Heat pump apparatus with ejector cycle

In a heat pump apparatus, switching between high efficiency operation, and high capacity operation, is performed according to the state of the load. A main refrigerant circuit uses an ejector. A first sub-refrigerant circuit connects a portion between a heat exchanger and an ejector to a portion between a gas-liquid separator and a heat exchanger A second sub-refrigerant circuit connects a portion between the heat exchanger and the ejector to an injection pipe of a compressor. When the load is medium, refrigerant is circulated in the main refrigerant circuit to perform an efficient ejector aided operation. When the load is large, a high capacity injection operation is performed by flowing refrigerant to the second sub-refrigerant circuit. When the load is small, a simple bypass operation prevents degradation of efficiency by flowing refrigerant to the first sub-refrigerant circuit.

TECHNICAL FIELD

The present invention relates to a heat pump apparatus equipped with an ejector, for example.

BACKGROUND ART

In Patent Literature 1, there is disclosed an air conditioning apparatus that performs switching, depending on the situation, between a power recovery operation utilizing an ejector and a decompression operation using a general expansion valve, without using the ejector.

In this air conditioning apparatus, the operation is switched from the power recovery operation to the decompression operation when pressure decreases at the high pressure side. Thereby, it is possible to inhibit the efficiency degradation due to shortage of the amount of refrigerant circulated to the evaporator caused by shortage of driving force of the ejector.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the air conditioning apparatus disclosed in the Patent Literature 1, when the load is low, such as the case of performing a heating operation in a high outdoor temperature, degradation of efficiency can be inhibited. However, when the load is high, such as the case of performing a heating operation in a low outdoor temperature, it is impossible to perform an operation with high capacity.

An object of the present invention is to provide a heat pump apparatus which, according to the state of the load, is capable of switching between high efficiency operation, being efficient, and high capacity operation, having high capacity. Particularly, the present invention aims to provide a heat pump apparatus having a circuit configuration that can efficiently perform both the high efficiency operation and the high capacity operation.

Solution to Problem

A heat pump apparatus according to the present invention, for example, includes:

a main refrigerant circuit, through which refrigerant circulates, configured by connecting a discharge side of a compressor and one mouth of a first heat exchanger by piping, other mouth of the first heat exchanger and a first inlet of an ejector by piping, an outlet of the ejector and an inlet of a gas-liquid separator by piping, a gas side outlet of the gas-liquid separator and an intake side of the compressor by piping, a liquid side outlet of the gas-liquid separator and one mouth of a second heat exchanger by piping, and other mouth of the second heat exchanger and a second inlet of the ejector by piping;

a first sub-refrigerant circuit configured by connecting by piping a first connection point between the other mouth of the first heat exchanger and the first inlet of the ejector in the main refrigerant circuit to a second connection point between the liquid side outlet of the gas-liquid separator and the one mouth of the second heat exchanger in the main refrigerant circuit, and being provided with a first expansion mechanism in middle of the piping;

a second sub-refrigerant circuit that makes a part of refrigerant flowing through a third connection point between the other mouth of the first heat exchanger and the first inlet of the ejector in the main refrigerant circuit bypass the ejector so as to flow into the compressor, and is provided in its middle with a second expansion mechanism, and

a third heat exchanger that performs heat exchange between refrigerant flowing between the first connection point and the first expansion mechanism in the first sub-refrigerant circuit and refrigerant after passing through the second expansion mechanism in the second sub-refrigerant circuit.

Advantageous Effects of Invention

The heat pump apparatus according to the present invention includes a main refrigerant circuit that utilizes an ejector, and two sub-refrigerant circuits that bypass the ejector. It is possible to perform switching between the high efficiency operation and the high capacity operation by, according to the state of the load, switching the circuit through which the refrigerant flows. Moreover, since the branching positions of the main refrigerant circuit and the two sub-refrigerant circuits, the installation position of the third heat exchanger, and the like are optimized, both the high efficient operation and the high capacity operation can be operated efficiently.

DESCRIPTION OF EMBODIMENTS

First, the structure of a heat pump apparatus100according to Embodiment 1 will be explained.

FIG. 1shows a block diagram of the heat pump apparatus100according to Embodiment 1.

As shown inFIG. 1, the heat pump apparatus100includes a main refrigerant circuit101represented by a solid line, and sub-refrigerant circuits102and103represented by dashed lines.

In the main refrigerant circuit101, a discharge port1B of a compressor1and a heat exchanger2(first heat exchanger) are connected by piping through a four-way valve7. The heat exchanger2and a first inlet41of an ejector4are connected by piping. An outlet46of the ejector4and an inlet5A of a gas-liquid separator5are connected by piping. A gas side outlet5B of the gas-liquid separator5and a suction port1A of the compressor1are connected by piping. A liquid side outlet5C of the gas-liquid separator5and a heat exchanger3(second heat exchanger) are connected by piping. The heat exchanger3and a second inlet42of the ejector4are connected by piping through the four-way valve7.

The four-way valve7performs switching between a first flow path (flow path of the solid line in the four-way valve7ofFIG. 1) and a second flow path (flow path of the dashed line in the four-way valve7ofFIG. 1). The first flow path connects the discharge port1B of the compressor1and the heat exchanger2, and also connects the heat exchanger3and the second inlet42of the ejector4. On the other hand, the second flow path connects the discharge port1B of the compressor1and the heat exchanger3, and also connects the heat exchanger2and the second inlet42of the ejector4.

