JP2010007975A - Economizer cycle refrigerating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more raise the supercooling degree of a main refrigerant at an outlet of an economizer. <P>SOLUTION: A part of the main refrigerant subjected to heat exchange with a branch refrigerant in the economizer 13 is decompressed by an expansion valve 16 for the economizer and then introduced into the economizer 13 again, and the main refrigerant and the branch refrigerant are made into opposed flows used as the branch refrigerant for cooling the main refrigerant. Therefore, even if the main refrigerant runs short, the branch refrigerant before the expansion valve 16 for the economizer can maintain a supercooling state to prevent the capacity shortage and the occurrence of hunting in the expansion valve 16 for the economizer. Furthermore, the supercooling degree of the main refrigerant can be raised than that a the conventional refrigerating cycle apparatus, and when a refrigerant circulating amount is equal, the refrigerating capacity can be increased. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides an economizer cycle refrigeration apparatus including a compressor having at least an intermediate injection port, an economizer, and an expansion valve for the economizer, and an opening degree of the expansion valve for the economizer in the economizer cycle refrigeration apparatus The present invention relates to an expansion valve control device that controls the valve.

  As a refrigeration cycle apparatus including an intermediate injection compressor, an economizer, and an expansion valve for the economizer, there is one disclosed in Japanese Patent Application Laid-Open No. 2007-205612 (Patent Document 1).

  In this refrigeration cycle apparatus, as shown in FIG. 4, a compressor 1, an oil separator 2, a condenser 3, an economizer 4, in which a low pressure stage compression chamber 1a and a high pressure stage compression chamber 1b are connected in two stages, The main expansion valve 6 and the evaporator 7 are provided with a circulating refrigerant flow path that is sequentially connected. Hereinafter, the refrigerant circulating through the circulation refrigerant flow path is referred to as a main refrigerant. Further, this refrigeration cycle apparatus branches from the circulating refrigerant flow path on the output side of the condenser 3 and introduces the refrigerant decompressed by the second expansion valve 5 into the economizer 4, and the economizer 4 After the heat exchange is performed, a branch channel that returns to the low-pressure stage compression chamber 1a of the compressor 1 is provided. Hereinafter, the refrigerant passing through the branch flow path is referred to as a branch refrigerant.

  FIG. 5 shows a Mollier diagram according to the refrigeration cycle apparatus shown in FIG. In FIG. 5, “a” indicates the suction port of the compressor 1, “b” indicates the discharge port of the compressor 1, “c” indicates the outlet of the condenser 3, and “e” indicates the economy of the main refrigerant. "F" indicates the outlet of the main expansion valve 6, and "g" indicates a point on the saturated liquid line at the outlet pressure of the economizer 4 of the branched refrigerant.

  In the above configuration, the outlet pressure of the economizer 4 of the branched refrigerant is taken in, and the saturated liquid temperature (temperature at the point “g” in FIG. 5) at the outlet pressure is calculated. Then, a difference between the main refrigerant temperature at the outlet of the economizer 4 and the saturated liquid temperature obtained by the above calculation is obtained as an approach temperature, and a second expansion valve composed of an electronic expansion valve is set so that the approach temperature becomes a desired temperature. By controlling the opening degree of 5, an increase in the refrigerating capacity by the economizer cycle is always obtained effectively.

  However, the conventional refrigeration cycle apparatus has the following problems. FIG. 6 shows the relationship between the distance from the main refrigerant inlet side and the refrigerant temperature in the economizer 4 regarding the main refrigerant and the branched refrigerant. As shown in FIG. 4, the refrigerant exiting the condenser 3 is divided into the main refrigerant that flows through the circulation refrigerant flow path and the branch refrigerant that flows through the branch flow path. The branch refrigerant flowing through the branch flow path is decompressed by the second expansion valve 5 and then flows into the economizer 4 together with the main refrigerant flowing through the circulation refrigerant flow path.

  As shown in FIG. 6, the temperatures of the main refrigerant and the branch refrigerant immediately after flowing into the economizer 4 have a large temperature difference due to the decompression of the branch refrigerant by the second expansion valve 5. Then, the low-temperature and low-pressure branch refrigerant evaporates by taking latent heat of evaporation from the main refrigerant while flowing in the economizer 4 from B1 to B2 in FIG. 4, and at the point “i” in FIG. , The branched refrigerant enters the superheated steam region near the outlet of the economizer 4, and the temperature of the superheated steam refrigerant rises as shown in FIG.

