Defrosting control method for variable frequency heat pump air conditioner and outdoor heat exchanger system

Abstract

The invention relates to the technical field of air conditioners, discloses a defrosting control method for a variable frequency heat pump air conditioner and an outdoor heat exchanger system, and aims to solve the problems that condensate water affects the heat exchange efficiency and the indoor temperature fluctuates in an existing heat pump air conditioner. The super-hydrophobic fins of the outdoor heat exchanger promote the condensed water to fall off quickly so as to maintain the heat exchange efficiency; when it is detected that the temperature of the outdoor heat exchanger is continuously lower than 0 DEG C and reaches a first preset time threshold value, a defrosting mode is controlled to be started; in the defrosting mode, the expansion valve is controlled to be opened to the maximum opening degree so as to reduce or stop throttling, the air speed of the indoor fan is reduced, and meanwhile the heating flow direction of the four-way valve is kept unchanged; and when it is detected that the temperature of the outdoor heat exchanger is continuously higher than 0 DEG C and reaches a second preset time threshold value, the defrosting mode is controlled to exit, and normal control is recovered. According to the invention, the energy efficiency and reliability during conventional operation are improved, and the indoor temperature fluctuation during defrosting is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air conditioning, in particular to a defrosting control method for a variable frequency heat pump air conditioner and an outdoor heat exchanger system. BACKGROUND

[0002] When a heat pump air conditioner is running in heating mode in winter, its outdoor heat exchanger is used as an evaporator. The low-temperature and low-pressure liquid refrigerant evaporates and absorbs heat in it, so that the surface temperature of the outdoor heat exchanger fin is much lower than the dew point temperature of the ambient air, causing the water vapor in the air to condense into water on its surface.

[0003] To prevent condensation water from bridging between fins to block the air duct, increase air resistance and noise, traditional outdoor heat exchangers generally use hydrophilic aluminum foil fins. The hydrophilic fins form a water film on their surface and flow down the fins to drain water, which solves the water bridge problem, but cannot avoid the fact that a layer of water film is always covered on the surface of the fins. This layer of water film will increase the heat transfer resistance, hinder the effective heat exchange between air and fins, and cause the air volume to attenuate, resulting in the continuous decline of the heating capacity of the heat pump in actual operation.

[0004] When the ambient temperature is low and the air humidity is high, the surface temperature of the outdoor heat exchanger fin will drop below 0℃, and the condensation water will freeze into frost. The thermal conductivity of the frost layer is extremely low, and its formation and thickening will drastically worsen the heat exchange efficiency, resulting in a decrease in the system evaporation temperature and a significant decline in the heating capacity. The existing technology mainly uses the "reverse cycle defrosting" scheme, that is, by reversing the four-way valve, the system is switched to the refrigeration mode, and the high-temperature refrigerant flows through the outdoor heat exchanger (which is used as a condenser at this time) to melt the frost layer. This scheme has obvious drawbacks: first, during the defrosting process, the system stops heating the room, instead absorbing heat from the room for defrosting, resulting in significant fluctuations in indoor temperature and poor user experience comfort; second, the reversing of the four-way valve will bring about a drastic change in the flow direction of the refrigerant, producing hydraulic shock and abnormal noise, which poses a threat to the long-term reliability and stability of the system. SUMMARY

[0005] The present application aims to solve the problems of existing heat pump air conditioners in heating, such as the influence of condensation water on heat exchange efficiency and the fluctuations in indoor temperature and system reliability caused by the defrosting process, and proposes a defrosting control method for a variable frequency heat pump air conditioner and an outdoor heat exchanger system.

