JP2009109065A - Refrigeration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide both prevention of shortage of a lubricant in a compressor and energy-saving in a region of a small operating capacity of the compressor, in a refrigeration system. <P>SOLUTION: This refrigeration device 50 includes: a main refrigerating cycle 60; a liquid injection circuit 71; and a controller 15. The main refrigeration cycle 60 is composed of: operating capacity-variable compressors 1a, 1b; a condenser 2; a first flow channel 6a of a supercooling heat exchanger 6; pressure reducing mechanisms 11a, 11b; and evaporators 4a, 4b. The liquid injection circuit 71 includes: a liquid injection pipe 21 branched from the main refrigeration cycle 60 and communicated with an intermediate pressure portion of the compressors 1a, 1b; a flow rate control means 7 adjusting a flow rate of divided refrigerant; and a second flow channel 6b for supercooling the refrigerant of the first flow channel 6a by allowing the divided refrigerant to flow therein. The controller 15 adjusts a refrigerating capacity by controlling the flow rate control means 7 according to load variation of the main refrigeration cycle 60. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus, and is particularly suitable for a refrigeration apparatus including a refrigerator or an air conditioner equipped with a compressor having a variable operation capacity.

  The conventional refrigeration system controls the operating capacity of the compressor by combining multiple compressors or making the drive frequency variable, and changes the refrigeration capacity according to the load fluctuation of the low-pressure equipment unit. .

  During operation of the refrigeration system, a part of the lubricating oil that lubricates the compressor flows out of the compressor to the external refrigeration cycle, and returns to the compressor after circulating through the refrigeration cycle. The amount of oil going up from the compressor and the amount of oil returning to the compressor change as the operating capacity of the compressor (refrigerant circulation amount) changes, but in the region where the operating capacity of the compressor is small, the amount of oil return However, there is a problem that the refrigeration apparatus cannot be operated due to insufficient lubricating oil in the compressor.

  Therefore, as in the refrigeration apparatus described in Japanese Patent Laid-Open No. 8-200902 (Patent Document 1), the load on the low-pressure equipment unit (indoor unit) is reduced, and the operating capacity of the refrigeration apparatus is small. Thus, it has been devised to perform an oil return operation in which the operating capacity of the compressor is increased to increase the oil return amount.

Japanese Patent Laid-Open No. 8-200902

  However, in the refrigeration apparatus of Patent Document 1, in the region where the cooling load of the low-pressure equipment unit is small and the operating capacity of the compressor is small, the oil return operation is performed to increase the operating capacity of the compressor. There was a problem that energy-saving performance was impaired due to cooling. In addition, when the low-pressure equipment unit is a unit that cools the object to be cooled such as food, the temperature in the low-pressure equipment unit decreases more than necessary, so the amount of frost formation on the evaporator also increases, There was a problem that the temperature change also increased and the freshness of the object to be cooled was impaired.

  An object of the present invention is to obtain a refrigeration apparatus capable of achieving both prevention of lack of lubricating oil in a compressor and energy saving in a region where the operating capacity of the compressor is small.

  In order to achieve the above-mentioned object, the present invention provides a compressor having a variable operating capacity, a condenser for condensing gas refrigerant compressed by the compressor, and supercooling heat for supercooling the refrigerant condensed by the condenser. A main flow path having a first flow path of the exchanger, a pressure reducing mechanism for depressurizing the liquid refrigerant supercooled in the first flow path, an evaporator for evaporating the refrigerant depressurized by the pressure reducing mechanism, and a refrigerant pipe for sequentially connecting them. Liquid injection pipe branched from the refrigeration cycle and between the condenser and the pressure reducing mechanism and communicated with the intermediate pressure portion of the compressor, and a flow rate control means for adjusting the flow rate of the refrigerant divided into the liquid injection pipe A liquid injection circuit having a second flow path of the supercooling heat exchanger for flowing the refrigerant adjusted by the flow control means to supercool the refrigerant in the first flow path, the compressor, and the flow control means Control And a controller that, said controller, in response to the load variation of the main refrigeration cycle is to have a configuration to adjust the refrigerating capacity by controlling the flow control means.

