Refrigerator and control method thereof

1. A control method of a refrigerator to determine a supercooled state of a target object in a cooling compartment, the method comprising:

sensing a temperature of the target object at each interval of a specified time Δt;

calculating a difference between two of the sensed temperatures;

comparing the difference between the two sensed temperatures with a predetermined reference value ΔTc to determine the supercooled state of the target object; and

determining that supercooling is normally in progress if the difference between the two temperatures is smaller than the predetermined reference value.

2. The method according to claim 1 , further comprising determining whether supercooling of the target object is achieved comprising determining whether the temperature of the target object is equal to or lower than a target supercooling temperature if it is determined that supercooling is normally in progress.

3. The method according to claim 1 , further comprising determining that supercooling fails to be achieved if the difference between the two temperatures is equal to or larger than the predetermined reference value.

4. The method according to claim 3 , further comprising stopping cooling of the target object if it is determined that supercooling fails to be achieved.

5. The method according to claim 1 , wherein the reference value is larger than a temperature variation in the cooling compartment generated according to whether cool air is supplied to the cooling compartment or an opening/closing operation of the cooling compartment and is smaller than a temperature variation due to a rapid temperature increase when supercooling fails to be achieved.

6. The method according to claim 1 , further comprising varying the reference value according to a beverage type of the target object.

7. The method according to claim 6 , further comprising manually inputting a type of the target object by a user, or automatically inputting and identifying the type by a barcode or RFID.

8. The method according to claim 1 , further comprising designating the specified time using the predetermined reference value and a temperature inclination due to a temperature increase when the supercooling fails to be achieved.

9. The method according to claim 1 , further comprising displaying determination results of the supercooled state.

10. The method according to claim 1 , wherein the calculating a difference between two sensed temperatures is performed when the sensed temperatures are lower than a freezing point of the target object.

11. A refrigerator which determines a supercooled state of a target object, comprising:

a cooling compartment, the target object being in the cooling compartment;

a temperature sensor which senses a temperature of the target object in the cooling compartment; and

a controller which calculates a difference between two temperatures of the sensed temperatures at specified time intervals and compares the difference between the two temperatures with a predetermined reference value ΔTc to determine the supercooled state of the target object;

wherein the controller determines that supercooling is normally in progress if the difference between the two temperatures is smaller than the predetermined reference value.

12. The refrigerator according to claim 11 , further comprising:

a memory which stores reference values according to a type of the target object,

wherein the controller varies the predetermined reference value ΔTc according to a type of the target object.

13. The refrigerator according to claim 12 , further comprising an input unit, wherein the type of the object is input to the input unit by a user.

14. The refrigerator according to claim 12 , further comprising a reader to automatically read a type of the target object.

15. The refrigerator according to claim 11 , further comprising a display unit which displays determination results of the supercooled state.