EP1878985A2

EP1878985A2 - Air conditioning system and method of controlling the same

Info

Publication number: EP1878985A2
Application number: EP07112181A
Authority: EP
Inventors: Won Hee Lee
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2006-07-11
Filing date: 2007-07-10
Publication date: 2008-01-16
Anticipated expiration: 2027-07-10
Also published as: EP1878985A3; KR100821729B1; JP5313467B2; EP1878985B1; KR20080006055A; JP2008020181A; ES2432756T3

Abstract

Provided are an air conditioning system and a controlling method thereof. According to the system and method, frost on an outdoor heat exchanger can be removed while a heating mode operation is continuously performed, and power consumption can be reduced. Also, refrigerant of higher temperature than that of a heating mode is supplied to the outdoor heat exchanger to extend defrosting mode period.

Description

The present invention relates to an air conditioning system and a method of controlling the same. More particularly, the present invention relates to an air conditioning system that can perform a defrosting mode while continuously performing a heating mode and a method of controlling the air conditioning system.
Generally, an air conditioner is a system that is used to control a temperature of an indoor space. The air conditioner performs a cooling mode or a heating mode depending on a circulation direction of a refrigerant. In the air conditioner, frost is formed on an outdoor heat exchanger when a temperature of an outdoor side is reduced to be less than a predetermined temperature during the heating mode operation. This causes the deterioration of the performance of the outdoor heat exchanger.
The conventional air conditioner has however the following problems.
In order to perform the defrosting mode, the conventional air conditioner must be changed into a cooling cycle after a heating cycle is stopped. Therefore, the air conditioner cannot keep operating with the heating cycle. In addition, since cool air is discharged into an indoor space during the defrosting mode, a user may feel discomfort.
Further, since an indoor heat exchanger is cooled during the defrosting mode, the indoor heat exchanger must be reheated whenever the heating mode starts again after the defrosting mode is finished. This causes increase of the electric power consumption.
Furthermore, since the frost forming speed increases exponentially as an outdoor temperature is reduced, a defrosting mode performing period is shortened.
Accordingly, the present invention is directed to an air conditioning system and a method of controlling the same that substantially obviate one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an air conditioning system that can perform a defrosting mode for an outdoor heat exchanger while keeping performing a heating mode and a method of controlling the air conditioning system.
Another object of the present invention is to provide an air conditioning system in which there is no need to reheat an indoor heat exchanger even after the defrosting of an outdoor heat exchange is completed and a method of controlling the air conditioning system.
Still another object of the present invention is to provide an air conditioning system that can prolong a defrosting mode performing period for an outdoor heat exchanger and a method of controlling the air conditioning system.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided an air conditioning system An air conditioning system including: a compression unit for compressing a refrigerant; an indoor heat exchange unit connected to the compression unit; an expansion unit connected to the indoor heat exchange unit; an outdoor heat exchange unit disposed on a refrigerant tube between the expansion unit and an inlet side of the compression unit; a bypass tube branched off from an outlet side of the compression unit and connecting an outlet side of the expansion unit to an inlet side of the compression unit in a heating mode; and a valve disposed on the bypass tube.
In another aspect of the present invention, there is provided an air conditioning system including: a compression unit for compressing a refrigerant; a conversion unit for converting the refrigerant discharged from the compression unit; an indoor heat exchange unit connected to the conversion unit; an expansion unit connected to the indoor heat exchange unit; an outdoor heat exchange unit disposed on a refrigerant tube between the expansion unit and the conversion unit; a bypass tube branched off from a refrigerant tube between an outlet side of the compression unit and the conversion unit and connecting an outlet side of the expansion unit to an inlet side of the compression unit in a heating mode; and a valve disposed on the bypass tube.
