An adjustable large temperature span cascade phase change thermal storage mixed working fluid high temperature heat pump system

Abstract

The present invention discloses an adjustable large-temperature step-cross phase-change heat storage mixed working fluid high-temperature heat pump system, which belongs to the technical field of high-temperature heat pump systems. It includes a high-temperature heat pump circulation module and an open water supply module; the high-temperature heat pump circulation module is a circulation loop on the working fluid side, including a compressor, the working fluid side of three condensers, two gas-liquid separators, an evaporator and the working fluid side of three heat accumulators, and the circulating working fluid is an environmentally friendly binary non-azeotropic mixture; the open water supply module is an open loop on the water side, including a water pump, the water side of three condensers and the water side of three heat accumulators, and the working fluid on the water side is water. The present invention has three working conditions, namely direct heating working condition, heat accumulator heat storage working condition, and heat accumulator heat release working condition; the direct heating working condition achieves a reduction of irreversible losses by at least 14%; the heat accumulator heat storage working condition achieves a reduction of irreversible losses in the heat exchange process by at least 9%; the heat accumulator heat release working condition achieves an effective reduction of irreversible losses in the heat release process by at least 31%, thereby improving energy utilization.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature heat pump systems, and in particular relates to a mixed working medium high-temperature heat pump system that combines gas-liquid separation regulation with cascade phase change heat storage. Background Art

[0002] Industrial heat energy is mainly obtained by burning industrial boilers. This traditional way of obtaining heat energy is not only inefficient, but also emits a large amount of carbon dioxide and other harmful gases during the combustion process, which has a serious impact on the environment. Heat pump is an advanced and efficient electric heat conversion technology, which is of great significance for energy conservation and carbon reduction in industrial production. In industrial applications (for example, power plant waste heat recovery converts high-pressure water from 40 o C increased to 150 o C) Heat pumps typically require condensing and heating over a wide temperature span. However, existing heat pump cycles primarily use pure working fluids. Their phase-change isothermal characteristics result in poor temperature matching between the working fluid and the variable-temperature heat source, leading to high irreversible heat exchange losses throughout the cycle and significantly reducing heat pump efficiency. Therefore, improving temperature matching and reducing irreversible heat exchange losses are key to improving heat pump efficiency.

[0003] In the application of heat pump technology, the use of non-azeotropic mixed working fluids can improve the overall performance and flexibility of the system. Non-azeotropic mixed working fluids are mixtures of two or more pure working fluids (hereinafter collectively referred to as components) with different boiling points. The advantages of non-azeotropic mixed working fluids can be summarized as follows: (1) Due to the different boiling points of the components of the non-azeotropic mixed working fluid, its phase change process has a variable temperature characteristic (also known as a temperature glide characteristic), which can form a good match with the variable temperature cold and heat source, reduce the irreversible loss of heat exchange, and improve the energy efficiency of the heat pump system; (2) Non-azeotropic mixed working fluids can achieve complementary performance by mixing single working fluids with different characteristics. A disclosed large temperature difference multi-stage compression mixed working fluid heat pump system suitable for recovering waste heat from power plants adopts three-stage compression to improve the thermal performance and efficiency of the system, and consists of a high-pressure compressor, an intermediate-pressure compressor, a low-pressure compressor, a gas-liquid separator, an evaporator, a low-pressure throttle valve, a first intermediate cooler, an intermediate-pressure throttle valve, a second intermediate cooler, a high-pressure throttle valve, a liquid reservoir and a condenser. The binary non-azeotropic mixture of R134a and R245fa as the components is circulated as the circulating working fluid, and its unique temperature glide characteristics are utilized to further optimize the heat pump cycle efficiency. However, the inventors found that the current mixed working fluid heat pump system has the following problems: the potential of the non-azeotropic mixed working fluid is affected by the characteristics of the cold and heat sources. Once the heat pump equipment structure, working fluid components and components are designed and determined, the system can only passively adjust to adapt to the fluctuations in the properties of the cold and heat sources. The temperature matching of the heat exchange process is prone to offset, resulting in limited performance improvement of the non-azeotropic mixed working fluid heat pump system. The poor ability to adjust the temperature matching under variable working conditions is a common problem currently faced by large-temperature cross-span heat pumps in terms of performance efficiency improvement. Solving this problem can promote the rapid development of large-temperature cross-span heat pump technology.

[0004] In addition, the use of cascade phase change heat storage technology is another effective way to improve temperature matching. The cascade phase change heat storage technology arranges a variety of phase change materials according to different temperature levels to form a zigzag temperature curve, which can improve the temperature matching of the heat exchange fluid and the material phase change heat storage process, greatly reduce the irreversible loss of heat exchange, and effectively improve the energy efficiency of the heat pump system. Another cascade phase change heat storage system based on power plant waste heat and high-temperature heat pump is mainly composed of a cooling water system, a high-temperature heat pump and a heat storage system. By coupling the evaporator of the high-temperature heat pump with the cooling water system and the condenser with the heat storage system, the heat storage rate and the amount of heat storage can be improved, and efficient recovery of exhaust steam waste heat and storage of high-quality thermal energy are achieved. The core of the heat storage system is a cascade heat storage device, which is composed of three phase change heat accumulators with decreasing temperatures in series. The phase change temperature in the first heat accumulator is set to 90 o C-100 o C phase change material, the second heat accumulator is set to a phase change temperature of 70 o C-80 o C phase change material, the phase change temperature in the third heat accumulator is set to 50 o C-60o C phase change material. During the heat storage process, the high-temperature working fluid enters the first heat accumulator, the second heat accumulator and the third heat accumulator in turn for heat exchange, and the heat gradient is transferred, effectively reducing the irreversible loss of the heat exchange process. However, the system has the following problems: (1) The maximum phase change temperature of the first heat accumulator is only 110 o C, however, in industrial production processes, more than 110 o The required heating temperature above C accounts for more than 50% of the total heat demand, and the heat storage temperature needs to be further increased; (2) The room temperature water in the heating process enters the first heat accumulator, the second heat accumulator and the third heat accumulator for heating respectively, rather than entering the first heat accumulator, the second heat accumulator and the third heat accumulator in sequence. The room temperature water temperature increases linearly during the heating process, while the phase change material in the heat accumulator undergoes isothermal phase change. There is still a high heat exchange temperature difference between the two heat exchange processes, the temperature matching is poor, and the irreversible heat exchange loss is large, resulting in a decrease in thermal energy conversion efficiency. Summary of the Invention

[0005] In order to improve the flexibility of the heat pump system, improve the temperature matching of the heat exchange process, and enhance the overall performance and efficiency of the high-temperature heat pump system, the present invention provides an adjustable large-temperature span cascade phase change thermal storage mixed working fluid high-temperature heat pump system.

