KR20100091644A - Control method of refrigerator - Google Patents

Abstract

PURPOSE: A method for controlling a refrigerator is provided to prevent food from being rotten by rapidly increasing the inner temperature of a refrigerator during a defrosting operation. CONSTITUTION: A method for controlling a refrigerator is as follows. A refrigerating operation is performed by repetitively turning on/off a compressor(S100). When external temperature is less than first setting temperature, the temperature and pressure of a refrigerant is ascended by stopping a ventilation fan which cools the compressor(S200). A defrosting operation is performed by operating a switching valve(S300).

Description

Control method of refrigerator {

The present invention relates to a refrigerator control method.

In general, a refrigerator is a home appliance that allows food to be stored at a low temperature in an interior storage space shielded by a door, and is stored by cooling the inside of the storage space using cold air generated through heat exchange with a refrigerant circulating in a refrigeration cycle. It is configured to keep foods in optimal condition.

In the evaporator provided in such a refrigerator, frost is generated by the implantation and freezing of moisture. When frost occurs on the evaporator, not only there is a hygiene problem, but also the cooling efficiency is lowered to increase the power consumption, the conventional evaporator is provided with a defrost heater for removing the frost (hereinafter referred to as 'defrost').

In addition, the defrost heater is operated for defrosting, and defrosting operation is performed such that components constituting the refrigerating cycle such as a compressor and a blower fan are stopped. It lasts until it is reached.

The defrosting operation is usually performed every set time, and can be repeatedly performed in consideration of the number of opening and closing times of the door or the cumulative time of opening and closing of the door and the operation rate of the compressor.

Such defrosting operation is a method of heating by a defrost heater or a method of bypassing the high temperature refrigerant discharged from the compressor to the evaporator side by means of a switching valve and heating it with hot gas. Can be adopted.

An embodiment of the present invention is to provide a refrigerator control method for supplying a hot gas to the evaporator at a higher temperature during the defrosting operation by operating the compressor in a state in which the blowing fan is stopped for a predetermined time before the start of the defrosting operation. It is done.

Another embodiment of the present invention, by operating the compressor in a state in which the blowing fan is stopped for a predetermined time before the start of the defrosting operation to supply hot gas to the evaporator at a higher temperature during the defrosting operation, the temperature of the outside air during the defrosting operation It is an object of the present invention to provide a refrigerator control method for varying the rotational speed of a compressor.

Refrigerator control method according to an embodiment of the present invention, the compressor is repeatedly on / off normal operation step of performing a conventional refrigeration operation; When the outside air temperature is less than the first set temperature before the defrost operation start signal is input, during the first set time, the compressor is driven and the blower fan cooling the compressor is stopped to raise the temperature and pressure of the compressor outlet refrigerant. Driving step; A defrosting operation step of operating a switching valve by inputting a defrosting operation start signal and directing discharged refrigerant of the compressor to the evaporator side to perform defrosting; and after completion of the defrosting operation step, returns to the normal operation step. Characterized in that.

In addition, the refrigerator control method according to another embodiment of the present invention, the compressor is repeatedly on / off normal operation step of performing a normal refrigeration operation; When the defrost operation start signal is reached before the set time input, when the outside temperature is lower than the first set temperature (D1), the defrost operation step of driving the compressor in a state in which the blowing fan for cooling the compressor is stopped ; A defrosting operation step of operating the switching valve by input of the defrosting operation start signal and directing the high temperature and high pressure refrigerant of the compressor outlet to the evaporator side. In the defrosting operation step, the outside air temperature is higher than the second set temperature (D2). The low temperature defrosting operation of rotating the compressor at high speed is performed when low, and the high temperature defrosting operation of rotating the compressor at a relatively low speed is performed when the outside temperature is greater than or equal to the second set temperature (D2).

According to the refrigerator control method according to the embodiment of the present invention, the compressor is driven immediately before the defrosting operation, and the blowing fan for cooling the compressor is stopped for a set time.

The coolant discharged from the compressor and supplied to the evaporator enables the supply of cold air into the refrigerator before the defrosting operation, thereby preventing the food from being damaged by a rapid increase in the internal temperature of the defrosting operation.

In addition, the refrigerant discharged from the compressor may be in a higher temperature state, so that the temperature of the hot gas supplied to the evaporator during the defrosting operation becomes higher, thereby improving the defrosting efficiency.

