JPWO2020188756A1 - Room air conditioner - Google Patents

Abstract

An object of the present invention is to provide an air conditioner capable of reducing the amount of refrigerant retained in the liquid side connection pipe and contributing to saving refrigerant when applying a flammable refrigerant or the like. In the air conditioner, the compressor (1), the outdoor heat exchanger (3), the expansion valve (5), and the indoor heat exchanger (11) are connected by pipes, and the refrigerant circulates in the first refrigeration cycle. Between the circuit and the outdoor heat exchanger (3) and the expansion valve (5), there is an overcooling means for overcooling the refrigerant to 10 K or more, and the liquid side connection pipe (102) of the refrigerant circuit is provided. It is formed by a pipe having an inner diameter of less than 4.75 mm and an inner diameter of 1.5 mm or more.

Description

The present invention relates to the structure of an air conditioner using a flammable refrigerant.

Air conditioners are required to switch to refrigerants with a lower global warming coefficient in order to reduce the impact on the environment. Hydrocarbon-based refrigerants such as propane (R290) are naturally occurring substances, and in particular, their global warming coefficient is lower than that of difluoromethane (R32) currently used. However, hydrocarbon-based refrigerants are generally highly flammable. Therefore, in order to use a hydrocarbon-based refrigerant in an air conditioner, it is desirable to minimize the amount of refrigerant used.

On the other hand, in order to make effective use of resources, it is desirable that the diameter of the connecting pipe is as small as possible. Compact connection pipes with a small diameter improve the design of pipes that run through the walls inside and outside the house in household air conditioners.

Patent Document 1 describes a technique for reducing the liquid temperature of a high-pressure liquid refrigerant to 5 ° C. or lower and thinning the low-pressure side piping by providing a supercooling means in an air conditioner using a refrigerant having a low refrigerant density at low pressure. Has been done.

Further, Patent Document 2 shows that the inner diameter of the pipe can be made smaller by using R32 as the refrigerant than by using the liquid side pipe of the air conditioner using R22 as the refrigerant.

Further, Patent Document 3 describes that refrigerant saving can be realized by providing a fluid resistance structure between the indoor unit and the connecting pipe when a flammable refrigerant is used.

International Publication No. 2012/101672 Japanese Patent No. 4815656 Japanese Unexamined Patent Publication No. 2003-148755

In order to apply flammable refrigerant to products, it is required to enclose the amount of refrigerant as small as possible in order to minimize the risk of refrigerant leakage. A large amount of refrigerant is present inside the air conditioner in the heat exchanger on the condensing side and the piping on the liquid side. Therefore, it is possible to reduce the amount of the refrigerant filled in by making these pipes as thin as possible.

Patent Document 1 describes a method of reducing the pressure loss of the evaporator and the extension pipe by using the supercooling means, and reducing the diameter of the pipe on the gas side, particularly when a refrigerant having a low gas density is used. ing. However, the density of the liquid of the hydrocarbon refrigerant is smaller than that of R32 currently used and HFO1234ze and HFO1234yf described in Patent Document 1. Therefore, even if the amount of refrigerant circulation is reduced by supercooling, the flow velocity of the liquid refrigerant does not decrease at least below R32, so that the pressure loss cannot be reduced.

Patent Document 2 describes that the liquid side piping can be made thinner by switching the refrigerant from R22 to R32. This is because the latent heat of R32 is larger than that of R22, so that the amount of refrigerant circulating required for exhibiting the same heating / cooling capacity can be reduced in R32. The latent heat of propane is greater than that of R32. However, the liquid density and gas density of propane are about half that of R32. Therefore, when propane is used as the refrigerant, the amount of refrigerant circulating is slightly lower than that of R32, but the speed of the refrigerant flowing in the pipe is higher in propane, and the pressure loss is also larger. Therefore, from the viewpoint of pressure loss, the pipe diameter cannot be reduced.

Further, Patent Document 3 realizes refrigerant saving by providing a fluid resistance structure between the indoor unit and the connecting pipe when using a flammable refrigerant, but it is not considered to reduce the diameter of the connecting pipe. .. No studies have been made on making the connecting pipes more compact.

The present invention is an invention for solving the above-mentioned problems, and is an air conditioner capable of reducing the amount of refrigerant retained in the liquid side connection pipe and contributing to saving refrigerant when applying a flammable refrigerant or the like. The purpose is to provide.

In order to achieve the above object, in the air conditioner of the present invention, the compressor, the outdoor heat exchanger, the first expansion valve (for example, the expansion valve 5), and the indoor heat exchanger are connected by a pipe, and the first A refrigerant circuit in which the refrigerant circulates in the refrigeration cycle and an overcooling means for overcooling the refrigerant by 10 K or more are provided between the outdoor heat exchanger and the first expansion valve, and the liquid side piping of the refrigerant circuit ( For example, the liquid side connecting pipe 102) is characterized in that it is formed of a pipe having an inner diameter of less than 4.75 mm and an inner diameter of 1.5 mm or more. Other aspects of the present invention will be described in embodiments described below.

According to the present invention, it is possible to reduce the amount of the refrigerant retained in the liquid side connecting pipe and contribute to saving the refrigerant when applying a flammable refrigerant or the like.

