EP4630741A1

EP4630741A1 - Enhancement of the thermoacoustic effect

Info

Publication number: EP4630741A1
Application number: EP23900170.4A
Authority: EP
Inventors: Yehuda Agnon; Guy Ramon; Avishai MEIR
Original assignee: Technion Research and Development Foundation Ltd
Current assignee: Technion Research and Development Foundation Ltd
Priority date: 2022-12-08
Filing date: 2023-12-08
Publication date: 2025-10-15
Also published as: WO2024121809A1

Abstract

A thermoacoustic device that includes a resonator, wherein the resonator includes a stack. During operation, a cold zone of the stack is configured to receive at least one fluid from a hot zone of the stack; wherein a temperature of the hot zone exceeds a temperature of the cold zone. The thermoacoustic device also includes a conveyor for conveying at least some of the at least one fluid from the cold zone of the stack to the hot zone of the stack.

Description

ENHANCEMENT OF THE THERMOACOUSTIC EFFECT

CROSS REFERENCE.

[001] This application claims priority of US provisional patent serial number 63/386,665 filing date 8 December 2023, which is incorporated herein in its entirety.

BACKGROUND

[002] Thermoacoustics - When interacting with a liquid or solid structure, oscillating gas flows (i.e., sound waves) can carry a net time-averaged flux of heat and mass. Moreover, when contained in a properly designed resonator, acoustic waves can be made to execute the cyclic thermodynamics of a heat engine, a heat pump, or a separation process. This process is controlled by placing a porous solid called a “stack” or “regenerator” under a temperature gradient. If the temperature gradient is high enough, work will be created by converting heat into acoustic oscillation. If acoustic oscillations are introduced by a source external to the stack, heat will be pumped from one side of the stack to the other, where a cold and a hot heat exchangers are placed.

[003] This type of devices based on acoustic energy conversion, are potentially cheap, highly reliable, simple, and environmentally benign, requiring no exotic or toxic materials, and comprising no moving mechanical elements. Such devices could be compressors, heat pumps, water pumps, and electrical generators, which can be driven by electrical power, heat, solar radiation, or any combination available. However, wide-scale commercial adoption has yet to be realized, mostly due to the following:

[004] A relatively low power density means that the gas within the resonator must be pressurized, typically above 30 bars to reach useful outputs, thus creating a sealing and safety challenge.

[005] Efficiently harvesting acoustic energy for electricity production still requires expensive mechanical devices such as specially designed linear alternators.

[006] At high amplitudes, non-linear phenomena contribute to significant energy losses, and are concurrently difficult to model and mitigate.

[007] Efficient heat exchange surfaces must minimize hindrance to the oscillating gas flow, while maximizing heat transfer to achieve high power and efficiency. Such heat exchangers are on one hand difficult to model with the absence of convenient approximations and correlations, and on the other hand crucially effect the thermal and acoustic fields. [008] Stack - in the heart of a thermoacoustic system is a porous solid referred to as “stack” or “regenerator” in some applications (see figure 1), which is usually fabricated from a ceramic material, and contains channels whose dimensions are determined by the characteristic frequency and working materials in the system. The current invention revolves around several aspects of the design of such stack to accommodate phase changes of the working material. SUMMARY

[009] There are provided thermoacoustic devices and methods for operating the thermoacoustic devices.

BRIEF DESCTIPTION OF THE DRAWINGS

[0010] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which

[0011] FIG. 1 illustrates an example of a stack;

[0012] FIG. 2 illustrates an example of a thermoacoustic device and performances of stacks;

[0013] FIG. 3 illustrates an example of experimental results from a thermoacoustic engine with a cellulose stack developed in the lab;

[0014] FIG. 4 illustrates an example of modeled results;

[0015] FIG. 5 illustrates an example of three vapor pressure versus location within the stack curves and of N channels;

[0016] FIG. 6 illustrates two example of channels;

[0017] FIG. 7 illustrates an example of illustrating N channels;

[0018] FIG. 8 illustrates an example of replenishing the liquid lost during system operation;

[0019] FIGs. 9-10 illustrate a liquid stream that replaces mass with the oscillating gas by absorbing and releasing a dissolve component;

[0020] FIG. 11 illustrates an example of a stack in a curved shape;

[0021] FIG. 12 illustrates an example of small semi permeable channels;

[0022] FIG. 13 illustrates a method for operating a thermoacoustic device;

[0023] FIG. 14 illustrates a method for operating a thermoacoustic device;

[0024] FIG. 15 illustrates a method for operating a thermoacoustic device;

[0025] FIG. 16 illustrates a method for operating a thermoacoustic device;

[0026] FIG. 17 illustrates a method for operating a thermoacoustic device;

[0027] FIG. 18 illustrates an example of a sidewall of a channel; [0028] FIG. 19 illustrates an example of a cross sectional view of a channel, taken along a longitudinal axis of the channel; and

[0029] FIG. 20 illustrates examples channels having different cross sections.