In addition, during the defrosting operation, the rotational speed of the compressor is varied according to the outside air temperature. In other words, if the temperature of the outside air is lower than the set temperature, the defrosting efficiency may decrease due to the influence of the outside air, but to compensate for this, the compressor is rotated faster than the compressor rotation speed in the normal defrosting operation to produce hot gas at a higher temperature. Allow discharge.

Therefore, even when the outside air temperature is lower than the set temperature, it is possible to smoothly remove the frost formed on the evaporator by the hotter hot gas discharged from the compressor, thereby improving the defrosting efficiency.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. However, it should be understood that the present invention is not limited to the embodiment shown in the drawings, and that other embodiments falling within the spirit and scope of the present invention may be easily devised by adding, .

1 is a cycle diagram showing a configuration of a refrigeration cycle of a refrigerator according to an embodiment of the present invention, Figure 2 is a block diagram showing the flow of control signals of the refrigerator according to an embodiment of the present invention.

Referring to the drawings, in the refrigerator according to the embodiment of the present invention, a compressor 10, a condenser 20, a capillary tube 30, an evaporator 40, and a liquid refrigerant tank 50 constituting a refrigeration cycle are sequentially connected in series. As the refrigerant is circulated, the refrigeration cycle can be driven. The bypass pipe 60 further includes a pipe connecting the compressor 10 and the condenser 20 to each other, and a pipe connecting the capillary 30 and the evaporator 40 to each other.

One end of the bypass pipe 60 is provided with a switching valve 70 connected to the pipe connecting the compressor 10 and the condenser 20. The switching valve 70 selectively branches the high temperature, high pressure refrigerant discharged from the outlet side of the compressor 10 to the condenser 20 or the evaporator 40, respectively, and the compressor 10 and the condenser 20, respectively. And it is configured to be connected to the bypass pipe 60 side.

In addition, a blower fan 11 for cooling the compressor 10 is provided at one side of the compressor 10. The blowing fan 11 is configured to cool the compressor 10 while rotating together with driving the compressor 10 during the normal operation of the refrigerator. In addition, one side of the evaporator 40 is provided with a cooling fan 41 for forcibly blowing the cold air generated by the heat exchange with the refrigerant in the evaporator 40 to the inside.

In addition, one side of the evaporator 40 is provided with a defrost heater 80 is generated during the defrosting operation of the refrigerator to remove frost formed on the evaporator 40. One side of the evaporator 40 having the defrost heater 80 is provided with a first temperature sensor 91 for measuring the temperature of the evaporator 40 side, the compressor 10 and the condenser 20 One side of the machine room or the refrigerator main body is provided with a second temperature sensor 92 for measuring the outside temperature. In addition, one side of the main body may be provided with a counter 90 for counting the time for defrosting operation.

The controller 100 is provided at one side of the main body. The control unit 100 is for controlling the driving of a plurality of electrical components provided in the refrigerator, by the signals received from the first temperature sensor 91, the second temperature sensor 92 and the counter 90 It is configured to adjust the driving of the compressor 10, the blowing fan 11, the cooling fan 41, the defrost heater (80) and the like.

Hereinafter, a refrigerator control method according to an embodiment of the present invention having the above configuration will be described in detail with reference to the accompanying drawings.

3 is a flow chart sequentially showing a refrigerator control method according to an embodiment of the present invention, Figure 4 is a flow chart showing the operation before defrost of the refrigerator control method according to an embodiment of the present invention in detail. And, Figure 5 is a flow chart showing in detail the defrosting operation of the refrigerator control method according to an embodiment of the present invention.

Referring to these drawings, a refrigerator drives a refrigeration cycle in a general driving environment, and as the compressor 10 constituting the refrigeration cycle is driven, a blower fan 11, a cooling fan 41, and the like operate. .

In addition, the rotational speed of the compressor 10 may be adjusted according to the input load. For this purpose, the compressor 10 may be an inverter-type compressor capable of changing the rotational speed according to an input voltage. .

The driving time of the compressor 10 may be adjusted according to the input load. In detail, after the temperature in the refrigerator reaches a set level or the compressor 10 is driven for a predetermined time or more, the compressor 10 is stopped for a predetermined period of time and then restarted. This process is repeated continuously. Normal operation step (S100)]

During the normal operation of the refrigerator, moisture of the air introduced upon inflow of external air due to opening and closing of the door may form on the surface of the evaporator 40, causing frost, and also by moisture generated from food stored therein. Frost may be generated on the surface of the evaporator 40.

