Wide-temperature-range cascade heat pump system, control method thereof and lubricating oil system

Abstract

The invention discloses a wide-temperature-range cascade heat pump system, a control method thereof and a lubricating oil system, and relates to the technical field of heat pump systems, in particular to the wide-temperature-range cascade heat pump system which comprises a low-temperature-section circulation subsystem and a high-temperature-section circulation subsystem. The low-temperature section circulation subsystem comprises a low-temperature section evaporator, a low-temperature section compressor, a low-temperature section condenser and a cascade heat exchanger; the high-temperature section circulation subsystem comprises a high-temperature section evaporator, a high-temperature section compressor and a high-temperature section condenser; according to the scheme provided by the invention, the energy consumption can be reduced, the carbon emission is reduced, and the reliability and operation efficiency of equipment are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pump systems, and in particular to a wide-temperature-range cascade heat pump system, a control method thereof, and a lubricating oil system. Background Art

[0002] According to the International Energy Agency (IEA), by 2023, global energy consumption will reach approximately 18 billion tons of standard coal equivalent (TCE), accounting for approximately 30% of global CO2 emissions. The industrial sector accounts for a whopping 37% of this total. Driven by the "dual carbon" goals, energy conservation and emission reduction in the industrial sector have become a key research focus for achieving sustainable development. Heavy-duty diesel engineering vehicles, critical equipment in industrial production and infrastructure construction, face significant operational challenges in extreme low-temperature environments (such as those in cold regions or during winter). As lubricating oil viscosity increases dramatically with temperature drop, its fluidity deteriorates, leading to low pump efficiency, engine starting difficulties, and even increased wear of mechanical components, shortening equipment life. Traditional solutions to this problem rely on resistance heating. However, this method has a theoretical maximum cost-effectiveness ratio (COP) of 1: Meaning, for every unit of electrical energy consumed, only one unit of heat is generated. This not only results in significant energy waste, but also slow heating rates and long preheating times, making it difficult to meet the requirements for efficient and energy-saving preheating.

[0003] Cascade heat pump technology has shown significant energy-saving potential in industrial and civilian fields due to its efficient heat transfer and conversion capabilities. Through multi-stage compression and condensation cycles, this technology can extract heat from low-temperature environments and raise it to a higher temperature level. Compared with traditional heating methods, its energy efficiency ratio (COP) is usually between 2-4, or even higher, thereby significantly reducing energy consumption and operating costs. However, the cascade heat pump technology currently on the market is mostly used in building heating, hot water supply and other fields. There is still a lack of dedicated designs for preheating lubricating oil tanks of heavy-duty diesel engineering vehicles, especially in extremely low-temperature environments. Existing technologies cannot effectively deal with the problem of high viscosity of lubricating oil at low temperatures, resulting in reduced vehicle performance and increased energy consumption, limiting its ability to operate in cold areas. Summary of the Invention

[0004] The purpose of the present invention is to provide a wide temperature range cascade heat pump system and its control method and lubricating oil system to solve the problems existing in the above-mentioned prior art, reduce energy consumption, reduce carbon emissions, and improve equipment reliability and operating efficiency.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a wide temperature range cascade heat pump system, comprising:

[0007] The low-temperature section circulation subsystem includes a low-temperature section evaporator, a low-temperature section compressor, a low-temperature section condenser, and a cascade heat exchanger; the hot side channels of the low-temperature section evaporator, the low-temperature section compressor, and the low-temperature section condenser are sequentially connected to form a first low-temperature section loop; the hot side channels of the low-temperature section evaporator, the low-temperature section compressor, and the cascade heat exchanger are sequentially connected to form a second low-temperature section loop;

[0008] The high-temperature section circulation subsystem includes a high-temperature section evaporator, a high-temperature section compressor, and a high-temperature section condenser; the hot side channels of the high-temperature section evaporator, the high-temperature section compressor, and the high-temperature section condenser are sequentially connected to form a first high-temperature section loop; the hot side channels of the high-temperature section compressor, the high-temperature section condenser, and the cold side channels of the cascade heat exchanger are sequentially connected to form a second high-temperature section loop;

[0009] The cold side channel inlet of the low-temperature section condenser is used to connect to the lubricating oil pump; the cold side channel outlet of the low-temperature section condenser is connected to the cold side channel inlet of the high-temperature section condenser, and the cold side channel outlet of the high-temperature section condenser is used to connect to the lubricating oil tank.

