DE4340463A1 - Exhaust system for IC engine - Google Patents

Abstract

An exhaust system (2) for an IC engine (1) has a catalyser with soot filter (3) plus a burner (6). There is at least one heat exchanger (7 to 9) to extract heat energy form the exhaust. At least one is sited between the burner and the catalyser and the flow of the heat-carrying medium through it is controllable. The heat-carrying medium for one of the exchangers has a thermal connection with the engine, eg with part of its coolant circuit. The flow of the medium through the exchangers is controlled depending on the temperature in the catalyser. The burner has its output controlled according to the engine temperature.

Description

The invention relates to an exhaust system of an internal combustion engine with one in one Exhaust pipe arranged exhaust gas treatment system (catalyst, soot filter), with a Burner, its hot exhaust gases upstream of the exhaust gas treatment system to ensure the operational readiness of the same can be introduced into the exhaust pipe and with at least a heat exchanger for taking thermal energy from the exhaust gas stream.

From DE-A1-31 44 349 an exhaust system is known in which a soot filter Exhaust gas treatment system is provided, which by means of a burner assigned to it Ensuring its operational readiness is burned free from time to time. At this Plant is also provided to heat the burner of the soot burning device of working and operating materials, such as intake air, cooling water or lubricating oil use. For this purpose, a heat exchanger is located downstream of the soot filter Exhaust pipe arranged. A similar arrangement is also from DE-A1 38 21 138 known. Here, too, there is a soot filter arranged downstream of a soot filter Heat exchanger in a heat-conducting connection with one in the cooling water pipe arranged second heat exchanger to residual heat from the exhaust gas for heating purposes use. A burner used to regenerate the soot filter can be stopped of the vehicle can therefore also be used for preheating purposes. Both known Arrangements have the disadvantage that when the burner is operated for preheating purposes the soot filter between the burner and the heat exchanger unnecessarily with is preheated and thereby takes part of the energy generated.  

DE-A1-39 20 159 discloses a device for heating a catalyst, in which a heat exchanger integrated in or connected to the catalyst Exhaust gas stream extracts thermal energy for heating purposes. The catalyst is always there electrically preheated, a device to increase the energy in the exhaust gas stream is provided for injecting fuel upstream of the catalyst. A disadvantage of this arrangement is that by electrically preheating the catalytic converter the vehicle A lot of energy is withdrawn from the battery, which is particularly the case with an accumulation of Short journeys can lead to their discharge. Furthermore applies to this arrangement same disadvantage as for those described above, with a soot burner Equipped devices, since here also in a pure operation for heating purposes Vehicle is always preheated with the catalyst and therefore not one takes insignificant portion of the energy.

The invention has for its object to an exhaust system of an internal combustion engine create, on the one hand, a quick production of the operational readiness of a Exhaust gas treatment system is guaranteed and at the other an optimal There is a heating effect in a preheating mode of a vehicle.

This object is achieved in the characterizing part of patent claim 1 specified means solved. The fact that a heat exchanger between the burner and Exhaust gas treatment system is arranged in which the flow of it flowing heat transfer medium can be approximately in a preheating mode the full energy generated by the burner is used for heating purposes in the vehicle, whereas the exhaust gas is ready for operation quickly preparation system by throttling the flow of the heat transfer medium to one value near zero the full thermal energy of the exhaust gas treatment system generated by the burner can be supplied. The system according to the invention thus brings a real one Double use of a burner provided in a vehicle on the one hand in the sense of a Auxiliary or auxiliary heating and on the other hand for the operational readiness of one Exhaust gas treatment system. When using a catalytic converter as exhaust gas treatment system is by using a burner instead of an electrical preheater rapid operational readiness guaranteed, which means that a effective reduction of pollutants in the exhaust gas of the internal combustion engine is achieved. Advantageous developments of the invention can be found in the subclaims.  

An advantageous possibility of using the exhaust gas by means of the heat transfer medium Extracted energy arises from the fact that the heat transfer medium with the internal combustion engine is in a thermally conductive connection. This causes the internal combustion engine to stop which enables rapid preheating. Optionally or additionally, the Heat transfer medium with an interior of a driven by the internal combustion engine Vehicle to heat it in a heat-conducting connection.

