Two-stage gravity field acting device and method

Abstract

The invention relates to the technical field of low-grade heat source power generation, and discloses a two-stage gravity field acting device which comprises a first-stage condenser, a second-stage condenser, a first-stage turbine, a second-stage turbine and a heater, a refrigerant channel of the heater, a refrigerant channel of the first-stage condenser, the first-stage turbine, a refrigerant channel of the second-stage condenser and the second-stage turbine are sequentially connected to form a refrigerant closed loop. And the cooling water inlet is connected to the cooling water outlet after passing through the cooling water channel of the second-stage condenser and the cooling water channel of the first-stage condenser in sequence. According to the invention, secondary weight differential pressure energy is generated through the refrigerant, and the circulation flow of the refrigerant is realized through the alternate action of weight pressure reduction and increase, and meanwhile, part of potential energy is converted into mechanical energy through the work of the turbine, so that the overall energy conversion efficiency of the system is obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of low-grade heat source power generation technology, specifically relating to a two-stage gravity field work device and method. Background Technology

[0002] Low-grade heat sources are widely distributed in industry and nature, and their energy conversion into electricity has become a hot application topic in recent years. The conventional Organic Rankine Cycle (ORC) is a commercially available technology, but it is typically used for heat sources above 80°C. Below this temperature, due to temperature pinch limitations, the cycle's utilization of the heat source is insufficient. In contrast, the triangular cycle primarily utilizes sensible and endothermic heat, exhibiting good temperature matching characteristics on the heating side, making it a suitable system for thermoelectric conversion of low-grade heat sources. However, it requires a two-phase expander with very low efficiency. To overcome this drawback, patent number ZL201711419509.X proposes a work-generating device utilizing the gravitational field thermosiphon effect. This device retains the characteristics of a triangular cycle while using a hydraulic turbine instead of an expander, achieving higher work-generating capacity. However, this device suffers from a problem: the contradiction between the increasing temperature difference between the hot and cold sources and the relatively constant system temperature difference results in a lack of adaptability to temperature boundary conditions, leading to performance degradation under off-design conditions. Therefore, further improvements are necessary. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a two-stage gravity field work device and method to adapt to changes in the temperature difference between cold and hot sources and achieve greater output work.

[0004] To solve the above-mentioned technical problems, the present invention provides a two-stage gravity field work device, including a first-stage condenser and a second-stage condenser located at a high position, and a first-stage turbine, a second-stage turbine, and a heater located at a low position. The refrigerant channel of the heater, the refrigerant channel of the first-stage condenser, the first-stage turbine, the refrigerant channel of the second-stage condenser, and the second-stage turbine are sequentially connected to form a refrigerant closed loop.

[0005] The cooling water inlet passes sequentially through the cooling water passages of the secondary condenser and the primary condenser before connecting to the cooling water outlet.

[0006] The hot water inlet is connected to the hot water outlet through the heater's heat medium passage.

[0007] As an improvement to the dual-stage gravity field work device of the present invention:

[0008] The refrigerant channel outlet of the heater is connected to the bottom inlet of the first-stage riser, the top outlet of the first-stage riser is connected to the refrigerant channel inlet of the first-stage condenser, the refrigerant channel outlet of the first-stage condenser is connected to the top inlet of the first-stage downcomer, the bottom outlet of the first-stage downcomer is connected to the inlet of the first-stage turbine, the outlet of the first-stage turbine is connected to the bottom inlet of the second-stage riser, the top outlet of the second-stage riser is connected to the refrigerant channel inlet of the second-stage condenser, the refrigerant channel outlet of the second-stage condenser is connected to the top inlet of the second-stage downcomer, the bottom outlet of the second-stage downcomer is connected to the inlet of the second-stage turbine, and the outlet of the second-stage turbine is connected to the refrigerant channel inlet of the heater.

[0009] As a further improvement to the dual-stage gravity field work-doping device of the present invention:

[0010] The primary riser, secondary riser, primary downcomer, and secondary downcomer are all insulated pipes, and there is the same height difference between the primary riser and the primary downcomer, and between the secondary riser and the secondary downcomer.

[0011] The present invention also provides a method for doing work using a two-stage gravity field work device:

[0012] Includes the following steps:

[0013] The working fluid is heated in the heater and becomes a subcooled working fluid after the first stage of potential energy-pressure energy conversion, which drives the first stage turbine to do work. Then, the working fluid flowing out of the first stage turbine becomes a subcooled working fluid again after the second stage of potential energy-pressure energy conversion, which drives the second stage turbine to do work. Then the working fluid flows back to the heater to be heated, and the next cycle begins.