  On the other hand, the main refrigerant is parallel to the branch refrigerant, and flows in the economizer 4 from A1 to A2 in the same direction as the branch refrigerant in FIG. At that time, as shown in FIG. 6, when the branched refrigerant is in the saturation region, the branched refrigerant is deprived of the latent heat of vaporization and cooled, and the temperature of the main refrigerant decreases. However, if the branched refrigerant enters the superheated steam region and the temperature rises, the temperature of the main refrigerant will not decrease.

Therefore, the degree of supercooling of the main refrigerant is reduced, and the refrigeration effect (the amount of change in specific enthalpy of the main refrigerant in the evaporator 7 is “fa”) is reduced. Therefore, there is a problem that the refrigerating capacity is reduced when the refrigerant circulation amount is the same. In addition, the cooling effect by the said branch refrigerant | coolant in the economizer 4 is "hj" in FIG.
JP 2007-205612 A

  Therefore, an object of the present invention is to provide an economizer cycle refrigeration apparatus capable of increasing the degree of supercooling of the main refrigerant at the economizer outlet.

In order to solve the above problems, the economizer cycle refrigeration apparatus of the present invention is:
A compressor having a suction port, a discharge port, and an intermediate injection port;
A condenser for condensing the refrigerant discharged from the discharge port of the compressor;
A first expansion mechanism that depressurizes the refrigerant condensed in the condenser;
An evaporator that evaporates the refrigerant decompressed by the first expansion mechanism and returns the evaporated refrigerant to the suction port of the compressor;
A branch flow path having one end connected to the circulating refrigerant flow path between the condenser and the first expansion mechanism and the other end connected to the intermediate injection port of the compressor;
A second expansion mechanism interposed in the branch flow path;
An upstream side of the connection point of the branch flow path in the circulation refrigerant flow path and a downstream side of the second expansion mechanism in the branch flow path are arranged so that the refrigerant flowing in both flow paths becomes a counter flow. An economizer heat exchanger for exchanging heat between the refrigerants flowing through the two flow paths,
A first temperature sensor for detecting an outlet temperature of the refrigerant flowing through the circulating refrigerant flow path from the economizer heat exchanger;
A second temperature sensor for detecting an inlet temperature of the refrigerant flowing through the branch channel to the economizer heat exchanger;
And a control device that controls the opening degree of the second expansion mechanism based on the temperature detected by the first temperature sensor and the temperature detected by the second temperature sensor.

  According to the above configuration, the refrigerant flowing through the circulation refrigerant flow path after the heat exchange with the refrigerant flowing through the branch flow path (hereinafter referred to as branch refrigerant) in the economizer heat exchanger (hereinafter referred to as main refrigerant). ) Is diverted to the branch flow path and introduced again into the economizer heat exchanger, and used as the branch refrigerant for cooling the main refrigerant. Therefore, even if the main refrigerant runs short of the refrigerant, the branched refrigerant before the second expansion mechanism can maintain a supercooled state, and a part of the main refrigerant condensed by the condenser is removed from the economizer. As in the case of introduction into the heat exchanger, it is possible to prevent the second expansion mechanism from being short of capacity or causing hunting.

  At that time, the main refrigerant after heat exchange in the economizer heat exchanger is depressurized by the second expansion mechanism interposed in the branch refrigerant, and then the economizer heat exchanger Supplied as a branching refrigerant. Furthermore, the main refrigerant and the branch refrigerant in the economizer heat exchanger are in counterflow. Accordingly, the inlet / outlet temperature of the branched refrigerant with respect to the economizer heat exchanger is sufficiently lower than the outlet / inlet temperature of the main refrigerant with respect to the economizer heat exchanger to allow heat exchange. As a result, the degree of supercooling of the main refrigerant at the outlet of the economizer heat exchanger can be made larger than when part of the condensed main refrigerant is used as the branched refrigerant.

