# Patent

## Title
Double-acting device for generating synthetic jets

## Abstract

A double-acting device for generating a synthetic jet is provided. The double-acting device includes a chamber having a cavity for a working fluid, a separating element for dividing the chamber into at least two sub-chambers, a control system connected to the chamber for controlling the separating element to act reciprocatingly, an input system connected to the chamber for inputting the working fluid to the chamber therethrough and an output system connected to the chamber for outputting the working fluid from the chamber therethrough. When the working fluid is pushed and pulled by a reciprocating action of the separating element, a train of vortices would be puffed and a non-zero-net-mass-flux fluid is generated through a designed structure and a defined arrangement of the input system and the output system.

## Background
CROSS REFERENCE TO RELATED APPLICATION
This application is a division of U.S. patent application Ser. No. 10/894,613, filed Jul. 20, 2004, now U.S. Pat. No. 7,527,086, which is incorporated by reference as if fully set forth.


FIELD OF THE INVENTION
The present invention is related to a fluid actuator for generating synthetic jets, especially to the fluid actuator, which is applied to control the mixing of fluid flows and to control the fluid field and the fluid actuator, which is used in a cooling system.
BACKGROUND OF THE INVENTION
Conventional synthetic jets are periodic jets generated by pushing and pulling a fluid through an orifice of an actuator. While the actuator reciprocatingly acts, the fluid would be revolvingly oscillated, and be sucked into or jetted out from the actuator due to the pressure variation therein. Since the mass flux of the fluid sucked into the actuator is equal to that of the fluid jetted out, i.e. a time-mean mass flux of the oscillated fluid through this orifice is zero, the synthetic jets is so called as “Zero-Net-Mass-Flux jets” in early days. Other common expressions for such a generation of jets are “Suction and Blowing” and “Oscillatory Blowing”.
Technically speaking, synthetic jets are generated by a periodic Zero-Net-Mass-Flux actuator, which can be arranged in various types. Please refer to FIG. 1(a), which illustrates the structure of a conventional Zero-Net-Mass-Flux actuator. The conventional Zero-Net-Mass-Flux actuator 1′ has a sealed chamber 10′ formed by a surrounding wall 11′. The surrounding wall 11′ has an input orifice 113′, at least one jetting element 115′, such as an orifice or a nozzle, on one side of the chamber 10′, and a diaphragm 12′ (or a piston) on the other end of the chamber 10′ for sealing. Mechanical energy for forcing the diaphragm 12′ is supplied to the Zero-Net-Mass-Flux actuator 1′ through various means, and the diaphragm 12′ is sorted accordingly, such as the electromagnetic diaphragm, the electrodynamic diaphragm, the piezoelectric diaphragm, the electrostatic diaphragm, the thermopneumatic diaphragm, the bimetallic diaphragm, the electrohydrodynamic diaphragm, the shape memory material diaphragm and the pneumatic diaphragm. In short, a feeding from any mechanical energy source will keep the diaphragm 12′ reciprocatingly acting.
Please refer to FIGS. 1(b) and 1(c), which illustrate the actions of the conventional Zero-Net-Mass-Flux actuator 1′. The diaphragm 12′ is actuated toward the U direction during the up-stroke. The pressure inside the chamber 10′ is hence getting lower, and a fluid 2′, which is originally outside the Zero-Net-Mass-Flux actuator 1′, would be sucked into the chamber 10′ through the input orifice 113′ for the pressure drop and hence forms a working fluid. The jetting element 115′ is closed at that time, as shown in FIG. 1(b).
Referring to FIG. 1(c), accordingly, while during the back-stroke, the working fluid 3′ in the chamber 10′ is pushed because the diaphragm 12′ is actuated toward the D direction. The pressure inside the chamber 10′ will be increased, and the working fluid 3′ sucked into the chamber 10′ during the up-stroke is hence pushed. The working fluid 3′ is pushed and jetted out through the input orifice 113′ and the jetting element 115′, and the jets are generated thereby.
Since the sucked working fluid in the up-stroke would be completely jetted out in the back-stroke, i.e. the mass flux of the sucked working fluid is equal to that of the jetted working fluid, the net mass flux of the working fluid, which flows in and out of the Zero-Net-Mass-Flux actuator 1′, is zero in each of the reciprocatingly acting process of the diaphragm 12′.
