REFRIGERANT DETECTION APPARATUS, COMPUTER READABLE MEDIUM, AND REFRIGERANT DETECTION METHOD

Abstract

When the subcooling degree is determined to be at zero kelvin, a calculation unit calculates a gas phase area ratio of the outdoor heat exchanger, using a first temperature difference which is a difference between an outdoor temperature and a condensation temperature of a refrigerant, a second temperature difference which is a difference between a refrigerant discharge temperature and the condensation temperature, an enthalpy difference of the refrigerant between an inlet and an outlet of the outdoor heat exchanger, and a specific heat at constant pressure gas of the refrigerant. The calculation unit compares the gas phase area ratio with a standard value set as a standard for the gas phase area ratio, and calculates a refrigerant amount in a refrigeration cycle apparatus, based on a comparison result.

Description

TECHNICAL FIELD

The present disclosure relates to a refrigerant detection apparatus, a refrigerant detection program, and a refrigerant detection method, to detect a refrigerant amount in a refrigerant circuit.

BACKGROUND

Conventional techniques include techniques to detect a refrigerant leakage amount in a refrigerant circuit (for example, Patent Literatures 1 and 2). In the conventional techniques, a subcooling degree SC of a refrigerant at an outlet of a condenser needs to be greater than 0° C. If a condition is imposed that the subcooling degree SC is greater than 0° C. when the refrigerant leakage amount is detected, it is possible to detect a leakage of 10% or more, for example. However, it is not possible to quantitatively detect whether the leakage amount of the refrigerant is 20% or 30%. Therefore, since a refrigerant amount to be added is not known, an operator needs to collect all of the refrigerant from the refrigerant circuit, and fill the refrigerant circuit with a standard refrigerant amount written in a catalog. Accordingly, there is a problem that a maintenance work is burdensome.

PATENT LITERATURE

• Patent Literature 1: JP 2019-066164 A
• Patent Literature 2: JP 5063346 B2

SUMMARY

The present disclosure aims to provide a refrigerant detection apparatus that can detect a refrigerant leakage amount even when a subcooling degree SC of a refrigerant at an outlet of a condenser is 0° C.

A refrigerant detection apparatus according to the present disclosure includes:

• • a determination unit to determine whether a subcooling degree of a refrigerant is at zero kelvin in a refrigeration cycle apparatus including a compressor, a condenser, an expansion valve and an evaporator, the refrigerant circulating in the refrigeration cycle apparatus;
  • a calculation unit, when the determination unit determines that the subcooling degree is at zero kelvin, to calculate a gas phase area ratio which is a gas phase volume rate of a total volume of the condenser, using a first temperature difference which is a difference between an outdoor temperature and a condensation temperature of the refrigerant, a second temperature difference which is a difference between a refrigerant discharge temperature of the compressor and the condensation temperature, an enthalpy difference of the refrigerant between an inlet of the condenser and an outlet of the condenser, and a specific heat at constant pressure gas of the refrigerant, to compare the calculated gas phase area ratio with a standard value set as a standard for the gas phase area ratio, and to calculate a refrigerant amount in the refrigeration cycle apparatus, based on a comparison result; and
  • an output unit to output a value obtained from the refrigerant amount calculated by the calculation unit.

Since a refrigerant detection apparatus of the present disclosure includes a calculation unit, a refrigerant leakage amount can be detected even when a subcooling degree SC of a refrigerant at an outlet of a condenser is 0° C. Therefore, it is possible to reduce a burden of refrigerant filling on an operator.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of Embodiment 1 and is a diagram illustrating a refrigeration cycle apparatus 50.

FIG. 2 is a diagram of Embodiment 1 and is a flowchart of operation of a refrigerant detection apparatus 100.

FIG. 3 is a diagram of Embodiment 1 and is a diagram illustrating a configuration in which the refrigeration cycle apparatus 50 has a plurality of indoor heat exchangers.

FIG. 4 is a diagram of Embodiment 1 and is a diagram illustrating an effect of a refrigerant amount detection mode at a time when there is the refrigerant amount detection mode of step S20.

FIG. 5 is a diagram of Embodiment 1 and is a diagram of a comparison example of FIG. 4 without the refrigerant amount detection mode of step S20.

FIG. 6 is a diagram of Embodiment 1 and is a diagram illustrating a case where a refrigerant amount transitions from a large amount state to an intermediate amount state.

FIG. 7 is a diagram of Embodiment 1 and is a diagram illustrating a case where the refrigerant amount transitions from the intermediate amount state to a small amount state.

FIG. 8 is a diagram of Embodiment 1 and is a diagram illustrating that refrigerant amount detection is possible within a total refrigerant amount by using A_L% and A_G% together.

FIG. 9 is a diagram of Embodiment 1 and is a diagram illustrating a hardware configuration of the refrigerant detection apparatus 100.

FIG. 10 is a diagram of Embodiment 1 and is a diagram illustrating another hardware configuration of the refrigerant detection apparatus 100.

DETAILED DESCRIPTION

In the description and drawings of embodiments, the same elements and corresponding elements are denoted by the same reference sign. Description of an element denoted by the same reference sign will be appropriately omitted or simplified. In the following embodiments, “unit” may be appropriately replaced by “circuit”, “stage”, “procedure”, “process”, or “circuitry”.

In FIGS. 1, 3, 4, and 5 to be described below, a liquid refrigerant is illustrated in black in an outdoor heat exchanger 2, a liquid pipe 5, an indoor heat exchanger 7, and an accumulator 10.

In the following embodiments, a value detected by a sensor is referred to as a detection value. A value that is set in a refrigerant detection apparatus 100 based on a specification of the apparatus rather than the detection value is referred to as a set value. The set value may also be referred to as a specification value.

Embodiment 1

The refrigerant detection apparatus 100 of Embodiment 1 will be described with reference to FIGS. 1 to 10.

FIG. 1 illustrates a refrigeration cycle apparatus 50 of Embodiment 1. The refrigeration cycle apparatus 50 has a refrigerant circuit 51 through which a refrigerant circulates.

The refrigerant detection apparatus 100 has the following features.

(1) The refrigerant detection apparatus 100 can detect a refrigerant amount even when a subcooling degree SC=0° C. at an outlet of a condenser and a refrigerant state at the outlet of the condenser is a two-phase.

In the refrigerant detection apparatus 100, an output unit 115 to be described below presents a refrigerant leakage amount in a quantitative value “**%”, like the “leakage amount **%” based on a “standard refrigerant amount (100%)”.

The output unit 115 can display the refrigerant leakage amount on displays of a computer and a tablet terminal, for example. Therefore, since an operator knows a refrigerant filling amount to be added, an operation time can be reduced. Further, in an air conditioning system using a combustible refrigerant, since it is known whether or not the refrigerant has reached an ignition limit concentration, an appropriate response to leakage can be taken depending on an ignition risk. The appropriate response to leakage can be taken, such as whether to ventilate or evacuate, for example.

(2) When detecting the refrigerant amount, the refrigerant detection apparatus 100 operates a refrigeration cycle apparatus in a refrigerant amount detection mode.

(3) The refrigerant detection apparatus 100 indirectly detects the refrigerant amount using A_L% to be described below under a condition where the subcooling degree SC is greater than 0° C., and using A_G% to be described below under another condition (SC=0).

(4) The refrigerant detection apparatus 100 improves accuracy of the refrigerant detection amount, by adding to each of A_L% and A_G%, a correction of a “condensation temperature-outdoor air” ratio depending on a refrigerant circulation amount ratio.

The refrigerant detection apparatus 100 will be specifically described below.

As illustrated in FIG. 1, the refrigeration cycle apparatus 50 includes an outdoor unit 20 and an indoor unit 30. The refrigeration cycle apparatus 50 constitutes a refrigeration cycle. The outdoor unit 20 includes a compressor 1, a four-way valve 9, the outdoor heat exchanger 2, an outdoor fan 2A, an HIC 3, an HIC-LEV 4, and the accumulator 10. The HIC 3 is a Heat Inter Changer. The Heat Inter Changer is referred to as the HIC 3. The HIC 3 has a double pipe that exchanges heat with the refrigerant injected into the compressor 1 and with the refrigerant that flows to the outdoor heat exchanger 2. The HIC-LEV 4 is a linear expansion valve for the HIC 3. The linear expansion valve is referred to as an LEV. The indoor unit 30 includes an LEV 6, the indoor heat exchanger 7, and an indoor fan 7A. The LEV 6 is a linear expansion valve for the indoor heat exchanger 7.

The HIC-LEV 4 and the LEV 6 are expansion valves.

