Refrigerating and air-conditioning apparatus and method for controlling refrigerating and air-conditioning apparatus

A refrigerating and air-conditioning apparatus, which includes a compressor, a condenser, an expansion device, and an evaporator, has a refrigeration cycle configured by these components being connected by a refrigerant pipe, and uses a non-azeotropic refrigerant mixture as a refrigerant circulating through the refrigeration cycle, includes operating state detection means which detect a pressure of the refrigerant at the compressor, a temperature of the refrigerant at the compressor, and a rotation speed of the compressor, output detection means which detects an output of the compressor, and composition detection means which calculates a correlation between the pressure of the refrigerant at the compressor, the temperature of the refrigerant at the compressor, the rotation speed of the compressor, the output of the compressor, and a refrigerant composition and retains data indicating the correlation.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application of International Application No. PCT/JP2011/003895 filed on Jul. 7, 2011.

TECHNICAL FIELD

The present invention relates to a refrigerating and air-conditioning apparatus that uses a non-azeotropic refrigerant mixture as a refrigerant, and particularly relates to a refrigerating and air-conditioning apparatus that is modified to improve accuracy of detecting the composition of the refrigerant.

BACKGROUND ART

In a refrigerating and air-conditioning apparatus that uses a non-azeotropic refrigerant mixture, since the boiling points of refrigerants included in the non-azeotropic refrigerant mixture are different from each other, the composition of the circulating refrigerant may change. Particularly, when the size of a refrigerating and air-conditioning apparatus is large, a change in the refrigerant composition becomes noticeable. As described above, when the refrigerant composition changes, changes in the condensing temperature or the evaporating temperature may occur even there is no change in the pressure. In other words, an improper refrigerant saturation temperature at a heat exchanger hinders the refrigerant from being readily condensed and liquefied or evaporated and gasified at the heat exchanger, and the heat exchange efficiency may be reduced.

In addition, when the refrigerant composition changes, changes in superheat or subcooling may occur even there are no changes in the temperature and pressure at the refrigerant discharge side of the heat exchanger. In other words, owing to improper superheat before the refrigerant is sucked onto a compressor, a liquid refrigerant flows into the compressor, whereby the compressor may consequently be damaged; or owing to improper subcooling before the refrigerant flows into an expansion valve, the refrigerant comes into a gas-liquid two-phase state, whereby generation of refrigerant sound or an unstable phenomenon may consequently occur.

Here, it is known that a refrigerating and air-conditioning apparatus including a refrigerant storage container (receiver) at a high-pressure side has a smaller fluctuation range of the composition of a circulating refrigerant than that of a refrigerating and air-conditioning apparatus including a refrigerant storage container (accumulator) at a low-pressure side. However, when refrigerant leak occurs at a refrigeration cycle, the fluctuation range of the refrigerant composition is increased regardless of whether the refrigerant storage container is at the low-pressure side or the high-pressure side. In other words, it is possible to detect refrigerant leak by detecting a fluctuation of the refrigerant composition.

Thus, various refrigerating and air-conditioning apparatuses including means for detecting a refrigerant composition in order to suppress reduction in heat exchange efficiency, to avoid compressor damage, to suppress generation of refrigerant sound, to suppress an unstable phenomenon, and to detect refrigerant leak, have been proposed.

As such a refrigerating and air-conditioning apparatus, a refrigerating and air-conditioning apparatus has been proposed which includes a bypass connected so as to bypass a compressor and in which a double pipe heat exchanger and a capillary tube are connected to the bypass (e.g., see Patent Literature 1). In the technology described in Patent Literature 1, the temperature at the refrigerant inflow side of the capillary tube, the temperature at the refrigerant outflow side of the capillary tube, and the pressure at the refrigerant outflow side of the capillary tube are detected, and a refrigerant composition is calculated on the basis of these detection results.

In addition, as such a refrigerating and air-conditioning apparatus, a refrigerating and air-conditioning apparatus has been proposed which detects an excess refrigerant amount within an accumulator and calculates a refrigerant composition (e.g., see Patent Literature 2). In other words, in the technology described in Patent Literature 2, a refrigerant composition is calculated on the basis of a correlation between information such as the number of operating indoor units and the outside air temperature and a previously obtained refrigerant composition, an excess refrigerant amount within the accumulator is detected, and the calculated refrigerant composition is corrected, whereby the composition of a circulating refrigerant is calculated.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 11-63747 (e.g., see paragraphs [0027] to [0029] of the specification)

Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2001-99501 (e.g., see paragraphs [0041], [0042], and [0051] to [0053] of the specification)

SUMMARY OF INVENTION

Technical Problem

The technology described in Patent Literature 1 is configured to detect a composition on the basis of states before and after an expansion process at the capillary tube. For example, when a plurality of expansion processes are present in parallel in a refrigeration cycle of the refrigerating and air-conditioning apparatus, the detection accuracy of a refrigerant composition to be detected may be decreased.

In the technology described in Patent Literature 1, since the bypass is provided, an amount of the refrigerant circulating through the refrigeration cycle is reduced. Thus, the capability exerted by the refrigerating and air-conditioning apparatus is diminished, and the operation reliability of the refrigerating and air-conditioning apparatus may be decreased.

In addition, in the technology described in Patent Literature 1, when a liquid refrigerant flows into the compressor during a transient operation and a two-phase refrigerant flows out also from a refrigerant pipe at the discharge side of the compressor, the refrigerant having the same refrigerant composition as that of the refrigerant circulating through the refrigeration cycle may not flow into the bypass when branching into the bypass. In this case, even when a refrigerant composition is detected in the bypass path, it does not mean that a composition of the refrigerant circulating through the refrigeration cycle is detected. Therefore, even when a liquid refrigerant flows into the compressor, the detection thereof is failed whereby the compressor may consequently be damaged, and accordingly, the operation reliability of the refrigerating and air-conditioning apparatus may be decreased.

Furthermore, in the technology described in Patent Literature 1, since the double pipe heat exchanger and the capillary tube are provided, the cost is increased.

In the technology described in Patent Literature 2, since a liquid level detector is provided in the accumulator, the cost is increased.

In addition, in the technology described in Patent Literature 2, it is necessary to previously grasp a refrigerant composition from an operating state of the refrigerating and air-conditioning apparatus, and a considerable amount of evaluation work or simulation is required for each refrigerating and air-conditioning apparatus. Thus, the load and the cost of development are increased.

A refrigerating and air-conditioning apparatus according to the present invention intends to provide a refrigerating and air-conditioning apparatus that has improved accuracy of detecting the composition of a circulating refrigerant and has improved operation reliability during operation while suppressing a cost increase.

