Patent Publication Number: US-2020292224-A1

Title: Refrigerator and control method thereof

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/325,813, filed on Jan. 12, 2017, which is U.S. National Phase Application under 35 U.S.C. § 371 of International Application PCT/KR2015/007341, filed on Jul. 15, 2015, which claims the benefit of Korean Application No. KR 10-2014-0092179, Korean Application No. KR 10-2014-0092180, and Korean Application No. KR 10-2014-0092181, all filed on July. 21, 2014, the entire contents of which are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a refrigerator and a control method thereof. 
     BACKGROUND ART 
     Generally, a refrigerator has a plurality of storage chambers for accommodating stored things to keep food frozen or refrigerated, and one surface of each of the storage chambers is formed to be opened for the food to be received or taken out. The plurality of storage chambers include a freezing chamber for keeping the food frozen and a refrigerating chamber for keeping the food refrigerated. 
     In the refrigerator, a refrigeration system in which a refrigerant is circulated is driven. The refrigeration system includes a compressor, a condenser, an expander and an evaporator. The evaporator may include a first evaporator which is provided at one side of the refrigerating chamber, and a second evaporator which is provided at one side of the freezing chamber. 
     Recently, a refrigerator in which the evaporator and the expander are installed at the refrigerating chamber and the freezing chamber, respectively has been developed. In this refrigerator, an amount of the refrigerant supplied from the compressor to each evaporator is adjusted by controlling each expander, and each internal temperature of the refrigerating chamber and the freezing chamber are maintained at a cold temperature and a freezing temperature. 
     Also, in consideration of target temperatures of the freezing chamber and the refrigerating chamber that are considerably different from each other, a refrigerator in which a compressor for freezing and a compressor for refrigeration having different refrigeration capacities from each other are installed has been developed. In this refrigerator, each compressor is controlled based on the target temperatures of the refrigerating chamber and the freezing chamber, and thus each internal temperature of the refrigerating chamber and the freezing chamber are maintained at the target temperatures. 
     Here, the refrigeration capacity of the compressor for refrigeration is reduced to about 60% of that of a conventional compressor to increase an evaporation temperature of the refrigeration cycle for cooling the refrigerating chamber. 
     That is, the refrigeration further includes a small compressor having a small refrigeration capacity to increase the evaporation temperature of the refrigeration cycle for cooling the refrigerating chamber. 
     However, in a conventional refrigeration system, a subsidiary condenser may be provided so that a plurality of condensing processes are performed in the refrigeration cycle in some cases, but, in this case, there is a problem in that a radiant value of a main condenser is lowered due to the subsidiary condenser, and thus cooling efficiency is reduced. 
     TECHNICAL PROBLEM The present disclosure is directed to providing a refrigerator in which an expander is additionally provided between a condenser and a subsidiary condenser to effectively cool a plurality of storage chambers. 
     Technical Solution 
     One aspect of the present disclosure provides a refrigerator including a main body having a storage chamber; a compressor configured to compress a refrigerant; a condenser configured to condense the refrigerant compressed by the compressor; an evaporation expander configured to depressurize the refrigerant condensed by the condenser; a first evaporator configured to evaporate the refrigerant depressurized by the evaporation expander and thus to cool the storage chamber; a condensing expander installed between the condenser and the evaporation expander and configured to depressurize the refrigerant condensed by the condenser; and a subsidiary condenser installed between the condensing expander and the evaporation expander and configured to condense the refrigerant depressurized by the condensing expander. 
     The refrigerator may further include a refrigerant pipe configured to guide a flow of the refrigerant condensed by the condenser; a first branch passage branched from the refrigerant pipe; a second branch passage branched from the refrigerant pipe and in which the condensing expander is installed; and a valve device installed at the refrigerant pipe and configured to branch the refrigerant to the first and second branch passages, and the evaporation expander, the first evaporator, the condensing expander, and the subsidiary condenser are installed at the second branch passage. 
     A cold storage expander configured to depressurize the refrigerant condensed by the condenser and a cold storage evaporator configured to evaporate the refrigerant depressurized by the cold storage expander may be installed at the first branch passage. 
     The refrigerator may further include a cold storage part having a phase change material (PCM) therein and in which the subsidiary condenser and the cold storage evaporator are installed, and the cold storage part may exchange heat with each of the subsidiary condenser and the cold storage evaporator. 
     The valve device may be a three-way valve having one inlet port and first and second outlet ports, and the first branch passage may be connected with the first outlet port, and the second branch passage may be connected with the second outlet port. 
     The refrigerator may further include an input part configured to receive an input of a desired temperature of the storage chamber, and a temperature sensor provided at an inside of the storage chamber, and, when a temperature detected by the temperature sensor satisfies the desired temperature, the first outlet port is opened and the second outlet port is closed by the valve device and thus the refrigerant is guided to flow to the cold storage evaporator. 
     When the temperature detected by the temperature sensor does not satisfy the desired temperature, the second outlet port is opened and the first outlet port is closed by the valve device and thus the refrigerant is guided to flow to the first evaporator. 
     The refrigerator may further include a check valve installed at an entrance side of the first evaporator to guide a one-way flow of the refrigerant. 
     The storage chamber may include a refrigerating chamber and a freezing chamber, and the first evaporator may be installed at a rear wall of the freezing chamber, and the cold storage evaporator and the subsidiary condenser may be installed at a rear wall of the refrigerating chamber. 
     The refrigerator may further include a second evaporator installed at an exit side of the cold storage evaporator to evaporate again the refrigerant evaporated by the cold storage evaporator. 
     Another aspect of the present disclosure provides a refrigerator including a first refrigeration system including a first compressor, a first condenser, a first evaporation expander, and a first evaporator; and a second refrigeration system including a second compressor, a second condenser, a second evaporation expander and a second evaporator and configured to exchange heat with the first refrigeration system, wherein the second refrigeration system include a condensing expander configured to depressurize a refrigerant condensed by the second condenser, and a subsidiary condenser installed between the second evaporation expander and the condensing expander and configured to further condense the refrigerant depressurized by the condensing expander. 
     The refrigerator may further include a subsidiary evaporator configured to evaporate the refrigerant depressurized by the first evaporation expander. 
     Still another aspect of the present disclosure provides a method of controlling a refrigerator which includes a compressor, a condenser, an evaporator configured to cool a storage chamber, an evaporation expander provided at an entrance side of the evaporator to depressurize a refrigerant, and a cold storage evaporator configured to store cold air in a cold storage part, including driving the compressor, and introducing the refrigerant passing through the condenser into at least one of the evaporator and the cold storage evaporator by a valve device; and determining whether a temperature of the storage chamber satisfies a desired temperature, wherein, when the temperature of the storage chamber does not satisfy the desired temperature, the refrigerant flows through a condensing expander provided at an entrance side of the evaporator and a subsidiary condenser, and is introduced into the evaporator. 
     When the temperature of the storage chamber satisfies the desired temperature, the refrigerant flows through a cold storage expander provided at an entrance side of the cold storage evaporator and a subsidiary condenser, and is introduced into the cold storage evaporator. 
     Advantageous Effects 
     According to the embodiment proposed in the present disclosure, the radiant value of the condenser can be prevented from being lowered due to the subsidiary condenser, and thus the cooling efficiency of the refrigeration cycle can be increased. 
     Also, since the phase change material (PCM) is used as the cold storage material, the heat exchanging efficiency of the heat exchanger can be enhanced, and the internal temperature of the refrigerator can be constantly maintained. 
     Also, since a separate device for increasing the cooling efficiency, except the additional expander, is not provided, an internal design of the refrigerator is simple, and the space of the storage chamber can be effectively used. 
     Also, since the present disclosure has a simple cycle structure, the manufacturing cost thereof can be reduced. 
