Refrigeration cycle, air conditioner and method

Abstract

To provide a refrigerating cycle, an air conditioner and a method for properly adjusting an opening of an expansion valve.SOLUTION: This refrigerating cycle includes an expansion valve 23 and a compressor 24, and circulates a refrigerant, and includes a target delivery pressure calculating part 330 for calculating a range of a target value of the pressure of the refrigerant delivered from the compressor 24, and an expansion valve opening control part 350 for controlling opening of the expansion valve 23 so that the pressure becomes within the range calculated by the target delivery pressure calculating part 330.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a refrigeration cycle, an air conditioning apparatus, and a method for achieving power saving and improved compressor reliability. [Background technology]

[0002] The expansion valve in a refrigeration cycle throttles and expands high-pressure liquid refrigerant, forcing it into the evaporator. If the expansion valve is opened too wide, liquid refrigerant is more likely to return to the compressor. If the opening is too small, the pressure difference between before and after the expansion valve becomes too large, resulting in excessive refrigerant superheat at the evaporator outlet. Therefore, it is necessary to appropriately adjust the opening of the expansion valve.

[0003] In this regard, for example, International Publication No. 2016 / 171052 (Patent Document 1) discloses a technology for adjusting the opening degree of an expansion valve based on the discharge temperature of the refrigerant from the compressor and the degree of superheat of the refrigerant at the evaporator outlet.

[0004] However, Patent Document 1 does not take into consideration the deterioration of compressor reliability due to an increase in the discharge pressure of the refrigerant discharged from the compressor. In particular, when the operating frequency of the compressor is low during heating operation, adjusting the opening of the expansion valve based on the discharge temperature or superheat of the refrigerant tends to throttle the expansion valve when the discharge temperature decreases, resulting in an increase in discharge pressure. Therefore, there has been a demand for a further technology to improve operating efficiency and compressor reliability by controlling the expansion valve independently of the discharge temperature or superheat of the refrigerant. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2016 / 171052 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above-mentioned problems in the prior art, and has an object to provide a refrigeration cycle, an air conditioning apparatus, and a method for appropriately adjusting the opening degree of an expansion valve. [Means for solving the problem]

[0007] That is, according to the present invention, A refrigeration cycle including an expansion valve and a compressor, in which a refrigerant circulates, a calculation means for calculating a range of target values ​​for the pressure of the refrigerant discharged from the compressor; a control means for controlling the opening degree of the expansion valve so that the pressure falls within the range calculated by the calculation means; and A refrigeration cycle is provided, including: [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a refrigeration cycle, an air conditioning apparatus, and a method for appropriately adjusting the opening degree of an expansion valve. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing a schematic configuration of an air conditioning apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram showing a hardware configuration included in the control device of the present embodiment. [Figure 3] FIG. 2 is a software block diagram included in the air conditioning apparatus of the present embodiment. [Figure 4] 4 is a flowchart showing a process for controlling the opening degree of the expansion valve in the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described below with reference to embodiments, but the present invention is not limited to the embodiments described below. In the drawings referred to below, the same reference numerals will be used for common elements, and their description will be omitted as appropriate.

[0011] FIG. 1 is a diagram showing the schematic configuration of an air conditioner 1 of this embodiment. The air conditioner 1 of this embodiment is mainly composed of an outdoor unit 2 and an indoor unit 3. The outdoor unit 2 is composed of a control device 20, an outdoor heat exchanger 21, an outdoor fan 22, an expansion valve 23, a compressor 24, and a four-way valve 25. The indoor unit 3 is composed of an indoor heat exchanger 31 and an indoor fan 32. Note that the configuration of the air conditioner 1 in FIG. 1 is one example and does not limit the embodiment. Therefore, in other embodiments, the air conditioner 1 may be equipped with, for example, multiple indoor units 3.