Solution to Problem

A refrigerating and air-conditioning apparatus according to the present invention includes a compressor, a condenser, an expansion device, and an evaporator, has a refrigeration cycle configured by these components being connected by a refrigerant pipe, and uses a non-azeotropic refrigerant mixture as a refrigerant circulating through the refrigeration cycle. The refrigerating and air-conditioning apparatus includes: operating state detection means for detecting an operating state of the compressor; output detection means for detecting an output of the compressor; and composition detection means for calculating a correlation between the operating state, the output, and a refrigerant composition and retaining data indicating the correlation. The composition detection means calculates a composition of the refrigerant circulating through the refrigeration cycle on the basis of a detection result of the operating state detection means, a detection result of the output detection means, and the data indicating the correlation.

Advantageous Effects of Invention

In the refrigerating and air-conditioning apparatus according to the present invention, the composition detection means calculates the composition of the refrigerant circulating through the refrigeration cycle, on the basis of the detection result of the operating state detection means, the detection result of the output detection means, and the data indicating the correlation. Thus, while suppressing a cost increase, the improvement in accuracy of detecting the composition of the circulating refrigerant is ensured, and this improves the operation reliability during operation.

DESCRIPTION OF EMBODIMENTS

FIG. 1shows an example of a refrigerant circuit configuration of a refrigerating and air-conditioning apparatus100according to Embodiment 1 of the present invention.

The refrigerating and air-conditioning apparatus100according to Embodiment 1 uses a non-azeotropic refrigerant mixture as a refrigerant, and performs control of various devices such as an opening degree of an expansion device (corresponding to a pressure reducing mechanism4described later) by detecting the refrigerant composition of the refrigerant. The refrigerating and air-conditioning apparatus100according to Embodiment 1 is modified to improve accuracy of detecting the composition of the refrigerant.

It should be noted that in the following description, a composition (refrigerant composition) refers to the composition of a refrigerant circulating through a refrigeration cycle, and is not the composition of a refrigerant to be charged and the composition of a refrigerant present within a component of the refrigeration cycle.

As shown inFIG. 1, the refrigerating and air-conditioning apparatus100includes a compressor2which compresses the refrigerant, a condenser3which condenses and liquefies the refrigerant, the pressure reducing mechanism4which reduces the pressure of the refrigerant to expand the refrigerant, an evaporator5which evaporates and gasifies the refrigerant, and an accumulator6which stores an excess refrigerant, and has a refrigeration cycle configured by these components being connected by a refrigerant pipe. Here, the refrigerating and air-conditioning apparatus100uses the non-azeotropic refrigerant mixture as a refrigerant circulating through the refrigeration cycle. In Embodiment 1, as the non-azeotropic refrigerant mixture, R32 (a charged composition of R32 is 54 wt %) is used as a low-boiling-point refrigerant, and HFO1234yf (the charged composition thereof is 46 wt %) is used as a high-boiling-point refrigerant. It should be noted that in the case of this charged refrigerant composition, the global warming potential (GWP) of the non-azeotropic refrigerant mixture is 300.

In addition, the refrigerating and air-conditioning apparatus100includes various devices for detecting the composition of the non-azeotropic refrigerant mixture. Specifically, the refrigerating and air-conditioning apparatus100includes suction-side pressure detection means11which detects the pressure of the refrigerant sucked into the compressor2, suction-side temperature detection means12which detects the temperature of the refrigerant sucked into the compressor2, discharge-side pressure detection means13which detects the pressure of the refrigerant discharged from the compressor2, rotation speed detection means14which detects the rotation speed of the compressor2, and output detection means15which detects an output of the compressor2.

Furthermore, the refrigerating and air-conditioning apparatus100includes composition detection means20which detects a refrigerant composition on the basis of detection results of these detection means11to15, and a controller21which integrally controls the rotation speed of the compressor2and various devices.

The compressor2sucks the refrigerant, compresses the refrigerant into a high-temperature and high-pressure state, and discharges the refrigerant. The compressor2is connected at a discharge side thereof to the condenser3and connected at a suction side thereof to the accumulator6. The compressor2may be, for example, a capacity-controllable inverter compressor or the like.

The condenser3condenses and liquefies the high-temperature and high-pressure refrigerant supplied from the compressor2. The condenser3is connected at one end thereof to the compressor2and connected at another end thereof to the pressure reducing mechanism4. It should be noted that the condenser3is equipped with a fan (not shown) and prompts heat exchange between the refrigerant and air supplied from the fan. The air that is heat-exchanged with the refrigerant is blown out to, for example, the outside of a room or the like by the action of the fan.

The pressure reducing mechanism4reduces the pressure of a liquid refrigerant flowing thereinto from the condenser3, to expand the liquid refrigerant. The pressure reducing mechanism4may be a mechanism whose opening degree is variably controllable, such as an electronic expansion valve. The pressure reducing mechanism4is connected at one end thereof to the condenser3and connected at another end thereof to the evaporator5.

The evaporator5evaporates and gasifies a gas-liquid two-phase refrigerant flowing thereinto from the pressure reducing mechanism4. The evaporator5is connected at one end thereof to the pressure reducing mechanism4and connected at another end thereof to the accumulator6. It should be noted that the evaporator5is equipped with a fan (not shown) and prompts heat exchange between the refrigerant and air supplied from the fan. The air that is heat-exchanged with the refrigerant is blown out to an air-conditioned space (e.g., the inside of a room, a storehouse, etc.) by the action of the fan.

The accumulator6stores an excess refrigerant caused by a change of a transient operation (e.g., a change of the output of the compressor2). The accumulator6is connected at one end thereof to the evaporator5and connected at another end thereof to the suction side of the compressor2.

The suction-side pressure detection means11detects the pressure of the refrigerant sucked into the compressor2(low-pressure-side refrigerant pressure), and is, for example, a pressure sensor or the like. In other words, the suction-side pressure detection means11detects the pressure of the refrigerant whose pressure is reduced by the action of the pressure reducing mechanism4, in order to detect a refrigerant composition. In addition, the suction-side pressure detection means11is connected to the composition detection means20. Here,FIG. 1illustrates an example where the suction-side pressure detection means11is installed on a refrigerant pipe near an inlet of the compressor2, but the present invention is not limited thereto. Specifically, the suction-side pressure detection means11may be installed on a refrigerant pipe (including the evaporator5and the accumulator6) from a refrigerant outlet of the pressure reducing mechanism4to the inlet of the compressor2. By so doing, it is possible to commonalize the suction-side pressure detection means11with a pressure detection sensor (not shown) for controlling the rotation speed of the fan of the condenser3, the opening degree of the pressure reducing mechanism4, and the like, into one unit, and thus it is possible to reduce the cost.

The suction-side temperature detection means12detects the temperature of the refrigerant sucked into the compressor2(low-pressure-side refrigerant temperature), and is, for example, a temperature sensor or the like. In addition, the suction-side temperature detection means12is connected to the composition detection means20. Here,FIG. 1illustrates an example where the suction-side temperature detection means12is installed on a refrigerant pipe connecting the accumulator6to the compressor2, but the present invention is not limited thereto. Specifically, the suction-side temperature detection means12may be installed inside the compressor2and at a position before the refrigerant is compressed (at a position before entering a compression process).

