JP5828131B2 - Refrigeration apparatus and refrigeration unit constituting the refrigeration apparatus - Google Patents

Description

The present invention relates to a vapor compression refrigeration apparatus used for refrigeration, air conditioning, and the like, and a refrigeration unit constituting the refrigeration apparatus, and more specifically, a two-stage compression / two-stage expansion refrigeration apparatus and a refrigeration constituting the refrigeration apparatus. Regarding the unit .

  A compressor, a radiator, a first throttle means, a receiver tank, a second throttle means, and an evaporator, and the refrigerant discharged from the radiator is decompressed to an intermediate pressure higher than the evaporation pressure by the first throttle means; So-called two-stage compression, in which gas-phase refrigerant is introduced in the middle of the compression process of the compressor, and the liquid-phase refrigerant is further reduced to the evaporation pressure by the second throttling means and flows to the evaporator. A two-stage expansion type refrigeration apparatus has been conventionally known (for example, Patent Document 1). In this type of refrigeration system, the gas-phase refrigerant separated in the receiver tank is returned to the intermediate pressure portion of the compressor without reducing the vapor pressure to the evaporation pressure, and is returned to the intermediate pressure portion of the compressor. Power for compressing from the pressure to the intermediate pressure becomes unnecessary, and the pressure loss of the evaporator can be reduced, so that the efficiency of the refrigeration cycle can be improved.

JP 2005-214444 A

  In the above-described two-stage compression and two-stage expansion refrigeration cycle, the amount and enthalpy of refrigerant flowing to the evaporator vary depending on the state of the refrigerant at the intermediate pressure after being depressurized by the first throttling means, that is, the refrigerant in the receiver tank. . Therefore, it is important to appropriately control the state of the intermediate pressure refrigerant. In order to increase the refrigeration efficiency, for example, it is necessary to detect the pressure and temperature of the intermediate pressure portion and perform operation control so that those detected values are within a suitable range. In addition, it is required to increase the separation efficiency of the gas-phase refrigerant and the liquid-phase refrigerant in the receiver tank, and ideally complete gas-liquid separation is desirable.

  However, in an actual refrigeration apparatus, since the size of the receiver tank is limited, complete gas-liquid separation is difficult. Depending on the operating conditions, gas-phase refrigerant may be mixed into the liquid-phase refrigerant and flow to the evaporator side. When the gas-phase refrigerant is mixed with the liquid-phase refrigerant in this way, the gas-phase refrigerant that does not exhibit the refrigeration effect flows in the low-pressure side circuit such as the evaporator, so that the pressure loss in the evaporator increases, and in the compressor Power for compressing the refrigerant from the evaporation pressure to the intermediate pressure is required. Therefore, even if the pressure and temperature of the intermediate pressure portion are controlled within a predetermined range as described above, there is a problem that the efficiency of the refrigeration apparatus is lowered.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a refrigeration apparatus capable of stable operation with high efficiency in response to changes in ambient conditions and cooling loads.

In the refrigeration apparatus according to the first aspect of the invention, the first compression means, the intermediate cooler, the second compression means, the radiator, the first throttle means, the receiver tank, the second throttle means, and the evaporator are sequentially connected to form a closed circuit. In the refrigeration apparatus provided with a bypass path for flowing the refrigerant from the receiver tank to the suction portion of the second compression means, the gas with respect to the total amount that is the sum of the gas-phase refrigerant and the liquid-phase refrigerant in the refrigerant flowing into the receiver tank The mass ratio of the phase refrigerant is the first control variable, the mass ratio of the refrigerant amount flowing through the bypass path to the refrigerant amount flowing into the receiver tank is the second control variable, and the gas-liquid separation in the receiver tank is incomplete. refrigeration system, characterized in that a first control device for controlling the opening of the first throttle means so that a difference between the second control variable and the first control variable is within the predetermined range in the state Provided It is characterized in.

  A refrigeration apparatus according to a second aspect of the present invention is the refrigeration apparatus according to the first aspect, wherein the refrigerant is compressed by the second compression means and detects the pressure of the refrigerant flowing into the first throttle means, and the pressure is reduced by the first throttle means and the first 2 an intermediate pressure detector for detecting the pressure of the refrigerant sucked into the compression means, a pre-expansion temperature detector for detecting the temperature of the refrigerant exiting the radiator and flowing into the first throttle means, and the intermediate cooling A pre-merging temperature detector for detecting the temperature of the refrigerant before flowing into the bypass path after flowing out of the container, and a suction temperature detector for detecting the temperature of the refrigerant sucked into the second compression means The first control device calculates the first control variable from the pressure detected by the high pressure detector and the intermediate pressure detector and the temperature detected by the pre-expansion temperature detector, The pressure detected by the medium pressure detector and the pressure And calculates the second control variable from the temperature and detected by flow front temperature detector and the suction temperature detector.

  The refrigeration apparatus according to a third aspect of the present invention is the refrigeration apparatus according to the first aspect, wherein the high pressure detector detects the pressure of the refrigerant compressed by the second compression means and flows into the first throttle means, An intermediate pressure temperature detector for detecting the temperature of the refrigerant, a pre-expansion temperature detector for detecting the temperature of the refrigerant exiting the radiator and flowing into the first throttle means, and after flowing out the intermediate cooler A first pre-merging temperature detector for detecting a temperature of the refrigerant before joining the refrigerant flowing through the bypass path; and a suction temperature detector for detecting a temperature of the refrigerant sucked into the second compression means. The apparatus calculates the first control variable from the pressure detected by the high pressure detector and the temperatures detected by the intermediate pressure temperature detector and the pre-expansion temperature detector, and the intermediate pressure temperature detector In the pre-merging temperature detector and the suction temperature detector Characterized in that from the out temperature calculating said second control variable.

  The refrigeration apparatus according to a fourth aspect of the present invention is the refrigeration apparatus according to any one of the first to third aspects, wherein the opening of the first throttle means is greater when the first control variable is larger than the second control variable beyond a predetermined range. It is characterized by increasing.

  A refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to any one of the first to fourth aspects of the present invention, an evaporating temperature detector for detecting the temperature of the refrigerant flowing into the evaporator or the refrigerant in the evaporator, and the outflow from the evaporator An evaporator outlet temperature detector for detecting a temperature of the refrigerant to be cooled, and the first control device is configured such that a difference between temperatures detected by the evaporator outlet temperature detector and the evaporation temperature detector is a predetermined target temperature difference. The opening degree of the second throttle means is controlled so that the target temperature difference is increased when the first control variable is larger than the second control variable beyond a predetermined range. .

A refrigeration unit according to a sixth aspect of the present invention includes a second squeezing means and an evaporation unit provided with an evaporator and the unit.
In a refrigeration unit connected to a pipe to constitute a refrigeration apparatus, the refrigeration unit includes a first compression means, an intermediate cooler, a second compression means, a radiator, a first throttle means, a receiver tank, and the receiver tank. A bypass path connecting the suction portion of the second compression means is provided, and the mass ratio of the gas phase refrigerant to the total amount that is the sum of the gas phase refrigerant and the liquid phase refrigerant in the refrigerant flowing into the receiver tank is controlled first. And a mass ratio of the amount of refrigerant flowing through the bypass path to the amount of refrigerant flowing into the receiver tank is a second control variable, and in the state where gas-liquid separation in the receiver tank is incomplete, the first control variable and the A first control device is provided for controlling the opening degree of the first throttle means so that the difference from the second control variable is within a predetermined range.

