Permanent magnet frequency conversion single-machine two-stage compression screw type high-temperature hot water unit

Abstract

The utility model relates to the field of high-temperature hot water units, in particular to a permanent magnet frequency conversion single-machine two-stage compression screw type high-temperature hot water unit. The unit comprises a compressor, a lubricating oil separator, a condenser, an evaporator, an economizer and an oil cooler, an exhaust port of the compressor is sequentially communicated with the lubricating oil separator and the condenser and finally communicated with an air suction port of the compressor to form a main loop. The main loop is also provided with a first line and a second line which are finally communicated with the main loop; the lubricating oil separator is provided with a pressure maintaining valve communicated with the compressor. Through frequency conversion design of the unit, load adjustment is more accurate and stable, 85 DEG C high-temperature water outlet can be achieved, ultra-efficient oil separation design is adopted in the unit, freezing lubricating oil entering a heat exchanger is reduced to the maximum extent, the influence of the lubricating oil on heat exchange is reduced, and due to the fact that the unit uses an economizer circulating system, the energy efficiency of the whole unit can be improved.

Description

Technical Field

[0001] The utility model relates to the field of high-temperature hot water units, in particular to a permanent magnet variable frequency single-machine two-stage compression screw type high-temperature hot water unit. Background Art

[0002] Water source heat pumps are widely valued as an energy-saving technology. They can absorb heat from low-grade heat sources and transfer it into high-grade heat sources that can be used by users. However, the operation of water source heat pumps is subject to conditions: when ordinary water source heat pumps are used for heating, the inlet water temperature of low-grade heat sources is generally lower than 15°C, and the outlet water temperature of high-grade heat sources is generally not more than 55°C. Since the outlet water temperature of high-grade heat sources is generally not very high, it is necessary to develop a water source heat pump unit with a low-grade heat source below 15°C and a high-grade heat source above 85°C. Due to its energy-saving and environmentally friendly characteristics, it can become a solution to replace boilers. Utility Model Content

[0003] In order to solve the above technical problems, the purpose of the utility model is to provide a permanent magnet frequency conversion single-machine two-stage compression screw type high-temperature hot water unit.

[0004] In order to achieve the above-mentioned purpose, the utility model adopts the following technical solutions:

[0005] A permanent magnet frequency conversion single-machine two-stage compression screw high-temperature hot water unit, the unit comprises a compressor, a lubricating oil separator, a condenser, an evaporator, an economizer and an oil cooler; the exhaust port of the compressor is connected to the lubricating oil separator and the condenser in sequence, and finally connected to the air intake port of the compressor to form a main circuit; the lubricating oil separator is also provided with a first circuit, the first circuit is connected from the lubricating oil separator to the oil cooler, and finally connected to the oil supply port of the compressor; the condenser is also provided with a second circuit, the second circuit is connected from the condenser to the economizer and the evaporator in sequence, and finally connected to the main circuit; wherein the lubricating oil separator is provided with a pressure maintaining valve connected to the compressor; the second circuit is provided with a main liquid circuit solenoid valve located between the condenser and the economizer; the economizer is also provided with a shunt circuit, the shunt point of the shunt circuit is after the second circuit flows through the economizer, and finally connected to the compressor and the evaporator;

[0006] The compressor adopts a permanent magnet variable frequency single-machine two-stage compression screw compressor, the high / low pressure stages of the compressor adopt independent permanent magnet variable frequency motors, and the high / low pressure stages adopt independent adjustable content ratio slide valves.

[0007] Preferably, an oil filter pressure difference switch and a lubricating oil filter are provided on the first circuit, and the oil filter pressure difference switch and the lubricating oil filter are arranged on the circuit between the lubricating oil filter and the oil cooler.

[0008] Preferably, the first circuit is also provided with an oil flow switch, a compressor oil supply solenoid valve, a compressor oil supply pressure sensor and a compressor oil supply temperature sensor, the oil flow switch is located between the lubricating oil filter and the oil cooler, and the compressor oil supply solenoid valve, the compressor oil supply pressure sensor and the compressor oil supply temperature sensor are sequentially arranged between the oil cooler and the compressor.