[0010] Preferably, the low-temperature section circulation subsystem further includes a low-temperature section three-way valve, and the low-temperature section compressor, the low-temperature section condenser and the cascade heat exchanger are connected through the low-temperature section three-way valve.

[0011] Preferably, the high-temperature section circulation subsystem further includes a high-temperature section three-way valve, and the high-temperature section compressor, the high-temperature section evaporator and the cascade heat exchanger are connected through the high-temperature section three-way valve.

[0012] Preferably, the low-temperature section circulation subsystem also includes a low-temperature section gas-liquid separator and a low-temperature section throttle valve. The low-temperature section gas-liquid separator is arranged on the loop between the low-temperature section evaporator and the low-temperature section compressor; the low-temperature section throttle valve is arranged on the loop between the low-temperature section evaporator and the low-temperature section condenser and on the loop between the cascade heat exchanger and the low-temperature section evaporator.

[0013] Preferably, the high-temperature section circulation subsystem also includes a high-temperature section gas-liquid separator and a high-temperature section throttle valve. The high-temperature section gas-liquid separator is arranged on the loop between the high-temperature section three-way valve and the high-temperature section compressor; the high-temperature section throttle valve is arranged on the loop between the high-temperature section evaporator and the high-temperature section condenser and on the loop between the cascade heat exchanger and the high-temperature section condenser.

[0014] Preferably, the circulating working fluid in the second low-temperature section circuit and the first low-temperature section circuit is R410A.

[0015] Preferably, the circulating working fluid in the second high-temperature section loop and the first high-temperature section loop is R124.

[0016] The present invention also provides a lubricating oil system, comprising: a lubricating oil pump, a lubricating oil tank, and the wide temperature range cascade heat pump system as described above, wherein the lubricating oil pump, the cold side channel of the low-temperature section condenser, the cold side channel of the high-temperature section condenser, and the lubricating oil tank are connected in sequence to form a lubricating oil circuit.

[0017] The present invention further provides a control method for the wide temperature range cascade heat pump system as described above, comprising:

[0018] Extremely low temperature environment: In the early preheating stage, the circulating medium in the low-temperature section circulation subsystem is controlled to circulate in the first low-temperature section loop and the second low-temperature section loop; the circulating medium in the high-temperature section circulation subsystem is controlled to circulate only in the second high-temperature section loop;

[0019] In the later preheating stage, the circulating medium in the low-temperature section circulation subsystem is controlled to circulate only in the second low-temperature section loop; the circulating medium in the high-temperature section circulation subsystem is controlled to circulate in the second high-temperature section loop;

[0020] Under normal temperature environment: only the high-temperature section circulation subsystem is controlled to operate and the circulating working medium therein is controlled to circulate only in the first high-temperature section loop.

[0021] Preferably, the environment temperature is detected to distinguish whether it is an extremely low temperature environment or a normal temperature environment; and the temperature of the lubricating oil is measured to determine whether it exceeds a set threshold to distinguish whether it belongs to the early preheating stage or the late preheating stage.