<Refrigerant Circuit 51>

The refrigerant circuit 51 will be described below. In the outdoor unit 20, the compressor 1, the four-way valve 9, the outdoor heat exchanger 2, and the HIC 3 are connected in this order by pipes. The HIC 3, the HIC-LEV 4, the HIC 3, the accumulator 10, and the compressor 1 are connected in this order by pipes. A gas pipe 8, the four-way valve 9, and the accumulator 10 are connected in this order by pipes. In the indoor unit 30, the liquid pipe 5, the LEV 6, the indoor heat exchanger 7, and the gas pipe 8 are connected in this order by pipes. The refrigerant circuit 51 is formed by connecting the outdoor unit 20 and the indoor unit 30 with the gas pipe 8 and the liquid pipe 5. A branch path passes through the HIC-LEV 4 from a branch point B1, passes through the HIC 3, and connects to a branch point B2. The LEV 6 is a first expansion valve and the HIC-LEV 4 is a second expansion valve.

<Flow of Refrigerant>

In Embodiment 1, the outdoor heat exchanger 2 functions as a condenser and the indoor heat exchanger 7 functions as an evaporator. A case where the outdoor heat exchanger 2 functions as the condenser and the indoor heat exchanger 7 functions as the evaporator is referred to as cooling operation. A flow of the refrigerant in the case where the outdoor heat exchanger 2 is the condenser will be described below. In FIG. 1, a plurality of arrows indicate flowing directions of the refrigerant. The refrigerant flows to the compressor 1, the four-way valve 9, and the outdoor heat exchanger 2, and exchanges heat with an outdoor air in the outdoor heat exchanger 2. The outdoor fan 2A is installed in the outdoor heat exchanger 2 to facilitate the heat exchange. The black portion of the outdoor heat exchanger 2 indicates the liquid refrigerant. The refrigerant that has flowed out of the outdoor heat exchanger 2 passes through the HIC 3, and branches to two directions at the branch point B1. The refrigerant branched to one side goes to the liquid pipe 5, and the refrigerant branched to the other side goes to the HIC-LEV 4. The refrigerant branched to the one side passes through the liquid pipe 5, flows into the LEV 6, and expands. The refrigerant that has flowed out of the LEV 6 flows into the indoor heat exchanger 7 that functions as the evaporator, and exchanges heat with an indoor air. The indoor fan 7A is installed in the indoor heat exchanger 7 to facilitate the heat exchange. The black portion of the indoor heat exchanger 7 indicates the liquid refrigerant. The refrigerant that has flowed out of the indoor heat exchanger 7 passes through the gas pipe 8, and flows into the four-way valve 9 of the outdoor unit 20. The refrigerant that has flowed out of the four-way valve 9 joins at the branch point B2, the refrigerant that has flowed out of the HIC 3, and flows into the accumulator 10. The refrigerant that has flowed out of the accumulator 10 flows into the compressor 1. The refrigerant branched to the other side at the branch point B1 flows into the HIC-LEV 4 and expands. The refrigerant that has flowed out of the HIC-LEV 4 flows into the HIC 3, and exchanges heat with the refrigerant that flows to the branch point B1 from the HIC 3. The refrigerant that has flowed out of the HIC 3 joins at the branch point B2, the refrigerant that flows from the four-way valve 9 to the branch point B2, and flows to the accumulator 10.

<Refrigerant Detection Apparatus 100>

A plurality of temperature sensors and a plurality of pressure sensors are installed in the refrigerant circuit 51 of the refrigeration cycle apparatus 50. Further, the refrigerant detection apparatus 100 is connected to the refrigeration cycle apparatus 50. The refrigerant detection apparatus 100 detects the refrigerant leakage amount in the refrigerant circuit 51. The refrigerant detection apparatus 100 acquires detection values of the plurality of temperature sensors and the plurality of pressure sensors disposed in the refrigerant circuit 51, and controls each of actuators of the refrigeration cycle apparatus 50, based on the acquired plurality of detection values. Each of the actuators here is the compressor 1, the outdoor fan 2A, the HIC-LEV 4, or the four-way valve 9, in the outdoor unit 20, and is the LEV 6 or the indoor fan 7A, in the indoor unit 30. Further, the refrigerant detection apparatus 100 acquires the detection values of the plurality of temperature sensors and the plurality of pressure sensors disposed in the refrigerant circuit 51, and detects the refrigerant leakage amount in the refrigerant circuit 51 based on the acquired plurality of detection values.

Details of the refrigerant detection apparatus 100 will be described below.

<Sensor>

The following ten types of sensors are disposed in the refrigerant circuit 51. A reference sign of a sensor may be used as a detection value of the sensor in Embodiment 1.

(1) Pressure Sensor HS:

A pressure sensor HS is disposed on a discharge side of the compressor 1. The pressure sensor HS detects high pressure inside a pipe on the discharge side. A condensation temperature T_c of the refrigerant can be obtained as a saturation temperature of the pressure detected by the pressure sensor HS.

(2) Pressure Sensor LS:

A pressure sensor LS is disposed on a suction side of the compressor 1. The pressure sensor LS detects low pressure inside a pipe on the suction side.

(3) Temperature Sensor TH2:

A temperature sensor TH2 is disposed at an outlet where the refrigerant that has flowed out of the HIC-LEV 4 flows out of the HIC 3. The temperature sensor TH2 detects an outlet temperature of the refrigerant that flows from the HIC-LEV 4 into the HIC 3, and flows out of the HIC 3.

(4) Temperature Sensor TH3:

A temperature sensor TH3 is disposed at an outlet of the outdoor heat exchanger 2. The temperature sensor TH3 detects an outlet temperature of the refrigerant of the outdoor heat exchanger 2 when the outdoor heat exchanger 2 functions as the condenser.

(5) Temperature Sensor TH4:

A temperature sensor TH4 is disposed on the discharge side of the compressor 1. The temperature sensor TH4 detects a temperature of the refrigerant discharged from the compressor 1.

(6) Temperature Sensor TH5:

A temperature sensor TH5 is disposed on the suction side of the compressor 1. The temperature sensor TH5 detects a temperature of the refrigerant that flows into the compressor 1.

(7) Temperature Sensor TH7:

A temperature sensor TH7 is disposed the circumstance of the outdoor fan 2A. The temperature sensor TH7 detects an ambient air temperature of the outdoor unit 20. That is, the temperature sensor TH7 detects an outdoor temperature.

(8) Frequency Sensor Sf:

A frequency sensor Sf is disposed in the compressor 1. The frequency sensor Sf detects a frequency of the compressor 1.

(9) Opening Sensor S4:

An opening sensor S4 is disposed in the HIC-LEV 4. The opening sensor S4 detects an opening of the HIC-LEV 4. The opening sensor S4 detects a pulse that controls the opening of the HIC-LEV 4.

(10) Opening Sensor S6:

An opening sensor S6 is disposed in the LEV 6. The opening sensor S6 detects an opening of the LEV 6. The opening sensor S6 detects a pulse that controls the opening of the LEV 6.

(11) Although the various sensors of (1) to (10) described above are disposed in the refrigeration cycle apparatus 50, a sensor other than these sensors may be disposed.

The refrigerant detection apparatus 100 will be described in detail. The refrigerant detection apparatus 100 includes an acquisition unit 111, a control unit 112, a determination unit 113, a calculation unit 114, and the output unit 115.

(1) The acquisition unit 111 acquires the detection values from the various sensors.

(2) The control unit 112 controls each of the actuators of the refrigeration cycle apparatus 50 based on the detection values of the various sensors acquired by the acquisition unit 111. Thereby, the control unit 112 controls operation of the refrigeration cycle apparatus 50.

(3) The determination unit 113 determines whether or not the subcooling degree SC is S>0 (kelvin). In other words, the determination unit 113 determines whether or not the subcooling degree SC is SC=0 (kelvin). SC=0 (kelvin) or SC=0° C. may be referred to as SC=0. Details will be described below. The subcooling degree SC may be simply referred to as SC. The unit of the subcooling degree SC may be kelvin or ° C. (4) The calculation unit 114 calculates either the refrigerant amount based on a liquid phase area ratio A_L% or the refrigerant amount based on a gas phase area ratio A_G% depending on a determination result of the determination unit 113. The liquid phase area ratio A_L% indicates a liquid phase area ratio which is a liquid phase volume rate of a total volume of the outdoor heat exchanger 2 that functions as the condenser. The gas phase area ratio A_G% indicates a gas phase area ratio which is a gas phase volume rate of the total volume of the outdoor heat exchanger 2 that functions as the condenser. Hereinafter, the liquid phase area ratio A_L% and the gas phase area ratio A_G% may be simply referred to as A_L% and A_G%. Details of A_L% and A_G% will be described below. When SC=0, the calculation unit 114 calculates the refrigerant amount based on A_G%. When SC>0, the calculation unit 114 calculates the refrigerant amount based on A_L%.