[0006] An adjustable large-temperature cross-stage phase-change heat storage mixed working medium high-temperature heat pump system includes a high-temperature heat pump circulation module and an open water supply module;

[0007] The high-temperature heat pump circulation module is a circulation loop on the working medium side, and the circulating working medium is an environmentally friendly binary non-azeotropic mixture; the open water supply module is an open loop on the water side, and the working medium on the water side is water;

[0008] The high-temperature heat pump circulation module includes a compressor 1, a working fluid side of a first condenser 2, a working fluid side of a second condenser 3, a working fluid side of a third condenser 4, a first gas-liquid separator 5, a second gas-liquid separator 6, a working fluid side of an evaporator 8, a working fluid side of a first heat accumulator 11, a working fluid side of a second heat accumulator 10, and a working fluid side of a third heat accumulator 9;

[0009] The outlet of the compressor 1 is connected to the working medium inlet of the first condenser 2 and the working medium inlet of the first heat accumulator 11 respectively through a three-way pipe. The working medium outlet of the first condenser 2 and the working medium outlet of the first heat accumulator 11 are connected in parallel to the gas inlet of the first gas-liquid separator 5. The working medium inlet of the first condenser 2 is connected in series with the third stop valve 15, and the working medium inlet of the first heat accumulator 11 is connected in series with the sixth stop valve 18.

[0010] The gas outlet of the first gas-liquid separator 5 is connected to the working medium inlet of the second condenser 3 and the working medium inlet of the second heat accumulator 10 respectively through a three-way pipe. The working medium outlet of the second condenser 3 and the working medium outlet of the second heat accumulator 10 are connected in parallel to the gas inlet of the second gas-liquid separator 6. The working medium inlet of the second condenser 3 is connected in series with the fourth stop valve 16, and the working medium inlet of the second heat accumulator 10 is connected in series with the seventh stop valve 19.

[0011] The gas outlet of the second gas-liquid separator 6 is connected to the working medium inlet of the third condenser 4 and the working medium inlet of the third heat accumulator 9 respectively through a tee pipe; the working medium outlet of the third condenser 4 and the working medium outlet of the third heat accumulator 9 are connected in parallel, and one of the parallel ports is connected to the liquid outlet of the second gas-liquid separator 6 and the liquid outlet of the first gas-liquid separator 5 through a tee pipe, and the other is connected to the working medium inlet of the evaporator 8; the working medium outlet of the evaporator 8 is connected to the inlet of the compressor 1; the working medium inlet of the third condenser 4 is connected in series with the fifth stop valve 17, and the working medium inlet of the third heat accumulator 9 is connected in series with the eighth stop valve 20; the liquid outlet of the second gas-liquid separator 6 is connected in series with the second stop valve 14, and the liquid outlet of the first gas-liquid separator 5 is connected in series with the first stop valve 13; the working medium inlet of the evaporator 8 is connected in series with the throttle valve 7;

[0012] The phase change temperature of the high-temperature phase change material in the first heat accumulator 11 is 150°C-180°C;

[0013] The phase change temperature of the medium-temperature phase change material in the second heat accumulator 10 is 100°C-150°C;

[0014] The phase change temperature of the low-temperature phase change material in the third heat accumulator 9 is 60°C-100°C;

[0015] The open water supply module includes a water pump 12, a water side of the first condenser 2, a water side of the second condenser 3, a water side of the third condenser 4, a water side of the third heat accumulator 9, a water side of the second heat accumulator 10 and a water side of the first heat accumulator 11;

[0016] The water outlet of the water pump 12 is divided into two paths by a three-way pipe, one path is connected in series with the water side of the third condenser 4, the water side of the second condenser 3 and the water side of the first condenser 2 in sequence, and the other path is connected in series with the water side of the third heat accumulator 9, the water side of the second heat accumulator 10 and the water side of the first heat accumulator 11 in sequence; the water outlet of the water side of the first condenser 2 and the water outlet of the water side of the first heat accumulator 11 are connected in parallel with a thirteenth stop valve 25; a ninth stop valve 21 is connected in series between the water outlet of the water pump 12 and the water inlet of the water side of the third condenser 4; a tenth stop valve 22 is connected in series between the water outlet of the water pump 12 and the water inlet of the water side of the third heat accumulator 9; an eleventh stop valve 23 is provided between the water side of the third heat accumulator 9 and the water side of the second heat accumulator 10 through a three-way pipe; a twelfth stop valve 24 is provided between the water side of the second heat accumulator 10 and the water side of the first heat accumulator 11 through a three-way pipe;

[0017] During operation, the other side of the evaporator 8 is connected to the circulation pipeline of the waste heat circulating water of the power plant, and the working fluid side of the evaporator 8 performs heat exchange with the waste heat circulating water of the power plant.

[0018] Further technical solutions are as follows:

[0019] The high-temperature heat pump system with a large-temperature step-by-step phase-change heat storage and mixed working medium has three working conditions, namely direct heating condition, heat storage condition in the heat accumulator, and heat release condition in the heat accumulator.

[0020] The direct heating mode achieves good temperature matching between the working medium on the working medium side of the high-temperature heat pump circulation module and the water cooling source on the water side of the open water supply module, reducing irreversible losses by at least 14%;

[0021] The heat storage working condition realizes step-by-step heat storage with a large temperature span, making the heat storage process closer to the temperature change of the non-azeotropic mixed working fluid, reducing the irreversible loss of the heat exchange process by at least 9%;

[0022] The heat release working condition of the heat accumulator uses the three temperature levels of the stepped phase change heat accumulator in the high-temperature heat pump circulation module to make the temperature change of the heat release process of the phase change material more closely match the temperature change of water, thereby effectively reducing the irreversible loss of the heat release process by at least 31% and improving energy utilization.