In still another aspect of the present invention, there is provided an air conditioning system including: a compression unit having at least two compressors; an indoor heat exchange unit connected to the compression unit; an expansion unit connected to the indoor heat exchange unit; an outdoor heat exchange unit disposed on a refrigerant tube between the expansion unit and an inlet side of the compression unit; a bypass tube branched off from an outlet side refrigerant tube of at least one of the compressors of the compression unit and connecting an outlet side of the expansion unit to an inlet side of the compression unit in a heating mode; and a valve disposed on the bypass tube.
The bypass tube may be connected to an inlet side refrigerant tube of the outdoor heat exchange unit in the heating mode.
A pressure regulating unit for regulating pressure of the refrigerant may be disposed on the bypass tube.
The bypass tube may be connected to a refrigerant tube between the inlet side of the compression unit and the outdoor heat exchange unit.
A valve may be installed on a refrigerant tube between a branched portion of the bypass tube and the conversion unit.
In still yet another aspect of the present invention, there is provided a method of controlling an air conditioning system, including: starting a heating mode; determining if an outdoor heat exchange unit reaches a preset defrosting condition; and allowing, when it is determined that the outdoor heat exchange unit reaches the preset defrosting condition, a portion of a refrigerant discharged from a compression unit to be directed to an inlet side of the outdoor heat exchange unit by opening a valve.
When a temperature of the outdoor heat exchange unit is equal to or less than a preset reference temperature, it may be determined that the outdoor heat exchange unit reaches the preset defrosting condition.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment (s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:
FIG. 1 is a circuit diagram of an air conditioning system according to a first embodiment of the present invention;
FIG. 2 is a flowchart illustrating a method of controlling the air conditioning system of FIG. 1;
FIG. 3 is a P-h graph of the air conditioning system of FIG. 1;
FIG. 4 is a circuit diagram of an air conditioning system according to a second embodiment of the present invention;
FIG. 5 is a P-h graph of the air conditioning system of FIG. 3; and
FIG. 6 is a circuit diagram of an air conditioning system according to a third embodiment of the present invention.
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.
The following will describe an indoor unit of an air conditioning system according to a first embodiment of the present invention.
FIG. 1 is a circuit diagram of an air conditioning system according to a first embodiment of the present invention, FIG. 2 is a flowchart illustrating a method of controlling the air conditioning system of FIG. 1, and FIG. 3 is a P-h graph of the air conditioning system of FIG. 1.
Referring to FIG. 1, the air conditioning system includes a compression unit 10. The compression unit 10 may include a main compressor 11 and a sub-compressor 12. The main compressor 10 operates in all of modes and the sub-compressor 10 operates if required. Alternatively, the compression unit 10 may be formed with a single compressor.
A check valve 15 for preventing a refrigerant discharged from the compression unit 10 from reversely flowing is disposed on an outlet side refrigerant tube 111.
A conversion unit 20 is connected to the outlet side refrigerant tube 111 of the compression unit 10. A 4-way valve may be used as the conversion unit 20. The conversion unit 20 controls a circulation direction of the refrigerant.
An indoor heat exchange unit 30 is connected to the conversion unit 20. An expansion unit 40 is connected to the indoor heat exchange unit 30. A linear expansion valve (LEV) or a capillary tube may be used as the expansion unit 40.
An outdoor heat exchange unit 50 is connected to the expansion unit 40. The conversion unit 20 is connected to the outdoor heat exchanger 50.
An accumulator 60 is disposed on an inlet side refrigerant tube 114 of the conversion unit 20 and the compression unit 10. The accumulator 60 provides only a gas-phase refrigerant of the refrigerant directed from the conversion unit 20 to the compression unit 10. A separate heating unit (not shown) for heating the refrigerant may be installed on the accumulator 60.
A bypass tube 110 is breached off from the outlet side refrigerant tube 111 of the compression unit 10. At this point, the bypass tube 110 may be branched off from the outlet side refrigerant tube 111 of the compressor 12 of the compression unit 10. That is, the bypass tube 110 may be branched off from the outlet side refrigerant tube 111 of one or all of the compressors 11 and 12.
The bypass tube 110 may be connected to a refrigerant tube 112 connecting an outlet side of the expansion unit 40 to an inlet side of the compression unit 10. For example, in the heating mode, the bypass tube 110 is connected between the outlet side of the expansion unit 40 and the inlet side refrigerant tube 112 of the outdoor heat exchange unit 50.
