Single two-stage switching and combined heat pump
By using a single-stage/dual-stage switching and combined heat pump system, the problems of low efficiency and excessive exhaust pressure of heat pump systems under different seasonal ambient temperatures are solved, achieving efficient and stable heating and air conditioning, and improving the seasonal energy efficiency ratio (SEER) of the system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUAZHONG UNIV OF SCI & TECH
- Filing Date
- 2023-10-26
- Publication Date
- 2026-07-03
AI Technical Summary
Existing heat pump systems struggle to operate efficiently under varying seasonal ambient temperatures, particularly in ultra-low temperature environments such as Northeast China, where they suffer from low system efficiency and excessive exhaust pressure during summer air conditioning.
The system employs a single-stage/dual-stage switching and combined heat pump system. Through a heat pump cycle structure composed of components such as a high-pressure compressor, a four-way valve, a heat exchanger, a throttling valve, and a low-pressure compressor, it achieves single-stage/dual-stage switching to adapt to different seasonal ambient temperatures. It uses two-stage compression for heating and single-stage compression for cooling, and utilizes solenoid valves and check valves to regulate the flow path and solve the problem of high pressure exceeding limits.
The system's seasonal energy efficiency ratio (SEER) has been improved, ensuring stable operation under different ambient temperatures, avoiding the risk of excessive exhaust pressure, and improving system efficiency and stability.
Smart Images
Figure CN117329731B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of the heat pump industry, and in particular to a single-stage / dual-stage switching and combined heat pump. Background Technology
[0002] Currently, due to the need for carbon peaking and carbon emission reduction, various heating devices are gradually being replaced by heat pumps. Because heat pumps have an energy efficiency COP greater than 3.0 when operating at room temperature, they have been widely used.
[0003] In the application of heat pump heating, the ambient temperature varies greatly throughout the year, especially in places like Northeast China where the winter temperature can drop to around -30°C in some areas. However, in summer, it is desirable to achieve air conditioning functionality. Currently, a quasi-two-stage vapor compression cycle is used for heating, or a single-stage compression cycle is used directly for air conditioning. However, the heat pump refrigerant used for air conditioning has the risk of exceeding the exhaust pressure limit in summer. Therefore, it is mostly used for single-function applications. Existing technologies either make it into a quasi-two-stage compression heat pump or a two-stage compression heat pump for heating in ultra-low temperature environments, without considering summer air conditioning, or consider summer air conditioning by using a single-stage vapor compression refrigeration cycle. If used in vehicles, there is a risk of exceeding the exhaust pressure limit.
[0004] Appropriate cycles are applied under each season's ambient temperature conditions to ensure the heat pump air conditioning system operates within its optimal performance range to the maximum extent possible. This avoids sacrificing efficiency most of the time to meet a few extremely unfavorable environmental conditions, thus preventing a reduction in the system's seasonal energy efficiency (SEER). For example, when using a jet-induced enthalpy-enhanced quasi-two-stage compression heat pump cycle for tobacco curing, only the last one or two boilers require two-stage compression due to severe environmental conditions. The other 6-8 boilers use a single-stage cycle for higher efficiency. However, to meet the needs of the last two runs, two-stage compression is used for the other 6-8 runs as well, which actually reduces system efficiency. In this case, single-stage compression is used under normal ambient temperature conditions, while two-stage compression is only used for the last two runs under severe ambient temperature conditions, achieving a reasonable match in system efficiency.
[0005] In practice, this involves using a system that switches between single and dual stages based on season and ambient temperature conditions. In ultra-low temperature environments, two-stage compression heating is beneficial for pressure ratio control, the operating conditions of each stage compressor, and system stability. In summer, single-stage compression has higher cycle efficiency, but when used in vehicle air conditioning, the heat pump refrigerant may exceed the compressor pressure limit, so overpressure treatment is required for single-stage compression.
