Air energy heat pump unit with low-temperature efficient heating function

Abstract

The invention relates to a low-temperature efficient heating air energy heat pump unit, discloses a low-temperature efficient heating air energy heat pump unit, and belongs to the technical field of heat pump air conditioners. The unit is composed of a compressor, an evaporator, a condenser, a throttling valve, a defrosting module, a refrigerant adjusting module and a control unit. The surfaces of fins of the evaporator are coated with polytetrafluoroethylene modified hydrophobic frost-resistant coatings, and the frosting amount can be inhibited by 60% or above; the defrosting module adopts a bypass coupling scheme of a 500-800W electric heating wire and a high-temperature refrigerant, and the defrosting time is less than or equal to 8min and is shortened by 30% compared with a traditional scheme; the refrigerant adjusting module dynamically adjusts the refrigerant temperature of an inlet of the evaporator through the bypass electromagnetic valve and the refrigerant mixing cavity, so that the compressor still maintains 100% of the rotating speed at-25 DEG C without frequency reduction, the COP is larger than or equal to 2.0, and the heating capacity is kept 75% or above of the normal temperature value. The system solves the industrial problems of frequent frosting, high defrosting energy consumption and large heating attenuation under the low-temperature and high-humidity working conditions, and can be widely applied to heating systems in household, commercial and high-humidity and low-temperature areas.

Description

Technical Field

[0001] This invention relates to the field of air source heat pump technology, and in particular to a low-temperature, high-efficiency air source heat pump unit. Background Technology

[0002] Traditional air-source heat pumps are prone to frost buildup on the evaporator surface under low-temperature and high-humidity conditions, leading to reduced airflow, decreased heat transfer coefficient, and a sharp decline in heating capacity. Existing reverse circulation defrosting (RCD) requires frequent switching of the four-way valve, resulting in large indoor temperature fluctuations, high energy consumption, and the risk of compressor liquid slugging. Hot gas bypass (HGBP) defrosting, while eliminating the need for reversing, suffers from insufficient heat and long defrosting times. Electric defrosting consumes a lot of electricity and is prone to localized overheating, which can burn out the fins. Furthermore, hydrophilic or ordinary hydrophobic coatings on the evaporator surface are prone to failure below -15°C, allowing frost to adhere firmly and further reducing defrosting efficiency.

[0003] The lack of synergy between existing technologies such as surface modification, active air-side heating, and refrigerant-side hot gas bypass results in a break in the entire "prevention-defrosting-control" chain. The industry urgently needs a systematic solution that deeply integrates anti-frost coatings, multi-heat source heat coupling, and intelligent predictive control to achieve continuous, efficient heating at low temperatures and minute-level low-energy defrosting. Therefore, it is evident that the existing air source heat pump units still have inconveniences and shortcomings in their methods and applications, requiring further improvement. To address the problems of air source heat pump units, manufacturers have spared no effort in seeking solutions, but a suitable design has yet to be developed, and conventional methods lack appropriate approaches and structures to solve the aforementioned issues. This is clearly a problem that the industry urgently needs to solve.

[0004] Therefore, there is an urgent need for a new defrosting technology that is "low-energy, fast-response, and provides uninterrupted heating." In view of the shortcomings of existing low-temperature, high-efficiency air source heat pump units, the inventor, based on years of practical experience and professional knowledge in the design and manufacture of such products, and combining theoretical research, actively researched and innovated to create a new low-temperature, high-efficiency air source heat pump unit that can improve upon existing low-temperature, high-efficiency air source heat pump units, making them more practical. After continuous research, design, and repeated trials and improvements, this invention, with proven practical value, was finally created. Summary of the Invention

[0005] The main objective of this invention is to overcome the shortcomings of existing low-temperature, high-efficiency air source heat pump units, such as large heating capacity at -30℃, high defrosting energy consumption, and significant room temperature fluctuations. The invention provides a new low-temperature, high-efficiency air source heat pump unit. The technical problem to be solved is to maintain a COP ≥ 2.0 at -30℃ and indoor temperature fluctuation ≤ 1℃ during the defrosting process, thus making it more practical and having industrial application value.

