Patent Publication Number: US-11035605-B2

Title: Refrigerator and method for controlling same, using a differential pressure sensor for defrost control

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage application under 35 U.S.C. § 371 of International Application No. PCT/KR2017/012732, filed on Nov. 10, 2017, which claims the benefit of Korean Patent Application No. 10-2016-0150248, filed on Nov. 11, 2016. The disclosures of the prior applications are incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to a refrigerator and a method for controlling the same, and more particularly, to a refrigerator having improved energy efficiency and a method for controlling the same. 
     BACKGROUND ART 
     In general, a refrigerator includes a machinery compartment, which is located at the lower part of a main body of the refrigerator. The machinery compartment is generally installed at the lower part of the refrigerator in consideration of the center of gravity of the refrigerator and in order to improve assembly efficiency and to achieve vibration reduction. 
     A refrigeration cycle device is installed in the machinery compartment of the refrigerator in order to keep the interior of the refrigerator frozen/refrigerated using the property of a refrigerant, which absorbs external heat when a low-pressure liquid refrigerant is changed to a gaseous refrigerant, whereby food is kept fresh. 
     The refrigeration cycle device of the refrigerator includes a compressor for changing a low-temperature, low-pressure gaseous refrigerant to a high-temperature, high-pressure gaseous refrigerant, a condenser for changing the high-temperature, high-pressure gaseous refrigerant, changed by the compressor, to a low-temperature, low-pressure liquid refrigerant, and an evaporator for changing the low-temperature, high-pressure liquid refrigerant, changed by the condenser, to a gaseous refrigerant in order to absorb external heat. 
     When the compressor is driven, the temperature of the evaporator is lowered, whereby ice may be formed on the evaporator. When the amount of ice formed on the evaporator increases, the efficiency of heat exchange between the evaporator and air is lowered, which makes it difficult to smoothly cool air to be supplied to a storage compartment. As a result, the compressor is required to be driven a larger number of times for a longer time. 
     In addition, when ice is formed on the evaporator, a heater is driven to remove the ice from the evaporator. When the heater is unnecessarily frequently driven, the amount of power consumed by the refrigerator increases. 
     In particular, power consumption of refrigerators produced in recent years has increased according to increase in storage capacity of the refrigerators. Research has thus been conducted into reduction of power consumption. 
     DISCLOSURE 
     Technical Problem 
     An object of the present invention is to provide a refrigerator having improved energy efficiency and a method for controlling the same. 
     Another object of the present invention is to provide a refrigerator capable of determining whether operation of the refrigerator is normally performed, and a method for controlling the same. 
     Another object of the present invention is to provide a refrigerator capable of determining a defrosting time using a differential pressure sensor and a method for controlling the same. 
     Technical Solution 
     The object of the present invention can be achieved by providing a refrigerator including a cabinet provided with a storage compartment, a door configured to open and close the storage compartment, a case having a discharge port, air being discharged into the storage compartment through the discharge port, an evaporator provided in the case to perform heat exchange with air to supply cooled air, a fan installed at the discharge port and configured to generate an air flow for discharging the air heat-exchanged by the evaporator to the storage compartment, and a differential pressure sensor provided with a first conduit having one end positioned at a portion through which air is drawn to the fan, and a second conduit having one end positioned at a portion through which air is discharged from the fan. 
     The first conduit may sense a pressure of flow of the air drawn to the fan. 
     The second conduit may sense a pressure of flow of the air discharged from the fan. 
     The differential pressure sensor may sense a difference between pressures measured by the first conduit and the second conduit. 
     The first conduit may have a first through hole formed at one end thereof, wherein the first through hole may be disposed perpendicular to the air flow generated by the fan. 
     The second conduit may have a second through hole formed at one end thereof, wherein the second through hole may be disposed perpendicular to the air flow generated by the fan. 
     The fan may be disposed between one end of the first conduit and one end of the second conduit. 
     The first conduit may be exposed to a low pressure portion subjected to a relatively low pressure and the second conduit may be exposed to a high pressure portion subjected to a relatively high pressure. 