(5) The output unit 115 outputs a calculation result of the calculation unit 114. The output of the calculation result by the output unit 115 is various, such as display to a display device, generation of sound by a sound generation device, or output of a calculation value to a storage device.

The operation of the cooling operation by the refrigeration cycle apparatus 50 will be described. In the cooling operation, the high-temperature and high-pressure gas refrigerant discharged from the compressor 1 passes through the four-way valve 9 to reach the outdoor heat exchanger 2 and then is condensed. The condensation temperature T_c at this time can be obtained as the saturation temperature of the pressure of the pressure sensor HS attached to the discharge side of the compressor 1. Further, the subcooling degree of the refrigerant at the outlet of the outdoor heat exchanger 2 is obtained from a difference between the condensation temperature T_c and the temperature sensor TH3. The condensed refrigerant passes through the HIC 3. The refrigerant branched to the one side at the branch point B1 flows through the liquid pipe 5 into the LEV 6.

The refrigerant branched to the one side will be described. The refrigerant that has flowed into the LEV 6 is decompressed. The refrigerant that has left the LEV 6 evaporates in the indoor heat exchanger 7. After that, the refrigerant returns to the compressor 1 via the gas pipe 8, the four-way valve 9, the branch point B2, and the accumulator 10.

The refrigerant branched to the other side at the branch point B1 flows into the HIC-LEV 4. The refrigerant that has flowed out of the HIC-LEV 4 exchanges heat at the HIC 3, with the refrigerant that has flowed out of the outdoor heat exchanger 2, and returns to the compressor 1 via the branch point B2 and the accumulator 10.

*** Description of Operation ***

FIG. 2 is a flowchart of operation of detecting the refrigerant leaked in the refrigerant circuit 51, performed by the refrigerant detection apparatus 100. The refrigerant detection operation by the refrigerant detection apparatus 100 will be described with reference to FIG. 2.

<Step S10>

In step S10, the control unit 112 starts the operation of the refrigeration cycle apparatus 50 in the refrigerant amount detection mode.

<Step S20>

Step S20 indicates control of the refrigerant amount detection mode by the control unit 112. Each of the control of (1) to (5) indicated in step S20 of FIG. 2 has the following effects. That is, in order to improve detection accuracy of the refrigerant amount using A_L% and A_G%, it is preferable that distribution of the liquid refrigerant in the refrigerant circuit 51 does not depend on an environmental condition and an operational state. The gas refrigerant is inside the accumulator 10 by the control of (1) to (5) of step S20. Therefore, most of the liquid refrigerant can stay in the liquid pipe 5 and the outdoor heat exchanger 2 which is the condenser. Further, a refrigerant temperature of the liquid pipe 5 is substantially constant by the control to the HIC-LEV 4 by the control unit 112. Therefore, it is possible to avoid a change in refrigerant density in the liquid pipe 5, due to a difference in the outdoor air. The control from (1) to (5) will be specifically described.

In step S20, the control unit 112 controls each of the actuators of the refrigeration cycle apparatus 50, using the detection values of the various sensors acquired by the acquisition unit 111. Thereby, the control unit 112 operates the refrigeration cycle apparatus 50 in the refrigerant amount detection mode.

(1) The control unit 112 performs the cooling operation of the refrigeration cycle apparatus 50. Therefore, the outdoor heat exchanger 2 functions as the condenser and the indoor heat exchanger 7 functions as the evaporator.

(2) The control unit 112 fixes rotations of the outdoor fan 2A and the indoor fan 7A at full speeds. A feature is that all of the fans are fixed at the full speeds. A change in the refrigerant amount in the outdoor heat exchanger 2 due to a change in the refrigerant filling amount is directly linked to pressure and temperature around the outdoor heat exchanger 2 by setting all of the fans at the full speeds, and the detection accuracy of the refrigerant amount using such as A_L% and A_G% is improved. If a fan speed changes, the detection accuracy of the refrigerant amount decreases since it is not known whether the pressure and temperature have changed due to the change in the refrigerant filling amount or the pressure and temperature have changed due to the change in the fan speed.

(3) The control unit 112 automatically controls (controls at an evaporation temperature ET 0° C.) the compressor 1.

(4) The control unit 112 controls a superheat degree SHs at an outlet of the LEV 6, by controlling the LEV 6. The control unit 112 controls the LEV 6 so that the superheat degree SHs of the LEV 6 is equal to or greater than 0° C.

(5) The control unit 112 controls a superheat degree SHb at an outlet of the HIC-LEV 4, by controlling the HIC-LEV 4. The control unit 112 controls the HIC-LEV 4 so that the superheat degree SHb of the HIC-LEV 4 is equal to or greater than 0° C.

<Step S30>

In step S30, the determination unit 113 determines whether or not SC>0. In other words, the determination unit 113 determines whether the outlet of the outdoor heat exchanger 2 that functions as the condenser is in a subcooling state or a two-phase state. The subcooling degree is obtained by SC=Tc−TH3. When the subcooling degree SC=0, the process proceeds to step S40. When the subcooling degree SC>0, the process proceeds to step S50. However, the outlet of the condenser may be in the two-phase state even if SC>0 due to an effect such as a detection error of the temperature sensors and the pressure sensors or a refrigerant pressure loss. Therefore, the determination formula of step S30 may be set to SC>0.5, for example. Note that 0.5 in SC>0.5 is an example. It is not limited to 0.5, and a value greater than zero may be adopted instead of 0.5. A feature of the refrigerant detection apparatus 100 is particularly in step S40. In step S40, the calculation unit 114 calculates A_G%, and calculates the refrigerant amount in the refrigerant circuit 51 using A_G%. In step S50, the calculation unit 114 calculates A_L%, and calculates the refrigerant amount in the refrigerant circuit 51 using A_L%. The calculation unit 114 calculates the refrigerant amount based on A_G% and the refrigerant amount based on A_L%, using the various detection values acquired by the acquisition unit 111.

<Description of A_L% and A_G%>

Since A_L% and A_G% have common and similar portions, they will be described together.

First, the following (Formula 1) to (Formula 5) are indicated for A_L% and A_G%.

$\begin{array}{cc}{A}_L\%=-\mathrm{Ln}\left(1-\mathrm{SC}/{\mathrm{dT}}_c\right)*\left\{{\mathrm{dT}}_c*{\left[{\mathrm{dT}}_{c\_\mathrm{corr}}\right]}^{-1}*C_{\mathrm{pL}}^{\prime }\right\}/\Delta h_{\mathrm{con}}& \left(\mathrm{Formula}1\right)\end{array}$ $\begin{array}{cc}{A}_G\%=-\mathrm{Ln}\left({\mathrm{dT}}_c/\left({\mathrm{dT}}_c+{\mathrm{SH}}_d\right)\right)*\left\{{\mathrm{dT}}_c*{\left[{\mathrm{dT}}_{c\_\mathrm{corr}}\right]}^{-1}*C_{\mathrm{pg}}^{\prime }\right\}/\Delta h_{\mathrm{con}}& \left(\mathrm{Formula}2\right)\end{array}$ $\begin{array}{cc}{C}_{\mathrm{pL}}^{\prime }=f_1\left({\mathrm{dT}}_c*{\left[{\mathrm{dT}}_{c\_\mathrm{corr}}\right]}^{-1}+\mathrm{TH}7\right)& \left(\mathrm{Formula}3\right)\end{array}$ $\begin{array}{cc}{C}_{\mathrm{pg}}^{\prime }=f_2\left({\mathrm{dT}}_c*{\left[{\mathrm{dT}}_{c\_\mathrm{corr}}\right]}^{-1}+\mathrm{TH}7\right)& \left(\mathrm{Formula}4\right)\end{array}$ $\begin{array}{cc}{\mathrm{dT}}_{c\_\mathrm{corr}}=A*{\left(G_{r\_\mathrm{ratio}}\right)}^B& \left(\mathrm{Formula}5\right)\end{array}$

The meaning of the symbols in each of the formulas is as follows.

(a) SC:

The subcooling degree SC is a difference between the condensation temperature T and the outlet temperature TH3 of the outdoor heat exchanger 2. That is, SC=T_c−TH3. The outlet temperature TH3 is a liquid temperature when SC>0.

The condensation temperature T_c is also referred to as a condensation temperature. The condensation temperature T_c can be obtained by converting the detection value of the pressure sensor HS into a saturated gas temperature. The determination unit 113 converts the detection value of the pressure sensor HS into the saturated gas temperature, using a physical property table for converting pressure into temperature. An auxiliary storage device 130 stores the physical property table.

The outlet temperature TH3 is the detection value of the temperature sensor TH3.

The determination unit 113 calculates the subcooling degree SC and determines whether or not the subcooling degree SC is greater than zero.

(b) dT_c:

dT_c is a difference between the condensation temperature T_c and the outdoor temperature TH7. That is, dT_c=T_c−TH7. dT_c is a first temperature difference. TH7 is detected by the temperature sensor TH7.

