GB2573891A

GB2573891A - Refrigeration cycle device

Info

Publication number: GB2573891A
Application number: GB1908964.8A
Authority: GB
Inventors: Ariyama Tadashi
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2017-02-07
Filing date: 2017-02-07
Publication date: 2019-11-20
Anticipated expiration: 2037-02-07
Also published as: GB201908964D0; WO2018146719A1; JPWO2018146719A1; JP6715961B2; GB2573891B

Abstract

A refrigeration cycle device has: a main refrigerant circuit in which a compressor, a load-side heat exchanger, a load-side throttle device, a heat source-side heat exchanger, and a gas-liquid separator are connected through refrigerant piping, and a foreign matter collection circuit in which the gas-liquid separator, an open/close valve, and a foreign matter collector are connected through bypass piping that connects the lower portion of the gas-liquid separator and the intake side of the compressor, and comprises an oil sensor that is provided in the gas-liquid separator and that measures the permittivity of the refrigeration oil stored in the gas-liquid separator.

Description

REFRIGERATION CYCLE APPARATUS

Technical Field [0001]

The present invention relates to a refrigeration cycle apparatus including a foreign matter collecting circuit branching off from a main refrigerant circuit. Background Art [0002]

Some known refrigeration cycle apparatuses are configured such that refrigerant can be replaced with another refrigerant and existing refrigerant pipes included in the apparatuses are used without being replaced by other pipes. In such a refrigeration cycle apparatus, at least one existing unit included in the apparatus is replaceable with a new unit. The refrigeration cycle apparatus is used as, for example, an air-conditioning apparatus or a water heating apparatus. Hereinafter, such a refrigeration cycle apparatus in which a unit included in the apparatus is replaceable with a new unit will be referred to as a replace-type refrigeration cycle apparatus.

[0003]

Units included in the replace-type refrigeration cycle apparatus include at least a heat source side unit and a load side unit. The heat source side unit is used as, for example, an outdoor unit. The load side unit is used as, for example, a use side unit or an indoor unit.

[0004]

In the replace-type refrigeration cycle apparatus, a unit is replaced with a new unit and the new unit is then connected to existing refrigerant pipes. After that, a refrigeration cycle is filled with new refrigerant for the new unit, thus updating the replace-type refrigeration cycle apparatus. In other words, the replace-type refrigeration cycle apparatus can perform an air-conditioning operation using the existing refrigerant pipes without any need to arrange new refrigerant pipes for the new unit in a space above a ceiling, for example.

[0005]

The term update or updating a replace-type refrigeration cycle apparatus as used herein refers to a series of work steps that include removing an existing unit and disposing a new unit, or replacing the existing unit with the new unit, and that are required to perform the air-conditioning operation using the new unit.

[0006]

In a replace-type refrigeration cycle apparatus, therefore, replacing a unit with a new unit does not involve various kinds of work for arranging new refrigerant pipes. This can shorten the period of work for updating the replace-type refrigeration cycle apparatus. Since the period of work for updating the replace-type refrigeration cycle apparatus can be shortened, update of the replace-type refrigeration cycle apparatus in, for example, an office, can be completed at intervals between business days. [0007]

In a replace-type refrigeration cycle apparatus, copper pipes used as existing refrigerant pipes can be used as they are. In addition, a heat insulating material wound around the refrigerant pipes in the replace-type refrigeration cycle apparatus can be used as it is. The replace-type refrigeration cycle apparatus, therefore, is excellent in terms of efficient use of resources. The replace-type refrigeration cycle apparatus is also excellent in terms of reduction of waste.

[0008]

Furthermore, a replace-type refrigeration cycle apparatus eliminates the need for arrangement of new refrigerant pipes, and uses existing refrigerant pipes of which the performance has been proven. Arrangement of new refrigerant pipes involves, for example, designing layout of the refrigerant pipes and brazing joints of the refrigerant pipes. In addition, the arrangement of the new refrigerant pipes needs measures against refrigerant leakage due to poor brazing, for example. In contrast, the replace-type refrigeration cycle apparatus, which uses the existing refrigerant pipes, eliminates the need for measures against refrigerant leakage, for example, and maintains high reliability.

[0009]

The reliability of a replace-type refrigeration cycle apparatus means that a problem, such as breakdown of a compressor or refrigerant leakage from a refrigerant pipe, occurs with low frequency.

[0010]

In a typical replace-type refrigeration cycle apparatus, a hydrochlorofluorocarbon (HCFC) refrigerant used in existing refrigerant pipes is replaced with, for example, a hydrofluorocarbon (HFC) refrigerant. The replacement of the refrigerant with another refrigerant involves replacement of a refrigerating machine oil with another one for the refrigerant newly used. Examples of refrigerating machine oils for HCFC refrigerants include mineral oil. Examples of refrigerating machine oils for HFC refrigerants include ester oil. Hereinafter, a refrigerating machine oil to be replaced will be referred to as old refrigerating machine oil and a refrigerating machine oil to be newly used instead of the old refrigerating machine oil will be referred to as new refrigerating machine oil.

[0011]

The refrigerant used before replacement may remain in the existing refrigerant pipes. The old refrigerating machine oil may also remain in the existing refrigerant pipes. Furthermore, the old refrigerating machine oil may contain a chlorine component derived from the refrigerant used before replacement.

[0012]

The old refrigerating machine oil may disadvantageous^ cause deterioration of the new refrigerating machine oil. Furthermore, the chlorine component contained in the old refrigerating machine oil may also cause deterioration of the new refrigerating machine oil. As a result, the new refrigerating machine oil may fail to fully achieve its effects. If the new refrigerating machine oil fails to fully achieve its effects, it may cause a compressor included in a refrigeration cycle to break. A breakdown of the compressor hinders circulation of the refrigerant through the refrigeration cycle, reducing the reliability of the refrigeration cycle apparatus.

[0013]

It is therefore preferred that a cleaning operation of collecting the old refrigerating machine oil be performed to achieve a highly reliable air-conditioning operation using a new unit. The cleaning operation enables residual foreign matter, such as a chlorine component, remaining in the existing refrigerant pipes to be collected together with the old refrigerating machine oil. Hereinafter, the old refrigerating machine oil and the residual foreign matter will be collectively referred to as foreign matter.

[0014]

Such a cleaning operation is typically performed in such a manner that a refrigerant flow rate and a refrigerant state suitable to collect foreign matter in the refrigerant pipes are provided for each operation mode. Specifically, the cleaning operation uses a method of collecting foreign matter by circulating the refrigerant discharged from the compressor in a manner similar to that in a normal airconditioning operation of the replace-type refrigeration cycle apparatus. Examples of operation modes implemented by the replace-type refrigeration cycle apparatus include a heating operation mode and a cooling operation mode.

[0015]

In other words, the cleaning operation is performed by circulating the refrigerant in a manner similar to that in the normal air-conditioning operation. The refrigerant discharged from the compressor during the cleaning operation contains foreign matter remaining in the existing refrigerant pipes. The foreign matter may mix with the new refrigerating machine oil. The new refrigerating machine oil that has mixed with the foreign matter will deteriorate. Suction of the new refrigerating machine oil that has deteriorated into the compressor leads to breakdown of the compressor. It is therefore necessary to prevent the new refrigerating machine oil moved from the compressor to the outside of the outdoor unit during the cleaning operation from being sucked into the compressor.

