JP7370712B2 - Outdoor unit and air conditioner - Google Patents

Description

The present invention relates to an evaporator, an outdoor unit equipped with the same, and an air conditioner.

An outdoor heat exchanger that exchanges heat with air is disclosed as an outdoor unit of an air conditioner. Patent Document 1 discloses that when an outdoor heat exchanger is operated as an evaporator, the upper part of the fin is subjected to hydrophilic treatment, and the lower part of the fin is subjected to water repellent treatment, in order to smoothly drain dew condensation generated on the fin. It is disclosed that it is administered.

JP2014-206325A

When the fins are subjected to hydrophilic treatment, condensed water wets the surface of the fins and flows uniformly, but during heating operation at low outside temperatures, the condensed water freezes and forms frost on the fin surfaces, causing air ventilation resistance. There is a risk that this will occur.
When water-repellent treatment is applied to the fins, water droplets are formed on the surface of the fins and roll, thereby suppressing freezing, but there is a risk that the water droplets may act as air ventilation resistance.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an outdoor unit and an air conditioner that can suppress frost formation on an evaporator and ventilation resistance.

An evaporator as a reference example according to one aspect of the present invention includes a heat transfer tube having an inlet portion and an outlet portion, through which a refrigerant flows, and a plurality of fins through which the heat transfer tube is inserted and around which air flows. The fin includes a water-repellent area that has been subjected to water-repellent treatment over a range corresponding to a predetermined distance from the inlet portion or the outlet portion, and a non-water-repellent area that has not been subjected to water-repellent treatment. The water repellent region is provided in accordance with a range in which the temperature of the refrigerant flowing through the heat transfer tube is 0° C. or lower.

When the temperature of the refrigerant flowing through the heat transfer tubes of the evaporator becomes 0° C. or lower, the heat transfer tubes and fins freeze. Therefore, we decided to provide water-repellent areas on the fins depending on the area where the refrigerant temperature is below 0°C. As a result, the adhering moisture becomes water droplets and rolls on the fins provided with the water-repellent region, so that frost formation can be suppressed. Therefore, frost formed on the fins does not increase ventilation resistance.
For example, a hydrophilic treatment can be applied to the non-water repellent region.

An outdoor unit according to one aspect of the present invention includes the above-mentioned evaporator and a compressor that sucks and compresses the refrigerant guided from the evaporator, and the refrigerant has a temperature when evaporated at equal pressure. A refrigerant having a changing temperature slip, the water-repellent region is provided over a range corresponding to a predetermined distance from the inlet, and in a ph diagram where p is the pressure and h is the enthalpy, It is determined by comparing the evaporation process of the refrigeration cycle at the minimum rotation speed of the compressor with an isotherm at 0°C to obtain the range below 0°C.

When a refrigerant having a temperature slip that changes temperature during evaporation under equal pressure, such as a non-azeotropic mixed refrigerant, is used, the temperature on the inlet side of the heat transfer tube tends to be 0° C. or lower. For this reason, when using a refrigerant having temperature slip, a water-repellent region is provided on the fins over a range corresponding to a predetermined distance from the inlet of the heat transfer tube.

An outdoor unit according to one aspect of the present invention includes the above-mentioned evaporator and a compressor that sucks and compresses the refrigerant guided from the evaporator, and the refrigerant has a temperature when evaporated at equal pressure. In a ph diagram where the refrigerant is a refrigerant with no changing temperature slip, the water-repellent region is provided over a range corresponding to a predetermined distance from the outlet, and the pressure is p and the enthalpy is h, It is determined by comparing the evaporation process of the refrigeration cycle at the minimum rotation speed of the compressor with an isotherm at 0°C to obtain the range below 0°C.

When using a refrigerant such as a single refrigerant or an azeotropic refrigerant mixture that does not have a temperature slip where the temperature changes during evaporation under equal pressure, the temperature at the outlet of the evaporator tends to be 0° C. or lower. Therefore, when using a refrigerant without temperature slip, a water-repellent region is provided over a range corresponding to a predetermined distance from the outlet of the heat transfer tube.

Furthermore, in the outdoor unit according to one aspect of the present invention, the water repellent area is determined based on the minimum rotation speed of the compressor.

