、縦軸は圧縮機入力である。そして、高元側圧縮機２１入力と低元側圧縮機１１入力とそれらの合計入力（二元冷凍装置全体の合計入力）とについて、それぞれ表している。図３に示すように、高元側圧縮機２１と低元側圧縮機１１のそれぞれの圧縮機入力が略同等となるときに合計入力が最も小さくなり、ＣＯＰ（Coefficient Of Performance：成績係数＝冷凍能力／（高元側圧縮機入力＋低元側圧縮機入力））が最大となることがわかる。 FIG. 3 is a diagram showing the relationship between the low-side condensation temperature and the compressor input. In FIG. 3, the horizontal axis is the low-side condensation temperature, and the vertical axis is the compressor input. And the high-side compressor 21 input, the low-side compressor 11 input, and those total inputs (total input of the entire binary refrigeration apparatus) are shown respectively. As shown in FIG. 3, when the compressor inputs of the high-side compressor 21 and the low-side compressor 11 are substantially equal, the total input becomes the smallest, and COP (Coefficient Of Performance: coefficient of performance = refrigeration) It can be seen that the capacity / (high-end side compressor input + low-end side compressor input) is maximized.

以上より、二元冷凍装置ではＣＯＰが最大となるように高元側圧縮機入力と低元側圧縮機入力とを略同等とする運転制御を行っている。例えば、図２で説明すると、高元側圧縮機入力（＝エンタルピ差ＷＨ１×高元冷媒流量Ｇｒｈ）と、低元側圧縮機入力（＝エンタルピ差ＷＬ１×低元冷媒流量Ｇｒｌ）とが略同等となるように、制御装置３０は制御を行っている。 As described above, in the two-stage refrigeration apparatus, operation control is performed so that the high-side compressor input and the low-side compressor input are substantially equal so that the COP is maximized. For example, referring to FIG. 2, the high-end compressor input (= enthalpy difference WH1 × high-source refrigerant flow rate Grh) and the low-end compressor input (= enthalpy difference WL1 × low-source refrigerant flow rate Grl) are substantially equal. Thus, the control device 30 performs control.

ここで、図３を別の見方をすると、低元冷凍サイクル１０の低元側凝縮温度がＴｃのとき合計入力が最小となり、ＣＯＰが最大となる。よって、高元側圧縮機入力と低元側圧縮機入力とを略同等とする運転制御は、具体的には低元側凝縮温度を目標低元側凝縮温度Ｔｃに保つように低元冷凍サイクル１０を制御することになる。このとき、高元冷凍サイクル２０側は、目標低元側凝縮温度ＴｃよりもΔＴ℃低い温度を目標高元側蒸発温度として一定に保つ制御を行うことになる。このような制御を行うことにより、ＣＯＰを最大とすることができる。ここで、外気温度に応じて高元側高圧（高元側凝縮温度）は異なるため、高元側圧縮機２１入力も外気温度に伴い変化する。したがって、ＣＯＰを最大とする目標低元側凝縮温度Ｔｃも外気温度によって変化することになる。 Here, in another way of viewing FIG. 3, when the low-side refrigeration temperature of the low-source refrigeration cycle 10 is Tc, the total input is minimum and the COP is maximum. Therefore, the operation control that makes the high-side compressor input and the low-side compressor input substantially equal is specifically the low-source refrigeration cycle so as to keep the low-side condensation temperature at the target low-side condensation temperature Tc. 10 will be controlled. At this time, the high refrigeration cycle 20 side performs control to keep a temperature lower by ΔT ° C. than the target low original side condensation temperature Tc as the target high original side evaporation temperature. By performing such control, the COP can be maximized. Here, since the high-side high pressure (high-side condensation temperature) differs depending on the outside air temperature, the high-side compressor 21 input also varies with the outside air temperature. Therefore, the target low original side condensing temperature Tc that maximizes the COP also varies depending on the outside air temperature.

以上のことから、外気温度に基づいて高元側凝縮温度が決定し、高元側凝縮温度が決定すると目標低元側凝縮温度Ｔｃが決定する。そして、目標低元側凝縮温度Ｔｃが決定すると、高元冷凍サイクル２０では高元蒸発温度を目標低元側凝縮温度Ｔｃ−ΔＴ℃となるようにする制御を行う。これにより高元側圧縮機入力と低元側圧縮機入力とを略同等とする運転制御を実現することができ、ＣＯＰを最大とすることができる。ここで、高元冷凍サイクル２０を制御をする際、目標高元側蒸発温度を定めて高元蒸発温度を制御するようにしたが、低元側凝縮温度を直接検知して制御するようにしてもよい。また、高元側圧縮機入力と低元側圧縮機入力とを直接検知して高元冷凍サイクル２０を制御するようにしてもよい。 From the above, the high-side condensation temperature is determined based on the outside air temperature, and when the high-side condensation temperature is determined, the target low-side condensation temperature Tc is determined. When the target low element side condensation temperature Tc is determined, the high element refrigeration cycle 20 performs control so that the high element evaporation temperature becomes the target low element side condensation temperature Tc−ΔT ° C. As a result, it is possible to realize operation control in which the high-side compressor input and the low-side compressor input are substantially equivalent, and the COP can be maximized. Here, when controlling the high-source refrigeration cycle 20, the high-source evaporation temperature is controlled by determining the target high-source evaporation temperature. However, the low-source condensation temperature is directly detected and controlled. Also good. Alternatively, the high-source refrigeration cycle 20 may be controlled by directly detecting the high-source compressor input and the low-source compressor input.

以上の説明において、低効率の低元冷凍サイクル１０の消費電力を抑えるために低元側高圧（低元側凝縮温度）を低下させるものとしたが、これは制御原理上の説明であって、実運転上において低元側高圧を低下させるという意味ではない。実運転上は、上述したように目標低元側凝縮温度Ｔｃに一定に保つ制御を行うことになる。 In the above description, in order to reduce the power consumption of the low-efficiency low-source refrigeration cycle 10, the low-source-side high pressure (low-source-side condensation temperature) is reduced, but this is an explanation on the control principle, This does not mean that the low-side high pressure is reduced in actual operation. In actual operation, as described above, control is performed to keep the target low-side condensation temperature Tc constant.

