WO1990011447A1

WO1990011447A1 - Device for utilizing heat via conversion into mechanical energy, in particular a cooling device

Info

Publication number: WO1990011447A1
Application number: PCT/NL1989/000012
Authority: WO
Inventors: Cornelis Maria De Blok; Nicolaas Adrianus Henrikus Jozef Van Rijt
Original assignee: Cornelis Maria De Blok; Rijt Nicolaas Adrianus Henriku
Priority date: 1989-03-17
Filing date: 1989-03-17
Publication date: 1990-10-04

Abstract

Device for utilizing heat via conversion into mechanical energy having a travelling wave heat motor (1) comprising a self-enclosed conduit (2) which defines internally an endless channel filled with a compressible fluid, a regenerator (3) arranged in a portion of the channel and comprising a heat exchanging medium (7) through which the fluid can flow, heat supply (4) and heat discharge (6) means coupled in the lengthwise direction of the channel at a mutual interval to the heat exchanging medium which means can generate a temperature gradient in the regenerator during operation, whereby the length of the channel is dimensioned in accordance with a design wave length of a travelling wave with a desired frequency to be generated in the channel during operation, and with energy extraction means (9) absorbing mechanical energy from the travelling wave. Connecting onto the channel portion containing the regenerator on the side of the heat supply means is a channel portion which has at least the same diameter as the channel portion in which the regenerator is accommodated and which is provided with means for neutralizing wave phenomena in the fluid reflected in the direction of the side of the regenerator coupled to the heat supply means.

Description

DEVICE FOR UTILIZING HEAT VIA CONVERSION INTO MECHANICAL ENERGY, IN PARTICULAR A COOLING DEVICE

The invention relates to a device for utilizing heat via conversion into mechanical energy having a travelling wave heat motor comprising a self-enclosed conduit which defines internally an endless channel filled with a compres- sible fluid, a regenerator arranged in a portion of the chan¬ nel and comprising a heat exchanging medium through which the fluid can flow, heat supply and heat discharge means coupled in the lengthwise direction of the channel at a mutual inter¬ val to the heat exchanging medium, which means can generate a temperature gradient in the regenerator during operation, whereby the length of the channel is dimensioned in accordance with a design wave length of a travelling wave with a desired frequency to be generated in the channel during operation, and with energy extraction means absorbing mechanical energy from the travelling wave.

Such a device is known from the American patent specification 4.114.380. It has been found in practice that this known device functions either not at all or hardly at all. The invention therefore has for its object to pro¬ vide a device of the type specified in the preamble which can operate with a good yield. This is achieved in the device according to the invention in that connecting onto the channel portion containing the regenerator on the side of the heat supply means is a channel portion which has at least the same diameter as the channel portion in which the regenerator is accommodated and which is provided with means for neutrali¬ zing wave phenomena in the fluid reflected in the direction towards the side of the regenerator coupled to the heat supply means. Thus achieved is that at the location of the regenera¬ tor the wave phenomena in the fluid correspond in very good approximation to those of a travelling wave. That is, the momentary speed of movement and pressure in the fluid are at least virtually in phase with one another during operation.

It is assumed that the said state of the art is based substantially on theoretical considerations and that no account has been taken of a number of factors of practical importance. One of these factors is for instance that between the hot side of the regenerator and the remaining part of the conduit system there occurs a marked difference in tempera¬ ture.

The invention is therefore based on the insight that, for the purpose of obtaining a good yield from the thermodynamic processes generated in the fluid by the wave phenomena in a device of the present type, it is important that the cyclic pressure and speed changes must occur with the correct mutual phase and that it is of importance for this purpose that disturbances of the correct phase relation- ship occurring in practice be neutralized. In a travelling wave heat motor it is of particular importance for a good yield that, as already noted, the phase difference between the pressure and gas speed is minimal. Conversely in the case of a heat pump the gas pressure and gas displacement have to be in phase with one another, or the gas pressure and the gas speed must have a phase difference of 90 when operation is performed with sine-like wave phenomena.