     The refrigerator may further include a controller configured to defrost the evaporator according to information sensed by the differential pressure sensor. 
     The refrigerator may further include a heater provided in the case, wherein the controller may drive the heater to defrost the evaporator. 
     The refrigerator may further include a door switch configured to sense whether the door opens or closes the storage compartment, wherein, when the door senses the door close the storage compartment, the controller may sense a pressure difference by the differential pressure sensor. 
     The refrigerator may further include a timer configured to measure an elapse time, wherein the controller may sense the pressure difference by the differential pressure sensor when a time determined by the timer elapses. 
     When the fan is driven, the controller may sense a pressure difference by the differential pressure sensor. 
     In another aspect of the present invention, provided herein is a method for controlling a refrigerator, including sensing a pressure difference by a differential pressure sensor configured to measure a difference in pressure between a portion through which air is introduced into a fan and a portion through which the air is discharged from the fan, the fan discharging air heat-exchanged by an evaporator into a storage compartment, and defrosting the evaporator when the pressure difference is greater than a set pressure. 
     The method may further include determining whether the fan is driven before the sensing of the pressure difference. 
     The method may further include determining that a door for opening and closing the storage compartment closes the storage compartment before the sensing of the pressure difference. 
     The method may further include determining whether a predetermined time has elapsed after the door is closed. 
     The defrosting of the evaporator may include driving a heater configured to heat the evaporator. 
     The defrosting of the evaporator may include terminating the driving of the heater to terminate the defrosting when a temperature of the evaporator reaches a set temperature. 
     The sensing of the pressure difference may include rotating the fan at a constant rotational speed. 
     Advantageous Effects 
     According to the present invention, since information necessary for a refrigerator is obtained using one differential pressure sensor, errors according to measurement may be reduced, compared to the case where two or more sensors are used. When two values are compared using two or more sensors, different influences may be caused by temperatures at the positions where the respective sensors are installed, turbulence, door opening/closing, and thus different errors may be generated in the two sensors. Accordingly, when the values of two sensors are compared with each other, the error may be larger than when one sensor is used. 
     Further, according to the present invention, compared to the case where two pressure sensors are used, power consumption may be reduced and necessary resources such as wires for installing two pressure sensors may be reduced. 
     Further, according to the present invention, since termination of defrosting is determined by the information measured by an evaporator temperature sensor, reliability of determination of the defrosting termination may be secured. Further, since defrosting is terminated according to the temperature sensed by the evaporator temperature sensor, the number of times of driving the heater to defrost the evaporator may be reduced, thereby reducing the actual power consumption. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side cutaway view of a refrigerator according to one embodiment of the present invention. 
         FIG. 2  is a conceptual diagram of one embodiment. 
         FIG. 3  is a view showing a portion to which one end of a first conduit of a differential pressure sensor is exposed. 
         FIG. 4  is a view showing a portion to which one end of a second conduit of the differential pressure sensor is exposed. 
         FIG. 5  depicts an embodiment. 
         FIG. 6  is a control block diagram according to an embodiment of the present invention. 
         FIG. 7  is a control flowchart for sensing frosting of the evaporator according to one embodiment. 
     
    
    
     BEST MODE 
     Hereinafter, preferred embodiments of the present invention capable of realizing the above object will be described with reference to the accompanying drawings. 
     It will be appreciated that for simplicity and clarity of illustration, the dimensions or shapes of some of the elements shown in the drawings may be exaggerated. In addition, terms specifically defined in consideration of the configuration and operation of the present invention may be replaced by other terms based on intensions of the user or operator, customs, or the like. The terms used herein should be construed based on the whole content of this specification. 
     In an embodiment of the present invention, one differential pressure sensor is used, which is a technical difference from a case where two pressure sensors are used. When two pressure sensors are used, the pressure difference between the two positions may be calculated using pressures measured by the two pressure sensors. 