[0006] Another objective of this invention is to provide a low-temperature, high-efficiency air-source heat pump unit. The technical problem to be solved is to make its defrosting time ≤3min and its defrosting energy consumption <3% of the cycle heating capacity, thereby making it more suitable for practical use.

[0007] Another objective of this invention is to provide a low-temperature, high-efficiency air-source heat pump unit. The technical problem to be solved is to extend the evaporator defrosting cycle by more than 2 times and reduce the number of defrostings per year by ≥40%, thereby making it more suitable for practical use.

[0008] Another objective of this invention is to provide a low-temperature, high-efficiency air-source heat pump unit. The technical problem to be solved is to ensure that the compressor has no risk of liquid slugging, the exhaust temperature is ≤100℃, and the system oil return is reliable, thus making it more suitable for practical use.

[0009] The objective of this invention and the technical problem it solves are achieved by the following technical solution. According to this invention, a low-temperature, high-efficiency air-source heat pump unit includes: a compressor, a condenser, a finned tube evaporator, a throttling valve, a defrosting module, a refrigerant regulation module, and a control unit. The evaporator fins are coated with a 3-8 μm polytetrafluoroethylene-modified hydrophobic anti-frost coating, with a fin spacing of 1.8-2.5 mm and Ra≤0.4 μm. The defrosting module includes a 500-800W nickel-chromium electric heating wire and a fin temperature sensor. The refrigerant regulation module consists of a bypass solenoid valve and a refrigerant mixing chamber with spiral mixing blades. The control unit is configured to: initiate defrosting when the fin temperature is <0℃ for 5 minutes, operate the electric heating wire at full power, and linearly adjust the opening of the bypass solenoid valve according to the ambient temperature, so that the high-temperature refrigerant and the throttled refrigerant mix and heat up to 20-50℃ within ≤0.3 seconds before entering the evaporator, achieving synergistic defrosting by three heat sources: hot air, electric heating, and hot air.

[0010] The objectives of this invention and the technical problems it addresses can be further achieved by the following technical measures.

[0011] The aforementioned low-temperature high-efficiency heating air source heat pump unit, wherein the evaporator fin surface is further provided with a 2-4μm hydrophilic bottom layer, located below the hydrophobic coating, to prevent frost from forming in high humidity environments.

[0012] The aforementioned low-temperature high-efficiency air-source heat pump unit has a built-in humidity sensor in its control unit. When RH≥85% and Tf≤2℃, a defrost warning is initiated 5 minutes in advance: the opening of the bypass solenoid valve is gradually increased to 50% of the set value and the compressor frequency is reduced by 5%-10% to delay the thickening of the frost layer.

[0013] The aforementioned low-temperature, high-efficiency air-source heat pump unit, wherein the defrosting module further includes a hot air circulation channel, introducing 50-70℃ hot air from the condenser outlet during defrosting, with an air volume of 300m³.3 / h, working synchronously with electric heating and hot gas bypass.

[0014] The aforementioned low-temperature high-efficiency heating air source heat pump unit uses a jet enthalpy-increasing rotary compressor or a two-stage compression screw compressor with an intermediate gas injection pressure of 0.35-0.55 MPa to ensure that the exhaust temperature is ≤100℃ at a low temperature of -30℃.

[0015] The objectives of this invention and the solutions to its technical problems are also achieved by the following technical solutions. According to the control method of a low-temperature, high-efficiency air-source heat pump unit proposed in this invention, the control unit uses an MPC model prediction algorithm to minimize defrosting energy consumption and room temperature deviation as optimization objectives, and updates the bypass valve opening, compressor frequency, and electric heating duty cycle every 10 seconds to achieve adaptive defrosting under all operating conditions.

[0016] Compared with the prior art, the present invention has significant advantages and beneficial effects. As can be seen from the above technical solution, in order to achieve the aforementioned objectives, the main technical contents of the present invention are as follows:

[0017] This invention proposes a low-temperature, high-efficiency air source heat pump unit, characterized by comprising: a compressor; a condenser; an evaporator, wherein the evaporator is a finned tube structure with the fin surface coated with a hydrophobic anti-frost coating; a throttling valve connected between the condenser and the evaporator; and a defrosting module, wherein the defrosting module comprises:

[0018] Electric heating wires are arranged in the gaps between the evaporator fins, with a power of 500W-800W;

[0019] A fin temperature sensor is used to detect the evaporator fin temperature in real time; a refrigerant regulation module includes:

[0020] The bypass solenoid valve has its inlet end connected to the compressor's exhaust port.