It is a cycle block diagram at the time of cooling of the air conditioner which concerns on 1st Embodiment. It is a Moriel diagram at the time of cooling of the air conditioner which concerns on 1st Embodiment. It is a cycle block diagram at the time of heating of the air conditioner which concerns on 1st Embodiment. It is a Moriel diagram at the time of heating of the air conditioner which concerns on 1st Embodiment. This is a calculation example of the minimum pipe diameter according to the first embodiment. It is a structural drawing of the pipe insulation which concerns on 1st Embodiment. It is a cross-sectional structure of a pipe used in the description which concerns on 1st Embodiment. It is a cycle block diagram at the time of cooling of the air conditioner which concerns on 2nd Embodiment. It is a cycle block diagram at the time of heating of the air conditioner which concerns on 2nd Embodiment. It is a cycle block diagram at the time of cooling of the air conditioner which concerns on 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and various modifications and applications are included in the technical concept of the present invention.

<< First Embodiment >>
FIG. 1 is a cycle configuration diagram of the air conditioner according to the first embodiment during cooling. This embodiment is commercially available as a household air conditioner, and targets an air conditioner generally called a room air conditioner. The feature is that the indoor unit and the outdoor unit are connected one-to-one, and the cooling capacity is 9.0 kW or less.

The indoor unit 101 is installed indoors, the outdoor unit 100 is installed outdoors, and the indoor unit 101 and the outdoor unit 100 are connected by a liquid side connection pipe 102 and a gas side connection pipe 103, which are refrigerant connection pipes. The air conditioner is a refrigerant circuit in which a compressor 1, an outdoor heat exchanger 3, an expansion valve 5 (first expansion valve), and an indoor heat exchanger 11 are connected by piping, and the refrigerant circulates in the first refrigeration cycle. Has.

As the refrigerant, propane or propylene is used as the flammable refrigerant. Table 1 shows a table comparing the physical property values of the saturated state at 0 ° C. with the conventional refrigerant. The higher the refrigerant density, the more the flow velocity of the refrigerant inside the pipe can be suppressed and the pressure loss tends to be smaller, and the higher the latent heat, the smaller the amount of refrigerant circulation can be, so the pipe pressure loss tends to be small. The hydrocarbon-based refrigerants shown in Table 1 are propylene, propane, butane, and isobutane. As of 2019, the refrigerant used in many of the newly released room air conditioners is R32. All of the hydrocarbon-based refrigerants shown in Table 1 have a large latent heat with respect to R32. Therefore, it is considered that the amount of refrigerant circulating can be reduced with respect to R32. However, the liquid density and the gas density are less than half that of R32, and it is considered that the pressure loss of the pipe becomes larger than the decrease in the circulation amount due to the latent heat. Therefore, it is assumed that butane and isobutane having a particularly low gas density are excluded, and propylene or propane is used in this embodiment.

In order to make the liquid side piping thinner, the circulating flow rate of the flowing refrigerant is reduced so that the flow loss of the internal refrigerant does not increase, and the dryness of the refrigerant is as low as possible, that is, the amount of gas phase is small. It is conceivable to let it flow in a state. However, in a home air conditioner such as a room air conditioner, the expansion valve 5 is located only on the outdoor unit 100 side, and it is necessary to flow the refrigerant that has passed through the expansion valve 5 and expanded under reduced pressure to the liquid side piping during cooling. By reducing the pressure with the expansion valve 5, a part of the refrigerant for which a sufficient degree of supercooling has not been obtained is gasified, and a gas-liquid two-phase flow always flows through the refrigerant-side connecting pipe. If the liquid side connection pipe 102 is made thinner than the current state in this state, the pressure loss may become too large and the evaporation pressure may decrease.

The compressor 1 inside the outdoor unit 100 compresses the refrigerant in the low-pressure and low-temperature states, and discharges the gas refrigerant in the high-temperature and high-pressure states. The high-temperature, high-pressure gas refrigerant discharged from the compressor 1 reaches the four-way valve 2. In the four-way valve 2, the valve is switched so that the gas flowing from the compressor 1 flows to the outdoor heat exchanger 3 side. The outdoor heat exchanger 3 includes a pipe through which a refrigerant flows and fins bonded to the surface thereof. The outdoor heat exchanger 3 is heated by the outdoor fan 4 to exchange heat with the outdoor air. In the case of cooling operation, a high-temperature and high-pressure gas refrigerant flows into the outdoor heat exchanger 3, and outdoor air having a temperature lower than that of the gas refrigerant flows through the outdoor heat exchanger 3 to cool and condense the gas refrigerant. Phase change to liquid refrigerant.

The refrigerant obtained by liquefying a part or all of the gas refrigerant in the outdoor heat exchanger 3 passes through the second expansion valve 21 and flows into the first flow path 221 of the supercooling heat exchanger 22, and the supercooling heat. It is divided into those flowing to the second flow path 222 of the exchanger 22. The supercooling heat exchanger 22 has a structure capable of heat exchange without mixing the refrigerant flowing through the first flow path 221 and the refrigerant flowing through the second flow path 222 inside. The refrigerant flowing to the first flow path 221 of the supercooling heat exchanger 22 is depressurized by the second expansion valve 21, and a part of the liquid refrigerant is gasified to lower the temperature. Then, gasification proceeds while cooling the refrigerant flowing through the second flow path 222 of the supercooling heat exchanger 22, and the refrigerant flows to the accumulator 6.