The refrigeration unit according to a seventh aspect of the present invention is the refrigeration unit according to the sixth aspect, wherein the high pressure detector detects the pressure of the refrigerant compressed by the second compression means and flows into the first throttling means, and is depressurized by the first throttling means. 2 an intermediate pressure detector for detecting the pressure of the refrigerant sucked into the compression means, a pre-expansion temperature detector for detecting the temperature of the refrigerant exiting the radiator and flowing into the first throttle means, and the intermediate cooling A pre-merging temperature detector for detecting the temperature of the refrigerant before flowing into the bypass path after flowing out of the container, and a suction temperature detector for detecting the temperature of the refrigerant sucked into the second compression means Prepared,
The first control device calculates the first control variable from the pressure detected by the high pressure detector and the intermediate pressure detector and the temperature detected by the pre-expansion temperature detector, and the intermediate pressure is calculated. The second control variable is calculated from the pressure detected by the pressure detector and the temperatures detected by the pre-merging temperature detector and the suction temperature detector.

The refrigeration unit according to an eighth aspect of the present invention is the refrigeration unit according to the sixth aspect, wherein the high pressure detector detects the pressure of the refrigerant compressed by the second compression means and flows into the first throttle means, and after being decompressed by the first throttle means An intermediate pressure temperature detector for detecting the temperature of the refrigerant, a pre-expansion temperature detector for detecting the temperature of the refrigerant exiting the radiator and flowing into the first throttle means, and after flowing out the intermediate cooler A pre-merging temperature detector for detecting the temperature of the refrigerant before joining the refrigerant flowing through the bypass path; and a suction temperature detector for detecting the temperature of the refrigerant sucked into the second compression means,
The first control device calculates the first control variable from the pressure detected by the high pressure detector and the temperatures detected by the intermediate pressure temperature detector and the pre-expansion temperature detector, and the intermediate pressure is calculated. The second control variable is calculated from a temperature detected by the temperature detector, the pre-merging temperature detector, and the temperature detected by the suction temperature detector.

  A refrigeration unit according to a ninth aspect of the present invention is the refrigeration unit according to any one of the sixth to eighth aspects, wherein the opening of the first throttling means is greater when the first control variable is larger than the second control variable beyond a predetermined range. It is characterized by increasing.

  The refrigeration unit according to a tenth aspect of the present invention is the refrigeration unit according to any one of the sixth to ninth aspects, wherein the first control device is configured such that the temperature of the refrigerant flowing out of the evaporator and the refrigerant flowing into the evaporator or in the evaporator A signal of a target temperature difference, which is a difference from the temperature of the refrigerant, is sent to a second control device provided in the evaporation unit.

  The refrigeration unit of the eleventh aspect of the present invention is the refrigeration unit according to any one of the sixth to tenth aspects of the present invention, wherein the first control device includes The target temperature difference is increased.

  According to the refrigeration apparatus of the first aspect of the invention and the refrigeration unit of the sixth aspect of the invention, the vapor that does not contribute to the cooling of the liquid refrigerant flowing to the evaporator side is prevented, preventing the gas-liquid separation in the receiver tank from becoming incomplete. Mixing of refrigerant can be avoided. Therefore, even when the ambient temperature and cooling load fluctuate, it is possible to prevent the cooling efficiency of the refrigeration cycle from significantly decreasing and maintain a suitable refrigeration cycle state. Can be improved.

  According to the refrigeration apparatus of the second aspect of the invention and the refrigeration unit of the seventh aspect of the invention, the state of gas-liquid separation in the receiver tank can be accurately grasped according to fluctuations in operating conditions. Therefore, it is possible to appropriately control the state of the intermediate pressure portion of the refrigeration cycle.

  According to the refrigeration apparatus of the third aspect of the invention and the refrigeration unit of the eighth aspect of the invention, it becomes possible to grasp the state of the intermediate pressure part of the refrigeration cycle more safely and easily.

  According to the refrigeration apparatus of the fourth invention and the refrigeration unit of the ninth invention, it is avoided that gas-phase refrigerant that does not contribute to cooling flows into the low-pressure side of the refrigeration cycle circuit, and the cooling performance of the refrigeration apparatus decreases. Can be prevented.

  According to the refrigeration apparatus of the fifth invention and the refrigeration units of the tenth and eleventh inventions, when a gas-phase refrigerant that does not contribute to cooling is mixed into the low-pressure side of the refrigeration cycle circuit, the amount of refrigerant in the receiver tank is increased, It is possible to prevent the vapor refrigerant from being mixed into the liquid refrigerant flowing to the second throttle means. Therefore, even when the outside air temperature and the load conditions vary, it is possible to prevent a significant decrease in the cooling efficiency of the refrigeration apparatus.

1 is a schematic configuration diagram of a refrigeration apparatus according to an embodiment of the present invention. It is sectional drawing of the receiver tank which concerns on embodiment of this invention. It is the pressure and enthalpy diagram which showed the refrigerating cycle of this invention. It is a control block diagram of the freezing apparatus which concerns on embodiment of this invention. It is the pressure and enthalpy diagram which showed the refrigerating cycle of this invention. It is the pressure and enthalpy diagram which showed the refrigerating cycle of this invention. It is a control flowchart of the freezing apparatus in embodiment of this invention.

  Hereinafter, a refrigeration apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a refrigeration apparatus according to an embodiment of the present invention. In the refrigeration apparatus according to the present embodiment, a two-stage compression compressor 1 including a first-stage compression element 1a as a first compression means and a second-stage compression element 1b as a second compression means is employed. The refrigeration cycle circuit according to the present embodiment includes a discharge unit of the second-stage compression element 1b of the compressor 1, a radiator 2, an expansion valve 3 as a first throttle means, a receiver tank 4, a strainer 9, and a second throttle. The refrigerant flows in order through the expansion valve 5, the evaporator 6, and the accumulator 8 as means, and is connected and configured by a refrigerant pipe so as to form a closed circuit that returns to the suction portion of the first-stage compression element 1 a of the compressor 1. Yes. Further, in the refrigeration cycle circuit, the refrigerant flows in order through the pipe 28, the intermediate cooler 7 and the pipe 31 through which the refrigerant discharged from the discharge portion of the first-stage compression element 1a of the compressor 1 flows. A refrigerant circuit returning to the suction portion of the stage compression element 1b is provided. Furthermore, the refrigeration cycle circuit includes a refrigerant pipe 29 that connects the receiver tank 4 and the pipe 31. The pipe 31 and the pipe 29 function as a bypass path for sucking the gas-phase refrigerant in the receiver tank 4 during the compression stroke of the compressor 1. In this refrigeration apparatus, carbon dioxide (R744) is used as the refrigerant.

  The compressor 1 is for compressing a low-pressure refrigerant into a high-pressure state. In the refrigeration apparatus according to the present embodiment, since carbon dioxide is used as the refrigerant, the pressure of the refrigerant discharged from the compressor 1 may exceed the critical pressure. The compressor 1 is a rotary type two-stage compression type including a first-stage compression element 1a, that is, a low-pressure side compression element, and a second-stage compression element 1b, that is, a high-pressure side compression element. By adopting a two-stage compression type, the pressure ratio of the compression elements in each stage can be reduced, and the refrigerant can be compressed to a high pressure with high efficiency. Further, by providing a refrigerant suction portion between the first-stage compression element 1a and the second-stage compression element 1b, a refrigeration cycle for sucking the gas-phase refrigerant separated in the receiver tank 4 during the compression process can be easily configured. be able to. As the compressor 1, other known compressors such as a scroll type, a reciprocating type, and a screw type can be used.

