Heat pump system and control method thereof

Abstract

The invention provides a heat pump system and a control method thereof, and relates to the technical field of heat pump systems.The heat pump system comprises a compressor, an exhaust port of the compressor is connected with an oil separator through a pipeline, one end of the oil separator is connected with a shell and tube condenser, an outlet of the shell and tube condenser is connected with an economizer main cavity, and the economizer main cavity is connected with a main expansion valve; the main expansion valve is connected with the evaporator, and the evaporator is connected with an air return port of the compressor; in the backwashing process, blocked oil liquid is discharged out of the filter element, backwashing gas is filtered, follow-up use is prevented from being disturbed, resetting is achieved through the first spring and the second spring after backwashing is completed so as to be used for washing of the next round, and the backwashing efficiency is improved. By means of the system, blocked oil can be flushed, and the situation that due to excessive oil blockage, the operation efficiency and safety of the whole unit are affected is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pump systems, and in particular to a heat pump system and a control method thereof. Background Art

[0002] The heat pump system transfers heat through four core components (compressor, condenser, expansion valve, and evaporator). During the use of the compressor, an oil separator is needed to separate the gas discharged from it. For example, the patent announcement number CN217402909U is a new vertical oil separator structure for a compressor, which includes: an oil separator shell, a top cover is fixedly connected to the top of the oil separator shell, an oil separator exhaust outlet is opened in the middle of the top cover, and the inner wall surface of the oil separator shell is coated with refrigeration oil; a starting exhaust flow channel is formed on the bottom of the outer wall of the oil separator shell, and a terminal exhaust flow channel is formed on the top of the outer wall of the oil separator shell, the terminal exhaust flow channel is connected to the interior of the oil separator shell, and the starting exhaust flow channel and the terminal exhaust flow channel are connected through the middle exhaust flow channel; the bottom of the oil separator exhaust outlet is connected to an exhaust guide plate.

[0003] During operation, the above-mentioned oil separator separates oil and gas through the filter element. However, after long-term operation, the outer side of the filter element hole will be clogged with oil, which will cause the filter element to be clogged during operation of the oil separator. Not only can the oil and gas be separated, but the internal gas cannot be discharged, which in turn causes the pressure inside the oil separator to be too high, which is prone to safety hazards. For this reason, the present application designs a heat pump system to ensure that the operating efficiency of the entire unit will not be affected by the blockage inside the oil separator during operation. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a heat pump system and a control method thereof, which solves the problem that the oil separator in the heat pump system may be blocked by a filter element during long-term use, resulting in excessive pressure inside the oil separator and thus causing safety hazards.

[0005] To achieve the above object, the technical solution adopted by the present invention is: A heat pump system, comprising a compressor, wherein the compressor exhaust port is connected to an oil separator through a pipeline, one end of the oil separator is connected to a shell and tube condenser, the shell and tube condenser outlet is connected to an economizer main cavity, the economizer main cavity is connected to a main expansion valve, the main expansion valve is connected to an evaporator, and the evaporator is connected to a compressor return air port; The lower end of the oil separator is connected to an oil tank, the oil tank is connected to the oil inlet of the oil cooler, the oil cooler is connected to the oil return port of the compressor and an oil temperature sensor is installed on the pipeline; The inlet of the economizer sub-cavity is connected to the economizer expansion valve, the outlet of the economizer sub-cavity is connected to the oil cooler expansion valve, the oil cooler expansion valve is connected to the oil cooler air inlet, and the oil cooler air outlet is connected to another air return port of the compressor; A branch pipe is provided on the pipeline between the main expansion valve and the economizer and is connected with an electric bypass valve. The electric bypass valve is connected to the pipeline between the shell and tube condenser and the main cavity of the economizer through the branch pipe.

[0006] Preferably, the oil separator comprises a shell, an upper cover is arranged on the upper side of the shell, an oil outlet valve is arranged on the lower side of the shell, a feed pipe is installed on one side of the shell, and the feed pipe is connected to the exhaust port of the compressor; The oil outlet valve is connected to the oil tank through a pipeline, the upper cover is provided with an air outlet pipe, and the air outlet pipe is connected to the shell and tube condenser through a pipeline. A buffer component for preventing excessive pressure is provided on one side of the shell, and a separation component for separation is installed between the upper cover and the shell.

[0007] Preferably, the separation component includes a fixed cover, a screw hole is opened on the surface of the shell, a bolt is arranged on the outer side of the upper cover, the bolt passes through the fixed cover and is threadedly engaged with the screw hole, a positioning frame is installed inside the fixed cover, a filter element is installed inside the positioning frame, and a plurality of through holes are opened on the surface of the fixed cover.

