WO2007094541A1

WO2007094541A1 - Supercooling apparatus and its method

Info

Publication number: WO2007094541A1
Application number: PCT/KR2006/003851
Authority: WO
Inventors: Su-Cheong Kim; Jong-Min Shin; Su-Won Lee; Cheol-Hwan Kim; Yong-Chol Kwon; Ku-Young Son
Original assignee: Lg Electronics, Inc.
Priority date: 2006-02-15
Filing date: 2006-09-27
Publication date: 2007-08-23
Also published as: BRPI0621353A2; EP2003993A4; AU2006338352A1; EP2003993A1; US20090064689A1

Abstract

The present invention discloses an apparatus and method for supercooling which can stably maintain the contents in a supercooled state for an extended period of time by controlling energy. The apparatus for supercooling includes a means for taking energy from the contents, and a means for causing at least one of rotation, vibration and translation to water molecules of the contents, by supplying energy smaller than the taken energy. The contents are maintained in a liquid state below a phase transition temperature.

Description

SUPERCOOLING APPARATUS AND ITS METHOD

Technical Field

[1] The present invention relates to an apparatus and method for supercooling, and more particularly, to an apparatus and method for supercooling which can stably maintain the contents in a supercooled state for an extended period of time by controlling energy. Background Art

[2] Supercooling means that a molten object or a solid cooled below a phase transition temperature in a balanced state is not changed. Each material has stable states in each temperature. If the temperature is slowly varied, elements of the material maintain the stable states in each temperature and accompany the variations of the temperature. However, if the temperature is sharply varied, the elements cannot be changed into the stable states in each temperature. Therefore, the elements of the material maintain the stable state of the start temperature, or some of the elements fail to be changed into the state of the final temperature.

[3] For example, when water is slowly cooled, it is not frozen temporarily at a temperature below O⁰C. However, when water is supercooled, it has a kind of quasi- stable state. Since the unstable balanced state is broken even by a slight stimilus, water tends to be changed into a more stable state. That is, if a small piece of liquid is put into the supercooled liquid, or if the liquid is suddenly shaken, the liquid is directly frozen so that the temperature of the liquid can reach the freezing point. Accordingly, the liquid maintains a stable balanced state in the temperature.

[4] Generally, foods such as vegetables, fruits, meats and beverages are refrigerated or frozen to be kept fresh. Such foods contain liquid elements such as water. If the liquid elements are cooled below a phase transition temperature, they can be transited to solid elements after a predetermined time.

[5] Fig. 1 is a graph showing phase transition by cooling. As shown in Fig. 1, when a keeping temperature of a refrigerator is maintained at about -TC, distilled water is maintained in a supercooled state for 1 to 5 hours in 1 air pressure. Phase transition suddenly occurs after about 5 hours, so that a temperature of water rises to about O⁰C which is a phase transition temperature.

[6] As described above, the contents such as water can be maintained in the supercooled state for a short time. However, it is necessary to maintain the foods in the supercooled state for a long time to keep the foods for an extended period of time. Disclosure of Invention Technical Problem

[7] The present invention is achieved to solve the above problems. An object of the present invention is to provide an apparatus and method for supercooling which can stably maintain the contents in a supercooled state for an extended period of time.

[8] Another object of the present invention is to provide an apparatus and method for supercooling which can stably maintain the contents in a supercooled state at a low temperature.

[9] Yet another object of the present invention is to provide an apparatus and method for supercooling which can set or control a non-freezing temperature of the contents by adjusting a quantity of energy.

[10] Yet another object of the present invention is to provide an apparatus and method for supercooling which can adjust and set applied energy by using relation between a quantity of energy and a non-freezing temperature of the contents.

[11] Yet another object of the present invention is to provide an apparatus and method for supercooling which can execute various types of non-freezing modes by enabling the user to select a non-freezing temperature of the contents.

[12] Yet another object of the present invention is to provide an apparatus and method for supercooling which can control a quantity of applied energy or a degree of non- freezing by adjusting a degree of cooling.

[13] Yet another object of the present invention is to provide an apparatus and method for supercooling which can minimize power consumption in a non-freezing mode for forming a non-frozen state, by controlling an execution time of the non-freezing mode.

[14] Yet another object of the present invention is to provide an apparatus and method for supercooling which can maintain a non-frozen state and minimize power consumption in the non-frozen state. Technical Solution

[15] In order to achieve the above-described objects of the invention, there is provided an apparatus for supercooling, including: a means for taking energy from the contents; and a means for causing at least one of rotation, vibration and translation to water molecules of the contents, by supplying energy smaller than the taken energy, whereby the contents are maintained in a liquid state below a phase transition temperature.

[16] Preferably, the causing means applies an electric field to the contents. [17] Preferably, the causing means sets the supplied energy by varying at least one of a voltage, a frequency and a current.

[18] Preferably, the taken energy is dependent upon a difference between a cooling temperature applied to the contents and a current temperature of the contents.

[19] Preferably, the taken energy is dependent upon a quantity of the contents.

[20] According to another aspect of the present invention, there is provided a method for supercooling, including the steps of: setting energy taken from the contents; taking the set energy from the contents; and causing at least one of rotation, vibration and translation to water molecules of the contents, by supplying energy smaller than the set energy, the above steps being sequentially or similtaneousry carried out, whereby the contents are maintained in a liquid state below a phase transition temperature.

[21] According to yet another aspect of the present invention, there is provided a method for supercooling, including the steps of: supplying energy to the contents; and taking more energy than the supplied energy, at least one of rotation, vibration and translation being caused to water molecules of the contents, whereby the contents are maintained in a liquid state below a phase transition temperature.

