REFRIGERATION CYCLE DEVICE

Abstract

 A refrigeration cycle apparatus includes a refrigerant circuit including a compressor, a load-side heat exchanger, a high-pressure side flow path of an internal heat exchanger, an expansion device, and a heat-source side heat exchanger, an injection circuit branched from between the internal heat exchanger and the expansion device and connected to an injection port of the compressor through another expansion device and a low-pressure side flow path of the internal heat exchanger, a suction temperature sensor measuring a suction temperature of the compressor, a suction pressure detection device measuring a suction pressure of the compressor, a discharge temperature sensor measuring a discharge temperature of the compressor, a discharge pressure sensor measuring a discharge pressure of the compressor, an internal heat exchanger outlet temperature sensor measuring a refrigerant temperature at an outlet of the high-pressure side flow path of the internal heat exchanger, and a controller configured to calculate subcooling at an outlet of the load-side heat exchanger by using a measured value of each of the suction temperature sensor, the suction pressure detection device, the discharge temperature sensor, the discharge pressure sensor, and the internal heat exchanger outlet temperature sensor, and information related to a position of the injection port in a compression unit of the compressor.

Description

Technical Field

[0001] The present invention relates to a refrigeration cycle apparatus, and in particular, relates to a refrigeration cycle apparatus capable of performing gas injection to improve heating capacity in a low outside air temperature.

Background Art

[0002] In a conventional refrigeration cycle apparatus, there has been a technique capable of improving heating capacity (hot-water supplying capacity) in a low outside air temperature by gas injection.

[0003] For example, Patent Literature 1 discloses an example using the technique. In Patent Literature 1, a heat pump water heater has as an object to prevent decrease in heating capacity even in a low outside air temperature, and has a refrigerant circuit including a compressor having an injection port, a load-side heat exchanger, an internal heat exchanger, a pressure vessel, a heat-source side heat exchanger, and an expansion device. Then, technical details for calculating subcooling (a degree of subcooling) at an outlet of the load-side heat exchanger and feeding the calculated subcooling back to control of the expansion device are described.

Citation List

Patent Literature

[0004] Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2009-186121

Summary of Invention

Technical Problem

[0005] In general, in a refrigeration cycle apparatus, heating capacity is controlled by calculating subcooling from a measured value of a discharge pressure measured by a discharge pressure sensor and a measured value of a refrigerant temperature measured by a temperature sensor provided at an outlet of a load-side heat exchanger and controlling an expansion device on the basis of the subcooling. Consequently, for exerting a capability of a refrigeration cycle apparatus, it is necessary to calculate the subcooling with accuracy.

[0006] In the above-described Patent Literature 1, the load-side heat exchanger and the internal heat exchanger are configured separately, and, as the temperature sensor for measuring a measured temperature value used for calculating the subcooling, a temperature sensor provided between the load-side heat exchanger and the internal heat exchanger is used. However, when the internal heat exchanger is placed directly downstream of the load-side heat exchanger, or, when the load-side heat exchanger and the internal heat exchanger will be integrally configured in future for responding to recent downsizing requests, it is impossible to provide the temperature sensor between the load-side heat exchanger and the internal heat exchanger. In this case, a problem of incapability to calculate the subcooling occurs.

[0007] The present invention has been made in consideration of the above situation and has as an object to provide a refrigeration cycle apparatus capable of calculating subcooling without using a refrigerant temperature between a load-side heat exchanger and an internal heat exchanger.

Solution to Problem

[0008] A refrigeration cycle apparatus according to an embodiment of the present invention includes a refrigerant circuit including a compressor, a load-side heat exchanger, a high-pressure side flow path of an internal heat exchanger, a first expansion device, and a heat-source side heat exchanger, an injection circuit branched from between the internal heat exchanger and the first expansion device and connected to an injection port of the compressor through a second expansion device and a low-pressure side flow path of the internal heat exchanger, a suction temperature sensor measuring a suction temperature of the compressor, a suction pressure detection device measuring a suction pressure of the compressor, a discharge temperature sensor measuring a discharge temperature of the compressor, a discharge pressure sensor measuring a discharge pressure of the compressor, an internal heat exchanger outlet temperature sensor provided at an outlet of the high-pressure side flow path of the internal heat exchanger and measuring a refrigerant temperature at the outlet of the high-pressure side flow path, and a controller configured to calculate subcooling at an outlet of the load-side heat exchanger by using a measured value of each of the suction temperature sensor, the suction pressure detection device, the discharge temperature sensor, the discharge pressure sensor, and the internal heat exchanger outlet temperature sensor, and information related to a position of the injection port in a compression unit of the compressor.