DETAILED DESCRIPTION OF THE DRAWINGS

[0030] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0031] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

[0032] Because the illustrated embodiments of the present invention may for the most part, be implemented using mechanical components and circuits known to those skilled in the art, details will not be explained in any greater extent than that considered necessary as illustrated above, for the understanding and appreciation of the underlying concepts of the present invention and in order not to obfuscate or distract from the teachings of the present invention. [0033] Any reference in the specification to a method should be applied mutatis mutandis to a system or a device capable of executing the method.

[0034] Any reference in the specification to a system or a device should be applied mutatis mutandis to a method that can be executed by the system or the device.

[0035] The term fluid refers to, at least one of a phase changing fluid, a sorption inducing fluid, a hydrates formation inducing fluid, or a sublimation inducing fluid.

[0036] Any reference to (i) either one of a fluid, a working fluid, a phase changing fluid, a sorption inducing fluid, a hydrates formation inducing fluid, or a sublimation inducing fluid - should be applied mutatis mutandis to (ii) any other one of a fluid, a working fluid, a phase changing fluid, a sorption inducing fluid, a hydrates formation inducing fluid, or a sublimation inducing fluid.

[0037] There are provided several methods to realize a completely new process of mixture separation using acoustic streaming based on boiling point differences. [0038] There are provided new geometries and characteristics for a thermoacoustic stack, which are fundamentally different from the current requirements.

[0039] There are provided methods to further optimize these structures, based on theoretical insight, using vapor mixtures

[0040] The suggested solutions enable significant reduction in the working temperature range of thermoacoustic engines.

[0041] The suggested solutions enable increased energy density, lowering the required pressure level in the resonator.

[0042] The suggested solutions introduces a completely new area of application for thermoacoustic devices - mixture separation.

[0043] Phase-change thermoacoustics - In general, thermoacoustics rely on heat conduction between gas and solid. However, it has also been suggested that a mixture containing a condensable vapor may offer potential improvements to the process, undergoing evaporation and condensation. We have taken this concept a step further, to consider any form of phase exchange - adsorption (gas/solid) or absorption (gas/liquid). The cycle is then augmented - with mass transfer. In our conceptualization of this mechanism, when the gas is displaced and compressed, heat is still exchanged in the process - but primarily as the latent heat of the phase change process, which can be far greater. Herein lies the potential of the mass transfer-based version of thermoacoustics, which has been shown to possess the potential to greatly improve the performance of thermoacoustic devices. Specifically, in an earlier project, the publications originating from the lab have demonstrated this potential, theoretically and experimentally. The phase-exchange process can be carried out at lower temperatures, yet still release large amounts of energy that can trigger and amplify the acoustic oscillations. This constitutes two main advantages over existing thermoacoustic technology:

[0044] Increasing energy density without the need for extreme pressures or temperatures.

[0045] Employing the transport phenomena of thermoacoustic phase change not only in heat engines, but also as a means for separation processes.

[0046] In the proposed patent we introduce new methods of thermoacoustic excitation that involves introducing multiple phase-changing components to the gas mixture. By doing so, we enable the system to operate at a large range of temperatures, while improving efficiency and energy density. Moreover, these methods also allow realizing a completely new process - mixture separation using acoustic streaming based on boiling point differences. [0047] These new methods and processes were partly tested in the lab and constitute the basis on which future development of the technology will be carried out, including in the framework of collaboration with external partners.

[0048] Following are several examples of how these methods may drastically enhance the performance of a thermoacoustic system compared to the classical “dry” mode of excitation. [0049] Enhancing the time period the engine can operate without losing the liquid source of the phase-changing component.

[0050] In figure 2 is an example of a thermoacoustic device 20 that includes a stack 50 that is located between a sealed top 23 and a sealed bottom 21. The stack is a ceramic stack that is compared with a cellulose stack developed in the lab. After one hour of heating to 220 degrees Celsius, the ceramic Cordierite stack loses its water content, as can be seen by the sudden rapid rise in temperature. In comparison, the absorbent cellulose stack maintains its water content by re-absorption, which limits the rise in temperature.

[0051] Reduction in the working temperature

[0052] Figure 3 presents a graph 30 that illustrates experimental results from a thermoacoustic engine with a cellulose stack developed in the lab. The temperature difference required to induce acoustic oscillations is significantly lower in the “wet” engine compared with the “dry” one. Moreover, for a similar resonator ambient pressure, a “wet” engine produces significantly more acoustic output than the “dry” engine, which means improved energy density.