Here, when the suction-side temperature detection means12is provided on the pipe surface, the suction-side temperature detection means12is susceptible to the ambient environment (disturbance). For example, when one type of compressors are installed in a plurality of different refrigerating and air-conditioning apparatuses, there is a possibility that the installation position of the suction-side temperature detection means12differs in each refrigerating and air-conditioning apparatus, and the suction-side temperature detection means12is affected by an error of detection results or the like caused by the difference in installation position.

However, installing the suction-side temperature detection means12inside the compressor2and at the position before the refrigerant is compressed, suppresses such disturbance, and it is therefore possible to detect a refrigerant composition with high accuracy.

The discharge-side pressure detection means13detects the pressure of the refrigerant discharged from the compressor2(high-pressure-side refrigerant pressure), and is, for example, a pressure sensor or the like. In other words, the discharge-side pressure detection means13detects the pressure of the refrigerant whose pressure is increased by the action of the compressor2. In addition, the discharge-side pressure detection means13is connected to the composition detection means20. Here,FIG. 1illustrates an example where the discharge-side pressure detection means13is installed on a refrigerant pipe near an outlet of the compressor2, but the present invention is not limited thereto. Specifically, the discharge-side pressure detection means13may be installed on a refrigerant pipe (including the condenser3) from the outlet of the compressor2to a refrigerant inlet of the pressure reducing mechanism4. By so doing, it is possible to commonalize the discharge-side pressure detection means13with a pressure detection sensor (not shown) for controlling the rotation speed of the fan of the evaporator5, the opening degree of the pressure reducing mechanism4, and the like, into one unit, and thus it is possible to reduce the cost.

The rotation speed detection means14detects the rotation speed of the compressor2, and is, for example, a non-contact rotation speed sensor or the like. It should be noted that a method of the rotation speed detection means14for detecting a rotation speed is not limited to this, and may be a method in which a command value output to the compressor2by control means21which controls the rotation speed of the compressor2is used as a rotation speed. In addition, the rotation speed detection means14is connected to the composition detection means20.

As described above, the suction-side pressure detection means11, the suction-side temperature detection means12, the discharge-side pressure detection means13, and the rotation speed detection means14detect an operating state of the compressor2, and these detection means11to14constitute operating state detection means.

The output detection means15detects the output of the compressor2. The output detection means15is connected between the compressor2and the controller21via a power supply line L. Thus, the output detection means15is able to detect power supplied from a power source, which is not shown, via a controller20to the compressor2. In addition, the output detection means15is connected to the composition detection means20.

The composition detection means20has stored therein functions described in formulas 1 to 8 described below, and calculates the power consumption of the compressor2on the basis of detection results of the suction-side pressure detection means11, the suction-side temperature detection means12, the discharge-side pressure detection means13, and the rotation speed detection means14and formulas 1 to 8. The composition detection means20is composed of, for example, a microcomputer or an electronic circuit equivalent to the microcomputer. The composition detection means20calculates a refrigerant composition on the basis of the calculated power consumption of the compressor2and a detection result of the output detection means15. It should be noted that it is stated that the composition detection means20has stored therein the functions described in formulas 1 to 8, and it means that the functions have been formulated by polynomials of arguments (Pd, Ps, Ts, α, N, etc.) and stored therein.

The composition detection means20is connected to the detection means11to15. It should be noted that the composition detection means20may be connected to the detection means11to15via wires or wirelessly, and the present invention is not particularly limited.

The composition detection means20may not be in a form in which the functions described in formulas 1 to 8 have been stored therein. The composition detection means2may be in a form in which a data table corresponding to formulas 1 to 8 has been created and stored so as to appropriately interpolate data therein. Accordingly, creating the data table can reduce a calculation time, and thus the controllability of the composition detection means20can be stabilized.

In addition, in the refrigerating and air-conditioning apparatus100according to Embodiment 1, the composition detection means20detects the refrigerant composition of the low-boiling-point refrigerant. Specifically, the composition detection means20has stored therein formulas for the low-boiling-point refrigerant, and a data table. When the value of the refrigerant composition of the low-boiling-point refrigerant is α, the refrigerant composition of the high-boiling-point refrigerant is calculated by 1−α.

Furthermore, the composition detection means20may previously have stored therein the formulas and the data table, and also may be the one capable of setting and updating the formulas and the data table later on.

The controller21controls operations such as the opening degree of the pressure reducing mechanism4, the rotation speed of the compressor2, and the rotation speeds of the fans provided in the condenser3and the evaporator5, respectively. The controller21of the refrigerating and air-conditioning apparatus100according to Embodiment 1 is able to control operations of the various devices descried above on the basis of a detection result of the composition detection means20. In addition, the controller21is connected to the power source which is not shown, and is connected to the output detection means15and the compressor2via the power supply line L.

A refrigerant operation of the refrigerating and air-conditioning apparatus100will be described. The high-temperature and high-pressure gas refrigerant compressed by the compressor2flows into the condenser3and condenses and liquefies. The liquid refrigerant having flowed out of the condenser3flows into the pressure reducing mechanism4and is reduced in pressure. The low-pressure gas-liquid two-phase refrigerant having flowed out of the pressure reducing mechanism4flows into the evaporator5and evaporates and gasifies. The gas refrigerant having flowed out of the evaporator5flows into the accumulator6in which an excess refrigerant occurring depending on an operating condition or a load condition of the refrigerating and air-conditioning apparatus100is stored. The gas refrigerant having flowed out of the accumulator6is sucked and compressed again by the compressor2.

Here, the reasons why the refrigerant composition changes will be described as the following three examples. It should be noted that a change in the refrigerant composition refers to a change in the composition of the refrigerant circulating through the refrigeration cycle with respect to the composition of the refrigerant charged in the refrigeration cycle.

(1) The refrigerant within the accumulator6is separated into a liquid phase in which the high-boiling-point refrigerant (HFO1234) is contained in a large amount and a gas phase in which the low-boiling-point refrigerant (R32) is contained in a large amount. Then, the liquid-phase refrigerant containing a large amount of the high-boiling-point refrigerant is stored in the accumulator6. On the other hand, the gas-phase refrigerant containing a large amount of the low-boiling-point refrigerant flows out of the accumulator6. Since the liquid-phase refrigerant containing a large amount of the high-boiling-point refrigerant is present within the accumulator6as described above, the composition of the low-boiling-point refrigerant relative to the entire refrigerant circulating through the refrigeration cycle is increased.

