CN116182612A - Natural circulation coupling phase-change heat storage loop system - Google Patents

Natural circulation coupling phase-change heat storage loop system Download PDF

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Publication number
CN116182612A
CN116182612A CN202211659491.1A CN202211659491A CN116182612A CN 116182612 A CN116182612 A CN 116182612A CN 202211659491 A CN202211659491 A CN 202211659491A CN 116182612 A CN116182612 A CN 116182612A
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China
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phase change
heat
natural circulation
heat storage
working medium
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CN202211659491.1A
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Inventor
陈伟雄
李敬宇
景浩
古真桢
种道彤
严俊杰
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Xian Jiaotong University
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Xian Jiaotong University
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Priority to CN202211659491.1A priority Critical patent/CN116182612A/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D20/02—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using latent heat
    • F28D20/021—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using latent heat the latent heat storage material and the heat-exchanging means being enclosed in one container
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C15/00—Cooling arrangements within the pressure vessel containing the core; Selection of specific coolants
    • G21C15/02—Arrangements or disposition of passages in which heat is transferred to the coolant; Coolant flow control devices
    • G21C15/14—Arrangements or disposition of passages in which heat is transferred to the coolant; Coolant flow control devices from headers; from joints in ducts
    • 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
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/14—Thermal energy storage

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Plasma & Fusion (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Other Air-Conditioning Systems (AREA)

Abstract

The invention discloses a natural circulation coupling phase change heat storage loop system, which comprises a natural circulation loop formed by sequentially connecting a cooling side, a left vertical pipe, a heating side and a right vertical pipe, wherein the left vertical pipe is used as an inner sleeve of a PCM phase change heat storage unit. The system is coupled with the phase change heat storage system and the natural circulation loop, and the phase change heat storage unit is coupled on the left vertical pipe of the natural circulation loop, so that the PCM continuously exchanges heat with working media in the loop in the flow fluctuation process of the loop, the flow field is regulated, the temperature fluctuation and the mass flow fluctuation are restrained, the stable operation of the natural circulation loop system is realized, and the stable operation power range of the loop is enlarged. The system can also realize PCM phase change heat storage, most of heat of the natural circulation loop working medium is taken away by a cold source, and the small part of heat is transferred to the PCM and stored in a phase change latent heat form, so that the effect of heat recycling is achieved.