${\left(c\right)\left[{\mathrm{dT}}_{c\_\mathrm{corr}}\right]}^{-1}$

• • [dT_{c_corr}]⁻¹ is a correction value of dT_c. As indicated in the above (Formula 5), [dT_{c_corr}]⁻¹ is a correction coefficient of dT_c decided from a refrigerant circulation ratio G_{r_ratio}.
  • [dT_{c_corr}]⁻¹ is a reciprocal value of dT_{c_corr}.
  • dT_{c_corr}, can be obtained as follows.

As described in (Formula 5),

${\mathrm{dT}}_{c\_\mathrm{corr}}=A*{\left(G_{r\_\mathrm{ratio}}\right)}^B$

where A and B are constant values.

$\begin{array}{cc}{G}_{r\_\mathrm{ratio}}=\mathrm{refrgerant}\mathrm{circulation}\mathrm{amount}{G}_r÷\mathrm{standard}\mathrm{refrigerant}\mathrm{circulation}\mathrm{amount}{G}_{\mathrm{std}}& \left(\mathrm{Formula}5.1\right)\end{array}$

The standard refrigerant circulation amount G_std is a set value for the refrigerant circuit 51. The meaning of G_{r_ratio} is as follows. G_{r_ratio} is a ratio of the refrigerant circulation amount G_r to the standard refrigerant circulation amount G_std (refrigerant circulation amount during rated capacity operation kg/h) when A_L% or A_G% is calculated. In a device with a rated capacity of 28 kW (circulation amount 614 kg/h), G_{r_ratio} is 0.5 when the device is operated at the circulation amount of 307 kg/h during A_L% calculation, for example. The standard refrigerant circulation amount G_std is a known set value. The refrigerant circulation amount G_r is an amount relating to the compressor 1 and can be calculated by (Formula 5.2). The meaning of the symbols in (Formula 5.2) is described below,

$\begin{array}{cc}{G}_r\left(\mathrm{kg}/s\right)=S_t*{\rho }_s*f*{\eta }_v& \left(\mathrm{Formula}5.2\right)\end{array}$

• • S_t: excluded volume,
  • ρ_s: suction density,
  • f: compressor frequency,
  • η_v: volumetric efficiency. The calculation unit 114 can calculate dT_{c_corr} by (Formula 5), (Formula 5.1) and (Formula 5.2).

That is, (Formula 5.3) is obtained.

$\begin{array}{cc}{G}_{r\_\mathrm{ratio}}=S_t*{\rho }_s*f*{\eta }_v÷G_{\mathrm{std}}& \left(\mathrm{Formula}5.3\right)\end{array}$

In (Formula 5.3), S_t, η_v and G_std are not parameters whose values are decided from the detection values of the sensors. S_t, η_v and G_std are specification values. ρ_s is decided according to a physical property table from the detection value of the temperature sensor TH5. The auxiliary storage device 130 stores this physical property table.

f is decided from the detection value of the frequency sensor Sf.

More specifically, S_t denotes the excluded volume. S_t is stroke volume and indicates volume of suction gas taken in by the compressor 1 per rotation. η_v is the volumetric efficiency. S_t is volume obtained geometrically, and actual effective volume is S_t×η_v. f is the number of rotations of the compressor. When G_{r_ratio} is decided, [dT_{c_corr}] is decided by (Formula 5).

As described above, the calculation unit 114 calculates the correction coefficient [dT_{c_corr}]⁻¹ that corrects the first temperature difference dT_c. The correction coefficient [dT_{c_corr}]⁻¹ is decided based on the circulation amount of the refrigerant in the refrigerant circuit 51 decided from a specification of the compressor 1 and an operational state of the compressor 1, and based on the standard refrigerant circulation amount decided as a specification of the refrigerant circuit 51. The calculation unit 114 corrects the first temperature difference dT_c with the decided correction coefficient [dT_{c_corr}]⁻¹.

(d) C′_pL

C′_pL is a specific heat of the liquid refrigerant. C′_pL is calculated by the above (Formula 3). TH7 in (Formula 3) is the detection value of the temperature sensor TH7 that detects the outdoor temperature. f₁ in (Formula 3) indicates a function. C′_pL is a value decided from refrigerant physical properties. That is, C′_pL is obtained by substituting dT_c obtained by the above (b), [dT_{c_corr}]⁻¹ obtained by the above (c), and the detection value of the detection sensor TH7, into the function f₁. C′_pL is the specific heat at constant pressure liquid.

(e) Δh_con.

Δh_con (Formula 1) and (Formula 2) is an enthalpy difference between an inlet and an outlet of the condenser.

That is, Δh_con is an enthalpy difference between the inlet and the outlet of the outdoor heat exchanger 2. Since SC>0 in (Formula 1), the outlet of the outdoor heat exchanger 2 is in a liquid phase, and the inlet of the outdoor heat exchanger 2 is in a gas phase. Therefore, enthalpy at the inlet and the outlet is decided from a temperature T and pressure P of the refrigerant.

Specifically, the enthalpy at the inlet of the outdoor heat exchanger 2 is obtained from the detection value of the pressure sensor HS and the detection value of the temperature sensor TH4.

The enthalpy at the outlet of the outdoor heat exchanger 2 is obtained from the detection value of the pressure sensor HS and the detection value of the temperature sensor TH3.

When the refrigerant is in a single-phase, among six values of refrigerant physical properties, that is, among pressure, temperature, density, enthalpy, entropy, and dryness, if two of the six values of the physical properties are specified, the other four values are confirmed.

Since the temperature sensors and the pressure sensors are installed in the refrigeration cycle apparatus, the values of the physical properties of the refrigerant are obtained from the temperature and pressure.

When the refrigerant is in the two-phase state, the temperature is stable under constant pressure. Therefore, the values of the physical properties such as the enthalpy and the density are obtained by specifying the dryness, like saturated gas (dryness 1) and saturated liquid (dryness 0).

(f) SH_d

SH_d in (Formula 2) is a difference between the discharge temperature TH4 and the condensation temperature (saturated gas temperature) T_c.

That is,

${\mathrm{SH}}_d=\mathrm{TH}4-T_c$

SH_d is obtained from detection values of the temperature sensor TH4 and the pressure sensor HS.

SH_d is a second temperature difference.

(g) C′_pg

C′_pg is a specific heat of the gas refrigerant. C′_pg is calculated by the above (Formula 4). The calculation of C′_pg is similar to that of C′_pL. In contrast with f₁ in (Formula 3), there is a function f₂ in (Formula 4). C′_pg is also a value decided from the refrigerant physical properties. That is, C′_pg is obtained by substituting dT_c, [dT_{c_corr}]⁻¹, and TH7 into the function f₂. C′_pg is the specific heat at constant pressure gas.

<Calculation of Δh_con of (Formula 2)>

The calculation unit 114 calculates the enthalpy difference Δh_con of the refrigerant at the subcooling degree SC=0, based on openings of expansion valves, the suction pressure LS of the compressor 1, the discharge pressure HS of the compressor 1, and the circulation amount G_{r_total} of the refrigerant.

The expansion valves are the HIC-LEV4, and LEVs 6-1, 6-2, and 6-3. Since (Formula 2) is calculation of A_G%, the subcooling degree SC is SC=0. That is, the refrigerant at the outlet of the outdoor heat exchanger 2 which is the condenser is in the two-phase. When a state of the refrigerant at the outlet of the condenser is the two-phase, the enthalpy at the outlet of the condenser cannot be calculated from the temperature and pressure. Therefore, the enthalpy of the refrigerant at the outlet of the outdoor heat exchanger 2 is estimated by the following method. Note that the refrigerant at the inlet of the outdoor heat exchanger 2 is in the gas phase. Therefore, the enthalpy of the refrigerant at the inlet can be calculated from the temperature and pressure as with the case of (Formula 1). (Formula 6) to (Formula 13) will be indicated below.

(Formula 6) to (Formula 13) assume the refrigeration cycle apparatus 50 of FIG. 3.

FIG. 3 illustrates a configuration in which the refrigeration cycle apparatus 50 has a plurality of indoor heat exchangers. The refrigeration cycle apparatus 50 includes an indoor heat exchanger 7-1. The LEV 6-1 and an indoor fan 7A-1 are disposed in the indoor heat exchanger 7-1. Similarly, the LEV 6-2 and an indoor fan 7A-2 are disposed in an indoor heat exchanger 7-2, and the LEV 6-3 and an indoor fan 7A-3 are disposed in an indoor heat exchanger 7-3. Opening sensors S6-1, S6-2, and S6-3 are disposed in the LEVs 6-1, 6-2, and 6-3, respectively. The refrigerant flows into the LEV 6-1, and then branches to the indoor heat exchangers 7-1, 7-2, and 7-3.