[0053] Improving energy density

[0054] Figure 4 presents a graph 34 that illustrates modeled results in which, under a similar temperature difference, a thermoacoustic “wet” engine may generate approximately twice the acoustic power under 1 bar of resonator pressure, compared to the same setup using a classical dry stack, where 70 bars of resonator pressure are required to reach onset in similar temperature conditions. In practice this means both enabling utilization of low-grade heat sources, and also a much simpler resonator construction.

[0055] Reactive component mixture

[0056] To expand the temperature range of a multi-phase thermoacoustic system, we propose mixing several working fluids, where each fluid boils at a different temperature, thus ensuring a high concentration of the reactive component across a large temperature span. A mixture can also sustain a boiling point temperature glide. An example is provided in figure 5. Figure 5 illustrates (i) Graph 34 includes three vapor pressure versus location within the stack curves 41, 42 and 43 - of three different components that boil at three different temperatures, and also illustrates (ii) N channels 50(l)-50(2), a low temperature (Tl(low) 61) of a cold zone and a high temperature (T2(high) 62) of a hot zone.

[0057] Open cell absorptive stack

[0058] To replenish the liquid lost from the stack during the work of the thermoacoustic system, we propose using an open cell absorptive stack , in which liquid that accumulates on one end of the solid, is quickly soaked into the wall, and driven back to the drier section where it reenters the thermoacoustic cycle. Two examples are provided in figure 6.

[0059] Corrugated channel stack

[0060] Another method to replenish liquid in the stack is by corrugating the side of the channels, thus creating a capillary force driving the liquid back to the high evaporation area in the stack. Figure 6 illustrates two example of channels (having body 74 that surrounds an inner space 75) - that differ from each other by the width of their grooves. The lower example also shows the capillary flow 74. The upper example (with the narrower grooves) exhibits a slower absorption of the phase changing fluid - in comparison to the lower example. In both cases there is a flow (through the wall) of fluid from the cold zone 71 to the hot zone 72.

[0061] Increased surface area in parallel plate stack

[0062] To support free liquid transfer and avoid clogging, a parallel plate stack is preferable over a rectangular or circular channel stack. Nevertheless, parallel plate stacks have less surface area than the former, channeled ones. To overcome this, a parallel plate stack can be designed as undulating plates, thus avoiding clogging in narrow channels, and still maintaining plenty available surface area. An example is provided in figure 7 - illustrating N channels 89(1)- 89(N).

[0063] Wicks and reservoirs

[0064] Figure 8 illustrates an example of replenishing the liquid lost during system operation, is by placing absorptive wicks (wicking elements 83) or sprayers (spraying elements 84) against the stack, which take liquid from a liquid reservoir 81 (where it accumulates), to the beginning of the process. These wicks can also be placed on both sides of the stack, and in contact with a liquid reservoir, where liquid is constantly drawn from one side of the reservoir and condensed and collected at the end of the processed cycle into the same reservoir. An example is provided in figure 8. Figure 8 illustrates both wicking elements and spraying elements for brevity of explanation - only one may exist).

[0065] Direct heat and mass transfer

[0066] As a replacement for solid heat exchangers, the working fluid can function also as the heat transfer fluid. Here, the fluid is inserted in the middle of the stack and flows through both sides of the stack in a spatially uniform manner. During flow, the fluid exchanges heat with both sides of the stack, where one stream is heated, and the other one cooled. The two streams can the exchange heat with an external source and sink and return to the starting location and inserted again.

[0067] Similarly, the liquid stream can replace mass with the oscillating gas by absorbing and releasing a dissolve component. An example is provided in figure figures 9 and 10. Figure 9 illustrates a fluid input 99 that is positioned between the hot zone 97 and the cold zone 97 and is configured to receive a fluid at an intermediate temperature (T1 92), the intermediate temperature is lower than the temperature of the hot zone (T2) and is higher than the temperature of the cold zone (T3); multiple first stack channel portions 91(1)-91(N) and multiple second stack channel portions 95(1)- 95(N) that form multiple stack channels.

[0068] Figure 9 also illustrates the liquid 92 removed from the multiple second stack channel portions 95(1)- 95(N) and the liquid 93 removed from the multiple first stack channel portions 91(1)- 91(N). Figure 10 illustrates an example of a diluted liquid 102 that is inserted to a stack having stack channels 101(l)-101(N), concentrated liquid 104 being released from the stack, and an accumulation of clear solvent 103.

[0069] Internal mixing

[0070] To accelerate the diffusive transport of mass to\from the stack channel surface into the bulk of gas, we propose structuring the stack in a curved shape or adding internal mixing structures on a sidewall (see examples 111, 112 and 113 of figure 11) , which will create an additional driving force and allow the expansion of the channel which is currently limited by the speed of diffusion.

