Thermoacoustic device, heat transfer system and method of operating the thermoacoustic device

Abstract

The present invention relates to a heat transfer system, thermo-acoustic device, heat pump system, heat engine system and a method for operating a thermo-acoustic device, which provides the advantages of compactness, low noise and high efficiency.

Description

Technical Field

[0001] This invention relates to a heat transfer system, for example, configured to provide space heating and / or domestic hot water heating. In order to utilize relatively low-temperature heat sources or heat sinks (e.g., geothermal, water, commercial and industrial waste heat, solar thermal energy, and ambient air, but also, for example, district heating), heat transfer systems typically include heat pumps that use a vapor compression cycle to allow heat to be transferred from a lower-temperature location to another higher-temperature location (i.e., heat transfer against the temperature gradient). Background Technology

[0002] To utilize a vapor compression cycle, a heat pump comprises two heat exchangers: a condenser that releases heat and an evaporator that absorbs heat. A compressor is used to increase the pressure and, consequently, the temperature of a low-temperature, low-pressure gas. This gas then passes through the condenser, where it releases heat to the surrounding environment as it cools and condenses completely. The cooled, high-pressure liquid then passes through an expansion valve, which abruptly reduces the pressure, causing a sharp drop in temperature. This low-temperature, low-pressure mixture of liquid and vapor now passes through the evaporator, where it completely vaporizes as it absorbs heat from the environment, before returning to the compressor to restart the cycle.

[0003] Many working fluids suitable for vapor compression cycles are environmentally unfriendly. Recent regulations have driven the industry to use working fluids with low greenhouse gas heating potential, such as propane. However, propane heat pumps present considerable challenges, including but not limited to the flammability of propane, high compressor noise, limited operating temperature range and / or limited service life, as well as system size and weight. Summary of the Invention

[0004] In view of the above, the object of the present invention is to provide an improved heat transfer system that alleviates at least one of the above problems.

[0005] According to a first aspect of the present invention, a heat transfer system is provided, comprising: - A first fluid circuit having a pump for circulating fluid in the first fluid circuit; - A second fluid circuit having a pump for circulating fluid in the second fluid circuit; - Control unit; - Thermoacoustic device, including: o An acoustic network having a loop and a working fluid disposed within the acoustic network; o Acoustic driver, used to provide acoustic energy to the acoustic network; and o A heat core, disposed in the loop, the heat core including a hot end heat exchanger, a cold end heat exchanger and a regenerator disposed between the hot end heat exchanger and the cold end heat exchanger. The control unit is configured to operate the acoustic driver; The hot-end heat exchanger is part of the first fluid loop; The cold-end heat exchanger is part of the second fluid loop; The acoustic driver includes two actuators; The control unit is configured to operate the two actuators synchronously. The two actuators are arranged such that they are operated synchronously by a control unit so that the forces applied to the housing or frame of the thermoacoustic device at least partially cancel each other out. Furthermore, the acoustic driver and acoustic network are configured such that the synchronous operation of the two actuators forms a traveling wave at the location of the hot core, thereby allowing heat to be moved from the cold end heat exchanger to the hot end heat exchanger.

[0006] Compared to vapor compression cycles, thermoacoustic devices offer several advantages, primarily based on the use of more environmentally friendly working fluids such as helium, argon, and nitrogen, which are inert and non-flammable. However, due to the low efficiency, relatively large size, relatively high cost, and / or inherent noise generated by the acoustic actuators of existing thermoacoustic devices, they have not yet been considered a good alternative to vapor compression cycles.

[0007] However, the thermoacoustic device according to the first aspect of the invention uses two actuators, both of which generate sound waves, but are arranged to operate synchronously such that the vibrations and / or reaction forces generated by these waves when they interact with the housing of the thermoacoustic device at least partially cancel each other out, thereby reducing the noise level outside the thermoacoustic device.

[0008] In one embodiment, synchronous operation means that the actuators move in phase, that is, the drive signals provided to the actuators are in phase. For example, when the moving parts of two actuators are arranged such that they move in opposite directions when moving the working fluid toward the loop.

[0009] In one embodiment, synchronous operation means that the actuators move out of phase, that is, the drive signals provided to the actuators are offset by 180 degrees relative to each other. For example, this is the case when the moving parts of two actuators are arranged such that they move in the same direction as the working fluid moves toward the loop.

[0010] In one embodiment, each of the two actuators is arranged such that an approximate standing wave can be generated on one side of each actuator. This approximate standing wave branches into two directions to propagate in opposite directions through the loop, thereby subsequently interfering with each other and generating a wave with traveling wave characteristics at the hot core.

[0011] The approximate standing wave generated by the actuator (which may be referred to as a standing wave throughout the specification) can be a pure standing wave, but in practice it may have more complex forms, such as a superposition of a pure standing wave and a pure traveling wave, in which the pure standing wave contributes the most.

[0012] Due to its traveling wave characteristics, the wave at the hot core will be referred to as a traveling wave throughout this specification. However, those skilled in the art will understand that the wave at the hot core is not necessarily a pure traveling wave, but may have a more complex form, such as a superposition of a pure standing wave and a pure traveling wave, in which the pure traveling wave contributes the most. Therefore, in short, the traveling wave expands at the cold-end heat exchanger and compresses at the hot-end heat exchanger via the regenerator. The advantage of the traveling wave is that the corresponding cycle best matches the Stirling cycle, which is more efficient than the Brayton cycle using pure or near-standing waves, and the improved thermal contact between the working fluid and the regenerator further enhances efficiency.

[0013] Therefore, each of the two actuators is capable of generating an approximate standing wave at the entrance of the loop, which branches in a first direction along the first loop portion (which may be referred to as the forward length) toward the hot-end heat exchanger side of the hot core, and in a second direction along the second loop portion (which may be referred to as the backward length) toward the cold-end heat exchanger side of the hot core, to interfere with each other. Each of the two actuators can interact with its own acoustic loop, or the two actuators can interact with the same loop. In the latter case, the two actuators can, for example, be arranged in the respective side arms of the T-connection.

[0014] In other words, each loop of the acoustic network includes a first loop extending between the acoustic transducer and the hot-end heat exchanger, and a second loop extending between the acoustic transducer and the cold-end heat exchanger. The first and second loops are connected to each other at the acoustic actuator such that during operation of the acoustic actuator, the first and second loops are in fluid communication with each other for most of the actuation cycle (possibly throughout the entire actuation cycle). This means that, for at most a relatively short period of time during the actuation cycle, the connection between the first and second loops may be closed by the moving part of the acoustic actuator.

[0015] In one embodiment, a spring-type separator element is provided in the loop, for example, between the acoustic actuator and the cold end heat exchanger of the hot core. The spring-type separator element is configured to close the cross section of the loop and be impermeable to the working fluid, while allowing pressure waves in the working fluid to be transmitted through the spring-type separator element.

[0016] This spring-type separator element, that is, a separator comprising elements having mechanical properties defined by their spring constant, is preferably configured to force a larger volumetric flow rate through the regenerator without increasing the fluid volume in the device. In addition to increasing the volumetric velocity and thus the power density, the spring-type separator element can also improve the phase between the pressure and velocity of the working fluid in the regenerator, and therefore also has a beneficial effect on efficiency. The spring-type separator element can also be used to suppress DC flow in the loop, that is, to suppress time-averaged flow in the loop.

[0017] The spring-type separator element can be or includes a membrane, in which case the spring-type separator element can be called a pressure-boosting membrane.