It should be noted that a fact that the composition of the low-boiling-point refrigerant relative to the entire refrigerant circulating through the refrigeration cycle may be decreased, will be described. For example, in the case where a refrigerating and air-conditioning apparatus includes a plurality of indoor units and these indoor units perform a heating operation, when some of the indoor units stop the heating operation within a short period of time, a liquid refrigerant may stay in the indoor units. Thus, the composition of the low-boiling-point refrigerant relative to the entire refrigerant circulating through the refrigeration cycle is decreased by the amount of the staying liquid refrigerant.

(2) When refrigerant leak occurs from a lower portion within the accumulator6, the liquid-phase refrigerant stored in the lower portion of the accumulator6leaks. Since the liquid-phase refrigerant contains a large amount of the high-boiling-point refrigerant, the composition of the low-boiling-point refrigerant relative to the entire refrigerant circulating through the refrigeration cycle is increased in this case.

(3) When refrigerant leak occurs at a refrigerant pipe, as with the refrigerant pipe connecting the condenser3to the pressure reducing mechanism4, through which a liquid single-phase refrigerant flows a large amount of the low-boiling-point refrigerant leaks since the low-boiling-point refrigerant is more likely to gasify. Thus, the composition of the high-boiling-point refrigerant relative to the entire refrigerant circulating through the refrigeration cycle is increased.

It should be noted that there is also a possibility that the liquid refrigerant leaks depending on a manner of refrigerant leak; and when no liquid refrigerant is present within the accumulator6, the refrigerant composition does not change.

Next, the formulas used when the composition detection means20of the refrigerating and air-conditioning apparatus100according to Embodiment 1 calculates a refrigerant composition will be described. Here, where the pressure of the refrigerant at the suction side of the compressor2is Ps, the temperature of the refrigerant at the suction side of the compressor2is Ts, the pressure of the refrigerant at the discharge side of the compressor2is Pd, the rotation speed of the compressor2is N, the refrigerant composition of the low-boiling-point refrigerant relative to the entire refrigerant is α the stroke volume of the compressor2is Vst, the refrigerant density of the refrigerant at the suction side of the compressor2is ρs, the entropy of the refrigerant at the suction side of the compressor2is Ss, an enthalpy difference between before and after the refrigerant is compressed by the compressor2is Δh, the compressor efficiency of the compressor2is ηc, the volume efficiency of the compressor2is ηv, an amount of the circulating refrigerant is Gr, and the power consumption of the compressor2is W, the following formulas are established.
Gr≡ρs·ηv·Vst·N[Math. 1]
W≡Gr·Δh/ηc[Math. 2]
Where:
ρsρPTα(Ps,Ts,α)  [Math. 3]
ηv=f1(Pd,Ps,Ts,N,α)  [Math. 4]
Δ=hdideal−hs=hPSα(Pd,Ss,α)−hPTα(Ps,Ts,α)  [Math. 5]
Ss=SPTα(Ps,Ts,α)  [Math. 6]
η0=f2(Pd,Ps,Ts,N,α)  [Math. 7]

Here, when solving for the compressor power consumption W by formulas 1 to 7, the following is obtained.
W=(ρs·Δh)×(N·Vst·ηv/η0)  [Math. 8]

Here, formulas 1 and 2 are definitional equations of the volume efficiency ηv and the compressor efficiency ηc, respectively. Formulas 3, 5, and 6 are functions determined by pressure, temperature, refrigerant composition, and entropy, Specifically, formula 3 is a function of pressure, temperature, and refrigerant composition. In addition, the first term of formula 5 is a function of pressure, entropy, and refrigerant composition, and the second term of formula 5 is a function of pressure, temperature, and refrigerant composition. Furthermore, formula 6 is a function of pressure, temperature, and refrigerant composition.

Formulas 4 and 7 are indexes for the performance of the compressor2and are expansions of formula 1, which is the definitional equation of the volume efficiency ηv, and formula 2, which is the definitional equation of the compressor efficiency ηc, respectively. Then, unit evaluation of the compressor2is conducted under a plurality of conditions, and the unit evaluation result and the expansion of the volume efficiency ηv described above and the expansion of the compressor efficiency ηc are curve-fitted to set various constants in each expansion. It should be noted that the volume efficiency ηv and the compressor efficiency ηc may be obtained by conducting prediction through simulation if its accuracy is high. In addition, the unit evaluation of the above-described compressor2and the simulation may be used in combination. In other words, the number of tests for unit evaluation described above is reduced, and the volume efficiency ηv and the compressor efficiency ηc are obtained by interpolating and extrapolating the obtained result through the simulation.

The power consumption W of the compressor2is represented by formula 8. Specifically, the term described in the first parenthesis is a term corresponding to refrigerant physical properties calculated from an operating state of the refrigerating and air-conditioning apparatus100, and the term described in the next parenthesis is a term corresponding to compressor characteristics calculated from an operating state of the refrigerating and air-conditioning apparatus100. It should be noted that the refrigerant physical properties are the refrigerant density ρs and the enthalpy difference Δh in the compression process. In addition, the compressor characteristics are the rotation speed N of the compressor2, the stroke volume Vst of the compressor2, the volume efficiency ηv, and the compressor efficiency ηc. It should be noted that the stroke volume Vst of the compressor2is specific to the compressor2and is a known numerical value.

In detecting a refrigerant composition, the composition detection means20performs various calculations of formulas 3 to 8, the arguments described in formulas 1 to 8 are not essential, and an argument having low sensitivity may be omitted if no problem arises. For example, as shown in formula 3, when the sensitivity of he refrigerant density ρs is low, the refrigerant density ρs in formula 8 may be a constant.

In the refrigerating and air-conditioning apparatus100according to Embodiment 1, the composition detection means20calculates power consumption W of the compressor2on the basis of formula 8 thus obtained, and calculates a refrigerant composition on the basis of the calculated power consumption and a detection result of the output detection means15. For a specific example of the method for calculating a refrigerant composition, refer to a description ofFIG. 6described later.

FIG. 2is a Mollier diagram illustrating a state change in the compression process by the compressor2when the refrigerant composition ratio of the low-boiling-point refrigerant is changed.FIG. 3is a graph illustrating a relationship between the proportion of the low-boiling-point refrigerant included in the circulating refrigerant and the refrigerant density.FIG. 4is a graph illustrating a relationship between the proportion of the low-boiling-point refrigerant included in the circulating refrigerant and an enthalpy difference in the compression process by the compressor2(before and after compression).FIG. 5is a graph illustrating a relationship between the proportion of the low-boiling-point refrigerant included in the circulating refrigerant and the power consumption of the compressor2. With reference toFIGS. 2 to 5, the Mollier diagram (FIG. 2) when the proportion of the low-boiling-point refrigerant (the composition ratio of the low-boiling-point refrigerant) is changed, the refrigerant density ρs (FIG. 3), the enthalpy difference Δh in the compression process (FIG. 4), and the power consumption W of the compressor2(FIG. 5) will be described.

