JP2014005962A - Refrigeration cycle device and hot water generator including the same - Google Patents

Abstract

A refrigeration cycle apparatus excellent in control stability and energy saving is provided.
A heat source side refrigerant circuit 2 for exchanging heat with a heat source side heat medium and a user side refrigerant circuit 3 for exchanging heat with a user side heat medium are thermally connected via a cascade heat exchanger 22. In the refrigeration cycle apparatus 1A including the original refrigeration cycle, the suction pressure of the use side compressor 31 is determined based on the heat source side heat medium temperature and the use side heat medium temperature, and the capacity of the heat source side compressor 21 is set with the suction pressure as a target. Since the control of the capacity of the use side compressor 31 is performed based on the use side heat medium temperature and the suction pressure, the control target value is stabilized and the stability of each refrigeration cycle is improved. The influence of interference between the refrigeration cycles is reduced, a highly efficient operation state can be maintained, and energy saving can be improved.
[Selection] Figure 1

Description

  The present invention relates to a refrigeration cycle apparatus including a dual refrigeration cycle in which a use side refrigerant circuit and a heat source side refrigerant circuit are connected via a cascade heat exchanger.

  Conventionally, a refrigeration cycle apparatus and a hot water generator of this type use a dual refrigeration cycle for the purpose of generating high-temperature hot air or hot water, or low-temperature cold air or cold water (for example, (See Patent Document 1).

  FIG. 4 shows a conventional refrigeration cycle apparatus described in Patent Document 1. As shown in FIG.

  As shown in FIG. 4, the refrigeration cycle apparatus 100 includes a heat source side refrigerant circuit 110 that circulates the heat source side refrigerant, a use side refrigerant circuit 120 that circulates the use side refrigerant, and a hot water circuit 130 that circulates hot water. Yes. The heat source side refrigerant circuit 110 includes a heat source side compressor 111, a heat source side four-way valve 112, a cascade heat exchanger 113 that exchanges heat with a use side refrigerant and functions as a condenser, a heat source side expansion valve 114, and air to exchange heat with an evaporator. The heat source side heat exchanger 115 that functions as a ring is connected by a pipe in a ring shape.

  The use side refrigerant circuit 120 includes a use side compressor 121, a use side four-way valve 122, a use side heat exchanger 123 that exchanges heat with hot water and functions as a condenser, a use side expansion valve 124, and a heat source side refrigerant and heat. A cascade heat exchanger 113 that exchanges and functions as an evaporator is configured to be connected annularly by piping.

  The hot water circuit 130 includes a circulation pump 131, a use side heat exchanger 123 that generates heat by exchanging heat with a use side refrigerant, and a radiator 132 such as a hot water storage tank or a fan convector connected in a ring shape by piping. It is configured.

  Furthermore, the refrigeration cycle apparatus 100 includes a heat source side pressure sensor 151 that detects a pressure (heat source side compressor discharge pressure) Pdl of refrigerant discharged from the heat source side compressor 111, and a refrigerant discharged from the use side compressor 121. A use-side pressure sensor 152 that detects pressure (use-side compressor discharge pressure) Pdu and a compressor control unit 141 are provided.

  The compressor control unit 141 sets a predetermined target heat source side discharge saturation temperature and a predetermined target use side discharge saturation temperature based on a predetermined target hot water temperature that is a temperature target value of hot water at the outlet of the use side heat exchanger 123. The capacity control of the heat source side compressor 111, that is, the compressor discharge refrigerant, is determined so that the heat source side discharge saturation temperature, which is the saturation temperature corresponding to the heat source side compressor discharge pressure Pdl, becomes the target heat source side discharge saturation temperature. Control the amount.

  Further, the capacity control of the use side compressor 121 is performed so that the heat source side discharge saturation temperature, which is a saturation temperature corresponding to the use side compressor discharge pressure Pdu, becomes a predetermined target use side discharge saturation temperature.

JP 2010-196951 A

  However, in the conventional configuration, the capacity control of one compressor is performed because the heat source side compressor individually controls the capacity with the heat source side discharge saturation temperature as a target and the use side compressor with the use side discharge saturation temperature as a target. Is changed, the heat absorption capacity or the heat radiation capacity of the cascade heat exchanger is changed, so that the compressor discharge saturation temperature of the other refrigeration cycle is also changed.

