Apparatus and method for improving the performance of an evaporator

Abstract

The present invention relates to the improvements of the performance of an evapo-rator, specifically adapted for a natural convection system. The evaporator com-prises tubes ( 11 ) intended to contain a refrigerant to be evaporated. An apparatus ( 13 ) is arranged inside at least one of the tubes and comprises means ( 21 ) for disin-tegrating vapour bubbles ( 27 ′) of a gaseous phase of the refrigerant inside the tube ( 11 ) during operation of the evaporator. Small vapour bubbles can much easier move through the liquid compared to big vapour bubbles, which easily get stuck in the tube thereby obstructing the movement of other vapour bubbles. Thus, by breaking up big bubbles into smaller bubbles the flow through the tubes ( 11 ) is in-creased as well as the heat emitting surfaces of the vapour bubbles ( 27 ″).

1 . Method for increasing the performance of a natural convection system evaporator ( 3 ) comprising tubes ( 11 ), in which tubes a contained refrigerant is intended to absorb heat during operation of the evaporator, whereby vapour bubbles ( 27 ′) of the refrigerant are formed,  
       characterised by the step of: 
 disintegrating said vapour bubbles ( 27 ′) inside the tubes ( 11 ) of the evaporator ( 3 ) into smaller vapour bubbles ( 27 ″).  
 
     
     
         2 . Natural convection system evaporator comprising tubes ( 11 ), in which tubes a contained refrigerant is intended to absorb heat during operation of the evaporator whereby vapour bubbles ( 27 ′) of the refrigerant are formed,  
       characterised by: 
 a first apparatus ( 13 ) being arranged inside at least one of said tubes ( 11 ), said apparatus ( 13 ) comprising means ( 21 ,  31 ) for disintegrating said vapour bubbles ( 27 ′) inside the tubes ( 11 ) of the evaporator ( 3 ) into smaller vapour bubbles ( 27 ″).  
 
     
     
         3 . Natural convection system evaporator according to  claim 2 , wherein said first apparatus ( 13 ) has a bottle-brush like shape.  
     
     
         4 . Natural convection system evaporator according to claim  2 - 3 , wherein said first apparatus ( 13 ) comprises a shaft ( 15 ) being substantially concentrically arranged with the longitudinal axis ( 17 ) of the tube ( 11 ), said shaft having a plurality of radially extending, peripherally separated bristles ( 21 ).  
     
     
         5 . Natural convection system evaporator according to  claim 2 , wherein said first apparatus ( 13 ) has a grid-like structure.  
     
     
         6 . Natural convection system evaporator according to any of claims  2 - 5 , wherein a second apparatus ( 33 ) is arranged downstream the first apparatus ( 13 ), wherein said second apparatus ( 33 ) comprises means ( 35 ) for rotation of the refrigerant about the longitudinal axis ( 17 ) of the tube ( 11 ) during operation of the evaporator ( 3 ), so as to radially separate a liquid phase (L) from a gaseous phase (G) of the refrigerant due to centrifugal action.  
     
     
         7 . Natural convection system evaporator according to any of claims  2 - 6 , wherein said tubes are vertical.