[0071] Internal mass injection

[0072] To accelerate the diffusive transport of mass to\from the stack channel surface into the bulk of gas, we propose structuring small semi permeable channels on, within (as a separate insert), or as the surface of the stack, which can actively drive the reactive component into the bulk of the gas. An example is provided in figure 12 - see stack channel 121, reactive component discharge 122 (from the surface of the stack channel).

[0073] There may be provide a method for operating a thermoacoustic device. According to an embodiment, the method includes operating any one of the thermoacoustic devices of the current application.

[0074] Figures 13-17 illustrate method 1300-1700, each including various steps executable during working - while making acoustic waves execute the cyclic thermodynamics of a heat engine, a heat pump, or a separation process. The role of the thermoacoustic system (for example - heat engine, a heat pump, or a separation process) defines at least a direction of propagation of the acoustic waves.

[0075] It should be noted that these examples refer to a reception, by a cold zone of a stack of a resonator of a thermoacoustic device, at least one fluid from a hot zone of the stack. The reception is attributed at least in part to the propagation of acoustic waves from the hot zone to the cold zone.

[0076] It should be noted that the propagation of acoustic waves can be from the cold zone to the hot zone - and that the al least one fluid can be received by the hot zone and from the cold zone - and any of the methods may include, for example, conveying, by a conveyor, at least some of the at least one fluid from the hot zone of the stack to the cold zone of the stack.

[0077] Any reference to a movement or reception of at least one fluid in one direction should be applied mutatis mutandis, to the movement of the at least one fluid to the opposite direction. Any reference to a hot zone should be applied mutatis mutandis to a reference to a cold zone. [0078] Figure 13 illustrates an method 1300 for operating a thermoacoustic device.

[0079] According to an embodiment, method 1300 includes step 1310 of receiving, by a cold zone of a stack of a resonator of a thermoacoustic device, at least one fluid from a hot zone of the stack. A temperature of the hot zone exceeds a temperature of the cold zone.

[0080] According to an embodiment, method 1300 also includes step 1320 of conveying, by a conveyor, at least some of the at least one fluid from the cold zone of the stack to the hot zone of the stack.

[0081] According to an embodiment, the conveyor is the stack.

[0082] According to an embodiment the conveyor differs from the stack.

[0083] According to an embodiment, the conveyor is an auxiliary phase changing fluid supplier.

[0084] According to an embodiment, the at least one fluid is at least one sorption inducing fluid.

[0085] According to an embodiment, the at least one fluid is at least one hydrates formation inducing fluid.

[0086] According to an embodiment, the at least one fluid is at least one sublimation inducing fluid.

[0087] According to an embodiment, the at least one fluid is at least one phase changing fluid. [0088] Figure 14 illustrates an example of method 1400.

[0089] According to an embodiment, method 1400 includes step 1410 of receiving, by a cold zone of a stack of a resonator of a thermoacoustic device, from a hot zone of the stack, a mixture of phase changing fluids that have different boiling temperatures. A temperature of the hot zone exceeds a temperature of the cold zone. The temperature of the cold zone is lower than each one of the different boiling temperatures.

[0090] Figure 15 illustrates an example of method 1500.

[0091] According to an embodiment, method 1500 includes step 1510 of receiving, by a cold zone of a stack of a resonator of a thermoacoustic device, from a hot zone of the stack, at least one fluid. The stack includes multiple stack structural elements that form multiple stack channels. The multiple stack structural elements are undulating along a traverse direction that is oriented to a longitudinal axis of the stack.

[0092] Step 1510 is executed while operating - while making acoustic waves to execute the cyclic thermodynamics of a heat engine, a heat pump, or a separation process.

[0093] Figure 16 illustrates an example of method 1600.

[0094] According to an embodiment, method 1600 includes step 1610 of receiving, by a cold zone of a stack of a resonator of a thermoacoustic device, from a hot zone of the stack, at least one fluid.

[0095] According to an embodiment, method 1600 also includes step 1620 of providing, by an auxiliary fluid supplier, at least a part of the at least one fluid to the hot zone of the stack.

[0096] According to an embodiment the auxiliary fluid supplier is an auxiliary phase changing fluid supplier. Other fluids mentions in the application can be provided by other auxiliary fluid suppliers.

[0097] Figure 17 illustrates an example of method 1700.

[0098] According to an embodiment, method 1700 includes step 1710 of receiving, by a fluid input, fluid at an intermediate temperature. The input is associated with a stack of a resonator of a thermoacoustic device. The stack has a cold zone and a hot zone. The intermediate temperature is between a temperature of the cold zone and a temperature of the hot zone. The fluid input is fed to an intermediate zone that is positioned between the hot zone and the cold zone. The hot zone is hotter than the cold zone.

[0099] According to an embodiment, step 1710 is followed by step 1720 of distributing the fluid at the intermediate temperature to (a) first stack channel portions that are formed between the hot zone and an intermediate zone, and (b) second stack channel portions that are formed between the intermediate zone and the cold zone.