A more preferable specific configuration example of the present invention is as follows.
(1) The liquid injection circuit is branched between the condenser and the first flow path, or between the first flow path and the pressure reducing mechanism, and communicates with an intermediate pressure portion of the compressor. thing.
(2) A pressure sensor for detecting the pressure on the suction side of the compressor is provided, and the controller estimates a load fluctuation of the main refrigeration cycle based on a pressure value detected by the pressure sensor, and controls the flow rate control means. To do.
(3) The compressor uses a variable capacity compressor with a variable driving frequency, and the controller controls the variable capacity compressor according to the load fluctuation of the main refrigeration cycle to increase the refrigerating capacity. While adjusting, the adjustment range of the refrigerating capacity by the control of the variable capacity compressor is divided from the adjustment range of the refrigerating capacity by the control of the flow rate control means.
(4) The adjustment range of the refrigerating capacity by the control of the flow rate control means is positioned above the adjustment range of the refrigerating capacity by the control of the variable capacity compressor.
(5) The operation capacity is variable by combining a plurality of the compressors.

  According to the refrigeration apparatus of the present invention, it is possible to achieve both prevention of compressor lubricant shortage and energy saving in a region where the operating capacity of the compressor is small.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. The same reference numerals in the drawings of the respective embodiments indicate the same or equivalent.
(First embodiment)
The refrigeration apparatus of 1st Embodiment of this invention is demonstrated using FIGS. 1-4.

  First, the entire refrigeration apparatus 50 of the present embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating an overall configuration of a refrigeration apparatus 50 according to the present embodiment. The refrigeration apparatus 50 of the present embodiment is an example of a multi-chiller for large stores such as a supermarket where the load greatly fluctuates, but the present invention is also applicable to an air conditioner or the like.

  The refrigeration apparatus 50 includes an apparatus main body unit 51 disposed outdoors and a plurality of low-pressure device units 52a and 52b disposed indoors. These units 51, 52 a and 52 b are connected via the refrigerant pipe 20. The plurality of low-voltage equipment units 52a and 52b are connected in parallel.

  The refrigeration apparatus 50 includes a main refrigeration cycle 60, a liquid injection circuit 70, a control system 80, a cooling fan 12, and the like.

  The main refrigeration cycle 60 includes a plurality of compressors 1a, 1b, a condenser 2, a receiver 5, a supercooler 3, a first flow path 6a of the supercooling heat exchanger 6, a plurality of decompression mechanisms 11a, 11b, and a plurality. The evaporators 4a and 4b, and the refrigerant pipe 20 that sequentially connects these evaporators 4a and 4b.

  The compressors 1a and 1b are composed of an inverter-controlled variable operating capacity scroll compressor or a rotary compressor. Note that the operating capacity may be made variable by a constant speed compressor combined with a plurality of units.

  Injection ports are formed in the intermediate pressure portions of the compressors 1a and 1b. The condenser 2 and the subcooler 3 are configured by a cross fin heat exchanger, and outdoor air is ventilated by the cooling fan 12. A liquid receiver 5 is provided between the condenser 2 and the supercooler 3, and the liquid refrigerant in the liquid receiver 5 flows out to the supercooler 3.

  The supercooling heat exchanger 6 includes a heat exchanger (for example, a plate heat exchanger) in which a first flow path 6a and a second flow path 6b are formed, and a refrigerant flowing through the first flow path 6a and a second flow path 6b. Heat exchange with the refrigerant flowing through

  The decompression mechanisms 11a and 11b are constituted by expansion valves and are disposed in the low-pressure equipment units 52a and 52b, respectively. The evaporators 4a and 4b are disposed in the low-pressure equipment units 52a and 52b, respectively, and cool an object to be cooled such as food. The decompression mechanism 11a and the evaporator 4a are connected in series, the decompression mechanism 11b and the evaporator 4b are connected in series, and these series circuits are connected in parallel.

  The liquid injection circuit 70 includes a first liquid injection circuit 71 for adjusting the refrigerating capacity, and a second liquid injection circuit 72 for preventing a temperature rise of the compressor. The first liquid injection circuit 71 adjusts the refrigerating capacity by controlling the degree of supercooling by the supercooling heat exchanger 6.

