CN202832848U

CN202832848U - Stirling circulating device

Info

Publication number: CN202832848U
Application number: CN 201220501544
Authority: CN
Inventors: 高桥隆志
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-09-28
Filing date: 2012-09-28
Publication date: 2013-03-27
Anticipated expiration: 2022-09-28

Abstract

The utility model provides a Stirling circulating device which can keep heat insulation between a high-temperature portion and a low-temperature portion and meanwhile can be used under a high-temperature. A replacer (70) and an upper portion air cylinder (10) which is used for containing the replacer (70) are made of ceramic materials. Therefore, compared with an existing Stirling circulating device with a replacer and an air cylinder made of resin materials, the Stirling circulating device can be operated continuously under the high temperature. In addition, compared with the existing Stirling circulating device with a replacer and an air cylinder made of metals such as stainless steel which is high in pyroconductivity, the Stirling circulating device is high in heat insulation performance on an expansion chamber in high temperature and a compression chamber in low temperature, and therefore power generation efficiency is improved.

Description

The Stirling circulation means

Technical field

The utility model relates to the Stirling circulation means that utilizes Stirling to loop generating and cooling etc.

Background technique

At present known have a Stirling circulation means that displacer and piston coaxial is disposed at the structure in the cylinder, and it is practical as generator and refrigerating machine etc.Simultaneously, in this Stirling circulation means, at piston permanent magnet is installed, and clamping this permanent magnet configuration stator and yoke.In the situation that generator, because of temperature difference working gas repeated compression and the expansion that gives from the outside, reciprocating motion of the pistons thus, this kinergety is transformed into electric energy by the electromagnetic action of permanent magnet and stator.On the other hand, in the situation that refrigerating machine, by flow through driving current in the electromagnetic coil of stator, reciprocating motion of the pistons is followed this to-and-fro motion, and working gas repeated compression and expansion produce the temperature difference of low-temp. portion and high-temperature portion thus.

In solar generation device, by the light optically focused with the sun, the temperature of high-temperature portion for example is 800 ℃ or more than it sometimes.In the situation that this electricity generating device is used the Stirling circulation means, being positioned at the displacer of high-temperature portion side and the resistance to heat of cylinder becomes problem.

Usually, displacer and the cylinder of accommodating it use the higher resin materials such as polyphenylene sulfide (PPS PolyPhenylene Sulfide) of heat resistance.Although the use critical temperature excellent heat resistance of resin material also for roughly below 300 ℃, can not use resin material in the device of continuous operation under 800 ℃ high temperature.

In order further to improve heat resistance, for example also consider to use stainless steel and other metal materials.But in the situation that displacer etc. use metallic material, pyroconductivity raises, and therefore, the heat-shielding performance of high-temperature portion and low-temp. portion reduces, the problem that exists thus generating efficiency to reduce.In addition, in the situation that use metallic material, the heavy problem of weight resin is compared in existence and number of spare parts increases and the problem of cost increase.

Summary of the invention

The utility model is in light of this situation and foundes, and its purpose is, provides a kind of when keeping high-temperature portion and low-temp. portion heat insulation, the Stirling circulation means that can use under high temperature.

The utility model provides a kind of Stirling circulation means, it has: make central shaft as one man be disposed at the first cylinder and the second cylinder in the shell, but to-and-fro motion ground inserts the displacer of described the first cylinder, but to-and-fro motion ground inserts the piston of described the second cylinder, expansion chamber towards the high temperature of an end of described displacer, pressing chamber towards the low temperature of the other end of described displacer and described piston, gas flow path with described expansion chamber and the connection of described pressing chamber, be accumulated in the heat exchanger of the heat of the mobile action gas of described gas flow path, at least one party of described the first cylinder and described displacer is formed by stupalith or material with carbon element.

Preferably, in the described Stirling circulation means, the slide part of the described displacer that slides with the inner face of described the first cylinder is formed by material with carbon element or stupalith.

Preferably, described displacer comprises: formed and towards the head of described expansion chamber, formed and keep the base portion of described head, formed and be located at the described slide part of the outside of described base portion by material with carbon element or stupalith by metal by stupalith.

Preferably, described slide part has the cross section and is the slip surface of the all-round ring-type of the circular described base portion of encirclement.

