Heat pump system, low-temperature waste heat recovery method, and adjustment method for heat pump system

Abstract

The application discloses a heat pump system, a low-temperature waste heat recovery method and a regulating method of the heat pump system, and relates to the technical field of waste heat recovery. The heat pump system comprises a low-temperature waste heat conveying pipeline, a low-temperature evaporator, a low-temperature compressor, an evaporation condenser, a high-temperature compressor, a high-temperature condenser, a high-temperature heat demand unit, a first connecting pipeline, a second connecting pipeline, a third connecting pipeline, a low-temperature expansion valve and a high-temperature expansion valve. The low-temperature waste heat conveying pipeline is connected with the low-temperature evaporator. The first connecting pipeline is connected with the low-temperature evaporator, the low-temperature compressor, the evaporation condenser and the low-temperature expansion valve in sequence and is closed. The second connecting pipeline is connected with the evaporation condenser, the high-temperature compressor, the high-temperature condenser and the high-temperature expansion valve in sequence and is closed. The third connecting pipeline is connected with the high-temperature condenser and the high-temperature heat demand unit and is closed. The heat pump system realizes the recycling and step-by-step upgrading of low-temperature waste heat, reduces the load and energy consumption of each stage compressor, reduces the performance attenuation of the heat pump system and improves the benefit of low-temperature waste heat recovery.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery technology, and in particular to a heat pump system, a low-temperature waste heat recovery method, and a method for regulating the heat pump system. Background Technology

[0002] In many industrial processes, such as petrochemicals, cooling towers and other equipment generate a significant amount of condensation heat at 30-40°C, which is difficult to utilize directly. However, industrial heating demands typically exceed 100°C. Due to the large temperature difference between the heat source and the heat demand, the pressure difference between the heat transfer medium in the evaporator and condenser increases. The compressor needs to overcome this greater pressure difference to compress the heat, thus increasing the compressor's load and energy consumption, and reducing the efficiency of low-temperature waste heat recovery. Summary of the Invention

[0003] The main objective of this invention is to propose a heat pump system that aims to reduce the load and energy consumption of the compressor, and to fully utilize the heat source generated by the heat pump and the heat at various temperature levels within the heat demand temperature range, thereby improving the efficiency of low-temperature waste heat recovery.

[0004] To achieve the above objectives, the heat pump system proposed in this invention includes a low-temperature waste heat delivery pipeline, a low-temperature evaporator, a low-temperature compressor, an evaporative condenser, a high-temperature compressor, a high-temperature condenser, a high-temperature heat demand unit, a first connecting pipeline, a second connecting pipeline, a third connecting pipeline, a low-temperature expansion valve, and a high-temperature expansion valve. The low-temperature waste heat delivery pipeline is connected to the low-temperature evaporator. The first connecting pipeline sequentially connects the low-temperature evaporator, the low-temperature compressor, and the evaporative condenser to form a closed loop. The second connecting pipeline sequentially connects the evaporative condenser, the high-temperature compressor, and the high-temperature condenser to form a closed loop. The third connecting pipeline connects the high-temperature condenser and the high-temperature heat demand unit to form a closed loop. The low-temperature expansion valve is located in the first connecting pipeline and downstream of the evaporative condenser. The high-temperature expansion valve is located in the second connecting pipeline and downstream of the high-temperature condenser.

[0005] In one embodiment, the heat pump system further includes a medium-temperature condenser, a fourth connecting pipe, and a medium-temperature heat demand unit; the medium-temperature condenser is disposed on the first connecting pipe and located downstream of the evaporator-condenser; the fourth connecting pipe connects the medium-temperature condenser and the medium-temperature heat demand unit to form a closed loop.

[0006] In one embodiment, the heat pump system further includes a fifth connecting pipe and a low-temperature cooling unit; the fifth connecting pipe connects the low-temperature evaporator and the low-temperature cooling unit to form a closed loop.

[0007] In one embodiment, the first and second connecting pipes are filled with refrigerant, and the third, fourth, and fifth connecting pipes are filled with secondary fluid.

[0008] The present invention also proposes a low-temperature waste heat recovery method, based on the heat pump system described in the above embodiments, comprising the following steps:

[0009] Low-temperature waste water is fed into a low-temperature waste heat transmission pipeline and passes through a low-temperature evaporator;

[0010] The heat from the low-temperature waste water is recovered through the low-temperature evaporator and used to heat the refrigerant in the first connecting pipe.

[0011] The refrigerant in the first connecting pipe is compressed by a low-temperature compressor to obtain medium-temperature heat.

[0012] The medium-temperature heat is recovered by an evaporator and used to heat the refrigerant in the second connecting pipe. The refrigerant in the second connecting pipe is compressed by a high-temperature compressor to obtain high-temperature heat.

[0013] The high-temperature heat is recovered by a high-temperature condenser and used to heat the high-temperature heat demand unit.

[0014] In one embodiment, after the steps of recovering the intermediate-temperature heat through an evaporator-condenser and using it to heat the refrigerant in the second connecting pipe, and compressing the refrigerant in the second connecting pipe to obtain high-temperature heat through a high-temperature compressor, the method further includes the following steps:

[0015] The medium-temperature heat is recovered by a medium-temperature condenser and used to heat the medium-temperature heat demand unit.

[0016] In one embodiment, before the step of compressing the refrigerant in the first connecting pipe to obtain intermediate-temperature heat using a cryogenic compressor, the following step is further included:

[0017] The heat of the secondary fluid in the fifth connecting pipe is recovered by the low-temperature evaporator and used to heat the refrigerant in the first connecting pipe;

[0018] Cooling is supplied to the low-temperature cooling unit through the secondary fluid in the fifth connecting pipe after cooling.

