An air duct system and working method for a wide-temperature-range air-cooled refrigerator

Abstract

The present invention discloses an air-cooled refrigerator air duct system and a working method in a wide temperature range. The system includes an evaporator, a fan, an electric heater, a refrigerating compartment, a variable temperature compartment, a freezing compartment, a supply air damper, a return air damper, a bypass air damper, and a supply and return air pipeline. According to the set refrigeration temperatures of each storage compartment by the user, the opening and closing states of various dampers in the air duct system are controlled to control the temperature of the compartment. The system provides two functions of capacity expansion and temperature expansion to meet the diverse usage needs of users. The variable temperature compartment can not only serve as an expansion area for the refrigerating compartment and the freezing compartment, but also widen its refrigeration temperature range to above 5°C to meet the higher temperature storage requirements of special items such as cosmetics and perfumes by users. By effectively controlling the air duct system of the air-cooled refrigerator, the present invention recovers the return air heat of the refrigerating compartment and the ineffective heat consumption of the defrosting heater, and widens the storage temperature range of the traditional air-cooled refrigerator.

Description

Technical Field

[0001] The present invention belongs to the technical field of refrigerator refrigeration, and particularly relates to an air duct system and a working method for a wide-temperature-zone air-cooled refrigerator. Background Art

[0002] Refrigerators are tasked with long-term low-temperature storage of food. In 2022, the sales volume of refrigerators in China exceeded 70 million units. Household refrigerators generally adopt two refrigeration temperature standards: freezing at -18°C and refrigerating at 5°C. With the improvement of residents' living standards, people's demand for the multi-temperature-zone storage function of household refrigerators is increasing day by day. For example, the optimal storage temperature for items such as precious cosmetics, red wine, and health products is usually higher than the conventional standard refrigeration temperature of 5°C (such as 5 - 10°C). Therefore, it is necessary to subdivide the existing refrigerator refrigeration temperature zones to broaden the refrigeration temperature zones of refrigerators and meet the diversified storage needs of users.

[0003] Under the existing refrigerator refrigeration technical conditions, there are three means to achieve multi-temperature-zone refrigeration technology: one is to design independent evaporator air duct systems for different refrigeration temperature requirements respectively. This technology uses multiple evaporators and compressors, with high temperature control accuracy, but the manufacturing, assembly, and transportation costs of refrigerator products increase, and the operating energy consumption of the multiple evaporator and compressor systems is high; the second is to use the phase equilibrium characteristics of non-azeotropic mixed refrigerants to adopt a partial condensation cycle system to achieve dual-temperature refrigeration. This technology has significant energy-saving effects, but there is a problem that the cost increases significantly due to the addition of new components (gas-liquid separators), and there is also a problem that it is difficult to accurately quantify the refrigerant filling during the later equipment maintenance of the mixed refrigerant refrigerator; the third is the currently widely used single evaporator system, which respectively sets a damper at the freezing compartment, the refrigerating compartment, and the variable-temperature compartment, and adjusts the temperature of the refrigerating compartment and the variable-temperature compartment by controlling the opening and closing of the damper. Compared with the first two means, the cost of this technology is greatly reduced. However, under the existing technology, the air temperature in the variable-temperature compartment is extremely vulnerable to the influence of the air temperature in the freezing compartment, and it is difficult to achieve a refrigeration temperature above 5°C, which is not conducive to the storage of items with higher storage temperature requirements. Summary of the Invention

[0004] The purpose of the present invention is to provide an air duct system and a working method for a wide-temperature-zone air-cooled refrigerator to achieve wide-temperature-zone refrigeration in an energy-saving manner. Different from the previous idea of respectively setting a damper at the freezing compartment, the refrigerating compartment, and the variable-temperature compartment, this refrigerator system adds a branch bypassing to the variable-temperature compartment at the return air branch pipe of the refrigerating compartment, which can not only achieve the refrigeration capacity in the temperature zone above 5°C in the variable-temperature compartment, but also recover the ineffective heat consumption of the return air in the refrigerating compartment and the defrosting heater. At the same time, the refrigeration temperature of the variable-temperature compartment can be set according to the user's own needs, and the variable-temperature compartment can be used as an expanded refrigerating area and an expanded freezing area.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] An air-cooling refrigerator air duct system with a wide temperature range, comprising an evaporator 101, a defrosting heater 102, a variable temperature compartment heater 103, a fan 104, a refrigerating compartment 105, a variable temperature compartment 106, a freezing compartment 107, a first air damper 108, a second air damper 109, a third air damper 110, a fourth air damper 111, a fifth air damper 112, a main air supply pipe 113, a refrigerating compartment air supply branch pipe 114, a variable temperature compartment air supply branch pipe 115, a freezing compartment air supply branch pipe 116, a refrigerating compartment air return branch pipe 117, a variable temperature compartment air return branch pipe 118, a freezing compartment air return branch pipe 119, a main air return pipe 120, and a variable temperature compartment bypass branch pipe 121;