[0016]

Specifically, it is preferred to perform the cleaning operation in the replace-type refrigeration cycle apparatus in such a manner that the newly enclosed refrigerant, the new refrigerating machine oil discharged from the compressor together with the refrigerant and foreign matter are not sucked into the compressor.

[0017]

A developed air-conditioning apparatus includes at least one load side unit having a load side heat exchanger and a load side expansion device connected in series, at least one heat source side unit having a compressor, an oil separator, a heat source side heat exchanger including upper and lower paths or elements, and an accumulator connected in series, and an oil storage circuit in which a first end of a lower heat exchanger that serves as the lower element of the heat source side heat exchanger is connected to high-pressure part downstream of the oil separator and a second end of the lower heat exchanger is connected to low-pressure part on a suction side of the compressor, and the oil storage circuit and the lower heat exchanger can be previously supplied with refrigerating machine oil (refer to Patent Literature 1, for example).

[0018]

In the air-conditioning apparatus disclosed in Patent Literature 1, new refrigerating machine oil previously stored in a container, such as an oil tank, is used to compensate a lack of new refrigerating machine oil because the refrigerating machine oil is moved out of the compressor by the cleaning operation. Specifically, the air-conditioning apparatus disclosed in Patent Literature 1 is configured such that the new refrigerating machine oil necessary for the air-conditioning operation after the cleaning operation is previously stored. The apparatus enables the previously stored new refrigerating machine oil to be supplied to the compressor in such a way not to be mixed with foreign matter.

Citation List

Patent Literature [0019]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2010-185585

Summary of Invention Technical Problem [0020]

In the air-conditioning apparatus disclosed in Patent Literature 1, the completion of the cleaning operation is determined based on a lapse of proven sufficient time. It may disadvantageously take much time to perform the cleaning operation depending on, for example, conditions of the existing refrigerant pipes in the air-conditioning apparatus disclosed in Patent Literature 1. Furthermore, whether the cleaning operation has normally been completed is not quantitatively determined in the air-conditioning apparatus disclosed in Patent Literature 1. In other words, the presence or absence of foreign matter collected is not determined in the air-conditioning apparatus disclosed in Patent Literature 1. The completion of the cleaning operation cannot be quantitatively determined in this apparatus.

[0021]

In the use of the existing refrigerant pipes, the diameter of each existing refrigerant pipe may differ from a designated diameter depending on, for example, refrigerant to be newly used. In such a case, the new refrigerating machine oil may accumulate in the refrigerant pipes depending on flow velocity of the refrigerant. Reusable air-conditioning apparatuses, therefore, may be constrained. Additionally, an optional operation of periodically increasing the frequency of the compressor to force the new refrigerating machine oil to circulate may need to be performed irrespective of the completion of the cleaning operation.

[0022]

The present invention has been made to overcome the above-described disadvantages, and aims to provide a refrigeration cycle apparatus in which a determination on the presence or absence of foreign matter in a gas-liquid separator is achieved with high accuracy.

Solution to Problem [0023]

A refrigeration cycle apparatus according to an embodiment of the present invention includes a main refrigerant circuit in which a compressor, a load side heat exchanger, a load side expansion device, a heat source side heat exchanger, and a gas-liquid separator are connected by refrigerant pipes, a foreign matter collecting circuit in which the gas-liquid separator, an on-off valve, and a foreign matter collector are connected by a bypass pipe connecting lower part of the gas-liquid separator and a suction side of the compressor, and an oil sensor disposed in the gas-liquid separator. The oil sensor measures a dielectric constant of refrigerating machine oil retained in the gas-liquid separator.

Advantageous Effects of Invention [0024]

Since the refrigeration cycle apparatus according to the embodiment of the present invention includes the oil sensor measuring the dielectric constant of the refrigerating machine oil, whether foreign matter is present in the gas-liquid separator can be determined with high accuracy.

Brief Description of Drawings [0025] [Fig. 1] Fig. 1 is a schematic diagram illustrating an exemplary refrigerant circuit configuration of a refrigeration cycle apparatus according to Embodiment of the present invention.

[Fig. 2] Fig. 2 is a schematic diagram illustrating the refrigerant circuit configuration in a cooling operation performed by the refrigeration cycle apparatus according to Embodiment of the present invention.

[Fig. 3] Fig. 3 is a schematic diagram illustrating the refrigerant circuit configuration in a heating operation performed by the refrigeration cycle apparatus according to Embodiment of the present invention.

[Fig. 4] Fig. 4 is a schematic diagram illustrating the refrigerant circuit configuration in a cleaning operation performed by the refrigeration cycle apparatus according to Embodiment of the present invention.

[Fig. 5] Fig. 5 is a flowchart schematically illustrating an update process, which involves replacement and the cleaning operation, for the refrigeration cycle apparatus according to Embodiment of the present invention.

Description of Embodiments [0026]

Embodiment of the present invention will be described with reference to the drawings. Note that the relationship between the sizes of components illustrated in the following drawings including Fig. 1 may differ from that of actual ones. Furthermore, note that components designated by the same reference signs in the following drawings including Fig. 1 are the same components or equivalents. This applies to the entire text herein. In addition, note that the forms of components described herein are intended to be illustrative only and the forms of the components are not intended to be limited to those described herein.

[0027]

Fig. 1 is a schematic diagram illustrating an exemplary refrigerant circuit configuration of a refrigeration cycle apparatus (hereinafter, referred to as a refrigeration cycle apparatus 100) according to Embodiment of the present invention. The refrigeration cycle apparatus 100 will be described with reference to Fig. 1. The refrigeration cycle apparatus 100 is used as, for example, a water heating apparatus or an air-conditioning apparatus for heating or cooling an air-conditioned space. In the following description, an explanation is made using as an example a case where the refrigeration cycle apparatus 100 is an air-conditioning apparatus.

[0028] <Configuration of Refrigeration Cycle Apparatus 100>

The refrigeration cycle apparatus 100 is a replace-type refrigeration cycle apparatus in which at least one of a heat source side unit 10 and a load side unit 50 is replaceable with a new unit. The refrigeration cycle apparatus 100 has a refrigerant circuit configuration illustrated in Fig. 1, irrespective of before and after replacement. The refrigerant circuit configuration of the refrigeration cycle apparatus 100 will now be described.

[0029]

The refrigeration cycle apparatus 100 includes a refrigerant circuit through which refrigerant is circulated, and performs a cooling operation or a heating operation by circulating the refrigerant through the refrigerant circuit. Specifically, the refrigeration cycle apparatus 100 causes a flow switching device 12 to switch between refrigerant flow directions and circulates the refrigerant through a main refrigerant circuit A to perform the cooling operation or the heating operation in the load side unit 50. The main refrigerant circuit A will be described later.

