Pulsating cooling system

Abstract

A cooling device comprising at least one transducer ( 1 ) having a membrane adapted to generate pressure waves at a working frequency, characterized by a first and a second cavity ( 3, 4 ), said transducer being arranged between said first and second cavities, such that said membrane forms an fluid tight seal between said cavities, each cavity having at least one opening ( 7, 8 ) adapted to emit a pulsating net output fluid flow, wherein said cavities and openings are formed such that, at said working frequency, a first harmonic fluid flow emitted by said opening(s) ( 7 ) of a first one of said cavities is in anti-phase with a second harmonic fluid flow emitted by said opening(s) ( 8 ) of a second one of said cavities, so that a sum of harmonic fluid flow from said openings is essentially zero. With this design, sound reproduction at the working frequency is largely cancelled due to the counter phase of the outlets resulting in a close to zero far-field volume velocity.

1 . A cooling device comprising at least one transducer ( 1 ) having a membrane adapted to generate pressure waves at a working frequency, characterized by
 a first and a second cavity ( 3 ,  4 ), said transducer being arranged between said first and second cavities, such that said membrane forms a fluid tight seal between said cavities,   each cavity having at least one opening ( 7 ,  8 ) adapted to emit a pulsating net output fluid flow,   wherein said cavities and openings are formed such that, at said working frequency, a first harmonic fluid flow emitted by said opening(s) ( 7 ) of a first one of said cavities is in anti-phase with a second harmonic fluid flow emitted by said opening(s) ( 8 ) of a second one of said cavities, so that a sum of harmonic fluid flow from said openings is essentially zero.   
   
   
       2 . The device according to  claim 1 , wherein each cavity has more than one opening. 
   
   
       3 . The device according to  claim 1 , wherein two transducers ( 34 ,  35 ) are arranged in opposite positions between said cavities ( 31 ,  32 ). 
   
   
       4 . The device according to  claim 1  wherein a distance d between any two openings is less than 0.2λ, and preferably less than 0.1λ, where λ is the wave length in said fluid corresponding to the working frequency. 
   
   
       5 . The device according to  claim 1  wherein said working frequency is chosen such that velocities of said first and second harmonic flows have a local maximum at this working frequency. 
   
   
       6 . The device according to  claim 1  wherein said cavities ( 3 ,  4 ) have essentially equal volume. 
   
   
       7 . The device according to  claim 1  wherein said openings ( 7 ,  8 ) have essentially equal cross section area. 
   
   
       8 . The device according to  claim 1  wherein said openings are connected to respective cavity via a channel ( 5 ,  6 ). 
   
   
       9 . The device according to  claim 8 , wherein said channels ( 5 ,  6 ) have essentially equal length. 
   
   
       10 . The device according to  claim 8 , wherein said channels ( 5 ,  6 ) have essentially equal cross section. 
   
   
       11 . The device according to  claim 8 , wherein a channel connecting at least one opening of said first cavity extends through said second cavity, so that said at least one opening is located on the same side of said device as the openings of said second cavity. 
   
   
       12 . The device according to  claim 1 , realized using micro electromechanical system (MEMS) technology. 
   
   
       13 . The device according to  claim 12 , wherein the transducer is formed by etching a silicon substrate. 
   
   
       14 - 15 . (canceled)