CN109405611B - Composite heat storage system with two-stage phase change heat storage device and steam storage tank - Google Patents
Composite heat storage system with two-stage phase change heat storage device and steam storage tank Download PDFInfo
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- CN109405611B CN109405611B CN201811071788.XA CN201811071788A CN109405611B CN 109405611 B CN109405611 B CN 109405611B CN 201811071788 A CN201811071788 A CN 201811071788A CN 109405611 B CN109405611 B CN 109405611B
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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
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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
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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
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/14—Thermal energy storage
Abstract
A composite heat storage system with a two-stage phase-change heat storage device and a steam storage tank adopts water and water vapor as heat transfer fluid, and a heat charging process steam distributor (1), a first-stage phase-change heat reservoir (2), the steam storage tank (3), a second-stage phase-change heat reservoir (4) and a heat releasing process steam collector (5) are sequentially arranged from bottom to top. The two-stage phase change heat reservoir comprises a phase change material and a heat exchange tube bundle. In the heat charging process, superheated steam flows in from the bottom of the heat storage system, so that the temperature of saturated water in the primary phase-change heat reservoir (2), the steam storage tank (3) and the secondary phase-change heat reservoir (4) is increased, and meanwhile, phase-change materials in the phase-change heat reservoir are heated and melted, and solid-liquid phase change is realized. The saturated water stored in the heat release process is subjected to flash evaporation and flows out of the top of the heat storage system, so that the temperature of the saturated water in the primary phase-change heat reservoir (2), the steam storage tank (3) and the secondary phase-change heat reservoir (4) is reduced, and meanwhile, the phase-change material in the phase-change heat reservoir is cooled and solidified, and liquid-solid phase change is realized.
Description
Technical Field
The invention relates to a composite heat storage system, in particular to a heat storage system using a two-stage phase change heat storage device and a steam storage tank.
Background
Solar thermal power plants generally comprise 4 sections: the solar heat power generation system comprises a light condensation system, a heat absorption system, a heat storage system and a heat-power conversion system, wherein the heat storage system is a key part for realizing large-scale commercial operation of the solar heat power generation station. The heat storage is divided into three main forms of sensible heat storage, latent heat storage and chemical reaction heat storage according to the heat storage principle, wherein the sensible heat storage is most widely applied to a solar thermal power generation system due to the simple and mature technology and low cost. The unit volume heat capacity of latent heat storage is large, the temperature basically keeps unchanged during phase change, and the method is the most studied heat storage mode at present. The chemical reaction heat storage has no large-scale application example in industry because the technology is complex and the cost is high. Sensible heat storage materials include liquid materials: such as water, heat transfer oil and molten salts, and solid materials: such as cast iron, iron ore, pebbles, gravels, ceramics, high-temperature concrete, etc. The fused salt has strong corrosivity, very strong destructiveness to a heat exchange pipeline in a heat storage system, and high solidification temperature of the fused salt, so that extra facilities are required to be added to prevent the fused salt from being solidified, and the cost of the system is increased. The heat conduction oil cannot be used for storing heat at the temperature of more than 400 ℃ due to the limitation of the use temperature, the cost of working media and the cost of a system are high, and the economy of large-scale application is poor. Although the high-temperature concrete has the advantages of stable high-temperature performance, low investment cost, convenience in operation and maintenance, long service life and the like, the parameters of the heat transfer fluid in the heat release process are continuously reduced due to the defects of low heat storage density, low heat conductivity coefficient and the like, and the popularization and application of the high-temperature concrete in the field of power generation are limited.
