Aluminum fin and tube heat exchanger

Abstract

A heat exchanger ( 10 ) is provided including at least one aluminum alloy tube ( 12 ) and a plurality of aluminum fins ( 26 ) arrayed on the aluminum alloy tube. The aluminum tube may be supported by tube sheets ( 24 ) made of aluminum alloy.

We claim:  
     
         1 . A heat exchanger comprising;
 at least one tube having a longitudinally extending tube length, the at least one tube made of a first aluminum alloy having a first galvanic potential; and   a plurality of heat exchange fins arrayed on the at least one tube, the plurality of heat exchange fins made of a second aluminum alloy, the second aluminum alloy having a second galvanic potential, the second galvanic potential being higher than the first galvanic potential.   
     
     
         2 . The heat exchanger as recited in  claim 1  wherein the difference in galvanic potential between the second aluminum alloy and the first aluminum alloy is greater than about 20 millivolts. 
     
     
         3 . The heat exchanger as recited in  claim 1  wherein the first aluminum alloy comprises aluminum alloy AA3003 and the second aluminum alloy comprises an aluminum alloy selected from the group consisting of AA1100 and AA7072. 
     
     
         4 . The heat exchanger as recited in  claim 1  wherein the first aluminum alloy comprises an aluminum alloy selected from the group consisting of AA30048 and AA3102 and the second aluminum alloy comprises aluminum alloy AA7072. 
     
     
         5 . A heat exchanger comprising:
 at least one serpentine tube having a plurality of longitudinally extending tube lengths; and   a plurality of heat exchange fins arrayed on the at least one tube, adjacent fins of the arrayed plurality of heat exchange fins having interlocking collars disposed about and contacting the at least one tube, the interlocking collars collectively forming a protective layer about the at least one tube.   
     
     
         6 . The heat exchanger as recited in  claim 5  wherein the protective layer about the at least one tube comprises a galvanically sacrificial layer relative to the at least one tube. 
     
     
         7 . The heat exchanger as recited in  claim 5  wherein the at least one tube comprises a tube made of a first aluminum alloy having a first galvanic potential; and the plurality of heat exchange fins comprise fins made of a second aluminum alloy, the second aluminum alloy having a second galvanic potential, the second galvanic potential being higher than the first galvanic potential. 
     
     
         8 . The heat exchanger as recited in  claim 5  wherein the at least one serpentine tube comprises a plurality of hairpin tubes supported between spaced tube sheets, each hairpin tube having a pair of longitudinally extending tube lengths and a hairpin turn, the plurality of hairpin tubes fluidly interconnected by a plurality of return bends. 
     
     
         9 . The heat exchanger as recited in  claim 8  wherein each tube sheet comprises a tube sheet made of a third aluminum alloy, the third aluminum alloy having a third galvanic potential, the third galvanic potential being higher than the first galvanic potential. 
     
     
         10 . The heat exchanger as recited in  claim 9  wherein the first aluminum alloy comprises aluminum alloy AA3003 and the third aluminum alloy comprises aluminum alloy AA5052. 
     
     
         11 . The heat exchanger as recited in  claim 1  wherein the first aluminum alloy comprises an aluminum alloy selected from the group consisting of AA30048 and AA3102 and the third aluminum alloy comprises aluminum alloy AA7072. 
     
     
         12 . The heat exchanger as recited in  claim 8  wherein the hairpin turns and the return bends are coated with a protective coating for enhancing corrosion resistance. 
     
     
         13 . The heat exchanger as recited in  claim 12  wherein the protective coating comprises a coating for enhancing corrosion resistance selected from the group including clear acrylic based solvent varnish, urethane based varnish, conversion coats, acrylic e-coats, epoxy e-coats, corrosion inhibitive e-coats, polyester powder, powder coats and pre-treated 2-part epoxies. 
     
     
         14 . The heat exchanger as recited in  8  wherein the heat exchanger is coated with a protective coating for further enhancing corrosion resistance. 
     
     
         15 . The heat exchanger as recited in  claim 14  wherein the protective coating comprises a coating for enhancing corrosion resistance selected from the group including trivalent chrome conversion coats, zirconium conversion coats, zinc phosphate coats and iron phosphate coats. 
     
     
         16 . A heat exchanger for use as an evaporator coil in connection with a transport refrigeration system, comprising:
 first and second longitudinally spaced tube sheets;   a plurality of aluminum alloy hairpin tubes supported between the spaced tube sheets, each hairpin tube having a pair of longitudinally extending tube lengths and a hairpin turn, the plurality of hairpin tubes fluidly interconnected by a plurality of return bends; and   a plurality of heat exchange fins arrayed on the longitudinally extending tube lengths of the plurality of hairpin tubes, adjacent fins of the arrayed plurality of heat exchange fins having interlocking collars disposed about and contacting the at least one tube, the interlocking collars collectively forming a protective layer about the at least one tube; the tube sheets the plurality of fins being galvanically sacrificial with respect to the hairpin tubes.   
     
     
         17 . The heat exchanger as recited in  claim 16  wherein the plurality of hairpin tubes are made of a first aluminum alloy having a first galvanic potential, the plurality of fins are made of a second aluminum alloy having a second galvanic potential, and the tube sheets are made of a third aluminum alloy having a third galvanic potential, each of the second and third galvanic potentials being greater than the first galvanic potential. 
     
     
         18 . The heat exchanger as recited in  claim 17  wherein the second aluminum alloy and the third aluminum alloy comprise the same aluminum alloy. 
     
     
         19 . The heat exchanger as recited in  claim 8  wherein each tube sheet has a plurality of tube holes therein, each tube hole receiving a tube length of a respective one of the plurality of hairpin tubes, each tube length having an outside diameter. D, and each hole having a clearance, Ts, relative to the tube length, wherein the ratio Ts/D has a value in the range of 0.0013 to 0.0363. 
     
     
         20 . The heat exchanger as recited in  claim 1  wherein the at least one tube comprises a tube having internal fins having a fin perimeter and a fin cross-section, the ratio of the fin perimeter to the fin cross-section having a value in the range of 400 to 650, as expressed in inch −1  dimension. 
     
     
         21 . The heat exchanger as recited in  claim 1  wherein the at least one tube comprises a tube having at least one parameter selected from the group of parameters presented in Table I having value in the corresponding range specified therefor in Table I.