[0018] In one embodiment, a partition element is provided in the loop, preferably located between the hot-end heat exchanger and the acoustic actuator, more preferably arranged closer to the hot-end heat exchanger than the acoustic actuator. The partition element is configured to close the cross section of the loop to suppress DC flow in the loop, while at the same time the partition element is acoustically transparent and allows waves to pass between the hot-end heat exchanger and the cold-end heat exchanger, and vice versa.

[0019] In this way, DC flow is reduced, and preferably blocked, and convective heat transfer between the hot-end heat exchanger and the rest of the loop is greatly reduced. As a result, less heat leaks from the hot-end heat exchanger, and therefore more heat can be transferred between the cold-end and hot-end heat exchangers, thereby improving the efficiency of the thermoacoustic device.

[0020] The separating element can be or includes a membrane, in which case the separating element can be called an anti-flow membrane.

[0021] The control unit can be dedicated to controlling the thermoacoustic device, and can be, for example, part of the thermoacoustic device, but can also be configured to control other components of the heat transfer system, such as pumps and / or valves in water circuits and / or fluid circuits.

[0022] In one embodiment, the control unit is configured to operate the acoustic driver based on a control signal representing the power demand of the heat transfer system. This control signal can be determined by the control unit itself, for example, based on user input and / or one or more sensor signals and / or one or more control rules and / or one or more databases. The control signal can also be received from a higher-level controller.

[0023] The control signal can be in the form of an absolute value or a percentage of the maximum power demand. The control unit is then configured to operate the acoustic driver at the required power demand or the closest achievable value.

[0024] In one embodiment, a sensor may be provided, for example, arranged in a first fluid circuit, to measure parameters such as power, pressure, temperature, and / or flow rate of the fluid in the first fluid circuit, and wherein the control unit is configured to operate the acoustic actuator based on the sensor output. Thus, for example, the control signal may be based on the sensor output. Therefore, the sensor may be a power sensor, a pressure sensor, a temperature sensor, or a flow sensor.

[0025] In one embodiment, the thermoacoustic device includes additional acoustic control elements that can be used, for example, actively or passively by a control unit, to adjust specific power within the hot core. An example of an additional passive acoustic control element could be a branched Helmholtz resonator used to force a larger volumetric flow through the regenerator, similar to the function of a pressure-boosting membrane.

[0026] In one embodiment, the control unit is configured to operate an acoustic driver to adjust the power output of the thermoacoustic device to a short-term variation, for example, represented by a control signal, and to operate additional acoustic control elements to adjust the power output of the thermoacoustic device to a long-term variation, for example, due to wear.

[0027] In one embodiment, the loop surrounds a central space, in which the acoustic driver is at least partially arranged. Its main advantage is that the device can be designed to be smaller.

[0028] In one embodiment, at least one actuator of the acoustic driver has a movable portion or part that is fully or at least partially located within the central space, such that the movable portion / part can at least partially move into and out of the central space, or the movable portion / part can be fully or mostly arranged in the central space.

[0029] In one embodiment, the loop inlet position on one side of at least one of the actuators is arranged in or facing the central space.

[0030] In one embodiment, the loop defines an extension through the center of the loop and parallel to the central plane of the loop, wherein two actuators are arranged on either side of the central plane such that the acoustic actuators extend substantially perpendicular to the central plane.

[0031] In one embodiment, one of the actuators of the acoustic actuator includes a piston that can move in a parallel direction.

[0032] In one embodiment, each of the two actuators separates the acoustic loop from the bounce chamber, preferably such that a positive and negative pressure differential can be generated using the fixed total volume of the loop and the bounce chamber.

[0033] In one embodiment, two actuators reciprocate around an equilibrium position, wherein when the two actuators are in the equilibrium position, the pressure inside the rebound chamber is equal to the pressure inside the acoustic loop.

[0034] In one embodiment, the heat transfer system includes a plurality of thermoacoustic devices arranged in series and / or in parallel.

[0035] In one embodiment, the thermoacoustic device includes a cooling circuit for controlling the temperature of components of the thermoacoustic device other than the heat core, wherein the cooling circuit is connected to or a portion of a second fluid circuit. This can have the advantage of stabilizing the temperature of the thermoacoustic device using the cooling circuit, thereby preventing damage due to overheating and / or increased efficiency. The connection between the cooling circuit and the second fluid circuit can be upstream or downstream of a cold-end heat exchanger. Such a connection can be a fluid connection, but it can also include only a thermal connection, where the fluids in the circuit are separate, but heat can be transferred using a separate heat exchanger.

[0036] In one embodiment, the thermoacoustic device includes a cooling circuit for controlling the temperature of components of the thermoacoustic device other than the heating core, wherein the cooling circuit is connected to or a portion of a first fluid circuit. This can have the advantage of stabilizing the temperature of the thermoacoustic device using the cooling circuit, thereby preventing damage due to overheating and / or increased efficiency. The connection between the cooling circuit and the first fluid circuit is preferably upstream of the hot-end heat exchanger. Other components of the thermoacoustic device are then used to preheat the first fluid, thereby improving efficiency. Such a connection can be a fluid connection, but it can also consist of only a thermal connection, where the fluids in the circuit are separate, but heat can be transferred using a separate heat exchanger.

[0037] In one embodiment, the thermoacoustic device is configured to allow heat generated in the acoustic driver to flow towards the cold-end heat exchanger via thermal conduction. This provides a passive way to cool the acoustic driver, preventing overheating and / or improving efficiency / performance.

[0038] In one example, the cooling circuit can be arranged outside the outer wall of the device, for example, using a coil-shaped wrapping around the device wall. This cooling circuit is part of a second fluid circuit upstream of the cold-end heat exchanger, thereby being able to receive heat transferred through the device wall (provided via thermal conduction and / or thermal convection), thus preheating the fluid in the second fluid circuit. This will stabilize the temperature of the device and improve the efficiency of the device.

[0039] Therefore, the heat generated due to inefficiency is used as an additional input to the thermoacoustic process.

[0040] In a preferred embodiment, the net forces applied to the housing or frame by the two actuators are substantially equal in magnitude, extend substantially in opposite directions, and are preferably aligned relative to each other. This has the advantage that the forces substantially completely cancel each other out and do not introduce torque into the housing or frame.

[0041] In one embodiment, the acoustic network includes two loops and a hot core for each loop. An acoustic driver is then configured to supply acoustic energy to both loops, thus creating a traveling wave at the location of each hot core.

[0042] The loops can be interconnected, for example, via connecting tubes / conduits / channels, wherein the acoustic actuators are arranged to generate an approximate standing wave in the connecting tubes / conduits / channels, which then branches in four directions (i.e., along the first and second loop portions of one loop and along the first and second loop portions of another loop) to propagate in two opposite directions through each loop (i.e., parallel through the first and second loop portions), thereby subsequently interfering with each other and generating a wave with traveling wave characteristics at the hot core of each loop.

[0043] Alternatively, the loops are arranged separately, wherein one of the two actuators is arranged to provide acoustic energy to one loop of the acoustic network, and the other of the two actuators is arranged to provide acoustic energy to another loop of the acoustic network.

[0044] In one embodiment, the first loop portion and / or the second loop portion may include two or more loop sections extending parallel to each other. These loop sections may be separate from each other. In one example, the first loop portion or the second loop portion includes two, three, four or more loop sections extending parallel between the thermal core and the acoustic actuator.

