US20150267930A1

US20150267930A1 - Air conditioner

Info

Publication number: US20150267930A1
Application number: US14/663,608
Authority: US
Inventors: Byoungjin Ryu; Byeongsu Kim; Younghwan Ko
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2014-03-20
Filing date: 2015-03-20
Publication date: 2015-09-24
Also published as: KR102242777B1; KR20150109748A; EP2924371B1; EP2924371A1

Abstract

An air conditioner is provided that injects a refrigerant into a compressor in a simple configuration by two steps. The air conditioner may include a compressor to compress a refrigerant; a condenser to condense the refrigerant compressed at the compressor; an evaporator to evaporate the refrigerant condensed at the condenser; and an injection module to separate the refrigerant flowing from the condenser to the evaporator into a vapor-phase refrigerant and liquid-phase refrigerant, expand the separated vapor-phase refrigerant, and inject the expanded vapor-phase refrigerant into the compressor, expand and evaporate a portion of the separated liquid-phase refrigerant and inject the expanded and evaporated liquid-phase refrigerant into the compressor.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority under 35 U.S.C. §119 to Korean Application Na. 10-2014-0032959 filed in Korea on Mar. 20, 2014, whose entire disclosure is hereby incorporated by reference.

BACKGROUND

1. Field
An air conditioner is disclosed herein.
2. Background
In general, an air conditioner including a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger heats or cools an indoor space using a refrigeration cycle. That is, the air conditioner may include a cooler to cool the indoor space, and a heater to hear the indoor space. In addition, the air conditioner may function to both heat and cool.
Such an air conditioner may inject some or a portion of a refrigerant condensed during a cooling or heating operation into a compressor, thereby enhancing an efficiency thereof. Injections having two steps for simultaneously injecting the refrigerant into a high pressure side and a low pressure side of the compressor to enhance the efficiency; however, there are problems in that structures for injections having two steps are complex, and manufacturing costs thereof increased.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein:

FIG. 1 is a schematic diagram of an air conditioner according to an embodiment;

FIG. 2 is a block diagram of the air conditioner according to an embodiment; and

FIG. 3 is a Pressure-Enthalpy Diagram (hereinafter, refers to as a “P-h Diagram”) on operating the air conditioner according to an embodiment.