In the main refrigerant circuit101, there is provided a third expansion valve13(on-off valve), which is an electronic expansion valve, in the pipe between a branch point21(first connection point, and third connection point) to be described later and the first inlet41of the ejector4. Moreover, in the main refrigerant circuit101, there is provided a fourth expansion valve14(on-off valve), which is an electronic expansion valve, in the pipe between the liquid side outlet5C of the gas-liquid separator5and a junction point22(second connection point) to be described later.

In addition, an HFC (hydrofluorocarbon) group refrigerant R410 or a natural refrigerant, such as propane and CO2, is enclosed in the main refrigerant circuit101.

The sub-refrigerant circuits102and103are provided such that their pipe branches from the main refrigerant circuit101, at the branch point21between the heat exchanger2and the first inlet41of the ejector4. The sub-refrigerant circuits102and103are branched at a branch point23into a first sub-refrigerant circuit102and a second sub-refrigerant circuit103.

The first sub-refrigerant circuit102connects piping from the branch point23to the junction point22which is between the liquid side outlet5C of the gas-liquid separator5and the heat exchanger3in the main refrigerant circuit101. In the first sub-refrigerant circuit102, there is provided a first expansion valve11(first expansion mechanism), which is an electronic expansion valve, in the middle of the piping.

The second sub-refrigerant circuit103connects from the branch point23to an injection pipe25provided at the compressor1. In the second sub-refrigerant circuit103, there is provided a second expansion valve12(second expansion mechanism), which is an electronic expansion valve, in the middle of the piping.

The injection pipe25is connected to the intermediate pressure space in the compressor1. The intermediate pressure space is a space where, when the compressor1compresses the refrigerant sucked in through the suction port1A from a low pressure to a high pressure, the pressure of the refrigerant sucked in through the suction port1A turns into an intermediate pressure higher than the low pressure and lower than the high pressure in the compressor1. That is, the intermediate pressure space is a space where the refrigerant sucked in through the suction port1A turns into an intermediate state of compression in the compressor1. For example, in the case of a two-stage compressor in which a low stage compression unit and a high stage compression unit are connected in series, the flow path connecting the low stage compression unit and the high stage compression unit is an intermediate pressure space. In the case of a single-stage compressor in which refrigerant sucked in through the suction port is compressed from a low pressure to a high pressure in one compression unit, the intermediate pressure space is a space in the compression unit (in the compression chamber) where the pressure of refrigerant sucked in through the suction port is an intermediate pressure. Thus, the second sub-refrigerant circuit103is a so-called injection circuit.

The heat pump apparatus100includes a third heat exchanger6(sub-cooler) that performs heat exchange between the refrigerant which flows between the branch point23and the first expansion valve11in the first sub-refrigerant circuit102and the refrigerant which flows between the second expansion valve12and the injection pipe25in the second sub-refrigerant circuit103.

FIG. 2is an explanatory diagram of a control unit10of the heat pump apparatus100.

As shown inFIG. 2, the heat pump apparatus100includes temperature sensors T1, T2, T3, and T4, and the control unit10.

The temperature sensor T1detects a refrigerant temperature at the discharge side of the compressor1.

The temperature sensor T2detects a refrigerant temperature at the outlet side of the heat exchanger2in the heating operation. That is, the temperature sensor T2detects a degree of subcoolinq, of the refrigerant in the heating operation.

The temperature sensor T3detects a refrigerant temperature at the outlet side of the heat exchanger3in the heating operation. That is, the temperature sensor T3detects a degree of superheating of the refrigerant in the heating operation.

The temperature sensor T4detects an outdoor temperature.

The control unit10controls opening degrees of the expansion valves11,12,13, and14according to the temperatures detected by the temperature sensors T1, T2, T3, and T4. For example, the control unit10controls the second expansion valve12according to the outdoor temperature detected by the temperature sensor T4and the refrigerant temperature detected by the temperature sensor T1. Moreover, the control unit10controls the third expansion valve13according to the outdoor temperature detected by the temperature sensor T4and the refrigerant temperature detected by the temperature sensor T2. Further, the control unit10controls the first expansion valve11and the fourth expansion valve14according to the outdoor temperature detected by the temperature sensor T4and the refrigerant temperature detected by the temperature sensor T3.

Furthermore, the control unit10controls the setting of the four-way valve7according to the contents of the operation, such as a heating operation, a cooling operation, and a defrosting operation.

The control unit10is a computer, such as a microcomputer.

Next, the structure and operation of the ejector4will be explained.

FIG. 3is a structure diagram of the ejector4.

As shown inFIG. 3, the ejector4includes two inlets, that is the first inlet41and the second inlet42, and one outlet46. Moreover, the ejector4includes a nozzle section43, a mixing section44, and a diffuser section45. The mixing section44and the diffuser section45are generically called a pressure boosting section.

High-pressure liquid refrigerant serving as a driving flow flows in through the first inlet41. Refrigerant which flowed in through the first inlet41is decompressed/expanded and accelerated in the nozzle section43, and jetted to the mixing section44. That is, the nozzle section43decompresses/expands the refrigerant by isentropically converting the pressure energy of the refrigerant to kinetic energy, and jets it to the mixing section44.