  The first liquid injection circuit 71 includes the first flow rate control means 7, the second flow path 6 b of the supercooling heat exchanger 6, the first liquid injection pipe 21 that sequentially connects these, and the like. One end of the first liquid injection pipe 21 communicates with the first liquid refrigerant outlet 16 that is downstream of the supercooler 3 and upstream of the supercooling heat exchanger 6. The other side of the first liquid injection pipe 21 is branched into a plurality on the outflow side of the second flow path 6b, and the other end is communicated with the injection ports of the compressors 1a and 1b.

  The second liquid injection circuit 72 includes a plurality of second flow rate control means 9a and 9b, a second liquid injection pipe 22, and the like. One end of the second liquid injection pipe 22 communicates with the second liquid refrigerant outlet 17 that is downstream of the second flow path 6b and upstream of the decompression mechanisms 11a and 11b. The other side of the second liquid injection pipe 22 is branched into a plurality, and the other side end is communicated with the injection port of each compressor 1a, 1b. The second flow rate control means 9a and 9b are provided in the branched pipe portions of the second liquid injection pipe 22, respectively.

  The control system 80 includes a pressure sensor 13, a discharge gas temperature sensor 14, a controller 15, and the like installed in the apparatus main body unit 51, and control devices installed in the low-pressure device units 52 a and 52 b.

  The pressure sensor 13 is provided to detect the load of the main refrigeration cycle 60 (load in the low-pressure equipment units 52 a and 52 b), detects the pressure on the suction side of the compressor 1, and inputs it to the controller 15. It is configured as follows. The discharge gas temperature sensor 14 is provided to detect the temperatures of the compressors 1a and 1b, and includes a plurality of temperature sensors 14a and 14b. Each discharge gas temperature sensor 14 a, 14 b is configured to detect the discharge gas temperature of each compressor 1 a, 1 b and input it to the controller 15. The controller 15 controls the compressors 1a and 1b, the first flow rate control means 7, and the second flow rate control means 9a and 9b based on the pressure and temperature detected by the pressure sensor 13 and the discharge gas temperature sensor 14.

  Next, the basic operation of the main refrigeration cycle 60 will be described with reference to FIGS. 1 and 2. FIG. 2 is a Mollier diagram related to the refrigeration apparatus of FIG.

  The gas refrigerant sucked into the compressors 1a and 1b is compressed by the compressors 1a and 1b and discharged as a high-temperature and high-pressure gas refrigerant. The discharged gas refrigerant is condensed by exchanging heat with outdoor air in the condenser 2 to be dissipated and flows into the liquid receiver 5. The liquid refrigerant in the liquid receiver 5 is guided to the supercooler 3 and is supercooled by exchanging heat with outdoor air in the supercooler 3.

  The liquid refrigerant supercooled by the supercooler 3 is guided to the first flow path 6 a of the supercooling heat exchanger 6. Here, when the refrigerant is flowing through the second flow path 6b, the refrigerant is further cooled by exchanging heat with the refrigerant.

  The liquid refrigerant flowing out of the first flow path 6a is decompressed by the decompression mechanisms 11a and 11b of the low-pressure equipment units 52a and 52b, and becomes a gas-liquid mixed refrigerant. The gas-liquid mixed refrigerant is evaporated by the evaporators 4a and 4b, absorbs heat from the surroundings (cools the object to be cooled), becomes a low-temperature and low-pressure gas refrigerant, and returns to the compressors 1a and 1b.

  The Mollier diagram of the main refrigeration cycle 60 in a state where the liquid injection circuit 70 is not operating is as shown by the dotted line 61 in FIG.

  Next, the basic operation of the first liquid injection circuit 71 will be described with reference to FIGS.

  When the cooling load fluctuation occurs in the low-pressure device units 52a and 52b, the pressure value detected by the pressure sensor 13 is input to the controller 15, and the pressure value determined according to the cooling temperature of the low-pressure device units 52a and 52b The first flow control means 7 of the first liquid injection circuit 71 is controlled to adjust the refrigeration capacity.