DETAILED DESCRIPTION

Embodiment will be described with reference to the drawings. Where possible, like reference numerals have been used to indicate like elements, and repetitive disclosure has been omitted.
FIG. 1 is a schematic diagram of an air conditioner according to an embodiment. The air conditioner 100 may include a compressor 110 to compress a refrigerant, a condenser 120 to condense the refrigerant compressed at the compressor 110, an evaporator 130 to evaporate the refrigerant condensed at the condenser 120, and an injection module 170 to separate the refrigerant flowing from the condenser 120 to the evaporator 130 into a vapor-phase refrigerant and a liquid-phase refrigerant, expand the separated vapor-phase refrigerant, and inject the expanded refrigerant into the compressor 110, expanding and evaporating some or a portion of the separated liquid-phase refrigerant and injecting the expanded and evaporated refrigerant into the compressor 110 according to an embodiment.
The compressor 110 may compress the refrigerant, having a low temperature and pressure, into the refrigerant having a high temperature and pressure. The compressor 110 may have various structures, and may be, for example, a reciprocating compressor using a cylinder and a piston, or a scroll compressor using an orbiting scroll and a fixed scroll. The compressor 110 may be a scroll compressor according to this embodiment.
The compressor 110 may include a first inlet port 111 to introduce the refrigerant evaporated at the evaporator 130 into the compressor 110, a second inlet port 112 and a third inlet port 113 to introduce the refrigerant expanded and evaporated at or in the injection module 170 into the compressor 110, and a discharge port 114 to discharge the compressed refrigerant. The second inlet port 112 may be formed at a low pressure side of a compression chamber to compress the refrigerant in the compressor 110, and the third inlet port 113 may be formed at a high pressure side of the compression chamber in the compressor 110.
The high pressure side of the compressor 110 has a temperature and pressure relatively higher than the low pressure side of the compressor 110. The low pressure side of the compressor 110 may be closer to the first inlet port 111 in the compression chamber, and the high pressure side of the compressor 110 may be closer to the discharge port 114 in the compression chamber. The refrigerant introduced into the first inlet port 111 of the compressor 110 may be introduced into an inside of the compression chamber and discharged to the discharge port 114 through the high pressure side via the low pressure side.
The compressor 110 may compress the refrigerant introduced into the first inlet port 111 at the compression chamber, combine the refrigerant with the refrigerant introduced into the second inlet port 112 formed at the low pressure side of the compression chamber, and compress the combined refrigerant. The compressor 110 may compress the combined refrigerant, combine the refrigerant with the refrigerant introduced into the third inlet port 113 formed at the high pressure side of the compression chamber, and compress the combined refrigerant. The compressor 110 may compress the combined refrigerant and discharge it to the discharge port 114.
The condenser 120 connected to the compressor 110 may condense the refrigerant compressed at the compressor 110. The condenser 120 may be disposed at or in an outdoor space and may function as an outdoor heat exchanger to heat-exchanges outdoor air with the refrigerant when the air conditioner is a cooler that cools the indoor space, and the condenser 120 may be disposed at or in an indoor space and may function as an indoor heat exchanger that heat-exchanges indoor air with the refrigerant when the air conditioner is a heater that heats the indoor space.
The condenser 120 may be connected to a first main expansion valve 140, and therefore, the refrigerant condensed at the condenser 120 may flow to the first main expansion valve 140. The first main expansion valve 140, connected to the condenser 120, may expand the refrigerant condensed at the condenser 120. The first main expansion valve 140 may be disposed between the condenser 120 and the injection module 170. The first main expansion valve 140 may be connected to the injection module 170, and therefore, the refrigerant expanded at the first main expansion valve 140 may be guided to the injection module 170. The first main expansion valve 140 may be omitted according to an embodiment, and in such a case, the refrigerant condensed at the condenser 120 may flow directly into the injection module 170 without passing through the first main expansion valve 140.
The injection module 170 disposed between the condenser 120 and evaporator 130 may be connected to the high pressure side and the low pressure side of the compressor 110. The injection module 170 may be connected to the second inlet port 112 of the compressor 110, the third inlet port 113 of the compressor 110, the first main expansion valve 140, and a second main expansion valve 150. The injection module 170, connected to the first main expansion valve 140, may inject the refrigerant expanded at the first main expansion valve 140 into the high pressure side and the low pressure side of the compressor 110.