また、低元側高圧を低下させる制御原理について補足して説明すると、高元冷凍サイクル２０で用いられるＨＦＯ冷媒は低元冷凍サイクル１０で用いられるＣＯ₂冷媒に比べると高効率な冷媒（高ＣＯＰとなるような冷媒）である。このため、高元冷凍サイクル２０において、高元側圧縮機２１の運転により導かれる図２のモリエル線図上の傾きθｈは低元側圧縮機１１の運転による傾きθｌより大きい。したがって、低元側凝縮温度を下げていっても、低元側凝縮温度が目標低元側凝縮温度Ｔｃに至るまでは高元側圧縮機入力が低元側圧縮機入力を超えることはない。そして、目標低元側凝縮温度Ｔｃにおいて、高元側圧縮機入力と低元側圧縮機入力とが等しくなる。 Further, to explain supplementarily the control principle for lowering the low-source side high pressure, the HFO refrigerant used in the high-source refrigeration cycle 20 is more efficient than the CO ₂ refrigerant used in the low-source refrigeration cycle 10 (high COP). Refrigerant). For this reason, in the high refrigeration cycle 20, the inclination θh on the Mollier diagram of FIG. 2 that is derived by the operation of the high original compressor 21 is larger than the inclination θl due to the operation of the low original compressor 11. Therefore, even if the low-side condensation temperature is lowered, the high-side compressor input does not exceed the low-side compressor input until the low-side condensation temperature reaches the target low-side condensation temperature Tc. Then, at the target low original side condensation temperature Tc, the high original compressor input and the low original compressor input are equal.

次に冷媒の運転効率について具体的に説明する。運転効率の指標であるＣＯＰ（＝蒸発器のエンタルピ差／圧縮過程のエンタルピ差）が高ければ、少ない圧縮動力で大きな蒸発潜熱を得られ、高効率な冷媒となる。例えば、外気温度３２℃で運転する一般の冷凍機の動作状態、すなわち蒸発温度−４０℃、凝縮温度４０℃（超臨界のＣＯ₂高圧は８．８ＭＰａとする）、吸入過熱度５℃、液過冷却度５℃の条件で各冷媒の理論上得られるＣＯＰは、ＣＯ₂：１．２５、Ｒ４０４Ａ：１．７６、Ｒ４１０Ａ：１．９１、Ｒ１３４ａ：２．０１、Ｒ３２：１．９８、プロパン：１．９９、イソブタン：２．０５、ＨＦＯ１２３４ｙｆ：１．８３となる。ＣＯ₂は、ＨＦＯ冷媒やＨＦＣ冷媒やＨＣ冷媒と比較しＣＯＰが低く、低効率な冷媒である。 Next, the operation efficiency of the refrigerant will be specifically described. If COP (= difference in enthalpy of evaporator / enthalpy difference in compression process) that is an index of operation efficiency is high, a large latent heat of evaporation can be obtained with a small amount of compression power, and a highly efficient refrigerant can be obtained. For example, the operating state of a general refrigerator operating at an outside air temperature of 32 ° C., that is, an evaporation temperature of −40 ° C., a condensation temperature of 40 ° C. (supercritical CO ₂ high pressure is assumed to be 8.8 MPa), suction superheat degree of 5 ° C., liquid The theoretically obtained COP of each refrigerant under the condition of a supercooling degree of 5 ° C. is CO ₂ : 1.25, R404A: 1.76, R410A: 1.91, R134a: 2.01, R32: 1.98, propane : 1.99, isobutane: 2.05, HFO1234yf: 1.83. CO ₂ is a low-efficiency refrigerant having a low COP compared to HFO refrigerant, HFC refrigerant, and HC refrigerant.

ここで、本実施の形態では低元冷凍サイクル１０においてＣＯ₂を冷媒として使用している。この場合、目標低元側凝縮温度Ｔｃは外気温度よりも低くなる。具体的には、例えば高外気条件である３２℃のとき、目標低元側凝縮温度Ｔｃが約２０℃となり、低外気条件である７℃のとき、目標低元側凝縮温度Ｔｃが約０℃となる。上述したように、低元側高圧（低元側凝縮温度）を下げると、運転効率が低い低元冷凍サイクル１０側における低元側圧縮機入力を下げることができるため、外気温度よりも低い温度領域内に目標低元側凝縮温度Ｔｃが位置することになる。ここで、外気温度よりも低い温度領域内に目標低元側凝縮温度Ｔｃが位置するのは、低元冷凍サイクル１０において低効率なＣＯ₂冷媒を適用した場合であって、低元冷凍サイクル１０と高元冷凍サイクル２０の冷媒種類の組み合わせによっては、この限りではない。例えば、低外気温度時は目標低元側凝縮温度Ｔｃの方が高くなり、高外気温度時は目標低元側凝縮温度Ｔｃの方が低くなるなど、外気温度変化に対して目標低元側凝縮温度Ｔｃと外気温度との相対関係が変化する場合もある。 Here, in the present embodiment, CO ₂ is used as a refrigerant in the low-source refrigeration cycle 10. In this case, the target low original side condensation temperature Tc is lower than the outside air temperature. Specifically, for example, when the high outside air condition is 32 ° C., the target low original side condensation temperature Tc is about 20 ° C., and when the low outside air condition is 7 ° C., the target low original side condensation temperature Tc is about 0 ° C. It becomes. As described above, lowering the low-source-side high pressure (low-source-side condensation temperature) can lower the low-source-side compressor input on the low-source refrigeration cycle 10 side where operating efficiency is low, so that the temperature is lower than the outside air temperature. The target low-side condensation temperature Tc is located in the region. Here, the target low original side condensation temperature Tc is located in the temperature range lower than the outside air temperature when the low-efficiency CO ₂ refrigerant is applied in the low original refrigeration cycle 10. Depending on the combination of the refrigerant types of the high-source refrigeration cycle 20, this is not the case. For example, the target low-side condensation temperature Tc is higher at low outside air temperatures, and the target low-side condensation temperature Tc is lower at high outside air temperatures. The relative relationship between the temperature Tc and the outside air temperature may change.