  Further, the outlet temperature of the main refrigerant detected from the economizer heat exchanger detected by the first temperature sensor, and the inlet temperature of the branched refrigerant detected by the second temperature sensor to the economizer heat exchanger. The value of the difference between the outlet temperature of the branched refrigerant and the economizer heat exchanger is sufficiently lower than the inlet temperature of the main refrigerant to the economizer heat exchanger. As described above, the opening degree of the second expansion mechanism can be controlled by the control device. Therefore, it becomes possible to set the degree of supercooling of the main refrigerant larger.

In the economizer cycle refrigeration system of one embodiment,
The control device flows through the branch flow path detected by the second temperature sensor and the outlet temperature of the refrigerant flowing through the circulating refrigerant flow path detected by the first temperature sensor from the economizer heat exchanger. The opening degree of the second expansion mechanism is controlled so that the difference value between the refrigerant and the inlet temperature to the economizer heat exchanger becomes a preset target value.

  According to this embodiment, for example, by setting the target value so that the temperature efficiency of the economizer heat exchanger becomes the target temperature efficiency, the temperature efficiency of the economizer heat exchanger is the optimum target. Heat exchange between the main refrigerant and the branch refrigerant in the economizer heat exchanger is controlled so as to achieve temperature efficiency.

  That is, according to the present invention, the degree of supercooling of the main refrigerant at the outlet of the economizer heat exchanger can be set larger, and the main refrigerant and the branch in the economizer heat exchanger can be set. Heat exchange with the refrigerant can be performed efficiently.

In the economizer cycle refrigeration system of one embodiment,
The target value is a fixed value set in advance so that the refrigerant on the outlet side in the branch flow path in the economizer heat exchanger becomes wet steam with a target dryness.

  According to this embodiment, the target value at the time of opening degree control of the second expansion mechanism by the control device is that the branch refrigerant on the outlet side of the economizer heat exchanger is the wet steam having the target dryness. It is set to a fixed value. Therefore, when the heat exchange between the main refrigerant and the branch refrigerant in the economizer heat exchanger is performed, the branch refrigerant does not become superheated steam, and the heat exchange in the economizer heat exchanger is efficiently performed. It can be carried out.

  Further, the target value is a fixed value. Therefore, it is not necessary to change the target value even if the conditions of the economizer cycle vary, and the opening degree control of the second expansion mechanism is facilitated.

In the economizer cycle refrigeration system of one embodiment,
A supercooling degree measurement unit for measuring the supercooling degree at the outlet of the economizer heat exchanger in the refrigerant flowing through the circulating refrigerant flow path;
The target value is a value proportional to the supercooling degree set in advance based on the supercooling degree measured by the supercooling degree measuring unit and the target temperature efficiency of the economizer heat exchanger.

  According to this embodiment, the main refrigerant in the economizer heat exchanger is obtained by setting a proportional constant for the supercooling degree in the target value to a value based on the target temperature efficiency of the economizer heat exchanger. And the branch refrigerant are controlled so that the temperature efficiency of the economizer heat exchanger becomes a target optimum temperature efficiency based on the degree of supercooling measured by the degree of supercooling measurement unit. The

  As is clear from the above, the economizer cycle refrigeration apparatus of the present invention again separates the main refrigerant after the heat exchange with the branch refrigerant in the economizer heat exchanger into the branch flow path. Since the refrigerant is introduced into the economizer heat exchanger and used as the branch refrigerant for cooling the main refrigerant, the branch refrigerant before the second expansion mechanism remains in a supercooled state even when the main refrigerant becomes insufficient. It can be maintained, and it is possible to prevent the second expansion mechanism from causing insufficient capacity and hunting.

  At that time, the main refrigerant after heat exchange in the economizer heat exchanger is supplied as the branched refrigerant to the economizer heat exchanger after being depressurized by the second expansion mechanism, and Since the main refrigerant and the branch refrigerant are counterflowed, the inlet / outlet temperature of the branch refrigerant with respect to the economizer heat exchanger is more than the outlet / inlet temperature of the main refrigerant with respect to the economizer heat exchanger. Can be made sufficiently low. Therefore, the degree of supercooling of the main refrigerant at the outlet of the economizer heat exchanger can be increased.