[00100] The fluid that passes through the first stack channels passes through a heat exchanging path back to the fluid input. [00101] The fluid that passes through the second stack channels passes through a heat exchanging path back to the fluid input.

[00102] According to an embodiment, the channels may have a cross section (taken along a transverse plane) of any shape - polygon, curved, elliptical, circular, and the like. The cross section of a channel may be the same along the longitudinal axis of the channel. Alternatively, the cross section can be changed in any manner (periodic, non-periodic, gradual change, non-gradual change, linear change, non-linear change).

[00103] One or more walls of the channel may be patterned - include recesses and/or grooves and/or perturbations of any shape and/or size.

[00104] Examples of different channels and/or grooves are illustrated in figures 18-20 - see grooves 1800 of figure 18, changing cross section of a channel 1900 of figure 19. Figure 20 illustrates examples of rectangular cross sections channels 2001(l)-2001(N), circular cross section channels 2002(l)-2002(N), an elliptical cross section channel 2004, a triangular cross section channel 2005, and a pentahedron cross section channel 2003. Figure 20 also illustrates a longitudinal axis 2010 of channels and transverse axis 2011 and 2012 that define an example of a transverse plane.

[00105] In figure 18, the surface grooves have a bone shape, or may have a similar variants of that shape - or have any other shape, figure 19 illustrates a cross section that changes along a longitudinal axis following as wave shape that may be are symmetrical or slanted or any other shapes. Another example of channels includes helical channels.

[00106] According to an embodiment, the channels of a stack may be arranged in a linear array or in a two dimensional array.

[00107] According to an embodiment, the stack includes multiple stack structural elements that form multiple stack channels.

[00108] According to an embodiment, the at least some of the stack structural elements are made from a porous material that includes capillary conduits for conveying the at least some of the at least one phase changing fluid from the cold zone of the stack to the hot zone of the stack.

[00109] According to an embodiment, the porous material is cellulose.

[00110] According to an embodiment, the at least some of the stack structural elements are shaped to form external capillary conduits for conveying the at least some of the at least one phase changing fluid from the cold zone of the stack to the hot zone of the stack.

[00111] According to an embodiment, the at least one phase changing fluid is a mixture of phase changing fluids that have different boiling temperatures. [00112] According to an embodiment, the temperature of the cold zone is lower than each one of the different boiling temperatures.

[00113] According to an embodiment, the temperature of the hot zone is higher than each one of the different boiling temperatures.

[00114] According to an embodiment, the temperature of the hot zone is lower than at least one of the different boiling temperatures.

[00115] According to an embodiment, the stack includes multiple stack structural elements that form multiple stack channels.

[00116] According to an embodiment, the stack includes multiple stack structural elements that form multiple stack channels wherein the multiple stack structural elements are undulating along a traverse direction that is oriented to a longitudinal axis of the stack

[00117] According to an embodiment, there is provided a thermoacoustic device that includes a resonator that includes a stack. During operation (i) a cold zone of the stack is configured to receive, from a hot zone of the stack, a mixture of phase changing fluids that have different boiling temperatures; wherein a temperature of the hot zone exceeds a temperature of the cold zone, and (ii) the temperature of the cold zone is lower than each one of the different boiling temperatures.

[00118] According to an embodiment, the temperature of the hot zone is higher than each one of the different boiling temperatures.

[00119] According to an embodiment, the temperature of the hot zone is lower than at least one of the different boiling temperatures.

[00120] According to an embodiment, the stack includes multiple stack structural elements that form multiple stack channels.

[00121] According to an embodiment, there is provided a thermoacoustic device that includes a resonator that includes a stack. The stack includes multiple stack structural elements that form multiple stack channels. During operation (i) a cold zone of the stack is configured to receive a phase changing fluid from a hot zone of the stack; wherein a temperature of the hot zone exceeds a temperature of the cold zone; and (ii) the multiple stack structural elements are undulating along a traverse direction that is oriented to a longitudinal axis of the stack.

[00122] According to an embodiment, there is provided a thermoacoustic device that includes a resonator that includes a stack. During operation a cold zone of the stack is configured to receive a phase changing fluid from a hot zone of the stack; wherein a temperature of the hot zone exceeds a temperature of the cold zone. The thermoacoustic device further includes an auxiliary phase changing fluid supplier that is configured to provide a phase changing fluid to the hot zone of the stack.

[00123] According to an embodiment, the auxiliary phase changing fluid supplier is configured to convey at least some of the phase changing fluid from the cold zone of the stack to the hot zone of the stack.

[00124] According to an embodiment, the auxiliary phase changing fluid supplier includes a collector for collecting phase changing fluid from the cold zone, a fluid conduit for conveying the phase changing fluid, and a wicking element for providing the phase changing fluid to the hot zone.