（低元側凝縮温度が外気温度よりも低い場合と高い場合の補助放熱器１５の放熱量の違いについて）
次に、補助放熱器１５の放熱量について考察する。本実施の形態の二元冷凍装置では、低元冷凍サイクル１０に運転効率の低いＣＯ₂冷媒を使用している関係から目標低元側凝縮温度Ｔｃが外気温度よりも低くなる。補助放熱器１５は冷媒が有する熱を外気に放熱するため、低元側圧縮機１１から吐出された冷媒と外気とを補助放熱器１５で熱交換しても、最大でも外気温度までしか冷媒の温度は下がらない。また、低元冷凍サイクル１０の低元側凝縮温度が外気温度よりも低い場合と高い場合とでは吐出温度の冷媒を補助放熱器１５で同じ外気温度まで下げるにあたっても、その放熱量は異なったものとなる。 (Difference in heat dissipation of auxiliary radiator 15 when the low-side condensation temperature is lower and higher than the outside air temperature)
Next, the heat radiation amount of the auxiliary radiator 15 will be considered. In the binary refrigeration apparatus of the present embodiment, the target low element side condensing temperature Tc is lower than the outside air temperature because the CO ₂ refrigerant having low operating efficiency is used in the low element refrigeration cycle 10. Since the auxiliary radiator 15 radiates the heat of the refrigerant to the outside air, even if heat is exchanged between the refrigerant discharged from the low-side compressor 11 and the outside air by the auxiliary radiator 15, the refrigerant only reaches the outside temperature at the maximum. The temperature does not drop. In addition, the amount of heat released differs even when the refrigerant at the discharge temperature is lowered to the same outside air temperature by the auxiliary radiator 15 depending on whether the low side condensing temperature of the low source refrigeration cycle 10 is lower or higher than the outside air temperature. It becomes.

例えば本実施の形態の二元冷凍装置においては、制御装置３０が低元側凝縮温度を目標低元側凝縮温度Ｔｃに一定になるように制御するものである。目標低元側凝縮温度Ｔｃは外気温度よりも低いため、低元側凝縮温度が外気温度よりも低い場合の補助放熱器１５の放熱量について考察する。ここでは、比較のため、圧縮機、放熱器、膨張弁及び蒸発器を備えた一般的な冷媒回路において凝縮温度が外気温度よりも高い場合の凝縮温度での放熱量についても考察する。 For example, in the binary refrigeration apparatus of the present embodiment, the control device 30 controls the low-side condensing temperature to be constant at the target low-side condensing temperature Tc. Since the target low-source-side condensation temperature Tc is lower than the outside air temperature, the heat radiation amount of the auxiliary radiator 15 when the low-source-side condensation temperature is lower than the outside air temperature will be considered. Here, for comparison, the amount of heat released at the condensation temperature when the condensation temperature is higher than the outside air temperature in a general refrigerant circuit including a compressor, a radiator, an expansion valve, and an evaporator is also considered.

図４は、低元側凝縮温度が外気温度よりも低い場合と高い場合の放熱量について説明するための図である。図４（１）は、凝縮温度が外気温度よりも高い場合の一般的な冷凍サイクルにおけるモリエル線図である。また、図４（２）は、低元側凝縮温度が外気温度よりも低い場合の低元冷凍サイクル１０のモリエル線図である。 FIG. 4 is a diagram for explaining the heat radiation amount when the low-side condensation temperature is lower and higher than the outside air temperature. FIG. 4 (1) is a Mollier diagram in a general refrigeration cycle when the condensation temperature is higher than the outside air temperature. FIG. 4 (2) is a Mollier diagram of the low-source refrigeration cycle 10 when the low-source side condensation temperature is lower than the outside air temperature.

（１）低元側凝縮温度が外気温度よりも高い場合
低元側圧縮機１１の吐出冷媒の温度（ａ点の温度）が例えば８０〜９０℃であり、外気温度が２０℃で、低元側凝縮温度が２５℃の場合について考える。補助放熱器１５は冷媒が有する熱を外気に放熱するため、図４（１）に示すように、８０〜９０℃の冷媒（ａ点）が放熱器での外気との熱交換により、まず、ガス状態のまま凝縮温度である２５℃（点ｂ）まで下がる。そして、２５℃を保ちながら凝縮して液状態となる（ｃ点）。外気温度は２０℃であるため、冷媒を更に放熱させることができ、液状態で２０℃（点ｄ）まで下げることができる。このように低元側凝縮温度が外気温度よりも高い場合は凝縮するため、相変化を伴う冷却を行うことができ、相変化を伴わない冷却を行う場合に比べて放熱量を大きくすることができる。 (1) When the low-end side condensing temperature is higher than the outside air temperature The temperature of the discharge refrigerant (point a) of the low-end side compressor 11 is, for example, 80 to 90 ° C, the outside air temperature is 20 ° C, Consider the case where the side condensation temperature is 25 ° C. Since the auxiliary radiator 15 radiates the heat of the refrigerant to the outside air, as shown in FIG. 4 (1), the refrigerant (point a) at 80 to 90 ° C. is first exchanged with the outside air by the radiator, It falls to 25 degreeC (point b) which is a condensation temperature with a gas state. And it is condensed and liquid state is maintained while maintaining 25 ° C. (point c). Since the outside air temperature is 20 ° C., the refrigerant can further dissipate heat and can be lowered to 20 ° C. (point d) in a liquid state. In this way, when the low-side condensation temperature is higher than the outside air temperature, it condenses, so cooling with phase change can be performed, and the amount of heat radiation can be increased compared with cooling without phase change. it can.

（２）低元側凝縮温度が外気温度よりも低い場合
次に、低元側圧縮機１１の吐出冷媒の温度（ａ点の温度）が例えば８０〜９０℃であり、外気温度が２０℃で低元側凝縮温度が１０℃の場合について考える。補助放熱器１５は外気に熱を放熱する放熱器であるため、上述したように８０〜９０℃の冷媒は、補助放熱器１５での外気との熱交換により、最大でも外気温度の２０℃までしか下がらない。したがって、図４（２）に示すように、８０〜９０℃の冷媒（ａ点）は、補助放熱器１５でガス状態のまま２０℃（点ｂ）となる。よって、２０℃まで下がった冷媒を凝縮させて更に１０℃（点ｃ）まで下げるための熱交換は低元側凝縮器１２側で行われることになる。このため、低元側凝縮温度が外気温度より低い場合は、補助放熱器１５では相変化を伴う冷却は行えず、相変化を伴わないガス冷却を行うことになる。つまり、補助放熱器１５はガス冷却域で使用されることになる。 (2) When the low-end side condensing temperature is lower than the outside air temperature Next, the temperature of the discharged refrigerant (point a) of the low-end side compressor 11 is, for example, 80 to 90 ° C, and the outside air temperature is 20 ° C. Consider the case where the low-side condensation temperature is 10 ° C. Since the auxiliary radiator 15 is a radiator that radiates heat to the outside air, as described above, the refrigerant of 80 to 90 ° C. can reach the maximum outside air temperature of 20 ° C. by heat exchange with the outside air in the auxiliary radiator 15. It only goes down. Therefore, as shown in FIG. 4 (2), the refrigerant at 80 to 90 ° C. (point a) becomes 20 ° C. (point b) in the gas state in the auxiliary radiator 15. Therefore, the heat exchange for condensing the refrigerant lowered to 20 ° C. and further lowering to 10 ° C. (point c) is performed on the low-source side condenser 12 side. For this reason, when the low-source side condensation temperature is lower than the outside air temperature, the auxiliary radiator 15 cannot perform cooling with phase change, and performs gas cooling without phase change. That is, the auxiliary radiator 15 is used in the gas cooling region.