The injection module 170 may separate the refrigerant flowing from the first main expansion valve 140 to the second main expansion valve 150 into a vapor-phase refrigerant and a liquid-phase refrigerant, expand the separated vapor-phase refrigerant, and inject the expanded refrigerant into the high pressure side of the compressor 110. The injection module 170 may expand and evaporate some or a first portion of the separated liquid-phase refrigerant and inject it into the low pressure side of the compressor 110. The injection module 170 may be connected to the second main expansion valve 150 and the other or a remaining or second portion of the separated liquid-phase refrigerant may flow into the second main expansion valve 150.
The injection module 170 may include an injection liquid-vapor separator 174, disposed between the condenser 120 and the evaporator 130, to separate the refrigerant into the vapor-phase refrigerant and liquid-phase refrigerant, a first injection expansion valve 171, connected to the injection liquid-vapor separator 174 and the compressor 110, to expand the vapor-phase refrigerant separated by the injection liquid-vapor separator 174, a second injection expansion valve 172, connected to the injection liquid-vapor separator 174, to expand some or a first portion of the separated liquid-phase refrigerant, and an injection heat exchanger 173, connected to the second injection expansion valve 172 and compressor 110 and disposed at the injection liquid-vapor separator 174, to evaporate the refrigerant expanded at the second injection expansion valve 172 according to an embodiment.
The injection liquid-vapor separator 174 may be disposed between the condenser 120 and the evaporator 130. The injection liquid-vapor separator 174 may be connected to the first main expansion valve 140, the second main expansion valve 150, the first injection expansion valve 171, and the second injection expansion valve 172. Further, the injection heat exchanger 173 may be disposed at an inside of the injection liquid-vapor separator 174.
The injection liquid-vapor separator 174 may be an accumulator to separate the vapor-phase refrigerant and the liquid-phase refrigerant using a pressure difference of the refrigerant. The injection liquid-vapor separator 174 according to this embodiment may be various apparatuses capable of separating the vapor-phase refrigerant and the liquid-phase refrigerant.
The injection liquid-vapor separator 174 may separate the refrigerant expanded at the first main expansion valve 140 into the vapor-phase refrigerant and the liquid-phase refrigerant. The vapor-phase refrigerant separated by the injection liquid-vapor separator 174 may flow to the first injection expansion valve 171. A first portion of the liquid-phase refrigerant separated by the injection liquid-vapor separator 174 may flow to the second injection expansion valve 172. A second portion of the liquid-phase refrigerant separated by the injection liquid-vapor separator 174 may flow to the second main expansion valve 150.
The first injection expansion valve 171 may be connected to the injection liquid-vapor separator 174 and the third inlet port 113 of the compressor 110. The first injection expansion valve 171 may expand the vapor-phase refrigerant separated by the injection liquid-vapor separator 174. The refrigerant expanded at the first injection expansion valve 171 may be injected into the high pressure side of the compressor 110 through the third inlet port 113.
The second injection expansion valve 172 may be connected to the injection liquid-vapor separator 174 and the injection heat exchanger 173. The second injection expansion valve 172 may expand some or the first portion of the liquid-phase refrigerant separated by the injection liquid-vapor separator 174. The refrigerant expanded at the second injection heat exchanger 172 may flow to the injection heat exchanger 173.
The injection heat exchanger 173 may be connected to the second injection expansion valve 172 and the second inlet port 112 of the compressor 110 and may be disposed at or in the injection liquid-vapor separator 174. The injection heat exchanger 173 may heat-exchange the refrigerant expanded at the second injection expansion valve 172 with the refrigerant in the injection liquid-vapor separator 174. The injection heat exchanger 173 may heat-exchange the refrigerant expanded at the second injection expansion valve 172 with the liquid-phase refrigerant in the injection liquid-vapor separator 174.
The injection heat exchanger 173 may heat-exchange the refrigerant expanded at the second injection expansion valve 172 with the liquid-phase refrigerant in the injection liquid-vapor separator 174 and evaporate the heat-exchanged refrigerant. The refrigerant evaporated at the injection heat exchanger 173 may be injected into the low pressure side of the compressor 110 through the second inlet port 112.
