WO2014156313A1

WO2014156313A1 - Air conditioner and method for operating air conditioner

Info

Publication number: WO2014156313A1
Application number: PCT/JP2014/052612
Authority: WO
Inventors: 横関　敦彦; 坪江　宏明; 修平多田; 野中　正之
Original assignee: 日立アプライアンス株式会社
Priority date: 2013-03-27
Filing date: 2014-02-05
Publication date: 2014-10-02
Also published as: CN106839499A; CN106839499B; JP5981376B2; CN105074353A; CN105074353B; JP2014190632A

Abstract

The present invention addresses the problem of providing an air conditioner that uses R32 as a refrigerant and that can reduce the load on a compressor, and a method for operating an air conditioner. Provided is an air conditioner (1), having: a refrigeration cycle in which at least a compressor (14), an outdoor heat exchanger (11), an indoor heat exchanger (21), an outdoor expansion valve (13), and an indoor expansion valve (23) are connected, and refrigerant containing 70 wt% or more of R32 is circulated; and a controller (1a). An upper limit, which regulates the pressure ratio of the compressor (14) so that the dryness fraction of the refrigerant in the intake side of the compressor (14) during operation is higher than 0.85, is set so as to decrease as the intake pressure of refrigerant in the compressor (14) increases. A method for operating the air conditioner (1) is also provided. When the air conditioner (1) is operating, the controller (1a) has the characteristic of adjusting the rotational speed of the compressor (14) so that the pressure ratio is less than the upper limit.

Description

Air conditioner and method of operating air conditioner

The present invention relates to an air conditioner and an operation method of the air conditioner.

For example, Patent Document 1 states that “the compressor (1) has an R32 refrigerant with a dryness of 0.65 or more and 0.85 or less, or a dryness containing at least 70% by weight of R32 is 0.65 or more and 0.00. "It sucks in and compresses a mixed refrigerant of 85 or less" (see claims).

Japanese Patent No. 3956589

In the refrigeration cycle of the air conditioner, the latent heat of vaporization is maximized by controlling the refrigerant state at the outlet of the heat exchanger acting as an evaporator to the vicinity of the saturated gas, thereby improving the operation efficiency. On the other hand, when R32 (HFC32: difluoromethane) having a lower global warming potential GWP than R410A (R32 + R125: 50 + 50 wt%) is used as a refrigerant, since the specific heat ratio of R32 is large, the refrigerant state at the outlet of the evaporator is When the refrigeration cycle is operated so as to be in the vicinity of the saturated gas, the refrigerant temperature discharged from the compressor becomes higher by about 10 to 15 ° C. than R410A. Therefore, when using R32 as a refrigerant, it is necessary to make the dryness of the refrigerant on the compressor inlet side smaller than when using R410A.
Patent Document 1 describes an air conditioner (refrigerator) that sets the dryness of the refrigerant (R32) on the compressor inlet side from 0.65 to 0.85.

However, if the degree of dryness on the compressor inlet side is reduced, an increase in discharge temperature can be suppressed, but the liquid component of the refrigerant sucked from the compressor inlet side increases. And the refrigerator oil in a compressor is diluted with the liquid component of a refrigerant | coolant, a viscosity falls, the lubrication performance deteriorates, the problem that the lifetime of a compressor becomes short, such as the abrasion of a mechanism part arises arises.

Therefore, an object of the present invention is to provide an air conditioner that can reduce the load on the compressor by using R32 as a refrigerant, and an operation method of the air conditioner.

In order to solve the above problems, the present invention has a refrigeration cycle in which a refrigerant containing R32 in an amount of 70 wt% or more circulates, and the compressor has a dryness higher than 0.85 on the inlet side of the compressor. An air conditioner in which an upper limit value for regulating the pressure ratio is set, and an operating method of the air conditioner. And it has the characteristics that it drive | operates so that a pressure ratio may become smaller than an upper limit.

According to the present invention, it is possible to provide an air conditioner that can reduce the load on the compressor by using R32 as a refrigerant, and an operation method of the air conditioner.

It is a figure which shows the structure of the air conditioner which concerns on a present Example. It is a Mollier diagram (PH diagram) of an air conditioner using R32 as a refrigerant. It is a Mollier diagram in the case where the pressure of the refrigerant on the inlet side of the compressor and the pressure of the refrigerant on the outlet side change. It is a graph which shows the relationship between the suction pressure and pressure ratio in which the suction dryness will be 0.85. It is a figure which shows the variable used for estimation of inhalation dryness. It is a flowchart which shows the procedure in which a control apparatus estimates the suction dryness by calculation. It is a graph which shows the relationship between discharge temperature, condensation temperature, and discharge superheat degree.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

FIG. 1 is a diagram illustrating a configuration of an air conditioner according to the present embodiment.
The air conditioner 1 of the present embodiment includes an outdoor unit 10, an indoor unit 20, and a control device 1a. The outdoor unit 10 includes an outdoor heat exchanger 11 (heat source side heat exchanger), an outdoor fan 12, an outdoor expansion valve 13, a compressor 14, an accumulator 15, and a four-way valve 16. On the other hand, the indoor unit 20 includes an indoor heat exchanger 21 (use side heat exchanger), an indoor fan 22, and an indoor expansion valve 23.
The outdoor unit 10 and the indoor unit 20 are connected by

pipes

30 and 31.
Moreover, the air conditioner 1 of a present Example is the compressor 14, the outdoor heat exchanger 11 (heat source side heat exchanger), the outdoor expansion valve 13, the indoor heat exchanger 21 (use side heat exchanger), and an indoor expansion valve. A refrigeration cycle is configured at 23, and R32 (difluoromethane) is used as a refrigerant circulating through the refrigeration cycle.