  In this way, the change in the state of one refrigeration cycle affects the state of the other refrigeration cycle, and the hunting phenomenon of the compressor occurs due to interference between the refrigeration cycles, resulting in an efficient and stable refrigeration cycle. It could not be formed and had a problem that the operating efficiency was lowered.

  Further, in the conventional configuration, since the target discharge saturation temperature of each compressor is determined based only on the target temperature of the use side heat medium, depending on the difference between the heat source side heat medium temperature and the use side heat load. Therefore, the target discharge saturation temperature in consideration of the operation efficiency cannot be set, and as a result, there is a problem that energy saving performance is lowered.

  The present invention solves the above-mentioned conventional problems, and by appropriately controlling the operating capacities of the heat source side compressor and the use side compressor, the stability and efficiency of the refrigeration cycle are improved and the energy saving property is high. An object is to provide a refrigeration cycle apparatus.

  In order to solve the conventional problems, a refrigeration cycle apparatus according to the present invention includes a heat source side compressor that compresses a heat source side refrigerant, a cascade heat exchanger that functions as a radiator or an evaporator of the heat source side refrigerant, and a heat source side expansion. Means, a heat source side refrigerant circuit that functions as an evaporator or a condenser of the heat source side refrigerant, a utilization side compressor that compresses the utilization side refrigerant, a radiator or evaporator of the utilization side refrigerant The cascade heat exchanger that functions as a use side heat exchanger, a use side expansion means, an evaporator or a condenser of the use side refrigerant, and exchanges heat between the heat source side refrigerant and the use side refrigerant, Disposed on the heat source side heat exchanger, a first temperature sensor that detects the temperature of the heat source side heat medium that exchanges heat with the heat source side refrigerant, and the user side heat exchanger. The above-mentioned interest A second temperature sensor that detects the temperature of the use side heat medium that exchanges heat with the side refrigerant, a pressure sensor that detects the pressure of the heat source side refrigerant or the use side refrigerant of the cascade heat exchanger, and a control device. And the control device is configured to control the heat source compressor so that a detection value of the pressure sensor becomes a target suction pressure determined based on detection values of the first temperature sensor and the second temperature sensor. In addition to controlling the operation, the control device operates the use-side compressor at a refrigerant circulation amount determined based on a detection value of the second temperature sensor and the target suction pressure. To do.

  As a result, the control target value of the compressor is determined based on the heat medium temperature on the heat source side and the use side where the state change speed is sufficiently slow compared with the pressure, so that the stability of each refrigeration cycle is improved. In addition, it is possible to improve the stability of the entire refrigeration cycle by reducing interference between the refrigeration cycles.

  Also, since the evaporation pressure or condensation pressure of each refrigeration cycle can be estimated from each heat medium temperature, the optimum point of efficiency of the suction refrigerant pressure of the use side compressor or the discharge refrigerant pressure of the heat source side compressor is estimated, It can be operated with high efficiency.

  ADVANTAGE OF THE INVENTION According to this invention, the stability and efficiency of a refrigerating cycle can be provided, and the refrigerating cycle apparatus excellent in energy saving property can be provided.

Schematic configuration diagram of a refrigeration cycle apparatus according to Embodiment 1 of the present invention. Graph showing refrigeration cycle aging during operation in a conventional refrigeration cycle apparatus Flowchart of operation control of the refrigeration cycle apparatus in Embodiment 1 of the present invention. Schematic configuration diagram of a conventional refrigeration cycle apparatus

