Patent Publication Number: US-2012023975-A1

Title: Refrigerator and control method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 2010-0074683, filed on Aug. 2, 2010 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Embodiments relate to a refrigerator in which a freezing compartment and a refrigerating compartment are respectively provided with evaporators to enable independent cooling of the freezing compartment and the refrigerating compartment, and a control method thereof. 
     2. Description of the Related Art 
     A refrigerator serves to keep food fresh at a low temperature for a long time by lowering the interior temperature of a storage compartment thereof via a refrigeration cycle in which refrigerant undergoes compression, condensation, expansion and evaporation. 
     Conventional refrigerators, in which a freezing compartment and a refrigerating compartment are respectively provided with evaporators, may be classified into parallel-cycle refrigerators using a 3-way valve to enable independent operation of the freezing compartment and the refrigerating compartment, and serial-cycle refrigerators in which the evaporators of the freezing compartment and the refrigerating compartment are connected in series without a valve. 
     The above described conventional refrigerators may have a risk of explosion if refrigerant leaks from a refrigerant pipe during defrosting of the evaporators of the freezing compartment and the refrigerating compartment. 
     In addition, the conventional cycle refrigerators may cause deterioration in cooling efficiency of the freezing compartment and increase energy consumption because of a higher evaporation temperature of the refrigerating compartment upon simultaneous cooling of the freezing compartment and the refrigerating compartment. 
     SUMMARY 
     Therefore, it is one aspect to provide a refrigerator and a control method thereof, in which a flow path to a freezing compartment evaporator and a refrigerating compartment evaporator is intercepted during defrosting, preventing explosion of the refrigerator. 
     It is another aspect to provide a refrigerator and a control method thereof, which may increase cooling efficiency of a freezing compartment upon simultaneous cooling of the freezing compartment and a refrigerating compartment. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention. 
     In accordance with one aspect, a refrigerator includes a compressor, a condenser to condense refrigerant compressed in the compressor, a freezing compartment evaporator and a refrigerating compartment evaporator installed respectively in a freezing compartment and a refrigerating compartment to evaporate the condensed refrigerant into gas-phase refrigerant, a valve to open or close a flow path of the refrigerant, and a control unit to close the valve if implementation of a defrosting operation of any one of the freezing compartment evaporator and the refrigerating compartment evaporator is determined. 
     The valve may be a 3-way valve connected to a discharge pipe of the condenser and suction pipes of the freezing compartment evaporator and the refrigerating compartment evaporator. 
     The valve may be an On-Off valve connected to a discharge pipe of the condenser and suction pipes of the freezing compartment evaporator and the refrigerating compartment evaporator. 
     The control unit may determine whether to perform the defrosting operation of the freezing compartment evaporator and the refrigerating compartment evaporator, closes the valve to prevent the refrigerant from moving into the freezing compartment evaporator and the refrigerating compartment evaporator if implementation of the defrosting operation of the freezing compartment evaporator and the refrigerating compartment evaporator is determined, performs a refrigerant collecting operation, and opens the closed valve upon completion of the defrosting operation. 
     The refrigerant collecting operation may be performed in such a manner that the compressor is operated in a closed state of the valve to move the refrigerant distributed in the freezing compartment evaporator and the refrigerating compartment evaporator into the condenser. 
     In accordance with another aspect, a control method of a refrigerator includes determining whether to perform a defrosting operation of a freezing compartment evaporator and a refrigerating compartment evaporator, closing the valve to prevent refrigerant from moving into the freezing compartment evaporator and the refrigerating compartment evaporator if implementation of the defrosting operation of the freezing compartment evaporator and the refrigerating compartment evaporator is determined, performing a refrigerant collecting operation, and opening the closed valve upon completion of the defrosting operation. 
     Implementation of the refrigerant collecting operation may include operating the compressor in a closed state of the valve to move the refrigerant distributed in the freezing compartment evaporator and the refrigerating compartment evaporator into the condenser. 