[0012] The operation of the refrigeration cycle in this embodiment will now be described with reference to Fig. 1. Note that the following description will be given taking as an example the refrigeration cycle when the air conditioner 1 is in heating operation. The arrows shown in Fig. 1 indicate the flow of refrigerant during heating operation, and the solid lines in the four-way valve 25 indicate the connection relationship of the refrigerant path during heating operation. Therefore, it should be noted that when the air conditioner 1 is in cooling operation, the refrigerant flows in the direction opposite to the arrows in Fig. 1, and the connection of the refrigerant path in the four-way valve 25 is also as shown by the dashed lines.

[0013] In heating operation, the refrigerant that has exchanged heat with the air in the indoor space in the indoor heat exchanger 31 and become a liquid flows into the outdoor unit 2. In the outdoor unit 2, the liquid refrigerant is expanded by the expansion valve 23 and flows into the outdoor heat exchanger 21 as a low-temperature, low-pressure liquid refrigerant. When the air conditioner 1 is in heating operation, the outdoor heat exchanger 21 acts as an evaporator. In the outdoor heat exchanger 21, heat is exchanged between the refrigerant and air blown by the outdoor fan 22. Therefore, the low-temperature, low-pressure liquid refrigerant exchanges heat with the outdoor air in the outdoor heat exchanger 21 and evaporates, becoming a low-temperature, low-pressure gas refrigerant.

[0014] The refrigerant gasified by the outdoor heat exchanger 21 passes through the four-way valve 25 and is drawn into the compressor 24. In the compressor 24, the gas refrigerant is compressed, and changes from a low-temperature, low-pressure gas refrigerant to a high-temperature, high-pressure gas refrigerant. The refrigerant discharged from the compressor 24 passes through the four-way valve 25 and flows into the indoor unit 3.

[0015] In the indoor unit 3, heat is exchanged between the air blown by the indoor fan 32 and the refrigerant, and the heated air is discharged into the indoor space. When the air conditioner 1 is in heating operation, the indoor heat exchanger 31 acts as a condenser. Thereafter, the refrigerant repeats the above-mentioned refrigeration cycle, and the air conditioner 1 performs heating operation.

[0016] The outdoor unit 2 in the embodiment to be described includes a control device 20 for controlling the operation of the refrigeration cycle components that make up the outdoor unit 2. The outdoor unit 2 and the indoor unit 3 may also include sensors that measure the temperature of the refrigerant, sensors that measure the pressure of the refrigerant, and sensors that measure the outside air temperature and room temperature. The control device 20 of this embodiment can control the operation of the components that make up the refrigeration cycle based on the measurements taken by the various sensors. The control device 20 may also be included in the indoor unit 3.

[0017] 2 is a diagram showing the hardware configuration included in the control device 20 of this embodiment. The control device 20 includes a CPU 201, a RAM 202, a ROM 203, a refrigeration cycle component I / F 204, a sensor I / F 205, and a communication I / F 206, and each piece of hardware is connected via a bus.

[0018] The CPU 210 is a device that executes programs that control the operation of various refrigeration cycle components and performs predetermined processing. The RAM 220 is a volatile storage device that provides an execution space for the programs executed by the CPU 210 and is used for storing and expanding programs and data. The ROM 230 is a non-volatile storage device that stores programs executed by the CPU 210, firmware, etc.

[0019] The refrigeration cycle component I / F 204 is an interface that connects the various components of the refrigeration cycle that make up the air conditioner 1 with the control device 20. The refrigeration cycle component I / F 204 of this embodiment can output control signals for, for example, controlling the rotation speed of the outdoor fan 22, the opening degree of the expansion valve 23, the operating frequency of the compressor 24, and switching the refrigerant path of the four-way valve 25.

[0020] The sensor I / F 205 is an interface that connects various sensors to the control device 20. The control device 20 can acquire, via the sensor I / F 205, measurement values ​​(for example, temperature, pressure, etc.) measured by the various sensors.

[0021] The communication I / F 206 is an interface that connects the outdoor unit 2 and the indoor unit 3. The communication I / F 206 of this embodiment can communicate, for example, measurement values ​​of various sensors and various control signals between the outdoor unit 2 and the indoor unit 3.