[22] According to yet another aspect of the present invention, there is provided a method for supercooling, including the steps of: applying energy to a storing space for storing the contents; and setting a non-freezing temperature of the storing space or the contents according to the quantity of applied energy.

[23] According to yet another aspect of the present invention, there is provided a method for supercooling, including the steps of: reading a degree of non-freezing of a storing space or the contents; and setting a quantity of applied energy according to the degree of non-freezing.

[24] According to yet another aspect of the present invention, there is provided a method for supercooling, including the steps of: cooling a storing space or the contents stored in the storing space; and executing a non-freezing mode before a phase transition temperature of the contents.

[25] According to yet another aspect of the present invention, there is provided a method for supercooling, including the steps of: cooling a storing space or the contents for a set time; and executing a non-freezing mode on the storing space or the contents.

[26] According to yet another aspect of the present invention, there is provided a method for supercooling, including a step for executing a non-freezing mode on a storing space or the contents stored in the storing space, the step for executing the non-freezing mode being discontinuously carried out. [27] According to yet another aspect of the present invention, there is provided a method for supercooling, including the steps of: executing a non-freezing mode; checking a proceeding degree of a non-frozen state; and controlling intensity of the non-freezing mode according to the result of the checking step.

Brief Description of the Drawings

[28] The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not limitative of the present invention, wherein: [29] Fig. 1 is a graph showing phase transition by cooling;

[30] Figs. 2 to 4 are views illustrating principles of an apparatus for supercooling in accordance with the present invention; [31] Fig. 5 is a block diagram illustrating the apparatus for supercooling in accordance with the present invention;

[32] Figs. 6 and 7 are structure views illustrating examples of the apparatus for supercooling in accordance with the present invention; [33] Figs. 8 and 9 are a structure view and a graph showing supercooling in the apparatus for supercooling in accordance with the present invention; [34] Figs. 10 and 11 are graphs showing correlation between power and a supercooling temperature in the simplified apparatus for supercooling in accordance with the present invention; [35] Fig. 12 is a graph showing relation between intensity of an electric field, a keeping temperature and a supercooling temperature in a method for supercooling in accordance with the present invention; [36] Fig. 13 is a flowchart showing a method for supercooling in accordance with a first embodiment of the present invention; [37] Fig. 14 is a flowchart showing a method for supercooling in accordance with a second embodiment of the present invention; [38] Figs. 15 and 16 are a flowchart showing a method for supercooling and a resulting control graph in accordance with a third embodiment of the present invention; [39] Figs. 17 and 18 are a flowchart showing a method for supercooling and a resulting control graph in accordance with a fourth embodiment of the present invention; [40] Fig. 19 is a control graph of a method for supercooling in accordance with a fifth embodiment of the present invention; and [41] Fig. 20 is a control graph of a method for supercooling in accordance with a sixth embodiment of the present invention. Mode for the Invention

[42] An apparatus and method for supercooling in accordance with the present invention will now be described in detail with reference to the accompanying drawings.

[43] Figs. 2 to 4 are views illustrating principles of the apparatus for supercooling in accordance with the present invention.

[44] Fig. 2 shows a process of taking energy Ql from liquid state water stored in a storing space S of a casing 1. Energy Ql is taken from water, thereby cooling water. For example, as shown in Fig. 1, when cooling is performed at about -7°C, energy Ql is proportional to a difference between a temperature Cw of water before cooling and a cooling keeping temperature Cr. Energy Ql is also influenced by specific heat and mass of the contents. For easy explanation, it is presumed that the specific heat and mass of the contents are identical in Figs. 2 to 4. Therefore, energy by temperature is explained in Figs. 2 to 4. As the taken energy Ql increases, motion between water molecules (for example, rotation, vibration, translation, etc.) is weakened and coupling of hydrogen is strengthened. Accordingly, phase transition occurs at any point of time as shown in Fig. 1.

[45] Fig. 3 shows a process of supplying energy Q2 to cause the motion to the water molecules of the contents. As the motion between the water molecules becomes active due to supply of energy Q2, the motion force between the water molecules is relatively larger than coupling of hydrogen. As a result, phase transition does not occur.

[46] Fig. 4 shows the processes of taking energy Ql and supplying energy Q2. By the process of taking energy Ql, a measured temperature C of water is lowered to 0⁰C (1 air pressure) which is a phase transition temperature, and then to -7°C as shown in Fig. 1. In the cooling process, energy Q2 is supplied to water, for maintaining water in a liquid state below the phase transition temperature. Here, even if the process of supplying energy Q2 and the process of taking energy Ql are carried out at the same time, they must use energy sources which do not affect each other. For example, if both processes use heat energy in the same manner, they affect each other. In this case, it cannot be applied to the present invention. In addition, energy Q2 must be generated from an energy source influencing the motion of the water molecules.

[47] The important factor is quantity of energy Q2 supplied to water. At the initial stage, the taken energy Ql can be calculated from the difference between the temperature Cw of water and the cooling keeping temperature Cr. However, since water is cooled by time, the taken energy Ql can be calculated from a difference between the current temperature C which is the measured temperature of water and the cooling keeping temperature Cr, or a difference between the current temperature C and a measured temperature Cm inside a storing space in which the casing 1 is kept. Energy Q2 must be equal to or smaller than energy Ql, so that the temperature C of water can be equal to or slightly higher than the cooling keeping temperature Cr or the measured inside temperature Cm.

