Variable-frequency high-temperature heat pump unit and control method thereof

Abstract

The invention discloses a variable-frequency high-temperature heat pump unit and a control method thereof. The variable-frequency high-temperature heat pump unit comprises a refrigerant pipeline and a waterway pipeline. A compressor, a condenser and an evaporator are mounted on the refrigerant pipeline, and a refrigerant can circularly flow in the refrigerant pipeline; the refrigerant pipeline and the waterway pipeline are both connected with the condenser, and heat exchange is conducted between the refrigerant pipeline and the waterway pipeline through the condenser; the water tank is connected with the waterway pipeline through the booster water pump, and the booster water pump can convey water in the water tank to the waterway pipeline for water and pressure supplementation. By means of the structure, high-temperature hot water can be provided within the water temperature range of 35-70 DEG C; high-temperature hot water within the water temperature range of 90-130 DEG C can be provided for the heat pump unit through the booster water pump; water can be supplemented to the waterway pipeline in time through the booster water pump and the water tank, the flow and the pressure in the waterway pipeline are controlled, and then the heat pump unit operates stably.

Description

Technical Field

[0001] The invention relates to the field of heat pump water heaters, and in particular to a variable frequency high temperature heat pump unit and a control method thereof. Background Art

[0002] The existing heat pump water heaters provide hot water in the temperature range of 40~55℃; they cannot provide high-temperature hot water of 90~130℃; the water temperature varies in the range of 10~35℃; they are not suitable for the high water temperature range of 35~70℃ under the condition of waste heat recovery; the compressor uses a fixed-frequency compressor and adopts traditional control technology, and the control system is relatively simple, which is not conducive to quickly and reliably ensuring the stability of water temperature.

[0003] In addition, the PID control method used in existing heat pump water heaters will have output upper and lower limit blind spots. Here, the frequency lower limit is set to 20HZ. When PID is in frequency reduction according to temperature comparison, although the lower limit frequency is set to 20HZ, the PID characteristic is a continuous operation. If the outlet water temperature is higher than the set temperature, it will always be in the frequency reduction state, and the PID internal calculation result will reach 0HZ. At this time, the actual control frequency is 20HZ. However, if the outlet water temperature is lower than the set temperature, the PID will be converted to the frequency increase state. At this time, the PID internal calculation starts from 0HZ and increases the frequency upward. If the internal calculation result is less than the lower limit of 20HZ, it will always be at 20HZ. The process from 0 to 20HZ may take up to 3 to 10 minutes. This is the existence of a blind spot, which will lead to untimely frequency control and affect the unit's operating stability and water temperature stability. Summary of the invention

[0004] In order to solve the problems of low outlet water temperature and small water temperature adjustment range of the unit in the prior art, the purpose of the present invention is to provide a variable frequency high-temperature heat pump unit and a control method thereof. The present application can effectively improve the outlet water temperature and adjustment range of the heat pump unit, thereby better matching more working scenarios.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a variable frequency high-temperature heat pump unit, including a refrigerant pipeline and a water pipeline; a compressor, a condenser and an evaporator are installed on the refrigerant pipeline, and the refrigerant can circulate in the refrigerant pipeline; the refrigerant pipeline and the water pipeline are both connected to the condenser, and the refrigerant pipeline and the water pipeline exchange heat through the condenser; the water tank is connected to the water pipeline through a booster water pump, and the booster water pump can send the water in the water tank to the water pipeline for water replenishment and pressure replenishment operations.

[0006] Preferably, a water supply valve is provided at the outlet of the booster water pump, and a second safety valve for pressure relief is also installed on the water pipeline.

[0007] Preferably, a pressure sensor for controlling the start and stop of the booster water pump is installed on the water pipeline, and the pressure sensor is arranged on the outlet side of the condenser.

[0008] Preferably, an inlet water temperature sensor and an outlet water temperature sensor are installed on the water pipeline. The inlet water temperature sensor is arranged at the inlet of the condenser, and the outlet water temperature sensor is installed at the outlet of the condenser.