  Furthermore, it is possible to provide two or more compressors 1, which makes it possible to perform capacity control (number control) according to the cooling load. Moreover, although the compressor 1 which concerns on this embodiment is an inverter drive system, a constant speed type is also employable. In the inverter drive system, it is possible to change the rotation speed of the compressor in accordance with the cooling load, and it is possible to operate with higher efficiency compared to the control of the number of constant speed compressors that repeatedly start and stop the compressor. The discharge pipe 21 of the second-stage compression element 1b of the compressor 1 is provided with a pressure sensor P1 that detects the pressure of the refrigerant and a refrigerant temperature sensor T1 that detects the temperature of the refrigerant.

  The radiator 2 is a heat exchanger for releasing the heat of the refrigerant to the atmosphere, and for example, a fin-and-tube heat exchanger can be adopted. The radiator 2 includes a fan 11 for supplying air that exchanges heat with the refrigerant. Note that when the refrigerant pressure inside the radiator 2 exceeds the critical pressure, the radiator 2 acts as a gas cooler. That is, the refrigerant does not condense inside the refrigerant flow path of the radiator 2, and its temperature decreases as it is radiated and cooled to the atmosphere. In addition, the outlet side pipe 22 of the radiator 2 is provided with a refrigerant temperature sensor T2 as a pre-expansion temperature detector and a pressure sensor P2 as a high-pressure detector. It is also possible to use the pressure sensor P1 as a high pressure detector.

  The expansion valve 3 as the first throttle means is for reducing the pressure of the refrigerant that has radiated heat to the atmosphere by the radiator 2 and lowered to the intermediate pressure by the expansion of the throttle. As the first throttle means, a capillary tube, a temperature type expansion valve, an electric expansion valve or the like can be adopted. In the refrigeration apparatus according to the present embodiment, an electric expansion valve is used. And the opening degree of the expansion valve 3 is controlled by the 1st control apparatus 90 with the control method mentioned later.

  The receiver tank 4 is for separating the gas-liquid two-phase refrigerant decompressed to the intermediate pressure by the expansion valve 3 into gas-liquid separation, that is, separating the refrigerant into vapor refrigerant (gas phase refrigerant) and liquid refrigerant (liquid phase refrigerant). is there. The receiver tank 4 also functions as a refrigerant receiver that stores excess refrigerant in order to appropriately maintain the amount of refrigerant circulating in the refrigeration cycle. FIG. 2 is a cross-sectional view of the receiver tank 4 according to the present embodiment. The receiver tank 4 includes a receiver container 4T, a refrigerant inlet 4d and a vapor refrigerant outlet 4e provided in the upper part of the receiver container 4T, and a liquid refrigerant outlet 4f for taking out the refrigerant in the lower part of the receiver container 4T. The receiver container 4T is configured by sealingly joining the upper end plate 4b to one end (upper end) of the cylindrical receiver body 4a and sealingly lower joint 4c to the other end (lower end). Yes. The refrigerant inlet 4d and the vapor refrigerant outlet 4e of the receiver tank 4 are provided with liquid refrigerant capturing members 4g and 4h, respectively, for efficiently performing gas-liquid separation. As the liquid refrigerant capturing members 4g and 4h, a wire net, a punching metal, a shielding plate or the like can be adopted. In the present embodiment, a wire mesh is used. Then, the wire mesh is rounded into a cylindrical shape, and the lower end portion is crushed and sealed and fixed, and is inserted and fixed to the inner end portion of the receiver tank 4 of the pipe that becomes the refrigerant inlet 4d and the vapor refrigerant outlet 4e. By adopting such a structure, processing is easy and gas-liquid separation can be performed with high efficiency. Further, the liquid refrigerant capturing member 4g can suppress the disturbance of the liquid level caused by the refrigerant flowing from the refrigerant inlet 4d colliding with the refrigerant liquid level, and has the effect of improving the gas-liquid separation performance.

  A pipe 29 is connected to the vapor refrigerant outlet 4 e of the receiver tank 4, and the pipe 29 is connected to a pipe 31. As a result, the gas-phase refrigerant in the receiver tank 4 can be introduced into the intermediate pressure part of the compression process of the compressor 1. In addition, a refrigerant outlet pipe 24 through which the liquid refrigerant in the receiver tank 4 flows to the evaporator 6 side is connected to the liquid refrigerant outlet 4 f of the receiver tank 4.

  Here, the pipe 29 is provided with a pressure sensor P3 as an intermediate pressure detector. Note that the piping between the expansion valve 3 and the expansion valve 5, that is, the piping 23, the piping 24, the piping 29, the piping 28, and the piping 31, all have substantially the same pressure (the intermediate pressure of the refrigeration cycle). The sensor P3 may be installed at any one of these positions.

  Moreover, since the state of the refrigerant that has passed through the expansion valve 3 is normally a gas-liquid two-phase state, a refrigerant temperature sensor (not shown) can be provided as an intermediate pressure temperature detector instead of the pressure sensor P3. . Thereby, it becomes possible to obtain | require the pressure of an intermediate | middle pressure part from the refrigerant | coolant temperature detected with the intermediate pressure temperature detector. In the method of installing the refrigerant temperature sensor instead of the pressure sensor P3, the sensor can be installed outside the refrigerant pipe, which is advantageous in that the sensor can be easily installed, and in particular, troubles such as refrigerant leakage are unlikely to occur. .

  The strainer 9 is for removing foreign matters in the refrigerant circuit and preventing problems such as clogging of the expansion valve 5, and is provided on the upstream side of the expansion valve 5 of the refrigerant going-out pipe 24.

  The expansion valve 5 as the second throttle means is for reducing the pressure of the medium-pressure and low-temperature liquid refrigerant flowing in through the refrigerant delivery pipe 24 by throttle expansion to obtain a low-pressure and low-temperature refrigerant (normal gas-liquid two-phase state). Thus, a capillary tube, a temperature expansion valve, an electric expansion valve, or the like can be employed. In the refrigeration apparatus according to the present embodiment, an electric expansion valve is used. Then, the second controller 91 detects the degree of superheat of the outlet side refrigerant of the evaporator 6, that is, the refrigerant temperature at the outlet of the evaporator 6 detected by a refrigerant temperature sensor T4 (evaporator outlet temperature detector) described later and the refrigerant described later. The opening degree of the expansion valve 5 is controlled so that the difference from the refrigerant temperature at the inlet of the evaporator 6 detected by the temperature sensor T3 (evaporation temperature detector) becomes a predetermined value (target temperature difference). The target temperature difference information is calculated by the first control device 90 and then sent from the integrated control device 92 to the second control device 91.

  The evaporator 6 is a heat exchanger for cooling food and the like by heat absorption due to the evaporation action of the refrigerant, and employs a fin-and-tube heat exchanger. The inlet pipe of the evaporator 6 is provided with a refrigerant temperature sensor T3 as an evaporation temperature detector for detecting the refrigerant temperature at the inlet of the evaporator 6, and the outlet pipe of the evaporator 6 has an outlet of the evaporator 6. A refrigerant temperature sensor T4 is provided as an evaporator outlet temperature detector for detecting the refrigerant temperature. Note that the refrigerant temperature sensor T3 is a piping part that forms the evaporator 6, and can be provided at a location where the state of the refrigerant is assumed to be a gas-liquid two-phase state. The evaporator 6 includes a fan 12 for supplying air to be cooled by exchanging heat with the refrigerant. In the evaporator 6, the air supplied by the fan 12 is cooled by evaporation of the refrigerant to become a low temperature, and then supplied to a cold storage space such as food.