In the following (Formula 6) to (Formula 13), (Formula 6) and (Formula 11) are conclusively represented by an unknown number xco and an unknown number xcc. xco is dryness of the refrigerant at the outlet of the outdoor heat exchanger 2 which is the condenser.

xcc is dryness of the refrigerant at the outlet on the high-pressure side of the HIC 3. xco and xcc are parameters.

Then, the calculation unit 114 performs convergence calculation for the parameters xco and xcc so that (Formula 6) and (Formula 11) are established. A value decided from the parameter xco or the parameter xcc is represented like <ρ_{m_co}>.

Since ρ_{m_HICLEV} is decided from xcc as in (Formula 7), ρ_{m_HICLEV} can be represented as <ρ_{m_HICLEV}>.

Since ρ_{m_co} is decided from xco as in (Formula 9), ρ_{m_co} can be represented as <ρ_{m_co}>.

G_{r_total} in (Formula 6) is the same as G in (Formula 5.2).

$\begin{array}{cc}{G}_{r\_\mathrm{total}}=G_{r\_\mathrm{LEV}}+G_{r\_\mathrm{HICLEV}}& \left(\mathrm{Formula}6\right)\end{array}$ $\begin{array}{cc}{G}_{r\_\mathrm{total}}=S_t*{\rho }_s*f*{\eta }_v& \left(\mathrm{Formula}6.1\right)\end{array}$ $\begin{array}{cc}{G}_{r\_\mathrm{LEV}}=\sum \{C_{v\_\mathrm{LEV}}*{\left\{<{\rho }_{m\_\mathrm{co}}>*\left(\mathrm{HS}-\mathrm{LS}\right)\right\}}^{1/2}& \left(\mathrm{Formula}6.2\right)\end{array}$ $\begin{array}{cc}{G}_{r\_\mathrm{HICLEV}}=\{C_{v\_\mathrm{HICLEV}}*{\left\{<{\rho }_{m\_\mathrm{HICLEV}}>*\left(\mathrm{HS}-\mathrm{LS}\right)\right\}}^{1/2}& \left(\mathrm{Formula}6.3\right)\end{array}$

(Formula 6) indicates the following meaning.

(Formula 6) represents a mass conservation law that indicates that the refrigerant circulation amount G_{r_total} of the compressor 1 equals to a total value of the refrigerant circulation amount that G_{r_total} flows through each of the indoor heat exchangers indicated in (Formula 6.2) and the refrigerant circulation amount G_{r_HICLEV} that flows through the HIC 3 indicated in (Formula 6.3). Σ in (Formula 6.2) relates to each of the indoor heat exchangers 7. G_{r_total} on the left side is the refrigerant circulation amount obtained from the specification and the number of rotations of the compressor 1 as indicated in (Formula 6.1).

The right side of (Formula 6) is a total of the refrigerant circulation amount G_{r_LEV} that passes through the LEV of each of the indoor heat exchangers and the refrigerant circulation amount G_{r_HICLEV} that passes through the HIC-LEV 4.

The meaning of each of the symbols is as follows.

C_{v_LEV}: flow coefficient according to the opening of the LEV 6.

C_{v_LEV} is a specification value for calculating from the refrigerant density at the inlet of the LEV 6 and a pressure difference between the inlet and the outlet of the LEV 6, a refrigerant flow amount that passes through the LEV 6.

ρ_{m_co}: refrigerant density at the outlet of the outdoor heat exchanger 2.

C_{v_HICLEV}: flow coefficient according to the opening of the HIC-LEV 4.

C_{v_HICLEV} is a specification value for calculating from the refrigerant density at the inlet of the HIC-LEV 4 and a pressure difference between the inlet and the outlet of the HIC-LEV 4, a refrigerant flow amount that passes through the HIC-LEV 4.

ρ_{m_HICLEV}: refrigerant density at the inlet of the HIC-LEV 4.

The following (Formula 7) to (Formula 10) are ρ_{m_HICLEV} and the like included in (Formula 6.2) and (Formula 6.3).

$\begin{array}{cc}{\rho }_{m\_\mathrm{HICLEV}}={\left\{\mathrm{xcc}/{\rho }_g+\left(1-\mathrm{xcc}\right)/{\rho }_L\right\}}^{-1}& \left(\mathrm{Formula}7\right)\end{array}$ $\begin{array}{cc}{C}_{v\_\mathrm{HICLEV}}=f_3\left(\mathrm{HICpulse}\right)& \left(\mathrm{Formula}8\right)\end{array}$ $\begin{array}{cc}{\rho }_{m\_\mathrm{co}}={\left\{\mathrm{xco}/{\rho }_g+\left(1-\mathrm{xco}\right)/{\rho }_L\right\}}^{-1}& \left(\mathrm{Formula}9\right)\end{array}$ $\begin{array}{cc}{C}_{v\_\mathrm{LEV}}=f_4\left(\mathrm{pulse}\right)& \left(\mathrm{Formula}10\right)\end{array}$

The meaning of each of the symbols is as follows.

• • ρ_g: saturated gas density at high pressure (HS).
  • ρ_L: saturated liquid density at high pressure (HS).
  • HICpulse: opening of the HIC-LEV 4.
  • pulse: opening of the LEV 6.

Here, the saturated gas density ρ_g is obtained from the detection value of the sensor HS on the discharge side and a table for obtaining the saturated gas density ρ_g from the detection value. The calculation unit 114 obtains the saturated gas density pg. Similarly, the saturated liquid density ρ_L is obtained from the detection value of the sensor HS on the discharge side and a table for obtaining the saturated liquid density ρ_L from the detection value. The calculation unit 114 obtains the saturated liquid density ρ_L.

(Formula 7) is the refrigerant density at a time when the inlet of the HIC-LEV 4 is in the gas-liquid two-phase, and the gas and the liquid are uniformly mixed.

(Formula 7) is a calculation formula of the refrigerant density at a time when the refrigerant dryness on the inlet of the HIC-LEV 4 is xcc.

(Formula 9) is a calculation formula of the refrigerant density at a time when the refrigerant dryness on the outlet of the outdoor heat exchanger 2 is xco.

(Formula 8) is a formula that indicates that when the opening of the HIC-LEV4 is decided. C_{v_HICLEV} is decided from a specification f₃ of the HIC-LEV 4. That is, C_{v_HICLEV} is decided from the detection value of the opening sensor S4 and the specification f₃.

(Formula 10) is a formula that indicates that when the opening of the LEV 6 is decided, C_{v_LEV} is decided from a specification f₄ of the LEV 6. That is, C_{v_LEV} is decided from the detection value of the opening sensor S6 and the specification f₄.

(Formula 11) will be represented next.

$\begin{array}{cc}{G}_{r\_\mathrm{total}}*\left(<\mathrm{Hco}\left(\mathrm{xco}\right)>-<\mathrm{Hcc}\left(\mathrm{xcc}\right)>\right)=<G_{r\_\mathrm{HICLEV}}\left(\mathrm{xcc}\right)>*\left(<\mathrm{Hco}\left(\mathrm{xco}\right)>-\mathrm{Hb}\right)& \left(\mathrm{Formula}11\right)\end{array}$

(Formula 11) means that a heat exchange amount on the high-pressure side of the HIC 3 equals to a heat exchange amount on the low-pressure side of the HIC 3.

The meaning of Hco, Hcc, and Hb is as follows.

• • Hco: enthalpy of the refrigerant at the outlet of the outdoor heat exchanger 2.
  • Hcc: enthalpy of the refrigerant at the outlet on the high-pressure side of the HIC 3.
  • Hb: enthalpy of the refrigerant on the low-pressure side of the HIC 3.

Hco and Hcc are represented by the following (Formula 12) and (Formula 13).

Hb can be decided from the detection value of the temperature sensor TH2 and the detection value of the pressure sensor LS.

$\begin{array}{cc}\mathrm{Hco}=f_5\left(\mathrm{HS},<\mathrm{xco}>\right)& \left(\mathrm{Formula}12\right)\end{array}$ $\begin{array}{cc}\mathrm{Hcc}=f_6\left(\mathrm{HS},<\mathrm{xcc}>\right)& \left(\mathrm{Formula}13\right)\end{array}$

(Formula 12) and (Formula 13) are decided from refrigerant physical properties. f₅ and f₆ indicate physical properties. The auxiliary storage device 130 stores a physical property table for each of f₅ and f₆.

Therefore, xco and xcc are unknown values in (Formula 6) and (Formula 11). (Formula 6) and (Formula 11) are represented as follows by specifying xco and xcc.