[0009] Preferably, an economizer, a liquid reservoir and a gas-liquid separator are also installed on the refrigerant pipeline. The economizer is arranged between the condenser and the evaporator, the liquid reservoir is arranged between the condenser and the economizer, and the gas-liquid separator is arranged between the evaporator and the compressor.

[0010] Preferably, a main electronic expansion valve is installed between the refrigerant pipeline and the evaporator.

[0011] Preferably, a return air temperature sensor and an evaporation pressure sensor are installed on the refrigerant pipeline between the gas-liquid separator and the evaporator.

[0012] Preferably, an auxiliary pipeline is also installed on the economizer, the inlet of the auxiliary pipeline is connected to the refrigerant pipeline between the economizer and the evaporator, the outlet of the auxiliary pipeline is connected to the air supply port of the compressor, and the refrigerant pipeline and the auxiliary pipeline exchange heat through the economizer.

[0013] Preferably, a heating belt is provided on the gas-liquid separator, and a crankcase heating belt is provided on the compressor.

[0014] The control method of the above-mentioned variable frequency high-temperature heat pump unit includes two parts: frequency control and boost control; in the compressor frequency, the frequency modulation cycle is dynamically controlled by the temperature difference between the outlet water temperature of the water pipeline and the user-set temperature, and the frequency modulation amplitude of the compressor in each frequency modulation cycle is dynamically adjusted by the temperature difference between the outlet water temperature of the water pipeline and the user-set temperature; in the boost control, when the outlet water temperature of the water pipeline is lower than the user-set temperature, the boost water pump is turned on to replenish the pressure of the water pipeline; when the outlet water temperature of the water pipeline is higher than the user-set temperature, the boost water pump is turned off.

[0015] The beneficial effects of the technical solution of the present invention are as follows: the above mechanism can provide high-temperature hot water within the water temperature range of 35-70°C; the booster water pump can provide high-temperature hot water within the water temperature range of 90-130°C for the heat pump unit; the booster water pump and the water tank can timely replenish water for the water pipeline, and control the flow and pressure in the water pipeline, thereby making the heat pump unit run stably; The above units can also replace gas boilers, coal-fired boilers, electric boilers and other heating equipment, and can be widely used in electroplating plants, slaughterhouses, petrochemical plants, dairy plants and other places with waste heat recovery needs. It can reduce the emission of atmospheric pollutants such as carbon dioxide and sulfur dioxide, which is beneficial to environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the system diagram of the variable frequency high temperature heat pump unit; Figure 2 This is the control flow chart of the variable frequency high temperature heat pump unit.

[0017] Figure numerals: 1, compressor; 2, high-pressure switch; 3, exhaust temperature sensor; 4, exhaust pipe needle valve; 5, condenser; 6, first safety valve; 7, condensing pressure sensor; 8, liquid storage tank; 9, economizer; 10, auxiliary electronic expansion valve; 11, copper mesh filter; 12, drying filter; 13, main electronic expansion valve; 14, evaporator; 15, evaporation pressure sensor; 16, heating belt; 17, gas-liquid separator; 18, suction pipe needle valve; 19, low-pressure switch ; 20. Crankcase heating belt; 21. Intermediate pressure sensor; 22. Air supply temperature sensor; 23. Condensing temperature sensor; 24. Water outlet temperature sensor; 25. Water inlet temperature sensor; 26. Economizer outlet temperature sensor; 27. Inlet temperature sensor; 28. Outlet temperature sensor; 29. ​​Return air temperature sensor; 30. Pressure sensor; 31. Second safety valve; 32. Water outlet valve; 33. Circulating water pump; 34. Water supply valve; 35. Booster water pump; 36. Water tank. DETAILED DESCRIPTION

[0018] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0019] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0020] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more, unless otherwise clearly specified.