[0006] The system can also achieve single-stage heat pump heating by using a variant. The overall idea and logic of the system is to build an operating mode with the best cycle efficiency under the corresponding ambient temperature conditions, thereby ensuring a high seasonal energy efficiency ratio (SEER) throughout the year. Summary of the Invention
[0007] The technical solution of the present invention to achieve the above objectives is as follows: a single-stage and dual-stage switching and combined heat pump, including a high-pressure compressor and a four-way valve, wherein the two ends of the high-pressure compressor are connected to the two ends of the four-way valve, one end of the four-way valve is connected to a first heat exchanger, and one end of the first heat exchanger is connected to a heat pump circulation structure.
[0008] The heat pump cycle structure includes: a throttle valve, a first check valve, a dryer, a sight glass, a second heat exchanger, a low-pressure compressor, a solenoid valve, and an intercooler;
[0009] The throttle valve, the first check valve, the dryer, the sight glass, the second heat exchanger, and the solenoid valve are connected in sequence.
[0010] The first path of the intercooler is connected to the first heat exchanger and the second heat exchanger at both ends, and the second path of the intercooler is located between the throttle valve and the first check valve at one end, and connected to the four-way valve at the other end.
[0011] One end of the low-pressure compressor is connected to the second heat exchanger, and the other end is connected to the second circuit of the intercooler.
[0012] Preferably, the heat pump cycle structure may further include: a first heat exchanger, a throttling valve, a first one-way valve, an ejector, and an intercooler;
[0013] One end of the first heat exchanger is connected to one end of the four-way valve, one end of the throttle valve is connected to one end of the first heat exchanger, the first one-way valve is located on one side of the throttle valve, one end of the injector is connected to one end of the throttle valve, one end of the intercooler is connected between the first heat exchanger and the throttle valve, and the other end is connected to the injector and one end of the first one-way valve.
[0014] Preferably, one end of the injector is provided with an air inlet pipe.
[0015] Preferably, the first heat exchanger and the second heat exchanger have the same structure.
[0016] Preferably, the throttle valve is a two-way throttle valve.
[0017] Preferably, a second one-way valve is provided between the intercooler and the second heat exchanger.
[0018] The single-stage and dual-stage switching and combined heat pump made using the technical solution of the present invention has the following advantages compared with the prior art: (1) Single-stage and dual-stage switching scheme adapted to ultra-low temperature heating and summer air conditioning cooling: One refrigeration system realizes heating at ultra-low temperature environment and summer air conditioning cooling, and both heating and cooling correspond to better system performance under the environmental temperature conditions. To cope with the single-stage and dual-stage switching of heating heat pump and summer air conditioning cooling in ultra-low temperature environment areas, the stable operation of the system is considered during the switching process. For ultra-low temperature environment in winter, a two-stage heat pump is used for circulating heating, while in summer, a single-stage compression is used to improve system efficiency, and the risk of excessive pressure is solved by refrigerant diversion; (2) Bidirectional throttling valve with different flow diameters: Through The solenoid valve is turned on and off and the one-way valve is realized. The throttling valve connected to the first heat exchanger has bidirectional throttling capability. The key is that the bidirectional throttling flow rate is different to adapt to the demand; (3) The pressure regulation is adopted when switching to the single-stage air conditioning refrigeration cycle to prevent high pressure over-limit. In summer, the vehicle air conditioner uses heat pump refrigerant and there is a risk that the high pressure exceeds the range of the compressor. Therefore, the high pressure over-limit problem is solved by adopting a two-way approach; (4) The heating and heating under the ultra-low temperature environment conditions with better performance is achieved; (5) The high pressure over-limit risk of heat pump refrigerant under the single-stage compression refrigeration cycle of air conditioning in summer is effectively prevented; (6) Corresponding cycles are adopted in different seasons to improve the seasonal energy efficiency ratio (SEER) of the system and improve the compressor operating conditions, which is conducive to the long-term stable operation of the system. Attached Figure Description
[0019] Figure 1 This is a schematic block diagram illustrating the first structural relationship of a single-stage / dual-stage switching and combined heat pump according to the present invention.
[0020] Figure 2 This is a schematic block diagram illustrating the second structural relationship of a single-stage / dual-stage switching and combined heat pump according to the present invention.