[0006] The technical solution adopted by the present application to solve the above technical problems is: In a first aspect, the present application provides a defrosting control method for a variable frequency heat pump air conditioner, the air conditioner comprising an outdoor heat exchanger with super-hydrophobic aluminum foil fins, a four-way valve, an expansion valve and an indoor fan, the method comprising: When the air conditioner is running in heating mode and the outdoor heat exchanger temperature is above 0℃, the super-hydrophobic fins promote the rapid shedding of condensation water to maintain the heat exchange efficiency; When it is detected that the outdoor heat exchanger temperature is continuously lower than 0℃ for a first preset time threshold, it is determined that the frosting condition is met, and the defrosting mode is started to control; In the defrosting mode, the expansion valve is controlled to open to the maximum opening degree to reduce or stop throttling, and the indoor fan speed is reduced, while the heating flow direction of the four-way valve is kept unchanged, so that the high-temperature refrigerant flowing out of the compressor directly flows through the outdoor heat exchanger for defrosting; When it is detected that the outdoor heat exchanger temperature is continuously higher than 0℃ for a second preset time threshold, it is determined that the defrosting is completed, and the defrosting mode is exited to restore the normal control of the expansion valve and the indoor fan.

[0007] Further, the condition for starting the defrosting mode further includes that the air conditioner continuously operates in the heating mode for a third preset time threshold.

[0008] Further, the third preset time threshold is 20 to 40 minutes.

[0009] Further, the third preset time threshold is 30 minutes.

[0010] Further, the first preset time threshold is 5 to 15 minutes.

[0011] Further, the first preset time threshold is 10 minutes.

[0012] Further, the second preset time threshold is 1 to 3 minutes.

[0013] Further, the second preset time threshold is 2 minutes.

[0014] In a second aspect, the present application provides an outdoor heat exchanger system for a variable frequency heat pump air conditioner, comprising an outdoor heat exchanger with super-hydrophobic aluminum foil fins, a four-way valve, an expansion valve, an indoor fan and a controller, the controller is configured to perform the following control method: When the air conditioner operates in the heating mode, and the outdoor heat exchanger temperature is higher than 0℃, the super-hydrophobic fins promote the condensate water to quickly fall off to maintain the heat exchange efficiency; When it is detected that the outdoor heat exchanger temperature is continuously lower than 0℃ for a first preset time threshold, it is determined that the frosting condition is met, and the defrosting mode is started to control; In the defrosting mode, the expansion valve is controlled to open to the maximum opening degree to reduce or stop throttling, and the indoor fan speed is reduced, while the heating flow direction of the four-way valve is kept unchanged, so that the high-temperature refrigerant flowing out of the compressor directly flows through the outdoor heat exchanger for defrosting; When it is detected that the outdoor heat exchanger temperature is continuously higher than 0℃ for a second preset time threshold, it is determined that the defrosting is completed, and the defrosting mode is exited to restore the normal control of the expansion valve and the indoor fan.

[0015] Further, the condition of starting the defrosting mode further comprises: the air conditioner continuously operates in the heating mode for reaching a third preset time threshold.

[0016] The beneficial effects of the present application are: the defrosting control method and the outdoor heat exchanger system for the variable frequency heat pump air conditioner provided by the present application systematically solve the traditional problems of condensate, frosting and defrosting of the heat pump air conditioner in the heating operation through the software and hardware cooperation of super-hydrophobic material and intelligent control strategy. Specifically, the super-hydrophobic aluminum foil fin is adopted, when the temperature of the outdoor heat exchanger is above 0℃, the unique super-hydrophobic property makes it difficult for the condensate to adhere, and it quickly rolls down in the form of water droplets, thereby reducing the problem of increased thermal resistance and wind attenuation caused by water film coverage, and improving the energy efficiency and reliability in the conventional operation; in the low-temperature heating frosting condition, the expansion valve is opened and the indoor fan speed is reduced, the outdoor heat exchanger is defrosted by using the high-temperature refrigerant of the system itself, and since the direction of the four-way valve always remains in the heating state, the system only reduces the heating capacity in the entire defrosting process without absorbing heat to the indoor, realizes the defrosting under continuous heating, reduces the indoor temperature fluctuation, and improves the user comfort; at the same time, the frequent reversing action of the four-way valve during defrosting is avoided, the hydraulic impact, vibration and abnormal noise caused by the sudden change of refrigerant flow are eliminated, which is beneficial to prolong the service life of the compressor, the four-way valve and other key components, and improves the reliability, stability and quietness of the system in long-term operation. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 FIG. 1 is a schematic diagram of condensate of an outdoor heat exchanger with hydrophilic fins in the prior art; Figure 2 FIG. 2 is a schematic diagram of condensate of an outdoor heat exchanger with super-hydrophobic aluminum foil fins provided in the embodiment; Figure 3 FIG. 3 is a flowchart of a defrosting control method for a variable frequency heat pump air conditioner provided in the embodiment; Figure 4 FIG. 4 is a flowchart of another defrosting control method for a variable frequency heat pump air conditioner provided in the embodiment; Figure 5 FIG. 5 is a structural schematic diagram of an outdoor heat exchanger system for a variable frequency heat pump air conditioner provided in the embodiment; BRIEF DESCRIPTION OF DRAWINGS 1-U-shaped tube of the outdoor heat exchanger; 2a-hydrophilic aluminum foil fin; 2b-super-hydrophobic aluminum foil fin; 3-water droplet. DETAILED DESCRIPTION

