Adjustable large-temperature-span cascade phase change heat storage mixed working medium high-temperature heat pump system

Abstract

The invention discloses an adjustable large-temperature-span cascade phase change heat storage mixed working medium high-temperature heat pump system, and belongs to the technical field of high-temperature heat pump systems. Comprising a high-temperature heat pump circulation module and an open type water supply module. The high-temperature heat pump circulation module is a circulation loop of a working medium side and comprises a compressor, the working medium side of three condensers, two gas-liquid separators, an evaporator and the working medium side of three heat accumulators, and a circulation working medium is an environment-friendly binary non-azeotropic mixture; the open type water supply module is an open loop of the water side and comprises a water pump, the water side of the three condensers and the water side of the three heat accumulators, and the working medium of the water side is water. The system has three working conditions, namely a direct heating working condition, a heat accumulator heat accumulation working condition and a heat accumulator heat release working condition; the irreversible loss is reduced by at least 14% under the direct heating working condition; the irreversible loss in the heat exchange process is reduced by at least 9% under the heat storage working condition of the heat accumulator; the irreversible loss in the heat release process is effectively reduced by at least 31% under the heat release working condition of the heat accumulator, and the energy utilization rate is increased.

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 combining gas-liquid separation regulation and 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 saving 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 usually need to be used for condensing and heating over a large temperature span. However, the existing heat pump cycle is mainly based on pure working fluids, and its phase change isothermal characteristics make the temperature matching between the working fluid and the variable temperature cold and heat source poor, the overall cycle heat exchange irreversible loss is high, and the heat pump energy efficiency is seriously reduced. Therefore, how to improve the temperature matching of the heat exchange process and reduce the irreversible heat exchange loss is the key to improving the energy efficiency of heat pumps.

[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 variable temperature characteristics (also known as temperature glide characteristics), which can form a good match with variable temperature cold and heat sources, reduce irreversible heat exchange losses, and improve the energy efficiency of the heat pump system; (2) Non-azeotropic mixed working fluids can achieve performance complementarity 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 is composed of a high-pressure compressor, a medium-pressure compressor, a low-pressure compressor, a gas-liquid separator, an evaporator, a low-pressure throttle valve, a first intermediate cooler, a medium-pressure throttle valve, a second intermediate cooler, a high-pressure throttle valve, a liquid receiver 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 used 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 deviation, resulting in limited performance improvement of the non-azeotropic mixed working fluid heat pump system. Poor variable operating temperature matching and regulation capabilities are 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 amount of heat can be improved, and efficient recovery of exhaust steam waste heat and storage of high-quality thermal energy can be 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 phase change temperature in the second heat accumulator is set to 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, which effectively reduces 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, instead of 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 the 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 stepped phase-change heat storage mixed working fluid high-temperature heat pump system.

[0006] An adjustable large temperature span stepped phase change heat storage mixed working medium high temperature heat pump system comprises 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, 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, and the working fluid on the water side is water; 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; 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 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; 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, and the working medium outlet of the second condenser 3 and the working medium outlet of the second heat accumulator 10 are connected to the gas inlet of the second gas-liquid separator 6 in parallel; 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; 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 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; 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; 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; 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 medium side of the evaporator 8 performs heat exchange with the waste heat circulating water of the power plant.

[0007] The further technical solution is as follows: The high-temperature heat pump system with large-temperature step-change heat storage and mixed working medium has three working conditions, namely direct heating working condition, heat storage working condition of heat storage device, and heat release working condition of heat storage device; The direct heating condition achieves good temperature matching between the working fluid on the working fluid side of the high-temperature heat pump circulation module and the water cooling source on the water side of the open water supply module, and the irreversible loss is reduced by at least 14%; The heat storage 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, and reducing the irreversible loss of the heat exchange process by at least 9%; The heat release condition of the heat accumulator makes the temperature change of the heat release process of the phase change material in the stepped phase change heat accumulator with three temperature levels in the high-temperature heat pump circulation module 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.

[0008] The first heat accumulator (11), the second heat accumulator (10) and the third heat accumulator (9) are all shell and tube type phase change energy storage heat exchangers.