[0030]

The refrigeration cycle apparatus 100 includes the heat source side unit 10 and the load side unit 50. The heat source side unit 10 and the load side unit 50 are interconnected by the refrigerant circuit in which components provided in these units are connected by refrigerant pipes. The refrigeration cycle apparatus 100 includes a liquid pipe 1, a gas pipe 2, and a bypass pipe 3 as refrigerant pipes. The components include a compressor 11, the flow switching device 12, a load side heat exchanger 51, a load side expansion device 52, a pressure regulating valve 20, a heat source side heat exchanger 13, a gas-liquid separator 16, an accumulator 14, an on-off valve 18, a foreign matter collector 15, and a check valve 17.

[0031]

The refrigerant circuit of the refrigeration cycle apparatus 100 includes the components provided in the heat source side unit 10 and those provided in the load side unit 50 connected by the liquid pipe 1 and the gas pipe 2. The refrigerant circuit of the refrigeration cycle apparatus 100 includes the main refrigerant circuit A and a foreign matter collecting circuit B.

[0032]

The main refrigerant circuit A includes the compressor 11, the flow switching device 12, the load side heat exchanger 51, the load side expansion device 52, the pressure regulating valve 20, the heat source side heat exchanger 13, the gas-liquid separator 16, and the accumulator 14 connected in series.

The foreign matter collecting circuit B includes the gas-liquid separator 16, the on-off valve 18, the foreign matter collector 15, and the check valve 17 connected in series by the bypass pipe 3. The foreign matter collecting circuit B is provided to remove foreign matter, which flows together with the refrigerant in a cleaning operation for the existing refrigerant pipes, from the main refrigerant circuit A and collect the separated foreign matter.

As described above, the foreign matter contains old refrigerating machine oil and residual foreign matter.

[0033] [Refrigerant Pipes (Liquid Pipe 1, Gas Pipe 2, Bypass Pipe 3)]

The main refrigerant circuit A is formed by connecting the components included in the main refrigerant circuit A with the liquid pipe 1 and the gas pipe 2.

The foreign matter collecting circuit B is formed by connecting the components included in the foreign matter collecting circuit B with the bypass pipe 3. [0034]

The liquid pipe 1 connecting the heat source side unit 10 and the load side unit 50 is a refrigerant pipe through which liquid (including two-phase gas-liquid) refrigerant condensed and liquefied by the load side heat exchanger 51 or the heat source side heat exchanger 13 flows.

The liquid pipe 1 may be made of any material and may have any diameter and any length.

[0035]

The gas pipe 2 connecting the heat source side unit 10 and the load side unit 50 is a refrigerant pipe through which gas refrigerant obtained by compression through the compressor 11 flows. The gas pipe 2 is also a refrigerant pipe through which gas refrigerant evaporated and gasified by the load side heat exchanger 51 or the heat source side heat exchanger 13 flows.

The gas pipe 2 may be made of any material and may have any diameter and any length.

[0036]

The bypass pipe 3 is a refrigerant pipe that connects lower part of the gasliquid separator 16 and a suction side of the compressor 11 and through which liquid refrigerant separated by the gas-liquid separator 16 flows. A concrete downstream connection of the bypass pipe 3 is located between a downstream side of the accumulator 14 and the suction side of the compressor 11.

The bypass pipe 3 may also be made of any material and may have any diameter and any length.

[0037] [Heat Source Side Unit 10]

The heat source side unit 10 is disposed in a space (e.g., an outdoor space, a loft, or a basement) different from the air-conditioned space, and functions to supply cooling energy or heating energy to the load side unit 50.

The heat source side unit 10 contains the compressor 11, the flow switching device 12, the heat source side heat exchanger 13, the accumulator 14, the foreign matter collector 15, the gas-liquid separator 16, the check valve 17, the on-off valve 18, and the pressure regulating valve 20. In other words, the heat source side unit 10 contains the foreign matter collecting circuit B and part of the main refrigerant circuit A. The functions of the components of the heat source side unit 10 will now be described in detail.

[0038]

The compressor 11 sucks low-temperature, low-pressure refrigerant, compresses the refrigerant into high-temperature, high-pressure gas refrigerant, and discharges the refrigerant. The refrigerant discharged from the compressor 11 is circulated through the main refrigerant circuit A, thus allowing the refrigeration cycle apparatus 100 to perform an air-conditioning operation. The compressor 11 can be, for example, a rotary compressor, a scroll compressor, a screw compressor, or a reciprocating compressor. The compressor 11 is typically of a type whose frequency can be adjusted by an inverter. The compressor 11 may be of a type whose rotation speed is constant.

[0039]

The flow switching device 12 is disposed on a discharge side of the compressor 11 and functions to switch between a refrigerant flow direction in the heating operation and that in the cooling operation. In other words, operating the flow switching device 12 causes the refrigerant flowing through the main refrigerant circuit A in the heating operation to flow in a direction opposite to that in the cooling direction and vice versa. The flow switching device 12 can be configured as, for example, a combination of two-way valves or three-way valves, or a four-way valve. Fig. 1 illustrates an exemplary case where the flow switching device 12 is a four-way valve. If the refrigeration cycle apparatus 100 is used exclusively for cooling or heating, the flow switching device 12 may be eliminated.

[0040]

The heat source side heat exchanger 13 functions as a condenser (radiator) in the cooling operation, functions as an evaporator in the heating operation, and exchanges heat between the refrigerant and a heat medium, such as ambient air. While the heat source side heat exchanger 13 functions as a condenser, the refrigerant exchanges heat with the heat medium, such as ambient air, and thus condenses and liquefies in the heat source side heat exchanger 13. While the heat source side heat exchanger 13 functions as an evaporator, the refrigerant exchanges heat with the heat medium, such as ambient air, and thus evaporates and gasifies in the heat source side heat exchanger 13.

[0041]

The heat source side heat exchanger 13 can be, for example, a fin-and-tube heat exchanger, a microchannel heat exchanger, a shell-and-tube heat exchanger, a heat pipe heat exchanger, a double-pipe heat exchanger, or a plate heat exchanger. For example, if the heat source side heat exchanger 13 is a heat exchanger that exchanges heat between the refrigerant and air, a fan (not illustrated) is disposed in proximity to the heat source side heat exchanger 13. A condensing capacity or an evaporating capacity of the heat source side heat exchanger 13 is adjusted by using a rotation speed of the fan.

[0042]

The accumulator 14 is disposed on the suction side of the compressor 11 and stores an excess of refrigerant resulting from the difference between a heating operation mode and a cooling operation mode. The accumulator 14 further stores an excess of refrigerant generated due to a transient operation change, for example, a change in the number of operating load side units 50. In addition, the accumulator 14 stores an excess of refrigerant generated due to a change in load conditions. Furthermore, the accumulator 14 separates two-phase gas-liquid refrigerant into liquid refrigerant and gas refrigerant. The gas refrigerant alone is supplied to the compressor 11.

[0043]

As described above, the accumulator 14 disposed on the suction side of the compressor 11 reduces or eliminates the likelihood that liquid refrigerant may be sucked into the compressor 11. Thus, the accumulator 14 reduces or eliminates the likelihood of breakdown or failure of the compressor 11 caused by liquid compression. The accumulator 14 is not essential to the refrigerant circuit configuration of the refrigeration cycle apparatus 100.