     In accordance with another aspect, a refrigerator includes a freezing compartment evaporator, a refrigerating compartment evaporator, a freezing compartment fan and a refrigerating compartment fan, which are independently installed in a freezing compartment and a refrigerating compartment, and a control unit to reduce revolutions per minute of the refrigerating compartment fan upon simultaneous cooling of the freezing compartment and the refrigerating compartment, wherein the freezing compartment evaporator is located at a front end of the refrigerating compartment evaporator and is connected in series to the refrigerating compartment evaporator. 
     In accordance with another aspect, a control method of a refrigerator including a refrigerating compartment evaporator, a freezing compartment evaporator located at a front end of the refrigerating compartment evaporator and connected in series thereto, a refrigerating compartment fan and a freezing compartment fan to enable independent cooling of a freezing compartment and a refrigerating compartment, includes determining whether or not a freezing compartment and a refrigerating compartment are simultaneously cooled, and reducing revolutions per minute of the refrigerating compartment fan to reduce evaporation capacity of the refrigerating compartment if simultaneous cooling of the freezing compartment and the refrigerating compartment is determined. 
     In accordance with another aspect, a refrigerator includes a first refrigerant circuit, through which refrigerant discharged from a compressor moves toward an entrance of the compressor by way of a condenser, a valve, a first expansion device, a first evaporator and a second evaporator, and a control unit to control opening/closing of the valve according to whether or not a defrosting operation of the first evaporator and the second evaporator is performed. 
     The control unit may determine whether to perform the defrosting operation of the first evaporator and the second evaporator, close the valve to prevent the refrigerant from moving into the first evaporator and the second evaporator if implementation of the defrosting operation of any one of the first evaporator and the second evaporator is determined, perform a refrigerant collecting operation, and open the closed valve upon completion of the defrosting operation. 
     The refrigerant collecting operation may be performed in such a manner that the compressor is operated in a closed state of the valve to move the refrigerant distributed in the first evaporator and the second evaporator into the condenser. 
     The valve may be an On-Off valve connected to a discharge pipe of the condenser and suction pipes of the first evaporator and the second evaporator. 
     The refrigerator may further include a second refrigerant circuit, through which the refrigerant discharged from the compressor moves toward a suction side of the compressor by way of the condenser, the valve, a second expansion device and the second evaporator. The valve may be a 3-way valve connected to a discharge pipe of the condenser and suction pipes of the first evaporator and the second evaporator. 
     In accordance with another aspect, a control method of a refrigerator including a first refrigerant circuit, through which refrigerant discharged from a compressor moves toward an entrance of the compressor by way of a condenser, a valve, a first expansion device, a first evaporator and a second evaporator, and a control unit to control opening/closing of the valve according to whether or not a defrosting operation of the first evaporator and the second evaporator is performed, includes determining whether to perform a defrosting operation of the first evaporator and the second evaporator, closing the valve to prevent refrigerant from moving into the first evaporator and the second evaporator if implementation of any one of the defrosting operation of the first evaporator and the second evaporator is determined, performing a refrigerant collecting operation, and opening the closed valve upon completion of the defrosting operation. 
     In accordance with a further aspect, a control method of a refrigerator including a first refrigerant circuit, through which refrigerant discharged from a compressor moves toward an entrance of the compressor by way of a condenser, a valve, a first expansion device, a first evaporator and a second evaporator, a second refrigerant circuit, through which the refrigerant discharged from the compressor moves toward a suction side of the compressor by way of the condenser, the valve, a second expansion device and the second evaporator, and a control unit to control opening/closing of the valve according to whether or not a defrosting operation of the first evaporator and the second evaporator is performed, the control method includes determining whether to perform a defrosting operation of the first evaporator and the second evaporator, closing the valve to prevent refrigerant from moving into the first evaporator and the second evaporator if implementation of any one of the defrosting operation of the first evaporator and the second evaporator is determined, performing a refrigerant collecting operation, and opening the closed valve upon completion of the defrosting operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a front view illustrating an exterior configuration of a refrigerator according to an embodiment; 
         FIG. 2  is a front view illustrating an interior configuration of the refrigerator according to the embodiment; 
         FIG. 3  is a control block diagram of the refrigerator according to the embodiment; 
         FIG. 4A  is a serial refrigerant circuit according to an embodiment; 
         FIG. 4B  is a parallel refrigerant circuit according to an embodiment; 
         FIG. 5  is a flow chart illustrating the valve control of the refrigerant circuit of  FIGS. 4A and 4B ; 
         FIG. 6  is a refrigerant circuit according to another embodiment; 
         FIG. 7  is a flow chart illustrating the fan control of the refrigerant circuit of  FIG. 6  upon simultaneous cooling of a freezing compartment and a refrigerating compartment; and 
         FIG. 8  is a refrigerant circuit according to a further embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
     Hereinafter, a refrigerator and a control method thereof according to an exemplary embodiment will be described in detail with reference to  FIGS. 1 to 8 . 