[0022] Compared with the prior art, the present invention has achieved the following technical effects:

[0023] 1. The wide-temperature range cascade heat pump system provided by the present invention absorbs heat from the environment through the low-temperature circulation subsystem at extremely low ambient temperatures and heats the cold lubricating oil to make it medium-temperature lubricating oil. At the same time, the heat of the low-temperature section circulating working fluid is transferred to the high-temperature section circulating working fluid, effectively reducing the heat load of the high-temperature section and the compressor power; the high-temperature circulation subsystem further heats the lubricating oil to heat the medium-temperature lubricating oil to become high-temperature lubricating oil; the cascade heat exchanger effectively reduces the heat load of the high-temperature section by thermally coupling the circulating working fluids between the low-temperature section and the high-temperature section; the low-temperature circulation subsystem stops working at normal temperature and directly absorbs heat from the environment through the high-temperature circulation subsystem, and uses the high-temperature circulation subsystem to heat the cold lubricating oil, thereby improving the matching of the system with the ambient temperature and improving its energy efficiency; the overall structure of the present invention is simple, can be used to improve heating energy efficiency, and adapt to different ambient temperatures. At the same time, its stable and efficient performance can provide a reliable solution for various heating needs.

[0024] 2. The present invention adopts R410A, a circulating medium with excellent working characteristics at medium and low temperatures, as the working medium in the low-temperature section circulation subsystem. R410A is suitable for absorbing heat from a low-temperature environment and has a high compression efficiency at low temperatures. It can effectively absorb ambient heat and transfer it to the condenser, thereby realizing the heating process in the low-temperature section, improving energy utilization, and reducing environmental pollution.

[0025] 3. The present invention adopts R124 as the working fluid in the high-temperature section circulation subsystem, which has good thermal stability at medium and high temperatures. It will not decompose or degrade in performance, has good temperature matching with the normal temperature environment, and has low pressure requirements at high temperatures. When it is operated alone at normal temperature to heat the lubricating oil, it can effectively reduce the power loss of the high-temperature section compressor, reduce the power loss of the compressor, and improve the overall energy efficiency of the system.

[0026] 4. Under extremely low ambient temperatures, the present invention adopts a wide temperature range cascade heat pump system based on cascade heat exchange, and the low-temperature section circulation subsystem and the high-temperature section circulation subsystem jointly realize the heating of the lubricating oil in the lubricating oil circulation subsystem. Through the cascade heat exchange design of the low-temperature section and the high-temperature section, two different circulating working fluids are used to achieve more efficient heat transfer and utilization. The low-temperature section first heats the cold lubricating oil to make it medium-temperature lubricating oil, and at the same time uses the low-temperature section circulating working fluid to preheat the high-temperature section circulating working fluid, and then further heats the medium-temperature lubricating oil through the high-temperature section to make it high-temperature lubricating oil, so that the actual heat transfer temperature difference between the lubricating oil and each circulating working fluid is reduced, the heat transfer process is optimized, and the heat load required by the high-temperature section and the power demand of the high-temperature section compressor are reduced. Under normal temperature environment, the low-temperature section circulation subsystem stops working. Through the reasonable matching of the single-stage heat pump and the ambient temperature, the high-temperature section circulation subsystem works alone to directly realize the heating of the lubricating oil in the lubricating oil circulation subsystem, which significantly improves the overall energy efficiency of the system.

[0027] 5. The present invention can operate efficiently over a wide temperature range. The combination of low-temperature and high-temperature sections enables the system to adapt to lower ambient temperatures, achieving efficient heating of lubricating oil from low temperature to high temperature, and meeting the needs of extreme low-temperature cold start application scenarios for heavy-duty diesel engineering vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 A schematic structural diagram of a wide temperature range cascade heat pump system provided in an embodiment of the present invention.

[0030] Figure markings: 1. Low-temperature section compressor; 2. Low-temperature section condenser; 3. Cascade heat exchanger; 4. Low-temperature section throttle valve; 5. Low-temperature section evaporator; 6. High-temperature section compressor; 7. High-temperature section condenser; 8. High-temperature section throttle valve; 9. Lubricating oil tank; 10. Lubricating oil pump; 11. Low-temperature section gas-liquid separator; 11-1. Low-temperature section injection valve; 11-2. Low-temperature section discharge valve; 12. High-temperature section gas-liquid separator; 12-1. High-temperature section injection valve; 12-2. High-temperature section discharge valve; 13. Low-temperature section three-way valve; 14. High-temperature section evaporator; 15. High-temperature section three-way valve. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 efforts are within the scope of protection of the present invention.

