Exhaust gas heat exchanger

Abstract

An exhaust gas heat exchanger has a tube which is made of a stainless steel and in which exhaust gas flows, and an inner fin which is made of a stainless steel and arranged in the tube to improve a heat exchange between the exhaust gas and cooling water. The cooling water flows at an outer side of the tube. The fin pitch fp of the inner fin is substantially in the range of 2 mm<fp≦12 mm, and the fin height fh of the inner fin is substantially in the range of 3.5 mm<fh≦12 mm.

1 . An exhaust gas heat exchanger in which exhaust gas generated due to combustion is heat-exchanged with cooling fluid, comprising:
 a tube in which the exhaust gas flows and outside which the cooling fluid flows; and   an inner fin which is arranged in the tube to improve a heat exchange between the exhaust gas and the cooling fluid, wherein:   the inner fin has a cross section which has a corrugated shape to include convex portions positioned at crests and troughs of the corrugated shape, and is constructed of an offset fin having lanced segments which are partially lanced and arrayed substantially in a flowing direction of the exhaust gas,   the crests and the troughs being alternately arranged, and the cross section being substantially perpendicularly to the flowing direction of the exhaust gas; and   a fin pitch fp and a fin height fh of the inner fin are substantially defined by following formulas
   3.5 mm<fh≦12 mm, 
   2 mm<fp≦12 mm, 
   wherein the fin pitch fp is a distance between central lines of the adjacent convex portions positioned at a side of one of the crest and the trough in the cross section of the inner fin, and the fin height fh is a distance between the convex portions which are respectively positioned at the side of the crest and the side of the trough in the cross section of the inner fin.   
   
   
       2 . An exhaust gas heat exchanger in which exhaust gas generated due to combustion is heat-exchanged with cooling fluid, comprising:
 a tube in which the exhaust gas flows and outside which the cooling fluid flows; and   an inner fin which is arranged in the tube to improve a heat exchange between the exhaust gas and the cooling fluid, wherein:   the inner fin has a cross section which has a corrugated shape to include convex portions positioned at crests and troughs of the corrugated shape, and is constructed of an offset fin having lanced segments which are partially lanced and arrayed substantially in a flowing direction of the exhaust gas,   the crests and the troughs being alternately arranged, and the cross section being substantially perpendicularly to the flowing direction of the exhaust gas; and   an equivalent circle diameter de is substantially defined by following formulas
   when 0<L<5 mm, 1.2 mm≦de≦6.1 mm, 
   when 5 mm≦L≦15 mm, 1.0 mm≦de≦4.3 mm, 
   wherein L is a length of the lanced segment in the flowing direction of the exhaust gas, and the equivalent circle diameter de is a diameter of an equivalent circle of a field C which is surrounded by the inner fin and the tube and positioned between the adjacent convex portions at a side of one of the crest and the trough in the cross section of the inner fin.   
   
   
       3 . The exhaust gas heat exchanger according to  claim 2 , wherein
 the equivalent circle diameter de is substantially defined by following formulas
   when 0<L<5 mm, 1.3 mm≦de≦5.3 mm, 
   when 5 mm<L<15 mm, 1.1 mm≦de≦4.0 mm. 
   
   
   
       4 . The exhaust gas heat exchanger according to  claim 2 , wherein
 the equivalent circle diameter de is substantially defined by following formulas
   when 0<L<5 mm, 1.5 mm≦de≦4.5 mm, 
   when 5 mm≦L≦15 mm, 1.3 mm≦de≦3.5 mm. 
   
   
   
       5 . An exhaust gas heat exchanger in which exhaust gas generated due to combustion is heat-exchanged with cooling fluid, comprising:
 a tube in which the exhaust gas flows and outside which the cooling fluid flows; and   an inner fin which is arranged in the tube to improve a heat exchange between the exhaust gas and the cooling fluid, wherein:   the inner fin has a cross section which has a corrugated shape to include convex portions positioned at crests and troughs of the corrugated shape, and is constructed of an offset fin having lanced segments which are partially lanced and arrayed substantially in a flowing direction of the exhaust gas,   the crests and the troughs being alternately arranged, and the cross section being substantially perpendicularly to the flowing direction of the exhaust gas; and   a length L of the lanced segment is substantially defined by following formulas
   when fh<7 mm and fp≦5 mm, 0.5 mm<L≦65 mm, 
   when fh<7 mm and fp>5 mm, 0.5 mm<L≦20 mm, 
   when fh≧7 mm and fp≦5 mm, 0.5 mm<L≦50 mm, 
   when fh≧7 mm and fp>5 mm, 0.5 mm<L≦15 mm, 
   wherein the length L is a dimension in the flowing direction of the exhaust gas, fp is a fin pitch which is a distance between central lines of the adjacent convex portions positioned at a side of one of the crest and the trough in the cross section of the inner fin, and fh is a fin height which is a distance between the convex portions which are respectively positioned at the side of the crest and the side of the trough in the cross section of the inner fin.   
   
   
       6 . The exhaust gas heat exchanger according to  claim 5 , wherein
 the length L of the lanced segment is substantially defined by following formulas
   when fh<7 mm and fp≦5 mm, 0.5 mm<L≦25 mm, 
   when fh<7 mm and fp>5 mm, 0.5 mm<L≦8 mm, 
   when fh≧7 mm and fp≧5 mm, 0.5 mm<L≦18 mm, 
   when fh≧7 mm and fp>5 mm, 0.5 mm<L≦6 mm. 
   