On the other hand, if the working fluid flows in and out of the actuator through different jetting elements, the mass flux of the sucked working fluid would be hence different from that of the jetted working fluid, which may be resulted from changing the structure and the arrangement of the jetting elements of the actuator. For the respectively different mass fluxes of the sucked working fluid and the jetted working fluid, the net mass flux would not be zero. Non-Zero-Net-Mass-Flux jets would be generated therefore.
Based on the basic principles involved in the fluid mechanics, for considering the limitation of the Reynolds Number of the fluid, it needs a quite complicated arrangement of a pipe structure and moving parts for the fluid flows mixing controlling, the fluid field controlling, such as the fluid stream vectoring and the turbulence controlling, and for generating the fluid for a small-scale cooling system conventionally. This may further restrict the application of the conventional fluid in the small-scale system as a result.
However, when the synthetic jets are jetted through a jetting element, a vortex will be accordingly generated in the shear layer thereof. The fluid surrounding to the actuator will be further rolled by the vortex to induce an enhancement of the vortex. Besides, due to the simpler structure, the actuator for generating the synthetic jets is more beneficial for the applications in a small-scale system. Therefore, the synthetic jets are respectably potential for applications in the micro fluid mixing and the fluid field precisely controlling, and are broadly applied for the relevant applications.
Since the mass flux of the working fluid sucked into the actuator is equal to that of the working fluid jetted out during the reciprocatingly action of the Zero-Net-Mass-Flux actuator, the efficiency of the heat transfer would be slashed and the actuator will fail in cooling if the temperature difference between the fluids sucked in and jetted out is extremely small. Therefore, if a simpler method and device for generating the Non-Zero-Net-Mass-Flux fluid is provided, the temperature difference between the fluids sucked in and jetted out is able to be increased by repeatedly injecting a fresh fluid outside the actuator thereto. By the increased temperature difference and the enhancement of the fluid field, the Non-Zero-Net-Mass-Flux fluid can not only be applied for the conventional fluid field controlling, but also effectively improves in solving the thorny problem of the heat, which is generated by the high power electrical device.
Based on the above, in order to overcome the drawbacks in the prior art, a double-acting device for generating a Non-Zero-Net-Mass-Flux fluid and a cooling method therefor are provided in the present invention.
SUMMARY OF THE INVENTION
In accordance with the main aspect of the invention, a double-acting device for generating synthetic jets having a Non-Zero-Net-Mass-Flux is provided. The double-acting device includes a chamber having a cavity for a working fluid, a separating element for dividing the chamber into at least two sub-chambers, a control system connected to the chamber for controlling the separating element to act reciprocatingly, an input system connected to the chamber for inputting the working fluid to the chamber therethrough, and an output system connected to the chamber for outputting the working fluid from the chamber therethrough.
Preferably, the working fluid is pushed and pulled by a reciprocating action of the separating element.
Preferably, a train of vortices are puffed and a non-zero-net-mass-flux fluid is generated through a designed structure and a defined arrangement of the input system and the output system.
Preferably, the separating element is a piston.
Preferably, the control system is a system of connecting rods.
Preferably, the separating element is a diaphragm.
Preferably, the diaphragm is one of a piezoelectric film and a photoelectric film.
Preferably, the control system is a control circuit.
Preferably, the input system and the output system further include a first control valve and a second control valve respectively.
Preferably, the first control valve and the second control valve are selected from an active valve and a passive valve.
Preferably, the input system further includes at least an input element.
Preferably, the input element is one of a diffuser and an orifice.
Preferably, the output system further includes at least two output elements respectively connected to the sub-chambers in the defined arrangement.
Preferably, the at least two output elements are selected from nozzles and orifices.
Preferably, the orifices are circular orifices.
Preferably, the output elements are coaxially arranged.
Preferably, the defined arrangement is one of a paired arrangement and an axisymmetric arrangement.
In accordance with another aspect of the present invention, a cooling method by generating a non-zero-net-mass-flux fluid is provided in the present invention, and the cooling method includes the steps of providing a heated body, providing a double-acting device having a chamber divided into at least two sub-chambers by a separating element, and controlling the separating element of the double-acting device to act reciprocatingly for passing a fluid in and out of each the sub-chamber and generating a train of vortices.
Preferably, the fluid is formed as antiphasely oscillating jets input to the sub-chamber through an input system and output from the sub-chamber through an output system, and the non-zero-net-mass-flux fluid is hence generated.