[0021] The refrigerant mixing chamber has its inlet end connected to both the outlet of the bypass solenoid valve and the outlet of the throttling valve, and its outlet end connected to the inlet of the evaporator. The control unit is electrically connected to the compressor, the fin temperature sensor, the electric heating wire, and the bypass solenoid valve. The control unit is configured to activate the defrosting mode when the fin temperature is below 0°C for more than 5 minutes: turn on the electric heating wire and control the opening of the bypass solenoid valve so that some of the high-temperature refrigerant and the throttled refrigerant are mixed in the refrigerant mixing chamber and then enter the evaporator to accelerate defrosting.

[0022] Preferably, the hydrophobic anti-frost coating is a polytetrafluoroethylene modified coating with a thickness of 3-8 μm and a water contact angle ≥120°.

[0023] Preferably, the evaporator fin spacing is 1.8-2.5 mm, and the fin surface roughness Ra≤0.4 μm.

[0024] Preferably, the electric heating wire is made of nickel-chromium alloy, with a single wire power of 150-300W, and 3-5 wires are arranged at equal intervals along the airflow direction.

[0025] Preferably, the refrigerant mixing chamber is equipped with spiral mixing blades, so that the high-temperature and low-temperature refrigerants can be fully mixed within ≤0.3s, and the temperature rises by 20-50℃ after mixing.

[0026] Preferably, the control unit has a built-in ambient temperature sensor for adjusting the opening of the bypass solenoid valve according to the ambient temperature: 15% opening at -15℃, 30% opening at -25℃, and 45% opening at -30℃, so as to maintain the compressor exhaust temperature ≤100℃.

[0027] Preferably, the compressor is a jet enthalpy-increasing rotary compressor or a two-stage compression screw compressor, with an intermediate gas injection pressure of 0.35-0.55 MPa.

[0028] Preferably, the defrosting module further includes a hot air circulation channel, one end of which is connected to the condenser outlet air duct, and the other end is connected to the evaporator air inlet side via an air valve. During defrosting, the control unit opens the air valve to introduce hot air at 50-70°C.

[0029] Preferably, the surface of the evaporator fins is further provided with a hydrophilic underlayer, the hydrophilic underlayer being 2-4 μm thick and located below the hydrophobic anti-frost coating, which is used to prevent frost from caking in a high humidity environment.

[0030] The air heat pump unit provided by the present invention is further configured to: when the ambient humidity is ≥85% and the fin temperature is ≤2℃, start the defrost warning mode 5 minutes in advance: gradually increase the opening of the bypass solenoid valve to 50% of the set value, and reduce the compressor frequency by 5%-10% to delay the thickening of the frost layer.

[0031] As can be seen from the above, the present invention can complete rapid defrosting and continuously supply heat to the room without the need for a four-way valve to switch, thus solving the problems of low-temperature performance degradation, high defrosting energy consumption, and poor comfort of traditional heat pumps.

[0032] By employing the above technical solution, the low-temperature, high-efficiency heating air source heat pump unit of the present invention has at least the following advantages:

[0033] Low-temperature strong heating: COP≥2.0 at -30℃, heating capacity increased by 28%;

[0034] Rapid defrosting: defrosting time ≤3min, energy consumption <3%, room temperature fluctuation ≤1℃;

[0035] Anti-frost durability: Double coating + early warning control, reducing the number of defrost cycles by ≥40% throughout the year;

[0036] Safe and reliable: The compressor has no liquid slugging, the exhaust temperature is ≤100℃, and the system has smooth oil return;

[0037] Green and low-carbon: Compared to the traditional RCD solution, annual carbon emissions are reduced by approximately 45%.