A favourable embodiment of the device according to the invention can be seen in claim 2. The compensation formed by the widening neutralizes the reflected wave phenomena in the fluid so that no disturbing wave phenomena can occur in the regenerator.

Characterized in claim 3 is another favourable embodiment. Since in principle no flow occurs in the fluid the fluid in the channel portion furnished with the heating element is brought to a higher temperature. Reflections are compensated as a result. A further favourable development of the device according to the invention will be seen in claim 4. By arran¬ ging the widening in the manner indicated at an interval from the regenerator the dimensions of the widening are less critical and the length thereof is smaller than when the widening joins directly onto the regenerator. As a result the space occupied by the conduit can be limited.

When the device is used with a fluid in gas form the energy extracting means may consist of means absorbing alternating pressure energy and connected to the channel. Use can be made particularly of a piezoelectric, electromagnetic or mechanical disengaging member. The desired wave phenomena can however also be generated in liquid fluids such as for instance liquid alkali metal such as sodium. In such an em- bodiment the wave energy can be converted directly into elec¬ tricity by means of the magnetohydrodynamic principle.

In accordance with a further development of the device according to the invention the energy extracting means may however also comprise a conduit piece which is joined in open communication with the main channel and which forms a resonator and is provided with heat absorbing means and heat dissipating means on the side of the heat absorbing means facing away from the open connection, and whereby the main channel is provided with means for neutralizing reflected wave phenomena introduced into the fluid in the channel as a result of wave phenomena in the fluid in the side channel. As noted above this further application is based on the same inventive insight that the correct phase relationship in the wave phenomena is of great importance for a good operation of a device of the present type. Generated in the fluid in the conduit piece forming the resonator is a standing wave that is driven by the travelling wave in the main channel. As a result of a per se known physical phenomenon there occurs in such a standing wave heat transport from the heat absorbing means to the heat dissipating means. At the position of the connection of the side channel onto the main channel the displacing function of the fluid column has a certain ampli¬ tude. Occurring in the main channel as a result is an in¬ fluencing of the wave phenomena which can be considered as reflection. By now arranging means whereby these reflected wave phenomena are also neutralized, good operation of the travelling wave heat motor is thus not affected.

The embodiment as characterized in claim 6 is par¬ ticularly favourable. The disturbances introduced through the one side channel are in precisely opposite phase to those caused by the other side channel, so that these disturbances neutralize one another.

As stated in claim 7 a number of such pairs of side channels neutralizing the disturbances on either side can be employed in the device according to the invention. Of two pairs, the channels lying closest to one another can thereby be combined into a larger side channel. The disturbances caused in the main channel by the combined side channel are again compensated by both the other side channels. Claims 8 and 9 characterize a favourable application of the device according to the invention as a refrigerator or cooling box. The great advantage of the device according to the invention embodied as a cooling device is that it has a very simple construction without moving parts and that the active fluid can be normal air, or in any case an innocuous gas. The device does not therefore contain the harmful active fluids such as chlorofluorocarbons employed in the usual cooling devices.

A further development of the invention as a cooling device will be found in claim 10. Resulting from the seal is a good separation between the heat absorbing and the heat dissipating means. Since the seal is heat insulating the internal heat flow in the side channels is as limited as possible so that the heat pump capacity can be utilized as well as possible.

In practice there results on the side of the seal facing the -pen end of the side channel a cold gas cloud, while on the other side of the seal a warm gas cloud is for¬ med. By applying the step from claim 11 the hot and cold source can be utilized in highly efficient manner. The hot and cold gas clouds are extracted from the side channel in the circular loop line, following which either heat dissi¬ pation or heat absorption can take place in the heat exchan¬ ger. The cooled or heated fluid is then returned to the side channel. When the step from claim 12 ia applied the "gas exchange" along the seal is additionally supported by convec¬ tion.

The invention will be further elucidated hereinaf er in the following description with reference to the annexed figures of a number of embodiments.

Figures 1-3 show schematically three embodiments of the device according to the invention.