It is also advantageous if the flow of the heat transfer medium is dependent on the Temperature of the exhaust gas treatment system is regulated. Such a regulation concedes the rapid production of the operational readiness of the exhaust gas treatment system highest Priority and thereby reduces the emission of harmful components in the exhaust gas Internal combustion engine already during its starting phase. As an alternative to temperature Controlled regulation is when using a catalyst as an exhaust gas treatment system also control the burner and the flow rate of the heat carrier in the Heat exchanger coupled to one initiated by starting the internal combustion engine Time interval conceivable. Such a time-dependent control can also be sent to the temperature-dependent control in such a way that the time interval is only at The burner falls below a certain operating temperature of the catalytic converter is going through.

For optimal operation as auxiliary heating in the event of a heat deficit in the vehicle space as it is with low outside temperatures and today's efficiency optimized internal combustion engines occurs easily, it is advantageous that the burner in its performance is adjustable. The regulation of the burner output can be advantageous either depending on the temperature of the internal combustion engine and / or in Depending on the temperature of the interior.

The use of a heat pipe as heat is particularly advantageous exchanger and heat-conducting connection to the internal combustion engine or to Inner space. Such heat pipes are due to their small size, the small amount the heat transfer medium to be heated, the good efficiency and the good ones Controllability of the transferred heat output by simply throttling the condensate return is ideal for use in vehicles due to its low weight suitable. Corresponding heat pipes are for example from DE-A1-25 23 645 for seen known for a transfer of heat in motor vehicles.  

When using a catalytic converter with lambda control, it is advantageous if A control flap is available between the burner and the junction on the exhaust pipe Introduction of the exhaust gases generated by the burner into the exhaust pipe or into one of the Exhaust gas treatment system is arranged passing branch line, being a Heat exchanger in this case between the burner and control flap or downstream of the Control flap is arranged. By providing such a control valve and the Arrangement of the heat exchanger, it is possible to use such a burner withdrawn heat output by the heat exchanger either as auxiliary heating or to use for preheating the catalyst and also without impairment the catalytic converter control when the control flap is switched on To enable internal combustion engine.

In any case, it is an additional advantage if - as from the above State of the art known per se - downstream of the exhaust gas treatment system further heat exchanger is arranged to absorb energy from the exhaust gases. By means of such an additional heat exchanger, the one of the Exhaust gas treatment system additionally use energy not required for heating purposes.

Exemplary embodiments of the invention are described below with reference to the drawing. It shows:

Fig. 1 is a schematic representation of a heat transfer circuit and an exhaust system with a burner arranged outside the exhaust gas flow.

Fig. 2 shows an alternative to Fig. 1 with a burner arranged in the exhaust gas flow.

In Fig. 1, 1 denotes an internal combustion engine of a vehicle, the exhaust gas of which is led outside via an exhaust pipe 2 and an exhaust gas treatment system 3 arranged therein. If the internal combustion engine is designed as a gasoline engine, the exhaust gas treatment system 3 is a catalyst. If the internal combustion engine is a diesel engine, the exhaust gas treatment system is optionally designed as a soot filter or, in addition, as an oxidation catalytic converter. Between the internal combustion engine 1 and the exhaust gas treatment system 2 , a burner exhaust line 5 opens into the exhaust pipe 2 at an opening 4 , the other end of which is connected to a burner 6 .

The burner 6 is a known burner, as is used for example for conventional parking heaters. In it, the same fuel with which the internal combustion engine 1 is operated is preferably processed and ignited with combustion air to form a combustible mixture, the resulting hot exhaust gas being introduced into the exhaust pipe 2 through the burner exhaust gas line 5 .

In the burner exhaust gas line 5 , in the exhaust pipe 2 between the mouth 4 and the exhaust gas treatment system 3 and in the exhaust pipe 2 downstream of the exhaust gas treatment system 3 , as explained below individually or in combination, a plurality of heat exchangers 7 , 8 , 9 are arranged. The first heat exchanger 7 in the burner exhaust gas line 5 is in heat-conducting connection with the internal combustion engine 1 . It is designed in the form of a heat pipe, also known as a heat pipe, and is used in the internal combustion engine 1 for preheating the lubricating oil and / or for preheating the cooling water thereof. In a known manner, the heat pipe is partially filled on the inside with an evaporable liquid, the part arranged in the region of the burner exhaust gas line 5 acting as an evaporator and the part arranged in the region of the internal combustion engine 1 acting as a condenser. By means of a controllable throttle valve arranged in the condensate return line, the heat transfer capacity of this first heat exchanger can be regulated continuously between zero and maximum capacity. In an alternative arrangement, the first heat exchanger 7 is in heat-conducting connection with a line of the cooling or heating water circuit instead of directly with the internal combustion engine 1 like the heat exchangers 8 and 9 described below.