[0008] Preferably, a collecting base is provided at the bottom of the fixed cover, a through socket is installed on one side of the upper cover, an oil extraction pipe is installed inside the through socket through a nut, the lower end of the oil extraction pipe is located inside the collecting base, and a liquid extraction pump is provided at the upper end of the oil extraction pipe, and the liquid extraction pump is connected to the oil tank.

[0009] Preferably, the buffer assembly includes an extension tube, which is arranged on one side of the shell, a sealing ring is arranged at one end of the extension tube, a sealing piston is arranged for movable sealing inside the sealing ring, a limiting ring is installed on the inner wall of the extension tube, and a compression spring is installed between the limiting ring and the sealing piston.

[0010] Preferably, an expansion rack is fixedly installed on the outer side of the shell, a buffer tank is fixedly installed inside the expansion rack, a one-way valve is installed at the lower end of the buffer tank, a connecting pipe is provided at the upper end of the buffer tank, and the one-way valve is connected to the expansion pipe.

[0011] Preferably, an air guide pipe is installed at the air outlet end of the one-way valve, an extrusion cover is installed on the air guide pipe body through a sealing slip ring, and an auxiliary spring is installed between the extrusion cover and the bottom of the buffer tank.

[0012] Preferably, a recoil pipe is installed in the center of the upper cover, the upper end of the recoil pipe is connected to the connecting pipe, a movable groove is opened inside the recoil pipe, a movable sleeve is installed inside the movable groove through a first spring, and a nozzle is arranged inside the movable sleeve.

[0013] Preferably, a transfer shell is provided at the bottom of the upper cover, and an air guide cover and an extension cover are provided at the bottom of the transfer shell, respectively. The air guide cover is aligned with the air outlet pipe, and the extension cover is aligned with the recoil pipe. An air guide turntable is rotatably installed inside the extension cover through a rotating shaft, and a plurality of scattered holes are opened on the outside of the extension cover; The inner wall of the transfer shell is provided with a matching slide rail, a blocking slider is slidably installed inside the matching slide rail, a second spring is installed between the blocking slider and the transfer shell, and the blocking slider and the end of the movable sleeve are both inclined and limitedly matched.

[0014] A control method for a heat pump system comprises the following steps: S1: Before the unit is started, the economizer expansion valve is fully open and the oil cooler expansion valve is fully closed; S2: After the unit is started, when the oil temperature sensor detects that the oil temperature is lower than the set value during the startup phase, the electric bypass valve is fully opened, the oil cooler expansion valve remains fully closed, and all refrigerant directly enters the main expansion valve through the electric bypass valve to participate in the main system refrigeration cycle, allowing the unit to achieve rapid heating; S3: When the oil temperature sensor detects that the oil temperature is higher than the set value, the electric bypass valve is gradually closed to full close, and the oil cooler expansion valve is gradually opened, and the oil temperature is controlled within the target range by adjusting the opening of the oil cooler expansion valve; S4: After the system runs stably, under the premise that the oil temperature is controlled within the target range as the first control factor, the system gradually reduces the opening of the economizer expansion valve and opens the oil cooler expansion valve to control the inlet subcooling of the main expansion valve to the target range, thereby improving the unit operation efficiency; S5: After the system compressor is fully loaded, the hot water temperature of the shell and tube condenser is lower than the target value. Under the premise that the oil temperature is controlled within the target range as the first control factor, the system gradually reduces the opening of the economizer expansion valve and opens the oil cooler expansion valve to control the inlet subcooling of the main expansion valve to the target range, thereby increasing the heating capacity of the unit.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This system can monitor the oil pressure and temperature of the heat pump unit in real time during operation to ensure that the unit's operating efficiency will not be affected by excessive oil temperature during continuous operation. When the oil temperature is too high, the electric bypass valve is gradually closed to full closure, and the oil cooler expansion valve is gradually opened. The oil temperature is controlled to be within the target range by adjusting the opening of the oil cooler expansion valve. After the system compressor is fully loaded, the hot water temperature of the shell and tube condenser is lower than the target value. Under the premise that the oil temperature is controlled within the target range as the first control factor, the system gradually reduces the opening of the economizer expansion valve and opens the oil cooler expansion valve to control the inlet subcooling of the main expansion valve to the target range, thereby increasing the heating capacity of the unit.