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] This invention addresses the problem of excessively high viscosity of low-temperature lubricating oil in existing heavy-duty diesel engineering vehicles during cold starts in extreme low-temperature environments, resulting in reduced starting performance and limited operational capacity. The present invention provides a wide-temperature range cascade heat pump system that replaces traditional resistance wire heating methods. This system uses a stepped heat exchange method to preheat the lubricating oil twice in extremely low-temperature environments, reducing the heat load and single-stage compressor power under a single preheating scheme. At room temperature, it switches to a high-efficiency single-stage heat pump circulation mode, improving the system's energy efficiency. This system enables efficient and rapid preheating of the lubricating oil in both extreme and normal temperature environments, significantly improving preheating efficiency, reducing energy consumption, and reducing carbon emissions.

[0034] The following combination Figure 1 , describing embodiments of the present invention.

[0035] Example 1

[0036] The embodiment of the present invention provides a wide temperature range cascade heat pump system, including: a low temperature section circulation subsystem and a high temperature section circulation subsystem, the low temperature section circulation subsystem includes a low temperature section evaporator 5, a low temperature section compressor 1, a low temperature section condenser 2 and a cascade heat exchanger 3; the hot side channels of the low temperature section evaporator 5, the low temperature section compressor 1 and the low temperature section condenser 2 are connected in sequence to form a first low temperature section loop; the hot side channels of the low temperature section evaporator 5, the low temperature section compressor 1 and the cascade heat exchanger 3 are connected in sequence to form a second low temperature section loop; the high temperature section circulation subsystem includes a high temperature section evaporator 14, a high temperature section compressor 15, a high temperature section condenser 26 and a high temperature section condenser 37. The hot side channels of the high temperature section evaporator 14, the high temperature section compressor 6 and the high temperature section condenser 7 are connected in sequence to form a first high temperature section loop; the hot side channels of the high temperature section compressor 6, the high temperature section condenser 7 and the cold side channels of the cascade heat exchanger 3 are connected in sequence to form a second high temperature section loop; the cold side channel inlet of the low temperature section condenser 2 is used to communicate with the lubricating oil pump 10; the cold side channel outlet of the low temperature section condenser 2 is connected to the cold side channel inlet of the high temperature section condenser 7, and the cold side channel outlet of the high temperature section condenser 7 is used to communicate with the lubricating oil tank 9.

[0037] The wide temperature range cascade heat pump system provided by the present invention absorbs heat from the environment through the low-temperature circulation subsystem at extremely low ambient temperatures and heats the cold lubricating oil to make it medium-temperature lubricating oil. At the same time, the heat of the low-temperature section circulating working fluid is transferred to the high-temperature section circulating working fluid, effectively reducing the heat load of the high-temperature section and the compressor power; the high-temperature circulation subsystem further heats the lubricating oil to heat the medium-temperature lubricating oil to become high-temperature lubricating oil; the cascade heat exchanger 3 effectively reduces the heat load of the high-temperature section by heat coupling between the low-temperature section and the high-temperature section circulating working fluid; the low-temperature circulation subsystem stops working at normal temperature and directly absorbs heat from the environment through the high-temperature circulation subsystem, and uses the high-temperature circulation subsystem to heat the cold lubricating oil, thereby improving the matching of the system with the ambient temperature and improving its energy efficiency; the overall structure of the present invention is simple, can be used to improve heating energy efficiency, and adapt to different ambient temperatures. At the same time, its stable and efficient performance can provide a reliable solution for various heating needs.

[0038] In some embodiments, the low-temperature section circulation subsystem further includes a low-temperature section three-way valve 13, and the low-temperature section compressor 1, the low-temperature section condenser 2 and the cascade heat exchanger 3 are connected through the low-temperature section three-way valve 13. The low-temperature section three-way valve 13 is preferably a solenoid valve.