[0009] Preferably, the evaporator is further provided with a third circuit, the third circuit is connected to the main circuit, and an ejector pump is provided at the connection.

[0010] Preferably, an exhaust pressure sensor and an exhaust temperature sensor are provided on the main circuit and are located between the compressor and the lubricating oil separator.

[0011] Preferably, the main circuit is provided with an intake temperature sensor and an intake pressure sensor, and are located on the line connecting the main circuit to the intake port of the compressor.

[0012] Preferably, the economizer adopts a brazed plate heat exchanger; the diversion circuit includes a first main diversion and a first diversion, a second diversion and a third diversion diverted from the first main diversion, the first diversion is connected to the economizer from the diversion point and finally connected to the compressor air supply port, the second diversion is connected to the low-pressure stage motor and the high-pressure stage motor of the compressor from the diversion point, and the third diversion is connected to the oil cooler and the evaporator in sequence from the diversion point; wherein, the first main diversion is provided with a main liquid circuit electronic expansion valve on the circuit after the diversion point, the first diversion is provided with an economizer liquid circuit solenoid valve and an economizer electronic expansion valve on the circuit before connecting to the economizer, the second diversion is provided with a high-pressure stage motor liquid spray cooling solenoid valve and a low-pressure stage motor liquid spray cooling solenoid valve, and the third diversion is provided with an oil cooling solenoid valve and an oil cooling electronic expansion valve on the circuit before connecting to the oil cooler.

[0013] Preferably, the first split flow is also provided with a supplementary air pressure sensor and a supplementary air temperature sensor, and is located between the economizer and the compressor.

[0014] Preferably, the economizer adopts a flash tank economizer; the diversion circuit includes a second main diversion, a fourth diversion and a fifth diversion; when the economizer adopts a flash tank economizer, a first-level throttling electronic expansion valve is provided on the second circuit between the flash tank economizer and the main liquid circuit solenoid valve, and a second-level throttling electronic expansion valve is provided on the second main diversion after the diversion point; wherein the fourth diversion is connected from the diversion point to the high-pressure stage motor and the low-pressure stage motor of the compressor, and the high-pressure stage motor liquid spray cooling solenoid valve and the low-pressure stage motor liquid spray cooling solenoid valve are provided on the circuit; the fifth diversion is connected from the diversion point to the oil cooler and the evaporator in sequence, and the oil cooling solenoid valve and the oil cooling electronic expansion valve are provided on the circuit before connecting to the oil cooler.

[0015] Preferably, the flash tank economizer is also connected to the air supply port of the compressor, and the air supply pressure sensor and air supply temperature sensor are provided on the connection line.

[0016] In summary, the advantages of the utility model are as follows:

[0017] 1. The unit is designed with variable frequency, and the load adjustment is more precise and stable.

[0018] 2. The compressor of the unit adopts permanent magnet synchronous motor and dual motor design. The high / low pressure stage motors are independently controlled to achieve independent adjustable optimization control of high and low pressure stage speeds, thereby achieving optimal interstage pressure and improving unit performance.

[0019] 3. The high / low pressure stages of the compressor of the unit adopt an independent content volume ratio slide valve design to achieve adjustable content volume ratio of the high / low pressure stages, thereby matching the system application conditions and further expanding the scope of use of the unit. At the same time, it can reduce the external power consumption caused by over-compression and under-compression of the screw compressor, thereby improving the overall energy efficiency.

[0020] 4. The unit adopts ultra-efficient oil separation design to minimize the entry of refrigeration lubricating oil into the heat exchanger and reduce the impact of lubricating oil on heat exchange.

[0021] 5. The unit uses an economizer circulation system to improve the energy efficiency of the unit.

