JP7710128B2 - Air conditioners - Google Patents

Description

This disclosure relates to an air conditioner.

Patent Document 1 discloses a refrigeration cycle control device that controls the refrigeration cycle of an air conditioner or a refrigerator that has an electric expansion valve. This refrigeration cycle control device includes an electric expansion valve, an opening control means for the electric expansion valve, a compressor control means, and an abnormality detection means for the refrigerant circuit. In the embodiment, the opening control means controls the opening of the electronic expansion valve in response 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.

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 evaporation temperature, and an opening control means that controls the opening of the electric expansion valve to bring the discharge temperature closer to the target discharge temperature.

Patent No. 3356303 Patent No. 2921254

Conventional air conditioners that use R22 or R32 as refrigerants can operate efficiently if the dryness level at the evaporator outlet is 1.0 and the degree of superheat is small. Therefore, the condensation temperature and evaporation temperature are detected, and the throttling is controlled so that the compressor discharge temperature or suction temperature is an appropriate temperature.

However, with R1234yf, which has attracted attention for its low global warming potential, there is an issue that it cannot be operated optimally using conventional throttle control.

This disclosure provides an air conditioner that appropriately controls the opening of an electric expansion valve and has excellent operating efficiency in a device that uses a refrigerant containing R1234yf.

The air conditioner of the present disclosure comprises a compressor that compresses a refrigerant, a condenser that condenses the refrigerant by heat exchange with air sent by a first blowing means, a throttling means that reduces the pressure and expands the refrigerant, and an evaporator that evaporates the refrigerant by heat exchange with air sent by a second blowing means, which are connected to form a refrigeration cycle, the refrigerant containing R1234yf, an air temperature detection means that detects the temperature of the air sent to the evaporator, a refrigerant temperature detection means that detects the temperature of the refrigerant at the outlet of the evaporator, and a control means that adjusts the throttling means, and 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.

The air conditioner disclosed herein can set the aperture 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 evaporator outlet. This allows for a throttling opening appropriate for the operating conditions of the air conditioner, enabling highly efficient operation.

FIG. 1 is a configuration diagram of an air conditioner according to a first embodiment of the present disclosure. Graph of theoretical COP ratio for different suction SH for each refrigerant

(Foundations and other information that form the basis of this disclosure)
In recent years, global warming has become an important issue, and refrigerants with low global warming potential have come to be selected for use in air conditioners, etc. One representative refrigerant is R1234yf, which has come to be used as a single component refrigerant or a mixed refrigerant.

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

Then, when a refrigeration cycle is constructed using a compressor, the thermal properties of the refrigerant were used to study what characteristics the theoretical cycle efficiency would exhibit under various conditions. As a result, as shown in Figure 2, it was found that R1234yf exhibits extremely unique characteristics in that the greater the degree of superheat at the compressor suction port, the higher the efficiency. Furthermore, it was also found that even in a mixed refrigerant of R1234yf and R32, the greater the degree of superheat at the suction port, the higher the efficiency would be if the weight ratio of R1234yf exceeded 70 percent.

Figure 2 shows the results of calculations for each refrigerant using REFPROP-V9.1, with the condensation temperature (liquid side) at 38°C, the condensation outlet at 36°C, and the evaporation temperature (gas side) at 19°C, and the theoretical COP ratio calculated by dividing the theoretical COP at an intake temperature of 26°C (SH7K) by the theoretical COP at an intake temperature of 20°C (SH1K).

For conventional refrigerants, it is desirable to adjust the opening of the expansion valve so that the refrigerant's quality level in the evaporator is 1.0 or a slight degree of superheat is obtained, based on the evaporation temperature.

On the other hand, with R1234yf, it is desirable to adjust the opening of the expansion valve in the evaporator so that the refrigerant temperature at the evaporator outlet is as close as possible to the intake air temperature, which is the theoretical limit, based on the intake air temperature.

Therefore, we believe that the intake air temperature is an important parameter when adjusting the expansion valve opening for R1234yf and other fuels, and this constitutes the subject of this disclosure.

The present disclosure provides an air conditioner with excellent operating efficiency in a device that uses a refrigerant containing R1234yf, by appropriately controlling the opening of the electric expansion valve by adjusting the throttling means based on the air temperature of the air sent to the evaporator and the refrigerant temperature at the evaporator outlet.

The following describes the embodiments in detail with reference to the drawings. However, more detailed explanations than necessary may be omitted. For example, detailed explanations of matters that are already well known or duplicate explanations of substantially identical configurations may be omitted.

The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

(Embodiment 1)
Hereinafter, the first embodiment will be described with reference to FIG.