[0021] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature. Example

[0023] like Figure 1 The variable frequency high temperature heat pump unit shown includes a refrigerant pipeline and a water pipeline; a compressor 1, a condenser 5 and an evaporator 14 are installed on the refrigerant pipeline, and the refrigerant can circulate in the refrigerant pipeline; the refrigerant pipeline and the water pipeline are both connected to the condenser 5, and the refrigerant pipeline and the water pipeline exchange heat through the condenser 5; The water tank is connected to the water pipeline through a booster water pump 35, and the booster water pump 35 can deliver the water in the water tank 36 to the water pipeline for water replenishment and pressure replenishment operations.

[0024] With such arrangement, the above mechanism can provide high-temperature hot water within the water temperature range of 35-70°C; the booster water pump 35 can provide high-temperature hot water within the water temperature range of 90-130°C for the heat pump unit; the booster water pump 35 and the water tank 36 can replenish water to the water pipeline in time, and control the flow and pressure in the water pipeline, thereby making the heat pump unit operate stably.

[0025] The above units can also replace gas boilers, coal-fired boilers, electric boilers and other heating equipment, and can be widely used in electroplating plants, slaughterhouses, petrochemical plants, dairy plants and other places with waste heat recovery needs. It can reduce the emission of atmospheric pollutants such as carbon dioxide and sulfur dioxide, which is beneficial to environmental protection.

[0026] In this embodiment, a water supply valve 34 is provided at the outlet of the booster water pump 35. By controlling the water supply valve 34, it is possible to control whether the water in the water tank 36 flows into the water pipeline. A second safety valve 31, a water inlet valve and a water outlet valve 32 are also installed on the water pipeline. The water outlet valve is provided at the outlet of the water pipeline, the water inlet valve is provided at the inlet of the water pipeline, and the second safety valve 31 is provided between the condenser 5 and the water outlet valve. Such a setting can effectively control the flow of the water pipeline; when the water pressure exceeds a predetermined value, the safety valve will release the pressure protectively.

[0027] In this embodiment, a pressure sensor 30 is installed on the water pipeline, and the pressure in the water pipeline is detected by the pressure sensor 30; the pressure sensor 30 is installed on the outlet side of the condenser 5. Further, an inlet water temperature sensor 25 and an outlet water temperature sensor 24 are installed on the water pipeline, and the inlet water temperature sensor 25 is arranged at the inlet of the condenser 5, and the outlet water temperature sensor 24 is installed at the outlet of the condenser 5. In this arrangement, the pressure and temperature in the water pipeline are detected by the sensor, and the working state of the heat pump unit can be effectively detected and controlled.

[0028] In this embodiment, a circulating water pump 33 is installed on the water pipeline, and the circulating water pump 33 is located between the condenser 5 and the booster water pump 35 .

[0029] In this embodiment, an economizer 9, a liquid storage tank 8 and a gas-liquid separator 17 are also installed on the refrigerant pipeline. The economizer 9 is arranged between the condenser 5 and the evaporator 14, the liquid storage tank 8 is arranged between the condenser 5 and the economizer 9, and the gas-liquid separator 17 is arranged between the evaporator 14 and the compressor 1. In this way, the economizer 9 is configured to ensure that the compressor 1 becomes a quasi-two-stage compression scroll compressor 1, expanding the operating range of the compressor 1; the liquid storage tank is configured to ensure that the electronic expansion valve can reliably adjust the refrigerant flow rate, avoid the flash refrigerant gas from affecting the throttling effect, and at the same time ensure that the liquid refrigerant entering the electronic expansion valve contains the lowest gaseous refrigerant.

[0030] Further preferably, a main electronic expansion valve 13 is installed on the refrigerant pipeline, and the main electronic expansion valve 13 is arranged between the economizer 9 and the evaporator 14; a drying filter 12 is also installed on the refrigerant pipeline, and the drying filter 12 is arranged between the economizer 9 and the main electronic expansion valve 13.

[0031] A return air temperature sensor 29 and an evaporation pressure sensor 15 are installed on the refrigerant pipeline between the gas-liquid separator 17 and the evaporator 14 .

[0032] A low-pressure switch 19 and a suction pipe needle valve 18 are installed on the refrigerant pipeline. The low-pressure switch 19 is arranged between the gas-liquid separator 17 and the compressor 1 , and the suction pipe needle valve 18 is arranged between the low-pressure switch and the gas-liquid separator 17 .