For example, Patent Document 1 described above describes that a refrigerant containing at least 70% (70% by weight) or more of R32 can exhibit the same merit as a refrigerant containing 100% of R32. Therefore, the refrigerant used in the air conditioner 1 of the present embodiment is not limited to the refrigerant containing 100% of R32, and may be a refrigerant (mixed refrigerant) containing 70% by weight or more of R32.

The control device 1a controls the outdoor unit 10 by starting and stopping the outdoor fan 12 of the outdoor unit 10, adjusting the valve opening degree of the outdoor expansion valve 13, adjusting the rotational speed Fr of the compressor 14, and controlling the four-way valve 16. Control. The control device 1a controls the indoor unit 20 by starting and stopping the indoor fan 22, adjusting the valve opening of the indoor expansion valve 23, and the like.

During the cooling operation, the control device 1 a controls the four-way valve 16 to connect the outlet side of the compressor 14 and the outdoor heat exchanger 11, and connects the accumulator 15 and the pipe 31. The control device 1a drives the compressor 14, the outdoor fan 12, and the indoor fan 22.
The refrigerant (gas) compressed by the compressor 14 flows into the outdoor heat exchanger 11 via the four-way valve 16, and is cooled and condensed by heat exchange with the outside air blown by the outdoor fan 12. The refrigerant (liquid) condensed in the outdoor heat exchanger 11 is introduced into the indoor unit 20 through the piping 30 via the outdoor expansion valve 13.

The refrigerant (liquid) introduced into the indoor unit 20 is decompressed by the indoor expansion valve 23 and flows into the indoor heat exchanger 21. The refrigerant (liquid or gas-liquid two-phase state) that has flowed into the indoor heat exchanger 21 is vaporized by heat exchange with the indoor air blown by the indoor fan 22. At this time, the refrigerant (liquid) vaporized in the indoor heat exchanger 21 takes the heat of vaporization from the indoor air and cools the indoor air.
The refrigerant (gas) vaporized in the indoor heat exchanger 21 flows through the pipe 31 and is introduced into the outdoor unit 10, flows through the four-way valve 16, and flows into the accumulator 15. The accumulator 15 functions as a buffer tank that stores the refrigerant (liquid) when the liquid refrigerant excessively flows in, thereby preventing liquid compression in the compressor 14. Accordingly, the dryness of the refrigerant increases in the accumulator 15, and the high dryness refrigerant flows into the compressor 14.

During the heating operation, the control device 1 a controls the four-way valve 16 to connect the outlet side of the compressor 14 and the pipe 31, and connects the outdoor heat exchanger 11 and the accumulator 15. The control device 1a drives the compressor 14, the outdoor fan 12, and the indoor fan 22.
The refrigerant (gas) compressed by the compressor 14 flows through the pipe 31 via the four-way valve 16 and is introduced into the indoor unit 20. The refrigerant (gas) introduced into the indoor unit 20 flows into the indoor heat exchanger 21, and is cooled and condensed by heat exchange with the indoor air blown by the indoor fan 22. At this time, the refrigerant (gas) condensed in the indoor heat exchanger 21 gives condensation heat to the indoor air to heat the indoor air. The refrigerant (liquid) condensed in the indoor heat exchanger 21 flows through the pipe 30 via the indoor expansion valve 23 and is introduced into the outdoor unit 10. The refrigerant (liquid) introduced into the outdoor unit 10 is decompressed by the outdoor expansion valve 13 and flows into the outdoor heat exchanger 11. The refrigerant (liquid) that has flowed into the outdoor heat exchanger 11 is vaporized by heat exchange with the outside air blown by the outdoor fan 12, and flows into the accumulator 15 via the four-way valve 16. Then, the refrigerant (gas or gas-liquid two-phase state) whose dryness is increased by the accumulator 15 flows into the compressor 14.

The outdoor unit 10 measures the discharge temperature sensor 10ta that measures the temperature of the refrigerant discharged from the compressor 14 (discharge temperature Td) and the pressure of the refrigerant at the outlet side of the compressor 14 (discharge pressure Pd). And a suction pressure sensor 10pb for measuring the refrigerant pressure (suction pressure Ps) on the inlet side of the compressor 14.
Further, the outdoor unit 10 includes a temperature sensor 10tb for measuring the refrigerant condensation temperature Tc (during cooling operation) or the evaporation temperature Te (during heating operation) in the outdoor heat exchanger 11. Is provided with a temperature sensor 20ta for measuring the refrigerant evaporating temperature Te (during cooling operation) or the condensing temperature Tc (during heating operation) in the indoor heat exchanger 21.
Instead of the discharge temperature Td, the chamber upper temperature of the compressor 14 may be measured and used.