The steam heat accumulator is widely applied to domestic and foreign waste heat utilization, solar thermal power generation and a plurality of intermittent steam occasions. But the defect of overhigh cost of the pressure container during large-capacity storage exists, and the application of the pressure container in a large-scale solar thermal power generation system is limited. Many technical researches for storing steam heat energy have been carried out at home and abroad, and Chinese patent CN102777874A proposes a phase-change heat storage system for directly generating steam and a preparation method of a phase-change heat storage agent, wherein graphite foam is adopted to reinforce a phase-change material, and the phase-change material is placed in a steam tank body. Chinese patent CN106287623A proposes a phase change heat storage type steam heat accumulator, in which phase change materials are uniformly arranged in a steam storage tank, so as to improve the heat storage density of the steam heat accumulator. However, the phase change material is arranged in the steam storage tank, so that the volume of the tank body is occupied, and certain cost is increased. Chinese patent CN106556165A proposes a solar steam heat storage system installed on the roof of a factory building, which uses a single steam heat accumulator to store steam heat. Chinese patents CN108061395A and CN107989759A propose a steam-heat energy storage system for a solar thermal power generation system, which uses concrete as a heat storage medium, and a plurality of steam-water separators are configured in the system to separate and adjust steam and water, so as to make good use of the material characteristics of steam and concrete. However, concrete is used for storing sensible heat, and the consumption of heat storage materials is large.
Disclosure of Invention
The invention aims to overcome the defect that the existing steam heat accumulator has overhigh cost when the volume is large, and provides a composite heat accumulation system which is simple in structure and low in cost by combining the basic principles of phase change heat accumulation and the traditional steam heat accumulator.
The invention adopts a method of combining a two-stage phase change heat reservoir and a steam storage tank, and selects a proper phase change material according to the temperature and pressure parameters of the steam heat charging and discharging process in the steam storage tank. The heat storage system comprises three parts, namely a first-stage phase-change heat reservoir, a steam storage tank and a second-stage phase-change heat reservoir. Water/steam is used as a heat transfer fluid for charging and discharging heat.
The main apparatus of the present invention is arranged in a bottom-up manner, depending on the thermophysical performance parameters of the water/steam and the operating process requirements. The first-stage phase-change heat reservoir is positioned at the bottom of the heat storage system, the steam storage tank is positioned in the middle of the heat storage system, and the second-stage phase-change heat reservoir is positioned at the top of the heat storage system. The upper part of the first-stage phase-change heat reservoir is connected with the lower part of the steam storage tank through a first heat exchange tube bundle, and the upper part of the steam storage tank is connected with the bottom of the second-stage phase-change heat reservoir through a second heat exchange tube bundle. The lower part of the first-stage phase-change heat reservoir is provided with a heat charging process steam distributor, a control valve and a connecting pipeline. The lower part of the first-stage phase-change heat reservoir is connected with a heat filling process steam distributor through a connecting pipeline, the heat filling process steam distributor is positioned below the first-stage phase-change heat reservoir, and a heat filling process valve is positioned at an inlet of the heat filling process steam distributor and used for adjusting the flow of steam during heat filling. And the upper part of the second-stage phase-change heat reservoir is provided with a heat release process steam collector, a heat release process valve and a connecting pipeline. The upper part of the second-stage phase-change heat reservoir is connected with a heat release process steam collector through a connecting pipeline, the heat release process steam collector is positioned at the upper part of the second-stage phase-change heat reservoir, and a heat release process valve is positioned at an outlet of the heat release process steam collector and used for regulating and controlling the steam flow in the heat release process. The primary phase-change heat reservoir and the secondary phase-change heat reservoir are both arranged in a manner of embedded heat exchange tube bundles, saturated water is in a heat exchange tube bundle in the primary phase-change heat reservoir, and saturated steam is in a heat exchange tube bundle in the secondary phase-change heat reservoir. The first-stage phase change heat reservoir is communicated with the steam storage tank through a second heat exchange tube bundle, the steam storage tank is communicated with the second-stage phase change heat reservoir through a first heat exchange tube bundle to jointly form a saturated steam space and a saturated water space, and the heat exchange tube bundle and the steam storage tank have the same pressure-bearing capacity. Parameters such as selection of phase change materials in the first-stage phase change heat reservoir and the second-stage phase change heat reservoir, arrangement mode of the heat exchange tube bundle, heat storage quantity and the like need to be designed according to heat transfer characteristics in heat charging and heat releasing processes.
The working principle of the heat storage system of the present invention during charging and discharging is described below.