[0023] The first heat accumulator (11), the second heat accumulator (10) and the third heat accumulator (9) are all shell and tube phase change energy storage heat exchangers.

[0024] The environmentally friendly binary non-azeotropic mixture is a mixture of 50% by mass of trans-1-chloro-3,3,3-trifluoropropene (R1233zd(E)) and 50% by mass of toluene (Toluene), and the critical temperature is 270.85 o C, the critical pressure is 5031.6kPa, the ozone depletion index (ODP) is 0, and the global warming potential (GWP) is less than 10.

[0025] The high-temperature phase change material is prepared by uniformly mixing a first phase change material, a second phase change material, and a third phase change material in a mass ratio of 1:1:1;

[0026] The first phase change material is made by mixing 55.4% by mass of lithium nitrate, 4.5% by mass of sodium nitrate and 40.1% by mass of potassium chloride. The phase change temperature is 160 o C;

[0027] The second phase change material is made of a mixture of 58.1% by mass of lithium nitrate and 41.9% by mass of potassium chloride, and the phase change temperature is 166 o C;

[0028] The third phase change material is made by mixing lithium nitrate with a mass fraction of 47.9%, lithium chloride with a mass fraction of 1.4%, and sodium nitrate with a mass fraction of 50.7%. o C.

[0029] The medium-temperature phase change material is prepared by uniformly mixing phase change material A, phase change material B and phase change material C in a mass ratio of 1:1:1;

[0030] The phase change material A is made by mixing 29% by mass of lithium nitrate, 17% by mass of sodium nitrate, 49.4% by mass of potassium nitrate and 4.6% by mass of strontium nitrate. o C;

[0031] The phase change material B is made by mixing 33% by mass of lithium nitrate and 67% by mass of potassium nitrate, and the phase change temperature is 133 o C;

[0032] The phase change material C is made by mixing 53% by mass of lithium nitrate, 40% by mass of sodium nitrite and 7% by mass of sodium nitrate. o C.

[0033] The low-temperature phase change material is prepared by uniformly mixing phase change material I, phase change material II and phase change material III in a mass ratio of 1:1:1;

[0034] The phase change material I is brown keto acid, and the phase change temperature is 61.4 o C;

[0035] The phase change material II is made by mixing 50% by mass of erythritol and 50% by mass of urea, and the phase change temperature is 79.6 o C;

[0036] The phase change material III is xylitol, and the phase change temperature is 98.6 o C.

[0037] The water pump 12 is a booster water pump.

[0038] All connecting pipes of the system are treated with thermal insulation.

[0039] The beneficial technical effects of the present invention are embodied in the following aspects:

[0040] 1. The gas-liquid separator of this invention utilizes the different boiling points of the components of a non-azeotropic mixture to separate the condensate during the condensation phase transition process, dividing the overall condensation process into three stages. The components can be adjusted stage by stage to alter the physical properties of the working fluid during the condensation phase transition, thereby controlling the temperature variation during the condensation phase transition. Furthermore, the overall temperature glide of the condensation process is equal to the sum of the temperature glides of the three heat exchange sections. This can accommodate large fluctuations in the operating conditions of the cold and heat sources during large temperature span condensation, effectively improving the flexibility and adaptability of the heat pump system under different operating conditions.

[0041] 2. The present invention adopts three-stage heat storage. The heat accumulator of each stage is filled with phase change materials with three different phase change temperatures. The phase change temperatures are arranged in series in the order of low temperature to high temperature, realizing step-by-step heat storage with a large temperature span. It can form a stepped temperature curve while improving the energy storage density, making its heat storage process closer to the temperature change of the non-azeotropic mixed working fluid, and the heat release process more closely matches the temperature change of cold water, effectively reducing the irreversible loss in the heat exchange process and improving energy utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the system structure of the present invention.

[0043] Figure 2 This is the cycle path diagram for direct heating operation.

[0044] Figure 3 Direct heating condition T - H picture.

[0045] Figure 4 This is the cycle path diagram of the heat storage working condition of the heat accumulator.

[0046] Figure 5 Heat storage condition for the heat accumulator T - H picture.

[0047] Figure 6 This is the cycle path diagram of the heat accumulator's heat release condition.

[0048] Figure 7 Heat storage condition T - H picture.

[0049] Figure 1Sequence number: compressor 1, first condenser 2, second condenser 3, third condenser 4, first gas-liquid separator 5, second liquid separator 6, throttle valve 7, evaporator 8, third heat accumulator 9, second heat accumulator 10, first heat accumulator 11, water pump 12, first stop valve 13, second stop valve 14, third stop valve 15, fourth stop valve 16, fifth stop valve 17, sixth stop valve 18, seventh stop valve 19, eighth stop valve 20, ninth stop valve 21, tenth stop valve 22, eleventh stop valve 23, twelfth stop valve 24, thirteenth stop valve 25. DETAILED DESCRIPTION

[0050] The present invention will be further described in detail below through embodiments with reference to the accompanying drawings. Example

[0051] See also Figure 1 An adjustable large-temperature-span cascade phase-change thermal storage mixed working medium high-temperature heat pump system includes a high-temperature heat pump circulation module and an open water supply module.

[0052] The high-temperature heat pump circulation module is the circulation loop on the working fluid side. The circulating working fluid is an environmentally friendly binary non-azeotropic mixture. The environmentally friendly binary non-azeotropic mixture is a mixture of 50% by mass of trans-1-chloro-3,3,3-trifluoropropene (R1233zd(E)) and 50% by mass of toluene (Toluene). The critical temperature is 270.85 o C, the critical pressure is 5031.6kPa, the ozone depletion index (ODP) is 0, and the global warming potential (GWP) is less than 10. The temperature glide at one atmosphere is 55.49 o C, the temperature glide is 43.39 at 2MPa o C, which can meet the purpose of large temperature span condensation in high temperature heat pumps.

[0053] The open water supply module is an open circuit on the water side, and the working medium on the water side is water.