[0007] The connection relationships of the above components are as follows: The fan 104 is connected to the main air supply pipe 113 and is located above the evaporator 101; the defrosting heater 102 is installed at the lower end of the evaporator 101; the refrigerating compartment air supply branch pipe 114, the variable temperature compartment air supply branch pipe 115, and the freezing compartment air supply branch pipe 116 are led out from the main air supply pipe 113 and are respectively communicated with the refrigerating compartment 105, the variable temperature compartment 106, and the freezing compartment 107; the refrigerating compartment air return branch pipe 117, the variable temperature compartment air return branch pipe 118, and the freezing compartment air return branch pipe 119 are respectively led out from the refrigerating compartment 105, the variable temperature compartment 106, and the freezing compartment 107 and are connected to the main air return pipe 120; the bypass branch pipe 121 bypassing to the variable temperature compartment is led out from the refrigerating air return branch pipe 117; the first air damper 108, the second air damper 109, the third air damper 110, the fourth air damper 111, and the fifth air damper 112 are respectively installed on the refrigerating compartment air supply branch pipe 114, the variable temperature compartment air supply branch pipe 115, the freezing compartment air supply branch pipe 116, the refrigerating compartment air return branch pipe 117, and the variable temperature compartment bypass branch pipe 121; the variable temperature compartment heater 103 is installed on the variable temperature compartment air supply branch pipe 115.

[0008] The first air damper 108, the third air damper 110, and the fourth air damper 111 adopt electromagnetic types to realize the adjustment of the switch state (0 or 100% opening state), the second air damper 109 and the fifth air damper 112 are of the electric type to realize the opening adjustment of 0-100%; the refrigerating temperatures of the refrigerating compartment 105, the variable temperature compartment 106, and the freezing compartment 107 can be independently set by the user, and the switch state of the electromagnetic air damper and the opening size of the electric air damper are controlled according to the deviation between the set temperature and the actual temperature to meet the refrigeration requirements of the user.

[0009] The variable temperature compartment 106 includes four working modes. One is that the variable temperature compartment 106 serves as an expansion area of the freezing compartment 107, the second is that the variable temperature compartment 106 serves as an expansion area of the refrigerating compartment 105, the third is that the refrigerating temperature of the variable temperature compartment 106 is between 5°C and 10°C, and the fourth is that the refrigerating temperature of the variable temperature compartment 106 is higher than 10°C.

[0010] The working method of the air duct system of a wide-temperature-range air-cooled refrigerator. When the variable-temperature compartment 106 serves as the expansion area of the refrigerating compartment 105, the refrigerating temperatures of the variable-temperature compartment 106 and the refrigerating compartment 105 are set to 5°C, the refrigerating temperature of the freezing compartment 107 is set to -18°C, and the temperature control deviation is set to ±0.5°C; the fourth air damper 111 is opened, and the opening degree of the fifth air damper 112 is set to 0; when the actual temperature of each storage compartment is lower than the lower limit of its set value, the first air damper 108 and the third air damper 110 are closed, and the opening degree of the second air damper 109 is adjusted smaller until the opening degree of the second air damper 109 is 0, then the fan 104 is turned off and the compressor stops; when the actual temperature of each storage compartment is higher than its set value, the first air damper 108 and the third air damper 110 are opened, and the opening degree of the second air damper 109 is adjusted larger.

[0011] The working method of the air duct system of a wide-temperature-range air-cooled refrigerator. When the variable-temperature compartment 106 serves as the expansion area of the freezing compartment 107, the refrigerating temperatures of the variable-temperature compartment 106 and the freezing compartment 107 are set to -18°C, the refrigerating temperature of the refrigerating compartment 105 is set to 5°C, and the control deviation is set to ±0.5°C; the fourth air damper 111 is opened, and the opening degree of the fifth air damper 112 is set to 0; when the actual temperature of each storage compartment is lower than the lower limit of its set value, the first air damper 108 and the third air damper 110 are closed, and the opening degree of the second air damper 109 is adjusted smaller until the opening degree of the second air damper 109 is 0, then the fan 104 is turned off and the compressor stops; when the actual temperature of each storage compartment is higher than its set value, the first air damper 108 and the third air damper 110 are opened, and the opening degree of the second air damper 109 is adjusted larger.