$\begin{array}{cc}{S}_t*{\rho }_s*f*{\eta }_v=\sum \{C_{v\_\mathrm{LEV}}*{\left\{<{\rho }_{m\_\mathrm{co}}\left(\mathrm{xco}\right)>*\left(\mathrm{HS}-\mathrm{LS}\right)\right\}}^{1/2}+\{C_{v\_\mathrm{HICLEV}}*{\left\{<{\rho }_{m\_\mathrm{HICLEV}}\left(\mathrm{xcc}\right)>*\left(\mathrm{HS}-\mathrm{LS}\right)\right\}}^{1/2}& \left(\mathrm{Formula}6\right)\end{array}$ $\begin{array}{cc}{G}_{r\_\mathrm{total}}*\left(<\mathrm{Hco}\left(\mathrm{xco}\right)>-<\mathrm{Hcc}\left(\mathrm{xcc}\right)>\right)=<G_{r\_\mathrm{HICLEV}}\left(\mathrm{xcc}\right)>*\left(<\mathrm{Hco}\left(\mathrm{xco}\right)>-\mathrm{Hb}\right)& \left(\mathrm{Formula}11\right)\end{array}$

xco is obtained by performing the convergence calculation on (Formula 6) and (Formula 11) represented using xco and xcc. The enthalpy Hco of the refrigerant at the outlet of the outdoor heat exchanger 2 can be calculated by substituting obtained xco into (Formula 12).

Further, the enthalpy of the refrigerant on the inlet side of the outdoor heat exchanger is obtained in the same manner as in the case of Δh_con in (Formula 1). In the cases of (Formula 1) and (Formula 2), the enthalpy of the refrigerant on the inlet side of the outdoor heat exchanger 2 may be obtained by substituting the discharge temperature and pressure of the compressor 1. Thus, Δh_con in (Formula 2) can be obtained. When Δh_con is decided, a value of A_G% in (Formula 2) is decided.

<Step S40>

When SC=0, the process proceeds to step S40. In step S40, the calculation unit 114 calculates A_G% indicated in (Formula 1) according to the contents described in (Formula 1) to (Formula 13), using the various detection values acquired by the acquisition unit 111. A_G% calculated by the calculation unit 114 is referred to as calculated A_G%. The calculation unit 114 compares the calculated gas phase area ratio A_G% with an A_G standard value set as a standard for A_G%, and calculates the refrigerant amount in the refrigeration cycle apparatus 50 based on a comparison result. The A_G standard value is a value that can be compared with the calculated A_G%, and is a value that can be used to calculate from the comparison result, the refrigerant amount correlating with the calculated A_G%. An example of the A_G standard value is A_G% calculated in the past by the calculation unit 114. Then, this A_G% calculated in the past is correlated with the refrigerant amount. The refrigeration cycle apparatus 50 is test operated at 80% of the standard refrigerant amount required for the refrigerant circuit 51, and the calculation unit 114 calculates as the A_G standard value, A_G% during the test operation, for example. A_G% obtained during this test operation can be used as the A_G standard value. A_G% during the test operation is correlated with the refrigerant amount that is 80% of the standard refrigerant amount.

The auxiliary storage device 130 to be described below stores the A_G standard value.

<Step S50>

When SC>0, the process proceeds to step S50. In step S50, when the determination unit 113 determines that the subcooling degree SC is greater than zero kelvin, the calculation unit 114 calculates the liquid phase area ratio A_L% which is the liquid phase volume rate of the total volume of the condenser, using the obtained subcooling degree SC, the first temperature difference dT_c, the enthalpy difference Δh_con of the refrigerant, the specific heat at constant pressure liquid C′_pL of the refrigerant, and the correction coefficient dT_{c_corr} The calculation unit 114 compares the calculated liquid phase area ratio A_L% with an A_L standard value set as a standard for the liquid phase area ratio, and calculates the refrigerant amount in the refrigeration cycle apparatus 50 based on a comparison result.

A specific description will be given below.

In step S50, the calculation unit 114 calculates A_L% indicated in (Formula 1) according to the contents described in (Formula 1) to (Formula 13), using the various detection values acquired by the acquisition unit 111. A_L% calculated by the calculation unit 114 is referred to as calculated A_L%. The calculation unit 114 compares the calculated A_L% with the A_L standard value set as the standard for A_L%. The A_L standard value is a value that can be compared with the calculated A_L%, and is a value that can be used to calculate from the comparison result, the refrigerant amount correlating with the calculated A_L%.

The A_L standard value is A_L% calculated in the past by the calculation unit 114. Then, this A_L% calculated in the past is correlated with the refrigerant amount. A_L% calculated by the calculation unit 114 for the refrigeration cycle apparatus 50 having the standard refrigerant amount as at installation can be used as the A_L, standard value, for example. This A_L% is correlated with the standard refrigerant amount. The auxiliary storage device 130 to be described below stores the A_L standard value.

<Step S60>

In step S60, the output unit 115 outputs a value obtained from the refrigerant amount calculated by the calculation unit 114. The output unit 115 may display the value as output, on a display device.

As for the value obtained from the calculated refrigerant amount, when the refrigerant amount calculated by the calculation unit 114 is greater than the standard refrigerant amount, the output unit 115 may output as an excess refrigerant amount, a difference between the calculated refrigerant amount and the standard refrigerant amount. When the refrigerant amount calculated by the calculation unit 114 is less than the standard refrigerant amount, the output unit 115 may outputs as a leakage refrigerant amount, a difference between the calculated refrigerant amount and the standard refrigerant amount. Alternatively, the output unit 115 may output as a current refrigerant amount, the refrigerant amount itself calculated by the calculation unit 114.

An output form by the output unit 115 may be a ratio such as %, or a refrigerant amount such as kg. The output form of the output unit 115 may be any value such as proportion or mass, as long as the detected refrigerant amount, the excess refrigerant amount, and the leaked refrigerant are known.

<Step S70>

In step S70, the refrigerant amount detection mode ends.

FIG. 4 illustrates an effect of the refrigerant amount detection mode at a time when there is the refrigerant amount detection mode of step S20.

FIG. 5 is a comparison example of FIG. 4 without the refrigerant amount detection mode of step S20. In FIGS. 4 and 5, the upper side diagrams illustrate a state in which the total refrigerant amount has decreased from a state on the lower side. Although A_L% is illustrated in FIGS. 4 and 5, the following description also applies to A_G%. When there is the refrigerant amount detection mode, the refrigerant in the accumulator 10 is gasified as illustrated in FIG. 4. Therefore, a decrease in the refrigerant amount appears in the outdoor heat exchanger 2. When there is no refrigerant amount detection mode, the liquid phase refrigerant is in the accumulator 10 as illustrated in FIG. 5. Therefore, when the total refrigerant amount decreases, the liquid phase refrigerant amount in the accumulator 10 decreases in FIG. 5, the decrease in the total refrigerant amount dose not easily appear in the outdoor heat exchanger 2. Therefore, since the decrease in the total refrigerant amount does not easily appear in the outdoor heat exchanger 2 when there is no refringent amount detection mode, the detection accuracy of the refrigerant leakage amount is lowered. That is, in order to improve the detection accuracy of the refrigerant amount using A_L% and A_G% it is preferable that the liquid temperature at the outlet of the high-pressure condenser or the gas temperature at the outlet of the high-pressure condenser changes only with a change in the refrigerant amount. Further, it is preferable that distribution of the refrigerant amount does not depend on an environmental condition and an operational state. The gas refrigerant is in the accumulator 10 by performing the control of (1) to (5) of the refrigerant amount detection mode of step S20. Therefore, most of the refrigerant can be retained in the liquid pipe 5 and the outdoor heat exchanger 2 which is the condenser. Further, the refrigerant temperature of the liquid pipe 5 can be kept substantially constant by an HIC-LEV control. Therefore, it is possible to avoid a change in the refrigerant density (liquid refrigerant amount) in the liquid pipe due to the outdoor temperature. Therefore, as in FIG. 4, since the decrease in the total refrigerant amount results in the decrease in the refrigerant amount of the condenser, it is possible to improve the detection accuracy of the refrigerant amount using A_L% and A_G%.

A state of the outdoor heat exchanger 2 which is the condenser is divided into a gas phase, a two-phase, and a liquid phase. When SC>0 and there is the liquid phase at the outlet of the condenser, A_G% does not change much even if the refrigerant amount decreases. Therefore, when SC>0, the refrigerant amount is detected using A_L%. This is illustrated in FIG. 6 to be described below. A reason why A_G% does not change much is that the denominator and the numerator in the parentheses of Ln( ) in (Formula 2) change to the same extent due to a high-pressure change.

Further, when the refrigerant amount decreases and SC=0, there is no liquid phase. Therefore, the refrigerant amount is detected using A_G%. When SC=0, the refrigerant amount cannot be detected using A_L%. A reason of this is that when SC=0, the inside of the parentheses of Ln( ) in (Formula 1) is 0, so that A_L% is 0.