[0054] The high-temperature heat pump circulation module includes a compressor 1, a working fluid side of the first condenser 2, a working fluid side of the second condenser 3, a working fluid side of the third condenser 4, a first gas-liquid separator 5, a second gas-liquid separator 6, a working fluid side of the evaporator 8, a working fluid side of the first heat accumulator 11, a working fluid side of the second heat accumulator 10 and a working fluid side of the third heat accumulator 9.

[0055] The outlet of the compressor 1 is connected to the working fluid inlet of the first condenser 2 and the working fluid inlet of the first heat accumulator 11 through a three-way pipe respectively. The working fluid outlet of the first condenser 2 and the working fluid outlet of the first heat accumulator 11 are connected in parallel to the gas inlet of the first gas-liquid separator 5; the working fluid inlet of the first condenser 2 is connected in series with the third stop valve 15, and the working fluid inlet of the first heat accumulator 11 is connected in series with the sixth stop valve 18.

[0056] The gas outlet of the first gas-liquid separator 5 is connected to the working fluid inlet of the second condenser 3 and the working fluid inlet of the second heat accumulator 10 respectively through a three-way pipe. The working fluid outlet of the second condenser 3 and the working fluid outlet of the second heat accumulator 10 are connected to the gas inlet of the second gas-liquid separator 6 in parallel; the working fluid inlet of the second condenser 3 is connected in series with the fourth stop valve 16, and the working fluid inlet of the second heat accumulator 10 is connected in series with the seventh stop valve 19.

[0057] The gas outlet of the second gas-liquid separator 6 is connected to the working medium inlet of the third condenser 4 and the working medium inlet of the third heat accumulator 9 respectively through a tee. The working medium outlet of the third condenser 4 and the working medium outlet of the third heat accumulator 9 are connected in parallel. One of the parallel outlets is connected to the liquid outlet of the second gas-liquid separator 6 and the liquid outlet of the first gas-liquid separator 5 through a tee, and the other is connected to the working medium inlet of the evaporator 8. The working medium outlet of the evaporator 8 is connected to the inlet of the compressor 1. The working medium inlet of the third condenser 4 is connected in series with the fifth stop valve 17, and the working medium inlet of the third heat accumulator 9 is connected in series with the eighth stop valve 20.

[0058] The liquid outlet of the second gas-liquid separator 6 is connected in series to the second stop valve 14 , the liquid outlet of the first gas-liquid separator 5 is connected in series to the first stop valve 13 ; the working medium inlet of the evaporator 8 is connected in series to the throttle valve 7 .

[0059] The phase change temperature of the high-temperature phase change material in the first heat accumulator (11) is 160°C-180°C.

[0060] The phase change temperature of the medium-temperature phase change material in the second heat accumulator (10) is 100°C-150°C.

[0061] The phase change temperature of the low-temperature phase change material in the third heat accumulator (9) is 60°C-100°C.

[0062] The high-temperature phase change material is made by mixing the first phase change material, the second phase change material and the third phase change material in a mass ratio of 1:1:1. The first phase change material is made by mixing 55.4% lithium nitrate, 4.5% sodium nitrate and 40.1% potassium chloride. The phase change temperature is 160 o C; the second phase change material is made by mixing 58.1% lithium nitrate and 41.9% potassium chloride by mass, and the phase change temperature is 166 o C; The third phase change material is made by mixing 47.9% lithium nitrate by mass, 1.4% lithium chloride by mass and 50.7% sodium nitrate by mass, and the phase change temperature is 180 o C.

[0063] The medium temperature phase change material is made by mixing phase change material A, phase change material B and phase change material C in a mass ratio of 1:1:1. Phase change material A is made by mixing 29% lithium nitrate, 17% sodium nitrate, 49.4% potassium nitrate and 4.6% strontium nitrate. The phase change temperature is 105 o C; B phase change material is made by mixing 33% by mass of lithium nitrate and 67% by mass of potassium nitrate, and the phase change temperature is 133 o C; C phase change material is made by mixing 53% lithium nitrate, 40% sodium nitrite and 7% sodium nitrate. The phase change temperature is 142 o C.

[0064] The low-temperature phase change material is prepared by mixing phase change material I, phase change material II and phase change material III in a mass ratio of 1:1:1. Phase change material I is brown keto acid, and the phase change temperature is 61.4 o C; Phase change material II is made by mixing 50% erythritol and 50% urea, and the phase change temperature is 79.6 o C; Phase change material III is xylitol, and the phase change temperature is 98.6 o C.

[0065] The open water supply module includes a water pump 12 , the water side of the first condenser 2 , the water side of the second condenser 3 , the water side of the third condenser 4 , the water side of the third heat accumulator 9 , the water side of the second heat accumulator 10 and the water side of the first heat accumulator 11 .

[0066] The water pump 12 is a booster type water pump.

[0067] The water outlet of the water pump 12 is divided into two paths through a three-way pipe, one path is connected in series with the water side of the third condenser 4, the water side of the second condenser 3 and the water side of the first condenser 2 in sequence, and the other path is connected in series with the water side of the third heat accumulator 9, the water side of the second heat accumulator 10 and the water side of the first heat accumulator 11 in sequence; the water outlet of the water side of the first condenser 2 and the water outlet of the water side of the first heat accumulator 11 are connected in parallel with the thirteenth stop valve 25; the ninth stop valve 21 is connected in series between the water outlet of the water pump 12 and the water inlet of the water side of the third condenser 4; the tenth stop valve 22 is connected in series between the water outlet of the water pump 12 and the water inlet of the water side of the third heat accumulator 9; an eleventh stop valve 23 is provided between the water side of the third heat accumulator 9 and the water side of the second heat accumulator 10 through a three-way pipe; and a twelfth stop valve 24 is provided between the water side of the second heat accumulator 10 and the water side of the first heat accumulator 11 through a three-way pipe.

[0068] The first heat accumulator 11 , the second heat accumulator 10 and the third heat accumulator 9 are all shell and tube phase change energy storage heat exchangers.

[0069] All connecting pipes of the system are treated with thermal insulation.

[0070] During operation, the other side of the evaporator 8 is connected to the circulation pipeline of the waste heat circulating water of the power plant, and the working fluid side of the evaporator 8 performs heat exchange with the waste heat circulating water of the power plant.

