Heat transfer apparatus with enhanced micro-channel heat transfer tubing

Abstract

Heat exchange apparatus includes elliptical cross section heat exchange tubing provided with a partition dividing the interior of the tubing into at least two parallel flow passages. The flow passages are delimited by inwardly projecting fins formed on the tubing wall and on the partition, the fins extending parallel to each other and having a height less than the anticipated thickness of the velocity boundary layer of heat exchange fluid flowing through the tubing passages. The tubing may be arranged in serpentine or coiled arrangements of the heat exchange apparatus or parallel tubes extending between heat exchanger header tanks. The heat exchange apparatus is particularly adapted for use in HVAC systems.

1 . Apparatus for transferring heat between fluids comprising: 
 micro-channel tubing having a generally curved cross sectional shape to be presented to a heat transfer fluid flowing thereover, said cross sectional shape being defined by a wall of said tubing;    said tubing including partition means dividing an interior space of said tubing into parallel longitudinal flow passages; and    generally parallel, longitudinal, spaced apart fins extending from said wall and said partition means into said flow passages, respectively, to provide enhanced heat transfer between fluids flowing over the exterior of said tubing and within said flow passages, respectively.    
   
   
       2 . The apparatus set forth in  claim 1  wherein: 
 said partition means comprises a partition extending along and substantially parallel to an axis of said cross sectional shape of said tubing.    
   
   
       3 . The apparatus set forth in  claim 2  wherein: 
 said axis is a minor axis of an ellipse.    
   
   
       4 . The apparatus set forth in  claim 3  wherein: 
 said ellipse defines said cross sectional shape of said tubing and said ellipse has a major axis which is approximately twice the length of said minor axis.    
   
   
       5 . The apparatus set forth in said  claim 4  wherein: 
 said apparatus is arranged to provide for flow of a heat exchange fluid over the exterior of said tubing generally normal to a minor axis of said elliptical cross section.    
   
   
       6 . The apparatus set forth in  claim 1  wherein: 
 the cross sectional shape of said tubing is substantially elliptical.    
   
   
       7 . The apparatus set forth in  claim 6  wherein: 
 said apparatus is formed as a serpentine coil of said tubing and said tubing is bent in reverse bends about an axis substantially parallel to a major axis of said elliptical cross sectional shape.    
   
   
       8 . The apparatus set forth in  claim 6  wherein: 
 said apparatus is formed in a continuous helical coil of said tubing which is bent about an axis substantially parallel to a major axis of said elliptical cross sectional shape.    
   
   
       9 . The apparatus set forth in  claim 1  wherein: 
 said fins have a substantially trapezoidal cross sectional shape.    
   
   
       10 . The apparatus set forth in  claim 1  wherein: 
 the height of said fins is less than the thickness of a velocity boundary layer of fluid flowing through said flow passages, respectively.    
   
   
       11 . The apparatus set forth in  claim 10  wherein: 
 the height of said fins is determined from the equation e=2·R 7 ·A/P where e=height of said fins, R is a variable having a value of from about 0.60 to 0.95, A is the cross sectional area of one of said flow passages and P is the perimeter length of said one flow passage.    
   
   
       12 . The apparatus set forth in  claim 1  wherein: 
 the thickness of said wall is in a range of about 70% to 80% of the thickness of said partition means.    
   
   
       13 . Apparatus for transferring heat between fluids comprising: 
 micro-channel tubing having a generally elliptical cross sectional shape to be presented to a heat transfer fluid flowing thereover, said cross sectional shape being defined by a wall of said tubing;    said tubing including a partition extending along and substantially parallel to an axis of said cross sectional shape of said tubing and dividing an interior space of said tubing into parallel longitudinal flow passages; and    generally parallel, longitudinal, spaced apart fins extending from said wall and said partition into said flow passages, respectively, said fins having a height less than the thickness of a velocity boundary layer of a fluid flowing through said flow passages to provide enhanced heat transfer between fluids flowing over the exterior of said tubing and within said flow passages, respectively.    
   
   
       14 . The apparatus set forth in  claim 13  wherein: 
 said axis is a minor axis of said elliptical cross sectional shape of said tubing.    
   
   
       15 . The apparatus set forth in  claim 14  wherein: 
 said elliptical cross sectional shape of said tubing has a major axis which is approximately twice the length of said minor axis.    
   
   
       16 . The apparatus set forth in  claim 13  wherein: 
 said fins have a substantially trapezoidal cross sectional shape.    
   
   
       17 . The apparatus set forth in  claim 13  wherein: 
 said apparatus is formed as a serpentine coil of said tubing and said tubing is bent in reverse bends about an axis substantially parallel to a major axis of said elliptical cross sectional shape.    
   
   
       18 . The apparatus set forth in  claim 13  wherein: 
 said apparatus is formed in a continuous helical coil of said tubing which is bent about an axis substantially parallel to a major axis of said elliptical cross sectional shape.    
   
   
       19 . Micro-channel tubing for transferring heat between fluids and having a generally curved cross sectional shape to be presented to a heat transfer fluid flowing thereover, said cross sectional shape being defined by a wall of said tubing; 
 said tubing including at least one partition dividing an interior space of said tubing into parallel longitudinal flow passages; and    generally parallel, longitudinal, spaced apart fins extending from said wall and said partition, respectively, into said flow passages, respectively, to provide enhanced heat transfer between fluids flowing over the exterior of said tubing and within said flow passages, respectively, said fins having a substantially trapezoidal cross sectional shape and a height less than the thickness of a velocity boundary layer of fluid flowing through said flow passages.    
   
   
       20 . The tubing set forth in  claim 19  wherein: 
 said cross sectional shape of said tubing is elliptical and includes a major axis and a minor axis and said partition is coincident with said minor axis.    
   
   
       21 . The tubing set forth in  claim 20  wherein: 
 the length of said major axis is about twice the length of said minor axis.    
   
   
       22 . The tubing set forth in  claim 19  wherein: 
 the height of said fins is determined from the equation e=2·R 7 ·A/P where e=height of said fins, R is a variable having a value of from about 0.60 to 0.95, A is the cross sectional area of one of said flow passages and P is the perimeter length of said one flow passage.    
   
   
       23 . Micro-channel tubing for transferring heat between fluids and having a generally curved cross sectional shape to be presented to a heat transfer fluid flowing thereover, said cross sectional shape being defined by a wall of said tubing; 
 said tubing including at least one partition dividing an interior space of said tubing into parallel longitudinal flow passages; and    generally parallel, longitudinal, spaced apart fins extending from said wall and said partition, respectively, into said flow passages, respectively, to provide enhanced heat transfer between fluids flowing over the exterior of said tubing and within said flow passages, respectively, said fins having a height determined from the equation e=2·R 7 ·A/P where e=height of said fins, R is a variable having a value of from about 0.60 to 0.95, A is the cross sectional area of one of said flow passages and P is the perimeter length of said one flow passage.    
   
   
       24 . The tubing set forth in  claim 23  wherein: 
 R has a value of about 0.87.