[0039] This embodiment can achieve the purpose of controlling the low-temperature section circulating medium to circulate simultaneously in the first low-temperature section loop and the second low-temperature section loop or to circulate solely in the first low-temperature section loop or solely in the second low-temperature section loop, thereby enabling the device to have more working modes.

[0040] In some embodiments, the high-temperature circulation subsystem further includes a high-temperature three-way valve 15, through which the high-temperature compressor 6, the high-temperature evaporator 14, and the cascade heat exchanger 3 are connected. The high-temperature three-way valve 15 and the low-temperature three-way valve 13 are preferably solenoid valves.

[0041] This embodiment can achieve the purpose of controlling the high-temperature section circulating medium to circulate simultaneously in the first high-temperature section loop and the second high-temperature section loop or to circulate solely in the first high-temperature section loop or solely in the second high-temperature section loop, thereby enabling the device to have more working modes.

[0042] In some embodiments, the low-temperature section circulation subsystem also includes a low-temperature section gas-liquid separator 11 and a low-temperature section throttle valve 4. The low-temperature section gas-liquid separator 11 is arranged on the loop between the low-temperature section evaporator 5 and the low-temperature section compressor 1; the low-temperature section throttle valve 4 is arranged on the loop between the low-temperature section evaporator 5 and the low-temperature section condenser 2 and on the loop between the cascade heat exchanger 3 and the low-temperature section evaporator 5.

[0043] The low-temperature section gas-liquid separator 11 in this embodiment includes a low-temperature section injection valve 11 - 1 and a low-temperature section discharge valve 11 - 2 .

[0044] In some embodiments, the high-temperature section circulation subsystem also includes a high-temperature section gas-liquid separator 12 and a high-temperature section throttle valve 8. The high-temperature section gas-liquid separator 12 is arranged on the loop between the high-temperature section three-way valve 15 and the high-temperature section compressor 6; the high-temperature section throttle valve 8 is arranged on the loop between the high-temperature section evaporator 14 and the high-temperature section condenser 7 and on the loop between the cascade heat exchanger 3 and the high-temperature section condenser 7.

[0045] The high-temperature section gas-liquid separator 12 in this embodiment includes a high-temperature section injection valve 12 - 1 and a high-temperature section discharge valve 12 - 2 .

[0046] In some embodiments, the circulating working fluid in the second low-temperature segment loop and the first low-temperature segment loop is R410A.

[0047] In the embodiment of the present invention, the circulating medium R410A with excellent working characteristics at medium and low temperatures is used as the working medium in the low-temperature section circulation subsystem. R410A is suitable for absorbing heat from a low-temperature environment and has a high compression efficiency at low temperatures. It can effectively absorb ambient heat and transfer it to the condenser, thereby realizing the heating process of the low-temperature section, improving energy utilization, and reducing environmental pollution.

[0048] In some embodiments, the circulating working fluid in the second high-temperature section loop and the first high-temperature section loop is R124.

[0049] In the embodiment of the present invention, the circulating medium R124 with good thermal stability at medium and high temperatures is used as the working medium in the high-temperature section circulation subsystem. It will not decompose or degrade in performance, has good temperature matching with the normal temperature environment, and has low pressure requirements at high temperatures. When it is operated alone at normal temperature to heat the lubricating oil, it can effectively reduce the power loss of the high-temperature section compressor 6, reduce the power loss of the compressor, and improve the overall energy efficiency of the system.

[0050] Example 2

[0051] An embodiment of the present invention provides a lubricating oil system, comprising: a lubricating oil pump 10, a lubricating oil tank 9, and the wide temperature range cascade heat pump system as described in the above embodiment, wherein the lubricating oil pump 10, the cold side channel of the low-temperature section condenser 2, the cold side channel of the high-temperature section condenser 7, and the lubricating oil tank 9 are connected in sequence to form a lubricating oil circuit.

