CN110273778B - Heater for Stirling engine and Stirling cycle system - Google Patents
Heater for Stirling engine and Stirling cycle system Download PDFInfo
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- CN110273778B CN110273778B CN201810205051.6A CN201810205051A CN110273778B CN 110273778 B CN110273778 B CN 110273778B CN 201810205051 A CN201810205051 A CN 201810205051A CN 110273778 B CN110273778 B CN 110273778B
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02G—HOT GAS OR COMBUSTION-PRODUCT POSITIVE-DISPLACEMENT ENGINE PLANTS; USE OF WASTE HEAT OF COMBUSTION ENGINES; NOT OTHERWISE PROVIDED FOR
- F02G1/00—Hot gas positive-displacement engine plants
- F02G1/04—Hot gas positive-displacement engine plants of closed-cycle type
- F02G1/043—Hot gas positive-displacement engine plants of closed-cycle type the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines
- F02G1/053—Component parts or details
- F02G1/055—Heaters or coolers
Abstract
The invention discloses a heater for a Stirling engine, which comprises a tube body and a cavity formed by the tube body, wherein a heat storage part is arranged in the cavity; one end of the tube body is connected with an expansion cavity of the Stirling engine, and the other end of the tube body is connected with a heat regenerator of the Stirling engine; the heat storage component is contacted with the gas working medium to change the flow characteristic of the heat storage component, strengthen the heat exchange between the gas working medium and the wall surface of the pipe body, and promote the heat absorption of the gas working medium in the heater; and simultaneously, the heat storage component absorbs and stores compression heat generated by compression carried by the gas working medium in the expansion cavity. The heater for the Stirling engine can reduce the thermal fatigue of the heater component, control the wall temperature in the heater structure, reduce the risk of tube explosion of the heater, prolong the service life of the heater and improve the overall efficiency and output work.
Description
Technical Field
The present invention relates to a heater for a stirling engine, and to a stirling cycle system using the heater.
Background
The Stirling engine is an external combustion engine, and the external combustion engine avoids the problem of the traditional internal combustion engine of performing work through vibration explosion, and has the characteristics of high efficiency, low noise, low pollution and low running cost. The external combustion engine may burn various combustible gases, such as: natural gas, marsh gas, liquid fuel such as diesel oil, liquefied petroleum gas, etc. can also be combusted. Stirling engines are also widely used as refrigerators, heat pumps or pressure generators, and their combination with solar energy is also attracting increasing attention as new energy sources are emerging.
The ideal Stirling cycle consists of four processes of isothermal expansion, isothermal heat release, isothermal compression, and isothermal heat absorption. The heater is a key part of the Stirling engine. And the most critical part of the heater is the heating pipe body of the heater. Since the heater determines the highest temperature inside the whole Stirling engine, it is also the system power source of the Stirling engine.
In an actual Stirling cycle, on one hand, the compression and expansion processes of working media can cause the temperature of the working media in the pipe to fluctuate greatly, so that the materials of the heating pipe body are easy to generate thermal fatigue. On the other hand, the heat of compression generated by the compression of the working medium may cause the temperature of the gas working medium in the heater tube body to be higher than the wall surface temperature of the heater tube body, which presents challenges for the temperature resistance and service life of the heater tube body material. The problems in the existing heater not only can reduce the overall efficiency of the Stirling engine, but also can cause the overtemperature tube explosion of the heating tube body when severe, so that the Stirling engine cannot operate.
Therefore, the heater in the existing Stirling engine has the problem of limited service life caused by thermal fatigue and compression heat generated by a gas working medium to heat a heating pipe body, and the problem that the heating pipe body bursts and the like can occur in serious cases. In addition, if the design is carried out according to the highest temperature that the heater pipe body can bear in consideration of the heating effect of the compression heat generated when the gas working medium is compressed on the heater pipe wall, the input heat of the Stirling engine is limited, so that the improvement of the output work and the efficiency of the whole machine is limited.
Disclosure of Invention
The invention provides a novel heat accumulating type Stirling heater, which aims at the defects of short service life, easy tube explosion and the like of the existing Stirling engine, and the heat accumulating part is arranged in the heater, so that heat exchange between a reinforced gas working medium and the wall surface (equivalent to an external heat source) of the tube body of the heater is realized, the heat absorption of the gas working medium in the heater is promoted, and compression heat carried by the gas working medium and generated due to compression is absorbed and stored, thereby effectively reducing the thermal fatigue of the heater part and effectively controlling the wall surface temperature of the heater to ensure that the heater operates at the design temperature.
