A highly efficient Brayton system for combined cooling, heating and power generation with wide applicability of heat sources and complete heat recovery.

Abstract

This invention relates to a highly efficient Brayton system for combined cooling, heating, and power (CCHP) with wide applicability to heat sources and complete heat recovery. The output of the heat source system is connected to the input of the high-temperature heater and high-temperature reheater of an SCO2 Brayton cycle. The output of the high-temperature heater and high-temperature reheater is connected to the low-temperature heater, and the output of the low-temperature heater is connected to the input of the heat source system. The carbon dioxide storage tank of the SCO2 Brayton cycle is connected to the input of the generator of an ammonia absorption refrigeration cycle and the input of the second evaporator of a regenerative SCO2 heat pump cycle. The output of the generator of the ammonia absorption refrigeration cycle and the output of the second evaporator of the regenerative SCO2 heat pump cycle are connected to the output of the precooler of the SCO2 Brayton cycle. This highly efficient CCHP system can completely recover heat from multiple forms of heat sources and has high heat source matching and energy conversion capabilities.

Description

Technical Field

[0001] This invention belongs to the field of multi-stage heat energy recovery and conversion and high-efficiency combined cooling, heating and power (CCHP) in thermal energy conversion. It relates to a high-efficiency CHP Brayton system with a wide range of heat source applicability and full heat recovery. In particular, it relates to an improved closed-loop supercritical carbon dioxide (SCO2) Brayton cycle that fully recovers the full gradient heat of the heat source, and a comprehensive power system that utilizes an ammonia absorption refrigeration cycle and a regenerative SCO2 heat pump cycle to recover the low-temperature waste heat in the SCO2 Brayton cycle to achieve high-efficiency CHP. Background Technology

[0002] In industrial production, the application of generating heat energy through various physical and chemical reactions and converting it into high-grade energy is very extensive. Among these, areas where mature heat source conversion applications are feasible include: 1. Natural energy industries such as solar and wind power; 2. Traditional fuel industries such as fossil fuels; and 3. The nuclear energy industry. However, the energy level distribution of the heat source forms provided in these areas is often not fixed, and relying on a single heat recovery system is difficult to adapt to all heat source forms and fully realize maximum and efficient energy recovery. Therefore, designing new heat recovery systems to fully explore the potential of cascaded heat energy applications aligns with the future goals of resource conservation and energy emission reduction. Taking the nuclear energy industry as an example, since the Fourth International Forum on Nuclear Energy Systems in 2002, research on fourth-generation advanced reactors has developed rapidly in various countries. The high-temperature gas-cooled fast reactor, as a fourth-generation closed-loop helium-cooled advanced reactor type, has advantages such as strong sustainability, providing ultra-high heat source temperatures, and clean and safe operation, making it an important research direction for future reactor development and design. In particular, the ALLEGRO gas-cooled fast reactor conceptual design is the first design prototype of gas-cooled fast reactor technology (DOI: 10.1016 / j.nucengdes.2019.02.006), and its research, design and testing are becoming increasingly mature.

[0003] Conventional nuclear reactors use basic steam power systems for heat recovery and power output. These systems are characterized by low cost, simple and stable structure, and are widely used in the nuclear power field. However, their large steam generators, boilers, and condensers result in bulky equipment and low thermal efficiency and power output. At the 4th International Forum on Nuclear Energy Systems in 2002, the SCO2 Brayton cycle emerged as a promising alternative to steam power cycles due to its compact size, stability, high thermal efficiency, and wide applicability. Using CO2 as the working fluid for heat transfer not only easily achieves supercritical conditions (30.98℃, 7.3773MPa), but SCO2 also possesses excellent liquid and gaseous thermophysical properties near the critical point (low viscosity, good compressibility, high specific heat capacity, etc.), further optimizing the heat exchange environment and efficiency within the Brayton cycle (DOI: 10.1016 / j.cja.2020.12.022). Furthermore, the heat exchangers used in conventional nuclear power systems are typically bulky plate heat exchangers. Therefore, conventional nuclear reactor systems struggle to meet the demands of environments requiring compact space and layout. Printed circuit board heat exchangers (PCHEs), as a novel type of heat exchanger with high heat transfer density and high compactness, have become a key heat exchange component in the Brayton advanced power cycle. They improve the heat transfer efficiency within the cycle, further enhancing the compactness of the Brayton cycle and making the practical and widespread application of complex and multi-effect Brayton systems more feasible.

[0004] Currently, one approach to optimizing the Brayton cycle is to improve the cycle structure, optimize the internal heat exchange environment, and enhance heat recovery capabilities. In the coupling of the Brayton cycle and the nuclear reactor cycle, without affecting the internal heat exchange efficiency and stable heat exchange of components, SCO2 struggles to fully recover the reactor's cooling heat (DOI: 10.1016 / j.enconman.2020.112649, DOI: 10.1002 / er.8076). For the Generation IV Allegro reactor, the reactor outlet temperature is typically above 500°C, while a single-stage recompression Brayton cycle can only recover about 150°C of reaction cooling heat. This results in a reactor inlet temperature higher than the original design temperature (260°C), with a large amount of cooling heat being released into the environment, leading to a lower net power output. Optimizing the Brayton cycle involves fully recovering the latent heat within the system's stages, efficiently and rationally recovering waste heat released into the environment through methods such as constructing combined cycles. Due to the excellent thermodynamic properties of SCO2 near its critical point, energy losses during compression can be significantly reduced. Typically, a precooler is needed to cool CO2 to its critical state before the compressor inlet. A large amount of SCO2 waste heat (60℃-90℃) is discharged into the environment through the precooler, resulting in extremely high cycle heat losses. If a top-bottom cycle approach is adopted, the waste heat lost in the SCO2 Brayton cycle through the precooler can be recovered, producing cooling, heating, and power generation effects, thus improving the overall thermodynamic performance of the system. Because multi-effect energy output cycles have complex inter-cycle coupling performance and large size, most current mature research focuses on the design and optimization of two-effect output cycles. Therefore, improving cycle layout, fully utilizing waste heat and residual heat potential, meeting different types of energy demands, and maintaining a simple and lightweight cycle layout with excellent cycle performance are future development trends. Summary of the Invention

