Multi-heat-source three-dimensional distributed hot gas bypass defrosting system and control method

Abstract

The application discloses a kind of multi-heat source three-dimensional distribution distributed hot gas bypass defrosting system and control method, compressor outlet end is connected with first three-way by pipeline;First three-way is connected with water pan heat exchanger by defrosting loop;Water pan heat exchanger is connected with second three-way, and second three-way other end is connected with evaporator;Water pan is arranged between water pan heat exchanger and second three-way, and refrigerant auxiliary heater is arranged on defrosting loop outside water pan heat exchanger;Foaming layer is arranged outside evaporator, and air duct auxiliary heater is arranged on evaporator outside water pan and close to foaming layer one end.The application uses multiple different auxiliary heat sources, supplements the deficiency of single heat source of compressor, uses hot gas defrosting from inside to outside to improve defrosting efficiency, fully utilizes the advantage that refrigerant auxiliary heater power is adjustable, and adapts to the non-steady power requirement of different stages of defrosting.At the same time, air duct auxiliary heater can effectively deal with a small amount of frost in heating air duct.

Description

Technical Field

[0001] This invention belongs to the field of home appliance refrigeration technology, specifically relating to a multi-heat source three-dimensional distributed hot gas bypass defrosting system and its control method. Background Technology

[0002] Refrigerators and freezers are two common household appliances used for freezing and refrigeration. To address the problems of frost and ice buildup in the freezer compartment, the technology has evolved from early direct cooling to today's predominantly indirect cooling (air-cooled) systems. In indirect cooling (air-cooled) refrigerators or freezers, water vapor in the humid air condenses into a frost layer on the surface of the air-cooled evaporator and the inner surface of the air ducts. Frost buildup obstructs airflow and reduces cooling performance, thus requiring periodic defrosting to ensure the refrigeration system maintains its cooling capacity.

[0003] Currently, there are two main types of defrosting methods for refrigerators and freezers with freezing functions: electric heating and hot air defrosting. Electric heating defrosting involves placing an electric heater near the evaporator. The Joule heat generated by the electric heater, exceeding 100°C, melts the frost layer from the outside in through radiation and natural convection. According to its heat transfer principle, the heat transfer efficiency from the outside (evaporator) to the inside is low, causing a large amount of heat to enter the freezer through the duct walls, leading to a decline in the quality of stored food or medicine. Furthermore, due to the low heat transfer efficiency, defrosting requires high energy consumption. According to research data from the literature: Bansal P., Fothergill D., Fernandes R. Thermal analysis of the defrost cycle in a domestic freezer[J]. Int. J. Refrig. 2010, 33: 589-599, the efficiency of electric heating defrosting is generally between 20% and 30%.

[0004] To improve defrosting efficiency, hot gas bypass defrosting can be used. Hot gas bypass defrosting uses high-temperature, high-pressure refrigerant generated by the compressor (heat source), which bypasses the condenser and throttling mechanism and directly enters the evaporator to release heat. Heat is transferred from inside the evaporator to the outside. Since the evaporator is covered by a layer of frost, virtually no excess heat enters the environment, resulting in high heat transfer and defrosting efficiency. According to the literature: Yuan Lifen, Qian Suxin, Yu Jianlin, Yan Gang. Experimental study on the performance of hot gas bypass defrosting in medical refrigerators [J]. Refrigeration and Air Conditioning. 2019, 19: 76-80, the defrosting efficiency of hot gas bypass can reach over 80%.

[0005] Although hot gas bypass defrosting is highly efficient, it is currently only used in commercial freezers using refrigerants with low standard boiling points such as R290 or R407C. It has not yet been widely adopted in household refrigerators using R600a. One key factor is that, under the same operating conditions, the density of R600a is much lower than that of R290 or R407C, making it insufficient to rely solely on the compressor as a heat source to meet the heat required for defrosting. This problem may be even more pronounced under low ambient temperature conditions.

