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.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a division of U.S. patent application Ser. No. 10/849,613, filed Jul. 20, 2004, which is incorporated by reference as if fully set forth. 
     
    
     FIELD OF THE INVENTION 
       [0002]    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 
       [0003]    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”. 
         [0004]    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. 
         [0005]    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 ). 
         [0006]    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. 
         [0007]    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 ′. 
         [0008]    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. 
         [0009]    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. 
         [0010]    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. 
         [0011]    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. 
         [0012]    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 
       [0013]    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. 
         [0014]    Preferably, the working fluid is pushed and pulled by a reciprocating action of the separating element. 
         [0015]    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. 
         [0016]    Preferably, the separating element is a piston. 
         [0017]    Preferably, the control system is a system of connecting rods. 
         [0018]    Preferably, the separating element is a diaphragm. 
         [0019]    Preferably, the diaphragm is one of a piezoelectric film and a photoelectric film. 
         [0020]    Preferably, the control system is a control circuit. 
         [0021]    Preferably, the input system and the output system further include a first control valve and a second control valve respectively. 
         [0022]    Preferably, the first control valve and the second control valve are selected from an active valve and a passive valve. 
         [0023]    Preferably, the input system further includes at least an input element. 
         [0024]    Preferably, the input element is one of a diffuser and an orifice. 
         [0025]    Preferably, the output system further includes at least two output elements respectively connected to the sub-chambers in the defined arrangement. 
         [0026]    Preferably, the at least two output elements are selected from nozzles and orifices. 
         [0027]    Preferably, the orifices are circular orifices. 
         [0028]    Preferably, the output elements are coaxially arranged. 
         [0029]    Preferably, the defined arrangement is one of a paired arrangement and an axisymmetric arrangement. 
         [0030]    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. 
         [0031]    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. 
         [0032]    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. 
         [0033]    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. 
         [0034]    Preferably, the separating element is controlled to pump by a control system connected to the chamber. 
         [0035]    Preferably, the output system further has at least two output elements. 
         [0036]    Preferably, the antiphasely oscillating jets are generated by a double-acting action of the separating element. 
         [0037]    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. 
         [0038]    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  
         [0039]      FIG. 1(   a ) is a diagram illustrating the structure of the conventional Zero-Net-Mass-Flux actuator according to the prior art; 
           [0040]      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; 
           [0041]      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; 
           [0042]      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; 
           [0043]      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; 
           [0044]      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; 
           [0045]      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; 
           [0046]      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; 
           [0047]      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; 
           [0048]      FIGS. 8(   a ) and  8 ( b ) illustrate the field distributions near the outlets of the jetting elements; 
           [0049]      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 
           [0050]      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  
       [0051]    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. 
         [0052]    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  10 A and  10 B. The input elements  4 A and the output element  3 A, and the input elements  3 A and the output element  3 B are respectively configured on the wall  11  of the sub-chamber  10 A and  10 B for respectively forming an input system  4  and an output system  3 . Accordingly, the output elements  3 A and  3 B, and the input elements  4 A and  4 B 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 . 
         [0053]    Please refer to  FIG. 2(   b ). The diaphragm  12  driven by the control circuit  2  acts in a direction toward to the sub-chamber  10 A, 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  10 A is increased, and some of the working fluid  30   a  in the sub-chamber  10 A is accordingly promoted to jet out through the output element  3 A to further form the principal jets  31   a.  Moreover, the increased pressure in the sub-chamber  10 A also results in a minor flowing of the fluid. In other words, some of the fluid  40   a  is accordingly jetted out from the sub-chamber  10 A through the input element  4 A to form minor jets  41   a,  if there is no additional check valve cooperated with the input element  4 A. Additionally, the mass flux of the minor jets  41   a  depends on the structure and the size of the input element  4 A. 
         [0054]    On the other hand, there is only a periodic difference between the actions of the fluid in the sub-chambers  10 A and  10 B. Therefore, the working fluids  30   b  and  40   b  in the sub-chamber  10 B will flow in a direction, which is opposite to that of the working fluids  30   a  and  40   a  in the sub-chamber  10 A. That is to say, as the pressure inside the sub-chamber  10 A is increased, the pressure inside the sub-chamber  10 B will be decreased, and the fluid  41   b  outside the double-acting device  1  will be accordingly sucked into the sub-chamber  10 B through the input element  4 B and forms the working fluid  40   b.  Similarly, the fluid  31   b  is accordingly sucked into the sub-chamber  10 B through the output element  3 B to form the working fluid  30   b,  if there is no additional check valves cooperated with the output element  3 B. 