The refrigerant is sucked into the mixing section44through the second inlet42by the entrainment action of the high-speed refrigerant flow jetted from the nozzle section43to the mixing section44. In the mixing section44, the refrigerant jetted from the nozzle section43and the refrigerant sucked in through the second inlet42are mixed. At this time, as the refrigerant is mixed such that the sum of the kinetic energy of the refrigerant jetted from the nozzle section43and the kinetic energy of the refrigerant sucked in through the second inlet42is preserved, the pressure of the refrigerant increases in the mixing section44, thereby the refrigerant turning into a gas-liquid two phase.

The flow path cross-sectional area of the diffuser section45gradually enlarges from the mixing section44side to the outlet46side. Therefore, in the diffuser section45, the speed energy of the refrigerant which flowed in from the mixing section44side is converted into pressure energy, and the pressure increases. Then, the refrigerant flows out of the outlet46.

Now, effect of the ejector cycle utilizing the ejector4will be explained.

FIG. 4is a P-h diagram of an ejector cycle. InFIG. 4, the solid line indicates an ejector cycle and the dashed line indicates a general expansion valve cycle. The general expansion valve cycle is a heat pump cycle in which a compressor, a condenser, an expansion valve, and an evaporator are connected by piping in series.

As shown inFIG. 4, in the ejector cycle, a high-temperature high-pressure refrigerant discharged from the compressor1radiates heat and is cooled in the heat exchanger2and flows into the ejector4through the first inlet41. As described above, the refrigerant having flowed into the ejector4through the first inlet41is decompressed and expanded in the nozzle section43. Moreover, the low temperature refrigerant jetted from the nozzle section43is mixed with the high temperature refrigerant flowed out of the heat exchanger3in the mixing section44, and its temperature increases. Furthermore, the refrigerant is pressure-boosted in the diffuser section45, and flows into the gas-liquid separator5to be separated into gas and liquid. A gaseous refrigerant separated in the gas-liquid separator5is sucked in into the compressor1, and a liquid refrigerant flows into the heat exchanger3.

By such operation, the pressure of the refrigerant sucked in by the compressor1in the ejector cycle is higher by ΔP than that of the refrigerant sucked in by the compressor in the general expansion valve cycle. Since the pressure of the refrigerant sucked in by the compressor1is higher by ΔP, the power to be supplied to the compressor1can be reduced by as much as ΔP, thereby increasing the COP (Coefficient of Capacity).

The ejector4is a two phase flow ejector including the nozzle section43, the mixing section44, and the diffuser section45as described above. The dimension of each part of the ejector4is tuned and designed to be optimal, based on high and low pressures and a circulation flow rate under the load (for example, outdoor temperature being higher than or equal to 2° C. and lower than 7° C.) in the heat pump cycle.

In the expansion valve generally used, pressure energy is lost when the refrigerant is expanded. On the other hand, in the ejector4, as described above, when the refrigerant is expanded in the nozzle section43, the pressure energy of the refrigerant is converted to kinetic energy, and further, the kinetic energy is converted to pressure energy in the mixing section44and the diffuser section45. By this, a part of pressure energy loss is recovered.

Next, the operation of the heat pump apparatus100according to Embodiment 1 will be explained. Here, heating operation is explained as an example. The heating operation described herein includes not only heating the air in a room but also heating water for supplying hot water.

FIGS. 5 to 8show a flow of the refrigerant in each operation state in the heat pump apparatus100. The arrows inFIGS. 5 to 8represent flows of the refrigerant. Moreover, the parenthesized “open” or “closed” shown beside the reference sign of the expansion valve11,12,13, or14represents an opening degree of the expansion valves11,12,13, or14. If it is “open”, it represents a state where the opening degree of the expansion mechanism concerned is larger than a predetermined opening degree and the refrigerant is in a flowing state. If it is “closed”, it represents a state where the opening degree of the expansion mechanism concerned is smaller (for example, closed completely) than a predetermined opening degree and the refrigerant is not in a flowing state. Moreover, the circuit shown in a solid line represents a circuit through which the refrigerant flows, and the circuit shown in a dashed line represents a circuit through which the refrigerant does not flow.

First, the case of performing an ejector aided operation utilizing the ejector4will be explained. The ejector aided operation is performed when the load is about medium. Concerning the load, it will be described in detail later. The case of the load being medium indicates the case where the outdoor temperature is higher than or equal to 2° C. and lower than 7° C., for example. “Outdoor temperature being higher than or equal to 2° C. and lower than 7° C.” is a standard temperature zone in an annual heating operation, and this temperature zone accounts for about half of the entire heating operation time. Therefore, increasing the operation efficiency (COP) in this temperature zone makes it possible to contribute most to improvement in efficiency of all the operations and thus to greatly reduce the electric power annually consumed by the heat pump apparatus. Although the ejector4is used for increasing the COP, since the effect of the ejector4cannot be derived if the high-pressure side pressure of the heat pump apparatus does not have a certain amount of height, the ejector4is not used at the temperature (in this case, higher than or equal to 7° C.) where the heating load is low.