[0006] Patent application CN103134235B discloses a coil-based step-by-step defrosting heat pump system, which includes multiple sets of independent defrosting pipe assembly modules. Each set of independent defrosting pipe assembly modules includes at least one set of coils, wherein the coils are double counter-current coils, and each set of coils consists of two coils arranged in a V-shape. The refrigerant flow direction in each set of coils is opposite to the air flow direction. Any one or more sets of independent defrosting pipe assembly modules can defrost independently, while the other sets of independent defrosting pipe assembly modules are in a heating cycle. Although this patent application sets up multiple independent defrosting pipe assembly modules that can independently control heating, this patent application cannot be applied to commercial freezers using refrigerants with higher standard boiling points, and this patent only heats the coils, which cannot effectively melt the local frost in the air duct. Summary of the Invention

[0007] In order to overcome the problems existing in the prior art, the purpose of this invention is to provide a multi-heat source three-dimensional distributed hot gas bypass defrosting system and control method, thereby solving the problem that the compressor as the only heat source is insufficient to meet the defrosting heat demand when using hot gas defrosting with existing high standard boiling point refrigerants, and can effectively melt the local frost in the air duct of refrigerators, freezers and other refrigeration appliances that is far from the heater.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A multi-heat-source, three-dimensional, distributed hot gas bypass defrosting system includes:

[0010] The compressor has an inlet end connected to an evaporator via a pipe; an outlet end connected to a first three-way valve via a pipe; one end of the other two ends of the first three-way valve is connected to a condenser, and the other end is connected to a water collection pan heat exchanger via a defrost circuit; the water collection pan heat exchanger is connected to a second three-way valve via a pipe, and one end of the other two ends of the second three-way valve is connected to a low-pressure liquid pipe or capillary tube, and the other end is connected to the evaporator via a pipe.

[0011] A water receiving pan is provided between the water receiving pan heat exchanger and the second three-way valve. A refrigerant auxiliary heater is provided on the outer sleeve of the defrosting circuit near the end of the water receiving pan heat exchanger. A foaming layer is provided on the outside of the evaporator. An air duct auxiliary heater is provided on the end of the evaporator away from the water receiving pan and near the foaming layer.

[0012] Optionally, a solenoid valve is provided at one end of the defrosting circuit near the first three-way valve; a first temperature sensor is provided between the refrigerant auxiliary heater and the first three-way valve; and a second temperature sensor is provided on the pipe connecting the evaporator and the compressor.

[0013] Optionally, the bottom of the water receiving tray is connected to a coaxial drain pipe, which is sleeved outside the defrosting circuit.

[0014] Optionally, the refrigerant auxiliary heater consists of a heating module controlled by multiple independent relays.

[0015] Optionally, the water receiving pan heat exchanger is disposed on the outer wall of the lower surface of the water receiving pan, and the water receiving pan heat exchanger is able to contact the water receiving pan for heat exchange.

[0016] Optionally, the water receiving tray heat exchanger is composed of multiple heat exchange tubes arranged in a serpentine or U-shape.

[0017] Optionally, a foaming layer is provided outside the refrigerant auxiliary heater and the defrosting circuit.

[0018] Optionally, when the refrigeration system uses R600 or R600a refrigerant, the rated power of the refrigerant auxiliary heater > the maximum power of the compressor > the rated power of the duct auxiliary heater;

[0019] When the refrigeration system uses pure R290 refrigerant, or a binary refrigerant mixture of R290 and R600, or a binary refrigerant mixture of R290 and R600a, the maximum power of the compressor > the rated power of the refrigerant auxiliary heater > the rated power of the duct auxiliary heater.

[0020] When the refrigeration system uses other pure or mixed refrigerants, the maximum power of the compressor > the rated power of the duct auxiliary heater ≥ the rated power of the refrigerant auxiliary heater.

[0021] A control method for a multi-heat-source three-dimensional distributed hot gas defrosting system includes the following steps:

[0022] S1: Open the solenoid valve, and the heating time t1 of the entire system and the heating time t2 of the auxiliary heater in the air duct will start from zero;

[0023] S2: Starting from when the solenoid valve is opened, the following procedure is executed sequentially once every time interval ta:

[0024] S2a: Detect whether the temperature measurement value T2 of the second temperature sensor exceeds the temperature threshold Temp_stop duration tb. If yes, end the defrosting program; otherwise, proceed to step S2b.