Since the outlet of the condenser is in the two-phase, the opening of the LEV is insufficient, and the gas phase expands (the discharge SHd increases) as the suction SHs increases. Therefore, as illustrated in FIG. 7 to be described below, the refrigerant amount can be detected using A_G%.

Refrigerant amount detection using A_L% of step S50 and refrigerant amount detection using A_G% of step S40 will be described with reference to FIGS. 6 and 7.

FIG. 6 illustrates a case where the refrigerant amount transitions from a large amount state to an intermediate amount state.

FIG. 7 illustrates a case where the refrigerant amount transitions from the intermediate state to a small amount state.

The upper side of FIG. 6 is a PH diagram, and the lower side of FIG. 6 illustrates a relation between a position of the outdoor heat exchanger 2 with respect to the PH diagram and a temperature of the refrigerant. In the diagram on the lower side of FIG. 6, the horizontal axis indicates the position of the outdoor heat exchanger 2, and the vertical axis indicates the temperature of the refrigerant. FIG. 7 is also the same.

FIG. 6 will be described. The PH diagram illustrates a refrigeration cycle with a large refrigerant amount and a refrigeration cycle with the refrigerant amount which has decreased and is about an intermediate level. The refrigeration cycle with the large refrigerant amount is the solid line of P1, Q1, R1, and S1. The refrigeration cycle with the intermediate level of the refrigerant amount is the dashed line of P1, Q2, R2, and S2. The PH diagram indicates Δh_con and dT_c. In FIG. 6, the inlet side of the refrigerant of the outdoor heat exchanger 2 is on the right side, and the outlet side of the refrigerant of the outdoor heat exchanger 2 is on the left side. The refrigeration cycle of P1, Q1, R1, and S1 correlates with the liquid phase refrigerant having the shape of v1, v2, v4, v5, and v1. With respect to the temperature, the temperature increases since v4 to v2 is in the liquid phase, and the temperature is constant since v2 to v1 is in the two-phase.

This temperature is T_c of the refrigeration cycle of P1, Q1, R1, and S1. The temperature rises toward TH4 since the right side of v1 is in the gas phase.

The refrigeration cycle of P1, Q2, R2, and S2 correlates with the liquid phase refrigerant having the shape of v1, v3, v4, v5, and v1.

In the shape of v1, v3, v4, v5, and v1, the liquid phase is decreased by ΔA_L% with respect to the shape of v1, v2, v4, v5, and v1.

A_G% hardly changes in the refrigeration cycle of P1, Q2, R2, and S2.

With respect to the temperature, the temperature increases since v4 to v3 is in the liquid phase, and the temperature is constant since v3 to v1 is in the two-phase. This temperature is Tc of the refrigeration cycle of P1, Q2, R2, and S2.

The temperature rises toward TH4 since the right side of v1 is in the gas phase.

In the refrigeration cycle of P1, Q2, R2, and S2, FIG. 6 indicates the subcooling degree SC and dTc.

FIG. 7 will be described. The PH diagram illustrates the refrigeration cycle with the intermediate level of the refrigerant amount and a refrigeration cycle with the refrigerant amount which has decreased and is small. The refrigeration cycle with the intermediate level of the refrigerant amount is P1, Q2, R2, and S2 described in FIG. 6. The refrigeration cycle with the small refrigerant amount is the solid line of P3, Q3, R3, and S3. The PH diagram indicates Δh_con and dT_c for the refrigeration cycle of P3, Q3, R3, and S3. The refrigeration cycle of P1, Q2, R2, and S2 correlates with the liquid phase refrigerant having the shape of v1, v3, v4, v5, and v1. The temperature is as described in FIG. 6.

The refrigeration cycle of P3, Q3, R3, and S3 correlates with the liquid phase refrigerant having the shape of v6, v7, v5, and v6. In the shape of v6, v7, v5, and v5, the gas phase is increased by ΔA_G% with respect to the shape of v1, v3, v4, v5, and v1. The temperature is constant since v7 to v6 is in the two-phase. This temperature is the condensation temperature T_c of the refrigeration cycle of P3, Q3, R3, and S3. The temperature rises toward TH4 since the right side of v6 is in the gas phase. The temperature rises toward TH4 since the right side of v1 is in the gas phase. The refrigeration cycle of P3, Q3, R3, and S3 indicates a superheat degree SHd in FIG. 7.

Effects of Embodiment 1

FIG. 8 illustrates that the refrigerant amount detection is possible within a range of the total refrigerant amount, by using A_L% and A_G% together. When the refrigerant leakage amount is detected using only A_L%, the leakage amount of the refrigerant has been only known up to about 10% of the standard refrigerant amount, as illustrated in FIG. 8. This is because when the leakage amount of the refrigerant exceeds 10% of the standard refrigerant amount, the refrigerant at the outlet of the condenser is in the two-phase state due to the decrease in the refrigerant amount, as illustrated in FIG. 7. When the refrigerant at the outlet of the condenser is in the two-phase state, the subcooling degree is SC=0 and the refrigerant amount could not have been conventionally estimated.

On the other hand, since the refrigerant detection apparatus 100 also uses A_G%, the refrigerant amount can be detected even when the leakage amount of the refrigerant exceeds 10% of the standard refrigerant amount, as illustrated in FIG. 8. Therefore, since it is sufficient to fill only an additional refrigerant amount without collecting all of the refrigerant, a maintenance work time can be shortened. Further, a cost of the refrigerant to be filled and a work cost of the filling refrigerant can be reduced.

In order to eliminate an effect due to a difference between operational states of the refrigeration cycle apparatus 50 at times of detection using A_L% and A_G%, it is preferable to fix the frequency of the compressor 1. However, since a rotational speed of the outdoor fan 2A of the outdoor heat exchanger 2 is fixed, reliability of the refrigeration cycle apparatus 50 may be highly degraded. Therefore, the frequency of the compressor 1 is not fixed. Thereby, the reliability of the refrigeration cycle apparatus 50 can be maintained.

A dT_c ratio with respect to the refrigerant circulation amount ratio G_{r_ratio} is corrected by using [dT_{c_corr}]⁻¹. By this correction, a standard state of the compressor 1 before the frequency changes is estimated, and an effect on the frequency change of the compressor 1 is excluded from the refrigerant amount detection. Therefore, the refrigerant amount detection with high accuracy is possible. According to the refrigerant amount detection with the high accuracy, a performance of the refrigeration cycle apparatus 50 can be maintained.

<Supplement of Hardware Configuration>

A hardware configuration of the refrigerant detection apparatus 100 will be supplemented below.

FIG. 9 illustrates the hardware configuration of the refrigerant detection apparatus 100. The hardware configuration of the refrigerant detection apparatus 100 will be described with reference to FIG. 9.

The refrigerant detection apparatus 100 is a computer. The refrigerant detection apparatus 100 includes a processor 110. The refrigerant detection apparatus 100 includes a plurality of pieces of hardware in addition to the processor 110. The plurality of pieces of hardware are a main storage device 120, the auxiliary storage device 130, an input IF 140, an output IF 150, and a communication IF 160. IF stands for interface. The processor 110 is connected to other pieces of hardware via a signal line 170 and controls the other pieces of hardware.

The refrigerant detection apparatus 100 includes the acquisition unit 111, the control unit 112, the determination unit 113, the calculation unit 114, and the output unit 115, as functional elements. Functions of the acquisition unit 111, the control unit 112, the determination unit 113, the calculation unit 114, and the output unit 115 are implemented by a refrigerant detection program 131 that detects the leakage amount of the refrigerant.

The processor 110 is a device that executes the refrigerant detection program 131. The processor 110 executes the refrigerant detection program 131 to implement the functions of the acquisition unit 111, the control unit 112, the determination unit 113, the calculation unit 114, and the output unit 115. The processor 110 is an Integrated Circuit (IC) that performs computation processing. Specific examples of the processor 110 are a Central Processing Unit (CPU), a Digital Signal Processor (DSP), and a Graphics Processing Unit (GPU).

The main storage device 120 is a storage device. Specific examples of the main storage device 120 are a Static Random Access Memory (SRAM) and a Dynamic Random Access Memory (DRAM). The main storage device 120 holds a computation result of the processor 110.

The auxiliary storage device 130 is a storage device that keeps data in a nonvolatile manner. A specific example of the auxiliary storage device 130 is a Hard Disk Drive (HDD). Further, the auxiliary storage device 130 may be a portable recording medium. Examples of the portable recording medium include a Secure Digital (SD: registered trademark) memory card, a NAND flash, a flexible disk, an optical disk, a compact disk, a Blu-ray (registered trademark) disk, and a Digital Versatile Disk (DVD). The auxiliary storage device 130 stores the refrigerant detection program 131.