[0022] 6. By using a permanent magnet variable frequency single-unit two-stage compression screw compressor, a higher condensing pressure can be obtained, so that the unit can produce high-temperature hot water at least 85°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of the first embodiment: the economizer of the unit is a brazed plate heat exchanger;

[0024] Figure 2 This is a schematic diagram of the structure of the second embodiment: the economizer of the unit is a flash tank economizer;

[0025] Figure numerals: 1, compressor; 2, lubricating oil separator; 3, condenser; 4, evaporator; 5, economizer; 6, oil cooler; 7, pressure maintaining valve; 8, main liquid circuit solenoid valve; 11, main circuit; 12, first circuit; 13, second circuit; 14, third circuit; 111, exhaust pressure sensor; 112, exhaust temperature sensor; 113, suction temperature sensor; 114, suction pressure sensor; 121, oil filter pressure difference switch; 122, lubricating oil filter; 123, oil flow switch; 124, compressor oil supply solenoid valve; 125, compressor oil supply pressure sensor; 126, compressor oil supply temperature sensor; 141, suction Ejector pump; 151, first main shunt; 152, first shunt; 153, second shunt; 154, third shunt; 155, main liquid circuit electronic expansion valve; 156, economizer liquid circuit solenoid valve; 157, economizer electronic expansion valve; 158, high-pressure motor spray cooling solenoid valve; 159, low-pressure motor spray cooling solenoid valve; 160, oil cooling solenoid valve; 161, oil cooling electronic expansion valve; 162, air supply pressure sensor; 163, air supply temperature sensor; 171, second main shunt; 172, fourth shunt; 173, fifth shunt; 174, first-stage throttling electronic expansion valve; 175, second-stage throttling electronic expansion valve. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0027] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0028] It should also be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition and explanation in subsequent drawings.

[0029] The specific implementation of the utility model is described in detail below in conjunction with the accompanying drawings.

[0030] like Figure 1 to Figure 2As shown, a permanent magnet frequency conversion single-machine two-stage compression screw type high temperature hot water unit, the main structural components of the unit include a compressor 1, a lubricating oil separator 2, a condenser 3, an evaporator 4, an economizer 5 and an oil cooler 6. The above-mentioned compressor 1 adopts a permanent magnet frequency conversion single-machine two-stage compression screw type compressor 1, the high / low pressure stage of the compressor 1 adopts an independent permanent magnet frequency conversion motor, and the high / low pressure stage adopts an independent adjustable internal volume ratio slide valve. The lubricating oil separator 2 is used to separate the lubricating oil, the condenser 3 is used to condense the high temperature and high pressure refrigerant gas into the high temperature and high pressure refrigerant liquid, the evaporator 4 is used to convert the low temperature and low pressure refrigerant liquid into the low temperature and low pressure refrigerant gas, and the oil cooler 6 is used to cool the lubricating oil.

[0031] A permanent magnet variable frequency single-machine two-stage compression screw compressor 1 is the core component of the entire unit. The exhaust port of the compressor 1 is connected to the lubricating oil separator 2 and the condenser 3 in sequence, and finally connected to the suction port of the compressor 1 to form a main circuit 11; while the compressor 1 is connected to the lubricating oil separator 2, a pressure maintaining valve 7 connected to the balance pipe of the compressor 1 is also provided on the lubricating oil separator 2, which is used to maintain the high pressure state of the lubricating oil separator 2.

[0032] Among them, an exhaust pressure sensor 111 and an exhaust temperature sensor 112 are provided on the main circuit 11, and are located between the compressor 1 and the lubricating oil separator 2; and an intake temperature sensor 113 and an intake pressure sensor 114 are also provided on the main circuit 11, and are located on the line connecting the main circuit 11 to the intake port of the compressor 1 (a high-pressure injection return oil solenoid valve is also provided on this section of the main circuit 11).

[0033] like Figure 1 to Figure 2 As shown, a first line 12 is further provided on the lubricating oil separator 2 , and the first line 12 is connected from the lubricating oil separator 2 to the oil cooler 6 , and finally connected to the oil supply port of the compressor 1 .

[0034] The first line 12 is provided with an oil filter pressure difference switch 121 and a lubricating oil filter 122, and the oil filter pressure difference switch 121 and the lubricating oil filter 122 are arranged on the line between the lubricating oil filter 122 and the oil cooler 6. Among them, the first line 12 is also provided with an oil flow switch 123, a compressor oil supply solenoid valve 124, a compressor oil supply pressure sensor 125 and a compressor oil supply temperature sensor 126, the oil flow switch 123 is located between the lubricating oil filter 122 and the oil cooler 6, and the compressor oil supply solenoid valve 124, the compressor oil supply pressure sensor 125 and the compressor oil supply temperature sensor 126 are arranged in sequence between the oil cooler 6 and the compressor 1.