ここで、図４（２）の点ａから点ｂまでの放熱はガス状態での放熱であるため、同じ外気温度２０℃まで温度を下げるにしても、凝縮させて２０℃まで下げる上記（１）の場合に比べて補助放熱器１５での放熱量を大きくすることができない。よって、低元側凝縮温度が外気温度より低い場合は、補助放熱器１５の補助放熱器ファン１６の風量を多くする、補助放熱器１５を伝熱面積の大きな放熱器を採用するなどしても、補助放熱器１５の放熱量を増やすことはできない。最大でも吐出冷媒がガス状態のまま外気温度に低下するまでの放熱量となる。 Here, since the heat radiation from the point a to the point b in FIG. 4 (2) is a heat radiation in a gas state, even if the temperature is lowered to the same outside air temperature 20 ° C., the heat is condensed and lowered to 20 ° C. (1 ) Cannot be increased in the auxiliary radiator 15 as compared with the case of). Therefore, when the low-side condensation temperature is lower than the outside air temperature, the airflow of the auxiliary radiator fan 16 of the auxiliary radiator 15 is increased, or a radiator having a large heat transfer area is adopted as the auxiliary radiator 15. The amount of heat released from the auxiliary radiator 15 cannot be increased. At most, the amount of heat released until the discharged refrigerant is reduced to the outside air temperature in a gaseous state.

以上のことから、本実施の形態の二元冷凍装置では、補助放熱器１５をガス冷却域での放熱に使用することとなり、その放熱量は最大でも吐出冷媒がガス状態のまま外気温度に低下するまでに放熱する放熱量となる。 From the above, in the binary refrigeration apparatus of the present embodiment, the auxiliary radiator 15 is used for heat dissipation in the gas cooling zone, and the amount of heat dissipation is reduced to the outside temperature while the discharged refrigerant remains in a gas state even at the maximum. It becomes the amount of heat dissipation that dissipates by the time.

（補助放熱器１５の放熱量とＣＯＰとの関係）
図５は、補助放熱器１５の放熱量とＣＯＰとの関係を説明するための図である。図５は低元冷凍サイクル１０のモリエル線図を示している。低元冷凍サイクル１０を構成するにあたり、補助放熱器１５での放熱量を、図５のＱｓｕｂ１にした場合とＱｓｕｂ２にした場合とを比較すると、Ｑｓｕｂ２にした場合の方が、対応する低元側凝縮器１２の放熱量Ｑｃ２（＜Ｑｃ１）を少なくすることができる。カスケードコンデンサＣでは、高元側蒸発器２４と低元側凝縮器１２とにおける熱交換量は等しくなる。よって、高元冷凍サイクル２０側は、低元側凝縮器１２での放熱量Ｑｃ２とのバランスを図ればよいため、補助放熱器１５の放熱量がＱｓｕｂ１である場合に比べて高元側圧縮機入力を小さくできる。 (Relationship between heat dissipation of auxiliary radiator 15 and COP)
FIG. 5 is a diagram for explaining the relationship between the heat dissipation amount of the auxiliary radiator 15 and the COP. FIG. 5 shows a Mollier diagram of the low-source refrigeration cycle 10. When the low-source refrigeration cycle 10 is configured, the amount of heat released by the auxiliary radiator 15 is compared with the case of Qsub1 and Qsub2 in FIG. The heat dissipation amount Qc2 (<Qc1) of the condenser 12 can be reduced. In the cascade condenser C, the heat exchange amounts in the high-side evaporator 24 and the low-side condenser 12 are equal. Therefore, since the high-source refrigeration cycle 20 side only needs to balance with the heat dissipation amount Qc2 in the low-source-side condenser 12, the high-end side compressor is compared with the case where the heat dissipation amount of the auxiliary radiator 15 is Qsub1. Input can be reduced.

二元冷凍装置では冷凍能力一定の制御が行われており、ＣＯＰ＝冷凍能力／（高元側圧縮機入力＋低元側圧縮機入力）であるため、高元側圧縮機入力を小さくすることができると、ＣＯＰを大きくすることができる。 In the dual refrigeration system, constant refrigeration capacity is controlled, and COP = refrigeration capacity / (high source side compressor input + low side compressor input), so the high side compressor input must be reduced. If it is possible, the COP can be increased.

以上の内容を整理すると、高元側圧縮機入力と低元側圧縮機入力とを同じとする運転制御によりＣＯＰを最大とすることができる。また、補助放熱器１５の放熱量を多くするほど、ＣＯＰの値を大きくすることができる。 If the above content is arranged, COP can be maximized by the operation control in which the high-side compressor input and the low-side compressor input are made the same. Further, the COP value can be increased as the heat radiation amount of the auxiliary radiator 15 is increased.

ここで、二元冷凍装置の消費電力は圧縮機入力がほとんどを占めるため、二元冷凍装置全体の運転効率の指標であるＣＯＰ＝冷凍能力／（高元側圧縮機入力＋低元側圧縮機入力）と定義した。ただ、二元冷凍装置において、本来は、放熱器に外気を送風する補助放熱器ファン１６及び高元側凝縮器ファン２５を運転する動力にも、電力の一部を消費するため、正確には各送風機の入力を考慮する必要がある。そこで、ＣＯＰ＝冷凍能力／（高元側圧縮機入力＋低元側圧縮機入力＋高元側凝縮器ファン入力＋補助放熱器ファン入力）と再定義する。 Here, since the compressor power occupies most of the power consumption of the binary refrigeration system, COP = refrigeration capacity / (high source side compressor input + low source side compressor), which is an index of the operation efficiency of the entire binary refrigeration system Input). However, in the two-stage refrigeration system, originally, a part of the electric power is consumed for the driving power of the auxiliary radiator fan 16 and the high-side condenser fan 25 that blow outside air to the radiator. It is necessary to consider the input of each blower. Therefore, COP = refrigeration capacity / (high-source compressor input + low-source compressor input + high-source condenser fan input + auxiliary radiator fan input) is redefined.