Advantageous Effects of Invention

[0009] According to an embodiment of the present invention, it is possible to obtain a refrigeration cycle apparatus capable of calculating subcooling without using a refrigerant temperature between a load-side heat exchanger and an internal heat exchanger.

Brief Description of Drawings

[0010] 

[Fig. 1] Fig. 1 is a system configuration view of an air-conditioning apparatus according to Embodiment 1 of the present invention.

[Fig. 2] Fig. 2 is a p-h diagram showing action in a refrigerant circuit of the air-conditioning apparatus in heating operation according to Embodiment 1 of the present invention.

Description of Embodiments

[0011] Hereinafter, an embodiment of the present invention will be described with reference to drawings. Note that the embodiment to be described below does not limit the present invention. Moreover, components assigned with the same reference signs are the same or corresponding components, and the reference signs are common in all of the sentences in the specification. Further, forms of components represented in all of the sentences in the specification are only examples, which do not limit the present invention to these descriptions.

[0012] Hereinafter, a configuration of an air-conditioning apparatus as an example of a refrigeration cycle apparatus will be described.

Embodiment 1

[0013] Fig. 1 is a system configuration view of an air-conditioning apparatus according to Embodiment 1 of the present invention. The air-conditioning apparatus can switch the cooling operation and the heating operation by switching a four-way valve 2. As the present invention can be applied to the heating operation, the following description will be focused on the heating operation.

[0014] The air-conditioning apparatus includes a refrigerant circuit provided with a compressor 1, the four-way valve 2, a load-side heat exchanger 3, a high-pressure side flow path of an internal heat exchanger 4, an expansion device 5, a pressure vessel 6, an expansion device 7, and a heat-source side heat exchanger 8. The refrigerant circuit of the refrigeration cycle apparatus according to the present invention is not limited to the refrigerant circuit in Fig. 1. For example, it is possible to adopt a configuration omitting the four-way valve 2 and the pressure vessel 6, or including one expansion device, although two expansion devices are provided here. In short, the refrigerant circuit of the refrigeration cycle apparatus according to the present invention may include at least the compressor 1, the load-side heat exchanger 3, the high-pressure side flow path of the internal heat exchanger 4, the expansion device (a first expansion device), and the heat-source side heat exchanger 8.

[0015] The air-conditioning apparatus further includes an injection circuit 15 that branches from between the internal heat exchanger 4 and the expansion device 5 to be connected to the compressor 1 for injection performed during compression. The injection circuit 15 is provided with an expansion device (a second expansion device) 9 and a low-pressure side flow path of the internal heat exchanger 4.

[0016] The load-side heat exchanger 3 is disposed in an indoor unit (not shown), and the heat-source side heat exchanger 8 is disposed in an outdoor unit (not shown). In Fig. 1, a state in which the load-side heat exchanger 3 and the internal heat exchanger 4 are configured separately is shown; however, the load-side heat exchanger 3 and the internal heat exchanger 4 may be configured integrally.

[0017] The refrigerant circuit described above is provided with a discharge temperature sensor 11, an internal heat exchanger outlet temperature sensor 12, a suction temperature sensor 13, a discharge pressure sensor 14, and a heat-source side heat exchanger temperature sensor 16. The discharge temperature sensor 11 measures the temperature of refrigerant discharged from the compressor 1. The internal heat exchanger outlet temperature sensor 12 measures the temperature of refrigerant having flowed from the high-pressure side flow path of the internal heat exchanger 4. The suction temperature sensor 13 measures the temperature of refrigerant to be sucked into the compressor 1. The discharge pressure sensor 14 measures the pressure of refrigerant discharged from the compressor 1.

[0018] The heat-source side heat exchanger temperature sensor 16 is disposed in the heat-source side heat exchanger 8 and measures the temperature of refrigerant flowing inside the heat-source side heat exchanger 8. The heat-source side heat exchanger temperature sensor 16 is disposed on an inlet side of the heat-source side heat exchanger 8, to be specific, at the middle part of the entire length of the pipe of the heat-source side heat exchanger 8 or on an inlet side of the middle part to make it possible to measure the evaporating temperature of the refrigerant in the two-phase state. As the suction pressure of refrigerant to be sucked into the compressor 1 can be obtained by saturation pressure conversion of the temperature measured by the heat-source side heat exchanger temperature sensor 16, the heat-source side heat exchanger temperature sensor 16 corresponds to a suction pressure detection device according to the present invention.