A heat filling process: high-temperature superheated steam flows into the heat storage system through the heat exchange tube bundle in the first-stage phase-change heat reservoir, the steam with high temperature is mixed with saturated water in the heat storage system to release latent heat of condensation, so that the temperature of the saturated water in the heat storage system is increased, the volume of the water is increased, meanwhile, the first heat exchange tube bundle in the first-stage phase-change heat reservoir is heated, and then a first phase-change material in the first-stage phase-change heat reservoir is heated. Along with the process, the water volume in the heat storage system is gradually increased, the pressure is increased, the saturated steam temperature is also continuously increased, and the steam space is gradually reduced. In the process, heat exchange is realized between the saturated steam and the second heat exchange tube bundle of the secondary phase-change heat reservoir, so that the second phase-change material in the secondary phase-change heat reservoir is heated, and inorganic salts, metal alloys and the like can be selected as the phase-change material according to steam parameters. The phase change materials in the first-stage phase change heat reservoir and the second-stage phase change heat reservoir can be the same or different. Saturated steam is condensed back into the steam storage tank. When the steam pressure in the heat storage system reaches a set value, the heat charging process is finished.
An exothermic process: and closing the steam inlet valve, wherein the water and steam space of the heat storage system is in a closed space, and the closed space is a mixture of saturated water and saturated steam. And saturated steam is positioned at the top of the heat storage system under the action of gravity, namely the second heat exchange tube bundle of the secondary phase-change heat reservoir and the upper space of the steam storage tank, and the saturated water is positioned in the lower space of the steam storage tank and the first heat exchange tube bundle of the primary phase-change heat reservoir. And opening a steam outlet valve in the heat release process, and allowing saturated steam in the heat storage system to flow out through the steam outlet valve under the action of steam pressure difference. Because the space of saturated steam and saturated water is closed, the outflow of the saturated steam causes the reduction of the steam pressure in the whole space, so that the saturated water is flashed, and the saturated steam is continuously generated. The process of flashing saturated water to saturated steam releases latent heat of vaporization. The temperature is continuously reduced, a convection heat exchange process is generated when saturated steam flows through the heat exchange tube bundle of the secondary phase-change heat reservoir, and the phase-change material in the secondary phase-change heat reservoir is subjected to the processes of liquid temperature reduction, solidification and solid temperature reduction, so that the stored heat is released to heat the saturated steam. The temperature of saturated water in the heat storage system is continuously reduced, and the saturated water stored in the first heat exchange tube bundle in the first-stage phase-change heat reservoir has a cooling effect on the phase-change material, so that the phase-change material in the first-stage phase-change heat reservoir undergoes the processes of liquid temperature reduction, solidification and solid temperature reduction.
The invention has the advantages that the gravity action is fully utilized, the phase change material heat storage process is organically combined with the steam condensation and flash evaporation process in the heat storage system, meanwhile, the heat exchange tube bundle in the phase change heat storage device is communicated with the steam storage tank, and the formed closed space is used for storing saturated steam and saturated water, thereby reducing the volume of the steam storage tank. The application of the first-stage phase-change heat reservoir and the second-stage phase-change heat reservoir can further increase the heat storage capacity and reduce the volume of the steam storage tank.
The invention is suitable for a system in which the heat transfer fluid is water/steam in the heat charging and heat releasing processes, and has wide application prospect in the fields of solar high-temperature thermal power generation, solar medium-temperature steam boilers, steam waste heat application and the like.
Drawings
FIG. 1 is a schematic diagram of a hybrid heat reservoir of the present invention incorporating a steam storage tank;
FIG. 2 is a schematic diagram of a hybrid heat reservoir of the present invention configured with two steam storage tanks;
FIG. 3 is a schematic view of a phase change heat reservoir with finned heat exchange tubes as a heat exchange tube bundle according to the present invention;
FIG. 4 is a schematic view of a phase change heat reservoir with a serpentine heat exchange tube bundle according to the present invention;
in the figure: the system comprises a 1 heat charging process steam distributor, a 2 primary phase change heat reservoir, a 3 steam storage tank, a 3' steam storage tank, a 4 secondary phase change heat reservoir, a 5 heat discharging process steam collector, 6 micro superheated steam, 7 heat charging process valves, 8 saturated water, 9 first heat exchange tube bundles, 10 first phase change materials, 11 water vapor, 12 second heat exchange tube bundles, 13 second phase change materials, 14 heat discharging process valves, 15 heat discharging process steam, 16 gas-liquid interfaces, 17 heat dissipation fins and 18 serpentine heat exchange tubes.