  Further, the outlet temperature of the main refrigerant detected from the economizer heat exchanger detected by the first temperature sensor, and the inlet temperature of the branched refrigerant detected by the second temperature sensor to the economizer heat exchanger. The value of the difference between the outlet temperature of the branched refrigerant and the economizer heat exchanger is sufficiently lower than the inlet temperature of the main refrigerant to the economizer heat exchanger. Thus, the opening degree of the second expansion mechanism can be controlled by the control device, and the degree of supercooling of the main refrigerant can be set larger.

  Also, the outlet temperature of the main refrigerant detected by the first temperature sensor from the economizer heat exchanger and the economizer heat exchange of the branched refrigerant detected by the second temperature sensor by the control device. If the opening degree of the second expansion mechanism is controlled so that the value of the difference from the inlet temperature to the vessel becomes a preset target value, the target value can be set to, for example, the economizer heat exchanger By setting the temperature efficiency of the economizer heat exchanger to be the target temperature efficiency, the main refrigerant in the economizer heat exchanger and the Heat exchange with the branching refrigerant can be controlled.

  That is, the degree of supercooling of the main refrigerant at the outlet of the economizer heat exchanger can be set larger, and heat exchange between the main refrigerant and the branched refrigerant in the economizer heat exchanger can be performed. It can be done efficiently.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a refrigerant circuit diagram of the economizer cycle refrigeration apparatus of the present embodiment.

  In this economizer cycle refrigeration apparatus, as shown in FIG. 1, an intermediate injection compressor 11 having an intermediate injection port 11a, a condenser 12, an economizer 13, a main expansion valve 14 as the first expansion mechanism, and The evaporator 15 is provided with a circulating refrigerant flow path that is sequentially connected. Hereinafter, the refrigerant circulating through the circulation refrigerant flow path is referred to as a main refrigerant. Further, the economizer cycle refrigeration apparatus branches from the circulating refrigerant flow path between the economizer 13 and the main expansion valve 14, and the economizer expansion valve 16 as the second expansion mechanism in order from the upstream side. An economizer 13 is interposed, the refrigerant decompressed by the economizer expansion valve 16 is introduced into the economizer 13, and heat exchange with the main refrigerant is performed by the economizer 13, and then the intermediate injection compressor 11. A branch flow path that returns to the intermediate injection port 11a is provided. Hereinafter, the refrigerant passing through the branch flow path is referred to as a branch refrigerant.

  FIG. 2 shows a Mollier diagram related to the economizer cycle refrigeration apparatus shown in FIG. In FIG. 2, “a ′” indicates the suction port of the intermediate injection compressor 11, “b ′” indicates the discharge port of the intermediate injection compressor 11, “c ′” indicates the outlet of the condenser 12, and “ “e ′” indicates the outlet of the economizer 13, and “f ′” indicates the outlet of the main expansion valve 14. Further, “k” indicates the outlet of the branch refrigerant economizer expansion valve 16, and “j ′” indicates the outlet of the branch refrigerant economizer 13.

  Thus, in the present embodiment, a part of the main refrigerant after heat exchange with the branch refrigerant in the economizer 13 is again introduced into the economizer 13 to cool the main refrigerant. It is used as the above-mentioned branch refrigerant. Therefore, in the case of the conventional refrigeration cycle apparatus disclosed in Patent Document 1 used as the branched refrigerant for introducing a part of the main refrigerant condensed in the condenser into the economizer and cooling the main refrigerant. In contrast, the main point of the branched refrigerant in the economizer 13 is shifted by shifting the introduction point of the branched refrigerant to the economizer 13 from the conventional “h ′” to “k” as shown in FIG. The cooling effect per unit flow rate of the refrigerant can be increased from the conventional “h ′ to j ′” to “k to j ′”.

  FIG. 3 shows the relationship between the distance from the main refrigerant inlet side and the refrigerant temperature in the economizer 13 regarding the main refrigerant and the branched refrigerant. As shown in FIG. 1, the refrigerant exiting the economizer 13 is divided into the main refrigerant flowing through the circulation refrigerant flow path and the branch refrigerant flowing through the branch flow path. The branch refrigerant flowing through the branch flow path is decompressed by the economizer expansion valve 16 and then introduced into the economizer 13 together with the main refrigerant flowing through the circulation refrigerant flow path.