[0014] As an improvement to the work-doing method of the two-stage gravity field work-doing device of the present invention:

[0015] The method for the first-stage potential energy to pressure energy conversion is as follows:

[0016] After flowing out of the heater, the working fluid flows upward along the first-stage riser pipe. As it flows upward, it is subjected to gravity pressure reduction, resulting in a decrease in temperature, a decrease in pressure, and an increase in dryness. Then it flows into the refrigerant passage of the first-stage condenser, where it exchanges heat with the refrigerant in the cooling water passage. After being completely condensed, it enters the first-stage downcomer pipe. As the working fluid flows downward along the first-stage downcomer pipe, it is subjected to gravity pressure increase, resulting in an increase in pressure and a rise in temperature, thus becoming a subcooled working fluid.

[0017] As a further improvement to the work-doing method of the two-stage gravity field work-doing device of the present invention:

[0018] The method for the second-stage potential energy to pressure energy conversion is as follows:

[0019] As the working fluid flowing from the first-stage turbine moves upward along the second-stage riser, it is subjected to gravity pressure reduction, causing its temperature and pressure to continue to decrease, while its dryness increases. Then it flows into the refrigerant passage of the second-stage condenser, where it exchanges heat with the refrigerant in the cooling water passage. After being completely condensed, it enters the second-stage downcomer. As the working fluid flows downward along the second-stage downcomer, it is subjected to gravity pressure increase, causing its pressure and temperature to rise, and it becomes a subcooled working fluid again.

[0020] As a further improvement to the work-doing method of the two-stage gravity field work-doing device of the present invention:

[0021] The refrigerant first flows through the cooling water channel of the secondary condenser to cool the working fluid, and then flows through the cooling water channel of the primary condenser to continue cooling the working fluid.

[0022] As a further improvement to the work-doing method of the two-stage gravity field work-doing device of the present invention:

[0023] The working fluid is a refrigerant;

[0024] The refrigerant is cooling water.

[0025] The beneficial effects of this invention are mainly reflected in:

[0026] 1. This invention, by setting a two-stage riser, downcomer and turbine in the refrigerant closed loop, enables the refrigerant to generate secondary pressure difference energy. The alternating action of pressure reduction and increase not only realizes the circulation of the refrigerant, but also converts part of the potential energy into mechanical energy through the work done by the turbine, thereby significantly improving the overall energy conversion efficiency of the system.

[0027] 2. This invention establishes a temperature difference adaptive adjustment mechanism for the power distribution of a two-stage turbine. The system temperature difference is changed according to the temperature difference driven by the cold and heat sources to achieve better following, ensure the high efficiency of the cycle process, and broaden the applicable temperature difference range of the system.

[0028] 3. This invention achieves greater output power by increasing the system temperature difference and reducing irreversible losses caused by the heat transfer temperature difference. Attached Figure Description

[0029] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] Figure 1 This is a schematic diagram of a dual-stage gravity field work device according to the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0032] Example 1: A two-stage gravity field work device, such as... Figure 1As shown, it mainly includes a refrigerant closed loop, in which the working medium circulates and converts energy through heat exchange with external cold and heat sources.

[0033] The primary condenser 2 and the secondary condenser 6 are located at the high position of the system, while the primary turbine 4, the secondary turbine 8, and the heater 9 are located at the low position of the system. The refrigerant passages of the heater 9, the primary condenser 2, the primary turbine 4, the secondary condenser 6, and the secondary turbine 8 are sequentially connected to form a refrigerant closed loop. Specifically, the refrigerant passage outlet of the heater 9 is connected to the bottom inlet of the primary riser pipe 1, the top outlet of the primary riser pipe 1 is connected to the refrigerant passage inlet of the primary condenser 2, the refrigerant passage outlet of the primary condenser 2 is connected to the top inlet of the primary downcomer pipe 3, the bottom outlet of the primary downcomer pipe 3 is connected to the inlet of the primary turbine 4, the outlet of the primary turbine 4 is connected to the bottom inlet of the secondary riser pipe 5, the top outlet of the secondary riser pipe 5 is connected to the refrigerant passage inlet of the secondary condenser 6, the refrigerant passage outlet of the secondary condenser 6 is connected to the top inlet of the secondary downcomer pipe 7, the bottom outlet of the secondary downcomer pipe 7 is connected to the inlet of the secondary turbine 8, and the outlet of the secondary turbine 8 is connected to the refrigerant passage inlet of the heater 9.

