JP6044238B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner that performs a dehumidifying operation.

In conventional air conditioners, an auxiliary heat exchanger is arranged on the back side of the main heat exchanger, and the refrigerant is evaporated only by the auxiliary heat exchanger to perform dehumidification locally, so that the load is reduced (compression) For example, there is an air conditioner in which dehumidification can be performed even when the difference between the room temperature and the set temperature is sufficiently small and the required cooling capacity is small. In this air conditioner, the evaporation region is limited to the auxiliary heat exchanger, and the temperature sensor is disposed downstream of the evaporation region, and is controlled to have a certain degree of superheat.

JP-A-9-14727

However, in the control to set a certain degree of superheat, when the load is relatively large, the evaporation temperature is lowered. However, if the evaporation temperature is too low, there is a possibility of freezing and evaporation. Lowering the temperature causes a reduction in the efficiency of the refrigeration cycle. On the other hand, when the load becomes very small, there is a problem that the evaporation temperature rises and dehumidification becomes impossible.

In view of this, the inventor of the present invention provides an air conditioner having a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are connected. It has been found that by controlling the compressor and the expansion valve so as to have an overheating region, dehumidification can be reliably performed even at low loads.

And in this air conditioner, by increasing the changeable range (heat exchange part) of the evaporation region in the indoor heat exchanger during the dehumidifying operation, a large amount of refrigerant can be evaporated even at the same evaporation temperature. Therefore, the range of change in the dehumidifying capacity can be increased. However, there is a problem that this heat exchange portion causes a large pressure loss during the cooling operation, thereby reducing the capacity of the indoor heat exchanger.

Accordingly, an object of the present invention is to provide an air conditioner that can reliably perform dehumidification even at a low load and can reduce pressure loss at a heat exchange portion for performing the dehumidifying operation. .

An air conditioner according to a first aspect of the present invention includes a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are connected, and a refrigerant in which R32 is mixed by 75% or more is used as a refrigerant. Auxiliary heat exchange wherein the indoor heat exchanger has a plurality of fins and heat transfer tubes expanded in the plurality of fins and is disposed on the most windward side in a predetermined dehumidifying operation mode And a main heat exchanger disposed downstream of the auxiliary heat exchanger, and in a predetermined dehumidifying operation mode, the refrigerant supplied from the liquid inlet flows through the auxiliary heat exchanger in one pass. After that, in the predetermined dehumidifying operation mode, an evaporating area where the liquid refrigerant evaporates is disposed in the auxiliary heat exchanger, and the evaporating area of the auxiliary heat exchanger is configured to flow in the main heat exchanger. superheat region on the downstream side of With the location, so that the range of the evaporation region in response to load changes in the auxiliary heat exchanger, said compressor and said expansion valve is controlled, the indoor heat exchanger in the predetermined dehumidification operation mode The inner diameter of the expanded heat transfer tube in a portion that can become an evaporation region is 4.4 mm or more.

In this air conditioner, a refrigerant mixed with 75% or more of R32 is used as a refrigerant, and the inner diameter of the expanded heat transfer tube in the portion that can be the evaporation region of the indoor heat exchanger in a predetermined dehumidifying operation mode is 4.4 mm. Since it is comprised above, it can suppress that the heat exchange part becomes a big pressure loss at the time of air_conditionaing | cooling operation, and can prevent that the capability of an indoor heat exchanger falls.
In this air conditioner, the portion that becomes the evaporation region of the indoor heat exchanger in a predetermined dehumidifying operation mode
However, since it is configured as an auxiliary heat exchanger, the heat transfer tube of the auxiliary heat exchanger is connected to the main heat exchanger.
The structure of the heat transfer tube can be easily different.

An air conditioner according to a second aspect of the present invention includes a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are connected, and R410A refrigerant is used as the refrigerant. The indoor heat exchanger has a plurality of fins and heat transfer tubes expanded in the plurality of fins, respectively, and the auxiliary heat exchanger disposed on the uppermost wind side in the predetermined dehumidifying operation mode and the auxiliary heat exchange A main heat exchanger disposed downstream of the heat exchanger, and in a predetermined dehumidifying operation mode, after the refrigerant supplied from the liquid inlet flows through the auxiliary heat exchanger in one pass, the main heat exchanger In the predetermined dehumidifying operation mode, an evaporating area where the liquid refrigerant evaporates is disposed in the auxiliary heat exchanger, and a superheat area downstream of the evaporating area of the auxiliary heat exchanger. Is placed As the range of the evaporation region in response to load changes in the auxiliary heat exchanger, said compressor and said expansion valve is controlled, the evaporation region capable of becoming part of the indoor heat exchanger in the predetermined dehumidification operation mode The inner diameter of the expanded heat transfer tube is 4.9 mm or more.

In this air conditioner, R410 refrigerant is used as the refrigerant, and the inner diameter of the expanded heat transfer tube in the portion that can become the evaporation region of the indoor heat exchanger in a predetermined dehumidifying operation mode is 4.9.
Since it is comprised in mm or more, it can suppress that the heat exchange part becomes a big pressure loss at the time of air_conditionaing | cooling operation, and can prevent that the capability of an indoor heat exchanger falls.