[0071] In this embodiment 1, the first heat accumulator 11 and the second heat accumulator 10 are used to meet high-temperature energy needs, such as steam production, industrial heating, etc. The third heat accumulator 9 is used to meet heat needs such as hot water supply and greenhouse temperature control.

[0072] The adjustable large temperature span cascade phase change thermal storage mixed working medium high temperature heat pump system of this embodiment 1 has three operating conditions, namely direct heating condition, thermal storage condition of thermal accumulator and thermal release condition of thermal accumulator. The working principles of the three operating conditions are described as follows:

[0073] See also Figure 2 The thick solid line represents the circulation path for direct heating operation. During direct heating operation, the sixth, seventh, and eighth shut-off valves 18, 19, and 20 of the high-temperature heat pump circulation module are closed, while the first, second, third, fourth, and fifth shut-off valves 13, 14, 15, 16, and 17 are open. The tenth, eleventh, and twelfth shut-off valves 22, 23, and 24 of the open water supply module are closed, while the ninth shut-off valve 21 is open. The mixed working fluid in the high-temperature heat pump circulation module exchanges heat with waste heat through the evaporator 8, enters the compressor 1 from the outlet of the evaporator 8 for pressurization into high-temperature and high-pressure gas, enters the first condenser 2 for partial condensation and becomes a two-phase state, and the two-phase working fluid enters the first gas-liquid separator 5 for gas-liquid separation. After separation, the saturated gaseous working fluid with a low boiling point enters the second condenser 3 for partial condensation and becomes a two-phase state. The two-phase working fluid enters the second gas-liquid separator 6 for gas-liquid separation. After separation, the saturated gaseous working fluid with a lower boiling point enters the third condenser 4 for complete condensation into a supercooled state, mixes with the condensed working fluid discharged from the first gas-liquid separator and the condensed working fluid discharged from the second gas-liquid separator, then enters the throttle valve 7 for isenthalpic decompression, and finally enters the evaporator to absorb heat, completing the cycle; the room temperature water in the open water supply module is pressurized by the water pump and enters the third condenser 4, the second condenser 3, and the first condenser 2 in sequence to absorb heat. According to actual heat demand, the compressor outlet pressure is adjusted, and the opening of the first stop valve 13 and the second stop valve 14 are adjusted to control the heat pump heating temperature, thereby adjusting the outlet hot water temperature. By properly adjusting the compressor outlet pressure and the openings of the first stop valve 13 and the second stop valve 14, a good temperature matching between the working medium and the cold source is achieved.

[0074] Adjustment process of direct heating condition:

[0075] 25 o Heat water to 150°C oThe circulating medium is pressurized by compressor 1 to become high-temperature and high-pressure gas (pressure 518.59 kPa, temperature 155 o C, mass component ratio is 0.5:0.5), enters the first condenser 2 working fluid side isobaric condensation heat release, set the adjustment dryness to 0.5, the circulating working fluid is partially condensed into a two-phase state (temperature 130.02 o C, mass component ratio is 0.5:0.5), enters the gas-liquid separator 5 for the first gas-liquid separation. In the gas-liquid separator 5, the density of the high-boiling-point component liquid of the two-phase working medium is greater than that of the low-boiling-point component gas. The high-boiling-point component liquid (mass component ratio is 0.24:0.76) will naturally settle to the lower layer, while the low-boiling-point component gas (mass component ratio is 0.76:0.24) will float on the upper layer. After the high-boiling-point component liquid is discharged, the low-boiling-point component gas enters the working medium side inlet of the second condenser 3 for isobaric condensation and heat release. After partial condensation, it becomes a two-phase state again (temperature is 94.9 o C, mass component ratio is 0.76:0.24), enters the gas-liquid separator 6 for the second gas-liquid separation. In the gas-liquid separator 6, the high boiling point component liquid (mass component ratio is 0.58:0.42) will naturally settle to the lower layer and be discharged, while the low boiling point component gas (mass component ratio is 0.94:0.06) will float on the surface to form a separation and enter the third condenser 4 to be completely condensed into liquid (temperature is 73.96 o C, with a mass component ratio of 0.94:0.06). The circulating working fluid at the outlet of the working fluid side of the third condenser 4 is mixed with the condensed working fluid discharged from the first gas-liquid separator 5 and the condensed working fluid discharged from the second gas-liquid separator 6, enters the throttle valve 7 for isenthalpic decompression, and then absorbs heat on the working fluid side of the evaporator 8 before entering the compressor 1, completing the cycle. After adjustment, the final condenser working fluid outlet temperature is 73.96 o C, compared with the condenser working fluid outlet temperature of 101.21 when not adjusted o C, the overall temperature glide increased by 27.25 o C, the irreversible loss in the condensation process was reduced by 14.53%.

[0076] Depend on Figure 3 It can be seen that the dotted line is the water temperature curve, and the inlet is 25 o C, export is 150 o C, temperature glide is 125 o C. The line is the temperature curve of the unregulated mixed working fluid, with the inlet temperature of 155 o C, outlet temperature 101.21 o C, the overall temperature glide is 53.79 o C. The solid line is the temperature curve of the mixed working fluid after adjustment. After two adjustments, the outlet temperature is 73.96o C, the overall temperature glide is 76.04 o C, the temperature glide increased by 27.25 compared with the unregulated o C. The area enclosed by the temperature curves of the circulating medium and water can represent the irreversible loss. After adjustment, the irreversible loss of the condensation process was reduced by 14.53%. Figure 3 Middle shadow area.