The slide part of the described piston that preferably, slides with the inner face of described the second cylinder is formed by material with carbon element or stupalith.

Preferably, the described stupalith that forms at least one party of described the first cylinder and described displacer is aluminium series ceramic material, zirconium oxide series ceramic material, silicon carbide series ceramic material, silicon nitride series stupalith, aluminium nitride series ceramic material, saponite series ceramic material or silicon aluminium oxygen nitrogen series ceramic material.(effect of model utility)

According to the utility model, can provide a kind of when keeping high-temperature portion and low-temp. portion heat insulation, the Stirling circulation means that can under high temperature, use.。

Description of drawings

Fig. 1 is the sectional drawing of one of formation example of the Stirling circulation means of expression the utility model mode of execution;

Fig. 2 is the figure of the major component of the displacer of diagram Stirling circulation means shown in Figure 1 and piston.

Symbol description

1 ... shell, 2 ... upper case, 3 ... the intermediate portion shell, 5 ... the cylinder holding part, 6 ... outer plate, 7 ... lower case, 8 ... cap, 10 ... upper cylinder, 11 ... lower cylinder, 12 ... expansion chamber, 13 ... endothermic plate, 14 ... heat exchanger (regenerator), 15 ... radiating fin, 16 ... intercommunicating pore, 17 ... pressing chamber, 18 ... yoke, 19 ... the yoke holding part, 20 ... piston, 21 ... base portion, 22 ... breakthrough part, 23,24 ... slide part, 25 ... magnet, 30 ... stator, 33 ... coil, 36 ... unshakable in one's determination, 40 ... support, 41 ... pillar, 43 ... the supporting base station, 51,52 ... spring members, 61,62 ... connecting rod, 70 ... displacer, 71 ... base portion, 72 ... slide part, 73 ... head.

Embodiment

Below, as the Stirling circulation means of the utility model mode of execution, describe as an example of the Stirling circulation means that is applicable to generator example.

Fig. 1 is the sectional drawing of one of formation example of the Stirling circulation means of expression the utility model mode of execution.In addition, Fig. 2 is the figure of the major component of the displacer of diagram Stirling circulation means shown in Figure 1 and piston.

Stirling circulation means shown in Figure 1 has shell 1, be contained in upper cylinder 10 and lower cylinder 11 in the shell 1, can reciprocally insert upper cylinder 10 displacer 70, can reciprocally insert the piston 20 of lower cylinder 11, with stator 30 and the yoke 18 of the inboard of piston 20 and the configuration of outside subtend, be installed on the magnet 25 of the wall cylindraceous section of piston 20, to the spring members (elastic member) 51 of displacer 70 application of forces, to the spring members (elastic member) 52 of piston 20 application of forces.

At this, shell 1 is one of shell of the present utility model example, upper cylinder 10 is one of the first cylinder of the present utility model example, lower cylinder 11 is one of the second cylinder of the present utility model example, displacer 70 is one of displacer of the present utility model example, and piston 20 is one of piston of the present utility model example.

Shell 1 is the seal container of having enclosed the working gas (helium etc.) of Stirling circulation means.In the example of Fig. 1, shell 1 combination upper case 2, intermediate portion shell 3, cylinder holding part 5, lower case 7 and form.

Upper case 2 and the intermediate portion shell 3 main columned inner spaces of accommodating upper cylinder 10 that form.The dome area of the inwall dome of the courtyard side of upper cylinder 10.Cylinder holding part 5 is the periphery butt of wall and lower cylinder 11 within it, keeps lower cylinder 11 in the mode of the position that determines central shaft.

Lower case 7 is main to be formed and accommodates lower cylinder 11, stator 30, yoke 18,

spring members

51,52 columned inner space.Near the bottom of lower case 7, be provided with the whole supporting base station 43 of mechanism's (upper cylinder 10, lower cylinder 11 etc.) in the downside supporting shell 1.Central authorities in the bottom of lower case 7 are provided with opening portion, and this opening portion is by cap 8 sealings.Cap 8 possesses for working gas being imported the inside of shell 1 or passing the not shown pipe of electric distribution.

Upper cylinder 10 and lower cylinder 11 have respectively the shape of tubular, and central shaft as one man is disposed in the shell 1.In the situation that upper cylinder 10 and lower cylinder 11 are seen as a cylinder, displacer 70 can reciprocally insert the upside of this cylinder, and piston 20 can reciprocally insert the lower side of this cylinder.Upper cylinder 10 and lower cylinder 11 also can connect other part and form, also can be integrally formed.