[0018] In order to solve the problems of condensate affecting heat exchange efficiency and indoor temperature fluctuation and system reliability caused by defrosting process during heating of the existing heat pump air conditioner, the technical scheme of the present application is proposed, the super-hydrophobic aluminum foil fin is used, under the condensation condition that the temperature of the outdoor heat exchanger is higher than 0 DEG C, the condensate can be quickly condensed into beads and rolled off, instead of forming a covering water film, so that the continuous dryness and cleanliness of the surface of the heat exchange fin are ensured, the additional thermal resistance and wind resistance caused by the water film attachment are fundamentally eliminated, the outdoor heat exchange efficiency is always kept in the best state, so that the efficient and stable output of the heat pump heating capacity is ensured.

[0019] The technical solutions in the embodiments will be clearly and completely described below with reference to the drawings in the embodiments.

[0020] Please refer to Figure 1, the existing outdoor heat exchanger is provided with hydrophilic aluminum foil fins 2a, and the low-temperature refrigerant flows in the U-shaped tube 1 of the outdoor heat exchanger, absorbs heat and reduces the temperature of the U-shaped tube 1 of the outdoor heat exchanger, and the U-shaped tube 1 of the outdoor heat exchanger and the hydrophilic aluminum foil fins 2a are connected together by expansion connection, the surface temperature of the hydrophilic aluminum foil fins 2a is also reduced, and when the temperature of the outdoor heat exchanger is above 0 DEG C, the moisture in the air will condense on the surface of the hydrophilic aluminum foil fins 2a, and with the accumulation of time, the condensed water attached to the fins will gradually form water droplets 3, when the water droplets increase to saturation, they will slide along the fins and be discharged by the drainage air, the original outdoor heat exchanger condensate to a certain extent, although the condensed water will be continuously discharged, but the surface still attaches a large amount of condensed water, increases the heat exchange air resistance, reduces the ventilation volume, causes the heating heat pump capacity to be greatly reduced.

[0021] In the existing outdoor heat exchanger air conditioning system, if the defrosting is attempted without reversing, the heat of the refrigerant flowing through the outdoor heat exchanger needs to melt is the thick frost layer which is closely attached and dense in texture, which requires a large amount of heat and a long time. During this period, due to the slow defrosting speed, the indoor fan runs at low speed, but the heating capacity is greatly reduced, which will cause the indoor temperature to continue to drop, and the user experience is even worse than that of the short-time reverse cycle defrosting. At the same time, the system runs in non-design condition for a long time, which may cause reliability problems.

