Evaporative heat exchange apparatus with finned elliptical tube coil assembly

Abstract

An improved finned coil tube assembly enhances evaporative heat exchanger performance, and includes tubes, preferably serpentine tubes, in the coil assembly. The tubes have a generally elliptical cross-section with external fins formed on an outer surface of the tubes. The fins are spaced substantially 1.5 to substantially 3.5 fins per inch (2.54 cm) along the longitudinal axis of the tubes, extend substantially 23.8% to substantially 36% of the nominal tube outside diameter in height from the tubes outer surface and have a thickness of substantially 0.007 inch (0.018 cm) to substantially 0.020 inch (0.051 cm). The tubes have a center-to-center spacing generally horizontally and normal to the longitudinal axis of the tubes of substantially 109% to substantially 125% of the nominal tube outside diameter, and a generally vertical center-to-center spacing of substantially 100% to about 131% of the nominal tube outside diameter.

1 . In an evaporative heat exchanger comprising a plenum having a generally vertical longitudinal axis, a distributor for distributing an external heat exchange liquid into the plenum, an air mover for causing air to flow in a direction through the plenum in a direction generally countercurrent to, generally parallel to, or generally across the longitudinal axis of the plenum, and a coil assembly having a major plane and being mounted within the plenum such that the major plane is generally normal to the longitudinal axis of the plenum and such that the external heat exchange liquid flows externally through the coil assembly in a generally vertical flow direction, wherein the coil assembly comprises inlet and outlet manifolds and a plurality of tubes connecting the manifolds, the tubes extending in a direction generally horizontally and having a longitudinal axis and a generally elliptical cross-sectional shape having a major axis and a minor axis where the average of the major axis length and the minor axis length is a nominal tube outside diameter, the tubes being arranged in the coil assembly such that adjacent tubes are generally vertically spaced from each other within planes generally parallel to the major plane, the adjacent tubes in the planes generally parallel to the major plane being staggered and spaced with respect to each other generally vertically to form a plurality of staggered generally horizontal levels in which every other tube is aligned in the same generally horizontal level generally parallel to the major plane, and wherein the tubes are spaced from each other generally horizontally and generally normal to the longitudinal axis of the tube,
 the improvement comprising the tubes having external fins formed on an outer surface of the tubes, wherein the fins have a spacing of 1.5 to 3.5 fins per inch (2.54 cm) along the longitudinal axis of the tubes, the fins having a height extending from the outer surface of the tubes a distance of substantially 23.8% to substantially 36% of the nominal tube outside diameter, the fins having a thickness of substantially 0.007 inch (0.018 cm) to substantially 0.020 inch (0.051 cm), the tubes having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the tubes of substantially 100% to substantially 131% of the nominal tube outside diameter, and the horizontally adjacent tubes having a generally vertical center-to-center spacing of substantially 110% to substantially 300% of the nominal tube outside diameter.   
     
     
         2 . In an evaporative heat exchanger according to  claim 1 , the improvement further comprising the fins having a spacing of substantially 2.75 to substantially 3.25 fins per inch (2.54 cm) along the longitudinal axis of the tubes. 
     
     
         3 . In an evaporative heat exchanger according to  claim 2 , the improvement further comprising the fins having a spacing of substantially 3 fins per inch (2.54 cm) along the longitudinal axis of the tubes. 
     
     
         4 . In an evaporative heat exchanger according to  claim 1 , the improvement further comprising the tubes having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the tubes of substantially 106% to substantially 118% of the nominal tube outside diameter. 
     
     
         5 . In an evaporative heat exchanger according to  claim 4 , the improvement further comprising the tubes having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the tubes of substantially 112% of the nominal tube outside diameter. 
     
     
         6 . In an evaporative heat exchanger according to  claim 1 , the improvement further comprising the tubes having a generally vertical center-to-center spacing of substantially 150% to substantially 205% of the nominal tube outside diameter. 
     
     
         7 . In an evaporative heat exchanger according to  claim 6 , the improvement further comprising the tubes having a generally vertical center-to-center spacing of substantially 179% of the nominal tube outside diameter. 
     
     
         8 . In an evaporative heat exchanger according to  claim 1 , the improvement further comprising the nominal tube outside diameter being substantially 1.05 inches (2.67 cm). 
     