[0005] Technical problems to be solved

[0006] To overcome the shortcomings of existing technologies, this invention proposes a highly efficient Brayton system for combined cooling, heating, and power (CCHP) with wide applicability to heat sources and complete heat recovery. This system is a high-efficiency CCHP system that couples an ammonia absorption refrigeration cycle with a regenerative SCO2 heat pump cycle to a Brayton cycle, enabling complete recovery of heat from various heat sources. This addresses the problems of insufficient utilization of heat sources and potential energy in existing waste heat recovery systems, limited energy output, and large component sizes. Composed of an SCO2 Brayton cycle, an ammonia absorption refrigeration cycle, and a regenerative SCO2 heat pump cycle, it can completely recover heat from different closed-loop heat sources, including some waste heat from the precooler in the Brayton cycle, and adjust the output to produce the required air conditioning cooling effect and hot water as needed. By applying printed circuit board heat exchangers to key heat exchange components of the CCHP cycle, the system's compactness and heat exchange performance are improved, enhancing the efficiency of the new Brayton system's cascaded heat recovery and conversion, and meeting the adaptability and matching requirements of the Brayton system under different operating conditions and the need for multiple energy efficiency outputs.

[0007] Technical solution

[0008] A highly efficient combined cooling, heating, and power (CCHP) Brayton system with a wide range of heat source applications and full heat recovery is characterized by comprising an SCO2 Brayton cycle, an ammonia absorption refrigeration cycle, and a regenerative SCO2 heat pump cycle. The output of the heat source system is connected to the input of the high-temperature heater 1 and the high-temperature reheater 2 of the SCO2 Brayton cycle. The outputs of the high-temperature heater 1 and the high-temperature reheater 2 are connected to the low-temperature heater 3, and the output of the low-temperature heater 3 is connected to the input of the heat source system. The carbon dioxide storage tank 16 of the SCO2 Brayton cycle is connected to the input of the generator 22 of the ammonia absorption refrigeration cycle and the input of the second evaporator 36 of the regenerative SCO2 heat pump cycle via a first flow valve 17. The outputs of the generator 22 of the ammonia absorption refrigeration cycle and the second evaporator 36 of the regenerative SCO2 heat pump cycle are connected to the output of the precooler 4 of the SCO2 Brayton cycle. The SCO2 Brayton cycle is a recompression-reheat type SCO2 Brayton cycle. All connections are pipeline connections.

[0009] The SCO2 Brayton cycle is a recompression-reheat type SCO2 Brayton cycle, including a high-temperature heater 1, a high-temperature reheater 2, a low-temperature heater 3, a precooler 4, a compressor 5, a recompressor 6, a first regenerator 7, a reheater 8, a first turbine 9, a second turbine 10, a third turbine 11, a fourth turbine 12, a second regenerator 13, a first generator 14, a first motor 15, a carbon dioxide storage tank 16, a first flow valve 17, and a second flow valve 18. Heat is supplied through the first flow valve 17 via an ammonia absorption refrigeration cycle, then cooled by the precooler 4 and compressed by the compressor 5. A portion of the SCO2 is diverted into the second regenerator 13 to increase superheat, and then the remaining heat is recovered by the low-temperature heater 3. The remaining heat then enters the third turbine 11 for expansion and work, flowing back into the second regenerator 13 to replenish the heat from the compressor 5. After preheating, SCO2 flows back into the fourth turbine 12 to expand and do work, and finally flows into the carbon dioxide storage tank 16. The second flow valve 18 controls a portion of the SCO2 in the carbon dioxide storage tank 16 to serve as a heat source for the refrigeration and heat pump cycle, while the other portion of SCO2 is sent to the recompressor 6 for compression and heating. The other portion of SCO2 flowing out of the compressor 5 is then enhanced in superheat by the first regenerator 7, and merges with the SCO2 controlled by the second flow valve 18 and compressed by the recompressor 6. After being further enhanced in superheat by the regenerator 8, it first absorbs heat from the high-temperature heater 1 and flows into the first turbine 9 to expand and do work. It then flows into the high-temperature heater 2 again to absorb heat from the heat source and flows into the second turbine 10 to expand and do work. Finally, after transferring heat to the cold-side SCO2 through the regenerator 8 and the first regenerator 7, it flows into the carbon dioxide storage tank 16, and the cycle continues.

[0010] The SCO2 Brayton cycle also includes various SCO2 Brayton cycle layouts such as regenerative, reheat, recompression, interstage cooling, or precompression.

[0011] The ammonia absorption refrigeration cycle includes: a distillation column 19, a first condenser 20, a first throttling valve 21, a generator 22, a solution heat exchanger 23, a second throttling valve 24, an absorber 25, a first evaporator 26, a second motor 27, and a solution pump 28. The ammonia solution in the generator 22 absorbs heat from SCO2 in the precooler 4 of the S-CO2 Brayton cycle and then enters the distillation column 19. After condensation and reflux by cooling water, ammonia gas is generated at the top, while a low-concentration ammonia solution is generated at the bottom. The ammonia gas flowing out from the top of the distillation column 19 is then passed through the first... After condensing into a liquid state in condenser 20, the ammonia expands isenthalpically into a two-phase ammonia through the first throttling valve 21. The ammonia absorbs ambient heat in the first evaporator 26 to achieve a cooling effect. The ammonia solution flowing out from the bottom of the distillation column 19 transfers heat through the solution heat exchanger 23, and is depressurized to saturation through the second throttling valve 24. It is then injected into the absorber 25 and fully mixed with the ammonia gas from the first evaporator 26. After some of the absorbed heat is carried away by the cooling water, it flows into the solution pump 28 and is pressurized to the generator pressure. After being heated by the solution heat exchanger 23 to increase the superheat, it flows into the generator 22, and the cycle continues.