It should be noted that inFIGS. 2 to 5, the pressure of the refrigerant at the suction side of the compressor2, the pressure of the refrigerant at the discharge side of the compressor2, subcooling at the outlet of the condenser3, and superheat at the outlet of the evaporator5are fixed, and the composition of the circulating refrigerant is changed. The reason why the pressure of the refrigerant at the suction side of the compressor2and the pressure of the refrigerant at the discharge side of the compressor2are fixed is to observe how the difference in refrigerant composition affects on the Mollier diagram (FIG. 2), the refrigerant density ρs (FIG. 3), the enthalpy difference Δh in the compression process (FIG. 4), and the power consumption W of the compressor2(FIG. 5). In addition, results shown inFIGS. 2 to 5indicate the similar tendency even when the temperature at the outlet of the condenser3is used instead of the subcooling at the outlet of the condenser3and the temperature at the outlet of the evaporator5is used instead of the superheat at the outlet of the evaporator5.

As shown inFIG. 2, as the composition ratio of the low-boiling-point refrigerant, that is, the proportion of the low-boiling-point refrigerant, increases, the compression process shifts to a high enthalpy side (the right side of the sheet surface) and the gradient in the compression process increases. In addition, as shown inFIG. 3, as the proportion of the low-boiling-point refrigerant increases, the refrigerant density ρs monotonously decreases. Moreover, as shown inFIG. 4, as the proportion of the low-boiling-point refrigerant increases, the enthalpy difference Δh in the compression process increases. Therefore, as shown inFIG. 5, the power consumption W of the compressor2monotonously increases.

In other words, monotonous increase in the power consumption W of the compressor2inFIG. 5is understandable, by making the fact that the degree of the increase of the enthalpy difference Δh in the compression process shown inFIG. 4surpasses the degree of the decrease of the refrigerant density ρs shown inFIG. 3correspond to formula 8.

In addition, inFIG. 5, the proportion of the refrigerant composition and the power consumption W of the compressor2have a simple correspondence relationship. The simple correspondence relationship suffices to be, for example, a one-to-one relationship such a linear line or a curve close to a linear line. Therefore, the composition detection means20of the refrigerating and air-conditioning apparatus100according to Embodiment 1 is able to assuredly detect a refrigerant composition.

In addition, changes in the volume efficiency ηv and the compressor efficiency ηc in response to a change in the proportion of the low-boiling-point refrigerant will be described. As shown inFIGS. 4 and 7, the volume efficiency ηv and the compressor efficiency ηc are certainly affected by a change in the proportion of the low-boiling-point refrigerant (a change in the refrigerant composition), however, the eventual extent of effects the change is having is rather limited.

For example, in a low pressure shell type compressor which comes into a compression process after a motor is cooled within the compressor2, the volume efficiency ηv decreases as the refrigerant density ρs decreases. However, the refrigerant density ρs itself does not change much, and thus a change in the volume efficiency ηv does not affect the power consumption W of the compressor2.

In addition, for example, in a scroll type compressor, the compressor efficiency ηc tends to have a peak at a proper compression ratio dependent on a fixed compression volume ratio. When the low-boiling-point refrigerant having a high density increases, the density ratio between the refrigerant at the suction side of the compressor and the refrigerant at the discharge side of the compressor changes. Thus, even when the compression volume ratio is fixed, the proper compression ratio changes. However, the degree of a change in the density ratio is as small as that of the refrigerant density ρs, and thus a change in the compressor efficiency ηc does not affect the power consumption W of the compressor.

Here, as shown inFIG. 2, when the composition of the circulating refrigerant changes, the enthalpy changes even there is no change in the pressure, and thus the performance of the refrigerating and air-conditioning apparatus100changes. In order for the refrigerating and air-conditioning apparatus100to exert a required level of performance, it is necessary to accurately detect the composition of the circulating refrigerant and perform operation control. In other words, the refrigerating and air-conditioning apparatus100according to Embodiment 1 performs refrigerant composition detection control described below, detects the composition of the circulating refrigerant with high accuracy, and uses the detection result for operation control.

FIG. 6is a flowchart illustrating control for detecting a refrigerant composition in the refrigerating and air-conditioning apparatus100according to Embodiment 1 of the present invention. With reference toFIG. 6, an example of control for detecting a refrigerant composition (refrigerant composition detection control) will be described.

A request signal for refrigerant composition detection control from the controller21is received by the composition detection means20, and the composition detection means20starts refrigerant composition detection control. Then, the processing proceeds to step S1.

The composition detection means20determines whether a given time period has elapsed.

When the given time period has elapsed, the processing proceeds to step S2.

When the given time period has not elapsed, step S1is repeated.

It should be noted that setting a different time interval for other control in the controller21from the given time period eliminates interference and stabilizes the controllability. Thus, for example, the given time period may be set as a short cycle such as 10 sec or 20 sec.

The suction-side pressure detection means11detects the pressure of the refrigerant at the suction side of the compressor2, the suction-side temperature detection means12detects the temperature of the refrigerant at the suction side of the compressor2, the discharge-side pressure detection means13detects the pressure of the refrigerant at the discharge side of the compressor2, and the rotation speed detection means14detects the rotation speed of the compressor2. Then, the processing proceeds to step S3.

The output detection means15detects power consumption Wdet as an output of the compressor2. Then, the processing proceeds to step S4.

Where the composition of the low-boiling-point refrigerant circulating through the refrigeration cycle is α, the composition detection means20assumes and sets the value of the refrigerant composition α as αtmp. Then, the processing proceeds to step S5.

It should be noted that the refrigerant composition α in the last refrigerant composition detection control may be set as a set value of αtmp in entering a loop of steps S4to S11for the first time. Thus, the number of loops required for convergence in steps S4to S11is reduced, and thereby stabilizing the controllability.

The composition detection means20calculates refrigerant physical properties. Specifically, the composition detection means20calculates the refrigerant density ρs of the refrigerant at the suction side of the compressor2, the enthalpy difference Δh in the compression process, and the entropy Ss of the refrigerant at the suction side of the compressor2on the basis of the detection results (Ps, Ts, Pt) of the suction-side pressure detection means11, the suction-side temperature detection means12, and the discharge-side pressure detection means13in step S2, αtmp set in step S4, and formulas 3, 5, and 6. Then, the processing proceeds to step S6.

The composition detection means20calculates compressor characteristics. Specifically, the composition detection means20calculates the volume efficiency ηv and the compressor efficiency ηc on the basis of the detection results (Ps, Ts, Pd, N) of the suction-side pressure detection means11, the suction-side temperature detection means12, the discharge-side pressure detection means13, and the rotation speed detection means14in step S2, the detection result Wdet of the output detection means15in step S3, αtmp set in step S4, and formula 4 for the volume efficiency ηv and formula 7 for the compressor efficiency ηc which are obtained by curve-fitting the unit evaluation result of the compressor2. Then, the processing proceeds to step S7.