  The first invention includes a heat source side compressor that compresses the heat source side refrigerant, a cascade heat exchanger that functions as a radiator or evaporator of the heat source side refrigerant, a heat source side expansion means, and an evaporator or condenser of the heat source side refrigerant. A heat source side refrigerant circuit that functions as a heat source side refrigerant circuit, a utilization side compressor that compresses the utilization side refrigerant, a utilization side heat exchanger that functions as a radiator or evaporator of the utilization side refrigerant, and utilization side expansion Means, a use side refrigerant circuit that functions as an evaporator or a condenser of the use side refrigerant and has the cascade heat exchanger that exchanges heat between the heat source side refrigerant and the use side refrigerant, and the heat source side heat A first temperature sensor that is disposed in the exchanger and detects a temperature of a heat source side heat medium that exchanges heat with the heat source side refrigerant, and a use that is disposed in the use side heat exchanger and exchanges heat with the use side refrigerant. Detect the temperature of the side heat medium A second temperature sensor; a pressure sensor that detects a pressure of the heat source side refrigerant or the usage side refrigerant of the cascade heat exchanger; and a control device, wherein the control device has a detection value of the pressure sensor, The operation of the heat source side compressor is controlled so that the target suction pressure is determined based on the detection values of the first temperature sensor and the second temperature sensor, and the control device In the refrigeration cycle apparatus, the side compressor is operated with a refrigerant circulation amount determined based on a detection value of the second temperature sensor and the target suction pressure.

  As a result, the suction pressure of the use side compressor is determined based on the heat medium temperature on the heat source side and the use side, where the rate of change of the state is sufficiently slower than the pressure, so the operating capacity of the use side compressor Is stable.

  Further, since the operation capacity of the use side compressor is stabilized, the influence of interference from the use side refrigerant circuit to the heat source side refrigerant circuit is reduced, and the control stability of the heat source side compressor is improved.

  Further, the evaporation pressure or condensation pressure of the refrigeration cycle in the heat source side refrigerant circuit can be estimated from the heat source side heat medium temperature, and the condensation pressure or evaporation pressure of the refrigeration cycle in the utilization side refrigerant circuit can be estimated from the use side heat medium temperature. it can.

  Thereby, the optimum point of the efficiency of the suction refrigerant pressure of the use side compressor or the discharge refrigerant pressure of the heat source side compressor can be estimated, and the refrigeration cycle can be operated with high efficiency.

  Therefore, it is possible to provide a refrigeration cycle apparatus with improved stability and efficiency and excellent energy saving.

  According to a second aspect of the invention, in particular, in the first aspect of the invention, the control device causes the use side compressor to detect a detected value of the second temperature sensor, the target suction pressure, and a target value of the temperature of the use side heat medium. The operation is performed with the refrigerant circulation amount determined based on the target utilization side heat medium temperature.

  Thereby, the heating capability or the cooling capability required on the use side can be determined by comparing the use heat medium temperature with the predetermined target use-side heat medium temperature. As a result, the operation capacity of the use side compressor can be set according to the required capacity, and the operation operation with insufficient capacity or excessive capacity can be suppressed.

  Therefore, even when the required capacity increases or decreases, high operating efficiency can be maintained and energy saving can be further improved.

  In a third aspect of the invention, particularly in the first or second aspect of the invention, the apparatus further comprises current / power detection means for detecting an operating current or power consumption of the refrigeration cycle apparatus, and the control device sets the target suction pressure to the current power. The correction is made such that the detection value of the detection means becomes small.

  Thereby, it is possible to always control the driving operation so as to reduce the power consumption of the dual refrigeration cycle.

  Therefore, high operating efficiency can be maintained and energy saving can be further improved under various operating environment conditions in the use side refrigerant circuit and the heat source side refrigerant circuit.

  According to a fourth aspect of the present invention, there is provided a warm water generator including the refrigeration cycle apparatus according to any one of the first to third aspects of the invention, wherein the use side heat medium is water or an antifreeze liquid, and the use side heat exchanger The heated use side heat medium is used for at least one of hot water supply and heating.

  Thereby, there is no need to limit a kind of radiator, such as a water-air heat exchanger or an antifreeze-water heat exchanger.

  Therefore, the heat medium heated by the use-side heat exchanger can be widely used for heating equipment (hot air heaters, radiators, floor heating panels, etc.) and hot water supply equipment, and the degree of freedom in using the heat medium is increased. be able to.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a schematic configuration diagram of a refrigeration cycle apparatus and a hot water generator in a first embodiment of the present invention. In FIG. 1, the refrigeration cycle apparatus 1A includes a heat source side refrigerant circuit 2 that circulates a heat source side refrigerant and a use side refrigerant circuit 3 that circulates a use side refrigerant. As the refrigerant, for example, a non-azeotropic refrigerant mixture such as R407C, a pseudo-azeotropic refrigerant mixture such as R410A, or a single refrigerant such as R134a can be used.