In the present embodiment, upper cylinder 10 is formed by stupalith.This stupalith uses the material higher and lower than the pyroconductivity of stainless steel and other metal materials than the heat resisting temperature of the resin materials such as PPS.

Lower cylinder 11 is fixed on the supporting base station 43 via a plurality of pillars 41.In the example of Fig. 1, pillar 41 forms tubular, and the hole of supporting base station 43 and the pillar 41 of tubular are located in bolt 42 perforations.By the external screw thread of the front end of bolt 42 and the following female thread of lower cylinder 11 are screwed togather, lower cylinder 11 is fixed on the supporting base station 43.Spring members 51 possesses the hole that bolt 42 connects, and is held between pillar 41 and the supporting base station 43 to be fixed.In the example of Fig. 1,3 spring members 51 are fixed on the supporting base station 43.

The space that is formed between the top and shell 1 of displacer 70 is expansion chamber 12, at this, and working gas heating and its volume increases.On the other hand, the space that is formed between displacer 70 and the piston 20 is pressing chamber 17, and at this, working gas is cooled and volume reduces.

The space cylindraceous that is surrounded by the inwall of the outer wall of upper cylinder 10 and shell 1 is the stream (gas flow path) of working gas that expansion chamber 12 and pressing chamber 17 are communicated with.Between upper cylinder 10 and lower cylinder 11, be provided with the intercommunicating pore 16 that is communicated with pressing chamber 17.Passing this intercommunicating pore 16 and above-mentioned cylindric space (gas flow path) is communicated with expansion chamber 12 and pressing chamber 17.

At above-mentioned space cylindraceous (gas flow path) configuration endothermic plate 13, heat exchanger (regenerator) 14 and radiating fin 15.Endothermic plate 13 is configured in the position near the expansion chamber 12 of upside, and radiating fin 15 is configured in the position near the pressing chamber 17 of downside, and heat exchanger 14 is disposed between endothermic plate 13 and the radiating fin 15.Heat exchanger 14 has and obtains the heat that flows to the working gas of pressing chamber 17 from expansion chamber 12 and carry out accumulation of heat, this accumulation of heat is given the function that flows to the working gas of expansion chamber 12 from pressing chamber 17.

Shell 1 possesses outer plate 6 in the part of joining with radiating fin 15.Outer plate 6 is to go out to the sink of the outside of shell 1 for the hot type with working gas.In the example of Fig. 1, outer plate 6 is fixed between intermediate portion shell 3 and the cylinder holding part 5.Outer plate 6 is cooled off by the cooling media (water etc.) of the not shown supplies such as pump, keeps the temperature of regulation.

On the other hand, upper case 2 be heat transmission that the thermal source from the outside is given to the heat sink of the working gas of expansion chamber 12, the inwall butt of endothermic plate 13 and upper case 2.

Displacer 70 comprises, the head 73 that arranges towards an end of expansion chamber 12, the base portion 71 that arranges towards the other end of pressing chamber 17, the slide part 72, the cylindrical body 74 that slide at the inner face of upper cylinder 10.

Head 73 is one of head of the present utility model example, and base portion 71 is one of base portion of the present utility model example, and slide part 72 is one of slide part of the present utility model example.

Head 73 consists of the wall of zoning expansion chamber 12.Head 73 is formed by the stupalith higher and lower than the pyroconductivity of stainless steel and other metal materials than the heat resisting temperature of the resin materials such as PPS.By forming head 73 by the low stupalith of pyroconductivity, blocking heat conduction of 17 from expansion chamber 12 to pressing chamber.

Base portion 71 consists of the wall of zoning pressing chamber 17.Base portion 71 keeps head 73 and slide part 72 such as being formed by metals such as aluminium or brass.By formed base portion 71 by metal, compare the situation that is formed base portion by resin etc., the amount of deformation of the part that temperature is brought reduces.Therefore, the precision that has suppressed machinery at high temperature reduces.

The mode that slide part 72 slides with the inner face in upper cylinder 10 is located at the outside of base portion 71, has the encirclement cross section and is the slip surface of the all-round ring-type of circular base portion 71.Slide part 72 is formed by the little material with carbon element of the high and hot amount of deformation that causes of heat resisting temperature than resin materials such as PPS.