    
    
     
       DESCRIPTION OF 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 view illustrating an internal structure of a refrigerator according to an embodiment of the present disclosure; 
         FIG. 2  is a system view illustrating a refrigeration cycle structure of the refrigerator according to the embodiment of the present disclosure; 
         FIG. 3  is a view illustrating a partial structure of the refrigerator according to the embodiment of the present disclosure; 
         FIG. 4  is a cross-sectional view taken along a line I-I′ of  FIG. 1 ; 
         FIG. 5  is a control block diagram of the refrigerator according to the embodiment of the present disclosure; 
         FIG. 6  is a flowchart illustrating a method of controlling the refrigerator according to the embodiment of the present disclosure; 
         FIG. 7  is a graph illustrating a P-H diagram of a refrigerant circulated in the refrigerator according to the embodiment of the present disclosure; 
         FIG. 8  is a system view illustrating a refrigeration cycle structure of a refrigerator according to another embodiment of the present disclosure; 
         FIG. 9  is a view illustrating a partial structure of the refrigerator according to another embodiment of the present disclosure; 
         FIG. 10  is a longitudinal cross-sectional view of the refrigerator according to another embodiment of the present disclosure; 
         FIG. 11  is a control block diagram of the refrigerator according to another embodiment of the present disclosure; 
         FIGS. 12 and 13  are flowcharts illustrating a method of controlling the refrigerator according to anoter embodiment of the present disclosure; 
         FIG. 14  is a graph illustrating a P-H diagram of a refrigerant circulated in the refrigerator according to another embodiment of the present disclosure; 
         FIG. 15  is a view illustrating an internal structure of a refrigerator according to still another embodiment of the present disclosure; 
         FIG. 16  is a transverse cross-sectional view taken along a line I-I′ of  FIG. 15 ; 
         FIG. 17  is a longitudinal cross-sectional view taken along a line II-II of  FIG. 15 ; 
         FIG. 18  is a view illustrating a refrigeration cycle structure of the refrigerator according to still another embodiment of the present disclosure; 
         FIG. 19  is a graph illustrating a P-H diagram of a refrigerant circulated in the refrigerator according to still another embodiment of the present disclosure; 
         FIG. 20  is a control block diagram of the refrigerator according to still another embodiment of the present disclosure; and 
         FIG. 21  is a flowchart illustrating a method of controlling the refrigerator according to still another embodiment of the present disclosure. 
     
    
    
     MODE FOR INVENTION 
     Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. The embodiments may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, alternate embodiments falling within the spirit and scope will fully convey the concept to those skilled in the art. 
       FIG. 1  is a view illustrating an internal structure of a refrigerator according to an embodiment of the present disclosure. 
     Referring to  FIG. 1 , the refrigerator  1  according to the embodiment of the present disclosure includes a main body  11  of which a front surface is opened, and a storage chamber which is formed at an inside of the main body  11 . 
     The storage chamber includes a refrigerating chamber  12  and a freezing chamber  13 . The refrigerating chamber  12  and the freezing chamber  13  may be divided by a division part  14 . The refrigerating chamber  12  and the freezing chamber  13  may be referred to as a “first storage chamber” and a “second storage chamber,” respectively. 
     The refrigerator  1  may include an outer case  15  which forms an exterior thereof, a refrigerating chamber inner case  16 , and a freezing chamber inner case (not shown). 
     The refrigerating chamber inner case  16  is disposed at an inside of the outer case  15  to form an inner surface of the refrigerating chamber  12 . Also, the freezing chamber inner case (not shown) is disposed at the inside of the outer case  15  to form an inner surface of the freezing chamber  13 . 
     The refrigerator  1  may further include a freezing chamber door  21  and a refrigerating chamber door  22  which are coupled to a front side of the main body  11  to selectively open and close the freezing chamber  13  and the refrigerating chamber  12 . 
     In the embodiment, a bottom freezer type in which the freezing chamber is formed at a lower portion thereof and the refrigerating chamber is formed at an upper portion thereof will be described as an example. However, the spirit of the present disclosure may be applied to not only the above-described structure of the refrigerator, but also a top mount type in which the freezing chamber is formed at an upper portion thereof and the refrigerating chamber is formed at a lower portion thereof, or a side-by-side type in which the freezing chamber and the refrigerating chamber are provided at left and right sides thereof. 
     The refrigerator  1  may further include a refrigerating chamber cover plate  23  provided at the refrigerating chamber  12 . The refrigerating chamber cover plate  23  may be provided at a rear surface of the refrigerating chamber  12 . 
     A cold air discharging part  18  through which cold air is discharged to the refrigerating chamber  12  may be provided at the refrigerating chamber cover plate  23 . 
     A refrigerating chamber cover plate (not shown) having cold air discharging part (not shown) through which cold air is discharged may be also provided at a rear surface of the freezing chamber  13 . 
       FIG. 2  is a system view illustrating a refrigeration cycle structure of the refrigerator according to the embodiment of the present disclosure. 
     Referring to  FIG. 2 , the refrigerator  1  according to the embodiment of the present disclosure includes a first refrigeration system  10  and a second refrigeration system  20 . Each of the first and second refrigeration systems  10  and  20  includes a plurality of devices for driving a refrigeration cycle. 
     The first refrigeration system  10  includes a first compressor  110  which compresses a first refrigerant flowing in the first refrigeration system  10  and discharges the first refrigerant in a high temperature and high pressure state, a first condenser  120  which condenses the first refrigerant compressed by the first compressor  110  and maintained in the high temperature and high pressure state through radiation of heat, a first expander  141  which receives and depressurizes the refrigerant condensed by the first condenser  120 , a subsidiary evaporator  153  which evaporates the refrigerant depressurized by the first expander  141 , and a first evaporator  150  which evaporates the first refrigerant flowing in the subsidiary evaporator  153 . The first expander  141  may be referred to as a “first evaporation expander.” 
     The first refrigeration system  10  includes a refrigerant pipe  100  which connect the first compressor  110 , the first condenser  120 , the first expander  141 , the subsidiary evaporator  153 , and the first evaporator  150  to guide a flow of the refrigerant. 
     The second refrigeration system  20  includes a second compressor  210  which compresses a second refrigerant flowing in the second refrigeration system  20  and discharges the second refrigerant in a high temperature and high pressure state, a second condenser  220  which condenses the second refrigerant compressed by the second compressor  210  and maintained in the high temperature and high pressure state through radiation of heat, a second expander  143  which receives and depressurizes the refrigerant condensed by the second condenser  220 , a subsidiary condenser  223  which condenses once more the second refrigerant depressurized by the second expander  143 , a third expander  145  which depressurizes the second refrigerant condensed by the subsidiary condenser  223 , and a second evaporator  250  which evaporates the second refrigerant depressurized by the third expander  145 . The second expander  143  performs depressurizing for subsidiary condensing, and thus may be referred to as a “condensation expander,” and the third expander  145  may be referred to as a “second evaporation expander.” 
     In the subsidiary condenser  223 , the refrigerant is condensed at a lower pressure than that in the second condenser  220 . The second expander  143  may prevent a radiant value of the condenser  120  from being reduced due to the subsidiary condenser  121 . 
     The subsidiary condenser  223  may be installed adjacent to the subsidiary evaporator  153  so as to exchange heat with the subsidiary evaporator  153 . Specifically, the second refrigerant flowing through the subsidiary condenser  223  may be condensed using the cold air generated when the subsidiary evaporator  153  evaporates the first refrigerant. The subsidiary condenser  223  and the subsidiary evaporator  153  may be in contact with each other, but heat may be exchanged using a heat exchange plate  190  which will be described later. 
     When the refrigerant condensed by the second condenser  220  is depressurized by the second expander  143 , and then introduced into and condensed once more by the subsidiary condenser  223 , cooling performance may be enhanced. Enhancement of the cooling efficiency will be described later in detail with reference to  FIG. 7 . 
     The first to third expanders  141 ,  143 , and  145  may be commonly referred to as an expander  140 , and may be opened and closed according to a driving signal of a control part. 
     Specifically, when a refrigeration temperature of the refrigerating chamber  12  is higher than a first target temperature, the first expander  141  may be opened so that the first refrigerant is supplied to the first evaporator  150 , and when the refrigeration temperature of the refrigerating chamber  12  arrives at the first target temperature, the first expander  141  may be closed so that the first refrigerant supplied to the first evaporator  150  is blocked. 
     When a freezing temperature of the freezing chamber  13  is higher than a second target temperature, the second and third expanders  143  and  145  may be opened so that the second refrigerant is supplied to the second evaporator  250 , and when the freezing temperature of the freezing chamber  13  arrives at the second target temperature, the second and third expanders  143  and  145  may be closed so that the refrigerant supplied to the second evaporator  250  is blocked. Even when one of the second and third expanders  143  and  145  is closed, the refrigerant supplied to the second evaporator  250  may be blocked. 
     That is, the refrigerant is supplied to the first and second evaporators  150  and  250  according to opening driving of each of the first to third expanders  141 ,  143  and  145 . The first to third expanders  141 ,  143 , and  145  may include capillary tubes. 
     When the first expander  141  is opened and thus the first refrigerant is supplied, the first evaporator  150  serves to cool surrounding air and air in the refrigerating chamber  12  due to an cooling effect, and thus to lower a temperature of the refrigerating chamber  12 , and when the second and third expanders  143  and  145  are opened and thus the second refrigerant is supplied, the second evaporator  250  serves to cool surrounding air and air in the freezing chamber  13  due to the cooling effect, and thus to lower a temperature of the freezing chamber  13 . 
     In the first and second refrigeration systems  10  and  20 , refrigerants which have different refrigeration capacities per unit volume may be circulated to perform a cooling operation. 
     The first refrigeration system  10  may further include blower fans  125  and  155  which are provided at one side of the first condenser  120  or the first evaporator  150  to blow air. The blower fans  125  and  155  may include a first condenser fan  125  which is provided at one side of the condenser  120 , and a first evaporator fan  155  which is provided at one side of the evaporator  150 . 