In this air conditioner, the portion that becomes the evaporation region of the indoor heat exchanger in the predetermined dehumidifying operation mode is configured as an auxiliary heat exchanger, so that the heat transfer tube of the auxiliary heat exchanger is connected to the main heat exchanger. It can be easily different from the structure of the heat transfer tube.

An air conditioner according to a third invention is the air conditioner according to the first or second invention, wherein the main heat exchanger is a front heat exchanger disposed on the front side in the indoor unit, A back heat exchanger disposed on the back side, and the auxiliary heat exchanger is disposed in front of the front heat exchanger.

In this air conditioner, since the area of the auxiliary heat exchanger can be increased, the range in which the evaporation region of the auxiliary heat exchanger can be increased.

  As described above, according to the present invention, the following effects can be obtained.

In the first invention, a refrigerant mixed with 75% or more of R32 is used as the refrigerant,
In the predetermined dehumidifying operation mode, the inner diameter of the expanded heat transfer tube in the portion that can become the evaporation region of the indoor heat exchanger is configured to be 4.4 mm or more, so that the heat exchange portion has a large pressure loss during the cooling operation. Can be suppressed, and the capacity of the indoor heat exchanger can be prevented from being lowered.
In the first invention, the portion that becomes the evaporation region of the indoor heat exchanger in a predetermined dehumidifying operation mode is
Since it is configured as an auxiliary heat exchanger, the heat transfer tube of the auxiliary heat exchanger is connected to the main heat exchanger.
It can be easily different from the structure of the heat tube.
In the second invention, R410 refrigerant is used as the refrigerant, and the inner diameter of the expanded heat transfer tube in the portion that can be the evaporation region of the indoor heat exchanger in the predetermined dehumidifying operation mode is 4.9 mm.
Since it is comprised above, it can suppress that the heat exchange part becomes a big pressure loss at the time of air_conditionaing | cooling operation, and can prevent that the capability of an indoor heat exchanger falls.
In the second invention, the portion that becomes the evaporation region of the indoor heat exchanger in the predetermined dehumidifying operation mode,
Since it is configured as an auxiliary heat exchanger, the heat transfer tube of the auxiliary heat exchanger can be easily different from the configuration of the heat transfer tube of the main heat exchanger.
In 3rd invention, since the area of an auxiliary heat exchanger can be enlarged, the range which the evaporation area of an auxiliary heat exchanger changes can be enlarged.

It is a circuit diagram which shows the refrigerant circuit of the air conditioner which concerns on embodiment of this invention. It is a schematic sectional drawing of the indoor unit of the air conditioner which concerns on embodiment of this invention. It is a figure explaining the structure of an indoor heat exchanger. It is a figure explaining the control part of the air conditioner which concerns on embodiment of this invention. An example of the flow rate change when the opening degree is changed in the expansion valve is shown. It is a figure explaining control in the case of driving in dehumidification operation mode. Fig.7 (a) is a figure which shows sectional drawing of the heat exchanger tube which does not have an inner surface groove | channel, FIG.7 (b) is a figure which shows sectional drawing of the heat exchanger tube which has an inner surface groove | channel. It is a graph which shows the evaluation at the time of changing the pipe diameter of the heat exchanger tube of an auxiliary heat exchanger.

  Hereinafter, an embodiment of an air conditioner 1 according to the present invention will be described.

<Overall configuration of the air conditioner 1>
As shown in FIG. 1, the air conditioner 1 of this embodiment includes an indoor unit 2 installed indoors and an outdoor unit 3 installed outdoor. The air conditioner 1 includes a refrigerant circuit in which a compressor 10, a four-way valve 11, an outdoor heat exchanger 12, an expansion valve 13, and an indoor heat exchanger 14 are connected. In the refrigerant circuit, the outdoor heat exchanger 1 is connected to the discharge port of the compressor 10 via the four-way valve 11.
2 is connected, and an expansion valve 13 is connected to the outdoor heat exchanger 12. One end of the indoor heat exchanger 14 is connected to the expansion valve 13, and the suction port of the compressor 10 is connected to the other end of the indoor heat exchanger 14 via the four-way valve 11. The indoor heat exchanger 14 has an auxiliary heat exchanger 20 and a main heat exchanger 21.

The air conditioner 1 can be operated in a cooling operation mode, a predetermined dehumidifying operation mode, and a heating operation mode. The remote controller selects one of the operations by a remote controller and performs an operation start operation, an operation switching operation or an operation. Stop operation can be performed. Further, the remote controller can change the air volume of the indoor unit 2 by setting a set temperature of the indoor temperature or changing the rotation speed of the indoor fan.

In the cooling operation mode and the predetermined dehumidifying operation mode, the refrigerant discharged from the compressor 10 flows from the four-way valve 11 to the outdoor heat exchanger 12, the expansion valve 13, the auxiliary heat exchanger 20, the main heat, as indicated by the solid arrows in the figure. A cooling cycle or a dehumidification cycle is formed in which the refrigerant flows in sequence to the exchanger 21 and the refrigerant that has passed through the main heat exchanger 21 returns to the compressor 10 through the four-way valve 11. That is, the outdoor heat exchanger 12 functions as a condenser, and the indoor heat exchanger 14 (auxiliary heat exchanger 20 and main heat exchanger 21) functions as an evaporator.