[0044]

The gas-liquid separator 16 is disposed upstream of the accumulator 14 in the main refrigerant circuit A and is disposed upstream of the foreign matter collector 15 in the foreign matter collecting circuit B. Specifically, the gas-liquid separator 16 separates the refrigerant flowing through the main refrigerant circuit A into liquid refrigerant and gas refrigerant. As illustrated in Fig. 1, the gas pipe 2 included in the main refrigerant circuit A is connected to a side of the gas-liquid separator 16, and the bypass pipe 3 included in the foreign matter collecting circuit B is connected to the lower part of the gas-liquid separator 16. The refrigerant flowing through the main refrigerant circuit A contains the refrigerating machine oil, which is used mainly in the compressor 11.

[0045]

An oil sensor 19 is disposed at a liquid outlet of the gas-liquid separator 16. The oil sensor 19 is a capacitance oil sensor that measures a dielectric constant of the refrigerating machine oil retained in the gas-liquid separator 16. Information about measurement by the oil sensor 19 is sent to a controller 40, which will be described later.

[0046]

The foreign matter collector 15 is disposed downstream of the gas-liquid separator 16 in the foreign matter collecting circuit B, and collects foreign matter reaching the gas-liquid separator 16 in the cleaning operation for the existing refrigerant pipes. It is only required that the foreign matter collector 15 is a hermetically sealed container capable of collecting foreign matter.

[0047]

The check valve 17 is disposed downstream of the foreign matter collector 15 and allows the refrigerant to flow in a direction from the foreign matter collector 15 only to the downstream side of the accumulator 14. In other words, the check valve 17 prevents the refrigerant from flowing into the foreign matter collecting circuit B from the main refrigerant circuit A on the downstream side of the accumulator 14. [0048]

The on-off valve 18 is disposed between the gas-liquid separator 16 and the foreign matter collector 15 in the foreign matter collecting circuit B, and opens or closes the bypass pipe 3. While the on-off valve 18 is opened, the liquid refrigerant separated by the gas-liquid separator 16 flows through the bypass pipe 3. While the on-off valve 18 is closed, the liquid refrigerant separated by the gas-liquid separator 16 does not flow through the bypass pipe 3.

[0049]

The pressure regulating valve 20 expands the refrigerant flowing from the load side heat exchanger 51 or the heat source side heat exchanger 13 to reduce the pressure of the refrigerant. The pressure regulating valve 20 is preferably, for example, an electric expansion valve capable of adjusting the flow rate of refrigerant. Usable examples of the pressure regulating valve 20 include a mechanical expansion valve including a diaphragm, serving as a pressure receiving part, and a capillary tube in addition to the electric expansion valve.

[0050]

The heat source side unit 10 further includes the controller 40 that controls the entire refrigeration cycle apparatus 100 in an integrated manner. Specifically, the controller 40 controls a driving frequency of the compressor 11 on the basis of a cooling or heating capacity needed. Furthermore, the controller 40 controls an opening degree of the pressure regulating valve 20 and that of the load side expansion device 52 for each operation state or mode. In addition, the controller 40 controls opening and closing of the on-off valve 18 according to whether to allow the refrigerant to flow through the foreign matter collecting circuit B. Additionally, the controller 40 controls switching of the flow switching device 12 for each operation state or mode.

[0051]

Specifically, the controller 40 controls actuators (the compressor 11, the pressure regulating valve 20, the load side expansion device 52, the on-off valve 18, and the flow switching device 12) by using information sent from temperature sensors (not illustrated) and pressure sensors (not illustrated) in response to an operation instruction from a user. Although a case where the controller 40 is included in the heat source side unit 10 is illustrated as an example, the controller 40 may be disposed at any position. For example, the controller 40 may be included in the load side unit 50. The controller 40 may be disposed outside the heat source side unit 10 and the load side unit 50.

[0052]

Furthermore, the controller 40 determines the dielectric constant of the refrigerating machine oil, separated by the gas-liquid separator 16 and retained in the gas-liquid separator 16, on the basis of the information sent from the oil sensor 19. Specifically, the controller 40 determines the presence or absence of foreign matter on the basis of the difference between the dielectric constant of normal refrigerating machine oil and that of foreign matter containing the refrigerating machine oil based on the information from the oil sensor 19. Thus, the controller 40 can detect the presence or absence of foreign matter in the existing refrigerant pipes with certainty.

This eliminates the need for an excessive cleaning time and enhances the reliability of foreign matter removal.

[0053]

Specifically, the dielectric constant of the refrigerating machine oil varies depending on, for example, the kind of oil, deterioration due to mixing of foreign matter into the oil, or deterioration due to mixing of moisture into the oil. The controller 40 compares the information (the dielectric constant of the refrigerating machine oil separated by the gas-liquid separator 16) sent from the oil sensor 19 with a refrigerating-machine-oil dielectric constant previously input to the controller to detect a change in capacitance, thus determining foreign matter collected in the gasliquid separator 16. A determination on whether the cleaning operation has been completed will be described in detail later. The absence of foreign matter includes non-existence of foreign matter and a state in which a detected change in capacitance is less than or equal to a predetermined threshold.

[0054]

The controller 40 can be configured by hardware, such as circuit devices that achieve functions of the controller, or can be configured by an arithmetic device, such as a microcomputer or a central processing unit (CPU), and software running on the device.

[0055]

Although Fig. 1 illustrates an exemplary case where one heat source side unit 10 is connected to one load side unit 50, any number of heat source side units 10 may be arranged. A plurality of heat source side units 10 may be arranged and connected in series or parallel with the load side unit 50.

[0056] [Load Side Unit 50]

The load side unit 50 is disposed in a space (e.g. a room or an indoor space that communicates with the air-conditioned space through a duct) from which cooling energy or heating energy is supplied to the air-conditioned space, and functions to cool or heat the air-conditioned space with cooling energy or heating energy supplied from the heat source side unit 10.

The load side unit 50 contains the load side heat exchanger 51 and the load side expansion device 52. In other words, the load side unit 50 contains part of the main refrigerant circuit A. The functions of the components of the load side unit 50 will now be described in detail.

[0057]

The load side heat exchanger 51 functions as an evaporator in the cooling operation, functions as a condenser (radiator) in the heating operation, and exchanges heat between the refrigerant and the heat medium, such as ambient air. While the load side heat exchanger 51 functions as an evaporator, the refrigerant exchanges heat with the heat medium, such as ambient air, and thus evaporates and gasifies in the load side heat exchanger 53. While the load side heat exchanger 51 functions as a condenser, the refrigerant exchanges heat with the heat medium, such as ambient air, and thus condenses and liquefies in the load side heat exchanger 51. [0058]

The load side heat exchanger 51 can be, for example, a fin-and-tube heat exchanger, a microchannel heat exchanger, a shell-and-tube heat exchanger, a heat pipe heat exchanger, a double-pipe heat exchanger, or a plate heat exchanger. For example, if the load side heat exchanger 51 is a heat exchanger that exchanges heat between the refrigerant and air, a fan (not illustrated) is disposed in proximity to the load side heat exchanger 53. An evaporating capacity or a condensing capacity of the load side heat exchanger 51 is adjusted by using a rotation speed of the fan. [0059]

The load side expansion device 52 expands the refrigerant flowing from the load side heat exchanger 51 or the heat source side heat exchanger 13 to reduce the pressure of the refrigerant. The load side expansion device 52 is preferably, for example, an electric expansion valve capable of adjusting the flow rate of refrigerant. Usable examples of the load side expansion device 52 include a mechanical expansion valve including a diaphragm, serving as pressure receiving part, and a capillary tube in addition to the electric expansion valve.