The heater for the Stirling engine comprises a tube body and a cavity formed by the tube body, wherein a heat storage part is arranged in the cavity; one end of the tube body is connected with an expansion cavity of the Stirling engine, and the other end of the tube body is connected with a heat regenerator of the Stirling engine; the heat storage component is arranged in a gas working medium flow path of the heater, and is contacted with the gas working medium to change the flow characteristic of the heat storage component, so that the heat exchange between the gas working medium and the wall surface of the pipe body is enhanced, and the heat absorption of the gas working medium in the heater is promoted; and simultaneously, the heat storage component absorbs and stores compression heat generated by compression carried by the gas working medium in the expansion cavity. By introducing the heat storage component into the heater, more turbulence is generated in the working medium gas in the heater, and the heat exchange effect between the working medium gas in the heater and an external heat source is enhanced.
In the heater for a stirling engine of the present invention, the heat storage member is preferably a porous medium including at least one of stacked wire mesh, metal fiber, foamed metal or sintered metal. By taking the porous medium as the heat storage component and utilizing the metal sensible heat mode to store and release heat, the porous medium heat storage component has larger heat exchange area, so that the gas working medium and the heat storage component have good heat exchange effect.
In the heater for a stirling engine of the present invention, the heat storage member is preferably a phase change member composed of a phase change material, and a wire mesh for fixing the phase change member in the chamber. The phase change component is used as the heat storage component, and the gas working medium and the heat storage component have good heat exchange effect by utilizing latent heat exchange.
In the heater for a stirling engine of the present invention, the heat storage member is a wire. By taking the metal wire as the heat storage part, the contact between the heat storage part and a heating pipe in the heater is reduced, so that a good heat exchange effect is achieved between the gas working medium and the heat storage part.
In the heater for a Stirling engine of the present invention, the wire is disposed in the chamber in parallel with and in non-contact with the tube.
In the heater for Stirling engine of the present invention, the wire is in the form of a spiral or has a screw structure, protrusions and/or grooves on its surface. The heat exchange area between the heat storage part and the gas working medium is increased by arranging the structure of the metal wire itself into a spiral shape, or a thread structure, a bulge and/or a groove are additionally arranged on the surface of the metal wire, so that the gas working medium is further turbulent, and the heat exchange between the gas working medium and an external heat source is enhanced.
In the heater for a Stirling engine of the present invention, the heat storage member includes a sleeve and a heat storage material disposed within the sleeve; the sleeve is arranged in the cavity, and a flow path for the gas working medium to flow is formed between the inner wall of the cavity and the outer wall of the sleeve. By adopting the sleeve and the mode of configuring the heat storage material in the sleeve, the gas working medium and the heat storage component have good heat exchange effect.
In the heater for a Stirling engine of the present invention, the heat storage material is preferably a porous medium, a phase change material or a chemical heat storage material.
In the heater for a Stirling engine of the invention, the outer wall of the sleeve has a raised or threaded configuration. Thereby generating more turbulence in the gas working medium in the heater and enhancing the heat exchange effect between the gas working medium in the heater and an external heat source.
The invention also provides a Stirling cycle system using the heater, which further comprises an expansion cavity and a compression cavity, wherein a regenerator is arranged between the expansion cavity and the compression cavity, the heater is arranged on one side of the expansion cavity, and a cooler is arranged on one side of the compression cavity; the heat storage component is used for absorbing and storing compression heat generated by compression carried by the gas working medium in the expansion cavity.
Compared with the prior art, the invention has the following advantages:
according to the heater with the heat storage component, the heat storage component arranged in the heating pipe is arranged in the flow path of the gas working medium, so that compression heat carried by the gas working medium in the expansion cavity and generated due to compression is absorbed and stored, heat exchange between the gas working medium and the wall surface of the pipe body can be enhanced, and heat absorption of the gas working medium in the heater is promoted.
Therefore, under the condition of given same heat flow, the heater can reduce temperature fluctuation in the working medium gas circulation process and reduce the influence of thermal fatigue on the heater, thereby prolonging the service life of the heater.