The injection heat exchanger 173 may heat-exchange the liquid-phase refrigerant in the injection liquid-vapor separator 174 with the refrigerant expanded at the second injection expansion valve 172 to supercool the heat-exchanged refrigerant. The refrigerant supercooled at the injection heat exchanger 173 may flow to the second main expansion valve 150 and the second injection expansion valve 172.
The second main expansion valve 150, connected to the injection module 170, may expand the refrigerant flowing to the second main expansion valve 150. The second main expansion valve 150 may be disposed between the injection module 170 and the evaporator 130. The second main expansion valve 150 may be connected to the evaporator 130, and the refrigerant expanded at the first main expansion valve 140 may be guided to the evaporator 130.
The evaporator 130 disposed between the second main expansion valve 150 and the compressor 110 may evaporate the refrigerant expanded at the second main expansion valve 150. The evaporator 130 disposed at or in the indoor space may be an indoor heat exchanger that heat-exchange indoor air with the refrigerant when the air conditioner is a cooler that cools the indoor space, and the evaporator 130 disposed outdoors may be an outdoor heat exchanger that heat-exchanges outdoor air with the refrigerant when the air conditioner is a heater that heats the indoor space.
The evaporator 130 may be connected to the first inlet port 111 of the compressor 110, and therefore, the refrigerant evaporated at the evaporator 130 may be introduced into the compressor 110 through the first inlet port 111.
FIG. 2 is a block diagram of the air conditioner according to an embodiment. Referring to FIG. 2, the air conditioner 100 may include a controller 10 that controls the air conditioner 100, a discharge temperature sensor 11 that measures a discharge temperature of the refrigerant discharged from the discharge port 114 of the compressor 110, a condensation temperature sensor 12 that measures a condensation temperature of the refrigerant condensed at the condenser 120, a suction temperature sensor 13 that measures a suction temperature of the refrigerant suctioned into the first inlet port 111 of the compressor 110, an evaporation temperature sensor 14 that measures an evaporation temperature of the refrigerant evaporated at the evaporator 130, an injection expansion temperature sensor 15 that measures a temperature of the refrigerant expanded at the second injection expansion valve 172, and an injection evaporation temperature sensor 16 that measures a temperature of the refrigerant evaporated at the injection heat exchanger 173 according to an embodiment.
The controller 10, which may control operation of the air conditioner, may control the compressor 110, the first main expansion valve 140, the second main expansion valve 150, the first injection expansion valve 171, and the second injection expansion valve 172. The controller 10 may control openings of the first main expansion valve 140, the second main expansion valve 150, the first injection expansion valve 171, and the first injection expansion valve 172 according to operation conditions.
The discharge temperature sensor 11 measures the discharge temperature of the refrigerant compressed at the compressor 110 and discharged to the discharge port 114. The discharge temperature sensor 11 may be disposed at various points, may measure the temperature of the refrigerant discharged from the compressor 110, and may be disposed at point b according to this embodiment.
The condensation temperature sensor 12 may measure the condensation temperature of the refrigerant condensed at the condenser 120. The condensation temperature sensor 12 may be disposed at various points, may measure the condensation temperature of the refrigerant, and may be disposed at point c according to this embodiment. According to this embodiment, the condensation temperature sensor 12 may be disposed at the condenser 120. A condensation pressure of the refrigerant may be converted from the condensation temperature of the refrigerant measured by the condensation temperature sensor 12 according to this embodiment.
The suction temperature sensor 13 may measure the suction temperature of the refrigerant evaporated at the evaporator 130 and introduced to the first inlet port 111 of the compressor 110. The suction temperature sensor 13 may be disposed at various paints, may measure the temperature of the refrigerant suctioned into the compressor 110, and may be disposed at point a according to this embodiment.
The evaporation temperature sensor 14 may measure the evaporation temperature of the refrigerant evaporated at the evaporator 130. The evaporation temperature sensor 14 may be disposed at various points, may measure the evaporation temperature of the refrigerant, and may be disposed at point i according to this embodiment. According to this embodiment, the evaporation temperature sensor 14 may be disposed at the evaporator 130. An evaporation pressure of the refrigerant may be converted from the evaporation temperature of the refrigerant measured by the evaporation temperature sensor 14 according to this embodiment.