     Generally, a pressure sensor measures pressure in units of 100 Pa. In the embodiment of the present invention, a differential pressure sensor is adopted and thus a pressure difference may be more precisely measured than when a general pressure sensor is used. The differential pressure sensor cannot measure the absolute pressure value at the measurement position, but facilitates measurement of a difference in small units compared to the general pressure sensor because the differential pressure sensor can calculate a pressure difference between two positions. 
     When two pressure sensors are used, a large cost and many resources such as wires for installing the two sensors are required because the two sensors are applied. On the other hand, using one differential pressure sensor may reduce the cost and resources for installing the sensor. 
     Hereinafter, preferred embodiments of the present invention capable of realizing the above object will be described with reference to the accompanying drawings. 
       FIG. 1  is a side cutaway view of a refrigerator according to one embodiment of the present invention, and  FIG. 2  is a conceptual diagram of one embodiment. 
     Hereinafter, description will be given with reference to  FIGS. 1 and 2 . 
     The refrigerator includes a cabinet  2  having a plurality of storage compartments  6  and  8  and a door  4  for opening and closing the storage compartments  6  and  8 . 
     The plurality of storage compartments  6  and  8  may be divided into a first storage compartment  6  and a second storage compartment  8 . Each of the first storage compartment  6  and second storage compartment  8  may form a refrigeration compartment or a freezer compartment. Alternatively, first storage compartment  6  and the first storage compartment  6  may be configured as a freezer compartment and a refrigeration compartment, respectively. Alternatively, both the first storage compartment  6  and the first storage compartment  6  may configured as refrigeration compartments or freezer compartments. 
     A case  35  for accommodating an evaporator  20  is provided at the rear of the storage compartments. 
     The case  35  is provided with a discharge port  38 , through which air can be supplied from the case  35  to the storage compartments, and an introduction port  32 , through which air is supplied from the storage compartments to the case  35 . 
     The introduction port  32  is provided with an introduction duct  30 , through which air is guided into the case  35 . Thus, the introduction duct may connect the storage compartments  6  and  8  with the case  35  to form an air flow passage. 
     The discharge port  38  may be provided with a fan  40  to cause an air flow by which air inside the case  35  can be moved to the storage compartments  6  and  8 . Since the case  35  has an entirely closed configuration except for the introduction port  32  and the discharge port  38 , an air flow from the introduction port  32  to the discharge port  38  is generated when the fan  40  is driven. 
     A duct  7  for guiding air to the first storage compartment  6  is provided, and thus cold air passing through the fan  40  may be supplied to the first storage compartment  6 . The air that passing through the fan  40  may also be supplied to the second storage compartment  8 . 
     The evaporator  20  is accommodated in the case  35 . In the evaporator, a refrigerant compressed by a compressor  60  is vaporized to cool the air. The air inside the case  35  is cooled through heat exchange with the evaporator  20 . 
     A heater  50  configured to generate heat to defrost the evaporator  20  is provided below the evaporator  20 . The heater  50  need not be installed below the evaporator  20 . The heater may be provided anywhere in the case  35  as long as it can heat the evaporator  20 . 
     The evaporator  20  is provided with an evaporator temperature sensor  92 , which may measure the temperature of the evaporator  20 . The evaporator temperature sensor  92  may sense a low temperature when the refrigerant passing through the inside of the evaporator  20  is vaporized, and may sense a high temperature when the heater  50  is driven. 
     The compressor  60  may be installed in a machinery compartment, which is provided to the cabinet  2 , and may compress the refrigerant to be supplied to the evaporator  20 . The compressor  60  is installed outside the case  35 . 
     The introduction port  32  is located below the evaporator  20  and the discharge port  38  is located above the evaporator  20 . The discharge port  38  is disposed at a higher position than the evaporator  20 , and the introduction port  32  is disposed at a lower position than the evaporator  20 . 
     Accordingly, when the fan  40  is driven, the air moves upward in the case  35 . The air introduced through the introduction port  32  undergoes heat exchange as it passes by the evaporator  20 , and is discharged from the case  35  through the discharge port  38   
     A differential pressure sensor  100  configured to measure a difference in pressure is provided at a portion adjacent to the discharge port  38 . 