Meanwhile, under the condition that the highest bearing temperature of the metal material of the pipe body of the given heater is the same, the heat storage part is arranged in the heater, so that the heat storage part can absorb and store compression heat carried by the gas working medium in the expansion cavity and generated by compression, the pipe body can bear larger heat flow, and the output work and efficiency of the whole machine are effectively improved.
Drawings
Fig. 1 is a schematic view of the structure of an α -type stirling engine to which the heater of the present invention is applied.
FIG. 2 is a schematic view of a heater for a Stirling engine according to the invention in embodiment 1;
FIG. 3 is a schematic view of a heater for a Stirling engine according to the invention in embodiment 2;
FIG. 4 is a schematic view of a heater for a Stirling engine according to the invention in embodiment 3;
FIG. 5 is a schematic view of a heater for a Stirling engine according to the invention in embodiment 4;
FIG. 6 is a graph showing the relationship between the crank angle and the gas working medium temperature of an alpha type Stirling engine to which the heater of the present invention is applied in example 5;
fig. 7 is a graph of the gas working substance P-V of the α -stirling engine of example 5 to which the heater of the present invention is applied.
Reference numerals illustrate:
1-a heater; a-a heat storage member; b-a tube body; 3-a tube body;
2-porous media; 4-phase change material forming a phase change member; 5-silk screen; 6-wire; 7-a sleeve; 8-a heat storage material;
10-an expansion chamber; 11-a regenerator; 12-a cooler; 13-compression chambers.
Detailed Description
The present invention will be described in further detail with reference to the following specific examples and drawings. The implementation of the present invention is not limited to the following embodiments, and various modifications, changes, combinations and improvements of the technical concept of the present invention, which are adopted within the knowledge of those skilled in the art, are all within the scope of the present invention.
Fig. 1 is a schematic view showing a structure in which the heater 1 of the present invention is applied to an α -type stirling engine. The gas working medium is heated by an external heat source (not shown) in the heater 1, and is heated and expanded to push a piston in the expansion cavity 10 to do work, and in the process, the temperature of the gas is kept unchanged under the action of the external heat source; then, the piston of the expansion chamber 10 and the piston of the compression chamber 13 synchronously move to the right direction in the drawing, and the gas working medium enters the regenerator 11 to store part of heat therein for an isovolumetric cooling process; the gas working medium entering the compression cavity 13 is compressed under the pushing of the piston in the compression cavity 13, and the generated heat is absorbed by the cooler 12; the compressed gas working medium reversely flows through the heat regenerator 11, and after the heat regenerator 11 absorbs a certain amount of heat, the gas working medium enters the heater 1 to absorb heat from an external heat source and enters the expansion cavity 10 to do work. The Stirling engine is driven by an external heat source to output mechanical work. The heater 1 is composed of a heat storage part a and a pipe body b, wherein the heat storage part a is positioned in a cavity formed by the pipe body b, and compression heat, generated in the compression process in the Stirling gas circulation process, carried by the gas working medium entering the cavity of the heater 1 can be absorbed and stored by the heat storage part a in the heater 1, so that the condition that the temperature is too high after the gas working medium absorbs the compression heat is avoided, and the gas working medium is prevented from heating and heating the wall surfaces of the heater 1 and the pipe body b to cause the temperature exceeding the working temperature and even cause pipe explosion at the too high temperature. When the gas working medium is cooled due to expansion, the heat storage part a can release the stored heat and absorb the stored heat by the gas working medium. Therefore, the invention reduces the temperature fluctuation of the gas working medium in the heater, thereby reducing the thermal fatigue of the heater and prolonging the service life of the heating pipe.
Meanwhile, under the condition of the given highest operation temperature of the heating pipe, the heater 1 provided with the heat storage part a can bear larger heat flow of the gas working medium; or, the storage heater 1 can work under an external heat source with higher temperature, so that the whole output work and efficiency of the Stirling engine are obviously improved.
Example 1
As shown in fig. 2, the storage heater 1 in the present embodiment includes two parts: a porous medium 2 (i.e., the heat storage member a of the present invention) and a tube body 3 of the heater 1. The heat storage member a here is constituted by using a porous medium 2 made of a metal material, mainly one or a combination of a stacked wire mesh, metal fiber, foamed metal, sintered metal, or the like. The porous medium 2 is arranged in a cavity formed by the pipe body 3 of the heater 1, and stores heat and releases heat by utilizing a metal sensible heat mode. The tube body 3 of the heater 1 may be made of a stainless steel material, and serves to support the heat storage member a (i.e., the porous medium 2) at the same time.