The temperature of the surface of the evaporator 40 is lowered by the continuous operation of the refrigeration cycle, and the frost formed on the surface of the evaporator 40 freezes and continuously grows to lower the heat exchange performance of the evaporator 40. This will eventually reduce the freezing capacity of the refrigerator. Therefore, in order to prevent this, a defrosting operation for removing frost frozen in the evaporator 40 is required.

Since the defrosting operation increases the temperature in the refrigerator, the defrosting operation is carried out at regular intervals in order to maintain storage performance. ) To determine the timing of defrosting operation.

On the other hand, the defrosting operation is started by the defrosting operation start signal output from the control unit 100, such a defrosting operation start signal can be repeatedly output at a predetermined period when the defrosting operation is required.

In order to increase the efficiency of the defrosting operation, the defrosting operation is performed before the defrosting operation is performed. To this end, the control unit 100 performs a defrost signal input determination step (S210) for checking whether a defrost operation start signal is input during normal operation.

When the defrosting operation start signal is input, the defrosting operation is performed. When the defrosting operation start signal is not input, a setting time determination step of determining whether the defrosting operation start signal is earlier than the set time T from the moment when the defrosting operation start signal is input. (S220). At this time, the set time T is approximately 30 minutes to increase the defrosting efficiency.

On the other hand, when the defrosting operation start signal is input earlier than the set time T from the moment when the defrosting operation start signal is input in the set time determining step (S220), the blower fan 11 is turned on when the compressor 10 is being driven. State is maintained, and normal operation is executed from the moment when the defrosting operation start signal is input until the set time is reached.

On the other hand, when the defrosting operation start signal is input from the moment when the defrosting operation start signal is input in the setting time determination step (S220), the temperature detected by the second temperature sensor 92 is converted to the first setting temperature (D1). The set temperature determination step (S230) to be compared with is performed. At this time, the first set temperature (D1) is approximately 15 ℃. When the outside air temperature is about 15 ° C. or higher, since the temperature of hot gas necessary for normal defrosting can be ensured even when the blowing fan 11 is not stopped, the first set temperature D1 is preferably about 15 ° C. .

Therefore, when the outside temperature detected by the second temperature sensor 92 is equal to or greater than the first set temperature D1, the blowing fan 11 maintains an ON state when the compressor 10 is being driven. In this case, normal operation is performed until the set time T is reached before the defrosting operation start signal is input.

When the outside temperature detected by the second temperature sensor 92 is lower than the first set temperature D1, the compressor 10 is driven to be in an ON state, and at the same time, the blower fan 11 ) Will stop.

Therefore, the forced cooling of the compressor 10 is not performed, and the refrigerant compressed in the compressor 10 becomes a higher temperature, and such an operating state can be maintained for a predetermined time.

That is, when the outside air temperature is less than or equal to the first set temperature D1, the blower fan 11 is driven by the blower fan 11 when the compressor 10 starts from the set time T before the defrosting operation starts. The temperature of the discharged coolant is increased to allow more effective defrosting at the start of the defrosting operation. [Defrost operation step (S200)]

On the other hand, when the defrosting operation start signal is input from the controller 100, the defrosting operation is started. When the start signal of the defrosting operation is input, the outside air temperature detected by the second temperature sensor 92 is compared with the second set temperature D2. At this time, when the detected outside temperature is higher than or equal to the second set temperature D2, a high temperature defrosting operation is performed. When the detected outside temperature is lower than the second set temperature D2, a low temperature defrosting operation is performed.

At this time, the second set temperature D2 serving as a reference for the high temperature defrosting operation and the low temperature defrosting operation is set to about 3 ° C. When the temperature of the outside air is lower than 3 ° C., the defrosting efficiency is inevitably lower than that when the temperature of the outside air is low and the temperature of the outside air is high, and according to the temperature of the outside air, the second set temperature ( Based on D2), the defrosting operation is divided.

First, in the case of the high temperature defrosting operation in which the outside air temperature is higher than the second set temperature D2, the compressor 10, the blowing fan 11, and the cooling fan 41 are stopped. The first temperature sensor 91 determines whether the temperature at the evaporator side reaches the third set temperature D3.