[0077] See also Figure 4 , the thick solid line is the circulation path of the heat accumulator heat storage condition. When the heat accumulator is in heat storage condition, the third stop valve 15, the fourth stop valve 16 and the fifth stop valve 17 of the high-temperature heat pump circulation module are closed, and the first stop valve 13, the second stop valve 14, the sixth stop valve 18, the seventh stop valve 19 and the eighth stop valve 20 are opened. The ninth stop valve 21, the tenth stop valve 22, the eleventh stop valve 23 and the twelfth stop valve 24 of the open water supply module are closed. The mixed working fluid of the high-temperature heat pump circulation module exchanges heat with the waste heat through the evaporator 8, enters the compressor 1 from the outlet of the evaporator 8 to be pressurized into a high-temperature and high-pressure gas, and enters the first heat accumulator 11 to release heat. The phase change material of the first heat accumulator 11 absorbs heat and melts from a solid state to a liquid state, storing heat in the form of latent heat. The working fluid is partially condensed and becomes a two-phase state. The two-phase working fluid enters the first gas-liquid separator 5 for gas-liquid separation. After separation, the saturated gaseous working fluid enters the second heat accumulator 10 to release heat. The second heat accumulator 10 The phase change material absorbs heat and melts from a solid state to a liquid state. The working fluid partially condenses and becomes a two-phase state. The two-phase working fluid enters the second gas-liquid separator 6 for gas-liquid separation. After separation, the saturated gaseous working fluid enters the third heat accumulator 9. The phase change material in the third heat accumulator 9 absorbs heat and melts from a solid state to a liquid state. The working fluid is completely condensed to a supercooled state and mixed with the condensed working fluid discharged from the first gas-liquid separator 5 and the condensed working fluid discharged from the second gas-liquid separator 6. It then enters the throttle valve 7 for isenthalpic decompression and finally enters the evaporator to absorb heat, completing the cycle. Through three-stage heat storage, the phase change temperatures are set in series in the order of low temperature to high temperature, achieving step-by-step heat storage with a large temperature span and forming a stepped temperature curve. This makes its heat storage process closer to the temperature change of the non-azeotropic mixed working fluid, reducing irreversible losses in the heat exchange process.

[0078] Adjustment process of heat storage working condition of heat accumulator:

[0079] The circulating medium is pressurized by compressor 1 to become high-temperature and high-pressure gas (pressure is 969.68kPa, temperature is 185 o C, the mass component ratio is 0.5:0.5), enters the working fluid inlet of the first heat accumulator 11 for isobaric condensation and heat release, and the adjustment dryness is set to 0.5. The mixed working fluid is partially condensed into a two-phase state (temperature 161.37 oC, with a mass component ratio of 0.5:0.5), the high-temperature phase change material in the first heat accumulator 11 absorbs heat and changes from solid to liquid, and the phase change temperature gradient is 180 o C. 166 o C and 160 o C. The two-phase working medium enters the first gas-liquid separator 5 for gas-liquid separation. After separation, the saturated gaseous working medium (temperature 161.37 o C, mass component ratio is 0.27:0.73) enters the working fluid inlet of the second heat accumulator 10 for isobaric condensation and heat release, and the dryness is set to 0.5. The circulating working fluid is partially condensed into a two-phase state again (temperature 129.47 o C, the mass component ratio is 0.27:0.73), the medium-temperature phase change material in the second heat accumulator 10 absorbs heat and melts from solid to liquid, and the phase change temperature gradient is 142 o C. 133 o C and 105 o C. The two-phase working medium enters the second gas-liquid separator 6 for gas-liquid separation. After separation, the saturated gaseous working medium (temperature 129.47 o C, with a mass component ratio of 0.9:0.1) entering the third heat accumulator 9, the working fluid is isobarically condensed to a saturated liquid state. The low-temperature phase change material in the third heat accumulator 9 absorbs heat and melts from a solid state to a liquid state. The phase change temperature gradient is 98.6 o C. 79.6 o C and 61.4 o C. The circulating medium is completely condensed into a supercooled state (temperature is 103.51 o C, with a mass component ratio of 0.9:0.1), mixed with the condensed working fluid discharged from the first gas-liquid separator 5 and the condensed working fluid discharged from the second gas-liquid separator 6, enters the throttle valve 7 for isenthalpic decompression, and absorbs heat on the working fluid side of the evaporator 8 before entering the compressor 1 to complete the cycle. After adjustment, the final condenser working fluid outlet temperature is 103.51 o C, compared with the condenser working fluid outlet temperature of 134.20 when not adjusted o C, the overall temperature glide increased by 30.69 o C, the irreversible loss of the heat storage process of the heat accumulator is reduced by 9.88%.

[0080] Depend on Figure 5 It can be seen that the dot-dash line is the temperature curve of the phase change material in the three-stage heat accumulator of the present invention, and the temperature gradient is 61.4 o C, 79.6 o C. 98.6 o C. 105 o C. 133 o C. 142 o C. 160o C. 166 o C. 180 o C. The line is the temperature curve of the unregulated mixed working fluid, with the inlet temperature of 185 o C, outlet temperature 134.20 o C, the overall temperature glide is 50.8 o C. The solid line is the temperature curve of the mixed working fluid after adjustment. After two adjustments, the outlet temperature is 103.51 o C, the overall temperature slip is 81.49 o C, the temperature glide increased by 30.69 compared with the unregulated o C. The area enclosed by the phase change temperature curve of the circulating working fluid and the phase change material in the heat accumulator can represent the irreversible loss. After adjustment, the irreversible loss of the heat storage process of the heat accumulator is reduced by 9.88%. Figure 5 Middle shadow area.

[0081] See also Figure 6 The thick solid line represents the circulation path during the heat accumulator's heat release operation. During this operation, the first, second, third, fourth, fifth, sixth, seventh, and eighth shut-off valves 13, 14, 15, 16, 17, 18, 19, and 20 of the high-temperature heat pump circulation module are closed, and compressor 1 stops. The tenth, eleventh, twelfth, and thirteenth shut-off valves 22, 23, 24, and 25 of the open water supply module are opened, while the ninth shut-off valve 21 is closed. The ambient-temperature water in the open water supply module is pressurized by a water pump 12 and then enters the third heat accumulator 9. The low-temperature phase-change material absorbs heat and solidifies from a liquid to a solid, releasing heat to heat the ambient-temperature water into low-temperature hot water. The low-temperature hot water then enters the second heat accumulator 10, where it absorbs heat. The medium-temperature phase-change material absorbs heat and solidifies from a liquid to a solid, releasing heat to heat the low-temperature hot water into medium-temperature hot water. The medium-temperature hot water then enters the first heat accumulator 11, where it absorbs heat. The high-temperature phase-change material absorbs heat and solidifies from a liquid to a solid, releasing heat to heat the medium-temperature hot water into high-temperature hot water. The open water supply module can supply low-temperature heat by opening and closing the eleventh shut-off valve 23, medium-temperature heat by opening and closing the twelfth shut-off valve 24, and high-temperature heat by opening and closing the thirteenth shut-off valve 25, depending on actual heat demand. The ambient-temperature water sequentially enters the three temperature-level cascade phase-change heat accumulators for heating. The temperature changes of the phase-change material during the heat release process more closely match the temperature changes of the water, effectively reducing irreversible losses during the heat release process and improving energy efficiency.