[0016] 2. The gas discharged from the compressor is introduced through the feed pipe, where the gas will be sprayed on the fixed cover. The through holes opened on the surface of the fixed cover allow the gas to enter the filter element and filter the oil contained in the gas so that the gas will be discharged along the air outlet pipe after passing through the filter element, thereby realizing the separation of the gas. During the separation process, as the amount of oil increases, the oil droplets will accumulate into oil liquid, causing part of the oil liquid to penetrate into the filter element. A collecting base is provided at the bottom of the fixed cover to collect the penetrated oil liquid. In order to avoid interference with the use of the filter element due to excessive accumulation of oil liquid, suction is provided inside the oil extraction pipe by starting the liquid extraction pump, and the bottom of the oil extraction pipe is provided at the collecting base, so that the oil liquid inside the collecting base is extracted outwardly. After the extraction, the liquid extraction pump stops and cooperates with the valve to close the oil extraction pipe channel to avoid affecting the subsequent separation effect.

[0017] 3. When the filter element is clogged by oil, the pressure inside the shell increases with the continuous intake of air through the feed pipe. During the process of increasing pressure, the sealing piston will shrink the pressure spring when subjected to the current pressure, and a gap will be created between the sealing piston and the sealing ring, thereby avoiding the problem of potential safety hazards caused by excessive pressure inside the shell, thereby ensuring the safety of the heat pump system during operation; The over-pressure gas enters the expansion pipe and then passes through the one-way valve, thereby entering the buffer tank and being located between the extrusion hood and the buffer tank. The internal space of the buffer tank can be changed, so that the buffer tank can collect the current gas and as the gas increases, the auxiliary spring contracts and the internal space of the buffer tank increases, thereby realizing backwashing charging. When the internal gas pressure of the buffer tank is greater than the pressure matched between the first spring and the second spring, the internal gas of the buffer tank will be transferred to the separation component for backwashing operation, and the auxiliary spring can be used to reduce the internal space of the buffer tank to ensure the continuity of the current gas during discharge and realize stable backwashing operation.

[0018] 4. When the charged gas is delivered to the recoil pipe, its pressure will be applied to the movable sleeve, causing the movable sleeve to move downward. During the movement, the movable sleeve is tilted and matched with the blocking slider to push open the blocking slider, so that the blocking slider blocks the air outlet pipe during the backwashing process to prevent the unfiltered gas from being discharged, and ensures that the current gas passes through the filter element in the reverse direction, and filters its own oil when backwashing the oil clogged inside the filter element. The filtered oil will fall into the collection base for subsequent processing. Through the above structure, the present application can discharge the clogged oil from the filter element during the backwashing process, and filter the backwashed gas to avoid interference with subsequent use. After the backwashing is completed, the first spring and the second spring are used to reset for the next round of flushing. Through the present application, the clogged oil can be flushed to avoid affecting the operating efficiency and safety of the entire unit due to excessive oil blockage. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of a heat pump system of the present invention; Figure 2 It is a three-dimensional structural diagram of the oil separator; Figure 3 It is a schematic diagram of the top view of the oil separator; Figure 4 yes Figure 3 Schematic diagram of the cross-section structure at AA in the middle; Figure 5 yes Figure 4 The enlarged structural diagram at a in the middle; Figure 6 yes Figure 4 The enlarged structural diagram at b in the middle; Figure 7 yes Figure 4 The enlarged structural diagram at c in the middle; Figure 8 yes Figure 3 Schematic diagram of the cross-section structure at BB; Fig. 9 yes Figure 8 The enlarged structural diagram at d in the middle; Fig.10 It is a schematic diagram of the front view structure of the oil separator; Fig.11 yes Fig.10 Schematic diagram of the cross-sectional structure at CC in the middle.