     The discharge port  38  is provided with the fan  40 , which generates an air flow for discharging the air heat-exchanged with the evaporator  20  into the storage compartments. When the fan  40  is driven, the air inside the case  35  may be moved to the storage compartments through the discharge port  38 . 
     The differential pressure sensor  100  includes a first through hole  110  located at a portion through which air is drawn into the fan  40  and a second through hole  120  located at a portion through which air is discharged from the fan  40 . 
     The differential pressure sensor  100  includes a first conduit  150  provided with a first through hole  110  at one end thereof and a second conduit  170  provided with the second through hole  120  at one end thereof. 
     The differential pressure sensor  100  includes a body portion connecting the first through hole  110  and the second through hole  120 . The body portion includes the first conduit  150  provided with the first through hole  110 , the second conduit  170  provided with the second through hole  120 , and a connection member  200  connecting the first conduit  150  and the second conduit  170  to each other. 
     Here, the connection member  200  may be disposed at a higher position than the evaporator  20 , such that water condensed on the evaporator  20  is not dropped onto the connection member  200 . The connection member  200  may be installed to be embedded in the case  35  as shown in  FIG. 2 . Alternatively, the connection member  200  may be installed on one side of the case  35 . 
     An electronic device may be installed on the connection member  200  because it is very likely to be damaged when contacting water drops. The water drops formed on the evaporator  20  will fall down due to gravity. When the connection member  200  is disposed above the evaporator  20 , the water drops formed on the evaporator  20  will not fall onto the connection member  200 . 
     The first through hole  110  and the second through hole  120  may be arranged perpendicular to the direction of an air flow generated by the fan  40 . 
     The first conduit  150  may sense the pressure of an air flow drawn into the fan  40 . In order to measure the static pressure of the air moving from the first conduit  150  to the fan  40 , the first through hole  110  may be disposed perpendicular to the air flow for the fan  40 . 
     As shown in  FIG. 2 , air is moved upward in the case  35  (corresponding to the right side in  FIG. 2 ) by the fan  40 . Accordingly, the first through hole  110  arranged perpendicular to the upward movement direction may sense the static pressure of air that moves upward. 
     The second conduit  170  may sense the pressure of an air flow discharged from the fan  40 . In order for the second conduit  170  to measure the static pressure of the air moving from the fan  40 , the second through hole  120  may be disposed perpendicular to the air flow of the fan  40 . 
     As shown in  FIG. 2 , the air discharged from the case  35  through the discharge port  38  is horizontally moved from right to left. Accordingly, the second through hole  120  may be vertically positioned with respect to the horizontal movement direction to sense a static pressure of the horizontally moving air. 
     The first conduit  150  and the second conduit  170  may be connected to each other by the connection member  200 . 
     The differential pressure sensor  100  senses a pressure difference between air passing by the first through hole  110  and air passing by the second through hole  120 . The pressure difference is generated because the through holes are arranged with the fan  40  placed therebetween. The second through hole  120  is a high pressure portion subjected to a relatively high pressure, and the first through hole  110  is a low pressure portion subjected to a relatively low pressure. Accordingly, the differential pressure sensor  100  senses the pressure difference. The first conduit  150  is exposed to the low pressure portion subjected to a relatively low pressure, while the second conduit  170  is exposed to the high pressure portion subjected to a relatively high pressure. 
     A portion of the fan  40  to which air is drawn may be a low pressure portion because air leaves therethrough, and a portion of the fan  40  from which air is discharged may be a high pressure portion. Accordingly, a pressure difference is generated across the fan  40 . 
     In particular, when the fan  40  is driven, an air flow is generated in the case  35 , and thus the pressure difference may be measured by the differential pressure sensor  100 . 
     The fan  40  is disposed between one end of the first conduit  150  and one end of the second conduit  170 . That is, because the fan  40  is disposed between the first through hole  110  and the second through hole  120 , and an air flow is generated by the fan  40 , there may be a difference between the pressured measured in the first through hole  110  and the pressured measured in the second through hole  120 . 
