Air conditioner

Abstract

To enable optimal operation to be performed with R1234yf noted for a small warming coefficient, which cannot be performed by conventional throttling controls.SOLUTION: An air conditioner 100 uses a refrigerant including R1234yf and comprises: a compressor 1; a condenser 2; throttle means 3; an evaporator 4; air temperature detection means 5; refrigerant temperature detection means 6; control means 7; first blowing means 8; and second blowing means 9. The air temperature detection means 5 detects a temperature of air supplied to the evaporator 4, the refrigerant temperature detection means 6 detects a temperature of the refrigerant at an outlet of the evaporator 4, and each transmit the respective temperature information to the control means 7. The control means 7 adjusts opening of the throttle means 3 on the basis of the air temperature detected by the air temperature detection means 5 and the refrigerant temperature detected by the refrigerant temperature detection means 6.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an air conditioner.

Background Art

[0002] Patent Document 1 discloses a refrigeration cycle control device that controls a refrigeration cycle such as an air conditioner or a refrigerator having an electric expansion valve. This refrigeration cycle control device includes an electric expansion valve, an opening degree control means for the electric expansion valve, a compressor control means, and an abnormality detection means for the refrigerant circuit. And in the embodiment, the opening degree control means controls the opening degree of the electronic expansion valve according to the deviation between the refrigerant temperature at the inlet of the indoor heat exchanger which is the evaporator and the refrigerant temperature at the compressor suction port.

[0003] Patent Document 2 includes a compressor, a discharge temperature sensor that detects the refrigerant discharge temperature of the compressor, a condenser, a condensation temperature sensor that detects the condensation temperature, an electric expansion valve, an evaporator, an evaporation temperature sensor, a target discharge temperature setting means that sets a target discharge temperature from the condensation temperature and the evaporation temperature, and an opening degree control means that controls the opening degree of the electric expansion valve so as to bring the discharge temperature closer to the target discharge temperature.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In conventional air conditioners using R22 or R32 as the refrigerant, efficient operation could be achieved by reducing the superheat degree with a dryness of 1.0 at the evaporator outlet. Therefore, the condensation temperature and the evaporation temperature were detected, and the throttle was controlled so that the discharge temperature or the suction temperature of the compressor became an appropriate temperature.

[0006] However, in the case of R1234yf, which is attracting attention due to its low global warming potential, there is a problem that optimal operation cannot be performed with conventional throttling control.

[0007] The present disclosure provides an air conditioner with excellent operating efficiency by appropriately controlling the opening degree of an electric expansion valve in an apparatus using a refrigerant containing R1234yf.

Means for Solving the Problem

[0008] The air conditioner according to the present disclosure connects a compressor that compresses a refrigerant, a condenser that condenses the refrigerant by exchanging heat with the air sent by the first air blowing means, a throttling means that decompresses and expands the refrigerant, and an evaporator that evaporates the refrigerant by exchanging heat with the air sent by the second air blowing means to form a refrigeration cycle. The refrigerant contains R1234yf, and includes an air temperature detection means for detecting the temperature of the air sent to the evaporator, a refrigerant temperature detection means for detecting the temperature of the refrigerant at the outlet of the evaporator, and a control means for adjusting the throttling means. The control means adjusts the throttling means based on the air temperature detected by the air temperature detection means and the refrigerant temperature detected by the refrigerant temperature detection means.

Effect of the Invention

[0009] The air conditioner according to the present disclosure can set the opening degree of the throttling means according to the characteristics of R1234yf by adjusting the throttling means based on the air temperature of the air sent to the evaporator and the refrigerant temperature at the outlet of the evaporator. Therefore, it is possible to realize a throttle opening suitable for the operating conditions of the air conditioner and perform an operation with excellent efficiency.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0011] (Findings and the like that form the basis of the present disclosure) In recent years, global warming has become an important issue, and refrigerants used in air conditioners and the like are increasingly being selected for their low global warming potential. One typical refrigerant is R1234yf, which has come to be used as a single-component refrigerant or as a mixed refrigerant.

[0012] R1234yf has a molecular weight of 114.0, a boiling point of -29.5°C, and a low global warming potential (100-year assessment) of 4. Compared with conventional refrigerants such as R22, R32, and R410A, it has the characteristics of a lower operating pressure range and a larger pressure loss.

[0013] When a refrigeration cycle is configured using a compressor, the characteristics of the efficiency of the theoretical cycle under various conditions were examined using the thermophysical properties of the refrigerant. As a result, as shown in FIG. 2, it was found that R1234yf exhibits extremely specific characteristics in that a higher degree of superheat at the compressor suction port indicates higher efficiency. Furthermore, it was also found that in a mixed refrigerant of R1234yf and R32, when the weight ratio of R1234yf exceeds 70 percent, a higher degree of superheat at the suction port indicates higher efficiency.