On the other hand, in the heating operation mode, when the four-way valve 11 is switched, the refrigerant discharged from the compressor 10 is transferred from the four-way valve 11 to the main heat exchanger 21 and the auxiliary heat exchanger 2 as indicated by broken arrows in the figure.
0, the expansion valve 13 and the outdoor heat exchanger 12 are sequentially flowed, and a heating cycle is formed in which the refrigerant passing through the outdoor heat exchanger 12 returns to the compressor 10 through the four-way valve 11. That is, the indoor heat exchanger 14
The (auxiliary heat exchanger 20 and the main heat exchanger 21) function as a condenser, and the outdoor heat exchanger 12 functions as an evaporator.

The indoor unit 2 has an air inlet 2a for indoor air on the upper surface, and an air outlet 2b for air conditioning at the lower front surface.
And have. An air flow path is formed in the indoor unit 2 from the suction port 2a toward the blowout port 2b, and an indoor heat exchanger 14 and a cross-flow type indoor fan 16 are disposed in the air flow path.
Therefore, when the indoor fan 16 rotates, room air is sucked into the indoor unit 1 from the suction port 2a. On the front side of the indoor unit 2, the intake air from the intake port 2 a flows to the indoor fan 16 side through the auxiliary heat exchanger 20 and the main heat exchanger 21. On the other hand, on the back side of the indoor unit 2, the intake air from the intake port 2 a flows through the main heat exchanger 21 to the indoor fan 16 side.

As described above, when the indoor heat exchanger 14 is operated in the cooling operation mode and the predetermined dehumidifying operation mode with the auxiliary heat exchanger 20, the main heat disposed on the downstream side of the auxiliary heat exchanger 20. An exchange 21 is provided. The main heat exchanger 21 has a front heat exchanger 21 a disposed on the front side of the indoor unit 2 and a back heat exchanger 21 b disposed on the back side of the indoor unit 2, and this heat exchanger 21 a and 21 b are arranged in an inverted V shape so as to surround the indoor fan 16. And the auxiliary heat exchanger 20 is arrange | positioned ahead of the front surface heat exchanger 21a. The auxiliary heat exchanger 20 and the main heat exchanger 21 (the front heat exchanger 21a and the back heat exchanger 21b) each have a large number of fins and heat transfer tubes expanded in the large number of fins. Yes.

In the cooling operation mode and the predetermined dehumidifying operation mode, as shown in FIG. 3, the auxiliary heat exchanger 2
The liquid refrigerant is supplied from the liquid inlet 17a disposed near the end portion below 0, and the supplied liquid refrigerant flows so as to approach the upper end of the auxiliary heat exchanger 20. And it flows out from the exit 17b arrange | positioned near the upper end of the auxiliary heat exchanger 20, and flows into the branch part 18a. The refrigerant branched in the branching portion 18a is supplied from the three inlets 17c of the main heat exchanger 21 to the lower and upper parts of the front heat exchanger 21a and the rear heat exchanger 21b, and then from the outlet 17d. It flows out and joins at the junction 18b. In the heating operation mode, the refrigerant flows in the direction opposite to the above.

In the air conditioner 1, when the operation in the predetermined dehumidifying operation mode is performed, the liquid refrigerant supplied from the liquid inlet 17 a of the auxiliary heat exchanger 20 is evaporated in the middle of the auxiliary heat exchanger 20. To do. Therefore, only a part of the auxiliary heat exchanger 20 near the liquid inlet 17a is an evaporation region where the liquid refrigerant evaporates. Therefore, when operating in the predetermined dehumidifying operation mode, in the indoor heat exchanger 14, only a part of the upstream side of the auxiliary heat exchanger 20 is an evaporation region and is downstream of the evaporation region of the auxiliary heat exchanger 20. Both the range on the side and the main heat exchanger 21 are overheated regions. Therefore, in the air conditioner 1 of the present embodiment, the heat transfer tube of the auxiliary heat exchanger 20 is an expanded heat transfer tube in a portion that can be an evaporation region of the indoor heat exchanger 14 in a predetermined dehumidifying operation mode.

Then, the refrigerant that has flowed through the superheated region near the upper end of the auxiliary heat exchanger 20 flows through the lower part of the front heat exchanger 21 a disposed on the leeward side of the lower part of the auxiliary heat exchanger 20. Therefore, in the suction air from the suction port 2a, the air cooled in the evaporation region of the auxiliary heat exchanger 20 is heated by the front heat exchanger 21a and then blown out from the blower outlet 2b. On the other hand, in the suction air from the suction port 2a, the air that has flowed through the superheated area of the auxiliary heat exchanger 20 and the front heat exchanger 21a and the air that has flowed through the back heat exchanger 21b are substantially the same as the room temperature. And it blows out from the blower outlet 2b.

In the air conditioner 1, as shown in FIG. 1, an evaporation temperature sensor 30 that detects the evaporation temperature on the downstream side of the expansion valve 13 in the refrigerant circuit is attached to the outdoor unit 3. Then, the indoor unit 2 detects the indoor temperature sensor 31 that detects the indoor temperature (the temperature of the intake air from the suction port 2a of the indoor unit 2), and the auxiliary heat exchanger 20 detects that the evaporation of the liquid refrigerant has ended. An indoor heat exchanger temperature sensor 32 is attached.