  The accumulator 8 is for preventing the liquid refrigerant from being sucked into the compressor 1, and has a function of performing gas-liquid separation inside and temporarily storing the liquid refrigerant. In particular, the function is exhibited at the time of start-up and defrosting operation. A pressure sensor P4 for detecting the pressure of the refrigerant sucked from the compressor is attached on the pipe 27 connected from the accumulator 8 to the suction port of the compressor.

  The intercooler 7 is a heat exchanger for performing heat exchange between the refrigerant discharged from the first-stage compression element 1a of the compressor 1 and the atmosphere and cooling the refrigerant. Thereby, the compression power of the compressor 1 can be reduced and cooling efficiency can be improved. The intercooler 7 is a fin-and-tube heat exchanger, and a fan 11 for supplying heat for exchanging heat with the refrigerant uses the fan 11 of the radiator 2. Further, the intermediate cooler 7 shares the radiator 2 and the cooling fins, and is configured integrally.

  The piping 31 connecting the outlet of the intercooler 7 and the suction port of the second-stage compression element 1b of the compressor 1 has a refrigerant temperature sensor T6 as a pre-merging temperature detector and a refrigerant temperature sensor T7 as a suction temperature detector. Is provided. The refrigerant temperature sensor T6 is provided on the upstream side of the junction 30 and detects the temperature of the refrigerant that has been cooled and flowed out by the intermediate cooler 7 and before the refrigerant flowing in from the receiver tank 4 is merged. Is. On the other hand, the refrigerant temperature sensor T7 is provided on the downstream side of the junction 30 and is sucked into the refrigerant temperature after having joined with the refrigerant flowing in from the receiver tank 4, that is, the second-stage compression element 1b of the compressor 1. It detects the temperature of the refrigerant.

  Further, if necessary, an inside for performing heat exchange between the medium-pressure liquid refrigerant flowing to the expansion valve 5 and the low-pressure refrigerant flowing out of the evaporator 6 to cool the medium-pressure refrigerant and heat the low-pressure refrigerant. It is also possible to provide a heat exchanger (not shown).

  Next, the structure of the unit which accommodates each refrigeration equipment will be described. The refrigeration apparatus according to the present embodiment is composed of a refrigeration unit 10 and a showcase 20 (evaporation unit) that accommodate and unitize refrigeration equipment (element parts) constituting a refrigeration circuit. The refrigeration unit 10 includes a compressor 1 that compresses refrigerant, an intermediate cooler 7 that cools an intermediate-pressure refrigerant discharged from the first-stage compression element 1a of the compressor 1, and a discharge from the second-stage compression element 1b of the compressor 1. A radiator 2 that cools the high-temperature and high-pressure refrigerant, an expansion valve 3 as a first throttle means, a receiver tank 4 that performs gas-liquid separation of the intermediate-pressure refrigerant decompressed by the expansion valve 3, and a compressor 1 An accumulator 8 is provided for preventing the liquid refrigerant from being sucked. As described above, the refrigerant discharge pipe 21 of the second-stage compression element 1 b of the compressor 1 is connected to the radiator 2 so that the refrigerant can flow, and the refrigerant suction pipe 27 of the compressor 1 is connected to the accumulator 8. . The refrigeration unit 10 includes a first control device 90, pressure sensors P1, P2, P3, P4, refrigerant temperature sensors T1, T2, T6, T7, and other temperature sensors and pressure sensors (not shown). The refrigeration unit 10 includes a refrigerant return pipe connection port connected to the liquid refrigerant outlet 4 f of the receiver tank 4 and a refrigerant return pipe connection port connected to the accumulator 8.

  The showcase 20 includes an expansion valve 5 that depressurizes the medium-pressure refrigerant, an evaporator 6 that cools food and the like by the evaporating action of the refrigerant, and a strainer 9 that removes foreign matter in the refrigerant circuit. In addition, the showcase 20 includes a second control device 91, refrigerant temperature sensors T3 and T4, other temperature sensors, a space for storing food, a display shelf, and the like. The showcase 20 includes a refrigerant inlet pipe connection port connected to the strainer 9 and a refrigerant outlet pipe connection port connected to the outlet side of the evaporator 6. In addition, the showcase 20 is not necessarily limited to the display of the objects to be cooled, and may be a cool box that is not intended for display.

  Here, the refrigerant going pipe 24 is formed by connecting the refrigerant going pipe connecting port of the refrigeration unit 10 and the refrigerant inlet pipe connecting port of the showcase 20 with a pipe. The refrigerant return pipe 26 is formed by connecting the refrigerant return pipe connection port of the refrigeration unit 10 and the refrigerant outlet pipe connection port of the showcase 20 with a pipe. A plurality of showcases 20 can be provided as necessary. In that case, the refrigerant inlet pipe connection port of each showcase 20 is connected to the refrigerant forward pipe 24 side, and the refrigerant outlet pipe connection port is connected to the refrigerant return pipe 26 side.

  Next, the operation of the refrigeration apparatus according to the first embodiment will be described.

  FIG. 3 is a pressure-specific enthalpy diagram showing the refrigeration cycle of the refrigeration apparatus according to the present invention. The horizontal axis represents the refrigerant specific enthalpy (kJ / kg), the vertical axis represents the refrigerant pressure (MPa), the symbol SL represents the saturated liquid line of the refrigerant, and SV represents the saturated vapor line. In this figure, the code | symbol C is the refrigerating cycle of this embodiment.

  In this refrigeration cycle circuit, the low-temperature refrigerant vapor shown in the state a in FIG. 3 is sucked from the first-stage intake port of the compressor 1, compressed by the first-stage compression element 1a, and discharged as high-temperature and intermediate-pressure refrigerant vapor. Is done. The refrigerant in this state is indicated by state b in FIG. This refrigerant enters the intercooler 7, where it is cooled by exchanging heat with the atmosphere, and the temperature drops to state c. Since the refrigerant discharged from the first-stage compression element 1a of the compressor 1 is cooled by the intermediate cooler 7 in this way, the temperature of the refrigerant discharged from the second-stage compression element 1b of the compressor 1 is kept low. It becomes possible, and the malfunction by the abnormally high temperature of the compressor 1 can be prevented. Further, by adopting the intermediate cooler 7, the compression power of the compressor 1 can be reduced, so that the cooling efficiency can be improved.

  The refrigerant shown in the state c exiting the intercooler 7 joins with the low-temperature refrigerant shown in the state j flowing from the bypass path side (pipe 29 side) at the junction 30 shown in FIG. The refrigerant after joining is indicated by a state d. The merged refrigerant is sucked from the second-stage suction port of the compressor 1, compressed by the second-stage compression element 1b of the compressor 1, and discharged as a high-temperature and high-pressure refrigerant (state e). In the present embodiment, carbon dioxide is used as the refrigerant in the refrigeration cycle, so the pressure of the refrigerant discharged from the compressor 1 may exceed the critical pressure as in the state e in FIG.

  The refrigerant discharged from the compressor 1 flows into the radiator 2 and is cooled by exchanging heat with the atmosphere. As shown in FIG. 3, when the pressure of the refrigerant in the radiator 2 exceeds the critical pressure, the refrigerant cooled there does not condense and its temperature decreases as it is cooled. The refrigerant cooled by the radiator 2 is indicated by a state f.