     Also, the second refrigeration system  20  may further include blower fans  225  and  255  which are provided at one side of the second condenser  220  or the second evaporator  250  to blow air. 
     The blower fans  225  and  255  may include a second condenser fan  225  which is provided at one side of the second condenser  220 , and a second evaporator fan  255  which is provided at one side of the second evaporator  250 . 
     Heat exchanging performance of the first and second evaporators  150  and  250  may be changed according to RPMs of the first and second evaporator fans  155  and  255 . For example, when more cold air is required due to an operation of the first evaporator  150 , the RPM of the first evaporator fan  155  may be increased, and when the cold air is sufficient, the RPM of the first evaporator fan  155  may be reduced. 
       FIG. 3  is a view illustrating a partial structure of the refrigerator according to the embodiment of the present disclosure, and  FIG. 4  is a cross-sectional view taken along a line I-I′ of  FIG. 1 . 
     Referring to  FIGS. 3 and 4 , the refrigerator  1  according to the embodiment of the present disclosure may include a machinery chamber  30  which is formed at the lower portion of the refrigerator  1 , a first refrigeration chamber  31  which supplies the cold air to the refrigerating chamber  12 , and a second refrigeration chamber  32  which supplies the cold air to the freezing chamber  13 . The cold air of the first and second refrigeration chambers  31  and  32  may be discharged to the refrigerating chamber  12  and the freezing chamber  13  through the cold air discharging part  18 . 
     The first and second compressors  110  and  210  and the first and second condensers  120  and  220  may be installed at the machinery chamber  30 . 
     The first refrigeration chamber  31  may be provided at a rear wall of the refrigerating chamber  12 , and may be formed between the refrigerating chamber inner case  16  and the refrigerating chamber cover plate  23 . The first evaporator  150 , the subsidiary condenser  223 , and the subsidiary evaporator  153  may be installed at the first refrigeration chamber  31 . 
     The first evaporator  150  may be in contact with the refrigerating chamber cover plate  23 , and may be fixed to the refrigerating chamber cover plate  23  by a holder (not shown). 
     The heat exchange plate  190  may be provided between the subsidiary condenser  223  and the subsidiary evaporator  153 . The subsidiary condenser  223 , the subsidiary evaporator  153 , and the heat exchange plate  190  may be in contact with each other in order, and the subsidiary condenser  223  may exchange heat with the subsidiary evaporator  153  through the heat exchange plate  190 . 
     The subsidiary evaporator  153  may be in contact with the refrigerating chamber inner case  16 . Also, the subsidiary evaporator  153  may be fixed by the holder (not shown) provided at the refrigerating chamber inner case  16 , and the subsidiary condenser  223  may be fixed to the heat exchange plate  190 . 
     As illustrated in the drawing, the subsidiary condenser  223  may be spaced from or in contact with the first evaporator  150 . 
     A refrigerant pipe  150   a  of the first evaporator  150 , a refrigerant pipe  153   a  of the subsidiary evaporator  153 , and a refrigerant pipe  223   a  of the subsidiary condenser  223  may be bent and extend vertically. 
     Since the refrigerant pipe  150   a  of the first evaporator  150 , the refrigerant pipe  153   a  of the subsidiary evaporator  153 , and the refrigerant pipe  223   a  of the subsidiary condenser  223  are vertically installed adjacent to each other, an installation space for the plurality of devices forming the refrigeration cycle may be reduced. Therefore, a storage space of the storage chamber may be prevented from being reduced. 
     The second refrigeration chamber  32  may be provided at a rear wall of the freezing chamber  13 , and may be formed between the freezing chamber inner case and the freezing chamber cover plate  24 . The second evaporator  250  may be installed at the second refrigeration chamber  32 . 
     A gas-liquid separator  180  which filters a liquid refrigerant out of the refrigerant evaporated by the first and second evaporators  150  and  250  and supplies a gas phase refrigerant to the first and second compressors  110  and  210  may be provided at one side of each of the first and second evaporators  150  and  250 . 
       FIG. 5  is a control block diagram of the refrigerator according to the embodiment of the present disclosure, and  FIG. 6  is a flowchart illustrating a method of controlling the refrigerator according to the embodiment of the present disclosure. 
     Referring to  FIGS. 5 and 6 , the refrigerator  1  according to the embodiment of the present disclosure may include a control part  50 , an input part  41  which allows a user to input a desired temperature of the freezing chamber and a desired temperature of the refrigerating chamber, a refrigerating chamber temperature sensor  42  which detects a temperature of the refrigerating chamber  12 , and a freezing chamber temperature sensor  43  which detects a temperature of the freezing chamber  13 . The refrigerating chamber temperature sensor  42  and the freezing chamber temperature sensor  43  may be referred to as a “first temperature sensor” and a “second temperature sensor,” and may be commonly called “temperature sensors.” 
     The control part  50  may control the first and second compressors  110  and  210 , the first and second condenser fans  125  and  225 , the first and second evaporator fans  155  and  255 , and the expanders  140  according to whether the temperatures detected by the temperature sensors  42  and  43  satisfy the desired temperatures. 
     A method of controlling the refrigerator  1  according to whether to satisfy the desired temperatures of the refrigerating chamber  12  and the freezing chamber  13  will be described with reference to  FIG. 6 . 
     The refrigerator is operated, and the control part  50  performs control so that the refrigeration cycle is circulated in the first refrigeration system  10 . Specifically, the control part  50  may control the first compressor  110  and the first evaporator fan  155  to be driven, and may also control the first expander  141  to be opened (S 1 ). 
     Also, the control part  50  performs control so that the refrigeration cycle is circulated in the second refrigeration system  20 . Specifically, the control part  50  may control the second compressor  210  and the second evaporator fan  255  to be driven, and may also control the second and third expanders  143  and  145  to be opened (S 2 ). 
     At this time, when a predetermined period of time passes after the first compressor  110  is driven, the second compressor  210  may be controlled to be driven, such that the first refrigeration system  10  starts a circulation operation before the second refrigeration system  20 . For example, after  3  minutes after the first compressor  110  is driven, the second compressor  210  may be controlled to be driven. 
     This is because circulation of the refrigerant occurs in the subsidiary evaporator  153  before the subsidiary condenser  223 , and thus the second refrigerant may be effectively condensed in the subsidiary condenser  223  due to the air cooled while the first refrigerant is evaporated in the subsidiary evaporator  153 . 
     Then, the desired temperature input by the user is received through the input part  41 , and internal temperatures are detected by the refrigerating chamber temperature sensor  42  and the freezing chamber temperature sensor  43  (S 3 ). A process of receiving the input of the desired temperature and a process of detecting the internal temperature may be performed in a different order, and the process of receiving the input of the desired temperature and detecting the internal temperature may be performed before the refrigeration cycle is driven. 
     First, by comparing the temperature detected by the refrigerating chamber temperature sensor  42  with the desired temperature, it is determined whether the temperature of the refrigerating chamber  12  satisfies the desired temperature (S 4 ). The desired temperature may be temperature range information which does not have a lower limit. That is, the desired temperature information may be set so that the temperature of the refrigerating chamber  12  is maintained to be a certain temperature or less. 
     When the temperature of the refrigerating chamber  12  satisfies the desired temperature, i.e., the temperature of the refrigerating chamber  12  is lower than the desired temperature, the control part  50  controls the refrigeration cycle of the first refrigeration system  10  to be stopped. Specifically, the control part  50  may control the first compressor  110  and the first evaporator fan  155  to be stopped, and also may control the first expander  141  to be closed (S 5 ). 
     However, when the temperature of the refrigerating chamber  12  does not satisfy the desired temperature, i.e., the temperature of the refrigerating chamber  12  is higher than the desired temperature, the control part  50  controls the first and second refrigeration systems  10  and  20  to be continuously circulated. 
     Then, by comparing the temperature detected by the freezing chamber temperature sensor  43  with the desired temperature, it is determined whether the temperature of the freezing chamber  13  satisfies the desired temperature (S 6 ). 
     When the temperature of the freezing chamber  13  satisfies the desired temperature, i.e., the temperature of the freezing chamber  13  is lower than the desired temperature, the control part  50  controls the refrigeration cycle of the second refrigeration system  20  to be stopped. Specifically, the control part  50  may control the second compressor  210  and the second evaporator  250  to be stopped, and also may control the second expander  143  or the third expander  145  to be closed. Even though one of the second and third expanders  143  and  145  is closed, the circulation of the refrigerant in the second refrigeration system  20  may be stopped (S 7 ). 
     On the contrary, when the temperature of the freezing chamber  13  does not satisfy the desired temperature, i.e., the temperature of the freezing chamber  13  is higher than the desired temperature, the control part  50  controls the first and second refrigeration systems  10  and  20  to be continuously circulated. 
     A control process according to whether the temperature of the refrigerating chamber  12  satisfies the desired temperature, and a control process according to whether the temperature of the freezing chamber  13  satisfies the desired temperature may be performed in a different order, and the control processes may be performed at the same time. 