As shown in FIG. 3, the indoor heat exchanger temperature sensor 32 is disposed on the leeward side near the upper end of the auxiliary heat exchanger 20. And in the superheat zone near the upper end of the auxiliary heat exchanger 20, the suction air from the suction inlet 2a is hardly cooled. Therefore, when the temperature detected by the indoor heat exchanger temperature sensor 32 is substantially the same as the indoor temperature detected by the indoor temperature sensor 31, the auxiliary heat exchanger 2
It can be detected that the evaporation is completed in the middle of 0 and that the range near the upper end of the auxiliary heat exchanger 20 is an overheated region. In addition, the indoor heat exchanger temperature sensor 32 is disposed in a heat transfer tube in an intermediate portion of the indoor heat exchanger 14. Therefore, the condensation temperature or evaporation temperature in the cooling / heating operation can be detected near the middle portion of the indoor heat exchanger 14.

As shown in FIG. 4, the control unit of the air conditioner 1 includes a compressor 10, a four-way valve 11, and an expansion valve 1.
3, a motor 16 a that drives the indoor fan 16, an evaporation temperature sensor 30, an indoor temperature sensor 31, and an indoor heat exchanger temperature sensor 32 are connected. Therefore, the control unit controls the command from the remote controller (operation start operation, set temperature of the room temperature, etc.), the evaporation temperature detected by the evaporation temperature sensor 30, the room temperature detected by the room temperature sensor 31 (the temperature of the intake air) ), The operation of the air conditioner 1 is controlled based on the intermediate heat exchange temperature detected by the indoor heat exchange temperature sensor 32.

In the air conditioner 1, in the predetermined dehumidifying operation mode, the auxiliary heat exchanger 20 has an evaporation region where the liquid refrigerant evaporates and a superheat region downstream of the evaporation region. The compressor 10 and the expansion valve 13 are controlled so as to change according to the above. Here, changing according to the load means changing according to the amount of heat supplied to the evaporation region, and the amount of heat is determined by, for example, the room temperature (the temperature of the intake air) and the room air volume. Also, the load is the required dehumidification capacity (
Necessary cooling capacity) can be detected, for example, based on the difference between the room temperature and the set temperature.

The compressor 10 is controlled based on the difference between the room temperature and the set temperature. The frequency of the compressor 10 is increased because the load is large when the difference between the room temperature and the set temperature is large, and the load is small when the difference between the room temperature and the set temperature is small. Controlled to decrease.

The expansion valve 13 is controlled based on the evaporation temperature detected by the evaporation temperature sensor 30. As described above, in a state where the frequency of the compressor 10 is controlled, the evaporation temperature is equal to the target evaporation temperature (
The expansion valve 13 is controlled so that the temperature is within a predetermined range (10 ° C.-14 ° C.) close to 12 ° C.). The predetermined range of the evaporation temperature is preferably controlled to be constant regardless of the frequency of the compressor 10. However, even if it slightly changes depending on the frequency, there is no problem as long as it is substantially constant.

As described above, in the predetermined dehumidifying operation mode, the compressor 10 and the expansion valve 13 according to the load.
By controlling this, the range of the evaporation region of the auxiliary heat exchanger 20 can be changed so that the evaporation temperature becomes a temperature within a predetermined range.

In the air conditioner 1, the auxiliary heat exchanger 20 and the front heat exchanger 21a each have 12 stages of heat transfer tubes. And when the number of stages used as the evaporation region of the auxiliary heat exchanger 20 in the predetermined dehumidifying operation mode is half or more of the number of stages of the front heat exchanger 21a, the range of the evaporation region of the auxiliary heat exchanger can be sufficiently widened. Sufficiently respond to load fluctuations. This is particularly effective when the load is large.

FIG. 5 shows a change in flow rate when the opening degree of the expansion valve 13 is changed. Expansion valve 13
The opening varies continuously according to the number of input drive pulses. And as the opening degree decreases, the flow rate of the refrigerant flowing through the expansion valve 13 decreases. The expansion valve 13 is in a fully closed state when the opening degree is t0, and between the opening degree t0 and t1, the flow rate increases as the opening degree increases.
The flow rate increases according to the second slope as the opening degree increases between the opening degrees t1 and t2. Here, the first slope is larger than the second slope.

Control when the air conditioner 1 is operated in a predetermined dehumidifying operation mode will be described with reference to FIG.

First, when a dehumidifying operation start operation is performed on the remote controller (step S1), it is determined whether the compressor frequency is lower than the upper limit frequency and the heat exchanger intermediate temperature is higher than the dehumidifying limit temperature. It is determined whether the state is small and cannot be dehumidified (step S2). In step S2, it is determined whether the compressor frequency is lower than the upper limit frequency in the dehumidifying operation mode, and the load is small in the cooling operation and the dehumidification is not possible.
Even if the compressor frequency is lower than the upper limit frequency, it can be considered that dehumidification is possible if the evaporation temperature is low. Therefore, if the evaporation temperature is lower than the dehumidification limit temperature, it is not judged that the load is too small to be dehumidified in the cooling operation. . Therefore, in step S2, the load is small,
When the evaporation temperature is higher than the dehumidification limit temperature, it is determined that the dehumidification is not possible in the cooling operation.