  The refrigerant that has exited the radiator 2 passes through the expansion valve 3 and is squeezed and expanded (equal enthalpy expansion) to be reduced to an intermediate pressure that is higher than the first-stage suction pressure of the compressor 1 and lower than the second-stage discharge pressure, As shown by the state g in FIG. 3, the gas-liquid two-phase state is entered and the receiver tank 4 is entered. In the receiver tank 4, the refrigerant is separated into a vapor refrigerant indicated by the state j and a liquid refrigerant indicated by the state h. Due to the density difference, the vapor refrigerant is located above the receiver container 4T and the liquid refrigerant is contained within the receiver container 4T. Flowing downward.

  Here, since the liquid refrigerant capturing member 4g is provided at the refrigerant inlet 4d of the receiver tank 4, the mist liquid refrigerant collides with the liquid refrigerant capturing member 4g and efficiently performs gas-liquid separation. Is possible. Further, the liquid refrigerant capturing member 4g is separated because the refrigerant flowing from the refrigerant inlet 4d can suppress the disturbance of the liquid level caused by the collision with the liquid level of the refrigerant stored below the receiver container 4T. It is possible to prevent re-misting by the refrigerant into which the liquid refrigerant flows, and the gas-liquid separation performance by the receiver tank 4 can be further improved. Further, since the liquid refrigerant capturing member 4h is provided at the vapor refrigerant outlet 4e of the receiver tank 4, the mist liquid refrigerant contained in the vapor refrigerant flowing out from the receiver tank 4 is captured and separated by the liquid refrigerant capturing member 4h. be able to. Therefore, the gas-liquid separation performance of the receiver tank 4 can be further improved.

  The liquid refrigerant in the state h separated from the gas and liquid in the receiver tank 4 flows out from the liquid refrigerant outlet 4f, flows through the pipe 24, and flows to the cooling load side (the evaporator 6 side). Since the specific enthalpy of the liquid refrigerant flowing out from the receiver tank 4 (state h) is smaller than the specific enthalpy of the refrigerant flowing into the receiver tank 4 (state g), an amount corresponding to the specific enthalpy difference between the state g and the state h, The refrigerant refrigeration effect in the evaporator 6 is increased.

  On the other hand, the vapor refrigerant in the state j separated from the gas and liquid in the receiver tank 4 flows through the pipe 29 from the vapor refrigerant outlet 4e and is merged with the refrigerant in the state c after being cooled by the intermediate cooler 7 as described above. And merges into state d. Then, the air is sucked from the second-stage suction port of the compressor 1. The vapor refrigerant (state j) separated by gas and liquid in the receiver tank 4 has a large specific enthalpy and cannot exhibit a refrigeration effect even if it flows into the evaporator 6. Therefore, the first stage compression element 1a is compressed by returning the vapor refrigerant in the state j in the middle of the compression stroke, that is, when returning the refrigerant to the first stage suction part. Power can be reduced. As a result, the refrigeration efficiency of the refrigeration cycle can be improved.

  The liquid refrigerant (state h) flowing out from the liquid refrigerant outlet 4 f of the receiver tank 4 flows through the pipe 24, passes through the strainer 9, undergoes throttle expansion (equal enthalpy expansion) by the expansion valve 5, and flows to the evaporator 6. . The refrigerant flowing into the evaporator 6 is represented by the state i and is in a low-pressure gas-liquid two-phase state. In the evaporator 6, the refrigerant exchanges heat with the air to be cooled supplied by the fan 12, cools the air, and the liquid phase portion evaporates. At the outlet of the evaporator 6, the refrigerant is a slightly superheated vapor and is represented by state a. The supply of the refrigerant to the evaporator 6 is adjusted by controlling the opening degree of the expansion valve 5 by the second controller 91. As described above, a predetermined superheated state at the outlet of the evaporator 6, that is, evaporation is performed. The temperature difference between the inlet and outlet is controlled to be the target temperature difference.

  The refrigerant flowing out of the evaporator 6 flows through the refrigerant return pipe 26, passes through the accumulator 8, where it is surely gas-liquid separated, and then flows to the first stage inlet of the compressor 1 and is compressed. As described above, the refrigeration cycle operates continuously, and the refrigeration capacity is exhibited in the evaporator 6. Then, the air cooled by the evaporator 6 circulates in the cool space, and the object to be cooled such as food is frozen and refrigerated.

  In the case where an internal heat exchanger (not shown) is provided, the medium-pressure and low-temperature refrigerant flowing out of the receiver tank 4 in the internal heat exchanger is the low-pressure and low-temperature refrigerant exiting the evaporator 6. It is cooled by heat exchange. In this case, since the intermediate-pressure refrigerant is cooled by the internal heat exchanger, generation of flash gas in the refrigerant delivery pipe 24 is prevented, and the low-pressure refrigerant is overheated, so that the compressor 1 is prevented from being wet-compressed. . Moreover, since the adoption of the internal heat exchanger can secure a large number of two-phase refrigerant regions having a high heat transfer coefficient inside the evaporator 6, the heat transfer performance of the evaporator 6 can be improved and the cycle performance can be improved. .

  FIG. 4 is a block diagram illustrating a control device for the refrigeration apparatus according to the present embodiment. The control device of this embodiment includes a first control device 90 provided in the refrigeration unit 10, a second control device 91 built in each showcase 20, and an integrated control device 92.

  The first control device 90 basically controls the operation means provided in the refrigeration unit 10, such as the expansion valve 3 (first expansion valve, first throttle means), the compressor 1, the fan 11, and the like. It is. The first control device 90 includes an input signal processing unit 90a that processes input from each sensor and an input signal from the setting input unit 95, a main calculation processing unit 90b that performs control calculation, and an operation result as an operation signal. And an operation signal output unit 90 c that converts the signal into the control operation means and a communication processing unit 90 d for performing communication with the integrated control device 92 and the first control device 90.

  The second control device 91 is basically for controlling the operation means provided in the showcase 20 such as the expansion valve 5 (second expansion valve, second throttle means) and the fan 12. Although not shown, the second control device 91 of the showcase 20 also has a configuration including a processing unit similar to the first control device 90.

The integrated control device 92 communicates bidirectionally with the first control device 90 of the refrigeration unit 10 and the second control device 91 of the showcase 20, and information such as detection values, control variables, control commands, and the like by the sensors. To control the entire refrigeration system. By providing the integrated control device 92, appropriate operation control corresponding to fluctuations in outside air conditions and load conditions is performed on the refrigeration apparatus configured of the refrigeration unit 10 and the showcase 20 that are normally installed at remote locations. Is possible.
In the present embodiment, the first control device 90 and the integrated control device 92 have been described as separate means. However, the object and effect of the present invention can also be achieved as a control device that combines these functions. Needless to say.

  The first control device 90, the second control device 91, and the integrated control device 92 include setting input means 95, 96, and 97 for inputting control setting data and operation commands, and a display for displaying the control data. (Not shown). Further, the integrated control device 92 has a remote communication function for monitoring operation data from outside the store and transmitting / receiving control setting data.

  Next, the flow of control signals for the first control device 90 will be described. Input signals detected by the sensors are first converted into predetermined detection values (control variables) by the input signal processing unit 90a. Then, in the main calculation processing unit 90b, the control operation is determined by calculation by the control method described later. Then, the calculation result is converted into a signal suitable for each operation means such as the expansion valve 3, the compressor 1, and the fan 11 by the operation signal output unit 90c and is output. Based on the operation signal, each operation means operates to perform appropriate operation control of the refrigeration apparatus.