  That is, the controller 15 operates the first flow rate control means 7 based on the pressure detected by the pressure sensor 13. Thereby, a part of the liquid refrigerant flowing in the main refrigeration cycle supercooled by the supercooler 3 is diverted from the first liquid refrigerant outlet 16 to the first liquid injection pipe 21. The divided liquid refrigerant is decompressed by the first flow rate control means 7, evaporated in the second flow path 6b, and absorbed heat from the liquid refrigerant in the first flow path 6a (the liquid refrigerant in the first flow path 6a is further removed). After supercooling), it is injected into the injection port of each compressor 1a, 1b.

  The Mollier diagram of the main refrigeration cycle 60 in a state in which the first liquid injection circuit 71 is operating is as shown by the solid line indicated by the reference numeral 62 in FIG. As is apparent from FIG. 2, the refrigeration capacity of the refrigeration apparatus 50 can be increased by operating the first injection circuit 71. That is, the refrigeration capacity is represented by multiplication of the refrigerant circulation amount and the enthalpy difference, but the first liquid injection circuit 71 is based on the enthalpy difference Δq1 in the state where the refrigerant circulation amount is the same and the first liquid injection circuit 71 does not operate. Since the enthalpy difference Δq2 in the state in which is operated becomes larger, the refrigeration capacity is increased.

  The control system 80 is configured to control the opening degree of the first flow rate control means 7 according to the pressure detected by the pressure sensor 13 (in other words, according to the load fluctuation of the main refrigeration cycle 60). Yes. The refrigerating capacity can be changed by controlling the opening degree of the first flow rate control means 7 and changing the pressure reduction amount (changing the amount of refrigerant flowing through the first liquid injection circuit 71). That is, by increasing the opening degree of the first flow rate control means 7, the amount of refrigerant flowing through the first liquid injection circuit 71 can be increased, and the amount of supercooling in the first flow path can be increased to increase the refrigerating capacity. Can be increased.

  By operating the first liquid injection circuit 71 in this way, the degree of supercooling of the liquid refrigerant can be increased and the discharge temperature of the compressor 1 can be lowered as shown by the solid line 62 in the Mollier diagram of FIG. can do. By changing the degree of supercooling of the liquid refrigerant supplied to the low pressure device units 52a and 52b by the first flow rate control means 7, the refrigerating capacity is controlled without changing the refrigerant circulation amount, and the low pressure device units 52a and 52b It is possible to prevent a reduction in the amount of oil return when the cooling load is low.

  Next, the basic operation of the second liquid injection circuit 72 will be described with reference to FIG.

  When the controller 15 operates the second flow rate control means 9a, 9b based on the detected temperatures of the discharge gas temperature sensors 14a, 14b, one of the liquid refrigerant supercooled in the first flow path of the supercooling heat exchanger 6 is obtained. The part is diverted from the second liquid outlet 17 to the second liquid injection pipe 22. The diverted liquid refrigerant is decompressed by the second flow rate control means 9a, 9b and then injected into the injection ports of the compressors 1a, 1b.

  Thus, by operating the 2nd liquid injection circuit 72, the compressor 1a, 1b can be cooled, the temperature rise can be prevented, and a reliability improvement can be aimed at.

  Next, the control operation of the pressure sensor 13 and the change in the refrigerating capacity based thereon will be described with reference to FIGS. FIG. 3 is a flowchart showing the control operation of the refrigeration apparatus 50 of FIG. 1, and FIG. 4 is a diagram for explaining an example of a change in refrigeration capacity based on the control operation of FIG.

  When the load fluctuation of the low-pressure equipment units 52a and 52b, which is the load fluctuation of the main refrigeration cycle 60, occurs, the detected pressure value Ps of the pressure sensor 13 is detected (step S1) and set by the low-pressure equipment units 52a and 52b. A set pressure range corresponding to the low-pressure side equipment cooling temperature is taken in (step S2).

  Next, it is determined whether or not the detected pressure value Ps is higher than the set pressure range (step S3). If it is determined that the detected pressure value Ps is higher, it is assumed that the refrigeration capacity needs to be increased. It is determined whether it is maximum (step S4).