The input IF 140 is a port to which data is input from the individual devices and the individual sensors. The output IF 150 is connected to various types of devices. The output IF 150 is a port through which data is output by the processor 110 to the various types of devices such as a display device, an audio device, and an external storage device. The communication IF 160 is a communication port through which the processor communicates with the other devices.

The processor 110 loads the refrigerant detection program 131 from the auxiliary storage device 130 to the main storage device 120. The processor 110 reads the loaded refrigerant detection program 131 from the main storage device 120 and executes the refrigerant detection program 131. The main storage device 120 also stores an Operating System (OS) in addition to the refrigerant detection program 131. The processor 110 executes the refrigerant detection program 131 while executing the OS. The refrigerant detection apparatus 100 may include a plurality of processors that substitute for the processor 110. The plurality of processors execute the refrigerant detection program 131 by sharing. Each of the processors is a device that executes the refrigerant detection program 131 in the same way as the processor 110. Data, information, a signal value, and a variable value which are utilized, processed, or output by the refrigerant detection program 131 are stored in the main storage device 120, the auxiliary storage device 130, or a register or a cache memory in the processor 110.

The refrigerant detection program 131 is a program that causes the computer to execute processes, procedures, or stages corresponding to the acquisition unit 111, the control unit 112, the determination unit 113, the calculation unit 114, and the output unit 115, each with its “unit” being replaced by “process”, “procedure”, or “stage”.

Further, a refrigerant detection method is a method that is performed by the refrigerant detection apparatus 100 which is the computer, as the refrigerant detection apparatus 100 executes the refrigerant detection program 131. The refrigerant detection program 131 may be provided as being stored in a computer readable recording medium or may be provided as a program product.

In the refrigerant detection apparatus 100 of FIG. 9, a function of the refrigerant detection apparatus 100 is implemented by software. However, the function of the refrigerant detection apparatus 100 may be implemented by hardware.

FIG. 10 illustrates a configuration in which the function of the refrigerant detection apparatus 100 is implemented by hardware. An electronic circuit 90 of FIG. 10 is a dedicated electronic circuit that implements the functions of the acquisition unit 111, the control unit 112, the determination unit 113, the calculation unit 114, and the output unit 115, of the refrigerant detection apparatus 10. The electronic circuit 90 is connected to a signal line 91. The electronic circuit 90 is specifically a single circuit, a composite circuit, a programmed processor, a parallel-programmed processor, a logic IC, a GA, an ASIC, or an FPGA. GA stands for Gate Array. ASIC stands for Application Specific Integrated Circuit. FPGA stands for Field-Programmable Gate Array. The functions of the constituent elements of the refrigerant detection apparatus 100 may be implemented by one electronic circuit, or may be implemented by a plurality of electronic circuits by sharing. Alternatively, some of the functions of the constituent elements of the refrigerant detection apparatus 100 may be implemented by an electronic circuit, and the remaining functions may be implemented by software.

Each of the processor 110 and the electronic circuit 90 is referred to as processing circuitry or circuitry. In the refrigerant detection apparatus 100, the functions of the acquisition unit 111, the control unit 112, the determination unit 113, the calculation unit 114, and the output unit 115 may be implemented by circuitry.

Embodiment 1 has been described above. Among a plurality of technical elements included in Embodiment 1, two or more elements may be performed in combination. Alternatively, one of the plurality of technical elements may be partially performed.

Claims

1. A refrigerant detection apparatus comprising: processing circuitry to determine whether a subcooling degree of a refrigerant is at zero kelvin in a refrigeration cycle apparatus including a compressor, a condenser, an expansion valve and an evaporator, the refrigerant circulating in the refrigeration cycle apparatus;when the processing circuitry determines that the subcooling degree is at zero kelvin, to calculate a gas phase area ratio which is a gas phase volume rate of a total volume of the condenser, using a first temperature difference which is a difference between an outdoor temperature and a condensation temperature of the refrigerant, a second temperature difference which is a difference between a refrigerant discharge temperature of the compressor and the condensation temperature, an enthalpy difference of the refrigerant between an inlet of the condenser and an outlet of the condenser, and a specific heat at constant pressure gas of the refrigerant, to compare the calculated gas phase area ratio with a standard value set as a standard for the gas phase area ratio, and to calculate a refrigerant amount in the refrigeration cycle apparatus, based on a comparison result; andto output a value obtained from the calculated refrigerant amount.

2. The refrigerant detection apparatus according to claim 1, wherein the compressor, the condenser, the expansion valve, and the evaporator are disposed in the refrigeration cycle apparatus to form a refrigerant circuit in which the refrigerant circulates, andthe processing circuitry decides a correction coefficient that corrects the first temperature difference, based on a circulation amount of the refrigerant in the refrigerant circuit decided from a specification of the compressor and an operational state of the compressor, and based on a standard refrigerant circulation amount decided as a specification of the refrigerant circuit, and corrects the first temperature difference with the decided correction coefficient.

3. The refrigerant detection apparatus according to claim 2, wherein the processing circuitry calculates the enthalpy difference of the refrigerant when the subcooling degree is at zero kelvin, based on an opening of the expansion valve, suction pressure of the compressor, discharge pressure of the compressor, and the circulation amount of the refrigerant.

4. The refrigerant detection apparatus according to claim 2, wherein the processing circuitry calculates the subcooling degree of the refrigeration cycle apparatus, and determines whether or not the calculated subcooling degree is greater than zero kelvin,the processing circuitry, when determining that the subcooling degree is greater than zero kelvin, calculates a liquid phase area ratio which is a liquid phase volume rate of a total volume of the condenser, using the calculated subcooling degree, the first temperature difference, the enthalpy difference of the refrigerant, a specific heat at constant pressure liquid of the refrigerant, and the correction coefficient, compares the calculated liquid phase area ratio with a standard value set as a standard for the liquid phase area ratio, and calculates a refrigerant amount in the refrigeration cycle apparatus, based on a comparison result, andthe processing circuitry outputs a value obtained from the calculated refrigerant amount using the liquid phase area ratio.

5. The refrigerant detection apparatus according to claim 1, wherein the compressor, the condenser, the expansion valve, and the evaporator are disposed in the refrigeration cycle apparatus to form a refrigerant circuit in which the refrigerant circulates,the refrigerant circuit includes a heat interchanger disposed between the condenser and the expansion valve, and a branch path that branches from a path between the heat interchanger and the expansion valve, passes through a second expansion valve which is different from a first expansion valve which is the expansion valve, passes through the heat interchanger, and connects to a path that connects the evaporator and the compressor, andthe processing circuitry calculates the enthalpy difference of the refrigerant when the subcooling degree is at zero kelvin, based on an opening of the first expansion valve, an opening of the second expansion valve, suction pressure of the compressor, discharge pressure of the compressor, a circulation amount of the refrigerant, and a temperature of a refrigerant that has flowed out of the heat interchanger in the branch path.

6. A non-transitory computer readable medium storing a refrigerant detection program causing a computer to execute: a determination process to determine whether a subcooling degree of a refrigerant is at zero kelvin in a refrigeration cycle apparatus including a compressor, a condenser, an expansion valve and an evaporator, the refrigerant circulating in the refrigeration cycle apparatus;a calculation process, when the determination process determines that the subcooling degree is at zero kelvin, to calculate a gas phase area ratio which is a gas phase volume rate of a total volume of the condenser, using a first temperature difference which is a difference between an outdoor temperature and a condensation temperature of the refrigerant, a second temperature difference which is a difference between a refrigerant discharge temperature of the compressor and the condensation temperature, an enthalpy difference of the refrigerant between an inlet of the condenser and an outlet of the condenser, and a specific heat at constant pressure gas of the refrigerant, to compare the calculated gas phase area ratio with a standard value set as a standard for the gas phase area ratio, and to calculate a refrigerant amount in the refrigeration cycle apparatus, based on a comparison result; andan output process to output a value obtained from the refrigerant amount calculated by the calculation process.

7. A refrigerant detection method comprising: determining whether a subcooling degree of a refrigerant is at zero kelvin in a refrigeration cycle apparatus including a compressor, a condenser, an expansion valve and an evaporator, the refrigerant circulating in the refrigeration cycle apparatus;when determining that the subcooling degree is at zero kelvin, calculating a gas phase area ratio which is a gas phase volume rate of a total volume of the condenser, using a first temperature difference which is a difference between an outdoor temperature and a condensation temperature of the refrigerant, a second temperature difference which is a difference between a refrigerant discharge temperature of the compressor and the condensation temperature, an enthalpy difference of the refrigerant between an inlet of the condenser and an outlet of the condenser, and a specific heat at constant pressure gas of the refrigerant, comparing the calculated gas phase area ratio with a standard value set as a standard for the gas phase area ratio, and calculating a refrigerant amount in the refrigeration cycle apparatus, based on a comparison result; andoutputting a value obtained from the calculated refrigerant amount.