[0012] The ammonia absorption refrigeration cycle also includes various ammonia refrigeration cycle layouts such as single-effect, multi-effect, and compression-absorption hybrid types.

[0013] The regenerative SCO2 heat pump cycle includes: a third throttle valve 29, a fifth turbine 30, a third regenerator 31, a second compressor 32, a second condenser 33, a second generator 34, a third motor 35, and a second evaporator 36. SCO2 absorbs heat from the precooler 4 of the S-CO2 Brayton cycle, is then heated by the third regenerator 31 and compressed by the second compressor 32. The cold-side working fluid is then heated in the second condenser 33 to provide heating. SCO2 exiting the second condenser 33 transfers heat from the third regenerator 31 to the SCO2 in the second evaporator 36. After the expansion of the fifth turbine 30 and the isenthalpic pressure reduction of the third throttle valve 29, SCO2 finally flows into the second evaporator 36, thus completing the cycle.

[0014] The regenerative SCO2 heat pump cycle also includes various regenerative SCO2 heat pump cycle layouts such as basic type, multi-stage compression, and compression-absorption hybrid type.

[0015] The high-temperature heater 1, high-temperature reheater 2, low-temperature heater 3, precooler 4, regenerator 7, reheater 8, second regenerator 13, first condenser 20, generator 22, solution heat exchanger 23, first evaporator 26, third regenerator 31, second condenser 33 and second evaporator 36 adopt single-sided or double-sided etched printed circuit board type heat exchangers.

[0016] The use of a highly efficient combined cooling, heating and power (CCHP) Brayton system with a widely applicable heat source and full heat recovery is characterized by: a circulating loop for heat source configurations where the inlet and outlet temperatures and pressures are known under all design conditions in the heat source system.

[0017] The heat source system includes a closed-loop layout with multiple heat source forms such as nuclear reactor loop, gas loop, solar loop, and geothermal loop.

[0018] The present invention describes a highly efficient combined cooling, heating, and power system that couples an ammonia absorption refrigeration cycle with a regenerative SCO2 heat pump cycle to a SCO2 Brayton cycle, enabling complete recovery of heat from multiple heat sources. In the bottom cycle, the ammonia absorption refrigeration cycle cannot completely recover the waste heat before compressor 5 in the SCO2 Brayton cycle, nor can it restore the SCO2 in the SCO2 Brayton cycle to its initial state. Therefore, a pre-cooler 4 is added to the SCO2 Brayton cycle to cool the SCO2 after it has provided heat to the ammonia absorption refrigeration cycle and the regenerative SCO2 heat pump cycle to the compressor inlet state, facilitating subsequent cycles.

[0019] Beneficial effects

[0020] This invention proposes a highly efficient Brayton system for combined cooling, heating, and power (CCHP) with a wide range of heat source applications and full heat recovery. The output of the heat source system is connected to the input of the high-temperature heater and high-temperature reheater of the SCO2 Brayton cycle. The output of the high-temperature heater and high-temperature reheater is connected to the low-temperature heater, and the output of the low-temperature heater is connected to the input of the heat source system. The carbon dioxide storage tank of the SCO2 Brayton cycle is connected to the input of the generator of the ammonia absorption refrigeration cycle and the input of the second evaporator of the regenerative SCO2 heat pump cycle. The output of the generator of the ammonia absorption refrigeration cycle and the output of the second evaporator of the regenerative SCO2 heat pump cycle are connected to the output of the precooler of the SCO2 Brayton cycle.

[0021] The high-efficiency cogeneration Brayton system described in this invention can completely recover heat from various forms of heat sources, exhibiting high heat source matching and energy conversion capabilities. Utilizing an ammonia absorption refrigeration cycle and a regenerative SCO2 heat pump cycle to recover waste heat emitted into the environment by the precooler in the S-CO2 Brayton cycle, the generated air conditioning cooling capacity and daily hot water consumption can be controlled according to different energy efficiency and usage requirements, achieving a highly efficient cogeneration effect. Compared to other existing waste heat recovery cycles, the combined cycle shows a significant improvement in thermal efficiency and net output power. In the high-efficiency cogeneration system described in this invention, the high-temperature heater, high-temperature reheater, low-temperature heater, precooler, regenerator, condenser, generator, solution heat exchanger, evaporator, condenser, and evaporator can be etched with PCHE (Polyethylene Chromium Chromatography) on both sides, improving the compactness, heat exchange effect, and heat energy cascade recovery and conversion efficiency of the new Brayton system, while also meeting the adaptability and matching requirements of the Brayton system under different operating conditions.

[0022] This invention employs the following in the system:

[0023] The fourth turbine has a large pressure-temperature difference on both sides. If the first turbine (Turbine 1) directly expands to the pressure of the ammonia absorption refrigeration cycle generator, it will cause negative temperature difference heat transfer in the Recu_LTC (that is, the temperature of the hot fluid is lower than that of the cold fluid). Therefore, the design of the Recu_LTC is ensured by controlling the pressure.

[0024] Therefore, the high-temperature and low-temperature sections of helium cooling heat can be recovered in the ALLEGRO loop.

[0025] Beneficial effects

[0026] The high-efficiency cogeneration Brayton system described in this invention utilizes both a conventional recompression-reheat Brayton cycle and an improved regenerative Brayton cycle to achieve cascaded recovery of heat from the heat source. In the improved regenerative Brayton cycle, the heat source form is not fixed and has a heat exchange temperature range, which affects the maximum operating temperature of the cycle and the heat exchange environment of the regenerator 13. If the operating pressure of the third turbine 11 expands directly to the compressor inlet pressure, as the maximum operating temperature of the improved regenerative Brayton cycle decreases, the temperature difference between the hot and cold fluids in the regenerator 13 will decrease, even leading to negative temperature difference heat exchange (where the hot and cold temperature change lines intersect). Therefore, compared to the conventional regenerative Brayton cycle, under the condition of a lower maximum operating temperature, the improved regenerative Brayton cycle ensures the lowest heat exchange temperature difference in the regenerator 13 by utilizing the pressure after the expansion of the third turbine 11, and increases the residual pressure energy of the SCO2 working fluid recovered by the fourth turbine 12 to improve the cycle's thermal efficiency.