FIG. 2 is a Mollier diagram (PH diagram) of an air conditioner using R32 as a refrigerant.
For example, when the air conditioner 1 (see FIG. 1) is operated for heating, the refrigerant (gas) in the state of the point A1 is compressed by the compressor 14 and the temperature (specific enthalpy) and pressure rise to increase the point A2. And is introduced into the indoor unit 20. The refrigerant (gas) introduced into the indoor unit 20 is condensed at substantially the same pressure in the indoor heat exchanger 21 to be in a state of point A3 (liquid) and introduced into the outdoor unit 10. The refrigerant (liquid) introduced into the outdoor unit 10 in the state of point A3 is decompressed by the outdoor expansion valve 13 to be in the state of point A4, and is vaporized in the outdoor heat exchanger 11 to be in the state of point A1 (gas). . Thus, in the air conditioner 1 that performs heating operation, the refrigerant (R32) circulates while changing the states of the points A1 to A4. That is, indoor air is heated when the refrigerant (gas) compressed by the compressor 14 (point A1 → A2) is condensed (point A2 → A3) by the indoor heat exchanger 21 of the indoor unit 20.

At this time, since the specific heat ratio of R32 is larger than that of R410A, when it is compressed by the compressor 14 (point A1 → A2), the refrigerant temperature (discharge temperature Td) at the outlet side of the compressor 14 is increased ( Td1). For example, the discharge temperature Td is about 10 to 15 ° C. higher than R410A. As a result, the discharge temperature Td of the compressed refrigerant exceeds the allowable upper limit temperature of the compressor 14, and an excessive load may be applied to the compressor 14. Therefore, when R32 is used as the refrigerant, it is required to lower the discharge temperature Td on the outlet side of the compressor 14 (for example, Td1 → Td2).

For example, when the valve opening degree of the outdoor expansion valve 13 is increased, the temperature drop in the outdoor expansion valve 13 is promoted, and the refrigerant temperature or dryness at the inlet side of the compressor 14 is lowered as shown by the broken line in FIG. (Point A1 ′). As a result, the refrigerant discharge temperature Td at the outlet side of the compressor 14 is lowered (point A2 → A2 ′).
However, when the refrigerant state (point A1 ′) on the inlet side of the compressor 14 becomes a temperature (or specific enthalpy) lower than the saturation line C100, the dryness of the refrigerant on the inlet side of the compressor 14 is lower than 1.00. Become.

A refrigerant with a low dryness has a high content of liquid components, and when a refrigerant with a low dryness flows into the compressor 14, the refrigeration oil of the compressor 14 is diluted by the liquid components contained in the refrigerant, and the mechanism portion is worn. Effects such as being promoted occur. That is, when a refrigerant having a low dryness flows into the compressor 14, a load on the compressor 14 increases. Therefore, a state where the dryness of the refrigerant on the inlet side of the compressor 14 is excessively low is not preferable.

Therefore, changes in the mechanical performance of the compressor 14 (accelerated wear state, etc.), the dryness of the refrigerant on the inlet side of the compressor 14 (hereinafter referred to as “suction dryness Xs”), and the freezing in the compressor 14 In an experiment for examining the correlation between the decrease in the viscosity of the machine oil, the boundary value of the suction dryness Xs that does not deteriorate the mechanical performance of the compressor 14 (or the deterioration is within an allowable range) was set to 0.85. In other words, it has been found that if the suction dryness Xs is higher than 0.85 (Xs> 0.85), the influence on the compressor 14 is in an allowable range, and the load on the compressor 14 can be reduced.
Therefore, the air conditioner 1 of this embodiment is configured to be operated in a state where the suction dryness Xs is higher than 0.85. The two-dot chain line shown in FIG. 2 indicates an “iso-dryness line C85” where the dryness becomes 0.85.

FIG. 3 is a Mollier diagram in the case where the refrigerant pressure (suction pressure Ps) on the inlet side of the compressor and the refrigerant pressure (discharge pressure Pd) on the outlet side change.
For example, as shown in FIG. 3, when the refrigerant discharge temperature Td on the outlet side of the compressor 14 is maintained at an upper limit temperature (Tdmax) that is equal to or lower than the allowable upper limit temperature of the compressor 14, The state is changed so that the point indicating the state (point A2-n: n = 1, 2, 3,...) Is on an isothermal line (one-dot chain line) where the discharge temperature Td indicates the upper limit temperature (Tdmax).
For example, when the allowable upper limit temperature of the compressor 14 is 120 ° C., the upper limit temperature of the refrigerant discharge temperature Td is set to about 100 ° C. (“Tdmax = 100 [° C.]”).

Further, the saturation line C100 is a line where the dryness becomes 1.00, and the “isodryness line C85” indicating the dryness 0.85 has a lower specific enthalpy than the saturation line C100 (illustrated by a two-dot chain line). . In order to set the suction dryness Xs to 0.85, the temperature of the refrigerant (specific enthalpy) at the inlet of the compressor 14 becomes the suction pressure Ps on the equal dryness line C85 indicating the dryness 0.85. The temperature indicated by (point A1-n: n = 1, 2, 3,...) May be set.
The pressure ratio ε (discharge pressure Pd / suction pressure Ps) of the compressor 14 is determined from the points A1-n and A2-n determined in this manner. That is, the pressure ratio ε with respect to the suction pressure Ps is determined.
As shown in FIG. 3, the higher the suction pressure Ps (Ps1 → Ps2 → Ps3), the higher the discharge pressure Pd (Pd1 → Pd2 → Pd3), but the discharge pressure is higher than the rate at which the suction pressure Ps increases. The rate at which Pd rises decreases. That is, the higher the suction pressure Ps, the smaller the pressure ratio ε needs to be.