When it is determined that the compressor frequency is lower than the upper limit frequency and the heat exchanger intermediate temperature is higher than the dehumidifying limit temperature (step S2: YES), the load is small in the cooling operation and dehumidification cannot be performed. And dehumidifying operation is started (step S3). Then, all of the liquid refrigerant supplied from the liquid inlet 17a of the auxiliary heat exchanger 20 evaporates in the middle of the auxiliary heat exchanger 20, and only a partial range near the liquid inlet 17a of the auxiliary heat exchanger 20 evaporates. The dehumidifying operation is started.

After the dehumidifying operation is started, it is determined whether the evaporation temperature is too low by determining whether the evaporation temperature detected by the evaporation temperature sensor 30 is lower than the lower limit value. (Step S4)
. When the evaporation temperature is lower than the lower limit value (lower limit value for preventing the expansion valve 13 from being blocked), it is considered that the expansion valve 13 is close to the closed state. Therefore, in step S4, it is determined whether the expansion valve 13 is close to the closed state, and it is determined whether it is necessary to increase the valve opening.

When it is determined that the evaporation temperature is lower than the lower limit (the expansion valve 13 is close to the closed state) (step S4: YES), the heat exchange intermediate temperature (on the leeward side near the upper end of the auxiliary heat exchanger 20). By determining whether or not (air temperature) is higher than the room temperature, it is determined whether or not the auxiliary heat exchanger 20 has completed evaporation (step S5). When the vicinity of the upper end of the auxiliary heat exchanger 20 is in the overheating region, the intake air from the suction port 2a is hardly cooled near the upper end of the auxiliary heat exchanger 20, so that the heat exchange detected by the indoor heat exchange temperature sensor 32 is performed. The intermediate temperature is close to the room temperature detected by the room temperature sensor 31 or higher than the room temperature. Therefore, in step S5, when the heat exchanger intermediate temperature is equal to or higher than the temperature lower than the room temperature by a correction amount, it is determined that the air temperature on the leeward side near the upper end of the auxiliary heat exchanger 20 is higher than the room temperature. It is determined that the range near the upper end of the heat exchanger 20 is a superheat region, and the auxiliary heat exchanger 20 has completed evaporation.

When the heat exchanger intermediate temperature (the air temperature on the leeward side near the upper end of the auxiliary heat exchanger 20) is lower than the room temperature (step S5: NO), the auxiliary heat exchanger 20 is in a state where evaporation has not ended. However, the valve opening is rapidly opened (step S6). Thereafter, the cooling operation is started in a state where the liquid refrigerant supplied from the liquid inlet 17a of the auxiliary heat exchanger 20 flows into the main heat exchanger 21 (step S7).

On the other hand, when the heat exchanger intermediate temperature (the air temperature on the leeward side near the upper end of the auxiliary heat exchanger 20) is higher than the room temperature (step S5: YES), the auxiliary heat exchanger 20 finishes evaporation, and the auxiliary heat exchanger 20 In a state where the heat exchanger 20 has an evaporation region and a superheat region, the valve opening is greatly opened (step S8). Thereafter, the compressor frequency is changed so that the room temperature approaches the room set temperature (
Step S9). Then, it is determined whether or not the compressor frequency is smaller than the upper limit frequency (step S10). When the compressor frequency is equal to or higher than the upper limit frequency (step S10: NO), since the dehumidification can be performed in the cooling operation, the cooling operation is started (step S7). When the compressor frequency is smaller than the upper limit frequency (step S10: YES), step S4 is shifted to the dehumidifying operation state.

If it is determined in step S2 that the compressor frequency is equal to or higher than the upper limit frequency or the heat exchanger intermediate temperature is equal to or lower than the dehumidifying limit temperature (step S2: NO), the cooling operation is started because the dehumidification is possible. (Step S7).

In step S4, when the evaporation temperature detected by the evaporation temperature sensor 30 is equal to or higher than the lower limit (step S4: NO), the heat exchange intermediate temperature (the air temperature on the leeward side near the upper end of the auxiliary heat exchanger 20) is By determining whether or not the temperature is higher than the room temperature, it is determined whether or not the auxiliary heat exchanger 20 has completed evaporation (step S11).

When the heat exchange intermediate temperature (the air temperature on the leeward side near the upper end of the auxiliary heat exchanger 20) is higher than the room temperature (step S11: YES), the auxiliary heat exchanger 20 finishes evaporation, and auxiliary heat exchange is performed. It is in a state where the vessel 20 has an evaporation region and a superheat region, and it is determined whether or not the evaporation temperature is within a predetermined range near the target evaporation temperature (step S12). Thus, in step S12,
It is determined whether it is necessary to change the valve opening so that the evaporation temperature detected by the evaporation temperature sensor 30 is a temperature within a predetermined range near the target evaporation temperature.