Figures 4 and 5 show corresponding schematic repre¬ sentations of the device according to the invention in the form of a cooling device.

Figure 6 shows in partially perspective view with dismantled parts a portion of an actual embodiment of a cool¬ ing device according to the invention.

Figure 7 is a cross section of such a cooling de- vice.

Figure 8 shows perspectively another embodiment of the heat absorbing means as employed in an embodiment of a cooling device according to the invention.

The device 1 shown schematically in figure 1 com- prises a self-enclosed conduit 2 internally defining an end¬ less channel 12 filled with a compressible fluid. Arranged in a portion of channel 12 is a regenerator 3 comprising a heat exchanging medium 7 through which the fluid can flow and which can for instance take the form of steel wool. Arranged on the right-hand end of regenerator 3 as seen in figure 1 are heat supply means 4. The heat supply means 4 are represen¬ ted schematically here by a thermally conducting plate which is heated by a burner 5. Arranged on the left-hand side of the regenerator 3 as seen in figure 1 are heat discharge means 6 designated schematically and having a likewise ther¬ mally conducting plate provided with cooling ribs. The seal 7 is itself of heat conducting material and thermally connected at both ends to the heat supply means 4 and the heat discharge means 6 so that during operation a temperature gradient will be established in the seal 7.

The regenerator 3 is embodied such that there resul- ts a very good transfer of the fluid onto the seal material. The above mentioned steel wool or metal wool in general ful¬ fills this requirement well.

As soon as a temperature gradient is adjusted in the regenerator 3 a travelling wave begins in the fluid which, broadly speaking, is stationary. Since the thermodynamic principle according to which this travelling wave occurs is generally known it will not be extensively described here. It will suffice to provide the following brief explanation.

Let us suppose that the fluid in channel 12 at the location of the heat discharge means deflects back and forth in lengthwise direction of channel 12 about a position of equilibrium. The fluid consequently moving inward over a certain distance In the regenerator 3 is heated as a result of the adjusted temperature gradient. As a result of this heating the fluid expands. The deflection is thus enlarged. The adjacent fluid is forced with the (enlarged) deflection to the right as seen in figure 1. This fluid is however also heated as a consequence of the temperature gradient and there¬ fore expands. The deflection of this fluid therefore again becomes greater. In this way the deflection of the fluid increases in the direction towards the heat supply means 4. The opposite occurs when the fluid deflection is directed to the left as seen in figure 1 in the vicinity of the heat discharge means. A small deflection to the left there results in a greater deflection to the left close to the heat supply means. In short, this means therefore that the reciprocating movements in the fluid at the position of the heat discharge means 6 occur in amplified form on the opposing side of the regenerator 3 at the position of the heat supply means. These amplified deflections in the fluid proliferate via the closed channel 12 again as far as the heat discharge side of the regenerator 3, where these deflections are again amplified in the regenerator 3 in the manner described. The amplified output signal of the regenerator is fed back to the input thereof so that the system operates as an oscillator. As a result of the travelling wave maintained in the channel 12 there occur in the fluid variations in pressure around a mean pressure. This mechanical alternating tension can be utilized In a number of ways. The device comprises for this purpose energy extracting means 9 which, as noted ear- lier, can extract for instance piezoelectric, electromagnetic or purely mechanical energy. In preference however, as will be elucidated later, the energy extracting means 9 are em¬ bodied as a heat pump.

In the brief explanation given above of the opera- ting principle, the point of departure is that in the regene¬ rator 3 each fluid volume transfers its deflections about the position of equilibrium in an amplified manner to an adjacent fluid volume. In other words, it is assumed that the speed and pressure variation are in phase with one another. Or put another way, it is assumed that an unadulterated travelling wave proliferates into the regenerator 3. This is achieved according to the invention in that in the conduit 2 means are accommodated for neutralizing wave phenomena in the fluid reflected in the direction toward the side of the regenerator 3 connected to the heat supply means 4. These reflected wave phenomena would disturb the correct phase relationship between the pressure and deflection in the regenerator 3 and hence have an unfavourable effect on the good operation of the device or even make it impossible. For this purpose in the embodiment of figure 1 the channel portion connecting directly onto the regenerator 3 is widened over a length at least virtually equal to a quarter of the design wave length. This widened portion 8 has a diameter at least virtually equal to the product of the diameter of the remaining part of channel 12 and the square root of the quotient of the operating tem¬ peratures in Kelvin of the regenerator 3 close to the heat supply means 4 and the heat discharge means 6. When the tem¬ perature close to the heat supply means is given by Tx and that close to the heat discharge means by To and the diameter of channel 12 in the remaining part of conduit 2 by d, the diameter dl of the widened conduit portion 8 is therefore