   
   
       7 . The exhaust gas heat exchanger according to  claim 5 , wherein
 the length L of the lanced segment is substantially defined by following formulas
   when fh<7 mm and fp≦5 mm, 0.5 mm<L≦7 mm, 
   when fh<7 mm and fp>5 mm, 0.5 mm<L≦1 mm, 
   when fh≧7 mm and fp≦5 mm, 0.5 mm<L≦4.5 mm, 
   when fh≧7 mm and fp>5 mm, 0.5 mm<L≦1.5 mm. 
   
   
   
       8 . An exhaust gas heat exchanger in which exhaust gas generated due to combustion is heat-exchanged with cooling fluid, comprising:
 a tube in which the exhaust gas flows and outside which the cooling fluid flows; and   an inner fin which is arranged in the tube to improve a heat exchange between the exhaust gas and the cooling fluid, wherein:   the inner fin has a cross section which has a corrugated shape to include convex portions positioned at crests and troughs of the corrugated shape, and is constructed of an offset fin having lanced segments which are partially lanced and arrayed substantially in a flowing direction of the exhaust gas,   the crests and the troughs being alternately arranged, and the cross section being substantially perpendicularly to the flowing direction of the exhaust gas; and   a fin pitch fp of the inner fin and a length L of the lanced segment are substantially defined by following formulas
   2 mm<fp≦12 mm, 
   1.1 mm≦X≦4.3 mm, wherein X=de×L 0.14 /fh 0.18 , 
   wherein the fin pitch fp is a distance between central lines of the adjacent convex portions positioned at a side of one of the crest and the trough in the cross section of the inner fin, the length L is a dimension in the flowing direction of the exhaust gas, fh is a fin height which is a distance between the convex portions respectively positioned at a side of the crest and a side of the trough in the cross section of the inner fin, de is an equivalent circle diameter which is a diameter of an equivalent circle of a field C, and the field D which is defined in the cross section of the inner fin is positioned between the adjacent convex portions of the side of one of the crest and the trough and surrounded by the inner fin and the tube, in which the inner fin is arranged.   
   
   
       9 . The exhaust gas heat exchanger according to  claim 8 , wherein
 the length L of the lanced segment is substantially defined by a following formula
   1.2 mm≦X≦3.9 mm, wherein X=de×L 0.14 /fh 0.18 . 
   
   
   
       10 . The exhaust gas heat exchanger according to  claim 8 , wherein
 the length L of the lanced segment is substantially defined by a following formula
   1.3 mm≦X≦3.5 mm, wherein X=de×L 0.14 /fh 0.08 . 
   
   
   
       11 . The exhaust gas heat exchanger according to  claim 1 , wherein
 in a cross section of the inner fin, a ratio of an offset area T to a area of a field C is substantially in a range from 25% to 40%,   the cross section being substantially perpendicular to the exhaust gas flowing direction,   the field D being positioned between the adjacent convex portions of the side of one of the crest and the trough and surrounded by the inner fin and the tube, in which the inner fin is arranged,   the offset area T being an area of a part, which is defined in the cross section of the inner fin and surrounded by the two lanced segments which are adjacent to each other in the exhaust gas flowing direction and offset from each other in the longitudinal direction of the inner fin.   
   
   
       12 . The exhaust gas heat exchanger according to  claim 1 , wherein
 the lanced segments which are adjacent to each other in the flowing direction of the exhaust gas deviate from each other at an offset amount s in a longitudinal direction of the inner fin, and the offset amount s is larger than about 0.5 mm.   
   
   
       13 . The exhaust gas heat exchanger according to  claim 1 , wherein
 the tube and the inner fin are arranged at a halfway portion of an exhaust gas recirculation passage through which the exhaust gas of an diesel engine having passed a diesel particulate filter is returned to a suction side of the diesel engine.   
   
   
       14 . The exhaust gas heat exchanger according to  claim 2 , wherein
 the tube and the inner fin are arranged at a halfway portion of an exhaust gas recirculation passage through which the exhaust gas of an diesel engine having passed a diesel particulate filter is returned to a suction side of the diesel engine.   
   
   
       15 . The exhaust gas heat exchanger according to  claim 5 , wherein
 the tube and the inner fin are arranged at a halfway portion of an exhaust gas recirculation passage through which the exhaust gas of an diesel engine having passed a diesel particulate filter is returned to a suction side of the diesel engine.   
   
   
       16 . The exhaust gas heat exchanger according to  claim 8 , wherein
 the tube and the inner fin are arranged at a halfway portion of an exhaust gas recirculation passage through which the exhaust gas of an diesel engine having passed a diesel particulate filter is returned to a suction side of the diesel engine.   
   
   
       17 . The exhaust gas heat exchanger according to  claim 1 , wherein:
 each of the tube and the inner fin is made of a stainless steel; and   the cooling fluid is cooling water.   
   
   
       18 . The exhaust gas heat exchanger according to  claim 2 , wherein:
 each of the tube and the inner fin is made of a stainless steel; and   the cooling fluid is cooling water.   
   
   
       19 . The exhaust gas heat exchanger according to  claim 5 , wherein:
 each of the tube and the inner fin is made of a stainless steel; and   the cooling fluid is cooling water.   
   
   
       20 . The exhaust gas heat exchanger according to  claim 8 , wherein:
 each of the tube and the inner fin is made of a stainless steel; and   the cooling fluid is cooling water.