[0022] Please refer to Figure 2 , the outdoor heat exchanger in the embodiment is an outdoor heat exchanger with super-hydrophobic aluminum foil fins 2b, the low-temperature refrigerant flows in the U-shaped tube 1 of the outdoor heat exchanger, absorbs heat and reduces the temperature of the U-shaped tube 1 of the outdoor heat exchanger, and the U-shaped tube 1 of the outdoor heat exchanger and the super-hydrophobic aluminum foil fins 2b are connected together by expansion connection, the surface temperature of the super-hydrophobic aluminum foil fins 2b is also reduced, when the temperature of the outdoor heat exchanger is above 0 DEG C, the moisture in the air will condense on the surface of the super-hydrophobic aluminum foil fins 2b, but due to the characteristics of super-hydrophobic material, the condensed water cannot be attached to the surface of the fins, the condensed water droplets will be immediately bounced away and discharged, therefore the outdoor heat exchanger with super-hydrophobic aluminum foil fins 2b will not attach condensed water on the surface of the fins when heating and the temperature of the outdoor heat exchanger is above 0 DEG C, which will not affect the outdoor ventilation volume, the heating heat pump capacity can maintain stable output, and improve user comfort.

[0023] The outdoor heat exchanger with super-hydrophobic aluminum foil fins in the embodiment provides a physical basis for the control strategy of non-reversing defrosting. Please refer to Figure 3 and Figure 4 , the defrosting control method for the variable frequency heat pump air conditioner provided by the embodiment comprises the following steps: Step 1, when the air conditioner runs in heating mode and the temperature of the outdoor heat exchanger is above 0 DEG C, the super-hydrophobic fins promote the rapid falling of condensed water to maintain the heat exchange efficiency.

[0024] It can be understood that, in the normal temperature heating (outdoor heat exchanger temperature > 0℃), the low surface energy of the super-hydrophobic fin of the outdoor heat exchanger and its micro-nano structure make the condensate water have a high contact angle and a low rolling angle, and cannot spread into a film, but only form water droplets that can roll off, thereby promoting the rapid shedding of the condensate water to maintain the heat exchange efficiency. At this time, there is no condensate water accumulation in the outdoor heat exchanger, and the outdoor heat exchange air volume and heat exchange efficiency can be kept stable and not attenuated, thereby improving the heating capacity.

[0025] Step 2, when it is detected that the outdoor heat exchanger temperature continuously drops below 0℃ for a first preset time threshold, it is determined that the frosting condition is met, and the defrosting mode is controlled to be started.

[0026] In the low temperature / ultra-low temperature heating (outdoor heat exchanger temperature < 0℃), even if the super-hydrophobic fin, the condensate water will condense into a frost layer on its surface, and the frost layer has a very low thermal conductivity. The formation and thickening of the frost layer will sharply deteriorate the heat exchange efficiency, resulting in a decrease in the system evaporation temperature and a significant attenuation of the heating capacity. At this time, the defrosting mode needs to be started.

[0027] In the present embodiment, the condition for starting the defrosting mode further includes that the air conditioner continuously operates in the heating mode for a third preset time threshold. This is because the system needs to run for a period of time to reach a stable state after starting. The third preset time threshold is used to filter out temporary temperature fluctuations during the system startup stage, to ensure that the outdoor heat exchanger temperature < 0℃ detected by the controller is a true signal that the system has entered a stable low temperature operating state, and to prevent false triggering of the defrosting.

[0028] In the present embodiment, the third preset time threshold is 20 to 40 minutes, preferably 30 minutes. This time threshold is a statistical optimal range obtained through experiments and experience based on the system charge amount, pipeline length, compressor performance and other parameters of most models of air conditioners. If the time is too short, the system is not stable; if the time is too long, the frost may have already become too severe.

[0029] In the present embodiment, the first preset time threshold is 5 to 15 minutes, preferably 10 minutes. Since the outdoor heat exchanger temperature < 0℃ for a short time may be caused by environmental temperature fluctuations, it does not necessarily form an effective frost layer that affects performance. This time threshold is used to confirm that the frosting process is continuously ongoing and has already had a measurable impact on performance, to avoid false triggering of the defrosting.

[0030] Step 3, in the defrosting mode, the expansion valve is controlled to be opened to the maximum opening degree to reduce or stop throttling, the speed of the indoor fan is reduced, and the heating flow direction of the four-way valve is kept unchanged, so that the high-temperature refrigerant flowing out of the compressor directly flows through the outdoor heat exchanger for defrosting.

