Apparatus and methods for converting cryogenic fluid into gas

Abstract

An apparatus for vaporizing a cryogenic fluid comprises a heat transfer fluid closed circulation loop at least partially defined by an ambient air heat exchanger, a heater, and a vaporizer. The heat exchanger is configured to direct air downward across a plurality of heat exchanger tubes. A cryogenic fluid flows through the vaporizer. The plurality of tubes comprise a first tube having a first fin of a height, h 1 , and a second tube spaced adjacent the first tube, where the second tube has a second fin of a height, h 2 , wherein h 2 is different from h 1 .

1 . An apparatus for vaporizing a cryogenic fluid, comprising: 
 a heat transfer fluid closed circulation loop at least partially defined by an ambient air heat exchanger, a heater, and a vaporizer, wherein the heat exchanger is configured to direct air downward across a plurality of heat exchanger tubes;    a cryogenic fluid flow path through the vaporizer;    wherein, the plurality of tubes comprise:    a first tube having a first fin of a height, h 1 ; and    a second tube spaced adjacent the first tube, the second tube having a second fin of a height, h 2 , wherein h 2  is different from h 1 .    
   
   
       2 . The apparatus of  claim 1 , wherein the cryogenic fluid comprises liquefied natural gas (LNG).  
   
   
       3 . The apparatus of  claim 2 , wherein h 1  is less than h 2 .  
   
   
       4 . The apparatus of  claim 2 , further comprising a third tube spaced adjacent the second tube, the third tube having a third fin of a height, h 3 .  
   
   
       5 . The apparatus of  claim 4 , wherein h 2  is less than h 3 .  
   
   
       6 . The apparatus of  claim 2 , wherein h 1  is substantially zero.  
   
   
       7 . The apparatus of  claim 2 , wherein the first tube comprises a plurality of vertically spaced horizontal rows of first tubes.  
   
   
       8 . The apparatus of  claim 2 , wherein the second tube comprises a plurality of vertically spaced horizontal rows of second tubes.  
   
   
       9 . The apparatus of  claim 4 , wherein the third tube comprises a plurality of vertically spaced horizontal rows of third tubes.  
   
   
       10 . The apparatus of  claim 1 , wherein the heat transfer fluid is chosen from the group consisting of: (i) an aqueous potassium formate solution, (ii) propane, (iii) refrigerant R-22, (iv) ammonia, (v) a glycol/water solution; and (vi) liquefied natural gas.  
   
   
       11 . The apparatus of  claim 1 , wherein the apparatus is operated under conditions such that at least a portion of the plurality of tubes has moisture condensed thereon.  
   
   
       12 . The apparatus of  claim 1 , wherein the apparatus operates under conditions that do not require defrosting.  
   
   
       13 . A method of vaporizing a cryogenic fluid, comprising: 
 transferring heat from ambient air to a heat transfer fluid by circulating the heat transfer fluid in a closed loop through a plurality of tubes of an air heat exchanger by directing ambient air downwardly across the plurality of tubes in the ambient air heat exchanger; and    transferring a portion of the heat from the heat transfer fluid to vaporize at least a portion of the cryogenic fluid;    wherein the plurality of tubes comprise:    a first tube having a first fin of a height, h 1 ; and    a second tube spaced adjacent the first tube, the second tube having a second fin of a height, h 2 , wherein h 2  is different from h 1 .    
   
   
       14 . The method of  claim 13 , wherein the apparatus operates under conditions such that at least a portion of the plurality of tubes has moisture condensed thereon.  
   
   
       15 . The method of  claim 13 , wherein the apparatus operates under conditions that do not require defrosting.  
   
   
       16 . The method of  claim 13 , wherein h 1  is less than h 2 .  
   
   
       17 . The method of  claim 13 , further comprising a third tube spaced adjacent the second tube, the third tube having a third fin of a height, h3.  
   
   
       18 . The method of  claim 17 , wherein h 2  is less than h 3 .  
   
   
       19 . The method of  claim 16 , wherein h 1  is substantially zero.  
   
   
       20 . The method of  claim 16 , wherein the heat transfer fluid is chosen from the group consisting of: (i) an aqueous potassium formate solution, (ii) propane, (iii) refrigerant R-22, (iv) ammonia, (v) a glycol/water solution; and (vi) liquefied natural gas.