  Next, the basic control of this embodiment will be specifically described. The operation of the compressor 1 during the cooling operation of the refrigeration cycle is controlled by a first control device 90 built in the refrigeration unit 10. Specifically, the rotational speed control and start / stop control of the compressor 1 are performed so that the pressure of the low-pressure refrigerant detected by the pressure sensor P4 provided in the refrigerant suction pipe 27 falls within a predetermined pressure range. The predetermined pressure range is determined so as to obtain a suitable refrigeration cycle by reading the cold set temperature of the space to be cooled by communication with the second control device 91 provided in the showcase 20. Thereby, highly efficient cooling corresponding to the cooling load is performed.

  The opening degree of the expansion valve 3 as the first throttle means is controlled by the first controller 90 so that the intermediate pressure detected by the pressure sensor P3 attached to the pipe 29 becomes a predetermined value. That is, the first control device 90 performs control to reduce the opening degree of the expansion valve 3 if the intermediate pressure is higher than a predetermined target value, and to increase the opening degree of the expansion valve 3 if the intermediate pressure is lower than the predetermined value. . Here, the predetermined target value is obtained by multiplying a geometric coefficient of the low pressure detected by the pressure sensor P4 and the high pressure detected by the pressure sensor P1 or P2 by a predetermined coefficient. As a result, the intermediate pressure of the refrigeration cycle can be controlled appropriately, so that the compression ratio of the first-stage compression element 1a and the second-stage compression element 1b of the compressor 1 is suitably maintained, and the refrigerant flowing toward the evaporator 6 side and The specific enthalpy and flow rate of the refrigerant flowing through the bypass path are appropriately maintained, and a highly efficient cooling operation can be performed.

  It is also possible to control the opening degree of the expansion valve 3 as the first throttle means so that the high pressure detected by the pressure sensor P1 or P2 becomes a predetermined value. That is, the control means 90 performs control to increase the opening degree of the expansion valve 3 if the high pressure is higher than a predetermined target value, and to decrease the opening degree of the expansion valve 3 if the high pressure is lower than the predetermined target value. The predetermined target value is obtained according to the temperature of the refrigerant flowing into the expansion valve 3, that is, the temperature of the refrigerant detected by the refrigerant temperature sensor T2. In a refrigeration cycle in which the pressure on the high pressure side exceeds the critical pressure, changing the pressure on the high pressure side changes the compression power of the compressor 1 and changes the enthalpy of the refrigerant (state f in FIG. 3) flowing into the expansion valve 3. It changes greatly and the freezing effect changes greatly. Therefore, the efficiency of the refrigeration apparatus can be improved by setting and controlling a predetermined high pressure target value according to the temperature of the refrigerant flowing into the expansion valve 3. In addition, since the temperature of the refrigerant flowing into the expansion valve 3, that is, the temperature of the refrigerant after radiating heat to the outside air with the radiator 2, depends on the outside air temperature, in the calculation of the target value of the high pressure, the above-mentioned Instead of the temperature of the refrigerant flowing into the expansion valve 3, the outside air temperature can be used as a reference.

  Further, as the control of the expansion valve 3 as the first throttle means, the above-described intermediate pressure control and high pressure control can be performed in combination. That is, it is possible to perform control so that the intermediate pressure detected by the pressure sensor P3 and the high pressure detected by the pressure sensor P1 or P2 become the respective target values (target ranges). As a result, it is possible to perform more stable and highly efficient operation against fluctuations in the outside air temperature and load.

  The expansion valve 5 serving as the second throttle means includes a degree of superheat of the refrigerant on the outlet side of the evaporator 6, that is, the refrigerant temperature at the outlet of the evaporator 6 detected by the refrigerant temperature sensor T4 (evaporator outlet temperature detector) and the refrigerant temperature sensor. The second controller 91 controls the difference between the refrigerant temperature at the inlet of the evaporator 6 detected by T3 (evaporation temperature detector) to be a predetermined value (target temperature difference). Specifically, the second controller 91 increases the opening degree of the expansion valve 5 if the degree of superheat is greater than a predetermined target value, and decreases the opening degree of the expansion valve 5 if the degree of superheat is smaller than the target value. Control. Accordingly, an appropriate amount of refrigerant according to the cooling load can be supplied to the evaporator 6, and a predetermined cooling capacity can be exhibited while maintaining efficient heat exchange in the evaporator 6.

  By the way, in the case of performing the basic control described above, ideally, the refrigerant that is completely gas-liquid separated in the receiver tank 4 and that flows to the expansion valve 5 is only the liquid refrigerant, and the bypass path side (pipe 29 side) It is desirable that the refrigerant flowing into () is only a vapor refrigerant. Therefore, as described above, the receiver tank 4 is devised such as providing the liquid refrigerant capturing members 4g and 4h in order to promote gas-liquid separation. However, in the actual machine, the refrigerant in the receiver container 4T is in a state where the liquid-phase refrigerant and the gas-phase refrigerant are mixed in the form of bubbles, or in the state where there are many mist-like liquid refrigerants in the gas-phase refrigerant. It is difficult to completely separate the gas-phase refrigerant and the liquid-phase refrigerant. Such a problem can be reduced if the size of the receiver tank 4 is very large, but the size is actually limited. Therefore, depending on the state of the load, the vapor refrigerant may be mixed into the liquid refrigerant flowing toward the low pressure side, or the liquid refrigerant may be mixed into the vapor refrigerant flowing toward the medium pressure side. In particular, when the cooling load is large under high outside air temperature conditions, it is necessary to increase the amount of refrigerant on the high-pressure side and the low-pressure side of the refrigeration cycle, and the amount of refrigerant in the receiver tank 4 decreases, so gas-liquid separation is not possible. It becomes complete, and vapor mixing into the liquid refrigerant is likely to occur.

  The refrigeration cycle C2 in FIG. 5 shows the refrigeration cycle in which the gas-liquid separation is incomplete and the refrigerant flowing into the low pressure side is mixed with the gas phase refrigerant. FIG. 6 is a plot in which an ideal refrigeration cycle C1 (solid line) and a refrigeration cycle C2 (dashed line) with incomplete gas-liquid separation are superimposed. 5 and 6, as in FIG. 3, the horizontal axis represents the specific enthalpy (kJ / kg) of the refrigerant, the vertical axis represents the refrigerant pressure (MPa), the symbol SL represents the saturated liquid line of the refrigerant, and SV represents the saturation. The vapor line is shown. Moreover, the code | symbol which shows the state about the same location as the refrigerating cycle C shown in FIG.

  As shown in FIG. 5 and FIG. 6, the refrigerant at the outlet of the receiver tank 4 in the refrigeration cycle C2 shown in the state h2 is not on the saturated liquid line SL because the gas-phase refrigerant is mixed, and compared with the saturated liquid. Enthalpy is large. Since the refrigerant shown in this state h2 is decompressed by the expansion valve 3 to become the state i2 and flows to the evaporator 6, the specific enthalpy of the refrigerant at the inlet of the evaporator 6 is also compared with the state i1 in the ideal refrigeration cycle C1. Become bigger. And the refrigerating effect (specific enthalpy difference between the state a2 and the state i2) is smaller than that of the refrigerating cycle C1. Moreover, since the refrigerant | coolant flow volume qL2 by the side of low pressure becomes larger than the refrigerating cycle C1, the pressure loss in the evaporator 6 increases and the refrigerant | coolant compression work in the 1st stage | paragraph compression element 1a of the compressor 1 increases. As a result, the refrigeration efficiency of the refrigeration apparatus is significantly reduced.