[0019] The present invention also proposes a method for regulating a heat pump system, based on the heat pump system described in the above embodiments, comprising the following steps:

[0020] Obtain the heating demand of the high-temperature heat demand unit and define it as Q. h Obtain the heating demand of the medium-temperature heat demand unit and define it as Q. m The average heat exchange temperature of the high-temperature condenser is obtained and defined as t.h The average heat exchange temperature of the medium-temperature condenser is obtained and defined as t. m ;

[0021] Adjusting the frequency of the cryogenic compressor and the high-temperature compressor to make t h Stable within the temperature range required by the high-temperature heating unit and meet Q h ;

[0022] Adjust the frequency of the cryogenic compressor and the flow rate of the second connecting pipe to make t m Stable within the temperature range required by the medium-temperature heating unit and meeting Q m .

[0023] In one embodiment, the heating demand of the high-temperature heat demand unit is obtained and defined as Q. h Obtain the heating demand of the medium-temperature heat demand unit and define it as Q. m The average heat exchange temperature of the high-temperature condenser is obtained and defined as t. h The average heat exchange temperature of the medium-temperature condenser is obtained and defined as t. m Following the steps above, the following steps are also included:

[0024] Obtain the cooling demand of the low-temperature cooling unit and define it as Q. c ;

[0025] Comparison and judgment Q c With Q h The size of Q c Greater than Q h This increases the heat exchange capacity of the medium-temperature condenser (11). If Q c Less than Q h This reduces the heat exchange capacity of the medium-temperature condenser (11).

[0026] The heat pump system proposed in this invention includes a low-temperature waste heat delivery pipeline, a low-temperature evaporator, a low-temperature compressor, an evaporative condenser, a high-temperature compressor, a high-temperature condenser, a high-temperature heat demand unit, a first connecting pipeline, a second connecting pipeline, a third connecting pipeline, a low-temperature expansion valve, and a high-temperature expansion valve. The low-temperature waste heat delivery pipeline is connected to the low-temperature evaporator. The first connecting pipeline sequentially connects the low-temperature evaporator, the low-temperature compressor, and the evaporative condenser to form a closed loop, forming a low-temperature compression heat pump cycle. The second connecting pipeline sequentially connects the evaporative condenser, the high-temperature compressor, and the high-temperature condenser to form a closed loop, forming a high-temperature compression heat pump cycle. The third connecting pipeline connects the high-temperature condenser and the high-temperature heat demand unit to form a closed loop, forming a high-temperature heating cycle. The low-temperature expansion valve is located in the first connecting pipeline and downstream of the evaporative condenser. The high-temperature expansion valve is located in the second connecting pipeline and downstream of the high-temperature condenser. In this way, low-temperature waste heat is recovered and utilized through low-temperature section compression heat pump cycle loop, high-temperature section compression heat pump cycle loop and high-temperature heating loop, and the quality is improved step by step. This reduces the load and energy consumption of the compressor in each loop, reduces the performance degradation of the heat pump system, and makes full use of the heat at each temperature level, thereby improving the efficiency of low-temperature waste heat recovery. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of a structure of an embodiment of the heat pump system provided by the present invention;

[0029] Figure 2 A flowchart of an embodiment of the low-temperature waste heat recovery method provided by the present invention;

[0030] Figure 3 A flowchart of another embodiment of the low-temperature waste heat recovery method provided by the present invention;

[0031] Figure 4 A flowchart of yet another embodiment of the low-temperature waste heat recovery method provided by the present invention;

[0032] Figure 5 A flowchart of another embodiment of the low-temperature waste heat recovery method provided by the present invention;

[0033] Figure 6 A flowchart of an embodiment of the adjustment method provided by the present invention;

[0034] Figure 7 A flowchart of yet another embodiment of the adjustment method provided by the present invention;

[0035] Figure 8 for Figure 1 Schematic diagram of the operation mode of a medium-temperature heat pump system.

[0036] Explanation of icon numbers:

[0037] 100. Heat pump system;

[0038] 1. Low-temperature waste heat transfer pipeline; 2. Low-temperature evaporator; 3. Low-temperature compressor; 4. Evaporator-condenser; 5. High-temperature compressor; 6. High-temperature condenser; 7. High-temperature heat demand unit; 8. First connecting pipeline; 9. Second connecting pipeline; 10. Third connecting pipeline; 11. Medium-temperature condenser; 12. Fourth connecting pipeline; 13. Medium-temperature heat demand unit; 14. Low-temperature expansion valve; 15. High-temperature expansion valve; 16. Fifth connecting pipeline; 17. Low-temperature cooling unit.

[0039] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0042] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0043] This invention proposes a heat pump system 100.

[0044] Please see Figure 1 In one embodiment of the present invention, the heat pump system 100 includes a low-temperature waste heat transmission pipeline 1, a low-temperature evaporator 2, a low-temperature compressor 3, an evaporative condenser 4, a high-temperature compressor 5, a high-temperature condenser 6, a high-temperature heat demand unit 7, a first connecting pipeline 8, a second connecting pipeline 9, a third connecting pipeline 10, a low-temperature expansion valve 14, and a high-temperature expansion valve 15; the low-temperature waste heat transmission pipeline 1 is connected to the low-temperature evaporator 2; the first connecting pipeline 8 sequentially connects the low-temperature evaporator 2, the low-temperature compressor 3, and the evaporative condenser 4 to form a closed loop; the second connecting pipeline 9 sequentially connects the evaporative condenser 4, the high-temperature compressor 5, and the high-temperature condenser 6 to form a closed loop; the third connecting pipeline 10 connects the high-temperature condenser 6 and the high-temperature heat demand unit 7 to form a closed loop; the low-temperature expansion valve 14 is located in the first connecting pipeline 8 and downstream of the medium-temperature condenser 11; the high-temperature expansion valve 15 is located in the second connecting pipeline 9 and downstream of the high-temperature condenser 6.