[0031] It can be understood that after the defrosting mode is started, the expansion valve is fully opened to stop the throttling effect, so that the high-pressure high-temperature liquid refrigerant of the indoor heat exchanger flows to the low-pressure side outdoor heat exchanger without obstruction, that is, a part of the system high pressure heat is directly introduced into the outdoor heat exchanger to provide a defrosting heat source; the indoor air speed is reduced to reduce the heat exchange amount between the indoor air and the indoor heat exchanger, thereby reducing the overall heat load of the system, so that more heat generated by the compressor work can be distributed to the outdoor side defrosting; the four-way valve is not switched to maintain the heating cycle flow direction and ensure that the defrosting heat comes from the compressor work and the reduced part of the indoor heat, rather than from the indoor air heat absorption, thereby realizing defrosting under continuous heating.

[0032] Step 4: When it is detected that the outdoor heat exchanger temperature continuously exceeds 0℃ for a second preset time threshold, it is determined that the defrosting is completed, the control exits the defrosting mode, and the normal control of the expansion valve and the indoor fan is restored.

[0033] It can be understood that when the defrosting is completed, it is necessary to restore the expansion valve and the indoor fan to the state before entering the defrosting, and the control can ensure that the original heating state and the user setting state remain unchanged.

[0034] In the embodiment, the second preset time threshold is 1 to 3 minutes, and preferably 2 minutes. Since the short-term outdoor heat exchanger >0℃ may only be the melting of surface frost, the second preset time threshold is used to confirm that the entire heat exchanger has been sufficiently and uniformly heated, and the frost layer has been completely melted, thereby avoiding the system from exiting the defrosting mode in the presence of residual frost, and improving the anti-interference ability and reliability of the control system.

[0035] In summary, the defrosting control method for the variable frequency heat pump air conditioner provided in the embodiment can completely eliminate the condensate film on the super-hydrophobic fin under the condensation condition of >0℃, keep the air duct unobstructed and the heat exchange efficiency, enable the heat pump to continuously and stably output the heating capacity, and avoid the performance decline caused by the traditional hydrophilic fin. Under the frosting condition, the innovative non-reversing defrosting control strategy can quickly complete the defrosting under the premise of continuously supplying heat to the indoor, completely eliminates the problems of cold air blowing and temperature sudden drop caused by the traditional reverse cycle defrosting, and improves the user experience comfort. Moreover, the frequent reversing action of the four-way valve during defrosting is completely avoided, the liquid pressure impact, vibration and abnormal noise caused thereby are fundamentally eliminated, the reliability and quietness of the system operation are significantly improved, and the equipment life is prolonged.

[0036] Based on the above technical solution, the embodiment further provides an outdoor heat exchanger system for a variable frequency heat pump air conditioner, please refer to Figure 5 , which comprises an outdoor heat exchanger with super-hydrophobic aluminum foil fins, a four-way valve, an expansion valve, an indoor fan and a controller, and the controller is configured to perform the following control method: When the air conditioner operates in the heating mode and the outdoor heat exchanger temperature is higher than 0℃, the super-hydrophobic fin promotes the rapid shedding of condensate water to maintain the heat exchange efficiency; When it is detected that the outdoor heat exchanger temperature is continuously lower than 0℃ for a first preset time threshold, it is determined that the frosting condition is met, and the defrosting mode is controlled to be started; In the defrosting mode, the expansion valve is controlled to be opened to the maximum opening degree to reduce or stop throttling, and the wind speed of the indoor fan is reduced, while the heating flow direction of the four-way valve is kept unchanged, so that the high-temperature refrigerant flowing out of the compressor directly flows through the outdoor heat exchanger for defrosting; When it is detected that the outdoor heat exchanger temperature is continuously higher than 0℃ for a second preset time threshold, it is determined that the defrosting is completed, the defrosting mode is controlled to be exited, and the normal control of the expansion valve and the indoor fan is restored.