[0014] FIG. 2 shows the results calculated for each refrigerant using REFPROP-V9.1, where the theoretical COP ratio is the value obtained by dividing the theoretical COP at a suction temperature of 26°C (SH7K) by the theoretical COP at a suction temperature of 20°C (SH1K), with a condensation temperature (liquid side) of 38°C, a condensation outlet of 36°C, and an evaporation temperature (gas side) of 19°C.

[0015] In the case of conventional refrigerants, it is desirable to adjust the opening degree of the expansion valve so that the dryness of the refrigerant in the evaporator reaches 1.0 or a slight degree of superheat is obtained, based on the evaporation temperature.

[0016] On the other hand, in the case of R1234yf, it is desirable to adjust the opening degree of the expansion valve so that the refrigerant temperature at the evaporator outlet in the evaporator approaches as closely as possible the suction air temperature, which is the theoretical limit, based on the temperature of the suction air.

[0017] Therefore, in adjusting the expansion valve opening, for R1234yf etc., the suction air temperature is considered an important parameter, leading to the formation of the subject matter of the present disclosure.

[0018] Accordingly, the present disclosure provides an air conditioner with excellent operating efficiency by appropriately controlling the opening of an electric expansion valve by adjusting throttle means based on the air temperature of the air sent to an evaporator and the refrigerant temperature at the outlet of the evaporator in an apparatus using a refrigerant containing R1234yf.

[0019] Embodiments will be described in detail below with reference to the drawings. However, detailed descriptions that are more than necessary may be omitted. For example, detailed descriptions of well-known matters, or duplicate descriptions of substantially the same configurations may be omitted.

[0020] Note that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0021] (Embodiment 1) Embodiment 1 will be described below with reference to FIG. 1.

[0022] [1-1. Configuration] In FIG. 1, the air conditioner 100 of Embodiment 1 includes a compressor 1, a condenser 2, a condenser blower which is a first air blowing means 8, an electric expansion valve which is a throttle means 3, an evaporator 4, an evaporator blower which is a second air blowing means 9, an air temperature detection means 5, a refrigerant temperature detection means 6, and a control means 7. And the refrigerant used is R1234yf with a small global warming potential.

[0023] The air conditioner 100 of Embodiment 1 is a cooling-only type, with the condenser 2 installed outdoors and the evaporator 4 installed indoors. The condenser 2 has the condensing-side air 10 sent by the first air blowing means 8, and the evaporator 4 has the evaporating-side air 11 sent by the second air blowing means 9. The evaporator 4 is composed of a two-row fin-tube heat exchanger having heat dissipation fins and heat transfer tubes, and the refrigerant is configured to flow from the windward row to the leeward row to enhance the temperature efficiency. The air temperature detection means 5 is attached to the leeward side of the evaporator 4 to detect the temperature of the evaporating-side air 11. The refrigerant temperature detection means 6 is arranged on the outlet pipe of the evaporator 4 to detect the temperature of the refrigerant after it exits the evaporator 4. The control means 7 sets the opening degree of the throttle means 3 based on the air temperature detected by the air temperature detection means 5 and the evaporator outlet refrigerant temperature detected by the refrigerant temperature detection means 6.

[0024] [1-2. Operation] Regarding the air conditioner 100 of Embodiment 1 configured as above, its operation and function will be described below.

[0025] First, in the compressor 1, the refrigerant R1234yf is compressed and discharged as a high-temperature and high-pressure superheated gas refrigerant. Then, the superheated gas refrigerant is cooled and condensed by the condensing-side air 10 supplied by the first air blowing means 8 in the condenser 2, and becomes a liquid refrigerant and is decompressed and expanded in the throttle means 3. Then, it evaporates by taking heat from the evaporating-side air 11 in the evaporator 4 and returns to the refrigerant suction port of the compressor 1.

[0026] At this time, the control means 7 uses the temperature information detected by the air temperature detection means 5 and the refrigerant temperature detection means 6 to adjust the opening degree of the throttle means 3 so that the operating efficiency of the air conditioner 100 is in a good state.

[0027] In order for the evaporator to exhibit a predetermined cooling capacity, the temperature difference between the air temperature of the evaporating-side air and the saturation temperature of the refrigerant needs to be a value corresponding to the cooling capacity.

[0028] And as described in the findings and the like that form the basis of the present disclosure, for conventional refrigerants such as R22, R410A, and R32, a state in which evaporation is complete in the evaporator is desirable, and the superheat degree of the refrigerant sucked by the compressor at that time is automatically determined. Therefore, the important temperature information in the opening degree control of the electric expansion valve is the saturation temperature of the refrigerant in the evaporator and the refrigerant temperature at the compressor suction port. If the saturation temperature of the refrigerant in the condenser and the refrigerant temperature at the compressor discharge port are used instead of the refrigerant temperature at the compressor suction port, a slight temperature change in the suction refrigerant can be detected as a large temperature change in the discharge refrigerant, and more accurate control can be performed.