[0035] like Figure 1 to Figure 2As shown, a second line 13 is also provided on the condenser 3, and the second line 13 is connected to the economizer 5 and the evaporator 4 in sequence from the condenser 3, and finally connected to the main circuit 11. Among them, a main liquid circuit solenoid valve 8 is provided on the second line 13, which is located between the condenser 3 and the economizer 5. The main liquid circuit solenoid valve 8 can cut off the delivery when the unit is shut down, so as to ensure the safety of the entire unit; and a shunt line is also provided on the economizer 5, and the shunt point of the shunt line is after the second line 13 flows through the economizer 5, and finally connected to the compressor 1 and the evaporator 4. (The specific relationship of the shunt line will be described in detail later)

[0036] like Figure 1 to Figure 2 As shown, a third line 14 is also provided on the evaporator 4, and the third line 14 is connected to the main circuit 11, and an ejector pump 141 is provided at the connection. The ejector pump 141 delivers the lubricating oil in the evaporator 4 to the compressor 1, realizing oil circuit circulation.

[0037] like Figure 1 As shown in the first embodiment, the economizer 5 adopts a brazed plate heat exchanger; when the economizer 5 adopts a brazed plate heat exchanger, the shunt circuit includes a first main shunt 151 and a first shunt 152, a second shunt 153 and a third shunt 154 shunted from the first main shunt 151, the first shunt 152 is connected to the economizer 5 from the shunt point and finally connected to the air supply port of the compressor 1, the second shunt 153 is connected from the shunt point to the low-pressure stage motor and the high-pressure stage motor of the compressor 1, and the third shunt 154 is connected from the shunt point to the oil cooler in sequence. cooler 6 and evaporator 4; wherein, the first main diversion 151 is provided with a main liquid circuit electronic expansion valve 155 on the line after the diversion point, the first diversion 152 is provided with an economizer liquid circuit solenoid valve 156 and an economizer electronic expansion valve 157 on the line before connecting to the economizer 5, the second diversion 153 is provided with a high-pressure motor liquid spray cooling solenoid valve 158 and a low-pressure motor liquid spray cooling solenoid valve 159, and the third diversion 154 is provided with an oil cooling solenoid valve 160 and an oil cooling electronic expansion valve 161 on the line before connecting to the oil cooler 6.

[0038] Specifically, a supplementary air pressure sensor 162 and a supplementary air temperature sensor 163 are further provided on the first split flow 152 and are located between the economizer 5 and the compressor 1 .

[0039] like Figure 2As shown in the second embodiment, the economizer 5 adopts a flash tank economizer; the shunt line includes a second main shunt 171, a fourth shunt 172 and a fifth shunt 173; when the economizer 5 adopts a flash tank economizer, a first-level throttling electronic expansion valve 174 is provided on the second line 13 and is located between the flash tank economizer and the main liquid circuit solenoid valve 8, and a second-level throttling electronic expansion valve is provided on the second main shunt 171 after the shunt point; wherein the fourth shunt 172 is connected from the shunt point to the high-pressure stage motor and the low-pressure stage motor of the compressor 1, and the high-pressure stage motor liquid spray cooling solenoid valve 158 and the low-pressure stage motor liquid spray cooling solenoid valve 159 are provided on the line; the fifth shunt 173 is connected from the shunt point to the oil cooler 6 and the evaporator 4 in sequence, and the oil cooling solenoid valve 160 and the oil cooling electronic expansion valve 161 are provided on the line before connecting the oil cooler 6.

[0040] The flash tank economizer is also connected to the air supply port of the compressor 1, and the air supply pressure sensor 162 and the air supply temperature sensor 163 are provided on the connection line.

[0041] The above-mentioned compressor 1 adopts a permanent magnet variable frequency single-machine two-stage compression screw compressor, and the main features of the compressor are: 1. The low-pressure stage and high-pressure stage of the compressor 1 are independently equipped with permanent magnet variable frequency high-efficiency motors, and the starting load of each motor is smaller; 2. The low-pressure stage and high-pressure stage of the compressor 1 are both equipped with independent internal volume ratio adjustment slide valves, which can make the load and internal volume ratio of the compressor 1 more matched.