At the end wall of pressing chamber 17 sides of base portion 71, with base portion 71 coaxial fixing cylindrical bodys 74 than base portion 71 paths.In the example of Fig. 1, at the conglobate recess of central part shape of the end wall of base portion 71, and the upper end of cylindrical body 74 inserted this recess.

Displacer 70 is connected with spring members 51 via the connecting rod 61 that the axle direction with cylinder (10,11) extends abreast.One end of connecting rod 61 is connected with base portion 71 by the cavity of the cylindrical body 74 of displacer 70.The other end of connecting rod 61 is connected with the tabular spring members 51 of installing at the supporting base station 43 of lower case 7.Displacer 70 elastic force by the spring members 51 that connects via connecting rod 61 is by in above-below direction (axle direction of the cylinder) application of force.

Piston 20 has: base portion 21 and the

slide part

23 and 24 of being located at the outside of base portion 21 with drum.One end of base portion 21 seals by end wall.

Towards displacer 70, its end wall consists of the wall of zoning pressing chamber 17 to base portion 21 in an end wall of sealing.Base portion 21 keeps

slide part

23,24 such as being formed by metals such as aluminium or brass.Because base portion 21 is formed by metal, thereby compare the situation that is formed base portion 21 by resin etc., the amount of deformation of the part that temperature is brought reduces, so the reduction of the mechanical precision under the high temperature is suppressed.

Slide part

23,24 divides in the outside of base portion 21 in the mode of sliding at the inner face of lower cylinder 11 and is arranged, and has respectively the slip surface that surrounds the all-round ring-type of base portion cylindraceous 21.

Slide part

23,24 is formed by the little material with carbon element of the high and hot amount of deformation that causes of heat resisting temperature than resin materials such as PPS.

Form the breakthrough part 22 of the cylindrical body 74 that receives displacer 70 in the central authorities towards the end wall of the base portion 21 of displacer 70.In the example of Fig. 1, this breakthrough part 22 is parallel with the axle direction of cylinder (10,11), and is cylindric extension.The cylindrical body 74 of displacer 70 pumps by breakthrough part 22.

A plurality of connecting rods 62 that the base portion 21 of piston 20 extends abreast via the axle direction with cylinder (10,11) are connected with tabular spring members 52.In the example of Fig. 1, spring members 52 is configured between lower cylinder 11 and the spring members 51, is fixed in lower cylinder 11(or supporting base station 43 via not shown pillar) on.Be formed for the through hole of break-through connecting rod 61 at the central part of spring members 52.One end of a plurality of connecting rods 62 be connected in breakthrough part 22 around the position of symmetry, the other end be connected in spring members 52 above-mentioned through hole around the position of symmetry.

Base portion 21 fixed magnets 25 at piston 20.Magnet 25 between

isolated slide part

23,24 to surround the all-round mode ring-type setting of base portion 21 cylindraceous.Towards the fixing yoke 18 of the inner face of the lower cylinder 11 of magnet 25.Yoke 18 is made of magnetic materials such as iron, forms for example ring-type in the mode of surrounding magnet 25.In the inboard of the base portion 21 of piston 20, with the position configuration stator 30 of yoke 18 subtends.Magnet 25 is held between stator 30 and the yoke 18, pumps with piston 20 cylinders.Magnet 25 produces the magnetic field to stator 30 and yoke 18 effects.

Stator 30 has the annular roll electric wire and the iron core 36 of the coil 33 that forms and clamping coil 33 and yoke 18 subtends.

Coil 33 is configured in the inboard of the base portion cylindraceous 21 of piston 20.In addition, coil 33 is with mode and piston 20 arranged coaxial of its circumferential lateral surface to the magnet 25 of piston 20.

Unshakable in one's determination 36 form the cross section shape on every side of surrounding the coil 33 vertical with the coiling direction of electric wire, magnet 25 and coil 33 towards part have gap (not surrounding part, the joint-cutting of coil 33).In the example of Fig. 1,36 two pieces (36A, 36B) that are divided in the above-below direction symmetry unshakable in one's determination.By the overlapping joint of plate (silicon steel plate etc.) with thin magnetic material, form respectively up and down two pieces (36A, 36B).