[0060]

Although Fig. 1 illustrates an exemplary case where one load side unit 50 is connected to one heat source side unit 10, any number of load side units 50 may be arranged. A plurality of load side units 50 may be arranged and connected in parallel with the heat source side unit 10.

[0061] [Usable Refrigerant in Refrigeration Cycle Apparatus 100]

Examples of refrigerant used in the refrigeration cycle apparatus 100 include a non-azeotropic refrigerant mixture, a near-azeotropic refrigerant mixture, and a single refrigerant.

[0062]

Examples of the non-azeotropic refrigerant mixture include R407C (R32/R125/R134a), serving as an HFC refrigerant. This non-azeotropic refrigerant mixture is a mixture of refrigerants having different boiling points, and therefore has characteristics in that the composition ratio of liquid phase refrigerant to gas phase refrigerant varies.

Examples of the near-azeotropic refrigerant mixture include R410A (R32/R125) and R404A (R125/R143a/R134a), serving as HFC refrigerants. Such a nearazeotropic refrigerant mixture has characteristics in that its operating pressure is approximately 1.6 times as high as that of R22 in addition to the same characteristics as those of the non-azeotropic refrigerant mixture.

[0063]

Examples of the single refrigerant include R22, serving as an HCFC refrigerant, and R134a, serving as an HFC refrigerant. Such a single refrigerant, which is not a mixture, has characteristics in that it is easy to handle. In particular, HCFC refrigerants, such as R22, used in conventional refrigeration cycle apparatuses have higher ozone depletion potentials than HFC refrigerants and cause significant adverse environment damage, as have been pointed out. Such circumstances promote shift toward refrigerants having lower ozone depletion potentials, such as HFC refrigerants and natural refrigerants. The circumstances also encourage the spread of refrigeration cycle apparatuses using existing refrigerant pipes.

[0064]

For the refrigerant that can be used in the refrigeration cycle of the refrigeration cycle apparatus 100, it is typically desirable to use a refrigerant having a low ozone depletion potential. The refrigerant that can be used in the refrigeration cycle of the refrigeration cycle apparatus 100 is not limited to any refrigerant having a low ozone depletion potential.

[0065] «Operations Performed by Refrigeration Cycle Apparatus 100>

Operations performed by the refrigeration cycle apparatus 100 will now be described with the flow of the refrigerant.

The refrigeration cycle apparatus 100 can perform the cooling operation or the heating operation in the load side unit 50 in response to an instruction from the load side unit 50. In addition, the refrigeration cycle apparatus 100 can perform the cleaning operation of cleaning the existing refrigerant pipes.

The controller 40 controls operations of the actuators. In the following description, the term existing refrigerant pipes refers to the existing liquid pipe 1 and the existing gas pipe 2.

[0066] [Cooling Operation]

The cooling operation performed by the refrigeration cycle apparatus 100 will now be described. Fig. 2 is a schematic diagram illustrating the refrigerant circuit configuration in the cooling operation performed by the refrigeration cycle apparatus 100. In Fig. 2, the refrigerant flow direction is represented by solid line arrows. The on-off valve 18 in a closed position is represented by a solid symbol in Fig. 2. The cooling operation of the refrigeration cycle apparatus 100 will be described by taking, as an example, a case where air is the heat medium to exchange heat with the refrigerant in the heat source side heat exchanger 13 and the load side heat exchanger 51.

[0067]

When the refrigeration cycle apparatus 100 performs the cooling operation, the flow switching device 12 in the heat source side unit 10 is switched so that the refrigerant discharged from the compressor 11 passes through the heat source side heat exchanger 13 and flows into the load side heat exchanger 51. Specifically, in the cooling operation, the refrigerant flows through the compressor 11, the flow switching device 12, the heat source side heat exchanger 13, the pressure regulating valve 20, the load side expansion device 52, the load side heat exchanger 51, the flow switching device 12, the gas-liquid separator 16, and the accumulator 14 in that order in the main refrigerant circuit A. The pressure regulating valve 20 is adjusted to a fully open position.

[0068]

The compressor 11 compresses low-temperature, low-pressure refrigerant into high-temperature, high-pressure gas refrigerant and discharges the refrigerant. The high-temperature, high-pressure gas refrigerant discharged from the compressor 11 passes through the flow switching device 12 and flows into the heat source side heat exchanger 13. The refrigerant that has flowed into the heat source side heat exchanger 13 exchanges heat with the air supplied from the fan disposed in proximity to the heat source side heat exchanger 13 (and condenses), thus turning into hightemperature, high-pressure liquid refrigerant. The refrigerant then flows out of the heat source side heat exchanger 13.

[0069]

The high-temperature, high-pressure liquid refrigerant that has flowed out of the heat source side heat exchanger 13 passes through the pressure regulating valve 20 and flows into the load side unit 50. The high-temperature, high-pressure liquid refrigerant that has flowed into the load side unit 50 is turned into low-temperature, low-pressure liquid refrigerant (or two-phase refrigerant) by the load side expansion device 52. The refrigerant then flows into the load side heat exchanger 51. The refrigerant that has flowed into the load side heat exchanger 51 exchanges heat with the air supplied from the fan disposed in proximity to the load side heat exchanger 51 (and evaporates), thus turning into low-temperature, low-pressure gas refrigerant. The refrigerant then flows out of the load side heat exchanger 51. In the load side heat exchanger 51, the refrigerant removes heat from the air, thus cooling the air. The cooled air is supplied to the space to be air-conditioned, thereby cooling the space to be air-conditioned.

[0070]

The refrigerant that has flowed out of the load side heat exchanger 51 flows into the heat source side unit 10. The refrigerant that has flowed into the heat source side unit 10 passes through the flow switching device 12, the gas-liquid separator 16, and the accumulator 14 and is then sucked into the compressor 11. While the cooling operation is continuing, the above-described cycle from the discharge of the refrigerant from the compressor 11 to the suction of the refrigerant into the compressor 11 is repeated.

[0071] [Heating Operation]

The heating operation performed by the refrigeration cycle apparatus 100 will now be described. Fig. 3 is a schematic diagram illustrating the refrigerant circuit configuration in the heating operation performed by the refrigeration cycle apparatus 100. In Fig. 3, the refrigerant flow direction is represented by dotted line arrows. The on-off valve 18 in the closed position is represented by the solid symbol in Fig. 3. The heating operation of the refrigeration cycle apparatus 100 will be described by taking, as an example, the case where the air is the heat medium to exchange heat with the refrigerant in the heat source side heat exchanger 13 and the load side heat exchanger 51.