     
         9 . In an evaporative heat exchanger according to  claim 1 , the improvement further comprising the fins having a spacing of substantially 2.75 to substantially 3.25 fins per inch (2.54 cm) along the longitudinal axis of the tubes, the fins having a height of substantially 28% to substantially 33% of the nominal tube outside diameter, the fins having a thickness of substantially 0.009 inch (0.023 cm) to substantially 0.015 inch (0.038 cm), the tubes having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the tubes of substantially 106% to substantially 118% of the nominal tube outside diameter, and the tubes having a generally vertical center-to-center spacing of substantially 150% to substantially 205% of the nominal tube outside diameter. 
     
     
         10 . In an evaporative heat exchanger according to  claim 9 , the improvement further comprising the nominal tube outside diameter being substantially 1.05 inches (2.67 cm). 
     
     
         11 . In an evaporative heat exchanger according to  claim 1 , the improvement further comprising the fins having a spacing of substantially 3 fins per inch (2.54 cm) along the longitudinal axis of the tubes, the fins having a height of substantially 29.76% of the nominal tube outside diameter, the fins having a thickness of substantially 0.01 inch (0.025 cm) to substantially 0.013 inch (0.033 cm), the tubes having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the tubes of about 112% of the nominal tube outside diameter, and the tubes having a generally vertical center-to-center spacing of about 179% of the nominal tube outside diameter. 
     
     
         12 . In an evaporative heat exchanger according to  claim 11 , the improvement further comprising the nominal tube outside diameter being substantially 1.05 inches (2.67 cm). 
     
     
         13 . In an evaporative heat exchanger according to  claim 1 , the improvement further comprising the nominal tube outside diameter being substantially 1.05 inches (2.67 cm), the fins having a center-to-center spacing of substantially 0.286 inch (0.726 cm) to substantially 0.667 inch (1.694 cm), the fins having a height of substantially 0.25 inch (0.635 cm) to substantially 0.375 inch (0.953 cm), the tubes having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the tubes of substantially 1.05 inches (2.67 cm) to substantially 1.38 inches (3.51 cm), and the horizontally adjacent tubes having a generally vertical center-to-center spacing of substantially 1.15 inches (2.92 cm) to substantially 3.15 inches (8.00 cm). 
     
     
         14 . In an evaporative heat exchanger according to  claim 13 , the improvement further comprising the fins having a center-to-center spacing of substantially 0.308 inch (0.782 cm) to substantially 0.364 inch (0.925 cm), a height of substantially 0.294 inch (0.747 cm) to substantially 0.347 inch (0.881 cm), the fins having a thickness of substantially 0.009 inch (0.023 cm) to substantially 0.015 inch (0.038 cm), and the horizontally adjacent tubes having a generally vertical center-to-center spacing of substantially 1.57 inches (3.99 cm) to about 2.15 inches (5.46 cm). 
     
     
         15 . In an evaporative heat exchanger according to  claim 14 , the improvement further comprising the fins having a center-to-center spacing of substantially 0.333 inch (0.846 cm), a height of substantially 0.3125 inch (0.794 cm), a thickness of substantially 0.01 inch (0.025 cm) to substantially 0.013 inch (0.033 cm), the tubes having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the segments of substantially 1.175 inches (2.985 cm), and the tubes having a generally vertical center-to-center spacing of substantially 1.88 inches (4.78 cm). 
     
     
         16 . In an evaporative heat exchanger according to  claim 1 , the improvement further comprising the major axes of the tubes being generally parallel to the longitudinal axis of the plenum. 
     
     
         17 . In an evaporative heat exchanger according to  claim 1 , the improvement further comprising the major axes of the tubes being angled with respect to the longitudinal axis of the plenum. 
     
     
         18 . In an evaporative heat exchanger according to  claim 17 , the improvement further comprising the major axes of the tubes of adjacent tubes on different vertical levels being angled in opposite directions with respect to each other and to the longitudinal axis of the plenum. 
     
     
         19 . In an evaporative heat exchanger according to  claim 18 , the improvement further comprising the angle of the major axes of the tubes on a first generally horizontal level being greater than 0° to about 25° degrees from the longitudinal axis of the plenum and the angle of the major axes of the tubes on the next vertically adjacent generally horizontal level being about 335° to less than 360° from the longitudinal axis of the plenum. 
     