[0034] An external cooling water source is connected to the cooling water channel inlet of the secondary condenser 6 via cooling water inlet 10. The cooling water channel outlet of the secondary condenser 6 is connected to the cooling water channel inlet of the primary condenser 2, and the cooling water channel outlet of the primary condenser 2 is connected to the cooling water outlet 11. Cooling water is discharged from the system through cooling water outlet 11. Through this series connection, cooling water can cool the two condensers sequentially, improving cooling efficiency.

[0035] The heat medium generated by an external heat source (such as industrial waste heat, solar energy, etc.) is connected to the heat medium channel inlet of the heater 9 through the hot water inlet 12. The heat medium channel outlet of the heater 9 is connected to the hot water outlet 13, where the heat medium is discharged from the system.

[0036] The primary riser 1, secondary riser 5, primary downcomer 3, and secondary downcomer 7 are all insulated pipes and do not exchange heat with the outside environment. There is a uniform height difference between primary riser 1 and primary downcomer 3, and between secondary riser 5 and secondary downcomer 7, ranging from tens to hundreds of meters. Specifically, the top outlet of primary riser 1 and the top inlet of primary downcomer 3 are at the same height, as are the bottom inlet of primary riser 1 and the bottom outlet of primary downcomer 3. Similarly, the top outlet of secondary riser 5 and the top inlet of secondary downcomer 7 are at the same height, and the bottom inlet of secondary riser 5 and the bottom outlet of secondary downcomer 7 are at the same height.

[0037] The method for performing work using a two-stage gravity field work device is as follows:

[0038] 1. The refrigerant in the refrigerant passage of heater 9 is heated by the heat medium in its heat medium passage;

[0039] 2. First-stage potential energy to pressure energy conversion:

[0040] 2.1 The refrigerant flowing out of heater 9 flows into the first-stage riser pipe 1. During the upward flow along the first-stage riser pipe 1, the temperature and pressure decrease due to the pressure reduction caused by gravity, while the dryness of the refrigerant increases.

[0041] 2.2 The refrigerant in the first-stage riser pipe 1 flows into the refrigerant passage of the first-stage condenser 2, exchanges heat with the cooling water in the cooling water passage, and after being completely condensed, enters the first-stage downcomer pipe 3.

[0042] As the refrigerant flows downwards in the first-stage downcomer 3, it is subjected to gravity pressure increase, resulting in an increase in pressure and a slight increase in temperature, thus becoming a refrigerant with a certain degree of subcooling.

[0043] 3. The subcooled refrigerant flows from the bottom outlet of the first-stage downcomer 3 into the first-stage turbine 4. After driving the first-stage turbine 4 to do work, the pressure decreases and the temperature decreases slightly, and then it flows into the second-stage riser 5.

[0044] 4. Second-stage potential energy to pressure energy conversion

[0045] 4.1 During the upward flow of the refrigerant in the secondary riser 5, the temperature and pressure continue to decrease due to the pressure reduction caused by gravity, while the refrigerant dryness increases.

[0046] 4.2 The refrigerant flows from the top outlet of the secondary riser 5 into the refrigerant channel of the secondary condenser 6, exchanges heat with the cooling water in the cooling water channel, and is completely condensed before entering the secondary downcomer 7.

[0047] As the refrigerant flows downwards in the secondary downcomer 7, it is subjected to gravity pressure increase, resulting in an increase in pressure and a slight increase in temperature, thus becoming a refrigerant with a certain degree of subcooling.

[0048] 5. The subcooled refrigerant flows from the bottom of the secondary downcomer 7 into the secondary turbine 8. After driving the secondary turbine 8 to do work, the pressure decreases and the temperature decreases slightly. Then it flows into the refrigerant channel of the heater 9.

[0049] 6. The refrigerant in heater 9 is reheated by the heat medium in the heat medium channel, increasing its temperature, and then flows into the first-stage riser pipe 1. This cycle continues.

[0050] 7. Hot water flows into the heat medium channel of heater 9, provides heat to the refrigerant, and then flows out from hot water outlet 13.

[0051] Cooling water first flows into the secondary condenser 6, cools the refrigerant flowing through the secondary condenser 6, and its temperature increases. Then it continues to flow into the primary condenser 2, cools the refrigerant flowing through the primary condenser 2, and its temperature increases again. Finally, it flows out from the cooling water outlet 11.