       FIG. 7  is a graph illustrating a P-H diagram of the refrigerant circulated in the refrigerator according to the embodiment of the present disclosure. 
     Referring to  FIG. 7 , R is a diagram representing a refrigerant cycle of the first refrigeration system  10 , and F is a diagram representing a refrigerant cycle of the second refrigeration system  20 . 
     When the first refrigerant is circulated in the first refrigeration system  10 , the refrigeration cycle is circulated in order of A→B→C→D, and when the refrigerator  1  is in the “freezing chamber operation mode”, the refrigeration cycle is circulated in order of A′→B′→C′→D′→E→F. When each of the first refrigerant and the second refrigerant has different refrigeration capacities per unit volume, there may be a difference in a refrigeration effect between the first and second refrigeration systems  10  and  20 , as illustrating in  FIG. 7 . 
     When the refrigerant is circulated in the first refrigeration system  10 , an A-phase refrigerant inhaled into the first compressor  110  is changed into a B-phase after compressed. And the refrigerant condensed by the first condenser  120  has a C-phase. 
     Then, the C-phase refrigerant is changed into a D-phase after depressurized by the first expander  141 , and the refrigerant evaporated by the subsidiary evaporator  153  and the first evaporator  150  has an A-phase. 
     Meanwhile, when the refrigerant is circulated in the second refrigeration system  20 , an A′-phase refrigerant inhaled into the second compressor  210  is changed into a B′-phase after compressed. And the refrigerant condensed by the second condenser  220  has a C′-phase. 
     Then, the C′-phase refrigerant is introduced into the second expander  143 . The refrigerant introduced into and depressurized by the second expander  143  has a D′-phase. 
     The D′-phase refrigerant depressurized by the second expander  143  is introduced into the subsidiary condenser  223 , and then condensed once more. The refrigerant introduced into and condensed by the subsidiary condenser  223  has an E-phase. 
     Then, the E-phase refrigerant condensed by the subsidiary condenser  223  is introduced into the third expander  145 , and depressurized once more. The refrigerant introduced into and depressurized by the third expander  145  has an F-phase. 
     The F-phase refrigerant depressurized by the first expander  145  is introduced into the second evaporator  250 , and the refrigerant introduced into and evaporated by the second evaporator  250  has an A′-phase. According to such a refrigeration cycle, an evaporation capacity at the second evaporator  250  is h 2 -h 1 ′. 
     In the subsidiary condenser  223 , the refrigerant is condensed at a lower pressure than that in the second condenser  220 , and the second expander  143  serves to prevent the radiant value of the condenser  220  from being reduced due to the subsidiary condenser  223 . 
     Meanwhile, in the case of the second refrigeration system  20 , when the second expander  143  is not provided at the refrigeration cycle, the C-phase refrigerant condensed by the second condenser  220  and the subsidiary condenser  223  is changed into a G-phase after depressurized by the third expander  145 , and the G-phase refrigerant is changed into the A′-phase while being evaporated by the second evaporator  250 . According to such a refrigeration cycle, the evaporation capacity at the second evaporator  250  is h 2 -h 1 . 
     Therefore, since the evaporation capacity when the second expander  143  is provided at the refrigeration cycle is h 2 -h 1 ′, and the evaporation capacity when the second expander  143  is not provided at the refrigeration cycle is h 2 -h 1 , the evaporation capacity in the case in which the second expander  143  is provided may be increased by Ah, compared to that in the case in which the second expander  143  is not provided. 
     Therefore, operation performance of the refrigerator may be improved, and a power consumption may be relatively reduced, compared with other refrigerators having the same operation performance. Eventually, operation efficiency of the refrigerator may be enhanced. 
     Hereinafter, a refrigerator according to another embodiment of the present disclosure will be described. 
       FIG. 8  is a system view illustrating a refrigeration cycle structure of a refrigerator according to another embodiment of the present disclosure. 
     The refrigerator of the embodiment is different from that of the previous embodiment in only the refrigerant cycle structure. Therefore, the description overlapping that of the previous embodiment will be omitted. Also, elements having the same or similar functions will be given like reference numerals. The element having the same reference numeral can quote the description in the previous embodiment, except particular portions. 
     Referring to  FIG. 8 , the refrigerator  2  according to the embodiment of the present disclosure includes a plurality of devices for driving the refrigeration cycle. 
     Specifically, the refrigerator  2  may include a compressor  310  which compresses a refrigerant, a condenser  320  which condenses the refrigerant compressed by the compressor  310 , a plurality of expanders  341 ,  343 , and  345  which depressurize the refrigerant condensed by the condenser  320 , a plurality of evaporators  350 ,  353 , and  360  which evaporate the refrigerant depressurized by the plurality of expanders  341 ,  343 , and  345 , and a subsidiary condenser  323  which condenses the refrigerant depressurized by one of the plurality of expanders  341 ,  343 , and  345 . 
     The refrigerator  2  includes a refrigerant pipe  300  which connects the compressor  310 , the condenser  320 , the expanders  341 ,  343 , and  345 , and the evaporators  350  and  360  to guide a flow of the refrigerant. 
     The plurality of evaporators  350 ,  353 , and  360  include a first evaporator  360  which generates cold air supplied to one of the refrigerating chamber  12  and the freezing chamber  13 , a second evaporator  350  which generates the cold air supplied to the other storage chamber, and a cold storage evaporator  353  which is installed adjacent to the subsidiary condenser  323 . The subsidiary condenser  323  may be in contact with the cold storage evaporator  353 . The first evaporator  360  may be referred to as a “freezing chamber evaporator,” and the second evaporator  350  may be referred to as a “refrigerating chamber evaporator.” 
     The first evaporator  360  may generate the cold air supplied to the freezing chamber  13 , and may be disposed at one side of the freezing chamber  13 . The second evaporator  350  may generate the cold air supplied to the refrigerating chamber  12 , and may be disposed at one side of the refrigerating chamber  12 . 
     A temperature of the cold air supplied to the freezing chamber  13  may be lower than that of the cold air supplied to the refrigerating chamber  12 , and thus a refrigerant evaporation pressure of the first evaporator  360  may be lower than that of the second evaporator  350 . 
     The refrigerant pipe  300  at exit sides of the first and second evaporators  360  and  350  extends to an entrance side of the compressor  310 . Therefore, the refrigerant passing through the first and second evaporators  360  and  350  may be introduced into the compressor  310 . 
     The refrigerator  2  may further include a cold storage part  370  which surrounds the subsidiary condenser  323  and the cold storage evaporator  353 , and exchanges heat with the subsidiary condenser  323  or the cold storage evaporator  353 . 
     It may be understood that the cold storage part  370  is an indirect cooling unit for cooling the refrigerating chamber  12 . Specifically, the cold storage part  370  includes a case  371  which defines a storage space, and a cold storage material  372  which is stored in an inside of the case  371 . 
     The cold storage material  372  may include a phase change material (PCM) of which a phase is changed at a low temperature to accomplish a cooling effect. For example, the PCM may include water or carbon dioxide. 
     When the PCM is used as the cold storage material, high density cold air may be stored through an inflow and outflow of a large quantity of cold air during a phase changing process, while a predetermined target temperature is maintained. Also, since a setting temperature may be maintained for a long period of time without external power supply, it is possible to contribute to energy saving. 
     The cold storage evaporator  353  may be installed at an inside of the case  371  of the cold storage part  370  to evaporate the refrigerant and thus to store the cold air in the cold storage material  372 , and the subsidiary condenser  323  may condense the refrigerant using the cold air stored in the cold storage material  372 . Also, the subsidiary condenser  323  may be directly in contact with the cold storage evaporator  353  to perform a heat exchanging operation therewith and thus to condense the refrigerant. 
     The refrigerator  2  includes first and second branch passages  301  and  302  which branch the refrigerant passing through the condenser  320 . The first and second branch passages  301  and  302  are branched from the refrigerant pipe  300 . 
     The refrigerator  2  may further include a valve device  330  which is installed at the refrigerant pipe  300  to branch the refrigerant into the first and second branch passages  301  and  302 . 
     The valve device  330  may include a three-way valve having one inlet port through which the refrigerant is introduced, and two outlet ports through which the refrigerant is discharged. The one inlet port is connected to the refrigerant pipe  300 , and a first outlet port of the two outlet ports is connected to the first branch passage  301 , and a second outlet port is connected to the second branch passage  302 . At least one of the first and second outlet ports may be opened according to control of the valve device  330 , and thus a flow route of the refrigerant may be changed. 
     The second evaporator  350  may be installed at an exit side of the cold storage evaporator  353  on the first branch passage  301 . 
     The first evaporator  360  and the third expander  345  installed at an entrance side of the first evaporator  360  to expand the refrigerant may be provided at the second branch passage  302 . The third expander  345  may include a capillary tube. The third expander  345  is referred to as a “first evaporation expander.” 