[0033] A high-pressure switch 2, an exhaust temperature sensor 3 and an exhaust pipe needle valve 4 are installed on the refrigerant pipeline. The high-pressure switch 2 is arranged between the compressor 1 and the condenser 5, the exhaust pipe needle valve 4 is arranged between the high-pressure switch and the condenser 5, and the exhaust temperature sensor 3 is arranged between the high-pressure switch and the condenser 5.

[0034] A first safety valve 6 is provided on the condenser 5, and a condensation pressure sensor 7 is provided between the condenser 5 and the liquid storage tank 8; An economizer outlet temperature sensor 26 is installed on the refrigerant pipeline, and the economizer outlet temperature sensor is arranged at the outlet of the economizer; A condensing temperature sensor 23 is provided between the liquid storage tank 8 and the economizer 9 ; an inlet temperature sensor 27 and an outlet temperature sensor 28 are installed on the evaporator 9 .

[0035] With such a configuration, the above-mentioned sensors can enable the heat pump unit to operate reliably and accurately according to predetermined rules: the main and auxiliary circuits use electronic expansion valve throttling; at the same time, the outlet temperature of condenser 5 and the outlet temperature of economizer 9 are configured to monitor the condensation temperature and the cooling effect of economizer 9. Prevent the condensation temperature from being too high and check the cooling effect of economizer 9. The outlet temperature sensor of condenser 5 is used to monitor the condensation temperature to prevent the condensation temperature from being too high, which may cause the electronic expansion valve to fail; at the same time, the outlet temperature of condenser 5 and the outlet temperature of economizer 9 are used to monitor the degree of supercooling generated by economizer 9. In this embodiment, an auxiliary pipeline is also installed on the economizer 9, the inlet of the auxiliary pipeline is connected to the refrigerant pipeline between the economizer 9 and the evaporator 14, the outlet of the auxiliary pipeline is connected to the air supply port of the compressor 1, and the refrigerant pipeline and the auxiliary pipeline exchange heat through the economizer 9.

[0036] Further preferably, an auxiliary electronic expansion valve 10 is installed on the auxiliary pipeline, and the auxiliary electronic expansion valve 10 is arranged between the economizer 9 and the refrigerant pipeline; a copper mesh filter 11 is also installed on the auxiliary pipeline, and the copper mesh filter 11 is arranged between the auxiliary electronic expansion valve 10 and the refrigerant pipeline; an intermediate pressure sensor 21 and an air supply temperature sensor 22 are installed on the auxiliary pipeline between the compressor 1 and the economizer 9.

[0037] In this embodiment, a heating belt 16 is provided on the gas-liquid separator 17 to prevent the refrigerant liquid from migrating into the gas-liquid separator 17 during a long shutdown process, causing the system to fail to start normally. A crankcase heating belt 20 is provided on the compressor 1.

[0038] In this embodiment, the compressor 1 is a variable frequency scroll compressor 1, so that the refrigeration capacity of the compressor 1 is adjustable. Example

[0039] A control method is used to control the above variable frequency high temperature heat pump unit, the control method includes two parts: frequency control and boost control; like Figure 2 As shown, in the compressor frequency, the frequency modulation cycle is dynamically controlled by the temperature difference between the outlet water temperature of the water pipeline and the temperature set by the user, and the frequency modulation amplitude of the compressor in each frequency modulation cycle is dynamically adjusted by the temperature difference between the outlet water temperature of the water pipeline and the temperature set by the user; this can solve the system problems caused by the large frequency increase and decrease caused by PID regulation, and can give full play to the advantages brought by PID regulation, ensuring the stability of the outlet water temperature and making the unit operation more energy-saving and reliable.

[0040] During boost control, when the outlet water temperature of the water pipeline is lower than the user-set temperature, the boost water pump starts to replenish the pressure of the water pipeline; when the outlet water temperature of the water pipeline is higher than the user-set temperature, the boost water pump shuts down.