In the invention, the porous medium 2 is arranged in the cavity formed by the pipe body 3, so that the heat exchange area is large, and a good heat exchange effect between the gas working medium and the heat storage part a can be realized. By using the porous medium 2 made of metal material as the heat storage component a, heat storage and heat release can be performed by fully utilizing the sensible heat of metal, and meanwhile, the heat storage component is ensured to have a larger heat exchange area by utilizing the characteristic that the porous medium has a larger specific surface area, so that a good heat exchange effect is achieved between the gas working medium and the heat storage component a. Furthermore, according to the field synergy theory, it is known that: the convective heat exchange intensity of the fluid depends on the degree of synergy of the velocity field and the hot flow field, and under the same boundary condition, the higher the degree of synergy of the velocity field and the hot flow field is, the higher the heat exchange intensity is. In this embodiment, by disposing the heat storage member a of the porous medium 2 structure in the chamber formed by the tube body 3, the radial temperature distribution of the gas working medium tends to be uniform, and the direction of the temperature gradient of the gas flow in the chamber formed by the tube body 3 is closer to the axial direction. Namely, the included angle between the speed field and the heat flow field of the gas working medium is reduced, and the convective heat transfer is obviously enhanced. Therefore, the porous medium 2 is arranged in the cavity formed by the pipe body 3, so that the heat storage and heat release effects on the heat carried by the gas working medium can be realized in the heater 1, the problem of pipe explosion caused by the unavoidable compression heat in the system is solved, the convection heat exchange of the gas working medium in the heater of the Stirling engine is effectively enhanced, and the heat exchange between the gas working medium and an external heat source is promoted.
Example 2
The names and actions of the components in embodiment 2 are the same as those in embodiment 1, and are not repeated, and only the differences are described in a targeted manner.
As a modification of the porous medium 2 in embodiment 1, as shown in fig. 3, the phase change member 4 composed of a phase change material is employed as the heat storage member a in this embodiment. Specifically, the phase change member 4 is made of a plurality of phase change capsules, the phase change capsules are stacked and arranged in a cavity formed by the tube body 3 of the heater 1, and two ends of the phase change member 4 are fixed by stainless steel wire meshes 5, so that the phase change member 4 formed of the phase change material is prevented from flowing out of the tube body 1 of the heater 1 along with the oscillation flow of the gas working medium. In other embodiments, stacked wire mesh may be optionally used as a support structure, with the phase change member 4 of phase change material disposed in a skeleton formed by the stacked wire mesh.
The phase change capsule is a granular energy storage material which is made of a phase change material serving as a capsule core and organic or inorganic polymers, metals (metal alloys can be also used) and the like serving as capsule walls. The phase change material has larger specific heat capacity and specific surface area and good heat exchange performance; compared with sensible heat storage, the heater 1 adopting the phase change part 4 as the heat storage part a has the advantages of large heat storage density and small temperature fluctuation. By using the phase change material 4 as the heat storage member a and utilizing the latent heat of the phase change material to make the heat storage member a have a larger heat storage density, the resistance of the heat storage member a to the flow of the gas working medium in the pipe body 3 of the heater 1 can be reduced, and the heat exchange efficiency between the gas working medium and the heat storage member a can be further improved.
For the operation principle and process of the heater in the present embodiment, for example, when the gas working medium flows from the heater 1 to the regenerator 11 and the cooler 12, the gas working medium inside the heater 1 is compressed, generating a part of the compression heat. Because the temperature of the gas working medium is higher at this moment, the phase change capsule absorbs a part of compression heat carried by the gas working medium to reduce the temperature of the gas working medium, and the normal temperature difference between the pipe wall of the pipe body 3 of the heater 1 and the gas is maintained, so that the heating effect of the gas working medium on the pipe wall is prevented, and the temperature of the pipe body 3 of the heater 1 is increased to even cause pipe explosion. In the process, the capsule wall of the phase-change capsule adopts a material with a higher melting point, and remains solid; the capsule core adopts a phase change material with a slightly lower melting point, absorbs heat under the influence of high-temperature gas working medium to generate phase change, and is converted from solid state to liquid state. When the gas working medium flows from the cooler 12 and the heat regenerator 11 to the heater 1, the temperature of the gas working medium in the heater 1 is lower, at the moment, the phase change capsule releases heat absorbed in the previous process, the capsule wall of the phase change capsule is still solid, and the heat released by the capsule core is changed from liquid to solid, so that the gas working medium is heated, the temperature difference between the low-temperature gas working medium and the pipe wall of the heater 1 is prevented from being overlarge, the alternating stress is prevented from being overlarge, and the thermal fatigue of the heater is reduced, and the service life of the pipe is prolonged.