FIG. 5shows the flow of the refrigerant in the case of performing an ejector aided operation.

When the load is about medium, the control unit10sets the first expansion valve11and the second expansion valve12to be fully closed, and the third expansion valve13and the fourth expansion valve14to be open larger than a predetermined opening degree so that a suitable amount of refrigerant may flow therethrough. Moreover, the control unit10sets the four-way valve7as the first flow path (the flow path shown in a solid line in the four-way valve7ofFIG. 5).

In such a case, a high-temperature high-pressure gaseous refrigerant discharged from the compressor1radiates heat and condenses in the heat exchanger2so as to be liquefied to be a medium-temperature high-pressure liquid refrigerant. That is, the heat exchanger2operates as a radiator (condenser) in the heating operation. As described above, the heating operation includes not only heating the air in a room but also heating water for supplying hot water. Therefore, the heat exchanger2may perform a heat exchange between the refrigerant and the air, or between the refrigerant and the water. Then, all of the medium-temperature high-pressure liquid refrigerant flows toward the ejector4side from the branch point21, and flows into the ejector4through the first inlet41.

As explained based onFIG. 3, the refrigerant which flowed into the ejector4through the first inlet41is decompressed and accelerated in the nozzle section43, and jetted to the mixing section44. The refrigerant jetted to the mixing section44is mixed with the refrigerant gas flowing in through the second inlet42, and turns into gas-liquid two phase since the pressure increases to some extent. Then, the pressure of the gas-liquid two phase refrigerant further increases in the diffuser section45to be flowed out of the outlet46of the ejector4.

The refrigerant having flowed out of the ejector4flows into the gas-liquid separator5. The gas-liquid two phase refrigerant which has flowed in the gas-liquid separator5is separated into liquid refrigerant and gaseous refrigerant. The separated gaseous refrigerant flows out of the gas side outlet5B to be sucked in by the compressor1. Moreover, an oil return hole, which is not shown, is provided in the U-tube configuring the gas side outlet5B, and oil accumulated in the gas-liquid separator5is returned to the compressor1. On the other hand, after flowing out of the liquid side outlet5C and being decompressed by the fourth expansion valve14, the separated liquid refrigerant takes heat from the air in the heat exchanger3to be evaporated and turned into a gaseous refrigerant. That is, the heat exchanger3operates as an evaporator in the heating operation. The gaseous refrigerant, which has flowed out of the heat exchanger3, is sucked in to the mixing section44through the second inlet42of the ejector4and mixed with the refrigerant jetted from the nozzle section43as described above.

Then, the refrigerant having been sucked in the compressor1is compressed to be a high-temperature high-pressure gaseous refrigerant to be discharged and flowed into the heat exchanger2again.

In the ejector aided operation, by recovering pressure energies which are lost in the general expansion valve by utilizing the ejector4, the pressure of the refrigerant to be sucked in by the compressor1increases. Therefore, the efficiency of the heat pump apparatus100is enhanced.

Next, the case of performing an injection operation without using the ejector4will be explained. The injection operation is executed when heating capacity is deficient along with that the outdoor temperature becomes low and heating capacity higher than that of the ejector aided operation is needed. That is, the injection operation is performed when the load is large. The case of the load being large indicates the case where the outdoor temperature is lower than 2° C., for example.

FIG. 6shows the flow of the refrigerant in the case of performing an injection operation.

When the load is large, the control unit10sets the third expansion valve13and the fourth expansion valve14to be fully closed, and the first expansion valve11and the second expansion valve12to be open larger than a predetermined opening degree such that a suitable amount of refrigerant flows therethrough. For example, the control unit10adjusts the flow amount of the refrigerant by controlling the opening degree of the first expansion valve11so that a super heat at the outlet of the heat exchanger3may become higher than or equal to 5° C. and lower than 10° C. Moreover, the control unit10adjusts the flow amount of the refrigerant by controlling the opening degree of the second expansion valve12so that a discharge temperature of the compressor1may become a suitable temperature not exceeding a predetermined temperature. Moreover, the control unit10sets the four-way valve7in the first flow path (the flow path shown in the solid line in the four-way valve7ofFIG. 6).

In such a case, as well as the case of the ejector aided operation, the high-temperature high-pressure gaseous refrigerant discharged from the compressor1radiates heat and condenses in the heat exchanger2so as to be liquefied to be a medium-temperature high-pressure liquid refrigerant. Then, all of the medium-temperature high-pressure liquid refrigerant flows into the sub-refrigerant circuits102and103from the branch point21, not flowing to the ejector4side. A part of the refrigerant flowing through the sub-refrigerant circuits102and103is distributed at the branch point23to the first sub-refrigerant circuit102, and the rest is distributed to the second sub-refrigerant circuit103.

The refrigerant distributed to the second sub-refrigerant circuit103is expanded by the second expansion valve12and turns into a gas-liquid two phase refrigerant. The refrigerant expanded by the second expansion valve12and flowing through the second sub-refrigerant circuit103, and the refrigerant flowing through the first sub-refrigerant circuit102are heat-exchanged in the third heat exchanger6, and thereby the refrigerant flowing through the second sub-refrigerant circuit103is heated and the refrigerant flowing through the first sub-refrigerant circuit102is cooled.