[48] When the measured inside temperature Cm is lowered and the quantity of energy

Ql is varied in the cooling process, the supplied energy Q2 is also varied. Accordingly, water is maintained in the supercooled state at a specific temperature below the phase transition temperature.

[49] If the mass of the contents is changed in the same conditions, the quantity of energy must be changed.

[50] Therefore, the supplied energy Q2 mist be determined according to the energy Ql taken from the contents, or the taken energy Ql must be determined according to the supplied energy Q2. Here, the supplied energy Q2 mist be equal to or smaller than the taken energy Ql, for activating the motion of the water molecules in the contents.

[51] Fig. 5 is a block diagram illustrating the apparatus for supercooling in accordance with the present invention, and Figs. 6 and 7 are structure views illustrating examples of the apparatus for supercooling in accordance with the present invention.

[52] The apparatus 100 for supercooling includes a load sensing unit 20 for sensing a state of a storing space A or B, and a state of the contents (not shown) stored in the storing space A or B, a freezing cycle 30 for cooling the storing space A or B, a voltage generating unit 40 for generating a voltage to apply an electric field to the storing space A or B, an electrode unit 50 for receiving the voltage and generating the electric field, a door sensing unit 60 for sensing opening and closing of a door 120, an input unit 70 for enabling the user to input a degree of cooling, execution of a supercooling mode, etc., a display unit 80 for displaying an operating state of the apparatus 100 for supercooling, and a microcomputer 90 for controlling freezing or refrigerating of the apparatus 100 for supercooling, and executing the supercooling mode. A power supply unit (not shown) is essentially installed to supply power to the aforementioned elements. However, power supply is easily recognized by those skilled in the art, and thus explanations thereof are omitted.

[53] In detail, the load sensing unit 20 senses or stores the state of the storing space A or

B and the state of the contents stored in the storing space A or B, and transmits the sensing result to the microcomputer 90. For example, the load sensing unit 20 can be a thermometer for storing information on a capacity of the storing space A or B which is the state of the storing space A or B, or sensing a temperature of the storing space A or B or the contents, or a hardness meter, an ammeter, a voltmeter, a scale, an optical sensor (or laser sensor) or a pressure sensor for deciding whether the contents have been stored in the storing space A or B. Especially, the load sensing unit 20 can be the ammeter or the voltmeter. When the storing space A or B is empty and when the contents are stored in the storing space A and B, an electric field applied resistor has different resistance values. Therefore, whether the contents have been stored can be checked by the different resistance values. The microcomputer 90 confirms a quantity and a moisture content of the contents according to the resistance value from the load sensing unit 20, and identifies a kind of the contents having the moisture content.

[54] The freezing cycle 30 is classified into indirect cooling and direct cooling according to a method of cooling the contents. Fig. 6 shows an indirect cooling type refrigerator and Fig. 7 shows a direct cooling type refrigerator, which will later be explained in detail.

[55] The voltage generating unit 40 generates an AC voltage according to a predetermined amplitude and frequency. The voltage generating unit 40 generates the AC voltage by varying at least one of the amplitude of the voltage and the frequency of the voltage. Especially, the voltage generating unit 40 applies the AC voltage generated according to the set values (amplitude of voltage, frequency of voltage, etc.) from the microcomputer 90 to the electrode unit 50, so that the resulting electric field can be applied to the storing space A or B. In accordance with the present invention, the voltage generating unit 40 can vary the amplitude of the voltage between 500V and 15kV by variably setting the frequency. In addition, the voltage generating unit 40 variably sets the frequency of the voltage in a radio frequency region of 1 to 500kHz.

[56] The electrode unit 50 converts the AC voltage from the voltage generating unit 40 into the electric field, and applies the electric field to the storing space A or B. Generally, the electrode unit 50 is a plate or conductive wire made of Cu or Pt.

[57] Since the electric field applied to the storing space A or B or the contents by the electrode unit 50 originates from the radio frequency AC voltage, polarity of the electric field is varied according to the frequency. The water molecules containing O having polarity and H having + polarity are continuously vibrated, rotated and translated by the electric field, and thus maintained in the liquid phase below the phase transition temperature without crystallization.

[58] The door sensing unit 60 stops the operation of the voltage generating unit 40 by opening of the door 120 for opening and closing the storing space A or B. The door sensing unit 60 can notify opening to the microcomputer 90 to perform the stop operation, or stop the voltage generating unit 40 by shorting out power applied to the voltage generating unit 40.

[59] The input unit 70 enables the user to input execution of the supercooling mode for the storing space A or B or the contents as well as temperature setting for freezing and refrigerating control, and selection of a service type (flake ice, water, etc.) of a dispenser. In addition, the user can input information on the contents such as the kind and quantity of the contents through the input unit 70. The input unit 70 can be a barcode reader or an RFID reader for providing the information on the contents to the microcomputer 90. The input unit 70 enables the user to input or select a supercooling temperature (temperature for maintaining the supercooled state) which is a degree of supercooling of the storing space A or B or the contents.

[60] The display unit 80 basically displays a freezing temperature, a refrigerating temperature and the service type of the dispenser, and additionally displays current execution of the supercooling mode.

[61] The microcomputer 90 basically controls freezing and refrigerating, and further executes the supercooling mode according to the present invention.