  As shown in FIG. 3, the temperature of the branched refrigerant at the position B1 immediately after being introduced into the economizer 13 is the main temperature at the position A2 from the economizer 13 due to the decompression by the economizer expansion valve 16. The temperature is lower than the refrigerant temperature. The low-temperature and low-pressure branched refrigerant evaporates from the main refrigerant while flowing in the economizer 13 from B1 to B2 in FIG. 1 (that is, from the downstream side to the upstream side of the circulating refrigerant flow path). When the latent heat is removed and evaporated and the saturated gas line is reached at the point “i ′” in FIG. 2, the branched refrigerant enters the superheated steam region near the outlet of the economizer 13, and as shown in FIG. The temperature rises.

  On the other hand, the main refrigerant is counterflow to the branch refrigerant, and flows in the economizer 13 from A1 to A2 in the opposite direction to the branch refrigerant in FIG. At that time, as shown in FIG. 3, the superheated steam region in which the temperature of the branched refrigerant rises is in the vicinity of the outlet of the economizer 13, and in the main refrigerant, in the vicinity of the inlet of the economizer 13. The temperature of the branch refrigerant in the superheated steam region is sufficiently lower than the temperature in the vicinity of the entrance of the economizer 13 in the main refrigerant, and the main refrigerant is cooled by the branch refrigerant and the temperature decreases. Go. Furthermore, when the branch refrigerant exits the superheated steam region and enters the saturation region, the branch refrigerant deprives the latent heat of evaporation and further cools, and the temperature of the main refrigerant further decreases.

  Therefore, according to the present embodiment, the degree of supercooling of the main refrigerant can be made larger than in the case of the conventional refrigeration cycle apparatus disclosed in Patent Document 1, and the refrigeration effect (the main refrigerant in the evaporator 15 can be reduced). The specific enthalpy change amount “f′˜a ′”) can be increased. Therefore, when the refrigerant circulation amount is the same, the refrigeration capacity can be increased.

  By the way, as in the case of the conventional refrigeration cycle apparatus disclosed in Patent Document 1, the branched refrigerant for introducing a part of the main refrigerant condensed in a condenser into an economizer to cool the main refrigerant. When the refrigerant is used near the outlet of the condenser (when the gas-liquid two-phase state is reached), the refrigerant in that state flows into the second expansion valve. It will lead to. On the other hand, in the present embodiment, the branched refrigerant is branched after heat exchange in the economizer 13, so even if the main refrigerant runs short of the refrigerant, it is in front of the expansion valve 16 for the economizer. The branched refrigerant can maintain a supercooled state, and the economizer expansion valve 16 does not cause insufficient capacity or hunting.

  Furthermore, in the economizer cycle refrigeration apparatus in the present embodiment, a first temperature sensor 17 for detecting the liquid temperature of the main refrigerant is attached to the outlet (A2) of the economizer 13 in the circulating refrigerant flow path. Moreover, the 2nd temperature sensor 18 which detects the temperature of the said branch refrigerant | coolant is attached to the inlet (B1) of the economizer 13 in the said branch flow path. Then, based on the temperature signal from the first temperature sensor 17 and the temperature signal from the second temperature sensor 18, the control device 19 causes the outlet temperature of the economizer 13 in the main refrigerant and the economizer 13 in the branch refrigerant. A difference from the inlet temperature is obtained as an approach temperature, and the opening degree of the economizer expansion valve 16 formed of an electronic expansion valve is controlled so that the approach temperature becomes a desired temperature.

  In this way, the controller 19 expands the economizer so that the difference between the outlet temperature of the economizer 13 in the main refrigerant and the inlet temperature of the economizer 13 in the branched refrigerant becomes a desired temperature T1. By controlling the opening degree of the valve 16, as can be seen from FIG. 3, the cooling effect of the main refrigerant by the branch refrigerant in the economizer 13 can be set to a desired value. Therefore, according to the present embodiment, the degree of supercooling of the main refrigerant can be set larger, and the refrigeration effect and the refrigeration capacity can be further increased.

  That is, according to this embodiment, it is possible to always effectively obtain an increase in the refrigerating capacity by the economizer cycle.

  By the way, the approach temperature is specifically determined so that the economizer 13 can be used at the highest efficiency point.