[0045] In this embodiment, the low-temperature evaporator 2 is connected to a low-temperature waste heat transfer pipeline 1. The first connecting pipeline 8 sequentially connects the low-temperature evaporator 2, the low-temperature compressor 3, and the evaporator-condenser 4 to form a closed loop, thus forming a low-temperature section compression heat pump circulation loop. The second connecting pipeline 9 sequentially connects the evaporator-condenser 4, the high-temperature compressor 5, and the high-temperature condenser 6 to form a closed loop, thus forming a high-temperature section compression heat pump circulation loop. The third connecting pipeline 10 connects the high-temperature condenser 6 and the high-temperature heat demand unit 7 to form a closed loop, thus forming a high-temperature heating cycle. The first connecting pipeline 8, the second connecting pipeline 9, and the third connecting pipeline 10 are all filled with a flowable heat transfer medium. Specifically, the first connecting pipeline 8 and the second connecting pipeline 9 are filled with refrigerant, and the third connecting pipeline 10 is filled with a secondary fluid.

[0046] In the low-temperature compression heat pump cycle, the refrigerant in the first connecting pipe 8 absorbs the heat from the low-temperature waste heat in the low-temperature evaporator 2 and is transferred to the low-temperature, low-pressure pipeline 1, becoming a low-temperature, low-pressure gas. This gas is then compressed by the low-temperature compressor 3 into a high-temperature, high-pressure gas, and subsequently enters the evaporator-condenser 4 and the medium-temperature condenser 11 to condense and release heat, becoming a high-temperature, high-pressure liquid. Finally, it returns to the low-temperature evaporator 2 to complete the low-temperature cycle. In the high-temperature compression heat pump cycle, the refrigerant in the second connecting pipe 9 absorbs the condensation heat of the refrigerant in the first connecting pipe 8 in the evaporator-condenser 4, becoming a low-temperature, low-pressure gas. This gas is then compressed by the high-temperature compressor 5 into a high-temperature, high-pressure gas, and subsequently enters the high-temperature condenser 6 to release heat, becoming a high-temperature, high-pressure liquid. Finally, it returns to the evaporator-condenser 4 to complete the high-temperature cycle. In the high-temperature heating cycle, the secondary fluid in the third connecting pipe 10 absorbs the condensation heat of the refrigerant in the second connecting pipe 9 in the high-temperature condenser 6 and is transported to the high-temperature heating unit 7.

[0047] Specifically, the low-temperature waste heat transfer pipeline 1 is used to transfer low-temperature waste heat of 30-40°C from the industrial process (e.g., cooling tower) to the low-temperature evaporator 2. The low-temperature evaporator 2 can utilize the low-temperature waste heat as a heat source, and through the heat absorption process of refrigerant evaporation in the first connecting pipeline 8, the low-temperature waste heat is transported to the evaporator condenser 4. During this process, the low-temperature compressor 3 compresses the low-temperature, low-pressure refrigerant gas into a high-temperature, high-pressure refrigerant gas, providing conditions for the refrigerant to release heat in the condenser. It should be noted that the above description of the refrigerant temperature / pressure is a comparison of the temperature / pressure of the refrigerant in the first connecting pipeline 8, and should not be considered a comparison with the refrigerant outside the first connecting pipeline 8. Similarly, the temperature / pressure descriptions mentioned below are limited to comparisons within the same closed loop, and will not be elaborated further. In the evaporator-condenser 4, the refrigerant in the first connecting pipe 8 and the refrigerant in the second connecting pipe 9 exchange heat. The refrigerant in the first connecting pipe 8 releases heat, while the low-temperature, low-pressure refrigerant in the second connecting pipe 9 absorbs heat and becomes a high-temperature, low-pressure refrigerant (medium-temperature heat of 60°C). The refrigerant in the second connecting pipe 9 is transported along the second connecting pipe 9 to the high-temperature condenser 6. During this process, the high-temperature compressor 5 compresses the high-temperature, low-pressure heat transfer medium gas into a high-temperature, high-pressure refrigerant gas, providing conditions for the refrigerant to release heat in the high-temperature condenser 6. In the high-temperature condenser 6, the refrigerant in the second connecting pipe 9 releases heat, generating high-temperature process heat (high-temperature heat above 100°C), which is then transported to the high-temperature heat demand unit 7 via the third connecting pipe 10. The high-temperature heat demand unit 7 receives the high-temperature process heat from the high-temperature condenser 6 for industrial production or other high-temperature needs (90–150°C).

[0048] The heat pump system 100 also includes a low-temperature expansion valve 14 and a high-temperature expansion valve 15; the low-temperature expansion valve 14 is located in the first connecting pipe 8 and downstream of the medium-temperature condenser 11; the high-temperature expansion valve 15 is located in the second connecting pipe 9 and downstream of the high-temperature condenser 6.

[0049] In this embodiment, the low-temperature expansion valve 14 and the high-temperature expansion valve 15 can respectively regulate the refrigerant flow rate in the low-temperature cycle and the high-temperature cycle, ensuring that the system achieves optimal heat exchange performance under different operating modes. The expansion valves can also reduce the refrigerant pressure through throttling, ensuring that the refrigerant reaches an appropriate evaporation pressure before entering the evaporator, thereby guaranteeing sufficient heat absorption through evaporation in the evaporator. For example, in the low-temperature cycle of the first connecting pipe 8, the refrigerant pressure decreases and its temperature drops accordingly due to the throttling effect of the low-temperature expansion valve 14, preparing it for entry into the low-temperature evaporator 2. This allows the refrigerant to more effectively absorb residual heat in the low-temperature evaporator 2, improving the heat exchange efficiency of the low-temperature cycle. Similarly, in the high-temperature cycle of the second connecting pipe 9, the refrigerant also needs to have its pressure and temperature reduced. The high-temperature expansion valve 15 achieves this goal through throttling, ensuring that the refrigerant reaches an appropriate evaporation pressure before entering the evaporator-condenser 4. This allows the refrigerant to more effectively absorb the heat transferred from the low-temperature cycle in the evaporator-condenser 4, providing a stable heat source for high-temperature processes. In addition, the expansion valve can control the superheat of the refrigerant, preventing excessive or incomplete evaporation of the refrigerant in the evaporator, thereby improving the system's heat exchange efficiency. Adjustment of the expansion valve can also prevent refrigerant from entering the compressor at excessively high or low pressures, thus protecting the compressor from damage.