A state in which the compressor is operated at the minimum rotation speed can be said to be a state in which the indoor temperature has reached the set temperature during heating operation. If frost forms at this time and a defrost operation is performed, the indoor heat exchanger becomes an evaporator due to the reverse cycle operation caused by the defrost operation, which may cause discomfort to the user. Therefore, we decided to define the water repellent area based on the minimum rotation speed of the compressor. Thereby, the water-repellent area can be provided only in the necessary range to suppress frost formation.
On the other hand, if the compressor is operating at a rotation speed higher than the minimum rotation speed, it means that the heating load is being applied to reach the set temperature, so if the indoor heat exchanger is in defrost operation and the indoor heat exchanger is evaporating. Even if the defrost operation is performed as a device, it can be said that the user can predict that the defrost operation will be performed, so it will not cause much discomfort to the user.
When using a refrigerant with temperature slippage, such as a non-azeotropic mixed refrigerant, increasing the rotation speed of the compressor increases the pressure loss, and the temperature at the outlet side of the heat transfer tube becomes 0°C or lower than at the inlet side. There is a risk. Even in such a case, since the rotation speed of the compressor is high, the user will not feel any discomfort.
The minimum rotation speed of the compressor can be determined by the specifications of the compressor, and refers to the rotation speed at which a command is given to maintain the set temperature after reaching the set temperature during heating operation.

Furthermore, in the outdoor unit according to one aspect of the present invention, the non-water repellent region is subjected to hydrophilic treatment.

Since there is no risk of frost formation in the non-water-repellent areas, it was decided that a hydrophilic treatment would be applied to the fins to uniformly wet the surface of the fins and drain the condensed water smoothly. Thereby, ventilation resistance can be reduced.

Further, an air conditioner according to one aspect of the present invention includes any of the outdoor units described above, and an indoor unit connected to the outdoor unit via refrigerant piping.

By limiting the water-repellent area formed on the fin to a predetermined range, frost formation on the evaporator and ventilation resistance can be suppressed.

1 is a schematic configuration diagram showing a refrigerant circuit of an air conditioner according to a first embodiment of the present invention. FIG. 2 is a front view showing the outdoor heat exchanger of FIG. 1. FIG. FIG. 3 is a partially enlarged front view showing a water-repellent region. FIG. 3 is a partially enlarged front view showing a hydrophilic region. FIG. 3 is a pH diagram when a non-azeotropic mixed refrigerant is used. It is a graph showing changes in evaporator temperature. FIG. 3 is a ph diagram when a refrigerant with no temperature slip is used.

Embodiments according to the present invention will be described below with reference to the drawings.
[First embodiment]
Hereinafter, a first embodiment of the present invention will be described using FIG. 1.
FIG. 1 shows a refrigerant circuit configuration of an air conditioner 1 according to this embodiment. The air conditioner 1 can perform heating operation and cooling operation by switching a four-way valve 4 provided on the discharge side of the compressor 3. In FIG. 1, the direction indicated by a solid arrow A1 indicates the refrigerant flow direction during heating operation, and the direction indicated by broken line arrow A2 indicates the refrigerant flow direction during cooling operation or defrost operation.

The air conditioner 1 uses R454C, which is a non-azeotropic refrigerant mixture of R32 and R1234yf, as a refrigerant. R32 is considered to be a low boiling point refrigerant that has a lower boiling point than R123yf. R1234yf is considered to be a high boiling point refrigerant that has a higher boiling point than R32. Note that instead of R454C, R454B or other non-azeotropic refrigerant in the R400 series may be used.

The air conditioner 1 includes a compressor 3 that compresses a non-azeotropic mixed refrigerant (hereinafter sometimes simply referred to as "refrigerant"), a four-way valve 4, an outdoor heat exchanger 5, an expansion valve 7, and an indoor It is equipped with a heat exchanger 9. The compressor 3, four-way valve 4, outdoor heat exchanger 5, expansion valve 7, and indoor heat exchanger 9 are connected by refrigerant piping to form a refrigerant circuit that performs a refrigeration cycle.