[62] In the case that the storing space A or B or the contents are maintained in the supercooled state, the microcomputer 90 stores relation information between the quantity of the energy Ql applied to the storing space A or B or the contents, the quantity of the taken energy Q2 and the cooling temperature. Accordingly, the microcomputer 90 can perform control operations, such as setting and application of energy Ql and Q2 by the supercooling temperature, or calculation of the quantities of energy Ql and Q2 and calculation of the supercooling temperature. Here, energy Q2 can be generated from various energy sources. In accordance with the present invention, energy Q2 is electric field energy. Since most of the contents contain a large quantity of moisture, the microcomputer 90 calculates the taken energy Ql by setting the specific heat of water as specific heat, sensing mass by the load sensing unit 20, and operating temperature information by the load sensing unit 20. For example, when the electric field energy is applied, the microcomputer 90 calculates the supplied energy Q2 from functions of current, voltage and frequency, which is easily understood by those skilled in the art.

[63] The microcomputer 90 acquires the state of the storing space A or B or the contents from the input unit 70 or the load sensing unit 20, and generates the AC voltage having the frequency and amplitude corresponding to the acquired information or load, thereby executing an artificially-intelligent non-freezing mode. [64] The microcomputer 90 which executes the supercooling mode can set or vary the supercooling temperature for executing the supercooling mode. The microcomputer 90 can perform the setting or varying operation according to the relation between the quantities of energy Ql and Q2 and the supercooling temperature discussed later. For this, the microcomputer 90 adjusts the quantity of energy Q2 by the electric field applied from the electrode unit 50, by controlling the voltage generating unit 40. The quantity of energy Q2 can be adjusted by controlling the amplitude of the voltage (or the amplitude of the current) and the frequency. The quantity of energy can be calculated from the correlation between the voltage, current and frequency. Calculation of energy is apparent to those skilled in the art, and thus not explained.

[65] The microcomputer 90 performs efficient control which reduces power consumption of the apparatus 100 for supercooling as in a power save mode and maintains the non-freezing mode, by controlling the operation of the non-freezing operating unit consisting of the voltage generating unit 40 and the electrode unit 50. The control method will be described later.

[66] Figs. 6 and 7 are structure views illustrating examples of the apparatus for supercooling in accordance with the present invention. In these examples, the present invention is applied to a refrigerator. Fig. 6 is a cross-sectional view illustrating an indirect cooling type refrigerator, and Fig. 7 is a cross-sectional view illustrating a direct cooling type refrigerator.

[67] The indirect cooling type refrigerator includes a casing 110 having one surface opened, and including a storing space A inside and a shelf 130 for partially partitioning the storing space A, and a door 120 for opening and closing the opened surface of the casing 110. A freezing cycle 30 of the indirect cooling type refrigerator includes a compressor 32 for compressing refrigerants, an evaporator 33 for generating cool air (tndicated by arrows) for cooling the storing space A or the contents, a fan 34 for forcibly flowing the cool air, a suction duct 36 for supplying the cool air to the storing space A, and a discharge duct 38 for inducing the cool air passing through the storing space A to the evaporator 33. Although not illustrated, the freezing cycle 30 farther includes a condenser, a drier and an expanding unit.

[68] Electrode units 50a and 50b are formed between the inner surfaces 112a and 112c facing the storing space A and the outer surface of the casing 110. The electrode units 50a and 50b are installed to face each other, for applying an electric field to the whole storing space A. The storing space A is separated from the ends of the electrode units 50a and 50b at predetermined intervals in the inner or center directions of the electrode units 50a and 50b, for applying the uniform electric field to the storing space A or the contents.

[69] The suction duct 36 and the discharge duct 38 are formed on the inner surface 112b of the casing 110. The inner surfaces 112a, 112b and 112c of the casing 110 are made of a hydrophobic material, and thus not frozen during the supercooling mode due to reduction of surface tension of water. The outer surface and the inner surfaces 112a, 112b and 112c of the casing 110 are made of an insulating material, thereby preventing the user from receiving an electric shock from the electrode units 50a and 50b, and preventing the contents from electrically contacting the electrode units 50a and 50b through the inner surfaces 112a, 112b and 112c.

[70] A casing 110, a door 120 and a shelf 130 of the direct cooling type refrigerator of

Fig. 7 are identical to those of the indirect cooling type refrigerator of Fig. 6. Inner surfaces 114a, 114b and 114c of the casing 110 are identical to the inner surfaces 112a, 112b and 112c of the casing 110 except for the suction duct 36 and the discharge duct 38.

[71] A freezing cycle 30 of the direct cooling type refrigerator of Fig. 7 includes a compressor 32 for compressing refrigerants, and an evaporator 39 installed in the casing 110 around the storing space B adjacently to the inner surfaces 114a, 114b and 114c of the casing 110, for evaporating the refrigerants. The direct cooling type freezing cycle 30 includes a condenser (not shown) and an expansion valve (not shown).

[72] Especially, electrode units 50a and 50d are inserted between the evaporator 39 and the casing 110, for preventing cool air from being blocked by the evaporator 39.

[73] Figs. 8 and 9 are a structure view and a graph showing supercooling in the apparatus for supercooling in accordance with the present invention.

[74] Fig. 8 shows an experiment structure and condition of Fig. 9. Referring to Fig. 8, a storing space Sl is formed in a casing 111, O.l^of distilled water is contained in the storing space Sl, and electrodes 50e and 5Of are inserted into the sidewalls of the casing 111 to be symmetrically disposed to the storing space Sl. The electrode surfaces of the electrodes 50e and 50f facing the storing surface Sl are wider than the surface of the storing space Sl . An interval between the electrodes 50e and 50f is 20mm. The casing 111 is made of an acrylic material. The casing 111 is kept and cooled in a storing space uniformly supplying cool air (refrigerating apparatus which does not have an additional electric field generator except the electrodes 50e and 50f).