         [0055]    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  10 A, i.e. along the D direction, in the back-stroke of the double-acting device  1 . The pressure inside the sub-chamber  10 A will be decreased, and the fluid  42   a  outside the double-acting device  1  will accordingly flow into the sub-chamber  10 A through the input element  4 A to form a principal input fluid  43   a.  Moreover, the decreased pressure in the sub-chamber  10 A also results in a minor flowing of the fluid. In other words, the fluid  32   a  is accordingly sucked into the sub-chamber  10 A through the output element  3 A to form the minor input fluid  33   a,  if there is no additional check valve cooperated with the output element  3 A. Additionally, the mass flux of the minor input fluid  33   a  depends on the structure and the size of the output element  3 A. 
         [0056]    Considering the situation for the sub-chamber  10 B, the fluid  33   b  inside the sub-chamber  10 B is jetted out through the output element  3 B owing to the increased pressure inside the sub-chamber  10 B. The jet fluid  32   b  is hence generated. Similarly, some of the fluid  43   b  inside the sub-chamber  10 B will be accordingly jetted out from the sub-chamber  10 B through the input element  4 B to form the jet fluid  42   b,  if there is no additional check valve cooperated with the input element  4 B. 
         [0057]    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 . 
         [0058]    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. 
         [0059]    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 ). 
         [0060]    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. 
         [0061]      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. 
         [0062]    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. 
         [0063]    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  10 A and  10 B, the output elements  3 A and  3 B, and the input element  4 B. As shown in  FIG. 6(   a ) and  6 ( b ), the double-acting device  1  has an axisymmetric structure with the symmetric axis  9 , and the output elements  3 A and  3 B are axisymmetrically arranged relative to the symmetric axis  9 . The action and function of the fluid  30   a,    31   a,    30   b,    31   b,    40   b,    41   b,    32   a,    33   a,    32   b,    33   b,    42   b  and  43   b , 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 ). 
         [0064]    In each reciprocating action of the diaphragm  12 , some fluid is sucked into the double-acting device  1  through the input element  4 B, and another fluid is simultaneously jetted out from the double-acting device  1  through the output elements  3 A and  3 B. 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  3 A and  3 B. More surrounding fluids are hence drawn and rolled by the enhanced vortices to further reinforce the cooling of the synthetic jets. 
         [0065]    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  3 A and  3 B 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  3 A and  3 B 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. 
         [0066]    As shown in  FIG. 7(   a ), the output system  3  includes a central output element  3 A with a round shape and a set of output elements  3 B with the same shape surrounding the central output element  3 A. In  FIG. 7(   b ), the output system  3  relates to an individual set of output elements  3 B with a segment shape arranged around the central output element  3 A with a round shape, and in  FIG. 7(   c ), the output system  3  has a central output element  3 A with a round shape and an annular output element  3 B, which rounds the central element  3 A. 
         [0067]    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 ). 
         [0068]    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  3 A and  3 B 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  10 A when the double-acting device is acting during the up-stroke. The fluid is pushed and jetted out from the sub-chamber  10 A through the output element  3 A, and the jets  31   a  are hence generated. The fluid field outside the double-acting device is changed by the generation of the jets  31   a,  and, accordingly, a pair of vortices  60  and  6   a  are formed. By an appropriate design for another output element  3 B, the fluid  31   b  outside the double-acting device is sucked into the sub-chamber  10 B, simultaneously. The flowing of the fluid  31   b  also results in a variation of the surrounding field, and such a variation further enhances the vortex  60  between the output elements  3 A and  3 B. After being enhanced, the vortex  60  will run downstream and away from the double-acting device. Similarly, a new pair of vortices  601  and  6   b  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  32   a  is sucked into the sub-chamber  10 A. 
         [0069]    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. 
         [0070]    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  6   a  and  6   b  and enhanced vortices  60  and  601  would be formed, and jets  31   a  and  32   b  would be generated. The jets  31   a  and  32   b  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  61   a  and  61   b.  As a result, heat of the heat body  13  is partially taken away. Moreover, vortices  6   a  and  6   b  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  6   a,    6   b,    60  and  601 . 
         [0071]    What worthy to say is that, for the variation of the fluid field surrounding the double-acting device, the fresh fluids  8   a  and  8   b  with a lower temperature are also involved in the field interaction. Moreover, the fluids  42   a  and  41   b,  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  10 A and  10 B through the input elements  4 A and  4 B. Therefore, the fluids in the sub-chambers  10 A and  10 B are exchangeable, which may further help the cooling for the heat body  13 . 
         [0072]    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  8   a  and  8   b  in the closed system having a heat body  13 , and the fluids  42   a  and  41   b  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 . 
         [0073]    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). 
         [0074]    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. 
         [0075]    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. 
         [0076]    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. 
         [0077]    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. 
         [0078]    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. 
         [0079]    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. 
         [0080]    Hence, the present invention not only has a novelty and a progressive nature, but also has an industry utility. 
         [0081]    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.