[0021] In the diagram: 1. High-pressure compressor, 2. Four-way valve, 3. First heat exchanger, 4. Throttling valve, 5. First check valve, 6. Dryer, 7. Sight glass, 8. Second heat exchanger, 9. Low-pressure compressor, 10. Solenoid valve, 11. Intercooler, 12. Injector, 13. Inlet pipe, 14. Second check valve. Detailed Implementation
[0022] The present invention will now be described in detail with reference to the accompanying drawings, such as... Figure 1-2 As shown, a single- or dual-stage switching and combined heat pump.
[0023] Example: A single-stage / dual-stage switching and combined heat pump includes a high-pressure compressor 1 and a four-way valve 2. Both ends of the high-pressure compressor 1 are connected to both ends of the four-way valve 2. One end of the four-way valve 2 is connected to a first heat exchanger 3, and one end of the first heat exchanger 3 is connected to a heat pump circulation structure. The heat pump circulation structure includes: a throttling valve 4, a first one-way valve 5, a dryer 6, a sight glass 7, a second heat exchanger 8, a low-pressure compressor 9, a solenoid valve 10, and an intercooler 11. The throttling valve 4, the first one-way valve 5, the dryer 6, the sight glass 7, the second heat exchanger 8, and the solenoid valve 10 are connected sequentially. The first path of the intercooler 11 is connected to the first heat exchanger 3 and the second heat exchanger 8 respectively. One end of the second path of the intercooler 11 is located between the throttling valve 4 and the first one-way valve 5, and the other end of the second path is connected to the four-way valve 2. The low-pressure compressor 9... One end of the compressor 9 is connected to the second heat exchanger 8, and the other end is connected to the second path of the intercooler 11. The heat pump cycle structure may also include: a first heat exchanger 3, a throttle valve 4, a first check valve 5, an ejector 12, and an intercooler 11. One end of the first heat exchanger 3 is connected to one end of the four-way valve 2, one end of the throttle valve 4 is connected to one end of the first heat exchanger 3, the first check valve 5 is located on one side of the throttle valve 4, one end of the ejector 12 is connected to one end of the throttle valve 4, one end of the intercooler 11 is connected between the first heat exchanger 3 and the throttle valve 4, and the other end is connected to the ejector 12 and one end of the first check valve 5. One end of the ejector 12 is provided with an air inlet pipe 13. The first heat exchanger 3 and the second heat exchanger 8 have the same structure. The throttle valve 4 is a two-way throttle valve 4. A second check valve 14 is provided between the intercooler 11 and the second heat exchanger 8.
[0024] Example 1: The system consists of two compressors (one low-pressure and one high-pressure), two heat exchangers, one intercooler 11, a four-way valve 2, a first check valve 5, some throttle valves 4 and accessories;
[0025] In ultra-low temperature environments, a two-stage heat pump cycle is used for heating (the flow path corresponding to the hollow arrows in the attached diagram). The exhaust gas from the high-pressure compressor 1 is discharged to the first heat exchanger 3 through the four-way valve 2 to provide heat. Here, the refrigerant condenses into a liquid. One path passes through the intercooler 11 for subcooling and then throttles before entering the second heat exchanger 8 for evaporation. Because it has been subcooled, the evaporation temperature here is low, corresponding to the ultra-low temperature environment. The low-pressure refrigerant vapor enters the low-pressure compressor 9 for compression. The refrigerant from the first heat exchanger 3 is throttled in the second path and enters the intercooler 11 to subcool the first path of refrigerant. The refrigerant vapor that comes out mixes with the refrigerant vapor compressed by the low-pressure compressor 9 and then enters the high-pressure compressor through the four-way valve 2 to complete the two-stage compression heat pump cycle.