Detailed Description
The invention is further described with reference to the following figures and detailed description.
As shown in fig. 1, the composite heat reservoir of the invention is formed by sequentially arranging a heat charging process steam distributor 1, a primary phase-change heat reservoir 2, a steam storage tank 3, a secondary phase-change heat reservoir 4, a heat discharging process steam collector 5, a heat charging process valve 7, a first heat exchange tube bundle 9, a first phase-change material 10, a second heat exchange tube bundle 12 and a second phase-change material 13 from bottom to top. The first-stage phase-change heat reservoir 2 is positioned at the bottom of the heat storage system, the steam storage tank 3 is positioned in the middle of the heat storage system, and the second-stage phase-change heat reservoir 4 is positioned at the top of the heat storage system. The lower parts of the upper primary phase-change heat reservoirs 2 of the primary phase-change heat reservoirs 2 are connected by a first heat exchange tube bundle 9, and the primary phase-change heat reservoirs 2 are communicated through the first heat exchange tube bundle 9; the upper part of the steam storage tank 3 is connected with the bottom of the second-stage phase-change heat reservoir 4 through a second heat exchange tube bundle 12, and the first-stage phase-change heat reservoir 2 is communicated with the second-stage phase-change heat reservoir 4 through the second heat exchange tube bundle 12. The first heat exchange tube bundle 9 penetrates through the first-stage phase-change heat reservoir 2, the upper portion of the first heat exchange tube bundle 9 is embedded in the steam storage tank 3, the lower portion of the first heat exchange tube bundle 9 is embedded in the heat charging process steam distributor 1, the first phase-change material 10 is located in the first-stage phase-change heat reservoir 2, and the first phase-change material 10 is a heat storage material such as inorganic salts and metal alloys. The first phase change material 10 is filled in a gap enclosed by the outer wall of the first heat exchange tube bundle 9 and the cavity of the first-stage phase change heat reservoir 2. The second heat exchange tube bundle 12 penetrates through the secondary phase-change heat reservoir 4, the lower part of the second heat exchange tube bundle 12 is embedded in the steam storage tank 3, the upper part of the second heat exchange tube bundle 12 is embedded in the heat release process steam collector 5, the second phase-change material 13 is located in the secondary phase-change heat reservoir 4, and the second phase-change material 13 is a heat storage material such as inorganic salt and metal alloy. The second phase change material 13 is filled in a gap defined by the outer wall of the second heat exchange tube bundle 12 and the cavity of the secondary phase change heat reservoir 4. The charging process valve 7 is located at the inlet of the charging process steam distributor 1 and the discharging process valve 14 is located at the outlet of the discharging process steam collector 5.
When the composite heat storage system is heated, the micro superheated steam 6 flows into the heating process steam distributor 1 through the heating process valve 7, the micro superheated steam 6 is dissolved into the saturated water 8 in the heating process steam distributor 1 to heat the saturated water 8, meanwhile, the liquid level of the saturated water 8 rises, the rising saturated water 8 slowly flows upwards in the first heat exchange tube bundle 9 of the primary phase-change heat reservoir 2, and heat is transferred to the first phase-change material 10 in the primary phase-change heat reservoir 2 in the flowing process. Because the micro superheated steam 6 is injected continuously, the water volume of the whole heat storage system is increased continuously, the pressure in the heat storage system is increased continuously, and the temperature of the steam 11 in the steam storage tank 3 is also increased continuously. The water vapor 11 with the increased temperature flows upwards to enter a second heat exchange tube bundle 12 in the secondary phase change heat reservoir 4, heat is transferred to a second phase change material 13 in the secondary phase change heat reservoir 4 in the flowing process, when the temperature of the second phase change material 13 is lower than the saturation temperature corresponding to the vapor pressure in the heat storage system, the water vapor 11 is cooled and condensed into condensed water, and the condensed water flows back to the steam storage tank 3 along the inner wall surface of the second heat exchange tube bundle 12 by means of gravity. When the temperature of the second phase change material 13 is close to the saturation temperature corresponding to the steam pressure in the heat storage system, the heat exchange amount between the steam 11 and the second phase change material 13 is small, the steam 11 cannot be cooled into condensed water, and the steam 11 stays in the second heat exchange tube bundle 12 and forms a steam space of the heat storage system together with the steam storage tank 3.