A first valve 101 may be disposed on the bypass tube 110. At this point, when the bypass tubes 110 are branched off from the outlet side refrigerant tubes of the compressors 11 and 12, the first valves 101 may be disposed on the respective bypass tubes 110. An opening/closing valve for opening and closing the bypass tube 110 may be used as the first valve 101.
A pressure regulating unit 103 may be disposed on the bypass tube 110. The pressure regulating unit 103 regulates the refrigerant discharged through the bypass tube 110 such that pressure of the refrigerant becomes similar to that of the refrigerant passing through the expansion unit 40.
In addition, a second valve 102 may be further installed between a branch portion of the bypass tube 110 and the conversion unit 20. The second valve 102 functions to discharge the refrigerant discharged from the compressors 11 and 12 only to the bypass tube 110.
The following will describe an operation of the above-described air conditioning system that can selectively operate with a cooling or heating mode. The following will describe the heating mode.
Referring to FIGs. 1 and 2, when the air conditioning system operates with the heating mode (S11), the refrigerant is compressed to a high pressure by the compression unit 10. At this point, only the main compressor 11 or both of the main compressor 11 and the sub compressor 12 can be operated depending on the heating capacity.
The compressed refrigerant is directed to the indoor heat exchange unit 30 by the conversion unit 20. At this point, the first valve 101 is closed and the second valve 102 is opened.
The refrigerant and the indoor air are heat-exchanged with each other in the indoor heat exchange unit 30. At this point, the refrigerant passing through the indoor heat exchange unit 30 is condensed by the heat exchange. Subsequently, the indoor air heat-exchanged in the indoor heat exchange unit 30 is discharged into the indoor space to heat the indoor space.
The refrigerant discharged from the heat exchange unit 30 is directed to the expansion unit 40. The refrigerant expands to a low temperature/low pressure state while passing through the expansion unit 40. The expanded refrigerant is directed to the outdoor heat exchange unit 50. The refrigerant of the outdoor heat exchange unit 50 absorbs heat from outdoor air to phase-changed into a gas-phase state.
The refrigerant discharged from the outdoor heat exchange unit 50 is directed into the conversion unit 20. The conversion unit 20 allows the refrigerant to be directed into the accumulator 60. The accumulator 60 allows only the gas-phase refrigerant to be directed into the compression unit 10.
Meanwhile, when the heating mode is performed in a state where the outdoor temperature is low, the surface of the outdoor heat exchange unit 50 is damp with humidity contained in the outdoor air. The humidity is changed into frost as the temperature of the outdoor heat exchange unit 50 is reduced. At this point, since the outdoor heat exchange unit 50 functions as an evaporator, the frost formed on the outdoor heat exchange unit 50 causes the deterioration of the heat exchange between the refrigerant and the outdoor air in the outdoor heat exchange unit 50. Therefore, since the temperature of the refrigerant discharged from the outdoor heat exchange unit 50 is lowered, the temperature of the refrigerant directed into the compression unit 10 is also lowered. Accordingly, the temperature of the refrigerant discharged from the compression unit 10 is lowered and thus the heating efficiency of the air conditioning system is deteriorated.
In order to prevent the deterioration in the heating efficiency of the air conditioning system, a defrosting mode for melding the frost formed on the outdoor heat exchange unit 50 is performed when a predetermined amount of the frost is formed on the outdoor heat exchange unit 50. At this point, the temperature of the outdoor heat exchange unit 50 is detected to determine if the detected temperature is lower than a reference temperature (S12). When the detected temperature is lower than the reference temperature, the defrosting mode is performed.
When the heating mode is performed for a predetermined time, the defrosting mode may be performed. At this point, the heating mode performing times will be preset in a control unit (not shown) to correspond to respective outdoor temperatures.
When the defrosting mode starts, the refrigerant discharged from the compression unit 10 flows successively along the conversion unit 20, the indoor heat exchange unit 30, the expansion unit 40, and the outdoor heat exchange unit 50. At this point, the high temperature refrigerant discharged from the compression unit 10 is continuously directed to the indoor heat exchange unit 30 to heat the indoor space. This refrigerant flow is substantially identical to that in the heating mode.