Unshakable in one's determination 36 by two parallel discoid plate member clampings, and this plate-like portion material is fixed in support 40 by not shown connection piece.Support 40 is fixed on the shell 1 with lower cylinder 11.

At this, the action of Stirling circulation means with above-mentioned formation is described.

When displacer 70 when piston 20 moves downwards, pressing chamber 17 narrows down, therefore, the working gas of pressing chamber 17 flows into the expansion chamber 12 of high temperature by intercommunicating pore 16, radiating fin 15, heat exchanger 14, endothermic plate 13.Flow into the working gas of expansion chamber 12 because of the heat volumetric expansion, so the pressure of expansion chamber 12 and pressing chamber 17 raises.When the pressure ratio of expansion chamber 12 and pressing chamber 17 was high by the pressure in the back pressure space 9 of the lower case 7 of piston 20 zonings, piston 20 was mobile downwards.

Mobile downwards by piston 20, the pressure decreased of expansion chamber 12 and pressing chamber 17, when the pressure than back pressure space 9 hanged down, displacer 70 was moved upward by this pressure difference.

When displacer 70 was moved upward, expansion chamber 12 narrowed down, and therefore, the working gas of expansion chamber 12 flows into the pressing chamber 17 of low temperature by endothermic plate 13, heat exchanger 14, radiating fin 15, intercommunicating pore 16.The working gas that flows into pressing chamber 17 is cooled, smaller volume, therefore, the pressure decreased of expansion chamber 12 and pressing chamber 17.When the pressure decreased of expansion chamber 12 and pressing chamber 17, the movement direction of piston 20 changes upper direction into from lower direction.

When being moved upward by piston 20, the pressure rise of expansion chamber 12 and pressing chamber 17, when the pressure than back pressure space 9 of becoming was high, displacer 70 was mobile downwards by this pressure difference.When displacer 70 when piston 20 moves downwards, working gas flows into expansion chambers 12 from pressing chamber 17 again, the pressure of expansion chamber 12 and pressing chamber 17 uprises, the movement direction of piston 20 changes lower direction into from upper direction.

By above repetition, displacer 70 and piston 20 pump respectively.

When piston 20 to-and-fro motion, magnet 25 moves up and down between yoke 18 and stator 30, and therefore the magnetic field cyclically-varying of coil 33, produces electromotive force, current flowing at coil 33.

As mentioned above, in the Stirling circulation means of present embodiment, displacer 70 and the upper cylinder 10 of accommodating it are formed by stupalith.Thus, compare the existing Stirling device that displacer and cylinder are formed by resin material, can under high temperature, all turn round continuously.Therefore, the Stirling circulation means of present embodiment for example goes for the solar generation device that high-temperature portion reaches the light-focusing type of the above temperature of 800 ℃ or its.

In addition, Stirling circulation means according to present embodiment, compare the existing Stirling circulation means that displacer and cylinder are formed by the high metals such as stainless steel of pyroconductivity, the performance that the pressing chamber of the expansion chamber of high temperature and low temperature is heat insulation is high, so can improve the efficient of generating.

In addition, according to the Stirling circulation means of present embodiment, replace the metallic material of Heavy Weight, the stupalith that operating weight is light can make the device lightweight thus.

And, according to the Stirling circulation means of present embodiment, because displacer 70 and upper cylinder 10 are used stupalith, thereby can use these parts of die forming, therefore, compare metallic material and can reduce number of spare parts.

In addition, in the Stirling circulation means of present embodiment, the slide part 72 of the displacer 70 that slides with

cylinder

10,11 inner face and the

slide part

23,24 of piston 20 are formed by material with carbon element.Thus, the slide part of comparing displacer and piston uses the existing Stirling circulation means of resin material, can turn round continuously under high temperature.Usually, resin material is owing to the amount of deformation that heat causes is large, so in the situation that slide part uses resin material, existing when becoming high temperature is to deform and the problem of sliding capability reduction.According to present embodiment, the material with carbon element that the amount of deformation that causes by serviceability temperature is little even at high temperature also can keep stable sliding capability, therefore, can carry out long continuous operation.

In addition, the utility model is not limited to above-mentioned mode of execution, also can comprise other various distortion.