The compressor 3, the four-way valve 4, the outdoor heat exchanger 5, and the expansion valve 7 are installed inside the outdoor unit 2. The indoor heat exchanger 9 is installed inside the indoor unit 10. Note that the expansion valve 7 may be installed inside the indoor unit 10.

The compressor 3 is, for example, a scroll compressor or a rotary compressor, and is driven by an electric motor (not shown). The electric motor is equipped with an inverter device, and the rotation speed can be arbitrarily changed by a command from a control section (not shown).

The four-way valve 4 is switched so that the refrigerant discharged from the compressor 3 is guided to the indoor heat exchanger 9 during heating operation, and the refrigerant discharged from the compressor 3 is guided to the outdoor heat exchanger 9 during cooling operation or defrost operation. It is switched to lead to 5. The four-way valve 4 is controlled by a control section (not shown).

The outdoor heat exchanger 5 operates as an evaporator during heating operation, and operates as a condenser during cooling operation or defrost operation. Air (outside air) is sent to the outdoor heat exchanger 5 from an outdoor fan 6.

The indoor heat exchanger 9 operates as a condenser during heating operation, and operates as an evaporator during cooling operation or defrost operation.

The expansion valve 7 expands the refrigerant that has been condensed and liquefied in the heat exchangers 5 and 9 that operate as condensers. The opening degree of the expansion valve 7 is controlled by a control section.

FIG. 2 shows a schematic configuration of the outdoor heat exchanger 5. The outdoor heat exchanger 5 is a fin-tube heat exchanger, and includes a heat transfer tube 12 through which a refrigerant flows, and a fin group 14A made up of a plurality of fins 14.

The heat exchanger tube 12 includes an inlet portion 12a and an outlet portion 12b. The inlet section 12a is located at the bottom, and the outlet section 12b is located at the top. The heat exchanger tube 12 is provided in a meandering manner between an inlet portion 12a and an outlet portion 12b. Note that the vertical positions of the inlet part 12a and the outlet part 12b are not limited to the present embodiment shown in FIG. An inlet portion 12a and an outlet portion 12b may be present.

The fin group 14A is composed of plate-shaped fins 14 extending in the vertical direction in FIG. 2 and arranged in the stacking direction (horizontal direction in FIG. 2) at a predetermined pitch. Therefore, the fin group 14A shown in FIG. 2 shows the outer shape of the stacked fins 14 when viewed from the front. Each fin 14 is made of metal, for example, aluminum alloy. A plurality of through holes are formed in each fin 14, and the heat exchanger tubes 12 are arranged so as to be inserted through these through holes. Each fin 14 and the heat exchanger tube 12 are in physical contact to ensure good heat conduction.

In the fin group 14A located on the inlet portion 12a side of the heat exchanger tube 12, that is, in the lower part of the fin group 14A indicated by hatching, a water-repellent region 14a is formed in which the lower part of each fin 14 is treated with water-repellent treatment. The water repellent treatment is performed, for example, by coating the base material (metal portion) of the fins 14 with a water repellent material.

A hydrophilic region (non-water repellent region) 14b that has been subjected to hydrophilic treatment is formed in the fin group 14A located above the water repellent region 14a, that is, on the outlet portion 12b side of the heat transfer tube 12. The hydrophilic treatment is performed, for example, by coating the base material (metal portion) of the fins 14 with a hydrophilic material. In this way, the fin group 14A is divided into two regions, the water-repellent region 14a and the hydrophilic region 14b.

FIG. 3 shows the state of condensed water in the water-repellent region 14a. In the water-repellent region 14a where the surface of the fin 14 is treated to be water-repellent, as shown in the figure, condensed water turns into droplets D, which roll downward due to gravity. In this manner, the droplets D roll and move in the water-repellent region 14a, making them less likely to freeze. However, depending on the size of the droplet D, it becomes a ventilation resistance for the air passing between the fins 14.