[0020] In the figure: 1. compressor; 2. oil separator; 201. shell; 2011. screw hole; 202. upper cover; 2021. bolt; 2022. air outlet pipe; 2023. recoil pipe; 2024. movable groove; 2025. first spring; 2026. movable sleeve; 2027. nozzle; 203. feed pipe; 204. buffer assembly; 2041. extension pipe; 2042. sealing ring; 2043. sealing piston; 2044. limit ring; 2045. pressure spring; 2046. extension frame; 2047. buffer tank; 2048. check valve; 2049. air guide pipe; 20410. extrusion cover; 20411. sealing slip ring; 20412. connecting pipe; 20413. auxiliary spring; 205. outlet Oil valve; 206, separation assembly; 2061, fixed cover; 2062, filter element; 2063, through hole; 2064, oil extraction pipe; 2065, collecting base; 2066, positioning frame; 2067, socket; 2068, liquid extraction pump; 207, transfer shell; 2071, blocking slider; 2072, second spring; 2073, air guide cover; 2074, extension cover; 2075, rotating shaft; 2076, air guide turntable; 2077, dispersion hole; 2078, matching slide rail; 3, shell and tube condenser; 4, economizer; 5, evaporator; 6, oil tank; 7, oil cooler; 8, oil temperature sensor; 9, main expansion valve; 901, electric bypass valve; 902, economizer expansion valve; 903, oil cooler expansion valve. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] like Figures 1 to 11 As shown, the heat pump system includes a compressor 1, the exhaust port of the compressor 1 is connected to the oil separator 2 through a pipeline, one end of the oil separator 2 is connected to the shell and tube condenser 3, the outlet of the shell and tube condenser 3 is connected to the main cavity of the economizer 4, the main cavity of the economizer 4 is connected to the main expansion valve 9, the main expansion valve 9 is connected to the evaporator 5, and the evaporator 5 is connected to the return air port of the compressor 1; The lower end of the oil separator 2 is connected to the oil tank 6, the oil tank 6 is connected to the oil inlet of the oil cooler 7, the oil cooler 7 is connected to the oil return port of the compressor 1 and an oil temperature sensor 8 is installed on the pipeline; The inlet of the 4th cavity of the economizer is connected to the economizer expansion valve 902, the outlet of the 4th cavity of the economizer is connected to the oil cooler expansion valve 903, the oil cooler expansion valve 903 is connected to the air inlet of the oil cooler 7, and the air outlet of the oil cooler 7 is connected to another air return port of the compressor 1; A branch pipe is provided on the pipeline between the main expansion valve 9 and the economizer 4 and is connected to an electric bypass valve 901 . The electric bypass valve 901 is connected to the pipeline between the shell and tube condenser 3 and the main cavity of the economizer 4 through the branch pipe.

[0023] The exhaust of compressor 1 is connected to oil separator 2, the outlet of oil separator 2 is connected to shell and tube condenser 3, the downstream of shell and tube condenser 3 is connected to the main cavity inlet of economizer 4, the main cavity outlet of economizer 4 is connected to main expansion valve 9 through pipeline, the main expansion valve 9 is connected to evaporator 5, and evaporator 5 is connected to the return air port of compressor 1. The above components and pipelines constitute the main loop of the heat pump system.

[0024] An oil temperature sensor 8 is arranged on the oil cooler 7 and the oil return port pipeline of the compressor 1 to detect the oil temperature; An oil pressure and temperature sensor is arranged at the inlet of the main expansion valve 9 to calculate the inlet subcooling degree of the main expansion valve 9; The electric bypass valve 901 performs bypass adjustment, and its opening range is 0% to 100%.

[0025] This system can monitor the oil pressure and temperature of the heat pump unit in real time during operation to ensure that the unit's operating efficiency will not be affected by excessive oil temperature during continuous operation. When the oil temperature is too high, the electric bypass valve 901 is gradually closed to full closure, and the oil cooler expansion valve 903 is gradually opened. The oil temperature is controlled to be within the target range by adjusting the opening of the oil cooler expansion valve 903. After the system compressor 1 is fully loaded, the hot water temperature of the shell and tube condenser 3 is lower than the target value. Under the premise that the oil temperature is controlled within the target range as the first control factor, the system gradually reduces the opening of the economizer expansion valve 902 and opens the oil cooler expansion valve 903 to control the inlet subcooling of the main expansion valve 9 to the target range, thereby increasing the heating capacity of the unit.

[0026] In this embodiment, the oil separator 2 includes a housing 201, an upper cover 202 is provided on the upper side of the housing 201, an oil outlet valve 205 is provided on the lower side of the housing 201, and a feed pipe 203 is installed on one side of the housing 201, and the feed pipe 203 is connected to the exhaust port of the compressor 1; The oil outlet valve 205 is connected to the oil tank 6 through a pipeline, the upper cover 202 is provided with an air outlet pipe 2022, and the air outlet pipe 2022 is connected to the shell and tube condenser 3 through a pipeline. A buffer component 204 for preventing excessive pressure is provided on one side of the shell 201, and a separation component 206 for separation is installed between the upper cover 202 and the shell 201.

