Counter-flow heat exchanger with optimal secondary cross-flow

Abstract

A method of exchanging heat that includes flowing a high pressure, high temperature fluid within a tubing generally along a first direction and flowing a low pressure, low temperature fluid within a first gap formed between a first wall and a first portion of the tubing positioned nearest the first wall and a second gap formed between a second wall and a second portion of the tubing that is positioned nearest the second wall.

We claim:  
     
         1 . A heat exchanger comprising: 
 a first wall that extends along a first direction and defines a first perimeter in a plane that is perpendicular to said first direction;    a second wall that defines a second perimeter and is positioned within said first perimeter, wherein said first wall and said second wall are spaced from one another so as to define a volume of space therebetween;    a lid attached to a top portion of said first wall and a top portion of said second wall;    a bottom attached to a bottom portion of said first wall and a bottom portion of said second wall;    a spiral tubing positioned within said volume of space, wherein at least a portion of said spiral tubing does not contact either said first wall or said second wall so that a first gap is formed between said first wall and a first portion of said spiral tubing positioned nearest said first wall and a second gap is formed between said second wall and a second portion of said spiral tubing that is positioned nearest said second wall; and    a first fluid that flows within said spiral tubing and a second fluid that flows within said first and second gaps.    
     
     
         2 . The heat exchanger of  claim 1 , wherein said spiral tubing in its entirety fails to contact either said first wall or said second wall.  
     
     
         3 . The heat exchanger of  claim 1 , wherein a second portion of said spiral tubing contacts both said first wall and said second wall.  
     
     
         4 . The heat exchanger of  claim 1 , wherein said first gap has a magnitude that ranges from 0.2 mm to 0.5 mm.  
     
     
         5 . The heat exchanger of  claim 1 , wherein said second gap has a magnitude that ranges from 0.2 mm to 0.5 mm.  
     
     
         6 . The heat exchanger of  claim 4 , wherein said second gap has a magnitude that ranges from 0.2 mm to 0.5 mm.  
     
     
         7 . The heat exchanger of  claim 1 , wherein a magnitude of said first gap is the same as a magnitude of said second gap.  
     
     
         8 . The heat exchanger of  claim 7 , wherein said magnitude of said first gap is approximately 0.3 mm.  
     
     
         9 . The heat exchanger of  claim 1 , wherein said magnitudes of said first and second gaps are chosen so as to reduce pressure drop without adversely affecting heat exchange performance.  
     
     
         10 . The heat exchanger of  claim 1 , wherein magnitudes of said first and second gaps are chosen so as to maximize heat exchanging.  
     
     
         11 . The heat exchanger of  claim 1 , wherein widths of said first and second gaps are varied as a function of distance between adjacent spiral tubing.  
     
     
         12 . The heat exchanger of  claim 11 , wherein said widths of said first and second gaps are varied so as to achieve an optimal combination of high heat transfer and low pressure drop.  
     
     
         13 . The heat exchanger of  claim 1 , wherein said spiral tubing is made of a highly thermally conductive material.  
     
     
         14 . The heat exchanger of  claim 1 , wherein said first wall is cylindrical in shape and said second wall is cylindrical in shape.  
     
     
         15 . The heat exchanger of  claim 14 , wherein said first wall and said second wall are co-axial with respect to one another.  
     
     
         16 . The heat exchanger of  claim 1 , wherein said first fluid is at a high temperature and high pressure.  
     
     
         17 . The heat exchanger of  claim 1 , wherein said second fluid is at a low temperature and a low pressure.  
     
     
         18 . The heat exchanger of  claim 16 , wherein said second fluid is at a low temperature and a low pressure.  
     
     
         19 . The heat exchanger of  claim 1 , wherein said first and second fluids generally flow in opposite directions with respect to one another.  
     
     
         20 . The heat exchanger of  claim 18 , wherein said first and second fluids generally flow in opposite directions with respect to one another.  
     
     
         21 . The heat exchanger of  claim 18 , wherein said first fluid is selected from the group consisting of CO 2  and R134a.  
     
     
         22 . The heat exchanger of  claim 18 , wherein said second fluid is selected from the group consisting Of CO 2  and R134a.  
     
     
         23 . The heat exchanger of  claim 21 , wherein said second fluid is selected from the group consisting of CO 2  and R134a.  
     
     
         24 . The heat exchanger of  claim 1 , wherein said tubing is connected to a gas cooler.  
     
     
         25 . The heat exchanger of  claim 1 , wherein said tubing is connected to a condenser.  
     
     
         26 . The heat exchanger of  claim 1 , further comprising a J-tube having one end in fluid communication with said volume of space.  
     
     
         27 . The heat exchanger of  claim 1 , wherein a first component of said second fluid flows along an exterior of said tubing and a second component of said second fluid flows within said first and said second gaps.  
     
     
         28 . A method of exchanging heat, comprising: 
 flowing a high pressure, high temperature fluid within a tubing generally along a first direction; and    flowing a low pressure, low temperature fluid within a first gap formed between a first wall and a first portion of said tubing positioned nearest said first wall and a second gap formed between a second wall and a second portion of said tubing that is positioned nearest said second wall.    
     
     
         29 . The method of  claim 28 , wherein said high-pressure, high temperature fluid flows in a helical path within said tube.  
     
     
         30 . The method of  claim 28 , further comprising accumulating said low pressure, low temperature fluid at a bottom of a volume of space defined at least in part by said first wall and said second wall.  
     
     
         31 . The method of  claim 30 , further comprising expelling a vapor portion of said low pressure, low temperature fluid present within said volume of space.  
     
     
         32 . The method of  claim 28 , further comprising flowing a portion of said low pressure, low temperature fluid along an exterior of said tubing.