[0019] The refrigerant circuit further includes a controller 20. The controller 20 is connected to various kinds of sensors to be able to receive measurement signals from the various kinds of sensors in the air-conditioning apparatus. Then, the controller 20 calculates subcooling SC at the outlet of the load-side heat exchanger 3 on the basis of the measurement signals from the various kinds of sensors and other information and feeds the calculated subcooling SC back to control of the expansion device 5. Intended air-conditioning capability can be exerted by controlling the expansion device 5 on the basis of the subcooling SC. The controller 20 can be composed of hardware, such as a circuit device that implements functions of the controller 20, or can be composed of a computing device, such as a microcomputer and a CPU, and software executed on the computing device.

[0020] Fig. 2 is a p-h diagram showing action in the refrigerant circuit of the air-conditioning apparatus in heating operation according to Embodiment 1 of the present invention. The horizontal axis indicates specific enthalpy [kJ/kg], and the vertical axis indicates a refrigerant pressure [MPa]. The reference signs A to F in Fig. 1 correspond to the reference signs A to F in Fig. 2 (the states I and J are not shown in Fig. 1).

[0021] The action in the refrigerant circuit in the heating operation will be described.

[0022] In the heating operation, gas refrigerant of high temperature and high pressure (the state A) discharged from the compressor 1 passes through the four-way valve 2 to flow into the load-side heat exchanger 3. The gas refrigerant of high temperature and high pressure is subjected to heat exchange in the load-side heat exchanger 3 to be liquid refrigerant of low temperature and high pressure in a subcooled state (the state B). The liquid refrigerant having flowed from the load-side heat exchanger 3 flows into the internal heat exchanger 4. In the internal heat exchanger 4, the high-pressure side refrigerant having flowed from the load-side heat exchanger 3 and having flowed into the high-pressure side flow path of the internal heat exchanger 4 exchanges heat with low-pressure side refrigerant in the low-pressure side flow path of the internal heat exchanger 4, and thereby, the high-pressure side refrigerant having flowed into the high-pressure side flow path of the internal heat exchanger 4 is cooled (the state C).

[0023] A part of the refrigerant having flowed from the high-pressure side flow path of the internal heat exchanger 4 is branched to the injection circuit 15 while a mainstream of the refrigerant flows into the expansion device 5 to be subjected to pressure reduction (the state E). The refrigerant subjected to pressure reduction in the expansion device 5 flows into the pressure vessel 6. Then, in the pressure vessel 6, the refrigerant provides heat to the low-temperature refrigerant on the suction side of the compressor 1 to lower the temperature of the refrigerant, and becomes liquid refrigerant to flow out (the state F). The refrigerant having flowed from the pressure vessel 6 is subjected to pressure reduction in the expansion device 7 (the state G), and then, flows into the heat-source side heat exchanger 8. The refrigerant having flowed into the heat-source side heat exchanger 8 exchanges heat with outside air and absorbs heat to be low-pressure gas refrigerant. Subsequently, the low-pressure gas refrigerant passes through the four-way valve 2, exchanges heat with high-pressure refrigerant in the pressure vessel 6, and is further heated (the state H) to be sucked into the compressor 1.

[0024] On the other hand, the refrigerant branched to the injection circuit 15 is subjected to pressure reduction in the expansion device 9 to an intermediate pressure (the state D), flows into the low-pressure side flow path of the internal heat exchanger 4, and exchanges heat with refrigerant in the high-pressure side flow path to be heated (the state K).

[0025] The compressor 1 sucks the low-pressure gas refrigerant heated in the pressure vessel 6 (the state H) and compresses the refrigerant to an intermediate pressure (the state I). Moreover, the compressor 1 sucks the refrigerant injected from the injection circuit 15 (the state K). Consequently, in the compressor 1, the refrigerant in the state I and the refrigerant in the state K merge to be refrigerant in the state J. The refrigerant in the state J is subjected to pressure rise to high pressure and discharged from the compressor 1 (the state A).

[0026] Next, description will be given of a calculation method of the subcooling SC, which is a measure for determining the state of the refrigerant. In general, the subcooling SC at the outlet of the load-side heat exchanger 3 can be calculated by the following expression.