[0027] In the present application, the separation component 206 includes a fixed cover 2061, a screw hole 2011 is opened on the surface of the shell 201, a bolt 2021 is arranged on the outside of the upper cover 202, the bolt 2021 passes through the fixed cover 2061 and is threadedly matched with the screw hole 2011, a positioning frame 2066 is installed inside the fixed cover 2061, a filter element 2062 is installed inside the positioning frame 2066, and a plurality of through holes 2063 are opened on the surface of the fixed cover 2061.

[0028] The oil separated by the oil separator 2 can be discharged and controlled through the oil outlet valve 205. Generally, the separated oil is discharged into the oil tank 6 when it is stored to a certain content. The separation component 206 can be quickly accessed by disassembling the bolts 2021, so that the filter element 2062 that has been used for a long time can be cleaned or replaced, thereby improving the operating efficiency of the entire heat pump unit.

[0029] It should be noted that a collecting base 2065 is provided at the bottom of the fixed cover 2061, a through socket 2067 is installed on one side of the upper cover 202, an oil extraction pipe 2064 is installed inside the through socket 2067 through a nut, the lower end of the oil extraction pipe 2064 is located inside the collecting base 2065, and a liquid extraction pump 2068 is provided at the upper end of the oil extraction pipe 2064, and the liquid extraction pump 2068 is connected to the oil tank 6.

[0030] The gas discharged from the compressor 1 is introduced through the feed pipe 203, wherein the gas will be sprayed on the fixed cover 2061, and the through hole 2063 opened on the surface of the fixed cover 2061 is used to make the gas enter the filter element 2062, and the oil contained in the gas is filtered, so that after the gas passes through the filter element 2062, the gas will be discharged through the air outlet pipe 2022, thereby realizing the separation of the gas. During the separation process, as the amount of oil increases, the oil droplets will accumulate into oil liquid, so that part of the oil liquid will penetrate into the filter element 2062, A collecting base 2065 is provided at the bottom of the fixed cover 2061 to collect the seeping oil. In order to prevent excessive accumulation of oil and interfere with the use of the filter element 2062, the inside of the oil extraction pipe 2064 is suctioned by starting the liquid pump 2068, and the bottom of the oil extraction pipe 2064 is provided at the collecting base 2065, so that the oil inside the collecting base 2065 can be pumped out. After the pumping, the liquid pump 2068 stops and cooperates with the valve to close the oil extraction pipe 2064 channel to avoid affecting the subsequent separation effect.

[0031] In the present application, the buffer assembly 204 includes an extension tube 2041, which is arranged on one side of the shell 201. A sealing ring 2042 is arranged at one end of the extension tube 2041. A sealing piston 2043 is arranged inside the sealing ring 2042 for movable sealing. A limiting ring 2044 is installed on the inner wall of the extension tube 2041, and a compression spring 2045 is installed between the limiting ring 2044 and the sealing piston 2043.

[0032] In the specific setting, an expansion frame 2046 is fixedly installed on the outside of the shell 201, a buffer tank 2047 is fixedly installed inside the expansion frame 2046, a one-way valve 2048 is installed at the lower end of the buffer tank 2047, a connecting pipe 20412 is provided at the upper end of the buffer tank 2047, and the one-way valve 2048 is connected to the expansion pipe 2041.

[0033] Among them, an air guide pipe 2049 is installed at the air outlet end of the one-way valve 2048, and an extrusion cover 20410 is installed on the body of the air guide pipe 2049 through a sealing slip ring 20411, and an auxiliary spring 20413 is installed between the extrusion cover 20410 and the bottom of the buffer tank 2047.

[0034] When the filter element 2062 is clogged by oil, the pressure inside the housing 201 increases as the feed pipe 203 continues to take in air. During the pressure increase, the sealing piston 2043 contracts the compression spring 2045 when subjected to the current pressure, and a gap is created between the sealing piston 2043 and the sealing ring 2042, thereby avoiding the problem of potential safety hazards caused by excessive pressure inside the housing 201, thereby ensuring the safety of the heat pump system during operation. And the over-pressure gas enters the extension pipe 2041 and then passes through the one-way valve 2048, thereby entering the buffer tank 2047 and being located between the extrusion cover 20410 and the buffer tank 2047. The internal space of the buffer tank 2047 can be changed, so that the buffer tank 2047 can collect the current gas and as the gas increases, the auxiliary spring 20413 contracts, and the internal space of the buffer tank 2047 increases, thereby realizing backwashing charging. When the internal gas pressure of the buffer tank 2047 is greater than the pressure matched between the first spring 2025 and the second spring 2072, the internal gas of the buffer tank 2047 will be transferred to the separation assembly 206 for backwashing operation, and the auxiliary spring 20413 can be used to reduce the internal space of the buffer tank 2047 to ensure the continuity of the current gas during discharge and realize stable backwashing operation.