[0022] So far, we have explained the hardware that constitutes the air conditioning apparatus 1 of this embodiment. Next, we will explain the functional means executed by each piece of hardware in this embodiment with reference to Fig. 3. Fig. 3 is a software block diagram included in the air conditioning apparatus 1 of this embodiment.

[0023] 3, the air conditioning apparatus 1 of this embodiment is configured to include the following functional means: a discharge pressure calculation unit 310, a temperature acquisition unit 320, a target discharge pressure calculation unit 330, a pressure comparison unit 340, and an expansion valve opening control unit 350. Each functional means will be described in detail below.

[0024] The discharge pressure calculation unit 310 is a means for calculating the pressure of the refrigerant discharged from the compressor 24 (hereinafter referred to as the discharge pressure Pd). The discharge pressure calculation unit 310 constitutes a first calculation means in this embodiment. The discharge pressure calculation unit 310 in this embodiment may calculate the refrigerant discharge pressure using, for example, a pressure sensor provided near the discharge portion of the compressor 24, or may calculate the discharge pressure from values ​​(such as the refrigerant temperature) measured by various other sensors.

[0025] The temperature acquisition unit 320 is a means for acquiring temperature values ​​measured by various temperature sensors via the sensor I / F 205. The temperature acquisition unit 320 constitutes an acquisition means in this embodiment. The temperature acquisition unit 320 in this embodiment can acquire, for example, the temperature of air blown out of the indoor unit 3. Furthermore, the temperature acquisition unit 320 in this embodiment can acquire the room temperature, the outside air temperature, the refrigerant temperature, etc.

[0026] The target discharge pressure calculation unit 330 is a means for calculating a target value for the pressure of the refrigerant discharged from the compressor 24 (hereinafter referred to as the target discharge pressure Pdo). The target discharge pressure calculation unit 330 constitutes a second calculation unit in this embodiment. The target discharge pressure calculation unit 330 in this embodiment can calculate the target discharge pressure based on, for example, the blown air temperature of the indoor unit 3 acquired by the temperature acquisition unit 320. The target discharge pressure calculation unit 330 may also calculate the target discharge pressure based on, for example, the condensing temperature of the refrigerant. The target discharge pressure calculation unit 330 in this embodiment can calculate the target discharge pressure and then calculate a predetermined numerical range including the target discharge pressure as the target discharge pressure range. The target discharge pressure range can be determined by taking into account, for example, overshooting and undershooting of the target discharge pressure, an increase in power consumption due to an increase in discharge pressure, and the like. Hereinafter, the upper limit of the target discharge pressure range will be referred to as PdoU, and the lower limit will be referred to as PdoL. Therefore, PdoL≦Pdo≦PdoU. By setting the target discharge pressure range in this manner, hunting can be prevented and the opening degree of the expansion valve 23 can be appropriately feedback-controlled.

[0027] The pressure comparison unit 340 is a means for comparing the discharge pressure calculated by the discharge pressure calculation unit 310 with the target discharge pressure range calculated by the target discharge pressure calculation unit 330. The pressure comparison unit 340 constitutes the comparison means in this embodiment. The pressure comparison unit 340 in this embodiment can compare the discharge pressure Pd with the target discharge pressure range and determine whether the discharge pressure is within the target discharge pressure range.

[0028] The expansion valve opening control unit 350 is a means for controlling the opening degree of the expansion valve 23. The expansion valve opening control unit 350 constitutes control means in this embodiment. The expansion valve opening control unit 350 in this embodiment can control the opening degree of the expansion valve 23 based on the result of the comparison by the pressure comparison unit 340. For example, when the discharge pressure Pd is higher than an upper limit value PdoU of the target discharge pressure range, the expansion valve opening control unit 350 controls to open the expansion valve 23. Also, for example, when the discharge pressure Pd is lower than a lower limit value PdoL of the target discharge pressure range, the expansion valve opening control unit 350 controls to close the expansion valve 23. Also, for example, when the discharge pressure Pd is within the target discharge pressure range, the expansion valve opening control unit 350 controls to maintain the opening degree of the expansion valve 23.