本実施の形態の二元冷凍装置では、上述したように補助放熱器１５はガス冷却域で使用されるため、補助放熱器１５の伝熱面積の大きさ等の構造に関わらず、最大放熱できても吐出温度の冷媒を外気温度に下げるまでである。また、上述したように補助放熱器１５の放熱量を多くするほど、ＣＯＰを大きくすることができる。よって、補助放熱器１５で吐出温度の冷媒を外気温度近くまで温度を下げられる程度に補助放熱器１５の放熱量を確保するようにする。以下、この放熱量を所要放熱量という。所要放熱量を達成するには、例えば、補助放熱器ファン１６の風量を制御したり、補助放熱器１５自体の構造的な設計を行ったりすることになる。このように補助放熱器１５の放熱量を所要放熱量とすることにより、所要放熱量よりも少ない放熱量とした場合に比べてＣＯＰを大きくすることができる。 In the dual refrigeration system of the present embodiment, as described above, the auxiliary radiator 15 is used in the gas cooling region, so that maximum heat dissipation can be achieved regardless of the structure of the heat transfer area of the auxiliary radiator 15 and the like. Even until the refrigerant at the discharge temperature is lowered to the outside temperature. Further, as described above, the COP can be increased as the heat radiation amount of the auxiliary radiator 15 is increased. Therefore, the heat radiation amount of the auxiliary radiator 15 is ensured to such an extent that the temperature of the refrigerant at the discharge temperature can be lowered to near the outside air temperature by the auxiliary radiator 15. Hereinafter, this heat radiation amount is referred to as a required heat radiation amount. In order to achieve the required heat dissipation amount, for example, the air volume of the auxiliary radiator fan 16 is controlled or the structural design of the auxiliary radiator 15 itself is performed. Thus, by setting the heat dissipation amount of the auxiliary radiator 15 as the required heat dissipation amount, the COP can be increased as compared with the case where the heat dissipation amount is smaller than the required heat dissipation amount.

ところで、所要放熱量は外気温度によって異なる。よって、年間を通じて大きなＣＯＰを確保するには、低外気条件のときの所要放熱量と高外気条件のときの所要放熱量を把握しておく必要がある。本実施の形態における二元冷凍装置では、上述のように補助放熱器１５はガス冷却域で使用され所要放熱量は小さい。しかし、起動時、冷却負荷変動時、外気温度変動時などにおいて、過渡的に低元側凝縮温度が外気温度よりも高い場合がある。このような場合には所要放熱量は増大する。ここで、前述したように、低元冷凍サイクル１０と高元冷凍サイクル２０とにおける冷媒種類の組み合わせによっては、例えば低外気温度時は目標低元側凝縮温度Ｔｃの方が高くなり、高外気温度時は目標低元側凝縮温度Ｔｃの方が低くなることがある。このため、外気温度変化に対して目標低元側凝縮温度Ｔｃとの相対関係が変化し、所要放熱量が変化する。 By the way, the required heat dissipation varies depending on the outside air temperature. Therefore, in order to secure a large COP throughout the year, it is necessary to grasp the required heat dissipation amount under low outdoor air conditions and the required heat dissipation amount under high outdoor air conditions. In the binary refrigeration apparatus in the present embodiment, the auxiliary radiator 15 is used in the gas cooling region as described above, and the required heat dissipation amount is small. However, there are cases where the low-side condensation temperature is transiently higher than the outside air temperature during startup, cooling load fluctuation, outside air temperature fluctuation, or the like. In such a case, the required heat dissipation increases. Here, as described above, depending on the combination of refrigerant types in the low-source refrigeration cycle 10 and the high-source refrigeration cycle 20, for example, at the low outside air temperature, the target low-source side condensation temperature Tc becomes higher, and the high outside air temperature In some cases, the target low-side condensation temperature Tc may be lower. For this reason, the relative relationship with the target low original side condensation temperature Tc changes with respect to the outside air temperature change, and the required heat dissipation changes.

例えば、低元側凝縮温度が外気温度より低い場合は、補助放熱器１５では相変化を伴う冷却は行えず、所要放熱量は低下する。このとき、最大でも吐出冷媒がガス状態のまま外気温度に低下するまでに放熱する放熱量となるため、補助放熱器ファン１６の風量を多くしても、補助放熱器１５の放熱量を増やすことはできない。逆に、補助放熱器ファン１６の回転数を抑制し、風量を最適化しなければ、無駄に補助放熱器ファン１６の入力を消費することになり、ＣＯＰ低下の要因となる。よって、低元側凝縮温度が外気温度より低い場合は、所要放熱量が小さいため、補助放熱器ファン１６の風量を減少させることで補助放熱器ファン入力を最適化し、二元冷凍装置全体のＣＯＰを向上させることが可能である。 For example, when the low-source side condensation temperature is lower than the outside air temperature, the auxiliary radiator 15 cannot perform cooling with a phase change, and the required heat radiation amount is reduced. At this time, since the amount of heat dissipated before the discharged refrigerant is reduced to the outside air temperature in the gas state at the maximum, the heat dissipation amount of the auxiliary radiator 15 is increased even if the air volume of the auxiliary radiator fan 16 is increased. I can't. Conversely, unless the rotational speed of the auxiliary radiator fan 16 is suppressed and the air volume is not optimized, the input of the auxiliary radiator fan 16 is unnecessarily consumed, which causes a reduction in COP. Therefore, when the low-side condensation temperature is lower than the outside air temperature, the required heat dissipation amount is small. Therefore, the auxiliary radiator fan input is optimized by reducing the air volume of the auxiliary radiator fan 16, and the COP of the entire dual refrigeration system is reduced. It is possible to improve.

一方、低元側凝縮温度が外気温度より高い場合は、補助放熱器１５で相変化を伴う冷却を行い、所要放熱量は増大する。このときは所要放熱量増大に伴い補助放熱器ファン１６の風量を増大させ、補助放熱器１５の放熱量を増やすことにより、二元冷凍装置全体のＣＯＰを向上させることが可能である。 On the other hand, when the low-side condensation temperature is higher than the outside air temperature, the auxiliary radiator 15 performs cooling accompanied by a phase change, and the required heat dissipation amount increases. At this time, the COP of the entire binary refrigeration apparatus can be improved by increasing the airflow of the auxiliary radiator fan 16 and increasing the heat dissipation of the auxiliary radiator 15 as the required heat dissipation increases.