Description

Natural circulation coupling phase-change heat storage loop system
Technical Field
The invention belongs to the technical field of passive natural circulation safe and efficient operation, and particularly relates to a natural circulation coupling phase-change heat storage loop system.
Background
Natural circulation refers to an energy transmission mode for driving fluid to circulate in a closed system by only relying on buoyancy force formed by density difference between cold and hot fluid. The natural circulation system constructed on the basis of the natural circulation principle is widely applied to various fields such as nuclear reactors, boilers, solar heat utilization systems and the like.
For a long time, as the probability of nuclear accidents is greatly increased due to the use of active facilities in the nuclear power plant, researchers have proposed the concept of passive technology of the nuclear power plant on the basis of active technology in order to improve the inherent safety of the nuclear power system. Since the failure of the three islands in the united states and the fukushima in japan, natural circulation has been an important means for improving the intrinsic safety of nuclear power plants as a typical passive technique, and has been widely and intensively studied. When the natural circulation mode is operated, the density difference and the height difference between the reactor core and the steam generator generate a natural circulation driving pressure head, a certain flow can be maintained, the heat of the reactor core is continuously transmitted to the secondary side of the steam generator, the heat is not limited by external power conditions, and a series of problems such as large break of a primary loop, power failure of the whole plant and the like can be effectively avoided.
Therefore, how to ensure safe and effective operation of the natural circulation loop system and to implement efficient cooling of the required cooling components has important research significance.
Disclosure of Invention
In order to solve the problems, the invention aims to provide a natural circulation coupling phase-change heat storage loop system, which integrates natural circulation and phase-change heat storage technologies, and suppresses mass flow fluctuation in a loop through a phase-change unit, so that the stability range of loop operation is improved, and the heat storage effect in the process of natural circulation loop operation is realized.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a natural circulation coupling phase change heat storage loop system is characterized in that: the system comprises a natural circulation loop formed by sequentially communicating a cooling side 1, a left vertical pipe 2, a heating side 5 and a right vertical pipe 4, wherein the left vertical pipe 2 is used as an inner sleeve of a PCM phase change heat storage unit 3; the system absorbs heat by utilizing the heating side 5 and transmits the heat to working fluid in a natural circulation loop through heat exchange of a pipeline; under the steady state of natural circulation loop operation, working medium is taken as positive direction in the natural circulation loop by anticlockwise movement, and enters the left vertical pipe 2 after flowing through the heating side 5 and moves upwards, and the working medium exchanges heat with the PCM phase change heat storage unit 3 in the movement process of the left vertical pipe 2 in a heat exchange mode; the working medium flows through the left vertical pipe 2, then enters the cooling side 1 and moves rightwards, and in the moving process of the working medium in the cooling side 1, heat is released to the cooling side 1 in a heat exchange mode; the working medium flows through the cooling side 1 and then enters the right vertical pipe 4 and moves downwards; the working medium flows through the right vertical pipe 4, then enters the heating side 5 and absorbs heat again, and the circulating movement process of the working medium in the natural circulation loop is completed.
In the operation process of the natural circulation loop, the heat of the working fluid is released through the cooling side 1 in a heat exchange mode, and is absorbed through the heating side 5; under the thermal boundary conditions of constant heating power and certain cooling temperature, the working fluid generates density difference required by passive natural circulation starting, and enters a stable operation stage after the mass flow rate of a period of time fluctuates, so that the effective heat transfer from the heating side 5 to the cooling side 1 is realized.
The working fluid in the natural circulation loop is liquid water.
The heating side 5 is a constant heat flux heating device.
The cooling side 1 is a constant temperature water tank.
The PCM phase-change heat storage unit 3 is a PCM phase-change heat storage device containing a phase-change heat storage material PCM, and is capable of absorbing heat to store heat when the ambient temperature is high and releasing heat to release heat when the ambient temperature is low.
The heat exchanger structure of the PCM phase change heat storage device is a fin sleeve type; the inner sleeve of the PCM phase change heat storage unit is a round light pipe, the fin pipes are round fin pipes, and the fins 301 are uniformly distributed at equal intervals.
The shell side working medium of the PCM phase-change heat storage device adopts a phase-change material 302, the phase-change material 302 is paraffin, and the tube side working medium is consistent with the working medium adopted by a natural circulation loop.
Before the natural circulation loop starts, the phase change material 302 is in a solid state, the temperature is lower and the solid phase point is not reached; both the solid phase point and the liquid phase point of the phase change material 302 are above the water temperature that can be maintained by the cooling water tank of the cooling side 1; during the operation of the natural circulation loop, the phase change material 302 continuously exchanges heat with the working medium of the natural circulation loop, and the phase change material 302 continuously heats up because the heat absorbed by the phase change material is more than the heat released by the phase change material; phase change material 302 stores heat in the form of sensible heat in a substance during a temperature increase process, referred to as sensible heat storage; when the temperature of the phase change material 302 reaches the solid phase point, the phase change material starts to melt and absorb latent heat, and stores the latent heat while absorbing the heat process (sensible heat storage) brought by the natural circulation loop working medium, which is called latent heat storage; in the process of heating from a solid phase point to a liquid phase point, the liquid phase rate of the phase change material 302 is continuously increased, natural convection phenomenon caused by density difference is generated, and the phase change material continuously moves in the PCM phase change heat storage unit 3 and strengthens the heat transfer effect with fins; after the temperature exceeds the liquidus point, the phase change material 302 is completely changed into a liquidus state, the latent heat of the phase change material is completely absorbed, and the phase change material returns to a sensible heat storage mode in the heating process.
The invention has the beneficial effects that:
(1) According to the natural circulation coupling phase-change heat storage loop system, the PCM phase-change heat storage unit is added to the left vertical pipe, so that the coupling of natural circulation and phase-change heat storage is realized, and the aim of regulating natural circulation in a phase-change heat storage mode is fulfilled. The cold and heat source arrangement of the natural circulation system is not a pure horizontal heating-horizontal cooling HHC mode, but is equivalent to adding a variable-temperature cold source, so that the system structure is not completely symmetrical, and the system stability is improved. The power supply has the remarkable advantages of wide power operation, strong stability and the like.
(2) According to the system disclosed by the invention, a part of energy of natural circulation operation is stored in the PCM phase change heat storage unit, so that the energy utilization efficiency is improved.
Drawings
Fig. 1 is a schematic structural diagram of a natural circulation coupled phase change heat storage loop system.
Fig. 2 is a schematic structural diagram of a PCM phase change heat storage unit.
Fig. 3 is a comparison diagram of the operation states of a natural circulation system formed by the coupled and uncoupled PCM phase change heat storage device under the same cold and heat source conditions.
The numbers in the figures correspond to: a cooling side 1, a left vertical pipe 2, a PCM phase change heat storage unit 3, a right vertical pipe 4 and a heating side 5; fins 301, phase change material 302, outer sleeve 303, inner sleeve 304.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings.
As shown in fig. 1, a schematic diagram of a natural circulation coupling phase-change heat storage loop system is shown, and the connection relationship of each main device is as follows: in the natural circulation coupling phase-change heat storage loop system, the outlet of the cooling side 1 is connected with the inlet of the right vertical pipe 4, the outlet of the right vertical pipe 4 is connected with the inlet of the heating side 5, the outlet of the heating side 5 is connected with the inlet of the left vertical pipe 2, the outlet of the left vertical pipe 2 is connected with the inlet of the cooling side 1, and the left vertical pipe 2 is used as an inner sleeve of the PCM heat storage unit 3.
Fig. 1 is a schematic diagram of a natural circulation coupling phase-change heat storage loop system, and the main working principle is as follows: the system utilizes a constant heat flux density heating device at the heating side 5 to absorb heat and transfer the heat to the working fluid in the natural circulation loop through heat exchange of the pipeline. Under the steady state of natural circulation loop operation, taking the working medium to anticlockwise move as the positive direction in the natural circulation loop, the working medium flows through the heating side 5 and then enters the left vertical pipe 2 and moves upwards, and the working medium exchanges heat with the PCM phase change heat storage unit 3 in the movement process of the left vertical pipe 2 in a heat exchange mode. The working medium flows through the left vertical pipe 2, then enters the cooling side 1 and moves rightwards, and in the movement process of the working medium in the cooling side 1, the working medium emits heat to the cooling side 1 in a heat exchange mode. The working medium flows through the cooling side 1 and then enters the right vertical pipe 4 and moves downwards. The working medium flows through the right vertical pipe 4, then enters the heating side 5 and absorbs heat again, and the circulating movement process of the working medium in the loop is completed.
Fig. 2 is a schematic structural diagram of a PCM phase change heat storage unit, and the main working principle is as follows: the PCM phase change heat storage unit is a fin double pipe heat exchanger; the inner sleeve 304 is arranged coaxially with the outer sleeve 303; the inner sleeve 304 is a circular finned tube, and the outer sleeve 303 is a circular light tube; the annular fins 301 are equally distributed on the outer surface of the inner sleeve 304; the working medium between the inner sleeve 304 and the outer sleeve 303 is phase change material 302. When the working medium flows through the space in the inner sleeve 304, heat exchange occurs between the working medium and the inner sleeve 304; and phase change material 302 heats up and melts upon receiving heat transferred from inner sleeve 304, creating a gravity-driven natural circulation flow in the inter-tube space.
According to the invention, the heat exchanger taking the PCM phase change material as the shell side working medium is wrapped on the left standpipe, so that the coupling of natural circulation and phase change heat storage is realized. The cold and heat source arrangement of the natural circulation system is not a pure horizontal heating-horizontal cooling HHC mode, but is equivalent to adding a variable-temperature cold source, so that the system structure is not completely symmetrical, and the system stability is improved. Under the conditions of 2.5kW of total heating power and 303K of cold source temperature, the natural circulation loop system cannot reach a stable state and can enter an unstable operation area with continuously fluctuating mass flow, and a new natural circulation system formed after the PCM phase-change heat storage device is coupled can reach the stable state under the same cold source condition, wherein the mass flow pair is shown in figure 3. From the graph, the original system does not reach a stable state even after undergoing multiple times of flow inversion, and the new natural circulation system enters the damping oscillation process after undergoing one time of flow inversion, and the mass flow curve in the natural circulation process is stable, so that the stable operation of the system is marked. Therefore, coupling PCM heat storage can widen the stability range of natural circulation systems. The heat storage quantity can continuously fluctuate along with the oscillation of the loop, and the heat storage quantity value fluctuates around 100W and gradually tends to be stable, so that a stable heat storage state is achieved. In the coupling heat transfer process of fluid motion and PCM in a natural circulation loop, the heat transfer mechanism is quite complex: the heat transfer is greater at higher fluid temperatures and faster speeds in the circuit; conversely, when the fluid temperature in the circuit is lower and the velocity is lower, the heat transfer is less.
The system is coupled with the phase change heat storage system and the natural circulation loop, and the phase change heat storage unit is coupled on the left vertical pipe of the natural circulation loop, so that the PCM continuously exchanges heat with working media in the loop in the flow fluctuation process of the loop, the flow field is regulated, the temperature fluctuation and the mass flow fluctuation are restrained, the stable operation of the natural circulation loop system is realized, and the stable operation power range of the loop is enlarged. The system can also realize PCM phase change heat storage, most of heat of the natural circulation loop working medium is taken away by a cold source, and the small part of heat is transferred to the PCM and stored in a phase change latent heat form, so that the effect of heat recycling is achieved.

