CN115493302B - Method for emptying heat transfer working medium of line focusing heat collecting system and line focusing heat collecting system thereof - Google Patents
Method for emptying heat transfer working medium of line focusing heat collecting system and line focusing heat collecting system thereof Download PDFInfo
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- CN115493302B CN115493302B CN202211452651.5A CN202211452651A CN115493302B CN 115493302 B CN115493302 B CN 115493302B CN 202211452651 A CN202211452651 A CN 202211452651A CN 115493302 B CN115493302 B CN 115493302B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
- F24S40/00—Safety or protection arrangements of solar heat collectors; Preventing malfunction of solar heat collectors
- F24S40/60—Arrangements for draining the working fluid
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
- F24S10/00—Solar heat collectors using working fluids
- F24S10/70—Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
- F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
- F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
- F24S23/79—Arrangements for concentrating solar-rays for solar heat collectors with reflectors with spaced and opposed interacting reflective surfaces
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
- F24S50/00—Arrangements for controlling solar heat collectors
- F24S50/20—Arrangements for controlling solar heat collectors for tracking
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
- F24S50/00—Arrangements for controlling solar heat collectors
- F24S50/40—Arrangements for controlling solar heat collectors responsive to temperature
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/40—Solar thermal energy, e.g. solar towers
- Y02E10/44—Heat exchange systems
Abstract
The invention discloses a method for emptying a heat transfer working medium by a line focusing heat collecting system and the line focusing heat collecting system, belonging to the technical field of solar heat systems and comprising the following steps: stopping the circulation of the heat transfer working medium, and keeping the focusing mode of the heat collecting pipe; the heat transfer working medium is drained to the storage tank through the heat collecting tube, in the process of draining the heat transfer working medium, the emptying section of the heat collecting tube is converted into an optical heat tracing mode from a focusing mode, the focusing mode comprises a focusing state, the defocusing state is increased and then the optical heat tracing mode is converted, the temperature of the heat collecting tube in the optical heat tracing mode is controlled by adjusting the time proportion occupied by the focusing state and the defocusing state, and the heat preservation is continuously carried out on the heat collecting tube; and after the heat transfer working medium is exhausted, stopping the light heat tracing mode. The invention can avoid the solidification of heat transfer working medium in the heat collecting pipe, improve the evacuation efficiency of the heat transfer working medium and reduce the energy loss; the problem of high energy consumption caused by low-speed circulation anti-condensation can be solved, and the freezing and blocking risks in the drainage process of the high-freezing-point heat transfer working medium can also be solved.
Description
Technical Field
The invention relates to the technical field of solar thermal systems, in particular to a method for emptying a heat transfer working medium by a line focusing heat collecting system and the line focusing heat collecting system.
Background
The solar photo-thermal power generation has the advantages of high energy conversion efficiency, low energy consumption in the manufacturing process, clean and pollution-free use process, large-scale heat storage and the like. The basic principle of solar photo-thermal power generation is that a large-scale reflector is adopted to converge solar radiation energy into a heat collection system for heating heat transfer working media such as water, heat transfer oil or molten salt in a heat collection device, so that the solar radiation energy with low energy flow density is converged into heat energy with high energy flow density.
According to the light-gathering form of the heat-gathering field, the current mainstream light-gathering solar photo-thermal power generation comprises four technical routes of a groove type, a tower type, a linear Fresnel type and a butterfly type. Wherein the groove type and the linear Fresnel type are linear focusing heat collecting modes. The heat transfer medium pipeline of the line focusing heat collection field is long and has large heat loss. In a traditional operation mode, a heat transfer working medium is heated and injected into a heat collection system at one time, or a heat collection pipeline is preheated in an electrical impedance heating mode and then the heat transfer working medium is injected at one time, then the heat collection system is removed from fault maintenance, and the like, the heat transfer working medium stays in a circulation pipeline all the time, the freezing points of heat transfer oil and molten salt are high, when a heat collection field is in a non-heat collection state, the heat transfer working medium needs to be prevented from being frozen and blocked in a low-speed circulation mode, in order to supplement heat loss of the heat collection system, the heat transfer working medium needs to be supplemented by external energy, and meanwhile, a large amount of energy needs to be consumed by a circulation pump.
For example, chinese patent with publication number CN 203479118U discloses a gravity flow salt-dredging molten salt energy storage system, which comprises a high-temperature molten salt tank, a low-temperature molten salt tank and a plurality of heat exchangers connected in series through molten salt pipelines, wherein the lowest point of the molten salt pipeline is higher than the molten salt liquid level in the high-temperature molten salt tank and the low-temperature molten salt tank, and the lowest point of the molten salt pipeline is connected with the high-temperature molten salt tank and the low-temperature molten salt tank through the salt-dredging pipelines. The scheme completely depends on gravity to realize the salt dispersing function of the molten salt, however, when the molten salt flows in the pipe, negative pressure can be generated in an evacuated area to influence further flow, or the flow speed is slow because the temperature of the molten salt is low, or the molten salt is solidified on the pipe wall to obstruct the flow due to low external temperature, and the like, so the scheme which only depends on gravity to disperse the salt is only suitable for a few working conditions.