Preferably, a heat exchange of the heated body is induced by directing the non-zero-net-mass-flux fluid and the train of vortices to a surface of the heated body and driving a surrounding fluid to flow and the heated body is cooled thereby.
Preferably, the chamber provides a cavity for the fluid working therein. The separating element is connected to the chamber for dividing the chamber into the two sub-chambers, the input system is connected to the chamber for inputting the fluid to the chamber therethrough, and the output system is connected to the chamber for outputting the fluid from the chamber therethrough.
Preferably, the separating element is controlled to pump by a control system connected to the chamber.
Preferably, the output system further has at least two output elements.
Preferably, the antiphasely oscillating jets are generated by a double-acting action of the separating element.
Preferably, a mutual interaction of the antiphasely oscillating jets is induced by a defined arrangement of the at least two output elements to enhance the train of vortices.
The foregoing and other features and advantages of the present invention will be more clearly understood through the following descriptions with reference to the drawings, wherein:



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1(a) is a diagram illustrating the structure of the conventional Zero-Net-Mass-Flux actuator according to the prior art;
FIGS. 1(b) and 1(c) are diagrams illustrating the fluid flowings during an up-stroke and a back-stroke of the conventional Zero-Net-Mass-Flux actuator, respectively;
FIG. 2(a) is a diagram illustrating the structure of the double-acting device for generating synthetic jets according to a first embodiment of the present invention;
FIGS. 2(b) and (c) are diagrams respectively illustrating the fluid flowing during an up-stroke and a back-stroke of the double-acting device for generating synthetic jets according to the first embodiment of the present invention;
FIG. 3 is a diagram illustrating the structure of the double-acting device for generating synthetic jets according to a second embodiment of the present invention;
FIGS. 4(a) to 4(d) are diagrams respectively illustrating the fluid flowing through four different jetting elements during the up-stroke of the double-acting device according to the present invention;
FIGS. 5(a) to f(d) are diagrams respectively illustrating the fluid flowing through four different jetting elements during the back-stroke of the double-acting device according to the present invention;
FIGS. 6(a) and 6(b) are diagrams illustrating the structures of the double-acting device for generating synthetic jets according to a third embodiment of the present invention;
FIGS. 7(a) to 7(c) are diagrams schematically illustrating the various arrangements of the output elements with different shapes in the double-acting device according to the third embodiment of the present invention;
FIGS. 8(a) and 8(b) illustrate the field distributions near the outlets of the jetting elements;
FIG. 9 is a diagram illustrating the cooling for an open system by the Non-Zero-Net-Mass-Flux fluid generated according to the present invention; and
FIG. 10 is a diagram illustrating the cooling for a closed system by the Non-Zero-Net-Mass-Flux fluid generated according to the present invention.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only; it is not intended to be exhaustive or to be limited to the precise form disclosed.
Please refer to FIGS. 2(a) to 2(c), which illustrate the structures of the double-acting device according to the first embodiment of the present invention. The double-acting device 1 of the present invention includes a sealed chamber 10 and a diaphragm 12 located therein to bisect the chamber 10 into two sub-chambers 10A and 10B. The input elements 4A and the output element 3A, and the input elements 3A and the output element 3B are respectively configured on the wall 11 of the sub-chamber 10A and 10B for respectively forming an input system 4 and an output system 3. Accordingly, the output elements 3A and 3B, and the input elements 4A and 4B are respectively arranged in two paired arrangements. A control circuit 2 is configured inside the chamber 10 to drive the diaphragm 12 and the electricity needed is provided by the power supply 20.
Please refer to FIG. 2(b). The diaphragm 12 driven by the control circuit 2 acts in a direction toward to the sub-chamber 10A, i.e. during the U direction, in the up-stroke. Due to the action of the diaphragm 12, the pressure of the fluid in the sub-chamber 10A is increased, and some of the working fluid 30a in the sub-chamber 10A is accordingly promoted to jet out through the output element 3A to further form the principal jets 31a. Moreover, the increased pressure in the sub-chamber 10A also results in a minor flowing of the fluid. In other words, some of the fluid 40a is accordingly jetted out from the sub-chamber 10A through the input element 4A to form minor jets 41a, if there is no additional check valve cooperated with the input element 4A. Additionally, the mass flux of the minor jets 41a depends on the structure and the size of the input element 4A.
