Patent Application
20250146731
The present disclosure relates to the fields of industrial refrigeration, energy storage, grid peak shaving, and the like, and specifically to an internal circulation type clathrate hydrate-based cold storage system and method.
With the increasingly acute contradiction between power supply and demand in China, it is becoming increasingly urgent to apply cold energy storage technology in fields such as central air conditioning. At present, commonly used cold storage working media include water, ice, eutectic salts, and hydrates. As a non-phase change cold storage working medium, water-based cold storage is a type of sensible heat storage for cold storage, which has a low cold storage density and takes up a lot of space, and therefore is gradually being phased out. As a representative phase change cold storage working medium, ice-based cold storage has the problems that the cold storage process needs to be carried out at low temperature, and the performance efficiency of the ice-based cold storage system is reduced, and the system suffers from severe energy loss due to increased energy consumption. Provided that the same cold load demand is met for air conditioning, the comprehensive energy consumption of the ice-based cold storage is about 30% higher than that of a conventional water chilling unit. Compared with the conventional cold storage working media such as water, ice, and eutectic salts, gaseous hydrate-based cold storage has a higher cold storage density and a higher heat transfer efficiency at lower costs. However, existing hydrate-based cold storage technologies generally suffer from the problems such as slow hydrate nucleation, unclear cyclic formation-decomposition stability, and higher cold energy loss during the cold storage process, leading to extra consumption of electric energy during the cold storage process and reducing the energy storage efficiency and the cost effectiveness.
The technical problem to be solved by the present disclosure is to overcome the deficiencies of slow hydrate nucleation and low energy storage conversion rate in the existing cold storage systems.
An internal circulation type clathrate hydrate-based cold storage system is provided, including a water chilling unit, a first solution pump, a first flow meter, a first one-way valve, a first two-way valve, a second one-way valve, a second solution pump, a heat exchange system, a third one-way valve, a fourth one-way valve, a second flow meter, a system monitoring device, a direct-current power supply and circuit control system, a concentration measurement system, a second gas pump, a second two-way valve, a gas distribution device, a hydrate-based cold storage tank, a gas disturbance device, a first branch pipeline, a second branch pipeline, a third branch pipeline, a fourth branch pipeline, a fifth branch pipeline, and a temperature sensor group, where an outlet end of the water chilling unit is in communication with an inlet of the heat exchange system through the first branch pipeline, and an inlet end of the water chilling unit is in communication with an outlet of the heat exchange system through the second branch pipeline; the first solution pump, the first flow meter, the first one-way valve, the second one-way valve, and the second solution pump are sequentially arranged on the first branch pipeline along a flow direction of a secondary refrigerant; the third one-way valve, the fourth one-way valve, and the second flow meter are sequentially arranged on the second branch pipeline along the flow direction of the secondary refrigerant; the hydrate-based cold storage tank is a sealed container filled therein with a hydrate-based cold storage working medium, and an evaporator coil is arranged in the hydrate-based cold storage tank and immersed in the hydrate-based cold storage working medium; the temperature sensor group is arranged in the hydrate-based cold storage tank, and a terminal of the temperature sensor group is connected to the system monitoring device; the first branch pipeline between the first one-way valve and the second one-way valve is in communication with a first end of the evaporator coil through the third branch pipeline, and the second branch pipeline between the third one-way valve and the fourth one-way valve is in communication with a second end of the evaporator coil through the fourth branch pipeline; the first two-way valve is arranged on the third branch pipeline, and the second two-way valve is arranged on the fourth branch pipeline;
Preferably, the internal circulation type clathrate hydrate-based cold storage system further includes a first pressure sensor, a first temperature sensor, a second pressure sensor, and a second temperature sensor, where the first pressure sensor and the first temperature sensor are arranged on the third branch pipeline and are located on a side close to the evaporator coil; the second pressure sensor and the second temperature sensor are arranged on the fourth branch pipeline and are located on a side close to the evaporator coil; and the first pressure sensor, the first temperature sensor, the second pressure sensor, and the second temperature sensor are each connected to the system monitoring device through a temperature-pressure sensor module.