[0026] In summer, a corresponding air conditioning refrigeration cycle is used (the flow path indicated by the solid arrows in the attached diagram). The high-pressure compressor 1 compresses the refrigerant vapor, which then passes through the four-way valve 2 in the direction of the solid arrow. At this time, the solenoid valve 10 is activated, and a portion of the refrigerant passes through the solenoid valve 10 and enters the second heat exchanger 8 for condensation. The condensed refrigerant liquid passes through the sight glass 7 and the dryer 6, mixing with another portion of the refrigerant exiting the intercooler 11. After throttling, it enters the first heat exchanger 3 for cooling, providing the air conditioning temperature for the user. During the refrigeration cycle, because the refrigerant temperature is low, a dryer 6 is installed on the pipeline to dry the moisture in the refrigerant, preventing moisture from entering the throttling valve 4 (or capillary tube) and clogging the pipeline. Also, because the exhaust pressure of the heat pump refrigerant used for air conditioning may exceed the compressor's pressure limit (e.g., R410A, 40...),... When refrigerants such as 7C are used as refrigerants in vehicle air conditioning, there is a possibility that the pressure exceeds the upper limit pressure of the compressor, so it needs to be treated. In this system, another part of the refrigerant coming out of the four-way valve 2 is cooled by the intercooler 11 and then mixed with the part of the refrigerant coming out of the second heat exchanger 8. The advantage of this treatment is that it can obtain a better subcooling effect by increasing the condensation area. Then, it is throttled into the first heat exchanger 3 to provide the air conditioning cooling temperature and achieve the purpose of air conditioning cooling. Since the system divides the refrigerant vapor discharged from the compressor into two paths, it will effectively reduce the condensation pressure of the second heat exchanger 8, thereby achieving high pressure regulation. The cycle switching is accomplished by the on / off of the solenoid valve 10 and the first one-way valve 5. The throttle valve 4 connected to the first heat exchanger 3 is a two-way throttle valve 4. When it is used for air conditioning cooling, the diameter is larger than the diameter for heating.
[0027] Example 2 is an alternative to this solution: mainly in the refrigeration and air conditioning process, the refrigerant liquid from the second heat exchanger 8 and the refrigerant from the intercooler 11 are mixed through an ejector 12, which is more conducive to pressure and temperature regulation because the ejector 12 itself has refrigeration capacity, which is more beneficial for regulating pressure and subcooling and improving circulation performance. When the heat pump is in circulation, it directly enters the intercooler 11 through a first one-way valve 5. In this way, the switching is more specific and clear depending on the situation. It only comes at the cost of the ejector 12 and the first one-way valve 5. The initial solution is simple mixing and has lower efficiency, but it saves equipment and costs.
[0028] The above technical solutions only embody the preferred technical solutions of the present invention. Any modifications that may be made by those skilled in the art to certain parts thereof embody the principles of the present invention and fall within the protection scope of the present invention.
Claims
1. A single-stage / dual-stage switching and combined heat pump, comprising a high-pressure compressor (1) and a four-way valve (2), characterized in that, The high-pressure compressor (1) is connected to both ends of the four-way valve (2). One end of the four-way valve (2) is connected to the first heat exchanger (3), and one end of the first heat exchanger (3) is connected to the heat pump circulation structure. The heat pump cycle structure includes: a throttle valve (4), a first check valve (5), a dryer (6), a sight glass (7), a second heat exchanger (8), a low-pressure compressor (9), a solenoid valve (10), and an intercooler (11). The throttle valve (4), the first check valve (5), the dryer (6), the sight glass (7), the second heat exchanger (8), and the solenoid valve (10) are connected in sequence; The first path of the intercooler (11) is connected to the first heat exchanger (3) and the second heat exchanger (8) respectively. One end of the second path of the intercooler (11) is located between the throttle valve (4) and the first check valve (5), and the other end of the second path is connected to the four-way valve (2). One end of the low-pressure compressor (9) is connected to the second heat exchanger (8), and the other end is connected to the second path of the intercooler (11); A second check valve (14) is provided between the intercooler (11) and the second heat exchanger (8). The first one-way valve (5) is open from the dryer (6) to the throttle valve (4); The second one-way valve (14) is open from the intercooler (11) to the second heat exchanger (8).
2. The single-stage / dual-stage switching and combined heat pump according to claim 1, characterized in that, The first heat exchanger (3) has the same structure as the second heat exchanger (8).
3. A single-stage / dual-stage switching and combined heat pump according to claim 1, characterized in that, The throttle valve (4) is a two-way throttle valve (4).