The heat release process is a saturated steam self-evaporation process, and is opposite to the heat charging process. When the composite heat storage system releases heat, the heat charging process valve 7 is closed, the heat releasing process valve 14 is opened, the pressure of an external space connected with the heat releasing process valve 14 in the composite heat storage system is kept to be higher than the pressure of the external space connected with the heat releasing process valve 14, and a space with steam pressure lower than the steam pressure in the heat reservoir is kept, saturated steam stored in the heat storage system is subjected to a self-evaporation phenomenon under the action of pressure difference, the saturated steam 11 is continuously evaporated, the rising saturated steam 11 slowly flows upwards in the second heat exchange tube bundle 12 in the second-stage phase change heat reservoir 4, the heat of a second phase change material 13 in the second-stage phase change heat reservoir 4 is absorbed in the flowing process, and the steam 11 flows out through the heat releasing process valve 14 after flowing into the heat releasing process steam collector 5 to. The gas-liquid interface 16 in the steam storage tank 3 is an interface of the saturated water 8 and the water vapor 11, and the gas-liquid interface 16 is kept moving up and down during the charging and discharging of heat. Along with the steam is continuously output from the heat release process valve 14, the steam space in the heat storage system is gradually increased, the water space is gradually reduced, and the pressure and the temperature of saturated water and saturated steam 11 are constantly reduced, so that the temperature of the saturated water in the first heat exchange tube bundle 9 in the first-stage phase-change heat reservoir 2 is lower than the temperature of the first phase-change material 10, the first phase-change material 10 transfers the heat to the saturated water through the wall surface of the first heat exchange tube bundle 9, and the stored heat is continuously released.
An embodiment of a set of phase change heat storage devices connected in parallel with two vapor storage tanks is described below with reference to fig. 2.
The heat storage system provided by the invention can be connected with a plurality of steam storage tanks 3 in parallel, and by taking fig. 2 as an example, a heat charging process steam distributor 1, a primary phase change heat reservoir 2, a steam storage tank 3', a secondary phase change heat reservoir 4, a heat discharging process steam collector 5, a heat charging process valve 7, a first heat exchange tube bundle 9, a first phase change material 10, a second heat exchange tube bundle 12 and a second phase change material 13 are sequentially arranged from bottom to top. The first heat exchange tube bundle 9 penetrates through the one-level phase-change heat reservoir 2, the upper portion of the first heat exchange tube bundle 9 is respectively embedded in the steam storage tank 3 and the steam storage tank 3', the lower portion of the first heat exchange tube bundle 9 is embedded in the heat filling process steam distributor 1, the first phase-change material 10 is located in the one-level phase-change heat reservoir 2, and the first phase-change material 10 is filled in a gap formed by the outer wall of the first heat exchange tube bundle 9 and the cavity of the one-level phase-change heat reservoir 2. The second heat exchange tube bundle 12 penetrates through the second-stage phase-change heat reservoir 4, the lower portion of the second heat exchange tube bundle 12 is embedded in the steam storage tank 3 and the steam storage tank 3', the upper portion of the second heat exchange tube bundle 12 is embedded in the heat release process steam collector 5, the second phase-change material 13 is located in the second-stage phase-change heat reservoir 4, and the second phase-change material 13 is filled in a gap formed by the outer wall of the second heat exchange tube bundle 12 and the cavity of the phase-change heat reservoir 4. The charging process valve 7 is located at the inlet of the charging process steam distributor 1 and the discharging process valve 14 is located at the outlet of the discharging process steam collector 5.