[0027] First, "condensing temperature of refrigerant" can be obtained by saturation temperature conversion of the measured pressure by the discharge pressure sensor 14.

[0028] Next, "temperature in state B" is obtained from, when the load-side heat exchanger 3 and the internal heat exchanger 4 are separately configured, the temperature sensor provided at the outlet of the load-side heat exchanger 3. However, for example, when the load-side heat exchanger 3 and the internal heat exchanger 4 are integrally configured, it is impossible to attach the temperature sensor to the outlet of the load-side heat exchanger 3. Moreover, even when the load-side heat exchanger 3 and the internal heat exchanger 4 are separately configured, a case is assumed in which the temperature sensor is not attached to the outlet of the load-side heat exchanger 3 from the standpoint of, for example, reducing the number of sensors. To obtain "temperature in state B" without attaching any temperature sensor to the outlet of the load-side heat exchanger 3 as described above, it is sufficient to obtain the pressure in the state B and the enthalpy in the state B. The pressure in the state B is obtained by the discharge pressure sensor 14. In the following, a method for obtaining the enthalpy in the state B will be described.

<Enthalpy in state B>

[0029] The enthalpy in the state B is calculated on the assumption that the heat exchange amount Q1 in the high-pressure side flow path of the internal heat exchanger 4 in the state B to the state C in Fig. 2 is equal to the heat exchange amount Q2 in the low-pressure side flow path of the internal heat exchanger 4 in the state D to the state K in Fig. 2.

[0030] The enthalpy at the outlet of the high-pressure side flow path of the internal heat exchanger 4 (the state C) is obtained from the measured temperature of the internal heat exchanger outlet temperature sensor 12 and the measured pressure of the discharge pressure sensor 14. Moreover, the enthalpy in the state D is the same as the enthalpy in the state C. Consequently, when the enthalpy in the state K is obtained, it is possible to obtain the heat exchange amount Q2 in the low-pressure side flow path of the internal heat exchanger 4. The enthalpy in the state K can be obtained by using the fact that the refrigerant in the state K and the refrigerant in the state I merge inside the compressor 1 to be the refrigerant in the state J.

[0031] First, the enthalpy in each of the state I and the state J can be obtained by using the suction pressure resulting from the saturation pressure conversion of the temperature measured by the heat-source side heat exchanger temperature sensor 16, the suction temperature measured by the suction temperature sensor 13, the discharge pressure measured by the discharge pressure sensor 14, the discharge temperature measured by the discharge temperature sensor 11, and the position of an injection port 10 in a compression chamber in the compressor 1. "Position of an injection port 10 in a compression chamber in the compressor 1" means that, for example, when a scroll compressor is taken as an example, a position (phase angle) at which the injection port 10 is placed in a scroll-shaped cylinder that forms the compression chamber.

[0032] When "position of an injection port 10" has already been known, how much the refrigerant is compressed from the suction state until injection can be known. Consequently, the enthalpy in the state I can be obtained from the information (how much the refrigerant is compressed from the suction state until injection), and the suction pressure and the suction temperature of the compressor 1. Moreover, when "position of an injection port 10" has already been known, how much the refrigerant is compressed from the state J until being discharged can be known. Consequently, the enthalpy in the state J can be obtained by back calculating from the state A by using the information (how much the refrigerant is compressed from the state J until being discharged), and the discharge pressure and the discharge temperature of the compressor 1.

[0033] Then, as the refrigerant in the state K and the refrigerant in the state I merge inside the compressor 1 to be the refrigerant in the state J, the enthalpy in the state K can be obtained from the enthalpies in the state I and the state J. As the enthalpy in the state D is equal to the enthalpy in the state C and is already obtained in the above, the heat exchange amount Q2 in the internal heat exchanger 4 can be obtained on the basis of the obtained enthalpy in the state K.

[0034] Then, in a case assumed that the heat exchange amount Q2 from the state D to the state K as obtained above is equal to the heat exchange amount Q1 from the state B to the state C, as the enthalpy in the state C has already been obtained, the enthalpy in the state B can be obtained.

[0035] The temperature in the state B can be obtained from the enthalpy in the state B calculated as described above and the pressure in the state B obtained by the discharge pressure sensor 14, and consequently, the subcooling SC can be obtained by the above [Expression 1].