[0009] 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 5031.6 kPa, the ozone depletion index (ODP) is 0, and the global warming potential (GWP) is less than 10.

[0010] 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 of a mixture of 55.4% lithium nitrate, 4.5% sodium nitrate and 40.1% potassium chloride. o C; The second phase change material is made of a mixture of 58.1% lithium nitrate and 41.9% potassium chloride. o C; The third phase change material is made of a mixture of 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.

[0011] 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 of a mixture of 33% by mass lithium nitrate and 67% by mass potassium nitrate, and the phase change temperature is 133 o C; The C phase change material 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.

[0012] 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.

[0013] The water pump 12 is a booster type water pump.

[0014] All connecting pipelines of the system are treated with thermal insulation.

[0015] The beneficial technical effects of the present invention are embodied in the following aspects: 1. The gas-liquid separator of the present invention utilizes the different boiling points of the components of the non-azeotropic mixed working fluid to separate the condensate during the condensation phase change process, and divides the overall condensation process into three sections. The components can be adjusted section by section to change the working fluid properties of the condensation phase change process, thereby controlling the temperature change of the condensation phase change process. At the same time, the overall temperature glide of the condensation process is equal to the sum of the temperature glide of the three heat exchange sections, which can cope with the situation where the cold and heat source working conditions fluctuate greatly during large temperature span condensation, and effectively improve the flexibility and adaptability of the heat pump system under different working conditions.

[0016] 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 heat storage with a large temperature span. It can form a step-type temperature curve while improving the energy storage density, making its heat storage process closer to the temperature change of non-azeotropic mixed working fluid, and the heat release process is more in line with the temperature change of cold water, effectively reducing the irreversible loss of the heat exchange process and improving energy utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the system structure of the present invention.

[0018] Figure 2 This is the cycle path diagram for direct heating conditions.

[0019] Figure 3 Direct heating condition T - H picture.

[0020] Figure 4 This is the cycle path diagram of the heat storage condition of the heat accumulator.

[0021] Figure 5 Heat storage condition for the heat storage device T - H picture.

[0022] Figure 6 This is the cycle path diagram of the heat storage device's heat release condition.

[0023] Figure 7 Heat storage condition T - H picture.

[0024] Figure 1 Sequence number: compressor 1, first condenser 2, first condenser 3, third condenser 4, first gas-liquid separator 5, first gas-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

[0025] The present invention will be further described in detail below through embodiments in conjunction with the accompanying drawings. Example

[0026] 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.

[0027] 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% trans-1-chloro-3,3,3-trifluoropropene (R1233zd(E)) and 50% toluene (Toluene) by mass fraction. The critical temperature is 270.85 oC, the critical pressure is 5031.6 kPa, the ozone depletion index (ODP) is 0, and the global warming potential (GWP) is less than 10. The temperature slip 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.

[0028] The open water supply module is an open circuit on the water side, and the working medium on the water side is water.

[0029] 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.

[0030] 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 respectively through a three-way pipe. The working fluid outlet of the first condenser 2 and the working fluid outlet of the first heat accumulator 11 are connected to the gas inlet of the first gas-liquid separator 5 in parallel; 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.

[0031] 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 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.

[0032] 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 , 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 .

[0033] The phase change temperature of the high-temperature phase change material in the first heat accumulator (11) is 160°C-180°C.

[0034] The phase change temperature of the medium-temperature phase change material in the second heat accumulator (10) is 100°C-150°C.

[0035] The phase change temperature of the low-temperature phase change material in the third heat accumulator (9) is 60°C-100°C.

[0036] 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% 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 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.

[0037] 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 by mass, 17% sodium nitrate by mass, 49.4% potassium nitrate by mass and 4.6% strontium nitrate by mass. The phase change temperature is 105 o C; B phase change material is made by mixing 33% by mass lithium nitrate and 67% by mass potassium nitrate, and the phase change temperature is 133 o C; C phase change material is made by mixing 53% lithium nitrate by mass, 40% sodium nitrite by mass and 7% sodium nitrate by mass, and the phase change temperature is 142 o C.