Further, the liquid refrigerant whose temperature is further lowered from the outlet temperature of the outdoor heat exchanger 3 by the overcooling heat exchanger 22 passes through the expansion valve 5 (first expansion valve) and passes through the liquid side connection pipe 102. It flows into the indoor heat exchanger 11. The refrigerant that has been decompressed by the expansion valve 5 and the liquid side connection pipe and has become low temperature flows in the indoor heat exchanger 11, and the air is flowed through the indoor fan 12 to cool the indoor air. .. In the indoor heat exchanger 11, the refrigerant heated by cooling the air is gasified, passes through the gas side connection pipe, and reaches the outdoor unit 100. The gas refrigerant returned to the outdoor unit 100 is flowed to the accumulator 6 side via the four-way valve 2. The accumulator 6 is intended as a temporary reservoir for preventing the liquid refrigerant from returning excessively to the compressor 1. The low-temperature, low-pressure gas refrigerant that has passed through the accumulator 6 is sucked into the compressor 1, compressed, and discharged as a high-temperature, high-pressure gas refrigerant.

Table 2 shows the outer diameter dimensions of the connection pipes currently used in room air conditioners. Both are copper pipes, and their wall thickness is 0.8 mm. Normally, the liquid side connection pipe 102 uses a pipe having an outer diameter of 6.35 mm and has a wall thickness of 0.8 mm. Therefore, the inner diameter of the pipe is 4.75 mm. This diameter is sized on the assumption that a refrigerant that has been decompressed by the expansion valve 5 and partially gasified will pass through.

In the present embodiment, the liquid side connection pipe 102 uses a pipe thinner than the pipe having an outer diameter of 6.35 mm, for example, a pipe having an outer diameter of 4 mm or less. When such a thin pipe is used, the pressure drop of the refrigerant in the liquid side connection pipe 102 is usually too large, and the evaporation pressure in the indoor heat exchanger 11 is too low. This leads to an increase in the input of the compressor 1, and thus impairs energy saving.

However, in the present embodiment, if the pressure drops below the predetermined evaporative pressure, the expansion valve 5 is first fully opened, and if the evaporative pressure is still lower than the predetermined evaporative pressure, it is usually used by fully closing. The second expansion valve 21 is properly opened, and the supercooling heat exchanger 22 overcools the liquid refrigerant flowing to the liquid side connection pipe 102 to a degree higher than the normal degree of supercooling. The liquid refrigerant that has been overcooled than usual has a slower gasification when the pressure drops due to the pressure loss due to the flow of the refrigerant in the liquid side connection pipe 102, which makes the liquid side connection pipe slower than usual. The pressure loss of the refrigerant in 102 can be controlled to be small. Normally, the degree of supercooling that can be obtained only with the outdoor heat exchanger 3 is up to about 5K, but if the configuration of this embodiment is used, supercooling of 10K (Kelvin) or more can be obtained.

FIG. 2 is a diagram of Moriel when the air conditioner according to the first embodiment is cooled. The pressure and enthalpy state of the refrigeration cycle during cooling of the present embodiment will be described with reference to FIG. FIG. 2 is a Moriel diagram in which the horizontal axis represents the specific enthalpy of the refrigerant and the vertical axis represents the pressure of the refrigerant. Since the refrigerant dissipates heat in the outdoor heat exchanger 3 from the point described as the compressor outlet, it reaches the outdoor heat exchanger outlet while reducing the enthalpy.

Here, the point at the outlet of the outdoor heat exchanger is to the right of the saturated liquid line. This means that the refrigerant is not completely single-phase at the outlet of the outdoor heat exchanger 3. In the conventional room air conditioner, the refrigerant has been liquefied inside the outdoor heat exchanger 3. This was necessary to improve the cooling capacity in air conditioners that do not have supercooling means. However, at the same time, in order to completely liquefy the refrigerant inside the heat exchanger and obtain supercooling, it was necessary to fill a part of the refrigerant piping inside the outdoor heat exchanger with the liquid refrigerant. However, in order to reduce the amount of refrigerant, it is not desirable to have a liquid single-phase region inside the heat exchanger. Therefore, in the present embodiment, the outdoor heat exchanger 3 is not supercooled, and the entire region inside the outdoor heat exchanger is in a gas or gas-liquid two-phase state. As a result, not only the amount of refrigerant can be reduced, but also all the heat transfer surfaces in the pipe inside the heat exchanger can be used as the condensing surface, so that the heat exchange performance is improved and the condensing pressure is lowered and the compressor power is lowered accordingly. , Leads to reduction of power consumption.

Although not generally applicable, in a conventional refrigeration cycle, if the amount of refrigerant is less than the appropriate amount, the cooling or heating capacity tends to decrease. This is because the area of the liquid single phase of the heat exchanger used as the condenser is reduced, making it difficult to obtain supercooling. If the amount of the refrigerant is more than the appropriate amount, the liquid single-phase region of the condenser increases too much and the two-phase region decreases, so that the condensation pressure rises, leading to an increase in the input of the compressor.