所要放熱量の変化に対して補助放熱器ファン１６の風量を制御するにあたり、補助放熱器１５の出口冷媒温度と外気温度との温度差が所定値（ここでは２℃程度）となるような制御を行うと、補助放熱器ファン１６の風量を適切に調節し、二元冷凍装置全体のＣＯＰを向上させることができる。具体的には、低元側凝縮温度が外気温度より低い場合は、所要放熱量が小さいため、無駄にファン入力を増大させることなく補助放熱器１５で吐出温度の冷媒を外気温度近くまで温度を下げられる程度に補助放熱器１５の放熱量を確保する。一方、低元側凝縮温度が外気温度より高い場合は、冷媒の冷却過程において凝縮が生じるため凝縮温度を一定に保つ。このため、冷媒温度が低下せず、補助放熱器ファン１６の風量を増大させ続け最大風量を得ることができる。 In controlling the air volume of the auxiliary radiator fan 16 with respect to the change in the required heat dissipation, control is performed such that the temperature difference between the outlet refrigerant temperature of the auxiliary radiator 15 and the outside air temperature becomes a predetermined value (here, about 2 ° C.). As a result, the air volume of the auxiliary radiator fan 16 can be adjusted appropriately, and the COP of the entire binary refrigeration apparatus can be improved. Specifically, when the low-source side condensing temperature is lower than the outside air temperature, the required heat radiation amount is small, so that the refrigerant at the discharge temperature is brought close to the outside air temperature by the auxiliary radiator 15 without increasing the fan input unnecessarily. The heat radiation amount of the auxiliary radiator 15 is ensured to the extent that it can be lowered. On the other hand, when the low source side condensation temperature is higher than the outside air temperature, condensation occurs in the cooling process of the refrigerant, so the condensation temperature is kept constant. For this reason, the refrigerant temperature does not decrease, and the maximum air volume can be obtained by continuously increasing the air volume of the auxiliary radiator fan 16.

補助放熱器ファン１６によって、外気温度に対する補助放熱器１５の放熱量を適切に制御することで、年間を通して高い省エネルギー効果を得ることができる。 By appropriately controlling the heat dissipation amount of the auxiliary radiator 15 with respect to the outside air temperature by the auxiliary radiator fan 16, a high energy saving effect can be obtained throughout the year.

補助放熱器１５は、所要放熱量が小さいガス冷却域で使用されることを想定した場合、高元側凝縮器２２の伝熱面積の１０〜２０％程度で充分な大きさとなる。一方、所要放熱量が大きい相変化を伴う放熱を行うことを想定した場合、補助放熱器１５の伝熱面積は高元側凝縮器２２の略同等まで拡大し、補助放熱器１５の放熱量を大きく増大させることで二元冷凍装置全体のＣＯＰを向上させることが可能である。また、補助放熱器１５と高元側凝縮器２２を同等とすることで部品の共通化を図ることができ、コスト低減も可能となる。 Assuming that the auxiliary radiator 15 is used in a gas cooling region where the required heat dissipation amount is small, the auxiliary radiator 15 has a sufficient size at about 10 to 20% of the heat transfer area of the high-side condenser 22. On the other hand, when it is assumed that heat dissipation accompanied by a large change in the required heat dissipation amount is performed, the heat transfer area of the auxiliary radiator 15 is expanded to substantially the same as that of the high-side condenser 22, and the heat dissipation amount of the auxiliary radiator 15 is increased. It is possible to improve the COP of the entire binary refrigeration apparatus by greatly increasing it. Further, by making the auxiliary radiator 15 and the high-side condenser 22 equivalent, parts can be shared, and costs can be reduced.

補助放熱器１５の伝熱面積を高元側凝縮器２２の略同等とした場合、所要放熱量の増大に伴い補助放熱器ファン１６の風量を増大させ、補助放熱器１５の放熱量を大きく増やすことができる。このとき、カスケードコンデンサＣの低元側凝縮器１２での放熱量が低下し、高元側の冷却能力も減少するため、高元側の冷却能力によって低元側凝縮器１２の放熱を促して低元側凝縮温度を制御することはできない。補助放熱器１５の放熱量が低元側凝縮器１２の放熱量を大きく上回るとき、低元側凝縮温度は補助放熱器１５の放熱量に依存する。 When the heat transfer area of the auxiliary radiator 15 is substantially the same as that of the high-end condenser 22, the amount of heat of the auxiliary radiator 15 is increased by increasing the air volume of the auxiliary radiator fan 16 as the required heat dissipation increases. be able to. At this time, the amount of heat radiation at the low-side condenser 12 of the cascade capacitor C is reduced, and the cooling capacity at the high-side is also reduced. The low-side condensation temperature cannot be controlled. When the heat dissipation amount of the auxiliary radiator 15 greatly exceeds the heat dissipation amount of the low-side condenser 12, the low-side condensation temperature depends on the heat dissipation amount of the auxiliary radiator 15.

上記の場合、高元冷凍サイクル２０側の冷却能力の減少に伴い高元側凝縮器ファン２５の風量も低下させる。このため、二元冷凍装置全体の消費電力は、低元側圧縮機入力と補助放熱器ファン１６の入力とがほとんどを占める。このため、ＣＯＰは、冷凍能力／（低元側圧縮機入力＋補助放熱器ファン入力）とほぼ同じとなり、低元側圧縮機入力と補助放熱器ファン１６の入力とを最適化すればＣＯＰ向上を図ることが可能となる。 In the above case, the air volume of the high-side condenser fan 25 is also reduced as the cooling capacity on the high-side refrigeration cycle 20 side decreases. For this reason, the power consumption of the entire binary refrigeration apparatus is mostly occupied by the low-source compressor input and the input of the auxiliary radiator fan 16. For this reason, the COP is almost the same as the refrigeration capacity / (low-source side compressor input + auxiliary radiator fan input), and the COP can be improved by optimizing the low-source side compressor input and the auxiliary radiator fan 16 input. Can be achieved.

補助放熱器ファン１６の風量を増大させればファン入力が増大するが、低元側凝縮温度を低下させることができるため、低元側圧縮機入力を低減することができる。低元側凝縮温度が外気温度に近づけば、補助放熱器ファン１６の風量を増大させても低元側凝縮温度が低下しなくなるため、無駄にファン入力が消費されてしまう。そこで、補助放熱器ファン１６によって低元側凝縮温度を制御し、低元側凝縮温度を外気温度より所定温度差（ここでは１０℃程度）となるようにすれば、低元側圧縮機入力と補助放熱器ファン入力を最適化することができ、二元冷凍装置全体のＣＯＰを向上させることが可能である。 If the air volume of the auxiliary radiator fan 16 is increased, the fan input increases, but the low-side condensing temperature can be lowered, so that the low-side compressor input can be reduced. If the low-side condensing temperature is close to the outside air temperature, the low-side condensing temperature does not decrease even if the air volume of the auxiliary radiator fan 16 is increased, so that fan input is wasted. Therefore, if the low-side condensation temperature is controlled by the auxiliary radiator fan 16 so that the low-side condensation temperature has a predetermined temperature difference (about 10 ° C. here) from the outside air temperature, the low-side compressor input and The auxiliary radiator fan input can be optimized and the COP of the entire binary refrigeration system can be improved.