  Normally, when the opening degree of the economizer expansion valve 16 is controlled, the discharge of the intermediate injection compressor 11 is used when the low pressure side pressure in the economizer cycle is lower and the high pressure side pressure is higher. In order to prevent the gas temperature from becoming excessively high, a compressor protection control for reducing the compressor temperature by supplying wet refrigerant mixed with liquid refrigerant from the intermediate injection port 11a according to the discharge pipe temperature is used together. ing. However, since the responsiveness of the compressor protection control depending on the discharge pipe temperature is poor, hunting is likely to occur, and the intermediate injection compressor 11 repeats an overheated state and a wet state, so that the reliability of the intermediate injection compressor 11 is improved. May fall.

  Therefore, in the present embodiment, the opening degree of the economizer expansion valve 16 is controlled so that the economizer 13 can be used at the highest efficiency point. By doing this, the state of the branch refrigerant on the outlet side of the economizer 13 in the branch flow path becomes a gas-liquid two-phase state with a dryness of about “0.8”, and thus the compressor protection by the discharge pipe temperature The control does not interfere with each other, and the opening degree of the economizer expansion valve 16 is stabilized.

  More specifically, for example, when the economizer 13 is designed so that the temperature efficiency becomes “0.85 to 0.90”, the temperature efficiency of the economizer 13 becomes “0.8”. The target value of the approach temperature is determined. Here, “temperature efficiency η” is “supercooling degree SC at the outlet of the economizer 13 in the main refrigerant” and “(outlet temperature TL of the economizer 13 in the main refrigerant) − (economic in the branched refrigerant)”. The inlet temperature Tm) of the mizer 13 = temperature difference α ”. Therefore, when “temperature difference α” is expressed by “supercooling degree SC” and “temperature efficiency η” and “temperature efficiency η” is “0.8”, “temperature difference α = supercooling degree SC × ( 1/4) ”.

  That is, in the present embodiment, the control device 19 determines that the approach temperature, which is the difference between the outlet temperature of the economizer 13 in the main refrigerant and the inlet temperature of the economizer 13 in the branched refrigerant, is the circulating refrigerant flow path. The degree of opening of the expansion valve 16 for the economizer is controlled so that the degree of supercooling SC at the outlet of the economizer 13 becomes 1/4. By doing so, the branch refrigerant on the outlet side of the economizer 13 in the branch flow path is in a gas-liquid two-phase state with a dryness of about “0.8”, so the superheated steam region shown in FIG. 3 is eliminated. The entire branch flow path in the economizer 13 is a saturated area. Therefore, heat exchange between the main refrigerant and the branched refrigerant in the economizer 13 can be performed more efficiently. Further, interference due to compressor protection control due to the discharge pipe temperature is eliminated, and the opening of the economizer expansion valve 16 can be stabilized.

  The “degree of supercooling SC at the outlet of the circulating refrigerant passage in the economizer 13” is a third temperature sensor (not shown) attached to the outlet of the condenser 12 in the circulating refrigerant passage. The control device 19 determines the difference between the outlet temperature of the condenser 12 in the main refrigerant detected by the third temperature sensor and the outlet temperature of the economizer 13 in the main refrigerant detected by the first temperature sensor 17. It can be obtained by seeking. That is, in the present embodiment, the first temperature sensor 17, the third temperature sensor, and the control device 19 constitute the supercooling degree measuring unit.

  By the way, in the above-mentioned, the said control apparatus 19 is calculating the difference of "the outlet temperature of the economizer 13 in the said main refrigerant | coolant" and "the inlet temperature of the economizer 13 in the said branch refrigerant | coolant" as the said approach temperature. . However, when the opening degree control of the economizer expansion valve 16 is more strictly performed, the inlet pressure of the economizer 13 in the branch flow path is changed to the second temperature sensor 18 that detects the temperature of the branch refrigerant. Install the pressure sensor to detect. The control device 19 first uses a table stored in, for example, a ROM (Read Only Memory) (not shown) provided in the control device 19 based on the pressure signal from the pressure sensor. The “saturated liquid temperature corresponding to the inlet pressure of the economizer 13 in the branched refrigerant” is calculated. Then, the difference between “the outlet temperature of the economizer 13 in the main refrigerant” and “the saturated liquid temperature corresponding to the inlet pressure of the economizer 13 in the branched refrigerant” is calculated to be the approach temperature. desirable.