Further, in many room air conditioners, the volume inside the pipe of the outdoor heat exchanger 3 is larger than the volume inside the pipe of the indoor heat exchanger 11 of the indoor unit 101. This is because the outdoor unit 100 generally has more space for installation. Therefore, reducing the amount of refrigerant used inside the outdoor heat exchanger 3 is particularly effective in reducing the amount of refrigerant charged in the room air conditioner, especially under cooling conditions in which the refrigerant accumulates in the outdoor heat exchanger 3.

The refrigerant exiting the outdoor heat exchanger 3 in FIG. 2 is further cooled by the supercooling means to reach the expansion valve inlet. In most room air conditioners, the expansion valve 5 is arranged on the outdoor unit 100 side, and the evaporation pressure is controlled by the expansion valve 5. The target value of the control may be the degree of superheat of the refrigerant at the inlet of the compressor or the temperature at the outlet of the compressor.

The refrigerant decompressed to a certain level by the expansion valve 5 exits the expansion valve 5 and flows to the liquid side connection pipe 102, is decompressed by the fluid loss inside the pipe, and flows to the indoor heat exchanger 11. When the refrigerant flowing through the expansion valve 5 is a liquid single phase, the pressure loss cannot be increased so much that the controllability of the evaporation pressure is lowered. Therefore, in the present embodiment, it is necessary to appropriately take the degree of supercooling by using the second expansion valve 21 that controls the supercooling means, and reduce the pressure to the evaporation pressure by the pressure loss of the liquid side connecting pipe 102. Therefore, if the inner diameter of the liquid side connecting pipe 102 is too small, the evaporation pressure is excessively lowered, but if it is thick, the effect of reducing the refrigerant cannot be obtained.

FIG. 3 is a cycle configuration diagram during heating of the air conditioner according to the first embodiment. The heating cycle configuration according to the first embodiment will be described with reference to FIG. The compressor 1 inside the outdoor unit 100 compresses the refrigerant in the low-pressure and low-temperature states, and discharges the gas refrigerant in the high-temperature and high-pressure states. The high-temperature, high-pressure gas refrigerant discharged from the compressor 1 reaches the four-way valve 2. In the four-way valve 2, the valve is switched so that the gas flowing from the compressor 1 flows to the indoor unit 101 side via the gas side connection pipe 103. The gas refrigerant that has reached the indoor unit 101 flows into the indoor heat exchanger 11 that includes a pipe through which the refrigerant flows and fins joined to the surface thereof. The high-temperature, high-pressure refrigerant discharged from the compressor 1 flows through the indoor heat exchanger 11, and the indoor fan 12 causes the air to flow there to heat the indoor air. Further, by flowing indoor air having a temperature lower than that of the gas refrigerant through the indoor heat exchanger 11, the gas refrigerant is cooled and condensed, and the phase is changed to the liquid refrigerant. In the indoor heat exchanger 11, the refrigerant obtained by liquefying a part or all of the gas refrigerant flows to the outdoor unit 100 via the liquid side connection pipe 102. The refrigerant returned to the outdoor unit 100 reaches the outdoor heat exchanger 3 via the expansion valve 5 and the supercooling heat exchanger 22.

In the present embodiment, by using the liquid side connection pipe 102 having a reduced diameter, the refrigerant liquefied by the indoor heat exchanger 11 is depressurized and the temperature is lowered. Further, if necessary, the expansion valve 5 is further throttled. Depressurize. Then, the refrigerant whose low pressure and low temperature are lowered by the reduced pressure flows to the outdoor heat exchanger 3. At this time, the refrigerant is lower than the outdoor air temperature that is passed through the outdoor heat exchanger 3 by the outdoor fan 4, and the refrigerant is heated and gasified by the air that flows through the outdoor heat exchanger 3. The gasified refrigerant flows to the accumulator 6 side via the four-way valve 2 and is finally sucked into the compressor 1.

In the conventional combination of the liquid side connection pipe 102 and the expansion valve 5, the inside of the liquid side connection pipe 102 is substantially filled with the liquid refrigerant during heating. This led to an increase in the amount of refrigerant used. However, in the present embodiment, by using a small diameter pipe of 4 mm or less, the internal volume is small in the first place, the pressure is reduced in the middle of the liquid side connection pipe 102, and a part of the refrigerant is gasified, so that it is retained. The amount of refrigerant can be reduced.

FIG. 4 is a Moriel diagram of the air conditioner according to the first embodiment during heating. The state of the pressure and the enthalpy of the refrigeration cycle at the time of heating of this embodiment will be described with reference to FIG. FIG. 4 is a Moriel diagram showing the specific enthalpy of the refrigerant on the horizontal axis and the pressure of the refrigerant on the vertical axis. Under heating conditions, the refrigerant condensed by the indoor heat exchanger 11 is released at a supercooling degree of about 10K. As described above, under the heating conditions, the degree of supercooling can be easily obtained by the indoor heat exchanger 11. This is because the indoor heat exchanger 11 is relatively small, and it is necessary to set the condensing pressure high (for example, the condensing temperature is 30 ° C. or higher) in order to raise the temperature of the blown air into the room. This is because the air temperature of the above is about 20 ° C. and a temperature difference is likely to occur.