It should be noted that curve fitting the unit evaluation result of the compressor2specifies as follows; only the compressor2is subjected to an evaluation conducted under a plurality of conditions, and curve-fit the compressor efficiency ηc obtained from the evaluation result to the expansion formula for the compressor efficiency ηc to determine various constants in the expansion formula.

The composition detection means20calculates power consumption Wcal of the compressor2on the basis of the detection result (Wdet) of the output detection means15in step S3, the refrigerant density ρs of the refrigerant at the suction side of the compressor2and the enthalpy difference Δh in the compression process which are calculated in step S5, the preset stroke volume Vst, the volume efficiency ηv and the compressor efficiency ηc which are calculated in step S6, and formula 8. Then, the processing proceeds to step S8.

The composition detection means20determines whether the power consumption Wcal calculated in step S7is equal to or less than Wdet+δW which is a restricted upper limit.

If the power consumption Weal is equal to or less than Wdet+δW which is the restricted upper limit, the processing proceeds to step S10.

If the power consumption Wcal is not equal to or less than Wdet+δW which is the restricted upper limit, the processing proceeds to step S9.

It should be noted that δW (>0) is an allowable error. In addition, δW may be a fixed value, or may be changed on the basis of the difference between Wcal and Wdet+δW.

The composition detection means20sets, as αtmp, a value obtained by subtracting a predetermined value δα from αtmp set in step S4. Then, the processing proceeds to step S4.

It should be noted that δα may be a fixed value, or may be changed on the basis of the difference between Wcal and Wdet+δW.

The composition detection means20determines whether the power consumption Wcal calculated in step S7is equal to or greater than Wdet−δW which is a restricted lower limit.

If the power consumption Wcal is equal to or greater than Wdet−δW which is the restricted lower limit, the processing proceeds to step S12.

If the power consumption Wcal is not equal to or greater than Wdet−δW which is the restricted lower limit, the processing proceeds to step S11.

It should be noted that δW (>0) is an allowable error. In addition, δW may be a fixed value, or may be changed on the basis of the difference between Wcal and Wdet−δW.

The composition detection means20set, as αtmp, a value obtained by adding a predetermined value δα to αtmp set in step S4. Then, the processing proceeds to step S4.

It should be noted that δα may be a fixed value, or may be changed on the basis of the difference between Weal and Wdet−δW.

The composition detection means20sets αtmp as a composition α of the refrigerant circulating through the refrigeration cycle. Then, the processing proceeds to step S13.

The composition detection means20ends the control for detecting the refrigerant composition.

Here, steps S5to S8are a process calculating the power consumption of the compressor2from the operating state of the compressor2. However, steps S5to S8may be integrated into a single step by assuming all operating states and calculating and tabling the power consumption of the compressor2.

It should be noted that in Embodiment 1, R32 and R1234yf are used as the non-azeotropic refrigerant mixture, but another low-boiling-point refrigerant and another high-boiling-point refrigerant may be used. For example, a hydrofluoroolefin-based refrigerant having double bonds may be used, a low flammable refrigerant may be used, or a flammable HC-based refrigerant may be used.

In addition, the non-azeotropic refrigerant mixture is composed of a mixture of two refrigerants, but may be composed of a mixture of three or more refrigerants. In the case of three or more refrigerants, for example, refrigerant compositions of the other refrigerants (composition relationship formula) relative to a refrigerant whose refrigerant composition is calculated may be calculated previously by an experiment, simulation, or the like. Thus, when the refrigerant composition of one refrigerant is calculated as in the refrigerating and air-conditioning apparatus100according to Embodiment 1, it is also possible to calculate the other refrigerant compositions.

In addition, the refrigerating and air-conditioning apparatus100according to Embodiment 1 uses the power consumption of the compressor as an output of the compressor2. Here, the connection position of the output detection means15may be a primary-side input including inverter loss, or may be a secondary-side input-output not including inverter loss. In calculating formula 7 or 4, when unit evaluation, simulation, or the like of the compressor2is conducted, a condition regarding the connection position of the output detection means15may be adjusted.

In addition, the power consumption of the compressor2is used as the output detected by the output detection means15, but a current of the compressor2may be used. The power consumption of the compressor2is defined as a product of a voltage, a current, and a power factor, and it has been confirmed in a real machine that the power consumption and the current have a one-to-one correlation under the same operating state of the compressor2.

Thus, it means that when the composition detection means20is enabled to calculate power consumption corresponding to a detected current, the output detection means15may be one (a current sensor) that detects the current of the compressor2. In this case, when the output detection means15is commonalized with one installed for the reason such as overcurrent protection, it is possible to reduce the cost.

The refrigerating and air-conditioning apparatus100according to Embodiment 1 detects a refrigerant composition through a control flow as in steps S0to S13. In other words, the refrigerating and air-conditioning apparatus100detects the composition of the refrigerant in accordance with a simple relationship between the refrigerant composition and the power consumption of the compressor2. Thus, the refrigerating and air-conditioning apparatus100is able to detect the composition with high accuracy even when the composition of the circulating refrigerant is changed due to the operating condition.

In addition, the refrigerating and air-conditioning apparatus100detects a refrigerant composition on the basis of the pressure and the temperature of the refrigerant at the suction side of the compressor2and the pressure of the refrigerant at the discharge side of the compressor2. In other words, once the specifications of the compressor2are determined, the refrigerating and air-conditioning apparatus100realizes the control for detecting the refrigerant composition, and does not depend on the specifications of the refrigerating and air-conditioning apparatus100. Thus, the necessity to grasp a refrigerant composition change for each specification of the refrigerating and air-conditioning apparatus100through real machine evaluation or simulation is eliminated, and the necessity to establish a control flow for detecting a refrigerant composition for each refrigerating and air-conditioning apparatus100is eliminated as well. Therefore, the load and the cost of development are reduced.

Furthermore, as shown inFIG. 2, the refrigerating and air-conditioning apparatus100according to Embodiment 1 does not perform composition detection at a branched refrigerant path. In other words, the refrigerating and air-conditioning apparatus100performs composition detection at a single path of the compression process, and hence enables composition detection even in a gas-liquid two-phase state. Thus, the compressor2of the refrigerating and air-conditioning apparatus100is restrained from being damaged, and hence it is possible to suppress reduction of the reliability.

In addition, the refrigerating and air-conditioning apparatus100according to Embodiment 1 detects a refrigerant composition with the components such as the suction-side pressure detection means11, the suction-side temperature detection means12, the discharge-side pressure detection means13, the rotation speed detection means14, and the output detection means15. In other words, the refrigerating and air-conditioning apparatus100does not use expensive components such as a bypass composed of a heat exchanger, an expansion mechanism, and the like and a liquid level detector of an accumulator, and thus the detection of refrigerant composition is able to be performed at low cost.

FIG. 7shows an example of a refrigerant circuit configuration of a refrigerating and air-conditioning apparatus200according to Embodiment 2 of the present invention. In addition, in Embodiment 2, the same parts as those in Embodiment 1 are denoted by the same reference characters, and the difference from Embodiment 1 will be mainly described.