[0029] However, when using R1234yf as the refrigerant as in the air conditioner 100 of Embodiment 1, the state in which evaporation is complete in the evaporator is not good, and a better operating efficiency can be obtained when the refrigerant temperature at the outlet of the evaporator 4 is as close as possible to the air temperature of the evaporation-side air 11.

[0030] That is, in the air conditioner 100, the air temperature detected by the air temperature detection means 5 and the refrigerant temperature at the evaporator outlet detected by the refrigerant temperature detection means 6 are important temperature information. Then, based on this temperature information, the control means 7 controls the opening degree of the throttle means 3, so that the air conditioner 100 using R1234yf as the refrigerant can adjust the opening degree of the throttle means 3 suitable for the operating situation and provide a device with excellent operating efficiency.

[0031] Furthermore, the refrigerant temperature at the outlet of the evaporator 4 has an upper limit of the air temperature detected by the air temperature detection means 5, and in an actual device, a temperature lower than the air temperature is a more suitable temperature according to various conditions. Therefore, if control is performed so that the temperature difference between the air temperature detected by the air temperature detection means 5 and the refrigerant temperature at the evaporator outlet detected by the refrigerant temperature detection means 6 becomes a predetermined value, one variable is reduced, and the opening degree of the throttle means 3 can be easily adjusted.

[0032] When the predetermined value of the temperature difference between the air temperature detected by the air temperature detection means 5 and the refrigerant temperature at the evaporator outlet detected by the refrigerant temperature detection means 6 is determined based on the performance of the evaporator 4, the rotational speed of the compressor 1 which is an index of the cooling capacity, and the output (rotational speed) of the second blowing means 9, a target setting suitable for the operating condition of the air conditioner 100 can be made. Therefore, the opening degree of the throttle means 3 can be adjusted to be suitable for the operating condition of the air conditioner 100.

[0033] The predetermined value of the temperature difference between the air temperature detected by the air temperature detection means 5 and the refrigerant temperature at the evaporator outlet detected by the refrigerant temperature detection means 6 is, for example, in the case of using R454C as the refrigerant, the dry bulb temperature of the condenser side air is 35°C, the wet bulb temperature is 24°C, the dry bulb temperature of the evaporator side air is 27°C, and the wet bulb temperature is 19°C. For a high-performance device with a high COP using a heat exchanger, if the air temperature detected by the air temperature detection means 5 is higher, it is 1°C to 10°C according to the capacity. For a device with a not-so-high COP, if the air temperature detected by the air temperature detection means 5 is higher, it is 8°C to 18°C, and it is about 5°C smaller under the same conditions compared to the case where the throttle means is adjusted with the conventional configuration.

[0034] Also, the evaporator 4 is composed of a two-row fin-tube type heat exchanger, and the refrigerant is configured to flow from the windward row to the leeward row. In the first embodiment, R1234yf is used as the refrigerant, which conforms to the characteristic that the performance improves as the superheat degree can be obtained, and the refrigerant temperature at the outlet of the evaporator 4 can be made closer to the air temperature. Therefore, an evaporator 4 with excellent heat exchange efficiency can be obtained.

[0035] Furthermore, in the first embodiment, R1234yf is used as the refrigerant, but a mixed refrigerant containing R1234yf may also be used. As the refrigerant to be mixed, R32 which has a small global warming potential of 675 (100-year impact) and excellent performance in the refrigeration cycle is preferable. And as shown in FIG. 2, when the weight ratio of R1234yf in the mixed refrigerant of R1234yf and R32 exceeds 70%, the same effect as that of the first embodiment can be obtained. Therefore, an air conditioner with little environmental impact and excellent operating efficiency can be provided.

[0036] [1-3. Effects, etc.] As described above, in this embodiment, the air conditioner 100 uses a refrigerant containing R1234yf, and includes a compressor 1, a condenser 2, throttling means 3, an evaporator 4, air temperature detection means 5, refrigerant temperature detection means 6, control means 7, first blowing means 8, and second blowing means 9. The air temperature detection means 5 detects the temperature of the air sent to the evaporator 4, and the refrigerant temperature detection means 6 detects the temperature of the refrigerant at the outlet of the evaporator 4, and transmits temperature information to the control means 7 respectively. The control means 7 adjusts the opening degree of the throttling means 3 based on the air temperature detected by the air temperature detection means 5 and the refrigerant temperature detected by the refrigerant temperature detection means 6.