Here, when propane and propylene having a saturation temperature of 30 ° C. and a supercooling degree of 10 K are depressurized, the liquid phase is maintained when the depressurized amount is 243 kPa or less for propane and 288 kPa or less for propylene. When the refrigerant is gasified in a liquid connection pipe with a small diameter, it is conceivable that the pressure loss in the pipe will increase sharply. In particular, this sudden change in pressure loss can also make the evaporation pressure unstable, which in turn can lead to instability of the entire refrigeration cycle. Therefore, it is considered that the controllability of the refrigeration cycle is higher when the liquid phase is maintained in the liquid side connection pipe 102 as much as possible.

Here, using the physical characteristics of propane at a saturation temperature of 30 ° C., the pipe diameter at which the pipe pressure loss is 250 kPa was calculated with respect to the heating capacity Q (kW). The enthalpy of the indoor heat exchange inlet is 278.8 kJ / kg, the indoor heat exchange outlet is 251.7 kJ / kg assuming a supercooling degree of 10 K, the enthalpy difference dh is 353.9 kJ / kg, and the refrigerant circulation amount Gr ( kg / s) was calculated by the number 1.

Inside the pipe, the diameter inside the pipe is d (m), the density of the liquid refrigerant is ρ (kg / m ³ ), the viscosity coefficient of the liquid is μ (Pa · s), the gravity acceleration g (m / s ² ), and the length of the connecting pipe is L (m). The Reynolds number Re of the flow of the refrigerant of the above is represented by the equation 2.

From Brazius's equation, the drag coefficient f is represented by Equation 3.

となる。 Therefore, the pressure loss dP (Pa) of the piping is

Will be.

FIG. 5 is a calculation example of the minimum pipe diameter according to the first embodiment. FIG. 5 shows the result of obtaining the pipe inner diameter d at which the pipe pressure loss dP is 243 Pa, where the connecting pipe length L = 5 m. In this way, although it depends on the capacity, the inner diameter can be smaller than the conventional outer diameter of 6.35 (inner diameter of 4.75 mm with a wall thickness of 0.8 mm) of 1.5 mm to 3.5 mm (inner diameter of less than 4.75 mm). it can). The formula that approximates the solid line in FIG. 5 is the following equation 5.

FIG. 6 is a structural diagram of pipe insulation according to the first embodiment. The surfaces of the liquid side connection pipe 102 and the gas side connection pipe 103 are covered with a heat insulating material, and the cross-sectional structure thereof is shown in FIG. As shown in FIG. 6, the structure is such that the pipe 52 is housed inside the pipe heat insulating material 51. This heat insulation is also to prevent the refrigerant from being heated or cooled by the air around the pipes to reduce energy saving, and to prevent dew condensation from dripping indoors due to dew condensation on the pipe surface especially during cooling. It is also to make it. The heat insulating material thickness 53 is designed to have a constant thermal resistance, but if the same thermal resistance is obtained, the smaller the diameter of the pipe 52, the smaller the heat insulating material thickness 53 can be. Therefore, the outer diameter of the pipe heat insulating material 51 can be made very compact by reducing the diameter of the inner pipe 52.

Further, as shown in FIG. 6, the connecting pipe has a smooth inner surface structure that is not the inner surface grooved pipe as shown in FIG. 7. The grooved pipe not only increases the pressure loss when the refrigerant flows, but also has the effect of improving the heat transfer coefficient of the refrigerant on the inner surface, so that the external heat intrusion into the liquid side connection pipe 102 is promoted. ..

Further, at the time of cooling, the second expansion valve 21 is opened and the supercooling heat exchanger 22 supercools the liquid refrigerant passing through the liquid side connection pipe 102, so that the amount of refrigerant circulation required to obtain the same cooling capacity is obtained. Can be reduced as compared with the case where no supercooling is performed. As a result, the flow velocity of the refrigerant flowing through the gas side connection pipe 103 can also be reduced, so that the diameter of the gas side connection pipe 103 can also be reduced. Since the high-pressure refrigerant passes through the gas side connection pipe 103 during heating, the flow velocity is originally slow and the influence is small even if the pipe diameter is reduced. As a result, the heat insulating material of the gas side connection pipe 103 can also be reduced, so that the entire connection pipe can be made compact.

In household air conditioners such as room air conditioners, the appearance may be annoying, especially when it is necessary to run the connection pipe against the wall indoors. If the connecting pipe can be made compact as in the present embodiment, the connecting pipe will be less noticeable than in the conventional case, and it is considered that the appearance will be improved.

Further, in the present embodiment, since the liquid side connecting pipe 102 having a reduced diameter is used as a decompressor during cooling and heating, the second expansion valve 21 and the expansion valve 5 are appropriately controlled particularly during cooling. There is a need. To do this, the compressor discharge temperature sensor 92 for checking the discharge temperature of the compressor 1, the indoor heat exchanger temperature sensor 91 for checking the evaporation pressure of the heat exchanger of the indoor unit 101, and the supercooling heat exchanger 22 are the first. In order to confirm the degree of superheat of the flow path 221 of No. 1, a supercooling heat exchanger temperature sensor 93 (see FIG. 1) is provided and controlled.

