Condensing air preheater with heat pipes

Abstract

An air preheater comprises flow conduits for heat transfer between a heating gas and combustion air which is to be pre-heated with heat pipes extending between the flow conduits for the two gas streams to provide heat transfer The fins on the heat pipes in at least the condensation zone of the flow conduit of the heating gas are provided with one or more serrations on the sides of the pipes facing away from the oncoming gas flow. The serrations assist in removing any liquid film which may accumulate on the fins during operation in the condensing mode. A corrosion resistant coating material such as glass may be provided on the condensing side of the finned heat pipes.

1 . An air preheater comprising:
 a first flow conduit for a heating gas,   a second flow conduit in heat transfer communication with the first flow conduit for a gas to be heated,   heat pipes extending from the first flow conduit into the second flow conduit, the heat pipes having: an evaporation zone located in the first flow conduit, a condensation zone located in the second conduit, and fins on the heat pipes which extend out from the heat pipes into the respective flow conduits, the fins on the heat pipes in at least the first flow conduit having at least one serration in the fins on the sides of the pipes facing away from the oncoming gas flow.   
     
     
         2 . An air preheater according to  claim 1  in which the fins on the heat pipes in at least the first flow conduit have a plurality of serrations on the sides of the pipes facing away from the oncoming gas flow. 
     
     
         3 . An air preheater according to  claim 1  in which the fins on the heat pipes in at least the first flow conduit have two or three serrations on the sides of the pipes facing away from the oncoming gas flow. 
     
     
         4 . An air preheater according to  claim 1  in which the fins on the heat pipes in at least the first flow conduit have a plurality of serrations extending around the entire periphery of the pipes. 
     
     
         5 . An air preheater according to  claim 1  in which serrated fins extend out from the heat pipes into both the first and second flow conduits, with at least one serration in the fins on the sides of the pipes facing away from the oncoming gas flow. 
     
     
         6 . An air preheater comprising:
 a first flow conduit for a heating gas comprising a vapor component which is susceptible to condensation upon cooling in the preheater, the first flow conduit in the preheater having a condensation region in which condensation of the vapor component of the heating gas is likely to occur;   a second flow conduit in heat transfer communication with the first flow conduit for a gas to be heated,   heat pipes extending from the first flow conduit into the second flow conduit, the heat pipes having: an evaporation zone located in the first flow conduit, a condensation zone located in the second conduit, and fins on the heat pipes which extend out from the heat pipes into the respective flow conduits, the fins on the heat pipes in at least the first flow conduit having at least one serration in the fins on the sides of the pipes facing away from the oncoming gas flow.   
     
     
         7 . An air preheater according to  claim 6  in which the fins on the heat pipes in the condensation region of the first flow conduit in have a plurality of serrations on the sides of the pipes facing away from the oncoming gas flow. 
     
     
         8 . An air preheater according to  claim 7  in which the fins on the heat pipes in the condensation region of the first flow conduit have two or three serrations on the sides of the pipes facing away from the oncoming gas flow. 
     
     
         9 . An air preheater according to  claim 6  in which only the fins on the heat pipes in the condensation region of the first flow conduit in have a plurality of serrations on the sides of the pipes facing away from the oncoming gas flow. 
     
     
         10 . An air preheater according to  claim 9  in which only the fins on the heat pipes in the condensation region of the first flow conduit have two or three serrations on the sides of the pipes facing away from the oncoming gas flow. 
     
     
         11 . An air preheater according to  claim 6  in which the fins on the heat pipes in the second flow conduit have a plurality of serrations extending around the entire periphery of the pipes. 
     
     
         12 . An air preheater according to  claim 6  in which serrated fins extend out from the heat pipes into both the first and second flow conduits, with at least one serration in the fins on the sides of the pipes facing away from the oncoming gas flow. 
     
     
         13 . An air preheater according to  claim 6  in which the fins are helical fins on the heat pipes. 
     
     
         14 . An air preheater according to  claim 11  in which the fins are helical fins on the heat pipes. 
     
     
         15 . An air preheater according to  claim 12  in which the fins are helical fins on the heat pipes.