Example 3
The names and actions of the components in embodiment 3 are the same as those in embodiment 1, and are not repeated, and only the differences are described in a targeted manner.
As shown in fig. 4, the heat storage member a in this embodiment employs a wire 6. The processing technology of the metal wire is simple, the cost is low, and the whole heat capacity of the heat storage part a is easy to adjust by adjusting the thickness or the number of the metal wire. The metal wire 6 is arranged in the tube of the heater 1, is not in direct contact with the tube wall of the tube body 3, and is arranged in the cavity of the heater 1 in a manner of being parallel to the flow direction of the tube body 3 and the gas working medium of the heater 1. Both ends of the wire 6 are welded to both sides of the inside of the tube body 3 of the heater 1 to thereby achieve fixation. Compared with the porous medium 2 type heat storage part, the metal wire structure adopted in the embodiment can effectively reduce the flow resistance of the gas working medium.
In addition, in practical application, the porous medium is easy to be in direct contact with the pipe wall of the pipe body 3 of the heater 1, so that the porous medium can be kept at a higher temperature in a cycle period in many cases, and the temperature of the gas working medium is also very high when the gas working medium is compressed to carry compression heat, so that the temperature difference between the heat storage part of the porous medium and the gas working medium is smaller, and the heat storage capacity of the heat storage part of the porous medium is limited. The heat storage part in the form of the metal wire 6 is alternatively adopted, so that the heat storage part can be prevented from being in direct large-area contact with the pipe wall of the heater 1, the metal wire 6 is not in contact with the inner wall of the chamber, and the damage to the inner wall caused by scraping with the inner wall can be prevented; meanwhile, because the heat storage part wire 6 can not directly absorb heat from an external heat source from the inner wall of the chamber, the solid temperature of the wire 6 is lower, and the wire is mainly used for absorbing compression heat generated by compression of a gas working medium in the chamber. Thereby increasing the heat exchange temperature difference with the gas working medium and increasing the heat storage capacity of the heat storage part.
The above describes a basic implementation of the heat storage member a using the wire 6, as shown in fig. 4 (a) which is a schematic diagram of the wire. Fig. 4 (b) is a schematic view of a wire in a spiral shape, fig. 4 (c) is a schematic view of a wire having grooves and protrusions on the surface thereof, fig. 4 (d) is a partially enlarged view of the wire shown in fig. 4 (c), fig. 4 (e) is a schematic view of a wire having threads on the surface thereof, and fig. 4 (f) is a schematic view of the wire shown in fig. 4 (e) in front view and in cross-sectional view. As shown in fig. 4 (b) - (f), the wire 6 is further helical or has a thread structure, and/or protrusions and/or grooves on its surface. By arranging the structure of the metal wire 6 into a spiral shape, the heat exchange area between the heat storage part a and the gas working medium can be increased in a certain cavity space. Or a thread structure and/or protrusions and/or grooves are additionally arranged on the surface of the metal wire 6, so that heat transfer between working medium gas and the metal wire 6 is further promoted, and the heat absorption and release efficiency of the heat storage part a is improved. Further, the metal wire 6 and the thread structure or the protrusion or groove structure arranged on the surface of the metal wire can destroy the flow field of the gas working medium in the pipe body 3 of the heater 1, destroy the flowing boundary layer and strengthen the heat transfer of the gas working medium and the heat exchange between the gas working medium and an external heat source.
Example 4
The names and actions of the components in embodiment 4 are the same as those in embodiment 1, and are not repeated, and only the differences are described in a targeted manner.