[0038] In summary, the novel low-temperature, high-efficiency air-source heat pump unit of this invention achieves a dual breakthrough in ultra-low-temperature, high-efficiency heating and low-energy-consumption, rapid defrosting through collaborative innovation in materials, thermodynamics, and control. It possesses numerous advantages and practical value, and is truly innovative as no similar designs have been publicly disclosed or used in similar methods. It represents a significant improvement in both method and function, a substantial technological advancement, and produces user-friendly and practical effects. Compared to existing air-source heat pump units, it offers several enhanced functions, making it more suitable for practical application and possessing broad industrial applicability. It is indeed a novel, progressive, and practical new design. The above description is merely an overview of the technical solution of this invention. To better understand the technical means of this invention and to facilitate its implementation according to the description, the following detailed description, using preferred embodiments of the invention and accompanying drawings, is provided.

[0039] The specific methods and structures of the present invention are given in detail in the following embodiments and accompanying drawings. Attached Figure Description

[0040] Figure 1 Schematic diagram of a low-temperature, high-efficiency air source heat pump unit;

[0041] In the diagram: 1. Compressor, 2. Evaporator, 3. Condenser, 4. Throttling valve, 5. Electric heating wire, 6. Fin temperature sensor, 7. Bypass solenoid valve, 8. Refrigerant mixing chamber, 9. Control unit. Detailed Implementation

[0042] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and preferred embodiments, describes the specific implementation methods, steps, structures, features, and effects of the low-temperature high-efficiency heating air source heat pump unit proposed according to the present invention.

[0043] Please see Figure 1 As shown, the preferred embodiment of the low-temperature, high-efficiency heating air source heat pump unit of the present invention mainly includes the following steps:

[0044] Step S1: System power-on self-test

[0045] The control unit (9) detects the feedback signals from the fin temperature sensor (6), ambient temperature / humidity sensor, compressor exhaust temperature, high and low pressure switches and bypass solenoid valve (7), and enters standby mode after confirming that there are no faults.

[0046] Step S2: Normal heating operation

[0047] The compressor (1) starts at the target frequency, and the refrigerant flows sequentially through the condenser (3) → throttle valve (4) → evaporator (2) → compressor (1) to form the main cycle; the jet enthalpy-increasing circuit automatically replenishes gas according to the intermediate pressure of 0.35–0.55MPa to maintain the exhaust temperature ≤100℃ at -30℃.

[0048] Step S3: Anti-frost coating and early warning work together to inhibit frost.

[0049] The hydrophilic bottom layer (2–4 μm) on the surface of the evaporator fins first adsorbs condensate, and the polytetrafluoroethylene modified hydrophobic layer (3–8 μm, contact angle ≥120°) causes the water film to roll off quickly. When RH≥85% and Tf≤2℃ lasts for 3 minutes, the control unit enters an early warning 5 minutes in advance: the bypass solenoid valve opening slowly increases to 50% of the set value, the compressor frequency decreases by 5%–10%, and the frost crystal nucleation is delayed.

[0050] Step S4: Defrosting Criterion Triggered

[0051] If the fin temperature Tf < 0℃ and remains so for 5 minutes, or if the Tf decreases by more than 3℃ / min, the control unit determines that the amount of frost has reached the threshold and starts the defrosting mode.

[0052] Step S5: Three heat sources work together to defrost

[0053] ① The electric heating wire (5) is put into operation at full power of 800W, and the four nickel-chromium alloy wires along the airflow direction heat up rapidly;

[0054] ② The bypass solenoid valve (7) is adjusted linearly according to Tamb (-15℃→15%, -25℃→30%). - 30℃→45%), 80℃ hot air and throttled refrigerant are uniformly mixed in the spiral mixing chamber (8) for ≤0.3s, and the temperature rises by 20–50℃ before entering the evaporator;

[0055] ③ Open the hot air circulation valve to introduce air into the condenser outlet at 55℃ and 300m. 3 / h hot air forms a three-dimensional defrosting field of "internal melting of hot air + external disturbance of electric heat + hot air convection".

[0056] Step S6: Defrosting off and heating resume

[0057] When the fin temperature Tf ≥ +8℃ or defrosting lasts for 120 seconds, the control unit sequentially shuts off the electric heating wire, bypass solenoid valve and hot air valve, the compressor frequency returns to the target value, and the system seamlessly switches back to conventional heating with room temperature fluctuation ≤ 1℃.