[0050] Thus, this embodiment recovers and utilizes low-temperature waste heat through a low-temperature section compression heat pump cycle loop, a high-temperature section compression heat pump cycle loop, and a high-temperature heating circuit. Furthermore, it improves the quality of each stage, reducing the load and energy consumption of the compressor in each circuit, reducing the performance degradation of the heat pump system by 100%, and improving the efficiency of low-temperature waste heat recovery. It can recover low-temperature waste heat of 30-40°C that is widely present in industrial processes such as petrochemicals.

[0051] Further, please refer to Figure 1 In one embodiment of the present invention, the heat pump system 100 further includes a medium-temperature condenser 11, a fourth connecting pipe 12, and a medium-temperature heat demand unit 13; the medium-temperature condenser 11 is disposed on the first connecting pipe 8 and located downstream of the evaporator condenser 4; the fourth connecting pipe 12 connects the medium-temperature condenser 11 and the medium-temperature heat demand unit 13 to form a closed loop.

[0052] In this embodiment, in the first connecting pipe 8, the refrigerant downstream of the evaporator-condenser 4 cools to approximately 60°C after releasing heat. If this heat were to directly return to the low-temperature evaporator 2, it would reduce heat utilization. Therefore, this embodiment also includes a medium-temperature condenser 11, a fourth connecting pipe 12, and a medium-temperature heat demand unit 13. The medium-temperature condenser 11 is located downstream of the evaporator-condenser 4 in the first connecting pipe 8. The fourth connecting pipe 12 connects the medium-temperature condenser 11 and the medium-temperature heat demand unit 13 to form a closed loop, thus creating a medium-temperature heating cycle. Thus, after the refrigerant completes heat exchange in the evaporator-condenser 4, its temperature drops to approximately 60°C. At this point, the refrigerant does not directly return to the low-temperature evaporator 2 but flows through the medium-temperature condenser 11. In the medium-temperature condenser 11, the refrigerant in the first connecting pipe 8 exchanges heat with the secondary fluid in the fourth connecting pipe 12, further releasing heat to meet the heat demand of the medium-temperature heat demand unit 13 (for hot water or heating, etc.), avoiding heat waste and improving the heat utilization rate of the heat pump system 100. Therefore, the refrigerant downstream of the evaporator condenser 4 returns to the low-temperature evaporator 2 for the next cycle after further cooling, improving the heat transfer efficiency of the low-temperature evaporator 2.

[0053] Further, please refer to Figure 1 In one embodiment of the present invention, the heat pump system 100 further includes a fifth connecting pipe 16 and a low-temperature cooling unit 17; the fifth connecting pipe 16 connects the low-temperature evaporator 2 and the low-temperature cooling unit 17 to form a closed loop.

[0054] In this embodiment, to more fully utilize the potential of the heat pump system 100, a fifth connecting pipe 16 and a low-temperature cooling unit 17 are added. The fifth connecting pipe 16 connects the low-temperature evaporator 2 and the low-temperature cooling unit 17, forming an independent closed loop, thus creating a low-temperature cooling cycle. The return water from the low-temperature cooling cycle (within the fifth connecting pipe 16) flows through the low-temperature evaporator 2 as a heat source and is cooled to 7°C to serve as chilled water. The fifth connecting pipe 16 then delivers the 7°C cooling capacity to the low-temperature cooling unit 17. In this way, the heat pump system 100 can not only provide medium- and high-temperature heat but also meet low-temperature cooling requirements.

[0055] Further, please refer to Figure 1 In one embodiment of the present invention, the first connecting pipe 8 and the second connecting pipe 9 are filled with refrigerant, and the third connecting pipe 10, the fourth connecting pipe 12 and the fifth connecting pipe 16 are filled with secondary fluid.

[0056] In this embodiment, to ensure efficient and stable heat transfer between the various parts of the heat pump system 100, different heat transfer media are filled in the first connecting pipe 8, the second connecting pipe 9, the third connecting pipe 10, the fourth connecting pipe 12, and the fifth connecting pipe 16. The heat transfer media is the substance filled in the pipes to transfer heat. In the heat pump system 100, the heat transfer media that can be used in the first connecting pipe 8 and the second connecting pipe 9 include refrigerants such as R290 or R600; the heat transfer media that can be used in the third connecting pipe 10, the fourth connecting pipe 12, and the fifth connecting pipe 16 include secondary fluids such as water and ethylene glycol solutions. These media have characteristics such as high thermal conductivity, low viscosity, and good chemical stability, and can effectively absorb, transfer, and release heat.

[0057] Please see Figure 8 In conjunction with the above embodiments, the heat pump system 100 proposed in this invention has seven operating modes, as follows:

[0058] Heating and process heat supply mode: During the building heating season, cooling water at 30-40℃ flows through the low-temperature evaporator 2 as a heat source, and is upgraded by a low-temperature compression heat pump to generate medium-temperature heat. This medium-temperature heat is divided into two parts: one part is allocated to the evaporator-condenser 4 for further upgrading by a high-temperature compression heat pump to generate high-temperature heat for industrial production; the other part is allocated to the medium-temperature condenser 11 to generate medium-temperature heat for heating or domestic hot water. In this mode, the available low-temperature waste heat is considered sufficient. The high-temperature and medium-temperature heat demands are denoted as Q. h and Q m The average heat exchange temperature in the medium-temperature condenser 11 is obtained and recorded as t. m First, by adjusting the frequencies of the low-temperature stage compressor and the high-temperature stage compressor, t... m It remains stable at around 60℃, meeting the medium-temperature heat demand, and satisfies Q. h Next, by adjusting the frequency of the low-temperature compressor 3 and the water flow rate of the medium-temperature heating circuit, t m It remains stable at around 60℃, meeting the medium-temperature heat demand, and satisfies Q. m .

