JP2011012625A - Exhaust heat recovery system and control method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an exhaust heat recovery system capable of preventing a refrigerant from being pyrolyzed due to becoming high in temperature and then preventing a contained oil from being carbonized by cooling a heat exchanger used for an exhaust gas of a rankine cycle without feeding electric power after an engine has stopped.SOLUTION: The exhaust heat recovery system is equipped with a first bypass flow channel for making a downstream side of a condenser in a circulating flow channel of a rankine cycle and an upstream side of the heat exchanger communicate with each other, a second bypass flow channel for making a downstream side of the heat exchanger in the circulating flow channel and an upstream side of the condenser communicate with each other, and first and second control valves provided in the first and second bypass flow channels, respectively. Then, the condenser is provided vertically above the heat exchanger.

Description

  The present invention relates to an exhaust heat regeneration system that regenerates exhaust heat discharged to the outside by cooling water or exhaust gas of an internal combustion engine such as an automobile engine as power or the like by a Rankine cycle.

  An exhaust heat regeneration system that regenerates exhaust heat discharged to the outside by cooling water or the like of an internal combustion engine (hereinafter referred to as an engine) as power by a Rankine cycle is a cooling fluid and Rankine cycle working fluid (also called refrigerant) from the engine. ) To generate power and electric power in the Rankine cycle. The engine is cooled by including a circuit (hereinafter referred to as a cooling water circuit) through which engine cooling water circulates. Rankine cycle is a heat exchanger that heats working fluid such as refrigerant with exhaust heat from the engine, an expander that expands the refrigerant to generate driving force, a condenser that condenses the refrigerant, and pumps and circulates the refrigerant. It consists of a refrigerant pump. When the refrigerant is heated by the exhaust heat from the engine, there is a configuration in which both exhaust heats of the engine coolant and the exhaust gas are heat-exchanged to the Rankine cycle refrigerant. In the conventional Rankine cycle that uses both exhaust heat of cooling water and exhaust gas, the refrigerant exchanges heat with the engine cooling water in the first heat exchanger, and the refrigerant exchanges with the second heat exchange. Heat is exchanged with the exhaust gas from the engine in the vessel to become a high-temperature refrigerant gas (see, for example, Patent Document 1).

  Generally, lubricating oil (containing oil) is added to the refrigerant in order to improve the lubricity of the refrigerant. In the Rankine cycle having the heat exchanger in which the exhaust gas from the engine and the refrigerant exchange heat in this way, the exhaust gas temperature reaches 300 to 400 ° C., so when the refrigerant becomes excessively high in temperature, There is a problem that the oil is carbonized or the refrigerant is thermally decomposed. If the refrigerant gets too hot, it occurs especially when the engine is stopped. This is because if the Rankine cycle is stopped simultaneously with the stop of the engine, the flow of the refrigerant also stops, and the refrigerant remaining in the heat exchanger that performs heat exchange between the exhaust gas and the refrigerant becomes high temperature due to the residual heat of the heat exchanger. As a countermeasure, the Rankine cycle operation is continued even after the engine is stopped to avoid abnormal temperature rise (see, for example, Patent Document 2).

JP 2006-144744 A (page 3, FIG. 1) JP 2006-250075 (page 3, FIG. 1)

  However, the conventional exhaust heat regeneration system has a problem that it is necessary to supply power to keep the Rankine cycle running even after the engine is stopped, that is, to supply power to the refrigerant pump. In addition, when the user leaves the vehicle with the ignition key turned off, the Rankine cycle operates, so that the user feels uncomfortable that the engine continues to operate and that the vehicle is turned off when the ignition key is turned off. There was a problem that the entire system could not be stopped.

  The present invention has been made to solve the above-described problems, and cools the heat exchanger for Rankine cycle exhaust gas without supplying power after the engine is stopped, so that the temperature of the refrigerant becomes high. The purpose is to obtain an exhaust heat regeneration system that can prevent thermal decomposition and carbonization of contained oil.

The exhaust heat regeneration system according to the present invention is:
A refrigerant pump for pumping the working fluid;
A circulation passage through which the working fluid circulates by the refrigerant pump;
A heat exchanger that is provided on the downstream side of the refrigerant pump in the circulation flow path and performs heat exchange between the exhaust gas discharged from the internal combustion engine and the working fluid;
An expander connected to the circulation channel downstream of the heat exchanger;
In the exhaust heat regeneration system having a Rankine cycle, which is connected to a downstream side of the expander of the circulation flow path and configured with a condenser provided vertically above the heat exchanger,
A first bypass channel that communicates the downstream side of the condenser and the upstream side of the heat exchanger in the circulation channel;
A second bypass passage that communicates the downstream side of the heat exchanger of the circulation passage and the upstream side of the condenser;
A first control valve and a second control valve provided in the first bypass channel and the second bypass channel, respectively.