As shown in fig. 5, the heat storage member a employs a cooperative combination of the sleeve 7 and the heat storage material 8. The metal sleeve 7 has a pipe diameter smaller than that of the pipe body 3 of the heater 1 and is disposed in the pipe body 3 of the heater 1. The sleeve 7 is not in direct contact with the pipe wall of the pipe body 3, and is parallel to the flow direction of the pipe body 3 and the gas working medium, so that the gas working medium can flow through an annular channel between the pipe wall of the pipe body 3 of the heater 1 and the metal sleeve 7, and a heat storage material is arranged in the metal sleeve 7. By adopting the sleeve 7 and the manner in which the heat storage material 8 is disposed therein, the heat storage member a can be prefabricated in advance, and the sleeve 7 together with the heat storage material 8 can be directly fitted into the heater 1, improving workability and fitting performance.
The metal sleeve 7 separates the gas working medium and the heat storage material, plays a role in supporting and protecting the heat storage material, and stainless steel with good heat conduction performance and heat resistance can be adopted as a suitable sleeve material in the invention.
Suitable thermal storage materials 8 in the present invention include any of sensible heat storage materials, latent heat storage materials, and chemical heat storage materials. The heat storage material 8 in the sleeve 7 is not particularly limited, and for example, when a porous medium is used, the porous medium can be fixed by the sleeve 7, and heat transfer between the gas working medium and the porous medium can be realized by utilizing a flow path formed between the inner wall of the chamber and the outer wall of the sleeve and a flow path formed by the porous medium, and when a phase change material or a chemical heat storage material is used, both ends of the sleeve can be closed to be used as a container of the heat storage material. The sensible heat storage material comprises stainless steel and Li 2 O、Al 2 O 3 And TiO 2 A mixed material formed by sintering at a constant temperature; the latent heat storage material comprises Mg (NO) 3 ) 2 ·6H 2 O、KNO 3 Dodecanol, palmitic acid, tetradecane, and the like. In addition, the chemical heat storage material is a heat storage material which realizes energy storage and release through the rupture and recombination of chemical bonds in chemical reaction, stores energy through endothermic reaction, and releases energy through reverse reaction. Compared with other sensible heat storage and latent heat storage, the chemical heat storage density is about 5 times of the latent heat and 10 times of the sensible heat, and the chemical bond is stable and the energy loss is small, so that a good heat storage material is formed. Suitable chemical heat storage materials in the present invention include sulfur trioxide, ethanol, magnesium oxide, cobalt oxide, copper oxide, and the like.
In fig. 5, fig. 5 (a) is a schematic view of a sleeve having grooves and protrusions on its surface, fig. 5 (b) is a partially enlarged view of the sleeve shown in fig. 5 (a), fig. 5 (c) is a schematic view of a sleeve having threads on its surface, and fig. 5 (d) is a schematic view of the sleeve shown in fig. 5 (c) in front view and in cross section. The above embodiment shows that the outer wall surface of the sleeve 7 has a protrusion or thread structure, thereby enhancing the heat exchange effect of the gas working medium in the heater 1 and the heat storage material in the sleeve 7.
Example 5
As shown in fig. 1, the use of the heater of the present invention in a stirling engine is illustrated with an α -type stirling engine. The alpha-type Stirling engine consists of an expansion cavity 10, a heater 1, a heat regenerator 11, a cooler 12 and a compression cavity 13, wherein a gas working medium absorbs heat in the heater 1, after expansion and work are performed in the expansion cavity 10, the gas working medium flows through the heat regenerator 11 to store a part of heat carried by the gas working medium, is cooled and compressed in the cooler 12 and the compression cavity 13, and then reversely flows through the heat regenerator 11 to absorb heat in the heat regenerator 11, and absorbs heat in the heater 1 and the expansion cavity 10 to expand and reciprocate.
In the process of compressing the gas working medium in the gas circulation, compression heat can be generated, so that the temperature of the gas working medium is increased. In the part of the heater 1, heat generated by compression of the gas working medium is absorbed by the heat storage part a, so that the phenomenon that the tube body b of the heater 1 is heated by the gas working medium and even the tube burst is caused by the overhigh temperature is avoided. When the gas working medium expands, the temperature of the air flow is reduced, and at the moment, the heat storage part a in the heater 1 releases heat, the air flow absorbs the heat to raise the temperature, so that the air flow temperature is prevented from being too low, and the heat stress damage caused by the too large temperature difference between the inner wall and the outer wall of the tube of the heater 1 is avoided. Therefore, the heat storage component a is arranged in the heater 1, so that temperature fluctuation caused by the compression and expansion of the gas working medium can be reduced, and the pipe body b of the heater 1 is prevented from being burst due to overhigh temperature or being lost due to thermal fatigue and thermal stress.