FIG. 4 is a graph showing the relationship between the suction pressure and the pressure ratio at which the suction dryness is 0.85, where the horizontal axis represents the suction pressure Ps and the vertical axis represents the pressure ratio ε (discharge pressure Pd / suction pressure Ps). .
Note that “εU” shown in FIG. 4 is the maximum value of the pressure ratio ε. The solid line indicates the upper limit value of the pressure ratio ε (pressure ratio upper limit εmax) at which the suction dryness Xs is higher than 0.85. The pressure ratio upper limit εmax is an upper limit value that regulates the pressure ratio ε so that the suction dryness Xs becomes higher than 0.85. The refrigerant is compressed (compressor 14) so that the pressure ratio ε is equal to or lower than the pressure ratio upper limit εmax. The rotation speed Fr) is limited, whereby the suction dryness Xs becomes higher than 0.85.
“PsL” is the suction pressure Ps at which the pressure ratio ε for setting the suction dryness Xs to 0.85 becomes the maximum value “εU”. That is, the region where the suction pressure Ps is equal to or lower than “PsL” is a region where the pressure ratio ε for setting the suction dryness Xs to 0.85 exceeds the maximum value “εU”.
“PsU” is an upper limit value of the suction pressure Ps in the air conditioner 1. The lower limit value “PsL” and upper limit value “PsU” of the suction pressure Ps and the maximum value “εU” of the pressure ratio ε shown in FIG. 4 are characteristic values of the air conditioner 1 and are determined for each air conditioner 1. It is a design value.

As shown in FIG. 4, the pressure ratio upper limit εmax is the maximum pressure ratio value “εU” (εmax = εU) in the region where the suction pressure Ps is lower than the lower limit value “PsL” (Ps ≦ PsL) (εmax = εU). In a region higher than the lower limit “PsL” (Ps> PsL), it is expressed by the following equation (1).

εmax = εU− (εU−εL) / (PsU−PsL) × (Ps−PsL)
... (1)

As shown in FIG. 3, the higher the suction pressure Ps, the smaller the pressure ratio ε. Therefore, as shown in FIG. 4, the higher the suction pressure Ps, the lower the pressure ratio upper limit εmax.

And in the air conditioner 1 (refer FIG. 1) of a present Example, the control apparatus 1a (refer FIG. 1) is a refrigerant | coolant (so that the pressure ratio (epsilon) may become smaller than the pressure ratio upper limit (epsilon) max shown by Formula (1). The compressor 14 (see FIG. 1) is operated at the rotational speed Fr for compressing R32). That is, the control device 1a adjusts the rotational speed Fr of the compressor 14 so that the pressure ratio ε is smaller than the pressure ratio upper limit εmax. Thereby, the suction dryness Xs of the air conditioner 1 is maintained higher than 0.85.

Further, the control device 1a (see FIG. 1) may be configured to adjust the rotational speed Fr of the compressor 14 so that the pressure ratio ε approaches the pressure ratio upper limit εmax. For example, when the pressure ratio ε is smaller than the pressure ratio upper limit εmax and an increase in air conditioning capacity is required, the control device 1a may increase the pressure ratio ε by increasing the rotational speed Fr of the compressor 14. Good. When the control device 1a is configured in this way, the air conditioner 1 (see FIG. 1) is operated in a state where the suction dryness Xs is close to 0.85.

In the air conditioner 1 shown in FIG. 1, the discharge pressure sensor 10pa measures the discharge pressure Pd, and the suction pressure sensor 10pb measures the suction pressure Ps. The control device 1a then calculates the pressure ratio ε (discharge pressure Pd (measured value) /) calculated from the measured value of the suction pressure Ps measured by the suction pressure sensor 10pb and the measured value of the discharge pressure Pd measured by the discharge pressure sensor 10pa. The air conditioner 1 is heated by adjusting the rotational speed Fr of the compressor 14 so that the suction pressure Ps (measured value) becomes the pressure ratio upper limit εmax calculated by the equation (1).

Here, instead of one or both of the discharge pressure sensor 10pa and the suction pressure sensor 10pb, a configuration may be provided in which a sensor (temperature sensor) for measuring the condensation temperature Tc and the evaporation temperature Te is provided.
During the heating operation, the condensation temperature Tc can be measured by a temperature sensor 20ta (see FIG. 1) provided in the indoor heat exchanger 21, and the evaporation temperature Te is measured by a temperature sensor 10tb (see FIG. 1) provided in the outdoor heat exchanger 11. It can be measured.
In general, a temperature sensor is less expensive than a pressure sensor, and inexpensive air conditioning is achieved by using a temperature sensor (temperature sensor 10tb, temperature sensor 20ta) instead of a pressure sensor (discharge pressure sensor 10pa, suction pressure sensor 10pb). Machine 1 can be used.