       FIG. 3  is a view showing a portion to which one end of a first conduit of a differential pressure sensor is exposed, and  FIG. 4  is a view showing a portion to which one end of a second conduit of the differential pressure sensor is exposed. 
     As shown in  FIG. 3 , the first through hole  110  of the first conduit  150  is exposed to a portion of the case  35  where the evaporator  20  is located. 
     The first through hole  110  may be disposed at a position higher than that of the evaporator  20  but lower than that of the fan  40  to sense the pressure of air that rises up toward the fan  40 . For reference, since the present invention employs one differential pressure sensor, the value of the pressure measured in the first through hole  110  is not an absolute but a value comparable with the value measured in the second through hole  120 . Thus, information for measuring a final pressure difference is obtained. 
       FIGS. 3 and 4  show an example in which a centrifugal fan is installed among other kinds of fans. 
     Since the first through hole  110  is disposed on the path along which air is drawn to the fan  40 , information for determining the pressure difference may be obtained through the first through hole  110 . 
     Since the first through hole  110  is disposed above the evaporator  20 , water drops cannot enter the through hole  110  even when defrosting of the evaporator  20  is performed and thus the ice formed on the evaporator  20  melts. Thus, the first through hole  110  may be prevented from being clogged even if the evaporator  20  is defrosted. Accordingly, a measurement error of the differential pressure sensor  100  may be reduced. 
     The second through hole  120  is disposed at a portion of the fan  40  from which air is discharged. Since the fan  40  is specified as a centrifugal fan in contrast with the case of  FIGS. 1 and 2 , the air discharged from the fan  40  in  FIG. 4  is guided downward from the fan  40 . 
     Accordingly, the second through hole  120  may be disposed perpendicular to the downward movement direction of air to obtain information for sensing a pressure difference. 
     For reference, in  FIG. 4 , the air discharged by the fan  40  is guided to a branch duct, and is then moved to the storage compartments along the respective ducts through the communication holes connected to the storage compartments. Here, the air discharged by the fan  40  is moved from the center of the fan  40  in a direction away from the center of the fan  40 . 
       FIG. 5  depicts an embodiment. 
     In  FIG. 5 , the x-axis represents the flow rate and the y-axis represents the difference in static pressure. The pressure difference on the y-axis may refer to the pressure difference value measured by the differential pressure sensor. 
     The dotted line in the graph depicts the pressure difference according to the flow rate when no ice is formed on the evaporator  20 . 
     The one-dot chain line in the graph depicts the pressure difference according to the flow rate when ice is formed on the evaporator  20  to such an extent that defrosting is needed. 
     The solid line in the graph depicts change in pressure with change in flow rate under the condition that the same input voltage is applied to the fan and the fan is rotated at substantially the same rpm. 
     As can be seen from  FIG. 5 , when ice is formed on the evaporator  20 , the pressure difference measured by the differential pressure sensor  100  increases as the flow rate by the fan  40  decreases. 
     That is, when the pressure difference measured by the differential pressure sensor  100  increases, ice may be expected to be formed on the evaporator  20 . Here, if the pressure difference measured by the differential pressure sensor  100  is greater than a predetermined value, it may be determined that ice has been formed on the evaporator  20  to such an extent that defrosting of the evaporator  20  is needed. 
       FIG. 6  is a control block diagram according to an embodiment of the present invention. 
     Referring to  FIG. 6 , the present invention includes a compressor  60  capable of compressing the refrigerant. The controller  96  may drive the compressor  60  to supply cooled air to the storage compartments when it is necessary to cool the storage compartment. Information on whether the compressor  60  is driven may be transmitted to the controller  96 . 
     The present invention further includes a fan  40  configured to generate an air flow for supplying cooled air to the storage compartments. Information on whether the fan  40  is driven may be transmitted to the controller  96 , and the controller  96  may transmit a signal instructing that the fan  40  should be driven. 