  However, the use of the second temperature sensor 18 is more advantageous in terms of cost than the use of the pressure sensor.

  In the above description, the target value of the approach temperature is “1/4 of the degree of supercooling SC”. Thus, when the target value is a function of the degree of supercooling SC, the degree of supercooling SC varies depending on the balance between the size of the economizer 13 and the circulation amount of the refrigerant. Therefore, the opening control of the expansion valve 16 for the economizer becomes complicated. Therefore, the “temperature difference α” is calculated from the maximum value SCmax of the degree of supercooling SC that appears in the economizer cycle refrigeration apparatus, using the relational expression “temperature difference α = supercooling degree SC × (1/4)”. It is also possible to set the target value to a fixed value by determining the obtained “temperature difference α” as the target value of the approach temperature. For example, assuming that the maximum value SCmax = 32 ° C. at the wet limit where the degree of supercooling SC is maximum, 32/4 ° C. = 8 ° C. is set as the target value of the approach temperature.

  As described above, in the present embodiment, a part of the main refrigerant after heat exchange with the branch refrigerant is performed in the economizer 13 again to cool the main refrigerant. It is used as the above-mentioned branch refrigerant. Therefore, even if the main refrigerant runs out of refrigerant, the branch refrigerant before the economizer expansion valve 16 can maintain a supercooled state, and a part of the main refrigerant condensed by the condenser is used as an economizer. As in the case of introduction, it is possible to prevent the economizer expansion valve 16 from being insufficient in capacity or causing hunting. Further, a part of the main refrigerant after the heat exchange with the branch refrigerant in the economizer 13 is decompressed by the economizer expansion valve 16 and then introduced into the economizer 13 again. The branch refrigerant is counterflowed. Therefore, the degree of supercooling of the main refrigerant can be made larger than that of the conventional refrigeration cycle apparatus disclosed in Patent Document 1, and the refrigeration capacity can be increased when the refrigerant circulation amount is the same.

  Further, the controller 19 controls the economizer expansion valve 16 so that the difference between the outlet temperature of the economizer 13 in the main refrigerant and the inlet temperature of the economizer 13 in the branched refrigerant becomes a desired temperature. The opening is controlled. Therefore, the cooling effect of the main refrigerant by the branched refrigerant in the economizer 13 can be set to a desired value. That is, the degree of supercooling of the main refrigerant can be set larger, and the refrigeration effect and refrigeration capacity can be further increased.

  Further, the approach temperature for controlling the opening of the economizer expansion valve 16 by the control device 19 is set to 1/4 of the degree of supercooling SC at the outlet of the economizer 13 in the circulating refrigerant flow path. . Therefore, the branch refrigerant on the outlet side of the economizer 13 in the branch flow path is in a gas-liquid two-phase state (that is, wet steam) with a dryness of about “0.8”, and the main refrigerant in the economizer 13 And heat exchange with the branching refrigerant can be performed more efficiently. Furthermore, since the interference by the compressor protection control due to the discharge pipe temperature is eliminated, the opening degree of the economizer expansion valve 16 can be stabilized.

  In addition, if the approach temperature is set to “maximum value SCmax × (1/4)” using the maximum value SCmax of the supercooling degree SC that appears, the target value can be set to a fixed value. The opening degree control of the expansion valve 16 can be simplified.

  In the above embodiment, the approach temperature is set to “1/4 of the supercooling degree SC” or “1/4 of the maximum value of the supercooling degree SCmax”. Is not limited to / 4 ", and can be appropriately set according to the design temperature efficiency of the economizer 13 so that the dryness of the branched refrigerant on the outlet side of the economizer 13 is about" 0.8 ". Good. Further, the approach temperature is not limited to “the degree of supercooling SC or a value proportional to the maximum value SCmax”, and the branch refrigerant on the outlet side of the economizer 13 in the branch flow path has a dryness of “0”. It is only necessary to be “a temperature difference between the outlet temperature of the economizer 13 in the main refrigerant and the inlet temperature of the economizer 13 in the branched refrigerant” so that wet steam becomes about .8 ”.