The refrigerant having been cooled by the third heat exchanger6and flowing through the first sub-refrigerant circuit102is expanded by the first expansion valve11and flows into the heat exchanger3. The refrigerant having flowed into the heat exchanger3takes heat from the air in the heat exchanger3to be evaporated and turned into a gaseous refrigerant. The gaseous refrigerant flowed out of the heat exchanger3flows into the gas-liquid separator5, passing through the second inlet42, the mixing section44and the diffuser section45of the ejector4. The refrigerant having flowed into the gas-liquid separator5does not flow out from the liquid side outlet5C since the fourth expansion valve14is closed, but flows out from the gas side outlet5B to be sucked into the compressor1to be compressed.

On the other hand, the refrigerant having been heated by the third heat exchanger6and flowing through the second sub-refrigerant circuit103is injected into the intermediate pressure space in the compressor1through the injection pipe25.

In the injection operation, the refrigerant which flowed out of the heat exchanger2(condenser) is injected into the intermediate pressure space of the compressor1. Consequently, the circulation amount of the refrigerant increases and the heating capacity is enhanced.

Next, the case of performing a simple bypass operation which does not use the ejector4nor performs the injection operation will be explained. The simple bypass operation is performed when the load is small. The case of the load being small indicates the case where the outdoor temperature is higher than or equal to 7° C., for example.

FIG. 7shows the flow of the refrigerant in the case of performing a simple bypass operation.

When the load is small, the control unit10sets the second expansion valve12, the third expansion valve13, and the fourth expansion valve14to be fully closed, and the first expansion valve11to be open larger than a predetermined opening degree so that a suitable amount of refrigerant may flow therethrough. For example, the control unit10adjusts the flow amount of the refrigerant by controlling the opening degree of the first expansion valve11so that a super heat at the outlet of the heat exchanger3may become higher than or equal to 5° C. and lower than 10° C. Moreover, the control unit10sets the four-way valve7in the first flow path (the flow path shown in the solid line in the four-way valve7ofFIG. 7).

In such a case, as well as the case of the ejector aided operation, the high-temperature high-pressure gaseous refrigerant discharged from the compressor1radiates heat and condenses in the heat exchanger2so as to be liquefied to be a medium-temperature high-pressure liquid refrigerant. Then, all of the medium-temperature high-pressure liquid refrigerant flows into the sub-refrigerant circuits102and103from the branch point21, not flowing to the ejector4side. All of the refrigerant having flowed into the sub-refrigerant circuits102and103is led, at the branch point23, to the first sub-refrigerant circuit102side. The refrigerant flowing through the first sub-refrigerant circuit102is expanded by the first expansion valve11, and flows into the heat exchanger3. The refrigerant having flowed into the heat exchanger3takes heat from the air in the heat exchanger3to be evaporated and turned into a gaseous refrigerant. The gaseous refrigerant flowed out of the heat exchanger3flows into the gas-liquid separator5, passing through the second inlet42, the mixing section44and the diffuser section45of the ejector4. The refrigerant having flowed into the gas-liquid separator5does not flow out from the liquid side outlet5C since the fourth expansion valve14is closed, but flows out from the gas side outlet5B to be sucked into the compressor1to be compressed.

That is, a general heating operation is performed in the simple bypass operation.

When the load is low, the pressure at the high pressure side becomes low. That is, the pressure of the refrigerant which flows in through the first inlet41becomes low. Therefore, a sufficient driving force cannot be obtained in the nozzle section43, and refrigerant cannot be sufficiently sucked in through the second inlet42in the mixing section44. As a result, the amount of refrigerant circulated to the heat exchanger3(evaporator) decreases, and the efficiency becomes degraded. However, in the simple bypass operation, by bypassing without using the ejector4, it becomes possible to prevent the amount of refrigerant circulated to the heat exchanger3from decreasing, and thereby degradation of the efficiency can be inhibited.

Next, a defrosting operation will be explained. In the case of performing a heating operation in a low outdoor temperature, since the heat exchanger3is frosted, the defrosting operation needs to be executed.

FIG. 8shows the flow of the refrigerant in the case of performing a defrosting operation.

When performing the defrosting operation, the control unit10sets the second expansion valve12, the third expansion valve13, and the fourth expansion valve14to be fully closed, and the first expansion valve11to be open larger than a predetermined opening degree so that a suitable amount of refrigerant may flow therethrough. For example, the control unit10adjusts the flow amount of the refrigerant by controlling the opening degree of the first expansion valve11so that a super heat at the outlet of the heat exchanger2may become higher than or equal to 5° C. and lower than 10° C. Moreover, the control unit10sets the four-way valve7in the second flow path (the flow path shown in the dashed line in the four-way valve7ofFIG. 8).

In such a case, the high-temperature high-pressure gaseous refrigerant discharged from the compressor1radiates heat to the air and condenses in the heat exchanger3so as to be liquefied to be a high pressure liquid refrigerant. At this time, the frost formed on the heat exchanger3is melted. That is, the heat exchanger3operates as a radiator (condenser) in the defrosting operation. The liquid refrigerant flowed out of the heat exchanger3is decompressed by the first expansion valve11. The refrigerant decompressed by the first expansion valve11flows into the heat exchanger2and absorbs heat to be evaporated to some extent. The gaseous refrigerant flowed out of the heat exchanger2flows into the gas-liquid separator5, passing through the second inlet42, the mixing section44and the diffuser section45of the ejector4. The refrigerant having flowed into the gas-liquid separator5does not flow out from the liquid side outlet5C since the fourth expansion valve14is closed, but flows out from the gas side outlet5B to be sucked into the compressor1to be compressed.