       FIG. 1  is a front view illustrating an exterior configuration of the refrigerator according to the embodiment, and  FIG. 2  is a front view illustrating an interior configuration of the refrigerator according to the embodiment. 
     Referring to  FIGS. 1 and 2 , the refrigerator according to the embodiment of the present invention includes a body  10  in which a freezing compartment  12  and a refrigerating compartment  14  are defined, and doors  13  and  15  hingedly coupled to the body  10  to open or close the freezing compartment  12  and the refrigerating compartment  14  respectively. 
     The freezing compartment  12  and the refrigerating compartment  14  are horizontally divided by a partition  11  provided in the body  10  to prohibit movement of cold air between the compartments  12  and  14 . A freezing compartment evaporator  32  and a refrigerating compartment evaporator  34  are individually installed in a rear region of the freezing compartment  12  and the refrigerating compartment  14 , to enable cooling of the respective compartments  12  and  14 . 
       FIG. 3  is a control block diagram of the refrigerator according to the embodiment. 
     Referring to  FIG. 3 , a control unit  110  is connected to an input unit  121 , a temperature sensing unit  122 , and a defrosting sensing unit  123 . 
     The input unit  121  serves to input a user control command to the control unit  110  and is provided with a plurality of buttons including, e.g., a mode selection button to control operations of the freezing compartment and the refrigerating compartment, and a temperature setting button to set respective temperatures of the freezing compartment and the refrigerating compartment. 
     The temperature sensing unit  122  is mounted, e.g., to inner walls of the freezing compartment and the refrigerating compartment. The temperature sensing unit  122  serves to sense the interior temperature of the freezing compartment and the refrigerating compartment and transmit the sensed temperature value to the control unit  110 . The temperature value constitutes data to determine the operational condition (simultaneous cooling or individual cooling) of the freezing compartment and the refrigerating compartment. 
     The temperature sensing operation using the temperature sensing unit  122  may be performed in response to a sensing command from the control unit  110 , or may be performed independently even without receiving the sensing command. 
     The defrosting sensing unit  123  may adopt a sensor, a resistance value of which varies based on the temperature of the freezing compartment evaporator and the refrigerating compartment evaporator. 
     Considering the principle of a defrosting sensing operation in detail, the freezing compartment evaporator and the refrigerating compartment evaporator are frosted by moisture because they perform a cooling operation as refrigerant received therein evaporates by absorbing heat from the surrounding air. The frosted evaporator may cause a variation in the resistance value of the sensor. Thereby, the control unit  100  determines whether to perform a defrosting operation upon receiving a voltage or current signal corresponding to the resistance value of the sensor from the defrosting sensing unit  123 . 
     The control unit  110  is also connected to a compressor drive unit  131 , a fan drive unit  132 , a valve drive unit  133 , a defrosting heater drive unit  134  and a display unit  135 . 
     The compressor drive unit  131  drives a compressor based on a drive control signal of the control unit  110 . If the compressor is a linear compressor, the compressor drive unit  131  performs, e.g., generation and application of a Pulse Width Modulation (PWM) signal for drive voltage application based on a command from the control unit  110 . 
     The fan drive unit  132  drives a freezing compartment fan  132   a , a refrigerating compartment fan  132   b , and a condenser fan  132   c  based on a drive control signal of the control unit  110 . The fan drive unit  132  may be a single unit as illustrated in  FIG. 3 , or may include a plurality of units corresponding to the respective fans  132   a ,  132   b  and  132   c.    