In the above-described embodiment, in displacer 70, be provided with the base portion 71 of metal and the slide part 72 of material with carbon element, but the utility model does not limit and this example.In other mode of execution of the present utility model, also can utilize base portion and the slide part of the integrally formed displacer of material with carbon element.

In addition, in the above-mentioned mode of execution, be provided with the base portion 21 of metal and the

slide part

23,24 of material with carbon element at piston 20, but in other mode of execution of the present utility model, also can be by base portion and the slide part of the integrally formed piston of material with carbon element.

In addition, in the above-described embodiment, formed the

slide part

72,23,24 of displacer 70 and piston 20 by material with carbon element, but the utility model is not limited to this.In other mode of execution of the present utility model, also can be formed by stupalith the slide part of displacer and displacer.In this situation, compare the existing Stirling circulation means that has resin material to form slide part, also can improve resistance to heat.

In addition, in other mode of execution of the present utility model, can be by base portion and the slide part of the integrally formed displacer of stupalith, also can be by the integrally formed integral body that comprises the displacer of head of stupalith.

In addition, in other mode of execution of the present utility model, also can be by base portion and the slide part of the integrally formed piston of stupalith.

In addition, in the above-described embodiment, formed the head 73 of displacer 70 by stupalith, but the utility model is not limited to this.In other mode of execution of the present utility model, also can be formed by material with carbon element the head of displacer.In this situation, also can be by the integrally formed integral body that comprises the displacer of base portion and slide part of material with carbon element.

In addition, in the above-described embodiment, form upper cylinder 10 by stupalith, but the utility model is not limited to this.In other mode of execution of the present utility model, also can form the cylinder of accommodating displacer by material with carbon element.In this situation, compare the existing Stirling circulation means of the cylinder that uses resin material, also can significantly improve heat resistance.

In the above-mentioned mode of execution, the employed stupalith of displacer and cylinder is arbitrarily, such as enumerate aluminium system (alumina) stupalith, zirconium oxide series ceramic material, silicon carbide series ceramic material, silicon nitride series stupalith, aluminium nitride series ceramic material, saponite (steatite) series ceramic material, silicon aluminium oxygen nitrogen (sialon) series ceramic material etc. as its example.The employed stupalith of the slide part of displacer and piston also is arbitrarily, for example enumerates each above-mentioned stupalith as its example.

In the above-mentioned mode of execution, enumerated the example of the generator of Stirling circulation means, but the utility model is not limited to this, also goes for cooling unit such as the Stirling circulation means etc.

Claims

1. Stirling circulation means, it has:

Make central shaft as one man be disposed at the first cylinder in the shell and the second cylinder,

But the displacer of described the first cylinder of to-and-fro motion ground insertion,

But the piston of described the second cylinder of to-and-fro motion ground insertion,

Towards the expansion chamber of the high temperature of an end of described displacer,

Towards the pressing chamber of the low temperature of the other end of described displacer and described piston,

The gas flow path that described expansion chamber and described pressing chamber are communicated with,

Be accumulated in the heat exchanger of the heat of the mobile action gas of described gas flow path,

At least one party of described the first cylinder and described displacer is formed by stupalith or material with carbon element.

2. Stirling circulation means as claimed in claim 1, wherein,

The slide part of the described displacer that slides with the inner face of described the first cylinder is formed by material with carbon element or stupalith.

3. Stirling circulation means as claimed in claim 2, wherein,

Described displacer comprises:

By stupalith form and towards the head of described expansion chamber,

By metal form and keep described head base portion,

Form and be located at the described slide part of the outside of described base portion by material with carbon element or stupalith.

4. Stirling circulation means as claimed in claim 3, wherein,

Described slide part has the cross section and is the slip surface of the all-round ring-type of the circular described base portion of encirclement.

5. such as each described Stirling circulation means in the claim 1 ~ 4, wherein,

The slide part of the described piston that slides with the inner face of described the second cylinder is formed by material with carbon element or stupalith.

6. such as each described Stirling circulation means in the claim 1 ~ 4, wherein,

The described stupalith that forms at least one party of described the first cylinder and described displacer is aluminium series ceramic material, zirconium oxide series ceramic material, silicon carbide series ceramic material, silicon nitride series stupalith, aluminium nitride series ceramic material, saponite series ceramic material or silicon aluminium oxygen nitrogen series ceramic material.

7. Stirling circulation means as claimed in claim 5, wherein,