  In the present invention, when the internal combustion engine is stopped, the working fluid is allowed to flow to the heat exchanger without supplying power to the refrigerant pump by using the difference in height between the condenser and the heat exchanger and the bypass flow path. Thus, it is possible to cool the heat exchanger, and therefore, it is possible to prevent the refrigerant from being heated to a high temperature and thermally decomposed or the contained oil to be carbonized.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the waste heat regeneration system of Embodiment 1 of this invention. It is a block diagram which shows the relationship between the installation height of the heat exchanger and condenser of the waste heat regeneration system of Embodiment 1 of this invention. It is a block diagram which shows the 1st control valve of Embodiment 1 of this invention. It is a block diagram which shows the 2nd control valve of Embodiment 1 of this invention. It is a characteristic view of the waste heat regeneration system of Embodiment 1 of this invention. It is a block diagram which shows the waste heat regeneration system of Embodiment 2 of this invention. It is a block diagram which shows the 3rd control valve of Embodiment 2 of this invention.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing an exhaust heat regeneration system according to Embodiment 1 for carrying out the present invention. The engine 1 is, for example, an internal combustion engine that generates driving force for driving a car. A cooling water circuit 3 for cooling the engine 1 is provided with a cooling water pump 3 for circulating the engine cooling water.

  In FIG. 1, Rankine cycle 5 is a circulating flow in which a working fluid circulates by connecting a refrigerant pump 11, a first heat exchanger 12, a second heat exchanger 13, an expander 14, and a condenser 15 in order. The road 10 is configured. The inside of the circulation channel 10 of the Rankine cycle 5 is filled with a working fluid (for example, the refrigerant R134a). The refrigerant pump 11 is driven by an electric motor, pressure-feeds the working fluid in a liquid state to the first heat exchanger 12, and circulates and circulates in the circulation channel 10. The first heat exchanger 12 is connected to the cooling water circuit 2 of the engine 1 and the circulation flow path 10 of the Rankine cycle 5 and is configured to exchange heat between the heated engine cooling water and the working fluid. ing. The second heat exchanger 13 is connected to the exhaust gas flow path 16 of the engine 1 and the circulation flow path 10 of the Rankine cycle 5, and is configured to exchange heat between the exhaust gas from the engine and the working fluid. ing. The expander 14 is configured to take out power by isotropically expanding the superheated steam of the working fluid generated by the first heat exchanger 12 and the second heat exchanger 13. The condenser 15 cools and condenses the steam working fluid sent from the expander 14, and is structured to be air-cooled by the fan 17.

  A power generator 20 and a battery 21 are connected to the expander 14 in series. The generator 20 has a function of generating electric power by being driven by the power recovered by the expander 14, and the electric power generated by the generator 20 is stored in the battery 21.

  In the downstream of the condenser 15 in the circulation channel 10 of the Rankine cycle 5, the working fluid liquefied in the condenser 15 is bypassed between the refrigerant pump 11 and the first heat exchanger 12, and the second heat exchanger 13. A first bypass channel 30 that flows to the upstream circulation channel 10 is provided. The first bypass passage 30 is provided with a first control valve 31 that switches the flow of the working fluid between the circulation passage 10 of the Rankine cycle 5 and the first bypass passage 30. Further, downstream of the second heat exchanger 13 in the circulation flow path 10 of the Rankine cycle 5, the working fluid heated and gasified by the second heat exchanger 13 is bypassed the expander 14 and the condenser 15 A second bypass channel 32 that flows to the upstream circulation channel 10 is provided. The second bypass passage 32 is provided with a second control valve 33 that switches the flow of the working fluid between the circulation passage 10 of the Rankine cycle 5 and the second bypass passage 32.