[0027] In the high-efficiency cogeneration Brayton system described in this invention, the operating pressure difference of SCO2 before and after compressor 32 is significant in the regenerative SCO2 heat pump cycle. Therefore, by increasing turbine 30 to recover the thermodynamic energy of SCO2 leaving the partial regenerator 31, the thermal efficiency within the regenerative SCO2 heat pump cycle is improved. Simultaneously, as the expansion ratio of turbine 30 increases, the temperature of SCO2 before the evaporator 36 inlet decreases. This means that the temperature of SCO2 leaving evaporator 36 in the improved recompression and reheat Brayton cycle is lower, resulting in a lower temperature of SCO2 before the precooler 4 in the improved recompression and reheat Brayton cycle and a reduction in heat dissipated into the environment through precooler 4. This is beneficial for improving the thermal energy utilization capacity of the high-efficiency cogeneration Brayton system.

[0028] Compared with existing technologies, the high-efficiency combined cooling, heating and power system of the present invention, which couples an ammonia absorption refrigeration cycle with a regenerative SCO2 heat pump cycle to a SCO2 Brayton cycle and can completely recover heat from multiple forms of heat sources, has the following advantages:

[0029] 1. This high-efficiency combined cooling, heating, and power (CCHP) system, applied in the field of heat energy recovery and conversion, employs an ammonia absorption refrigeration cycle coupled with a regenerative SCO2 heat pump cycle and an SCO2 Brayton cycle. Compared to other existing waste heat recovery cycles, it recovers waste heat discharged into the environment by the precooler. The generated air conditioning cooling capacity and daily hot water volume can be controlled according to different energy efficiency and usage requirements, achieving a highly efficient CCHP effect. The combined cycle thermal efficiency and net power output are significantly improved, meeting the comprehensive needs for air conditioning cooling and daily hot water under various operating conditions. According to simulation results, the CCHP system proposed in this invention can generate a total thermal efficiency of 54.2%, output a net power of 30.22MW, provide 1.722MW of air conditioning cooling at 20℃, and provide 8.724MW of heating at 98℃, demonstrating excellent waste heat recovery capabilities and CCHP efficiency.

[0030] 2. In this high-efficiency cogeneration system applied to the field of heat energy recovery and conversion, the high-temperature heater, high-temperature reheater, low-temperature heater, precooler, regenerator, condenser, generator, solution heat exchanger, evaporator, regenerator, condenser, and evaporator of the high-efficiency cogeneration system described in this invention can utilize single-sided and double-sided etched plate heat exchangers (PCHEs). This improves the compactness, heat exchange effect, and heat energy cascade recovery and conversion efficiency of the novel Brayton system, and meets the adaptability and matching capabilities of the Brayton system under different operating conditions. According to numerical simulation results, compared with traditional large plate heat exchangers, the application of printed circuit board heat exchangers in this high-efficiency cogeneration system significantly improves the cycle compactness and heat exchange performance.

[0031] 3. This high-efficiency combined cooling, heating, and power (CCHP) system, applied in the field of heat energy recovery and conversion, can completely recover heat from various heat sources. Based on different heat source types, while maintaining high overall thermodynamic efficiency and high net power output, the system adjusts cycle parameters within a small range to match different types of heat sources. Simultaneously, it satisfies the optimal heat exchange environment and efficiency of the internal components of the cycle, thereby maximizing thermal efficiency, cooling, heating, and power output under different operating conditions. According to numerical simulation results, the CCHP system proposed in this invention can completely recover 75MW of reactor cooling heat, producing a total thermal efficiency of 54.2%, outputting 30.22MW of net electrical power, providing 1.722MW of air conditioning cooling at 20℃, and 8.724MW of heating with 98℃ hot water, demonstrating the system's excellent heat source matching and energy conversion capabilities. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a high-efficiency combined cooling, heating and power system that can completely recover heat from multiple forms of heat sources by coupling an ammonia absorption refrigeration cycle with a regenerative SCO2 heat pump cycle and an SCO2 Brayton cycle.

[0033] Figure 2 The high-temperature heater 1, high-temperature reheater 2, low-temperature heater 3, precooler 4, regenerator 7, reheater 8, second regenerator 13, first condenser 20, generator 22, solution heat exchanger 23, first evaporator 26, third regenerator 31, second condenser 33, and second evaporator 36 are configured with single-sided or double-sided etched printed circuit board heat exchangers.

[0034] High-temperature heater 1, 2 High-temperature reheater, Low-temperature heater 3, Precooler 4, Compressor 5, Recompressor 6, 7 First regenerator, 8 Reheater, 9 First turbine, 10 Second turbine, 11 Third turbine, 12 Fourth turbine, 13 Second regenerator, 14 First generator, 15 First motor, Carbon dioxide storage tank 16, 17 First flow valve, 18 Second flow valve, Distillation column 19, 20 First condenser, 21 First throttle valve, Generator 22, Solution heat exchanger 23, 24 Second throttle valve, Absorber 25, 26 First evaporator, 27 Second motor, Solution pump 28, 29 Third throttle valve, 30 Fifth turbine, 31 Third regenerator, 32 Second compressor, 33 Second condenser, 34 Second generator, 35 Third motor, 36 Second evaporator. Detailed Implementation