[0037] It can be understood that, since the outdoor heat exchanger system for the variable frequency heat pump air conditioner described in the embodiment corresponds to the defrosting control method for the variable frequency heat pump air conditioner described in the embodiment, the system disclosed in the embodiment is described more simply, and the relevant part can be referred to the part of the method description.

Claims

1. A defrosting control method for a variable frequency heat pump air conditioner, characterized by, The air conditioner comprises an outdoor heat exchanger with super-hydrophobic aluminum foil fins, a four-way valve, an expansion valve, and an indoor fan, and the method comprises: When the air conditioner is running in heating mode and the outdoor heat exchanger temperature is higher than 0℃, the super-hydrophobic fins facilitate the rapid shedding of condensed water to maintain heat exchange efficiency; When it is detected that the outdoor heat exchanger temperature has been continuously lower than 0℃ for a first preset time threshold, it is determined that the frosting condition is met, and the defrosting mode is controlled to be started; In the defrosting mode, the expansion valve is controlled to be opened to the maximum degree to reduce or stop throttling, and the wind speed of the indoor fan is reduced, while the heating flow direction of the four-way valve remains unchanged, so that the high-temperature refrigerant flowing out of the compressor directly flows through the outdoor heat exchanger for defrosting; When it is detected that the outdoor heat exchanger temperature has been continuously higher than 0℃ for a second preset time threshold, it is determined that the defrosting is completed, and the defrosting mode is controlled to be exited, and the normal control of the expansion valve and the indoor fan is restored.

2. The defrost control method for a variable frequency heat pump air conditioner according to claim 1, characterized by, The condition for starting the defrosting mode further comprises that the air conditioner continuously runs in heating mode for a third preset time threshold.

3. The defrost control method for a variable frequency heat pump air conditioner according to claim 2, characterized by, The third preset time threshold is 20 to 40 minutes.

4. The defrost control method for a variable frequency heat pump air conditioner according to claim 3, characterized by, The third preset time threshold is 30 minutes.

5. The defrosting control method for a variable frequency heat pump air conditioner according to claim 1 or 2, characterized by, The first preset time threshold is 5 to 15 minutes.

6. The defrost control method for a variable frequency heat pump air conditioner according to claim 5, characterized by, The first preset time threshold is 10 minutes.

7. The defrosting control method for a variable frequency heat pump air conditioner according to claim 1 or 2, characterized by, The second preset time threshold is 1 to 3 minutes.

8. The defrost control method for a variable frequency heat pump air conditioner according to claim 7, characterized by, The second preset time threshold is 2 minutes.

9. An outdoor heat exchanger system for a variable frequency heat pump air conditioner, characterized by, Comprise: An outdoor heat exchanger with super-hydrophobic aluminum foil fins, a four-way valve, an expansion valve, an indoor fan, and a controller, wherein the controller is configured to perform the following control method: When the air conditioner is running in heating mode and the outdoor heat exchanger temperature is higher than 0℃, the super-hydrophobic fins facilitate the rapid shedding of condensed water to maintain heat exchange efficiency; When it is detected that the outdoor heat exchanger temperature has been continuously lower than 0℃ for a first preset time threshold, it is determined that the frosting condition is met, and the defrosting mode is controlled to be started; In the defrosting mode, the expansion valve is controlled to be opened to the maximum degree to reduce or stop throttling, and the wind speed of the indoor fan is reduced, while the heating flow direction of the four-way valve remains unchanged, so that the high-temperature refrigerant flowing out of the compressor directly flows through the outdoor heat exchanger for defrosting; When it is detected that the outdoor heat exchanger temperature has been continuously higher than 0℃ for a second preset time threshold, it is determined that the defrosting is completed, and the defrosting mode is controlled to be exited, and the normal control of the expansion valve and the indoor fan is restored.

10. The outdoor heat exchanger system for a variable frequency heat pump air conditioner according to claim 9, characterized by, The condition for starting the defrosting mode further comprises that the air conditioner continuously runs in heating mode for a third preset time threshold.

Images