For another example, chinese patent with publication number CN 210179929U discloses a solar thermal power plant salt dredging system arrangement structure, which comprises a salt dredging tank, a salt discharging groove, a salt dredging pump and a salt dredging pit, wherein the salt dredging tank is arranged at the bottom of the salt dredging pit, the salt dredging pump is arranged above the salt dredging tank, the salt discharging groove is arranged in the salt dredging pit, and the top surface of the salt discharging groove is lower than the bottom surface of the salt dredging tank; the salt dredging tank is communicated with the salt discharging groove through a pipeline, and a valve is arranged on the pipeline; the salt inlet of the salt dredging pump is communicated with the salt dredging tank, the salt dredging tank is provided with an exhaust port, and the exhaust port is connected with a pipeline for exhausting. According to the scheme, the salt dredging pump is used as power for the salt dredging process, if the temperature of the molten salt is low, the molten salt is not easy to be conveyed by the salt dredging pump, and modes such as electric tracing and the like are additionally adopted, so that the salt dredging efficiency is reduced, and the salt dredging cost is increased.
Disclosure of Invention
The invention aims to provide a method for emptying a heat transfer working medium of a line focusing heat collecting system and the line focusing heat collecting system thereof, which are used for solving the problems in the prior art.
In order to achieve the purpose, the invention provides the following scheme:
the invention provides a method for emptying a heat transfer working medium of a line focusing heat collecting system, which comprises the following steps:
when the heat transfer working medium needs to be emptied, the circulation of the heat transfer working medium is stopped, the heat collection device keeps the original heat collection mode of the heat collection tube, namely keeps the focusing mode, at the moment, the heat collection device is in the focusing state, and the heat transfer working medium is in a state convenient to flow in the heat collection tube;
the heat transfer working medium is drained to a storage tank through the heat collecting pipe, the position of the heat transfer working medium in the heat collecting pipe is monitored in the process of draining the heat transfer working medium, and the emptying section of the heat collecting pipe is judged according to the position of the heat transfer working medium in the heat collecting pipe, wherein the position is obtained through monitoring;
adjusting the heat collection mode of the heat collection device corresponding to the emptying section, and converting the heat collection mode into an optical heat tracing mode which comprises a focusing state and a defocusing state;
controlling the temperature of the heat collecting tube by adjusting the time proportion occupied by the focusing state and the defocusing state, and continuously preserving the heat of the emptying section;
after the heat transfer working medium is emptied, the heat collecting pipes are all converted into emptying sections, and meanwhile, the heat collecting devices are all converted into an optical heat tracing mode;
and stopping the optical heat tracing mode, and finishing the evacuation work of the heat transfer working medium.
Preferably, the heat collecting tube segments are matched with a tracking mechanism, and the tracking mechanism is used for controlling the heat collecting device to be in a focusing state or a defocusing state.
Preferably, a plurality of temperature measuring points are distributed on the heat collecting tube along the length direction, and the position state of the heat transfer working medium is judged according to the monitoring results of the temperature measuring points.
Preferably, the heat transfer working medium is drained to the storage tank by means of the gravity and/or the power of compressed gas; the storage tank is a drainage tank or a low-temperature tank.
The invention also provides a line focusing heat collecting system applying the method for evacuating the heat transfer medium by using the line focusing heat collecting system, which comprises a heat collecting pipe and a heat collecting device for focusing light rays to the heat collecting pipe, wherein a plurality of temperature measuring points for judging the evacuation section of the heat collecting pipe are distributed on the heat collecting pipe along the length direction, a heat collecting inlet of the heat collecting pipe is communicated with a low-temperature tank, a heat collecting outlet of the heat collecting pipe is respectively communicated with the low-temperature tank and the high-temperature tank through pipelines, a circulating pump for driving the heat transfer medium to circularly flow is arranged between the low-temperature tank and the heat collecting inlet, the heat collecting outlet is also communicated with an evacuation tank, the evacuation tank is communicated with the low-temperature tank through an evacuation pump and an evacuation pipeline, the heat collecting pipe is sectionally matched with a tracking mechanism, and in the process of evacuating the heat transfer medium, the tracking mechanism controls the heat collecting device corresponding to the evacuation section of the heat collecting pipe to be converted into a light heat tracing mode from a focusing mode.
Preferably, the heat collecting inlet is communicated with a compressed gas source for supplying compressed gas to the heat collecting pipe.
Preferably, the low temperature jar with through the pipeline intercommunication between the high temperature jar, be close to the low temperature jar is provided with cold jar backward flow valve, is close to the high temperature jar is provided with hot jar backward flow valve.
Preferably, the heat collecting device comprises a reflector controlled by the tracking mechanism, and the reflector is controlled to be in a focusing state or a defocusing state by changing whether the reflector focuses on the heat collecting tube.