[00125] According to an embodiment, the fluid conduit is located outside the stack channels.

[00126] According to an embodiment, the auxiliary phase changing fluid supplier is a spraying element.

[00127] According to an embodiment, there is provided a thermoacoustic device that includes a resonator that includes a stack. The stack includes (i) a hot zone and a cold zone, wherein a temperature of the hot zone exceeds a temperature of the cold zone; (ii) a phase changing fluid input that is positioned between the hot zone and the cold zone and is configured to receive a phase changing fluid at an intermediate temperature, the intermediate temperature is lower than the temperature of the hot zone and is higher than the temperature of the cold zone; and (iii) multiple first stack channel portions and multiple second stack channel portions that form multiple stack channels. The first stack channel portions are formed between the hot zone and an intermediate zone, the intermediate zone is fed by the phase changing fluid input. The second stack channel portions are formed between the intermediate zone and the cold zone.

[00128] According to an embodiment, the thermoacoustic device includes a first heat exchange unit that is configured to (i) receive, from the hot zone, the phase changing fluid, (ii) exchange heat, and (iii) output the phase changing fluid at the intermediate temperature.

[00129] According to an embodiment, the thermoacoustic device includes a second heat exchange unit that is configured to (i) receive, from the cold zone, the phase changing fluid, (ii) exchange heat, and (iii) output the phase changing fluid at the intermediate temperature.

[00130] According to an embodiment, the phase changing fluid input is configured to receive the phase changing fluid from each one of the first heat exchange unit and the second heat exchange unit. [00131] According to an embodiment, there is provided a thermoacoustic device that includes a resonator that includes a stack, the stack includes multiple stack structural elements that form multiple stack channels that are curved. During operation during operation a cold zone of the stack is configured to receive a phase changing fluid from a hot zone of the stack. A temperature of the hot zone exceeds a temperature of the cold zone.

[00132] The multiple stack channels are curved long a longitudinal axis of the stack.

[00133] According to an embodiment, there is provided a thermoacoustic device that includes a resonator that includes a stack. The stack includes multiple stack structural elements that form multiple stack channels. During operation, a cold zone of the stack is configured to receive a phase changing fluid from a hot zone of the stack, wherein a temperature of the hot zone exceeds a temperature of the cold zone. At least one of the multiple stack structural element is semi-permeable.

[00134] According to an embodiment, there is provided a thermoacoustic device that includes (i) a resonator that includes a stack; wherein during operation, a cold zone of the stack is configured to receive at least one fluid from a hot zone of the stack; wherein a temperature of the hot zone exceeds a temperature of the cold zone; and (ii) a conveyor for conveying at least some of the at least one fluid from the cold zone of the stack to the hot zone of the stack. [00135] According to an embodiment, the at least one fluid is an at least one phase changing fluid.

[00136] According to an embodiment, the conveyor is the stack.

[00137] According to an embodiment, the stack includes multiple stack structural elements that form multiple stack channels.

[00138] According to an embodiment, the at least some of the stack structural elements are made from a porous material that includes capillary conduits for conveying the at least some of the at least one phase changing fluid from the cold zone of the stack to the hot zone of the stack.

[00139] According to an embodiment, the porous material is cellulose. Other porous materials can be used.

[00140] According to an embodiment, the at least some of the stack structural elements are shaped to form external capillary conduits for conveying the at least some of the at least one phase changing fluid from the cold zone of the stack to the hot zone of the stack.

[00141] According to an embodiment, the at least one phase changing fluid is a mixture of phase changing fluids that have different boiling temperatures. [00142] According to an embodiment, the temperature of the cold zone is lower than each one of the different boiling temperatures.

[00143] According to an embodiment, the temperature of the hot zone is higher than each one of the different boiling temperatures.

[00144] According to an embodiment, the temperature of the hot zone is lower than at least one of the different boiling temperatures.

[00145] According to an embodiment, the stack includes multiple stack structural elements that form multiple stack channels.

[00146] According to an embodiment, the stack includes multiple stack structural elements that form multiple stack channels wherein the multiple stack structural elements are undulating along a traverse direction that is oriented to a longitudinal axis of the stack.

[00147] According to an embodiment, the conveyor is an auxiliary phase changing fluid supplier.

[00148] According to an embodiment, the auxiliary phase changing fluid supplier includes a collector for collecting phase changing fluid from the cold zone, a fluid conduit for conveying the phase changing fluid, and a wicking element for providing the phase changing fluid to the hot zone.

[00149] According to an embodiment, the fluid conduit is located outside the stack channels.

[00150] According to an embodiment, the auxiliary phase changing fluid supplier is a spraying element.

[00151] According to an embodiment, the stack includes multiple stack structural elements that form multiple stack channels that are curved.

[00152] According to an embodiment, the stack includes multiple stack structural elements wherein at least one of the multiple stack structural element is semi-permeable.