[0045] According to a second aspect of the present invention, a thermoacoustic device is provided, comprising: - An acoustic network having a loop and a working fluid disposed within the acoustic network; - A heat core, disposed in the loop, comprising a hot-end heat exchanger, a cold-end heat exchanger, and a regenerator located between the hot-end heat exchanger and the cold-end heat exchanger. - Acoustic transducers are used to convert acoustic energy in an acoustic network into other types of energy or vice versa; The ring road surrounds a central space; Furthermore, the acoustic transducer is at least partially located in the central space.

[0046] In one embodiment, the loop further includes a first loop portion extending between the acoustic transducer and the hot-end heat exchanger, and a second loop portion extending between the acoustic transducer and the cold-end heat exchanger, wherein the first loop portion and the second loop portion are connected to each other at the acoustic transducer. In other words, the first loop portion and the second loop portion are connected to each other at the acoustic transducer such that during operation of the acoustic transducer, the first loop portion and the second loop portion are in fluid communication with each other for most of the actuation cycle, preferably throughout the entire actuation cycle. This means that the connection between the first loop portion and the second loop portion may be closed by the moving part of the acoustic transducer for at most a relatively short period of time during the actuation cycle. Preferably, fluid communication may exist throughout the entire actuation cycle.

[0047] In one embodiment, the movable portion or part of the acoustic driver has a range of motion that is fully or at least partially located within the central space, such that the movable portion / part can at least partially move into and out of the central space, or the movable portion / part can be fully or mostly arranged in the central space.

[0048] In one embodiment, the loop defines an extension that passes through the center of the loop and is parallel to the central plane of the loop, wherein the acoustic transducer extends perpendicular to the central plane.

[0049] In one embodiment, the acoustic transducer includes one or more pistons movable in a direction of movement that may be substantially perpendicular to the plane defined by the central space.

[0050] In one embodiment, the piston of the acoustic transducer separates the loop from the bounce chamber. Preferably, the piston reciprocates around an equilibrium position, wherein when the piston is in the equilibrium position, the pressure inside the bounce chamber is equal to the pressure inside the acoustic loop.

[0051] In one embodiment, the thermoacoustic device further includes a cooling circuit for controlling the temperature of components of the thermoacoustic device other than the heat core, wherein the cooling circuit is connected to, or is part of, a first fluid circuit or a second fluid circuit leading to a hot-end heat exchanger and a cold-end heat exchanger, respectively. Alternatively or additionally, a thermal cooling path may be provided between the cold-end heat exchanger and the portion of the thermoacoustic device to be cooled to allow cooling via heat conduction. For example, the thermoacoustic device may be configured to allow heat to flow from the acoustic transducer to the cold-end heat exchanger.

[0052] In one example, the cooling circuit can be arranged outside the outer wall of the device, for example, using a coil-shaped wrapping around the device wall. This cooling circuit is part of a second fluid circuit upstream of the cold-end heat exchanger, thereby being able to receive heat transferred through the device wall (provided via thermal conduction and / or thermal convection), thus preheating the fluid in the second fluid circuit. This will stabilize the temperature of the device and improve the efficiency of the device.

[0053] Therefore, the heat generated due to inefficiency is used as an additional input to the thermoacoustic process.

[0054] In one embodiment, the acoustic transducer separates the loop from one or more bounce cavities to allow the generation of positive and negative differential pressures using a fixed total volume of the loop and one or more bounce cavities.

[0055] In one embodiment, the acoustic transducer includes two transducer units arranged such that the forces applied by the two transducer units to the housing or frame of the thermoacoustic device are or may be applied synchronously to at least partially cancel each other out.

[0056] According to a third aspect of the invention, a heat pump system is provided, comprising: a thermoacoustic device according to a second aspect of the invention; and a control unit, wherein the acoustic transducer includes an actuator for providing acoustic energy to an acoustic network, and wherein the control unit is configured to operate the acoustic transducer to transfer heat from a cold-end heat exchanger to a hot-end heat exchanger.

[0057] According to a fourth aspect of the invention, a heat engine system is provided, comprising: a thermoacoustic device according to a second aspect of the invention; a heat source; and a heat sink, wherein the heat source is connected to a hot-end heat exchanger and the heat sink is connected to a cold-end heat exchanger to provide a temperature difference between the hot-end and cold-end heat exchangers, wherein an acoustic network is configured to generate acoustic energy using the temperature difference, and wherein an acoustic transducer is configured to convert the acoustic energy into other types of energy.

[0058] According to a fifth aspect of the invention, a method is provided for operating a thermoacoustic device according to a first aspect of the invention, wherein two actuators are driven synchronously such that forces applied to the housing or frame of the thermoacoustic device at least partially cancel each other out.

[0059] In one embodiment, the method includes: determining the overall system resonance, and operating two actuators at or near the overall system resonance. This can have the advantage that changes in the overall system resonance, such as due to changes in operating temperature or ambient conditions, can be determined, and the operation of the thermoacoustic device can be adjusted accordingly to maintain the desired efficiency level. The overall system resonance may have different contributions, but it may be dominated by mechanical resonance.

[0060] As will be apparent to those skilled in the art, in order to avoid excessive repetition of features and embodiments, features and embodiments related to one aspect of the invention may be readily applied to other aspects of the invention where appropriate. Attached Figure Description

[0061] The invention will now be described in a non-limiting manner by reference to the accompanying drawings, in which similar parts are indicated by similar reference numerals, and in the drawings: Figure 1 A heat transfer system according to one embodiment of the present invention is schematically depicted; Figure 2 A thermoacoustic device according to an embodiment of the present invention is schematically depicted; Figure 3A A cross-sectional view of a thermoacoustic device according to another embodiment of the present invention is schematically depicted; Figure 3B schematically depicted Figure 3A Another cross-sectional view of the thermoacoustic device; Figure 4 A heat transfer system according to another embodiment of the present invention is schematically depicted; Figure 5 A cross-sectional view of a thermoacoustic device according to another embodiment of the present invention is schematically depicted; Figure 6 A cross-sectional view of a thermoacoustic device according to another embodiment of the present invention is schematically depicted; Figure 7 schematically depicted Figure 6 Another cross-sectional view of the thermoacoustic device; and Figure 8 schematically depicted Figure 5 A cross-sectional view of an alternative embodiment of the thermoacoustic device. Detailed Implementation

[0062] Figure 1 A heat transfer system 100 according to an embodiment of the present invention is schematically depicted. The heat transfer system 100 includes a first fluid circuit 110 having a pump 111 for circulating fluid in a first fluid circuit 110. The heat transfer system 100 also includes a second fluid circuit 120 having a pump 121 for circulating fluid in a second fluid circuit.

[0063] The heat transfer system 100 includes a thermoacoustic device 130 having an acoustic network 131 with a loop 132, an acoustic actuator 133, and a heat core 134 disposed in the loop 132. The acoustic network 131 is filled with a working fluid, such as helium, at a pressure of, for example, 40 to 80 bar, such as 60 bar. The acoustic actuator 133 is configured to provide acoustic energy to the acoustic network.

[0064] The heat core 134 includes a hot-end heat exchanger 134a, a cold-end heat exchanger 134b, and a regenerator 134c disposed between the hot-end heat exchanger 134a and the cold-end heat exchanger 134b. The hot-end heat exchanger 134a is part of a first fluid loop 110, and the cold-end heat exchanger 134b is part of a second fluid loop 120. The thermoacoustic device 130 can operate as will be described in more detail below to move heat from the cold-end heat exchanger 134b to the hot-end heat exchanger 134a, thereby moving heat from the second fluid loop 120 to the first fluid loop 110.