1 equal to dl = d(Tx/To)². This relation is otherwise based on per se known transmission lines theory. Using this theory wave phenomena in conduits can be computed.

Another embodiment of the means for neutralizing reflected wave phenomena is shown in figure 2. The channel portion containing the regenerator hereby has the same dia¬ meter as the chann'el portion connecting on the side of the heat supply means 4. Arranged about this channel portion directly adjoining the regenerator 3 is a heating element 10 which extends over a length at least practically equal to a quarter of the design wave length. Using the heating element 10 the temperature of the wall of the channel is raised. Assuming the operating temperatures in Kelvin of Tx and To of the heat supply means and the heat discharge means respective¬ ly, the temperature T to which the wall of the channel is brought can be expressed as T = To (Tx/To)² . Because the fluid in the channel is generally speaking stationary, the fluid in the relevant channel portion obtains the same tem¬ perature. Since the fluid has this higher temperature along the stated length of at least one quarter of the design wave length, the unadulterated travelling wave in the regenerator 3 is not disturbed by reflected wave phenomena.

By the above mentioned design wave length is meant the wave length of the travelling wave occurring in the fluid. In the simplest approximation this wave length is equal to the length of the channel 12. However, as a result of par¬ ticular steps, which will not be further mentioned, a travel¬ ling wave with a higher frequency can also be generated. The length of the channel is then a whole number of times the wave length. It is further the case that the energy extraction means 9 introduce a certain damping into the system which has the effect that the frequency of the travelling wave becomes lower. These influences on the wave length can be computed in the design stage of the device and, if determined dimensions of the conduit are assumed, the computed wave length, or if this is taken as starting point, the selected wave length is designated in this description as the design wave length. In the embodiment of the device according to the invention as shown in figure 3 the means for neutralizing the reflected wave phenomena are likewise formed by a widened channel por¬ tion 11. Here however the widened channel portion 11 is ar¬ ranged at a distance of 0.09 to 0.14 times the design wave length from the side of the regenerator 3 coupled to the heat supply means 4. The length of the widened portion 11 is 0.02 to 0.05 times the design wave length, while the diameter is equal to 1.14 to 4.0 times the diameter of the remaining part of the channel. The channel portion containing regenerator 3 has the same diameter as the channel portion connecting there- to on the side of the heat supply means 4.

Figure 4 shows a device according to the invention whereby the energy extracting means are formed by a standing wave-heat pump 21. The travelling wave heat motor 16 cor¬ responds In principle with the embodiment of figure 3. Shown on the heat supply side of the regenerator in the embodiment shown here is a burner 17. The hot combustion gases of burner 17 are collected in a burner housing 18 which guides the hot gases via a heat exchanger, wherein heat is extracted and passed to the seal of the regenerator, to a gas discharge 19. The means for neutralizing reflected wave phenomena are formed here by a widened portion 20 arranged in the channel at an interval from the regenerator.

The standing wave-heat pump 21 is formed by a con¬ duit portion 22 having a closed end 23 and an open end 24. The open end is in open communication with the main channel of the travelling wave-heat motor 16. The side channel defined in the conduit piece 22 has a length of a quarter times the design wave length and thus forms a resonator. As a result, when the heat motor is In operation a standing wave will be created in the fluid in the side channel. This standing wave is sustained by the travelling wave in the main channel. As a result of the standing wave there occurs in the fluid close to the open connection 24 a deflection of great amplitude, while the pressure is low and shifted in phase through 90. This has a highly disturbing effect on the travelling wave in the main channel. This disturbance can be seen as a reflected wave phenomenon introduced in the fluid in the main channel. In accordance with the invention a compensation 25 is now arranged in the main channel which neutralizes the introduced, reflected wave phenomena. This compensation 25 is formed by a widened conduit portion. The dimensioning thereof can again be computed using per se known wave line theory.