[0041] In this embodiment, during unit startup, the compressor is turned on after the circulating water pump and the main electronic expansion valve; wherein, the main electronic expansion valve maintains the initial opening for N seconds before being adjusted; specifically, the compressor is started 10 seconds after the main electronic expansion valve is opened; and the initial opening of the main electronic expansion valve is 50% of its full opening steps, and the main electronic expansion valve maintains the initial opening for 90 seconds before being adjusted.

[0042] Further preferably, before the unit is started for the first time, the water temperature on the evaporation side of the unit should be above 35°C, and the water temperature on the condensation side of the unit should be above 40°C before the compressor can operate.

[0043] Further preferably, before the compressor is started, the unit is powered in advance so that the unit's crankcase heater and heating belt can work in advance; wherein, the crankcase heater and the gas-liquid separator heating belt should work for no less than 6 hours.

[0044] In this embodiment, after the compressor is started, it runs at the initial frequency for M time and then enters the automatic adjustment state; wherein the initial frequency of the compressor is the lower limit of its operating frequency. Specifically, taking a compressor with an upper frequency limit of 130.0HZ and a lower frequency limit of 40.0HZ as an example, the compressor starts with an initial frequency of 40HZ and enters the automatic adjustment state after stabilizing for 3 minutes. This can ensure that the unit operates in the best working condition and operates safely.

[0045] In this embodiment, when adjusting the operating frequency of the compressor, it is first determined whether the operating frequency needs to be adjusted. If it needs to be changed, the operating frequency of the compressor is adjusted according to the difference between the user-set temperature and the outlet water temperature. Otherwise, the compressor operates in the current state.

[0046] It is further preferred that the compressor operating frequency needs to be adjusted according to the user-set temperature and the outlet water temperature; specifically, when the unit is in the loading area, the compressor operating frequency is increased; when the unit is in the holding area, the current compressor operating frequency is maintained; when the unit is in the unloading area, the unit reduces the compressor operating frequency. Wherein, loading area = outlet water temperature ≥ target temperature + upper limit of adjustment temperature difference; holding area = target temperature + lower limit of adjustment temperature difference > outlet water temperature < target temperature + upper limit of adjustment temperature difference; unloading area = outlet water temperature ≤ target temperature + lower limit of adjustment temperature difference; where both the lower limit of adjustment temperature difference and the upper limit of adjustment temperature difference are preset values.

[0047] Further preferably, the unit is equipped with a built-in PID controller, which can calculate the PID output frequency according to the user-set temperature and the outlet water temperature; wherein, the calculation method of the PID output frequency can refer to public documents such as publication numbers CN113834187A, CN108954892A and CN104833102A.

[0048] Further preferably, when the compressor operating frequency needs to be changed, the compressor operating frequency is adjusted according to the difference between the user-set temperature and the outlet water temperature. Specifically, the compressor operating frequency is adjusted as follows: frequency modulation amplitude = (temperature difference value - frequency modulation temperature difference lower limit) / (frequency modulation temperature difference upper limit - frequency modulation temperature difference lower limit) * (frequency modulation amplitude upper limit - frequency modulation amplitude lower limit) + frequency modulation amplitude lower limit; wherein, the temperature difference value is the difference between the user-set temperature and the outlet water temperature, the frequency modulation amplitude upper limit and the frequency modulation amplitude lower limit are both system settings, and the frequency modulation temperature difference upper limits are both preset values. Further, when the temperature difference value is negative, the temperature difference value is multiplied by -1 to always keep the temperature difference value at a positive value. Further, when the temperature difference value is greater than the allowable temperature difference upper limit, the temperature difference value is the allowable temperature difference upper limit; wherein the allowable temperature difference upper limit is a preset value. Taking the calculated temperature difference = 4.0℃, the set temperature difference upper limit = 5.0℃, the set temperature difference lower limit = 0.0℃, the frequency modulation amplitude upper limit = 5.0 HZ, the frequency modulation amplitude lower limit = 1.0 HZ and the frequency modulation amplitude = X as an example, X = (4.0- 0.0℃ / (5.0-0.0℃) * (5.0 HZ -1.0 HZ)+1.0 HZ. It is calculated that the frequency modulation amplitude of each time period calculated by the current temperature difference is 4.2HZ.