The injection expansion temperature sensor 15 may measure the temperature of the refrigerant expanded at the second injection expansion valve 171, that is, the injection expansion temperature. The injection expansion temperature sensor 15 may be disposed at various points, may measure the injection expansion temperature of the refrigerant to be injected, and may be disposed at point f according to this embodiment.
The injection evaporation temperature sensor 16 may measure the injection evaporation temperature of the refrigerant evaporated at the injection heat exchanger 173 and injected into the second inlet port 112 of the compressor 110. The injection evaporation temperature sensor 16 may be disposed at various points, may measure the injection evaporation temperature, and may be disposed at point g according to this embodiment.
The controller 10 may control an opening of the first main expansion valve 140 according to a discharge superheat, that is, a difference between the discharge temperature measured by the discharge temperature sensor 11 and the condensation temperature measured by the condensation temperature sensor 12. The controller 10 may control the opening of the first main expansion valve 140 so that the discharge superheat does not deviate from a preset or predetermined range.
The controller 10 may control an opening of the second main expansion valve 150 according to a suction superheat, that is, a difference between the suction temperature measured by the suction temperature sensor 13 and the evaporation temperature measured by the evaporation temperature sensor 14. The controller 10 may control the opening of the second main expansion valve 150 so that the suction superheat does not deviate from a preset or predetermined range.
The controller 10 may control an opening of the first injection expansion valve 171 according to an operation velocity of the compressor 110. The operation velocity of the compressor 110, which may be a rotational velocity of a motor (not shown) that generates a rotational force to compress the refrigerant in the compressor 110, may be represented in frequencies. The operation velocity of the compressor 110 may be proportional to a compression capacity of the compressor 110. The controller 10 may control the opening of the first injection expansion valve 171 according to the operation velocity of the compressor 110 or close the first injection expansion valve 171.
The controller 10 may control an opening of the second injection expansion valve 172 according to an injection superheat, that is, a difference between the injection evaporation temperature measured by the injection evaporation temperature sensor 16 and the injection expansion temperature measured by the injection expansion temperature sensor 15. The controller 10 may control the opening of the second injection expansion valve 172 so that the injection superheat is within a preset or predetermined value.
FIG. 3 is a Pressure-Enthalpy Diagram (hereinafter, refers to a “P-h Diagram”) on operating the air conditioner according to an embodiment. Referring to FIG. 1 and FIG. 3, operation of the air conditioner 100 according to an embodiment will be described hereinbelow.
The refrigerant compressed at the compressor 110 may be discharged through the discharge port 114. The refrigerant discharged through the discharge port 114 may flow to the condenser 120 via point b. The refrigerant flowing into the condenser 120 may be heat-exchanged with air and condensed. The refrigerant flowing into the condenser 120 may be heat-exchanged with outdoor air when the air conditioner is the cooler, and the refrigerant flowing into the condenser 120 may be heat-exchanged with indoor air when the air conditioner is the heater.
The refrigerant condensed at the condenser 120 may be expanded at the first main expansion valve 140 via point c. The opening degree of the first main expansion valve 140 may be controlled according to the discharge superheat. The refrigerant expanded at the first main expansion valve 140 may flow into the injection module 170 via point d.
The refrigerant flowing into the injection module 170 may be introduced into the injection liquid-vapor separator 174. The refrigerant introduced into the injection liquid-vapor separator 174 may be separated into the vapor-phase refrigerant and the liquid-phase refrigerant.
The vapor-phase refrigerant separated at the injection liquid-vapor separator 174 may flow into the first injection expansion valve 171. The refrigerant expanded at the first injection expansion valve 171 may be injected into the high pressure side of the compressor 110 through the third inlet port 113 of the compressor 110.
The liquid-phase refrigerant separated at the injection liquid-vapor separator 174 may be supercooled by the injection heat exchanger 173. A first portion of the liquid-phase refrigerant supercooled in the injection liquid-vapor separator 174 may flow into the second injection expansion valve 172 via point e and a second portion of the liquid-phase refrigerant supercooled in the injection liquid-vapor separator 174 may flow into the second main expansion valve 150 via point e.
The refrigerant flowing into the second injection expansion valve 172 may be expanded and flow into the injection heat exchanger 173 via point f. The opening of the second injection expansion valve 172 may be controlled according to the injection superheat.