[0025] S2b: Detect whether t2 is less than the second time threshold t_stop2. If yes, turn on the duct auxiliary heater; otherwise, proceed to step S2c.

[0026] S2c: Detect whether t1 is less than the first time threshold t_stop1. If not, proceed with the frosting and defrosting procedure; if yes, proceed to step S2d.

[0027] S2d: Adjusts the energy level of the refrigerant auxiliary heater proportionally. When Temp_set-T1≥Temp_max, the refrigerant auxiliary heater is turned on at full power; when Temp_set-T1<0℃, the refrigerant auxiliary heater is turned off; when Temp_max>Temp_set-T1≥0℃, the refrigerant auxiliary heater is turned on at a power proportional to (Temp_set-T1) / Temp_max*100%.

[0028] S3: Defrosting program complete: Close the solenoid valve, and shut down the duct auxiliary heater and refrigerant auxiliary heater.

[0029] Optionally, the first three-way valve is a three-way solenoid valve. In step S1, the defrost circuit of the first three-way valve is opened while the condenser circuit is closed. In step S3, the defrost circuit of the first three-way valve is closed while the condenser circuit is opened.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This invention, based on existing hot gas bypass defrosting technology, proposes a multi-heat-source distributed hot gas bypass defrosting system and a control method for this new process. This invention utilizes multiple different auxiliary heat sources, overcoming the limitation of insufficient heat from a single compressor heat source in existing hot gas defrosting technologies. Addressing the need for non-uniform intensity and non-steady-state power defrosting due to uneven frosting on the evaporator and ductwork, it employs inside-out hot gas defrosting. The heat sources include the compressor and a refrigerant auxiliary heater. Taking full advantage of the adjustable power of the refrigerant auxiliary heater, the refrigerant temperature through the hot gas bypass pipe serves as a feedback control signal, adapting to changes in compressor heat source heat at different ambient temperatures and accommodating the non-steady-state power requirements at different stages of defrosting. Meanwhile, for the small amount of frost in the air duct, a local low-power auxiliary heater for the air duct is set up. Spatially, it is closer to the frost layer in the air duct and near the air outlet, which can improve the radiative heat transfer coefficient. This avoids the limitation of relying solely on the compressor and refrigerant auxiliary heater in the evaporator tube, which are two heat sources, and cannot melt the local frost in the air duct over a long distance due to the low radiative heat transfer coefficient. In addition, the local air duct heater can adapt to the lower defrosting heat demand in the air duct with a shorter operating time, preventing the temperature of the items stored in the freezer and refrigerator from rising excessively.

[0032] Furthermore, the present invention includes a temperature sensor, which can adjust the heating time and heating power in real time according to the detected temperature setting.

[0033] Furthermore, the refrigerant auxiliary heater of the present invention consists of multiple heating modules, each of which is controlled by an independent relay to achieve graded power output.

[0034] Furthermore, the bottom of the water receiving tray of the present invention is connected to a coaxial drain pipe sleeved outside the defrost circuit, so that the liquid water formed after defrosting can flow in the opposite direction to the refrigerant in the defrost circuit for heat exchange. The high temperature of the refrigerant pipe inside the defrost circuit prevents the coaxial drain pipe from freezing and becoming blocked when discharging the defrost liquid water.

[0035] Furthermore, the refrigerant auxiliary heater of the present invention is provided with a foaming layer outside, and the air duct auxiliary heater is located on the side close to the foaming layer, which can realize the directional transfer of heat and avoid unnecessary heat loss.

[0036] Furthermore, the bottom outer side of the water receiving pan of the present invention is provided with a water receiving pan heat exchanger, which keeps the temperature of the water receiving pan above 0°C, so as to prevent the mixture of ice and water that has not been completely melted during defrosting from solidifying in the water receiving pan and blocking the drainage. Attached Figure Description

[0037] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely schematic to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. In the drawings:

[0038] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention;

[0039] Figure 2 This is a flowchart of the control method of the present invention.