When the heat storage system provided by the invention is used for heating, micro superheated steam 6 flows into the heat filling process steam distributor 1 through the heat filling process valve 7, the micro superheated steam 6 is dissolved into saturated water 8 in the heat filling process steam distributor 1 to heat the saturated water 8, meanwhile, the liquid level of the saturated water 8 rises, the rising saturated water 8 slowly flows upwards in the first heat exchange tube bundle 9 of the primary phase change heat reservoir 2, and heat is transferred to the first phase change material 10 in the primary phase change heat reservoir 2 in the flowing process. Because the micro superheated steam 6 is injected continuously, the water volume of the whole heat storage system is increased continuously, the pressure in the system is increased continuously, and the temperature of the steam 11 in the steam storage tank 3 and the steam storage tank 3' is also increased continuously. The water vapor 11 with the increased temperature flows upwards to enter a second heat exchange tube bundle 12 in the secondary phase change heat reservoir 4, heat is transferred to a second phase change material 13 in the secondary phase change heat reservoir 4 in the flowing process, when the temperature of the second phase change material 13 is lower than the saturation temperature corresponding to the vapor pressure in the system, the water vapor 11 is cooled and condensed into condensed water, and the condensed water flows back to the steam storage tank 3 and the steam storage tank 3' along the inner wall surface of the second heat exchange tube bundle 12 by means of gravity. When the temperature of the second phase change material 13 is close to the saturation temperature corresponding to the steam pressure in the system, the heat exchange amount between the steam 11 and the second phase change material 13 is very small, the steam 11 cannot be cooled into condensed water, and the steam 11 stays in the second heat exchange tube bundle 12 to form a steam space of the heat storage system together with the steam storage tank 3 and the steam storage tank 3'.
The heat release process is a saturated steam self-evaporation process, and is opposite to the heat charging process. When the composite heat reservoir releases heat, the heat charging process valve 7 is closed, the heat releasing process valve 14 is opened, the steam pressure in the composite heat reservoir is kept higher than the pressure of an external space connected with the heat releasing process valve 14, saturated steam in the heat reservoir generates a self-evaporation phenomenon under the action of pressure difference, the saturated steam 11 is continuously evaporated, the rising saturated steam 11 slowly flows upwards in the second heat exchange tube bundle 12 in the secondary phase change heat reservoir 4, the heat of a second phase change material 13 in the secondary phase change heat reservoir 4 is absorbed in the flowing process, and the steam 11 flows out through the heat releasing process valve 14 after flowing into the heat releasing process steam collector 5 to form heat releasing process steam 15. The gas-liquid interface 16 in the steam storage tank 3 and the steam storage tank 3' is an interface of the saturated water 8 and the water vapor 11, and is kept moving up and down during the charging and discharging of heat. Along with the continuous output from valve 14 of steam, the gas space in the heat-retaining system is crescent, and the water space reduces gradually, and the pressure and the temperature of saturated water and saturated steam constantly reduce for the saturated water temperature in first heat exchanger tube bank 9 in one-level phase change heat reservoir 2 is less than the temperature of first phase change material 10, and first phase change material 10 transmits the heat to the saturated water through the wall of first heat exchanger tube bank 9, and the heat of storage obtains constantly releasing.
The steam storage tank 3 and the steam storage tank 3' in fig. 2 can be used in parallel, or can be operated independently by arranging a corresponding regulation system. Two or more steam storage tanks can share one set of primary phase change heat storage 2 and one set of secondary phase change heat storage 4. Because the large-capacity steam storage tank is high in manufacturing cost, the large-capacity steam storage can be realized by connecting a plurality of low-capacity steam storage tanks with relatively low cost in parallel.
Fig. 3 is a schematic diagram of a phase change heat reservoir with finned heat exchange tubes, and the outer tube wall of the first heat exchange tube bundle 9 in the primary phase change heat reservoir 2 shown in fig. 1 and 2 and the outer tube wall of the second heat exchange tube bundle 12 in the secondary phase change heat reservoir 4 may be provided with needle-shaped, column-shaped, or strip-shaped heat dissipation fins 17, which are intended to increase the contact area between the first heat exchange tube bundle 9 and the first phase change material 10, and between the second heat exchange tube bundle 12 and the second phase change material 13, and to improve the heat transfer rate of the primary phase change heat reservoir 2 or the secondary phase change heat reservoir 4 in the processes of charging and discharging heat.