     The first expander  341  and the cold storage evaporator  353  installed at an exit side of the first expander  341  to evaporate the refrigerant depressurized by the first expander  341  may be installed at the first branch passage  301 . The first expander  341  may include a capillary tube. 
     The refrigerant flows through the first branch passage  301  and then is introduced into the cold storage evaporator  353 , and the cold air may be stored in the PCM while the refrigerant is evaporated in the cold storage evaporator  353 . The first expander  341  is referred to as a “second evaporation expander.” 
     In order for the refrigerant evaporation pressure of the first evaporator  360  to be formed lower than that of the second evaporator  350 , a diameter of the capillary tube of the third expander  345  may be smaller than that of the capillary tube of the first expander  341 . 
     The third expander  345 , the subsidiary condenser  323  which is installed at an entrance side of the third expander to condense the refrigerant, and the second expander  343  which is installed at an entrance side of the subsidiary condenser  323  to depressurize the refrigerant condensed by the condenser  320  may be installed at the second branch passage  302 . The second expander  343  may include a capillary tube, and may be referred to as a “condensing expander,” because the second expander  343  performs a depressurizing operation for a subsidiary condensing operation. 
     The cooling performance may be enhanced by depressurizing the refrigerant condensed in the condenser  320  and then condensing the refrigerant in the subsidiary condenser  323  (referring to  FIG. 14 ). 
     The valve device  330  may be controlled so that the flow route of the refrigerant is changed according to an operation mode of the refrigerator. Here, the operation mode of the refrigerator may include a “simultaneous operation mode” in which the cooling operations of the refrigerating chamber and the freezing chamber are performed, a “refrigerating chamber operation mode” in which the cooling operation of the refrigerating chamber is performed, a “freezing chamber operation mode” in which the cooling operation of the freezing chamber is performed, and a “cold storage operation mode” in which the cold energy is stored in the cold storage part  370 . The “cold storage operation mode” may be simultaneously performed with the “refrigerating chamber operation mode.” 
     As an example, when the simultaneous operation mode is performed, the valve device  330  may be controlled so that the refrigerant is branched and supplied to the first and second branch passages  301  and  302 . That is, the valve device  330  may be operated so that all of the two outlet ports are opened. 
     As another example, when the refrigerating chamber operation mode is performed, the refrigerant is supplied to the second evaporator  350 . And the valve device  330  may be controlled so that the refrigerant is branched and supplied to the first branch passage  301 . That is, the valve device  330  may be operated so that the first outlet port connected to the first branch passage  301  is opened. 
     When the first outlet port is opened, the refrigerant passes through the first branch passage  301 , is depressurized by the first expander  341 , flows to the cold storage evaporator  353  to be evaporated and thus to store the cold air in the cold storage material  372 , and then flows to the second evaporator  350 . Then, while the refrigerant is evaporated at the second evaporator  350 , peripheral heat is absorbed to cool the air. 
     As still another example, when the freezing chamber operation mode is performed, the refrigerant is supplied to the first evaporator  360 . And the valve device  330  may be controlled so that the second outlet port connected to the second branch passage  302  is opened. 
     When the second outlet port is opened, the refrigerant passes through the second branch passage  302 , is depressurized by the second expander  343 , flows to the subsidiary condenser  323  to be condensed, and then flows to the first evaporator  360 . Then, while the refrigerant is evaporated at the first evaporator  360 , the peripheral heat is absorbed to cool the air. 
     As yet another example, when the cold storage operation mode is performed, the flow of the refrigerant and the operation of the valve device  330  are the same as those in the refrigerating chamber operation mode, but as described later, there is a difference in only whether the evaporator fan is operated. 
     The above described operation mode may be performed based on whether to satisfy the internal temperature of the refrigerator  2 , and a detailed method according to whether to satisfy the internal temperature may be described later with reference to  FIG. 12 . 
     Meanwhile, the refrigerator  2  may include blower fans  325 ,  355  and  365  which are respectively provided at one side of the heat exchanger to blow the air. The blower fans  325 ,  355 , and  365  include a condenser fan  325  which is provided at one side of the condenser  320 , a first evaporator fan  355  which is provided at one side of the second evaporator  350 , and a second evaporator fan  365  which is provided at one side of the first evaporator  360 . 
     Heat exchanging performance of the first and second evaporators  350  and  360  may be changed according to RPMs of the first and second evaporator fans  355  and  365 . For example, when more cold air is required due to an operation of the second evaporator  350 , the RPM of the first evaporator fan  355  may be increased, and when the cold air is sufficient, the RPM of the first evaporator fan  355  may be reduced. 
       FIG. 9  is a view illustrating a partial structure of the refrigerator according to another embodiment of the present disclosure, and  FIG. 10  is a longitudinal cross-sectional view of the refrigerator according to another embodiment of the present disclosure. 
     Referring to  FIGS. 9 and 10 , the refrigerator  2  according to another embodiment of the present disclosure may include a machinery chamber  30  which is formed at a lower portion of the refrigerator  2 , a first refrigeration chamber  31  which supplies the cold air to the refrigerating chamber  12 , and a second refrigeration chamber  32  which supplies the cold air to the freezing chamber  13 . The cold air of the first and second refrigeration chamber  31  and  32  may be discharged to the refrigerating chamber  12  and the freezing chamber  13  through the cold air discharging part  18 . 
     The compressor  310  and the condenser  320  may be installed at the machinery chamber  30 . 
     The first refrigeration chamber  31  may be provided at a rear wall of the refrigerating chamber  12 , and may be formed between the refrigerating chamber inner case  16  and the refrigerating chamber cover plate  23 . The second evaporator  350 , the cold storage part  370 , and the subsidiary condenser  323  and the cold storage evaporator  353  which are provided at an inside of the cold storage part  370  may be installed at the first refrigeration chamber  31 . 
     The second evaporator  350  may be in contact with the refrigerating chamber cover plate  23 , and may be fixed thereto by a holder (not shown). 
     The cold storage part  370  may be in contact with the refrigerating chamber inner case  16 , and may be fixed thereto by a holder (not shown). The second evaporator  350  and the cold storage part  370  may be spaced from each other, as illustrated in the drawing. However, the second evaporator  350  may be in contact with the cold storage part  370 . 
     A refrigerant pipe  350   a  of the second evaporator  350 , a refrigerant pipe  353   a  of the cold storage evaporator  353  and a refrigerant pipe  323   a  of the subsidiary condenser  323  may be bent and extend vertically. 
     Since the refrigerant pipe  350   a  of the second evaporator  350 , the refrigerant pipe  353   a  of the cold storage evaporator  353  and the refrigerant pipe  323   a  of the subsidiary condenser  323  are installed adjacent to each other, an installation space for the plurality of devices forming the refrigeration cycle may be reduced. Thus, a storage space of the storage chamber may be prevented from being reduced. 
     The second refrigeration chamber  32  may be provided at a rear wall of the freezing chamber  13 , and may be formed between the freezing chamber inner case and the freezing chamber cover plate  24 . The first evaporator  360  may be installed at the second refrigeration chamber  32 . 
     A gas-liquid separator  180  which filters a liquid refrigerant out of the refrigerant evaporated by the first and second evaporators  350  and  360  and supplies a gas phase refrigerant to the compressors  310  may be provided at one side of each of the first and second evaporators  350  and  360 . 
       FIG. 11  is a control block diagram of the refrigerator according to another embodiment of the present disclosure, and  FIGS. 12 and 13  are flowcharts illustrating a method of controlling the refrigerator according to the embodiment of the present disclosure. 
     Referring to  FIGS. 11 to 13 , the refrigerator  2  according to the embodiment of the present disclosure may include a control part  50 , an input part  41  which allows a user to input a desired temperature of the freezing chamber and a desired temperature of the refrigerating chamber, a refrigerating chamber temperature sensor  42  which detects a temperature of the refrigerating chamber  12 , and a freezing chamber temperature sensor  43  which detects a temperature of the freezing chamber  13 . The refrigerating chamber temperature sensor  42  and the freezing chamber temperature sensor  43  may be referred to as a “first temperature sensor” and a “second temperature sensor”. 
     The control part  50  may control the compressor  310 , the condenser fan  325 , the first evaporator fan  355 , the second evaporator fan  365  and the valve device  330  according to whether the temperatures detected by the temperature sensors  42  and  43  satisfy the desired temperatures. 
     A method of controlling the refrigerator  2  according to whether to satisfy the desired temperature of the refrigerating chamber  12  will be described with reference to  FIG. 12 . 
     The refrigerator is operated, and the desired temperature input by the user is received through the input part  41 , and the temperature of the refrigerating chamber  12  is detected by the refrigerating chamber temperature sensor  42  (S 11 ). A process of receiving the input of the desired temperature and a process of detecting the temperature may be performed in a different order. 