[0040] Among them, 1-first pipe, 2-second pipe, 3-third pipe, 4-fourth pipe, 101-compressor, 1021-first tee, 1022-second tee, 103-solenoid valve, 104-coaxial drain pipe, 105-refrigerant auxiliary heater, 106-water tray heat exchanger, 107-water tray, 108-evaporator, 1091-first cover plate, 1092-second cover plate, 110-air duct auxiliary heater, 201-first temperature sensor, 202-second temperature sensor. Detailed Implementation

[0041] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0042] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0044] The present invention will now be described in detail with reference to the accompanying drawings.

[0045] like Figure 1 As shown, the present invention provides a multi-heat source three-dimensional distributed hot gas bypass defrosting system, comprising:

[0046] A compressor 101 and a first three-way valve 1021 are provided. The inlet end of the compressor 101 is connected to an evaporator 108 via a pipe, and the outlet end of the compressor 101 is connected to a straight end of the first three-way valve 1021 via a pipe. One of the other two ends of the first three-way valve 1021 is connected to a condenser, and the other end is connected to a water tray heat exchanger 106 via a defrost circuit. The water tray heat exchanger 106 is connected to a second three-way valve 1022 via a pipe. The other two ends of the second three-way valve 1022 are both straight ends, one end of which is connected to a low-pressure liquid pipe or capillary tube, and the other end is connected to the evaporator 108 via a pipe. A water tray 107 is provided between the water tray heat exchanger 106 and the second three-way valve 1022. The water tray 107 is tapered, and the water tray heat exchanger 106 is disposed on its lower surface, allowing the water tray heat exchanger 106 to contact the water tray 107 for heat exchange. Optionally, the first three-way valve 1021 is a T-type three-way valve or a three-way solenoid valve. During defrosting, the first three-way valve 1021 only connects to the defrosting circuit; during non-defrosting, it only connects to the condenser. The end of the first three-way valve 1021 connected to the condenser is normally open, and the end connected to the water tray heat exchanger 106 is normally closed.

[0047] The defrosting circuit includes a first pipe 1, a second pipe 2, and a heating pipe, wherein the heating pipe includes a third pipe 3 and a fourth pipe 4. The first pipe 1 is perpendicular to the pipe connecting the first tee 1021 and the compressor 101. One end of the first pipe 1 is connected to the first tee 1021, and the other end is connected to and perpendicular to the second pipe 2. Optionally, the axis of the second pipe 2 passes through the center of the water receiving tray 107. The second pipe 2 is connected to and perpendicular to the third pipe 3. The third pipe 3 is connected to and perpendicular to the fourth pipe 4, and the other end of the fourth pipe 4 is connected to the water receiving tray heat exchanger 106.

[0048] A solenoid valve 103 is installed on the first pipe 1, and a first temperature sensor 201 is installed between the solenoid valve 103 and the second pipe 2. A coaxial drain pipe 104 is connected to the bottom of the water receiving tray 107, and the coaxial drain pipe 104 is connected to the evaporating dish. The coaxial drain pipe 104 is sleeved on the outside of the second pipe 2. The coaxial drain pipe 104 is aligned with the axis of the second pipe 2. The space between the inside of the coaxial drain pipe 104 and the outside of the second pipe 2 is used for the flow of liquid water formed after defrosting. This liquid water can exchange heat with the refrigerant in the second pipe 2 by flowing counter-currently. The high temperature of the refrigerant pipe inside the second pipe 2 prevents the coaxial drain pipe 104 from freezing and becoming blocked when discharging the defrosting liquid water.

[0049] The water receiving pan heat exchanger 106 is composed of multiple heat exchange tubes arranged in a serpentine or U-shape. Optionally, the heat exchange tubes of the water receiving pan heat exchanger 106 are smooth circular tubes with an outer diameter of less than 10 mm. Optionally, the heat exchange tubes of the water receiving pan heat exchanger 106 are circular tubes with an internal micro-ribbed reinforcement structure. Optionally, the heat exchange tubes of the water receiving pan heat exchanger 106 are D-shaped tubes, wherein the flat surface of the D-shaped tube contacts the water receiving pan 107. Optionally, the heat exchange tubes of the water receiving pan heat exchanger 106 are microchannel flat tubes, wherein one side plane of the microchannel flat tube contacts the water receiving pan 107.