     In the present embodiment, the fan drive unit  132  functions to reduce revolutions per minute of the refrigerating compartment fan  132   b  upon simultaneous cooling of the freezing compartment and the refrigerating compartment. This may reduce the evaporation capacity of the refrigerating compartment evaporator, thereby preventing an increase in the evaporation temperature of the freezing compartment. 
     The valve drive unit  133  performs opening/closing of a valve based on a drive control signal of the control unit  110 . The valve may be a 3-way valve or On-Off valve. 
     In the present embodiment, the valve drive unit  133  closes the valve to intercept a flow path to the freezing compartment evaporator and the refrigerating compartment evaporator if any one of the freezing compartment and the refrigerating compartment is subjected to a defrosting operation. The valve drive unit  133  again opens the valve to enable movement of refrigerant upon completion of the defrosting operation. Opening or closing the valve by the valve drive unit  133  according to whether the defrosting operation is performed or not may eliminate any risk of explosion due to leakage of refrigerant from a refrigerant pipe during the defrosting operation. 
     The defrosting heater drive unit  134  drives defrosting heaters provided in the freezing compartment and the refrigerating compartment. The defrosting heater drive unit  134  supplies heat to the freezing compartment evaporator and the refrigerating compartment evaporator based on a drive control signal of the control unit  110 . The supplied heat acts to remove frost formed on the freezing compartment evaporator and the refrigerating compartment evaporator. 
     The display unit  135  displays the operational state of the refrigerator, various setting values, temperature, and so on. 
     A memory unit  140  stores temperature control values and defrosting conditions based on the operational condition of the freezing compartment and the refrigerating compartment determined by the control unit  110 . The memory unit  140  stores a control factor for a valve control operation to intercept the flow path to the freezing compartment evaporator and the refrigerating compartment evaporator during the defrosting operation. The memory unit  140  also stores a control factor to reduce revolutions per minute of the refrigerating compartment fan  132   b  upon simultaneous cooling of the freezing compartment and the refrigerating compartment. 
     The control unit  110  determines whether to perform startup of the refrigerator by comparing the temperatures of the freezing compartment and the refrigerating compartment sensed by the temperature sensing unit  122  with preset temperatures stored in the memory unit  140 . 
     If the temperature of the freezing compartment or the refrigerating compartment is higher than a preset temperature by a predetermined value or more, the compressor is operated after load of the compartment is calculated according to a temperature difference. The startup time of the refrigerator is the operation time of the compressor. 
     The control unit  110  also compares the defrosting signal transmitted from the defrosting sensing unit  123  with the defrosting conditions stored in the memory unit  140 . If any one(s) of the evaporators fulfills the defrosting conditions, the control unit  110  controls the corresponding evaporator(s) to perform a defrosting operation. The defrosting conditions may be set by, e.g., a reference voltage value or a reference current value. 
     In the present embodiment, if it is determined to perform a defrosting operation upon the freezing compartment and the refrigerating compartment, the control unit  110  transmits a valve closing control signal to the valve drive unit  133 . After completion of the defrosting operation, the control unit  110  again opens the valve, allowing the refrigerant to move into the freezing compartment evaporator and the refrigerating compartment evaporator. 
     In the present embodiment, the control unit  110  reduces revolutions per minute of the refrigerating compartment fan  132   b  upon simultaneous cooling of the freezing compartment and the refrigerating compartment. 
       FIG. 4A  is a serial refrigerant circuit according to an embodiment. 
     In  FIG. 4A , the serial refrigerant circuit  200  according to the embodiment of the present invention includes a compressor  210 , a condenser  220 , a valve  230 , an expansion device  240 , a refrigerating compartment evaporator  250 , and a freezing compartment evaporator  260 . 
     The compressor  210  compresses suctioned low-temperature and low-pressure gas-phase refrigerant to discharge high-temperature and high-pressure gas-phase refrigerant. 
