Heat exchanger for exhaust gas cooling; method for operating a heat exchanger; system with a heat exchanger for exhaust gas cooling

Abstract

A heat exchanger, in particular for cooling the exhaust of a motor vehicle internal combustion engine, is disclosed, the heat exchanger comprising a first partial heat exchanger with at least one first flow channel through which a medium to be cooled is to flow and at least one third flow channel through which a first coolant is to flow, at least one second partial heat exchanger with at least one second flow channel through which a medium to be cooled is to flow and at least one fourth flow channel through which a second coolant is to flow, wherein the at least one first flow channel and the at least one second flow channel are fluidly connected, and the at least one first flow channel and the at least one second flow channel have at least one first specific heat transfer surface and at least one second heat transfer surface, wherein second specific heat transfer surface area, divided by first specific heat transfer surface area, yields a quotient (ψ), the at least one first flow channel having a larger quotient (ψ) than second flow channel.

1 . A heat exchanger for cooling the exhaust of a motor vehicle internal combustion engine, comprising
 a first partial heat exchanger with at least one first flow channel through which a medium to be cooled is to flow and at least one third flow channel through which a first coolant is to flow,   at least one second partial heat exchanger with at least one second flow channel through which a medium to be cooled is to flow and at least one fourth flow channel through which a second coolant is to flow, wherein the at least one first flow channel and the at least one second flow channel are fluidly connected, and the at least one first flow channel and the at least one second flow channel have at least one first specific heat transfer surface having a first specific heat transfer surface area and at least one second heat transfer surface having a second specific heat transfer surface area;   wherein the second specific heat transfer surface area, divided by the first specific heat transfer surface area, yields a quotient (ψ), the at least one first flow channel having a larger quotient (ψ) than second flow channel.   
   
   
       2 . The heat exchanger according to  claim 1 , wherein the quotient (ψ) of the at least one first flow channel has a value of 1.0-2.5 and/or the quotient (ψ) of the at least one second flow channel has a value of 0-1.5. 
   
   
       3 . The heat exchanger according to  claim 1 , wherein the first flow channel and second flow channel form a constructive unit. 
   
   
       4 . The heat exchanger according to  claim 1 , wherein the first coolant has a higher temperature than the second coolant. 
   
   
       5 . The heat exchanger according to  claim 1 , wherein the at least one first flow channel is tubular and has a first tube interior surface that forms the first heat transfer surface. 
   
   
       6 . The heat exchanger according to  claim 1 , wherein the at least one second flow channel is tubular and has a second tube interior surface that forms the first heat transfer surface. 
   
   
       7 . The heat exchanger according to  claim 1 , wherein the at least one first flow channel has first turbulence elements and/or the at least one second flow channel has second turbulence elements. 
   
   
       8 . The heat exchanger according to  claim 7 , wherein the first turbulence elements have a first turbulence element height and/or the second turbulence elements have a second turbulence element height. 
   
   
       9 . The heat exchanger according to  claim 7 , wherein the
 first turbulence elements are first dimples or first turbulence plates with first rib segments and/or the second turbulence elements are second dimples or second turbulence plates with second rib segments.   
   
   
       10 . The heat exchanger according to  claim 7 , wherein the first turbulence plates and/or the second turbulence plates have the second heat transfer surface. 
   
   
       11 . The heat exchanger according to  claim 9 , wherein the first turbulence elements have a first turbulence element height and/or the second turbulence elements have a second turbulence element height. 
   
   
       12 . The heat exchanger according to  claim 8  wherein the first turbulence element height is greater than the second turbulence element height. 
   
   
       13 . The heat exchanger according to  claim 7 , wherein a first turbulence element density is defined by the number of first turbulence elements relative to a first length of first flow channel and/or a second turbulence element density is defined by the number of second turbulence elements relative to a second length of second flow channel. 
   
   
       14 . The heat exchanger according to  claim 7 , wherein a first turbulence element thickness is greater than a second turbulence element thickness. 
   
   
       15 . The heat exchanger according to  claim 7 , wherein a first turbulence element thickness is less than a second turbulence element thickness. 
   
   
       16 . The heat exchanger according to  claim 1 , wherein the heat exchanger is a U-flow heat exchanger. 
   
   
       17 . The heat exchanger according to  claim 1 , where in the heat exchanger is an I-flow heat exchanger. 
   