[0082] Adjustment process of heat accumulator heat release condition:

[0083] The supply water of the open water supply module (pressure is 101.325kPa, temperature is 25 oC) After being pressurized to 10 atmospheres by a water pump, it enters the water side inlet of the third heat accumulator 9. The low-temperature phase change material absorbs heat and solidifies from liquid to solid. The phase change temperature gradient is 61.4 o C. 79.6 o C and 98.6 o C. Normal temperature water is heated to low temperature hot water (temperature 80 o C); low-temperature hot water enters the water side inlet of the second heat accumulator 10 to absorb heat, and the medium-temperature phase change material absorbs heat and solidifies from liquid to solid. The phase change temperature gradient is 105 o C. 133 o C and 142 o C. Low temperature hot water is heated to medium temperature hot water (temperature 120 o C); the medium-temperature hot water enters the water side inlet of the first heat accumulator 11 to absorb heat, and the high-temperature phase change material absorbs heat and solidifies from liquid to solid. The phase change temperature gradient is 160 o C. 166 o C and 180 o C. The medium temperature hot water is heated to high temperature hot water (temperature 150 o C). The open water supply module can supply low-temperature heat by opening and closing the eleventh shut-off valve 23, medium-temperature heat by opening and closing the twelfth shut-off valve 24, and high-temperature heat by opening and closing the thirteenth shut-off valve 25, depending on actual heat demand. Normal-temperature water sequentially enters the third, second, and first heat accumulators, each with different temperature levels, for heating. The temperature change of the phase-change material during the heat release process more closely matches the temperature changes of the water, effectively reducing irreversible losses during the heat release process by 31.91% and improving energy efficiency.

[0084] Depend on Figure 7 It can be seen that the solid line is the water temperature curve, and the inlet is 25 o C, export is 150 o C. The dotted line represents a conventional three-stage phase change heat accumulator, in which the phase change temperature of the phase change material of the first heat accumulator 11 is 180 o , the phase change temperature of the phase change material of the second heat accumulator 10 is 142 o C, the phase change temperature of the phase change material of the third heat accumulator 9 is 98.6 o The dotted line is the temperature curve of the phase change material in the three-stage heat storage device with large temperature span of the present invention, and the temperature gradient is 61.4 o C, 79.6 o C. 98.6 o C. 105 o C. 133 o C. 142 o C. 160 o C. 166 o C. 180 oC. The area enclosed by the temperature curves of the phase change material and water represents the irreversible loss of the heat release process. The use of the large temperature span three-stage heat accumulator of the present invention can reduce the heat exchange temperature difference between the first heat accumulator 11 and the water by 14 o C-38 o C, the heat exchange temperature difference between the second heat accumulator 10 and water is reduced by 9 o C-37 o C, the heat exchange temperature difference between the third heat accumulator 9 and water is reduced by 19 o C-37.2 o C, the irreversible loss of the exothermic process is reduced by 31.91%, see Figure 7 Middle shadow area.

[0085] It will be easily understood by those skilled in the art that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An adjustable high-temperature heat pump system with a large temperature span and a phase-change thermal storage system, characterized by: Including high temperature heat pump circulation module and open water supply module; The high-temperature heat pump circulation module is a circulation loop on the working medium side, and the circulating working medium is an environmentally friendly binary non-azeotropic mixture; the open water supply module is an open loop on the water side, and the working medium on the water side is water; The high-temperature heat pump circulation module comprises a compressor (1), a working fluid side of a first condenser (2), a working fluid side of a second condenser (3), a working fluid side of a third condenser (4), a first gas-liquid separator (5), a second gas-liquid separator (6), a working fluid side of an evaporator (8), a working fluid side of a first heat accumulator (11), a working fluid side of a second heat accumulator (10), and a working fluid side of a third heat accumulator (9); The outlet of the compressor (1) is connected to the working medium inlet of the first condenser (2) and the working medium inlet of the first heat accumulator (11) respectively through a three-way pipe, and the working medium outlet of the first condenser (2) and the working medium outlet of the first heat accumulator (11) are connected in parallel to the gas inlet of the first gas-liquid separator (5); the working medium inlet of the first condenser (2) is connected in series to the third stop valve (15), and the working medium inlet of the first heat accumulator (11) is connected in series to the sixth stop valve (18); The gas outlet of the first gas-liquid separator (5) is connected to the working fluid inlet of the second condenser (3) and the working fluid inlet of the second heat accumulator (10) respectively through a three-way pipe, and the working fluid outlet of the second condenser (3) and the working fluid outlet of the second heat accumulator (10) are connected in parallel to the gas inlet of the second gas-liquid separator (6); the working fluid inlet of the second condenser (3) is connected in series with the fourth stop valve (16), and the working fluid inlet of the second heat accumulator (10) is connected in series with the seventh stop valve (19); The gas outlet of the second gas-liquid separator (6) is connected to the working medium inlet of the third condenser (4) and the working medium inlet of the third heat accumulator (9) respectively through a three-way pipe; the working medium outlet of the third condenser (4) and the working medium outlet of the third heat accumulator (9) are connected in parallel, and one of the parallel ports is connected to the liquid outlet of the second gas-liquid separator (6) and the liquid outlet of the first gas-liquid separator (5) through a three-way pipe, and the other is connected to the working medium inlet of the evaporator (8); the working medium outlet of the evaporator (8) is connected to the inlet of the compressor (1); the working medium inlet of the third condenser (4) is connected in series with the fifth stop valve (17), and the working medium inlet of the third heat accumulator (9) is connected in series with the eighth stop valve (20); the liquid outlet of the second gas-liquid separator (6) is connected in series with the second stop valve (14), and the liquid outlet of the first gas-liquid separator (5) is connected in series with the first stop valve (13); the working medium inlet of the evaporator (8) is connected in series with the throttle valve (7); The phase change temperature of the high-temperature phase change material in the first heat accumulator (11) is 150°C-180°C; The phase change temperature of the medium-temperature phase change material in the second heat accumulator (10) is 100°C-150°C; The phase change temperature of the low-temperature phase change material in the third heat accumulator (9) is 60°C-100°C; The open water supply module comprises a water pump (12), a water side of the first condenser (2), a water side of the second condenser (3), a water side of the third condenser (4), a water side of the first heat accumulator (11), a water side of the second heat accumulator (10), and a water side of the third heat accumulator (9); The water outlet of the water pump (12) is divided into two paths through a three-way pipe, one path being connected in series with the water side of the third condenser (4), the water side of the second condenser (3) and the water side of the first condenser (2), and the other path being connected in series with the water side of the third heat accumulator (9), the water side of the second heat accumulator (10) and the water side of the first heat accumulator (11); the water outlet of the water side of the first condenser (2) and the water outlet of the water side of the first heat accumulator (11) are connected in parallel with the thirteenth stop valve (25); the water pump ( A ninth stop valve (21) is connected in series between the water outlet of the water pump (12) and the water inlet of the water side of the third condenser (4); a tenth stop valve (22) is connected in series between the water outlet of the water pump (12) and the water inlet of the water side of the third heat accumulator (9); an eleventh stop valve (23) is provided between the water side of the third heat accumulator (9) and the water side of the second heat accumulator (10) via a three-way pipe; a twelfth stop valve (24) is provided between the water side of the second heat accumulator (10) and the water side of the first heat accumulator (11) via a three-way pipe; During operation, the other side of the evaporator (8) is connected to a circulation pipe of waste heat circulating water of the power plant, and the working fluid side of the evaporator (8) performs heat exchange with the waste heat circulating water of the power plant.