Preferably, the internal circulation type clathrate hydrate-based cold storage system further includes the concentration measurement system, a solid-liquid separator, and an automatic sampling device, where the concentration measurement system is connected to the solid-liquid separator through a first pipeline, the solid-liquid separator is connected to the automatic sampling device through a second pipeline, and the automatic sampling device is in communication with the hydrate-based cold storage working medium in the hydrate-based cold storage tank through a third pipeline.
Preferably, the concentration measurement system includes a data acquisition and analysis terminal, a concentration measurement probe, a sample solution, and a test bottle, where the test bottle is connected to the solid-liquid separator through the first pipeline, the sample solution is placed in the test bottle, a first end of the concentration measurement probe is connected to the data acquisition and analysis terminal, and a second end of the concentration measurement probe is penetrated into the sample solution in the test bottle.
Preferably, the hydrate-based cold storage working medium in the hydrate-based cold storage tank is one selected from a group consisting of an alkane hydrate, a carbon dioxide hydrate, a water-soluble organic hydrate, and a mixed hydrate.
Preferably, a formula for calculating a cold storage capacity in the hydrate-based cold storage tank is:
Preferably, the internal circulation type clathrate hydrate-based cold storage system further includes a crystallization promoting device and a first gas pump, where the crystallization promoting device is in communication with an interior of the hydrate-based cold storage tank through a fourth pipeline, and the first gas pump is arranged on the fourth pipeline between the crystallization promoting device and the hydrate-based cold storage tank.
Preferably, the crystallization promoting device includes a thermal insulation cotton, a volumetric flask, and hydrate particles, where the hydrate particles are contained in the volumetric flask, the thermal insulation cotton is wrapped outside the volumetric flask, and the volumetric flask is in communication with the interior of the hydrate-based cold storage tank through the fourth pipeline.
Preferably, the temperature sensor group arranged in the hydrate-based cold storage tank includes a third temperature sensor, a fourth temperature sensor, a fifth temperature sensor, and a sixth temperature sensor, where the third temperature sensor is mounted at a bottom of the hydrate-based cold storage tank, the fourth temperature sensor is mounted at a central position of the hydrate-based cold storage tank, the fifth temperature sensor is mounted in the hydrate-based cold storage tank and close to a wall surface of the hydrate-based cold storage tank, and the sixth temperature sensor is mounted on a top air side of the hydrate-based cold storage tank.
The present disclosure further provides an internal circulation type clathrate hydrate-based cold storage method, including:
The gas disturbance device at the bottom of the hydrate-based cold storage tank creates gas disturbance on the hydrate-based cold storage working medium in the hydrate-based cold storage tank, so as to induce the hydrate nucleation and accelerate energy storage. With the use of the intelligent crystallization promoting device, when the temperature in the hydrate-based cold storage tank reaches a required working condition of hydrate nucleation, an appropriate amount of small hydrate particles are added to the hydrate solution to promote the large-scale crystallization of the hydrate and improve the crystallization efficiency. The energy storage conversion rate and the cooling capacity are improved by the evaporator coil in the hydrate-based cold storage tank and the finned tube heat exchanger with the fan in the heat exchange system. Through the internal circulation design, cold air in the top of the hydrate-based cold storage tank is pumped to the gas distribution device by the second gas pump, and then distributed to the gas disturbance device at the bottom for gas disturbance. In this way, the internal circulation of air in the hydrate-based cold storage tank is realized, to prevent heat exchange between outside hot air and the hydrate-based cold storage tank, thereby reducing extra consumption of electric energy in the cold storage process and improving the energy storage efficiency and the cost-effectiveness.
In addition, the present disclosure provides a complete cold charge-cold discharge system, where the water chilling unit stores cold energy at night, and supplies cold energy to the heat exchange system through the hydrate-based cold storage tank during daytime. In addition, three functions can be realized according to different requirements on the cooling capacity: cold energy supply by the hydrate-based cold storage tank, cold energy supply by the water chilling unit, and cold energy supply by the water chilling unit and the hydrate-based cold storage tank, thereby broadening the range of usage scenarios of the internal circulation type clathrate hydrate-based cold storage system. To sum up, according to the present disclosure, latent heat generated during phase change of the clathrate hydrate is fully utilized. In addition, according to the memory effect of the clathrate hydrate serving as the hydrate-based cold storage working medium, higher nucleation rate and cold storage capacity can be achieved after several times of cold charge-cold discharge. Therefore, the present disclosure has the advantages of high efficiency, energy saving, and long-term stable operation, and is especially suitable for scenarios that require continuous cold energy supply.