When the temperature of the evaporator 40 is about 3 ° C., the third set temperature D3 may be determined to have been defrosted. If the temperature is less than 3 ° C., the third set temperature D3 may be continuously defrosted.

At the beginning of the high temperature defrosting operation, that is, immediately after the compressor 10, the blowing fan 11, and the cooling fan 41 are stopped, the temperature at the side of the evaporator 40 becomes 3 ° C. or less at a temperature below zero, and the switching is performed at this time. By switching the valve 70, the high temperature and high pressure refrigerant discharged from the compressor 10 may be guided to the evaporator 40 through the bypass pipe 60.

After the operation of the switching valve 70, the compressor 10 starts to be driven again, and the high temperature and high pressure refrigerant discharged from the compressor 10 is supplied to the evaporator 40. Therefore, the inside of the evaporator 40 may be filled with hot gas so that the surface of the evaporator 40 may be heated, and the removal of frost frozen on the surface of the evaporator 40 starts.

At this time, after switching the path of the switching valve 70, the compressor 10 may be driven after about 5 seconds, and the refrigerant discharged at a high temperature and high pressure by switching between the switching valve 70 and a time difference. From the switching valve 70 and to protect the entire system.

The defrost heater 80 may be driven immediately before or after the switching of the refrigerant flow path by the operation of the switching valve 70. In particular, in the initial stage of defrosting, since the evaporator 40 or the adjacent portion of the evaporator 40 must be heated with higher heat, defrosting can be performed faster by driving the defrost heater 80.

On the other hand, the defrosting operation is repeatedly performed continuously until the temperature detected by the first temperature sensor 91 is greater than or equal to the third set temperature (D3). When the temperature at the first temperature sensor 91 is equal to or higher than the third set temperature D3, the driving of the compressor 10 and the defrost heater 80 are stopped, and the switching valve 70 is turned off. The high temperature defrosting operation is terminated by changing the path so that the refrigerant discharged from the compressor 10 is directed back to the condenser 20 side.

The refrigeration cycle is in a state where normal operation is possible by changing the path of the switching valve 70, and the high temperature defrosting operation is terminated and the normal cycle returns to the normal operation step (S100). Of course, the above-described process is repeated at regular intervals. [Defrost operation step (S300)].

6 is a graph showing a change in input voltage during low temperature defrosting of the refrigerator control method according to an exemplary embodiment of the present invention. 6 shows a change in the rotational speed of the compressor 10 according to the time change during the high temperature defrosting operation.

Referring to the drawings in detail, the compressor 10 is operated to sequentially pass through the first section, the second section, the third section, and the fourth section during the high temperature defrosting operation, and the compressor 10 in each section. Rotation speed and rotation speed change are different.

More specifically, in the first section, the compressor 10 has an initial input voltage of 120 V (rms) and continuously increases the input voltage for approximately 6 seconds to reach 130 V (rms). Accordingly, the compressor continuously increases from the initial rotational speed V 0 to reach the maximum rotational speed V 2.

The voltage input to the compressor 10 in the second section is 130V (rms), and maintains the input voltage for about 3 minutes. Therefore, the compressor 10 maintains the maximum rotational speed V2 and the temperature of the refrigerant discharged to the compressor 10 is increased, so that defrosting can be more effectively performed.

On the other hand, if the compressor 10 maintains the maximum rotational speed (V2), the pressure of the refrigerant discharged from the compressor 10 is also increased to increase the noise due to the increase in pressure on the suction side of the evaporator 40 do. Therefore, the rotation speed of the compressor 10 should be lowered after approximately three minutes of being the threshold of the noise tolerance level.

In the third section, the compressor 10 gradually lowers the rotational speed at the highest rotational speed V2 to lower the noise. Therefore, the input voltage of the compressor 10 continuously decreases at 130V (rms), and the input voltage is approximately 100V (rms) at a point approximately 14 minutes from the start of the defrosting operation. Therefore, at about 14 minutes from the start of the defrosting operation, the compressor 10 is rotated at the minimum rotational speed V3.