  Here, when it is determined that the refrigerant circulation amount is not maximum, the compressor 1a is configured to increase the refrigerant circulation amount by increasing the capacity of the compressors 1a and 1b based on the detected pressure value Ps. 1b is inverter-controlled (step S5). With this compressor capacity control, as shown in the compressor capacity control region of FIG. 4, the refrigeration capacity is adjusted in the range of 50% to 100% and the refrigeration capacity in the range of 40% to 80%.

  If it is determined in step S4 that the refrigerant circulation amount is the maximum, it is not possible to expect an increase in the refrigerating capacity due to the compressor operation capacity control, so it is determined whether the subcooling flow rate is the maximum ( Step S6). This supercooling flow rate is the amount of refrigerant flowing through the second flow path 6b of the supercooling heat exchanger 6, and is determined by the opening degree of the first flow rate control means 7 of the first liquid injection circuit 71. It is the amount of refrigerant. Therefore, by determining whether the first flow rate control means 7 has the maximum opening, it is possible to determine whether the subcooling flow rate is maximum.

  If it is determined that the subcooling flow rate is not maximized, the opening degree of the first flow rate control means 7 is increased based on the detected pressure value Ps to increase the subcooling flow rate. The first flow rate control means 7 is controlled (step S7). With this supercooling flow rate control, as shown in the supercooling flow rate control region of FIG. 4, the refrigeration capacity is adjusted in the range of 80% to 100% with the refrigerant circulation rate being 100%.

  If it is determined in step S6 that the subcooling flow rate is maximized, the refrigeration capacity is maximized, and the operating state is maintained (step S8).

  If the detected pressure value Ps is not higher than the set pressure range in step S3, it is determined whether the detected pressure value Ps is lower than the set pressure range (step S9). If it is determined here that it is low, it is assumed that it is necessary to reduce the refrigerating capacity, so it is determined whether the subcooling flow rate is minimized (step S10).

  If it is determined in this determination that the subcooling flow rate is not at a minimum, the opening degree of the first flow rate control means 7 is reduced based on the detected pressure value Ps to decrease the subcooling flow rate. Thus, the first flow rate control means 7 is controlled (step S11).

  If it is determined in step S10 that the subcooling flow rate is not minimized, based on the detected pressure value Ps, the capacity of the compressors 1a and 1b is reduced to reduce the refrigerant circulation rate. The compressors 1a and 1b are controlled by an inverter, and the oil return operation is intermittently combined (step S12). By compressor capacity control combined with this oil return operation, as shown in FIG. 4, the refrigeration capacity is changed within a range of 50% or less and a refrigerating capacity within a range of 40% or less.

  If it is determined in step S9 that the detected pressure value Ps is not lower than the set pressure range, the detected pressure value Ps is determined to be within the set pressure range, and the operation state is maintained (step S13).

  When the required maximum refrigeration capacity is 100% and the lower limit of the refrigerant circulation amount by the capacity control of the compressors 1a and 1b that does not cause a shortage of lubricating oil is 50%, the above-described control of this embodiment For example, by adjusting the supercooling flow rate control by the first liquid injection circuit 71 in the high refrigerating capacity range (80% or more range), as shown in the solid line characteristic diagram of FIG. The refrigerating capacity can be adjusted to a low range (up to 40%) by operating capacity control of 1a and 1b. On the other hand, in the conventional example without supercooling flow rate control, the lower limit of the refrigerating capacity is as high as 50% as shown in the characteristic diagram shown by the dotted line in FIG.

As described above, according to the present embodiment, the oil return for increasing the operating capacity of the compressors 1a and 1b in the region where the cooling load of the low-pressure equipment units 52a and 52b is small and the operating capacity of the compressors 1a and 1b is small. It is not necessary to perform the operation, and it is possible to achieve both prevention of lack of lubricating oil and energy saving, and to maintain the freshness of the food stored in the low-pressure device units 52a and 52b.
(Second Embodiment)
Next, the refrigeration apparatus 50 according to the second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a diagram showing the overall configuration of the refrigeration apparatus 50 according to the second embodiment of the present invention. The second embodiment is different from the first embodiment in the points described below, and the other points are basically the same as those in the first embodiment, and thus redundant description is omitted.