     The condenser  220  is connected to a high-pressure discharge pipe of the compressor  210  and condenses the compressed high-temperature and high-pressure gas-phase refrigerant from the compressor  210  into liquid-phase refrigerant via heat exchange with the surrounding air. 
     The valve  230  is an On-Off valve to open or close the flow path of the refrigerant having passed through the condenser  220 . 
     In the present embodiment, the valve  230  opens or closes the flow path to the refrigerating compartment evaporator and the freezing compartment evaporator according to whether the defrosting operation of the refrigerator is performed or not. 
     The room-temperature and high-pressure liquid-phase refrigerant, condensed in the condenser  220 , is introduced into the expansion device  240  by way of the valve  230 . The expansion device  240  includes a capillary tube or an expansion valve to expand and decompress the room-temperature and high-pressure liquid-phase refrigerant into low-temperature and low-pressure two-phase refrigerant in the mixture of liquid-phase and gas-phase components. 
     The freezing compartment evaporator  260  and the refrigerating compartment evaporator  250  evaporate the expanded low-temperature and low-pressure liquid-phase refrigerant from the expansion device  240  into gas-phase refrigerant by absorbing heat from the surrounding air, thereby supplying cold air. The freezing compartment evaporator  260  and the refrigerating compartment evaporator  250  constitute a serial circulation configuration to enable independent operation of the&#39;freezing compartment and the refrigerating compartment. 
     In the serial refrigerant circuit  200 , the refrigerant circulates in the sequence of the compressor  210 →the condenser  220 →the valve  230 →the expansion device  240 →the refrigerating compartment evaporator  250 →the freezing compartment evaporator  260 →the compressor  210 . 
     In addition, the condenser  220  is provided with a condenser fan  221  and a condenser fan motor  222  to drive the condenser fan  221 . The refrigerating compartment evaporator  250  and the freezing compartment evaporator  260  are respectively provided with a refrigerating compartment fan  252  and a freezing compartment fan  262  to blow cold air generated from the respective evaporators  250  and  260 . Also, a refrigerating compartment fan motor  253  and a freezing compartment fan motor  263  are provided respectively to drive the refrigerating compartment fan  252  and the freezing compartment fan  262 , and defrosting heaters  251  and  261  are provided to remove frost formed on the refrigerating compartment evaporator  250  and the freezing compartment evaporator  260 . 
       FIG. 4B  is a parallel refrigerant circuit according to an embodiment. 
     In  FIG. 4B , the parallel refrigerant circuit  300  according to the embodiment of the present invention includes a compressor  310 , a condenser  320 , a valve  330 , a first expansion device  341 , a second expansion device  342 , a refrigerating compartment evaporator  350 , and a freezing compartment evaporator  360 . 
     The valve  330  is a 3-way valve having a single entrance and two exits to selectively switch the flow path of the refrigerant having passed through the condenser  320  based on an operational mode (simultaneous or individual operation of the freezing compartment). The single entrance is connected to a discharge pipe of the condenser  320  and the two exits are connected respectively to the first expansion device  341  and the second expansion device  342 . 
     In the present embodiment, the valve  330  opens or closes a flow path to the refrigerating compartment evaporator  350  and a flow path to the freezing compartment evaporator  360  according to whether the defrosting operation of the refrigerator is performed or not. 
     In the parallel refrigerant circuit  300 , the refrigerant circulates in the sequence of the compressor  310 →the condenser  320 →the valve  330 →the first expansion device  341 →the refrigerating compartment evaporator  350 →the freezing compartment evaporator  360 →the compressor  310 , or in the sequence of the compressor  310 →the condenser  320 →the valve  330 →the second expansion device  342 →the freezing compartment evaporator  360 →the compressor  310 . 
     Other configurations are identical to those of  FIG. 4A , and a description thereof is replaced by that of  FIG. 4A . 
     Hereinafter, a control method of the above described refrigerant circuit and effects thereof will be described. 
     A conventional refrigerant circuit control method may cause explosion during a defrosting operation using a defrosting heater because if leakage of explosive refrigerant occurs during driving of the defrosting heater, the temperature of the leaked refrigerant may rise to a spontaneous combustion point. The refrigerant circuit control method according to the present embodiment, which may eliminate the explosion risk of the conventional refrigerant circuit control method, will be described hereinafter with reference to  FIG. 5 . 