  The heat source side refrigerant circuit 2 includes a capacity variable type heat source side compressor 21, a heat source side four-way valve 25, a cascade heat exchanger 22 that exchanges heat with a use side refrigerant and functions as a condenser or an evaporator, a heat source side expansion valve (heat source Side expansion means) 23 and a heat source side heat exchanger 24 functioning as an evaporator or a condenser are connected in an annular shape by piping.

  In addition, the capacity | capacitance here refers to the refrigerant | coolant amount discharged from a compressor for every period. Therefore, by changing the rotation speed of the compressor, the amount of refrigerant discharged from the compressor is controlled, and the discharge pressure of the compressor varies accordingly.

  The use side refrigerant circuit 3 includes a variable capacity type use side compressor 31, a use side four-way valve 35, a use side heat exchanger 32 functioning as a condenser or an evaporator, a use side expansion valve (use side expansion means) 33, and A cascade heat exchanger 22 that exchanges heat with the heat-source-side refrigerant and functions as an evaporator or a condenser is connected in a ring shape by piping.

  The heat source side refrigerant of the heat source side refrigerant circuit 2 and the usage side refrigerant of the usage side refrigerant circuit 3 are independent of each other and do not mix, but are configured to be able to exchange heat via the cascade heat exchanger 22. Yes. As the cascade heat exchanger 22, a double tube heat exchanger or a plate heat exchanger is used.

  In the present embodiment, the refrigeration cycle apparatus 1A constitutes a heating means of a hot water generation apparatus that uses hot water generated by the heating means for hot water supply or heating. In the use side heat exchanger 32, the use side refrigerant and water Heat exchanger is used to heat water. As the use side heat exchanger 32, a double tube heat exchanger or a plate heat exchanger is used.

  Specifically, there is provided a hot water circuit 7 in which a use side heat exchanger 32, a water pump 71, and a radiator 72 such as a hot water storage tank or a fan convector are annularly connected by a pipe, The hot water heated by the heat exchanger 32 is radiated by the radiator 72, and heat storage and heating are performed.

  In normal operation, in the heat source side refrigerant circuit 2, the refrigerant discharged from the heat source side compressor 21 is sent to the cascade heat exchanger 22 via the four-way valve 25, and the usage side refrigerant circuit 3 is supplied from the usage side compressor 31. The discharged refrigerant is sent to the use side heat exchanger 32 via the four-way valve 35.

  On the other hand, in the defrost operation, in the heat source side refrigerant circuit 2, the refrigerant discharged from the heat source side compressor 21 is sent to the heat source side heat exchanger 24 via the four-way valve 25, and the use side refrigerant circuit 3 The refrigerant discharged from the machine 31 is sent to the cascade heat exchanger 22 via the four-way valve 35. In FIG. 1, the direction of refrigerant flow during normal operation is indicated by arrows.

  Hereinafter, the state change of the refrigerant in the normal operation will be described.

  In the heat source side refrigerant circuit 2, the high pressure heat source side refrigerant discharged from the heat source side compressor 21 flows into the cascade heat exchanger 22, and the low pressure use side refrigerant and heat in the refrigeration cycle circulating in the use side refrigerant circuit 3. Replace and dissipate heat. The high-pressure heat-source-side refrigerant that has flowed out of the cascade heat exchanger 22 is decompressed and expanded by the heat-source-side expansion valve 23, and then flows into the heat-source-side heat exchanger 24. The low-pressure heat source side refrigerant flowing into the heat source side heat exchanger 24 absorbs heat from the air and evaporates. The low-pressure heat source side refrigerant evaporated in the heat source side heat exchanger 24 is again sucked into the heat source side compressor 21.

  On the other hand, in the usage-side refrigerant circuit 3, the low-pressure usage-side refrigerant in the refrigeration cycle circulating in the usage-side refrigerant circuit 3 is heated and evaporated by the heat radiation of the heat-source-side refrigerant in the cascade heat exchanger 22. The low-pressure use-side refrigerant evaporated in the cascade heat exchanger 22 is sucked into the use-side compressor 31, compressed to a high pressure in the refrigeration cycle, and then discharged. The high-pressure use-side refrigerant discharged from the use-side compressor 31 flows into the use-side heat exchanger 32 and exchanges heat with the aqueous medium circulating in the hot water circuit 7 by the circulation pump 71 to radiate heat. The high-pressure use-side refrigerant that has flowed out of the use-side heat exchanger 32 is decompressed and expanded by the use-side expansion valve 33 and then flows into the cascade heat exchanger 22 again.