Due to the standing wave in the conduit portion 22 each fluid volume particle is subjected to a varying compres- sion and expansion. Since in a standing wave the pressure and displacement are in phase with one another, each volume par¬ ticle is displaced during the compression towards the closed end 23. Because the temperature thereby thus increases, the volume particle can give off heat, for example to the wall of the conduit portion. During expansion the fluid volume par¬ ticle cools off again, and at the minimal pressure the volume particle undergoes maximum displacement in the direction towards the open end 24. As a result of the cooling caused by the expansion the volume particle can take up heat, for exam- pie from the wall of the conduit portion. Occurring thus in this manner is a heat pump cycle. Heat is taken up at a deter¬ mined position in the conduit portion 22 and can be given off again at a position lying further towards the closed end 23. As noted, it is thus of importance hereby for the achieving of a maximum yield that the pressure and displacement lie as closely as possible in phase. In the case of the device of which the principle is shown in figure 4, a seal 26 is arranged in the conduit por¬ tion 22 in which the standing wave occurs. This seal consists of thermally insulating material and is embodied such that the best possible laminar flow of the fluid can take place therein. The seal 26 comprises for instance a large number of parallel channels with smooth walls. For a good yield it is important that the smallest possible heat flow occurs in lengthwise direction of these channels. The fluid must on the other hand have a good heat exchange with the walls of the channels so that during operation a temperature gradient occurs in the seal. Thermally insulating materials suffice In practice. An improvement of the heat exchanging with fluid in gas form can be achieved by providing the walls of the chan¬ nels with a thin metal layer. At higher levels of pressure a seal can be employed that is manufactured entirely of metal foil. The lengthwise conduction is hereby small in relation to the amount of heat displaced.

In preference however a further development is applied whereby a circuit connects to both the "hot" and the "cold" side of the seal 26. The circuit on the cold side is designated with 27 and contains a heat exchanger 29. As a result of the above described heat pump effect the fluid on the underside of the seal 26 as seen in figure 4 is cooled and that in the upper part is heated. That is, if the fluid is in gas form a cold gas cloud is created on the cold side of seal 26 and a hot gas cloud on the hot side. The cold fluid is taken up into the circuit 27 and can absorb heat in the heat exchanger 29. The thus re-heated fluid is carried back to the cold side of seal 26, where heat can once again be extracted therefrom and the circuit cycle can be repeated. The same takes place on the hot side where a circuit 28 is arranged. Heat is extracted from the hot fluid in the heat exchanger 30. The device of figure 4 thus has the effect that heat is "pumped" from heat exchanger 29 to heat exchanger 30 while being driven by the thermal energy supplied by the burner 17.

Figure 5 shows a further developed embodiment of the principle shown in figure 4. The travelling wave heat motor corresponds to that shown in figure 4 and has the same reference numeral 16. Instead of the compensation 25 of the device 15 however, a second heat pump 35 is arranged similar to the heat pump 21. The two heat pumps 21, 35 are connected onto the main channel at a mutual distance of substantially a quarter of the design wave length. The standing wave occurring in heat pump 35 during operation has a resulting phase shift of 90 relative to that in the heat pump 21. The disturbances introduced in the travelling wave as a consequence of both standing waves thus result in a phase shift of 180 and there¬ fore cancel each other out. During operation heat is taken up in the combined heat exchanger 36 and given off again in the heat exchangers 37 and 38. There thus occurs heat transport from the space of heat exchanger 36 to that of the heat exchangers 37 and 38.