[0035] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0036] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] In industrial production, it is often necessary to recover and utilize various heat sources to convert them into high-quality energy and work. However, the energy level distribution of heat sources is usually not fixed, and it is difficult to achieve maximum and efficient energy recovery by relying on a single heat recovery system. Taking the nuclear energy industry as an example, the heat recovery and work output system of a conventional nuclear reactor is a basic steam power system, equipped with large steam generators, boilers, and condensers. This not only results in large equipment sizes but also low thermal efficiency and work output. The heat exchangers used in general nuclear power systems are bulky plate heat exchangers. Therefore, conventional nuclear reactor systems are difficult to meet the environmental conditions that require compact space and layout. At the same time, in the coupling of the Brayton cycle and the nuclear reactor cycle, under the condition of not affecting the heat exchange efficiency inside the cycle and the stable heat exchange of the components, SCO2 is unlikely to fully recover the cooling heat of the nuclear reactor. For the fourth-generation reactor ALLEGRO, the reactor outlet temperature is generally above 500°C, while a single-stage recompression Brayton cycle can only recover about 150°C of reaction cooling heat. This would cause the reactor inlet temperature to exceed the original design temperature (260°C), resulting in a significant amount of cooling heat being released into the environment, thus lowering the net power output of the cycle. Furthermore, due to the excellent thermodynamic properties of SCO2 near its critical point, a precooler is typically required to cool CO2 to its critical state before the compressor inlet. A large amount of SCO2 waste heat (60°C-90°C) is released into the environment through the precooler, resulting in extremely high cycle heat losses. Therefore, improving the cycle layout, fully utilizing waste heat and residual heat potential, meeting different types of energy demands, and maintaining a simple and lightweight cycle layout with excellent cycle performance are future development trends.

[0038] This invention utilizes the SCO2 Brayton cycle, an ammonia absorption refrigeration cycle, and a regenerative SCO2 heat pump cycle to completely recover heat from different closed-loop heat sources. It also recovers a portion of the waste heat from the precooler in the Brayton cycle, adjusting the output to produce the required air conditioning cooling and hot water as needed. By applying printed circuit board heat exchangers to key heat exchange components of the combined cooling, heating, and power (CCHP) cycle, it improves the cycle's compactness and heat exchange performance, enhancing the efficiency of the new Brayton system's cascaded heat recovery and conversion. This also meets the adaptability and matching requirements of the Brayton system under different operating conditions, as well as the demands for diverse energy outputs. This achieves highly efficient CCHP, addressing the problems of insufficient utilization of heat source heat and potential energy, limited energy output methods, and large cycle component size in existing waste heat recovery systems.

[0039] Figure 1 The paper demonstrates the main components and basic flow of a highly efficient combined cooling, heating and power system that fully recovers heat from multiple heat sources by coupling an ammonia absorption refrigeration cycle with a regenerative SCO2 heat pump cycle. The system includes the S-CO2 Brayton cycle, the ammonia absorption refrigeration cycle, and the regenerative SCO2 heat pump cycle.

[0040] The heat source described in this embodiment is not limited to... Figure 1 The ALLEGRO reactor loop cooling heat shown in this embodiment is exemplary and should not be construed as a limitation of the present invention. The system described herein is applicable to closed-loop heat source cycles with known inlet and outlet temperatures and pressures under all design conditions, including but not limited to closed-loop layouts of various heat source forms such as nuclear reactor loop cycles, gas loop cycles, solar loop cycles, and geothermal loop cycles.

[0041] The SCO2 Brayton cycle is not limited to Figure 1 The modified recompression-reheat SCO2 Brayton cycle shown in this embodiment is exemplary and should not be construed as a limitation of the present invention. The system described herein is applicable to all SCO2 Brayton cycles where the CO2 cooling endpoint is near the critical point and the cooling starting point belongs to the category of low-temperature heat sources, including but not limited to various SCO2 Brayton cycle layouts such as regenerative, reheat, recompression, interstage cooling, and precompression types.

[0042] First, a portion of the SCO2 in the carbon dioxide storage tank 16 is used as a heat source to provide heat for the refrigeration and heat pump cycle through the control of the first flow valve 17 and the second flow valve 18, while the other portion of SCO2 is sent to the compressor 6 for compression and heating. After the first portion of SCO2 provides heat for the refrigeration and heat pump cycle, it is cooled by the precooler 4 and compressed by the compressor 5. Then, a portion of SCO2 is diverted to the second regenerator 13 to increase the superheat. The remaining heat source heat is recovered by the low-temperature heater 3, and then it enters the third turbine 11 to expand and do work. After flowing into the second regenerator 13 to preheat the SCO2 from the compressor 5, it flows into the fourth turbine 12 again to expand and do work, and finally flows into the carbon dioxide storage tank 16. The other part of SCO2 flowing out of compressor 5 is superheated by the first reheater 7 and then merges with SCO2 controlled by the second flow valve 18 and compressed by the recompressor 6. After being further superheated by reheater 8, it first absorbs heat from the heat source of the high-temperature heater 1 and flows into the first turbine 9 to expand and do work. Then it flows into the heat source of the high-temperature reheater 2 and flows into the second turbine 10 to expand and do work. Finally, after transferring heat to the cold side SCO2 through reheater 8 and the first reheater 7, it flows into the carbon dioxide storage tank 16, and so on.

[0043] The ammonia absorption refrigeration cycle is not limited to Figure 1The single-effect ammonia absorption refrigeration cycle shown in this embodiment is exemplary and should not be construed as a limitation of the present invention. The system described herein is applicable to all ammonia refrigeration cycles in which the CO2 cooling endpoint in the Brayton cycle is near the critical point and the cooling starting point belongs to the category of low-temperature heat sources, including but not limited to single-effect, multi-effect, and compression-absorption hybrid ammonia refrigeration cycle layouts.