[0050] A refrigerant auxiliary heater 105 is installed on the heating pipe. Optionally, the refrigerant auxiliary heater 105 is sleeved on the outside of the heating pipe. Optionally, the refrigerant auxiliary heater 105 is composed of multiple heating modules, each module being controlled by an independent relay to achieve graded power output.

[0051] For pure or mixed working fluids with high standard boiling points, the refrigerant auxiliary heater 105 can compensate for the limitation of insufficient heat from the compressor 101 to melt the frost layer. Optionally, the refrigerant auxiliary heater 105 is a ceramic heating sleeve. Optionally, the refrigerant auxiliary heater 105 is a glass fiber heating strip wound around the heating pipe. Optionally, the refrigerant auxiliary heater 105 is disposed inside the heating pipe, and the refrigerant auxiliary heater 105 is a steel tube heating wire, a quartz tube heating wire, or an aluminum tube heating wire. Optionally, the heating pipe is a circular tube with an internal micro-ribbed reinforcement structure.

[0052] A foamed layer is provided on the outer side of the lower surface of the water receiving tray 107, and the water receiving tray heat exchanger 106 is embedded in the foamed layer. The heating pipe is also embedded in the foamed layer. A first cover plate 1091 and a second cover plate 1092 are provided on the outer side wall of the evaporator 108. The second cover plate 1092 is away from the compressor 101, and the first cover plate 1091 is close to the compressor 101. A foamed layer is provided on the side of the second cover plate 1092 away from the evaporator 108. An air duct auxiliary heater 110 is provided on the side of the second cover plate 1092 close to the evaporator 108. Optionally, the air duct auxiliary heater 110 is an aluminum tube distributed heater, a steel tube heater, or an electric heating film. A second temperature sensor 202 is provided on the pipe connecting the evaporator 108 and the compressor 101.

[0053] For refrigeration systems using R600 or R600a refrigerant, the rated power of the refrigerant auxiliary heater 105 > the maximum power of the compressor 101 > the rated power of the duct auxiliary heater 110;

[0054] For refrigeration systems using pure R290, or binary refrigerants consisting of R290 and R600 or R600a, the maximum power of compressor 101 > the rated power of refrigerant auxiliary heater 105 > the rated power of duct auxiliary heater 110.

[0055] For refrigeration systems using other pure or mixed refrigerants, the maximum power of compressor 101 > the rated power of duct auxiliary heater 110 > the rated power of refrigerant auxiliary heater 105.

[0056] This invention can rationally configure the power of three heat sources according to the differences in the physical properties of different refrigerants, and rationally allocate the power of the heat sources over time according to the distribution characteristics of the frost amount in the system, so as to achieve efficient and rapid defrosting at different locations in the air-cooled refrigerator and freezer system. Based on the spatial distribution characteristics of the frost layer, this invention sets up a distributed multi-heat source for defrosting, which includes a compressor 101, a refrigerant auxiliary heater 105, and a duct auxiliary heater 110. While the heat from the refrigerant auxiliary heater 105 and the compressor 101 efficiently melts the frost layer on the evaporator 108 from the inside to the outside of the pipe, the duct auxiliary heater 110 can melt the frost layer attached to the surface of the first cover plate 1091 on the side of the duct near the foaming layer and the second cover plate 1092 attached away from the duct, so as to achieve three-dimensional distributed defrosting.

[0057] like Figure 2 As shown, the control method for a multi-heat-source three-dimensional distributed hot gas defrosting system includes the following steps:

[0058] Step 1: Set the first timer to record the running time t1 of the entire system, and set the second timer to record the time t2 of the auxiliary heater 110 in the air duct; when the defrosting program starts, open the solenoid valve 103 and reset the start time of the first and second timers.

[0059] Step 2: Starting from when solenoid valve 103 is opened, run the following program sequentially once every time interval ta;

[0060] Step 2a: Detect whether the temperature measurement value T2 of the second temperature sensor 202 continuously exceeds the temperature threshold Temp_stop for time tb. If yes, end the defrosting program; if no, proceed to step 2b.