The second heat exchanger 8 between the opening 4 of the burner exhaust gas line 5 into the exhaust pipe 2 and the exhaust gas treatment system 3 is in heat-conducting connection with a supply line 12 A of a cooling water circuit of the internal combustion engine 1, designated overall by 12. In the same way, it is preferably designed in the form of a heat pipe and its heat exchanger output can be regulated continuously between zero and maximum output by means of an adjustable throttle valve in the condensate return line. The heat is removed from the exhaust pipe in which the evaporator part of the heat pipe of the second heat exchanger 8 is located and the heat is transferred to the flow line 12 A, in the area of which the condenser part of the second heat exchanger 8 is arranged. By means of the second heat exchanger 8 , due to its arrangement in the exhaust pipe 2, it is possible to extract heat both from the exhaust gas generated by the burner 6 when the internal combustion engine 1 is at a standstill and from the exhaust gas generated by the combustion engine 1 while it is running.

A third heat exchanger 9 is in turn advantageously arranged in the form of a heat pipe downstream of the exhaust gas treatment system 3 in such a way that its evaporator part is in the area of the exhaust pipe 2 and its condenser part is in the area of the feed line 12 A. The heat exchanger output of the third heat exchanger 3 is also infinitely variable by means of an adjustable throttling of the condensate return line.

Between the burner exhaust gas line 5 and the exhaust pipe 2 , a branch line 10 is provided branching downstream of the first heat exchanger 7, which branches off downstream of the exhaust gas treatment system 3 into the exhaust pipe 2 . At the branch point of the branch line 10 from the burner exhaust gas line 5 , a control flap 11 is arranged such that it either blocks the branch line 10 or the flow of fuel gas to the mouth 4 . As an alternative to a junction of the branch line 10 downstream of the exhaust gas treatment system 3 , this can also open out directly as a branch line 10 A with a further heat exchanger 18 arranged therein, as shown in broken lines in FIG. 1. In this case, the first heat exchanger 7 is unnecessary.

The cooling water circuit 12 includes, in addition to the feed line 12 A, a return line 12 B, which connects a vehicle heat exchanger 13 to the internal combustion engine 1 . A pump 14 is also provided in the cooling water circuit 12 and can circulate the heat transfer medium in the circuit even without the internal combustion engine 1 operating. On the outlet side, the vehicle heat exchanger 13 projects into an interior 15 of the vehicle which is driven by the internal combustion engine 1 . A blower 16 is assigned to the vehicle heat exchanger 13 on the inflow side, by means of which heating air can be conveyed through the vehicle heat exchanger 13 into the interior 15 .

Of the heat exchangers 7 , 8 , 9 and 18 , only one of the heat exchangers 7 , 8 and 18 is required to achieve the object according to the invention. The heat exchanger 9 is only additionally present in a particularly advantageous embodiment. The variant in which only the first heat exchanger 7 is present, the other heat exchangers 8 , 9 and 18 and the branch line 10 or 10 A together with the control flap 11, on the other hand, are not to be described. In this simple first variant, when the burner 6 is in operation, the hot fuel gas discharged into the burner exhaust gas line 5 when the throttle valve of the first heat exchanger 7 is closed can be fed fully via the junction 4 to the exhaust gas treatment system 3 for the production of its production, ready for operation. If the exhaust gas treatment system 3 is a catalytic converter, it is heated up very quickly to the necessary operating temperature by the hot combustion gases of the burner 6 in order to convert a large part of the harmful substances contained in its exhaust gases into harmless ones when the internal combustion engine is started. If the exhaust gas treatment system 3 is a soot filter, the hot combustion gases from the burner 6 can be used to achieve the temperatures required for combustion, that is to say for regeneration of this filter. In the latter case, this can also take place during ongoing operation if the energy contained in the exhaust gas and the residual oxygen content are not sufficient for regeneration.