       FIG. 5  is a flow chart illustrating the valve control of the refrigerant circuit of  FIGS. 4A and 4B . 
     First, if power is input to the refrigerator, the defrosting sensing unit senses a resistance value of the sensor that varies depending on the temperature of the evaporator of the refrigerator, and transmits a voltage or current signal corresponding to the resistance value to the control unit. The control unit compares the voltage or current signal transmitted from the defrosting sensing unit with preset defrosting conditions, thereby determining whether to perform a defrosting operation of the refrigerating compartment evaporator and the freezing compartment evaporator ( 410 ). 
     If implementation of the defrosting operation of the freezing compartment evaporator or the refrigerating compartment evaporator is determined, the control unit closes the valve before the defrosting operation of the corresponding evaporator begins ( 420 ). This may intercept movement of refrigerant to the refrigerating compartment evaporator and the freezing compartment evaporator prior to the defrosting operation. 
     After closing the valve in operation  420 , a refrigerant collecting operation is performed to collect and move the refrigerant distributed in the freezing compartment evaporator and the refrigerating compartment evaporator into the condenser ( 430 ). 
     In the refrigerant collecting operation  430 , the compressor is turned on in a closed state of the valve to allow the refrigerant distributed in the refrigerating compartment evaporator and the freezing compartment evaporator to be moved into the condenser. The refrigerant collecting operation  430  may prevent the refrigerant from being present in the refrigerating compartment evaporator and the freezing compartment evaporator. 
     Once the refrigerant collecting operation  430  is completed, the defrosting operation of the refrigerating compartment evaporator or the freezing compartment evaporator is performed ( 440 ), and the compressor is turned off. 
     After implementation of the defrosting operation  440 , the control unit determines whether or not the defrosting operation is completed ( 450 ). If completion of the defrosting operation of the corresponding evaporator is determined, the control unit again opens the closed valve ( 460 ) and restarts the compressor. 
     With the valve control of the refrigerant circuit illustrated in  FIG. 5 , no refrigerant is present in the refrigerating compartment evaporator and the freezing compartment evaporator during the defrosting operation, thereby eliminating any risk of explosion due to refrigerant leakage. 
     Meanwhile, the conventional refrigerant circuit and control method thereof may cause deterioration in the cooling efficiency of the freezing compartment upon simultaneous cooling of the freezing compartment and the refrigerating compartment because the temperature of the refrigerating compartment is higher than the temperature of the freezing compartment. This may make it difficult to store food fresh and may increase energy consumption. 
     A refrigerant circuit and control method thereof to prevent deterioration of the cooling efficiency and the increased energy consumption will be described with reference to  FIGS. 6 and 7 . 
       FIG. 6  is a refrigerant circuit according to another embodiment. 
     In  FIG. 6 , the refrigerant circuit  500  according to the present embodiment includes a compressor  510 , a condenser  520 , an expansion device  530 , a freezing compartment evaporator  540 , and a refrigerating compartment evaporator  550 . 
     In the refrigerant circuit  500  of the present embodiment, the freezing compartment evaporator  540  is located at a front end of the refrigerating compartment evaporator  550  and is connected in series to the refrigerating compartment evaporator  550 . Thus, refrigerant is circulated in the sequence of the compressor  510 →the condenser  520 →the expansion device  530 →the freezing compartment evaporator  540 →the refrigerating compartment evaporator  550 →the compressor  510 . That is, as the refrigerant is first supplied into the freezing compartment evaporator  540  and thereafter, is supplied into the refrigerating compartment evaporator  550 , it may be possible to prevent deterioration in the cooling efficiency of the freezing compartment due to a higher evaporation temperature of the refrigerating compartment evaporator  550 . 
     Further, the refrigerant circuit  500  of the present embodiment enables omission of the valve, achieving cost reduction. 
     Other configurations are identical to those of  FIG. 4A , and a description thereof is replaced by that of  FIG. 4A . 