  In the configuration of the refrigeration cycle apparatus 1A of the present embodiment, as described above, the low-pressure use-side refrigerant circulating in the use-side refrigerant circuit 3 is heated by the heat radiation of the high-pressure heat source-side refrigerant circulating in the heat source-side refrigerant circuit 2. Therefore, the condensation temperature of the refrigeration cycle in the use side refrigerant circuit 3 can be higher than the condensation temperature of the refrigeration cycle in the heat source side refrigerant circuit 2.

  Therefore, a high-temperature aqueous medium can be obtained by the heat radiation of the usage-side refrigerant in the usage-side heat exchanger 32.

  However, since each refrigeration cycle formed by the heat source side refrigerant circuit 2 and the use side refrigerant circuit 3 is thermally connected by the cascade heat exchanger 22, the operating capacity of the compressor in one refrigerant circuit has changed. In this case, the heat absorption capability or heat dissipation capability in the cascade heat exchanger 22 changes, and the state of the refrigeration cycle of the other refrigerant circuit also changes.

  That is, since the refrigeration cycle on the heat source side and the use side interfere with each other due to the change in the operation capacity of each compressor, for example, the operation capacity of each compressor is set to a predetermined target value for the discharge pressure of the refrigeration cycle corresponding to each compressor. 2, a hunting phenomenon occurs in each compressor due to a change in the compressor operating capacity, and the discharge pressure of the compressor vibrates in the vicinity of the target value, as shown in FIG. There is a possibility that the operation efficiency is lowered and the energy saving property is impaired.

  In order to operate the dual refrigeration cycle with high efficiency, the heat source side condensing temperature or the use side evaporating temperature in the cascade heat exchanger 22 is set to the evaporation temperature in the heat source side refrigerant circuit 2 and the condensing temperature in the use side refrigerant circuit 3. It is necessary to adjust to an appropriate temperature corresponding to.

  Therefore, in order to generate and utilize a high-temperature aqueous medium in a wide range of applications and environmental conditions while ensuring energy saving, the operating capacities of the heat source side compressor 21 and the use side compressor 31 should be appropriately controlled. is important.

  Hereinafter, the operation of the operation control in the present embodiment will be described.

  The heat source side refrigerant circuit 2 is provided with a first temperature sensor 51 that detects the temperature (air temperature) Ta of the air medium on the air medium inlet side of the heat source side heat exchanger 24. A pressure sensor 61 that detects the pressure (use side suction pressure) Ps of the refrigerant sucked into the side compressor 31 is provided.

  On the other hand, the hot water circuit 7 is provided with a second temperature sensor 52 that detects the temperature (warm water temperature) Tw of the aqueous medium flowing out from the use side heat exchanger 32.

  Further, the control device 4 is provided with a current sensor 41 for detecting the operating current Ia of the refrigeration cycle apparatus 1A.

  Based on the detection values detected by the current sensor 41, the first temperature sensor 51, the second temperature sensor 52, and the pressure sensor 61, the control device 4 rotates the rotation speeds of the heat source side compressor 21 and the use side compressor 31, The switching of the heat source side four-way valve 25 and the use side four way valve 35 and the opening degree of the heat source side expansion valve 23 and the use side expansion valve 33 are operated.

  In the present embodiment, the control device 4 first determines a predetermined pressure target value Pst from the air temperature Ta and the hot water temperature Tw, and then corrects the pressure target value Pst so that the operating current Ia is minimized. However, the operating capacity of the heat source side compressor 21 is controlled so that the use side suction pressure Ps becomes a predetermined pressure target value Pst.

  Further, the control device 4 uses a hot water temperature Tw, a deviation between the hot water temperature Tw and a predetermined target hot water temperature Twt that is a preset target value of the hot water temperature Tw by using an operation remote controller (not shown), The use side compressor 31 is operated at a compressor capacity determined based on the predetermined pressure target value Pst.