[0052] This embodiment has all the advantages described above, which will not be described in detail here.

[0053] Example 3

[0054] An embodiment of the present invention provides a control method for the wide temperature range cascade heat pump system as described in the above embodiment, comprising:

[0055] Extremely low temperature environment: During the early preheating stage, the circulating medium in the low-temperature segment circulation subsystem is controlled to circulate in the first low-temperature segment loop and the second low-temperature segment loop; the circulating medium in the high-temperature segment circulation subsystem is controlled to circulate only in the second high-temperature segment loop;

[0056] In the later preheating stage, the circulating medium in the low-temperature section circulation subsystem is controlled to circulate only in the second low-temperature section loop; the circulating medium in the high-temperature section circulation subsystem is controlled to circulate in the second high-temperature section loop;

[0057] Under normal temperature environment: only the high-temperature section circulation subsystem is controlled to operate and the circulating working fluid therein is controlled to circulate only in the first high-temperature section loop.

[0058] This embodiment has all the advantages described above, which will not be described in detail here.

[0059] In some embodiments, the ambient temperature is detected to distinguish whether the environment is an extremely low temperature environment or a normal temperature environment; and the early preheating stage or the late preheating stage is distinguished by measuring whether the temperature of the lubricating oil exceeds a set threshold.

[0060] The specific working process is as follows:

[0061] In an extremely low temperature environment, the system undergoes two working processes: (1) First, the low-temperature lubricating oil is preheated. At this time, in the low-temperature section circulation subsystem, the low-temperature section circulating working fluid absorbs the heat in the environment in the low-temperature section evaporator 5 and evaporates into gas. After flowing through the low-temperature section gas-liquid separator 11, it is compressed by the low-temperature section compressor 1 to increase the temperature and pressure. Subsequently, the low-temperature section circulating working fluid flowing out of the outlet of the low-temperature section compressor 1 is divided into two circuits. One part enters the low-temperature section condenser 2 and transfers the heat to the cold lubricating oil, heating the cold lubricating oil to make it medium-temperature lubricating oil. The other part enters the cascade heat exchanger 3 and transfers the heat to the high-temperature section circulating working fluid. The low-temperature section circulating working fluid is respectively transferred from the low-temperature section condenser to the high-temperature section circulating working fluid. 2 and the cascade heat exchanger 3 and then merge, and are reduced in pressure by the low-temperature section throttle valve 4, and finally return to the low-temperature section evaporator 5; the high-temperature section circulating working medium absorbs heat and evaporates into gas in the cascade heat exchanger 3, flows through the high-temperature section gas-liquid separator 12, and is compressed by the high-temperature section compressor 6 to increase the temperature and pressure, and then flows out from the outlet of the high-temperature section compressor 6, transfers heat to the medium-temperature lubricating oil through the high-temperature section condenser 7, and is reduced in pressure by the high-temperature section throttle valve 8, and then returns to the cascade heat exchanger 3; the cold lubricating oil in the lubricating oil circulation subsystem exchanges heat with the low-temperature section condenser 2, is heated to become medium-temperature lubricating oil, and the medium-temperature lubricating oil enters the high-temperature section condenser 7 for heat exchange, and is further heated to become high-temperature lubricating oil. (2) The second step is to further heat the lubricating oil. At this time, the lubricating oil temperature has risen to the upper limit of the heating temperature of the low-temperature section circulation subsystem. The low-temperature section circulation subsystem can no longer achieve further preheating of the lubricating oil. Therefore, the low-temperature section circulating working fluid flowing out of the outlet of the low-temperature section compressor 1 enters the cascade heat exchanger 3, transfers all the heat to the high-temperature section circulating working fluid, and then reduces the pressure through the low-temperature section throttle valve 4, and finally returns to the evaporator; further heating of the lubricating oil will be achieved solely through the high-temperature section condenser 7 until the lubricating oil reaches the temperature required for the efficient operation of the engineering vehicle engine.