At the same time, the first valve 101 is opened (S13), and the second valve 102 is closed. At this point, a portion of the refrigerant in the compression unit 10 flows along the bypass tube 110. The pressure of the refrigerant in the bypass tube 110 is uniformly regulated by the pressure regulating unit 103. In addition, by slightly opening the second valve 102, an amount of the refrigerant directed to the conversion unit 20 may be increased.
The high temperature refrigerant in the bypass tube 110 is directed to the inlet side refrigerant tube 112 of the outdoor heat exchange unit 50. At this point, the high temperature refrigerant in the bypass tube 110 is mixed with a low temperature refrigerant discharged from the expansion unit 40. Therefore, the temperature of the mixed refrigerant in the inlet side refrigerant tube 112 of the outdoor heat exchange unit 50 becomes significantly higher than the refrigerant discharged from the expansion unit 40.
The mixed refrigerant in the refrigerant tube 112 is directed into the outdoor heat exchange unit 50. The mixed refrigerant melts the frost formed on the surface of the outdoor heat exchange unit 50. At this point, the refrigerant discharged from the outdoor heat exchange unit 50 has a higher temperature than that of the refrigerant discharged in the heating mode. Therefore, the temperature of the refrigerant increases at the inlet side of the compression unit 10, the overall performance of the air conditioning system is improved.
As described above, by bypassing the high temperature refrigerant at the inlet side of the outdoor heat exchange unit 50, the indoor space can be heated and at the same time the frost formed on the outdoor heat exchange unit 50 can be removed (S14). Therefore, there is no need to stop the heating mode operation for the defrosting mode operation.
In the above description, although the mode for removing the frost from the outdoor heat exchange unit 50 is referred to as the defrosting mode, the defrosting mode substantially means that the heating and defrosting modes are simultaneously performed.
Referring to FIG. 3, when it is assumed that the heating mode cycle and the defrosting mode cycle are ideally performed, the refrigerant varies along a line C1-C2-C3-C4-C1 in the heating mode cycle and varies along a line C6-C7-C3-C5-C7 in the defrosting mode cycle.
At this point, in the heating mode cycle, the outlet side pressure of the compression unit becomes P1 and the outlet side pressure of the expansion unit 40 becomes P2.
On the other hand, when the defrosting mode cycle is performed, the outlet side pressure of the compression unit becomes P1. At this point, a portion of the compressed refrigerant bypasses to the inlet side refrigerant 111 of the outdoor heat exchange unit 50 through the bypass tube 110 and thus the pressure of the refrigerant becomes P3 while passing through the expansion valve 40. In addition, the bypassing refrigerant is mixed with the outlet side refrigerant of the expansion unit 40 and thus the pressure of the mixed refrigerant increases to P3 and the temperature thereof also increases. At this point, since the inlet side temperature of the outdoor heat exchange unit 50 is higher than that in the heating mode cycle, the frost formed on the surface of the outdoor heat exchange unit 50 increases. Accordingly, the defrosting mode cycle moves upward and thus the overall efficiency of the air conditioning system is improved.
The following will describe an air conditioning system according to a second embodiment of the present invention.
FIG. 4 is a circuit diagram of an air conditioning system according to a second embodiment of the present invention, and FIG. 5 is a P-h graph of the air conditioning system of FIG. 3.
Referring to FIG. 4, an air conditioning system of this second embodiment is identical to that of the first embodiment except that a bypass tube 120 is connected to a refrigerant tube 113 between an outlet side of an outdoor heat exchange unit 50 and a conversion unit 20. Like elements in the first and second embodiments will be assigned with like reference numbers and will not be described.
When the defrosting mode starts, the refrigerant discharged from the compression unit 10 flows successively along the conversion unit 20, the indoor heat exchange unit 30, the expansion unit 40, and the outdoor heat exchange unit 50. At this point, the high temperature refrigerant discharged from the compression unit 10 is continuously directed to the indoor heat exchange unit 30 to heat the indoor space.