List of reference numerals: 1. water chilling unit; 2. crystallization promoting device; 3. first solution pump; 4. first flow meter; 5. first one-way valve; 6. first two-way valve; 7. second one-way valve; 8. second solution pump; 9. heat exchanger; 10. heat exchange system; 11. third one-way valve; 12. fourth one-way valve; 13. second flow meter; 14. system monitoring device; 15. direct-current power supply and circuit control system; 16. first pressure sensor; 17. first temperature sensor; 18. fifth temperature sensor; 19. sixth temperature sensor; 20. first gas pump; 21. concentration measurement system; 22. solid-liquid separator; 23. automatic sampling device; 24. second gas pump; 25. second two-way valve; 26. second pressure sensor; 27. second temperature sensor; 28. gas distribution device; 29. hydrate-based cold storage tank; 30. third temperature sensor; 31. gas disturbance device; 32. fourth temperature sensor; 33. evaporator coil; 34. first branch pipeline; 35. second branch pipeline; 36. third branch pipeline; 37. fourth branch pipeline; 38. fifth branch pipeline; 39. thermal insulation cotton; 40. volumetric flask; 41. hydrate particle; 42. data acquisition and analysis terminal; 43. concentration measurement probe; 44. sample solution; 45. test bottle.
The present disclosure will be further described in detail below with reference to specific examples and the accompanying drawings.
Example 1: Referring to
The hydrate-based cold storage tank 29 is a sealed container filled therein with a hydrate-based cold storage working medium. A size of the hydrate-based cold storage tank 29 is preferably 3 m×2.5 m×3 m, and the hydrate-based cold storage working medium accounts for 9/10 of the space in the hydrate-based cold storage tank 29. An evaporator coil 33 is arranged in the hydrate-based cold storage tank 29 and immersed in the hydrate-based cold storage working medium. A fin spacing of the evaporator coil 33 is preferably 5 cm. The temperature sensor group is arranged in the hydrate-based cold storage tank 29. A terminal of the temperature sensor group is connected to the system monitoring device 14. The first branch pipeline 34 between the first one-way valve 5 and the second one-way valve 7 is in communication with a first end of the evaporator coil 33 through the third branch pipeline 36. The second branch pipeline 35 between the third one-way valve 11 and the fourth one-way valve 12 is in communication with a second end of the evaporator coil 33 through the fourth branch pipeline 37. The first two-way valve 6 is arranged on the third branch pipeline 36, and the second two-way valve 25 is arranged on the fourth branch pipeline 37. When the hydrate-based cold storage tank 29 needs to store cold energy, the secondary refrigerant is conveyed to the hydrate-based cold storage tank 29 by the first solution pump 3, and exchanges heat with the hydrate-based cold storage working medium through the evaporator coil 33 for a heat exchange, and fully absorbs heat in the hydrate-based cold storage tank 29 for a hydrate-based phase change energy storage. After the heat exchange is completed, the secondary refrigerant flows back to the water chilling unit 1 to be cooled again to complete a cold storage cycle.
When the hydrate-based cold storage tank 29 needs to supply cold energy, the secondary refrigerant in the hydrate-based cold storage tank 29 is pumped by the second solution pump 8 to the heat exchange system 10 sequentially through the first two-way valve 6 and the second one-way valve 7, fully absorbs heat in the heat exchange system 10 through the finned tube heat exchanger 9 with the fan, then flows back to the hydrate-based cold storage tank 29 sequentially through the third one-way valve 11 and the second two-way valve 25, and is cooled again through a heat exchange with the hydrate-based cold storage working medium at a low temperature in the evaporator coil 33 to complete a cold energy supply cycle.
