Abstract:
The invention relates to a device for cooling media or liquids, in particular the inlet air and exhaust gas from a motor vehicle.

Description:
BACKGROUND 
   The invention relates to an apparatus for cooling media or fluids, in particular charge air and recirculated exhaust gases in exhaust-gas recirculation systems, in particular for a motor vehicle or for large engines. 
   According to the prior art, turbochargers or other mechanical supercharging systems, such as compressors or the like, are used to increase the power of engines by compressing the air which is to be fed for combustion or the charge air. The fluid, gas or medium, such as in particular air, which is in the process heated as a result of the compression operation, is then generally cooled by a charge-air cooler. This is done also in order to further increase the air density and to limit the combustion peak temperatures. The charge air flows through a heat exchanger, which, by way of example, has ambient air or a cooling medium flowing through it and is thereby cooled. This allows the charge air to be cooled to a temperature which is approximately 20–90 K above the temperature of the ambient air or is as close as possible to this temperature. 
   In apparatuses with exhaust-gas recirculation, the exhaust gas is cooled in a dedicated heat exchanger and is then admixed or fed to the cooled charge air. This typically results in the temperature of the exhaust-gas/charge-air mixture being higher than the charge-air temperature at the outlet of the charge-air cooler. 
   This results in a significant drawback with regard to demands relating to reduced emissions, in particular of NOx, and reduced consumption, which are certain to rise in future. 
   SUMMARY 
   It is an object of the invention to provide an apparatus in which the temperature of the exhaust-gas/charge-air mixture is reduced compared to known apparatuses. 
   According to the invention, this object is achieved by an apparatus for cooling charge air and exhaust gas in particular in a motor vehicle or for large engines with internal combustion engine, having a recirculated exhaust-gas stream and a charge-air stream, in which the exhaust-gas stream is cooled by means of a first and a second heat exchanger, the charge-air stream is cooled by means of a third heat exchanger, before the exhaust-gas stream and charge-air stream which have been cooled in this manner are combined and mixed. 
   According to a further concept of the invention, the object of the invention is achieved by an apparatus for cooling charge air and exhaust gas in particular in a motor vehicle with internal combustion engine, having a recirculated exhaust-gas stream and a charge-air stream, in which the exhaust-gas stream is cooled by means of a first heat exchanger, the cooled exhaust-gas stream is combined with the charge-air stream, and the mixed exhaust-gas/charge-air stream is then cooled by means of a second heat exchanger. 
   According to a further concept of the invention, the object of the invention is achieved by an apparatus for cooling charge air and exhaust gas in particular in a motor vehicle with internal combustion engine, having a recirculated exhaust-gas stream and a charge-air stream, in which the exhaust-gas stream is combined with the charge-air stream and the mixed exhaust-gas/charge-air stream is then cooled by means of a heat exchanger. 
   In this context, it is advantageous if the recirculated exhaust-gas stream can be controlled by means of a valve. A valve of this type may preferably be a disk valve. However, a different type of valve can also be used in other exemplary embodiments of the invention. 
   Furthermore, it may be expedient if the first heat exchanger and the second heat exchanger are formed as separate heat exchangers. In a further exemplary embodiment, it is expedient if the first heat exchanger and the second heat exchanger, as separate heat exchangers, are formed as a structural unit. Furthermore, in a further exemplary embodiment it is expedient if the first and/or the second and/or the third heat exchanger are formed as a structural unit. 
   According to the invention, it is expedient if at least one of the heat exchangers is cooled by means of a first coolant, such as air, coolant, such as cooling water with or without additives, refrigerant from a refrigerant circuit in particular of an air-conditioning system. 

   
     BRIEF DESCRIPTION OF THE DETAILS 
     In the text which follows, the invention is explained in detail on the basis of a number of exemplary embodiments and with reference to the drawing, in which: 
       FIG. 1  shows an apparatus in accordance with a first exemplary embodiment of the invention; 
       FIG. 2  shows an apparatus in accordance with a second exemplary embodiment of the invention; 
       FIG. 3  shows an apparatus in accordance with a third exemplary embodiment of the invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows an apparatus  1  for cooling fluids, such as in particular for cooling exhaust gas and charge air. The exhaust gas from the internal combustion engine  2  is discharged through the pipes  3  and, for example, passed via a turbine  4 . Part of the exhaust-gas stream is recirculated via a valve  5 . The recirculated exhaust gas is cooled by a first heat exchanger  6 . At the outlet, it reaches a first temperature T 1 . Then, the exhaust gas which has been cooled to T 1  is cooled to temperature T 2  by a second heat exchanger. 
   The charge air is compressed by means of the element  4 . The compressed charge air is fed by means of the pipes  8  to a third heat exchanger  9 , which cools the charge air to a temperature T 3 . After it has emerged from the third heat exchanger, the cooled charge air is mixed with the exhaust gas, which has been cooled twice, and fed back to the engine  2  by means of the pipe  10 . 
   It is advantageous if the exhaust gas in the first heat exchanger is cooled by means of engine cooling water as cooling medium. The second heat exchanger  7  can then use air, a low-temperature coolant or a refrigerant as cooling medium in order to further cool the exhaust gas. The low-temperature coolant is in this case a coolant at a temperature which is lower than the temperature of the engine cooling water used in the first heat exchanger. 