[0042] By applying the above-mentioned compressor 1, the compressor 1 inhales refrigerant gas with a lower temperature, and then discharges refrigerant medium with a higher temperature and pressure after being compressed by the two-stage compressor 1, and finally releases heat to water through the shell and tube heat exchanger, thereby achieving a higher hot water outlet temperature, and the overall energy efficiency of the unit is relatively high.

[0043] In summary, the advantages of the utility model are as follows:

[0044] 1. The unit is designed with variable frequency, and the load adjustment is more precise and stable.

[0045] 2. The compressor of the unit adopts permanent magnet synchronous motor and dual motor design. The high / low pressure stage motors are independently controlled to achieve independent adjustable optimization control of high and low pressure stage speeds, thereby achieving optimal interstage pressure and improving unit performance.

[0046] 3. The high / low pressure stages of the compressor of the unit adopt an independent content volume ratio slide valve design to achieve adjustable content volume ratio of the high / low pressure stages, thereby matching the system application conditions and further expanding the scope of use of the unit. At the same time, it can reduce the external power consumption caused by over-compression and under-compression of the screw compressor, thereby improving the overall energy efficiency.

[0047] 4. The unit adopts ultra-efficient oil separation design to minimize the entry of refrigeration lubricating oil into the heat exchanger and reduce the impact of lubricating oil on heat exchange.

[0048] 5. The unit uses an economizer circulation system to improve the energy efficiency of the unit.

[0049] 6. By using a permanent magnet variable frequency single-unit two-stage compression screw compressor, a higher condensing pressure can be obtained, so that the unit can produce high-temperature hot water at least 85°C.

[0050] The above is a description of the embodiments of the utility model. Through the above description of the disclosed embodiments, professionals and technicians in the field can implement or use the utility model. Various modifications to these embodiments will be obvious to professionals and technicians in the field. The general principles defined in this article can be implemented in other embodiments without departing from the spirit or scope of the utility model. Therefore, the utility model will not be limited to these embodiments shown in this article, but will conform to the widest range consistent with the principles and novelties disclosed in this article.

Claims

1. A permanent magnet frequency conversion single-machine two-stage compression screw type high temperature hot water unit, characterized in that: The unit comprises a compressor (1), a lubricating oil separator (2), a condenser (3), an evaporator (4), an economizer (5) and an oil cooler (6); the exhaust port of the compressor (1) is connected to the lubricating oil separator (2) and the condenser (3) in sequence, and finally connected to the air intake port of the compressor (1) to form a main circuit (11); the lubricating oil separator (2) is also provided with a first circuit (12), and the first circuit (12) is connected from the lubricating oil separator (2) to the oil cooler (6), and finally connected to the oil supply port of the compressor (1); the condenser (3) is also provided with a second circuit ( 13), the second line (13) is connected from the condenser (3) to the economizer (5) and the evaporator (4) in sequence, and finally connected to the main circuit (11); wherein the lubricating oil separator (2) is provided with a pressure maintaining valve (7) connected to the compressor (1); the second line (13) is provided with a main liquid circuit solenoid valve (8) located between the condenser (3) and the economizer (5); the economizer (5) is also provided with a shunt line, the shunt point of the shunt line is after the second line (13) flows through the economizer (5), and finally connected to the compressor (1) and the evaporator (4); The compressor (1) adopts a permanent magnet variable frequency single-machine two-stage compression screw compressor, the high / low pressure stages of the compressor (1) adopt independent permanent magnet variable frequency motors, and the high / low pressure stages adopt independent adjustable internal volume ratio slide valves.

2. According to claim 1, a permanent magnet frequency conversion single-machine two-stage compression screw type high temperature hot water unit is characterized in that: The first line (12) is provided with an oil filter pressure difference switch (121) and a lubricating oil filter (122), and the oil filter pressure difference switch (121) and the lubricating oil filter (122) are arranged on the line between the lubricating oil filter (122) and the oil cooler (6).