[0029] The software blocks described above correspond to functional means realized by causing each piece of hardware to function as a result of the CPU 201 executing the program of this embodiment. The functional means shown in each embodiment may be realized entirely by software, or some or all of them may be implemented as hardware that provides equivalent functions.

[0030] Next, the processing executed by the above-mentioned functional means will be described with reference to FIG. 4. FIG. 4 is a flowchart showing the processing for controlling the opening degree of the expansion valve 23 in this embodiment. The air conditioner 1 starts the processing from step S1000. The processing shown in FIG. 4 is executed when the air conditioner 1 is performing heating operation. That is, this embodiment can prevent the degree of refrigerant superheat at the evaporator outlet from increasing due to a decrease in the opening degree of the expansion valve 23. During cooling operation, for example, the condensation pressure can be controlled by controlling the air volume of the outdoor fan 22. However, during heating operation, the air volume on the condenser side (indoor unit 3 side) is set by the user, making it difficult to control the condensation pressure by the air volume. Therefore, the processing of the embodiment to be described is particularly effective during heating operation.

[0031] In step S1001, the discharge pressure calculation unit 310 calculates the pressure Pd of the refrigerant discharged from the compressor 24. The discharge pressure Pd may be calculated directly from a value acquired from a sensor provided at the discharge portion of the compressor 24, or may be estimated from a value acquired by another sensor, for example.

[0032] Next, in step S1002, the temperature acquisition unit 320 acquires the temperature of the air blown out of the indoor unit 3. After that, in step S1003, the target discharge pressure calculation unit 330 calculates a target value for the pressure of the refrigerant discharged from the compressor 24. The target discharge pressure calculation unit 330 of this embodiment can calculate the target discharge pressure based on the blown out temperature acquired by the temperature acquisition unit 320 in step S1002.

[0033] Here, the calculation of the target discharge pressure will be described. First, the capacity Φ generated during heating operation (hereinafter referred to as generating capacity Φ) can be calculated by the following formula 1.

[0034]

number

[0035] The above formula 1 is a calculation of the generation capacity based on the temperature of the air blown out from the indoor unit 3. In the above formula 1, q ma is the mass flow rate of intake air, h i is the intake air enthalpy, h o is the outlet air enthalpy, ρ a is the air density, q a is the volumetric flow rate of intake air, c a is the specific heat of the intake air, T i is the intake air temperature, T o is the temperature of the outlet air.

[0036] The generating capacity Φ can also be calculated using the following formula 2.

[0037]

number

[0038] The above formula 2 is a calculation of the generation capacity based on the condensation temperature of the refrigerant. In the above formula 2, K is the heat transfer coefficient based on the pipe outer area of ​​the indoor heat exchanger 31, A is the pipe outer area of ​​the indoor heat exchanger 31, ΔT m is the logarithmic mean temperature difference between the refrigerant and the air, T k is the condensation temperature. The region through which the refrigerant passes in the indoor heat exchanger 31 during heating operation can be divided into three regions: the superheated gas region, the condensation region, and the supercooled region. Assuming that the condensation region is dominant, the refrigerant temperature in the indoor heat exchanger 31 is k Therefore, the above equation 2 can be transformed into the following equation 3.

[0039]

number

[0040] Furthermore, from the above formulas 1 and 3, the following formula 4 can be obtained.

[0041]

number

[0042] Here, the air-side average heat transfer coefficient αa and the passing air velocity V of the indoor heat exchanger 31 in equation 4 can be calculated from equations 5 and 6 below.

[0043]

number

[0044]

number

[0045] Note that α1 and α2 in Equation 5 are coefficients determined by the shape of the indoor heat exchanger 31. If the heat transfer coefficient on the refrigerant side is constant, the overall heat transfer coefficient K of the indoor heat exchanger 31 can be calculated.

[0046] By rearranging the above equations, the optimum condensing temperature T for the current generation capacity is obtained. k can be calculated using the following formula (7).

[0047]

number

[0048] Here, the constant c in equation 7 is calculated from the following equation (8).