[0061] Step 2b: Check if the time t2 of the second timer is less than the second time threshold t_stop2. If yes, proceed to step 2d; otherwise, proceed to step 2c.

[0062] Step 2c: Check if the time t1 of the first timer is less than the first time threshold t_stop1. If yes, proceed to step 2e; otherwise, proceed with the frosting and defrosting procedure.

[0063] Step 2d: Turn on the auxiliary heater 110 in the air duct;

[0064] Step 2e: Adjust the energy level of the refrigerant auxiliary heater 105 proportionally. When Temp_set-T1 ≥ Temp_max℃, the refrigerant auxiliary heater 105 is turned on at full power; when Temp_set-T1 < 0℃, the refrigerant auxiliary heater 105 is turned off; when Temp_max > Temp_set-T1 ≥ 0℃, the refrigerant auxiliary heater 105 is turned on at a power proportional to Temp_set-T1 / Temp_max*100%.

[0065] Step 3: End of defrosting process: Close solenoid valve 103.

[0066] Optional, Temp_max ≥ 10℃.

[0067] Optional, Temp_set > Temp_stop + 10℃.

[0068] Optional, ta is 10s, tb is 30s.

[0069] Optionally, the first three-way valve 1021 is a three-way solenoid valve. In step 1, the defrost circuit of the first three-way valve 1021 is closed while the condenser circuit of the first three-way valve 1021 is opened. In step 3, the air duct auxiliary heater 110 and the refrigerant auxiliary heater 105 of the first three-way valve 1021 are closed.

[0070] Optionally, in step 2, Temp_max is 15℃; the refrigerant auxiliary heater 105 consists of four modules with the same power, forming five energy levels: 0%, 25%, 50%, 75%, and 100%. The adjustment is based on the difference between the target temperature Temp_set and the temperature measurement value T1 of the first temperature sensor 201: when Temp_set-T1≥15℃, the refrigerant auxiliary heater 105 is turned on at full power; when 15℃>Temp_set-T1≥10℃, the refrigerant auxiliary heater 105 is turned on at 75%; when 10℃>Temp_set-T1≥5℃, the refrigerant auxiliary heater 105 is turned on at 50%; when 5℃>Temp_set-T1≥0℃, the refrigerant auxiliary heater 105 is turned on at 25%; and when Temp_set-T1<0℃, the refrigerant auxiliary heater 105 is turned off.

[0071] Example

[0072] The following is combined Figure 1 The specific embodiments of the present invention will be further described below.

[0073] Reference Figure 1This is an implementation example of the present invention in a single (evaporator) refrigeration system air-cooled refrigerator using R600a refrigerant. In this embodiment, the rated power (full load power) of the refrigerant auxiliary heater 105 is 2 to 5 times the input power of the compressor 101. In this embodiment, the refrigerant auxiliary heater 105 is a ceramic heating sleeve. In this embodiment, the refrigerant auxiliary heater 105 consists of 2 to 10 heating modules. In this embodiment, the water receiving pan heat exchanger 106 is composed of four parallel heat exchange circular tubes wound in a serpentine pattern. ta is 10s, and tb is 30s.

[0074] When the defrosting process starts, the solenoid valve 103 opens, and the high-temperature, high-pressure, superheated refrigerant generated by the compressor 101 flows from the first three-way valve 1021 on the exhaust pipe to the hot gas bypass pipe and the condenser. Because the pressure drop of the defrosting circuit is much lower than that of the condenser-capillary tube circuit, most of the refrigerant will enter the defrosting circuit.

[0075] After passing through solenoid valve 103, the refrigerant will enter the second pipe 2, flowing upwards and releasing heat. As the temperature decreases, it exchanges heat with the liquid water formed during defrosting in a countercurrent manner, maintaining the temperature of the defrosting water and preventing it from freezing and clogging. Defrosting water flows between the coaxial drain pipe 104 and the second pipe 2.