[0072]

When the refrigeration cycle apparatus 100 performs the heating operation, the flow switching device 12 in the heat source side unit 10 is switched so that the refrigerant discharged from the compressor 11 passes through the load side heat exchanger 51 and flows into the heat source side heat exchanger 13. Specifically, in the heating operation mode, the refrigerant flows through the compressor 11, the flow switching device 12, the load side heat exchanger 51, the load side expansion device 52, the pressure regulating valve 20, the heat source side heat exchanger 13, the flow switching device 12, the gas-liquid separator 16, and the accumulator 14 in that order in the main refrigerant circuit A. The pressure regulating valve 20 is adjusted to the fully open position.

[0073]

The compressor 11 compresses low-temperature, low-pressure refrigerant into high-temperature, high-pressure gas refrigerant and discharges the refrigerant. The high-temperature, high-pressure gas refrigerant discharged from the compressor 11 passes through the flow switching device 12 and flows into the load side heat exchanger 51. The refrigerant that has flowed into the load side heat exchanger 51 exchanges heat with the air supplied from the fan disposed in proximity to the load side heat exchanger 51 (and condenses), thus turning into high-temperature, highpressure liquid refrigerant. The refrigerant then flows out of the load side heat exchanger 51. In the load side heat exchanger 51, the refrigerant transfers heat to the air, thus heating the air. The heated air is supplied to the air-conditioned space, thereby heating the space to be air-conditioned.

[0074]

The high-temperature, high-pressure liquid refrigerant that has flowed out of the load side heat exchanger 51 is turned into low-temperature, low-pressure liquid refrigerant (or two-phase refrigerant) by the load side expansion device 52. The refrigerant passes through the pressure regulating valve 20 and flows into the heat source side heat exchanger 13 in the heat source side unit 10. The refrigerant that has flowed into the heat source side heat exchanger 13 exchanges heat with the air supplied from the fan disposed in proximity to the heat source side heat exchanger 13 (and evaporates), thus turning into low-temperature, low-pressure gas refrigerant. The refrigerant then flows out of the heat source side heat exchanger 13. [0075]

The refrigerant that has flowed out of the heat source side heat exchanger 13 passes through the flow switching device 12, the gas-liquid separator 16, and the accumulator 14 and is then sucked into the compressor 11. While the heating operation is continuing, the above-described cycle from the discharge of the refrigerant from the compressor 11 to the suction of the refrigerant into the compressor 11 is repeated.

[0076] [Cleaning Operation]

The cleaning operation performed by the refrigeration cycle apparatus 100 will now be described. Fig. 4 is a schematic diagram illustrating the refrigerant circuit configuration in the cleaning operation performed by the refrigeration cycle apparatus 100. In Fig. 4, the refrigerant flow direction is represented by solid line arrows and alternate long and short dashed line arrows. The on-off valve 18 in an open position is represented by an outlined symbol in Fig. 4. In Fig. 4, the refrigerant in the main refrigerant circuit A during the cleaning operation flows in the same direction as that during the cooling operation. The refrigerant in the main refrigerant circuit A during the cleaning operation may flow in the same direction as that during the heating operation.

[0077]

The cleaning operation, which is performed after at least one of the heat source side unit 10 and the load side unit 50 is replaced with a new unit, is an operation of collecting the old refrigerating machine oil, which is used in the units before replacement, together with residual foreign matter.

[0078]

When the refrigeration cycle apparatus 100 performs the cleaning operation, the flow switching device 12 in the heat source side unit 10 is switched so that the refrigerant discharged from the compressor 11 passes through the heat source side heat exchanger 13 and flows into the load side heat exchanger 51. The on-off valve 18 is opened so that the refrigerant flows through the foreign matter collecting circuit B. Furthermore, the opening degree of the pressure regulating valve 20 is adjusted so that the pressure of the refrigerant is lower than a withstand pressure of the existing refrigerant pipes. A pressure of the refrigerant reduced by the pressure regulating valve 20 will be referred to as an intermediate pressure.

[0079]

The compressor 11 compresses low-temperature, low-pressure refrigerant into high-temperature, high-pressure gas refrigerant and discharges the refrigerant. The high-temperature, high-pressure gas refrigerant discharged from the compressor 11 passes through the flow switching device 12 and flows into the heat source side heat exchanger 13. The refrigerant that has flowed into the heat source side heat exchanger 13 exchanges heat with the air supplied from the fan disposed in proximity to the heat source side heat exchanger 13 (and condenses), thus turning into hightemperature, high-pressure liquid single-phase refrigerant or low-quality, two-phase gas-liquid refrigerant. The refrigerant then flows out of the heat source side heat exchanger 13.

[0080]

The high-temperature, high-pressure liquid single-phase refrigerant or lowquality, two-phase gas-liquid refrigerant that has flowed out of the heat source side heat exchanger 13 is throttled to the intermediate pressure by the pressure regulating valve 20. The intermediate-pressure, two-phase gas-liquid refrigerant or liquid single-phase refrigerant flows through the liquid pipe 1 into the load side unit 50. The intermediate-pressure, two-phase gas-liquid refrigerant or liquid single-phase refrigerant that has flowed into the load side unit 50 is throttled to a low pressure by the load side expansion device 52. The low-pressure, liquid single-phase refrigerant or two-phase gas-liquid refrigerant flows into the load side heat exchanger 51. The refrigerant that has flowed into the load side heat exchanger 51 exchanges heat with the air supplied from the fan disposed in proximity to the load side heat exchanger 51 (and evaporates), thus turning into low-temperature, low-pressure gas refrigerant. The refrigerant then flows out of the load side heat exchanger 51.

[0081]

The refrigerant that has flowed out of the load side heat exchanger 51 flows through the gas pipe 2 and flows into the heat source side unit 10. The refrigerant that has flowed into the heat source side unit 10 passes through the flow switching device 12 and flows into the gas-liquid separator 16. In the gas-liquid separator 16, the refrigerant that has flowed into the separator is separated into gas refrigerant and liquid refrigerant. The gas refrigerant returns to the compressor 11 and the liquid refrigerant flows into the foreign matter collecting circuit B. The refrigerant that has flowed into the gas-liquid separator 16 contains foreign matter remaining in the existing refrigerant pipes. The foreign matter is separated together with the liquid refrigerant from the gas refrigerant in the gas-liquid separator 16.

[0082]

The liquid refrigerant that has flowed into the foreign matter collecting circuit B flows into the foreign matter collector 15. In the foreign matter collector 15, the foreign matter contained in the liquid refrigerant accumulates. The liquid refrigerant from which the foreign matter has been removed flows through the check valve 17 and returns to the downstream side of the accumulator 14. The foreign matter accumulating in the foreign matter collector 15 is collected by the foreign matter collector 15 without returning to the main refrigerant circuit A.

[0083]

The controller 40 determines, based on measurement information from the oil sensor 19, whether the cleaning operation has been completed. When determining that the cleaning operation has been completed, the controller 40 closes the on-off valve 18 to interrupt the flow of the refrigerant into the foreign matter collecting circuit B.

[0084] <Update Process for Refrigeration Cycle Apparatus 100 Involving Replacement and Cleaning Operation>

An update process, which involves replacement and the cleaning operation, for the refrigeration cycle apparatus 100 will now be described. Fig. 5 is a flowchart schematically illustrating the update process, involving replacement and the cleaning operation, for the refrigeration cycle apparatus 100.