  FIG. 2 is a configuration diagram showing the relationship between the installation heights of the second heat exchanger 13 and the condenser 15 in the present embodiment. The condenser 15 is usually installed in front of the engine 1 in the hood of the automobile and at a place where cooling air from the outside can be taken. The condenser 15 and the engine 1 are air-cooled by the fan 17. The second heat exchanger 13 is installed in the middle of the exhaust gas passage 16 in order to exchange heat with the exhaust gas from the engine 1. Since the exhaust gas flow channel 16 is normally disposed under the floor of the automobile, the second heat exchanger 13 is disposed at a lower position vertically below the condenser 15 as shown in FIG.

  FIG. 3 is a configuration diagram showing the structure and operation of the first control valve 31 in the present embodiment. As shown in FIG. 3, the first control valve 31 has a three-way valve structure, and switches the three connected flow paths by rotating the three-way valve. In the normal operation mode, the first control valve 31 is rotated to the position shown in FIG. 3A, and the working fluid flows from the condenser 15 to the refrigerant pump 11 side through the circulation flow path 5 of the Rankine cycle 5. Controlled to form a path. In the cooling mode, the first control valve 31 is rotated to the position shown in FIG. 3B, and the path downstream of the condenser 15 communicates with the upstream of the second heat exchanger 13 via the first bypass flow path 30. Is controlled to form. In the stop mode, the first control valve 31 is rotated to the position shown in FIG. 3C, and the first bypass flow path 30 is controlled to form a path communicating with the upstream of the refrigerant pump 11. The refrigerant pump 11 is driven in the operation mode, but is stopped in the cooling mode and the stop mode.

  FIG. 4 is a configuration diagram showing the structure and operation of the second control valve 33 in the present embodiment. As shown in FIG. 4, the second control valve 33 also has a three-way valve structure like the first control valve 31. In the normal operation mode, the second control valve 33 is rotated to the position shown in FIG. 4A, and the circulation flow path 5 of the Rankine cycle 5 is communicated so that the working fluid flows from the expander 14 to the condenser 15. Controlled to form. In the cooling mode, the second control valve 33 is rotated to the position shown in FIG. 4B, and is controlled so that the second bypass flow path 32 forms a path communicating with the upstream of the condenser 15. In the stop mode, the second control valve 33 is rotated to the position shown in FIG. 4C and controlled so that the second bypass flow path 32 forms a path communicating with the downstream side of the expander 14.

  Next, the operation of the exhaust heat regeneration system in the present embodiment will be described. First, an operation mode corresponding to a traveling state for an automobile will be described. The engine coolant that circulates in the coolant circuit 2 by the coolant pump 3 is heated while the engine 1 is cooled, and the temperature rises. When the engine coolant temperature detected by the water temperature sensor (not shown) of the coolant circuit 2 is low, the refrigerant pump 11 is stopped. When the coolant temperature becomes equal to or higher than a set temperature (for example, 90 ° C.), the refrigerant pump 11 is driven to circulate the working fluid in the circulation flow path 10 to operate the Rankine cycle 5.

  The liquid working fluid sent out from the refrigerant pump 11 is heat-exchanged with engine cooling water of typically about 90 ° C. to 100 ° C. in the first heat exchanger 12, and the working fluid becomes high-temperature and high-pressure steam of about 90 ° C. . The working fluid that has become high-temperature steam at about 90 ° C. is sent to the second heat exchanger 13 via the circulation path 10. The working fluid sent to the second heat exchanger 13 is usually heat-exchanged with exhaust gas from the engine at 300 to 400 ° C. to become superheated steam at about 120 to 130 ° C. The high-temperature and high-pressure superheated steam is sent to the expander 14 via the circulation path 10. The heated steam that has flowed into the expander 14 expands in the expander 14, and the expansion energy is converted into power. The power generated by the expander 14 is converted into electric power by the generator 20 and stored in the battery 21.

  The expanded working fluid in a low-pressure gas state (for example, steam at about 70 ° C.) discharged from the expander 14 is condensed because the second control valve 33 is set to the position of FIG. 4A in the operation mode. Flows to vessel 15. The working fluid is cooled by a condenser 15 that is air-cooled by a fan 17 and condensed while radiating heat to the outside air to become a liquid (for example, about 30 ° C.). Since the first control valve 31 is set at the position shown in FIG. 3A, the working fluid that has become liquid returns to the refrigerant pump 11 and circulates in the circulation flow path 10 again.