     Door switches  70  capable of obtaining information on whether the doors  4  for opening and closing the storage compartments open or close the storage compartments is provided. The door switches  70  may be individually provided to the respective doors to sense whether each door opens or closes the storage compartments. 
     In addition, a timer  80  configured to sense an elapse time is provided. The time measured by the timer  80  is transmitted to the controller  96 . For example, after the controller  96  obtains, from the door switches  70 , signals indicating that the doors  4  close the storage compartments, the controller may receive information about the time that elapses after the doors  4  close the storage compartments, according to the time measured by the timer  80 . 
     When defrosting is performed, the temperature information measured by the evaporator temperature sensor  92 , which is capable of measuring the temperature of the evaporator, may also be transmitted to the controller  96 . The controller  96  may terminate defrosting of the evaporator according to the temperature information measured by the evaporator temperature sensor  92 . 
     Further, a heater  50  configured to heat the evaporator may be provided, and the controller  96  may issue a command to drive the heater  50 . When the defrosting operation is started, the controller  96  may drive the heater  50 . When the defrosting operation is completed, the controller  96  may stop driving the heater  50 . 
       FIG. 7  is a control flowchart of sensing frosting of the evaporator according to one embodiment. 
     Referring to  FIG. 7 , an embodiment of the present invention includes sensing a pressure difference by one differential pressure sensor  100  configured to measure a difference in pressure between a portion through which air is introduced into a fan  40  for discharging air heat-exchanged by the evaporator  20  to the storage compartments  6  and  8 , and a portion through which air is discharged from the fan  40 , and defrosting the evaporator  40  when the pressure difference is greater than a set pressure. 
     As used herein, the term pressure difference may refer to a pressure difference value measured once, or an average value of pressure differences measured several times. The pressure measured by the differential pressure sensor  100  may temporarily have an anomalous value due to various external factors. When an average value of the pressure differences is used, reliability of the pressure difference measured by the differential pressure sensor  100  may increase. 
     If the pressure difference measured by the differential pressure sensor  100  is greater than a set pressure, this means that the pressure difference between the first through hole  110  and the second through hole  120  is large. The large pressure difference may mean that the amount of ice formed on the evaporator  20  is increased and the evaporator  20  has difficulty in performing smooth heat exchange. In this case, cooled air is not smoothly supplied from the evaporator  20  to the storage compartments  6  and  8 , and thus defrosting may be needed. 
     Before the pressure difference is sensed, it may be determined whether the fan  40  is being driven (S 20 ). 
     Only when the fan  40  is driven, an air flow may be generated between the first through hole  110  and the second through hole  120  in the differential pressure sensor  100 , and the differential pressure sensor  100  may smoothly measure the pressure difference. 
     Accordingly, when the fan  40  is not driven, the differential pressure sensor  100  may not measure the pressure difference. 
     The door switch  70  may determine whether a predetermined time has elapsed after the door  4  closes the storage compartments  6  and  8 . If the predetermined time has not elapsed, the differential pressure sensor  100  may not sense the pressure difference (S 30 ). The timer  80  may measure the elapse time after the door switch  70  determines whether the door  4  is closed. Here, the elapse time may refer to approximately 1 minute, but may be changed to various values. 
     If the door  4  has not closed the storage compartments  6  and  8 , the air flow in the case  35  may be changed. 
     If the predetermined time has not elapsed after the door  4  is closed, an unexpected air flow to the introduction port  32  or the discharge port  38  may be generated by closing of the door  4 . 
     Therefore, in this case, when the pressure difference is measured by the differential pressure sensor  100 , the measured pressure difference may provide erroneous information. If the defrosting time of the evaporator  20  is determined using such erroneous information, the heater  50  may be driven unnecessarily frequently or may not defrost the evaporator  20  by driving the heater  50  when defrosting is needed. 
     A pressure difference between the first through hole  110  and the second through hole  120  is measured by the differential pressure sensor  100  (S 40 ). Then, the information on the measured pressure difference may be transmitted to the controller  96 . 