[0076] After passing through the coaxial drain pipe 104, the refrigerant enters the refrigerant auxiliary heater 105 located in the foam layer, and absorbs heat from the refrigerant auxiliary heater 105 to compensate for the limitation of insufficient heat source power of the R600a compressor 101.

[0077] A foamed layer is provided on the outside of the refrigerant auxiliary heater 105. Since the foamed layer is approximately insulating, all the heater's power is used to heat the superheated refrigerant. The output power level of the refrigerant auxiliary heater 105 is controlled by the temperature feedback signal T1 from the first temperature sensor 201 located at the outlet of the solenoid valve 103. This control adapts to changes in the power of the compressor 101 under different ambient temperatures and accommodates varying heating power requirements at different defrosting stages. The power is highest at the beginning of defrosting and gradually decreases as the defrosting process progresses. Different defrosting target temperatures (Temp_set) can be used for different refrigerants.

[0078] The refrigerant absorbs heat from the refrigerant auxiliary heater 105 and enters the water collection pan heat exchanger 106. The refrigerant releases heat as it flows horizontally back and forth, thus reducing its temperature. Because one side of the water collection pan heat exchanger 106 is in contact with the water collection pan 107, and the rest is embedded in the foam layer, providing near-insulation, the released heat is entirely used to heat the liquid defrost water and the mixture of liquid-solid two-phase defrost water and frost accumulated in the water collection pan 107, preventing the defrost water from freezing and clogging within the water collection pan 107.

[0079] After the refrigerant releases heat to the water pan heat exchanger 106, it enters the second three-way valve 1022 and mixes with a small amount of refrigerant from the capillary tube or low-pressure liquid line. This mixture then enters the evaporator 108, releasing the main heat to melt the frost layer adhering to the surface of the evaporator 108 from the inside out. Because the defrosting of the evaporator 108 requires a large amount of heat, the superheat of the refrigerant decreases within the evaporator 108, resulting in some condensation. As the defrosting process continues, the amount of frost remaining on the surface of the evaporator 108 decreases, and the heat released by the refrigerant in the evaporator 108 continuously decreases, causing the outlet temperature of the evaporator 108 to continuously rise. A second temperature sensor 202 installed on the outlet pipe of the evaporator 108 can detect the reduction in the frost layer on the evaporator 108. When the temperature signal T2 on the second temperature sensor 202 is higher than the stop temperature threshold Temp_stop for more than 30 seconds, the defrosting program is stopped to avoid premature termination due to temperature sensor measurement errors or large fluctuations in refrigerant temperature.

[0080] An auxiliary heater 110 with an electrothermal film structure is provided on one side of the foam layer. Due to the small amount of frost formation in the air duct, the rated power of the auxiliary heater 110 is lower than that of the compressor 101. To prevent the auxiliary heater 110 from overheating and causing a temperature rise, the maximum on-time of the auxiliary heater, i.e., the second time threshold t_stop2, is set to be less than the maximum running time of the defrosting program, i.e., the first time threshold t_stop1.