  In the second embodiment, the liquid refrigerant outlet 16 is provided on the downstream side of the second flow path 6b and on the upstream side of the decompression mechanisms 11a and 11b. Thereby, the supercooling in the supercooling heat exchanger 6 can be performed more efficiently.

It is a figure which shows the whole structure of the freezing apparatus of 1st Embodiment of this invention. FIG. 2 is a Mollier diagram related to the refrigeration apparatus of FIG. 1. It is a flowchart figure which shows the control action of the freezing apparatus of FIG. It is a figure explaining an example of the change of the refrigerating capacity based on the control action of FIG. It is a figure which shows the whole structure of the freezing apparatus of 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1a, 1b ... Compressor, 2 ... Condenser, 3 ... Supercooler, 4a, 4b ... Evaporator, 5 ... Liquid receiver, 6 ... Supercooling heat exchanger, 6a ... 1st flow path, 6b ... 2nd Flow path, 7 ... first flow rate control means, 9a, 9b ... second flow rate control means, 11a, 11b ... pressure reducing mechanism, 12 ... cooling fan, 13 ... pressure sensor, 14a, 14b ... discharge gas temperature sensor, 15 ... Controller, 16 ... First liquid refrigerant outlet, 17 ... Second liquid refrigerant outlet, 20 ... Refrigerant pipe, 21 ... First liquid injection pipe, 22 ... Second liquid injection pipe, 50 ... Refrigeration apparatus , 51 ... apparatus main body unit, 52a, 52b ... low pressure device unit, 60 ... main refrigeration cycle, 70 ... liquid injection circuit, 71 ... first liquid injection circuit, 72 ... second liquid injection circuit, 80 ... control system.

Claims (6)

Compressor with variable operating capacity, condenser for condensing gas refrigerant compressed by the compressor, first flow path of a supercooling heat exchanger for supercooling the refrigerant condensed by the condenser, the first flow path A decompression mechanism for decompressing the liquid refrigerant supercooled in the evaporator, an evaporator for evaporating the refrigerant decompressed by the decompression mechanism, a main refrigeration cycle having a refrigerant pipe for sequentially connecting them,
A liquid injection pipe branched from between the condenser and the pressure reducing mechanism and communicated with the intermediate pressure portion of the compressor, a flow rate control means for adjusting a flow rate of the refrigerant divided into the liquid injection pipe, and the flow rate control A liquid injection circuit having a second flow path of the supercooling heat exchanger for flowing the refrigerant adjusted by the means to supercool the refrigerant in the first flow path;
A controller for controlling the compressor and the flow rate control means,
The said controller controls the said flow control means according to the load fluctuation | variation of the said main refrigerating cycle, and adjusts refrigerating capacity, The refrigerating device characterized by the above-mentioned.   2. The liquid injection circuit according to claim 1, wherein the liquid injection circuit is branched from between the condenser and the first flow path, or between the first flow path and the pressure reducing mechanism, and communicates with an intermediate pressure portion of the compressor. A refrigeration apparatus.   2. The pressure sensor according to claim 1, further comprising a pressure sensor that detects a pressure on the suction side of the compressor, wherein the controller estimates a load fluctuation of the main refrigeration cycle based on a pressure value detected by the pressure sensor, and the flow rate control unit. A refrigeration apparatus characterized by controlling the temperature.   2. The variable capacity compressor according to claim 1, wherein the compressor has a variable drive frequency, and the controller controls the variable capacity compressor in accordance with a load fluctuation of the main refrigeration cycle. A refrigeration apparatus characterized by adjusting the capacity and dividing the adjustment range of the refrigeration capacity by the control of the variable capacity compressor and the adjustment range of the refrigeration capacity by the control of the flow rate control means.   5. The refrigeration apparatus according to claim 4, wherein the refrigeration capacity adjustment range controlled by the flow rate control means is positioned above the refrigeration capacity adjustment range controlled by the variable capacity compressor.   2. The refrigeration apparatus according to claim 1, wherein an operating capacity is variable by combining a plurality of the compressors.

Images