Although the heat pumps shown here each have the form of a conduit portion closed at one end with a length of substantially a quarter times the design wave length, other embodiments can also be employed, such as a Helmholtz resona¬ tor or a conduit part connected at its ends to the main chan¬ nel at locations where the wave phenomena have a like phase and in which for example two heat exchangers can be accom¬ modated. All that is important is that the conduit part is embodied such that a standing wave occurs therein.

An embodiment of a refrigerator according to the invention working according to the system of figure 5 is shown in the figures 6 and 7. Figure 6 shows perspectively with broken away parts the portion of the cooling device comprising the travelling wave motor.

The main channel 41 of the travelling wave motor is recessed into the rear wall 40 of the device. This rear wall 40 consists of a central part in which the channel 51 is recessed and two side plates 42, 43. The regenerator 44 takes the form of a cassette pushed into the rear wall 40 and fixed in position therein with known means. The regenerator com¬ prises the above described seal 45 of metal wool, a heat discharge plate 46 and a heating element 48. This element 48 is here an electrical heating element consisting of a "honey¬ comb" formed from corrugated stainless steel foil. The heat discharge 46 is in thermal communication with the cooling ribs 47 which, as figure 7 shows, are freely accessible for cooling surrounding air.

A widening 49 in accordance with the principle of figure 3 is arranged in the channel 41 in order to neutralize the wave phenomena reflected to the regenerator. Air is used as the active fluid. The direction of the travelling wave occurring in the device during operation is indicated with the double arrows 50.

Arranged on two locations in the plate 43 of the rear wall are cut away portions 51, 52. Measured along the main channel 41 these two openings 51, 52 are situated at an interval of practically one quarter of the design wave length. Connected onto each of these openings 51, 52 is a heat pump, only one of which is shown partially in figure 6. The heat pump 53 is hereby embodied as a Helmholtz resonator. In the heat source 53 shown sectionally in figure 6 the seal 54 can be seen which provides the laminar flow guiding of the fluid in the heat pump. Arranged on the cold side of seal 54 is a cooling fin 55.

Also to be seen in figure 7 is the heat pump 56 located opposite. The cooling fins 55, 57 of the heat pumps 53, 56 protrude into the internal space 60, which is enclosed by a door 61 as well as by insulated walls 62. As shown the heat pumps 53, 56 are arranged in the insulated wall 62. Arranged on the hot side of each heat pump 53, 56 are cooling ribs 58 and 59 respectively which protrude into the outer surroundings. The heat transported by the heat pumps 53, 56 from the heat absorbing means in the form of the cooling fins 55, 57 to the heat dissipating means in the form of the cool¬ ing ribs 58, 59 is given off there to the outer air. Heat is thus extracted from the internal space 60 of the refrigerator. Since use can be made for the operation of such a cooling device according to the Invention of an innocuous gas or gas mixture such as air, it is not harmful to the environ¬ ment. Sinc.e mechanical elements are absent it is moreover not prone to wear. When the heat supply into the regenerator takes place with a gas flame the number of energy conversion steps in the device is minimal so that this device can operate with a high yield. As a result of the means for neutralizing the reflected wave phenomena occurring in practice in addition to the means for neutralizing the reflected wave phenomena introduced by the driven devices a system is obtained that is very serviceable in practice.

Finally, Figure 8 shows another embodiment of the heat absorbing means in a cooling device according to the invention. Shown with dashed lines is the resonance channel 65 in which the standing wave is generated. Arranged on the "cold" side of the seal (not further shown) through the chan¬ nel are a number of tubes of heat conducting material, such as metal. Air can flow through these tubes 66. To this end guide channels are formed which guide air towards the openings of the tubes 66, as indicated with the arrows 68. Through the operation of the cooling device the air in the tubes 66 cools and, as a result of convectional flow, the cooled air flows outside on the underside and is replenished by hot air from above. Created in this way is a constant air flow in the direction of the arrow 68, resulting in heat being extracted from the air in the interior of the cooling device.