Preferably, the speculum includes primary reflector and secondary reflector, the secondary reflector is the curved surface and encircles the lock and be in the thermal-collecting tube circumference outside, through primary reflector collects light to the secondary reflector, recycles the secondary reflector focuses on light the thermal-collecting tube is last.
Compared with the prior art, the invention achieves the following technical effects:
(1) In the process of evacuating the heat transfer working medium, the light heat tracing mode is adopted for the evacuation section continuously, so that the heat transfer working medium in the heat collecting tube can be kept in a state convenient to flow, the solidification and residue of the heat transfer working medium on the inner wall of the heat collecting tube can be avoided, the residual quantity of the heat transfer working medium in the heat collecting tube is reduced, the blockage of the heat collecting tube due to incomplete evacuation of the heat transfer working medium is avoided, the evacuation efficiency of the heat transfer working medium is improved, the energy consumption is reduced, meanwhile, the flowing obstacle caused by the solidification of the heat transfer working medium on the inner wall of the heat collecting tube when the heat transfer working medium is injected next time is avoided, and the influence on the next injection process is avoided; the invention can realize the daily operation of emptying the heat transfer working medium in the heat collection field, solves the problem of high energy consumption caused by low-speed circulation condensation prevention, and can also solve the risk of freezing and blocking in the process of evacuating the heat transfer working medium with a high freezing point;
(2) The optical heat tracing mode comprises a focusing state and a defocusing state, and the temperature of the heat collecting tube in the optical heat tracing mode can be controlled by adjusting the time proportion occupied by the focusing state and the defocusing state, so that the heat collecting tube is always in a proper temperature range, the heat collecting tube is not damaged due to overhigh temperature, the solidification of a heat transfer working medium due to overlow temperature is avoided, and the heat transfer working medium is finally ensured to be drained cleanly and thoroughly;
(3) According to the invention, the heat collecting pipe is provided with a plurality of temperature measuring points along the length direction, and the position state of the heat transfer working medium in the heat collecting pipe can be judged according to the monitoring result through the temperature change monitored by the temperature measuring points, so that a basis is provided for the change of the heat collecting state;
(4) The invention can utilize the self weight of the heat transfer working medium to dredge when the heat collecting pipe is obliquely arranged, and meanwhile, the power of compressed gas can be utilized to assist the flow of the heat transfer working medium, thereby further improving the efficiency of dredging the heat transfer working medium.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required in the embodiments will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic view of the overall structure of a line focus heat collecting system according to the present invention;
FIG. 2 is a schematic view of the optical heat tracing evacuation heat transfer working medium of the present invention;
FIG. 3 is a schematic view illustrating a focusing state of the heat collecting device according to the present invention;
FIG. 4 is a schematic view illustrating a defocused state of the heat collecting device according to the present invention;
wherein, 1, a low-temperature tank; 2. a circulation pump; 3. a cold working medium main pipe; 4. measuring a pressure point; 5. a heat collection inlet valve; 6. compressing a gas source; 7. a compressed air valve; 8. a heat collecting pipe; 9. a heat collection device; 91. a secondary reflector; 92. a primary mirror; 93. light rays; 10. measuring a temperature point; 11. a thermal state working medium main pipe; 12. a cold tank reflux valve; 13. a hot tank reflux valve; 14. a high temperature tank; 15. a drain valve; 16. a drainage tank; 17. a drainage pump; 18. dredging and discharging pipelines; 19. a heat transfer working medium; 20. the gas is compressed.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The invention aims to provide a method for evacuating a heat transfer working medium by using a line focusing heat collecting system and the line focusing heat collecting system, which are used for solving the problems in the prior art, and can keep the heat transfer working medium in a heat collecting tube in a convenient flowing state by continuously adopting an optical heat tracing mode for an evacuation section in the evacuation process of the heat transfer working medium, prevent the heat transfer working medium from being solidified and remained on the inner wall of the heat collecting tube, reduce the residual quantity of the heat transfer working medium in the heat collecting tube, avoid the blockage of the heat collecting tube due to incomplete evacuation of the heat transfer working medium, improve the evacuation efficiency of the heat transfer working medium and reduce the energy loss.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
As shown in fig. 1~4, the present invention provides a method for evacuating a heat transfer working medium 19 from a line focus heat collecting system, where the line focus heat collecting system includes a heat collecting loop and a heat collecting device 9 for performing focus heating on a heat collecting tube 8 in the heat collecting loop, the heat collecting device 9 may adopt a linear fresnel type heat collecting or trough type heat collecting structure, and the heat transfer working medium 19 may be water, heat conducting oil, or molten salt. The method comprises the following steps:
when evacuation work is required, the circulating pump 2 in the line-focusing heat collecting system is firstly closed, the circulation of the heat transfer working medium 19 in the system is stopped, at this time, the heat collecting state of the heat collecting tube 8 by the original heat collecting device 9 is kept, namely, a focusing mode is still adopted, the focusing mode is shown in fig. 3, namely, light rays 93 of sunlight can irradiate on the heat collecting tube 8 to heat the tube wall of the heat collecting tube 8, meanwhile, the heat transfer working medium 19 in the heat collecting tube 8 is subjected to heat transfer, and the heat transfer working medium 19 is kept in a molten (liquid) state convenient to flow. When a linear fresnel structure is adopted, the primary reflector 92 reflects the light 93 to the secondary reflector 91 or directly to the tube wall of the heat collecting tube 8, and the secondary reflector 91 focuses the light 93 on the tube wall of the heat collecting tube 8, so that the heat collecting tube 8 is uniformly heated in the circumferential direction.