The internal circulation type clathrate hydrate-based cold storage system includes a plurality of gas disturbance devices 31 arranged at a bottom of the hydrate-based cold storage tank 29. The fifth branch pipeline 38 is arranged outside the hydrate-based cold storage tank 29. An upper end of the fifth branch pipeline 38 is in communication with a top of an inner wall of the hydrate-based cold storage tank 29. A lower end of the fifth branch pipeline 38 is connected to the gas distribution device 28. The gas distribution device 28 is connected to the gas disturbance device 31 arranged in the hydrate-based cold storage tank 29 through a hose. The second gas pump 24 is arranged on the fifth branch pipeline 38. Through the internal circulation design, cold air in the hydrate-based cold storage tank 29 is pumped to the gas distribution device 28 by the second gas pump 24, and then distributed to the gas disturbance device 31 at the bottom for gas disturbance. The arrangement of the gas disturbance device 31 in the above technical solution can accelerate the hydrate nucleation and improve the cold storage rate. In conventional technical means, outside air needs to be conveyed into the gas disturbance device 31 to disturb the solution in the hydrate-based cold storage tank 29. The outside air has a high temperature and will absorb heat after being conveyed into the hydrate-based cold storage tank 29, affecting the cold storage rate. To avoid the above problem, the fifth branch pipeline 38, the second gas pump 24, and the gas distribution device 28 are designed, so that cold air in the hydrate-based cold storage tank 29 can be directly recycled through internal circulation, thereby preventing heat exchange between outside hot air and the hydrate-based cold storage tank and improving the energy storage efficiency and the cost-effectiveness while accelerating the hydrate nucleation.
Example 2: Compared with Example 1, the system of this example further includes a first pressure sensor 16, a first temperature sensor 17, a second pressure sensor 26, and a second temperature sensor 27. The first pressure sensor 16 and the first temperature sensor 17 are arranged on the third branch pipeline 36 and are located on a side close to the evaporator coil 33. The second pressure sensor 26 and the second temperature sensor 27 are arranged on the fourth branch pipeline 37 and are located on a side close to the evaporator coil 33. The system monitoring device 5 can monitor a temperature change and a pressure change before and after heat absorption by the secondary refrigerant through the first pressure sensor 10, the first temperature sensor 11, the second pressure sensor 23, and the second temperature sensor 24, so as to detect the changing temperature difference and pressure difference of the secondary refrigerant in the hydrate-based cold storage tank.
Example 3: Compared with Example 1, the system of this example further includes the concentration measurement system 21, a solid-liquid separator 22, and an automatic sampling device 23. The concentration measurement system 21 is connected to the solid-liquid separator 22 through a first pipeline. The solid-liquid separator 22 is connected to the automatic sampling device 23 through a second pipeline. The automatic sampling device 23 is in communication with the hydrate-based cold storage working medium in the hydrate-based cold storage tank 29 through a third pipeline. The automatic sampling device 23 is inserted into the hydrate-based cold storage working medium through a thermal insulation pipe, and periodically draws a sample solution 44, which is filtered by the solid-liquid separator 22 and conveyed to the concentration measurement system 21 for analysis and testing. When the mass fraction of the hydrate in the sample solution 44 is low, an upper cover of the hydrate-based cold storage tank 29 may be manually removed, and an additional amount of the hydrate-based cold storage working medium may be added, to ensure a stable and efficient cold storage process.
Example 4: Compared with Example 3, the concentration measurement system 21 includes a data acquisition and analysis terminal 42, a concentration measurement probe 43, the sample solution 44, and a test bottle 45. The test bottle 45 is connected to the solid-liquid separator 22 through the first pipeline. The sample solution 44 is placed in the test bottle 45. A first end of the concentration measurement probe 43 is connected to the data acquisition and analysis terminal 42. A second end of the concentration measurement probe 43 is penetrated into the sample solution 44 in the test bottle 45. The data acquisition and analysis terminal 42 can drive the concentration measurement probe 43 to draw the solution sample 44 in the test bottle 45 and measure the solution concentration.
Example 5: Compared with Example 1, the hydrate-based cold storage working medium in the hydrate-based cold storage tank 29 may be selected from the group consisting of an alkane hydrate, a freon hydrate, a carbon dioxide hydrate, a water-soluble organic hydrate, and a mixed hydrate. The alkane hydrate may be methane, cyclopentane, or the like. The freon hydrate may be R134a. The water-soluble organic hydrate may be tetrahydrofuran (THF), tetrabutylammonium bromide (TBAB), tetrabutylphosphonium bromide (TBPB), or the like. The mixed hydrate may be TBAB-CH4, TBAB-THF, or the like. The hydrate-based cold storage working medium is preferably a 40 wt % TBAB solution.