[0035] In the present application, a recoil tube 2023 is installed in the center of the upper cover 202, the upper end of the recoil tube 2023 is connected to the connecting tube 20412, a movable groove 2024 is opened inside the recoil tube 2023, a movable sleeve 2026 is installed inside the movable groove 2024 through a first spring 2025, and a nozzle 2027 is arranged inside the movable sleeve 2026.

[0036] In the specific configuration, a transfer shell 207 is provided at the bottom of the upper cover 202, and an air guide cover 2073 and an extension cover 2074 are provided at the bottom of the transfer shell 207, respectively. The air guide cover 2073 is aligned with the air outlet pipe 2022, and the extension cover 2074 is aligned with the recoil pipe 2023. An air guide turntable 2076 is rotatably installed inside the extension cover 2074 through a rotating shaft 2075, and a plurality of dispersed holes 2077 are opened on the outside of the extension cover 2074; A matching slide rail 2078 is provided on the inner wall of the transfer shell 207, and a blocking slider 2071 is slidably installed inside the matching slide rail 2078. A second spring 2072 is installed between the blocking slider 2071 and the transfer shell 207. The ends of the blocking slider 2071 and the movable sleeve 2026 are both inclined and limited.

[0037] When the charged gas is sent into the recoil pipe 2023, its pressure will be applied to the movable sleeve 2026, causing the movable sleeve 2026 to move downward. During the movement, the movable sleeve 2026 is tilted and matched with the blocking slider 2071, thereby pushing the blocking slider 2071 open, so that the blocking slider 2071 blocks the air outlet pipe 2022 during the backwashing process to prevent the unfiltered gas from being discharged, and ensure that the current gas passes through the filter element 2062 in the reverse direction, realizing the reverse flushing of the oil blocked inside the filter element 2062 while also flushing its own oil. The filtered oil will fall into the collection base 2065 for subsequent processing. The above structure can enable the present application to discharge the blocked oil from the filter element 2062 during the backwashing process, and filter the backwashing gas to avoid interference with subsequent use. After the backwashing is completed, the first spring 2025 and the second spring 2072 are reset for the next round of flushing. The present application can flush the blocked oil to avoid affecting the operating efficiency of the entire unit due to excessive oil blockage.

[0038] A control method for a heat pump system comprises the following steps: S1: Before the unit is started, the economizer expansion valve 902 is fully opened and the oil cooler expansion valve 903 is fully closed; S2: After the unit is started, when the oil temperature sensor 8 detects that the oil temperature is lower than the set value during the startup phase, the electric bypass valve 901 is fully opened, and the oil cooler expansion valve 903 remains fully closed. All refrigerant directly enters the main expansion valve 9 through the electric bypass valve 901 to participate in the main system refrigeration cycle, so that the unit can achieve rapid heating; S3: When the oil temperature sensor 8 detects that the oil temperature is higher than the set value, the electric bypass valve 901 is gradually closed to full closure, and the oil cooler expansion valve 903 is gradually opened, and the oil temperature is controlled to the target range by adjusting the opening of the oil cooler expansion valve 903; S4: After the system is running stably, under the premise that the oil temperature is controlled within the target range as the first control factor, the system gradually reduces the opening of the economizer expansion valve 902 and opens the oil cooler expansion valve 903 to control the inlet subcooling of the main expansion valve 9 to the target range, thereby improving the unit operation efficiency; S5: After the system compressor 1 is fully loaded, the hot water temperature of the shell and tube condenser 3 is lower than the target value. Under the premise that the oil temperature is controlled within the target range as the first control factor, the system gradually reduces the opening of the economizer expansion valve 902 and opens the oil cooler expansion valve 903, and controls the inlet subcooling of the main expansion valve 9 to the target range, thereby increasing the heating capacity of the unit.