In addition, under the condition that the highest bearing temperature of the metal materials of the pipe body b of the heater 1 is the same, a heat storage component a made of a heat storage material in a proper form is additionally arranged, so that the heat flow born by the pipe body b of the heater 1 is larger; or the heater 1 can work under an external heat source with higher temperature, and the output work and the efficiency of the whole machine are obviously improved.
In order to solve the problem of tube explosion of the heater, the invention has been found by simulation experiments that the temperature of the gas working medium just entering the heater is 871K under the condition that the wall surface is kept at 900K by adopting isothermal wall surface arrangement. Due to the existence of compression heat, the highest temperature of the internal gas working medium can reach 951K and exceed the rated wall working temperature of the system. After the heat storage member a in the form of a wire of example 3 was added to the heater 1, it was found by numerical calculation that the maximum temperature of the gas working medium was reduced from 951K to 908K, the cycle ratio of the overtemperature time was reduced from 0.25 to 0.119, and the temperature fluctuation range was reduced from 160K to 58K, as shown in fig. 6. Therefore, when the regenerative heater is applied to a Stirling engine, the risk of thermal fatigue of the heater and a tube body thereof is greatly reduced, and the service life of the heater is prolonged. The average temperature of the tube body of the heater provided with the heat storage member is raised from 852K to 872K (fig. 6); the corresponding cycle indicated work was also increased from 1.72kW to 2.23kW, 29.7% increase, 3.1% increase in thermal efficiency, as shown in fig. 7.
The heater of the stirling engine with a heat storage member and the operation process thereof according to the present invention are described in detail. Any obvious modifications thereof, which would be apparent to those skilled in the art without departing from the true spirit of the present invention, would fall within the scope of the present patent claims.
Claims (8)
1. A heater for a stirling engine comprising
The heat storage device comprises a pipe body and a cavity formed by the pipe body, wherein the pipe body is a stainless steel pipe, a heat storage part is arranged in the cavity, the heat storage part comprises a metal material, and the heat storage part is arranged in the cavity in a parallel and non-contact manner with the pipe body;
one end of the tube body is connected with an expansion cavity of the Stirling engine, the other end of the tube body is connected with a heat regenerator of the Stirling engine,
the heat storage component is contacted with the gas working medium to change the flow characteristic of the heat storage component, strengthen the heat exchange between the gas working medium and the wall surface of the pipe body, and promote the heat absorption of the gas working medium in the heater; and simultaneously, the heat storage component absorbs and stores compression heat generated by compression carried by the gas working medium in the expansion cavity.
2. The heater for a stirling engine of claim 1 wherein the heat accumulating member is a porous medium comprising at least one of stacked wire mesh, metal fibers, foam metal or sintered metal.
3. A heater for a stirling engine in accordance with claim 1 wherein the heat accumulating member is a wire.
4. A heater for a stirling engine in accordance with claim 3 wherein the wire is helical or has a thread formation and/or protrusions and/or grooves on its surface.
5. A heater for a stirling engine in accordance with claim 1 wherein the thermal storage member comprises a sleeve and a thermal storage material disposed within the sleeve; the sleeve is arranged in the cavity, and a flow path for the gas working medium to flow is formed between the inner wall of the cavity and the outer wall of the sleeve.
6. A heater for a stirling engine according to claim 5 wherein the thermal storage material is a porous medium or a phase change material or a chemical thermal storage material.
7. A heater for a stirling engine according to claim 5 wherein the outer wall of the sleeve has a protrusion or thread formation.
8. A stirling cycle system employing the heater of any one of claims 1-7, further comprising an expansion chamber and a compression chamber, a regenerator disposed between the expansion chamber and the compression chamber, the heater disposed on one side of the expansion chamber, and a cooler disposed on one side of the compression chamber; the heat storage component is used for absorbing and storing compression heat generated by compression carried by the gas working medium in the expansion cavity.
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| JPH08296501A (en) * | 1995-03-02 | 1996-11-12 | Aisin Seiki Co Ltd | Heater for stirling engine |
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