[0036] As described above, according to Embodiment 1 of the present invention, without using the refrigerant temperature between the load-side heat exchanger 3 and the internal heat exchanger 4, it is possible to calculate the subcooling SC by use of the measured value of each of the discharge temperature sensor 11, the internal heat exchanger outlet temperature sensor 12, the suction temperature sensor 13, the discharge pressure sensor 14, and the heat-source side heat exchanger temperature sensor 16, and the position of the injection port 10. Consequently, even in a configuration in which the temperature sensor cannot be provided between the load-side heat exchanger 3 and the internal heat exchanger 4 due to the internal heat exchanger 4 being placed immediately downstream of the load-side heat exchanger 3 or the load-side heat exchanger 3 and the internal heat exchanger 4 being configured integrally, it is possible to calculate the subcooling SC.

[0037] As the subcooling SC can be calculated as described above, it is possible to exert the capability of the air-conditioning apparatus sufficiently.

[0038] Moreover, in Embodiment 1 of the present invention, description is given by taking the air-conditioning apparatus as an example; however, the present invention can be used for other arbitrary facility appliances. For example, the present invention is applicable to facility appliances, such as a water heater and a water cooler.

[0039] Various embodiments and modifications can be made to the present invention as long as the various embodiments and modifications do not depart from the broad spirit and scope of the present invention. The above-described embodiment is intended to be illustrative of the present invention, but not limiting the scope of the present invention. Specifically, for example, the heat-source side heat exchanger temperature sensor 16 is described to correspond to the suction pressure detection device of the present invention; however, the suction pressure detection device may be configured as follows. That is, as indicated by the dotted line in Fig. 1, a suction pressure sensor 17 that measures the suction pressure of the refrigerant to be sucked into the compressor 1 is provided on the suction side of the compressor 1, and the suction pressure sensor 17 may correspond to the suction pressure detection device of the present invention. Moreover, in Fig. 1, the suction pressure sensor 17 is provided between the compressor 1 and the pressure vessel 6; however, the suction pressure sensor 17 may be provided between the pressure vessel 6 and the four-way valve 2, or, when the case is limited to the heating operation, between the four-way valve 2 and the heat-source side heat exchanger 8.

Reference Signs List

[0040] 1 compressor 2 four-way valve 3 load-side heat exchanger 4 internal heat exchanger 5 expansion device 6 pressure vessel 7 expansion device 8 heat-source side heat exchanger 9 expansion device 10 injection port 11 discharge temperature sensor 12 internal heat exchanger outlet temperature sensor 13 suction temperature sensor 14 discharge pressure sensor 15 injection circuit 16 heat-source side heat exchanger temperature sensor 17 suction pressure sensor 20 controller

Claims

1. A refrigeration cycle apparatus comprising:

a refrigerant circuit including a compressor, a load-side heat exchanger, a high-pressure side flow path of an internal heat exchanger, a first expansion device, and a heat-source side heat exchanger;

an injection circuit branched from between the internal heat exchanger and the first expansion device and connected to an injection port of the compressor through a second expansion device and a low-pressure side flow path of the internal heat exchanger;

a suction temperature sensor measuring a suction temperature of the compressor;

a suction pressure detection device measuring a suction pressure of the compressor;

a discharge temperature sensor measuring a discharge temperature of the compressor;

a discharge pressure sensor measuring a discharge pressure of the compressor;

an internal heat exchanger outlet temperature sensor provided at an outlet of the high-pressure side flow path of the internal heat exchanger and measuring a refrigerant temperature at the outlet of the high-pressure side flow path; and

a controller configured to calculate subcooling at an outlet of the load-side heat exchanger by using a measured value of each of the suction temperature sensor, the suction pressure detection device, the discharge temperature sensor, the discharge pressure sensor, and the internal heat exchanger outlet temperature sensor, and information related to a position of the injection port in a compression unit of the compressor.

2. The refrigeration cycle apparatus of claim 1, wherein the controller is configured to calculate the subcooling by using equality between a heat exchange amount in the low-pressure side flow path of the internal heat exchanger and a heat exchange amount in the high-pressure side flow path of the internal heat exchanger.

3. The refrigeration cycle apparatus of claim 1 or 2, wherein the suction pressure detection device includes a heat-source side heat exchanger temperature sensor measuring a refrigerant temperature at an inlet side of the heat-source side heat exchanger to obtain the suction pressure by saturation conversion of a measured temperature of the heat-source side heat exchanger temperature sensor.

4. The refrigeration cycle apparatus of claim 1 or 2, wherein the suction pressure detection device comprises a suction pressure sensor measuring the suction pressure of the compressor.

Drawing