[0062] Under normal temperature environment, the system working experience is as follows: the low-temperature section circulation subsystem stops working, and the working fluid of the high-temperature section circulation subsystem absorbs heat from the environment through the high-temperature section evaporator 14 and evaporates into gas. After flowing through the high-temperature section gas-liquid separator 12, it is compressed by the high-temperature section compressor 6 to increase the temperature and pressure, and then flows out from the outlet of the high-temperature section compressor 6, transfers heat to the medium-temperature lubricating oil through the high-temperature section condenser 7, reduces the pressure through the high-temperature section throttle valve 8, and then returns to the high-temperature section evaporator 14. The heating of the lubricating oil is only realized through the high-temperature section circulation subsystem, which greatly saves equipment energy consumption while fully utilizing the matching between the ambient temperature and the working temperature zone of the high-temperature section circulation subsystem, thereby improving the energy efficiency and economy of the system.

[0063] The low-temperature circulation subsystem of the present invention adopts the operating principle of a heat pump and uses R410A, a circulating fluid with excellent operating characteristics at medium and low temperatures, as the circulating fluid, thereby improving energy utilization and reducing environmental pollution. The high-temperature circulation subsystem of the present invention also adopts the operating principle of a heat pump and uses R124, a circulating fluid with excellent thermal stability at medium and high temperatures, as the circulating fluid, thereby reducing compressor power loss and improving the overall energy efficiency of the system.

[0064] The present invention adopts a wide temperature range cascade heat pump system based on cascade heat exchange, and the low-temperature section circulation subsystem and the high-temperature section circulation subsystem jointly realize the heating of the lubricating oil in the lubricating oil circulation subsystem. The present invention realizes more efficient heat transfer and utilization by using two different circulating working fluids through the cascade heat exchange design of the low-temperature section and the high-temperature section. The low-temperature section circulating working fluid first heats the cold lubricating oil to make it medium-temperature lubricating oil. At the same time, the low-temperature section circulating working fluid preheats the high-temperature section circulating working fluid, and then further heats the medium-temperature lubricating oil through the high-temperature section to make it high-temperature lubricating oil, so that the heat transfer temperature difference between the lubricating oil and the circulating working fluid is reduced, reducing the heat load required for the high-temperature section and the power requirement of the high-temperature section compressor 6, optimizing the heat transfer process, and significantly improving the overall energy efficiency of the system. The present invention can operate efficiently within a wide temperature range. The combination of the low-temperature section and the high-temperature section enables the system to adapt to different ambient temperatures, achieve a wide range of applicability from low temperature to high temperature, and meet the needs of various application scenarios.

[0065] The present invention utilizes a cascade heat exchanger 3 as a coupling component between the low-temperature and high-temperature circulation subsystems, transferring some of the heat from the high-temperature, high-pressure circulating fluid in the low-temperature section to the low-temperature circulating fluid in the high-temperature section. This fully considers the heat exchange between the low-temperature and high-temperature sections, thereby improving system energy efficiency. By reducing temperature differences and optimizing heat distribution, the cascade heat exchanger 3 effectively reduces the heat load and compressor power requirements in the high-temperature section, improving heat utilization, and becoming a key component in enhancing the overall performance and energy efficiency of cascade high-temperature heat pump systems.

[0066] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A wide temperature range cascade heat pump system, characterized by: include: The low-temperature section circulation subsystem includes a low-temperature section evaporator, a low-temperature section compressor, a low-temperature section condenser, and a cascade heat exchanger; the hot side channels of the low-temperature section evaporator, the low-temperature section compressor, and the low-temperature section condenser are sequentially connected to form a first low-temperature section loop; the hot side channels of the low-temperature section evaporator, the low-temperature section compressor, and the cascade heat exchanger are sequentially connected to form a second low-temperature section loop; The high-temperature section circulation subsystem includes a high-temperature section evaporator, a high-temperature section compressor, and a high-temperature section condenser; the hot side channels of the high-temperature section evaporator, the high-temperature section compressor, and the high-temperature section condenser are sequentially connected to form a first high-temperature section loop; the hot side channels of the high-temperature section compressor, the high-temperature section condenser, and the cold side channels of the cascade heat exchanger are sequentially connected to form a second high-temperature section loop; The cold side channel inlet of the low-temperature section condenser is used to connect to the lubricating oil pump; the cold side channel outlet of the low-temperature section condenser is connected to the cold side channel inlet of the high-temperature section condenser, and the cold side channel outlet of the high-temperature section condenser is used to connect to the lubricating oil tank.