Further, the air conditioner 1 (see FIG. 1) of the present embodiment may be configured such that the control device 1a (see FIG. 1) estimates the suction dryness Xs by calculation. And the control apparatus 1a may be the structure which controls the compressor 14 (refer FIG. 1) so that the estimated suction dryness Xs may become higher than 0.85.
FIG. 5 is a diagram showing variables used for estimating the suction dryness, and FIG. 6 is a flowchart showing a procedure for the controller to estimate the suction dryness by calculation.

When estimating the suction dryness Xs, the control device 1a provided in the air conditioner 1 of the present embodiment performs the discharge temperature Td, the discharge pressure Pd, the suction pressure Ps, and the rotation of the compressor 14 according to the procedure shown in FIG. The suction dryness Xs is estimated by calculation based on the speed Fr and the physical property value of the refrigerant (R32). Then, the control device 1a operates the air conditioner 1 (for example, heating operation) so that the estimated suction dryness Xs becomes higher than 0.85. The control device 1a is configured to estimate (calculate) the suction dryness Xs in a predetermined cycle when the air conditioner 1 is operated.

With reference to FIG. 6, the procedure by which the control device 1a estimates the suction dryness Xs by calculation will be described (see FIGS. 1 to 5 as appropriate).
The control device 1a includes a measured value of the discharge temperature Td measured by the discharge temperature sensor 10ta, a measured value of the discharge pressure Pd measured by the discharge pressure sensor 10pa, a measured value of the suction pressure Ps measured by the suction pressure sensor 10pb, Based on the measured value of the rotational speed Fr measured by a tachometer (not shown) provided in the compressor 14, the discharge temperature Td, the discharge pressure Pd, the suction pressure Ps, and the rotational speed Fr of the compressor 14 are determined. Obtain (step S1).
Then, the control device 1a calculates the discharge gas ratio enthalpy hd based on the acquired discharge temperature Td and the discharge pressure Pd (step S2).
As shown in FIG. 5, the discharge gas specific enthalpy hd indicates the specific enthalpy of the refrigerant on the outlet side of the compressor 14.

Further, the control device 1a assumes the suction dryness Xs (step S3), and further, based on the suction pressure Ps and the physical property value of the refrigerant (the physical property value of R32), the saturated liquid ratio enthalpy hsL at the suction pressure Ps, and A saturated gas ratio enthalpy hsG at the suction pressure Ps is calculated (step S4).
For example, in step S3, the control device 1a sets the estimated value of the suction dryness Xs calculated in the previous cycle as the assumed value of the suction dryness Xs.
Further, the control device 1a calculates the saturated liquid ratio enthalpy hsL and the saturated gas ratio enthalpy hsG at the suction pressure Ps based on an approximate expression set in advance (step S4). This approximate expression is preferably set in advance as a characteristic expression of R32.

Then, the control device 1a uses the assumed suction dryness Xs, the calculated saturated liquid ratio enthalpy hsL, and the calculated saturated gas ratio enthalpy hsG, and based on the following expression (2), the suction ratio enthalpy hs is calculated (step S5).

Xs = (hs−hsL) / (hsG−hsL) (2)

Further, the control device 1a calculates the suction ratio entropy Ss based on the suction pressure Ps, the calculated suction ratio enthalpy hs, and the physical property value of R32 (step S6), and further calculates the calculated suction ratio entropy Ss. Based on the discharge pressure Pd and the physical property value of R32, the adiabatic compression discharge gas ratio enthalpy hd ′ is calculated (step S7).
In step S6, the control device 1a is configured to calculate the suction ratio entropy Ss at the suction pressure Ps and the suction ratio enthalpy hs based on a preset approximate expression. This approximate expression is preferably set in advance as a characteristic expression of R32.

Further, the adiabatic compression discharge gas ratio enthalpy hd ′ calculated by the control device 1a in step S7 is the refrigerant having the suction dryness Xs assumed by the control device 1a in step S3 as shown in FIG. The specific enthalpy at the discharge pressure Pd in the case of isentropic compression (ηt = 1) with (compressor efficiency ηt) being “1” is shown. In FIG. 5, isentropic compression is indicated by a broken line.

In this case, the compressor efficiency (temporary efficiency) ηt _real ′ of the compressor 14 with respect to the suction dryness Xs assumed by the control device 1a in step S3 is expressed by the following equation (3).

ηt _real '= (hd′−hs) / (hd−hs) (3)

Based on the discharge gas ratio enthalpy hd calculated in step S2, the suction ratio enthalpy hs calculated in step S5, and the adiabatic compression discharge gas ratio enthalpy hd ′ calculated in step S7, the control device 1a calculates a temporary The efficiency ηt _real 'is calculated (step S8
).

Further, the actual efficiency (actual efficiency) ηt _real of the compressor 14 is expressed by the following equation (4).

ηt _real = f (Xs, Pd, Ps, Fr) (4)

Note that “f (Xs, Pd, Ps, Fr)” is a function that represents the characteristics of the compressor 14 using the suction dryness Xs, the discharge pressure Pd, the suction pressure Ps, and the rotational speed Fr of the compressor 14 as variables. The function is preset for each type of compressor 14.
Then, the control device 1a calculates the actual efficiency from the equation (4) based on the suction dryness Xs assumed in step S3, the discharge pressure Pd, the suction pressure Ps, and the rotational speed Fr of the compressor 14 acquired in step S1. ηt _real is calculated (step S9).