[0058] Step S7: Post-evaluation and self-learning

[0059] The control unit records the defrosting time, energy consumption, ambient temperature / humidity, and frost thickness estimate for this defrosting cycle, updates the MPC model parameters, and achieves self-optimization of the defrosting strategy for the next cycle.

[0060] Example 1:

[0061] The unit uses a jet-induced enthalpy-increasing rotary compressor with a displacement of 24 cm³. 3 The frequency is 15–90Hz, with an intermediate gas injection pressure of 0.35MPa. The evaporator is an aluminum finned copper tube structure with a fin spacing of 1.8mm and a surface roughness Ra = 0.4μm. It is first coated with a 2μm hydrophilic epoxy-silica underlayer, then covered with a 3μm polytetrafluoroethylene modified hydrophobic layer, with a water contact angle of 120°. The electric heating wire is Ni80Cr20, 0.4mm in diameter, 150W per wire, with 5 wires evenly spaced along the airflow direction, for a total power of 750W. The bypass solenoid valve is a normally closed DN10 type, the refrigerant mixing chamber is Φ25mm×80mm, with built-in three-headed spiral blades, and a theoretical residence time of 0.25s. The control unit uses a 32-bit MCU with a 1s sampling cycle and built-in temperature and humidity sensors.

[0062] The experiment was conducted at -30℃ and 90% RH, with influent water at 40℃ and a flow rate of 1.0 m³ / h. 3 h-1, fan air volume 1800m³ 3 h -1 After the unit ran in steady state for 45 minutes, the fin temperature dropped to -1℃ and remained there for 5 minutes. The control unit then initiated defrosting: the 750W electric heater was fully activated, the bypass valve was opened to 45%, the compressor frequency dropped from 75Hz to 67Hz, and hot air was introduced at 70℃ and 300m². 3 H-1 hot air. High-temperature exhaust gas and low-temperature refrigerant reach 30°C at the mixing chamber outlet and enter the evaporator. After 120 seconds, the fin temperature reaches +8°C, defrosting ends, 210g of water is drained, the frost layer is completely removed, and the maximum room temperature fluctuation is 0.9°C. Records show that defrosting takes 120 seconds, consumes 0.025kWh of electricity, accounting for 2.7% of the cycle heating capacity; after 200 consecutive defrosting cycles, the coating contact angle is 121°, the compressor exhaust peak temperature is 98°C, there is no liquid slugging, and oil return is normal.

[0063] Example 2:

[0064] Replace the compressor with a two-stage screw compressor, with an intermediate injection pressure of 0.55 MPa and a discharge volume of 60 m³ / h. 3 h -1 The remaining components are the same as in Example 1. Under operating conditions of -25℃ and RH 85%, defrosting is triggered when Tf < 0℃ for 5 minutes, the bypass valve is opened to 30%, the 800W electric heater is fully activated, and the mixing chamber outlet temperature rises by 50℃, reaching 40℃. Defrosting is completed in 100 seconds, the COP recovers from 2.0 to 2.12, and the exhaust temperature reaches 96℃, verifying that the two-stage compression scheme is also reliable.

[0065] Example 3:

[0066] A 100mm diameter hot air circulation channel was added, and the electric butterfly valve has a rated air volume of 500m³ / h. 3 h-1. The experiment was conducted at -15℃ and RH 80%. During defrosting, the air valve was opened to 60%, and air was introduced at 50℃ and 300m. 3 The h-1 hot air system uses only 500W of electric heating with the bypass valve open at 15%. Defrosting is completed in 110 seconds, with hot air supply accounting for 42% of the total defrosting heat, significantly reducing power consumption. The coating surface roughness remains at 0.4μm, with no high-temperature burn-off.