In step S12, when the evaporation temperature is within a predetermined range near the target evaporation temperature (step S12: YES), there is no need to change the valve opening, and the process proceeds to step S9.

On the other hand, when the evaporation temperature is not within a predetermined range near the target evaporation temperature (step S1).
2: NO), it is determined whether the evaporation temperature is lower than the target evaporation temperature (step S13). When the evaporation temperature is lower than the target evaporation temperature (step S13: YES), the valve opening is slightly opened so that the evaporation temperature approaches the target evaporation temperature (step S14). On the other hand, when the evaporation temperature is higher than the target evaporation temperature (step S13: NO), the valve opening is slightly closed so that the evaporation temperature approaches the target evaporation temperature (step S15). Thereafter, the process proceeds to step S9.

In step S11, when the heat exchange intermediate temperature (air temperature on the leeward side near the upper end of the auxiliary heat exchanger 20) is equal to or lower than the room temperature (step S11: NO), the evaporation is finished in the auxiliary heat exchanger 20. Therefore, the valve opening is largely closed (step S16). Thereafter, the process proceeds to step S9.

Thus, in the air conditioner 1, control is performed so that the range of the evaporation region of the auxiliary heat exchanger 20 changes in a predetermined dehumidifying operation mode. For example, in a predetermined dehumidifying operation mode, when the load increases when the range of the evaporation region of the auxiliary heat exchanger 20 is a predetermined area, the frequency of the compressor 10 is increased and the opening degree of the expansion valve 13 is increased. Is greatly changed. Therefore, even if the range of the evaporation area of the auxiliary heat exchanger 20 is larger than a predetermined area and the air volume sucked into the indoor unit 2 is constant, the air volume that actually passes through the evaporation area increases.

On the other hand, in the predetermined dehumidifying operation mode, when the load becomes small when the range of the evaporation region of the auxiliary heat exchanger 20 is a predetermined area, the frequency of the compressor 10 is reduced and the expansion valve 1
The opening degree of 3 is changed small. Therefore, even if the range of the evaporation area of the auxiliary heat exchanger 20 is smaller than the predetermined area and the air volume sucked into the indoor unit 2 is constant, the air volume that actually passes through the evaporation area decreases.

As described above, in the predetermined dehumidifying operation mode of the air conditioner 1, dehumidification can be performed even when the load is very small, but a predetermined cooling capacity is also required in the predetermined dehumidifying operation mode. . Therefore, in the air conditioner 1, it is necessary that the auxiliary heat exchanger 20 has about 10 stages of heat transfer tubes, but when the tube diameter of the heat transfer tubes of the auxiliary heat exchanger 20 is small, it is large during the cooling operation. It may become a pressure loss, and the capability of the indoor heat exchanger 14 may be reduced.

Therefore, in the predetermined dehumidifying operation mode, with respect to the auxiliary heat exchanger 20 having about 10 stages of heat transfer tubes capable of obtaining a predetermined cooling capacity, by changing the tube diameter of the heat transfer tubes of the auxiliary heat exchanger 20, the predetermined cooling is performed. We evaluated whether ability was acquired. In this embodiment, the case where R32 is used as the refrigerant and the case where R410A is used are evaluated by changing the tube diameter of the heat transfer tube in the auxiliary heat exchanger 20 having 10 heat transfer tubes.
The room temperature is 27 ° C., the outlet evaporation temperature of the auxiliary heat exchanger 20 is 15 ° C., and the auxiliary heat exchanger 2
Evaluation was performed with a width of 0 (length along the heat transfer tube) set to 600-670 mm.

Table 1 shows the evaluation for six types of heat transfer tubes when R32 is used as the refrigerant, and Table 2 shows the evaluation for the six types of heat transfer tubes when R410A is used as the refrigerant.

In Tables 1 and 2, for the six types of heat transfer tubes, the outer diameter and inner diameter of the heat transfer tube before the expansion, and the outer diameter and inner diameter of the heat transfer tube after the expansion are described. FIG. 7A is a cross-sectional view along the longitudinal direction of a heat transfer tube having no inner surface groove and a vertical cross-sectional view with respect to the longitudinal direction, and FIG. 7B is a view of the heat transfer tube having an inner surface groove. They are sectional drawing along the longitudinal direction, and a perpendicular sectional view with respect to the longitudinal direction. In Table 1 and Table 2, the inner diameter r of the heat transfer tube after the expansion is as shown in FIG.
In the case of a heat transfer tube that does not have an inner surface groove, it is the diameter of the inner surface of the heat transfer tube after expansion. As shown in FIG. 7B, in the case of a heat transfer tube having an inner surface groove in which a plurality of grooves extend in parallel and spirally on the inner surface of the heat transfer tube and a convex portion is disposed between the grooves. Is the inner diameter r of the heat transfer tube after tube expansion is the distance (maximum inner diameter) between the tip of the convex portion between the grooves on the inner surface of the heat transfer tube after pipe expansion and the tip of the convex portion facing 180 degrees ).

And each of the six types of heat transfer tubes is used as the heat transfer tube of the auxiliary heat exchanger 20, and 5.6
When kW cooling operation was performed, evaluation was performed based on the temperature difference between the inlet evaporation temperature of the auxiliary heat exchanger 20 and the room temperature (temperature of the intake air).