[0052] When the temperature difference between the cold and hot sources is small, the work done by the first-stage turbine 4 decreases, while the work done by the second-stage turbine 8 increases, which can correspondingly reduce the system temperature difference in the refrigerant closed loop. When the work done by the first-stage turbine 4 decreases to 0, the adjustment limit is reached, and the temperature difference in the refrigerant closed loop no longer decreases.

[0053] When the temperature difference between the hot and cold sources is large, the work done by the first-stage turbine 4 increases, while the work done by the second-stage turbine 8 decreases, which can correspondingly increase the system temperature difference in the refrigerant closed loop. When the work done by the second-stage turbine 8 decreases to 0, the adjustment limit is reached, and the temperature difference in the refrigerant closed loop no longer increases.

[0054] experiment:

[0055] The simulation calculation parameters for Implementation Example 1 are shown in Table 1. The system height is 170m, the working fluid is R143a, the turbine efficiency is set to 80%, the riser efficiency to 85%, the downcomer efficiency to 98%, and the heat source and cold source to be water. When the driving temperature of the cold and heat source is 60℃ / 25℃, the system temperature difference achieved in Example 1 is 25.5℃, the total turbine work per unit mass of hot water is 1.52kJ / kg, and the thermal efficiency is 1.45%. In contrast, the system temperature difference of a typical gravity field work system (such as the work device proposed in ZL201711419509.X) is 18.9℃, the total turbine work per unit mass of hot water is 1.33kJ / kg, and the thermal efficiency is 1.27%. When the driving temperature range of the cold and heat source is expanded to 65℃ / 15℃, the system temperature difference achieved in Example 1 is 46℃, the total turbine work per unit mass of hot water is 3.01kJ / kg, and the thermal efficiency is 1.861%. In contrast, the system temperature difference of a typical gravity field work system is 20.3℃, the total turbine work per unit mass of hot water is 2.57kJ / kg, and the thermal efficiency is 1.53%. Therefore, it can be seen that by adopting a two-stage gravity field power system, the system temperature difference can be adjusted. Under the two cold and hot source conditions of 60℃ / 25℃ and 65℃ / 15℃, the system temperature difference is 25.5℃ and 46℃ respectively, achieving the tracking of the cold and hot source temperature difference. In contrast, the general gravity field power system is limited by the height difference, and the system temperature difference is 18.9℃ and 20.3℃ respectively, which is basically unchanged. This means that the system proposed in this paper can reduce the irreversible loss caused by the heat transfer temperature difference due to the increased system temperature difference, so that the turbine output power is increased by 14.2% and 17.1% respectively compared with the general gravity field power system, thus effectively achieving the original intention of this invention.

[0056] Table 1 Comparison of results between Implementation Example 1 and a general gravity field work system (based on 1 kg of hot water)

[0057] project Implementation Example 1 Typical gravitational field work system Implementation Example 1 Typical gravitational field work system unit Cold and heat source temperature 60℃ / 25℃ 60℃ / 25℃ 65℃ / 20℃ 65℃ / 20℃ ---- System height 170 Tongzuo Tongzuo Tongzuo m hot water inlet temperature 60 Tongzuo Tongzuo Tongzuo ℃ Cooling water inlet temperature 25 Tongzuo 15 Tongzuo ℃ Heater pinch temperature difference 4 Tongzuo Tongzuo Tongzuo ℃ Condenser pinch temperature difference 3 Tongzuo Tongzuo Tongzuo ℃ hot water outlet temperature 35.0 35.1 25.3 24.9 ℃ Cooling water outlet temperature 28.96 27 19.1 17 ℃ Refrigerant cycle ratio 0.346 0.314 2.61 5.03 ---- Cooling water circulation ratio 2.15 3.87 9.48 19.8 ---- System temperature difference 25.5 18.9 46 20.3 ℃ Heat absorption 104.4 104.5 166.1 168.2 kJ / kg Level 1 Turbine Power 0.03 ---- 2.95 ---- kJ / kg Second-level turbine power 1.49 ---- 0.058 ---- kJ / kg Total turbine power 1.52 1.33 3.01 2.57 kJ / kg heater outlet temperature 50.5 48.9 56 40.3 ℃ Heater inlet temperature 31 31.1 21.3 20.9 ℃ Thermal efficiency 1.45 1.27 1.81 1.53 %

[0058] In the above implementation examples, the design parameters of the system can be reasonably determined by comprehensively considering specific usage conditions and requirements, technical and economic performance, etc., so as to balance the applicability and economy of the system.

[0059] In summary, this invention achieves efficient energy utilization and adaptive temperature difference regulation in a refrigerant circulation system through the synergistic effect of differential pressure, phase change heat transfer, and multi-stage turbine energy conversion, demonstrating good energy-saving effects and promising engineering applications.