Fig. 4 is a schematic diagram of a phase change heat reservoir with serpentine heat exchange tubes, and for the primary phase change heat reservoir 2 and the secondary phase change heat reservoir 4 shown in fig. 1 and 2, the serpentine heat exchange tubes 18 are used to replace the first heat exchange tube bundle 9 and the second heat exchange tube bundle 12, so that the contact area between the first heat exchange tube bundle 9 and the first phase change material 10, and the contact area between the second heat exchange tube bundle 12 and the second phase change material 13 can be increased, and the heat transfer rate of the primary phase change heat reservoir 2 or the secondary phase change heat reservoir 4 in the processes of heat charging and heat releasing can be increased.
Claims (6)
1. The utility model provides a compound heat-retaining system with two-stage phase transition heat-retaining device and steam storage tank which characterized in that: the composite heat storage system comprises a primary phase-change heat reservoir (2), a steam storage tank (3) and a secondary phase-change heat reservoir (4); the primary phase-change heat reservoir (2), the steam storage tank (3) and the secondary phase-change heat reservoir (4) are arranged from bottom to top: the primary phase-change heat reservoir (2) is positioned at the bottom of the heat storage system, the steam storage tank (3) is positioned in the middle, and the secondary phase-change heat reservoir (4) is positioned at the top; the upper part of the first-stage phase-change heat reservoir (2) is connected with the lower part of the steam storage tank (3) through a first heat exchange tube bundle (9), and the upper part of the steam storage tank (3) is connected with the bottom of the second-stage phase-change heat reservoir (4) through a second heat exchange tube bundle (12).
2. The composite thermal storage system of claim 1, wherein: the lower part of the first-stage phase change heat reservoir (2) is connected with the heat charging process steam distributor (1) through a connecting pipeline; the heat charging process valve (7) is positioned at the inlet of the heat charging process steam distributor (1) and is used for adjusting the flow of the heat charging steam; the upper part of the second-stage phase change heat reservoir (4) is provided with a heat release process steam collector (5), a heat release process valve (14) and a connecting pipeline; the upper part of the secondary phase-change heat reservoir (4) is connected with the heat release process steam collector (5) through a connecting pipeline, and a heat release process valve (14) is positioned at the outlet of the heat release process steam collector (5) and used for regulating and controlling the steam flow in the heat release process; the primary phase-change heat reservoir (2) and the secondary phase-change heat reservoir (4) are both arranged in a manner of embedded heat exchange tube bundles, a first heat exchange tube bundle (9) embedded in the primary phase-change heat reservoir (2) is saturated water, and a second heat exchange tube bundle (12) embedded in the secondary phase-change heat reservoir (4) is saturated steam; the primary phase-change heat reservoir (2) is communicated with the steam storage tank (3) through a first heat exchange tube bundle (9), the steam storage tank (3) is communicated with the secondary phase-change heat reservoir (4) through a second heat exchange tube bundle (12) to jointly form a saturated steam space and a saturated water space, and the heat exchange tube bundles and the steam storage tank have the same pressure-bearing capacity.
3. The composite thermal storage system of claim 2, wherein: a first heat exchange tube bundle (9) penetrates through the primary phase-change heat reservoir (2), the upper part of the first heat exchange tube bundle (9) is embedded in the steam storage tank (3), and the lower part of the first heat exchange tube bundle (9) is embedded in the steam distributor (1) in the heat charging process; the first phase-change material (10) is positioned in the primary phase-change heat reservoir (2), and the first phase-change material (10) is filled in a gap formed by the outer wall of the first heat exchange tube bundle (9) and the cavity of the primary phase-change reservoir (2); second heat exchange tube bank (12) run through second grade phase change heat reservoir (4), the lower part of second heat exchange tube bank (12) is buried in steam storage tank (3), the upper portion of second heat exchange tube bank (12) is buried in exothermic process steam collector (5), second phase change material (13) are located second grade phase change heat reservoir (4), second phase change material (13) are full of in the space that the outer wall of second heat exchange tube bank (12) and second grade phase change heat reservoir (4) cavity enclose.