[75] Here, the microcomputer 90 makes the voltage generating unit 40 apply 0.91kV(6.76mA) and 2OkHz of Ac voltage to the electrode unit 50, and the temperature of the storing space is about -7°C. As shown in the supercooling graph of Fig. 9, since the non-freezing refrigerator 100 maintains supercooling at -6.5°C below the phase transition temperature, it keeps the non-frozen state of water over 50 hours.

[76] According to the experiment result of the present inventors, application of the electric field shows the following disinfecting effect.

[77] The present inventors investigated the survival rate of Giardias, flagellates causing diarrhea to a human body before and after electric field processing. 408 Giardias were used in a non-nutrient state. The present inventors investigated the survival rate of Giardias with the existence and absence of the electric field. When the electric field was not used, 396 Giardias were left, namely, the survival rate was 96.6%. It means that Giardias were not naturally removed. Conversely, when the electric field was used, no Giardia was left. The above experiment result was obtained in the non- nutrient state. However, it was expected that the similar result would be obtained in the nutrient state, namely, the food keeping state of the refrigerator. As described above, the electric field serves to efficiently remove microorganisms causing decay such as Giardia.

[78] Figs. 10 and 11 are graphs showing correlation between power and the non-freezing temperature in the simplified apparatus for supercooling in accordance with the present invention. Figs. 10 and 11 are applied to the experiment structure of Fig. 8. The keeping temperature (control temperature) in the storing space in which the casing 111 is kept, namely, the inside temperature is fixed to -6°C. Here, the microcomputer 90 sets and applies a plurality of quantities of power energy to the voltage generating unit 40, and measures resulting variations of the non-freezing temperature. That is, the taken energy Ql is constant and the supplied energy Q2 is variable.

[79] Fig. 10 is a graph showing the non-freezing temperature of water supplied with different quantities of power energy. As depicted in Fig. 10, in a reference line 0 which is not supplied with power energy, water is maintained in the non-frozen state to -5°C by cooling, and phase-transited to the frozen state 3 hours from cooling.

[80] In a first energy line 1 (1.38W), since the quantity of the energy Q2 applied to water is much larger than the quantity of the taken energy Ql , even if water is cooled at the phase transition temperature (O⁰C in 1 air pressure), it is maintained at almost O⁰C and not supercooled.

[81] In a second energy line II (0.98W), water is maintained in the supercooled state, and the supercooling temperature ranges from -3 to -3.5°C. [82] In a third energy line IE (0.91W), water is maintained in the supercooled state, and the supercooling temperature ranges from -4 to -5°C.

[83] In a fourth energy line IV (0.62W), water is maintained in the supercooled state, and the supercooling temperature ranges from -5.5 to -5.8°C.

[84] In a fifth energy line V (0.36W), water is frozen (phase transition) without reaching the supercooled state.

[85] Fig. 11 is a graph showing correlation between the first to fifth energy lines I to V of Fig. 10. As shown in Fig. 11, in the cool air supply state, the quantity of the energy Q2 applied to water and the supercooling temperature of water have proportional relation. That is, when the quantity of the energy Q2 applied to the contents is large, the supercooling temperature rises, and when the quantity of the energy Q2 applied to the contents is small, the supercooling temperature falls. However, if the quantity of energy Q2 is too small, it does not cause the motion of the water molecules and adjust the supercooled state, thereby reaching the result of the fifth energy line V.

[86] In this experiment, the supercooling temperature is determined according to the quantity of energy applied when the keeping temperature (indoor temperature, inside temperature) is -6°C. If the keeping temperature is changed, namely, if the quantity of the taken energy Ql is changed, the quantity of the applied energy Q2 mist be changed.. When the keeping temperature is constant, the microcomputer 90 stores the simple correlation information between the quantities of energy Ql and Q2 and the supercooling temperature. In the case that the keeping temperature is adjusted or varied, the microcomputer 90 rmst store the correlation information between the quantities of energy Ql and Q2 and the supercooling temperature in consideration of the variations of the keeping temperature.

[87] Fig. 12 is a graph showing relation between intensity of the electric field, the keeping temperature and the supercooling temperature in the method for supercooling in accordance with the present invention.

[88] As illustrated in Fig. 12, the supercooling temperature Cs of the contents is calculated from the correlation between the intensity of the electric field (supplied energy Q2) and the keeping temperature Cm (taken energy Ql).

[89] For example, in the intensity Wl of the electric field and the keeping temperature

Cm, when the contents are stable at the supercooling temperature Cs, if the keeping temperature Cm falls to a keeping temperature Cm , namely, if the taken energy Ql increases, the supercooling temperature Cs is varied into a supercooling temperature Cs . The contents are stabilized by Cs < Cs. As another example, if the keeping temperature Cm rises to a keeping temperature Cm , namely, if the taken energy Ql decreases, the supercooling temperature Cs is varied into a supercooling temperature Cs . The contents are stabilized by Cs > Cs.

[90] The taken energy Ql and the supplied energy Q2 can be adjusted from the relations of Figs. 10, 11 and 12, thereby controlling the supercooling temperature Cs of the contents.

[91] Fig. 13 is a flowchart showing a method for supercooling in accordance with a first embodiment of the present invention.

[92] In detail, in S71, the microcomputer 90 decides whether the user can select the degree of non-freezing through the input unit 70. If so, the microcomputer 90 goes to S72, and if not, the microcomputer 90 goes to S73.

[93] In S72, the microcomputer 90 sets the degree of non-freezing according to selection of the user inputted or previously inputted through the input unit 70. The input or selection of the degree of non-freezing can consist of specific temperatures (for example, -6°C, -8°C), or high, middle and low indicating the degree of the temperature.