[0065] The first fluid loop 110 may be arranged, for example, in a building to heat one or more spaces using a heat exchanger 112 (e.g., in the form of a radiator, convection unit, fan coil unit, or underfloor heating), and / or may be used to provide domestic hot water. Although Figure 1 A single heat exchanger 112 is shown, but it is envisioned that multiple heat exchangers 112 are arranged, either in series or in parallel. The fluid in the first fluid loop can be a liquid, such as water or brine, but it can also be a gas, such as air.

[0066] The second fluid loop 120 can be arranged, for example, to extract heat from the environment surrounding the building. This can be accomplished, for example, by circulating air from the environment directly through the cold-end heat exchanger of the thermoacoustic device. The pump 121 can then be embodied in the form of a fan to circulate air in the second fluid loop 120.

[0067] However, it is also possible to use, such as Figure 1 The heat exchanger 122, shown in the second fluid loop, indirectly extracts heat from the environment. A fan 123 can then be provided, for example, to allow heat to be extracted from the air blown by the fan 123 across the heat exchanger 122 and supplied to the fluid in the second fluid loop. Heat can then be extracted from the fluid in the second fluid loop from the cold-end heat exchanger 134b of the thermoacoustic device 130 to be transferred to the first fluid loop 110 via the hot-end heat exchanger 134a.

[0068] Therefore, the fluid in the second fluid loop can be a gas (e.g., air) or a liquid (e.g., water or brine). In one embodiment, the fluid in the first fluid loop is the same as the fluid in the second fluid loop, for example, both fluids are water. The advantage of this is that the fluids in the first and second fluid loops are interchangeable, allowing for the inclusion of valves and piping to change the function of the heat transfer system. In the example above, the second fluid loop is used to extract heat from the environment, and the first fluid loop is used to heat the space within the building. Additional valves and piping can allow pump 111 and heat exchanger 112 to be connected to the cold-end heat exchanger 134b of the thermoacoustic device 130, and pump 121 and heat exchanger 122 to be connected to the hot-end heat exchanger 134a of the thermoacoustic device 130, thereby reversing the function from heating to cooling. Heat can then be extracted from the space within the building and transferred to the environment.

[0069] Alternatively or additionally, this function can be used to defrost the outdoor heat exchanger (in this case, heat exchanger 122). In winter, when the second fluid in heat exchanger 122 is below 0 degrees Celsius, water present in the air passing through heat exchanger 122 will condense on the fins normally present in heat exchanger 122 and subsequently freeze. This ice hinders heat transfer. By altering the function of the heat transfer system, the ice can be melted because heat is no longer extracted from the air in heat exchanger 122 but is now being delivered to the air in the heat exchanger. However, alternatively or additionally, other means of defrosting the heat exchanger can be used, including but not limited to using resistance heating to heat the second fluid and / or the fins or other components of heat exchanger 122.

[0070] When the first and second fluids are not the same, for example, water as the first fluid and brine as the second fluid, it may be impossible to switch between heating and cooling as described above without allowing the first and second fluids to mix and / or using devices to prevent or reverse the mixing of the first and second fluids. However, when switching functions is not possible or desired, a defrosting function may still be necessary. As mentioned above, this can be provided by resistance heating, but alternatively or additionally, a buffer container containing the second fluid may be used, for example, to indirectly heat the first fluid. When defrosting is required, the relatively warm second fluid in the buffer container can be used to defrost the heat exchanger 122, for example, by circulating the second fluid from the buffer container through the heat exchanger. Fluid communication between the buffer container and the heat exchanger 122 is not a problem because both contain the same second fluid.

[0071] The acoustic actuator 133 includes two actuators, including two pistons 135 in this embodiment, which are capable of operating in parallel with... Figure 1The actuator moves back and forth in the direction of arrow AD. Each actuator / piston 135 is arranged in a corresponding side arm of the T-shaped connection to the loop. The operation of the actuators is controlled by a control unit 150 configured to operate the two actuators synchronously. In this example, synchronous operation causes the pistons 135 to move in opposite directions. Therefore, the forces applied by the actuators to the housing or frame of the thermoacoustic device 130 are also in opposite directions and thus at least partially cancel each other out.

[0072] The acoustic driver 133 and the acoustic network 131 are configured such that the synchronous operation of the two actuators forms a traveling wave at the location of the hot core 134, thereby allowing heat to be moved from the cold end heat exchanger 134b to the hot end heat exchanger 134a.

[0073] exist Figure 1 In the example, the control unit 150 is configured not only to control the operation of the actuator, but also to control pumps 111 and 121 and / or any valves (not shown) in the first fluid circuit and / or the second fluid circuit. Furthermore, in Figure 1 In one example, the first fluid loop includes a temperature sensor 113 for measuring the temperature of the fluid in the first fluid loop (preferably the fluid exiting the hot-end heat exchanger 134a). The output of the temperature sensor 113 is provided to the control unit 150 to operate the acoustic driver 133 and / or pumps 111 and 121 based on the measured temperature of the fluid in the first fluid loop. In one embodiment, the control unit 150 uses the output of the temperature sensor 113 to determine a control signal representing the power requirements of the thermoacoustic device 130, and then uses this control signal to operate the acoustic driver 133. Alternatively or additionally, the control signal may be based on other signals or information, such as user input, other sensor signals, etc.

[0074] exist Figure 1 In the example, piston 135 communicates with loop 132 on one side and with a corresponding back volume 137 on the opposite side, which may also be referred to as a rebound chamber. By filling back volume 137 with a compressible fluid (preferably the same working fluid used in the loop), the back volume acts as a gas spring for piston 135, allowing for minimization of the work required by the piston. Alternatively or additionally, a mechanical spring may be provided to provide the same function as the back volume.

[0075] Piston 135 may have a central position, and preferably, when piston 135 is in the central position, the pressure in the back cavity is equal to the pressure in the loop, such that the (average) force exerted by the fluid in the back cavity and the working fluid is in balance, and / or fluid leakage above piston 135 is minimized, and / or the electrical power used to maintain the central position of piston is minimized.

[0076] In this example, loop 132 is provided with two separating elements 132a and 132b. In this embodiment, hot core 134 is arranged between the two separating elements 132a and 132b. Both separating elements suppress DC flow in loop 132. By placing the separating elements near the hot core, circulating flow patterns in or near the hot core are also prevented.

[0077] The partition element 132a on the hot-end heat exchanger side of the hot core 134 is preferably acoustically transparent and allows waves to pass between the hot-end and cold-end heat exchangers, and vice versa. In this way, convective heat transfer is greatly reduced compared to thermoacoustic devices without partition element 132a on the hot-end heat exchanger side of the hot core.

[0078] The partition element 132b on the cold end heat exchanger side of the hot core 134 is preferably a spring-type partition element with mechanical properties defined by its spring constant, and is configured to force a larger volumetric flow rate through the regenerator 134c without increasing the fluid volume to the device.