[0085]

Updating the refrigeration cycle apparatus 100 is started (step S101). After updating the refrigeration cycle apparatus 100 is started, an existing unit is removed (step S102). For example, it is assumed herein that the heat source side unit 10 is removed. After the existing heat source side unit 10 is removed, a new heat source side unit 10 is disposed (step S103). The existing refrigerant pipes are connected to the new heat source side unit 10 (step S104).

[0086]

After the existing refrigerant pipes are connected to the new heat source side unit 10, the gas pipe 2, the liquid pipe 1, the heat source side unit 10, and the load side unit 50 are evacuated and the apparatus is then filled with new refrigerant (step S105). As for the amount of new refrigerant with which the apparatus is filled, it is only required that the amount of refrigerant provides a flow velocity required to remove foreign matter from the existing refrigerant pipes and collect the foreign matter in the foreign matter collector 15 during the cleaning operation.

[0087]

Then, an on-off valve (not illustrated) disposed between the heat source side unit 10 and the load side unit 50 is opened, thus performing the cleaning operation (step S106). The cleaning operation is achieved by washing the foreign matter, that remains in the existing refrigerant pipes, out with the new refrigerant. The washedout foreign matter flows together with the refrigerant into the gas-liquid separator 16. The controller 40 determines the dielectric constant of the refrigerating machine oil that has been separated by the gas-liquid separator 16 and has been retained in the gas-liquid separator 16 on the basis of information from the oil sensor 19 disposed in the gas-liquid separator 16. Specifically, the controller 40 compares the dielectric constant of the refrigerating machine oil separated by the gas-liquid separator 16 with the previously input dielectric constant of the normal refrigerating machine oil to detect a change in capacitance, thus determining the presence or absence of the foreign matter.

[0088]

When detecting the presence of the foreign matter in the gas-liquid separator

16, the controller 40 opens the on-off valve 18. The on-off valve 18 in the open position allows the foreign matter separated by the gas-liquid separator 16 to flow into the foreign matter collecting circuit B. The foreign matter separated by the gas-liquid separator 16 contains the new refrigerant and new refrigerating machine oil enclosed together with the new refrigerant. The refrigerating machine oil that has flowed into the foreign matter collecting circuit B accumulates in the foreign matter collector 15. The presence of the foreign matter can be determined based on a determination on whether a change in capacitance is greater than the predetermined threshold.

[0089]

Since the foreign matter is collected in the foreign matter collector 15, the new refrigerating machine oil returns together with the new refrigerant to the main refrigerant circuit A. After that, the controller 40 determines the presence or absence of the foreign matter on the basis of the dielectric constant of the refrigerating machine oil separated by the gas-liquid separator 16, and closes the on-off valve 18 to terminate the cleaning operation. After the cleaning operation is terminated, an operation of adjusting the amount of refrigerant in the refrigeration cycle apparatus 100 is performed (step S107).

[0090]

Then, whether the cooling operation and the heating operation are normally performed is determined by testing the cooling operation and the heating operation in the refrigeration cycle apparatus 100 (step S108). When it is determined, by testing, that the cooling operation and the heating operation have been normally performed, updating the refrigeration cycle apparatus 100 is completed (step S109).

[0091]

A determination on whether the cleaning operation has been completed will now be described.

As for terminating the cleaning operation, the controller 40 terminates the cleaning operation on the basis of measurement information from the oil sensor 19. Specifically, the controller 40 compares the dielectric constant, sent from the oil sensor 19, of the refrigerating machine oil separated by the gas-liquid separator 16 with the refrigerating-machine-oil dielectric constant previously input to the controller and determines, based on the comparison, whether the cleaning operation has been completed.

[0092]

The oil sensor 19 measures the dielectric constant of the refrigerating machine oil in the gas-liquid separator 16 and sends information representing the measured dielectric constant to the controller 40. The controller 40 compares this dielectric constant with the dielectric constant of the normal refrigerating machine oil. The controller 40 detects a change in capacitance on the basis of the difference between the dielectric constants to determine the presence or absence of foreign matter. The controller 40 determines whether a change in capacitance is greater than the predetermined threshold to determine the presence or absence of foreign matter. In the refrigeration cycle apparatus 100, therefore, the absence of the foreign matter, which remained in the existing refrigeration pipes, derived from the refrigerant and the refrigerating machine oil used before replacement can be detected with certainty. This eliminates the need for an excessive cleaning time and enhances the reliability of foreign matter removal.

[0093]

It is only required that an extra amount of oil to be separated by the gas-liquid separator 16 and accumulate in the foreign matter collector 15 in the cleaning operation is stored in the accumulator 14 prior to shipment.

[0094]

After the above-described operation is performed for a predetermined period of time, the controller 40 controls the devices so that the refrigerant flowing through the liquid pipe 1 is liquid refrigerant. Furthermore, the controller 40 controls the devices so that the refrigerant flowing through the gas pipe 2 is gas refrigerant. As described above, in the refrigeration cycle apparatus 100, refrigerant amount adjustment is performed to provide a refrigerant distribution state similar to that in the normal cooling operation.

[0095]

In the use of the existing refrigerant pipes, the diameter of each existing refrigerant pipe may differ from a designated diameter depending on, for example, refrigerant to be newly used. For example, the diameter of each existing refrigerant pipe may be greater than a refrigerant pipe diameter designated by specifications of refrigerant to be used after replacement. In such a case, a small operating load and a low flow rate of the refrigerant result in a low flow velocity of the refrigerant through the existing refrigerant pipes. Unfortunately, the refrigerating machine oil can accumulate in the pipes and fail to return to the heat source side unit. If such an operation continued for a long period of time, the refrigerating machine oil would not be supplied to the compressor 11, leading to a lack of refrigerating machine oil in the compressor 11.

[0096]

In contrast, in the refrigeration cycle apparatus 100, a state of retention of foreign matter in the gas-liquid separator 16 is determined based on a dielectric constant measured by the oil sensor 19. If no retention of foreign matter continues for more than a predetermined period of time, the controller 40 determines a lack of refrigerating machine oil circulated. The controller 40 temporarily increases an output of the compressor 11, or temporarily increases the frequency of the compressor 11. This achieves an increase in flow velocity of the refrigerant, so that the accumulating refrigerating machine oil can be returned to the heat source side unit 10.

[0097]

With the above-described operation, the refrigeration cycle apparatus 100 can relieve constraints on the pipes that enable replacement. Furthermore, the refrigeration cycle apparatus 100 can circulate the refrigerating machine oil in reuse of the existing refrigerant pipes and continuously supply the refrigerating machine oil to the compressor 11. Consequently, the refrigeration cycle apparatus 100 significantly reduces a lack of refrigerating machine oil in the compressor 11 and enhances the reliability accordingly.

[0098] <Advantageous Effects of Refrigeration Cycle Apparatus 100>

As described above, the refrigeration cycle apparatus 100 includes the main refrigerant circuit A in which the compressor 11, the load side heat exchanger 51, the load side expansion device 52, the heat source side heat exchanger 13, and the gasliquid separator 16 are connected by the refrigerant pipes, the foreign matter collecting circuit B in which the gas-liquid separator 16, the on-off valve 18, and the foreign matter collector 15 are connected by the bypass pipe 3 connecting the lower part of the gas-liquid separator 16 and the suction side of the compressor 11, the controller 40 opening and closing the on-off valve 18, and the oil sensor 19 disposed in the gas-liquid separator 16. The oil sensor 19 measures the dielectric constant of the refrigerating machine oil retained in the gas-liquid separator 16. The controller 40 calculates the dielectric constant of the refrigerating machine oil retained in the gas-liquid separator 16 on the basis of information from the oil sensor 19, and opens or closes the on-off valve 18.