At the same time, the first valve 101 is opened, and the second valve 102 is closed. At this point, a portion of the refrigerant in the compression unit 10 flows along the bypass tube 120. For example, the refrigerant discharged from the compressor 11 is directed to the conversion unit 20 and the refrigerant discharged from the compressor 12 flows along the bypass tube 120. The pressure of the refrigerant in the bypass tube 120 is uniformly regulated by the pressure regulating unit 103 to be identical or similar to that of the refrigerant in the outlet side refrigerant tube 113.
The high temperature refrigerant in the bypass tube 120 is directed to the outlet side refrigerant tube 113 of the outdoor heat exchange unit 50. At this point, the high temperature refrigerant in the bypass tube 110 is mixed with a low temperature refrigerant discharged from the outdoor heat exchange unit 40. Therefore, the temperature of the mixed refrigerant becomes significantly higher than the refrigerant discharged from the outdoor heat exchange unit 50.
The mixed refrigerant in the refrigerant tube 113 is directed into the accumulator 60 through the conversion unit 20. Therefore, since the temperature of the refrigerant at the inlet side of the compression unit 10 increases, the compression efficiency of the compression unit is improved.
The outlet side refrigerant of the compression unit 10 becomes higher than that in the heating mode. The refrigerant discharged from the compression unit 10 flows along the conversion unit 20, the indoor heat exchange unit 30, and the expansion unit 40 successively.
At this point, the inlet side refrigerant of the outdoor heat exchange unit 50 has a higher temperature than that of the refrigerant discharged in the heating mode. Therefore, the forming of the frost on the surface of the outdoor heat exchange unit 50 is retarded as the refrigerant flows through the outdoor heat exchange unit 50. As described above, as the defrosting cycle increases and thus the defrosting period can be prolonged.
Referring to FIG. 5, the refrigerant varies along a line C11-C12-C13-C14-C11 in the heating mode cycle and varies along a line C15-C16-C17-C18-C15 in the defrosting mode cycle.
At this point, in the heating mode cycle, the outlet side pressure of the compression unit 10 becomes P1 and the outlet side pressure of the expansion unit 40 becomes P2.
On the other hand, since the refrigerant compressed in the compression unit 10 bypasses to the outlet side of the outdoor heat exchange unit 50 through the bypass tube 120, the pressure of the refrigerant at the outlet side of the outdoor heat exchange unit 50 becomes P4 and the inlet side refrigerant of the compression unit 10 becomes P4. At this point, since the pressure P5 of the refrigerant discharged from the compression unit 10 becomes higher than that in the heating mode, the pressure P4 of the inlet side refrigerant of the outdoor heat exchange unit 50 also increases. In addition, the temperature of the refrigerant directed to the outdoor heat exchange unit 50 increases, the temperature of the surface of the outdoor heat exchange unit 50 increases. Accordingly, the forming of the frost on the outdoor heat exchange unit 50 can be retarded. Since the defrosting mode cycle moves upward, the overall efficiency of the air conditioning system is improved.
The following will describe an air conditioning system according to a third embodiment of the present invention.
FIG. 6 is a circuit diagram of an air conditioning system according to a third embodiment of the present invention.
Referring to FIG. 6, an air conditioning system of this second embodiment is identical to that of the first embodiment except that a bypass tube 130 is connected to a refrigerant tube 114 between a refrigerant outlet side of a conversion unit 20 and an inlet side of an accumulator 60. Like elements in the first and second embodiments will be assigned with like reference numbers and a detailed description thereof will be omitted herein. The third embodiment is identical in an operation to the second embodiment in that the bypass tube 130 is connected to the outlet side refrigerant tube 114 of the outdoor heat exchange unit 50, the operation of the third embodiment will not be described herein.
As described above, by bypassing the high temperature refrigerant at the outlet side of the outdoor heat exchange unit 50, the indoor air is heated and at the same time the forming of the frost on the outdoor heat exchange unit 50 can be prevented.
The air conditioning system of the present invention has the following effects.
Since the refrigerant discharged from the compression unit partly bypasses to the inlet side refrigerant tube of the outdoor heat exchange unit, the heating and defrosting modes can be simultaneously performed. Furthermore, there is no need to stop the heating mode operation for performing the defrosting mode operation.
In addition, since the refrigerant discharged from the compression unit partly bypasses to the outlet side refrigerant tube of the outdoor heat exchange unit, the defrosting mode performing period can be prolonged.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