[0059] Cooling, (heating), and process heat supply modes: During the building's cooling season, the return water from the low-temperature cooling cycle (within the fifth connecting pipe 16) flows through the low-temperature evaporator 2 as a heat source and is cooled to 7°C for use as chilled water supply. The low-temperature cooling demand, medium-temperature heating demand, and high-temperature heating demand are denoted as Q, respectively. c Q m Q h Because it is the building's cooling season, there is no specific medium-temperature heating demand Q in the scenario. m Therefore, Q will be satisfied first. c and Q hThis can reduce the power of the intermediate-temperature condenser 11 or even shut it down to reduce the load on the low-temperature compressor 3. If Q is satisfied at this time... c and Q h If there is still excess heat, the medium-temperature condenser 11 can be activated to produce medium-temperature hot water to meet some of the domestic heating needs. When Q h / Q c When the value is large, the Q value can be met by increasing the frequencies of the low-temperature stage compressor and the high-temperature stage compressor. c and Q h This refers to both cooling and process heating modes. When Q... h / Q c When the value is small, Q should be satisfied first. c At this time, the low-temperature compressor 3 is kept running at a higher frequency, the frequency of the high-temperature compressor 5 is reduced, and the heat exchange efficiency of the medium-temperature condenser 11 is increased, so that t m The temperature is stabilized at around 60℃ for medium-temperature heat demand, and the excess Q in the low-temperature section of the compression heat pump cycle (first connecting pipe 8) m The heat is carried away by the medium-temperature heating cycle (fourth connecting pipe 12), causing the temperature of the heat transfer medium returning to the low-temperature evaporator 2 to decrease. The heat transfer medium in the low-temperature evaporator 2 can more effectively absorb heat from the low-temperature cooling cycle (fifth connecting pipe 16) to better supply cooling to the low-temperature cooling unit 17, thus forming a cooling, heating, and process heat supply mode. Furthermore, if there is no precise quantity of Q... h and Q c , then t m The frequency of the high-temperature compressor 5 can be adjusted according to the principle of maximizing energy efficiency. First, fix the frequency of the high-temperature compressor 5, and change the frequency of the low-temperature compressor 3 to achieve the optimal intermediate temperature (average heat exchange temperature of the intermediate-temperature condenser 11). Increasing the frequency of the low-temperature compressor 3 will raise the intermediate temperature, and decreasing the frequency of the low-temperature compressor 3 will lower the intermediate temperature. When the intermediate temperature is at its optimal value, the energy consumption of both the low-temperature compressor 3 and the high-temperature compressor 5 will be minimized.

[0060] Cooling and heating mode: During the building's cooling season, the high-temperature stage compressor does not need to be turned on, so the heat pump system 100 becomes a residential cooling and heating system in the normal temperature range. In this mode, the frequency of the high-temperature compressor 5 can be reduced or the high-temperature section compression heat pump cycle can be shut down. By increasing the frequency of the low-temperature stage compressor and the heat exchange efficiency of the medium-temperature condenser 11, priority is given to meeting Q. c The heat generated by the low-temperature compressor 3 is used to prepare medium-temperature domestic hot water.

[0061] Cooling mode: During the building's cooling season, no medium-temperature hot water is needed, and the medium-temperature condensation heat is dissipated, which constitutes a single cooling mode. This can be achieved by increasing the frequency of the low-temperature stage compressor to meet Q. c .

[0062] Heating Mode: During the building's heating season, the high-temperature stage compressor does not need to be turned on, so the heat pump system 100 is a residential heating system operating within the normal temperature range. In this mode, the heat generated by the low-temperature evaporator 2 using low-temperature waste heat is utilized by the medium-temperature condenser 11 and supplied to the medium-temperature heat demand unit 13. The heating needs of Q can be met by increasing the frequency of the low-temperature stage compressor. m .

[0063] Process heat supply mode: During non-heating and non-cooling seasons, only process heat is required. In this mode, the low-temperature evaporator 2 recovers and utilizes low-temperature waste heat, which is then upgraded by the low-temperature compressor 3 and the high-temperature compressor 5, generating high-temperature process heat in the high-temperature condenser 6 and transported to the high-temperature heat demand unit 7 through the third connecting pipeline 10.

[0064] Please see Figure 2 and Figure 5 The present invention also proposes a low-temperature waste heat recovery method, based on the heat pump system 100 described in the above embodiments, comprising the following steps:

[0065] Low-temperature waste water is fed into low-temperature waste heat transmission pipeline 1 and passes through low-temperature evaporator 2;

[0066] The heat from the low-temperature waste water is recovered through the low-temperature evaporator 2 and used to heat the refrigerant in the first connecting pipe 8;

[0067] The refrigerant in the first connecting pipe 8 is compressed by the low-temperature compressor 3 to obtain medium-temperature heat.

[0068] The medium-temperature heat is recovered by the evaporator condenser 4 and used to heat the refrigerant in the second connecting pipe 9. The high-temperature heat is obtained by compressing the refrigerant in the second connecting pipe 9 by the high-temperature compressor 5.

[0069] The high-temperature heat is recovered by the high-temperature condenser 6 and used to heat the high-temperature heat demand unit 7.

[0070] In this embodiment, in order to recover the condensation heat (30-40°C) from many industrial processes such as petrochemicals and use it for industrial heating (>90°C), a low-temperature waste heat recovery method is proposed based on the above embodiment, specifically as follows:

[0071] First, the low-temperature waste water is introduced into the low-temperature waste heat transfer pipeline 1 and then through the low-temperature evaporator 2. This step is the initial stage of low-temperature waste heat recovery, drawing the 30-40°C low-temperature waste heat generated during the industrial process to the low-temperature evaporator 2 via the low-temperature waste heat transfer pipeline 1. It is important to ensure stable flow and temperature of the low-temperature waste water during this process to maintain the effective operation of the low-temperature evaporator 2. The low-temperature waste heat transfer pipeline 1 should have good insulation properties to reduce heat loss during transmission. The medium (such as water, air, etc.) within the low-temperature waste heat transfer pipeline 1 carries the heat into the low-temperature evaporator 2.