Claims (8)

1. A natural circulation coupling phase change heat storage loop system is characterized in that: the system comprises a natural circulation loop formed by sequentially communicating a cooling side (1), a left vertical pipe (2), a heating side (5) and a right vertical pipe (4), wherein the left vertical pipe (2) is used as an inner sleeve of a PCM phase change heat storage unit (3); the system absorbs heat by utilizing a heating side (5) and transmits the heat to working fluid in a natural circulation loop through heat exchange of a pipeline; under the running steady state of the natural circulation loop, the working medium flows through the heating side (5) and then enters the left vertical pipe (2) to move upwards by taking the anticlockwise movement of the working medium in the natural circulation loop as the positive direction, and the working medium exchanges heat with the PCM phase change heat storage unit (3) in the movement process of the working medium in the left vertical pipe (2) in a heat exchange mode; the working medium flows through the left vertical pipe (2) and then enters the cooling side (1) to move rightwards, and in the moving process of the working medium in the cooling side (1), the working medium emits heat to the cooling side (1) in a heat exchange mode; the working medium flows through the cooling side (1) and then enters the right vertical pipe (4) and moves downwards; the working medium flows through the right vertical pipe (4) and then enters the heating side (5) and absorbs heat again, so that the circulating movement process of the working medium in the natural circulation loop is completed; in the operation process of the natural circulation loop, the heat of the working fluid is released through a cooling side (1) in a heat exchange mode, and is absorbed through a heating side (5); under the thermal boundary conditions of constant heating power and certain cooling temperature, the working fluid generates density difference required by passive natural circulation starting, and enters a stable operation stage after the mass flow fluctuation for a period of time, so that the heat is effectively transferred from the heating side (5) to the cooling side (1).
2. The natural circulation coupled phase change thermal storage loop system of claim 1, wherein the working fluid in the natural circulation loop is liquid water.
3. Natural circulation coupled phase change heat storage circuit system according to claim 1, characterized in that the heating side (5) is a constant heat flux heating means.
4. Natural circulation coupled phase change heat storage circuit system according to claim 1, characterized in that the cooling side (1) is a thermostatic water tank.
5. Natural circulation coupled phase change heat storage circuit system according to claim 1, characterized in that the PCM phase change heat storage unit (3) is a PCM phase change heat storage device comprising phase change heat storage material PCM, capable of absorbing heat for heat storage when ambient temperature is high and releasing heat for heat release when ambient temperature is low.
6. The natural circulation coupled phase change heat storage loop system of claim 5, wherein the heat exchanger structure of the PCM phase change heat storage device is a fin-sleeve type; the outer sleeve of the PCM phase change heat storage unit is a round light pipe, the inner fin pipe is a round fin pipe, and fins (301) are uniformly distributed at equal intervals.
7. The natural circulation coupling phase-change heat storage loop system according to claim 5, wherein a shell side working medium of the PCM phase-change heat storage device adopts a phase-change material (302), the phase-change material (302) is paraffin, and the tube side working medium is consistent with a working medium adopted by the natural circulation loop.
8. The natural circulation coupled phase change thermal storage loop system of claim 7, wherein the phase change material (302) is in a solid state and the temperature does not reach a solidus point before the natural circulation loop is started; both the solid phase point and the liquid phase point of the phase change material (302) are positioned above the water temperature which can be maintained by the cooling water tank of the cooling side (1); during the operation of the natural circulation loop, the phase change material (302) continuously exchanges heat with the working medium of the natural circulation loop, and the phase change material (302) continuously heats up because the heat absorbed by the phase change material is more than the heat released by the phase change material; the phase change material (302) stores heat in the form of sensible heat in a substance during a temperature rise process, referred to as sensible heat storage; when the temperature of the phase change material (302) reaches a solid phase point, the phase change material starts to melt and absorb latent heat, and stores the latent heat, namely the sensible heat and the heat storage, while absorbing the heat process brought by the working medium of the natural circulation loop, namely the latent heat and the heat storage; in the process of heating from a solid phase point to a liquid phase point, the liquid phase rate of the phase change material (302) is continuously increased, natural convection phenomenon caused by density difference is generated, and the phase change material continuously moves in the PCM phase change heat storage unit (3) and strengthens the heat transfer effect with fins; after the temperature exceeds the liquidus point, the phase change material (302) is completely changed into a liquidus state, the latent heat of the phase change material is completely absorbed, and the phase change material returns to a sensible heat storage mode in the heating process.
CN202211659491.1A 2022-12-22 2022-12-22 Natural circulation coupling phase-change heat storage loop system Pending CN116182612A (en)

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CN116182612A true CN116182612A (en) 2023-05-30

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