  FIG. 5 shows the flow rate per unit time of the refrigerant pump 11, the flow rate per unit time of the working fluid in the first bypass flow path 30, and the second bypass flow path 32 in the operation mode of the exhaust heat regeneration system in the present embodiment. FIG. 5 is a characteristic diagram showing the relationship between the flow rate of working fluid per unit time and the temperature of the second heat exchanger 13. As described above, in the operation mode, the refrigerant pump 11 operates at a constant flow rate, and the first bypass flow path 30 and the second bypass flow path 32 are closed by the first control valve 32 and the second control valve 33, respectively. Therefore, the flow rate per unit time of the working fluid in these flow paths is zero, and the second heat exchanger 13 has a constant temperature because the temperature of the exhaust gas from the engine is almost constant. It will be kept.

  Here, a cooling mode corresponding to a case where the user turns off the ignition key to stop the engine 1 will be described. At this time, since the power supply to the refrigerant pump 11 is stopped, the flow rate of the working fluid from the refrigerant pump 11 per unit time becomes zero as shown in FIG. At the same time, the first control valve 31 and the second control valve 33 are switched to the positions shown in FIGS. 3B and 4B, respectively, and set to the cooling mode. The second bypass channel 32 is opened. By controlling in this way, the working fluid that makes a round so as to return from the condenser 15 to the condenser 15 via the first bypass flow path 30, the second heat exchanger 13, and the second bypass flow path 32 is closed. A circuit is formed.

  Since the inside of the condenser 15 is at a low temperature, it is filled with a working fluid in a liquid state, and the working fluid passes through the first bypass passage 30 and is located at a lower position vertically below the condenser 15. It flows to. The second heat exchanger 13 immediately after the stop of the engine 1 is at a high temperature, and when the working fluid that has flowed evaporates into a gas, the second heat exchanger 13 is cooled by latent heat of vaporization. The evaporated working fluid returns to the condenser 15 via the second bypass channel 32 and is condensed. In the cooling mode, power supply to the refrigerant pump 11 is not performed, so that the working fluid circulates using the height difference and the phase change. Therefore, during this cooling mode, the working fluid flows through the first bypass passage 30 and the second bypass passage 32 as shown in FIG.

  Since the engine 1 is stopped in the cooling mode, the exhaust gas from the engine does not flow through the exhaust gas passage 16. Therefore, when the amount of heat remaining in the second heat exchanger 13 is cooled by the refrigerant, the temperature of the second heat exchanger 13 gradually decreases with time as shown in FIG. Accordingly, since the temperature difference between the condenser 15 and the second heat exchanger 13 is gradually reduced at the start of the cooling mode, the working fluid flowing through the first bypass flow path 30 and the second bypass flow path 32 per unit time. The flow rate of the water gradually decreases.

  Since the second heat exchanger 13 performs heat exchange using a large temperature difference between the high-temperature (300 to 400 ° C.) exhaust gas and the refrigerant (120 to 130 ° C.) that is the working fluid, the heat transfer characteristics are good. A small heat exchanger can be used. Therefore, the heat capacity of the second heat exchanger 13 is smaller than that of the condenser 15, and the refrigerant is cooled by the difference in heat capacity and natural convection outside the condenser 15 without operating the fan 17 of the condenser 15. It is possible. When the temperature of the condenser 15 rises, it is possible to cool the fan 17 by rotating it, but it is preferable not to operate the fan 17 as much as possible from the viewpoint of power consumption.

  When the temperature of the second heat exchanger 13 falls below a preset temperature (Tc in FIG. 5), the cooling mode is terminated, and the first control valve 31 is moved to the position of FIG. Is switched to the position shown in FIG. In this stop mode, the liquid working fluid inside the condenser 15 does not flow anywhere. Therefore, the flow rate per unit time of the working fluid flowing through the first bypass channel 30 and the second bypass channel 32 is zero.

  When the engine 1 is started again and the first control valve 31 is switched to the position shown in FIG. 3A and the second control valve 33 is switched to the position shown in FIG. Since the liquid working fluid is filled in the vessel 15, the working fluid can be quickly supplied to the refrigerant pump 11, and the Rankine cycle 5 can be favorably started.

  As described above, in the exhaust heat regeneration system of the present embodiment, the working fluid of the condenser is allowed to flow to the second heat exchanger via the bypass flow path without supplying power to the refrigerant pump when the engine is stopped. Since the cooling of the second heat exchanger is made possible, it is possible to prevent the refrigerant from becoming high temperature and thermally decomposing and the contained oil to be carbonized.