In Embodiment 1, the unit evaluation of the compressor2is conducted under a plurality of conditions, and the unit evaluation result and the expansion formula for the compressor efficiency ηc are curve-fitted to each other to determine various constants in the expansion formula for ηv. In other words, whereas the composition detection means20of the refrigerating and air-conditioning apparatus100according to Embodiment 1 performs unit evaluation and calculation such as curve fitting for calculating ηv and calculates the refrigerant composition α, the composition detection means20of the refrigerating apparatus200according to Embodiment 2 calculates the refrigerant composition α without using formula 4. Thus, it is possible to reduce the load of development, reduce the load of a storage device, and improve the arithmetic processing speed.

In the refrigerating and air-conditioning apparatus200according to Embodiment 2, an outdoor unit51including an accumulator6, a compressor2, a four-way valve53, an outdoor heat exchanger54, etc. and indoor units52each including an indoor heat exchanger57and a pressure reducing mechanism56are connected to each other via a liquid extension pipe55and a gas extension pipe58to form a refrigeration cycle. It should be noted thatFIG. 7illustrates an example where the refrigerating and air-conditioning apparatus200includes two indoor units52, but the present invention is not limited thereto, and the refrigerating and air-conditioning apparatus200may include three or more indoor units52.

The outdoor unit51includes the compressor2which compresses a refrigerant, the four-way valve53which switches a refrigerant flow path, the outdoor heat exchanger54which serves as a condenser during a cooling operation and as an evaporator during a heating operation, and the accumulator6which stores an excess refrigerant.

In addition, the outdoor unit51includes the suction-side pressure detection means11, the suction-side temperature detection means12, the discharge-side pressure detection means13, and the rotation speed detection means14which are described in Embodiment 1. In addition to these detection means11to14, the outdoor unit51includes discharge-side temperature detection means16which detects the temperature of the refrigerant discharged from the compressor2. It should be noted that the outdoor unit51does not include the output detection means15described in Embodiment 1.

Furthermore, the outdoor unit51includes composition detection means20which detects a refrigerant composition on the basis of detection results of these detection means11to14and16; and a controller21which integrally controls the rotation speed of the compressor2and various devices.

Each indoor unit52includes the indoor heat exchanger57which serves as an evaporator during a cooling operation and as a condenser during a heating operation; and the pressure reducing mechanism56which reduces the pressure of the refrigerant to expand the refrigerant.

The liquid extension pipe55and the gas extension pipe58are pipes connecting the outdoor unit51to the indoor units52. The liquid extension pipe55is connected at one end to the outdoor heat exchanger54and connected another end to each pressure reducing mechanism56. In addition, the gas extension pipe58is connected at one end to the four-way valve53and connected at another end to each indoor heat exchanger57.

The four-way valve53switches the refrigerant flow path. The four-way valve53is switched to connect the compressor2to the outdoor heat exchanger54and connect the accumulator6to each indoor heat exchanger57during a cooling operation, and is switched to connected the compressor2to each indoor heat exchanger57and connect the outdoor heat exchanger54to the accumulator6during a heating operation.

The discharge-side temperature detection means16(constituting operating state detection means) detects the temperature of the refrigerant discharged from the compressor2(high-pressure-side refrigerant pressure). In addition, the discharge-side temperature detection means16is connected to the composition detection means20. Here,FIG. 7illustrates an example where the discharge-side temperature detection means16is installed on a refrigerant pipe connecting the accumulator6to the compressor2, but the present invention is not limited thereto. In other words, the discharge-side temperature detection means16may be installed within the compressor2and at a position after the refrigerant is compressed (a position after a compression process). Thus, it is possible to detect a refrigerant composition with high accuracy.

It should be noted that when, similarly to the suction-side temperature detection means12, installing the discharge-side temperature detection means16within the compressor2and at the position before the refrigerant is compressed also suppresses such disturbance, and it is therefore possible to detect a refrigerant composition with high accuracy.

The composition detection means20has stored therein a function described in formula 9, in addition to the functions described in formulas 5 to 7 described in Embodiment 1. The composition detection means20is able to calculate the temperature of the refrigerant at the discharge side of the compressor2on the basis of detection results of the suction-side pressure detection means11, the suction-side temperature detection means12, the discharge-side pressure detection means13, and the rotation speed detection means14, the above formulas 5 to 7, and formula 9. The composition detection means20calculates a refrigerant composition on the basis of the calculated refrigerant temperature and a detection result of the discharge-side temperature detection means16.

Next, the formulas used when the composition detection means20of the refrigerating and air-conditioning apparatus200according to Embodiment 2 calculates a refrigerant composition will be described. Here, where the temperature of the refrigerant at the discharge side of the compressor2is T, formula 9 is obtained from formulas 5 to 7.
T≡TPHα(Pd,Δh/ηc+hs,α)  [Math. 9]

That is, the composition detection means20of the refrigerating and air-conditioning apparatus200according to Embodiment 2 calculates the temperature T of the refrigerant at the discharge side of the compressor2on the basis of the detection results of the suction-side pressure detection means11, the suction-side temperature detection means12, the discharge-side pressure detection means13, and the rotation speed detection means14and formula 9. The composition detection means20calculates a refrigerant composition on the basis of the calculated temperature T of the refrigerant at the discharge side and the detection result of the discharge-side temperature detection means16. For a specific example of the method for calculating a refrigerant composition, refer to a description ofFIG. 9described later.

FIG. 8is a graph illustrating a relationship between the proportion of a low-boiling-point refrigerant included in the circulating refrigerant and the temperature at the discharge side of the compressor2. With reference toFIG. 8, the temperature of the refrigerant at the discharge side of the compressor2when the proportion of the low-boiling-point refrigerant (the composition ratio of the low-boiling-point refrigerant) is changed will be described. It should be noted that inFIG. 8as well, similarly toFIGS. 2 to 5described above, the pressure of the refrigerant at the suction side of the compressor2, the pressure of the refrigerant at the discharge side of the compressor2, subcooling at the outlet of the condenser3, and superheat at the outlet of the evaporator5are fixed, and the composition of the circulating refrigerant is changed.

As shown inFIG. 8, the temperature of the refrigerant at the discharge side of the compressor2monotonously increases. The proportion of the refrigerant composition and the temperature of the refrigerant at the discharge side of the compressor2have a simple correspondence relationship. Therefore, the composition detection means20of the refrigerating and air-conditioning apparatus200according to Embodiment 2 is able to assuredly detect a refrigerant composition.

FIG. 9is a flowchart illustrating control for detecting a refrigerant composition in the refrigerating and air-conditioning apparatus200according to Embodiment 2 of the present invention. With reference toFIG. 9, a method for detecting a refrigerant composition will be described.