Now, the relation between the load and the heating capacity and the relation between the load and the COP concerning the heat pump apparatus100will be explained. In here, explanation will be given using an outdoor temperature as an index showing a load.

FIG. 9shows a relation between an outdoor temperature and a heating capacity and a relation between an outdoor temperature and COP concerning the heat pump apparatus100according to Embodiment 1. InFIG. 9, the solid lines show the heating capacity and the COP of the heat pump apparatus100, and whereas the dashed lines show the heating capacity and the COP of a general heat pump apparatus. The portion where the solid line and the dashed line are overlapped is shown only by the solid line. Therefore, the portion where both the solid line and the dashed line are shown is a portion where there is a difference between a general heat pump apparatus and the heat pump apparatus100.

That is, concerning COP in the case of the outdoor temperature being higher than or equal to 2° C. and lower than 7° C., there is a difference between the heat pump apparatus generally used and the heat pump apparatus100of the present invention, and concerning heating capacity in the case of the outdoor temperature being lower than 2° C., there is also a difference between them.

When the outdoor temperature is higher than or equal to 2° C. and lower than 7° C., the heat pump apparatus100performs an ejector aided operation. In the ejector aided operation, as described above, the pressure energy in the decompression process is recovered by the ejector4. Therefore, the COP (the COP represented by the sign32ofFIG. 9) of the heat pump apparatus100is higher compared with the COP (the COP represented by the sign33ofFIG. 9) of a general heat pump apparatus.

When the outdoor temperature is lower than 2 degrees, the heat pump apparatus100performs an injection operation. In the injection operation, as described above, the refrigerant is injected into the intermediate pressure space of the compressor1, and the refrigerant flow amount increases. Therefore, the heating capacity (the heating capacity represented by the sign30ofFIG. 9) of the heat pump apparatus100is higher compared with the heating capacity (the heating capacity represented by the sign31ofFIG. 9) of the general heat pump apparatus.

When the outdoor temperature is higher than or equal to 7° C., the heat pump apparatus100performs a simple bypass operation. As described above, the simple bypass operation performs bypassing without using the ejector4. Therefore, it does not occur that the amount of refrigerant circulated to the heat exchanger3which operates as an evaporator becomes insufficient due to a driving force shortage of the ejector4caused by a decrease of the load resulting from an increase of the outdoor temperature. Accordingly, the COP does not become lower compared with the general heat pump apparatus.

As described above, the heat pump apparatus100can perform a high efficiency and high capacity operation as a whole by performing, depending on the state of the load, switching of the circuit to flow the refrigerant.

In the explanation described above, the control unit10controls the expansion valves11,12,13,14, etc. according to the outdoor temperature at the time of performing a heating operation. The heat pump apparatus100herein includes a load detection unit (not shown), by which the outdoor temperature is detected.

In the explanation described above, the control unit10controls the expansion valves11,12,13,14, etc. depending on whether the outdoor temperature at the time of performing a heating operation is lower than 2° C., higher than or equal to 2° C. and lower than 7° C., or higher than or equal to 7° C. However, the temperatures 2° C. and 7° C. are just examples, and it is not limited thereto.

Moreover, in the explanation described above, an outdoor temperature is used as an index for determining a load. However, the index for determining a load is not limited to the outdoor temperature.

The load herein is a required load being a heat amount necessary for making a temperature of fluid, which is heat-exchanged with refrigerant flowing through the main refrigerant circuit101in the heat exchanger2, be a predetermined temperature. That is, the load is a heat amount necessary for letting the temperature of the air in a room be a predetermined temperature in the case of an air conditioning operation, and is a temperature necessary for letting the temperature of the water to be supplied be a predetermined temperature in the case of a hot-water supply operation.

Therefore, the load detection unit may detect, as an index for determining the load, not an outdoor temperature but an evaporating pressure or a temperature of the heat exchanger3, or may detect a compressor frequency which serves as an index of a refrigerant circulation amount. Moreover, the load detection unit may detect a temperature at the load side, such as a room temperature to be warmed in air conditioning, a supply water temperature, and a feed water temperature, or may detect information at the high pressure side, such as a condensing pressure and a temperature of the heat exchanger2. The supply water temperature indicates a temperature of liquid such as water after being heated by the heat exchanger2when the heat exchanger2is a heat exchanger performing a heat exchange between refrigerant and liquid such as water. The feed water temperature indicates a temperature of liquid such as water before being heated by the heat exchanger2when the heat exchanger2is a heat exchanger performing a heat exchange between refrigerant and liquid such as water.

Then, the control unit10may control the expansion valves11,12,13,14, etc. by judging the size of the load based on these indices.

Moreover, the load detection unit may judge the load by detecting a plurality of indices.