And opening the evacuation valve 15, evacuating the heat transfer working medium 19 into the storage tank by the heat collecting pipe 8, wherein the storage tank can be an evacuation tank 16 or a low-temperature tank 1. The heat transfer working medium 19 can be driven by the pump body to be drained, flows by self weight to be drained or adopts compressed gas 20 to assist in drainage and the like. In the process of evacuating the heat transfer working medium 19, the heat collecting device 9 corresponding to the evacuation section of the heat collecting tube 8 is switched from the focusing mode to the light tracing mode, so that heat preservation is continuously performed on the heat collecting tube 8, and the heat collecting tube 8 is prevented from being damaged by high temperature in the focusing mode. The conversion of the focusing mode can be performed on the heat collecting tube 8 in sections, and is determined according to the position state of the heat transfer working medium 19 in the heat collecting tube 8 obtained through monitoring. The light tracing mode refers to heat preservation and heating of the heat collecting tube 8 by heat generated by solar illumination, the heat collecting energy in the light tracing mode is less than that in the focusing mode, and the light tracing mode can be realized by adopting an intermittent focusing mode. Further, as shown in fig. 3 and 4, the light tracing mode may include a focusing state and a defocusing state, in the focusing state, the light 93 can be finally collected to the heat collecting tube 8, and at this time, the heat collecting tube 8 is heated; in the defocused state, the light 93 cannot be collected to the heat collecting tube 8, and the heat collecting tube 8 is not heated at this time. By adjusting the time proportion occupied by the focusing state and the defocusing state, the time length for heating the heat collecting tube 8 can be adjusted, and intermittent heating is realized, so that the temperature of the heat collecting tube 8 in the light heat tracing mode can be controlled to be in a proper range, the temperature range cannot damage the heat collecting tube 8 due to overhigh temperature, the solidification of the heat transfer working medium 19 due to overlow temperature cannot be caused, and finally the residual quantity of the heat transfer working medium 19 can be reduced. In practical applications, different light tracing modes can be selected according to the temperature and the weather conditions, for example, when the temperature in the heat collecting tube 8 is higher than 400 ℃, slow heat tracing (the proportion of time occupied by the defocusing state is high) is performed under the condition of fine weather, and focused heat tracing (the proportion of time occupied by the focusing state is high) is performed under the condition of low irradiation. When a certain section of the heat collecting pipe 8 is over-temperature or low-temperature, the heat preservation range is adjusted by controlling the time proportion of the focusing state and the defocusing state, namely, the time of the defocusing state is increased when the temperature is high, and the time of the focusing state is increased when the temperature is low, so that the temperature of the heat collecting pipe 8 is controlled to be always kept in a certain range.
After the heat transfer working medium 19 in the heat collection tube 8 is emptied, at this time, the heat collection tube 8 does not have the heat transfer working medium 19 any more or has little residual heat transfer working medium 19, the light heat tracing mode of the heat collection device 9 to the heat collection tube 8 is stopped, and the process of evacuating the heat transfer working medium 19 is ended.
In the process of evacuating the heat transfer working medium 19, the invention can keep the heat transfer working medium 19 in the heat collection tube 8 in a state convenient for flowing by continuously adopting an optical heat tracing mode for the evacuation section, can avoid the solidification and residue of the heat transfer working medium 19 on the inner wall of the heat collection tube 8, reduce the residual quantity of the heat transfer working medium 19 in the heat collection tube 8, avoid the obstruction to the evacuation process caused by the blockage of the heat collection tube 8 due to the incomplete evacuation of the heat transfer working medium 19, improve the evacuation efficiency of the heat transfer working medium 19, reduce the energy consumption, and simultaneously avoid the obstruction of flowing when the heat transfer working medium 19 is injected next time due to the solidification of the heat transfer working medium 19 on the inner wall of the heat collection tube 8, and influence the next injection process; the invention can realize the daily operation of emptying the heat transfer working medium 19 in the heat collection field, solves the problem of high energy consumption caused by low-speed circulation condensation prevention, and can also solve the freezing and blocking risks in the process of evacuating the heat transfer working medium 19 with a high freezing point.