[0081] Unless otherwise specified, the equipment components involved in the above embodiments are all conventional equipment components, and the structural settings, working methods or control methods involved are all conventional settings, working methods or control methods in the art unless otherwise specified.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A multi-heat-source, three-dimensional distributed hot gas bypass defrosting system, characterized in that, include: The compressor (101) has an inlet end connected to an evaporator (108) via a pipe; its outlet end is connected to a first tee (1021) via a pipe; one end of the other two ends of the first tee (1021) is connected to a condenser, and the other end is connected to a water tray heat exchanger (106) via a defrost circuit; the water tray heat exchanger (106) is connected to a second tee (1022) via a pipe, and one end of the other two ends of the second tee (1022) is connected to a low-pressure liquid pipe or a capillary tube, and the other end is connected to the evaporator (108) via a pipe; A water receiving tray (107) is provided between the water receiving tray heat exchanger (106) and the second three-way valve (1022). On the defrosting circuit, a refrigerant auxiliary heater (105) is provided on the end of the water receiving tray heat exchanger (106). A foaming layer is provided on the outside of the evaporator (108). An air duct auxiliary heater (110) is provided on the end of the evaporator (108) away from the water receiving tray (107) and close to the foaming layer. The water receiving tray heat exchanger (106) is provided on the outer wall of the lower surface of the water receiving tray (107). The water receiving tray heat exchanger (106) can contact the water receiving tray (107) for heat exchange. The bottom of the water receiving tray (107) is connected to a coaxial drain pipe (104), which is sleeved outside the defrosting circuit. The defrosting circuit includes a first pipe (1) and a second pipe (2). One end of the first pipe (1) is connected to a first tee (1021), and the other end is connected to the second pipe (2). The coaxial drain pipe (104) is sleeved outside the second pipe (2), and the space between the inside of the coaxial drain pipe (104) and the outside of the second pipe (2) is used for the passage of liquid water formed after defrosting. The refrigerant auxiliary heater (105) and the defrosting circuit are both provided with a foaming layer. When the refrigeration system uses R600 or R600a refrigerant, the rated power of the refrigerant auxiliary heater (105) > the maximum power of the compressor (101) > the rated power of the duct auxiliary heater (110); When the refrigeration system uses pure R290 refrigerant, or a binary mixture of R290 and R600, or a binary mixture of R290 and R600a, the maximum power of the compressor (101) > the rated power of the refrigerant auxiliary heater (105) > the rated power of the duct auxiliary heater (110). When the refrigeration system uses other pure or mixed refrigerants, the maximum power of the compressor (101) > the rated power of the duct auxiliary heater (110) ≥ the rated power of the refrigerant auxiliary heater (105).

2. The multi-heat source three-dimensional distributed hot gas bypass defrosting system according to claim 1, characterized in that, On the defrosting circuit, a solenoid valve (103) is provided at one end near the first tee (1021); a first temperature sensor (201) is provided between the refrigerant auxiliary heater (105) and the first tee (1021); a second temperature sensor (202) is provided on the pipe connecting the evaporator (108) and the compressor (101).

3. The multi-heat source three-dimensional distributed hot gas bypass defrosting system according to claim 1, characterized in that, The refrigerant auxiliary heater (105) consists of a heating module controlled by multiple independent relays.

4. The multi-heat source three-dimensional distributed hot gas bypass defrosting system according to claim 1, characterized in that, The water receiving pan heat exchanger (106) is composed of multiple heat exchange tubes arranged in a serpentine or U-shape.

5. A control method for a multi-heat source three-dimensional distributed hot gas bypass defrosting system according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Open the solenoid valve (103), and start counting from zero for the heating time t1 of the entire system and the heating time t2 of the auxiliary heater (110) in the air duct; S2: Starting from the opening of solenoid valve (103), the following procedure is executed sequentially once every time interval ta: S2a: Detect whether the temperature measurement value T2 of the second temperature sensor (202) exceeds the temperature threshold Temp_stop duration tb. If yes, end the defrosting program; otherwise, proceed to step S2b. S2b: Detect whether t2 is less than the second time threshold t_stop2. If yes, turn on the duct auxiliary heater (110); otherwise, proceed to step S2c. S2c: Detect whether t1 is less than the first time threshold t_stop1. If not, proceed with the frosting and defrosting procedure; if yes, proceed to step S2d. S2d: The energy level of the refrigerant auxiliary heater (105) is adjusted proportionally. When Temp_set-T1≥Temp_max, the refrigerant auxiliary heater (105) is turned on at full power; when Temp_set-T1<0℃, the refrigerant auxiliary heater (105) is turned off; when Temp_max>Temp_set-T1≥0℃, the refrigerant auxiliary heater (105) is turned on at a power of (Temp_set-T1) / Temp_max*100% proportionally. S3: Defrosting program ends: Close solenoid valve (103), close duct auxiliary heater (110) and refrigerant auxiliary heater (105).

6. The control method for a multi-heat source three-dimensional distributed hot gas bypass defrosting system according to claim 5, characterized in that, The first three-way valve (1021) is a three-way solenoid valve. In step S1, the defrost circuit of the first three-way valve (1021) is opened while the condenser circuit is closed. In step S3, the defrost circuit of the first three-way valve (1021) is closed while the condenser circuit is opened.

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