  In FIG. 5, the temperature of the second heat exchanger 13 in the operation mode is set to be substantially constant. However, when the output of the engine fluctuates as in the case of traveling of an automobile, it may fluctuate. Further, the flow rate per unit time of the first and second bypass flow paths has been described as being the same. However, when part of the working fluid remains in the second heat exchanger 13, the flow rate is the structure of the bypass flow path. Some may be different.

  Furthermore, in this Embodiment, since the example provided with the 1st heat exchanger in order to utilize the exhaust heat of a cooling water was shown, it is not necessary to necessarily provide a 1st heat exchanger.

  In the present embodiment, the generator 20 is connected to the expander 14 of the Rankine cycle 5 and stored in the battery 21, and the exhaust heat is reused as electric power. However, the expander 14 and the engine 1 are shown. The output shaft of the expander 14 is coupled directly or indirectly with a pulley or belt, and the rotational force of the expander 14 is reused as engine power, or the rotational shaft of the expander 14 and the refrigerant pump 11 is directly or indirectly coupled. The exhaust heat may be reused as power, such as a configuration in which the rotational force of the expander 14 is reused as power of the refrigerant pump 11.

Embodiment 2. FIG.
FIG. 6 is a configuration diagram illustrating an exhaust heat regeneration system according to the second embodiment. In the first embodiment, two bypass channels are used, but in the present embodiment, one bypass channel and an on-off valve are combined. In FIG. 6, the description of the same parts as those in Embodiment 1 is omitted.

  In FIG. 6, the configuration in which the first bypass flow path 30 and the first control valve 31 are installed between the second heat exchanger 13 and the condenser 15 is the same as that of the first embodiment. A third control valve 34 similar to the first control valve 31 is provided at the other end. Further, a first opening / closing valve 35 is provided on the downstream side of the circulation flow path 10 of the second heat exchanger 13, and a second opening / closing valve 36 is provided on the upstream side of the circulation flow path 10 of the condenser 15.

  FIG. 7 is a configuration diagram showing the structure and operation of the third control valve 34 in the present embodiment. The structure and operation of the first control valve 31 are the same as those in the first embodiment. As shown in FIG. 7, the third control valve 34 has a three-way valve structure in the same manner as the first control valve. In the normal operation mode, the third control valve 34 is rotated to the position shown in FIG. 7A, and the circulation flow path 5 of the Rankine cycle 5 is communicated with the first heat exchanger 12 to the second heat exchanger 13. It is controlled to form a path through which the working fluid flows. In the cooling mode, the third control valve 34 is rotated to the position shown in FIG. 7B, and the first bypass flow path 30 is controlled to form a path communicating with the upstream side of the second heat exchanger 13. In the stop mode, the second control valve 33 is rotated to the position shown in FIG. 7C, and the first bypass flow path 30 is controlled to form a path that communicates with the downstream side of the first heat exchanger 12.

  The first on-off valve 35 and the second on-off valve 36 are opened so as to communicate with the circulation channel 5 in the operation mode, and are closed so as to close the circulation channel 5 in the cooling mode and the stop mode. Be controlled.

  Next, the operation of the exhaust heat regeneration system in the present embodiment will be described. About an operation mode, it is the same as that of Embodiment 1, and abbreviate | omits description. A cooling mode corresponding to the case where the user turns off the ignition key to stop the engine 1 will be described. At this time, since the power supply to the refrigerant pump 11 is stopped, the flow rate of the working fluid from the refrigerant pump 11 per unit time becomes zero. At the same time, the first control valve 31 and the third control valve 34 are switched to the position positions shown in FIGS. 3B and 7B, respectively, so that the cooling mode is set. Opened. Furthermore, the first on-off valve 35 and the second on-off valve 36 are controlled to be closed. By being controlled in this way, a closed circuit of the working fluid communicating from the condenser 15 to the second heat exchanger 13 via the first bypass flow path 30 is formed. By doing in this way, between the condenser 15 and the 2nd heat exchanger 13, the thermosiphon type heat pipe circuit using a height difference is formed.

  The difference between the present embodiment and the first embodiment is that, in the first embodiment, the working fluid in the cooling mode returns from the condenser 15 via the second heat exchanger 13 to the condenser 15 and makes a round. In contrast, such a closed circuit is formed, but in the present embodiment, a single-circuit closed circuit from the condenser 15 to the second heat exchanger is formed.