The heat collecting device 9 comprises a tracking mechanism and a control system for controlling the action of the tracking mechanism, the tracking mechanism is matched with the heat collecting tubes 8 in sections, the control system is used for controlling the action of the tracking mechanism, the angle of the reflector is adjusted by the action of the tracking mechanism, and then whether the light rays 93 are converged to the corresponding heat collecting tubes 8 can be adjusted, specifically, one group of tracking mechanisms corresponds to one section of the heat collecting tubes 8, and at the moment, the group of tracking mechanisms controls the action of the reflector to change the heat collecting state of the heat collecting device 9 at the section of the heat collecting tubes 8; or multiple groups of tracking mechanisms correspond to the same section of the heat collecting tube 8, and at this time, the multiple groups of tracking mechanisms control the action of the reflecting mirror, so that the heat collecting state of the heat collecting device 9 at the section of the heat collecting tube 8 can be changed. Namely, one or more groups of tracking mechanisms are controlled to control the heat collecting device 9 corresponding to a certain section of the heat collecting tube 8 to be in a focusing state or a defocusing state.
As shown in fig. 1, a plurality of temperature measuring points 10 are distributed on the heat collecting tube 8 along the length direction thereof, each temperature measuring point 10 can monitor the temperature value and the variation form of the corresponding position, and the temperature of the heat collecting tube 8 at the position where the heat transfer working medium 19 exists and the temperature of the heat collecting tube 8 at the position where the heat transfer working medium 19 does not exist are different, so that the position state of the heat transfer working medium 19 can be judged according to the monitoring result of the temperature measuring points 10. Specifically, when the heat transfer working medium 19 flows through a certain temperature measuring point 10, the temperature of the temperature measuring point 10 changes significantly, and the position where the heat transfer working medium 19 arrives can be confirmed section by section according to the change of the temperature measuring point 10, that is, the evacuation section is judged. Accordingly, the heating modes of different positions of the heat collecting tube 8 are changed, and therefore basis can be provided for changing the heat collecting state of the heat collecting tube 8 within a certain section range.
In the evacuation process of the heat transfer working medium 19, if the heat collecting tube 8 is obliquely arranged, evacuation can be performed by means of the self-weight flow of the heat transfer working medium 19, meanwhile, the power of the compressed gas 20 can be used for assisting the flow of the heat transfer working medium 19, especially, the heat transfer working medium 19 cannot automatically flow under the condition that the heat collecting tube 8 has no inclination, at the moment, the compressed gas 20 can provide main power to drive the heat transfer working medium 19 to be evacuated, so that the efficiency of evacuation of the heat transfer working medium 19 can be further improved by means of the compressed gas 20, and the residual quantity of the heat transfer working medium 19 in the heat collecting tube 8 can be further reduced by means of the scouring capability of the compressed gas 20. In addition, when the compressed gas 20 is used for providing driving force, the compressed gas 20 with different pressures can be adopted to assist the rapid evacuation of the heat transfer working medium 19 according to the flowing state or the requirement of the heat transfer working medium 19 in the heat collecting pipe 8. The pressure of the compressed gas 20 is mainly determined by two factors, namely, the larger the gradient of the heat collecting pipe 8 is, the faster the self-weight backflow is, the smaller the required pressure is, the smaller the gradient is, the slower the self-weight backflow is, and the larger the required pressure is; another is that the pressure of the compressed gas 20 can be increased when the grade is constant, if it is desired to increase the evacuation rate or to drain cleaner.
The storage tank may be a evacuation tank 16, the heat transfer medium 19 in the heat collecting tube 8 may be evacuated into the evacuation tank 16 for temporary storage, and the heat transfer medium 19 in the evacuation tank 16 may be pumped back into the low temperature tank 1 through an evacuation pump 17 and an evacuation pipeline 18.
Referring to fig. 1~4 again, the present invention further provides a line focusing heat collecting system, which includes a heat collecting tube 8 and a heat collecting device 9 for focusing light 93 to the heat collecting tube 8, wherein a heat collecting inlet of the heat collecting tube 8 is communicated with the low temperature tank 1, a heat collecting outlet of the heat collecting tube 8 is communicated with the high temperature tank 14, a circulating pump 2 for driving a heat transfer working medium 19 to circularly flow is disposed between the low temperature tank 1 and the heat collecting inlet, the low temperature tank 1 is communicated with the heat collecting tube 8 through a cold working medium main tube 3, and the high temperature tank 14 is communicated with the heat collecting tube 8 through a hot working medium main tube 11. A pressure measuring point 4 and a heat collecting inlet valve 5 can be further arranged on the cold working medium main pipe 3, the pressure state of the pipeline can be monitored by using the pressure measuring point 4, and the problem that the circulating pump 2 or the pipeline is damaged due to high pressure caused by pipeline blockage and the like is avoided. The heat collecting tube 8 is provided with a heat collecting device 9 in a matching manner, the heat collecting device 9 is used for carrying out focusing heat collection on the heat collecting tube 8, the low-temperature tank 1 is used for storing a heat transfer working medium 19 with relatively low temperature, the high-temperature tank 14 is used for storing the heat transfer working medium 19 with relatively high temperature (absorbing heat through solar energy), and the heat transfer working medium 19 flows to the high-temperature tank 14 after being driven by the circulating pump 2, and is absorbed by the heat collecting tube 8 from the low-temperature tank 1. The heat collection outlet is also communicated with a drainage tank 16, and the drainage tank 16 is used for temporarily storing the heat transfer medium 19 when the line focusing heat collection system needs drainage work. The heat collecting device 9 comprises a plurality of groups of tracking mechanisms and a control system for controlling the tracking mechanisms to act, each group of tracking mechanisms corresponds to one section of the heat collecting tube 8, namely the heat collecting tube 8 is matched with the corresponding tracking mechanism in a segmented mode, the tracking mechanisms are controlled by the control system, the reflection angle of the primary reflector 92 can be changed, and therefore whether the light 93 is reflected to the secondary reflector 91 (or the heat collecting tube 8) or not can be changed, the heat collecting mode (switching between a focusing mode and a defocusing mode) can be further changed, and the heat collecting device 9 corresponding to the emptying section of the heat collecting tube 8 can be smoothly switched from the focusing mode to the light heat tracing mode in the process of evacuating the heat transfer working medium 19.