[0079] The loop includes a first loop portion LP1 extending between the acoustic actuator and the hot-end heat exchanger 134a. Therefore, a separating element 132a is arranged in the first loop portion LP1. The loop also includes a second loop portion LP2 extending between the acoustic actuator and the cold-end heat exchanger 134b. Therefore, a separating element 132b is arranged in the second loop portion LP2. The first loop portion LP1 and the second loop portion LP2 converge at a T-shaped connection where the actuator / piston 135 is provided, such that the first loop portion and the second loop portions LP1, LP2 are connected to each other at the acoustic actuator, i.e., fluidly connected. Therefore, the substantial standing wave generated by the synchronous operation of the two actuators 135 can branch in two directions, through the first loop portion LP1 and through the second loop portion LP2, to interfere with each other at the hot core 134.

[0080] like Figure 1 As schematically depicted, the loop 132 of the acoustic network surrounds the central space 136, and the acoustic actuator 133 is at least partially arranged in the central space 136, in this case by movably arranging the actuator / piston 135 in the central space, i.e., the moving part moves entirely within the central space 136. This saves valuable space and makes the thermoacoustic device smaller.

[0081] Figure 2 A thermoacoustic device 130 according to an embodiment of the present invention is schematically depicted, and this thermoacoustic device can be alternatively used for Figure 1In the heat transfer system 100, the thermoacoustic device 130 has an acoustic network 131 having a loop 132 and a working fluid disposed within the acoustic network 131. An acoustic driver 133 is provided to supply acoustic energy to the acoustic network 131. A heat core 134 is arranged in the loop 132, the heat core having a hot-end heat exchanger 134a, a cold-end heat exchanger 134b, and a regenerator 134c disposed between the hot-end heat exchanger 134a and the cold-end heat exchanger 134b.

[0082] The acoustic driver 133 includes two actuators, each comprising a piston 135 movable in a direction parallel to arrow AD. Each actuator is arranged in a corresponding branch at the loop's inlet position EL, where it supplies acoustic waves to the loop. The control unit (not included in...) Figure 2 (As shown in the figure) The acoustic driver 133 is configured to operate by synchronously operating two actuators, such that the pistons move in substantially opposite directions. Therefore, the forces applied by the two actuators to the housing or frame of the thermoacoustic device 130 at least partially cancel each other out, thereby reducing vibrations emitted into the surrounding environment.

[0083] The synchronized operation of the two actuators generates an approximate standing wave between them (i.e., in the space between the two inlet positions EL). This approximate standing wave branches into the loop in two opposite directions: along the first loop portion LP1 toward the hot-end heat exchanger 134a and along the second loop portion LP2 toward the cold-end heat exchanger 134b. Subsequently, interference at the hot core 134 forms a traveling wave, allowing heat to be moved from the cold-end heat exchanger 134b to the hot-end heat exchanger 134a.

[0084] Loop 132 surrounds central space 136. Acoustic driver 133 is arranged such that a portion of it is disposed within central space 136, i.e. Figure 2 The right-side actuator in the loop. In other words, the loop corresponds to... Figure 2 The inlet position EL of the right actuator faces the central space 136. The piston 135 (i.e., the movable part) thus moves into and out of the central space 136, or moves completely (or at least most) inside the central space 136.

[0085] Figure 3A and Figure 3B Different cross-sectional views of a thermoacoustic device 130 according to another embodiment of the present invention are depicted. The thermoacoustic device 130 is suitable for use in... Figure 1 In the heat transfer system 100. Figure 3A yes Figure 3B The cross-sectional view of plane AA depicted in the figure, and Figure 3B yes Figure 3A The cross-sectional view of plane BB is depicted in the figure.

[0086] The thermoacoustic device 130 has an acoustic network 131, which has a loop 132 and a working fluid disposed in the acoustic network 131. An acoustic actuator 133 is provided to supply acoustic energy to the acoustic network 131. A heat core 134 is arranged in the loop 132, which has a hot-end heat exchanger 134a, a cold-end heat exchanger 134b, and a regenerator 134c disposed between the hot-end heat exchanger 134a and the cold-end heat exchanger 134b. A first loop portion LP1 is disposed between the acoustic actuator 133 and the hot-end heat exchanger 134a. A second loop portion LP2 is disposed between the acoustic actuator 133 and the cold-end heat exchanger 134b.

[0087] The acoustic driver 133 includes two actuators, each comprising a piston 135 movable in a direction parallel to arrow AD. The control unit (not included) Figure 3A and Figure 3B (As shown in the figure) The acoustic driver 133 is configured to operate by synchronously operating two actuators, such that the pistons move in substantially opposite directions. Therefore, the forces applied by the two actuators to the housing or frame of the thermoacoustic device 130 at least partially cancel each other out, thereby reducing vibrations emitted into the surrounding environment.

[0088] The synchronized operation of the two actuators generates a near-standing wave between them. This near-standing wave branches into the loop in two opposite directions: via the first loop portion LP1 towards the hot-end heat exchanger 134a and via the second loop portion LP2 towards the cold-end heat exchanger 134b. Interference at the hot core 134 results in the formation of a traveling wave, allowing heat to be moved from the cold-end heat exchanger 134b to the hot-end heat exchanger 134a.

[0089] Loop 132 surrounds central space 136 and defines a plane 138 extending through the center of the loop and parallel to the loop 132. Figure 1 and Figure 2 In the previously illustrated embodiment, the acoustic driver 133 is arranged in the same plane as or parallel to the loop 132, such that the two actuators are arranged in a plane parallel to the plane defined by the loop 132. Figure 3A and Figure 3B In this embodiment, the acoustic driver 133 extends perpendicular to the plane 138, such that the actuator is arranged on either side of the plane 138. In other words, the acoustic driver extends through the loop 132.

[0090] Acoustic loop 132 is arranged in the middle section MS of device 130, such as Figure 3AAs best shown. The advantage of arranging the two actuators 135 perpendicular to plane 138 is that the back cavity 137 (which can alternatively be called the bounce cavity) can be arranged on both sides of the middle section MS, which, according to the orientation in the figures themselves, will be referred to as the right section RS and the left section LS. The two actuators 135 separate the respective back cavities 137 from the acoustic loop 132. The total volume of the loop 132 and the two back cavities 137 remains constant regardless of the position of the actuators 135. Thus, positive and negative pressure differentials can be obtained for a constant total volume. By being able to arrange the back cavities 137 in the right and left sections adjacent to the middle section, a compact thermoacoustic device can be obtained.

[0091] Figure 3A and Figure 3B The advantage of this configuration is that the housing of device 130 can also be divided into three parts corresponding to the middle segment MS, the right segment RS, and the left segment LS. Therefore, the middle segment MS is the first housing portion, which includes a space for the acoustic driver surrounded by the loop 132. Consequently, the right and left segments are formed by corresponding second and third housing portions connected to the first housing portion, thus forming a back cavity 137 next to the loop and the acoustic driver. This allows for a compact design.

[0092] Figure 4 A heat transfer system 100 according to another embodiment of the present invention is schematically depicted. The heat transfer system 100 includes a first fluid circuit 110 having a pump 111 for circulating fluid in a first fluid circuit 110. The heat transfer system 100 also includes a second fluid circuit 120 having a pump 121 for circulating fluid in a second fluid circuit.

[0093] The heat transfer system 100 includes a thermoacoustic device 130, which can be similar to... Figure 1 , Figure 2 , Figure 3A and Figure 3B The thermoacoustic device of the illustrated embodiment. (As in conjunction with...) Figures 1 to 3B As described, the thermoacoustic device includes a hot-end heat exchanger 134a and a cold-end heat exchanger 134b, and the thermoacoustic device is operable to move heat from the cold-end heat exchanger 134b to the hot-end heat exchanger 134a, thereby moving heat from the second fluid circuit to the first fluid circuit.