An air conditioning system comprising:
a compression unit for compressing a refrigerant;

an indoor heat exchange unit connected to the compression unit;

an expansion unit connected to the indoor heat exchange unit;

an outdoor heat exchange unit disposed on a refrigerant tube between the expansion unit and an inlet side of the compression unit;

a bypass tube branched off from an outlet side of the compression unit and connecting an outlet side of the expansion unit to an inlet side of the compression unit in a heating mode; and

a valve disposed on the bypass tube.
The air conditioning system according to claim 1, wherein the bypass tube is connected to an inlet side refrigerant tube of the outdoor heat exchange unit in the heating mode.
The air conditioning system according to claim 1 or 2, further comprising a pressure regulating unit for regulating pressure of the refrigerant is disposed on the bypass tube.
The air conditioning system according to claim 1, wherein the bypass tube is connected to a refrigerant tube between the inlet side of the compression unit and the outdoor heat exchange unit.
An air conditioning system comprising:
a compression unit for compressing a refrigerant;

a conversion unit for converting the refrigerant discharged from the compression unit;

an indoor heat exchange unit connected to the conversion unit;

an expansion unit connected to the indoor heat exchange unit;

an outdoor heat exchange unit disposed on a refrigerant tube between the expansion unit and the conversion unit;

a bypass tube branched off from a refrigerant tube between an outlet side of the compression unit and the conversion unit and connecting an outlet side of the expansion unit to an inlet side of the compression unit in a heating mode; and

a valve disposed on the bypass tube.
The air conditioning system according to claim 5, wherein the bypass tube is connected to an inlet side refrigerant tube of the outdoor heat exchange unit in the heating mode.
The air conditioning system according to claim 5 or 6, wherein a pressure regulating unit for regulating pressure of the refrigerant is disposed on the bypass tube.
The air conditioning system according to any of claims 5 to 7, further comprising a valve is installed on a refrigerant tube between a branched portion of the bypass tube and the conversion unit.
The air conditioning system according to claim 5, wherein the bypass tube is connected to an outlet side refrigerant tube of the outdoor heat exchange unit in the heating mode.
An air conditioning system comprising:
a compression unit having at least two compressors;

an indoor heat exchange unit connected to the compression unit;

an expansion unit connected to the indoor heat exchange unit;

an outdoor heat exchange unit disposed on a refrigerant tube between the expansion unit and an inlet side of the compression unit;

a bypass tube branched off from an outlet side refrigerant tube of at least one of the compressors of the compression unit and connecting an outlet side of the expansion unit to an inlet side of the compression unit in a heating mode; and

a valve disposed on the bypass tube.
The air conditioning system according to claim 10, wherein the bypass tube is connected to an inlet side refrigerant tube of the outdoor heat exchange unit in the heating mode.
The air conditioning system according to claim 10, wherein the bypass tube is connected to an outlet side refrigerant tube of the outdoor heat exchange unit in the heating mode.
The air conditioning system according to any of claims 10 to 12, further comprising a pressure regulating unit for regulating pressure of the refrigerant is disposed on the bypass tube.
A method of controlling an air conditioning system, the method comprising:
performing a heating mode;

determining if an outdoor heat exchange unit reaches a preset defrosting condition; and

allowing, when it is determined that the outdoor heat exchange unit reaches the preset defrosting condition, a portion of a refrigerant discharged from a compression unit to be directed to an inlet side of the outdoor heat exchange unit by opening a valve.
The method of claim 15, wherein, when a temperature of the outdoor heat exchange unit is equal to or less than a preset reference temperature, it is determined that the outdoor heat exchange unit reaches the preset defrosting condition.