[0044] First, the ammonia solution in generator 22 absorbs heat from SCO2 in the S-CO2 Brayton cycle precooler 4, and then enters the distillation column 19 for distillation. After condensation and reflux by cooling water, ammonia gas is generated at the top, while a low-concentration ammonia solution is generated at the bottom. The ammonia gas flowing out from the top of the distillation column 19 is condensed into liquid by the first condenser 20, and then expands isenthalpically into two-phase ammonia through the first throttling valve 21. It absorbs ambient heat in the first evaporator 26 to achieve a cooling effect. The ammonia solution flowing out from the bottom of the distillation column 19 transfers heat through the solution heat exchanger 23, and then is depressurized to saturation through the second throttling valve 24. It is then injected into the absorber 25 to mix thoroughly with the ammonia gas from the first evaporator 26. After some of the absorbed heat is carried away by cooling water, it flows into the solution pump 28 and is pressurized to the generator pressure. After being heated by the solution heat exchanger 23 to increase the superheat, it flows back into the generator 22, and the cycle continues.

[0045] The regenerative SCO2 heat pump cycle is not limited to Figure 1 The regenerative SCO2 heat pump cycle shown in this embodiment is exemplary and should not be construed as a limitation of the present invention. The system described herein is applicable to all SCO2 heat pump cycles that can utilize and recover CO2 cooling endpoints near the critical point and cooling starting points within the low-temperature heat source range, including but not limited to basic type, multi-stage compression, compression-absorption hybrid type, and other SCO2 heat pump cycle layouts.

[0046] First, SCO2 absorbs heat from the SCO2 in the S-CO2 Brayton cycle precooler 4, then is heated by the third regenerator 31 and compressed by the second compressor 32. In the second condenser 33, it heats the cold-side working fluid to provide heating. The SCO2 exiting the second condenser 33 transfers heat from the SCO2 in the third regenerator 31 to the SCO2 in the second evaporator 36. After the expansion of the fifth turbine 30 and the isenthalpic pressure reduction by the third throttle valve 29, it finally flows back into the second evaporator 36, thus completing the cycle.

[0047] This embodiment describes a highly efficient combined cooling, heating, and power system that fully recovers heat from multiple heat sources by coupling an ammonia absorption refrigeration cycle with a regenerative SCO2 heat pump cycle and an SCO2 Brayton cycle. This embodiment is exemplary and should not be construed as limiting the invention.

[0048] The high-temperature heaters 1 and 2, high-temperature reheaters, low-temperature heaters 3, precoolers 4, first reheaters 7, reheaters 8, second reheaters 13, first condensers 20, generators 22, solution heat exchangers 23, first evaporators 26, third reheaters 31, second condensers 33, and second evaporators 36 can utilize single-sided and double-sided etched printed circuit board heat exchangers, which can effectively improve the compactness of the cycle and the heat exchange performance.

[0049] The high-temperature heaters 1 and 2, high-temperature reheaters, low-temperature heaters 3, precoolers 4, first regenerators 7 and 8, second regenerators 13, first condensers 20, generators 22, solution heat exchangers 23, first evaporators 26, third regenerators 31, second condensers 33, and second evaporators 36 are all of the same type of heat exchangers, as shown in the schematic diagram below. Figure 2 As shown. The heat exchanger adopts a counter-flow arrangement and can be a single-sided or double-sided etched printed circuit board type heat exchanger.

[0050] In the high-temperature heater 1, the heat exchange medium on the hot side is a high-temperature working fluid of the heat source, and the heat exchange medium on the cold side is high-pressure low-temperature SCO2 after heat exchange in the reheater 8.

[0051] In the aforementioned high-temperature reheater, the heat exchange medium on the hot side is a high-temperature working fluid from the heat source, and the heat exchange medium on the cold side is SCO2 after it has expanded and done work through the first turbine 9.

[0052] The heat exchange medium on the hot side of the low-temperature heater 3 is the working fluid flowing out of the high-temperature heaters 1 and 2 and the high-temperature reheater, while the heat exchange medium on the cold side is SCO2 after heat exchange in the second reheater 13.

[0053] In the precooler 4, the heat exchange medium on the hot side is SCO2 flowing out of the generator 22 and the second evaporator 36, and the heat exchange medium on the cold side is cooling water.

[0054] The heat exchange medium on the hot side of the first reheater 7 is SCO2 flowing out of the reheater 8, and the heat exchange medium on the cold side is low-temperature, high-pressure SCO2 compressed by the compressor 5.

[0055] The heat exchange medium on the hot side of the reheater 8 is high-temperature, low-pressure SCO2 after it has expanded and done work through the second turbine 10, and the heat exchange medium on the cold side is SCO2 that has flowed out of the first reheater 7 and been compressed by the recompressor 6.

[0056] In the second regenerator 13, the heat exchange medium on the hot side is high-temperature, low-pressure SCO2 after expansion and work done by the third turbine 11, and the heat exchange medium on the cold side is low-temperature, high-pressure SCO2 after compression by the compressor 5.

[0057] The heat exchange medium on the hot side of the first condenser 20 is superheated ammonia gas flowing out from the top of the distillation column 19, and the heat exchange medium on the cold side is cooling water.

[0058] The heat exchange medium on the hot side of the generator 22 is SCO2 flowing out of the carbon dioxide storage tank 16 and controlled by the flow valve 17, and the heat exchange medium on the cold side is an ammonia solution flowing out of the solution heat exchanger 23.

[0059] In the solution heat exchanger 23, the heat exchange medium on the hot side is an ammonia solution flowing out of the bottom of the distillation column 19, and the heat exchange medium on the cold side is an ammonia solution pressurized by the solution pump 28.

[0060] In the first evaporator 26, the heat exchange medium on the hot side is air or other working fluid in the environment that needs to be cooled, and the heat exchange medium on the cold side is a two-phase ammonia that has been throttled and depressurized by the first throttling valve 21.

[0061] In the third regenerator 31, the heat exchange medium on the hot side is SCO2 flowing out of the second condenser 33, and the heat exchange medium on the cold side is SCO2 flowing out of the second evaporator 36.

[0062] The heat exchange medium on the hot side of the second condenser 33 is SCO2 compressed by the second compressor 32, and the heat exchange medium on the cold side is water waiting to be heated.