  Therefore, in the refrigeration apparatus according to the present embodiment, the control of the expansion valve 3 serving as the first throttling means is described below in detail in place of or in combination with the above-described intermediate pressure control and high pressure control. Control to do.

  FIG. 7 is a diagram illustrating a control flow of the expansion valve 3 of the refrigeration apparatus according to the present embodiment. During the refrigeration operation, the first controller 90 detects the temperature and pressure of each part of the refrigeration circuit using each sensor (step S1). Next, the first control device 90 expands from the refrigerant temperature Tf flowing into the expansion valve 3 detected by the refrigerant temperature sensor T2 and the high pressure PH detected by the pressure sensor P2 in the main arithmetic processing unit 90b. The specific enthalpy hf of the refrigerant (state f) flowing into the valve 3 is calculated (step S2). Note that the specific enthalpy calculation method includes a method based on an approximate expression created in advance assuming an operating range, or a data table created by dividing numerical values by a predetermined width and stored in a memory. Various methods are conceivable, such as a method of searching for and reading a value to be read.

Next, from the specific enthalpy hf obtained as described above and the intermediate pressure PM detected by the pressure sensor P3, as the first control variable X, the gas phase refrigerant in the refrigerant (state g2) flowing into the receiver tank 4 The mass ratio of the gas-phase refrigerant to the total amount, which is the sum of the liquid-phase refrigerant, that is , the dryness x is calculated (step S3).

  Next, the refrigerant (state) after being cooled by the intermediate cooler 7 from the refrigerant temperature Tc detected by the refrigerant temperature sensor T6 and the intermediate pressure PM and before joining the refrigerant from the receiver tank 4 The specific enthalpy hc of c) is calculated (step S4). Further, the specific enthalpy hj (saturated steam specific enthalpy) of the vapor refrigerant (state j) flowing out from the receiver tank 4 to the bypass path is obtained from the intermediate pressure PM (step S5). Further, the specific enthalpy hd of the refrigerant (state d) after merging, that is, the refrigerant (state d) sucked into the second-stage compression element 1b of the compressor 1 from the refrigerant temperature Td detected by the refrigerant temperature sensor T7 and the intermediate pressure PM. Is obtained (step S6).

  Then, based on the specific enthalpies hc, hj, hd of the refrigerant at each point obtained as described above, a bypass for the refrigerant quantity qH flowing through the radiator 2 as the second control variable Y from the enthalpy balance before and after the refrigerant merge. A mass ratio of the refrigerant quantity qM flowing through the path is calculated (step S7). That is, the second control variable Y = qM / qH = (hc−hd) / (hc−hj).

  Next, the dryness x (first control variable X) of the refrigerant flowing into the receiver tank 4 is compared with the mass flow rate ratio qM / qH (second control variable Y) of the refrigerant flowing through the bypass path (step 8). When the dryness x is larger than the mass flow rate ratio qM / qH, the opening degree of the expansion valve 3 is increased (step S9). As a result, the opening ratio between the expansion valve 3 and the expansion valve 5 changes, so that a sufficient amount of refrigerant is supplied to the receiver tank 4, the intermediate pressure PM rises slightly, and the refrigerant flows from the receiver tank 4 to the expansion valve 5. The gas-phase refrigerant mixed in is reduced. That is, in FIG. 6, the state of the refrigerant flowing to the expansion valve 5 approaches from the state h2 in which the vapor refrigerant is mixed to the state h1 in which only the saturated liquid refrigerant is present. As a result, the refrigeration effect in the evaporator 6 is increased and the refrigerant flow rate qL on the low pressure side is decreased, so that the refrigeration efficiency of the refrigeration cycle can be improved.

  On the other hand, the dryness x (first control variable X) of the refrigerant flowing into the receiver tank 4 is compared with the mass flow rate ratio qM / qH (second control variable Y) of the refrigerant flowing through the bypass path (step 10). When the degree x is smaller than the mass flow ratio qM / qH, it can be determined that the liquid refrigerant is mixed in the vapor refrigerant separated in the receiver tank 4 and is flowing to the bypass path side. When the cooling load is reduced and the number of evaporators 6 that perform the cooling operation is reduced under the low outside air temperature condition, it is necessary to reduce the refrigerant amounts on the refrigeration cycle high-pressure side and low-pressure side. As a result, the refrigerant in the receiver tank 4 Since the amount increases, the liquid refrigerant is likely to be mixed into the vapor refrigerant in this way. Therefore, in this case, the first control device 90 performs control to reduce the opening degree of the expansion valve 3 (step S11). As a result, the intermediate pressure PM is slightly lowered, the amount of refrigerant in the receiver tank 4 is reduced, and mixing of liquid refrigerant into the bypass path can be reduced.

  In the comparison of the dryness x and the mass flow rate ratio qM / qH in Step 8 and Step 10 described above, a predetermined control range (allowable width, dead zone) can be provided in order to stabilize the control operation. In FIG. 7, symbols ka and kb are coefficients indicating a predetermined control range. When the difference between the dryness x and the mass flow rate ratio qM / qH becomes larger than a predetermined range while the above-described intermediate pressure control and high pressure control are used as a basis by giving the predetermined width in this way. It is also possible to combine this control operation only with the above.

  Further, in step 9, in addition to or instead of the operation of increasing the opening degree of the expansion valve 3, it is also possible to perform control for increasing the target temperature difference (target superheat degree) in the opening degree control of the expansion valve 5. Specifically, the first control device 90 of the refrigeration unit 10 performs the arithmetic processing by the main arithmetic processing unit 90b, and the second control device of the showcase 20 via the communication processing unit 90d and the integrated control device 92. 91 is communicated, and a command to increase the target temperature difference is sent to the second controller 91. The second control device 91 of the showcase 20 controls the expansion valve 5 by changing the target temperature difference based on the signal from the first control device 90. As a result, the opening degree of the expansion valve 5 is controlled in a decreasing direction, and the amount of refrigerant inside the evaporator 6 is reduced. As a result, since the amount of refrigerant in the receiver tank 4 increases, the gas-liquid separation efficiency in the receiver tank 4 is improved, and mixing of vapor refrigerant into the liquid refrigerant flowing from the receiver tank 4 to the expansion valve 5 is suppressed.

  As described above, according to the refrigeration apparatus of the present invention, even when the gas-liquid separation in the receiver tank 4 becomes insufficient due to fluctuations in the outside air condition and the cooling load condition, the state is detected, and the ideal air Since the liquid separation state can be obtained, a highly efficient cooling operation can be stably maintained.

  The above-described embodiment shows a specific example of the present invention. Therefore, the embodiment of the present invention is not limited to this, and various modifications can be made.

  The refrigeration apparatus of the present invention can be used as a refrigeration apparatus for freezing and refrigeration of food and the like in supermarkets, convenience stores, restaurants, and the like, and also in other uses that require cooling.