     By comparing the temperature detected by the refrigerating chamber temperature sensor  42  with the desired temperature, it is determined whether the temperature of the refrigerating chamber  12  satisfies the desired temperature (S 12 ). The desired temperature may be temperature range information which does not have a lower limit. That is, the desired temperature information may be set so that the temperature of the refrigerating chamber  12  is maintained to be a certain temperature or less. 
     When the temperature of the refrigerating chamber  12  satisfies the desired temperature, the control part  50  controls the refrigeration cycle to be stopped (S 13 ). Specifically, the control part  50  may control the compressor  310  and the first evaporator fan  355  to be stopped (S 14 ). 
     As described above, when the refrigeration cycle is stopped, a cooling effect due to the refrigeration cycle does not occur, and the internal temperature of the refrigerator may be maintained in a certain level due to an indirect cooling effect by the cold storage part  370 . 
     However, when the temperature of the refrigerating chamber  12  does not satisfy the desired temperature, the control part  50  controls the refrigerator  2  to be driven in the refrigerating chamber operation mode, and at the same time, a cold storage operation is also performed (S 15 ). Specifically, the control part  50  may control the compressor  310  and the first evaporator fan  355  to be driven (S 16 ). Also, the valve device  330  is controlled so that the first outlet port is opened and the second outlet port is closed (S 17 ). 
     Therefore, the refrigerant may flow to the cold storage evaporator  353  and the second evaporator  350 . Specifically, when the refrigerant depressurized by the first expander  341  is evaporated in the cold storage evaporator  353 , the cold storage operation in which the cold air is stored in the cold storage material is performed, and when the refrigerant passing through the cold storage evaporator  353  is evaporated in the second evaporator  350 , the refrigerating chamber operation mode in which the air flowing in the first refrigeration chamber  31  is cooled is performed. 
     When the control according to whether the temperature of the refrigerating chamber  12  satisfies the desired temperature is finished, another control according to whether the temperature of the freezing chamber  13  satisfies the desired temperature may be performed. A detained control method according to whether the temperature of the freezing chamber  13  satisfies the desired temperature will be described with reference to  FIG. 13 . 
     The refrigerator is operated, and the desired temperature input by the user is received through the input part  41 , and the temperature of the freezing chamber  13  is detected by the freezing chamber temperature sensor  43  (S 21 ). A process of receiving the input of the desired temperature and a process of detecting the temperature may be performed in a different order. 
     By comparing the temperature detected by the freezing chamber temperature sensor  43  with the desired temperature, it is determined whether the temperature of the freezing chamber  13  satisfies the desired temperature (S 22 ). The desired temperature may be set so that the temperature of the freezing chamber  13  is maintained below a certain temperature. 
     When the temperature of the freezing chamber  13  satisfies the desired temperature, the control part  50  controls the refrigeration cycle to be stopped (S 23 ). Specifically, the control part  50  may control the compressor  310  and the first evaporator fan  355  to be stopped (S 24 ). Also, the valve device  330  may be controlled so that the first and second outlet ports are closed (S 25 ). 
     However, when the temperature of the freezing chamber  13  does not satisfy the desired temperature, the control part  50  controls the refrigerator  2  to be driven in the freezing chamber operation mode (S 26 ). Specifically, the control part  50  may control the compressor  310  and the second evaporator fan  365  to be driven (S 27 ). Also, the valve device  330  is controlled so that the second outlet port is opened and the first outlet port is closed (S 28 ). 
     Therefore, the refrigerant may flow to the subsidiary condenser  323  and the first evaporator  360 . Specifically, the refrigerant depressurized by the second expander  343  is condensed in the subsidiary condenser  323 , and the refrigerant passing through the subsidiary condenser  323  is depressurized again in the third expander  345  and then evaporated in the first evaporator  360 , and thus the air flowing in the second refrigeration chamber  32  is cooled. In the subsidiary condenser  323 , the refrigerant is condensed at a lower pressure than that in the condenser  320 . Since a condensing and expanding process of the refrigerant is added, the cooling efficiency may be increased, and a detailed principle thereof will be described in  FIG. 14 . 
     A control process according to whether the temperature of the refrigerating chamber  12  satisfies the desired temperature, and a control process according to whether the temperature of the freezing chamber  13  satisfies the desired temperature may be performed in a different order, and the control processes may be performed at the same time. At this time, when both of the temperatures of the refrigerating chamber  12  and the freezing chamber  13  do not satisfy the desired temperatures, the simultaneous operation mode in which the refrigerant simultaneously flows to the first and second evaporators  350  and  360  may be performed. At this time, the flow of the refrigerant in each of the refrigerating chamber operation and the freezing chamber refrigeration operation quotes the description in the refrigerating chamber operation mode and the freezing chamber operation mode. 
       FIG. 14  is a graph illustrating a P-H diagram of the refrigerant circulated in the refrigerator according to another embodiment of the present disclosure. 
     Referring to  FIG. 14 , R is a diagram representing a refrigerant cycle in the refrigerating chamber operation mode, and F is a diagram representing a refrigerant cycle in the freezing chamber operation mode. 
     When the refrigerator  2  is in the “refrigerating chamber operation mode,” the refrigeration cycle is circulated in order of A→B→C→D, and when the refrigerator  2  is in the “freezing chamber operation mode,” the refrigeration cycle is circulated in order of A′→B′→C′→D′→E→F. 
     In the case of the refrigerating chamber operation mode, an A-phase refrigerant inhaled into the compressor  310  is changed into a B-phase after compressed. And the refrigerant condensed by the condenser  320  has a C-phase. 
     Then, the refrigerant passing through the valve device  330  and depressurized by the first expander  341  has a D-phase, and the refrigerant evaporated in the cold storage evaporator  353  and the second evaporator  350  has an A-phase. 
     Meanwhile, in the case of the freezing chamber operation mode, an A′-phase refrigerant inhaled into the compressor  310  is changed into a B′-phase after compressed. And the refrigerant condensed by the condenser  320  has a C-phase. 
     And the C-phase refrigerant passes through the valve device  330  and is introduced into the second expander  343 . The refrigerant introduced into and depressurized by the second expander  343  has a D′-phase. 
     The D′-phase refrigerant depressurized in the second expander  343  is introduced into the subsidiary condenser  323  and then condensed once more. The refrigerant introduced into and condensed by the subsidiary condenser  323  has an E-phase. 
     Then, the E-phase refrigerant condensed in the subsidiary condenser  323  is introduced into the third expander  345  and condensed once more. The refrigerant introduced into and depressurized by the third expander  345  has an F-phase. 
     The F-phase refrigerant depressurized in the first expander  341  is introduced into the first evaporator  360 , and the refrigerant introduced into and evaporated by the first evaporator  360  has an A′-phase. According to such a refrigeration cycle, an evaporation capacity at the first evaporator  360  is h 2 -h 1 ′. 
     In the subsidiary condenser  323 , the refrigerant is condensed at a lower pressure than that in the condenser  320 , and the second expander  343  serves to prevent the radiant value of the condenser  320  from being reduced due to the subsidiary condenser  323 . 
     Meanwhile, in the refrigerating chamber operation mode, when the second expander  343  is not provided at the refrigeration cycle, the C-phase refrigerant condensed by the condenser  320  and the subsidiary condenser  323  is changed into a G-phase after depressurized by the third expander  345 , and the G-phase refrigerant is changed into the A′-phase while being evaporated by the first evaporator  360 . According to such a refrigeration cycle, the evaporation capacity at the first evaporator  360  is h 2 -h 1 . 
     Therefore, since the evaporation capacity, when the second expander  343  is provided at the refrigeration cycle, is h 2 -h 1 ′, and the evaporation capacity when the second expander  343  is not provided at the refrigeration cycle is h 2 -h 1 , the evaporation capacity in the case in which the second expander  343  is provided may be increased by Ah, compared to that in the case in which the second expander  343  is not provided. 
     Therefore, operation performance of the refrigerator may be improved, and a power consumption may be relatively reduced, compared with other refrigerators having the same operation performance. Eventually, operation efficiency of the refrigerator may be enhanced. 
     Hereinafter, a refrigerator according to still another embodiment will be described. 
       FIG. 15  is a view illustrating an internal structure of a refrigerator according to still another embodiment of the present disclosure. 
     In the refrigerator according to the embodiment, the description overlapped with the previous embodiment will be omitted. Also, elements having the same or similar functions will be given like reference numerals. The element having the same reference numeral can quote the description in the previous embodiment, except particular portions. 
     Referring to  FIG. 15 , the refrigerator  3  according to the embodiment of the present disclosure includes a main body  61  of which a front surface is opened, and a storage chamber which is formed at an inside of the main body  61 . The storage chamber includes a freezing chamber  62  and a refrigerating chamber  63 . The freezing chamber  62  and the refrigerating chamber  63  may be divided by a division part  64 . 