Next, capacity control of the heat source side compressor and the use side compressor at the start of normal operation of the control device 4 will be described in detail with reference to the flowchart shown in FIG.

  The control device 4 always operates the timer, and periodically performs the processing from step S1 to step S14 at regular time intervals. The subscript (n) below indicates the number of loops in the control cycle.

  First, the control device 4 detects the air temperature Ta (n) with the first temperature sensor 51, and detects the hot water temperature Tw (n) with the second temperature sensor (step S1). Next, a predetermined pressure target value Pst (n) is calculated and determined by Pst (n) = f {Ta (n), Tw (n)} (step S2).

  The function f {Ta (n), Tw (n)} is a function of the use-side compressor 31 in which the operating efficiency of the refrigeration cycle apparatus 1A becomes substantially maximum under a number of operating conditions based on combinations of the air temperature Ta and the hot water temperature Tw. This is a formula derived by experimentally obtaining the suction pressure Ps.

  Then, the use side suction pressure Ps (n) is detected by the pressure sensor 61 (step S3), and the heat source side compressor 21 is set so that the use side suction pressure Ps (n) is equal to a predetermined pressure target value Pst (n). Is adjusted (step S4).

  Next, the control device 4 calculates a deviation ΔTwt (n) between the predetermined target hot water temperature Twt and the current hot water temperature Tw (n) by ΔTwt (n) = Twt−Tw (n) (step S5). Then, the operating capacity Ru (n) of the use side compressor 31 is calculated and adjusted by Ru (n) = f {ΔTwt (n), Tw (n), Pst (n)} (step S6).

  The function f {ΔTwt (n), Tw (n), Pst (n)} is the relationship between the deviation ΔTwt and the required heating capacity, the heating capacity and the use side compressor in many combinations of the hot water temperature Tw and the pressure target value Pst. The relationship between 31 operating capacities is obtained experimentally, and is derived from these two relationships.

  Thereafter, the control device 4 sets the absolute value ΔTa (n) of the difference between the air temperature Ta (n−1) detected in the previous control cycle and the air temperature Ta (n) detected in the current control cycle to ΔTa (n ) = | Ta (n) −Ta (n−1) | and ΔTa (n) is compared with a predetermined first deviation, and ΔTa (n) is set to a predetermined first value. It is determined whether or not the deviation is less than.

  At the same time, the absolute value ΔTw (n) of the difference between the hot water temperature Tw (n−1) detected in the previous control cycle and the hot water temperature Tw (n) detected in the current control cycle is expressed as ΔTw (n) = | Tw (N) −Tw (n−1) | is calculated and ΔTw (n) is compared with a predetermined second deviation, and ΔTw (n) is less than the predetermined second deviation. It is determined whether or not (step S7).

  If ΔTa (n) is not less than the predetermined first deviation or ΔTw (n) is not less than the predetermined second deviation (NO in step S7), the change in air temperature Ta or hot water temperature Tw is large. Then, it is determined that the refrigeration cycle is not in a stable state, and the process returns to step S1 without correcting the pressure target Pst with the operating current Ia.

  On the other hand, if ΔTa (n) is less than the predetermined first deviation and ΔTw (n) is less than the predetermined second deviation (YES in step S7), the change in the air temperature Ta or the hot water temperature Tw is small, and the refrigeration It is determined that the cycle is in a stable state, and correction of the pressure target Pst by the operating current Ia is executed.

  Therefore, the control device 4 detects the operating current Ia (n) with the current sensor 41 (step S8), and the operating current Ia (n-1) detected in the previous control cycle and the operating current detected in the current control cycle. Ia (n) is compared to determine whether or not the current operating current Ia (n) is less than the previous operating current Ia (n-1) (step S9).

  If the current operating current Ia (n) is less than the previous operating current Ia (n−1) (YES in step S9), it is determined that the operating efficiency has been improved by correcting the current pressure target value Pst, and the coefficient 1 is substituted into A (step S10).

  On the other hand, if the current operating current Ia (n) is greater than or equal to the previous operating current Ia (n−1) (NO in step S9), it is determined that the operating efficiency has decreased due to the correction of the current pressure target value Pst. Then, −1 is assigned to the coefficient A (step S11).