[0012] The working method of the air duct system of a wide-temperature-range air-cooled refrigerator. When the refrigerating temperature of the variable-temperature compartment 106 is between 5°C and 10°C, the working method is as follows:

[0013] 1) Set the refrigerating temperature of the freezing compartment 107 to -18°C, the refrigerating temperature of the refrigerating compartment 105 to 5°C, and the refrigerating temperature of the variable-temperature compartment 106 can be set by the user to any temperature between 5°C and 10°C, and the control deviation is set to ±0.5°C;

[0014] 2) When the actual temperature of the freezing compartment 107 is lower than the lower limit of its set temperature, the third air damper 110 is closed; if the actual temperature of the freezing compartment 107 is higher than the upper limit of its set temperature, the third air damper 110 is opened;

[0015] 3) The refrigerating compartment 105 and the variable-temperature compartment 106 adopt a temperature linkage control strategy based on the priority of the variable-temperature compartment:

[0016] ①If the actual temperature of the variable-temperature compartment 106 is lower than the lower limit of its set temperature, the opening degree of the second air damper 109 is set to 0, the fourth air damper 111 is closed, the first air damper 108 is opened, the opening degree of the fifth air damper 112 is adjusted smaller, the supply and return air temperature difference of the refrigerating compartment 105 is increased, and the temperature of the variable-temperature compartment 106 is quickly increased; until the opening degree of the fifth air damper 112 is adjusted to 0, if the actual temperature of the refrigerating compartment 105 is lower than the lower limit of the set temperature, the first air damper 108 is closed;

[0017] ②If the actual temperature of the variable-temperature compartment 106 is higher than the upper limit of its set temperature, the fourth air damper 111 is closed, the first air damper 108 is opened, and the opening degrees of the second air damper 109 and the fifth air damper 111 are adjusted larger to reduce the supply and return air temperature difference of the refrigerating compartment 105 and quickly reduce the temperature of the variable-temperature compartment 106;

[0018] ③If the first air damper 108, the second air damper 109, and the third air damper 110 are all closed, the blower 104 is closed and the compressor stops.

[0019] The working method of the air duct system of a wide-temperature zone air-cooled refrigerator described above, the control method for the working mode when the refrigerating temperature of the variable-temperature compartment 106 is higher than 10°C is as follows:

[0020] 1) During the normal operation stage of the refrigerator, if the actual temperature of the variable-temperature compartment 106 is lower than the lower limit of its set temperature, the opening degree of the second air damper 109 is adjusted larger, the variable-temperature compartment heater 103 is turned on, and it maintains low-power operation to increase the supply air temperature of the variable-temperature compartment;

[0021] 2) During the defrosting stage of the refrigerator, if the actual temperature of the variable-temperature compartment 106 is lower than the lower limit of its set temperature, the compressor stops, the defrosting heater 102 is turned on, the first air damper 108 and the third air damper 110 are both closed, the opening degree of the second air damper 109 is adjusted larger, the blower 104 is turned on, and the ineffective heat dissipated by the defrosting heater is recovered and sent to the variable-temperature compartment 106 to increase the air temperature of the variable-temperature compartment;

[0022] 3) If the actual temperature of the variable-temperature compartment 106 is higher than the upper limit of its set temperature, the fourth air damper 111 is closed, the first air damper 108 is opened, and the opening degrees of the second air damper 109 and the fifth air damper 111 are adjusted larger to reduce the supply and return air temperature difference of the refrigerating compartment 105 and lower the temperature of the variable-temperature compartment 106.

[0023] Based on the third single-evaporator system, the present invention uses the interlocking control between the variable-temperature compartment and the refrigerating compartment to recover the ineffective heat consumption of the refrigerating compartment and the defrosting heater, and realizes the expansion of the refrigerating temperature zone above 5°C. It has significant practical value and theoretical significance for the low-cost realization and low-energy consumption operation of multi-temperature zone refrigeration of the refrigerator. Compared with the prior art, the present invention has the following obvious advantages:

[0024] 1) Through the linkage control of single-evaporator refrigeration and five air dampers, multi-mode expansion and multi-temperature refrigeration are achieved. The control logic is easy to implement, the air dampers are inexpensive, and the system cost increases less.