As shown in fig. 1, a drain valve 15 is arranged between the drain tank 16 and the heat collecting tube 8, and the system is in a heat collecting working state or enters a drain working state by controlling the opening and closing of the drain valve 15. The evacuation tank 16 is communicated with the low-temperature tank 1 through an evacuation pump 17 and an evacuation pipeline 18, and the heat transfer working medium 19 temporarily stored in the evacuation tank 16 can be conveyed into the low-temperature tank 1 under the power of the evacuation pump 17. The low-temperature tank 1 can be provided with a heat preservation heating device, the low-temperature tank 1 can be kept within a certain temperature range all the time, and when normal heat collection work is needed, the heat transfer working medium 19 in the low-temperature tank 1 can be injected into the heat collection pipe 8 through the circulating pump 2 again and circulated.
The heat collecting inlet can also be communicated with a compressed air source 6 for supplying compressed air 20 (specifically, compressed air or nitrogen and the like) to the heat collecting tube 8, and the compressed air valve 7 is used for controlling whether the compressed air source 6 supplies the compressed air 20 to the heat collecting tube 8. It should be noted that the supply position of the compressed gas 20 and the evacuation position of the heat transfer working medium 19 are located at two ends of the heat collecting tube 8, and the heat transfer working medium 19 can be assisted to flow in the evacuation direction by supplying the compressed gas 20 to the heat collecting tube 8.
The low-temperature tank 1 and the high-temperature tank 14 can be communicated through a pipeline, a cold tank return valve 12 is arranged at a position close to the low-temperature tank 1, and a hot tank return valve 13 is arranged at a position close to the high-temperature tank 14. The heat transfer working medium 19 in the heat collecting tube 8 can flow back to the evacuation tank 16, or can flow back to the low temperature tank 1 or the high temperature tank 14, and can be selected according to the temperature of the heat transfer working medium 19, for example, if the temperature of the heat transfer working medium 19 is higher and meets the condition of entering the high temperature tank 14, the heat transfer working medium can directly flow back to the high temperature tank 14. The selection of each tank body and the flow direction of the heat transfer working medium 19 are respectively controlled by the drain valve 15, the cold tank return valve 12 and the hot tank return valve 13.
The heat collecting device 9 may adopt a linear fresnel structure or a groove structure, and includes a reflector controlled by a tracking mechanism, and controls the heat collecting tube 8 to be in a preheating preparation state, a focusing state or a defocusing state by changing whether the reflector focuses on the heat collecting tube 8. When adopting linear fresnel structure, the speculum includes primary reflector 92 and secondary reflector 91, primary reflector 92 lays the area and is far greater than secondary reflector 91, secondary reflector 91 is the curved surface and encircles the lock in the 8 circumference outsides of thermal-collecting tube, can collect secondary reflector 91 with light 93 through primary reflector 92, recycle secondary reflector 91 with light 93 focus on thermal-collecting tube 8, with can all focus on each position of the circumference of thermal-collecting tube 8 and heat. Meanwhile, part of the light 93 reflected by the primary reflector 92 can be directly focused on the heat collecting tube 8 without being reflected by the secondary reflector 91. The primary mirror 92 is controlled by a tracking mechanism and corresponds to different segments of the secondary mirror 91 to enable focusing on different positions of the collector tube 8. Whether the primary reflector 92 focuses the light 93 to the secondary reflector 91 or not is controlled and changed by the tracking mechanism so as to control the heat collecting tube 8 to be in a focusing state or a defocusing state.
The invention also provides the following specific embodiments:
the first embodiment is as follows:
the heat collection field (including a plurality of heat collection tubes 8) is evacuated as a whole and has a certain gradient.
When the heat transfer working medium 19 is exhausted, the circulating pump 2 is closed, the evacuation valve 15 is opened, the heat transfer working medium 19 in the heat collecting pipe 8 flows back into the evacuation tank 16, and the heat transfer working medium 19 in the evacuation tank 16 is conveyed into the low-temperature tank 1 through the evacuation pump 17.