The refrigerant supercooled at the second injection expansion valve 172 and flowing into the injection heat exchanger 173 may be heated and evaporated. The refrigerant evaporated at the injection heat exchanger 173 may be injected into the low pressure side of the compressor 110 through the second inlet port 112 via point g.
The refrigerant flowing from the injection liquid-vapor separator 174 of the injection module 170 to the second main expansion valve 150 may be expanded. The opening of the second main expansion valve 150 may be controlled according to the suction superheat. The refrigerant expanded at the second main expansion valve 150 may flow into the evaporator 130 via point h.
The refrigerant flowing into the evaporator 130 may be heat-exchanged with air and evaporated. The refrigerant flowing into the evaporator 130 may be heat-exchanged with indoor air when the air conditioner is the cooler, and the refrigerant flowing into the evaporator 130 may be heat-exchanged with outdoor air when the air conditioner is the heater.
The refrigerant evaporated in the evaporator 130 may flow into the first inlet port 111 of the compressor 110 via points i and a. The refrigerant flowing into the first inlet port 111 may be compressed at the compressor 110 and may be combined with the refrigerant injected into the second inlet port 112 and third inlet port 113. The refrigerant compressed at the compressor 110 may be discharged into the discharge port 114.
Referring to FIG. 3, one cycle, configured with the discharge port 114 of the compressor 110, the condenser 120, the injection liquid-vapor separator 174, the first injection expansion valve 171, and the third inlet port 113 of the compressor 110, forms one or a first injection step. In addition, one cycle, configured with the discharge port 114 of the compressor 110, the condenser 120, the injection liquid-vapor separator 174, the injection expansion valve 172, the injection heat exchanger 173, and the second inlet port 112 of the compressor 110, forms one or a second injection step.
Although embodiments are shown and described, embodiments are not limited to the described embodiments and may be variously modified by one skilled in the art without losing the gist, such that the modified embodiment is not to be understood separately from technical ideas or views.
An air conditioner according to embodiments disclosed herein has at least the following advantages.
First, refrigerant may be injected into a high pressure side and a low pressure side of a compressor in a simple configuration.
Second, configurations and their controls of a liquid-vapor separator, heat exchanger, and expansion valve may implement injections having two steps, thereby enhancing efficiency of the air conditioner.
Third, supercooling of the refrigerant and injections having two steps may be implemented with one module.
Embodiments disclosed herein provide an air conditioner that injects a refrigerant into a compressor in a simple configuration by two steps.
Embodiments disclosed herein are not limited to the mentioned problems, and other problems, which are not described above, may be obviously understood to those skilled in the art from this description.
Embodiments disclosed herein provide an air conditioner that may include a compressor to compress a refrigerant; a condenser to condense the refrigerant compressed at the corn pressor; an evaporator to evaporate the refrigerant condensed at the condenser: and an injection module to separate the refrigerant flowing from the condenser to the evaporator into a vapor-phase refrigerant and a liquid-phase refrigerant, expand the separated vapor-phase refrigerant, and inject the expanded refrigerant into the compressor, expand and evaporate some or a portion of the separated liquid-phase refrigerant and inject the expanded and evaporated refrigerant into the compressor.
Embodiments disclosed herein further provide an air conditioner that may include a compressor to compress a refrigerant; a condenser to condense the refrigerant compressed at the compressor; an evaporator to evaporate the refrigerant condensed at the condenser; an injection liquid-vapor separator, disposed at the condenser and the evaporator, to separate the refrigerant into a vapor-phase refrigerant and a liquid-phase refrigerant; a first injection expansion valve, connected to the injection liquid-vapor separator and the compressor, to expand the vapor-phase refrigerant separated from the injection liquid-vapor separator; a second injection expansion valve, connected to the injection liquid-vapor separator, to expand some or a portion of the separated vapor-phase refrigerant; and an injection heat exchanger, connected to the second injection expansion valve and the compressor and disposed at the injection liquid-vapor separator, to evaporate the refrigerant expanded at the second injection expansion valve.
The embodiments are not limited to the mentioned effects, and other effects, which are not described above, may be obviously understood to those skilled in the art from the claims.
Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