For example, the load detection unit may detect an outdoor temperature and a feed water temperature. In that case, for example, the control unit10performs an ejector aided operation when the outdoor temperature is higher than or equal to 2° C. and lower than 7° C. and the feed water temperature is high (for example, higher than or equal to 35° C.). Moreover, the control unit10may perform an injection operation when the outdoor temperature is lower than 2° C. or the feed water temperature is low (for example, lower than 35° C.), and perform a simple bypass operation when the outdoor temperature is higher than or equal to 7° C.

Moreover, for example, the load detection unit may detect an outdoor temperature and a compressor frequency. In that case, for example, the control unit10may perform an ejector aided operation when the outdoor temperature is higher than or equal to 2° C. and lower than 7° C. and the compressor frequency is large (for example, a frequency being greater than or equal to 90% of the rated capacity of the compressor1). Moreover, the control unit10may perform an injection operation when the outdoor temperature is lower than 2° C. or the compressor frequency is low (for example, a frequency being less than 90% of the rated capacity of the compressor1), and perform a simple bypass operation when the outdoor temperature is higher than or equal to 7° C.

In any case of whichever index is used for judging the load, when the control unit10judges that the load is larger than a first load which has been pre-set, it controls to execute an injection operation. Moreover, when the control unit10judges that the load is lower than the first load and larger than a second load which has been set to be lower than the first load, it controls to execute an ejector aided operation. Moreover, when the control unit10judges that the load is smaller than the second load, it controls to execute a simple bypass operation.

The first load and the second load shall be preset in the memory included in the control unit10.

Moreover, the control unit10may perform controlling to execute an injection operation or a simple bypass operation when, other than the size of the load, the throttle amount of the nozzle section43of the ejector4is insufficient or superfluous, or the nozzle section43of the ejector4is occluded by dust, etc. When the ejector4is in the state described above, if the operation utilizing the ejector4is performed, the efficiency becomes degraded. Then, by performing an injection operation or a simple bypass operation in which refrigerant flows bypassing the ejector4, the efficiency degradation can be prevented.

As shown inFIG. 3, if the nozzle section43of the ejector4is a fixed throttle whose throttling amount cannot be adjusted, the amount of throttling of the ejector4becomes insufficient or superfluous since the evaporation temperature increases or decreases with the change of the outdoor temperature and the room temperature. Therefore, the load detection unit can detect a state where the amount of throttling of the ejector4is insufficient or superfluous by detecting an outdoor temperature and a room temperature. Moreover, the load detection unit can also detect a state where the throttling amount of the ejector4is insufficient or superfluous, based on a temperature and a pressure of each part of the refrigerant circuit. Further, the load detection unit may detect a state where the nozzle section43of the ejector4is occluded, by detecting that the super heat at the outlet of the heat exchanger3is higher than a predetermined temperature.

In the explanation described above, the fourth expansion valve14is an electronic expansion valve, but it may also be a check valve. When the fourth expansion valve14is a check valve, it is necessary to provide, in the pipe connecting the gas-liquid separator5and the junction point22, a throttle mechanism which is connected to the fourth expansion valve14in series.

In the above explanation, as shown inFIG. 3, the example of the ejector4being a fixed throttle is described. However, as shown inFIG. 10, it is also acceptable that the ejector4includes an electromagnetic coil47and a needle48and controls the flow amount of refrigerant passing through the nozzle section43by controlling the electromagnetic coil47in order to change the diameter of the nozzle section43by using the needle48.

In the above explanation, the flow amount of refrigerant flowing in through the first inlet41of the ejector4is adjusted by controlling the opening degree of the third expansion valve13. However, in the case that the flow amount of refrigerant passing through the nozzle section43can be controlled with the needle48by controlling the electromagnetic coil47, it is also acceptable to adjust the flow amount of the refrigerant flowing in through the first inlet41of the ejector4by controlling the electromagnetic coil47.

Moreover, in the above explanation, R410 and propane are cited as examples of the refrigerant. However, the refrigerant is not limited to propane. It is also acceptable to use a refrigerant of HFO (hydro fluoro olefin) system having low GWP (Global Warming Potential) or a mixed refrigerant produced by mixing refrigerants of HFO system. These refrigerants are flammable or low flammable. However, in the case that the heat exchanger2is provided in the outdoor unit, a flammable refrigerant does not flow into the space at the interior side, and thereby it can be used safely.

The heat pump apparatus100according to Embodiment 1 performs an ejector aided operation when the outdoor temperature is higher than or equal to 2° C. and lower than 7° C., and performs an injection operation without using the ejector4when the outdoor temperature is lower than 2° C. That is, in Embodiment 1, the operation utilizing the ejector4and the injection operation are alternatively switched according to the outdoor temperature.

The heat pump apparatus100according to Embodiment 2 newly sets up a reference temperature B ° C., which is lower than 2° C., as the outdoor temperature. When the outdoor temperature is higher than or equal to B ° C. and lower than 2° C., the heat pump apparatus100performs a compound operation which utilizes the ejector4and makes the refrigerant flow also to the second sub-refrigerant circuit103. Moreover, the heat pump apparatus100performs an injection operation using no ejector4when the outdoor temperature is lower than B ° C.

That is, the control unit10included in the heat pump apparatus100according to Embodiment 2 controls to execute a compound operation when the load is higher than the first load and smaller than a third load that has been set higher than the first load. Moreover, the control unit10controls to execute an injection operation when the load is larger than the third load.