In Table 1 and Table 2, when the inlet evaporation temperature of the auxiliary heat exchanger 20 is equal to or lower than the room temperature, the evaluation is “Good”, and when the inlet evaporation temperature of the auxiliary heat exchanger 20 is higher than the room temperature, did.
As described above, when the inlet evaporation temperature of the auxiliary heat exchanger 20 is equal to or lower than the room temperature, the evaluation of ◯ is that the auxiliary heat exchange is performed when the inlet evaporation temperature of the auxiliary heat exchanger 20 is higher than the room temperature. Vessel 20
This is because it acts as a condenser rather than an evaporator. Therefore, when the inlet evaporation temperature of the auxiliary heat exchanger 20 is higher than the room temperature, the diameter of the heat transfer tube of the auxiliary heat exchanger 20 is small, so that a large pressure loss occurs during the cooling operation, and the indoor heat exchanger during the cooling operation. Was evaluated as x.

In Table 1, for example, when R32 refrigerant is used and the inner diameter of the heat transfer tube of the auxiliary heat exchanger 20 after expansion is 5.99 mm, the inlet evaporation temperature is 17.6 ° C. Since the inlet evaporation temperature is lower than the intake air temperature (indoor temperature) of 27 ° C., it is evaluated as “Good”.

In Table 2, for example, when the R410A refrigerant is used, and the inner diameter of the auxiliary heat exchanger 20 after expansion of the heat transfer tube is 5.99 mm, the inlet evaporation temperature is 19.3 ° C. Since the inlet evaporation temperature is lower than the intake air temperature (indoor temperature) of 27 ° C., it is evaluated as “Good”.

FIG. 8 is a graph corresponding to the evaluation in Tables 1 and 2 above. In FIG. 8, the horizontal axis is
It is an internal diameter after a pipe expansion, Comprising: A vertical axis | shaft is a temperature difference with an inlet | evaporation temperature and the temperature (indoor temperature) of suction air.

From FIG. 8, when the R32 refrigerant is used and the inner diameter after expansion of the heat transfer tube of the auxiliary heat exchanger 20 is 4.4 mm or more, the inlet evaporation temperature of the auxiliary heat exchanger 20 is the intake air. It can be seen that the temperature (indoor temperature) is 27 ° C. or lower and the evaluation is “◯”.

When the R410A refrigerant is used and the inner diameter of the heat transfer tube of the auxiliary heat exchanger 20 after expansion is 4.9 mm or more, the inlet evaporation temperature of the auxiliary heat exchanger 20 is the temperature of the intake air. (Indoor temperature) It is 27 degrees C or less, Comprising: It turns out that it is evaluation of (circle).

Thus, in the air conditioner 1, when the R32 refrigerant is used, the auxiliary heat exchanger 20
When the inner diameter after expansion of the heat transfer tube is 4.4 mm or more and the R410A refrigerant is used, if the inner diameter after expansion of the heat transfer tube of the auxiliary heat exchanger 20 is 4.9 mm or more, the auxiliary heat exchanger 20 Since the pressure loss is small during the cooling operation, it is possible to prevent the capacity of the indoor heat exchanger 14 from decreasing during the cooling operation. In the air conditioner 1 of the present embodiment, as the heat transfer tube of the auxiliary heat exchanger 20, a heat transfer tube having an inner diameter after expansion of 7.58 mm or less (a heat transfer tube having an outer diameter before expansion of 8 mm or less).
Is used.

<Characteristics of the air conditioner of this embodiment>
In the air conditioner 1 of the present embodiment, the R32 refrigerant is used as the refrigerant, and the heat transfer tube of the auxiliary heat exchanger 20 (the portion where the portion that can be the evaporation region of the indoor heat exchanger 14 in a predetermined dehumidifying operation mode is expanded). By making the inner diameter of the heat pipe) 4.4 mm or more, the auxiliary heat exchanger 20 is
It can suppress that it becomes a big pressure loss at the time of air_conditionaing | cooling operation, and can prevent that the capability of the indoor heat exchanger 14 falls.

Further, in the air conditioner 1 of the present embodiment, the R410A refrigerant is used as the refrigerant, and the heat transfer pipe of the auxiliary heat exchanger 20 (the portion that can be an evaporation region of the indoor heat exchanger 14 in a predetermined dehumidifying operation mode is expanded). By setting the inner diameter of the heat transfer tube) to 4.9 mm or more, the auxiliary heat exchanger 20 can be prevented from having a large pressure loss during the cooling operation, and the capacity of the indoor heat exchanger 14 can be prevented from being lowered. .

Further, in the air conditioner 1 of the present embodiment, the amount of air sucked into the indoor unit 2 is constant because the range of the evaporation region where the liquid refrigerant is evaporated in the auxiliary heat exchanger 20 changes according to the load. Even if it exists, the air volume that actually passes through the evaporation zone changes. As a result, in order to complete the evaporation in the auxiliary heat exchanger 20 when the load is large, it is possible to continue dehumidification over a wide load range without excessively lowering the evaporation temperature and deteriorating the COP. And since there is no need to extremely lower the evaporation temperature, freezing does not occur and defrosting operation is not necessary. Moreover, since the dehumidification can be performed even if the air volume is increased, dehumidification can be performed while uniformly cooling the entire room even at a low load, and it is not necessary to feel the heat of sultry.