  Next, the control device 4 compares the current pressure target value Pst (n) with the previous pressure target value Pst (n−1), and the current pressure target value Pst (n) is the previous pressure target value Pst ( n-1) It is judged whether it is less than (step S12).

  If the current pressure target value Pst (n) is less than the previous pressure target value Pst (n-1) (YES in step S12), it is determined that the pressure target value Pst is set lower than the previous time in the current control cycle. Then, the current pressure target value Pst (n) is subtracted by multiplying the predetermined amount B by the coefficient A to determine the next pressure target value Pst (n) (step S13), and the process returns to step S3.

  On the other hand, when the current pressure target value Pst (n) is equal to or greater than the previous pressure target value Pst (n-1) (NO in step S12), the pressure target value Pst is set higher than the previous time in the current control cycle. Is added to the current pressure target value Pst (n) multiplied by the coefficient A to determine the next pressure target value Pst (n) (step S14), and the process returns to step S3.

  In this way, by comparing the current value and pressure target value in a certain control loop with the current value and pressure target value in the previous control loop, the pressure target value Pst is corrected so that the power consumption is always reduced. .

  As described above, in the present embodiment, the control device 4 including the current sensor 41 that detects the operating current Ia of the refrigeration cycle apparatus 1A and the first temperature that detects the air temperature Ta in the heat source side refrigerant circuit 2. The sensor 51, the use side refrigerant circuit 3 includes a pressure sensor 61 that detects the use side suction pressure Ps, and the warm water circuit 7 includes a second temperature sensor 52 that detects the warm water temperature Tw.

  Further, the control device 4 determines a predetermined pressure target value Pst based on the air temperature Ta detected by the first temperature sensor 51 and the hot water temperature Tw detected by the second temperature sensor 52, and the pressure sensor 61. The capacity of the heat source side compressor 21 is controlled so that the detected value becomes the pressure target value Pst, and the use side compressor 31 is preset with the hot water temperature Tw detected by the second temperature sensor 52. The compressor is operated with a compressor capacity determined from a predetermined target hot water temperature Twt and a pressure target value Pst.

  As a result, the operating capacity of the use side compressor 31 is determined based on the hot water temperature Tw and the air temperature Ta, which are less affected by the capacity change of the heat source side compressor 21 and whose state change speed is sufficiently slower than the pressure. Therefore, interference due to the capacity change of the heat source side compressor 21 can be suppressed, and the operation capacity of the use side compressor 31 is stabilized.

  In addition, since the operation capacity of the use side compressor 31 is stabilized, the use side suction pressure that is the capacity control target of the heat source side compressor 21 is stabilized by reducing the interference effect of the refrigeration cycle. The control stability of the machine 21 is improved.

  Further, the heating capacity required on the use side can be determined by comparing the hot water temperature Tw with a predetermined target hot water temperature Twt. As a result, the operating capacity of the use-side compressor 31 can be set according to the required capacity, and operation with insufficient capacity or excessive capacity can be prevented.

  Further, the evaporation pressure of the refrigeration cycle in the heat source side refrigerant circuit 2 can be estimated from the air temperature Ta, and the condensation pressure of the refrigeration cycle in the use side refrigerant circuit 3 can be estimated from the hot water temperature Tw. As a result, in the operating two-way refrigeration cycle, the suction refrigerant pressure of the use-side compressor 31 with high efficiency can be estimated. Therefore, in various operating states, the target refrigerant pressure with high operating efficiency is set and controlled. It becomes possible.

  Therefore, the state of the refrigeration cycle is stabilized and the operation is performed under the optimum target value, thereby improving the energy saving performance of the dual refrigeration cycle.

  Further, the control device 4 corrects the pressure target value Pst so that the operating current Ia detected by the current sensor 41 is minimized.

  As a result, the capacity of the heat source side compressor 21 is controlled so that the operating current of the dual refrigeration cycle is always reduced.

  Therefore, it is possible to always operate with high operation efficiency with respect to changes in a wide range of operating environment conditions on the use side and the heat source side.

