Apparatus for enhancing condensation and boiling of a fluid

Abstract

An apparatus enhances the condensation and boiling of a fluid in heat exchange machines, by directly applying time-periodic acoustic waves with a resonance oscillation frequency to liquid drops and/or bubbles formed on a solid surface, when the fluid is in the process of condensation or boiling, thereby effectively removing them therefrom. The apparatus comprises a signal generator for generating a driving signal based on a resonant oscillation frequency of at least one of the liquid drops and the bubbles; and a vibrator, in response to the driving signal, for providing an acoustic pressure wave to said at least one of the liquid drops and the bubbles, to thereby detach them from the solid surface.

What is claimed is:  
     
         1 . An apparatus for enhancing condensation and boiling of a fluid in heat exchange machines by separating at least one of liquid drops and bubbles from a solid surface with which the fluid contacts, the apparatus comprising: 
 means for generating a driving signal based on a resonant oscillation frequency of said at least one of the liquid drops and the bubbles; and    means, in response to the driving signal, for providing an acoustic pressure wave to said at least one of the liquid drops and the bubbles, to thereby detach them from said solid surface.    
     
     
         2 . The apparatus according to  claim 1 , wherein the resonant oscillation frequency corresponds to a first natural oscillation frequency ƒ 1  of each of the liquid drops, and 
 the first natural oscillation frequency ƒ 1  is calculated as follow:  
           f   1     =         1     2      π            [       n        (     n   -   1     )            (     n   +   2     )          σ     ρ                   a   3           ]         1   2                       
 wherein n is a vibration mode number for determining the shape of a vibration; and σ, ρ, and a represent the surface tension, the density, and the diameter of said each of the liquid drops, respectively.  
 
     
     
         3 . The apparatus according to  claim 1 , wherein the resonant oscillation frequency corresponds to a second natural oscillation frequency ƒ 2  of each of the bubbles, and the second natural oscillation frequency ƒ 2  is calculated as follow:  
       
         
           
             
               
                 f 
                 2 
               
               = 
               
                 
                   
                     1 
                     
                       2 
                        
                       π 
                     
                   
                    
                   
                     [ 
                     
                       
                         ( 
                         
                           n 
                           + 
                           1 
                         
                         ) 
                       
                        
                       
                         ( 
                         
                           n 
                           - 
                           1 
                         
                         ) 
                       
                        
                       
                         ( 
                         
                           n 
                           + 
                           2 
                         
                         ) 
                       
                        
                       
                         σ 
                         
                           ρ 
                            
                           
                               
                           
                            
                           
                             a 
                             3 
                           
                         
                       
                     
                     ] 
                   
                 
                 
                   1 
                   2 
                 
               
             
           
           
           
               
           
         
       
       wherein n is a vibration mode number for determining the shape of a vibration; and σ, ρ denote the surface tension and the density of a surrounding liquid, respectively, and a is the diameter of said each of the bubbles.  
     
     
         4 . The apparatus according to  claim 1 , further comprising means for amplifying the driving signal to a predetermined signal level.  
     
     
         5 . The apparatus according to  claim 4 , wherein the signal generation means, the providing means, and the amplification means are integrated as one unit.  
     
     
         6 . The apparatus according to  claim 1 , wherein the driving signal includes one of a sinusoidal, triangular, saw-tooth, and rectangular wave signals.  
     
     
         7 . The apparatus according to  claim 1 , wherein the providing means includes a membrane, piston, acoustic speaker, and piezoelectric device.  
     
     
         8 . The apparatus according to  claim 2 , wherein the acoustic pressure wave has a resonant oscillation frequency that depends on the first natural oscillation frequency ƒ 1 , wherein the liquid drops are vibrated with said resonant oscillation frequency.  
     
     
         9 . The apparatus according to  claim 3 , wherein the acoustic pressure wave has a resonant oscillation frequency that depends on the second natural oscillation frequency ƒ 2 , wherein the bubbles are vibrated with said resonant oscillation frequency.  
     
     
         10 . The apparatus according to  claim 1 , wherein the resonant oscillation frequency is several tens of hertz (Hz).