On the other hand, there is only a periodic difference between the actions of the fluid in the sub-chambers 10A and 10B. Therefore, the working fluids 30b and 40b in the sub-chamber 10B will flow in a direction, which is opposite to that of the working fluids 30a and 40a in the sub-chamber 10A. That is to say, as the pressure inside the sub-chamber 10A is increased, the pressure inside the sub-chamber 10B will be decreased, and the fluid 41b outside the double-acting device 1 will be accordingly sucked into the sub-chamber 10B through the input element 4B and forms the working fluid 40b. Similarly, the fluid 31b is accordingly sucked into the sub-chamber 10B through the output element 3B to form the working fluid 30b, if there is no additional check valves cooperated with the output element 3B.
Please refer to FIG. 2(c). The diaphragm 12 driven by the control circuit 2 is pushed toward the direction away from the sub-chamber 10A, i.e. along the D direction, in the back-stroke of the double-acting device 1. The pressure inside the sub-chamber 10A will be decreased, and the fluid 42a outside the double-acting device 1 will accordingly flow into the sub-chamber 10A through the input element 4A to form a principal input fluid 43a. Moreover, the decreased pressure in the sub-chamber 10A also results in a minor flowing of the fluid. In other words, the fluid 32a is accordingly sucked into the sub-chamber 10A through the output element 3A to form the minor input fluid 33a, if there is no additional check valve cooperated with the output element 3A. Additionally, the mass flux of the minor input fluid 33a depends on the structure and the size of the output element 3A.
Considering the situation for the sub-chamber 10B, the fluid 33b inside the sub-chamber 10B is jetted out through the output element 3B owing to the increased pressure inside the sub-chamber 10B. The jet fluid 32b is hence generated. Similarly, some of the fluid 43b inside the sub-chamber 10B will be accordingly jetted out from the sub-chamber 10B through the input element 4B to form the jet fluid 42b, if there is no additional check valve cooperated with the input element 4B.
Please refer to FIG. 3, which illustrates the structure of the double-acting device for generating synthetic jets according to the second embodiment of the present invention. The arrangement inside the chamber 10 is completely the same as that of the double-acting device 1 according to the first embodiment, which is described in FIG. 2(a) in detail. In the double-acting device 1 according to the second embodiment, however, the control circuit 2 is configured outside the chamber 10, and the electricity needed is provided by the power supply 20.
Such a configuration makes the design of the chamber 10 much simpler and prevents the additional heat generation inside the chamber 10, however, it is necessary to be mentioned that an additional connector 21, such as a mechanical connector or an electromagnetic connector, is needed to be located between the control circuit 2 and the diaphragm 12 for helping the control circuit 2 drive the diaphragm 12. Moreover, an independent heat sink configured on the control circuit 2 is also permitted. By a design of the extended surfaces 22, the heat radiation and convection are enhanced to achieve a great cooling effect. Furthermore, the control circuit 2 is able to be arranged partially inside the chamber 10 and partially outside the chamber 10, if necessary.
Please refer to FIGS. 4(a) to 4(d) and FIGS. 5(a) to 5(d), which respectively illustrate the fluids flowing through four different fluid jetting elements, wherein the arrows represent the flowing direction of the fluid. Such jetting elements are further applied for being the input elements and the output elements in the double-acting device of the present invention. The jetting element, as shown in FIGS. 4(a) and 5(a), is a symmetric element, such as a slot or an orifice. The shape and the structure of such a element is symmetric, so that the flow rate and the field distribution at both sides of the element have no significant differences, when the fluids are flowing through the jetting element from the left side to the right side thereof, as shown in FIG. 4(a), or flowing oppositely, as shown in FIG. 5(a).
Referring to FIG. 4(b) and FIG. 5(b), when the fluids are flowing through a passive asymmetric element, such as a nozzle or a vortex valve, the fluids would be rectified by such a jetting element. Owing to the asymmetric shape of the jetting element and the absence of valves, there would be a difference in flowing when the fluid flows from a different side of the jetting element. This may further result in variations in the flow rate or the velocity in various directions. FIG. 4(b) illustrates the fluid flowing from the left side of the jetting element to the right side, and on the other hand, FIG. 5(b) illustrates the fluid, which flows oppositely. As shown in FIG. 5(b), a large pressure difference between both sides of the asymmetric element is generated due to the asymmetric structure of the jetting element when the fluid flows from the right side to the left side. Such a pressure difference will result in the decrement of the flow rate, and moreover, it is able to be considered that the jetting element is at a partially closed state.