[1-1. Configuration]
1, an air conditioner 100 of the first embodiment includes a compressor 1, a condenser 2, a condensing fan which is a first blowing means 8, an electric expansion valve which is a throttling means 3, an evaporator 4, an evaporating fan which is a second blowing means 9, an air temperature detection means 5, a refrigerant temperature detection means 6, and a control means 7. The refrigerant used is R1234yf, which has a small global warming potential.

The air conditioner 100 of the first embodiment is a cooling-only machine, and the condenser 2 is installed outdoors and the evaporator 4 is installed indoors. Condensation-side air 10 is sent to the condenser 2 by the first blowing means 8, and evaporation-side air 11 is sent to the evaporator 4 by the second blowing means 9. The evaporator 4 is composed of two rows of fin-tube heat exchangers having heat dissipation fins and heat transfer tubes, and is configured so that the refrigerant flows from the downwind row to the upwind row to increase temperature efficiency. The air temperature detection means 5 is attached to the upwind side of the evaporator 4 and detects the temperature of the evaporation-side air 11. The refrigerant temperature detection means 6 is disposed in the outlet piping of the evaporator 4 and detects the temperature of the refrigerant after it leaves the evaporator 4. The control means 7 sets the opening degree of the throttling means 3 based on the air temperature detected by the air temperature detection means 5 and the evaporation outlet refrigerant temperature detected by the refrigerant temperature detection means 6.

[1-2. Operation]
The operation and function of the air conditioner 100 of the first embodiment configured as above will be described below.

First, the refrigerant R1234yf is compressed in the compressor 1 and discharged as a high-temperature, high-pressure superheated gas refrigerant. The superheated gas refrigerant is then cooled and condensed in the condenser 2 by the condensation side air 10 supplied by the first blowing means 8, becoming a liquid refrigerant, which is then reduced in pressure and expanded in the throttling means 3. The refrigerant then absorbs heat from the evaporation side air 11 in the evaporator 4, evaporates, and returns to the refrigerant intake port of the compressor 1.

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 of the throttling means 3 so that the operating efficiency of the air conditioner 100 is good.

In order for the evaporator to achieve a given cooling capacity, the temperature difference between the air temperature on the evaporating side and the saturation temperature of the refrigerant must be a value that corresponds to the cooling capacity.

And, as described in the findings that form the basis of this disclosure, for conventional refrigerants such as R22, R410A, and R32, it is desirable for the refrigerant to be in a state where it has completely evaporated in the evaporator, and the degree of superheat of the refrigerant drawn into the compressor at that time is automatically determined. Therefore, the important temperature information in controlling the opening degree of the electric expansion valve is the saturation temperature of the refrigerant in the evaporator and the refrigerant temperature at the compressor intake 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 intake port, a slight change in temperature of the drawn refrigerant can be detected as a large change in temperature of the discharged refrigerant, allowing for even more precise control.

However, when R1234yf is used as the refrigerant, as in the air conditioner 100 of embodiment 1, it is not desirable for the refrigerant to completely evaporate in the evaporator, and 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.

In other words, in the air conditioner 100, the air temperature detected by the air temperature detection means 5 and the evaporation outlet refrigerant temperature detected by the refrigerant temperature detection means 6 are important temperature information. Then, the control means 7 controls the opening degree of the throttling means 3 based on this temperature information, so that the air conditioner 100 that uses R1234yf as a refrigerant can adjust the opening degree of the throttling means 3 to suit the operating conditions, providing a device with excellent operating efficiency.

Furthermore, the outlet refrigerant temperature of the evaporator 4 is limited to the air temperature detected by the air temperature detection means 5, and in an actual device, a temperature lower than the air temperature is appropriate depending on various conditions. Therefore, if the temperature difference between 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 is controlled to a predetermined value, one variable is reduced, and the opening of the throttling means 3 can be easily adjusted.

The predetermined value of the temperature difference between the air temperature detected by the air temperature detection means 5 and the evaporation outlet refrigerant temperature detected by the refrigerant temperature detection means 6 can be 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, allowing a target setting appropriate for the operating conditions of the air conditioner 100. Therefore, the opening degree of the throttling means 3 can be adjusted to suit the operating conditions of the air conditioner 100.

The specified value of the temperature difference between 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 is, for example, when R454C is used as the refrigerant, the condenser side air has a dry bulb temperature of 35°C, a wet bulb temperature of 24°C, and the evaporator side air has a dry bulb temperature of 27°C and a wet bulb temperature of 19°C. In a device with a high COP that uses a high performance heat exchanger, the air temperature detected by the air temperature detection means 5 will be 1°C to 10°C higher depending on the capacity, while in a device with a less high COP, the air temperature detected by the air temperature detection means 5 will be 8°C to 18°C higher, which is a maximum of 5°C lower under the same conditions compared to when the throttling means is adjusted while maintaining the conventional configuration.