実施の形態２．
図６は本発明の実施の形態２における二元冷凍装置の構成を表す図である。構成機器については実施の形態１と同様である。ただ、制御によって、二元冷凍装置の高元冷凍サイクル２０を停止させるものである。 Embodiment 2. FIG.
FIG. 6 is a diagram showing the configuration of the binary refrigeration apparatus in Embodiment 2 of the present invention. The constituent devices are the same as those in the first embodiment. However, the high-source refrigeration cycle 20 of the binary refrigeration apparatus is stopped by the control.

例えば二元冷凍装置を低外気温度で運転させると、高元側凝縮温度が低下し、それに伴って低元側凝縮温度も低下する。低元冷凍サイクル１０と高元冷凍サイクル２０とは低圧縮比の運転となり、圧縮機の性能が低下するとともに、圧縮機で定められた運転範囲を逸脱し、信頼性を保持できない。また、二元冷凍装置ではカスケードコンデンサＣにおいて温度差ΔＴが生じるために高元側蒸発温度が低下し、低元側凝縮温度が上昇するためＣＯＰが低下することとなり、低圧縮比運転時は特に影響が大きくなる。 For example, when the binary refrigeration apparatus is operated at a low outside air temperature, the high-side condensing temperature is lowered, and accordingly, the low-side condensing temperature is also lowered. The low-source refrigeration cycle 10 and the high-source refrigeration cycle 20 operate at a low compression ratio, and the performance of the compressor is deteriorated. The operation range determined by the compressor is deviated, and the reliability cannot be maintained. Further, in the binary refrigeration system, the temperature difference ΔT is generated in the cascade condenser C, so that the high-side evaporation temperature is lowered, and the low-side condensation temperature is raised, so that the COP is lowered. The impact will increase.

そこで、本実施の形態の二元冷凍装置では、上記のような性能低下と信頼性低下とを回避するため、制御装置３０が、低圧縮比運転となるような所定の外気温度に低下したものと判断すると、高元冷凍サイクル２０を停止させ、低元冷凍サイクル１０のみ運転させるようにする。具体的には、低元側圧縮機１１で圧縮されて吐出された冷媒を、補助放熱器１５のみで冷却するようにし、低元側膨張弁１３で減圧し、低元側蒸発器１４で蒸発して、低元側圧縮機１１へ還流するようにする。 Therefore, in the binary refrigeration apparatus of the present embodiment, in order to avoid the above-described performance degradation and reliability degradation, the control device 30 has been lowered to a predetermined outside air temperature that results in a low compression ratio operation. If it is judged, the high-source refrigeration cycle 20 is stopped and only the low-source refrigeration cycle 10 is operated. Specifically, the refrigerant compressed and discharged by the low-side compressor 11 is cooled only by the auxiliary radiator 15, decompressed by the low-side expansion valve 13, and evaporated by the low-side evaporator 14. Then, the refrigerant is returned to the low-source compressor 11.

上記のような運転を行うことにより、低元側圧縮機１１は適正な圧縮比を保ち、性能と信頼性を確保することができる。また、二元冷凍装置の特徴であるカスケードコンデンサＣの温度差ΔＴによる性能低下も同時に回避可能となる。よって、低外気温度時の運転制御適正化により、通年を通して高い省エネルギー性を実現可能とする。 By performing the operation as described above, the low-end compressor 11 can maintain an appropriate compression ratio and ensure performance and reliability. In addition, it is possible to avoid the performance deterioration due to the temperature difference ΔT of the cascade capacitor C, which is a characteristic of the binary refrigeration apparatus, at the same time. Therefore, high energy savings can be realized throughout the year by optimizing operation control at low outside air temperatures.

ここで、低元冷凍サイクル１０のみの運転の場合、補助放熱器１５にて全熱量を放熱する必要がある。このため、補助放熱器１５の伝熱面積を拡大した方がより放熱量を増大することができる。例えば、高元側凝縮器２２と同等の大きさに拡大すれば部品の共通化を図ることができ、コスト低減も可能となる。 Here, in the case of operation of only the low-source refrigeration cycle 10, it is necessary to radiate the total amount of heat with the auxiliary radiator 15. For this reason, the direction of expansion of the heat transfer area of the auxiliary radiator 15 can further increase the heat radiation amount. For example, if the size is increased to the same size as the high-side condenser 22, the parts can be shared, and the cost can be reduced.

補助放熱器１５の放熱量の増加に伴い、補助放熱器ファン１６の風量を増大させ、補助放熱器１５の放熱量を大きく増やす。補助放熱器ファン１６の風量を増大させればファン入力が増大するが、低元側凝縮温度を低下させて低元側圧縮機入力を低減することができる。低元側凝縮温度が外気温度に近づけば、補助放熱器ファン１６の風量を増大させても低元側凝縮温度が低下しなくなるため、無駄にファン入力が消費されてしまう。 As the heat dissipation amount of the auxiliary radiator 15 increases, the airflow of the auxiliary radiator fan 16 is increased, and the heat dissipation amount of the auxiliary radiator 15 is greatly increased. If the air volume of the auxiliary radiator fan 16 is increased, the fan input increases. However, the low-side compressor temperature can be reduced by lowering the low-side condensation temperature. If the low-side condensing temperature is close to the outside air temperature, the low-side condensing temperature does not decrease even if the air volume of the auxiliary radiator fan 16 is increased, so that fan input is wasted.

そこで、補助放熱器ファン１６によって低元側凝縮温度を制御し、低元側凝縮温度を外気温度より所定温度差（ここでは１０℃程度）となるようにすれば、低元側圧縮機入力と補助放熱器ファン１６の入力を最適化することができる。このため、低元冷凍サイクル１０のみを運転させたときのＣＯＰを向上させることが可能である。 Therefore, if the low-side condensation temperature is controlled by the auxiliary radiator fan 16 so that the low-side condensation temperature has a predetermined temperature difference (about 10 ° C. here) from the outside air temperature, the low-side compressor input and The input of the auxiliary radiator fan 16 can be optimized. For this reason, it is possible to improve the COP when only the low-source refrigeration cycle 10 is operated.