FIGS. 4(c) and 4(d), and FIGS. 5(c) and 5(d) are diagrams respectively illustrating the fluid flowing through a passive and an active asymmetric element, which have a characteristic of “full diode”, including the passive and active one-way valves. There are many known types of these valves. FIG. 4(c) and FIG. 5(c) respectively illustrate the motion of the fluid when the fluid flows from the left side to the right side of the passive asymmetric element, i.e. being at an open state, and the motion of the fluid when the fluid flows oppositely, i.e. being at a closed state. Moreover, FIG. 4(d) and FIG. 5(d) respectively show the motion of the fluid when the fluid flows from the left side to the right side of the active one-way element, i.e. being at an open state, and the motion of the fluid when the fluid flows oppositely, i.e. being at a closed state. That is to say, the fluid is only permitted to flow from the left sides of the jetting elements to the right side thereof, which results in a one-way flowing of the fluid.
Based on the above, while using the asymmetric elements as the input elements and the output elements in the double-acting device, the differences in the flow rates and the variation of the fluid field are generated when the fluid is sucked in and jetted out through the asymmetric input (output) elements by controlling the valves with cooperation of the various arrangements of the elements. Therefore, the Non-Zero-Net-Mass-Flux fluid is generated accordingly.
Please refer to FIGS. 6(a) and 6(b), which illustrate the structure of the double-acting device for generating synthetic jets according to a third embodiment of the present invention. Compared with the forgoing embodiments, is the difference therebetween are the structure of the double-acting device 1 and, accordingly, the arrangements of the sub-chambers 10A and 10B, the output elements 3A and 3B, and the input element 4B. As shown in FIGS. 6(a) and 6(b), the double-acting device 1 has an axisymmetric structure with the symmetric axis 9, and the output elements 3A and 3B are axisymmetrically arranged relative to the symmetric axis 9. The action and function of the fluid 30a, 31a, 30b, 31b, 40b, 41b, 32a, 33a, 32b, 33b, 42b and 43b, and the vortices 60 in the double-acting device 1 according to this embodiment are respectively similar to those according to the above embodiments as shown in FIGS. 2(b) and 2(c), no matter the double-acting device 1 is during the up-stroke, i.e. the diaphragm 12 acts toward the U direction, as shown in FIG. 6(a), or during the back-stroke, i.e. the diaphragm 12 acts toward the D direction, as shown in FIG. 6(b).
In each reciprocating action of the diaphragm 12, some fluid is sucked into the double-acting device 1 through the input element 4B, and another fluid is simultaneously jetted out from the double-acting device 1 through the output elements 3A and 3B. The fluids inside and outside the double-acting device 1 are hence exchanged effectively. Furthermore, two vortices 60 generated by means of the diaphragm 12 reciprocatingly acting will be further enhanced through the streams countered to each other, which are generated when the fluid flows through the axisymmetrical arranged output elements 3A and 3B. More surrounding fluids are hence drawn and rolled by the enhanced vortices to further reinforce the cooling of the synthetic jets.
Please further refer to FIGS. 7(a) to 7(c), which are sectional diagrams respectively illustrating the different shapes and axisymmetrical arrangements of the output elements 3A and 3B in the output system 3 of the double-acting device 1 according to the third embodiment of the present invention. Viewing the output system 3 along the symmetric axis 9 (in FIGS. 6(a) and 6(b)) from the outside of the double-acting device, the output elements 3A and 3B having different shapes are accordingly configured in the arrangements shown in FIGS. 7(a) to 7(c), and moreover, other shapes and arrangements are permitted to be used in the double-acting device.
As shown in FIG. 7(a), the output system 3 includes a central output element 3A with a round shape and a set of output elements 3B with the same shape surrounding the central output element 3A. In FIG. 7(b), the output system 3 relates to an individual set of output elements 3B with a segment shape arranged around the central output element 3A with a round shape, and in FIG. 7(c), the output system 3 has a central output element 3A with a round shape and an annular output element 3B, which rounds the central element 3A.
By such arrangements in FIGS. 7(a) to 7(c), more vortices would be generated for the antiphase oscillation of the fluid by the double-acting device 1 of the present invention. Such a result is similar to that of the paired arrangements of the output system 3 according to the first embodiment in FIG. 2(a).