[0039] In S4, "after the system is running stably" means that after the target hot water temperature has been reached, the total refrigeration capacity of the refrigerant evaporation in the economizer 4 and the oil cooler 7 is increased through the linkage control of the economizer expansion valve 902 and the oil cooler expansion valve 903. The refrigerant refrigeration capacity in the oil cooler 7 is maintained unchanged, so that the oil temperature is maintained not exceeding the target temperature + / -5°C. This is the deviation that the compressor 1 can allow. The increased refrigerant evaporation refrigeration capacity occurs in the economizer 4, which serves to condense the high-pressure saturated refrigerant in the main circuit, thereby establishing a certain target supercooling degree. Supercooling can make the refrigerant liquid temperature lower than the saturation temperature, reduce the generation of flash gas during throttling, and retain more refrigerant in liquid state. After entering the evaporator 5, it can effectively evaporate and absorb heat, thereby improving the cooling capacity / heating capacity and energy efficiency. The increase in heating capacity causes the hot water temperature to deviate from the target value, and the target hot water temperature is controlled by adjusting the load of the compressor 1.

[0040] The difference between S5 and S4 is that the compressor 1 is fully loaded but the hot water temperature has not reached the target temperature. This means that the system heating capacity is lower than the demand. The total cooling capacity of the refrigerant evaporation in the economizer 4 and the oil cooler 7 is increased through the linkage control of the economizer expansion valve 902 and the oil cooler expansion valve 903. The cooling capacity of the refrigerant in the oil cooler 7 is maintained unchanged, so that the oil temperature is maintained at a temperature not exceeding the target temperature + / -5°C. This is the allowable deviation of the compressor 1. The increased cooling capacity of the refrigerant evaporation occurs in the economizer 4, which serves to condense the high-pressure saturated refrigerant in the main circuit, thereby establishing a certain target supercooling degree. Supercooling can make the refrigerant liquid temperature lower than the saturation temperature, reduce the generation of flash gas during throttling, and retain more refrigerant in liquid state. After entering the evaporator 5, it can effectively evaporate and absorb heat, thereby improving the cooling capacity, heating capacity and unit energy efficiency. Based on the heat pump unit using the screw compressor 1, in which the refrigerator uses R134a refrigerant, a reasonable design of the economizer 4 can effectively increase the system heating capacity by 5%-10%.

[0041] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A heat pump system comprising a compressor (1), characterized in that: The exhaust port of the compressor (1) is connected to the oil separator (2) via a pipeline; one end of the oil separator (2) is connected to the shell and tube condenser (3); the outlet of the shell and tube condenser (3) is connected to the main cavity of the economizer (4); the main cavity of the economizer (4) is connected to the main expansion valve (9); the main expansion valve (9) is connected to the evaporator (5); and the evaporator (5) is connected to the air return port of the compressor (1); The lower end of the oil separator (2) is connected to an oil tank (6), the oil tank (6) is connected to the oil inlet of an oil cooler (7), the oil cooler (7) is connected to the oil return port of the compressor (1) and an oil temperature sensor (8) is installed on the pipeline; The inlet of the secondary cavity of the economizer (4) is connected to the economizer expansion valve (902), the outlet of the secondary cavity of the economizer (4) is connected to the oil cooler expansion valve (903), the oil cooler expansion valve (903) is connected to the air inlet of the oil cooler (7), and the air outlet of the oil cooler (7) is connected to another air return port of the compressor (1); A branch pipe is provided on the pipeline between the main expansion valve (9) and the economizer (4) and is connected to an electric bypass valve (901); the electric bypass valve (901) is connected to the pipeline between the shell and tube condenser (3) and the main cavity of the economizer (4) through the branch pipe; The oil separator (2) comprises a housing (201), an upper cover (202) is arranged on the upper side of the housing (201), a buffer component (204) for preventing excessive pressure is arranged on one side of the housing (201), and a separation component (206) for separation is installed between the upper cover (202) and the housing (201); The separation component (206) comprises a fixed cover (2061), a positioning frame (2066) is installed inside the fixed cover (2061), and a filter element (2062) is installed inside the positioning frame (2066); The buffer assembly (204) comprises an extension tube (2041), the extension tube (2041) being arranged on one side of the housing (201), a sealing ring (2042) being arranged at one end of the extension tube (2041), a sealing piston (2043) being arranged inside the sealing ring (2042) for movable sealing, an extension frame (2046) being fixedly mounted on the outside of the housing (201), a buffer tank (2047) being fixedly mounted inside the extension frame (2046), a one-way valve (2048) being mounted at the lower end of the buffer tank (2047), a connecting tube (20412) being arranged at the upper end of the buffer tank (2047), and the one-way valve (2048) being connected to the extension tube (2041); A through socket (2067) is installed on one side of the upper cover (202), and an oil extraction pipe (2064) is installed inside the through socket (2067) via a nut; A recoil pipe (2023) is installed at the center of the upper cover (202), the upper end of the recoil pipe (2023) is connected to the connecting pipe (20412), a transfer shell (207) is arranged at the bottom of the upper cover (202), and an air guide cover (2073) and an extension cover (2074) are respectively arranged at the bottom of the transfer shell (207), and the extension cover (2074) is aligned with the recoil pipe (2023).