[0072] Secondly, the heat from the low-temperature waste water is recovered by the low-temperature evaporator 2 and used to heat the refrigerant in the first connecting pipe 8. The refrigerant in the first connecting pipe 8 is then compressed by the low-temperature compressor 3 to obtain medium-temperature heat. In this process, the low-temperature evaporator 2 absorbs the heat from the low-temperature waste water, causing the refrigerant in the first connecting pipe 8 to evaporate. The low-temperature compressor 3 then compresses the evaporated low-temperature, low-pressure refrigerant gas to increase its temperature and pressure, thereby obtaining medium-temperature heat.

[0073] Next, the intermediate-temperature heat is recovered through the evaporator-condenser 4 and used to heat the refrigerant in the second connecting pipe 9. The high-temperature compressor 5 then compresses the refrigerant in the second connecting pipe 9 to obtain high-temperature heat. In this process, the intermediate-temperature heat is released in the evaporator-condenser 4 to heat the refrigerant in the second connecting pipe 9, while the high-temperature compressor 5 further increases the heat of the refrigerant in the second connecting pipe 9 to a higher level.

[0074] Finally, the high-temperature heat is recovered through the high-temperature condenser 6 and used to heat the high-temperature heat demand unit 7. In this process, the refrigerant with high-temperature heat releases heat in the high-temperature condenser 6 and delivers a stable high-temperature heat source to the high-temperature heat demand unit 7 via the third connecting pipe 10. After releasing heat in the high-temperature condenser 6, the refrigerant changes from a gaseous state to a liquid state and then returns to the evaporator-condenser 4 for the next cycle.

[0075] Understandably, this low-temperature waste heat recovery method recovers low-temperature waste heat through a low-temperature evaporator 2 and, after two stages of upgrading and transfer, can be used in industrial heating with high temperature requirements, reducing energy waste and achieving the goal of energy conservation and emission reduction.

[0076] Further, please refer to Figure 3 and Figure 5 After the steps of recovering the medium-temperature heat through the evaporator-condenser 4 and using it to heat the refrigerant in the second connecting pipe 9, and compressing the refrigerant in the second connecting pipe 9 to obtain high-temperature heat through the high-temperature compressor 5, the following steps are also included:

[0077] The medium-temperature heat is recovered by the medium-temperature condenser 11 and used to heat the medium-temperature heat demand unit 13.

[0078] In this embodiment, to further meet the demand for medium-temperature heating, realize the cascade utilization of energy in the heat pump system 100, and fully leverage the flexibility of the heat pump system 100's energy supply, after the steps of recovering the medium-temperature heat through the evaporator-condenser 4 and using it to heat the refrigerant in the second connecting pipe 9, and compressing the refrigerant in the second connecting pipe 9 with the high-temperature compressor 5 to obtain high-temperature heat, the following step is performed: recovering the medium-temperature heat through the medium-temperature condenser 11 and using it to heat the medium-temperature heat demand unit 13. This step further recovers the medium-temperature heat, realizes the cascade utilization of thermal energy, and improves the overall energy efficiency of the system. The recovered heat is used by the medium-temperature condenser 11 to heat the medium-temperature heat demand unit 13, meeting the demand for medium-temperature thermal energy in industrial or other applications. After releasing heat in the evaporator-condenser 4, the temperature of the refrigerant that originally had medium-temperature heat decreases, and some of the refrigerant may change from a gaseous state to a liquid state. Subsequently, this part of the refrigerant flows into the medium-temperature condenser 11. In the medium-temperature condenser 11, the refrigerant further releases heat, completely liquefies, and finally returns to the low-temperature evaporator 2 to prepare for the next cycle. Through this step, the heat pump system 100 not only achieves efficient recovery and utilization of low-temperature waste heat, but also further expands the application range of thermal energy (it can be used for medium-temperature heating, etc.), improving the overall economic and environmental benefits of the system.

[0079] Please see Figure 4 and Figure 5 Before the step of compressing the refrigerant in the first connecting pipe 8 using the low-temperature compressor 3 to obtain medium-temperature heat, the following steps are also included:

[0080] The heat of the secondary fluid in the fifth connecting pipe 16 is recovered by the low-temperature evaporator 2 and used to heat the refrigerant in the first connecting pipe 8;

[0081] Cooling is supplied to the low-temperature cooling unit 17 through the secondary fluid in the fifth connecting pipe 16 after cooling.

[0082] In this embodiment, to further meet the demand for low-temperature cooling, realize the cascade utilization of energy in the heat pump system 100, and fully leverage the flexibility of the heat pump system 100's energy supply, the secondary fluid in the fifth connecting pipe 16 is passed through the low-temperature evaporator 2. The low-temperature evaporator 2 absorbs the heat from the secondary fluid in the fifth connecting pipe 16 to heat the refrigerant in the first connecting pipe 8. After flowing through the low-temperature evaporator 2, the secondary fluid in the fifth connecting pipe 16 is cooled and supplied to the low-temperature cooling unit 17. This step realizes the reuse of low-temperature cold energy and improves energy utilization efficiency. By cooling the secondary fluid in the fifth connecting pipe 16, cooling capacity can be provided to the low-temperature cooling unit 17 to meet the low-temperature cooling needs of certain industrial processes or equipment. Through this step, the heat pump system 100 achieves the combined supply of heat and cold energy, further improving the overall performance and economic benefits of the system.

[0083] Please see Figure 6 The present invention also proposes a method for adjusting a heat pump system 100, based on the heat pump system 100 described in the above embodiments, comprising the following steps:

[0084] Obtain the heating demand of high-temperature heat demand unit 7 and define it as Q. h Obtain the heating demand of the medium-temperature heat demand unit 13 and define it as Q. m The average heat exchange temperature of the high-temperature condenser 6 is obtained and defined as t. h The average heat exchange temperature of the medium-temperature condenser 11 is obtained and defined as t. m ;

[0085] Adjusting the frequency of cryogenic compressor 3 and high-temperature compressor 5 to make t h Stable within the temperature range required by the high-temperature heating unit and meet Q h ;

[0086] Adjust the frequency of the cryogenic compressor 3 and the flow rate of the second connecting pipe 9 to make t m Stable within the temperature range required by the medium-temperature heating unit and meeting Q m .

