Bowed fin for heat exchanger

Abstract

A heat exchanger includes a plurality of first fluid passages configured to receive a first stream and a plurality of second fluid passages each formed between two first fluid passages. Each first fluid passage includes a first plate and a second plate parallel to the first plate. The first plate and second plate are connected by two closure bars. The first fluid passage also includes a fin pack having a plurality of fins connected to the first and second plate, and configured for the first stream to flow around the fins. The fins have a cross-sectional profile that is bowed at non-operational temperatures and is configured to flex under a thermal load without exceeding the tensile or fatigue strength of the fin. Each second fluid passage is configured to receive a second stream and is configured to allow heat to indirectly exchange between the first stream and the second stream.

1 . A heat exchanger comprising:
 a plurality of first fluid passages configured to receive a first stream, each first fluid passage comprising:
 a first plate; 
 a second plate parallel to the first plate, wherein the first plate and second plate are connected by two closure bars; 
 a fin pack having a plurality of fins connected to the first and second plate, and configured for the first stream to flow around the fins, wherein the fins have a cross-sectional profile that is bowed at non-operational temperatures and is configured to flex under a thermal load without exceeding the tensile or fatigue strength of the fin; and 
   a plurality of second fluid passages each formed between two first fluid passages, wherein each second fluid passage is configured to receive a second stream, and wherein the second fluid passage is configured to allow heat to indirectly exchange between the first stream and the second stream.   
     
     
         2 . The heat exchanger of  claim 1 , wherein the fin further comprises:
 a plurality of first fin base portions parallel and adjacent to the first plate;   a plurality of second fin base portions parallel and adjacent to the second plate;   a plurality of first and second bowed fin portions connected between the first and second fin base portions, wherein the first and second bowed fin portions are oppositely bowed and are configured to flex under a thermal load without exceeding the tensile or fatigue strength of the fin.   
     
     
         3 . The heat exchanger of  claim 2 , wherein each fin extends from a first end of the first fluid passage to a second end of the first fluid passage between the first and second plates, and where the profile of each fin is consistent between the first and second end of the first fluid passage. 
     
     
         4 . The heat exchanger of  claim 2 , wherein the first and second fin base portions and first and second bowed fin portions extend from a first end of the first fluid passage to a second end of the first fluid passage, and wherein the portions form a plurality of fin sections that are offset between the first and second end of the first fluid passage such that adjacent fin sections are offset from each other moving from the first end of the first fluid passage to the second end of the first fluid passage. 
     
     
         5 . The heat exchanger of  claim 1 , wherein each fin extends from a first end of the first fluid passage to a second end of the first fluid passage between the first and second plates, and wherein the profile of the fin is consistent between the first and second end of the fin. 
     
     
         6 . The heat exchanger of  claim 1 , wherein the heat exchanger is a dual heat exchanger having a primary and a secondary heat exchanger. 
     
     
         7 . The heat exchanger of  claim 6 , wherein the primary heat exchanger is configured to receive bleed air from a gas turbine engine and is configured to receive ram air that has passed through the secondary heat exchanger. 
     
     
         8 . The heat exchanger of  claim 7 , wherein the heat exchanger further comprises a second fin disposed in some of the fluid passages, wherein the second fin has a cross-sectional profile that is not bowed. 
     
     
         9 . The heat exchanger of  claim 8 , wherein the fins having a profile that is bowed are only used in first fluid passages near local areas of the primary heat exchanger subject to a high thermal load and the second fin is used throughout the remainder of the heat exchanger. 
     
     
         10 . The heat exchanger of  claim 9 , wherein each fin extends from a first end of the first fluid passage to a second end of the first fluid passage, and wherein the profile of the fin is consistent between the first and second end of the first fluid passage. 
     
     
         11 . An environmental control system comprising:
 a heat exchanger comprising:
 a plurality of first fluid passages configured to receive a first stream, each first fluid passage comprising: 
 a first plate; 
 a second plate parallel to the first plate, wherein the first plate and second plate are connected by two closure bars; 
 a fin pack having a plurality of fins connected to the first and second plate, and configured for the first stream to flow around the fins, wherein the fins have a cross-sectional profile that is bowed at non-operational temperatures and is configured to flex under a thermal load without exceeding the tensile or fatigue strength of the fin; and 
 a plurality of second fluid passages each formed between two first fluid passages, wherein each second fluid passage is configured to receive a second stream, and wherein the second fluid passage is configured for heat to indirectly exchange between the first stream and the second stream. 
   a gas turbine bleed source for providing the first stream to the heat exchanger;   at least one ram air fan for providing the second stream to the heat exchanger; and   an air cycle machine for receiving the first stream from the heat exchanger.   
     
     
         12 . The heat exchanger of  claim 11 , wherein the fin further comprises:
 a plurality of first fin base portions parallel and adjacent to the first plate;   a plurality of second fin base portions parallel and adjacent to the second plate;   a plurality of first and second bowed fin portions connected between the first and second fin base portions, wherein the first and second bowed fin portions are oppositely bowed and are configured to flex under a thermal load without exceeding the tensile or fatigue strength of the fin.   
     
     
         13 . The heat exchanger of  claim 12 , wherein each fin extends from a first end of the first fluid passage to a second end of the first fluid passage between the first and second plates, and where the profile of the fin is consistent between the first and second end of the first fluid passage. 
     
     
         14 . The heat exchanger of  claim 12 , wherein the first and second fin base portions and first and second bowed fin portions extend from a first end of the first fluid passage to a second end of the first fluid passage, and wherein the portions form a plurality of fin sections that are offset between the first and second end of the first fluid passage such that adjacent fin sections are offset from each other moving from the first end of the first fluid passage to the second end of the first fluid passage. 
     
     
         15 . The environmental control system of  claim 14 , wherein the secondary heat exchanger is configured to receive ram air from a ram air inlet, and discharge ram air into the primary heat exchanger, and wherein the primary heat exchanger is configured to receive bleed air from a gas turbine engine and discharge the bleed air into the air machine.