[0049]

number

[0050] The target discharge pressure calculation unit 330 of this embodiment calculates the temperature T k The target discharge pressure calculation unit 330 calculates the saturation pressure at the temperature T k The corrected temperature T k The saturation pressure at "'" may be calculated as the target discharge pressure Pdo. Furthermore, the target discharge pressure calculation unit 330 can calculate the upper and lower limit values ​​of the target discharge pressure range for the target discharge pressure Pdo calculated as described above, taking into account overshoot, undershoot, an increase in power consumption due to an increase in discharge pressure, and the like.

[0051] If the air conditioning device 1 includes multiple indoor units 3, the temperature T k Calculate the highest temperature T k may be determined as the optimum condensation temperature.

[0052] After step S1003, in step S1004, the process branches depending on whether the discharge pressure is greater than the upper limit of the target discharge pressure range. The process of step S1004 can be performed by the pressure comparison unit 340 comparing the discharge pressure Pd calculated in step S1001 with the upper limit PdoU of the target discharge pressure range calculated in step S1003. If the discharge pressure is greater than the upper limit of the target discharge pressure range (YES), the process proceeds to step S1005.

[0053] If the discharge pressure is higher than the upper limit of the target discharge pressure range, the discharge pressure will be higher than necessary, resulting in increased power consumption. Therefore, in step S1005, the expansion valve opening control unit 350 controls the expansion valve 23 to open. The amount of control of the opening in step S1005 can be determined, for example, based on the difference between the discharge pressure Pd and the upper limit PdoU of the target discharge pressure range. Thereafter, the process returns to step S1001, and the above processing is repeated.

[0054] On the other hand, if the discharge pressure is smaller than the upper limit of the target discharge pressure range (NO), the process proceeds to step S1006. In step S1006, the process branches depending on whether the discharge pressure is smaller than the lower limit of the target discharge pressure range. The process of step S1006 can be performed by the pressure comparison unit 340 comparing the discharge pressure Pd calculated in step S1001 with the lower limit PdoL of the target discharge pressure range calculated in step S1003. If the discharge pressure is smaller than the lower limit of the target discharge pressure range (YES), the process proceeds to step S1007.

[0055] If the discharge pressure is lower than the lower limit of the target discharge pressure range, the generation capacity will be insufficient, resulting in a loss of comfort. Therefore, in step S1007, the expansion valve opening control unit 350 performs control to close the expansion valve 23. The control amount of the opening in step S1007 can be determined, for example, based on the difference between the discharge pressure Pd and the lower limit PdoL of the target discharge pressure range. Thereafter, the process returns to step S1001, and the above processing is repeated.

[0056] On the other hand, if the discharge pressure is greater than the lower limit of the target discharge pressure range (NO), the process returns to step S1001. In this case, since the discharge pressure is within the target discharge pressure range, the opening degree of the expansion valve 23 is appropriate and there is no need to adjust the opening degree, so the process returns to step S1001 and repeats the above process.

[0057] 4 makes it possible to appropriately adjust the opening of the expansion valve 23. As a result, the air conditioner 1 of this embodiment can ensure the condensation pressure required to generate the necessary heating capacity, thereby saving power, and can prevent an excessive increase in discharge pressure, thereby improving the reliability of the compressor 24.

[0058] In the embodiments described so far, the opening degree of the expansion valve 23 is adjusted based on the discharge pressure, but the air conditioner 1 does not have to always perform this adjustment. Therefore, the air conditioner 1 may adjust the opening degree of the expansion valve 23 by combining, for example, the method shown in Fig. 4 with a method in the prior art.

[0059] For example, immediately after the compressor 24 is started, the heat exchanger's capacity is likely to be insufficient, which can lead to liquid backflow and a sudden change in the state of the refrigerant. Therefore, immediately after the compressor 24 is started, it is preferable to maintain the refrigerant drawn into the compressor 24 in a suitable state to prevent liquid backflow in order to ensure the reliability of the compressor 24. Therefore, the air conditioning apparatus 1 may adjust the opening of the expansion valve 23 based on the refrigerant discharge temperature or the degree of superheat at the evaporator outlet, as in the prior art, rather than adjusting the opening of the expansion valve 23 based on the discharge pressure when the compressor 24 is started. After a predetermined condition is met after the compressor 24 is started, the air conditioning apparatus 1 may transition to a mode in which the control of this embodiment is performed, as shown in FIG. 4 . The transition between modes may occur, for example, when a predetermined time has elapsed since the compressor 24 was started or when the refrigerant temperature meets a predetermined condition.