FIG. 11shows the flow of the refrigerant in the case of performing a compound operation.

When performing the compound operation, the control unit10sets the opening degrees of the first expansion valve11, the second expansion valve12, the third expansion valve13, and the fourth expansion valve14to be open larger than a predetermined opening degree so that a suitable amount of refrigerant may flow therethrough. Moreover, the control unit10sets the four-way valve7in the first flow path (the flow path shown in the solid line in the four-way valve7ofFIG. 11).

The high-temperature high-pressure gaseous refrigerant discharged from the compressor1radiates heat and condenses in the heat exchanger2so as to be liquefied to be a medium-temperature high-pressure liquid refrigerant, whose part flows into the ejector4from the branch point21and the rest flows into the sub-refrigerant circuits102and103. A part of the refrigerant which has flowed into the sub-refrigerant circuits102and103is distributed, at the branch point23, to the first sub-refrigerant circuit102and the rest is distributed to the second sub-refrigerant circuit103. That is, the refrigerant flows through all the circuits.

The heat pump apparatus100according to Embodiment 2, as well as the heat pump apparatus100according to Embodiment 1, performs an operation utilizing the ejector4when the outdoor temperature is higher than or equal to 2° C. and lower than 7° C. and thus the load is about medium. Moreover, the heat pump apparatus100performs a simple bypass operation when the outdoor temperature is higher than or equal to 7° C. and thus the load is small. Moreover, the heat pump apparatus100performs an injection operation using no ejector4when the outdoor temperature is lower than B ° C.

FIG. 12shows a relation between an outdoor temperature and a heating capacity and a relation between an outdoor temperature and COP concerning the heat pump apparatus100according to Embodiment 2. Regarding the relation between an outdoor temperature and a heating capacity and the relation between an outdoor temperature and COP shown inFIG. 12, only a part differing fromFIG. 9will now be explained.

When the outdoor temperature is higher than or equal to B ° C. and lower than 2° C., the heat pump apparatus100performs a compound operation. Therefore, the heating capacity (the heating capacity represented by the sign34inFIG. 12) of the heat pump apparatus100according to Embodiment 2 is higher compared with the heating capacity (the heating capacity represented by the sign31inFIG. 12) of a general heat pump apparatus. However, the heating capacity of the heat pump apparatus100according to Embodiment 2 is a little lower compared with the heating capacity (the heating capacity represented by the sign30ofFIG. 9) of the heat pump apparatus100according to Embodiment 1.

On the other hand, when the outdoor temperature is higher than or equal to B ° C. and lower than 2° C., COP (COP represented by the sign35inFIG. 12) of the heat pump apparatus100according to Embodiment 2 is higher compared with COP (COP represented by the36inFIG. 12) of a general heat pump apparatus. That is, COP of the heat pump apparatus100according to Embodiment 2 is higher compared with COP of the heat pump apparatus100according to Embodiment 1.

Thus, compared with the heat pump apparatus100according to Embodiment 1, the heat pump apparatus100according to Embodiment 2 can perform an operation balanced between the capacity and the efficiency when the load is large.

As well as Embodiment 1, the index for judging the load may be not only the outdoor temperature but also other index.

To sum up the above, the heat pump apparatus100is characterized in that it includes a refrigerating cycle apparatus including a refrigerant circuit which is configured by, circularly connecting in series by piping, a compressor, a radiator that radiates heat to cool refrigerant discharged from the compressor, an ejector that decompresses and expands the refrigerant discharged from the radiator and increases the inlet pressure of the compressor by converting the expansion energy to the pressure energy, a gas-liquid separator that separates the refrigerant discharged from the ejector into a gaseous refrigerant and a liquid refrigerant, and an evaporator that evaporates the liquid refrigerant separated from the gas-liquid separator, and a sub-refrigerant circuit in which the liquid refrigerant outlet portion of the gas-liquid separator and the high-pressure side inlet portion of the ejector are connected by piping through a first throttling device, wherein a sub-cooler is provided between the high-pressure side upstream portion and the first throttling device in the sub-refrigerant circuit.

Moreover, the heat pump apparatus100is characterized in that there is provided an on-off valve at the liquid refrigerant outlet portion of the gas-liquid separator.

Furthermore, it is characterized in that the on-off valve is a check valve.

Furthermore, it is characterized in that the cold heat source of the sub-cooler is a low-pressure two phase refrigerant obtained by decompressing a part of the refrigerant of the sub-refrigerant circuit.

Moreover, it is characterized in that the refrigerant evaporated by the sub-cooler is bypassed to the intermediate pressure portion, which is in the middle of compression, of the compressor.

It is characterized in that the refrigerant circuit and the sub-refrigerant circuit are switched according to an outdoor temperature.

It is characterized in that the outdoor temperature includes a first outdoor temperature being comparatively high and a second outdoor temperature being comparatively low.

It is characterized in that the sub-cooler is not used when higher than or equal to the first outdoor temperature, and the sub-cooler is used when lower than the first outdoor temperature.

It is characterized in that the ejector is not used when higher than or equal to the second outdoor temperature, and the ejector is used when higher than or equal to the first outdoor temperature and lower than the second outdoor temperature.

REFERENCE SIGNS LIST