The control device 1a calculates a ratio (ηt _real '/ ηt _real ) obtained by dividing the temporary efficiency ηt _real ' calculated in step S8 by the actual efficiency ηt _real calculated in step S9 (step S10), and this value is predetermined. If it is greater than or equal to the lower limit value and less than or equal to the predetermined upper limit value (step S10 → Yes), the suction dryness Xs assumed in step S3 is determined as the estimated value of the suction dryness Xs.

On the other hand, if the value of the ratio (ηt _real '/ ηt _real ) calculated in step S10 is less than a predetermined lower limit value or greater than a predetermined upper limit value (step S10 → No), the control device 1a performs the procedure step Returning to S3, the procedure from step S3 to step S10 is executed assuming a new suction dryness Xs.
For example, when the value of the ratio (ηt _real '/ ηt _real ) calculated in step S10 is less than a predetermined lower limit value, the control device 1a changes the suction dryness Xs in the direction in which the temporary efficiency ηt _real ' increases. The value is assumed to be a new value of the suction dryness Xs.

The predetermined lower limit value and upper limit value that the control device 1a compares with “ηt _real '/ ηt _real ” in step S10 are preferably set as appropriate based on the required calculation accuracy of the suction dryness Xs. . For example, if the lower limit value is “0.999” and the upper limit value is “1.001”, the control device 1a can estimate (calculate) the suction dryness Xs with an error of “± 0.1%”. .

Then, the control device 1a (see FIG. 1) operates the air conditioner 1 (see FIG. 1) while estimating (calculating) the suction dryness Xs according to the procedure shown in FIG. 6 (for example, heating operation). At this time, the control device 1a controls the air conditioner 1 so that the estimated suction dryness Xs becomes higher than 0.85. Specifically, the control device 1a adjusts the pressure ratio ε by adjusting the rotational speed Fr of the compressor 14 so that the suction dryness Xs estimated by the calculation becomes higher than 0.85.
When the suction dryness Xs estimated by the calculation decreases and approaches 0.85, the control device 1a decreases the rotation speed Fr of the compressor 14 and decreases the pressure ratio ε. For example, the control device 1a controls the compressor 14 so as to decrease the rotational speed Fr of the compressor 14 that is operated at the rotational speed Fr that becomes the pressure ratio upper limit εmax. As a result, the discharge pressure Pd is reduced, the refrigerant on the inlet side of the compressor 14 is less likely to be wet, and the suction dryness Xs is increased.

As described above, the control device 1a (see FIG. 1) estimates the suction dryness Xs and operates the air conditioner 1 (see FIG. 1) so that the estimated suction dryness Xs becomes higher than 0.85. Thus, the suction dryness Xs can be more reliably maintained higher than 0.85.

Further, the control device 1a (see FIG. 1) of the present embodiment prevents the discharge superheat degree TdSH (= Td−Tc), which is the difference between the condensation temperature Tc and the discharge temperature Td, from exceeding a preset target value. The air conditioner 1 (see FIG. 1) may be configured to perform a heating operation.

FIG. 7 is a graph showing the relationship between the discharge temperature, the condensation temperature, and the discharge superheat degree. The vertical axis represents temperature (discharge temperature Td, condensation temperature Tc, discharge superheat degree TdSH), and the horizontal axis represents discharge pressure Pd.
Further, the solid line in FIG. 7 indicates the condensation temperature Tc, and the alternate long and short dash line indicates the discharge temperature Td. A broken line indicates a target value (target superheat degree SHtgt) of the discharge superheat degree TdSH for each discharge pressure Pd. As described above, the discharge superheat degree TdSH is the difference (Td−Tc) between the discharge temperature Td and the condensation temperature Tc at the same discharge pressure Pd, and the target superheat degree SHtgt is, for example, as shown by the broken line in FIG. Is set.

The condensing temperature Tc is a refrigerant-specific value (physical property value) determined corresponding to the discharge pressure Pd, and the control device 1a is based on the measured value of the discharge pressure Pd measured by the discharge pressure sensor 10pa (see FIG. 1). The condensation temperature Tc can be calculated.
For example, the control device 1a can calculate the condensing temperature Tc from an approximate expression indicating the relationship between the discharging pressure Pd and the condensing temperature Tc based on the discharging pressure Pd measured by the discharging pressure sensor 10pa. This approximate expression is preferably set in advance as a characteristic expression of R32.

In the example shown in FIG. 7, when the discharge pressure Pd is a predetermined value (boundary discharge pressure: Pda), the discharge temperature Td becomes the upper limit temperature (Tdmax) of the compressor 14, so the discharge pressure Pd is the boundary discharge pressure ( In a region higher than Pda), the target superheat degree SHtgt is set so that the discharge temperature Td becomes the upper limit temperature (Tdmax).