[0063] The heat exchange medium on the hot side of the second evaporator 36 is SCO2 flowing out of the carbon dioxide storage tank 16 and controlled by the flow valve 17, while the heat exchange medium on the cold side is SCO2 flowing out of the third throttle valve 29.

[0064] In the highly efficient combined cooling, heating, and power (CCHP) system that couples the ammonia absorption refrigeration cycle with the regenerative SCO2 heat pump cycle to the SCO2 Brayton cycle, which can fully recover heat from various heat sources, the high-temperature heaters 1 and 2, the high-temperature reheaters, the low-temperature heater 3, the precooler 4, the first reheater 7, the reheater 8, the second reheater 13, the first condenser 20, the generator 22, the solution heat exchanger 23, the first evaporator 26, the third reheater 31, the second condenser 33, and the second evaporator 36 can be etched with PCHE on one or both sides. By applying PCHE to the key heat exchange parts of the CCHP cycle, the compactness of the cycle and the heat exchange performance can be improved, thereby enhancing the heat energy cascade recovery and conversion efficiency of the new Brayton system and meeting the adaptability and matching capabilities of the Brayton system under different operating conditions.

[0065] The aforementioned ammonia absorption refrigeration cycle coupled with a regenerative SCO2 heat pump cycle and an SCO2 Brayton cycle constitutes a highly efficient combined cooling, heating, and power (CCHP) system capable of fully recovering heat from various heat sources. Utilizing the ammonia absorption refrigeration cycle and the regenerative SCO2 heat pump cycle to recover waste heat emitted into the environment from the S-CO2 Brayton cycle via the precooler, the generated air conditioning cooling capacity and daily hot water consumption can be controlled according to different energy efficiency and usage requirements, achieving highly efficient CCHP. Compared to other existing waste heat recovery cycles, the aforementioned combined cycle exhibits significantly improved thermal efficiency and net power output, meeting the comprehensive needs for air conditioning cooling and daily hot water consumption under various operating conditions. According to numerical simulation results, under the same conditions, the recompression-reheat Brayton cycle has a cycle thermal efficiency of 46.62% and can output a net electrical power of 13.628MW. The combined cooling, heating and power system can generate a total thermal efficiency of 54.2%, output a net electrical power of 30.22MW, provide a total air conditioning cooling effect of 1.722MW at 20℃, and provide a total heating effect of 8.724MW at 98℃, demonstrating the system's ability to recover waste heat and the effectiveness of combined cooling, heating and power.

[0066] The aforementioned ammonia absorption refrigeration cycle coupled with a regenerative SCO2 heat pump cycle and a SCO2 Brayton cycle is a highly efficient cogeneration system capable of fully recovering heat from multiple heat sources. This system can adjust cycle parameters within a small range to match different types of heat sources while maintaining high overall thermodynamic efficiency and high net power output. Simultaneously, it satisfies the optimal heat exchange environment and efficiency of the internal components of the cycle, such as the working fluid flow rate and split ratio in the Brayton cycle, to maximize thermal efficiency, cogeneration, and power output under different operating conditions. According to numerical simulation results, under the same conditions, the total reactor cooling heat of the recompression-reheat Brayton cycle is 75MW, but only 29.233MW of cooling heat can be recovered, resulting in a cycle thermal efficiency of 46.62% and a net power output of 13.628MW. In contrast, the combined cooling, heating, and power (CCHP) system can fully recover 75MW of reactor cooling heat, achieving a total thermal efficiency of 54.2%, a net power output of 30.22MW, and providing 1.722MW of air conditioning cooling at 20℃ and 8.724MW of heating at 98℃. This demonstrates the system's excellent heat source matching and energy conversion capabilities.

[0067] Based on simulation results from the embodiments, the thermodynamic performance of the improved recompression-reheat Brayton cycle, the conventional recompression-reheat Brayton cycle, and the conventional regenerative Brayton cycle were compared under conditions of coupling the ALLEGRO reactor without coupling the cooling and heat pump cycles. The improved recompression-reheat Brayton cycle and the conventional regenerative Brayton cycle can achieve complete heat recovery from the ALLEGRO reactor, while the conventional recompression-reheat Brayton cycle cannot. The thermodynamic performance of the three cycles is shown in Table 1.

[0068] Table 1. Comparison of thermodynamic performance of the three cycles coupled only with the ALLERGRO reactor.

[0069]

[0070] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention. Such changes, modifications, substitutions, or variations do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of this application.

Claims

1. A highly efficient Brayton system for combined cooling, heating and power generation with wide applicability of heat sources and complete heat recovery, characterized in that... Including SCO2 Brayton cycle, ammonia absorption refrigeration cycle, and regenerative SCO2 heat pump cycle; The output of the heat source system is connected to the input of the high-temperature heater (1) and high-temperature reheater (2) of the SCO2 Brayton cycle. The output of the high-temperature heater (1) and high-temperature reheater (2) is connected to the low-temperature heater (3). The output of the low-temperature heater (3) is connected to the input of the heat source system. The carbon dioxide storage tank (16) of the SCO2 Brayton cycle is connected to the input of the generator (22) of the ammonia absorption refrigeration cycle and the input of the second evaporator (36) of the regenerative SCO2 heat pump cycle through the first flow valve (17). The output of the generator (22) of the ammonia absorption refrigeration cycle and the output of the second evaporator (36) of the regenerative SCO2 heat pump cycle are connected to the output of the precooler (4) of the SCO2 Brayton cycle. The SCO2 Brayton cycle adopts a recompression-reheat type SCO2 Brayton cycle. All connections are pipeline connections.