[0099]

In the refrigeration cycle apparatus 100 with such a configuration, the presence or absence of foreign matter in the gas-liquid separator 16 is determined based on the dielectric constant of the refrigerating machine oil measured by the oil sensor 19. Thus, collected foreign matter can be detected with accuracy.

[0100]

In the refrigeration cycle apparatus 100, the controller 40 compares the dielectric constant, sent from the oil sensor 19, of the refrigerating machine oil separated by the gas-liquid separator 16 with the refrigerating-machine-oil dielectric constant previously input to the controller to calculate the dielectric constant of the refrigerating machine oil retained in the gas-liquid separator 16.

In the refrigeration cycle apparatus 100 with such a configuration, since the dielectric constant of the refrigerating machine oil is calculated based on the capacitance of the refrigerating machine oil retained in the gas-liquid separator 16, the certainty of determination on the presence or absence of foreign matter is enhanced.

[0101]

The refrigeration cycle apparatus 100 is configured as follows. The compressor 11, the heat source side heat exchanger 13, the gas-liquid separator 16, the on-off valve 18, and the foreign matter collector 15 are provided in the heat source side unit 10. The load side heat exchanger 51 and the load side expansion device 52 are provided in the load side unit 50. At least one of the heat source side unit 10 and the load side unit 50 is replaceable with a new unit using the refrigerant pipes included in the main refrigerant circuit A.

Such a configuration of the refrigeration cycle apparatus 100 enhances the reliability of circulation of refrigerating machine oil through the existing refrigerant pipes after replacement. A constant amount of new refrigerating machine oil containing no impurities, such as old refrigerating machine oil, can be supplied to the compressor 11.

[0102]

When at least one of the heat source side unit 10 and the load side unit 50 is replaced with a new unit, the refrigeration cycle apparatus 100 performs the cleaning operation of circulating refrigerant through the main refrigerant circuit A to clean the existing refrigerant pipes. The controller 40 terminates the cleaning operation when the difference between the dielectric constant, sent from the oil sensor 19, of the refrigerating machine oil separated by the gas-liquid separator 16 and the refrigerating-machine-oil dielectric constant previously input to the controller is greater than the predetermined threshold.

[0103]

Such a configuration of the refrigeration cycle apparatus 100 enables accurate calculation of the dielectric constant of the refrigerating machine oil retained in the gas-liquid separator 16, thus enhancing the certainty of determination on whether the cleaning operation after replacement has been completed. In addition, this configuration of the refrigeration cycle apparatus 100 optimizes duration of the cleaning operation after replacement, thus enhancing the reliability of the refrigeration cycle apparatus 100.

[0104]

In the refrigeration cycle apparatus 100, the controller 40 opens the on-off valve 18 to allow the refrigerating machine oil separated by the gas-liquid separator 16 to flow through the foreign matter collecting circuit B in the cleaning operation, and closes the on-off valve 18 to terminate the cleaning operation.

In the refrigeration cycle apparatus 100, such a simple operation of closing the on-off valve 18 enables the foreign matter collecting circuit B to be disconnected from the main refrigerant circuit A, thus further optimizing the duration of the cleaning operation.

[0105]

In the refrigeration cycle apparatus 100, the controller 40 increases the frequency of the compressor 11 when no retention of the refrigerating machine oil in the gas-liquid separator 16 continues for more than the predetermined period of time in an operation after the cleaning operation.

Such a configuration of the refrigeration cycle apparatus 100 can relieve constraints on the use of the existing refrigerant pipes.

Reference Signs List [0106] liquid pipe 2 gas pipe 3 bypass pipe 10 heat source side unit 11 compressor 12 flow switching device 13 heat source side heat exchanger 14 accumulator 15 foreign matter collector 16 gas-liquid separator 17 check valve 18 on-off valve 19 oil sensor 20 pressure regulating valve 40 controller 50 load side unit 51 load side heat exchanger 52 load side expansion device 53 load side heat exchanger 100 refrigeration cycle apparatus A main refrigerant circuit B foreign matter collecting circuit

Claims

A refrigeration cycle apparatus comprising:

a main refrigerant circuit in which a compressor, a load side heat exchanger, a load side expansion device, a heat source side heat exchanger, and a gas-liquid separator are connected by refrigerant pipes;

a foreign matter collecting circuit in which the gas-liquid separator, an on-off valve, and a foreign matter collector are connected by a bypass pipe connecting lower part of the gas-liquid separator and a suction side of the compressor; and an oil sensor disposed in the gas-liquid separator, the oil sensor measuring a dielectric constant of refrigerating machine oil retained in the gas-liquid separator. [Claim 2]

The refrigeration cycle apparatus of claim 1, further comprising:

a controller configured to control opening and closing of the on-off valve, wherein the controller determines, based on the dielectric constant measured by the oil sensor, whether foreign matter is present in the gas-liquid separator, and controls opening and closing of the on-off valve by using a determination result. [Claim 3]

The refrigeration cycle apparatus of claim 2, wherein the controller compares the dielectric constant, of the refrigerating machine oil retained in the gas-liquid separator, sent from the oil sensor and with a refrigerating-machine-oil dielectric constant previously input to the controller to determine whether foreign matter is present in the gas-liquid separator. [Claim 4]

The refrigeration cycle apparatus of any one of claims 1 to 3, wherein the compressor, the heat source side heat exchanger, the gas-liquid separator, the on-off valve, and the foreign matter collector are provided in a heat source side unit, wherein the load side heat exchanger and the load side expansion device are provided in a load side unit, and wherein at least one of the heat source side unit and the load side unit is replaceable with a new unit using the existing refrigerant pipes included in the main refrigerant circuit.

[Claim 5]

The refrigeration cycle apparatus of claim 4 as dependent on claim 2, wherein the apparatus performs a cleaning operation of circulating refrigerant through the main refrigerant circuit to clean the existing refrigerant pipes when at least one of the heat source side unit and the load side unit is replaced with a new unit, and wherein the controller terminates the cleaning operation when a difference between the dielectric constant, sent from the oil sensor, of the refrigerating machine oil separated by the gas-liquid separator and a refrigerating-machine-oil dielectric constant previously input to the controller is greater than a predetermined threshold. [Claim 6]

The refrigeration cycle apparatus of claim 5, wherein the controller opens the on-off valve to allow the refrigerating machine oil separated by the gas-liquid separator to flow through the foreign matter collecting circuit during the cleaning operation, and wherein the controller closes the on-off valve to terminate the cleaning operation.

[Claim 7]

The refrigeration cycle apparatus of claim 5 or 6, wherein, in an operation after the cleaning operation, the controller increases a frequency of the compressor when a state where the refrigerating machine oil is not retained in the gas-liquid separator continues for more than a predetermined period of time.