Please refer to FIGS. 8(a) and 8(b), which illustrate the field distributions near the outlets of the output elements, wherein the output elements 3A and 3B are passive asymmetric output elements as shown in FIG. 4 (b), such as nozzles or vortex valves, with rectification effects. Referring to FIG. 8(a), the diaphragm 12 acts toward the U direction and pushes the fluid in the sub-chamber 10A when the double-acting device is acting during the up-stroke. The fluid is pushed and jetted out from the sub-chamber 10A through the output element 3A, and the jets 31a are hence generated. The fluid field outside the double-acting device is changed by the generation of the jets 31a, and, accordingly, a pair of vortices 60 and 6a are formed. By an appropriate design for another output element 3B, the fluid 31b outside the double-acting device is sucked into the sub-chamber 10B, simultaneously. The flowing of the fluid 31b also results in a variation of the surrounding field, and such a variation further enhances the vortex 60 between the output elements 3A and 3B. After being enhanced, the vortex 60 will run downstream and away from the double-acting device. Similarly, a new pair of vortices 601 and 6b would be formed by the diaphragm 12 acting toward the D direction, and at the same moment, the vortex 601 is enhanced when the fluid 32a is sucked into the sub-chamber 10A.
Therefore, when the double-acting device of the present invention acts, a train of enhanced vortices would be always generated, no matter which direction the diaphragm 12 acts toward. Additionally, the enhanced vortices could further force the fluid outside the double-acting device to flow and convect for a more effective cooling.
Please refer to FIG. 9, which illustrates the cooling for an open system having a heat body therein by the Non-Zero-Net-Mass-Flux fluid generated by the double-acting device according to the present invention. First, a double-acting device 1, which is mentioned above, is provided on one side of the surface of the heat body 13, which needs to be cooled. Then, the diaphragm 12 of the double-acting device 1 is controlled to make the diaphragm 12 reciprocatingly act. Accordingly, when a reciprocating full action including the up-stroke and the back-stroke of the diaphragm 12 is completed, vortices 6a and 6b and enhanced vortices 60 and 601 would be formed, and jets 31a and 32b would be generated. The jets 31a and 32b would be directly and vertically impinged to the surface of the heat body 13 orderly, and further horizontally flowed away from the heat body 13, such as the fluids 61a and 61b. As a result, heat of the heat body 13 is partially taken away. Moreover, vortices 6a and 6b and enhanced vortices 60 and 601 also help for the heat dissipation of the heat body 13 for the continuous mutual interactions among the vortices 6a, 6b, 60 and 601.
What worthy to say is that, for the variation of the fluid field surrounding the double-acting device, the fresh fluids 8a and 8b with a lower temperature are also involved in the field interaction. Moreover, the fluids 42a and 41b, which have a much lower temperature and are much far from the heat body 13 and less influenced thereby, are respectively sucked into the sub-chamber 10A and 10B through the input elements 4A and 4B. Therefore, the fluids in the sub-chambers 10A and 10B are exchangeable, which may further help the cooling for the heat body 13.
Please refer to FIG. 10, which illustrates the cooling for a closed system having a heat body therein by the Non-Zero-Net-Mass-Flux fluid generated by the double-acting device according to the present invention. Compared with the cooling for the open system in FIG. 9, the fluids 8a and 8b in the closed system having a heat body 13, and the fluids 42a and 41b would have higher temperatures. However, owing to the reciprocating action of the double-acting device 1, the fluid is pumped for flowing roundly in the closed system 50, which improves the heat of the closed system 50 transferring out from the internal wall 51 of the closed system 50. Besides, both of the internal wall 51 and the external wall 52 can be constituted as extended surfaces, such as fins, to augment the heat transfer of the closed system 50.
Based on the above, it is known that the Non-Zero-Net-Mass-Flux jets have more advantages when compared with the conventional Zero-Net-Mass-Flux jets. Therefore, the range of the parameters, which are necessary to be controlled for the heat transfer and the fluidic applications, is broadened by the present invention. Accordingly, the present invention is more potential in the fluid controlling in not only the common scales, but also the micro scales, such as in the micro electromechanical system (MEMS).