4. The composite thermal storage system of claim 2, wherein: and needle-shaped, cylindrical or bar-shaped radiating fins (17) are arranged on the outer pipe wall of the first heat exchange pipe bundle (9) of the first-stage phase-change heat reservoir (2) and the outer pipe wall of the second heat exchange pipe bundle (12) of the second-stage phase-change heat reservoir (4).
5. The composite heat storage system according to claim 2 or 3, characterized in that: when the heat storage system is heated, micro superheated steam (6) flows into the heat filling process steam distributor (1) through the heat filling process valve (7), the micro superheated steam (6) is dissolved into saturated water (8) in the heat filling process steam distributor (1) to heat the saturated water (8), meanwhile, the liquid level of the saturated water (8) rises, the rising saturated water (8) flows upwards in a first heat exchange tube bundle (9) of the first-stage phase-change heat reservoir (2), and heat is transferred to a first phase-change material (10) in the first-stage phase-change heat reservoir (2) in the flowing process; because the micro superheated steam (6) is injected continuously, the water volume of the whole heat storage system is increased continuously, the pressure in the heat storage system is increased continuously, and the temperature of the steam (11) in the steam storage tank (3) is also increased continuously; the water vapor (11) with the increased temperature flows upwards to enter a second heat exchange tube bundle (12) in the secondary phase-change heat reservoir (4), and heat is transferred to a second phase-change material (13) in the secondary phase-change heat reservoir (4) in the flowing process; when the temperature of the second phase change material (13) is lower than the saturation temperature corresponding to the steam pressure in the heat storage system, the steam (11) is cooled and condensed into condensed water, and the condensed water flows back to the steam storage tank (3) along the inner wall surface of the second heat exchange tube bundle (12) by means of gravity; when the temperature of the second phase change material (13) is close to the saturation temperature corresponding to the steam pressure in the heat storage system, the heat exchange amount between the steam (11) and the second phase change material (13) is small, the steam (11) cannot be cooled into condensed water, and the steam (11) stays in the second heat exchange tube bundle (12) and forms a gas space of the heat storage system together with the steam storage tank (3).
6. The composite heat storage system according to claim 2 or 3, characterized in that: when the heat storage system releases heat, the heat charging process valve (7) is closed, the heat releasing process valve (14) is opened, the steam pressure in the composite heat storage system is kept higher than the pressure of an external space connected with the heat releasing process valve (14), under the action of pressure difference, saturated steam in the composite heat storage system generates a self-evaporation phenomenon and continuously evaporates saturated steam (11), the ascending saturated steam (11) flows upwards in a second heat exchange tube bundle (12) in the secondary phase-change heat reservoir (4), the heat of a second phase-change material (13) in the secondary phase-change heat reservoir (4) is absorbed in the flowing process, and the steam (11) flows into the heat releasing process steam collector (5) and then flows out through the heat releasing process valve (14) to form heat releasing process steam (15); the gas-liquid interface (16) in the steam storage tank (3) is the interface of saturated water (8) and water vapor (11), and the gas-liquid interface (16) in the steam storage tank (3) keeps moving up and down in the processes of heat filling and heat releasing; along with the continuous follow heat release process valve (14) output of vapor, the vapor space in the heat-retaining system increases gradually, and the water space reduces gradually, and the pressure and the temperature of saturated water and saturated vapor constantly reduce for the saturated water temperature in first heat exchanger tube bank (9) in one-level heat reservoir (2) is less than the temperature of first phase change material (10), and first phase change material (10) give saturated water with heat through the wall transmission of first heat exchanger tube bank (9), and the heat of storage obtains constantly releasing.
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| CN111278255B (en) * | 2019-12-31 | 2021-09-21 | 南京理工大学 | Phase change heat storage device based on condensation heat transfer and key parameter determination method thereof |
| CN113028874A (en) * | 2020-02-18 | 2021-06-25 | 强野机械科技(上海)有限公司 | Step phase change heat reservoir |
| CN112414193B (en) * | 2020-12-22 | 2022-04-22 | 华北电力大学 | Multi-cascade phase change heat storage device with built-in fins and enhanced heat transfer method |
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