   The two heat exchangers  6  and  7  may in this case be formed as separately formed heat exchangers or may be formed as a structural unit. It is also possible for one of the two heat exchangers  6  or  7  or both of these heat exchangers to be formed as a structural unit with the third heat exchanger  9 . However, the latter may also be formed as a separate heat exchanger. 
   In the case of heat exchangers which have been combined as a structural unit, the fluid passages for exhaust gas and charge air are routed and cooled separately. 
   It is preferable for the heat exchanger  7  to be fixed to the engine or arranged or integrated in a cooling module, in which various coolers, radiators or heat exchangers are combined. 
   It is preferable for charge air and exhaust gas to be mixed in a mixing chamber  11 , which can also be cooled. For this purpose, the mixing chamber may be part of a module or a heat exchanger. 
     FIG. 2  shows an apparatus  101  for cooling fluids, such as in particular for cooling exhaust gas and charge air. The exhaust gas from the internal combustion engine  102  is discharged through the pipes  103  and, for example, passed across a turbine  104  or the like. Some of the exhaust-gas stream is recirculated to the engine  102  via a valve  105 . The recirculated exhaust gas is cooled by a first heat exchanger  106 . It reaches a first temperature T 1  at the outlet. Then, the exhaust gas which has been cooled to T 1  is mixed with the compressed charge air from line  108 . 
   The charge air which has been mixed with exhaust gas is fed, by means of the pipes  108   a,  to a second heat exchanger  107 , which cools the exhaust gas/charge air mixture to a temperature T 2 . After it emerges from the second heat exchanger  107 , the cooled exhaust gas/charge air mixture is fed back to the engine  102  by means of the pipe  109 . 
   It is advantageous if the exhaust gas in the first heat exchanger  106  is cooled by means of engine cooling water as cooling medium. The second heat exchanger  107  can then use engine cooling water, air, a low-temperature coolant or a refrigerant as cooling medium for further cooling of the exhaust gas/charge air mixture. The low-temperature coolant is in this case a coolant which is at a temperature that is lower than the temperature of the engine cooling water used in the first heat exchanger. 
   The two heat exchangers  106  and  107  may be formed as separately formed heat exchangers or may be formed as a structural unit. If they are formed as a structural unit, the coolers, radiators or heat exchangers can be formed in such a manner that the media, in particular exhaust gas and charge air, are routed in different fluid passages. 
   It is preferable for charge air and exhaust gas to be mixed in a mixing chamber  110 , which may also be cooled. For this purpose, the mixing chamber may be part of a module or of a heat exchanger. 
   It is preferable for the heat exchanger  106  and/or  107  to be arranged fixed to the engine or arranged or integrated in a cooling module in which various coolers, radiators or heat exchangers are combined. 
     FIG. 3  shows an apparatus  201  for cooling fluids, such as in particular for cooling exhaust gas and charge air. The exhaust gas from the internal combustion engine  202  is discharged through the pipes  203  and passed, for example across a turbine  204 . Some of the exhaust-gas stream is recirculated to the engine  202  via a valve  205 . The recirculated exhaust gas is mixed with the compressed charge air from pipe  207  upstream of the heat exchanger  206 . 
   The charge air is compressed by means of the element  204 . The compressed charge air is fed, by means of the pipes  207 , to a mixing chamber  210 , in which the charge air and the recirculated exhaust gas are mixed. The mixing chamber  210  may advantageously be cooled. For this purpose, the mixing chamber may be part of a module or a heat exchanger. 
   The mixed exhaust gas/charge air mixture is cooled to temperature T by means of the heat exchanger  206 . 
   After it has emerged from the heat exchanger  206 , the cooled exhaust gas/charge air mixture is fed back to the engine  202  by means of the pipe  211 . 
   It is advantageous if the first heat exchanger is operated and supplied by means of engine cooling water, air, a low-temperature coolant or a refrigerant in order to cool the exhaust gas/charge air mixture. The low-temperature coolant is in this case a coolant which is at a temperature that is lower than the temperature of the engine cooling water used in the first heat exchanger. It is also possible for a plurality of the abovementioned coolants to be used in one heat exchanger in order to cool the temperature T of the exhaust gas/charge air mixture as far as possible. For this purpose, separate circuits are provided for the coolants in the heat exchanger. 
   It is preferable for the heat exchanger  206  to be arranged fixed to the engine or to be arranged or integrated in a cooling module in which various coolers, radiators or heat exchangers are combined. 
   In the exemplary embodiments described, the exhaust gas is recirculated upstream of the turbine, i.e. the exhaust gas is tapped off upstream of the turbine and partially recirculated. In corresponding exemplary embodiments, it is also possible for the exhaust gas to be tapped off from the low-pressure side of the turbine and recirculated. 
   In exemplary embodiments in which they flow separately through the heat exchangers, the exhaust gas and the charge air may preferably be mixed downstream of the heat exchanger. 
   If the exhaust gas and charge air flow through one heat exchanger, they can be mixed before entering the heat exchanger or in the inlet chamber thereof. It is also possible for the mixing to take place at the end of the heat exchanger, in its end chamber, or outside the heat exchanger. 
   The invention is not restricted only to the exemplary embodiments mentioned above. It is also possible for individual features of the exemplary embodiments to be combined with one another.