     The main body  61  may include an outer case  65  which defines an exterior of the refrigerator  3 , a freezing chamber inner case  66  which is disposed at an inside of the outer case  65  to form an inner surface of the freezing chamber  62 , and a refrigerating chamber inner case  67  which is disposed at the inside the outer case  65  to form an inner surface of the refrigerating chamber  63 . The freezing chamber inner case  66  and the refrigerating chamber inner case  67  may be commonly referred to as “inner cases”. 
     Also, the refrigerator  3  may further include a freezing chamber door  71  and a refrigerating chamber door  72  which are rotatably coupled to a front side of the main body  61  to selectively open and close the freezing chamber  62  and the refrigerating chamber  63 . 
     In the embodiment, a side-by-side type in which the freezing chamber and the refrigerating chamber are provided at left and right sides thereof will be described as an example. However, the spirit of the present disclosure may be applied to not only the above-described structure of the refrigerator, but also a top mount type in which the freezing chamber is formed at an upper portion thereof and the refrigerating chamber is formed at a lower portion thereof, or a bottom freezer type in which the freezing chamber is formed at a lower portion thereof and the refrigerating chamber is formed at an upper portion thereof. 
     The freezing chamber  62  may include a freezing chamber damper  82  through which air cooled by an evaporator  450  (referring to  FIG. 16 ) which will be described later is discharged to the freezing chamber  62 . The freezing chamber damper  82  may be provided at a rear surface of the freezing chamber  62 , and may be formed at the freezing chamber cover plate  73 . The evaporator  450  is disposed at a rear side of the freezing chamber cover plate  73 . 
     A refrigerating chamber cover plate  74  having a cold air discharging part (not shown) through which cold air is discharged may be also provided at a rear surface of the refrigerating chamber  63 . 
       FIG. 16  is a transverse cross-sectional view taken along a line I-I′ of  FIG. 15 ,  FIG. 17  is a longitudinal cross-sectional view taken along a line II-IF of  FIG. 15 , and  FIG. 18  is a view illustrating a refrigeration cycle structure of the refrigerator according to still another embodiment of the present disclosure. 
     Referring to  FIGS. 16 to 18 , the refrigerator  3  according to the embodiment of the present disclosure may include a refrigeration chamber  81  which is provided at an inside of the refrigerator  3 , the evaporator  450  which is installed at the refrigeration chamber  81  to evaporate a refrigerant, a refrigerating chamber damper  69  which controls a flow of the air cooled by the evaporator  450  in the refrigerating chamber  63 , the freezing chamber damper  82  which controls a flow of the air cooled by the evaporator  450  in the freezing chamber  62 , and a cold storage part  460  which is installed between the refrigerating chamber inner case  67  and the refrigerating chamber cover plate  74 . The cold storage part  460  may be fixed to the refrigerating chamber cover plate  74  by a holder (not shown), but is not limited thereto. 
     The refrigerating chamber damper  69  may be installed at the division part  64  which divides the freezing chamber  62  and the refrigerating chamber  63 . When the refrigerating chamber damper  69  is opened, the cold air in the refrigeration chamber  81  may be introduced into the refrigerating chamber  63  through the refrigerating chamber damper  69 . 
     It may be understood that the cold storage part  460  is an indirect cooling unit for cooling the refrigerating chamber  63 . Specifically, the cold storage part  460  includes a case  461  which defines a storage space, and a cold storage material  462  which is stored at an inside of the case  461 . 
     The cold storage material  462  may include a phase change material (PCM) of which a phase is changed at a low temperature to perform a cooling operation. For example, the PCM may include water or carbon dioxide. 
     When the PCM is used as the cold storage material, high density cold air may be stored through an inflow and outflow of a large quantity of cold air during a phase changing process, while a predetermined target temperature is maintained. Also, since a setting temperature may be maintained for a long period of time without external power supply, it is possible to contribute to energy conservation. 
     A cold storage evaporator  451  which evaporates the refrigerant to store cold air in the cold storage material  462 , and a subsidiary condenser  421  in which the refrigerant is condensed by the cold storage material  462  may be installed at an inside of the case  461  of the cold storage part  460 . 
     A refrigerant pipe  451   a  of the cold storage evaporator  451  may be bent and extend vertically. And a refrigerant pipe  421   a  of the subsidiary condenser  421  may be bent and extend vertically. 
     Since the refrigerant pipe  451   a  of the cold storage evaporator  451 , the refrigerant pipe  421   a  of the subsidiary condenser  421  are vertically installed adjacent to each other, an installation space for the cold storage evaporator  451  and the subsidiary condenser  421  may be reduced. Thus, a storage space of the storage chamber may be prevented from being reduced. 
     A machinery chamber  80  may be formed at the lower portion of the refrigerator  3 . A compressor  410  which compresses the refrigerant evaporated in the evaporator  450  and a condenser  420  which condenses the refrigerant compressed in the compressor  410  may be included at an inside of the machinery chamber  80 . 
     The refrigerator  3  includes a refrigerant pipe  400  which connects the compressor  410  and the condenser  420  so as to guide the flow of the refrigerant. 
     The refrigerator  3  includes first and second branch passages  401  and  402  which branch the refrigerant passing through the condenser  420 . The refrigerator  3  includes a valve device  430  which is installed at the refrigerant pipe  400  to branch the refrigerant into the first and second branch passages  401  or  402 . The valve device  430  may include a three-way valve having one inlet port through which the refrigerant is introduced, and two outlet ports through which the refrigerant is discharged. The one inlet port is connected to the refrigerant pipe  400 , and a first outlet port of the two outlet ports is connected to the first branch passage  401 , and a second outlet port is connected to the second branch passage  402 . At least one of the first and second outlet ports may be opened according to a control operation of the valve device  330 , and thus a flow route of the refrigerant may be changed. 
     The cold storage evaporator  451  which evaporates the refrigerant and the first and a first expander  441  which is installed at an entrance side of the cold storage evaporator  451  may be installed at the first branch passage  401 . The first expander  441  may include a capillary tube. 
     When the refrigerant condensed by the condenser  420  flows through the first branch passage  401  and then is introduced into the cold storage evaporator  451 , the cold energy may be stored in the PCM while the refrigerant is evaporated in the cold storage evaporator  451 . The first expander  441  is referred to as a “cold storage expander.” 
     The subsidiary condenser  421  which condenses the refrigerant and the second expander  442  which is installed at an entrance side of the subsidiary condenser  421  to depressurize the refrigerant may be installed at the second branch passage  402 . The second expander  442  may include a capillary tube, and may be referred to as a “condensing expander”, because the second expander  343  performs a depressurizing operation for a subsidiary condensing operation. 
     When the refrigerant condensed in the condenser  420  flows through the second branch passage  402 , and is then introduced into the subsidiary condenser  421 , the cooling performance may be enhanced by depressurizing the refrigerant condensed in the condenser  420  and then condensing the refrigerant in the subsidiary condenser  421  (referring to  FIG. 19 ). 
     The evaporator  450  which is installed at the entrance side of the subsidiary condenser  421  and a third expander  443  which is installed at an entrance side of the evaporator  450  may be installed at the second branch passage  402 . The third expander  443  may include a capillary tube. The third expander  443  is referred to as an “evaporation expander”. 
     A control operation of the valve device  430  may be performed based on whether an internal temperature of the refrigerator  3  satisfies the desired temperature. 
     When the internal temperature of the refrigerator  3  satisfies the desired temperature, the refrigerator  3  is controlled to perform a “low cold energy operation” in which cold air is stored in the cold storage material  462 . Specifically, the valve device  430  is controlled so that the first outlet port is opened and thus the refrigerant flows to the cold storage evaporator  451  through the first branch passage  401 . At this time, the second outlet port may be closed. 
     However, when the internal temperature of the refrigerator  3  does not satisfy the desired temperature, the refrigerator  3  is controlled to perform a “high cold energy operation.” Specifically, the valve device  430  is controlled so that the second outlet port is opened and thus the refrigerant flows to the second branch passage  402 . At this time, the first outlet port may be closed. 
     A detailed control method in the high cold air operation or the low cold air operation will be described in  FIG. 21 . 
     The refrigerant evaporated in the evaporator  450  is introduced into the compressor  410 , and a check valve  470  which prevent a back flow of the refrigerant may be installed at the refrigerant pipe  400  between the evaporator  450  and the compressor  410 . 
     The refrigerator  3  may further include blower fans  425  and  455  which are provided at one side of the condenser  420  or the evaporator  450  to blow the air. The blower fans  425  and  455  includes a condenser fan  425  which is provided at one side of the condenser  420 , and an evaporator fan  455  which is provided at one side of the evaporator  450 . 
     Heat exchanging performance of the evaporator  450  may be changed according to an RPM of the evaporator fan  455 . For example, when more cold air is required due to an operation of the evaporator  450 , the RPM of the evaporator fan  455  may be increased, and when the cold air is sufficient, the RPM of the evaporator fan  455  may be reduced. 