Claims

What is claimed is:

1. An air conditioner, comprising:

a compressor to compress a refrigerant;

a condenser to condense the refrigerant compressed at the compressor;

an evaporator to evaporate the refrigerant condensed at the condenser; and

an injection module to separate the refrigerant flowing from the condenser to the evaporator into a vapor-phase refrigerant and a liquid-phase refrigerant, expand the separated vapor-phase refrigerant, and inject the expanded vapor-phase refrigerant into the compressor, expand and evaporate a portion of the separated liquid-phase refrigerant and inject the expanded and evaporated refrigerant into the compressor.

2. The air conditioner according to claim 1, further comprising:

a first main expansion valve, disposed between the condenser and the injection module, to expand the refrigerant; and

a second main expansion valve, disposed between the injection module and the evaporator, to expand the refrigerant.

3. The air conditioner according to claim 2, wherein the first main expansion valve is controlled according to a discharge superheat, that is, a difference between a temperature of the refrigerant discharged from the compressor and a temperature of the refrigerant condensed at the condenser.

4. The air conditioner according to claim 3, wherein the second main expansion valve is controlled according to a suction superheat, that is, a difference between a temperature of the refrigerant suctioned into the compressor and a temperature of the refrigerant evaporated at the evaporator.

5. The air conditioner according to claim 4, further comprising:

a discharge temperature that senses the temperature of the refrigerant discharged from the compressor;

a condensation temperature that senses the temperature of the refrigerant condensed at the condenser;

a suction temperature sensor that senses the temperature of the refrigerant suctioned into the compressor; and

an evaporation temperature sensor that senses the temperature of the refrigerant evaporated at the evaporator.

6. The air conditioner according to claim 1, wherein the injection module comprises:

an injection liquid-vapor separator that separates the refrigerant flowing from the condenser to the evaporator into the vapor-phase refrigerant and the liquid-phase refrigerant;

a first injection expansion valve, connected to the injection liquid-vapor separator and the compressor, to expand the vapor-phase refrigerant separated by the injection liquid-vapor separator;

a second injection expansion valve, connected to the injection liquid-vapor separator, to expand a portion of the liquid-phase refrigerant separated by the injection liquid-vapor separator; and

an injection heat exchanger, connected to the second injection expansion valve and the compressor and disposed at the injection liquid-vapor separator, to evaporate the portion of the liquid-phase refrigerant expanded at the second injection expansion valve.

7. The air conditioner according to claim 6, further comprising:

an injection expansion temperature sensor to measure a temperature of the refrigerant expanded at the second injection expansion valve; and

an injection evaporation temperature sensor to measure a temperature of the refrigerant evaporated at the injection heat exchanger.

8. The air conditioner according to claim 6, wherein the first injection expansion valve is located between the injection liquid-separator and a high pressure side of the compressor, and wherein the injection heat exchanger is connected to a low pressure side of the compressor.

9. The air conditioner according to claim 1, further comprising a controller that controls operation of the air conditioner.

10. An air conditioner, comprising:

a compressor to compress a refrigerant;

a condenser to condense the refrigerant compressed at the compressor;

an evaporator to evaporate the refrigerant condensed at the condenser;

an injection liquid-vapor separator, disposed between the condenser and the evaporator, to separate the refrigerant into a vapor-phase refrigerant and a liquid-phase refrigerant;

an injection heat exchanger, connected to the second injection expansion valve and compressor and disposed at the injection liquid-vapor separator, to evaporate the portion of the separated liquid-phase refrigerant expanded at the second injection expansion valve.

11. The air conditioner according to claim 10, further comprising:

12. The air conditioner according to claim 10, wherein the second injection expansion valve is controlled according to an injection superheat, that is, a difference between the temperature measured by the injection evaporation temperature sensor and the temperature measured by the injection expansion temperature sensor.

13. The air conditioner according to claim 10, further comprising:

14. The air conditioner according to claim 13, wherein the first main expansion valve is controlled according to a discharge superheat, that is, a difference between a temperature of the refrigerant discharged from the compressor and a temperature of the refrigerant condensed at the condenser.

15. The air conditioner according to claim 14, wherein the second main expansion valve is controlled according to a suction superheat, that is, a difference between a temperature of the refrigerant suctioned into the compressor and a temperature of the refrigerant evaporated at the evaporator.

16. The air conditioner according to claim 15, further comprising:

17. The air conditioner according to claim 9, further comprising a controller that controls operation of the air conditioner.

18. An air conditioner, comprising:

a compressor to compress a refrigerant;

a condenser to condense the refrigerant compressed at the compressor;

an evaporator to evaporate the refrigerant condensed at the condenser;

an injection heat exchanger, connected to the second injection expansion valve and compressor and disposed at the injection liquid-vapor separator, to evaporate the portion of the separated liquid-phase refrigerant expanded at the second injection expansion valve, wherein the first injection expansion valve is located between the injection liquid-separator and a high pressure side of the compressor, and wherein the injection heat exchanger is connected to a low pressure side of the compressor,

19. The air conditioner according to claim 18, further comprising:

20. The air conditioner according to claim 19, wherein the second injection expansion valve is controlled according to an injection superheat, that is, a difference between the temperature measured by the injection evaporation temperature sensor and the temperature measured by the injection expansion temperature sensor.