If, on the other hand, the throttle valve in the condensate return line of the first heat exchanger 7 is opened, a large part of the thermal energy is extracted from the combustion gases of the burner 6 by means of the heat exchanger 7 and the internal combustion engine 1 or alternatively the heating or cooling water circuit 12 for preheating the lubricating oil and / or of the cooling water supplied. The residual heat is still used to preheat the catalytic converter, which thus reaches its operating temperature much faster when the internal combustion engine is started. Optionally, the pump can be put into operation 14 at a pre-heating of the cooling water at a sufficient temperature to thereby supply by circulation of cooling water with simultaneous operation of the fan 16 heat energy from the cooling water through the heat exchanger 13 to the interior 15th If the internal combustion engine 1 is a diesel internal combustion engine and the exhaust gas treatment system 3 is a soot filter, then as a third operating mode it is also possible to heat up during the ongoing operation of the internal combustion engine 1 . Here, as with preheating, a large part of the thermal energy is withdrawn from the combustion gases generated by the burner 6 and fed to the internal combustion engine 1 with the throttle valve of the condensate return line fully open via the first heat exchanger 7 . In diesel internal combustion engines with high efficiency and at low outside temperatures, this auxiliary heating serves to compensate for heat deficits for heating the interior 15 .

If, however, the internal combustion engine 1 is a gasoline engine and the exhaust gas treatment system 3 is a regulated catalytic converter with λ control, the first simple variant described above is advantageously a second variant of the branch line 10 or 10 A and the control flap 11 expanded. As a result, a heating operation by means of the heat exchangers 7 or 18 is also possible during operation of the internal combustion engine (gasoline engine) 1 , in which the control flap 11 is pivoted into the position shown in dashed lines in FIG. 1 and thereby blocks the passage to the mouth 4 and the branch line 10 or 10 A releases. After leaving the heat exchanger 7 , the fuel gas of the burner 6 is not fed into the exhaust pipe 2 before the exhaust gas treatment system 3 , but only downstream of the latter. The sensitive λ control of a catalytic converter is not affected by the operation of the burner 6 . This first and second variant with the first heat exchanger 7 with or without branch line 10 or 10 A and control flap 11 can optionally be joined by the third heat exchanger 9 , which is advantageous for transferring the residual heat contained in the exhaust gases to the supply line 12 A of the cooling water circuit 12 is.

In a third variant, the first heat exchanger 7 , the branch line 10 and the control flap 11 are missing. Only the second heat exchanger 8 is present . If, in this variant, the burner 6 is in operation and supplies hot fuel gas via the opening 4 into the exhaust pipe 2 , with the throttle valve in the condensate return line of the second heat exchanger 8 closed, approximately the entire thermal energy can be made available for heating the exhaust gas treatment system 3 . When the condensate return line of the second heat exchanger 8 is opened, a large part of the thermal energy contained in the exhaust gases of the burner 6 is transferred to the supply line 12 A. On the one hand, this can be done in preheating mode, in which internal combustion engine 1 is out of operation. However, this operating mode is also conceivable for a diesel internal combustion engine, the waste heat given off to the cooling water is not sufficient for heating the interior 15 and which, in the phases in which no regeneration of the exhaust gas treatment system (soot filter) is required, includes one contained in the exhaust gas of the internal combustion engine Proportion of thermal energy and during operation of the burner 6, the thermal energy contained in its hot combustion gases can be extracted. In order to be able to carry out a heating operation in the third variant with the second heat exchanger 8, even in the case where the exhaust gas treatment system 3 is a catalyst with λ control, it is necessary that the heat exchanger 9 or 18 and the branch line 10 or 10 A and the control valve 11 are added as additional means. In this case, the control valve is performed whereby the exhaust gas of the burner 6 through the branch line 10 to the third heat exchanger 9 and via the branch line 10 A to heat exchanger 18 is in the heating operation pivoted to the dotted position 11 by the burner 6. The heat exchanger 9 or 18 then transfers the thermal energy contained in the fuel gas to the flow line 12 A of the cooling water circuit 12 .

In FIG. 2, the exhaust gases of an internal combustion engine 21 are passed outside via an exhaust pipe 22 and an exhaust gas treatment system 23 . A burner 26 is arranged in the exhaust gas flow between the internal combustion engine 21 and the exhaust gas treatment system 23 . A secondary air line 19 opens into the exhaust pipe 22 between the internal combustion engine 21 and this burner 26 and is connected to a secondary air blower 20 .