<< Second Embodiment >>
FIG. 8 is a cycle configuration diagram of the air conditioner according to the second embodiment during cooling. The cooling cycle configuration of the second embodiment will be described with reference to FIG. The indoor unit 101 is installed indoors, the outdoor unit 100 is installed outdoors, and the indoor unit 101 and the outdoor unit 100 are connected by a liquid side connection pipe 102 and a gas side connection pipe 103, which are refrigerant connection pipes. The second embodiment, unlike the first embodiment, has a second refrigeration cycle 110.

The compressor 1 inside the outdoor unit 100 compresses the refrigerant in the low-pressure and low-temperature states, and discharges the gas refrigerant in the high-temperature and high-pressure states. The high-temperature, high-pressure gas refrigerant discharged from the compressor 1 reaches the four-way valve 2. In the four-way valve 2, the valve is switched so that the gas flowing from the compressor 1 flows to the outdoor heat exchanger 3 side. The outdoor heat exchanger 3 includes a pipe through which a refrigerant flows and fins bonded to the surface thereof. The outdoor heat exchanger 3 is heated by the outdoor fan 4 to exchange heat with the outdoor air. In the case of cooling operation, a high-temperature and high-pressure gas refrigerant flows into the outdoor heat exchanger 3, and outdoor air having a temperature lower than that of the gas refrigerant flows through the outdoor heat exchanger 3 to cool and condense the gas refrigerant. Phase change to liquid refrigerant.

The refrigerant obtained by liquefying a part or all of the gas refrigerant in the outdoor heat exchanger 3 passes through the first flow path 231 of the evaporator 23 of the second cycle of the second refrigeration cycle 110, passes through the expansion valve 5, and passes through the expansion valve 5. It passes through the liquid side connection pipe 102 and flows into the indoor heat exchanger 11. The refrigerant that has been decompressed by the expansion valve 5 and the liquid side connection pipe and has become low temperature flows in the indoor heat exchanger 11, and the air is flowed through the indoor fan 12 to cool the indoor air. ..

In the indoor heat exchanger 11, the refrigerant heated by cooling the air is gasified, passes through the gas side connection pipe 103, and reaches the outdoor unit 100. The gas refrigerant returned to the outdoor unit 100 is flowed to the accumulator 6 side via the four-way valve 2. The accumulator 6 is intended as a temporary reservoir for preventing the liquid refrigerant from returning excessively to the compressor 1. The low-temperature, low-pressure gas refrigerant that has passed through the accumulator 6 is sucked into the compressor 1, compressed, and discharged as a high-temperature, high-pressure gas refrigerant.

In the second embodiment, the second refrigeration cycle 110 is used in order to obtain supercooling of the refrigerant flowing through the liquid side connection pipe 102. In the second refrigeration cycle 110, the high-temperature and high-pressure refrigerant discharged from the compressor 27 in the second cycle reaches the condenser 25 in the second cycle. In the condenser 25 of the second cycle, the refrigerant cooled by the air flowed by the fan 26 of the second cycle is liquefied, depressurized by the expansion valve 24 of the second cycle, becomes low temperature and low pressure, and evaporates in the second cycle. It flows through the second flow path 232 of the vessel 23. At this time, the refrigerant flowing through the second flow path 232 of the evaporator 23 in the second cycle takes heat from the refrigerant flowing to the liquid side connection pipe 102 flowing through the first flow path 231 of the evaporator 23 in the second cycle. , Gasifies. The gasified refrigerant passes through the accumulator 28 in the second cycle and is sucked into the compressor 27 in the second cycle. By using such a second refrigeration cycle 110, for example, the temperature of the refrigerant flowing to the liquid side connection pipe 102 is greatly supercooled so as to be equal to or lower than the saturation temperature corresponding to the evaporation pressure in the indoor heat exchanger 11. Easy to get the degree.

Further, the second refrigeration cycle 110 is placed outdoors so as to be installed close to or built in the outdoor unit 100. Therefore, even if a flammable refrigerant or the like is used as the refrigerant, when the refrigerant leaks, it easily diffuses into the atmosphere and the risk is reduced. Therefore, R455A, propane, and R454C are used as the refrigerant in the second refrigeration cycle 110.

FIG. 9 is a cycle configuration diagram during heating of the air conditioner according to the second embodiment. The heating cycle configuration of the second embodiment will be described with reference to FIG. The flow of the refrigerant is almost the same as that of the first embodiment. The compressor 1 inside the outdoor unit 100 compresses the refrigerant in the low-pressure and low-temperature states, and discharges the gas refrigerant in the high-temperature and high-pressure states. The high-temperature, high-pressure gas refrigerant discharged from the compressor 1 reaches the four-way valve 2. In the four-way valve 2, the valve is switched so that the gas flowing from the compressor 1 flows to the indoor unit 101 side via the gas side connection pipe 103. The gas refrigerant that has reached the indoor unit 101 flows into the indoor heat exchanger 11 that includes a pipe through which the refrigerant flows and fins joined to the surface thereof. The high-temperature, high-pressure refrigerant discharged from the compressor 1 flows through the indoor heat exchanger 11, and the indoor fan 12 causes the air to flow there to heat the indoor air. Further, by flowing indoor air having a temperature lower than that of the gas refrigerant through the indoor heat exchanger 11, the gas refrigerant is cooled and condensed, and the phase is changed to the liquid refrigerant. The refrigerant obtained by liquefying a part or all of the gas refrigerant in the indoor heat exchanger 11 flows to the outdoor unit 100 via the liquid side connection pipe 102. The refrigerant returned to the outdoor unit 100 reaches the outdoor heat exchanger 3 via the expansion valve 5 and the evaporator 23 in the second cycle. At this time, the second refrigeration cycle 110 is stopped.