[0060] Furthermore, as described above, even after transitioning from a control mode like the conventional technology to a mode performing the control of this embodiment, the air conditioner 1 may be configured to transition back to the control mode of the conventional technology depending on the conditions. For example, if the refrigerant discharge temperature or the degree of superheat at the evaporator outlet is outside the normal range during a mode in which the aperture of the expansion valve 23 is adjusted based on the discharge pressure and the discharge pressure is within the target discharge pressure range, the air conditioner 1 may be configured to transition to a mode in which the aperture of the expansion valve 23 is adjusted based on the refrigerant discharge temperature or the degree of superheat at the evaporator outlet in order to prevent a decrease in the reliability of the compressor 24.

[0061] According to the embodiments of the present invention described above, it is possible to provide a refrigeration cycle, an air conditioning apparatus, and a method for appropriately adjusting the opening degree of an expansion valve.

[0062] Each function of the above-described embodiments of the present invention can be realized by a device-executable program written in C, C++, C#, Java (registered trademark), etc., and the program of this embodiment can be stored and distributed on a device-readable recording medium such as a hard disk drive, CD-ROM, MO, DVD, flexible disk, EEPROM (registered trademark), EPROM, etc., and can also be transmitted over a network in a format that can be used by other devices.

[0063] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above-described embodiments, and any embodiment that can be conceived by a person skilled in the art is included in the scope of the present invention as long as it exhibits the functions and effects of the present invention. [Explanation of symbols]

[0064] 1...Air conditioning equipment, 2...Outdoor unit, 3...Indoor unit, 20...control device, 21...Outdoor heat exchanger, 22...Outdoor fan, 23...Expansion valve, 24...Compressor, 25...Four-way valve, 31...Indoor heat exchanger, 32...Indoor fan, 201...CPU, 202...RAM, 203...ROM, 204... Refrigeration cycle parts I / F, 205...Sensor I / F, 206...Communication I / F, 210...CPU, 220…RAM, 230...ROM, 310...Discharge pressure calculation unit, 320...Temperature acquisition section, 330...target discharge pressure calculation unit, 340...pressure comparison unit, 350...Expansion valve opening control unit

Claims

1. A refrigeration cycle including an expansion valve and a compressor, in which a refrigerant circulates, a calculation means for calculating a range of target values ​​for the pressure of the refrigerant discharged from the compressor; a control means for controlling the opening degree of the expansion valve so that the pressure falls within the range calculated by the calculation means; and Refrigeration cycle, including

2. The calculation means calculates the range based on the temperature of air blown out from the indoor unit. The refrigeration cycle according to claim 1.

3. The control means performs control to open the expansion valve when the pressure is higher than the upper limit value of the range. The refrigeration cycle according to claim 1.

4. the control means performs control to close the expansion valve when the pressure is lower than the lower limit value of the range. The refrigeration cycle according to claim 1.

5. The control means When the compressor is started, the opening degree of the expansion valve is controlled based on the temperature of the refrigerant discharged from the compressor or the degree of superheat at an outlet of an evaporator; After a predetermined condition is satisfied, the opening degree of the expansion valve is controlled so that the pressure falls within the range calculated by the calculation means. The refrigeration cycle according to claim 1.

6. The control means When the temperature of the refrigerant discharged from the compressor and the degree of superheat at the outlet of the evaporator are outside a predetermined range, and when the pressure is within the range, the opening degree of the expansion valve is controlled based on the temperature or the degree of superheat. The refrigeration cycle according to claim 1.

7. An air conditioner comprising the refrigeration cycle according to any one of claims 1 to 6.

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