DESCRIPTION OF SYMBOLS 1 ... Compressor 1a ... First stage compression element (1st compression means)
1b... Second stage compression element (second compression means)
2 ... Radiator 3 ... Expansion valve (first throttle means)
4 ... Receiver tank 5 ... Expansion valve (second throttle means)
6 ... Evaporator 7 ... Intermediate cooler 8 ... Accumulator 9 ... Strainer 10 ... Refrigeration unit 11 ... Fan 12 ... Fan 20 ... Showcase (evaporation unit)
29, 31 ... Refrigerant piping (bypass path)
30 ... Merging point 90 ... First control device 91 ... Second control device 92 ... Integrated control device P2 ... Pressure sensor (high pressure detector)
P3 ... Pressure sensor (intermediate pressure detector) or refrigerant temperature sensor (intermediate pressure detector)
T2 ... Refrigerant temperature sensor (temperature detector before expansion)
T3 ... Refrigerant temperature sensor (evaporation temperature detector)
T4 ... refrigerant temperature sensor (evaporator outlet temperature detector)
T6 ... Refrigerant temperature sensor (Temperature detector before joining)
T7 ... Refrigerant temperature sensor (suction temperature detector)
X: Dryness x (first control variable)
Y: Refrigerant mass flow ratio (second control variable)

Claims (11)

A first compression unit, an intermediate cooler, a second compression unit, a radiator, a first throttle unit, a receiver tank, a second throttle unit, and an evaporator are sequentially connected to form a closed circuit, and the second from the receiver tank In the refrigeration apparatus provided with a bypass path for flowing the refrigerant to the suction portion of the compression means,
Refrigerant flowing through the bypass path with respect to the amount of refrigerant flowing into the receiver tank, with the mass ratio of the vapor phase refrigerant to the total amount, which is the sum of the vapor phase refrigerant and liquid phase refrigerant in the refrigerant flowing into the receiver tank, as a first control variable The mass ratio of the quantity is set as a second control variable, and when the gas-liquid separation in the receiver tank is incomplete , the difference between the first control variable and the second control variable is within a predetermined range. A refrigeration apparatus comprising a first control device for controlling the opening of one throttle means. A high pressure detector for detecting the pressure of the refrigerant compressed by the second compression means and flowing into the first throttle means; and the pressure of the refrigerant reduced in pressure by the first throttle means and sucked into the second compression means. An intermediate pressure detector, a pre-expansion temperature detector that detects the temperature of the refrigerant that exits the radiator and flows into the first throttle means, and a refrigerant that flows through the bypass path after flowing out the intermediate cooler A pre-merging temperature detector that detects the temperature of the refrigerant before the suction, and a suction temperature detector that detects the temperature of the refrigerant sucked into the second compression means,
The first control device calculates the first control variable from the pressure detected by the high pressure detector and the intermediate pressure detector and the temperature detected by the pre-expansion temperature detector, and the intermediate pressure is calculated. The refrigeration apparatus according to claim 1, wherein the second control variable is calculated from a pressure detected by a pressure detector and temperatures detected by the pre-merging temperature detector and the suction temperature detector. A high pressure detector for detecting the pressure of the refrigerant compressed by the second compression means and flowing into the first throttle means; and an intermediate pressure temperature detector for detecting the temperature of the refrigerant after being reduced in pressure by the first throttle means; A pre-expansion temperature detector that detects the temperature of the refrigerant that exits the radiator and flows into the first throttle means, and the temperature of the refrigerant that has flowed out of the intermediate cooler and before joining the refrigerant flowing through the bypass path And a pre-merging temperature detector for detecting the refrigerant, and a suction temperature detector for detecting the temperature of the refrigerant sucked into the second compression means,
The first control device calculates the first control variable from the pressure detected by the high pressure detector and the temperatures detected by the intermediate pressure temperature detector and the pre-expansion temperature detector, and the intermediate pressure is calculated. The refrigeration apparatus according to claim 1, wherein the second control variable is calculated from a temperature detected by the temperature detector, the pre-merging temperature detector, and the temperature detected by the suction temperature detector. 4. The opening degree of the first throttle means is increased when the first control variable is larger than the second control variable beyond a predetermined range. 5. The refrigeration apparatus described. An evaporation temperature detector for detecting the temperature of the refrigerant flowing into the evaporator or the refrigerant in the evaporator, and an evaporator outlet temperature detector for detecting the temperature of the refrigerant flowing out of the evaporator,
The first control device controls the opening of the second throttling means so that the difference between the temperatures detected by the evaporator outlet temperature detector and the evaporation temperature detector becomes a predetermined target temperature difference, and The refrigeration apparatus according to any one of claims 1 to 4, wherein the target temperature difference is increased when the first control variable is larger than the second control variable beyond a predetermined range. In the refrigeration unit that constitutes the refrigeration apparatus connected to the evaporation unit including the second throttle means and the evaporator and the pipe between the units,
The refrigeration unit includes a first compression unit, an intermediate cooler, a second compression unit, a radiator, a first throttling unit, a receiver tank, and a bypass path connecting the receiver tank and the suction portion of the second compression unit The bypass for the amount of refrigerant flowing into the receiver tank, wherein the mass ratio of the gas phase refrigerant to the total amount that is the sum of the gas phase refrigerant and liquid phase refrigerant in the refrigerant flowing into the receiver tank is a first control variable The mass ratio of the amount of refrigerant flowing through the path is the second control variable, and the difference between the first control variable and the second control variable is within a predetermined range when the gas-liquid separation in the receiver tank is incomplete. A refrigeration unit comprising a first control device for controlling the opening degree of the first throttle means. A high pressure detector for detecting the pressure of the refrigerant compressed by the second compression means and flowing into the first throttle means; and the pressure of the refrigerant reduced in pressure by the first throttle means and sucked into the second compression means. An intermediate pressure detector, a pre-expansion temperature detector that detects the temperature of the refrigerant that exits the radiator and flows into the first throttle means, and a refrigerant that flows through the bypass path after flowing out the intermediate cooler A pre-merging temperature detector that detects the temperature of the refrigerant before the suction, and a suction temperature detector that detects the temperature of the refrigerant sucked into the second compression means,
The first control device calculates the first control variable from the pressure detected by the high pressure detector and the intermediate pressure detector and the temperature detected by the pre-expansion temperature detector, and the intermediate pressure is calculated. The refrigeration unit according to claim 6, wherein the second control variable is calculated from a pressure detected by a pressure detector and a temperature detected by the pre-merging temperature detector and the suction temperature detector. A high pressure detector for detecting the pressure of the refrigerant compressed by the second compression means and flowing into the first throttle means; and an intermediate pressure temperature detector for detecting the temperature of the refrigerant after being reduced in pressure by the first throttle means; A pre-expansion temperature detector that detects the temperature of the refrigerant that exits the radiator and flows into the first throttle means, and the temperature of the refrigerant that has flowed out of the intermediate cooler and before joining the refrigerant flowing through the bypass path And a pre-merging temperature detector for detecting the refrigerant, and a suction temperature detector for detecting the temperature of the refrigerant sucked into the second compression means,
The first control device calculates the first control variable from the pressure detected by the high pressure detector and the temperatures detected by the intermediate pressure temperature detector and the pre-expansion temperature detector, and the intermediate pressure is calculated. The refrigeration unit according to claim 6, wherein the second control variable is calculated from a temperature detector, a pre-merging temperature detector, and a temperature detected by the suction temperature detector. 9. The opening degree of the first throttle means is increased when the first control variable is larger than the second control variable beyond a predetermined range. 9. The refrigeration unit described. The first control device is provided with a signal of a target temperature difference, which is a difference between the temperature of the refrigerant flowing out of the evaporator and the temperature of the refrigerant flowing into the evaporator or the refrigerant in the evaporator, in the evaporation unit. The refrigeration unit according to any one of claims 6 to 9, wherein the refrigeration unit is sent to a second control device. The said 1st control apparatus enlarges the said target temperature difference, when the said 1st control variable is larger than the said 2nd control variable exceeding a predetermined range, The any of Claim 6 thru | or 10 characterized by the above-mentioned. A refrigeration unit according to claim 1.

Images