A heat exchanger 28 is arranged between the burner 26 and the exhaust gas treatment system 23 , which absorbs heat from the exhaust gases flowing past and transfers it to a flow line 32 A belonging to a cooling or heating water circuit. The flow line 32 A of the cooling water circuit is analogous to FIG. 1 in turn connected to a vehicle heat exchanger, not shown here, and leads via a return line 32 B back to the internal combustion engine 21 . A further heat exchanger 29 is arranged in the exhaust gas stream downstream of the exhaust gas treatment system 23 . It serves to absorb the residual heat contained in the exhaust gases and also to transfer it to the feed line 32 A of the cooling or heating water circuit. In the exemplary embodiment, the exhaust gas treatment system 23 is a regulated catalytic converter which is preceded by a λ probe 27 and whose component temperature is monitored by means of a temperature sensor 37 . If the λ probe 27 is omitted, the exhaust gas treatment system 23 can be designed as a soot particle filter of a diesel internal combustion engine.

The system shown in Fig. 2 enables the following modes of operation:
when the internal combustion engine 21 is not running, the burner 26 , which is also equipped with a fuel supply line (not shown) and electrical means for ignition and flame monitoring, is supplied with combustion air via the secondary air line 19 and the secondary air blower 20 . This combustion air is processed with the fuel into a combustible mixture and ignited electrically. The resulting hot fuel gases can be used on the one hand for heating the exhaust gas treatment system 23 to produce its operational readiness. The heat flow in the heat exchanger 28 , which in turn is preferably designed as a heat pipe, is blocked by means of the throttle valve in the condensate return line. The heat exchanger 28 therefore takes up only a very small part of the thermal energy contained in the exhaust gases of the burner 26 , whereby a rapid heating of the exhaust gas treatment system 23 is ensured. The residual heat still contained in the exhaust gases after leaving the exhaust gas treatment system 23 is advantageously removed from the exhaust gas stream by means of the heat exchanger 29 and, with the throttle valve open in the condensate return line, this heat exchanger, which is designed as a heat pipe, is fed into the feed line 32 A.

Secondary air blower 20 and secondary air line 19 are now part of the standard equipment of a vehicle equipped with a regulated catalytic converter. They are operated there to compensate for the oxygen deficit in the exhaust gas during a mixture enrichment with fuel during the starting phase of an internal combustion engine 21 . The burner arranged in the main flow of the exhaust gas is thus supplied with combustion air via the secondary air line 19 when the internal combustion engine is at a standstill, and on the other hand it can also be operated partially with the residual oxygen contained in the exhaust gases while the internal combustion engine 21 is running. Because of an impairment of the control of the catalyst, such a heating operation is only provided when the internal combustion engine 21 is designed as a diesel internal combustion engine and the corresponding design of the exhaust gas treatment system 23 is used as a soot particle filter.

The control of the burner 6 or 26 and the control of the throttle valves in the condensate return lines of the heat exchangers 7 , 8 , 9 , 18 , 28 and 29 is preferably carried out by means of a control device (not shown) depending on that by means of a temperature sensor 17 or 27 on the exhaust gas treatment system 3 or 23 determined operating temperature. Such an arrangement is in any case expedient if the exhaust gas treatment system 3 or 23 is a catalytic converter. If the exhaust gas treatment system 3 or 23 is a soot filter, it is expedient that an additional pressure sensor for measuring the exhaust gas back pressure is used to determine its operating temperature, which can be used to determine whether the soot filter is hot enough to burn off the soot particles is present, by means of which it can be determined whether the loading state of the filter requires regeneration.

When used as an auxiliary heater or additional heater, the burner 6 or 26 can additionally be started by means of conventional control means, as are known from the auxiliary heaters. Both an immediate start by means of an operating element arranged in the interior 15 , a time-dependent start by means of a clock arranged in the interior 15 , a temperature-controlled start by means of a temperature measuring device arranged in the interior 15 , as well as a remote start by means of a radio remote control.

When using the burner 6 or 26 for preheating a catalytic converter as an exhaust gas preparation system 3 or 23, it is sensible to control the burner 6 or 26 in such a way that when the internal combustion engine 1 , 21 starts, the temperature of the temperature sensor 17 , 37 is determined to check whether the catalytic converter has a sufficient operating temperature. If this is not the case, by actuating the starter of the internal combustion engine 1, the burner 6 or 26 can be started at the same time and operated for a predetermined time interval or alternatively until a predetermined operating temperature of the catalytic converter is reached. Once this operating temperature has been reached, the residual heat can immediately be removed from the exhaust gases of the burner 6 , 26 by means of the heat exchanger 7 or the heat exchanger 8 , 28 and made available for heating purposes.