At this time, the rotational speed of the compressor 10 is continuously reduced, and as the pressure of the refrigerant discharged from the compressor 10 decreases, the noise on the suction side of the evaporator 40 may be reduced to lower the noise. By lowering the rotational speed of the compressor 10 it is possible to maintain the temperature level of the hot gas discharged from the compressor 10 within an acceptable range.

In the fourth section, the input voltage of the compressor 10 is approximately 100V (rms), and the compressor 10 performs defrosting operation while maintaining the minimum rotational speed V3, until the end of the defrosting operation. After maintaining the most recent rotational speed (V3) and with the end of the defrosting operation, the input voltage supplied to the compressor 10 is turned off (OFF), the compressor 10 is stopped.

On the other hand, when the defrosting operation start signal is input from the controller 100 to start the defrosting operation, when the outside air temperature detected by the second temperature sensor 92 is lower than the second set temperature D2, The defrosting operation is performed. Low temperature defrosting operation is also operated while going through the same process as the above-described high temperature defrosting operation, there is a difference only in the operating state of the compressor (10).

That is, when the outside air temperature is lower than the second set temperature D2, the compressor 10, the blowing fan 11, and the cooling fan 41 are turned off. When the temperature of the evaporator 40 detected by the first temperature sensor 91 is less than or equal to the third set temperature D3, the defrost heater 80 is operated and the operation of the switching valve 70 causes the defrost heater 80 to operate. The hot gas discharged from the compressor 10 may be guided to the evaporator 40 to heat the evaporator 40.

The defrost heater 80 and the compressor 10 are continuously operated until the temperature at the side of the evaporator 40 becomes greater than or equal to the third set temperature D3, and the defrost heater 80 and the compressor 10 are detected by the first temperature sensor 91. When the temperature at the side of the evaporator 40 becomes equal to or higher than the third set temperature D3, the defrost heater 80 and the compressor 10 are stopped, and the switching valve 70 is again the compressor 10 and the condenser 20. ) Is switched to the connection state and the low temperature defrosting operation is terminated. After completion of the low temperature defrosting operation, the process returns to the normal operation step S100 again.

On the other hand, during the low temperature defrosting operation, the compressor 10 rotates at a higher speed than the above-described high temperature defrosting operation, and maintains the high speed rotation state until the defrosting operation is completed.

7 is a graph showing a change in input voltage during low temperature defrosting operation of the refrigerator control method according to an embodiment of the present invention. FIG. 7 illustrates a change in the input voltage of the compressor 10 according to the time change during the low temperature defrosting operation.

Looking at this in detail with reference to the drawings, when the low temperature defrosting operation is started, the compressor 10 can be rotated at an initial rotational speed (V0) by the voltage input to the compressor (10). At this time, the initial voltage input is 120V (rms), and increases the voltage continuously input for approximately 20 seconds to allow the compressor to rotate at the maximum rotational speed (V1) after 20 seconds.

When the compressor 10 rotates at the highest rotational speed V1, the voltage input to the compressor 10 becomes approximately 180V (rms). Since the compressor 10 rotates at a high speed, it is possible to discharge the refrigerant having a relatively high temperature and high pressure than the refrigerant temperature during the high temperature defrosting operation, and even when the refrigerant having a high temperature and high pressure is discharged, the temperature of the outside air is lowered. The suction side pressure of 40 is relatively low to satisfy the noise level.

Therefore, when the compressor 10 reaches the maximum rotational speed, the voltage input to the compressor 10 is constantly maintained at 180 V (rms), and the temperature at the evaporator 40 side reaches a third set temperature ( When D3) becomes approximately 3 ° C., the voltage supply to the compressor 10 is stopped to stop the compressor 10.

That is, during low temperature defrosting operation, the voltage input to the compressor 10 is increased from the first 120V (rms) to 180V (rms), and then the input voltage is 180V so that the compressor 10 can maintain the maximum rotational speed (V1). will remain at (rms). At the end of the full-temperature defrosting operation, the voltage supplied to the compressor 10 is turned off to stop the compressor 10.

1 is a cycle diagram showing the configuration of a refrigeration cycle of a refrigerator according to an embodiment of the present invention.

Figure 2 is a block diagram showing the flow of the control signal of the refrigerator according to an embodiment of the present invention.

3 is a flow chart sequentially showing a refrigerator control method according to an embodiment of the present invention.

Figure 4 is a flow chart showing in detail before the defrost operation of the refrigerator control method according to an embodiment of the present invention.