In the process of flowing the heat transfer working medium 19, the temperature measuring point 10 corresponding to the heat collecting tube 8 is monitored to determine the position of the heat transfer working medium 19 in the heat collecting tube 8. After the heat transfer medium 19 flows out for a certain distance, in order to avoid negative pressure formed by the outflow of the heat transfer medium 19 at the evacuation section of the heat collection tube 8, the compression air valve 7 needs to be opened to supplement gas (air or nitrogen, etc.) to the empty tube part (evacuation section) in the heat collection tube 8, meanwhile, when the heat transfer medium 19 at a certain section in the heat collection tube 8 is already evacuated, the heat collection device 9 corresponding to the section of the heat collection tube 8 is switched from the focusing mode to the light heat tracing mode (as shown in fig. 3 and 4), so that the reflector is switched between the focusing state and the defocusing state, the temperature of the heat collection tube 8 during light tracing is controlled by adjusting the time proportion occupied by the focusing state and the defocusing state, the heat preservation is continuously performed on the heat collection tube 8, and the heat transfer medium 19 remained on the inner wall of the heat collection tube 8 is evacuated.
And when the heat transfer working medium 19 in the heat collecting pipe 8 is exhausted, closing the compression air valve 7, resetting all reflectors of the heat collecting device 9, and finishing the exhausting of the heat transfer working medium 19.
The second embodiment:
the heat collection field is emptied integrally, the heat collection field has no gradient, and the compressed gas 20 is adopted to provide thrust to push the heat transfer working medium 19 to flow back into the storage tank.
When the heat transfer working medium 19 is exhausted, the circulating pump 2 is closed, the evacuation valve 15 is opened, the compression air valve 7 is opened, the supplemented air pressure is gradually increased, the heat transfer working medium 19 is pushed to flow to the evacuation tank 16, and then the heat transfer working medium 19 is conveyed into the low-temperature tank 1 through the evacuation pump 17.
In the process that the heat transfer working medium 19 flows, the temperature measuring point 10 corresponding to the heat collecting tube 8 is monitored to judge the position of the heat transfer working medium 19 in the heat collecting tube 8, when the heat transfer working medium 19 of a certain section in the heat collecting tube 8 is exhausted, the heat collecting device 9 corresponding to the section of the heat collecting tube 8 is switched from a focusing mode to an optical heat tracing mode (as shown in fig. 3 and 4), the reflector is switched between a focusing state and a defocusing state, the temperature of the heat collecting tube 8 during optical heat tracing is controlled by adjusting the time proportion occupied by the focusing state and the defocusing state, and heat preservation is continuously carried out on the heat collecting tube 8.
When the compressed gas 20 is discharged from the evacuation tank 16 through the heat collecting tube 8, it can be determined that most of the heat transfer medium 19 in the heat collecting tube 8 is already evacuated, the compressed gas valve 7 is closed, all the reflectors of the heat collecting device 9 are reset, and evacuation of the heat transfer medium 19 is finished.
Example three:
the heat collection field comprises a plurality of heat collection loops (each heat collection loop comprises one heat collection tube 8 or a plurality of heat collection tubes 8 arranged in parallel), each heat collection loop is provided with an inlet valve and an outlet valve, and in the heat collection process, a single heat collection loop in the heat collection field needs to be independently evacuated.
And when the heat transfer working medium 19 is emptied, the circulating pump 2 is closed, and the inlet valve and the outlet valve of the heat collection loops needing to continue heat collection are closed, so that the heat transfer working medium 19 continues to be left in the heat collection loops, and the reflectors corresponding to the heat collection loops are switched from the focusing mode to the optical heat tracing mode, so that the heat transfer working medium 19 is kept warm.
Opening an evacuation valve 15 and an air valve of a heat collection loop to be evacuated, gradually increasing the pressure, rapidly flowing a heat transfer working medium 19 in the heat collection loop into a hot working medium main pipe 11 or an evacuation tank 16, monitoring a temperature measuring point 10 corresponding to a heat collection tube 8 in the heat collection loop to judge the position of the heat transfer working medium 19 in the heat collection tube 8, when the heat transfer working medium 19 in a certain section of the heat collection tube 8 is exhausted, switching a heat collection device 9 corresponding to the section of the heat collection tube 8 from a focusing mode to an optical heat tracing mode (as shown in fig. 3 and 4), switching a reflector between a focusing state and a defocusing state, controlling the temperature of the heat collection tube 8 during optical heat tracing by adjusting the time proportion occupied by the focusing state and the defocusing state, and continuously preserving the heat of the heat collection tube 8.
And after the heat collection loop is completely emptied, closing the inlet valve and the outlet valve of the loop to be cut off, closing the drain valve 15, restarting the circulating pump 2, opening the inlet valves and the outlet valves of other heat collection loops to allow the heat transfer working medium 19 to continue circulating, and switching the heat collection loop from the light tracing mode to the focusing mode to operate.
Example four:
heat collection can not be continued according to weather conditions, and the heat transfer working medium 19 needs to be emptied.
At this time, according to the condition of the actual heat collecting field, the operation is performed according to the contents of the first embodiment or the second embodiment.