The evaporator 4 is also made up of two rows of fin tube heat exchangers, with the refrigerant configured to flow from the downwind row to the upwind row. In the first embodiment, R1234yf is used as the refrigerant, which has the characteristic that the more the degree of superheat is reduced, the better the performance, and the outlet refrigerant temperature of the evaporator 4 can be brought closer to the air temperature. Therefore, an evaporator 4 with excellent heat exchange efficiency is obtained.

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

[1-3. Effects, etc.]
As described above, in this embodiment, the air conditioner 100 uses a refrigerant containing R1234yf, and is equipped with the compressor 1, the condenser 2, the throttling means 3, the evaporator 4, the air temperature detection means 5, the refrigerant temperature detection means 6, the control means 7, the first blower means 8, and the second blower 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 each transmits temperature information to the control means 7. 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.

This makes it easy to adjust the opening of the throttling means 3 to suit the characteristics of refrigerants including R1234yf. This makes it possible to provide an air conditioner with excellent operating efficiency.

As in this embodiment, when adjusting the opening of the throttling means 3 based on the air temperature detected by the air temperature detection means 5 and the evaporation outlet refrigerant temperature detected by the refrigerant temperature detection means 6, control may be performed so that the air temperature and the evaporation outlet refrigerant temperature have a predetermined temperature difference.

This reduces the number of variables to be handled during control, making it easier to adjust the opening of the throttling means 3. As a result, it is possible to provide an air conditioner 100 with excellent controllability.

Furthermore, 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 evaporation outlet refrigerant temperature detected by the refrigerant temperature detection means 6 may be 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.

This makes it possible to set a predetermined value for the temperature difference between the air temperature detected by the air temperature detection means 5 and the evaporation outlet refrigerant temperature detected by the refrigerant temperature detection means 6 depending on the operating conditions of the air conditioner 100, making it possible to provide an air conditioner 100 with excellent operating efficiency even when the operating conditions change.

The evaporator 4 is preferably made up of multiple heat transfer tubes with heat dissipation fins, and the path of the heat transfer tubes is preferably configured so that the refrigerant flows out from the heat transfer tube that is furthest upwind of the evaporator 4.

As a result, the temperature of the refrigerant leaving the evaporator 4 becomes closest to the temperature of the evaporation side air 11, making it possible to more accurately detect the results of the expansion valve control, and providing an air conditioner 100 with excellent operating efficiency.

In addition, the refrigerant should be a mixture of R1234yf, which has a small global warming potential, and R32, which has a relatively small global warming potential and excellent refrigerant performance, and the weight ratio of R1234yf should be 70% or more.

This allows the refrigerant temperature at the outlet of the evaporator 4 to be as close as possible to the evaporation side air temperature, resulting in excellent operating efficiency and providing an air conditioner 100 with a small global warming potential and excellent performance.

The above-described embodiments are intended to illustrate the technology disclosed herein, and various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

This disclosure is applicable to air conditioners that use refrigerants containing R1234yf. Specifically, it is widely applicable to room air conditioners, vending machines, showcases, etc.

REFERENCE SIGNS LIST 1 Compressor 2 Condenser 3 Throttle means 4 Evaporator 5 Air temperature detection means 6 Refrigerant temperature detection means 7 Control means 8 First blower means 9 Second blower means 10 Condensation side air 11 Evaporation side air

Claims (5)

a refrigeration cycle is configured by connecting a compressor which compresses a refrigerant, a condenser which condenses the refrigerant by heat exchange with air sent by a first blowing means, a throttling means which reduces the pressure of the refrigerant and expands it, and an evaporator which evaporates the refrigerant by heat exchange with air sent by a second blowing means, the refrigerant containing R1234yf, and comprising: an air temperature detection means which detects the temperature of the air sent to the evaporator; a refrigerant temperature detection means which detects the temperature of the refrigerant at an outlet of the evaporator; and a control means which adjusts 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,
The air conditioner according to claim 1, 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. The air conditioner according to claim 1, characterized in that 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. The air conditioner according to claim 2, characterized in that the predetermined value is determined based on the performance of the evaporator, the rotation speed of the compressor, and the output of the second blowing means. An air conditioner according to any one of claims 1 to 3, characterized in that the evaporator is made up of multiple heat transfer tubes with heat dissipation fins, and the path of the heat transfer tubes is configured so that the refrigerant flows out from the heat transfer tube that is most upwind of the evaporator. An air conditioner according to any one of claims 1 to 4, characterized in that the refrigerant is a mixed refrigerant of R1234yf and R32, with R1234yf being 70% or more by weight.