  The working fluid that has become a liquid in the condenser 15 flows by gravity to the second heat exchanger 13 via the first bypass flow path 30, and the working fluid evaporated in the second heat exchanger 13 serves as the first bypass flow as a gas. It flows back in the path 30 and returns to the condenser 15. By such a flow of the working fluid, the operation mode, the cooling mode, and the operation mode similar to those of the first embodiment shown in FIG. 5 are controlled, and the second heat exchanger can be cooled.

  As described above, in the exhaust heat regeneration system of the present embodiment, the working fluid of the condenser is allowed to flow to the second heat exchanger via the bypass flow path without supplying power to the refrigerant pump when the engine is stopped. Since the cooling of the second heat exchanger is made possible, it is possible to prevent the refrigerant from becoming high temperature and thermally decomposing and the contained oil to be carbonized.

  Moreover, since the number of bypass flow paths can be reduced to one, the exhaust heat regeneration system can be downsized as compared with the first embodiment.

DESCRIPTION OF SYMBOLS 1 Engine, 2 Cooling water circuit, 3 Cooling water pump, 5 Rankine cycle 10 Circulation flow path, 11 Refrigerant pump, 12 1st heat exchanger, 13 2nd heat exchanger 14 Expander, 15 Condenser, 16 Exhaust gas flow path , 17 fans,
30 1st bypass flow path, 31 1st control valve, 32 2nd bypass flow path 33 2nd control valve, 34 3rd control valve, 35 1st on-off valve, 36 2nd on-off valve

Claims (7)

A refrigerant pump for pumping the working fluid;
A circulation passage through which the working fluid circulates by the refrigerant pump;
A heat exchanger that is provided on the downstream side of the refrigerant pump in the circulation flow path and performs heat exchange between the exhaust gas discharged from the internal combustion engine and the working fluid;
An expander connected to the circulation channel downstream of the heat exchanger;
In the exhaust heat regeneration system having a Rankine cycle, which is connected to a downstream side of the expander of the circulation flow path and configured with a condenser provided vertically above the heat exchanger,
A first bypass channel that communicates the downstream side of the condenser and the upstream side of the heat exchanger in the circulation channel;
A second bypass passage that communicates the downstream side of the heat exchanger of the circulation passage and the upstream side of the condenser;
An exhaust heat regeneration system comprising a first control valve and a second control valve provided in the first bypass channel and the second bypass channel, respectively. 2. The second heat exchanger for exchanging heat between the cooling water of the internal combustion engine and the working fluid is provided between the refrigerant pump and the heat exchanger in the circulation flow path. Exhaust heat regeneration system. A control method for an exhaust heat regeneration system according to claim 1,
During the operation of the internal combustion engine, the first bypass channel and the second bypass channel are closed by the first control valve and the second control valve, respectively.
A control method for an exhaust heat regeneration system, wherein when the internal combustion engine is stopped, the first bypass passage and the second bypass passage are opened by the first control valve and the second control valve, respectively. When the temperature of the heat exchanger becomes equal to or lower than a predetermined temperature after the internal combustion engine is stopped, the first bypass flow path and the second bypass flow path are closed by the first control valve and the second control valve, respectively. The method for controlling an exhaust heat regeneration system according to claim 3, wherein: 4. The method for controlling an exhaust heat regeneration system according to claim 3, wherein when the internal combustion engine is started, the first bypass flow path and the second bypass flow path are closed by the first control valve and the second control valve, respectively. A refrigerant pump for pumping the working fluid;
A circulation passage through which the working fluid circulates by the refrigerant pump;
A heat exchanger that is provided on the downstream side of the refrigerant pump in the circulation flow path and performs heat exchange between the exhaust gas discharged from the internal combustion engine and the working fluid;
An expander connected to the circulation channel downstream of the heat exchanger;
In the exhaust heat regeneration system having a Rankine cycle, which is connected to a downstream side of the expander of the circulation flow path and configured with a condenser provided vertically above the heat exchanger,
A bypass channel communicating the downstream side of the condenser and the upstream side of the heat exchanger in the circulation channel;
A pair of control valves respectively provided at both ends of the bypass flow path;
A first on-off valve provided downstream of the heat exchanger in the circulation channel;
An exhaust heat regeneration system comprising: a second on-off valve provided on the downstream side of the expander in the circulation channel. A control method for an exhaust heat regeneration system according to claim 6,
During the operation of the internal combustion engine, the bypass flow path is closed by the pair of control valves and the first on-off valve and the second on-off valve are opened,
When the internal combustion engine is stopped, the bypass flow path is opened by the pair of control valves, and the first on-off valve and the second on-off valve are closed.

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