The principle and the implementation mode of the invention are explained by applying a specific example, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (9)
1. A method for emptying a heat transfer working medium of a line focusing heat collecting system is characterized by comprising the following steps:
when the heat transfer working medium needs to be emptied, the circulation of the heat transfer working medium is stopped, the heat collection device keeps the original heat collection mode of the heat collection tube, namely keeps the focusing mode, at the moment, the heat collection device is in the focusing state, and the heat transfer working medium is in a state convenient to flow in the heat collection tube;
the heat transfer working medium is drained to a storage tank through the heat collecting pipe, the position of the heat transfer working medium in the heat collecting pipe is monitored in the process of draining the heat transfer working medium, and the emptying section of the heat collecting pipe is judged according to the position of the heat transfer working medium in the heat collecting pipe, wherein the position is obtained through monitoring;
adjusting the heat collection mode of the heat collection device corresponding to the emptying section, and converting the heat collection mode into an optical heat tracing mode which comprises a focusing state and a defocusing state;
controlling the temperature of the heat collecting tube by adjusting the time proportion of the focusing state and the defocusing state, and continuously preserving the heat of the emptying section;
after the heat transfer working medium is emptied, the heat collecting tubes are all converted into emptying sections, and meanwhile, the heat collecting devices are all converted into an optical heat tracing mode;
and stopping the optical heat tracing mode, and finishing the evacuation work of the heat transfer working medium.
2. The method for exhausting the heat transfer working medium of the line focusing heat collecting system according to claim 1, wherein the method comprises the following steps: the heat collecting tube is matched with a tracking mechanism in a segmented mode, and the tracking mechanism is used for controlling the heat collecting device to be in a focusing state or a defocusing state.
3. The method for evacuating the heat transfer medium of the line focusing heat collecting system according to claim 2, wherein: a plurality of temperature measuring points are distributed on the heat collecting tube along the length direction, and the position state of the heat transfer working medium is judged according to the monitoring results of the temperature measuring points.
4. The method for exhausting the heat transfer working medium of the line focusing heat collecting system according to claim 3, wherein the method comprises the following steps: the heat transfer working medium is drained to the storage tank by means of self weight and/or power of compressed gas, and the storage tank is a drainage tank or a low-temperature tank.
5. A line focus heat collecting system using the method for evacuating heat transfer medium of the line focus heat collecting system as claimed in any one of claims 1 to 4, wherein: the solar heat collector comprises a heat collecting tube and a heat collecting device used for focusing light rays to the heat collecting tube, wherein a plurality of temperature measuring points used for judging the emptying section of the heat collecting tube are distributed on the heat collecting tube along the length direction, a heat collecting inlet of the heat collecting tube is communicated with a low-temperature tank, a heat collecting outlet of the heat collecting tube is respectively communicated with the low-temperature tank and a high-temperature tank through pipelines, a circulating pump used for driving heat transfer working media to flow circularly is arranged between the low-temperature tank and the heat collecting inlet, the heat collecting outlet is also communicated with an emptying tank, the emptying tank is communicated with the low-temperature tank through an emptying pump and an emptying pipeline, the heat collecting tube is matched with a tracking mechanism in a segmented mode, and the tracking mechanism controls the heat collecting device corresponding to the emptying section of the heat collecting tube to be switched to a light heat tracing mode from a focusing mode in the heat transfer working media emptying process.
6. The line focus heat collection system of claim 5, wherein: the heat collecting inlet is communicated with a compressed gas source for supplying compressed gas to the heat collecting pipe.
7. The line focus heat collection system of claim 5, wherein: the low-temperature tank with through the pipeline intercommunication between the high-temperature tank, be close to the low-temperature tank is provided with cold jar backward flow valve, is close to the high-temperature tank is provided with hot jar backward flow valve.
8. The line focus heat collection system of claim 5, wherein: the heat collection device comprises a reflecting mirror, the reflecting mirror is controlled by the tracking mechanism, and whether the reflecting mirror focuses on the heat collection tube or not is changed, so that the heat collection device is controlled to be in a focusing state or a defocusing state.
9. The line focus heat collection system of claim 8, wherein: the speculum includes primary reflector and secondary reflector, the secondary reflector is the curved surface and encircles the lock and be in the thermal-collecting tube circumference outside, through primary reflector collects light to the secondary reflector, recycles the secondary reflector focuses on light the thermal-collecting tube is last.
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| CN210399547U (en) * | 2019-09-04 | 2020-04-24 | 中国电建集团中南勘测设计研究院有限公司 | Fused salt emptying device of fused salt linear Fresnel type heat collector |
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| FR2478803A1 (en) * | 1980-03-24 | 1981-09-25 | Technologie Innovations Indles | Frost protection for solar heat collector - has thermostat to stop circulating-pump during freezing and overflow tank for water expansion |
| JPS57179538A (en) * | 1981-04-28 | 1982-11-05 | Sanyo Electric Co Ltd | Solar heat collector |
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| CN115493302A (en) | 2022-12-20 |
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