2. The high-efficiency combined cooling, heating and power Brayton system with a widely applicable heat source and complete heat recovery as described in claim 1, characterized in that: The SCO2 Brayton cycle adopts a recompression-reheat type SCO2 Brayton cycle, including a high-temperature heater (1), a high-temperature reheater (2), a low-temperature heater (3), a precooler (4), a compressor (5), a recompressor (6), a first regenerator (7), a reheater (8), a first turbine (9), a second turbine (10), a third turbine (11), a fourth turbine (12), a second regenerator (13), a first generator (14), a first motor (15), a carbon dioxide storage tank (16), a first flow valve (17), and a second flow valve (18). After heat is provided by the ammonia absorption refrigeration cycle through the first flow valve (17), it is cooled by the precooler (4) and compressed by the compressor (5). After being diverted into a portion of SCO2, it flows into the second regenerator (13) to increase the superheat. Then, the remaining heat source heat is recovered through the low-temperature heater (3), and then it enters the third turbine (11) to expand and do work, flowing into the second regenerator (13) to... After the SCO2 from the compressor (5) is preheated, it flows back into the fourth turbine (12) to expand and do work, and finally flows into the carbon dioxide storage tank (16). The control of the second flow valve (18) uses part of the SCO2 in the carbon dioxide storage tank (16) as a heat source to provide heat for the refrigeration and heat pump cycle, and the other part of the SCO2 is sent to the recompressor (6) for compression and heating. The other part of the SCO2 flowing out of the compressor (5) is superheated by the first regenerator (7), and then merges with the SCO2 controlled by the second flow valve (18) and compressed by the recompressor (6). After the superheat is further increased by the reheater (8), it first absorbs the heat source heat of the high temperature heater (1) and flows into the first turbine (9) to expand and do work. Then it flows into the heat source heat of the high temperature heater (2) and flows into the second turbine (10) to expand and do work. Finally, after the heat is transferred to the cold side of the SCO2 by the reheater (8) and the first regenerator (7), it flows into the carbon dioxide storage tank (16) and repeats this cycle.

3. The high-efficiency combined cooling, heating and power Brayton system with a widely applicable heat source and complete heat recovery as described in claim 1, characterized in that: The SCO2 Brayton cycle also includes various SCO2 Brayton cycle layouts such as regenerative, reheat, recompression, interstage cooling, or precompression.

4. The high-efficiency combined cooling, heating and power Brayton system with a widely applicable heat source and complete heat recovery as described in claim 1, characterized in that: The ammonia absorption refrigeration cycle includes: a distillation column (19), a first condenser (20), a first throttle valve (21), a generator (22), a solution heat exchanger (23), a second throttle valve (24), an absorber (25), a first evaporator (26), a second motor (27), and a solution pump (28); the ammonia solution in the generator (22) absorbs heat from SCO2 in the precooler (4) of the S-CO2 Brayton cycle and then enters the distillation column (19) for distillation. After being refluxed by cooling water, ammonia gas is generated at the top, while a low-concentration ammonia solution is generated at the bottom; the ammonia gas flowing out from the top of the distillation column (19) After being condensed into a liquid state in the first condenser (20), the ammonia expands isenthalpically into a two-phase ammonia through the first throttle valve (21). The ammonia absorbs ambient heat in the first evaporator (26) to achieve a cooling effect. The ammonia solution flowing out from the bottom of the distillation column (19) transfers heat through the solution heat exchanger (23), and is depressurized to saturation through the second throttle valve (24). It is then injected into the absorber (25) and fully mixed with the ammonia from the first evaporator (26). After some of the absorbed heat is carried away by the cooling water, it flows into the solution pump (28) and is pressurized to the generator pressure. After being heated by the solution heat exchanger (23) to increase the superheat, it flows into the generator (22) and repeats this cycle.

5. The high-efficiency combined cooling, heating and power Brayton system with a widely applicable heat source and complete heat recovery as described in claim 1, characterized in that: The ammonia absorption refrigeration cycle also includes various ammonia refrigeration cycle layouts such as single-effect, multi-effect, and compression-absorption hybrid types.

6. The high-efficiency combined cooling, heating and power Brayton system with a widely applicable heat source and complete heat recovery as described in claim 1, characterized in that: The regenerative SCO2 heat pump cycle includes: a third throttle valve (29), a fifth turbine (30), a third regenerator (31), a second compressor (32), a second condenser (33), a second generator (34), a third motor (35), and a second evaporator (36). After SCO2 absorbs heat from the precooler (4) of the S-CO2 Brayton cycle, it is heated by the third regenerator (31) and compressed by the second compressor (32). Then, it heats the cold-side working fluid in the second condenser (33) to output a heating effect. After the SCO2 flowing out of the second condenser (33) transfers heat to the SCO2 from the second evaporator (36) in the third regenerator (31), it undergoes expansion work by the fifth turbine (30) and isenthalpic pressure reduction by the third throttle valve (29), and finally flows into the second evaporator (36) in this cycle.

7. The high-efficiency combined cooling, heating and power Brayton system with a widely applicable heat source and complete heat recovery as described in claim 1, characterized in that: The regenerative SCO2 heat pump cycle also includes various regenerative SCO2 heat pump cycle layouts such as basic type, multi-stage compression, and compression-absorption hybrid type.

8. The high-efficiency combined cooling, heating and power Brayton system with a widely applicable heat source and complete heat recovery as described in claim 1, characterized in that: The high-temperature heater (1), high-temperature reheater (2), low-temperature heater (3), precooler (4), regenerator (7), reheater (8), second regenerator (13), first condenser (20), generator (22), solution heat exchanger (23), first evaporator (26), third regenerator (31), second condenser (33) and second evaporator (36) adopt single-sided or double-sided etched printed circuit board heat exchangers.

9. The use of a highly efficient combined cooling, heating and power (CCHP) Brayton system with a widely applicable heat source and complete heat recovery as described in any one of claims 1 to 8, characterized in that: This is used for circulation loops in heat source systems where the inlet and outlet temperatures and pressures are known under all design conditions.

10. The use of the high-efficiency combined cooling, heating and power Brayton system with a widely applicable heat source and complete heat recovery as described in claim 9, characterized in that: The heat source system includes a closed-loop layout with multiple heat source forms such as nuclear reactor loop, gas loop, solar loop, and geothermal loop.

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