FIG. 4 shows the state of condensed water in the hydrophilic region 14b. In the hydrophilic region 14b where the surface of the fin 14 has been subjected to hydrophilic treatment, as shown in the figure, condensed water forms a water film F that wets the surface of the fin 14, spreads uniformly, and flows downward by gravity. In this manner, the water film F spreads uniformly in the hydrophilic region 14b and flows as a thin film, so that the ventilation resistance of the air passing between the fins 14 is smaller than that in the case of the droplet D (see FIG. 3). However, since the water film F continues to adhere to the surface of the fins 14, there is a risk of freezing and frost formation.

As shown in FIGS. 3 and 4, the water-repellent region 14a and the hydrophilic region 14b are appropriately defined depending on the flow state of dew condensation water in each of the water-repellent region 14a and the hydrophilic region 14b. That is, the water-repellent region 14a is employed in a region where there is a risk of condensed water freezing, thereby suppressing freezing of dew condensed water. A hydrophilic region 14b is employed in a region where there is no risk of condensed water freezing to increase ventilation resistance.

The boundary between the water-repellent region 14a and the hydrophilic region 14b is determined according to the temperature of the refrigerant flowing through the heat exchanger tubes 12. That is, the region corresponding to the range where the temperature of the refrigerant flowing through the heat exchanger tubes 12 is 0° C. or less is defined as the water-repellent region 14a, and the region corresponding to the range where the temperature of the refrigerant flowing through the heat exchanger tube 12 exceeds 0° C. is defined as the hydrophilic region 14b. .
Note that the refrigerant temperature that defines the boundary between the water-repellent region 14a and the hydrophilic region 14b does not need to be strictly 0°C, and may be set within a range of, for example, 0°C to 3°C or -3°C to 0°C. . However, if the boundary is set at a refrigerant temperature of 0°C or lower, there is a risk of freezing in the hydrophilic region 14b, so it is preferable to set the boundary at 0°C or higher.

In the non-azeotropic mixed refrigerant, there is a region where the refrigerant temperature is 0° C. or lower over a predetermined range from the inlet portion 12 a side of the heat transfer tube 12 . Therefore, as shown in FIG. 2, the water-repellent region 14a is defined in a predetermined region from the inlet portion 12a, that is, in a predetermined region formed from the bottom to the top.

FIG. 5 shows the reason why the refrigerant temperature becomes 0° C. or lower on the inlet portion 12a side of the heat transfer tube 12 when a non-azeotropic mixed refrigerant is used. FIG. 5 is a pH diagram when a non-azeotropic mixed refrigerant is used. That is, the horizontal axis shows enthalpy h, and the vertical axis shows pressure p. The thick solid line shows the saturated liquid line S1 and the saturated vapor line S2, the thin solid line shows the refrigeration cycle C, and the broken line shows the isothermal line T at 0°C. As can be seen from the figure, the non-azeotropic mixed refrigerant has a temperature slip where the temperature changes during evaporation at equal pressure, so in the wet vapor region between the saturated liquid line S1 and the saturated vapor line S2, the isothermal line T slopes down to the right. On the other hand, in the evaporation process of the refrigeration cycle C showing the outdoor heat exchanger 5 during heating operation, the lines are substantially parallel. The evaporation process of the refrigeration cycle C is slightly downward to the right, but this is due to the pressure loss of the refrigerant flowing inside the heat exchanger tubes 12.

As can be seen from FIG. 5, when a non-azeotropic mixed refrigerant is used, temperature slip occurs, so the area below the isotherm T at 0°C is on the inlet 12a side of the heat transfer tube 12 (left side in FIG. 5) Become. Therefore, a water-repellent region 14a is formed on the inlet portion 12a side of the heat exchanger tube 12, and as shown in FIG. A water repellent region 14a is formed in a predetermined range from the bottom to the top.

FIG. 6 shows the influence of the refrigerant temperature on the rotation speed of the compressor 3. In the figure, the horizontal axis shows the evaporator area [%], and the vertical axis shows the evaporator temperature [°C]. Here, the evaporator means the outdoor heat exchanger 5 during heating operation. The evaporator area on the horizontal axis is the heat transfer area of the fins 14 integrated from the inlet portion 12a of the heat transfer tube 12. Therefore, 0% indicates the inlet portion 12a and 100% indicates the outlet portion 12b. The evaporator temperature is the temperature of the refrigerant flowing through the heat transfer tubes 12.