Further, as in the first embodiment, the compressor discharge temperature sensor 92 for checking the discharge temperature of the compressor 1, the indoor heat exchanger temperature sensor 91 for checking the evaporation pressure of the indoor heat exchanger 11, and the evaporation of the second cycle. Second cycle compressor discharge temperature sensor 95 that checks the discharge temperature of the outlet temperature sensor 94 of the evaporator 23 of the second cycle or the compressor 27 of the second cycle in order to confirm the degree of overheating of the second flow path of the vessel 23. Is provided to control the expansion valve 24 in the second cycle.

<< Third Embodiment >>
FIG. 10 is a cycle configuration diagram of the air conditioner according to the third embodiment during cooling. The cooling cycle configuration of the third embodiment will be described with reference to FIG. The configuration is almost the same as that of the first embodiment, but the expansion valve 5 arranged in front of the connecting pipe is eliminated. As a result, during cooling, only the degree of supercooling is controlled by the second expansion valve 21, and the evaporation pressure is adjusted. At the time of heating, the evaporation pressure is adjusted by the pressure loss of the supercooling heat exchanger. That is, the evaporation pressure is determined only by the pressure loss of the liquid side connection pipe 102 and the supercooling heat exchanger 22. However, here as well, the second expansion valve 21 can be adjusted to further cool and liquefy the refrigerant vaporized inside the supercooling heat exchanger 22, so that the refrigerant inside the supercooling heat exchanger 22 can be further cooled and liquefied. Pressure loss can be controlled.

であることが望ましい。 In the third embodiment, it is desirable that the pipe diameter is smaller than the pipe diameter shown in FIG. 5, for example, so that the decompression performance is not insufficient. That is, the inner diameter d (mm) of the liquid side piping is defined as the heating capacity Q (kW).

Is desirable.

Further, as is common to the first to third embodiments, the amount of refrigerant circulating to the indoor unit can be reduced by using a large amount of supercooling during cooling. Therefore, there is a possibility that a pipe thinner than the one used in the current R32 can be used for the gas side pipe.

Summarizing the above, by using the air conditioner of the present embodiment, the refrigerant condensed and liquefied by the outdoor unit 100 during the cooling operation has been decompressed by the expansion valve 5, but is decompressed by the liquid side connecting pipe 102. Will be done. If the required cooling capacity is large at this time, the amount of refrigerant circulating becomes too large, and it is conceivable that the evaporation pressure of the refrigerant in the indoor heat exchanger 11 in the indoor unit 101 is unnecessarily reduced and the energy saving performance is impaired. Therefore, by further cooling the liquid refrigerant condensed by the outdoor heat exchanger 3 of the outdoor unit 100 with the supercooling heat exchanger 22, the circulation amount of the refrigerant is reduced to obtain the same cooling capacity, and the diameter of the liquid side is reduced. The connecting pipe 102 can also be appropriately depressurized.

At the same time, in the conventional cooling operation, the degree of supercooling of the refrigerant is obtained by the outdoor heat exchanger 3 of the outdoor unit 100, but this is not necessary because the supercooling heat exchanger 22 can obtain the degree of supercooling. In order to obtain supercooling with the outdoor heat exchanger 3, it is necessary to have a large liquid phase region in the piping, which leads to an increase in the amount of refrigerant retained. That is, since it is not necessary to take supercooling, the entire inside of the outdoor heat exchanger 3 of the outdoor unit 100 can be in a gas-liquid two-phase state at the time of cooling, and the amount of refrigerant charged can be reduced.

Further, by reducing the outer diameter of the liquid side connecting pipe 102, heat intrusion from the surface of the connecting pipe is reduced, and gasification of the refrigerant in the connecting pipe is suppressed as much as possible. This prevents the pressure loss inside the connecting pipe from changing due to the sudden generation of air bubbles, and can maintain control stability. In addition, the connection piping can be made compact.

Due to these effects, the amount of the refrigerant retained in the liquid-side connecting pipe 102 can be reduced, and it is possible to contribute to saving refrigerant when applying a flammable refrigerant or the like.