[94] In S73, since a special means or service for enabling the user to input or select the degree of non-freezing is not provided, the microcomputer 90 reads the fixed degree of non-freezing. For example, the degree of non-freezing can be -6⁰C or -8°C.

[95] In S74, the microcomputer 90 decides whether the degree of cooling can be adjusted by controlling the freezing cycle 30 for cooling the storing space A or B or the contents. This step S74 is not necessary when the freezing cycle 30 is formed merely to cool the storing space A or B as shown in Figs. 4a and 4b. However, in the case of a vegetable chamber or a meat chamber of the refrigerator controlled at a constant degree of cooling (control temperature, inside temperature, etc.), the degree of cooling is not controllable. Therefore, the method for setting the quantity of energy is changed. In this case, the above step S74 is needed. If the degree of cooling is not controllable by a mechanical method or software, the microcomputer 90 goes to S75, and if the degree of cooling is controllable, the microcomputer 90 goes to S77.

[96] In S75, the microcomputer 90 sets the quantity of the energy applied to the storing space A or B or the contents according to the set or fixed degree of non-freezing. When the degree of cooling is constant, the microcomputer 90 can set the quantity of energy merely by the relation of the degree of non-freezing and the quantity of energy.

[97] In S76, since the degree of cooling is not controllable or variable as described above, the microcomputer 90 cools the storing space A or B or the contents at the constant degree of cooling. [98] In S77, the microcomputer 90 sets the degree of cooling according to the set or fixed degree of non-freezing, and performs cooling by the freezing cycle 30. For example, if the degree of non-freezing is -8°C, the cooling temperature of the storing space A or B or the contents mast be set lower than at least -8°C. In the same degree of non-freezing, if the current cooling temperature is -10⁰C, the cooling temperature can be set slightly lower than -8⁰C, thereby reducing power consumption by cooling.

[99] In S78, the microcomputer 90 sets the quantity of energy according to the set or fixed degree of non-freezing. Here, the cooling temperature set in S77 must be considered.

[100] In S79, the microcomputer 90 applies energy set in S75 or S78 to the storing space

A or B or the contents, thereby carrying out non-freezing keeping.

[101] In this embodiment, S77 and S78 can be performed at the same time. That is, the microcomputer 90 simultaneously sets the degree of cooling and the quantity of energy according to the degree of non-freezing. In the setting process, the microcomputer 90 considers the relation between the degree of cooling and the quantity of energy.

[102] Fig. 14 is a flowchart showing a method for supercooling in accordance with a second embodiment of the present invention.

[103] The second embodiment shows a control method when the quantity of energy, namely, the intensity of the electric field which the microcomputer 90 can generate through the voltage generating unit 40 is constant.

[104] In detail, in S 81, the microcomputer 90 applies the preset fixed energy to the storing space A or B or the contents through the non-freezing operating unit including the voltage generating unit 40 and the electrode unit 50. That is, the microcomputer 90 cannot control the intensity of the electric field.

[105] In S82, the microcomputer 90 decides whether the user can select the degree of non-freezing in the same manner as S71 of Fig. 13.

[106] In S83, the microcomputer 90 sets the selected or inputted degree of non-freezing.

[107] In S 84, in order to attain the set degree of non-freezing by the fixed energy, the microcomputer 90 sets the degree of cooling by the freezing cycle 30, and cools the storing space A or B or the contents at the set degree of cooling. That is, in the fixed energy state, the degree of cooling is increased (the control temperature is lowered) to lower the temperature by the degree of non-freezing, and the degree of cooling is decreased (the control temperature is raised) to raise the temperature.

[108] In S85, the microcomputer 90 reads the fixed degree of non-freezing.

[109] In S86, to attain the fixed degree of non-freezing by the fixed quantity of energy, the microcomputer 90 cools the storing space A or B or the contents by the constant degree of cooling.

[110] Fig. 15 is a flowchart showing a method for supercooling in accordance with a third embodiment of the present invention. The method for supercooling of Fig. 15 (power save mode) sets the starting point of the non-freezing mode according to the temperature of the storing space A or B or the contents.

[Ill] In detail, in S91, the microcomputer 90 cools the storing space A or B by controlling the freezing cycle 30. Since the microcomputer 90 does not yet execute the non-freezing mode, the microcomputer 90 slowly cools the storing space A or B or the contents by turning off the means for forcibly flowing cool air such as the fan 34 of the freezing cycle 30 of the indirect cooling type refrigerator.

[112] In S92, the microcomputer 90 senses the temperature T of the storing space A or B or the contents by the temperature sensor which is the load sensing unit 20.

[113] In S93, the microcomputer 90 compares the sensed temperature T with a phase transition temperature TO of the contents. If the sensed temperature T is different from the phase transition temperature TO within a set temperature (a), the microcomputer 90 goes to S94. If not, the microcomputer 90 goes to S92. In this step S93, the contents are not phase-transited until the sensed temperature T reaches the phase transition temperature TO. Therefore, the microcomputer 90 needs not to execute the non- freezing mode. However, the temperature of the storing space A or B or the contents may sharply fall by cooling of the freezing cycle 30. Accordingly, the microcomputer 90 does not execute the non-freezing mode so far as the difference exists within the set temperature (a), thereby reducing power consumption. Since the volume of water is minimized at 4°C, the motion between the water molecules may be varied. Preferably, the set temperature (a) ranges from 0 to 4°C.