[0094] The first fluid loop 110 includes two branches 110a and 110b. Branch 110a includes two heat exchangers 112 arranged in parallel for heating one or more spaces. Each of the two heat exchangers 112 can be controlled using a valve 116.

[0095] Branch 110b can be used for domestic hot water supply. Two three-way valves 115 allow switching between branches 110a and 110b. Branch 110b is thermally connected to water circuit 119 via heat exchanger 114. Water circuit 119 includes a water pump 120 for circulating water between heat exchanger 114 and storage tank 117. Water from storage tank 117 is then directed through heat exchanger 114 to be heated using the fluid in branch 110b and returned to storage tank 117. Fresh water can be supplied to storage tank 117 using a water supply WS. Tap water or domestic water can then be extracted from storage tank using valve 118. Since storage tank 117 only needs to be filled from time to time, domestic hot water supply can be temporarily switched from space heating using branch 110a to domestic hot water supply using branch 110b.

[0096] exist Figure 4 In an alternative embodiment not shown, the heat exchanger 114 is arranged inside the water tank 117 to directly transfer heat from branch 110b to the water inside the water tank 117. In this way, the water pump 120 and the water circuit 119 can be omitted. The heat exchanger 114 can then be embodied, for example, as a coil (serpentine tube).

[0097] In a further alternative embodiment, when heat exchanger 134a is configured such that the flow for heating and the flow for domestic hot water supply within heat exchanger 134a are separated from each other—that is, branches 110a and 110b are separate but both pass through heat exchanger 134a—heat exchanger 114 can be omitted. In other words, heat exchanger 134a has two separate flow channels, one for domestic hot water supply and one for heating. In this way, the water supply WS can be directly connected to branch 110b, and heat exchanger 134a takes over the function of heat exchanger 114.

[0098] In another alternative embodiment, heat exchanger 114 is arranged parallel to heat exchanger 112, without using valve 115. In this way, the water inside water tank 117 can be heated simultaneously while using heat exchanger 112 for space heating.

[0099] A potential benefit of using thermoacoustic device 130 is that, for a given supply temperature and heat power output, the efficiency of the device may remain substantially unaffected or increase with decreasing mass flow rate and subsequently increasing temperature difference across the hot-end heat exchanger. This flexibility allows for the use of lower mass flow rates to achieve the same heating power, thereby reducing the power consumption of the circulating pump and / or enabling the use of thinner, existing diameter water pipes without replacement. Furthermore, heat transfer system 100 can therefore be designed to raise the water temperature from, for example, 10 or 20 degrees Celsius to 40 to 60 degrees Celsius in a single pass.

[0100] Figure 5A cross-sectional view of a thermoacoustic device 130 according to another embodiment of the invention is schematically depicted. In this particular example, the thermoacoustic device 130 has a substantially symmetrical design with a plane of symmetry indicated by dashed lines and reference numeral SD. Therefore, a substantially symmetrical design can include some degree of asymmetry.

[0101] The device 130 includes an acoustic network having a first loop 132.1 and a second loop 132.2. The first loop 132.1 is connected to the back cavity 137a via a conduit SB1. The second loop 132.2 is connected to the back cavity 137b via a conduit SB2.

[0102] The advantage of a symmetrical design is that it allows for a slender, cigar-shaped design, enabling the acoustic network to be arranged within a conduit or duct structure. In this embodiment, device 130 has five conduit elements P1 to P5. A first loop 132.1 is arranged in conduit element P1. A conduit SB1 is arranged in conduit element P2. Back cavities 137a and 137b are arranged in conduit element P3. A conduit SB2 is arranged in conduit element P4, and a second loop 132.2 is arranged in conduit element P5.

[0103] When device 130 has a cigar-shaped form, its length is much greater than its width and thickness, and the width and thickness are substantially the same; for example, the width and thickness can often be referred to as diameters. However, other proportions are also possible. The width may, for example, be longer than the thickness of device 130, and the length may be greater or less. As an example, the length-to-diameter ratio L / D (where L is the length of design 130 and D is its diameter) may be in the range of 2 to 10, for example, 5.

[0104] The acoustic network is filled with a working fluid, such as helium, at a pressure of, for example, 40 to 80 bar, or, for example, 60 bar.

[0105] The first and second loops 132.1 and 132.2 have a coaxial design, in which the two halves of the corresponding loops share a common axis.

[0106] The device 130 also includes an acoustic actuator having a first actuator 135a disposed in conduit SB1 and a second actuator 135b disposed in conduit SB2. The acoustic actuator is configured to provide acoustic energy to an acoustic network. The first actuator 135a is configured to provide acoustic energy to a first loop 132.1, and the second actuator 135b is configured to provide acoustic energy to a second loop 132.2. The acoustic actuator is operated using a control unit (not shown). The control unit is configured to synchronously operate the first and second actuators 135a and 135b.

[0107] The first and second loops 132.1 and 132.2 each include heat cores 134.1 and 134.2. Each heat core 134a and 134b includes a hot-end heat exchanger, a cold-end heat exchanger, and a regenerator disposed between the hot-end and cold-end heat exchangers. The hot-end and cold-end heat exchangers can be connected to the first and second fluid loops for cooling and / or heating purposes. This has already been described with respect to other embodiments, and will not be repeated here.

[0108] exist Figure 5 In the cross-sectional view, both the first loop 132.1 and the second loop 132.2 are formed by four loop portions indicated by reference numerals LPA, LPB, LPC, and LPD. Loop portions LPA and LPB extend from the respective conduits along the sidewalls of the respective piping elements to meet on opposite sides of the respective piping elements and form half of the respective loop. Loop portion LPC extends from loop portions LPA and LPB to the hot-end heat exchanger, while loop portion LPD extends from the cold-end heat exchanger to loop portions LPA and LPB. Both loop portions LPC and LPD extend through the central portion of the respective piping elements and together form the other half of the respective loop. Loop portions LPA, LPB, and LPC together form a first loop portion between the actuator and the hot core. Loop portion LPD forms a second loop portion between the actuator and the hot core. Loop portions LPA and LPB can be parallel extending separate loop portions, or they can be two parts of a single loop portion.

[0109] The first and second actuators 135a and 135b are operated to generate an approximate standing wave that branches to propagate along the first and second loop portions, thus propagating in opposite directions through the loops. The wave passing through the first loop portion interferes with the wave passing through the second loop portion to generate a wave with traveling wave characteristics at the respective hot core. The hot cores are arranged such that the traveling wave expands at the cold-end heat exchanger and propagates through the regenerator to compress at the hot-end heat exchanger, thereby transferring heat from the cold-end heat exchanger to the hot-end heat exchanger.

[0110] The first and second actuators 135a and 135b may include pistons that reciprocate about an equilibrium position. During operation, the actuation of the pistons generates a reaction force applied to the piping element. Therefore, the control unit is configured to operate the two actuators synchronously, i.e., the pistons move in phase and thus simultaneously toward the first and second loops and simultaneously away from the first and second loops, respectively. This has the advantage that the forces applied to the housing of the thermoacoustic device at least partially cancel each other out.

[0111] Actuators 135a and 135b are connected to corresponding loops of the acoustic network on one side and to corresponding back cavities on the opposite side. Back cavities 137a and 137b are preferably filled with the same working fluid as in the corresponding loops and are preferably at the same pressure as the working fluid in the loops when the actuators are in the equilibrium position.