[0037] Thereby, it is possible to easily adjust the opening degree of the throttling means 3 suitable for the characteristics of the refrigerant containing R1234yf. Therefore, an air conditioner with excellent operating efficiency can be provided.

[0038] When adjusting the opening degree of the throttling means 3 based on the air temperature detected by the air temperature detection means 5 and the refrigerant temperature at the evaporator outlet detected by the refrigerant temperature detection means 6 as in this embodiment, control may be performed so that the air temperature and the refrigerant temperature at the evaporator outlet have a predetermined temperature difference.

[0039] Thereby, the number of variables to be handled during control is reduced by one, and the opening degree of the throttling means 3 can be easily adjusted. Therefore, an air conditioner 100 with excellent controllability can be provided.

[0040] Also, as in this embodiment, the predetermined value of the temperature difference between the air temperature detected by the air temperature detection means 5 and the refrigerant temperature at the evaporator outlet detected by the refrigerant temperature detection means 6 is preferably determined based on the performance of the evaporator 4, the rotation speed of the compressor 1 which is an index of the cooling capacity, and the output (rotation speed) of the second blowing means 9.

[0041] Thereby, according to the operating situation of the air conditioner 100, the predetermined value of the temperature difference between the air temperature detected by the air temperature detection means 5 and the refrigerant temperature at the evaporator outlet detected by the refrigerant temperature detection means 6 can be set, and an air conditioner 100 with excellent operating efficiency can be provided even when the operating conditions change.

[0042] Also, the evaporator 4 is composed of a plurality of heat transfer tubes having heat dissipation fins, and it is preferable to configure the path of the heat transfer tubes so that the refrigerant flows out from the heat transfer tube on the most windward side of the evaporator 4.

[0043] As a result, the temperature of the refrigerant exiting the evaporator 4 becomes closest to the temperature of the evaporation-side air 11, making it possible to more accurately detect the result of the expansion valve control, and an air conditioner 100 with excellent operating efficiency can be provided.

[0044] Further, the refrigerant is a mixed refrigerant of R1234yf with a small global warming potential and R32 which has a relatively small global warming potential and excellent refrigerant performance, and it is preferable that the weight ratio of R1234yf is 70% or more.

[0045] As a result, by making the refrigerant temperature at the outlet of the evaporator 4 closest to the evaporation-side air temperature, an air conditioner 100 with excellent operating efficiency can be achieved, and an air conditioner 100 with a small global warming potential and excellent performance can be provided.

[0046] Note that the above-described embodiments are for exemplifying the technology in the present disclosure, and various changes, replacements, additions, omissions, etc. can be made within the scope of the claims or their equivalents.

Industrial Applicability

[0047] The present disclosure is applicable to air conditioners using a refrigerant containing R1234yf. Specifically, it is also widely applicable to room air conditioners, vending machines, showcases, etc.

Explanation of Signs

[0048] 1 Compressor 2 Condenser 3 Throttling means 4 Evaporator 5 Air temperature detection means 6 Refrigerant temperature detection means 7 Control means 8 First blowing means 9 Second blowing means 10 Condensed-side air 11 Evaporated-side air

Claims

Claim 1 A compressor that compresses a refrigerant, a condenser that exchanges heat with the air sent by the first air blowing means to condense the refrigerant, a throttling means that decompresses and expands the refrigerant, and a second air blowing means are connected to form a refrigeration cycle. The refrigerant contains R1234yf, and includes an air temperature detection means for detecting the temperature of the air sent to the evaporator, a refrigerant temperature detection means for detecting the temperature of the refrigerant at the outlet of the evaporator, and a control means for adjusting the throttling means. The control means adjusts the throttling means based on the air temperature detected by the air temperature detection means and the refrigerant temperature detected by the refrigerant temperature detection means. An air conditioner, wherein the control means adjusts the throttling means so that the refrigerant temperature detected by the refrigerant temperature detection means approaches the air temperature detected by the air temperature detection means. Claim 2 The air conditioner according to claim 1, wherein the control means adjusts the throttling means so that the temperature difference between the air temperature detected by the air temperature detection means and the refrigerant temperature detected by the refrigerant temperature detection means becomes a predetermined value. Claim 3 The air conditioner according to claim 2, wherein the predetermined value is determined based on the performance of the evaporator, the rotation speed of the compressor, and the output of the second air blowing means. Claim 4 The air conditioner according to any one of claims 1 to 3, wherein the evaporator is composed of a plurality of heat transfer tubes having heat radiation fins, and the path of the heat transfer tubes is configured so that the refrigerant flows out from the heat transfer tube on the most upstream side of the evaporator. Claim 5 The air conditioner according to any one of claims 1 to 4, wherein the refrigerant is a mixed refrigerant of R1234yf and R32, and R1234yf is 70% or more by weight.

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