[0025] 2) Achieve wide-temperature refrigeration in the variable-temperature compartment from -18°C to 10°C. Compared with ordinary refrigerators, the refrigeration temperature range of the present invention is extended to more than 5°C, which can meet the diverse storage needs of users.

[0026] 3) By recovering the return air of the refrigerated compartment and the ineffective dissipated heat of the defrost heater, it is beneficial to reduce the heat load of the compartment and the operating energy consumption of the refrigerator system, playing an energy-saving role. Brief Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of the air duct system of the wide-temperature air-cooled refrigerator of the present invention. Detailed Embodiments

[0028] In order to make the objectives, technical solutions and advantages of the present invention clearer and more concise, the present invention will be further described in detail below with reference to the accompanying drawings and an embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] Embodiment

[0030] As Figure 1 shown, an air duct system of a wide-temperature air-cooled refrigerator includes an evaporator 101, a defrost heater 102, a variable-temperature compartment heater 103, a fan 104, a refrigerated compartment 105, a variable-temperature compartment 106, a freezer compartment 107, a first air damper 108, a second air damper 109, a third air damper 110, a fourth air damper 111, a fifth air damper 112, a main air supply pipe 113, a refrigerated compartment air supply branch pipe 114, a variable-temperature compartment air supply branch pipe 115, a freezer compartment air supply branch pipe 116, a refrigerated compartment return air branch pipe 117, a variable-temperature compartment return air branch pipe 118, a freezer compartment return air branch pipe 119, a main return air pipe 120, and a variable-temperature compartment bypass branch pipe 121.

[0031] The total volume of the air-cooled refrigerator is 350L, among which the volume of the refrigerated compartment is 170L, the volume of the variable-temperature compartment is 70L, and the volume of the freezer compartment is 120L. The temperatures of the refrigerated compartment, the variable-temperature compartment, and the freezer compartment are represented by T RC 、T VC 、T FC respectively, and the control deviation is represented by ΔT.

[0032] When the user selects the working mode with the variable-temperature compartment as the expansion area of the refrigerated compartment, T RC 、T VC are both set to 5°C, T FCSet to -18°C, ΔT is set to ±0.5°C, use the variable temperature compartment as a refrigerating compartment, and increase the volume of the refrigerating area to 240L.

[0033] When the user selects the working mode with the variable temperature compartment as the freezer expansion area, T VC and T FC are both set to -18°C, T RC is set to 5°C, ΔT is set to ±0.5°C, use the variable temperature compartment as a freezer, and increase the volume of the freezing area to 190L.

[0034] When the user selects the working mode with the refrigerating temperature of the variable temperature compartment between 5°C and 10°C, the refrigerating temperature of the variable temperature compartment can be set to any temperature between 5°C and 10°C. For example, T VC is set to 8°C:

[0035] 1) When T VC is lower than 7.5°C, the control system closes the second air damper and the fourth air damper, opens the first air damper, and reduces the opening degree of the fifth air damper. When the opening degree of the fifth air damper is reduced to zero, it is judged whether T RC is lower than 5°C. If it is lower than 5°C, the first air damper is closed; if it is higher than 5°C, the first air damper is opened.

[0036] 2) When T VC is higher than 8.5°C, the control system closes the fourth air damper, opens the first air damper, increases the opening degree of the fifth air damper, and quickly reduces T VC ;

[0037] 3) When T VC is between 7.5°C and 8.5°C, the first air damper, the second air damper, and the third air damper are closed, the fan is turned off, and the compressor is turned off, and it is in the standby state.

[0038] When the user selects the working mode with the refrigerating temperature of the variable temperature compartment above 10°C, such as T VC = 13°C, it is controlled according to the actual operating state of the refrigerator:

[0039] 1) During the normal operation stage of the refrigerator, if T VC is lower than 12.5°C, the opening degree of the second air damper 109 is increased, the variable temperature chamber heater 103 is turned on, and a heating power of 20W is provided to increase the air supply temperature of the variable temperature chamber;

[0040] 2) During the defrosting stage of the refrigerator, the defrosting heater is turned on, the refrigeration system is turned off, the first air damper and the third air damper are closed, the opening degree of the second air damper is increased, the fan is turned on, and the ineffective dissipated heat of the defrosting heater is recovered and sent into the variable temperature compartment to heat the chamber air;

[0041] 3) If T VCWhen the temperature is higher than 13.5°C, the fourth air damper 111 closes, the first air damper 108 opens, and the opening degrees of the second air damper 109 and the fifth air damper 111 are increased to reduce the temperature difference between the supply and return air in the refrigerated compartment 105 and quickly lower the temperature in the variable temperature compartment 106.