As shown in FIG. 6, when the rotation speed of the compressor 3 is at the minimum operation, the evaporator temperature is 0° C. or lower over a predetermined range from the inlet portion 12a side. In the case shown in the figure, the water-repellent region 14a is formed over a range in which the area of the evaporator is 0% or more and 34.5% or less.

When the rotational speed of the compressor 3 increases from the minimum operation to intermediate operation, the evaporator temperature exceeds 0° C. from the inlet portion 12a to the outlet portion 12b. This is because the pressure loss in the heat transfer tubes 12 increases as the rotational speed of the compressor 3 increases, and the straight line representing the evaporation process of the refrigeration cycle C in the pH diagram shown in FIG. 5 slopes upward to the left. be.

When the rotational speed of the compressor 3 further increases to reach maximum operation, the evaporator temperature becomes 0° C. or lower over a predetermined range from the outlet portion 12b side. This is because the pressure loss in the heat transfer tubes 12 further increases, the straight line representing the evaporation process of the refrigeration cycle C becomes further upward to the left, and the suction pressure of the compressor 3 decreases. As described above, when the rotation speed of the compressor 3 is at its maximum, the temperature on the outlet portion 12b side becomes 0° C. or lower, but in this embodiment, it is a hydrophilic region 14b and is not a water-repellent region 14a. Therefore, if the rotation speed of the compressor 3 is high, there is a risk of freezing on the outlet portion 12b side. However, even if the hydrophilic region 14b is frozen and frosted and defrost operation is performed, if the rotation speed of the compressor 3 is high, it means that the heating load is applied to reach the set temperature. Even if the indoor heat exchanger 9 operates as an evaporator during defrost operation, it can be said that the user can predict that the defrost operation will occur, so the user will not feel much discomfort.

The minimum rotation speed of the compressor 3 during minimum operation can be determined by the specifications of the compressor 3. Alternatively, the minimum rotational speed of the compressor 3 can be determined as the rotational speed at which the control unit commands to maintain the set temperature after reaching the set temperature during heating operation.

According to this embodiment, the following effects are achieved.
When the refrigerant flowing through the heat transfer tubes 12 of the outdoor heat exchanger 5 that operates as an evaporator during heating operation becomes 0° C. or lower, the heat transfer tubes 12 and fins 14 freeze. Therefore, it was decided to form water-repellent areas 14a on the fins 14 according to the area where the temperature of the refrigerant is 0° C. or lower. As a result, the attached moisture becomes water droplets and rolls on the fins 14 provided with the water-repellent regions 14a, so that frost formation can be suppressed. Therefore, frost formed on the fins 14 does not increase ventilation resistance.

When a refrigerant having a temperature slip in which the temperature changes during evaporation under equal pressure, such as a non-azeotropic mixed refrigerant, is used, the temperature on the inlet portion 12a side of the heat transfer tube 12 tends to be 0° C. or lower. Therefore, in the case of using a refrigerant having a temperature slip, the fins 14 are provided with a water-repellent region 14a over a range corresponding to a predetermined distance from the inlet portion 12a of the heat transfer tube 12. Thereby, the water-repellent area can be applied only to the area necessary to suppress frost formation.

A state in which the compressor 3 is operated at the minimum rotation speed can be said to be a state in which the indoor temperature has reached the set temperature during heating operation. If frost forms and a defrost operation is performed at this time, the indoor heat exchanger 9 becomes an evaporator due to the reverse cycle operation caused by the defrost operation, which may cause discomfort to the user. Therefore, it was decided to define the water repellent area based on the minimum rotation speed of the compressor 3. This can improve the user's feeling.

The non-water repellent area other than the water repellent area 14a was designated as the hydrophilic area 14b since there is no risk of frost formation. Thereby, the condensed water generated on the fins 14 is smoothly discharged so as to uniformly wet the surface of the fins 14, thereby reducing ventilation resistance.

[Second embodiment]
Next, a second embodiment of the present invention will be described using FIG. 7. The present embodiment uses a different refrigerant from the first embodiment, and the range of the water repellent region differs accordingly. The other configurations are the same as those in the first embodiment, so their explanation will be omitted.