[0049] Further preferably, when the compressor operating frequency needs to be changed, the frequency modulation period of the compressor is adjusted according to the difference between the user set temperature and the outlet water temperature; specifically, the frequency modulation period = (temperature difference value - frequency modulation temperature difference lower limit) / (frequency modulation temperature difference upper limit - frequency modulation temperature difference lower limit) * (maximum frequency modulation period - minimum frequency modulation period) + minimum frequency modulation period; wherein the maximum frequency modulation period and the minimum frequency modulation period are both preset values. Taking the temperature difference value = 3.0℃, the set temperature difference value upper limit = 5.0℃, the set temperature difference value lower limit = 0.0℃, the minimum frequency modulation period = 5.0 S, the maximum frequency modulation period = 20.0 S, and the frequency modulation period = X as an example, X = (3.0- 0.0℃ / (5.0-0.0℃) * (20.0 S -5.0 S) + 1.0 HZ. The frequency modulation period is calculated to be 11.0 S.

[0050] Take the condition of frequency modulation amplitude = 4.2HZ and frequency modulation period = 11.0S as an example: when the unit is in the loading area, PID output frequency – 2.0HZ > current frequency < upper frequency limit, the current frequency increases by 4.2HZ every 11.0S until it reaches the PID output frequency or the upper frequency limit, then the frequency increase stops. When the unit is in the holding area: current frequency = PID output frequency ±2.0HZ, no frequency increase or decrease. When the unit is in the unloading area: PID output frequency + 2.0HZ < current frequency > lower frequency limit, the current frequency decreases by 4.2HZ every 11.0S until it reaches the PID output frequency or the lower frequency limit, then the frequency reduction stops.

[0051] In order to solve the PID control blind spot and make the PID action timely, in this embodiment, the unit has a built-in timer instruction. When the compressor is in a frequency reduction state and the PID output frequency is less than the compressor frequency lower limit, the timer instruction is triggered; During the operation of the timer command, if the unit always meets the two conditions that the compressor is in the frequency reduction state and the PID output frequency is less than the compressor frequency lower limit, the manual intervention state will be triggered after the timer command ends, and the PID output frequency will be forcibly specified as the compressor frequency lower limit; During the operation of the timer command, if the unit cannot meet any of the two conditions that the compressor is in a frequency reduction state and the PID output frequency is less than the lower limit of the compressor frequency, the timer command ends and the unit operates normally. This setting shields the blind area of ​​the compressor in the 0HZ~20HZ range, allowing the PID control to quickly adjust according to temperature changes.

[0052] In order to ensure stable operation of the unit and avoid operation under extreme conditions, in this embodiment, the operating frequency of the compressor is controlled according to the condensing pressure and the evaporating pressure.

[0053] Specifically: when the system condensing pressure is detected to be greater than or equal to 25 bar, the compressor operating frequency remains unchanged; when the system condensing pressure is detected to be greater than 25.1 bar, the compressor operating frequency is reduced by 0.5 Hz for every 0.1 bar overshoot, to prevent the unit from operating unstably or causing an alarm due to continuous pressure increase; When it is detected that the system evaporation pressure is less than or equal to 1 bar, the compressor operating frequency stops loading and the compressor maintains the current operating frequency to prevent the compressor capacity from loading too quickly and causing a low pressure alarm; when the evaporation pressure is greater than 1.5 bar, the compressor returns to normal loading state.

[0054] In this embodiment, since the outlet water temperature of the unit is as high as 130°C, the pressure in the corresponding water pipeline must be guaranteed at each temperature point. If the pressure is low, the hot water will boil and cannot reach the set temperature; Therefore, a corresponding pressure value needs to be set at each temperature point, and the pressure in the current water pipeline is detected by the pressure sensor, and the pressure corresponding to the current outlet water temperature is compared with the pressure corresponding to the preset outlet water temperature; if the pressure corresponding to the current outlet water temperature is lower than the pressure corresponding to the preset outlet water temperature, the booster pump is turned on for boosting, and if the pressure corresponding to the current outlet water temperature is higher than the pressure corresponding to the preset outlet water temperature + 500pa, the booster pump is turned off. The corresponding values ​​of water temperature and pressure can be referred to Table 1.