The control device 1a (see FIG. 1) calculates the discharge superheat degree TdSH from the discharge temperature Td measured by the discharge temperature sensor 10ta (see FIG. 1) and the condensation temperature Tc calculated based on the measured value of the discharge pressure Pd. . And the control apparatus 1a carries out heating operation of the air conditioner 1 (refer FIG. 1) so that the discharge superheat degree TdSH calculated may approach the target superheat degree SHtgt shown with the broken line in FIG. For example, when the discharge superheat degree TdSH to be calculated becomes lower than the target superheat degree SHtgt, the control device 1a decreases the valve opening degree of the outdoor expansion valve 13. The temperature drop of the refrigerant in the outdoor expansion valve 13 is suppressed, and the discharge temperature Td rises. On the other hand, since the suction pressure Ps and the discharge pressure Pd do not change so much, the change in the condensation temperature Tc is small. Therefore, the discharge superheat degree TdSH (Td−Tc) increases and approaches the target superheat degree SHtgt.
Thus, the control device 1a controls the outdoor expansion valve 13 so as to maintain the calculated discharge superheat degree TdSH in the vicinity of the target superheat degree SHtgt, and adjusts the valve opening degree.

For example, when the upper limit (upper limit temperature) of the discharge temperature Td is set and the rotation speed Fr of the compressor 14 (see FIG. 1) is adjusted so that the discharge temperature Td becomes the upper limit temperature, the rotation speed Fr of the compressor 14 is adjusted. As the pressure changes, the discharge pressure Pd and the discharge temperature Td change. The suction dryness Xs changes corresponding to both the discharge pressure Pd and the discharge temperature Td. Therefore, in order to maintain the suction dryness Xs higher than 0.85, the control device 1a (see FIG. 1) adjusts the discharge pressure Pd and the discharge temperature Td in an integrated manner, and the air conditioner 1 (FIG. 1). Control) is complicated.

On the other hand, when the target superheat degree SHtgt is set and the valve opening degree of the outdoor expansion valve 13 (see FIG. 1) is adjusted so that the discharge superheat degree TdSH approaches the target superheat degree SHtgt, the discharge pressure Pd is not so much. The discharge temperature Td changes without changing. Therefore, the suction dryness Xs changes corresponding to the discharge pressure Pd.
Therefore, the control device 1a (see FIG. 1) may adjust the valve opening degree of the outdoor expansion valve 13 so as to maintain the suction dryness Xs higher than 0.85, and the air conditioner 1 (see FIG. 1). Control is simplified.

As described above, the control device 1a (see FIG. 1) adjusts the rotational speed Fr of the compressor 14 so that the pressure ratio ε approaches the pressure ratio upper limit εmax, and the discharge superheat degree TdSH is the target superheat. The structure which adjusts the valve opening degree of the outdoor expansion valve 13 may be sufficient as the control apparatus 1a so that it may approach degree SHtgt.
For example, when the pressure ratio ε is smaller than the pressure ratio upper limit εmax and the calculated discharge superheat degree TdSH is smaller than the target superheat degree SHtgt, the control device 1a increases the rotational speed Fr of the compressor 14 to increase the pressure ratio ε, The valve opening degree of the outdoor expansion valve 13 is decreased to increase the discharge superheat degree TdSH.
According to this configuration, the pressure ratio ε is maintained in the vicinity of the pressure ratio upper limit εmax, and the discharge superheat degree TdSH is maintained in the vicinity of the target superheat degree SHtgt. Thus, the control device 1a (see FIG. 1) can maintain the suction dryness Xs of the air conditioner 1 (see FIG. 1) close to 0.85, and can set the discharge temperature Td high. As a result, the air conditioner 1 is operated in a state where the discharge temperature Td is as high as possible, and the latent heat of vaporization is utilized to the maximum, thereby realizing an efficient operation state.

As described above, the control device 1a of the present embodiment shown in FIG. 1 controls the compressor 14 and the outdoor expansion valve 13 to perform the discharge temperature Td, the discharge pressure Pd, and the suction when the air conditioner 1 is heated. The pressure Ps and the rotational speed fr of the compressor 14 are adjusted to maintain the suction dryness Xs higher than 0.85. Thereby, even when R32 is used as the refrigerant, the discharge temperature Td can be maintained below the upper limit temperature (Tdmax) of the compressor 14. Further, the load applied to the compressor 14 by the liquid component contained in the refrigerant can be reduced.

In addition, this invention is not limited to an above-described Example. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.
Further, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment.

For example, although the above description is a case where the air conditioner 1 (see FIG. 1) is operated for heating, the control device 1a (see FIG. 1) is also used for the air conditioner when the air conditioner 1 is operated for cooling. 1 is controlled similarly.
When the air conditioner 1 is in cooling operation, the control device 1a adjusts the rotational speed Fr of the compressor 14 and the valve opening degree of the indoor expansion valve 23 to maintain the suction dryness Xs higher than 0.85. The discharge superheat degree TdSH is maintained in the vicinity of the upper limit value.
That is, the control device 1a adjusts the rotational speed Fr of the compressor 14 so that the pressure ratio ε becomes the pressure ratio upper limit εmax calculated based on the equation (1).
Further, the control device 1a calculates and estimates the suction dryness Xs by the procedure shown in FIG. 6, and controls the air conditioner 1 so that the estimated suction dryness Xs becomes higher than 0.85.
Furthermore, the control device 1a adjusts the valve opening degree of the indoor expansion valve 23 so that the discharge superheat degree TdSH approaches the preset target superheat degree SHtgt.
In this way, the control device 1a controls the compressor 14 and the indoor expansion valve 23 to perform the cooling operation of the air conditioner 1.