[0112] exist Figure 5 In this embodiment, the spring-type separating element 132b is arranged in the loop portion LPD of the first and second loops on the cold end heat exchanger side of the corresponding hot core. The spring-type separating element 132b is configured to force a larger volumetric flow rate through the regenerator of the corresponding hot core without increasing the fluid volume to the device.

[0113] Figure 6 and Figure 7 Different cross-sectional views of the thermoacoustic device 130 are schematically depicted. The thermoacoustic device includes a housing 200 having space for an acoustic transducer 135 capable of converting acoustic energy in the acoustic network 131 into another type of energy, or vice versa.

[0114] The acoustic network includes a loop 132 and a heat core 134 disposed within the loop 132. The heat core includes a hot-end heat exchanger, a cold-end heat exchanger, and a regenerator located between the hot-end and cold-end heat exchangers. The loop defines a first loop portion extending between the acoustic transducer 135 and the heat core, i.e., the hot-end heat exchanger side of the heat core 134. A second loop portion LP2 extends between the acoustic transducer 135 and the heat core, i.e., the cold-end heat exchanger side of the heat core 134. The first loop portion includes four separate sections, three of which are located within... Figure 6 and Figure 7 It can be seen in the image and is labeled as LPA, LPB, and LPD.

[0115] The sound waves generated by the acoustic transducer can propagate to the hot core along the first loop and the second loop LP2, or the sound waves generated by the hot core can propagate to the acoustic transducer along the first loop and the second loop LP2.

[0116] Figure 8 A cross-sectional view of a thermoacoustic device 130 according to an embodiment of the present invention is schematically depicted, and the thermoacoustic device is described as follows: Figure 5 An alternative implementation of the thermoacoustic device 130. Figure 8 Pipe components P1 and P5 in Figure 5 The corresponding piping components P1 and P5 are the same. To avoid redundancy, these components will not be described in full here, and to maintain... Figure 8The figures are not clearly labeled, and not all reference numerals are shown. Only the reference numerals for pipe elements P1 and P5 are depicted, namely, first loop 132.1 and second loop 132.2. For all other reference numerals, please refer to [reference needed] where applicable. Figure 5 .

[0117] Piping elements P1 and P5 are connected to each other via piping element P6. This piping element is depicted as a single element, but can be formed using multiple sub-piping elements (not shown). The first and second loops 132.1 and 132.2 are connected to each other via conduit SB. Extending from conduit SB are first branches SB1 and second branches SB2, respectively, connecting conduit SB to cavities 137a and 137b.

[0118] The device 130 also includes an acoustic driver having a first actuator 135a disposed in a first conduit SB1 and a second actuator 135b disposed in a second conduit SB2. The acoustic driver is configured to provide acoustic energy to the acoustic network and thus to the two loops 132.1 and 132.2.

[0119] An approximate standing wave can be generated in the space SPA of the conduit SB located between the first actuator 135a and the second actuator 135b. This approximate standing wave then branches in four directions (i.e., along the first and second loop portions of the first loop 132.1 and along the first and second loop portions of the second loop 132.2) to propagate in two opposite directions through each loop 132.1, 132.2 (i.e., parallel to the first and second loop portions), thereby subsequently interfering with each other and generating waves with traveling wave characteristics at the hot cores 134.1, 134.2 of the first and second loops 132.1, 132.2, respectively.

[0120] The first and second actuators 135a and 135b may include pistons that reciprocate about an equilibrium position. During operation, the actuation of the pistons generates a reaction force applied to the conduit element P6. Therefore, the control unit is configured to operate the two actuators synchronously, i.e., the pistons move in phase and thus simultaneously toward and away from the conduit SB, respectively. This has the advantage that the forces applied to the housing of the thermoacoustic device at least partially cancel each other out.

[0121] Although the examples include a single thermoacoustic device, it is explicitly mentioned herein that it is possible to use more than one thermoacoustic device in the heat transfer system, heat pump system, or heat engine system according to the invention. Multiple thermoacoustic devices can be arranged in parallel, wherein the hot-end heat exchangers of the multiple thermoacoustic devices are connected to each other, and wherein the cold-end heat exchangers of the multiple thermoacoustic devices are connected to each other. Alternatively, multiple thermoacoustic devices can be arranged in series, wherein the cold-end heat exchanger of one thermoacoustic device is connected to the hot-end heat exchanger of the next thermoacoustic device. Combinations of series and parallel connections are also possible.

[0122] The advantage of multiple thermoacoustic devices is that, for a given flow rate, more fluids can achieve the same temperature difference and / or the temperature difference can be increased.

[0123] Although the working fluid is not always specified in the above description, it is preferably a gas, such as an inert gas. The working fluid may be, for example, helium, neon, argon, nitrogen, or hydrogen. Preferably, the working fluid is an inert gas, and more preferably, it is non-flammable. Alternatively, the working fluid may be a compressible liquid.

[0124] Although two actuators (e.g., pistons) are used in the above description and examples, it is contemplated that the invention can also be applied to embodiments using acoustic drivers having three or more actuators arranged to provide acoustic energy to an acoustic network. In the case of three actuators, these actuators can be arranged to operate in corresponding directions rotated 120 degrees relative to the direction of another actuator. In the case of an even number of actuators, these actuators can be arranged in pairs, wherein each pair of actuators operates in opposite directions (i.e., directions rotated 180 degrees relative to each other).

[0125] Although examples have been given of the first loop section including one, two, or four separate loop sections, it is also conceivable that any number of loop sections and multiple loop sections for the second loop section are also possible.

[0126] This invention can also be summarized by the following terms: 1. A heat transfer system, comprising: - A first fluid circuit having a pump for circulating fluid in the first fluid circuit; - A second fluid circuit having a pump for circulating fluid in the second fluid circuit; - Control unit; - Thermoacoustic device, including: o An acoustic network having a loop and a working fluid disposed within the acoustic network; o Acoustic driver, used to provide acoustic energy to the acoustic network; and o A heat core, disposed in the loop, the heat core including a hot end heat exchanger, a cold end heat exchanger and a regenerator disposed between the hot end heat exchanger and the cold end heat exchanger. The control unit is configured to operate the acoustic driver; The hot-end heat exchanger is part of the first fluid loop; The cold-end heat exchanger is part of the second fluid loop; The acoustic driver includes two actuators; The control unit is configured to operate the two actuators synchronously. The two actuators are arranged such that they are operated synchronously by a control unit so that the forces applied to the housing or frame of the thermoacoustic device at least partially cancel each other out. Furthermore, the acoustic driver and acoustic network are configured such that the synchronous operation of the two actuators forms a traveling wave at the location of the hot core, thereby allowing heat to be moved from the cold end heat exchanger to the hot end heat exchanger.

[0127] 2. The heat transfer system according to Clause 1, wherein a sensor is arranged in a first fluid loop to measure parameters of the fluid in the first fluid loop, and wherein the control unit is configured to operate the acoustic actuator according to the output of the sensor.

[0128] 3. A heat transfer system according to Clause 1 or 2, wherein the loop surrounds a central space, and wherein the acoustic actuator is arranged at least partially in the central space.

[0129] 4. The heat transfer system according to Clause 3, wherein the loop defines an extension through the center of the loop and parallel to the central plane of the loop, and wherein two actuators are arranged on either side of the central plane such that the acoustic actuators extend substantially perpendicular to the central plane.