[00153] According to an embodiment, the stack includes multiple stack structural elements wherein at least one of the multiple stack structural element is semi-permeable.

[00154] According to an embodiment, the at least one fluid is at least one sorption inducing fluid.

[00155] According to an embodiment, the at least one fluid is at least one hydrates formation inducing fluid.

[00156] According to an embodiment, the at least one fluid is at least one sublimation inducing fluid. [00157] According to an embodiment there is provided a method of operating a thermoacoustic device. Examples of thermoacoustic devices being operated by the method are illustrated above and/or in any of the figures.

[00158] According to an embodiment there is provided a method of operating a thermoacoustic device, the method includes receiving, by a cold zone of a stack of a resonator of a thermoacoustic device, at least one fluid from a hot zone of the stack; wherein a temperature of the hot zone exceeds a temperature of the cold zone; and conveying, by a conveyor of the stack, at least some of the at least one fluid from the cold zone of the stack to the hot zone of the stack.

[00159] According to an embodiment, the at least one fluid is at least one sorption inducing fluid.

[00160] According to an embodiment, the at least one fluid is at least one hydrates formation inducing fluid.

[00161] According to an embodiment, the at least one fluid is an at least one phase changing fluid.

[00162] According to an embodiment, the at least one phase changing fluid is a mixture of phase changing fluids that have different boiling temperatures.

[00163] According to an embodiment, the conveyor is the stack.

[00164] According to an embodiment, the conveyor is an auxiliary phase changing fluid supplier.

[00165] According to an embodiment, there is provided a thermoacoustic device that includes a resonator that includes wherein the resonator includes a stack, wherein the stack includes (a) a hot zone and a cold zone; wherein a temperature of the hot zone exceeds a temperature of the cold zone; (ii) a fluid input that is positioned between the hot zone and the cold zone and is configured to receive a fluid at an intermediate temperature, the intermediate temperature is lower than the temperature of the hot zone and is higher than the temperature of the cold zone; and (iii) multiple first stack channel portions and multiple second stack channel portions that form multiple stack channels. The first stack channel portions are formed between the hot zone and an intermediate zone, the intermediate zone is fed by the fluid input. The second stack channel portions are formed between the intermediate zone and the cold zone.

[00166] According to an embodiment, the at least one fluid is an at least one phase changing fluid. [00167] According to an embodiment, the thermoacoustic device includes a first heat exchange unit that is configured to (i) receive, from the hot zone, the phase changing fluid, (ii) exchange heat, and (iii) output the phase changing fluid at the intermediate temperature.

[00168] According to an embodiment, the thermoacoustic device includes a second heat exchange unit that is configured to (i) receive, from the cold zone, the phase changing fluid, (ii) exchange heat, and (iii) output the phase changing fluid at the intermediate temperature.

[00169] According to an embodiment, the phase changing fluid input is configured to receive the phase changing fluid from each one of the first heat exchange unit and the second heat exchange unit.

[00170] Any reference to the term “comprising” or “having” should be interpreted also as referring to, mutatis mutandis to “consisting” and/or mutatis mutandis to “essentially consisting of’.

[00171] In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein without departing from the broader spirit and scope of the invention as set forth in the appended claims.

[00172] Moreover, the terms “front,” “back,” “top,” “bottom,” “over,” “under” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.

[00173] Any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality may be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being "operably connected," or "operably coupled," to each other to achieve the desired functionality.

[00174] Furthermore, those skilled in the art will recognize that boundaries between the above described operations merely illustrative. The multiple operations may be combined into a single operation, a single operation may be distributed in additional operations and operations may be executed at least partially overlapping in time. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in various other embodiments.

[00175] However, other modifications, variations and alternatives are also possible. The specifications and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense.

[00176] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word ‘comprising’ does not exclude the presence of other elements or steps then those listed in a claim. Furthermore, the terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an." The same holds true for the use of definite articles. Unless stated otherwise, terms such as “first" and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

[00177] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

We claim

1. A thermoacoustic device comprising: a resonator; wherein the resonator comprises a stack; wherein during operation, a cold zone of the stack is configured to receive at least one fluid from a hot zone of the stack; wherein a temperature of the hot zone exceeds a temperature of the cold zone; and a conveyor for conveying at least some of the at least one fluid from the cold zone of the stack to the hot zone of the stack.

2. The thermoacoustic device according to claim 1, wherein the at least one fluid is an at least one phase changing fluid.

3. The thermoacoustic device according to claim 2, wherein the conveyor is the stack.

4. The thermoacoustic device according to claim 3, wherein the stack comprises multiple stack structural elements that form multiple stack channels.

5. The thermoacoustic device according to claim 4, wherein at least some of the stack structural elements are made from a porous material that comprises capillary conduits for conveying the at least some of the at least one phase changing fluid from the cold zone of the stack to the hot zone of the stack.