[0038] 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.

[0039] 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 .

[0040] The water pump 12 is a booster type water pump.

[0041] 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.

[0042] The first heat accumulator 11, the second heat accumulator 10 and the third heat accumulator 9 are all shell and tube type phase change energy storage heat exchangers.

[0043] All connecting pipes of the system are treated with thermal insulation.

[0044] 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 medium side of the evaporator 8 performs heat exchange with the waste heat circulating water of the power plant.

[0045] 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, greenhouse temperature control, etc.

[0046] The adjustable large temperature span stepped phase change heat storage mixed working medium high temperature heat pump system of this embodiment 1 has three working conditions, namely direct heating condition, heat storage condition of heat storage device and heat release condition of heat storage device. The working principles of the three working conditions are described as follows: See also Figure 2, the thick solid line is the circulation path of the direct heating condition. In the direct heating condition, the sixth stop valve 18, the seventh stop valve 19 and the eighth stop valve 20 of the high temperature heat pump circulation module are closed, and the first stop valve 13, the second stop valve 14, the third stop valve 15, the fourth stop valve 16 and the fifth stop valve 17 are opened. The tenth stop valve 22, the eleventh stop valve 23 and the twelfth stop valve 24 of the open water supply module are closed, and the ninth stop valve 22 is opened. The mixed working medium 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 for pressurization to become a high-temperature and high-pressure gas, enters the first condenser 2 and partially condenses to become a two-phase state, and the two-phase working medium enters the first gas-liquid separator 5 for gas-liquid separation. After separation, the saturated gaseous working medium with a low boiling point enters the second condenser 3 for partial condensation to become a two-phase state, and the two-phase working medium enters the second gas-liquid separator 6 for gas-liquid separation. After separation, the saturated gaseous working medium with a lower boiling point enters the third condenser 4 and is completely condensed to a supercooled state, mixed with the condensed working medium discharged from the first gas-liquid separator and the condensed working medium discharged from the second gas-liquid separator, and then enters the throttle valve 7 for isenthalpic pressure reduction, and finally enters the evaporator to absorb heat to complete the cycle; the room temperature water of 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 turn to absorb heat. According to the actual heat demand, the compressor outlet pressure is adjusted, and the opening of the first stop valve 13 and the second stop valve 14 is 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 match between the working medium and the cold source can be achieved.

[0047] Adjustment process of direct heating condition: 25 o Heat water to 150°C o The circulating medium is pressurized by compressor 1 to become high-temperature and high-pressure gas (pressure is 518.59 kPa, temperature is 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 fluid 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 fluid 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 oC, 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, the mass component ratio is 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 enters the compressor 1 after absorbing heat on the working fluid side of the evaporator 8 to complete the cycle. After adjustment, the final outlet temperature of the working fluid side of the condenser 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 of the condensation process was reduced by 14.53%.

[0048] 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 dashed line is the temperature curve of the unregulated mixed working fluid, with an inlet temperature of 155 o C, outlet temperature 101.21 o C, the overall temperature slip 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 73.96 o C, the overall temperature glide is 76.04 o C, the temperature glide increased by 27.25 compared to the unregulated o C. The area enclosed by the temperature curve 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%, see Figure 3 Middle shaded area.

[0049] 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, and stores heat in the form of latent heat. The working fluid partially condenses 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 solid to liquid, and the working fluid partially condenses and changes into 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 of the third heat accumulator 9 absorbs heat and melts from solid to liquid. The working fluid is completely condensed into 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. Then it enters the throttle valve 7 for isenthalpic decompression, and finally enters the evaporator to absorb heat to complete the cycle. Through three-stage heat storage, the phase change temperature is set in series in the order of low temperature to high temperature, realizing step heat storage with a large temperature span and forming a step-type temperature curve, making its heat storage process closer to the temperature change of non-azeotropic mixed working fluids, reducing irreversible losses in the heat exchange process.