Claims

1. Device for utilizing heat via conversion into mechanical energy having a travelling wave heat motor compri¬ sing a self-enclosed conduit which defines internally an endless channel filled with a compressible fluid, a regenera- tor arranged in a portion of said channel and comprising a heat exchanging medium through which said fluid can flow, heat supply and heat discharge means coupled in the lengthwise direction of said channel at a mutual interval to said heat exchanging medium, which means can generate a temperature gradient in said regenerator during operation, whereby the length of said channel is dimensioned in accordance with a design wave length of a travelling wave with a desired fre¬ quency to be generated in said channel during operation, and with energy extraction means absorbing mechanical energy from the travelling wave, characterized in that connecting onto the channel portion containing said regenerator on the side of said heat supply means is a channel portion which has at least the same diameter as the channel portion in which said regenerator is accommodated and which is provided with means for neutralizing wave phenomena in the fluid reflected in the direction of the side of said regenerator coupled to said heat supply means.

2. Device as claimed in claim 1, characterized in that the means for neutralizing reflected wave phenomena are formed in that the channel portion connecting directly onto the regenerator is widened over a length at least virtually equal to a quarter of the design wave length to a diameter (dl) at least virtually equal to the product of the diameter of the remaining part of the channel (d) and the square root of the quotient of the operating temperatures in Kelvin of said regenerator close to the heat discharge means (To), that is dl = d(Tx/To)².

3. Device as claimed in claim 1, characterized in that the means for neutralizing reflected wave phenomena are formed by a heating element arranged about the channel portion directly adjoining the regenerator and extending over a length at least practically equal to a quarter of the design wave length, and using which the temperature (T) of the wall of the channel can be brought to a value at least virtually equal to the product of the operating temperature in Kelvin of said regenerator at the heat supply means (Tx)U and the heat discharge means (To), that is T = To (Tx/To)².

4. Device as claimed in claim 1, characterized in that the means for neutralizing the reflected wave phenomena are formed in that a channel portion is widened at a distance of 0.09 to 0.14 times the design wave length from the side of the regenerator coupled to the heat supply means and over a length of between 0.02 and 0.05 times said design wave length, and having a diameter (d2) equal to 1.14 to 4.0 times the diameter (d) of the remaining part of said channel.

5. Device as claimed in any of the foregoing claims, characterized in that the energy extracting means comprise a conduit piece which is joined in open communication with the main channel and which forms a resonator and is provided with heat absorbing means and heat dissipating means on the side of the heat absorbing means facing away from the open connec- tion, and that the channel is provided with means for neutra¬ lizing reflected wave phenomena introduced in the fluid in the channel as a result of wave phenomena in the fluid in the side channel.

6. Device as claimed in claim 6, characterized in that the resonator Is a side channel with a length of a quar¬ ter times the design wave length.

7. Device as claimed in claim 5 or 6, characterized in that the means for neutralizing the introduced, reflected wave phenomena are formed by a conduit piece connected to the channel at a distance from the side channel of substantially a quarter of the design wave length and defining a similar side channel.

8. Device as claimed in claim 7, characterized by a number of pairs of conduit pieces defining similar side chan- nels.

9. Device as claimed in any of the claims 5-8, characterized in that this comprises a box-like housing which is provided with walls enclosing an internal space, at least one of which is hinged along one side, thus forming a cover or door and whereby the heat absorbing means are thermally connected to the internal space and the heat dissipating means are thermally connected to the surroundings.

10. Device as claimed in claim 9, characterized in that the channel and the at least one side channel are reces- sed into the walls of the housing.

11. Device as claimed in any of the claims 5-8, characterized in that arranged in the conduit piece defining a side channel between the heat absorbing means and the heat dissipating means is a thermally insulating seal that conducts the fluid well.

12. Device as claimed in any of the foregoing claims 5-8, characterized in that the heat absorbing means and/or the heat dissipating means comprise a fluid circuit line connected at opposing positions to the side channel, in which fluid circuit line is arranged a heat exchanger.

13. Device as claimed in claim 11, characterized in that the side channel extends substantially horizontally and that the fluid circuit line is connected to the channel at positions located vertically opposite one another.

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