[0067] Example 4:

[0068] Under conditions of -5℃, RH 95%, and Tf = 2℃, the control unit initiates a warning 5 minutes in advance: the bypass valve slowly rises to 22.5%, and the compressor frequency drops from 60Hz to 57Hz. During the warning phase, the frost crystal formation rate decreases by 55%, the frost thickness during actual defrosting is only 0.3mm, the defrosting time is shortened to 80s, and the power consumption is 0.018kWh, verifying the effectiveness of the early warning function.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the methods and techniques disclosed above without departing from the scope of the present invention to create equivalent embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. An air energy heat pump unit with low temperature and high efficiency heating, characterized in that, Comprise: Compressor (1); Condenser (3); evaporator (2), the evaporator is finned tube structure, the fin surface is coated with hydrophobic frost resistant coating; Throttle valve (4) is connected between the condenser (3) and the evaporator (2); Defrosting module, the defrosting module comprises: Electric heating wire (5) is arranged in the evaporator fin gap, power 500W-800W; Fin temperature sensor (6) for real-time detection of evaporator fin temperature; refrigerant adjusting module, the refrigerant adjusting module comprises: Bypass solenoid valve (7), the inlet end is communicated with the compressor exhaust port; Refrigerant mixing chamber (8), the inlet end is communicated with the bypass solenoid valve outlet and the throttle valve outlet simultaneously, and the outlet end is communicated with the evaporator inlet; control unit (9) is electrically connected with the compressor, fin temperature sensor, electric heating wire and bypass solenoid valve respectively; the control unit is configured to: when the fin temperature is below 0 DEG C and lasts more than 5 min, start defrosting mode: turn on the electric heating wire and control the opening of the bypass solenoid valve, make part of high-temperature refrigerant and throttled refrigerant mix in the refrigerant mixing chamber and then enter the evaporator, so as to accelerate the defrosting.

2. The air-to-water heat pump unit according to claim 1, characterized in that, The hydrophobic frost resistant coating is a polytetrafluoroethylene modified coating, the thickness is 3-8 μm, and the water contact angle is ≥120°.

3. Air-to-water heat pump unit according to claim 1 or 2, characterized in that The evaporator fin spacing is 1.8-2.5 mm, and the fin surface roughness Ra is ≤0.4 μm.

4. The air-to-water heat pump unit according to claim 1, characterized in that, The electric heating wire is made of nickel-chromium alloy material, the single power is 150-300 W, and 3-5 wires are arranged at equal intervals along the airflow direction.

5. The air-to-water heat pump unit according to claim 1, characterized in that, The refrigerant mixing chamber (8) is provided with spiral mixing blades, so that the high-temperature and low-temperature refrigerant is fully mixed in ≤0.3 s, and the temperature is increased by 20-50 DEG C after mixing.

6. The air-to-water heat pump unit of claim 1, wherein, The control unit (9) is provided with an ambient temperature sensor, which is used to adjust the opening of the bypass solenoid valve according to the ambient temperature: the opening is 15% at-15 DEG C, the opening is 30% at-25 DEG C, and the opening is 45% at-30 DEG C, so as to keep the compressor exhaust temperature ≤100 DEG C.

7. The air-to-water heat pump unit according to claim 1, characterized in that, The compressor (1) is a jet enthalpy increasing type rotor compressor or a double-stage compression screw compressor, and the intermediate air supply pressure is 0.35-0.55 MPa.

8. The air-to-water heat pump unit according to claim 1, characterized in that, The defrosting module further comprises a hot air circulation channel, one end of the hot air circulation channel is communicated with the condenser outlet air duct, the other end is connected with the evaporator air inlet side through an air valve, and the control unit opens the air valve to introduce 50-70 DEG C hot air during defrosting.

9. The air-to-water heat pump unit according to claim 1, characterized in that, The evaporator fin surface is further provided with a hydrophilic bottom layer, the thickness of the hydrophilic bottom layer is 2-4 μm, and the hydrophilic bottom layer is located below the hydrophobic frost resistant coating and is used to prevent frost layer from caking in a high-humidity environment.

10. Air-to-water heat pump unit according to any of claims 1-9, characterized in that The control unit (9) is further configured to: when the ambient humidity is ≥85% and the fin temperature is ≤2 DEG C, start the defrosting early warning mode 5 min in advance: gradually increase the opening of the bypass solenoid valve to 50% of the set value, and reduce the compressor frequency by 5%-10%, so as to delay the thickening of the frost layer.

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