[0050] Adjustment process of heat storage condition of heat storage device: The circulating medium is pressurized by compressor 1 to become high-temperature and high-pressure gas (pressure is 969.68 kPa, 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 dryness is set to 0.5. The mixed working fluid is partially condensed into a two-phase state (temperature 161.37 o C, the mass component ratio is 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 fluid enters the first gas-liquid separator 5 for gas-liquid separation. After separation, the saturated gaseous working fluid (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 oC, 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 fluid enters the second gas-liquid separator 6 for gas-liquid separation. After separation, the saturated gaseous working fluid (temperature 129.47 o C, the mass component ratio is 0.9:0.1) and the working fluid inlet entering the third heat accumulator 9 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 gradients are 98.6 o C. 79.6 o C and 61.4 o C. The circulating fluid is completely condensed to a supercooled state (temperature is 103.51 o C, mass component ratio is 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 enters the compressor 1 after absorbing heat on the working fluid side of the evaporator 8 to complete the cycle. After adjustment, the final outlet temperature of the working fluid side of the condenser 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%.

[0051] Depend on Figure 5 It can be seen that the dotted line is the temperature curve of the phase change material in the three-stage heat storage device 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 o C. The dashed line is the temperature curve of the unregulated mixed working fluid, with an 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 oC. The area enclosed by the phase change temperature curve of the phase change material in the circulating medium and the heat storage device can represent the irreversible loss. After adjustment, the irreversible loss of the heat storage process of the heat storage device was reduced by 9.88%, see Figure 5 Middle shaded area.

[0052] See also Figure 6 , the thick solid line is the circulation path of the heat accumulator heat release condition. When the heat accumulator is in heat release condition, the first stop valve 13, the second stop valve 14, the third stop valve 15, the fourth stop valve 16, the fifth stop valve 17, the sixth stop valve 18, the seventh stop valve 19 and the eighth stop valve 20 of the high-temperature heat pump circulation module are closed, and the compressor 1 stops running. The tenth stop valve 22, the eleventh stop valve 23, the twelfth stop valve 24 and the thirteenth stop valve 25 of the open water supply module are opened, and the ninth stop valve 21 is closed. The room temperature water of the open water supply module is pressurized by the water pump 12 and enters the third heat accumulator 9. The low temperature phase change material absorbs heat and solidifies from liquid to solid, releasing heat to heat the room temperature water into low temperature hot water; the low temperature hot water enters the second heat accumulator 10 to absorb heat, the medium temperature phase change material absorbs heat and solidifies from liquid to solid, releasing heat to heat the low temperature hot water into medium temperature hot water; the medium temperature hot water enters the first heat accumulator 11 to absorb heat, the high temperature phase change material absorbs heat and solidifies from liquid to 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 switching the eleventh stop valve 23, supply medium temperature heat by switching the twelfth stop valve 24, and supply high temperature heat by switching the thirteenth stop valve 25 according to actual heat demand. The room temperature water enters the stepped phase change heat accumulator with three temperature levels in turn for heating. The temperature change of the heat release process of the phase change material is more in line with the temperature change of water, which effectively reduces the irreversible loss of the heat release process and improves energy utilization.

[0053] Adjustment process of heat storage device heat release condition: The supply water of the open water supply module (pressure is 101.325kPa, temperature is 25 o C) After being pressurized to 10 atmospheres by a water pump, it enters the water side inlet of the third heat accumulator 9, and 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 oC); 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. 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 switching the eleventh stop valve 23, medium-temperature heat by switching the twelfth stop valve 24, and high-temperature heat by switching the thirteenth stop valve 25 according to the actual heat demand. Normal temperature water enters the third heat accumulator, the second heat accumulator, and the first heat accumulator of different temperature levels in turn for heating. The temperature change of the heat release process of the phase change material is more in line with the temperature change of water, effectively reducing the irreversible loss of the heat release process by 31.91% and improving energy utilization.

[0054] 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 storage device, in which the phase change temperature of the phase change material of the first heat storage device 11 is 180 o , the phase change temperature of the phase change material of the second heat storage device 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 a 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 o C. The area enclosed by the temperature curve 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 shaded area.

[0055] It will be easily understood by those skilled in the art that the above are only 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 protection scope of the present invention.