The double-acting device provided by the present invention and the cooling method used the same adopt a device of double-chamber in cooperation with an arrangement of at least one input element and plural output elements to make the fluid with Non-Zero-Net-Mass-Flux jets to be jetted due to the working fluid circulating in each reciprocating action of the diaphragm. Since the fluid is sucked into the chamber and jetted out at the same time when the double-acting device is operated for the jets generation, the antiphase jets are accordingly formed. Furthermore, by the mutual interaction of the antiphase jets, the vortex formed by the double-acting device is further enhanced.
Therefore, the double-acting device of the present invention provides a more effective heat dissipation and a better cooling effect than that provided by the conventional ones, which only generates a Zero-Net-Mass-Flux fluid in a full working cycle including the up-stroke and the back-stroke. The double-acting device of the present invention is more constitutive in the improvements for the highly heat dissipating technology.
In conclusion, the double-acting device of the present invention is able to be used as a stand-alone device for cooling and accordingly has the following advantages.
First, the Non-Zero-Net-Mass-Flux jets generated by the double-acting device according to the present invention would make the surface of the heat body have an extremely high heat transfer efficiency, because the jets directly impinge to a heat surface and the fluid for cooling would be exchanged and the vortex is able to be enhanced.
Second, the geometrical structure of the double-acting device is quite simple. Additional devices, such as the pipes, blowers and some other moving parts, which are necessary in the conventional actuators, are not required in the double-acting device of the present invention. Therefore, the cooling system, which has the double-acting device provided by the present invention, exhibits a great flexibility in designs and applications, and would be very compact, spatially economical and cost-effective.
Finally, the double-acting device and the cooling method used the same provided by the present invention can be further applied in a closed system, and the heat body therein is able to be effectively cooled by a forced heat convection. No additional fluid outside the closed system is required.
Hence, the present invention not only has a novelty and a progressive nature, but also has an industry utility.
While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.

## Claims

1. A cooling method for a heated body, comprising:
providing a double-acting device, said double-acting device comprising a chamber divided into at least two sub-chambers by a separating element;
providing an input system connected to said chamber for passing a fluid into said chamber;
providing an output system including a passive asymmetric element and at least two sets of passages respectively connected to said at least two sub-chambers for outputting the fluid to the heated body;
controlling said separating element of said double-acting device to act reciprocatingly for antiphasely passing said fluid out of each of said at least two sub-chambers so that two oscillating jets and a train of vortices of said fluids are generated by the antiphase passing of said fluid; and
allowing said fluid to flow through the passive asymmetric element for enhancing said train of vortices,
wherein an enhancement of heat exchange of said heated body is induced by said two oscillating jets directing to a surface of said heated body and said train of vortices driving a surrounding fluid with a relatively low temperature rolling thereinto.

2. The method according to claim 1, wherein
said chamber provides a cavity for said fluid working therein;
said input system is connected to said chamber and disposed on a side far from the heated body for inputting a relatively cold fluid to said chamber; and
said output system is connected to said chamber and disposed on a side near to said surface of said heated body for outputting said fluid from said chamber onto said surface.

3. The method according to claim 1, wherein said input system has a relatively higher flow rate at a flow direction through said input system into the sub-chamber than that at a flow direction through said input system out of the sub-chamber.

4. The method according to claim 1, wherein said output system has a relatively higher flow rate at a flow direction through said output system out of the sub-chamber than that at a flow direction through said output system into the sub-chamber.

5. A cooling method for a heated body, comprising:
providing a double-acting device, said double-acting device comprising a chamber divided into at least two sub-chambers by a separating element;
providing an output system including a passive asymmetric element and at least two sets of passages respectively connected to said at least two sub-chambers for outputting a working fluid to the heated body;
providing an input system connected to said chamber for passing a relatively cold fluid into each of said at least two sub-chambers, so that said working fluid outputted from said at least two sub-chambers is a non-zero-net-mass-flux fluid with a relatively cold temperature;
controlling said separating element of said double-acting device to act reciprocatingly for antiphasely pushing said working fluid out from and pulling back into each of said at least two sub-chambers so that two oscillating jets and a train of vortices of said working fluids are generated by the antiphase passing of said working fluid in and out of each of said at least two sub-chambers; and
allowing said working fluid to flow through the passive asymmetric element for enhancing said train of vortices,
wherein an enhancement of heat exchange of said heated body is induced by said two oscillating jets directing to a surface of said heated body and said train of vortices driving a surrounding fluid with a relatively low temperature rolling thereinto.