3. A permanent magnet frequency conversion single-machine two-stage compression screw type high temperature hot water unit according to claim 2, characterized in that: The first line (12) is also provided with an oil flow switch (123), a compressor oil supply solenoid valve (124), a compressor oil supply pressure sensor (125) and a compressor oil supply temperature sensor (126); the oil flow switch (123) is located between the lubricating oil filter (122) and the oil cooler (6); the compressor oil supply solenoid valve (124), the compressor oil supply pressure sensor (125) and the compressor oil supply temperature sensor (126) are sequentially arranged between the oil cooler (6) and the compressor (1).

4. A permanent magnet frequency conversion single-machine two-stage compression screw type high temperature hot water unit according to claim 1, characterized in that: The evaporator (4) is also provided with a third line (14), the third line (14) is connected to the main circuit (11), and an ejector pump (141) is provided at the connection point.

5. The permanent magnet frequency conversion single-machine two-stage compression screw type high temperature hot water unit according to claim 1 is characterized in that: The main circuit (11) is provided with an exhaust pressure sensor (111) and an exhaust temperature sensor (112), and is located between the compressor (1) and the lubricating oil separator (2).

6. The permanent magnet frequency conversion single-machine two-stage compression screw type high temperature hot water unit according to claim 1 is characterized in that: The main circuit (11) is provided with an intake temperature sensor (113) and an intake pressure sensor (114), and is located on a line connecting the main circuit (11) to the intake port of the compressor (1).

7. A permanent magnet frequency conversion single-unit two-stage compression screw high-temperature hot water unit according to any one of claims 1 to 6, characterized in that: The economizer (5) adopts a brazed plate heat exchanger; the flow diversion circuit includes a first main flow diversion (151) and a first flow diversion (152), a second flow diversion (153) and a third flow diversion (154) diverted from the first main flow diversion (151); the first flow diversion (152) is connected to the economizer (5) from the diversion point and finally connected to the air supply port of the compressor (1); the second flow diversion (153) is connected to the low-pressure stage motor and the high-pressure stage motor of the compressor (1) from the diversion point; and the third flow diversion (154) is connected to the oil cooler (6) and the evaporator (4) in sequence from the diversion point; The first main branch (151) is provided with a main liquid circuit electronic expansion valve (155) on the line after the branch point, the first branch (152) is provided with an economizer liquid circuit solenoid valve (156) and an economizer electronic expansion valve (157) on the line before connecting to the economizer (5), the second branch (153) is provided with a high-pressure motor liquid spray cooling solenoid valve (158) and a low-pressure motor liquid spray cooling solenoid valve (159), and the third branch (154) is provided with an oil cooling solenoid valve (160) and an oil cooling electronic expansion valve (161) on the line before connecting to the oil cooler (6).

8. The permanent magnet frequency conversion single-machine two-stage compression screw type high temperature hot water unit according to claim 7 is characterized in that: The first split flow (152) is also provided with a supplementary air pressure sensor (162) and a supplementary air temperature sensor (163), and is located between the economizer (5) and the compressor (1).

9. A permanent magnet frequency conversion single-unit two-stage compression screw type high temperature hot water unit according to claim 8, characterized in that: The economizer (5) is a flash tank economizer; the flow diversion circuit includes a second main flow diversion (171), a fourth flow diversion (172) and a fifth flow diversion (173); when the economizer (5) is a flash tank economizer, a primary throttling electronic expansion valve (174) is provided on the second circuit (13) and is located between the flash tank economizer and the main liquid circuit solenoid valve (8); and a secondary throttling electronic expansion valve (175) is provided on the second main flow diversion (171) after the diversion point; wherein The fourth flow diversion (172) is connected from the diversion point to the high-pressure motor and the low-pressure motor of the compressor (1), and the high-pressure motor liquid spray cooling solenoid valve (158) and the low-pressure motor liquid spray cooling solenoid valve (159) are arranged on the line; the fifth flow diversion (173) is connected from the diversion point to the oil cooler (6) and the evaporator (4) in sequence, and the oil cooling solenoid valve (160) and the oil cooling electronic expansion valve (161) are arranged on the line before the oil cooler (6).

10. A permanent magnet frequency conversion single-unit two-stage compression screw type high temperature hot water unit according to claim 9, characterized in that: The flash tank economizer is also connected to the air supply port of the compressor (1), and the air supply pressure sensor (162) and the air supply temperature sensor (163) are provided on the connection line.

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