[114] In S94, the microcomputer 90 starts execution of the non-freezing mode by controlling the non-freezing operating unit including the voltage generating unit 40 and the electrode unit 50. Here, the microcomputer 90 uniformly cools the storing space A and the contents by operating the means for forcibly flowing cool air such as the fan 34 of the freezing cycle 30.

[115] In S95, the microcomputer 90 reduces a cooling speed of the freezing cycle 30, executing the non-freezing mode by the non-freezing operating unit. If a temperature outside the storing space A or B or the contents is sharply varied during the non- freezing mode, the non-freezing mode may be released and phase transition to the frozen state may occur. Accordingly, the microcomputer 90 prevents the sharp variation of the temperature by reducing the cooling speed by controlling the cooling force of the compressor 32, thereby stably executing the non-freezing mode.

[116] In S96, the microcomputer 90 decides whether the storing space A or B or the contents have been stabilized in the non-frozen state. The microcomputer 90 can decide stabilization on the basis of information on a stabilization time of the non- frozen state by load, or an average time spent to stabilize the storing space A or B or contents in the non-frozen state. After the non-frozen state is stabilized, the microcomputer 90 goes to S97.

[117] In S97, the microcomputer 90 reduces the frequency of the voltage applied to the electrode unit 50 by controlling the voltage generating unit 40, thereby reducing power consumption. When the non-frozen state is stabilized, the motion of the water molecules becomes constant. Even if the frequency of the voltage is reduced, it rarely affects the motion. Therefore, the non-frozen state is continuously stabilized.

[118] Fig. 16 is a control graph of the method for supercooling of Fig. 15. The graph of

Fig. 16 shows a temperature curve of the storing space A or B or the contents. When the sensed temperature T is larger than T0+a, the electric field is off, and when the sensed temperature T is equal to or smaller than T0+a, the electric field is on.

[119] Fig. 17 is a flowchart showing a method for supercooling in accordance with a fourth embodiment of the present invention. The method for supercooling of Fig. 17 (power save mode) controls the starting point of the non-freezing mode according to a set time tl.

[120] In detail, SlOl is identical to S91 of Fig. 15.

[121] In S102, the microcomputer 90 calculates a cooling time of the freezing cycle 30 by a built-in timer, and decides whether the cooling time exceeds the set time tl . If the cooling time does not reach the set time tl, the microcomputer 90 maintains a standby state, and if the cooling time reaches the set time tl, the microcomputer 90 goes to S103.

[122] S103 to S105 are identical to S94 to S96 of Fig. 15.

[123] In S106, when the storing space A or B or the contents are stabilized in the non- frozen state, the microcomputer 90 discontinuously executes the non-freezing mode by discontinuously turning on the electric field applied to the storing space A or B or the contents. During the discontinuous execution, although the voltage is not applied from the voltage generating unit 40 to the electrode unit 50, the electrode unit 50 performs a capacitor operation for a predetermined time, thereby maintaining the motion of water for the predetermined time. The discontinuous execution of the non-freezing mode reduces power consumption.

[124] Fig. 18 is a control graph of the method for supercooling of Fig. 17. The graph of

Fig. 18 shows a temperature curve of the storing space A or B or the contents and on/ off sections of the electric field. As shown in Fig. 18, before the cooling time reaches the set time tl, the electric field is off, and when the cooling time reaches the set time tl, the electric field is on.

[125] Fig. 19 is a control graph of a method for supercooling in accordance with a fifth embodiment of the present invention. The control graph of Fig. 19 shows a temperature curve of the storing space A or B or the contents, and corresponds to the control process of S 106 of Fig. 18. When the storing space or the contents are stabilized in the non-frozen state in a first on section, the microcomputer 90 turns off the electric field for t2 to t3, and turns on the electric field in t3 in a second on section, thereby discontinuously executing the non-freezing mode. As seen from the temperature curve, the non-frozen state of the storing space A or B or the contents is stably maintained in spite of the discontinuous execution of the non-freezing mode.

[126] S97 of Fig. 15 and S106 of Fig. 17 can be selectively used after stabilization of the non-frozen state.

[127] Fig. 20 is a control graph of a method for supercooling in accordance with a sixth embodiment of the present invention. As illustrated in Fig. 20, before the microcomputer 90 reaches the steps S93 and S94 of Fig. 15 or the steps S102 and S103 of Fig. 17, namely, when the storing space A or B or the contents are not frozen, the microcomputer 90 make the voltage generating unit 40 apply a voltage having a amplitude and a frequency corresponding to region I to the electrode unit 50. The region I has a low frequency low voltage characteristic. In the section in which phase transition (freezing) does not occur, a weak electric field is applied to the storing space A or B or the contents.

[128] When the microcomputer 90 reaches the steps S93 and S94 of Fig. 15 or the steps

S102 and S103 of Fig. 17, namely, when the storing space A or B or the contents can be frozen, the microcomputer 90 make the voltage generating unit 40 apply a voltage having a amplitude and a frequency corresponding to region II to the electrode unit 50. The region II has a high frequency high voltage characteristic. In the section in which phase transition may occur, a strong electric field is applied to the storing space A or B or the contents.

[ 129] When the non-frozen state is stabilized in S96 of Fig. 15 and S 105 of Fig. 17, the microcomputer 90 applies the electric field by the voltage corresponding to region I. [130] Accordingly, the microcomputer 90 can reduce power consumption in the non- freezing mode and stably execute the non-freezing mode, by changing the amplitude and the frequency of the voltage for generating the electric field according to the proceeding degree of the non-frozen state.

[131] As discussed earlier, the apparatus and method for supercooling can stably maintain the contents in the supercooled state for the extended period of time.