2. The wide temperature range cascade heat pump system according to claim 1, characterized in that: The low-temperature section circulation subsystem further includes a low-temperature section three-way valve, through which the low-temperature section compressor, the low-temperature section condenser and the cascade heat exchanger are connected.

3. The wide temperature range cascade heat pump system according to claim 1, characterized in that: The high-temperature section circulation subsystem further includes a high-temperature section three-way valve, through which the high-temperature section compressor, the high-temperature section evaporator and the cascade heat exchanger are connected.

4. The wide temperature range cascade heat pump system according to claim 2, characterized in that: The low-temperature section circulation subsystem also includes a low-temperature section gas-liquid separator and a low-temperature section throttle valve. The low-temperature section gas-liquid separator is arranged on the circuit between the low-temperature section evaporator and the low-temperature section compressor; the low-temperature section throttle valve is arranged on the circuit between the low-temperature section evaporator and the low-temperature section condenser and on the circuit between the cascade heat exchanger and the low-temperature section evaporator.

5. The wide temperature range cascade heat pump system according to claim 3, characterized in that: The high-temperature section circulation subsystem also includes a high-temperature section gas-liquid separator and a high-temperature section throttle valve. The high-temperature section gas-liquid separator is arranged on the circuit between the high-temperature section three-way valve and the high-temperature section compressor; the high-temperature section throttle valve is arranged on the circuit between the high-temperature section evaporator and the high-temperature section condenser and on the circuit between the cascade heat exchanger and the high-temperature section condenser.

6. The wide temperature range cascade heat pump system according to claim 1, characterized in that: The circulating working fluid in the second low-temperature section circuit and the first low-temperature section circuit is R410A.

7. The wide temperature range cascade heat pump system according to claim 2, characterized in that: The circulating working fluid in the second high-temperature section loop and the first high-temperature section loop is R124.

8. A lubricating oil system, characterized in that: include: A lubricating oil pump, a lubricating oil tank, and a wide temperature range cascade heat pump system according to any one of claims 1 to 7, wherein the lubricating oil pump, the cold side channel of the low-temperature section condenser, the cold side channel of the high-temperature section condenser, and the lubricating oil tank are connected in sequence to form a lubricating oil circuit.

9. A control method for a wide temperature range cascade heat pump system according to any one of claims 1 to 7, characterized in that: include: Extremely low temperature environment: in the early preheating stage, the circulating working medium in the low temperature section circulation subsystem is controlled to circulate in the first low temperature section circuit and the second low temperature section circuit; Controlling the circulating working medium in the high-temperature section circulation subsystem to circulate only in the second high-temperature section circuit; In the later preheating stage, the circulating medium in the low-temperature section circulation subsystem is controlled to circulate only in the second low-temperature section loop; the circulating medium in the high-temperature section circulation subsystem is controlled to circulate in the second high-temperature section loop; Under normal temperature environment: only the high-temperature section circulation subsystem is controlled to operate and the circulating working medium therein is controlled to circulate only in the first high-temperature section loop.

10. The control method of the wide temperature range cascade heat pump system according to claim 9, characterized in that: By detecting the ambient temperature, it can be distinguished whether the environment is an extremely low temperature environment or a normal temperature environment; by measuring whether the temperature of the lubricating oil exceeds the set threshold, it can be distinguished whether it is in the early preheating stage or the late preheating stage.

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