       FIG. 7  is a flow chart illustrating the fan control of the refrigerant circuit of  FIG. 6  upon simultaneous cooling of the freezing compartment and the refrigerating compartment. 
     First, it is determined whether or not the compressor is in operation ( 610 ). If it is determined that the compressor is not in operation, both the freezing compartment fan and the refrigerating compartment fan are stopped ( 630 ). In this case, the temperature of each compartment of the refrigerator is a preset temperature or less. 
     On the other hand, if it is determined that the compressor is in operation, it is determined whether or not cooling of the freezing compartment is performed ( 620 ). If cooling of the freezing compartment is being performed, it is determined whether or not cooling of the refrigerating compartment is performed ( 640 ). 
     The refrigerating compartment fan is controlled to reduce revolutions per minute thereof upon simultaneous cooling of the freezing compartment and the refrigerating compartment ( 660 ). In this case, the temperature of each compartment of the refrigerator is a preset temperature or more. 
     If cooling of any one of the freezing compartment and the refrigerating compartment is being performed ( 640  and  650 ), revolutions per minute of each fan is kept normal ( 670 ). 
     With the control to reduce revolutions per minute of the refrigerating compartment fan upon simultaneous cooling of the freezing compartment and the refrigerating compartment, the evaporation capacity of the refrigerating compartment evaporator may be reduced, thereby improving the cooling efficiency of the freezing compartment. 
       FIG. 8  is a refrigerant circuit according to a further embodiment. 
     Referring to  FIG. 8 , a compressor  710 , a condenser  720 , a valve  730 , an expansion device  740 , a freezing compartment evaporator  750  and a refrigerating compartment evaporator  760  are connected to one another via a refrigerant pipe, thereby defining a single closed-loop refrigerant circuit. Other configurations are identical to those of  FIG. 4A , and a description thereof is replaced by that of  FIG. 4A . 
     In the present embodiment, the valve  730  is an On-Off valve to prevent explosion due to leakage of refrigerant from the refrigerant pipe during defrosting. The valve  730  is closed before the defrosting operation of any one of the refrigerating compartment evaporator and the freezing compartment evaporator begins. Then, the valve  730  is again opened upon completion of the defrosting operation of the corresponding evaporator, enabling movement of refrigerant. 
     To allow the refrigerant to be supplied first into the freezing compartment evaporator  750 , the freezing compartment evaporator  750  is located at a front end of the refrigerating compartment evaporator  760  and is connected in series to the refrigerating compartment evaporator  760 . Also, to prevent the temperature of the freezing compartment from rising upon simultaneous operation of the freezing compartment and the refrigerating compartment, a control operation to reduce revolutions per minute of a refrigerating compartment fan  762  is performed. Thereby, the evaporation capacity of the refrigerating compartment evaporator  760  is reduced, restricting an increase in the evaporation temperature of the refrigerant in the freezing compartment and the temperature of the refrigerant suctioned into the compressor. This may improve the cooling efficiency of the freezing compartment and reduce energy consumption of the refrigerator. 
     The refrigerator and the control method thereof according to the exemplary embodiments have been described in detail. Although the double door type refrigerator in which the doors are provided side by side at the freezing compartment and the refrigerating compartment has been described, the embodiments are also applicable to a top mount type refrigerator in which a freezing compartment is located in an upper region of the refrigerator, and a bottom freezer type refrigerator having triple doors. 
     As is apparent from the above description, a refrigerator and a control method thereof according to the embodiment may intercept a refrigerant flow path to a refrigerating compartment evaporator and a freezing compartment evaporator during defrosting, thereby preventing explosion due to leakage of refrigerant. 
     Further, as a result of locating the freezing compartment evaporator at a front end of the refrigerating compartment evaporator and connecting the freezing compartment evaporator to the refrigerating compartment evaporator in series, it may be possible to reduce revolutions per minute of a refrigerating compartment fan upon simultaneous cooling of the freezing compartment and the refrigerating compartment, resulting in an improvement in the cooling efficiency of the freezing compartment. This may achieve energy reduction and also, may achieve cost reduction due to omission of a valve to open or close the refrigerant flow path. 
     Although a few embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.