2. The adjustable large temperature span cascade phase change thermal storage mixed working medium high temperature heat pump system according to claim 1, characterized in that: The high-temperature heat pump system with a large-temperature step-by-step phase-change heat storage and mixed working medium has three working conditions, namely direct heating condition, heat storage condition in the heat accumulator, and heat release condition in the heat accumulator. The direct heating mode achieves good temperature matching between the working medium on the working medium side of the high-temperature heat pump circulation module and the water cooling source on the water side of the open water supply module, reducing irreversible losses by at least 14%; The heat storage working condition realizes step-by-step heat storage with a large temperature span, making the heat storage process closer to the temperature change of the non-azeotropic mixed working fluid, reducing the irreversible loss of the heat exchange process by at least 9%; The heat release working condition of the heat accumulator uses the three temperature levels of the stepped phase change heat accumulator in the high-temperature heat pump circulation module to make the temperature change of the heat release process of the phase change material more closely match the temperature change of water, thereby effectively reducing the irreversible loss of the heat release process by at least 31% and improving energy utilization.

3. The adjustable large temperature span cascade phase change thermal storage mixed working medium high temperature heat pump system according to claim 1, characterized in that: The first heat accumulator (11), the second heat accumulator (10) and the third heat accumulator (9) are all shell and tube phase change energy storage heat exchangers; each heat accumulator is filled with three phase change materials with different phase change temperatures, and the mass ratio of the three phase change materials with different phase change temperatures is 1:1:

1.

4. The adjustable large temperature span cascade phase change thermal storage mixed working medium high temperature heat pump system according to claim 1, characterized in that: The environmentally friendly binary non-azeotropic mixture is a mixture of 50% by mass of trans-1-chloro-3,3,3-trifluoropropene and 50% by mass of toluene, and the critical temperature is 270.85 o C, the critical pressure is 5031.6kPa, the ozone depletion index is 0, and the global warming potential is less than 10.

5. The adjustable large temperature span cascade phase change thermal storage mixed working medium high temperature heat pump system according to claim 1, characterized in that: The high-temperature phase change material is prepared by uniformly mixing a first phase change material, a second phase change material, and a third phase change material in a mass ratio of 1:1:1; The first phase change material is made by mixing 55.4% by mass of lithium nitrate, 4.5% by mass of sodium nitrate and 40.1% by mass of potassium chloride. The phase change temperature is 160 o C; The second phase change material is made of a mixture of 58.1% by mass of lithium nitrate and 41.9% by mass of potassium chloride, and the phase change temperature is 166 o C; The third phase change material is made by mixing lithium nitrate with a mass fraction of 47.9%, lithium chloride with a mass fraction of 1.4%, and sodium nitrate with a mass fraction of 50.7%. o C.

6. The adjustable large temperature span cascade phase change thermal storage mixed working medium high temperature heat pump system according to claim 1, characterized in that: The medium-temperature phase change material is prepared by uniformly mixing phase change material A, phase change material B and phase change material C in a mass ratio of 1:1:1; The phase change material A is made by mixing 29% by mass of lithium nitrate, 17% by mass of sodium nitrate, 49.4% by mass of potassium nitrate and 4.6% by mass of strontium nitrate. o C; The phase change material B is made by mixing 33% by mass of lithium nitrate and 67% by mass of potassium nitrate, and the phase change temperature is 133 o C; The phase change material C is made by mixing 53% by mass of lithium nitrate, 40% by mass of sodium nitrite and 7% by mass of sodium nitrate. o C.

7. The adjustable large temperature span cascade phase change thermal storage mixed working medium high temperature heat pump system according to claim 1, characterized in that: The low-temperature phase change material is prepared by uniformly mixing phase change material I, phase change material II and phase change material III in a mass ratio of 1:1:1; The phase change material I is brown keto acid, and the phase change temperature is 61.4 o C; The phase change material II is made by mixing 50% by mass of erythritol and 50% by mass of urea, and the phase change temperature is 79.6 o C; The phase change material III is xylitol, and the phase change temperature is 98.6 o C.

8. The adjustable large temperature span cascade phase change thermal storage mixed working medium high temperature heat pump system according to claim 1, characterized in that: The water pump (12) is a booster type water pump.

9. The adjustable large temperature span cascade phase change thermal storage mixed working medium high temperature heat pump system according to claim 1, characterized in that: All connecting pipes of the system are treated with thermal insulation.

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