A request signal for refrigerant composition detection control from the controller21is received by the composition detection means20, and the composition detection means20starts refrigerant composition detection control. Then, the processing proceeds to step S51.

The composition detection means20determines whether a given time period has elapsed,

When the given time period has elapsed, the processing proceeds to step S52.

When the given time period has not elapsed, step S51is repeated.

It should be noted that setting a different time interval for other control in the controller21from the given time period eliminates interference and stabilizes the controllability. Thus, for example, the given time period may be set as a short cycle such as 10 sec or 20 sec.

The suction-side pressure detection means11detects the pressure of the refrigerant at the suction side of the compressor2, the suction-side temperature detection means12detects the temperature of the refrigerant at the suction side of the compressor2, the discharge-side pressure detection means13detects the pressure of the refrigerant at the discharge side of the compressor2, and the rotation speed detection means14detects the rotation speed of the compressor2. Then, the processing proceeds to step S53.

The discharge-side temperature detection means16detects a temperature Tdet of the refrigerant at the discharge side of the compressor2. Then, the processing proceeds to step S54.

Where the refrigerant composition of the low-boiling-point refrigerant circulating through the refrigeration cycle is α, the composition detection means20sets the value of the refrigerant composition α as αtmp. Then, the processing proceeds to step S55.

It should be noted that the refrigerant composition α in the last refrigerant composition detection control may be set as a set value of αtmp in entering a loop of steps S54to S61for the first time. Thus, the number of loops required for convergence in steps S54to S61is small, and it is possible to stabilize the controllability.

The composition detection means20calculates refrigerant physical properties. Specifically, the composition detection means20calculates the entropy Ss of the refrigerant at the suction side of the compressor2and the enthalpy difference Δh in the compression process on the basis of the detection results (Ps, Ts, Td) of the suction-side pressure detection means11, the suction-side temperature detection means12, and the discharge-side pressure detection means13in step S2, αtmp set in step S54, and formulas 3, 5, and 6. Then, the processing proceeds to step S56.

The composition detection means20calculates a compressor characteristic. Specifically, the composition detection means20calculates compressor efficiencyηc on the basis of the detection results (Ps, Ts, Pd, N) of the suction-side pressure detection means11, the suction-side temperature detection means12, the discharge-side pressure detection means13, and the rotation speed detection means14in step S52, the detection result Tdet of the discharge-side temperature detection means16in step S53, αtmp set in step S54, and formula 7 for the compressor efficiency ηc which is obtained by curve-fitting the unit evaluation result of the compressor2. Then, the processing proceeds to step S57.

The composition detection means20calculates a temperature Tcal of the refrigerant at the discharge side of the compressor2on the basis of the detection result (Tdet) of the discharge-side temperature detection means16in step S53, the enthalpy difference Δh in the compression process which is calculated in step S55, the compressor efficiency ηc which is calculated in step S56, and formula 9. Then, the processing proceeds to step S58.

The composition detection means20determines whether the temperature Tcal calculated in step S57is equal to or less than Tdet+δT which is a restricted upper limit.

If the temperature Tcal is equal to or less than Tdet+δT which is the restricted upper limit, the processing proceeds to step S60.

If the temperature Tcal is not equal to or less than Tdet+δT which is the restricted upper limit, the processing proceeds to step S59.

It should be noted that δT (>0) is an allowable error. In addition, δT may be a fixed value, or may be changed on the basis of the difference between Tcal and Tdet+δT.

The composition detection means20sets, as αtmp, a value obtained by subtracting a predetermined value δT from αtmp set in step S54. Then, the processing proceeds to step S54.

It should be noted that δT may be a fixed value, or may be changed on the basis of the difference between Tcal and Tdet+δT.

The composition detection means20determines whether the temperature Tcal calculated in step S57is equal to or greater than Tdet−δT which is a restricted lower limit.

If the temperature Tcal is equal to or greater than Tdet−δT which is the restricted lower limit, the processing proceeds to step S62.

If the temperature Tcal is not equal to or greater than Tdet−δT which is the restricted lower limit, the processing proceeds to step S61.

It should be noted that δT (>0) is an allowable error. In addition, δT may be a fixed value, or may be changed on the basis of the difference between Tcal and Tdet−δT.

The composition detection means20sets, as αtmp, a value obtained by adding a predetermined value δT to αtmp set in step S54. Then, the processing proceeds to step S54.

It should be noted that δT may be a fixed value, or may be changed on the basis of the difference between Tcal and Tdet−δT.

The composition detection means20sets αtmp as a composition α of the refrigerant circulating through the refrigeration cycle. Then, the processing proceeds to step S63.

The composition detection means20ends the control for detecting the refrigerant composition.

The refrigerating and air-conditioning apparatus200according to Embodiment 2 detects a refrigerant composition through a control flow as in steps S50to S63. In other words, the refrigerating and air-conditioning apparatus200detects the composition of the refrigerant in accordance with a simple relationship between the refrigerant composition and the temperature of the refrigerant at the discharge side of the compressor2. Thus, the refrigerating and air-conditioning apparatus200is able to detect the composition with high accuracy even when the composition of the circulating refrigerant is changed depending on the operating condition.

In addition, the refrigerating and air-conditioning apparatus200detects a refrigerant composition on the basis of the pressure and the temperature of the refrigerant at the suction side of the compressor2and the temperature of the refrigerant at the discharge side of the compressor2. In other words, in the refrigerating and air-conditioning apparatus200, the control for detecting the refrigerant composition is capable of being realized when the specifications of the compressor2alone are determined, and does not depend on the specifications of the refrigerating and air-conditioning apparatus200(unit). Thus, it is not necessary to grasp a refrigerant composition change for each specification of the refrigerating and air-conditioning apparatus200through real machine evaluation or simulation, and it is not necessary to establish a control flow for detecting a refrigerant composition for each refrigerating and air-conditioning apparatus200. Therefore, it is possible to reduce the load and the cost of development.

Furthermore, as shown inFIG. 1, the refrigerating and air-conditioning apparatus100according to Embodiment 1 does not perform composition detection at a branched refrigerant path. In other words, the refrigerating and air-conditioning apparatus100performs composition detection at a single path of the compression process, and hence enables composition detection even in a gas-liquid two-phase state. Thus, the compressor2of the refrigerating and air-conditioning apparatus100is restrained from being damaged, and hence it is possible to suppress reduction of the reliability.

In addition, the refrigerating and air-conditioning apparatus200according to Embodiment 2 detects a refrigerant composition with the components such as the suction-side pressure detection means11, the suction-side temperature detection means12, the discharge-side pressure detection means13, the rotation speed detection means14, and the output detection means15. In other words, the refrigerating and air-conditioning apparatus200does not use expensive components such as a bypass composed of a heat exchanger, an expansion mechanism, and the like and a liquid level detector of an accumulator, and thus is able to detect a refrigerant composition at low cost.

REFERENCE SIGNS LIST