[0055] Table 1: Correspondence between boiling point and pressure of water In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0056] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A variable frequency high temperature heat pump unit, characterized in that: The invention comprises a refrigerant pipeline and a water pipeline; a compressor (1), a condenser (5) and an evaporator (14) are installed on the refrigerant pipeline, and the refrigerant can circulate in the refrigerant pipeline; the refrigerant pipeline and the water pipeline are both connected to the condenser (5), and the refrigerant pipeline and the water pipeline exchange heat through the condenser (5); The water tank is connected to the water pipeline via a booster water pump (35), and the booster water pump (35) can deliver water in the water tank (36) to the water pipeline for water replenishment and pressure replenishment operations.

2. A variable frequency high temperature heat pump unit according to claim 1, characterized in that: A water supply valve (34) is provided at the outlet of the booster water pump (35), and a second safety valve (31) for pressure relief is also installed on the water pipeline.

3. A variable frequency high temperature heat pump unit according to claim 1, characterized in that: A pressure sensor (30) for controlling the start and stop of the booster water pump (35) is installed on the water pipeline, and the pressure sensor (30) is arranged on the outlet side of the condenser (5).

4. A variable frequency high temperature heat pump unit according to claim 1, characterized in that: An inlet water temperature sensor (25) and an outlet water temperature sensor (24) are installed on the water pipeline; the inlet water temperature sensor (25) is arranged at the inlet of the condenser (5), and the outlet water temperature sensor (24) is installed at the outlet of the condenser (5).

5. The variable frequency high temperature heat pump unit according to claim 1, characterized in that: An economizer (9), a liquid storage tank (8) and a gas-liquid separator (17) are also installed on the refrigerant pipeline. The economizer (9) is arranged between the condenser (5) and the evaporator (14), the liquid storage tank (8) is arranged between the condenser (5) and the economizer (9), and the gas-liquid separator (17) is arranged between the evaporator (14) and the compressor (1).

6. A variable frequency high temperature heat pump unit according to claim 5, characterized in that: A main electronic expansion valve (13) is also installed on the refrigerant pipeline. The main electronic expansion valve (13) is arranged between the economizer (9) and the evaporator (14).

7. A variable frequency high temperature heat pump unit according to claim 5, characterized in that: A return air temperature sensor (29) and an evaporation pressure sensor (15) are installed on the refrigerant pipeline between the gas-liquid separator (17) and the evaporator (14).

8. The variable frequency high temperature heat pump unit according to claim 1, characterized in that: An auxiliary pipeline is also installed on the economizer (9), the inlet of the auxiliary pipeline is connected to the refrigerant pipeline between the economizer (9) and the evaporator (14), the outlet of the auxiliary pipeline is connected to the air supply port of the compressor (1), and the refrigerant pipeline and the auxiliary pipeline exchange heat through the economizer (9).

9. The variable frequency high temperature heat pump unit according to claim 1, characterized in that: A heating belt (16) is provided on the gas-liquid separator (17), and a crankcase heating belt (20) is provided on the compressor (1).

10. A control method for a variable frequency high temperature heat pump unit according to any one of claims 1 to 9, characterized in that: It includes two parts: frequency control and boost control; In the compressor frequency, the frequency modulation cycle is dynamically controlled by the temperature difference between the outlet water temperature of the water pipeline and the user-set temperature, and the frequency modulation amplitude of the compressor in each frequency modulation cycle is dynamically adjusted by the temperature difference between the outlet water temperature of the water pipeline and the user-set temperature; During boost control, when the outlet water temperature of the water pipeline is lower than the user-set temperature, the boost water pump starts to replenish the pressure of the water pipeline; when the outlet water temperature of the water pipeline is higher than the user-set temperature, the boost water pump shuts down.

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