[0087] Based on the above-described 100 embodiments of the heat pump system, the adjustment method proposed in this invention aims to ensure that the system efficiently and stably meets the heating demands at different temperature levels. The following is a detailed description of each step. It is understood that the following adjustments can be automatically implemented by setting up an intelligent control system, which is faster and more precise than manual adjustment:

[0088] Obtain the heating demand Q of high-temperature heat demand unit 7 h Measuring or calculating the heat required by the high-temperature heat demand unit 7 is crucial for system regulation. Obtaining the heating demand Q of the medium-temperature heat demand unit 13 is also essential. mSimilarly, measure or calculate the heat required by the intermediate-temperature heat demand unit 13. Obtain the average heat exchange temperature t of the high-temperature condenser 6. h Monitor the average temperature of the high-temperature condenser 6 during the heat exchange process. Obtain the average heat exchange temperature t of the medium-temperature condenser 11. m : Monitor the average temperature of the medium-temperature condenser 11 during the heat exchange process.

[0089] Adjusting the frequencies of the low-temperature compressor 3 and the high-temperature compressor 5 to achieve the average heat exchange temperature t of the high-temperature condenser 6 h The temperature remains stable within the range required by the high-temperature heating unit and meets the heating demand Q of the high-temperature heating unit 7. h This process controls the heat exchange temperature and heat output of the high-temperature condenser 6 by adjusting the operating frequencies of the low-temperature compressor 3 and the high-temperature compressor 5, thereby changing the compression degree and circulation speed of the heat transfer medium. Specifically:

[0090] First, the average heat exchange temperature t of the high-temperature condenser 6 is monitored in real time using a temperature sensor. h According to t h The value is compared with the temperature range required by the high-temperature heating unit, and the difference is calculated; the frequencies of the low-temperature compressor 3 and the high-temperature compressor 5 are adjusted according to the difference. If t h If the temperature is below the required range, the heat output of the high-temperature condenser 6 needs to be increased; therefore, the frequencies of the low-temperature compressor 3 and the high-temperature compressor 5 should be increased. Increasing the frequency will accelerate the circulation speed and compression of the heat transfer medium, thereby increasing the heat exchange temperature of the high-temperature condenser 6. If t h If the temperature exceeds the required range, the heat output of the high-temperature condenser 6 needs to be reduced. Therefore, the frequencies of the low-temperature compressor 3 and the high-temperature compressor 5 should be lowered. Lowering the frequency will slow down the circulation speed and compression of the heat transfer medium, thereby reducing the heat exchange temperature of the high-temperature condenser 6.

[0091] Adjust the frequency of the cryogenic compressor 3 and the flow rate of the second connecting pipe 9 to make t m Stable within the temperature range required by the medium-temperature heating unit and meeting Q m This process involves real-time monitoring of the average heat exchange temperature t of the intermediate-temperature condenser 11 using a temperature sensor. m According to t m The value is compared with the temperature range required by the medium-temperature heating unit, and the difference is calculated; based on the difference, the control system issues instructions to adjust the frequency of the low-temperature compressor 3 and the refrigerant flow rate in the second connecting pipe 9. If t m If the temperature is below the required range, the heat output of the intermediate-temperature condenser 11 needs to be increased. Therefore, the frequency of the low-temperature compressor 3 should be increased and the flow rate of the second connecting pipe 9 should be increased. Increasing the frequency and flow rate will accelerate the refrigerant circulation speed and heat transfer rate, thereby increasing the heat exchange temperature of the intermediate-temperature condenser 11. If tm If the temperature exceeds the required range, the heat output of the intermediate-temperature condenser 11 needs to be reduced. Therefore, the frequency of the low-temperature compressor 3 should be lowered and the flow rate of the second connecting pipe 9 should be reduced. Lowering the frequency and reducing the flow rate will slow down the refrigerant circulation and heat transfer, thereby lowering the heat exchange temperature of the intermediate-temperature condenser 11. It is important to note that the system's response speed needs to be considered during the adjustment process to avoid over-adjustment or under-adjustment.

[0092] Through this adjustment method, the heat pump system 100 can flexibly adapt to the heating needs of different temperature levels, achieving efficient and stable heat energy supply.

[0093] Please see Figure 7 Obtain the heating demand of high-temperature heat demand unit 7 and define it as Q. h Obtain the heating demand of the medium-temperature heat demand unit 13 and define it as Q. m The average heat exchange temperature of the high-temperature condenser 6 is obtained and defined as t. h The average heat exchange temperature of the medium-temperature condenser 11 is obtained and defined as t. m Following the steps above, the following steps are also included:

[0094] Obtain the cooling demand of the low-temperature cooling unit 17 and define it as Q. c ;

[0095] Comparison and judgment Q c With Q h The size of Q c Greater than Q h This increases the heat exchange capacity of the intermediate-temperature condenser 11. If Q c Less than Q h This reduces the heat exchange capacity of the medium-temperature condenser 11.

[0096] In this embodiment, in order to more accurately meet cooling and heating needs and reduce energy waste, a comparison and judgment Q is performed. c With Q h The size of Q is determined, and the heat exchange rate of the medium-temperature condenser 11 is adjusted based on the comparison results. If Q c Greater than Q h This indicates that the low-temperature cooling unit 17 has a high cooling demand, and it needs to remove as much medium-temperature heat as possible through the medium-temperature condenser 11 to avoid all the medium-temperature heat accumulating in the evaporator-condenser 4 and being converted into high-temperature heat through the high-temperature heat pump cycle, thus preventing complete consumption and waste. If Q c Less than Q hThis indicates that the high-temperature heat demand unit 7 has a high heat demand and needs to prioritize meeting the heat supply demand. At this time, the heat exchange rate of the medium-temperature condenser 11 is reduced by reducing the flow rate of the heat transfer medium in the medium-temperature condenser 11 or increasing its operating pressure to weaken the heat exchange effect. At the same time, the heat exchange efficiency of the evaporator condenser 4 is increased, and more heat is transferred by the evaporator condenser 4 to the high-temperature section compression heat pump cycle (second connecting pipe 9) and used to meet the high-temperature process heat supply demand.