Example 6: A formula for calculating a cold storage capacity in the hydrate-based cold storage tank in the present disclosure is:
A conventional calculation formula is:
In the conventional calculation formula, due to the heat transfer between the hydrate-based cold storage tank and the environment during the cold storage process of the hydrate-based cold storage working medium, there are errors in the measured values. Therefore, the heat transfer temperature difference of the solution of the secondary refrigerant between the inlet and the outlet of the hydrate-based cold storage tank is used for calculation to improve the measurement accuracy.
Example 7: Compared with Example 1, the system of this example further includes a crystallization promoting device 2. The crystallization promoting device 2 is in communication with an interior of the hydrate-based cold storage tank 29 through a fourth pipeline. A first gas pump 20 is arranged on the fourth pipeline between the crystallization promoting device 2 and the hydrate-based cold storage tank 29. When the hydrate-based cold storage tank 29 starts to store cold, the secondary refrigerant is conveyed to the hydrate-based cold storage tank 29 by the first solution pump 3, and at this moment, the crystallization promoting device 2 introduces hydrate particles 41 into the hydrate-based cold storage tank 29 through the first gas pump 20 at a time, to induce large-scale crystallization of the hydrate to improve the crystallization efficiency, and induce the rapid nucleation of the hydrate-based cold storage working medium to accelerate energy storage.
Example 8: Compared with Example 7, the crystallization promoting device 2 includes a thermal insulation cotton 39, a volumetric flask 40, and the hydrate particles 41. Small hydrate particles of about 1 mm3 are contained in the volumetric flask 40. The thermal insulation cotton 39 is wrapped outside the volumetric flask 40. The volumetric flask 40 has a volume of about 250 mL and is in communication with the interior of the hydrate-based cold storage tank 29 through the fourth pipeline.
Example 9: Compared with Example 1, the temperature sensor group arranged in the hydrate-based cold storage tank 29 includes a third temperature sensor 30, a fourth temperature sensor 32, a fifth temperature sensor 18, and a sixth temperature sensor 19. The third temperature sensor 30 is mounted at a bottom of the hydrate-based cold storage tank 29. The fourth temperature sensor 32 is mounted at a central position of the hydrate-based cold storage tank 29. The fifth temperature sensor 18 is mounted in the hydrate-based cold storage tank 29 and close to a wall surface of the hydrate-based cold storage tank 29. The sixth temperature sensor 19 is mounted on a top air side of the hydrate-based cold storage tank 29. The first pressure sensor 16, the first temperature sensor 17, the second pressure sensor 26, and the second temperature sensor 27, and the temperature sensor group are each connected to the system monitoring device 14 through a temperature-pressure sensor module. The system monitoring device 14 monitors a temperature change and a pressure change before and after the heat exchange between the secondary refrigerant and the hydrate-based cold storage working medium through the first pressure sensor 16, the first temperature sensor 17, the second pressure sensor 26, and the second temperature sensor 27, and monitors a temperature change of the hydrate-based cold storage working medium in the hydrate-based cold storage tank 29 through the temperature sensor group.
Example 10: An internal circulation type clathrate hydrate-based cold storage method is provided by using the internal circulation type clathrate hydrate-based cold storage system that is obtained by combining the technical solutions of Example 1 to Example 9.
The water chilling unit 1 provides the secondary refrigerant at a low temperature of 5° C. The secondary refrigerant is an ethylene glycol aqueous solution with a concentration of 30%. The secondary refrigerant is conveyed to the hydrate-based cold storage tank 29 by the first solution pump 3 through the first flow meter 4, the first one-way valve 5, and the first two-way valve 6, and exchanges heat with the hydrate-based cold storage working medium through the evaporator coil 33 for a heat exchange and fully absorbs heat in the hydrate-based cold storage tank 29 for a hydrate-based phase change energy storage. After the heat exchange is completed, the secondary refrigerant flows back to the water chilling unit 1 through the second two-way valve 25, the fourth one-way valve 12, and the second flow meter 13 to be cooled to 5° C. again to complete a cold storage cycle. A theoretical energy storage density in the cold storage process is 53 kW·h/m3.