  Further, the intermediate injection compressor 11 may be a compressor having a two-stage compression chamber as in the conventional refrigeration cycle apparatus disclosed in Patent Document 1, or may be a single-stage intermediate injection compressor. That is, any compressor having an intermediate injection port may be used, and it is not necessary to limit the type of the compressor. Further, the same effect can be obtained even in a two-stage compression cycle constituted by two compressors and an intermediate injection port instead of the intermediate injection compressor.

It is a refrigerant circuit figure in the economizer cycle refrigerating device of this invention. It is a Mollier diagram which concerns on the economizer cycle freezing apparatus shown in FIG. It is a figure which shows the relationship between the distance from the main refrigerant | coolant inlet side in the economizer regarding the main refrigerant | coolant and branch refrigerant | coolant in FIG. 1, and refrigerant | coolant temperature. It is a refrigerant circuit diagram in the conventional refrigeration cycle apparatus. It is a Mollier diagram which concerns on the refrigerating-cycle apparatus shown in FIG. It is a figure which shows the relationship between the distance from the main refrigerant | coolant inlet side in the economizer regarding the main refrigerant | coolant and branch refrigerant | coolant in FIG. 4, and refrigerant | coolant temperature.

Explanation of symbols

11 ... Intermediate injection compressor,
11a ... Intermediate injection port,
12 ... Condenser,
13 ... Economizer,
14 ... main expansion valve,
15 ... Evaporator,
16 ... Expansion valve for economizer,
17 ... 1st temperature sensor,
18 ... second temperature sensor,
19: Control device.

Claims (4)

A compressor (11) having a suction port, a discharge port, and an intermediate injection port (11a);
A condenser (12) for condensing the refrigerant discharged from the discharge port of the compressor (11);
A first expansion mechanism (14) for depressurizing the refrigerant condensed in the condenser (12);
An evaporator (15) for evaporating the refrigerant decompressed by the first expansion mechanism (14) and returning the evaporated refrigerant to the suction port of the compressor (11);
One end is connected to the circulating refrigerant flow path between the condenser (12) and the first expansion mechanism (14), and the other end is connected to the intermediate injection port (11a) of the compressor (11). Branched flow paths,
A second expansion mechanism (16) interposed in the branch flow path;
The refrigerant flowing in both the flow paths is opposed to the upstream side of the connection point of the branch flow paths in the circulation refrigerant flow path and the downstream side of the second expansion mechanism (16) in the branch flow paths. An economizer heat exchanger (13) that is disposed in the heat exchanger to perform heat exchange between the refrigerants flowing through the two flow paths,
A first temperature sensor (17) for detecting an outlet temperature of the refrigerant flowing through the circulating refrigerant flow path from the economizer heat exchanger (13);
A second temperature sensor (18) for detecting an inlet temperature of the refrigerant flowing through the branch channel to the economizer heat exchanger (13);
A control device (19) for controlling the opening of the second expansion mechanism (16) based on the temperature detected by the first temperature sensor (17) and the temperature detected by the second temperature sensor (18); An economizer cycle refrigeration system characterized by that. In the economizer cycle refrigeration apparatus according to claim 1,
The control device (19) includes an outlet temperature of the refrigerant flowing through the circulating refrigerant flow path detected by the first temperature sensor (17) from the economizer heat exchanger (13), and the second temperature sensor ( 18), the second expansion mechanism so that the difference between the refrigerant flowing through the branch flow path and the inlet temperature to the economizer heat exchanger (13) is a preset target value. The economizer cycle refrigeration apparatus characterized by controlling the opening degree of (16). In the economizer cycle refrigeration apparatus according to claim 2,
The target value is a fixed value set in advance so that the refrigerant on the outlet side in the branch flow path in the economizer heat exchanger (13) becomes wet steam with a target dryness. A featured economizer cycle refrigeration system. In the economizer cycle refrigeration apparatus according to claim 2,
A supercooling degree measuring unit for measuring the supercooling degree at the outlet of the economizer heat exchanger (13) in the refrigerant flowing through the circulating refrigerant flow path;
The target value is a value proportional to the supercooling degree set in advance based on the supercooling degree measured by the supercooling degree measuring unit and the target temperature efficiency of the economizer heat exchanger (13). An economizer cycle refrigeration system characterized by

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