     
         20 . In an evaporative heat exchanger according to  claim 19 , the improvement further comprising the angle of the major axes of the tubes on a first generally horizontal level being about 20 degrees from the plane of the return bends and the angle of the major axes of the tubes on the next vertically adjacent generally horizontal level being about 340 degrees from the longitudinal axis of the plenum. 
     
     
         21 . In an evaporative heat exchanger according to  claim 1 , the improvement further comprising the fins having undulations in and out of a plane of material used to make the fins. 
     
     
         22 . In an evaporative heat exchanger according to  claim 1 , wherein the finned tubes are galvanized such that the fins after galvanization are thicker at a base proximal to the outer surface of the tube than at a tip of the fins distal from the outer surface of the tube. 
     
     
         23 . In an evaporative heat exchanger according to  claim 1 , wherein the tubes are serpentine tubes having a plurality of segments and a plurality of return bends, the return bends being oriented in generally vertical planes, the segments of each tube connecting the return bends of each tube and extending between the return bends in a direction generally horizontally, the segments having a longitudinal axis and a generally elliptical cross-sectional shape having a major axis and a minor axis where the average of the major axis length and the minor axis length is a nominal tube outside diameter, the segments being arranged in the coil assembly such that the segments of adjacent tubes are generally vertically spaced from each other within planes generally parallel to the major plane, the segments of adjacent tubes in the planes generally parallel to the major plane being staggered and spaced with respect to each other generally vertically to form a plurality of staggered generally horizontal levels in which every other segment is aligned in the same generally horizontal level generally parallel to the major plane, and wherein the segments are spaced from each other generally horizontally and generally normal to the longitudinal axis of the segment connected to the return bend,
 the improvement comprising the segments having external fins formed on an outer surface of the tubes, wherein the fins have a spacing of substantially 1.5 to substantially 3.5 fins per inch (2.54 cm) along the longitudinal axis of the segments, the fins having a height extending from the outer surface of the segments a distance of substantially 23.8% to substantially 36% of the nominal tube outside diameter, the fins having a thickness of substantially 0.007 inch (0.018 cm) to substantially 0.020 inch (0.051 cm), the segments having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the segments of substantially 100% to substantially 131% of the nominal tube outside diameter, and the horizontally adjacent segments having a generally vertical center-to-center spacing of substantially 110% to substantially 300% of the nominal tube outside diameter.   
     
     
         24 . In an evaporative heat exchanger according to  claim 23 , the improvement further comprising the fins having a spacing of substantially 2.75 to substantially 3.25 fins per inch (2.54 cm) along the longitudinal axis of the segments, the fins having a height of substantially 28% to substantially 33% of the nominal tube outside diameter, the fins having a thickness of substantially 0.009 inch (0.023 cm) to substantially 0.015 inch (0.038 cm), the segments having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the segments of substantially 106% to substantially 118% of the nominal tube outside diameter, and the horizontally adjacent segments having a generally vertical center-to-center spacing of substantially 150% to substantially 205% of the nominal tube outside diameter. 
     
     
         25 . In an evaporative heat exchanger according to  claim 24 , the improvement further comprising the fins having a spacing of substantially 3 fins per inch (2.54 cm) along the longitudinal axis of the segments, the fins having a height of substantially 29.76% of the nominal tube outside diameter, the fins having a thickness of substantially 0.01 inch (0.025 cm) to substantially 0.013 inch (0.033 cm), the segments having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the segments of substantially 112% of the nominal tube outside diameter, and the horizontally adjacent segments having a generally vertical center-to-center spacing of substantially 179% of the nominal tube outside diameter. 
     
     
         26 . In an evaporative heat exchanger according to  claim 23 , the improvement further comprising the return bends having a circular cross-section with an outside diameter of substantially 1.05 inches (2.67 cm) and the nominal tube outside diameter being substantially 1.05 inches (2.67 cm). 
     
     
         27 . In an evaporative heat exchanger according to  claim 23 , the improvement further comprising the return bends having a generally elliptical cross-section and the nominal tube outside diameter being substantially 1.05 inches (2.67 cm). 
     
     
         28 . In an evaporative heat exchanger according to  claim 23 , the improvement further comprising the major axes of the segments being generally parallel to the plane of the return bends. 
     
     
         29 . In an evaporative heat exchanger according to  claim 23 , the improvement further comprising the major axes of the segments being angled with respect to the plane of the return bends. 
     