[0060] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A two-stage gravity field work-doping device, characterized in that: It includes a primary condenser (2) and a secondary condenser (6) located at a high position, and a primary turbine (4), a secondary turbine (8) and a heater (9) located at a low position. The refrigerant passage of the heater (9), the refrigerant passage of the primary condenser (2), the primary turbine (4), the refrigerant passage of the secondary condenser (6) and the secondary turbine (8) are connected in sequence to form a refrigerant closed loop. The cooling water inlet (10) passes through the cooling water passage of the secondary condenser (6) and the cooling water passage of the primary condenser (2) in sequence before connecting to the cooling water outlet (11); The hot water inlet (12) is connected to the hot water outlet (13) through the heat medium passage of the heater (9).

2. The dual-stage gravity field work-doping device according to claim 1, characterized in that: The refrigerant channel outlet of the heater (9) is connected to the bottom inlet of the first-stage riser (1), the top outlet of the first-stage riser (1) is connected to the refrigerant channel inlet of the first-stage condenser (2), the refrigerant channel outlet of the first-stage condenser (2) is connected to the top inlet of the first-stage downcomer (3), the bottom outlet of the first-stage downcomer (3) is connected to the inlet of the first-stage turbine (4), the outlet of the first-stage turbine (4) is connected to the bottom inlet of the second-stage riser (5), the top outlet of the second-stage riser (5) is connected to the refrigerant channel inlet of the second-stage condenser (6), the refrigerant channel outlet of the second-stage condenser (6) is connected to the top inlet of the second-stage downcomer (7), the bottom outlet of the second-stage downcomer (7) is connected to the inlet of the second-stage turbine (8), and the outlet of the second-stage turbine (8) is connected to the refrigerant channel inlet of the heater (9).

3. The dual-stage gravity field work-doping device according to claim 2, characterized in that: The primary riser (1), secondary riser (5), primary downcomer (3) and secondary downcomer (7) are all insulated pipes, and there is the same height difference between the primary riser (1) and the primary downcomer (3), and between the secondary riser (5) and the secondary downcomer (7).

4. A method for performing work using a dual-stage gravity field work device as described in any one of claims 1-3, characterized in that... Includes the following steps: The working fluid is heated in the heater (9) and becomes a subcooled working fluid after the first stage of potential energy-pressure energy conversion, which drives the first stage turbine (4) to do work. Then the working fluid flowing out of the first stage turbine (4) becomes a subcooled working fluid again after the second stage of potential energy-pressure energy conversion, which drives the second stage turbine (8) to do work. Then the working fluid flows back to the heater (9) to be heated and the next cycle begins.

5. The method for doing work using a dual-stage gravity field work device according to claim 4, characterized in that: The method for the first-stage potential energy to pressure energy conversion is as follows: After flowing out of the heater (9), the working fluid is subjected to gravity pressure reduction during the upward flow along the first-stage riser (1), resulting in a decrease in temperature, a decrease in pressure, and an increase in dryness. Then it flows into the refrigerant channel of the first-stage condenser (2), exchanges heat with the refrigerant in the cooling water channel, and is completely condensed before entering the first-stage downcomer (3). During the downward flow of the working fluid along the first-stage downcomer (3), it is subjected to gravity pressure increase, resulting in an increase in pressure and a rise in temperature, thus becoming a subcooled working fluid.

6. The method for doing work using a dual-stage gravity field work device according to claim 5, characterized in that: The method for the second-stage potential energy to pressure energy conversion is as follows: As the working fluid flowing out of the first-stage turbine (4) flows upward along the second-stage riser (5), it is subjected to gravity pressure reduction, and its temperature and pressure continue to decrease, while its dryness increases. Then it flows into the refrigerant channel of the second-stage condenser (6), where it exchanges heat with the refrigerant in the cooling water channel. After being completely condensed, it enters the second-stage downcomer (7). As the working fluid flows downward along the second-stage downcomer (7), it is subjected to gravity pressure increase, and its pressure and temperature increase, becoming a subcooled working fluid again.

7. The method for doing work using a dual-stage gravity field work device according to claim 6, characterized in that: The refrigerant first flows through the cooling water channel of the secondary condenser (6) to cool the working fluid, and then flows through the cooling water channel of the primary condenser (2) to continue cooling the working fluid.

8. The method for doing work using a dual-stage gravity field work device according to claim 7, characterized in that: The working fluid is a refrigerant; The refrigerant is cooling water.

Images