Claims

1. A working method of an air duct system for a wide-temperature-range air-cooled refrigerator, characterized in that: The system includes an evaporator (101), a defrost heater (102), a variable-temperature chamber heater (103), a blower (104), a refrigerating chamber (105), a variable-temperature chamber (106), a freezing chamber (107), a first air damper (108), a second air damper (109), a third air damper (110), a fourth air damper (111), a fifth air damper (112), a main air supply duct (113), a refrigerating chamber air supply branch duct (114), a variable-temperature chamber air supply branch duct (115), a freezing chamber air supply branch duct (116), a refrigerating chamber air return branch duct (117), a variable-temperature chamber air return branch duct (118), a freezing chamber air return branch duct (119), a main air return duct (120), and a variable-temperature chamber bypass branch duct (121); The connection relationships of the above components are as follows: The blower (104) is connected to the main air supply duct (113) and is located above the evaporator (101); the defrost heater (102) is installed at the lower end of the evaporator (101); the refrigerating chamber air supply branch duct (114), the variable-temperature chamber air supply branch duct (115), and the freezing chamber air supply branch duct (116) are led out from the main air supply duct (113) and are respectively communicated with the refrigerating chamber (105), the variable-temperature chamber (106), and the freezing chamber (107); the refrigerating chamber air return branch duct (117), the variable-temperature chamber air return branch duct (118), and the freezing chamber air return branch duct (119) are respectively led out from the refrigerating chamber (105), the variable-temperature chamber (106), and the freezing chamber (107) and are connected to the main air return duct (120); the bypass branch duct (121) that bypasses to the variable-temperature chamber is led out from the refrigerating air return branch duct (117); the first air damper (108), the second air damper (109), the third air damper (110), the fourth air damper (111), and the fifth air damper (112) are respectively installed on the refrigerating chamber air supply branch duct (114), the variable-temperature chamber air supply branch duct (115), the freezing chamber air supply branch duct (116), the refrigerating chamber air return branch duct (117), and the variable-temperature chamber bypass branch duct (121); the variable-temperature chamber heater (103) is installed on the variable-temperature chamber air supply branch duct (115); The variable-temperature chamber (106) includes four working modes. One is that the variable-temperature chamber (106) serves as an expansion area of the freezing chamber (107). The second is that the variable-temperature chamber (106) serves as an expansion area of the refrigerating chamber (105). The third is that the refrigeration temperature of the variable-temperature chamber (106) is between 5°C and 10°C. The fourth is that the refrigeration temperature of the variable-temperature chamber (106) is higher than 10°C; For the working mode in which the refrigeration temperature of the variable-temperature chamber (106) is between 5°C and 10°C, the working method is as follows: 1) Set the refrigeration temperature of the freezing chamber (107) to -18°C, set the refrigeration temperature of the refrigerating chamber (105) to 5°C, and the refrigeration temperature of the variable-temperature chamber (106) is set by the user independently to any temperature between 5°C and 10°C, and the control deviation is set to ±0.5°C; 2) When the actual temperature of the freezing compartment (107) is lower than the lower limit of its set temperature, the third air damper (110) closes; if the actual temperature of the freezing compartment (107) is higher than the upper limit of its set temperature, the third air damper (110) opens; 3) The refrigerating compartment (105) and the variable-temperature compartment (106) adopt a temperature linkage control strategy based on the priority of the variable-temperature compartment: ① If the actual temperature of the variable-temperature compartment (106) is lower than the lower limit of its set temperature, the opening degree of the second air damper (109) is set to 0, the fourth air damper (111) closes, the first air damper (108) opens, the opening degree of the fifth air damper (112) is adjusted smaller, the supply and return air temperature difference of the refrigerating compartment (105) is increased, and the temperature of the variable-temperature compartment (106) is quickly increased; until the opening degree of the fifth air damper (112) is adjusted to 0, if the actual temperature of the refrigerating compartment (105) is lower than the lower limit of its set temperature, the first air damper (108) closes; ② If the actual temperature of the variable-temperature compartment (106) is higher than the upper limit of its set temperature, the fourth air damper (111) closes, the first air damper (108) opens, and the opening degrees of the second air damper (109) and the fifth air damper (112) are adjusted larger to reduce the supply and return air temperature difference of the refrigerating compartment (105) and quickly reduce the temperature of the variable-temperature compartment (106); ③ If the first air damper (108), the second air damper (109), and the third air damper (110) are all closed, the fan (104) closes and the compressor stops.