By means of the system of an exhaust gas system described above in several variants, the operational readiness of an exhaust gas processing system can be maintained in any case by means of a single burner and, at the same time, it can be used as an auxiliary or additional heater. The heat is always transferred at such points and with such means (heat pipes) that enable optimal use of the thermal energy in the exhaust gases of the internal combustion engine and the burner 6 or 26 .

Reference list

1 , 21 internal combustion engine
2 , 22 exhaust pipe
3 , 23 exhaust gas treatment system
4 confluence
5 burner flue pipe
6 , 26 burners
7 first heat exchanger
8 , 28 second heat exchanger
9 , 29 third heat exchanger
10 , 10 A branch line
11 control flap
12 heating or cooling water circuit
12 A, 32 A supply line
12 B, 32 B return line
13 vehicle heat exchanger
14 pump
15 interior
16 blowers
17 , 37 temperature sensor
18 fourth heat exchanger
19 secondary air line
20 secondary air blowers
27 λ probe

Claims (11)

1. Exhaust system of an internal combustion engine ( 1 , 21 ) with an exhaust gas treatment system ( 3 , 23 ) (catalytic converter, soot filter) arranged in an exhaust pipe ( 2 , 22 ) with a burner ( 6 , 26 ), the hot exhaust gases of which are upstream of the exhaust gas treatment system ( 3 , 23 ) to ensure the operational readiness thereof are introduced into the exhaust pipe ( 2 , 22 ) and with at least one heat exchanger ( 7 , 8 , 9 , 18 , 28 , 29 ) for removing thermal energy from the exhaust gas stream, characterized in that at least one heat exchanger ( 7 , 8 , 18 , 28 ) is provided for removing thermal energy between the burner ( 6 ) and the exhaust gas treatment system ( 3 ) and that the flow of a heat carrier flowing through the heat exchanger ( 7 , 8 , 18 , 28 ) can be regulated. 2. Exhaust system according to claim 1, characterized in that the heat carrier of one of the heat exchangers ( 7 ) with the internal combustion engine ( 1 ) is in a heat-conducting connection. 3. Exhaust system according to one of the preceding claims, characterized in that the heat transfer medium via a part ( 12 A, 32 A) of a heating or cooling water circuit with an interior ( 15 ) of a by the internal combustion engine ( 1 , 21 ) driven vehicle is a thermally conductive connection. 4. Exhaust system according to one of the preceding claims, characterized in that the flow of the heat transfer medium through the heat exchanger ( 7 , 8 , 9 , 18 , 28 , 29 ) is regulated as a function of the temperature of the exhaust gas treatment system ( 3 , 23 ). 5. Exhaust system according to one of the preceding claims, characterized in that the burner ( 6 , 26 ) is adjustable in its performance. 6. Exhaust system according to claim 5, characterized in that the power control of the burner ( 6 , 26 ) in dependence on the temperature of the internal combustion engine ( 1 , 21 ). 7. Exhaust system according to claim 5 or 6, characterized in that the power control of the burner ( 6 , 26 ) takes place as a function of the temperature of the interior ( 15 ). 8. Exhaust system according to one of the preceding claims, characterized in that another. Heat exchanger ( 9 , 29 ) is arranged downstream of the exhaust gas treatment system ( 3 , 23 ). 9. Exhaust system according to one of the preceding claims, characterized in that between the burner ( 6 ) and an opening ( 4 ) on the exhaust pipe ( 2 ), a control flap ( 11 ) for optional introduction of the exhaust gases generated by the burner ( 6 ) into the exhaust pipe ( 2nd ) or in a branch line ( 10 , 10 A) leading past the exhaust gas treatment system ( 3 ). 10. Exhaust system according to one of the preceding claims, characterized in that a heat pipe (heat pipe) is used as the heat exchanger ( 7 , 8 , 9 , 18 , 28 , 29 ) and heat-conducting connection. 11. Exhaust system according to claim 10, characterized in that the flow of Heat transfer medium through the heat pipe by means of a throttle valve in the condensate return line can be controlled or regulated.