       FIG. 19  is a graph illustrating a P-H diagram of a refrigerant circulated in the refrigerator according to still another embodiment of the present disclosure. 
     Referring to  FIGS. 18 and 19 , when the refrigerator according to the embodiment of the present disclosure performs the “low cold air operation,” the refrigeration cycle is circulated in order of A→B→C→D. At this time, it is assumed that performance of the cold storage evaporator  451  is the same as that of the evaporator  450 , and performance of the first expander  441  is the same as that of the third expander  443 . Therefore, it may be understood that the two cycles are different from each other in whether the second expander  442  and the subsidiary condenser  421  are installed. 
     Specifically, an A-phase refrigerant introduced into the compressor  410  is changed into a B-phase after compressed. And the refrigerant condensed by the condenser  420  has a C-phase. 
     Then, the refrigerant passing through the valve device  430  and depressurized by the first expander  441  has a D-phase, and the refrigerant depressurized by the first expander  441  is introduced into the cold storage evaporator  451 , and the refrigerant evaporated by the cold storage evaporator  451  has an A-phase. 
     According to such as refrigeration cycle, an evaporation capacity at the cold storage evaporator  450  is h 2 -h 1 . This is a result when it is assumed that the performance of the cold storage evaporator  451  is the same as that of the evaporator  450 . 
     However, when the first expander  441  is provided at the refrigeration cycle, i.e., the “high cold energy operation” is performed, the refrigeration cycle is circulated in order of A→B→C→D′→E→F. 
     Specifically, an A-phase refrigerant introduced into the compressor  410  is changed into a B-phase after compressed. And the B-phase refrigerant is introduced into and condensed by the first condenser  120 , and then changed into a C-phase. 
     Then, the C-phase refrigerant passes through the valve device  430  and is introduced into the second expander  442 . The refrigerant introduced into and depressurized by the second expander  442  has a D′-phase. 
     The D′-phase refrigerant depressurized by the second expander  442  is introduced into the subsidiary condenser  421 , and then condensed once more. The refrigerant introduced into and condensed by the subsidiary condenser  421  has an E-phase. 
     Then, the refrigerant condensed by the subsidiary condenser  421  is introduced into the first expander  441 , and depressurized once more. The refrigerant introduced into the third expander  443  and depressurized has an F-phase. 
     The F-phase refrigerant depressurized by the third expander  443  is introduced into the evaporator  450 , and the refrigerant introduced into and evaporated by the evaporator  450  has an A-phase. 
     In the subsidiary condenser  421 , the refrigerant is condensed at a lower pressure than that in the condenser  420 , and the second expander  442  serves to prevent the radiant value of the condenser  420  from being reduced due to the subsidiary condenser  421 . 
     According to such as refrigeration cycle, an evaporation capacity at the evaporator  450  is h 2 -h 1 ′. 
     It can be understood that h 2 -h 1 ′ which is the evaporation capacity at the evaporator  450  is larger than h 2 -h 1  which is the evaporation capacity at the cold storage evaporator  451  by Ah due to the depressurizing operation of the refrigerant in the second expander  442 . Since this is a result when it is assumed that the performance of the cold storage evaporator  451  is the same as that of the evaporator  450 , and the performance of the first expander  441  is the same as that of the third expander  443 , it may be understood that the evaporation capacity is increased by adding the second expander  442  to the refrigeration cycle, and the cooling efficiency is also increased. 
     Therefore, operation performance of the refrigerator may be improved, and a power consumption may be relatively reduced, compared with other refrigerators having the same operation performance. Eventually, operation efficiency of the refrigerator may be enhanced. 
       FIG. 20  is a control block diagram of the refrigerator according to still another embodiment of the present disclosure. 
     Referring to  FIG. 20 , the refrigerator  3  according to the embodiment of the present disclosure may include a control part  50 , an input part  41  which allows a user to input a desired temperature of the freezing chamber and a desired temperature of the refrigerating chamber, a freezing chamber temperature sensor  43  which detects a temperature of the freezing chamber  62 , and a refrigerating chamber temperature sensor  42  which detects a temperature of the refrigerating chamber  63 . The freezing chamber temperature sensor  43  and the refrigerating chamber temperature sensor  42  may be commonly called “temperature sensors”. 
     The control part  50  may control the compressor  410 , the condenser fan  425 , the valve device  430 , the evaporator fan  455 , the freezing chamber damper  82  and the refrigerating chamber damper  69  according to whether the temperatures detected by the temperature sensors  42  and  43  satisfy the desired temperatures. 
     The control part  50  may primarily control the freezing chamber damper  82  and the refrigerating chamber damper  69  according to whether the temperatures detected by the temperature sensors  42  and  43  satisfy the desired temperatures, and thus may control the internal temperature of the refrigerator. 
     Specifically, when the temperature detected by the freezing chamber temperature sensor  43  does not satisfy the desired temperatures, the control part  50  may control the freezing chamber damper  82  to be maximally opened, and thus the cold air is introduced into the freezing chamber  62 . When the temperature detected by the freezing chamber temperature sensor  43  satisfies the desired temperatures, the control part  50  may control the freezing chamber damper  82  so that the cold air is not introduced into the freezing chamber  62 . 
     Also, when the temperature detected by the refrigerating chamber temperature sensor  42  does not satisfy the desired temperatures, the control part  50  may control the refrigerating chamber damper  60  to be maximally opened, and thus the cold air is introduced into the refrigerating chamber  63 . When the temperature detected by the refrigerating chamber temperature sensor  42  satisfies the desired temperatures, the control part  50  may control the refrigerating chamber damper  69  so that the cold air is not introduced into the refrigerating chamber  63 . 
     Meanwhile, when the temperatures detected by the temperature sensors  42  and  43  do not satisfy the desired temperatures even though the dampers  82  and  69  are controlled, the control part  50  may control the compressor  410 , the condenser fan  425 , the valve device  430  and the evaporator fan  455 , and thus may control the refrigeration cycle to perform the high cold energy operation or the low cold energy operation. A detailed control method thereof will be described in  FIG. 21 . 
       FIG. 21  is a flowchart illustrating a method of controlling the refrigerator according to still another embodiment of the present disclosure. The method of controlling the refrigerator according to still another embodiment of the present disclosure will be described with reference to  FIG. 21 . 
     When an operation the refrigerator  3  is started, the control part  50  drives the compressor  410 , and thus the refrigeration cycle is circulated (S 31 ). 
     Then, the desired temperatures of the refrigerating chamber and the freezing chamber are input and received through the input part  41  by the user (S 32 ), and the internal temperature of the refrigerator is detected using the freezing chamber temperature sensor  43  or the refrigerating chamber temperature sensor  42  (S 33 ). 
     When the internal temperature of the refrigerator is detected by the sensor, the control part  50  determines whether the internal temperature of the refrigerator satisfies the desired temperature (S 34 ). 
     When the internal temperature of the refrigerator satisfies the desired temperature, i.e., the temperature of the refrigerating chamber or the freezing chamber satisfies the desired temperature, the control part  50  controls the refrigeration cycle to perform the cold storage operation (low cold energy operation) (S 35 ). 
     Specifically, the control part  50  controls the evaporator fan  455  to be stopped (S 36 ), and controls the valve device  430  so that the first outlet port is opened and the second outlet port is closed (S 37 ). 
     When the internal temperature of the refrigerator does not satisfy the desired temperature, the control part  50  controls the refrigeration cycle to perform the high cold air operation, and thus cools an inside of the refrigerator (S 38 ). The case in which the internal temperature of the refrigerator does not satisfy the desired temperature is a case in which the temperature of the freezing chamber  62  does not satisfy the desired temperature. When the temperature of the freezing chamber  62  satisfies the desired temperature, but the temperature of the refrigerating chamber  63  does not satisfy the desired temperature, the refrigerating chamber damper  69  is controlled to be opened, such that the cold air in the refrigeration chamber  81  is introduced into the refrigerating chamber  63 . 
     Specifically, the evaporator fan  455  is controlled to be driven (S 39 ), and the valve device  430  is controlled so that the second outlet port is opened and the first outlet port is closed (S 40 ). Sequentially, the internal temperature of the refrigerator  3  may be detected, and then it is determined whether to satisfy the desired temperature. 
     According to the embodiment proposed in the present disclosure, the radiant value of the condenser can be prevented from being lowered due to the subsidiary condenser, and thus the cooling efficiency of the refrigeration cycle can be increased. 
     Also, since the phase change material (PCM) is used as the cold storage material, the heat exchanging efficiency of the heat exchanger can be enhanced, and the internal temperature of the refrigerator can be constantly maintained. 
     Also, since a separate device for increasing the cooling efficiency, except the additional expander, is not provided, an internal design of the refrigerator is simple, and the space of the storage chamber can be effectively used. 
     Also, since the present disclosure has a simple cycle structure, the manufacturing cost thereof can be reduced. 
     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.