Evaporatively cooled thermosiphon

Abstract

A thermosiphon cooling assembly cools an electronic device with a first refrigerant disposed in the lower boiling chamber of a housing for liquid-to-vapor transformation and a second refrigerant disposed in an upper evaporating chamber of a housing for liquid-to-vapor transformation. The partition separating the lower boiling chamber of the housing from the upper evaporating chamber of the housing creates a series of vapor chambers within the lower boiling portion for condensing vapor boiled off the first refrigerant. The upper evaporating chamber contains a series of refrigerant pockets interleaved vertically with the vapor chambers to increase the surface area for heat transfer between the refrigerant vapor and the second refrigerant for absorbing heat by the second refrigerant for liquid-to-vapor transformation.

1 . A thermosiphon cooling assembly for cooling an electronic device, comprising; 
 a housing having a partition defining a lower boiling chamber for receiving heat from the electronic device and an upper evaporating chamber,    a first refrigerant disposed below said partition in said lower boiling chamber of said housing for liquid-to-vapor transformation,    a second refrigerant disposed above said partition in said upper evaporating chamber of said housing for liquid-to-vapor transformation,    said partition defining a plurality of vapor chambers extending upwardly above said lower boiling chamber for condensing vapor boiled off said first refrigerant, and    said upper evaporating chamber including a plurality of refrigerant pockets interleaved with said vapor chamber for holding said second refrigerant and an open space above said refrigerant pockets for condensing vapor boiled off said second refrigerant.    
   
   
       2 . An assembly as set forth in  claim 1  wherein said first refrigerant has a higher boiling temperature than the boiling temperature of said second refrigerant.  
   
   
       3 . An assembly as set forth in  claim 2  wherein said first refrigerant has a first heat capacity (mh fg ) 1  and said second refrigerant has a second heat capacity (mh fg ) 2  and  
       (mh fg ) 1 =(mh fg ) 2    wherein    m is the refrigerant mass and    h fg  is the latent heat of evaporation of the refrigerant and is defined as        h   fg =α(1 −T/T   c ) 3/8      wherein    T is the absolute temperature of interest and    T c  is the critical temperature of the refrigerant and    α is a constant and is defined as    α=β RT   c   /J          wherein    R is the gas constant of the refrigerant and    T c  is the critical temperature of the refrigerant and    J is the mechanical-to-thermal energy conversion factor and is    J=778.163 ft*lb f /Btu    β is a dimensionless constant and is defined as      β=ln( P   n   /P   c )/(1 −T   c   /T   n )    wherein    P n  is the atmospheric pressure and    P c  is the critical pressure for the refrigerant and    T c  is the critical temperature of the refrigerant and    T n  is the normal boiling temperature of the refrigerant.    
   
   
       4 . An assembly as set forth in  claim 2  including a condensing unit operatively attached to said upper evaporating unit.  
   
   
       5 . An assembly as set forth in  claim 4  including a capillary tube interconnecting said upper evaporating chamber of said housing and said condensing unit.  
   
   
       6 . An assembly as set forth in  claim 5  including a wick material disposed on said refrigerant pockets and said wick material disposed in said upper evaporating chamber of said housing and extending into said capillary tube for conveying liquid from said condensing unit to said refrigerant pockets.  
   
   
       7 . An assembly as set forth in  claim 6  wherein said capillary tube is flexible for moving said condensing unit relative to said housing.  
   
   
       8 . An assembly as set forth in  claim 4  wherein said condensing unit defines a lower portion and an upper portion with said upper portion having a plurality of spaced radiation chambers extending through said condensing unit and a plurality of condensing fins disposed within said radiation chambers.  
   
   
       9 . An assembly as set forth in  claim 8  including an air moving device for moving air through said radiation chambers and over said condensing fins.  
   
   
       10 . An assembly as set forth in  claim 2  including a plurality of boiler fins disposed in said lower boiling chamber of said housing for enhancing heat transfer to said first refrigerant.  
   
   
       11 . An assembly as set forth in  claim 5  including a plurality of capillary fins disposed on said capillary tube for enhancing heat transfer from said second refrigerant.  
   
   
       12 . A thermosiphon cooling assembly for cooling an electronic device, comprising; 
 a housing having a partition defining a lower boiling chamber for receiving heat from the electronic device and an upper evaporating chamber,    a first refrigerant disposed below said partition in said lower boiling chamber of said housing for liquid-to-vapor transformation,    a plurality of boiler fins disposed in said lower boiling chamber of said housing for enhancing heat transfer to said first refrigerant,    a second refrigerant disposed above said partition in said upper evaporating chamber of said housing for liquid-to-vapor transformation,    a condensing unit defining a lower portion and an upper portion with said upper portion having a plurality of spaced radiation chambers extending through said condensing unit,    a plurality of condensing fins disposed within said radiation chambers,    an air moving device for moving air through said radiation chambers and over said condensing fins,    a capillary tube interconnecting said upper evaporating chamber of said housing and said lower portion of said condensing unit,    said capillary tube being flexible for moving said condensing unit relative to said housing,    a plurality of capillary fins disposed on said capillary tube for enhancing heat transfer from said second refrigerant,    a wick material disposed in said upper evaporating chamber of said housing and extending into said capillary tube for conveying liquid from said condensing unit to said upper evaporating chamber of said housing,    said partition defining a plurality of spaced vapor chambers extending upwardly above said lower boiling chamber for condensing vapor boiled off said first refrigerant,    said upper evaporating chamber including a plurality of refrigerant pockets interleaved with said vapor chambers for holding said second refrigerant and an open space above said refrigerant pockets for condensing vapor boiled off said second refrigerant,    said wick material disposed on said refrigerant pockets, and    said first refrigerant having a higher boiling temperature than the boiling temperature of said second refrigerant,    
   
   
       13 . An assembly as set forth in  claim 12  wherein said first refrigerant has a first heat capacity (mh fg ) 1  and said second refrigerant has a second heat capacity (mh fg ) 2  and  
       (mh fg ) 1 =(mh fg ) 2    wherein    m is the refrigerant mass and    h fg  is the latent heat of evaporation of the refrigerant and is defined as        h   fg =α(1 −T/T   c ) 3/8      wherein    T is the absolute temperature of interest and    T c  is the critical temperature of the refrigerant and    α is a constant and is defined as      α=β RT   c   /J      wherein    R is the gas constant of the refrigerant and    T c  is the critical temperature of the refrigerant and    J is the mechanical-to-thermal energy conversion factor and is    J=778.163 ft*lb f /Btu    β=is a dimensionless constant and is defined as      β=ln( P   n   /P   c )(1 −T   c   /T   n )    wherein    P n  is the atmospheric pressure and    P c  is the critical pressure for the refrigerant and    T c  is the critical temperature of the refrigerant and    T n  is the normal boiling temperature of the refrigerant.    
   
   
       14 . A method of cooling an electronic device comprising the steps of; 
 generating heat by an electronic device,    transferring the heat generated by the electronic device to the lower boiling chamber of a housing,    a boiling a first refrigerant in the lower boiling chamber of the housing from liquid-to-vapor at a first temperature,    transferring heat from the vapor of the first refrigerant to a second refrigerant in the upper evaporating chamber of the housing, and    boiling the second refrigerant in the upper evaporating chamber of the housing from liquid-to-vapor at a second temperature lower than the first temperature.    
   
   
       15 . A method as set forth in  claim 14  including condensing the vapor of the second refrigerant in a condensing unit and wicking the condensed liquid refrigerant through a capillary tube to the upper evaporating chamber of the housing.