Figure 5 is a flow chart showing in detail the defrosting operation of the refrigerator control method according to an embodiment of the present invention.

6 is a graph showing a change in input voltage during the high temperature defrosting operation of the refrigerator control method according to an embodiment of the present invention.

7 is a graph showing a change in input voltage during low temperature defrosting operation of the refrigerator control method according to an embodiment of the present invention.

Claims (15)

A normal operation step in which the compressor is repeatedly on / off and performs a conventional freezing operation; When the outside air temperature is less than the first set temperature before the defrost operation start signal is input, during the first set time, the compressor is driven and the blower fan cooling the compressor is stopped to raise the temperature and pressure of the compressor outlet refrigerant. Driving step; A defrosting operation step in which a switching valve is operated by an input of a defrosting operation start signal to direct the discharged refrigerant of the compressor to the evaporator to perform defrosting; After the completion of the defrosting operation step refrigerator control method, characterized in that to return to the normal operation step. The method of claim 1, The pre-defrost operation step is a refrigerator control method characterized in that the continuously performed until the defrost operation start signal is input. The method of claim 1, The defrosting operation start signal is a refrigerator control method characterized in that the input periodically at a set time interval. The method of claim 1, In the pre-defrost operation step, the set time (T) is a refrigerator control method, characterized in that from the input of the defrost operation start signal to 30 minutes before the input of the defrost operation start signal. The method of claim 1, In the pre-defrost operation step, the first set temperature (D1) is a refrigerator control method, characterized in that 15 ℃. The method of claim 1, The defrosting operation step, Defrost signal input determination step of determining whether the defrost operation start signal input; A setting time determination step of determining whether the defrosting operation start signal is before the setting time T; And a set temperature determination step of comparing the outside temperature with the first set temperature (D1) before the set time (T). The method of claim 6, The control method of the refrigerator, characterized in that to return to the normal operation step if the set time (T) before the start of the defrosting operation in the set time determination step or the outside temperature is more than the first set temperature (D1). The method of claim 1, In the defrosting operation step, the refrigerator control method characterized in that for driving the variable speed of the compressor in accordance with the outside temperature. A normal operation step in which the compressor is repeatedly on / off and performs a conventional freezing operation; Defrost operation step of driving the compressor in a state in which the blowing fan for cooling the compressor is stopped when the outside temperature is lower than the first set temperature (D1) when the defrost operation start signal is reached before the set time input. ; A defrosting operation step in which a switching valve is operated by an input of a defrosting operation start signal to direct the high temperature and high pressure refrigerant of the compressor outlet to the evaporator side. In the defrosting operation step, When the outside air temperature is lower than the second set temperature (D2), the low temperature defrosting operation of rotating the compressor at high speed is performed. And a high temperature defrosting operation of rotating the compressor at a relatively low speed when the outside temperature is greater than or equal to the second set temperature (D2). The method of claim 9, In the low temperature defrosting operation, And the compressor is maintained from the initial rotational speed (V0) to the highest rotational speed (V1) until the defrosting operation is completed. The method of claim 9, In the high temperature defrosting operation, The compressor is a control method of the refrigerator, characterized in that the rotational speed is lowered again after being raised from the initial rotational speed (V0) to the maximum rotational speed (V2). The method of claim 9, The compressor in the defrosting operation step, the refrigerator control method characterized in that the deceleration at the maximum rotational speed (V2) at the moment when the refrigerant pressure sucked into the evaporator side exceeds the set pressure. The method of claim 9, The compressor during the high temperature defrosting operation, A first section rising from the initial rotational speed V0 to the highest rotational speed V2; A second section for maintaining a maximum rotation speed V2 for a predetermined period after reaching the maximum rotation speed V2; The third section which decelerates from the highest rotational speed (V2) to the lowest rotational speed (V3) after a certain time, After the minimum rotational speed (V3) reaches the fourth section that is maintained until the defrosting operation is finished, the refrigerator control method characterized in that it is operated sequentially. The method of claim 9, In the defrosting operation step, a defrost heater for heating the evaporator for defrosting characterized in that the drive control method. The method of claim 9, The control method of the refrigerator, characterized in that the defrosting operation step is terminated and the process returns to the normal operation step when the temperature at the evaporator side is greater than or equal to the third set temperature (D3) in the defrosting operation step.

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