Claims

1. An adjustable large temperature span stepped phase change heat storage mixed working medium high temperature heat pump system, characterized by: 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, 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, and the working fluid 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 fluid inlet of the first condenser (2) and the working fluid inlet of the first heat accumulator (11) respectively through a three-way pipe, and 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 to the third stop valve (15), and the working fluid 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 respectively connected to the working fluid inlet of the second condenser (3) and the working fluid inlet of the second heat accumulator (10) 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 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 to a fourth stop valve (16), and the working fluid inlet of the second heat accumulator (10) is connected in series to a seventh stop valve (19); The gas outlet of the second gas-liquid separator (6) is connected to the working fluid inlet of the third condenser (4) and the working fluid inlet of the third heat accumulator (9) respectively through a three-way pipe; the working fluid outlet of the third condenser (4) and the working fluid 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 fluid inlet of the evaporator (8); the working fluid outlet of the evaporator (8) is connected to the inlet of the compressor (1); the working fluid inlet of the third condenser (4) is connected in series with a fifth stop valve (17), and the working fluid inlet of the third heat accumulator (9) is connected in series with an eighth stop valve (20); the liquid outlet of the second gas-liquid separator (6) is connected in series with a second stop valve (14), and the liquid outlet of the first gas-liquid separator (5) is connected in series with a first stop valve (13); the working fluid inlet of the evaporator (8) is connected in series with a 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 a first condenser (2), a water side of a second condenser (3), a water side of a third condenser (4), a water side of a first heat accumulator (11), a water side of a second heat accumulator (10), and a water side of a 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 a 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 on 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 on 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; When in operation, the other side of the evaporator (8) is connected to a circulation pipeline of waste heat circulating water of a 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. According to claim 1, an adjustable large temperature span stepped phase change heat storage mixed working medium high temperature heat pump system is characterized by: The high-temperature heat pump system with large-temperature step-change heat storage and mixed working medium has three working conditions, namely direct heating working condition, heat storage working condition of heat storage device, and heat release working condition of heat storage device; The direct heating condition achieves good temperature matching between the working fluid on the working fluid side of the high-temperature heat pump circulation module and the water cooling source on the water side of the open water supply module, and the irreversible loss is reduced by at least 14%; The heat storage 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, and reducing the irreversible loss of the heat exchange process by at least 9%; The heat release condition of the heat accumulator makes the temperature change of the heat release process of the phase change material in the stepped phase change heat accumulator with three temperature levels in the high-temperature heat pump circulation module 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. According to claim 1, an adjustable large temperature span stepped phase change heat storage mixed working medium high temperature heat pump system is characterized by: 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. According to claim 1, an adjustable large temperature span stepped phase change heat storage mixed working medium high temperature heat pump system is characterized by: 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 5031.6 kPa, the ozone depletion index is 0, and the global warming potential is less than 10.

5. According to claim 1, an adjustable large temperature span stepped phase change heat storage mixed working medium high temperature heat pump system is characterized by: 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 of a mixture of 55.4% by mass lithium nitrate, 4.5% by mass sodium nitrate and 40.1% by mass potassium chloride, and the phase change temperature is 160 o C; The second phase change material is made of a mixture of 58.1% lithium nitrate and 41.9% potassium chloride. o C; The third phase change material is made of a mixture of 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.

6. According to claim 1, an adjustable large temperature span stepped phase change heat storage mixed working medium high temperature heat pump system is characterized by: 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 of a mixture of 33% by mass lithium nitrate and 67% by mass potassium nitrate, and the phase change temperature is 133 o C; The C phase change material 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. According to claim 1, an adjustable large temperature span stepped phase change heat storage mixed working medium high temperature heat pump system is characterized by: 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. According to claim 1, an adjustable large temperature span stepped phase change heat storage mixed working medium high temperature heat pump system is characterized by: The water pump (12) is a booster type water pump.

9. According to claim 1, an adjustable large temperature span stepped phase change heat storage mixed working medium high temperature heat pump system is characterized by: All connecting pipelines of the system are treated with thermal insulation.

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