Further, the control device 1a (see FIG. 1) of the present embodiment is configured to calculate the saturated liquid ratio enthalpy hsL by a preset approximate expression in step S4 shown in FIG. The map which shows the relationship between saturated liquid ratio enthalpy hsL and the memory | storage part which is not shown in figure may be sufficient.
With this configuration, the control device 1a can calculate the saturated liquid ratio enthalpy hsL with reference to the map based on the suction pressure Ps in step S4 shown in FIG. Thereby, the load when the control device 1a calculates the saturated liquid ratio enthalpy hsL can be reduced.

Similarly, a map showing the relationship between the suction pressure Ps and the saturated gas ratio enthalpy hsG may be stored in a storage unit (not shown), or a map showing the relationship between the suction pressure Ps and the suction ratio entropy Ss is shown. The structure memorize | stored in the memory | storage part not to be sufficient may be sufficient.
Moreover, the structure by which the map which shows the relationship between discharge pressure Pd and the condensation temperature Tc is memorize | stored in the memory | storage part which is not shown in figure may be sufficient.

In addition, the present invention is not limited to the above-described embodiments, and appropriate design changes can be made without departing from the spirit of the invention.
For example, as shown in FIG. 1, in the air conditioner 1 of the present embodiment, the compressor 14 is disposed in the outdoor unit 10, but the compressor 14 may be disposed in the indoor unit 20. Good.
Moreover, it may replace with the four-way valve 16 and the structure provided with a some on-off valve (not shown) may be sufficient. In the case of a configuration including a plurality of on-off valves, an on-off valve for opening and closing a pipe connecting the outlet side of the compressor 14 and the outdoor heat exchanger 11, an on-off valve for opening and closing a pipe connecting the accumulator 15 and the pipe 31, and a compression The on / off valve that opens and closes the pipe that connects the outlet side of the machine 14 and the pipe 31 and the on / off valve that opens and closes the pipe that connects the outdoor heat exchanger 11 and the accumulator 15 are provided. Good.

DESCRIPTION OF SYMBOLS 1 Air conditioner 1a Control apparatus 11 Outdoor heat exchanger (heat source side heat exchanger)
13 Outdoor expansion valve (expansion valve)
14 Compressor 21 Indoor heat exchanger (use side heat exchanger)
23 Indoor expansion valve (expansion valve)
Fr Rotational speed Pd Discharge pressure Ps Suction pressure SHtgt Target superheat (target value of discharge superheat)
Tc Condensation temperature Td Discharge temperature TdSH Discharge superheat degree Xs Suction dryness (dryness of refrigerant on the inlet side of the compressor)
ε Pressure ratio εmax Pressure ratio upper limit (pressure ratio upper limit)

Claims

A refrigeration cycle in which at least a compressor, a heat source side heat exchanger, a use side heat exchanger, and an expansion valve are connected to circulate a refrigerant containing R32 in an amount of 70% by weight or more;
A control device,
The upper limit value that regulates the pressure ratio of the compressor so that the dryness of the refrigerant on the inlet side of the compressor becomes higher than 0.85, so that it becomes lower as the suction pressure of the refrigerant in the compressor is higher. Set,
During operation, the control device
The air conditioner characterized by adjusting the rotational speed of the compressor so that the pressure ratio becomes smaller than the upper limit value.
A target value of the discharge superheat degree is set by subtracting the condensation temperature corresponding to the discharge pressure of the refrigerant in the compressor from the discharge temperature of the refrigerant in the compressor,
During operation, the control device
The rotation speed of the compressor is adjusted so that the pressure ratio approaches the upper limit value, and the valve opening degree of the expansion valve is adjusted so that the discharge superheat degree approaches the target value. Item 2. An air conditioner according to Item 1.
During operation, the control device
At least the discharge temperature of the refrigerant in the compressor;
A discharge pressure of the refrigerant in the compressor;
The suction pressure in the compressor;
The rotational speed of the compressor;
The dryness is estimated by calculation based on
The air conditioner according to claim 1 or 2, wherein the rotation speed of the compressor is adjusted so that the estimated dryness is higher than 0.85.
At least a compressor, a heat source side heat exchanger, a use side heat exchanger, and an expansion valve are connected to each other, and has a refrigeration cycle in which a refrigerant containing R32 in an amount of 70% by weight or more circulates. An air conditioner control device in which an upper limit value that regulates the pressure ratio of the compressor is set to be lower as the suction pressure of the refrigerant in the compressor is higher so that the dryness is higher than 0.85 Runs and
A procedure for calculating a pressure ratio based on a discharge pressure of the refrigerant in the compressor and an intake pressure of the refrigerant in the compressor;
And a procedure for adjusting the rotational speed of the compressor so that the calculated pressure ratio becomes smaller than the upper limit value.
The refrigerant is dried by a calculation based on at least the discharge temperature of the refrigerant in the compressor, the discharge pressure of the refrigerant in the compressor, the suction pressure in the compressor, and the rotational speed of the compressor. A procedure to estimate the degree,
The method of operating an air conditioner according to claim 4, further comprising a step of adjusting the rotational speed of the compressor so that the estimated dryness of the refrigerant is higher than 0.85.