1 Compressor 2 Four-way valve 3 Outdoor heat exchanger 4 Outdoor fan 5 Expansion valve (first expansion valve)
6 Accumulator 11 Indoor heat exchanger 12 Indoor fan 21 Second expansion valve 22 Supercooling heat exchanger (supercooling means)
23 Second cycle evaporator (supercooling means)
24 Second cycle expansion valve 25 Second cycle condenser 26 Second cycle fan 27 Second cycle compressor 28 Second cycle accumulator 51 Piping insulation 52 Piping 53 Insulation thickness 54 Pipe outer diameter 55 Pipe Inner diameter 56 Tube wall thickness 91 Indoor heat exchanger temperature sensor 92 Compressor discharge temperature sensor 93 Overcooling heat exchanger temperature sensor 94 Outlet temperature sensor 95 Second cycle compressor Discharge temperature sensor 100 Outdoor unit 101 Indoor unit 102 Liquid side connection piping (Liquid side piping)
103 Gas side connection piping (gas side piping)
110 Second refrigeration cycle 221 First flow path 222 Second flow path 231 First flow path of the evaporator of the second cycle 232 Second flow path of the evaporator of the second cycle

In order to achieve the above object, in the air conditioner of the present invention, the compressor, the outdoor heat exchanger, the first expansion valve (for example, the expansion valve 5), and the indoor heat exchanger are connected by a pipe, and the first A refrigerant circuit in which a hydrocarbon-based refrigerant circulates in a refrigeration cycle, and an overcooling means for overcooling the refrigerant by 10 K or more between the outdoor heat exchanger and the first expansion valve are provided in the refrigerant circuit. The liquid-side piping (for example, the liquid-side connecting piping 102) is characterized in that it is formed of a piping having an inner diameter of less than 4.75 mm and an inner diameter of 1.5 mm or more. Other aspects of the present invention will be described in embodiments described below.

The present invention relates to the structure of a household air conditioner (room air conditioner) using a flammable refrigerant.

The present invention is an invention for solving the above problems, reducing the holding amount of the refrigerant in the liquid side connecting pipe, household air which can contribute to the preservation of the refrigerant of the time of application, such as flammable refrigerant The purpose is to provide a harmonizer (room air conditioner).

In order to achieve the above object, in the room air conditioner of the present invention, the compressor, the outdoor heat exchanger, the first expansion valve (for example, the expansion valve 5), and the indoor heat exchanger are connected by a pipe, and the first refrigeration is performed. It has a refrigerant circuit in which a hydrocarbon-based refrigerant circulates in a cycle, and an overcooling means for overcooling the refrigerant by 10 K or more between the outdoor heat exchanger and the first expansion valve. The side piping (for example, the liquid side connecting piping 102) is characterized in that it is formed of a piping having an inner diameter of less than 3.5 mm and an inner diameter of 1.5 mm or more. Other aspects of the present invention will be described in embodiments described below.

Claims (7)

A refrigerant circuit in which the compressor, the outdoor heat exchanger, the first expansion valve, and the indoor heat exchanger are connected by piping and the refrigerant circulates in the first refrigeration cycle.
An overcooling means for supercooling the refrigerant to 10 K or more is provided between the outdoor heat exchanger and the first expansion valve.
An air conditioner characterized in that the liquid side piping of the refrigerant circuit is formed by piping having an inner diameter of less than 4.75 mm and an inner diameter of 1.5 mm or more. In claim 1,
The supercooling means is a supercooling heat exchanger that supercools the refrigerant flowing out from the outdoor heat exchanger, and is formed by a first flow path and a second flow path.
It branches from between the outdoor heat exchanger and the supercooling heat exchanger, is connected to one end of the first flow path via a second expansion valve, and the other end of the first flow path is compressed. It is connected to the suction side of the machine, one end of the second flow path is connected to the outdoor heat exchanger, and the other end of the second flow path is connected to the first expansion valve. Air conditioner. In claim 1,
It has a second refrigeration cycle via a second cycle compressor, a second cycle condenser, a second cycle expansion valve, and a second cycle evaporator.
The evaporator of the second cycle is arranged between the outdoor heat exchanger and the expansion valve, and the refrigerant flowing between the outdoor heat exchanger and the expansion valve is subjected to the second refrigeration cycle. An air conditioner characterized by cooling with a flowing refrigerant. In any one of claims 1 to 3,
An air conditioner characterized in that propylene or propane is used as the refrigerant in the first refrigeration cycle. In claim 3,
An air conditioner characterized in that R455A, propane, and R454C are used as the refrigerant in the second refrigeration cycle. In claim 2,
An air conditioner comprising a sensor for detecting the discharge vicinity temperature of the compressor, the piping temperature of the indoor heat exchanger, and the temperature of the second flow path of the supercooling heat exchanger. A refrigerant circuit in which the compressor, outdoor heat exchanger, and indoor heat exchanger are connected by piping and the refrigerant circulates in the refrigeration cycle.
An overcooling heat exchanger that supercools the refrigerant is provided between the outdoor heat exchanger and the indoor heat exchanger.
The supercooling heat exchanger is formed by a first flow path and a second flow path.
It branches from between the outdoor heat exchanger and the supercooling heat exchanger, is connected to one end of the first flow path via a second expansion valve, and the other end of the first flow path is compressed. It is connected to the suction side of the machine, one end of the second flow path is connected to the outdoor heat exchanger, and the other end of the second flow path is connected to the indoor heat exchanger.
The inner diameter d (mm) of the liquid side piping of the refrigerant circuit is defined as the heating capacity Q (kW).
d <-0.0118Q ² + 0.388Q + 0.80094
An air conditioner characterized by satisfying.

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