     
         30 . In an evaporative heat exchanger according to  claim 29 , the improvement further comprising the major axes of the segments of adjacent tubes on different vertical levels being angled in opposite directions with respect to each other and to the plane of the return bends. 
     
     
         31 . In an evaporative heat exchanger according to  claim 30 , the improvement further comprising the angle of the major axes of the segments on a first generally horizontal level being greater than 0° to about 25° degrees from the plane of the return bends and the angle of the major axes of the segments on the next vertically adjacent generally horizontal level being about 335° to less than 360° from the plane of the return bends. 
     
     
         32 . In an evaporative heat exchanger according to  claim 31 , the improvement further comprising the angle of the major axes of the segments on a first generally horizontal level being about 20 degrees from the plane of the return bends and the angle of the major axes of the segments on the next vertically adjacent generally horizontal level being about 340 degrees from the plane of the return bends. 
     
     
         33 . In an evaporative heat exchanger according to  claim 31 , the improvement further comprising the fins having a spacing of substantially 2.75 to substantially 3.25 fins per inch (2.54 cm) along the longitudinal axis of the segments, the fins having a height of substantially 28% to substantially 33% of the nominal tube outside diameter, the fins having a thickness of substantially 0.009 inch (0.023 cm) to substantially 0.015 inch (0.038 cm), the segments having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the segments of substantially 106% to substantially 118% of the nominal tube outside diameter, and the horizontally adjacent segments having a generally vertical center-to-center spacing of substantially 150% to substantially 205% of the nominal tube outside diameter. 
     
     
         34 . In an evaporative heat exchanger according to  claim 31 , the improvement further comprising the fins having a spacing of substantially 3 fins per inch (2.54 cm) along the longitudinal axis of the segments, the fins having a height of substantially 29.76% of the nominal tube outside diameter, the fins having a thickness of substantially 0.01 inch (0.025 cm) to substantially 0.013 inch (0.033 cm), the segments having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the segments of substantially 112% of the nominal tube outside diameter, and the segments having a generally vertical center-to-center spacing of substantially 179% of the nominal tube outside diameter. 
     
     
         35 . In an evaporative heat exchanger comprising a plenum having a generally vertical longitudinal axis, a distributor for distributing an external heat exchange liquid into the plenum, an air mover for causing air to flow in a direction through the plenum in a direction generally countercurrent to, generally parallel to, or generally across the longitudinal axis of the plenum, and a coil assembly having a major plane and being mounted within the plenum such that the major plane is generally normal to the longitudinal axis of the plenum and such that the external heat exchange liquid flows externally through the coil assembly in a generally vertical flow direction, wherein the coil assembly comprises inlet and outlet manifolds and a plurality of tubes connecting the manifolds, the tubes extending in a direction generally horizontally and having a longitudinal axis and a generally elliptical cross-sectional shape having a major axis and a minor axis where the average of the major axis length and the minor axis length is a nominal tube outside diameter, the tubes being arranged in the coil assembly such that adjacent tubes are generally vertically spaced from each other within planes generally parallel to the major plane, the adjacent tubes in the planes generally parallel to the major plane being staggered and spaced with respect to each other generally vertically to form a plurality of staggered generally horizontal levels in which every other tube is aligned in the same generally horizontal level generally parallel to the major plane, and wherein the tubes are spaced from each other generally horizontally and generally normal to the longitudinal axis of the tube,
 the improvement comprising at least one of the tubes being a finned tube having external fins formed on an outer surface of the tubes, wherein the fins have a spacing of 1.5 to 3.5 fins per inch (2.54 cm) along the longitudinal axis of the tubes, the fins having a height extending from the outer surface of the tubes a distance of substantially 23.8% to substantially 36% of the nominal tube outside diameter, the fins having a thickness of substantially 0.007 inch (0.018 cm) to substantially 0.020 inch (0.051 cm), the tubes having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the tubes of substantially 100% to substantially 131% of the nominal tube outside diameter, and the horizontally adjacent tubes having a generally vertical center-to-center spacing of substantially 110% to substantially 300% of the nominal tube outside diameter.   
     
     
         36 . In an evaporative heat exchanger according to  claim 35 , the improvement further comprising a plurality of the tubes in the coil assembly being the finned tubes. 
     
     
         37 . In an evaporative heat exchanger according to  claim 36 , the improvement further comprising a majority of the tubes in the coil assembly being the finned tubes.