  In FIG. 1, the pressure sensor 61 is provided in the vicinity of the outlet of the cascade heat exchanger 22 in the usage-side refrigerant circuit 3, but the pressure sensor 61 includes the usage-side expansion valve 33 and the usage-side in the usage-side refrigerant circuit 3. As long as it is on the piping through which the low-pressure refrigerant flows between the compressors 31, it may be provided at any position. Further, the pressure sensor 61 may be provided at any position as long as it is on a pipe through which the high-pressure refrigerant flows between the heat source side compressor 21 and the heat source side expansion valve 23 in the heat source side refrigerant circuit 2.

  Further, in the present embodiment, the second temperature sensor detects the temperature of the aqueous medium flowing out from the use side heat exchanger 32, but even with the temperature of the aqueous medium flowing into the use side heat exchanger 32, The temperature of the aqueous medium in the flow path of the use side heat exchanger 32 may be used.

  In the present embodiment, the pressure target value Pst is corrected so that the operating current Ia detected by the current sensor 41 is minimized. However, the power target is used to minimize the power consumption using the power sensor. Pst may be corrected.

  Furthermore, in the embodiment of the present invention, the aqueous medium is heated by the refrigeration cycle in the use-side refrigerant circuit 3, but the medium to be heated may be brine, and the radiator 72 may be a radiator or a fan controller. Vectors, floor heating panels and hot water storage tanks may be used.

As described above, the refrigeration cycle apparatus according to the present invention can improve the stability and energy saving of the refrigeration cycle by appropriately controlling the operating capacity of the compressor, so that hot water generation, hot water supply, air conditioning harmony It can be applied as a refrigeration cycle apparatus used for such applications.

DESCRIPTION OF SYMBOLS 1A Refrigeration cycle apparatus 2 Heat source side refrigerant circuit 3 Use side refrigerant circuit 4 Control device 21 Heat source side compressor 22 Cascade heat exchanger 23 Heat source side expansion valve (heat source side expansion means)
24 heat source side heat exchanger 31 use side compressor 32 use side heat exchanger 33 use side expansion valve (use side expansion means)
41 Current sensor (current power detection means)
51 First temperature sensor 52 Second temperature sensor 61 Pressure sensor

Claims (4)

Heat source side compressor that compresses the heat source side refrigerant, cascade heat exchanger that functions as a radiator or evaporator of the heat source side refrigerant, heat source side expansion means, heat source side heat that functions as an evaporator or condenser of the heat source side refrigerant A heat source side refrigerant circuit having an exchanger;
A user-side compressor that compresses a user-side refrigerant, a user-side heat exchanger that functions as a radiator or evaporator of the user-side refrigerant, a user-side expansion means, and functions as an evaporator or condenser of the user-side refrigerant, The cascade heat exchanger for exchanging heat between the heat source side refrigerant and the utilization side refrigerant, and a utilization side refrigerant circuit,
A first temperature sensor that is disposed in the heat source side heat exchanger and detects a temperature of a heat source side heat medium that exchanges heat with the heat source side refrigerant;
A second temperature sensor that is disposed in the use side heat exchanger and detects a temperature of a use side heat medium that exchanges heat with the use side refrigerant;
A pressure sensor for detecting the pressure of the heat source side refrigerant or the use side refrigerant of the cascade heat exchanger;
A control device,
The control device operates the heat source side compressor so that a detection value of the pressure sensor becomes a target suction pressure determined based on detection values of the first temperature sensor and the second temperature sensor. And control
The said control apparatus operates the said utilization side compressor by the refrigerant | coolant circulation amount determined based on the detected value of the said 2nd temperature sensor, and the said target suction pressure, The refrigeration cycle apparatus characterized by the above-mentioned. The control device determines the use side compressor based on a detection value of the second temperature sensor, the target suction pressure, and a target use side heat medium temperature that is a target value of the temperature of the use side heat medium. 2. The refrigeration cycle apparatus according to claim 1, wherein the refrigeration cycle apparatus is operated with a circulating amount of refrigerant. Current power detection means for detecting an operating current or power consumption of the refrigeration cycle apparatus is provided, and the control device corrects the target suction pressure so that a detection value of the current power detection means becomes small. The refrigeration cycle apparatus according to claim 1 or 2. The use side heat medium is water or antifreeze, and the use side heat medium heated by the use side heat exchanger is used for at least one of hot water supply and heating. A warm water generator comprising the refrigeration cycle apparatus according to any one of 1 to 3.

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