Moreover, in the air conditioner 1 of the present embodiment, the main heat exchanger 21 includes the front heat exchanger 21 a disposed on the front side in the indoor unit 2 and the back heat disposed on the back side in the indoor unit 2. Since the auxiliary heat exchanger 20 is arranged in front of the front heat exchanger 21a and the area of the auxiliary heat exchanger 20 can be increased, the evaporation area of the auxiliary heat exchanger 20 is increased. The range to change can be enlarged.

Moreover, in the air conditioner 1 of this embodiment, since the part used as the evaporation area | region of the indoor heat exchanger 14 is comprised as the auxiliary heat exchanger 20 in the predetermined dehumidification operation mode, the auxiliary heat exchanger 20 The heat transfer tube can be easily different from the configuration of the heat transfer tube of the main heat exchanger 21.

As mentioned above, although embodiment of this invention was described based on drawing, it should be thought that a specific structure is not limited to these embodiment. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes meanings equivalent to the scope of claims for patent and all modifications within the scope.

In the above-described embodiment, the auxiliary heat exchanger and the main heat exchanger may be configured integrally. Therefore, in this case, the indoor heat exchanger is integrally configured, a portion corresponding to the auxiliary heat exchanger is provided on the uppermost wind side of the indoor heat exchanger, and a portion corresponding to the main heat exchanger is provided on the leeward side thereof. Is provided.

In the above-described embodiment, the evaluation when the R32 refrigerant is used as the refrigerant has been described, but the same applies to the evaluation when the refrigerant in which R32 is mixed by 75% or more is used as the refrigerant.

In the above-described embodiment, the air conditioner that operates in the cooling operation mode, the predetermined dehumidifying operation mode, and the heating operation mode has been described. However, the dehumidifying operation that performs the dehumidifying operation by another method of the predetermined dehumidifying operation mode is described. An air conditioner that operates in the mode may be used.

By using the present invention, it is possible to reliably perform dehumidification even when the load fluctuates at low load, and it is possible to prevent the capacity of the indoor heat exchanger from decreasing during the cooling operation.

DESCRIPTION OF SYMBOLS 1 Air conditioner 2 Indoor unit 3 Outdoor unit 10 Compressor 12 Outdoor heat exchanger 13 Expansion valve 14 Indoor heat exchanger 16 Indoor fan 20 Auxiliary heat exchanger 21 Main heat exchanger

Claims (3)

Comprising a refrigerant circuit connecting a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger;
As the refrigerant, a refrigerant mixed with 75% or more of R32 is used,
The indoor heat exchanger has a plurality of fins and heat transfer tubes expanded in the plurality of fins, respectively, and the auxiliary heat exchanger disposed on the uppermost wind side in the predetermined dehumidifying operation mode and the auxiliary heat Having a main heat exchanger located downstream from the exchanger,
In a predetermined dehumidifying operation mode, the refrigerant supplied from the liquid inlet is configured to branch and flow in the main heat exchanger after flowing through the auxiliary heat exchanger in one pass,
In a predetermined dehumidifying operation mode, an evaporation region in which the liquid refrigerant evaporates is disposed in the auxiliary heat exchanger, a superheat region is disposed on the downstream side of the evaporation region of the auxiliary heat exchanger , and depending on a load, The compressor and the expansion valve are controlled so that the range of the evaporation zone changes in the auxiliary heat exchanger ,
The air conditioner characterized in that the inner diameter of the expanded heat transfer tube in a portion that can be an evaporation region of the indoor heat exchanger in the predetermined dehumidifying operation mode is 4.4 mm or more. Comprising a refrigerant circuit connecting a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger;
As the refrigerant, R410A refrigerant is used,
The indoor heat exchanger has a plurality of fins and heat transfer tubes expanded in the plurality of fins, respectively, and the auxiliary heat exchanger disposed on the uppermost wind side in the predetermined dehumidifying operation mode and the auxiliary heat Having a main heat exchanger located downstream from the exchanger,
In a predetermined dehumidifying operation mode, the refrigerant supplied from the liquid inlet is configured to branch and flow in the main heat exchanger after flowing through the auxiliary heat exchanger in one pass,
In a predetermined dehumidifying operation mode, an evaporation region in which the liquid refrigerant evaporates is disposed in the auxiliary heat exchanger, a superheat region is disposed on the downstream side of the evaporation region of the auxiliary heat exchanger , and depending on a load, The compressor and the expansion valve are controlled so that the range of the evaporation zone changes in the auxiliary heat exchanger ,
The air conditioner characterized in that an inner diameter of the expanded heat transfer tube in a portion that can be an evaporation region of the indoor heat exchanger in the predetermined dehumidifying operation mode is 4.9 mm or more. The main heat exchanger has a front heat exchanger disposed on the front side in the indoor unit, and a back heat exchanger disposed on the back side in the indoor unit,
Claim 1, wherein the auxiliary heat exchanger, characterized in that disposed in front of the front heat exchanger
Or the air conditioner of 2 .

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