2. The working method of an air duct system for a wide-temperature-range air-cooled refrigerator according to claim 1, characterized in that: The first air damper (108), the third air damper (110), and the fourth air damper (111) adopt electromagnetic types to realize the adjustment of the switch state, that is, the 0 or 100% opening degree state. The second air damper (109) and the fifth air damper (112) are selected as electric types to realize the opening degree adjustment of 0~100%; the refrigerating temperatures of the refrigerating compartment (105), the variable-temperature compartment (106), and the freezing compartment (107) are set independently by the user. According to the deviation between the set temperature and the actual temperature, the switch state of the electromagnetic air damper and the opening degree of the electric air damper are controlled to meet the refrigeration requirements of the user.

3. The working method of an air duct system for a wide-temperature-range air-cooled refrigerator according to claim 1, characterized in that: In the working mode where the variable-temperature compartment (106) serves as the expansion area of the refrigerating compartment (105), the refrigerating temperatures of the variable-temperature compartment (106) and the refrigerating compartment (105) are set to 5°C, and the refrigerating temperature of the freezing compartment (107) is set to -18°C. The temperature control deviation is set to ±0.5°C; the fourth air damper (111) opens, and the opening degree of the fifth air damper (112) is set to 0; when the actual temperature of each storage compartment is lower than the lower limit of its set value, the first air damper (108) and the third air damper (110) close, and the opening degree of the second air damper (109) is adjusted smaller. Until the opening degree of the second air damper (109) is 0, the fan (104) closes and the compressor stops; when the actual temperature of each storage compartment is higher than its set value, the first air damper (108) and the third air damper (110) open, and the opening degree of the second air damper (109) is adjusted larger.

4. The working method of an air duct system for a wide-temperature-range air-cooled refrigerator according to claim 3, characterized in that: In the operating mode where the variable-temperature compartment (106) serves as an expansion area of the freezer compartment (107), the refrigeration temperature of the variable-temperature compartment (106) and the freezer compartment (107) is set to -18°C, the refrigeration temperature of the fresh food compartment (105) is set to 5°C, and the control deviation is set to ±0.5°C; the fourth air damper (111) is opened, and the opening degree of the fifth air damper (112) is set to 0; when the actual temperature of each storage compartment is lower than the lower limit of its set value, the first air damper (108) and the third air damper (110) are closed, and the opening degree of the second air damper (109) is adjusted smaller. When the opening degree of the second air damper (109) reaches 0, the fan (104) is turned off and the compressor stops; when the actual temperature of each storage compartment is higher than its set value, the first air damper (108) and the third air damper (110) are opened, and the opening degree of the second air damper (109) is adjusted larger.

5. The working method of an air duct system for a wide-temperature-range air-cooled refrigerator according to claim 1, characterized in that: The control method for the operating mode where the refrigeration temperature of the variable-temperature compartment (106) is higher than 10°C is as follows: 1) During the normal operation stage of the refrigerator, if the actual temperature of the variable-temperature compartment (106) is lower than the lower limit of its set temperature, the opening degree of the second air damper (109) is adjusted larger, the variable-temperature compartment heater (103) is turned on, and it maintains low-power operation to increase the air supply temperature of the variable-temperature compartment; 2) During the defrosting stage of the refrigerator, if the actual temperature of the variable-temperature compartment (106) is lower than the lower limit of its set temperature, the compressor stops, the defrosting heater (102) is turned on, the first air damper (108) and the third air damper (110) are both closed, the opening degree of the second air damper (109) is adjusted larger, and the fan (104) is turned on to recover the ineffective dissipated heat of the defrosting heater and send it to the variable-temperature compartment (106) to increase the air temperature of the variable-temperature compartment; 3) If the actual temperature of the variable-temperature compartment (106) is higher than the upper limit of its set temperature, the fourth air damper (111) is closed, the first air damper (108) is opened, and the opening degrees of the second air damper (109) and the fifth air damper (112) are adjusted larger to reduce the supply and return air temperature difference of the fresh food compartment (105) and lower the temperature of the variable-temperature compartment (106).

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