After the cold storage cycle starts, the crystallization promoting device 2 introduces 1 g to 2 g of hydrate particles of about 1 mm3 into the hydrate-based cold storage tank 29 through the first gas pump 20 to induce a rapid nucleation of the hydrate-based cold storage working medium, and meanwhile, cold air from the top of the hydrate-based cold storage tank 29 is pumped by the second gas pump 24 to the gas distribution device 28 for a gas distribution, then conveyed to the gas disturbance device 31 for a continuous gas disturbance, and then pumped by the second gas pump 24 again for a gas internal circulation to reduce a loss of cold load and accelerate energy storage. The system monitoring device 14 monitors a temperature change before and after heat absorption by the secondary refrigerant, a temperature change of the hydrate-based cold storage working medium, and a temperature change in the hydrate-based cold storage tank in real time.
The present disclosure can realize three cold energy supply modes: cold energy supply by the hydrate-based cold storage tank 29 alone, cold energy supply by the water chilling unit 1 alone, and cold energy supply by the hydrate-based cold storage tank 29 in combination with the water chilling unit 1.
The secondary refrigerant containing ethylene glycol at 5° C. in the hydrate-based cold storage tank 29 is pumped by the second solution pump 8 to the heat exchange system 10 through the first two-way valve 6 and the second one-way valve 7, fully absorbs heat in the heat exchange system 10 through the finned tube heat exchanger 9 with the fan, then flows back to the hydrate-based cold storage tank 29 through the third one-way valve 11 and the second two-way valve 25, and is cooled again through a heat exchange with the hydrate-based cold storage working medium, i.e., TBAB, at a low temperature in the evaporator coil 33 to complete a cold energy supply cycle. This mode is configured for scenarios where the demand for cooling capacity is not large during daytime, and the demand can be met by using cold energy stored in the hydrate-based cold storage tank 29 at night, thereby achieving energy saving and environmental protection, and reducing carbon dioxide emissions.
The water chilling unit 1 provides the secondary refrigerant containing ethylene glycol at 5° C. The secondary refrigerant is pumped by the first solution pump 3 to the finned tube heat exchanger 9 in the heat exchange system 10 through the first flow meter 4, the first one-way valve 5, the second one-way valve 7, and the second solution pump 8 for heat absorption, and then flows back to the hydrate-based cold storage tank 29 through the third one-way valve 11, the fourth one-way valve 12, and the second flow meter 13 to be cooled to 5° C. again to complete a cold energy supply cycle. This mode is configured for scenarios that require uninterrupted cold energy supply throughout the day, and effectively meets the demand for continuous cold energy supply after the end of hydrate-based cold energy supply, thereby realizing continuous cold energy supply.
3. Mode of Cold Energy Supply by the Hydrate-Based Cold Storage Tank 29 in Combination with the Water Chilling Unit 1:
The water chilling unit 1 and the hydrate-based cold storage tank 29 simultaneously provide the secondary refrigerant containing ethylene glycol at 5° C. The secondary refrigerant is pumped by the first solution pump 3 and the second solution pump 8 to the heat exchange system 10. The finned tube heat exchanger 9 with the fan operates at full load to allow the secondary refrigerant at a low temperature to fully absorb heat in the heat exchange system 10. Then, a part of the secondary refrigerant flows back to the hydrate-based cold storage tank 29 and is cooled to a low temperature again through a heat exchange with the TBAB hydrate at a low temperature through the evaporator coil 33, and the other part of the secondary refrigerant flows back to the water chilling unit 1 and is cooled to 5° C. again to complete a combined cold energy supply cycle. This mode is configured for scenarios with large cooling capacity demand. The combined cold energy supply by the hydrate-based cold storage tank in combination with the water chilling unit ensures sufficient supply of cold energy. Thereby, the cold energy supply burden of the water chilling unit is alleviated while achieving environmental protection and carbon emission reduction.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202210084764.8 | Jan 2022 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2022/138007 | 12/9/2022 | WO |