     When the differential pressure sensor  100  measures the pressure difference, the controller  96  may maintain constant rpm of the fan  40  by setting the input voltage to the fan  40  to be constant. 
     When the rpm of the fan  40  changes, the pressure difference varies with the flow rate of the fan  40  according to another trend (along a plurality of lines rather than one line as shown in  FIG. 5 ), accordingly the pressure difference measured by the differential pressure sensor  100  varies. Therefore, it may not be accurately determined whether the evaporator  20  has been frosted to an extent that defrosting is needed, based on the pressure difference measured by the differential pressure sensor  100 . Therefore, in one embodiment, the input voltage to the fan  40  may be kept constant such that the differential pressure sensor  100  can sense only the pressure difference corresponding to the amount of ice formed on the evaporator  20  with the other conditions unchanged 
     The controller  96  compares the measured pressure difference, that is, the differential pressure, with the set pressure P 1  (S 50 ). When the differential pressure is greater than the set pressure P 1 , it may be determined that a large amount of ice has been formed on the evaporator  20  and thus defrosting is needed. When a large amount of ice is formed on the evaporator  20 , it is difficult for the evaporator  20  to sufficiently perform heat exchange, and thus it is difficult to supply sufficient cold air to the storage compartments  6  and  8 . The set pressure P 1  may be set to about 20 Pa, but may be changed in consideration of the capacity, size, and the like of the refrigerator. 
     The controller  96  drives the heater  50  to supply heat to the evaporator  20  to perform defrosting by (S 60 ). The evaporator  20  and the heater  50  are disposed in the same partitioned space inside the case  35 . Accordingly, when the heater  50  is driven, the temperature inside the case  35  may be increased, thereby increasing the temperature of the evaporator  20 . 
     Then, the ice that has adhered to the evaporator  20  may be partially melted and turned into water. A part of the ice may be detached from the evaporator  20  as it melts. Then, the area of the evaporator  20  that can come into direct thermal contact with air may be increased, thereby improving heat exchange efficiency of the evaporator  20 . 
     The evaporator temperature sensor  92  measures the temperature of the evaporator  20  while defrosting is being performed, i.e., while the heater  50  is being driven. When the temperature of the evaporator  20  increases above the predetermined temperature T 1 , it is determined that the evaporator  20  has been sufficiently defrosted (S 70 ). 
     That is, the controller  96  may stop driving the heater  50 . Increase in temperature of the evaporator  20  above the set temperature T 1  may indicate a state in which the evaporator  20  can change to a condition in which cold air can be supplied to the storage compartments  6  and  8 , rather than meaning that ice formed on the evaporator  20  is entirely removed. 
     If the temperature of the evaporator  20  is not increased to the predetermined temperature T 1 , it may be determined that the evaporator  20  has not been sufficiently defrosted, and thus the heater  50  may continue to be driven to supply heat. 
     In one embodiment, the defrosting time for the evaporator  20  is determined by the differential pressure measured by the differential pressure sensor  100 . In order to improve reliability of the differential pressure value measured by the differential pressure sensor  100 , a condition for stabilizing the air flow inside the case  35  may be added. 
     If defrosting of the evaporator  20  is excessively frequently performed, the heater  50  is frequently driven and the power consumption of the heater  50  is increased, thereby lowering the overall energy efficiency of the refrigerator. 
     Further, if heat supplied from the heater  50  is transferred into the storage compartments  6  and  8  through the introduction port or the discharge port, the food stored in the storage compartments may be deteriorated. The evaporator  20  may also be required to supply more cooled air in order to cool the air heated by the heat supplied by the heater  50 . 
     Therefore, in one embodiment, the defrosting time may be reliably determined, thereby reducing unnecessary power consumption and providing a refrigerator having energy efficiency improved as a whole and a method for controlling the same. 
     It is to be understood that the present invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     INDUSTRIAL APPLICABILITY 
     The present invention provides a refrigerator having improved energy efficiency and a method for controlling the same.