When using a refrigerant such as a single refrigerant or an azeotropic mixed refrigerant that does not have a temperature slip where the temperature changes during evaporation under equal pressure, the temperature at the outlet portion 12b of the heat transfer tube 12 tends to be 0° C. or lower. . Specifically, as shown in FIG. 7, for a refrigerant with no temperature slip, the 0°C isotherm T' in the wet steam region between the saturated liquid line S1' and the saturated vapor line S2' has a constant pressure. be. On the other hand, the straight line in the evaporation process of the refrigeration cycle C' slopes slightly downward to the right due to pressure loss. As a result, the temperature on the outlet portion 12b side becomes 0° C. or lower.
Therefore, when using a refrigerant without temperature slip, the water-repellent region 14a' is provided over a range corresponding to a predetermined distance from the outlet portion 12b of the heat transfer tube 12. Therefore, the hydrophilic region 14b' is provided on the inlet portion 12a side of the heat exchanger tube 12.

In each of the embodiments described above, the hydrophilic regions 14b, 14b are coated with a hydrophilic coating, but the hydrophilic regions may be formed by a treatment other than coating, such as hot water treatment. Alternatively, it may be a non-water repellent region that is not subjected to hydrophilic treatment or water repellent treatment. Even in this case, the effect of suppressing frost formation in the water-repellent region can be obtained.

1 Air conditioner 2 Outdoor unit 3 Compressor 4 Four-way valve 5 Outdoor heat exchanger (evaporator)
6 Outdoor fan 7 Expansion valve 9 Indoor heat exchanger 10 Indoor unit 12 Heat transfer tube 12a Inlet section 12b Outlet section 14 Fin 14A Fin group 14a Water repellent region 14b Hydrophilic region (non-water repellent region)
D Droplet F Water film

Claims (4)

a heat exchanger tube having an inlet portion and an outlet portion and in which a refrigerant flows;
a plurality of fins through which the heat exchanger tube is inserted and air circulates around the fins;
Equipped with
The fin has a water-repellent region that has been subjected to water-repellent treatment over a range corresponding to a predetermined distance from the inlet portion or the outlet portion, and a non-water-repellent region that has not been subjected to water-repellent treatment,
an evaporator in which the water-repellent region is provided in accordance with a range in which the refrigerant flowing through the heat transfer tube is 0° C. or lower;
a compressor that sucks and compresses the refrigerant guided from the evaporator;
Equipped with
The refrigerant is a refrigerant having a temperature slip in which the temperature changes during evaporation under equal pressure,
The water-repellent area is provided over a range corresponding to a predetermined distance from the inlet , and in a ph diagram where p is the pressure and h is the enthalpy, the refrigeration cycle at the minimum rotation speed of the compressor is The outdoor unit is determined by comparing the evaporation process of and the isothermal line at 0°C to obtain the range below 0°C . a heat exchanger tube having an inlet portion and an outlet portion and in which a refrigerant flows;
a plurality of fins through which the heat exchanger tube is inserted and air circulates around the fins;
Equipped with
The fin has a water-repellent region that has been subjected to water-repellent treatment over a range corresponding to a predetermined distance from the inlet portion or the outlet portion, and a non-water-repellent region that has not been subjected to water-repellent treatment,
an evaporator in which the water-repellent region is provided in accordance with a range in which the refrigerant flowing through the heat transfer tube is 0° C. or lower;
a compressor that sucks and compresses the refrigerant guided from the evaporator;
Equipped with
The refrigerant is a refrigerant that does not have temperature slip where the temperature changes during evaporation at equal pressure,
The water-repellent region is provided over a range corresponding to a predetermined distance from the outlet portion , and in a ph diagram where pressure is p and enthalpy is h, the refrigeration cycle at the minimum rotation speed of the compressor is The outdoor unit is determined by comparing the evaporation process of and the isothermal line at 0°C to obtain the range below 0°C . The outdoor unit according to claim 1 or 2, wherein the non-water repellent area is subjected to hydrophilic treatment. The outdoor unit according to any one of claims 1 to 3,
an indoor unit connected to the outdoor unit through refrigerant piping;
Air conditioner equipped with.

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