[0097] Through this dynamic adjustment method, the heat pump system 100 can more flexibly adapt to heating / cooling requirements of different temperature levels and needs, and achieve efficient and stable heat / cooling energy supply.

[0098] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A heat pump system, characterized in that, The heat pump system includes a low-temperature waste heat transmission pipeline (1), a low-temperature evaporator (2), a low-temperature compressor (3), an evaporative condenser (4), a high-temperature compressor (5), a high-temperature condenser (6), a high-temperature heat demand unit (7), a first connecting pipeline (8), a second connecting pipeline (9), a third connecting pipeline (10), a low-temperature expansion valve (14), and a high-temperature expansion valve (15). The low-temperature waste heat conveying pipeline (1) is connected to the low-temperature evaporator (2); The first connecting pipe (8) is connected in sequence to the low-temperature evaporator (2), the low-temperature compressor (3) and the evaporator-condenser (4) to form a closed loop; The second connecting pipe (9) is connected in sequence to the evaporator condenser (4), the high-temperature compressor (5) and the high-temperature condenser (6) to form a closed loop; The third connecting pipe (10) connects the high-temperature condenser (6) and the high-temperature heat demand unit (7) to form a closed loop; The low-temperature expansion valve (14) is located in the first connecting pipe (8) and downstream of the evaporator condenser (4); The high-temperature expansion valve (15) is located in the second connecting pipe (9) and downstream of the high-temperature condenser (6).

2. The heat pump system as described in claim 1, characterized in that, The heat pump system also includes a medium-temperature condenser (11), a fourth connecting pipe (12), and a medium-temperature heat demand unit (13); The medium-temperature condenser (11) is located in the first connecting pipe (8) and downstream of the evaporator condenser (4); The fourth connecting pipe (12) connects the medium-temperature condenser (11) and the medium-temperature heat demand unit (13) to form a closed loop.

3. The heat pump system as described in claim 2, characterized in that, The heat pump system also includes a fifth connecting pipe (16) and a low-temperature cooling unit (17); The fifth connecting pipe (16) connects the low-temperature evaporator (2) and the low-temperature cooling unit (17) to form a closed loop.

4. The heat pump system as described in claim 3, characterized in that, The first connecting pipe (8) and the second connecting pipe (9) are filled with refrigerant, and the third connecting pipe (10), the fourth connecting pipe (12) and the fifth connecting pipe (16) are filled with secondary fluid.

5. A low-temperature waste heat recovery method, implemented based on the heat pump system as described in claim 4, characterized in that, Includes the following steps: Low-temperature waste water is fed into the low-temperature waste heat transmission pipeline (1) and passes through the low-temperature evaporator (2); The heat of the low-temperature waste water is recovered through the low-temperature evaporator (2) and used to heat the refrigerant in the first connecting pipe (8); The refrigerant in the first connecting pipe (8) is compressed by the low-temperature compressor (3) to obtain medium-temperature heat; The medium-temperature heat is recovered by the evaporator condenser (4) and used to heat the refrigerant in the second connecting pipe (9). The high-temperature heat is obtained by compressing the refrigerant in the second connecting pipe (9) by the high-temperature compressor (5). The high-temperature heat is recovered by the high-temperature condenser (6) and used to heat the high-temperature heat demand unit (7).

6. The low-temperature waste heat recovery method as described in claim 5, characterized in that, After the steps of recovering the medium-temperature heat through the evaporator-condenser (4) and using it to heat the refrigerant in the second connecting pipe (9), and compressing the refrigerant in the second connecting pipe (9) to obtain high-temperature heat through the high-temperature compressor (5), the following steps are also included: The medium-temperature heat is recovered by the medium-temperature condenser (11) and used to heat the medium-temperature heat demand unit (13).

7. The low-temperature waste heat recovery method as described in claim 5, characterized in that, Before the step of compressing the refrigerant in the first connecting pipe (8) with the low-temperature compressor (3) to obtain medium-temperature heat, the following steps are also included: The heat of the secondary fluid in the fifth connecting pipe (16) is recovered through the low-temperature evaporator (2) and used to heat the refrigerant in the first connecting pipe (8); Cooling is supplied to the low-temperature cooling unit (17) through the secondary fluid in the fifth connecting pipe (16) after cooling.

8. A method for regulating a heat pump system, implemented based on the heat pump system as described in claim 4, characterized in that, Includes the following steps: Obtain the heating demand of the high-temperature heat demand unit (7) and define it as Q. h The heating demand of the medium-temperature heat demand unit (13) is obtained and defined as Q. m The average heat exchange temperature of the high-temperature condenser (6) is obtained and defined as t. h The average heat exchange temperature of the medium-temperature condenser (11) is obtained and defined as t. m ; Adjusting the frequencies of the cryogenic compressor (3) and the high-temperature compressor (5) to make t h Stable within the temperature range required by the high-temperature heating unit and meet Q h ; Adjust the frequency of the cryogenic compressor (3) and the flow rate of the second connecting pipe (9) to make t m Stable within the temperature range required by the medium-temperature heating unit and meeting Q m .

9. The adjustment method for a heat pump system as described in claim 8, characterized in that, Obtain the heating demand of the high-temperature heat demand unit (7) and define it as Q. h The heating demand of the medium-temperature heat demand unit (13) is obtained and defined as Q. m The average heat exchange temperature of the high-temperature condenser (6) is obtained and defined as t. h The average heat exchange temperature of the medium-temperature condenser (11) is obtained and defined as t. m Following the steps above, the following steps are also included: Obtain the cooling demand of the low-temperature cooling unit (17) and define it as Q. c ; Comparison and judgment Q c With Q h The size of Q c Greater than Q h This increases the heat exchange capacity of the medium-temperature condenser (11). If Q c Less than Q h This reduces the heat exchange capacity of the medium-temperature condenser (11).

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