[0130] 5. A heat transfer system according to any one of clauses 1 to 4, wherein the actuator of the two actuators of the acoustic actuator includes a piston capable of moving in a parallel direction.

[0131] 6. A thermoacoustic device, comprising: - An acoustic network having a loop and a working fluid disposed within the acoustic network; - A heat core, disposed in the loop, comprising a hot-end heat exchanger, a cold-end heat exchanger, and a regenerator located between the hot-end heat exchanger and the cold-end heat exchanger. - Acoustic transducers are used to convert acoustic energy in an acoustic network into other types of energy or vice versa; The ring road surrounds the central space; Furthermore, the acoustic transducer is at least partially located in the central space.

[0132] 7. The thermoacoustic device according to Clause 6, wherein the loop defines an extension extending through the center of the loop and parallel to the central plane of the loop, and wherein the acoustic transducer extends perpendicular to the central plane.

[0133] 8. The thermoacoustic apparatus according to Clause 6 further includes a cooling circuit for controlling the temperature of components of the thermoacoustic apparatus other than the heat core, wherein the cooling circuit is connected to or is part of a second fluid circuit.

[0134] 9. The thermoacoustic apparatus according to Clause 6 further includes a cooling circuit for controlling the temperature of components of the thermoacoustic apparatus other than the heat core, wherein the cooling circuit is connected to or is a part of the first fluid circuit.

[0135] 10. The thermoacoustic apparatus according to Clause 6, wherein the acoustic transducer separates the loop from one or more bounce cavities to allow the generation of positive and negative differential pressures using the fixed total volume of the loop and one or more bounce cavities.

[0136] 11. A heat pump system comprising: a thermoacoustic device according to Clause 6; and a control unit, wherein the acoustic transducer includes an actuator for providing acoustic energy to an acoustic network, and wherein the control unit is configured to operate the acoustic transducer to transfer heat from a cold-end heat exchanger to a hot-end heat exchanger.

[0137] 12. A heat engine system comprising: a thermoacoustic device according to Clause 6; a heat source; and a heat sink, wherein the heat source is connected to a hot-end heat exchanger and the heat sink is connected to a cold-end heat exchanger to provide a temperature difference between the hot-end and cold-end heat exchangers, wherein an acoustic network is configured to generate acoustic energy using the temperature difference, and wherein an acoustic converter is configured to convert the acoustic energy into other types of energy.

[0138] 13. A method for operating a thermoacoustic device according to Clause 6, wherein two actuators are driven synchronously such that forces applied to the housing or frame of the thermoacoustic device at least partially cancel each other out.

[0139] 14. The method according to Clause 13 further includes: determining the overall system resonance, and operating two actuators at or near the overall system resonance.

Claims

1. A heat transfer system (100), comprising: - A first fluid circuit (110) has a pump (111) for circulating fluid in the first fluid circuit. - Second fluid circuit (120) has a pump (121) for circulating fluid in the second fluid circuit. - Control unit (150); - Thermoacoustic device (130), comprising: o Acoustic network (131), having loop (132) and working fluid disposed in the acoustic network; an acoustic driver (133) for providing acoustic energy to the acoustic network; and o A heat core (134) is disposed in the loop, the heat core including a hot end heat exchanger (134a), a cold end heat exchanger (134b) and a regenerator (134c) disposed between the hot end heat exchanger and the cold end heat exchanger. The control unit is configured to operate the acoustic driver; The hot-end heat exchanger is part of the first fluid circuit; The cold-end heat exchanger is part of the second fluid circuit; The acoustic driver includes two actuators; The control unit is configured to operate the two actuators synchronously. The two actuators are arranged such that they are operated synchronously by the control unit so that the forces applied to the housing or frame of the thermoacoustic device at least partially cancel each other out. Furthermore, the acoustic driver and the acoustic network are configured such that the synchronous operation of the two actuators forms a traveling wave at the location of the hot core, thereby allowing heat to be transferred from the cold end heat exchanger to the hot end heat exchanger.

2. The heat transfer system according to claim 1, wherein, A sensor (113) is arranged in the first fluid circuit to measure parameters of the fluid in the first fluid circuit, and wherein the control unit is configured to operate the acoustic driver according to the output of the sensor.

3. The heat transfer system according to claim 1 or 2, wherein, The loop surrounds a central space (136), and the acoustic driver is arranged at least partially in the central space.

4. The heat transfer system according to claim 3, wherein, The loop defines an extension that extends through the center of the loop and is parallel to the central plane of the loop, wherein the two actuators are arranged on either side of the central plane such that the acoustic driver extends substantially perpendicular to the central plane.

5. The heat transfer system according to any one of claims 1 to 4, wherein, The actuator of the acoustic driver includes a piston (135) that can move in a parallel direction.

6. A thermoacoustic device, comprising: - An acoustic network having a loop and a working fluid disposed within the acoustic network; - A heat core, disposed in the loop, the heat core including a hot-end heat exchanger, a cold-end heat exchanger and a regenerator located between the hot-end heat exchanger and the cold-end heat exchanger; - An acoustic converter for converting acoustic energy in the acoustic network into other types of energy, or converting said other types of energy into the acoustic energy; The loop surrounds a central space; The loop further includes: a first loop portion extending between the acoustic transducer and the hot-end heat exchanger; and a second loop portion extending between the acoustic transducer and the cold-end heat exchanger; The first loop section and the second loop section are connected to each other at the acoustic converter; Furthermore, the acoustic transducer is at least partially arranged in the central space.

7. The thermoacoustic device according to claim 6, wherein, The loop defines an extension that extends through the center of the loop and is parallel to the central plane of the loop, wherein the acoustic transducer extends perpendicular to the central plane.

8. The thermoacoustic device according to claim 6, further comprising a cooling circuit for controlling the temperature of components of the thermoacoustic device other than the heat core, wherein, The cooling circuit is connected to the second fluid circuit or is a part of the second fluid circuit.

9. The thermoacoustic device according to claim 6, further comprising a cooling circuit for controlling the temperature of components of the thermoacoustic device other than the heating element, wherein, The cooling circuit is connected to the first fluid circuit or is a part of the first fluid circuit.

10. The thermoacoustic device according to claim 6, wherein, The acoustic transducer separates the loop from one or more bounce cavities to allow the generation of positive and negative pressure differentials using the fixed total volume of the loop and the one or more bounce cavities.

11. A heat pump system, comprising: The thermoacoustic device according to claim 6; and a control unit, wherein the acoustic converter includes an actuator for providing acoustic energy to the acoustic network, and wherein the control unit is configured to operate the acoustic converter to transfer heat from the cold end heat exchanger to the hot end heat exchanger.

12. A heat engine system, comprising: The thermoacoustic device according to claim 6; Heat source; The acoustic network is configured to generate acoustic energy using the temperature difference, and the acoustic converter is configured to convert the acoustic energy into other types of energy. The heat source is connected to the hot-end heat exchanger and the heat sink is connected to the cold-end heat exchanger to provide a temperature difference between the hot-end and cold-end heat exchangers.

13. A method for operating the thermoacoustic device according to claim 1, wherein, The two actuators are driven synchronously such that the forces applied to the housing or frame of the thermoacoustic device at least partially cancel each other out.

14. The method of claim 13, further comprising: Determine the overall system resonance; and operate the two actuators at or near the overall system resonance.

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