[132] The apparatus and method for supercooling can stably maintain the contents in the supercooled state at a low temperature by adjusting the supplied energy and the taken energy.

[133] The apparatus and method for supercooling can execute various types of non- freezing modes by setting or controlling the non-freezing temperature of the contents by adjusting the quantity of energy.

[134] The apparatus and method for supercooling can execute various types of non- freezing modes by enabling the user to select the non-freezing temperature of the contents.

[135] The apparatus and method for supercooling can execute the non-freezing mode for forming the non-frozen state and minimize power consumption in the non-freezing mode, by controlling the execution time of the non-freezing mode.

[136] The apparatus and method for supercooling can maintain the non-frozen state and minimize power consumption at the same time by discontinuously executing the non- freezing mode.

[137] Although the preferred embodiments of the present invention have been described, it is understood that the present invention should not be limited to these preferred embodiments but various changes and modifications can be made by one skilled in the art within the spirit and scope of the present invention as hereinafter claimed.

Claims

[1] An apparatus for supercooling, comprising: a means for taking energy from the contents; and a means for causing at least one of rotation, vibration and translation to water molecules of the contents, by supplying energy smaller than the taken energy, whereby the contents are maintained in a liquid state below a phase transition temperature.

[2] The apparatus for supercooling of claim 1, wherein the causing means applies an electric field to the contents.

[3] The apparatus for supercooling of claim 2, wherein the causing means sets the supplied energy by varying at least one of a voltage, a frequency and a current.

[4] The apparatus for supercooling of claim 1, wherein the taken energy is dependent upon a difference between a cooling temperature applied to the contents and a current temperature of the contents.

[5] The apparatus for supercooling of claim 1, wherein the taken energy is dependent upon a quantity of the contents.

[6] A method for supercooling, comprising the steps of: setting energy taken from the contents; taking the set energy from the contents; and causing at least one of rotation, vibration and translation to water molecules of the contents, by supplying energy smaller than the set energy, the above steps being sequentially or sirrultaneously carried out, whereby the contents are maintained in a liquid state below a phase transition temperature.

[7] The method for supercooling of claim 6, wherein the step for setting energy is dependent upon a difference between a cooling temperature applied to the contents and a current temperature of the contents.

[8] The method for supercooling of claim 6, wherein the step for setting energy is dependent upon a quantity of the contents.

[9] The method for supercooling of claim 6, wherein the causing step comprises the steps of: setting the applied energy; and setting a voltage, a frequency and a current according to the set energy.

[10] A method for supercooling, comprising the steps of: supplying energy to the contents; and taking more energy than the supplied energy, at least one of rotation, vibration and translation being caused to water molecules of the contents, whereby the contents are maintained in a liquid state below a phase transition temperature.

[11] A method for supercooling, comprising the steps of: applying energy to a storing space for storing the contents; and setting a non-freezing temperature of the storing space or the contents according to the quantity of applied energy.

[12] The method for supercooling of claim 11, wherein the setting step sets the non- freezing temperature by using proportional relation between the non-freezing temperature of the storing space or the contents and the quantity of energy.

[13] The method for supercooling of claim 11, farther comprising a step for cooling the storing space or the contents at a constant cooling speed.

[14] The method for supercooling of claim 11, wherein the setting step sets the non- freezing temperature according to the cooling temperature of the storing space or the contents and the quantity of energy.

[15] A method for supercooling, comprising the steps of: reading a degree of non-freezing of a storing space or the contents; and setting a quantity of applied energy according to the degree of non-freezing.

[16] The method for supercooling of claim 15, fiirther comprising a step for applying the set quantity of energy to the storing space or the contents.

[17] The method for supercooling of claim 15,. wherein the setting step sets the quantity of energy by using proportional relation between the degree of non- freezing and the quantity of energy.

[18] The method for supercooling of either claim 15 or 17, farther comprising a step for cooling the storing space or the contents at a constant cooling temperature.

[19] The method for supercooling of claim 15, wherein the reading step reads the degree of non-freezing selected by the user.

[20] The method for supercooling of claim 15, fiirther comprising a step for setting a degree of cooling for the storing space or the contents according to the degree of non-freezing.

[21] The method for supercooling of claim 20, which performs an energy application

, step using the set quantity of energy, and a cooling step using the set degree of cooling.

[22] A method for supercooling, comprising the steps of: cooling a storing space or the contents stored in the storing space; and executing a non-freezing mode before a phase transition temperature of the contents.

[23] The method for supercooling of claim 22, fiirther comprising a step for sensing a temperature of the storing space or the contents.

[24] The method for supercooling of claim 22, fiirther comprising a step for reducing a supply speed of cool air in the step for executing the non-freezing mode.

[25] A method for supercooling, comprising the steps of: cooling a storing space or the contents for a set time; and executing a non-freezing mode on the storing space or the contents.

[26] The method for supercooling of claim 25, which reduces a cooling speed of the cooling step during the step for executing the non-freezing mode.

[27] A method for supercooling, comprising a step for executing a non-freezing mode on a storing space or the contents stored in the storing space, the step for executing the non-freezing mode being discontinuously carried out.

[28] The method for supercooling of claim 27, wherein the non-freezing mode is discontinuously executed when the contents are in the non-frozen state.

[29] A method for supercooling, comprising the steps of: executing a non-freezing mode; checking a proceeding degree of a non-frozen state; and controlling intensity of the non-freezing mode according to the result of the checking step.

[30] The method for supercooling of claim 29, wherein the intensity of the non- freezing mode is associated with a amplitude of a voltage and a height of a frequency for generating an electric field.