2. The heat pump system according to claim 1, characterized in that: An oil outlet valve (205) is provided on the lower side of the shell (201), and a feed pipe (203) is installed on one side of the shell (201), wherein the feed pipe (203) is connected to the exhaust port of the compressor (1); The oil outlet valve (205) is connected to the oil tank (6) via a pipeline, and the upper cover (202) is provided with an air outlet pipe (2022), and the air outlet pipe (2022) is connected to the shell and tube condenser (3) via a pipeline.

3. The heat pump system according to claim 2, characterized in that: The shell (201) has a screw hole (2011) on its surface, the upper cover (202) has a bolt (2021) on its outer side, the bolt (2021) passes through the fixing cover (2061) and is threadedly engaged with the screw hole (2011), and the fixing cover (2061) has a plurality of through holes (2063) on its surface.

4. The heat pump system according to claim 3, characterized in that: A collecting base (2065) is provided at the bottom of the fixed cover (2061), and the lower end of the oil extraction pipe (2064) is located inside the collecting base (2065).

5. The heat pump system according to claim 4, characterized in that: A liquid extraction pump (2068) is provided at the upper end of the oil extraction pipe (2064), and the liquid extraction pump (2068) is connected to the oil tank (6).

6. The heat pump system according to claim 2, characterized in that: A limit ring (2044) is installed on the inner wall of the extension tube (2041), and a compression spring (2045) is installed between the limit ring (2044) and the sealing piston (2043).

7. The heat pump system according to claim 6, characterized in that: An air guide pipe (2049) is installed at the air outlet end of the one-way valve (2048); an extrusion cover (20410) is installed on the body of the air guide pipe (2049) via a sealing slip ring (20411); an auxiliary spring (20413) is installed between the extrusion cover (20410) and the bottom of the buffer tank (2047).

8. The heat pump system according to claim 6, characterized in that: A movable groove (2024) is provided inside the recoil pipe (2023), a movable sleeve (2026) is installed inside the movable groove (2024) via a first spring (2025), and a nozzle (2027) is provided inside the movable sleeve (2026).

9. The heat pump system according to claim 8, characterized in that: The air guide cover (2073) is aligned with the air outlet pipe (2022); an air guide turntable (2076) is rotatably mounted inside the extension cover (2074) via a rotating shaft (2075); and a plurality of dispersed holes (2077) are provided on the outside of the extension cover (2074); The inner wall of the transfer shell (207) is provided with a matching slide rail (2078), a blocking slider (2071) is slidably installed inside the matching slide rail (2078), a second spring (2072) is installed between the blocking slider (2071) and the transfer shell (207), and the ends of the blocking slider (2071) and the movable sleeve (2026) are both inclined and limited.

10. The control method of the heat pump system according to claim 1, characterized in that: The following steps are involved: S1: Before the unit is started, the economizer expansion valve (902) is fully opened and the oil cooler expansion valve (903) is fully closed; S2: After the unit is started, when the oil temperature sensor (8) detects that the oil temperature is lower than the set value during the startup phase, the electric bypass valve (901) is fully opened, the oil cooler expansion valve (903) remains fully closed, and all refrigerant directly enters the main expansion valve (9) through the electric bypass valve (901) to participate in the main system refrigeration cycle, so that the unit can achieve rapid heating; S3: When the oil temperature sensor (8) detects that the oil temperature is higher than the set value, the electric bypass valve (901) is gradually closed to fully closed, and the oil cooler expansion valve (903) is gradually opened, and the oil temperature is controlled to be within the target range by adjusting the opening of the oil cooler expansion valve (903); S4: After the system is running stably, under the premise that the oil temperature is controlled within the target range as the first control factor, the system gradually reduces the opening of the economizer expansion valve (902) and opens the oil cooler expansion valve (903) to control the inlet subcooling of the main expansion valve (9) to the target range, thereby improving the unit operation efficiency; S5: After the system compressor (1) is fully loaded, the hot water temperature of the shell and tube condenser (3) is lower than the target value. Under the premise that the oil temperature is controlled within the target range as the first control factor, the system gradually reduces the opening of the economizer expansion valve (902) and opens the oil cooler expansion valve (903) to control the inlet subcooling of the main expansion valve (9) to within the target range, thereby increasing the heating capacity of the unit.

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