   
       18 . The heat exchanger according to  claim 1 , wherein the heat exchanger has a third partial heat exchanger for reducing thermal stresses. 
   
   
       19 . The heat exchanger according to  claim 18 , wherein the third partial heat exchanger has ⅛ to ¼ of a heat exchanger length of the heat exchanger. 
   
   
       20 . The heat exchanger according to  claim 18 , wherein the first partial heat exchanger is arranged between the second partial heat exchanger and the third partial heat exchanger. 
   
   
       21 . The heat exchanger according to  claim 18 , wherein the first partial heat exchanger and/or second partial heat exchanger and/or third partial heat exchanger form a constructive unit. 
   
   
       22 . The heat exchanger according to  claim 18 , wherein the medium to be cooled, and/or the coolant, flow with or against the current in first partial heat exchanger and/or in second partial heat exchanger and/or in third partial heat exchanger. 
   
   
       23 . A method for operating a heat exchanger comprising
 a first partial heat exchanger with at least one first flow channel through which a medium to be cooled is to flow and at least one third flow channel through which a first coolant is to flow,   at least one second partial heat exchanger with at least one second flow channel through which a medium to be cooled is to flow and at least one fourth flow channel through which a second coolant is to flow, wherein the at least one first flow channel and the at least one second flow channel are fluidly connected, and the at least one first flow channel and the at least one second flow channel have at least one first specific heat transfer surface having a first specific heat transfer surface area and at least one second heat transfer surface having a second specific heat transfer surface area;   wherein the second specific heat transfer surface area, divided by the first specific heat transfer surface area, yields a quotient (ψ), the at least one first flow channel having a larger quotient (ψ) than second flow channel,   the method comprising passing exhaust gas to be cooled through the heat exchanger, condensing out at least water while flowing through second heat exchanger, and cleaning the second flow channel from fouling from the exhaust gas.   
   
   
       24 . The method according to  claim 23 , including condensing out at least water from the exhaust gas substantially at a second coolant temperature of less than 40° C. 
   
   
       25 . A system comprising at least one heat exchanger comprising
 a first partial heat exchanger with at least one first flow channel through which a medium to be cooled is to flow and at least one third flow channel through which a first coolant is to flow,   at least one second partial heat exchanger with at least one second flow channel through which a medium to be cooled is to flow and at least one fourth flow channel through which a second coolant is to flow, wherein the at least one first flow channel and the at least one second flow channel are fluidly connected, and the at least one first flow channel and the at least one second flow channel have at least one first specific heat transfer surface hang a first specific heat transfer surface area and at least one second heat transfer surface having a second specific heat transfer surface area;   wherein the second specific heat transfer surface area, divided by the first specific heat transfer surface area, yields a quotient (ψ), the at least one first flow channel having a larger quotient (ψ) than second flow channel;
 at least one second heat exchanger for cooling an internal combustion engine of a motor vehicle and 
 at least one third heat exchanger for cooling the second coolant. 
   
   
   
       26 . The system according to  claim 25 , further comprising at least one fourth heat exchanger for cooling the first coolant. 
   
   
       27 . The system according to  claim 25 , wherein the third heat exchanger is arranged first, as viewed in the direction of the air flow, followed by the second heat exchanger. 
   
   
       28 . The system according to  claim 26 , wherein the fourth heat exchanger is arranged downstream of second heat exchanger, as viewed in the direction of air flow. 
   
   
       29 . The system according to  claim 26 , wherein the fourth heat exchanger is arranged adjacent to second heat exchanger as viewed in the direction of air flow (LR) and/or essentially at the same height as second heat exchanger. 
   
   
       30 . The system according to  claim 26 , wherein the second heat exchanger and the fourth heat exchanger are identical. 
   
   
       31 . The system according to  claim 25 , further comprising a first control member for regulating the mass flow of the medium to be cooled and/or for bypassing the medium to be cooled around at least one partial heat exchanger, arranged on the inflow side of the first heat exchanger. 
   
   
       32 . The system according to  claim 31 , further comprising a second control member for regulating the mass flow of the medium to be cooled and/or for bypassing medium to be cooled around at least one partial heat exchanger arranged on the outflow side of first partial heat exchanger and on the inflow side of second partial heat exchanger.