6. The thermoacoustic device according to claim 5, wherein the porous material is cellulose.

7. The thermoacoustic device according to claim 4, wherein at least some of the stack structural elements are shaped to form external capillary conduits for conveying the at least some of the at least one phase changing fluid from the cold zone of the stack to the hot zone of the stack.

8. The thermoacoustic device according to claim 3, wherein the at least one phase changing fluid is a mixture of phase changing fluids that have different boiling temperatures.

9. The thermoacoustic device according to claim 8, wherein the temperature of the cold zone is lower than each one of the different boiling temperatures.

10. The thermoacoustic device according to claim 8, wherein the temperature of the hot zone is higher than each one of the different boiling temperatures.

11. The thermoacoustic device according to claim 8, wherein the temperature of the hot zone is lower than at least one of the different boiling temperatures. The thermoacoustic device according to claim 8, wherein the stack comprises multiple stack structural elements that form multiple stack channels. The thermoacoustic device according to claim 3, wherein the stack comprises multiple stack structural elements that form multiple stack channels wherein the multiple stack structural elements are undulating along a traverse direction that is oriented to a longitudinal axis of the stack. The thermoacoustic device according to claim 2, wherein the conveyor is an auxiliary phase changing fluid supplier. The thermoacoustic device according to claim 14, wherein the auxiliary phase changing fluid supplier comprises a collector for collecting phase changing fluid from the cold zone, a fluid conduit for conveying the phase changing fluid, and a wicking element for providing the phase changing fluid to the hot zone. The thermoacoustic device according to claim 15, wherein the fluid conduit is located outside the stack channels. The thermoacoustic device according to claim 15, wherein the auxiliary phase changing fluid supplier is a spraying element. The thermoacoustic device according to claim 2, wherein the stack comprises multiple stack structural elements that form multiple stack channels that are curved. The thermoacoustic device according to claim 2, wherein the stack comprises multiple stack structural elements wherein at least one of the multiple stack structural element is porous. The thermoacoustic device according to claim 2, wherein the stack comprises multiple stack structural elements wherein at least one of the multiple stack structural element is semi-permeable. The thermoacoustic device according to claim 1, wherein the at least one fluid is at least one sorption inducing fluid. The thermoacoustic device according to claim 1, wherein the at least one fluid is at least one hydrates formation inducing fluid. The thermoacoustic device according to claim 1, wherein the at least one fluid is at least one sublimation inducing fluid. A method of operating a thermoacoustic device, the method comprising: receiving, by a cold zone of a stack of a resonator of a thermoacoustic device, at least one fluid from a hot zone of the stack; wherein a temperature of the hot zone exceeds a temperature of the cold zone; and conveying, by a conveyor of the stack, at least some of the at least one fluid from the cold zone of the stack to the hot zone of the stack. The method according to claim 24, wherein the at least one fluid is at least one sorption inducing fluid. The method according to claim 24, wherein the at least one fluid is at least one hydrates formation inducing fluid. The method according to claim 24, wherein the at least one fluid is an at least one phase changing fluid. The method according to claim 27, wherein the at least one phase changing fluid is a mixture of phase changing fluids that have different boiling temperatures. The method according to claim 27, wherein the conveyor is the stack. The method according to claim 27, wherein the conveyor is an auxiliary phase changing fluid supplier. A thermoacoustic device comprising: a resonator; wherein the resonator comprises a stack, wherein the stack comprises: a hot zone; a cold zone; wherein a temperature of the hot zone exceeds a temperature of the cold zone; a fluid input that is positioned between the hot zone and the cold zone and is configured to receive a fluid at an intermediate temperature, the intermediate temperature is lower than the temperature of the hot zone and is higher than the temperature of the cold zone; and multiple first stack channel portions and multiple second stack channel portions that form multiple stack channels; wherein the first stack channel portions are formed between the hot zone and an intermediate zone, the intermediate zone is fed by the fluid input; and wherein the second stack channel portions are formed between the intermediate zone and the cold zone. The thermoacoustic device according to claim 31 , wherein the at least one fluid is an at least one phase changing fluid. The thermoacoustic device according to claim 32, comprising a first heat exchange unit that is configured to (i) receive, from the hot zone, the phase changing fluid, (ii) exchange heat, and (iii) output the phase changing fluid at the intermediate temperature. The thermoacoustic device according to claim 33, comprising a second heat exchange unit that is configured to (i) receive, from the cold zone, the phase changing fluid, (ii) exchange heat, and (iii) output the phase changing fluid at the intermediate temperature. The thermoacoustic device according to claim 32, wherein the phase changing fluid input is configured to receive the phase changing fluid from each one of the first heat exchange unit and the second heat exchange unit.