本実施の形態の二元冷凍装置は、冷媒のノンフロン化やフロン冷媒の削減、機器の省エネルギー化が要求されるショーケースや業務用冷凍冷蔵庫、自動販売機等の冷蔵あるいは冷凍機器にも広く適用できる。 The binary refrigeration apparatus of this embodiment is widely applicable to refrigeration or refrigeration equipment such as showcases, commercial refrigerators, and vending machines that require non-CFC refrigerants, CFC refrigerant reduction, and equipment energy saving. it can.

１０低元冷凍サイクル、１１低元側圧縮機、１２低元側凝縮器、１３低元側膨張弁、１４低元側蒸発器、１５補助放熱器、１６補助放熱器ファン、２０高元冷凍サイクル、２１高元側圧縮機、２２高元側凝縮器、２３高元側膨張弁、２４高元側蒸発器、２５高元側凝縮器ファン、３０制御装置、３１外気温度検出手段、Ｃカスケードコンデンサ。 DESCRIPTION OF SYMBOLS 10 Low original refrigeration cycle, 11 Low original side compressor, 12 Low original side condenser, 13 Low original side expansion valve, 14 Low original side evaporator, 15 Auxiliary radiator, 16 Auxiliary radiator fan, 20 High original refrigeration cycle , 21 High-end compressor, 22 High-end condenser, 23 High-end expansion valve, 24 High-end evaporator, 25 High-end condenser fan, 30 Control device, 31 Outside air temperature detection means, C Cascade condenser .

Claims

高元側圧縮機、高元側凝縮器、高元側絞り装置及び高元側蒸発器を配管接続し、冷媒を循環させる高元側冷媒回路を形成する高元冷凍サイクルと、
低元側圧縮機、補助放熱器、低元側凝縮器、低元側絞り装置及び低元側蒸発器を配管接続し、冷媒を循環させる低元側冷媒回路を形成する低元冷凍サイクルと、
前記高元側蒸発器と前記低元側凝縮器とにより構成し、前記高元側冷媒回路を流れる冷媒と前記低元側冷媒回路を流れる冷媒との間の熱交換を行うカスケードコンデンサと、
前記補助放熱器を流れる冷媒と熱交換させるための屋外空気を前記補助放熱器に通過させる送風機と、
前記低元冷凍サイクルにおける凝縮温度よりも、前記補助放熱器を通過させる前記屋外空気の温度の方が高いと判断すると、前記送風機の風量を減少させる制御を行う制御装置と
を備えることを特徴とする二元冷凍装置。 A high-source refrigeration cycle that forms a high-side refrigerant circuit that circulates refrigerant by pipe-connecting a high-source side compressor, a high-source side condenser, a high-end side expansion device, and a high-end side evaporator,
A low-source refrigeration cycle that forms a low-source-side refrigerant circuit that circulates refrigerant by pipe-connecting a low-source compressor, an auxiliary radiator, a low-source condenser, a low-source throttle device, and a low-generator evaporator;
A cascade capacitor configured by the high-side evaporator and the low-side condenser, and performing heat exchange between the refrigerant flowing through the high-side refrigerant circuit and the refrigerant flowing through the low-side refrigerant circuit;
A blower for allowing outdoor air to pass through the auxiliary radiator to exchange heat with the refrigerant flowing through the auxiliary radiator;
And a control device that performs control to reduce the air volume of the blower when it is determined that the temperature of the outdoor air passing through the auxiliary radiator is higher than the condensation temperature in the low-source refrigeration cycle. Dual refrigeration equipment.

前記制御装置は、前記低元冷凍サイクルにおける凝縮温度よりも、前記補助放熱器を通過させる前記屋外空気の温度の方が低いと判断すると、前記送風機の風量を増加させる制御を行うことを特徴とする請求項１に記載の二元冷凍装置。 When the control device determines that the temperature of the outdoor air passing through the auxiliary radiator is lower than the condensation temperature in the low-source refrigeration cycle, the control device performs control to increase the air volume of the blower. The binary refrigeration apparatus according to claim 1.

前記制御装置は、前記補助放熱器から流出する冷媒の温度と前記補助放熱器を通過させる前記屋外空気の温度との温度差を一定とするように前記送風機を制御することを特徴とする請求項１又は請求項２に記載の二元冷凍装置。 The said control apparatus controls the said air blower so that the temperature difference of the temperature of the refrigerant | coolant which flows out out of the said auxiliary heat radiator, and the temperature of the said outdoor air which passes the said auxiliary heat radiator may be made constant. The binary refrigeration apparatus according to claim 1 or 2.

前記制御装置は、前記屋外空気の温度が、前記高元側圧縮機及び前記低元側圧縮機が低圧縮比運転となるような温度以下であると判断すると、前記高元冷凍サイクルの運転を停止させ、前記低元冷凍サイクルだけを運転させる制御を行うことを特徴とする請求項１から請求項３のいずれかに記載の二元冷凍装置。 When the control device determines that the temperature of the outdoor air is equal to or lower than the temperature at which the high-side compressor and the low-side compressor operate at a low compression ratio, the operation of the high-source refrigeration cycle is performed. The dual refrigeration apparatus according to any one of claims 1 to 3, wherein control is performed to stop and operate only the low-source refrigeration cycle.

前記制御装置は、前記低元冷凍サイクルにおける凝縮温度と前記補助放熱器を通過させる前記屋外空気の温度との温度差を一定とするように前記送風機を制御することを特徴とする請求項２又は請求項４に記載の二元冷凍装置。 The said control apparatus controls the said air blower so that the temperature difference of the condensation temperature in the said low refrigeration cycle and the temperature of the said outdoor air which lets the said auxiliary radiator pass may be made constant. The binary refrigeration apparatus according to claim 4.

前記高元側凝縮器と前記補助放熱器とにおける伝熱面積が同等となるように構成することを特徴とする請求項１から請求項５のいずれかに記載の二元冷凍装置。 The binary refrigeration apparatus according to any one of claims 1 to 5, wherein heat transfer areas in the high-end condenser and the auxiliary radiator are equal.

前記低元冷凍サイクルに用いる冷媒よりも高効率となる冷媒を前記高元冷凍サイクルに用いることを特徴とする請求項１から請求項６のいずれかに記載の二元冷凍装置。 The binary refrigeration apparatus according to any one of claims 1 to 6, wherein a refrigerant having higher efficiency than a refrigerant used in the low-source refrigeration cycle is used in the high-source refrigeration cycle.

前記低元冷凍サイクルの冷媒として、二酸化炭素を用いることを特徴とする請求項１から請求項７のいずれかに記載の二元冷凍装置。 The binary refrigeration apparatus according to any one of claims 1 to 7, wherein carbon dioxide is used as a refrigerant of the low-source refrigeration cycle.